Biostratigraphy of the Akiyoshi Limestone Group,
Biostratigraphy of the Akiyoshi Limestone Group,
Biostratigraphy of the Akiyoshi Limestone Group,
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Bull. Kitakyusku Mus. Nat. Hist., 16: 1-97. March 28, 1997<br />
Middle Carboniferous and Lower Permian Fusulinacean<br />
<strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>,<br />
Southwest Japan. Part I<br />
Yasuhiro Ota<br />
Department <strong>of</strong> Earth and Planetary Sciences, Faculty <strong>of</strong> Science,<br />
Kyushu University33, Hakozaki, Fukuoka 812,Japan<br />
(Received October 31, 1996)<br />
Abstract The <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, one<strong>of</strong> <strong>the</strong> most representative stratigraphic<br />
standards <strong>of</strong>Japanese Carboniferous and Permian, is widely distributedin <strong>the</strong> <strong>Akiyoshi</strong><br />
Terrane, Southwest Japan.<br />
TheJigoku-dani area, <strong>the</strong> main area for investigation, is located in <strong>the</strong> northwestern<br />
part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> Plateau, where <strong>the</strong> Middle Carboniferous and Lower Permian<br />
limestones are widely exposed. They are mainly composed <strong>of</strong> micritic limestones,<br />
indicating a lagoonal facies, in <strong>the</strong> relatively low energy environments within <strong>the</strong><br />
<strong>Akiyoshi</strong> organicreefcomplex. The limestones are alsocharacterized by abundant and<br />
well-preserved fusulinaccans, and <strong>the</strong> following nine zones including seven subzones,<br />
were recognized in ascending order as: 1. Fusulinella biconica Zone, 2. Fusulina cf.<br />
shikokuensis Zone: 2-1. Fusulinella cf. obesa Subzone, 2-2. Pseud<strong>of</strong>usulitulla hidaensis<br />
Subzone, 3. Obsoletes obsolelus Zone: 3-1. Protriticites toriyamai Subzone, 3-2. Protriticites<br />
matsumotoi Subzone, 4. Montiparus sp. A Zone, 5. Triticites yayamadakensis Zone: 5-1.<br />
Triticites saurini Subzone, 5-2. Schwagerina sp. A Subzone, 5-3. Triticites biconicus Subzone,<br />
6. Schwagerina () cf. satoi Zone, 7. Pseudoschwagerina muong<strong>the</strong>nsis Zone, 8. Pseudqfusulina<br />
vulgaris globosa Zone, 9. Pseud<strong>of</strong>usulina afi". ambigua Zone. The distribution <strong>of</strong> <strong>the</strong>se<br />
fusulinacean zones shows well <strong>the</strong> inverted structure <strong>of</strong> limestones in this area.<br />
The second investigated AK area is located in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>-dai Museum <strong>of</strong><br />
Natural History, where limestones with nearly complete successions <strong>of</strong> <strong>the</strong> Middle<br />
Carboniferous to Lower Permian are well exposed. The following fusulinacean zones<br />
are discriminated alonga measured traverse, in ascending order:Pseud<strong>of</strong>usulinella hidaensis<br />
Zone, Protriticites matsumotoi Zone (s. I.), Montiparus sp. A Zone, Triticites simplex Zone (s.<br />
1.), Pseudoschwagerina muong<strong>the</strong>nsis Zone, and Pseud<strong>of</strong>usulina vulgaris Zone. Of <strong>the</strong>m,<br />
Protriticites matsumotoi Zone (s. I.) is tentatively subdivided into <strong>the</strong> lower Protriticites<br />
matsumotoi Zone (s. s.) and <strong>the</strong> upper Quasifusulinoides sp. A Zone. Triticites simplex Zone<br />
(s. 1.) is tentatively subdivided into <strong>the</strong> lower Schwagerina sp. A Zone and <strong>the</strong> upper<br />
Triticites simplex Zone (s. s.). <strong>Limestone</strong>s in this area mainly consist <strong>of</strong> alternation <strong>of</strong><br />
micritic limestones and those with sparry calcite matrices. The facies <strong>of</strong> limestones<br />
indicate that <strong>the</strong>y represent a marginal lagoon paleocnvironment. The limestones in<br />
this area explain <strong>the</strong> two sequences.<br />
The third investigated area, Mt. Maruyama, contains Middle and Upper Carbo<br />
niferous limestones. They represent a sedimentary environment <strong>of</strong> reef flat or bypass<br />
margin between <strong>the</strong> fore reef and open sea. They yield <strong>the</strong> primitive types <strong>of</strong><strong>the</strong>genus<br />
Protriticites, i.e., Protriticites yanagidai Ota, Protriticites masamichii Ota, and Protriticites
Yasuhiro Ota<br />
toriyamai Ota. From viewpoints <strong>of</strong> <strong>the</strong>ir morphological characters and affinities,<br />
Protriticites yanagidai Ota represents a primitive stage in <strong>the</strong> phylogenetic line between<br />
Protriticites yanagidai Ota and Protriticites matsumotoi (Kanmera), whereas Protriticites<br />
masamichii Ota is likely to be a transitional species to Montiparus matsumotoi injlatus,<br />
reported by Watanabe (1991).<br />
Based on <strong>the</strong>se fusulinacean assemblages and phylogenetic considerations, it is<br />
concluded that <strong>the</strong> variation <strong>of</strong> elements among fusulinacean assemblages is caused by<br />
change <strong>of</strong> lith<strong>of</strong>acies in development <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex. It has a<br />
large influence in recognition <strong>of</strong> <strong>the</strong> biostratigraphic units. The palcoenvironmental<br />
analysis <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex is indispensable for establishment <strong>of</strong> <strong>the</strong><br />
reexamined biostratigraphy.<br />
Introduction<br />
The study area is located in <strong>the</strong> <strong>Akiyoshi</strong> Terrane <strong>of</strong> Southwest Japan where <strong>the</strong><br />
Middle Carboniferous to Lower Permian <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> is widely dis<br />
tributed. The <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> which contains well-preserved fusulinaceans<br />
and many o<strong>the</strong>r well-preserved mega-fossils is considered to have originally<br />
formed as an organic reef complex upon a basaltic mound. This paper describes <strong>the</strong><br />
fusulinacean faunas and discusses <strong>the</strong> elements <strong>of</strong> <strong>the</strong> newly discriminated fusulina<br />
cean zones. It also examines <strong>the</strong> Middle Carboniferous to Early Permian fusulina<br />
cean phylogenetic transition in <strong>the</strong> Jigoku-dani area and two o<strong>the</strong>r related areas on<br />
<strong>the</strong> <strong>Akiyoshi</strong> limestone plateau.<br />
The principal survey area, Jigoku-dani, is located in <strong>the</strong> northwestern part <strong>of</strong> <strong>the</strong><br />
<strong>Akiyoshi</strong> Plateau. Karst topography characterized by lapie field, is well developed<br />
and a valley with a NE-SW trend is located in <strong>the</strong> middle <strong>of</strong> <strong>the</strong> area. Middle Car<br />
boniferous to Lower Permian limestones with a number <strong>of</strong> well-preserved fusulinaceans,<br />
are widely distributed. Consequently, this area was first selected for <strong>the</strong> ex<br />
amination <strong>of</strong> <strong>the</strong> transition <strong>of</strong> <strong>the</strong> fusulinacean assemblages during Middle Carbo<br />
niferous to Early Permian. M. Ota (1977) suggested that <strong>the</strong> general strikes and<br />
dips <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> in <strong>the</strong> area are nearly horizontal. The author<br />
set a starting point at an altitude <strong>of</strong> 355 m, and carried out field observation and<br />
sampling <strong>of</strong> materials with a measuring tape. The measured traverses (JI Traverse)<br />
were mainly drawn by crossing <strong>the</strong> general trend <strong>of</strong> <strong>the</strong> strike and sometimes drawn<br />
by lines parallel to strike. <strong>Limestone</strong> samples were carefully collected along <strong>the</strong><br />
measured traverses.<br />
The second investigated AK area was selected in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>-dai Muse<br />
um <strong>of</strong> Natural History. In this area, <strong>the</strong>re are nearly complete successions <strong>of</strong> Car<br />
boniferous to Lower Permian limestones with abundant fusulinaceans.<br />
also characterized by a lapie field.<br />
This area is<br />
The third investigated area, Mt. Maruyama is located in <strong>the</strong> Isa Quarry, Mine<br />
City. A principal traverse was set and measured along <strong>the</strong> eastern slope <strong>of</strong> Mt.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 3<br />
Maruyama at an elevation <strong>of</strong> about 200 m with <strong>the</strong> following abbreviation as MA<br />
Traverse. This traverse was established by crossing <strong>the</strong> general strike <strong>of</strong> E-W trend<br />
at right angles. <strong>Limestone</strong>s in this area are variable in <strong>the</strong>ir organic composition<br />
with rugose corals, ammonoids, phylloid algae, brachiopods and fusulinaceans occur<br />
ring alone or toge<strong>the</strong>r. The lithologic facies <strong>of</strong> limestones and <strong>the</strong>ir fossil compo<br />
nents suggest that <strong>the</strong> paleoenvironment <strong>of</strong> this area was a reef flat or bypass margin<br />
between <strong>the</strong> fore reef part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex and open sea (Fig. 1).<br />
m 1 ;<br />
Fig. 1. Simplified geologic map <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> area, showing locations <strong>of</strong> <strong>the</strong> investigation<br />
areas, Jigoku-dani area, AK area and Mt. Maruyama area. 1. <strong>Akiyoshi</strong> <strong>Limestone</strong><br />
<strong>Group</strong>. 2. Beppu and Ota <strong>Group</strong>s. 3. Tsuncmori <strong>Group</strong>. 4. Cretaceous sedimentary<br />
and igneous rocks. 5. Major thrust.
Yasuhiro Ota<br />
Historical review<br />
-I. Geology <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong><br />
The geology <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> and surrounding areas was first investi<br />
gated by Ozawa (1923), who established <strong>the</strong> biostratigraphy by <strong>the</strong> use <strong>of</strong> fusulina<br />
cean zones.<br />
He discovered <strong>the</strong> inverted succession <strong>of</strong> <strong>the</strong> fusulinacean zones and<br />
recognized <strong>the</strong> inverted sequences as an autochthonous recumbent fold caused by lat<br />
eral movement from south to north. Ozawa's interpretation was developed by<br />
Kobayashi (1935) and he proposed <strong>the</strong> <strong>Akiyoshi</strong> Phase for <strong>the</strong> first <strong>of</strong> <strong>the</strong> Mesozoic<br />
orogenic movements. Toriyama (1954a, b, 1958) reexamined <strong>the</strong> geology and<br />
fusulinacean paleontology <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> and <strong>the</strong> surrounding<br />
non-calcareous sedimentary rocks. He studied <strong>the</strong> Carboniferous and Permian<br />
fusulinaceans in detail and established refined fusulinacean zones on <strong>the</strong> Carbonif<br />
erous and Permian limestones. The fusulinacean zones by Toriyama (1963, 1967,<br />
1978) had been treated as a standard <strong>of</strong> <strong>the</strong> Carboniferous and Permian biostratigra<br />
phy in Japan. Along with <strong>the</strong> biostratigraphic work, Toriyama showed his interpre<br />
tation on <strong>the</strong> geologic structure <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. Later, Hasegawa<br />
(1958, 1963) and Murata (1961) showed different interpretations on <strong>the</strong> inverted<br />
structure <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>.<br />
Concurrently, a sedimentological study with <strong>the</strong> biostratigraphy, for <strong>the</strong> purpose<br />
<strong>of</strong> <strong>the</strong> paleoenvironmental examination had been started by M. Ota and o<strong>the</strong>rs.<br />
Eto (1967) examined <strong>the</strong> bio- and litho- facies <strong>of</strong> <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong><br />
<strong>Limestone</strong> <strong>Group</strong> in <strong>the</strong> Okubo area. He analyzed bi<strong>of</strong>acies <strong>of</strong> limestones and re<br />
constructed <strong>the</strong> sediment depositional process <strong>of</strong> limestones on <strong>the</strong> volcanic seamount.<br />
In 1968, M. Ota first suggested for <strong>the</strong> paleoenvironments <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong><br />
<strong>Limestone</strong> <strong>Group</strong> that it was formed as an organic reef complex on <strong>the</strong> basaltic seamount<br />
like an atoll <strong>of</strong> <strong>the</strong> present ocean. This is an epoch-making study from <strong>the</strong><br />
viewpoint <strong>of</strong> paleoenvironmental analysis on <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. The<br />
detailed lithology <strong>of</strong> <strong>the</strong> basal pyroclastic rocks was examined and described by<br />
Yanagida, M. Ota, Sugimura and Haikawa (1971). They showed <strong>the</strong> sedimentary<br />
sequence <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> in <strong>the</strong> Shishide-dai area with a columnar section<br />
and description <strong>of</strong> <strong>the</strong> biostratigraphy <strong>of</strong> <strong>the</strong> lowest part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong><br />
<strong>Group</strong>. Schwan and M. Ota (1977) carefully reexamined <strong>the</strong> geologic structures <strong>of</strong><br />
<strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> and surrounding non-calcareous rocks. They sug<br />
gested lateral and rotating pressures caused by gravity movement for <strong>the</strong> partly in<br />
verted succession <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>.<br />
The new interpretation for <strong>the</strong> tectonics <strong>of</strong> limestones and <strong>the</strong> surrounding noncalcareous<br />
rocks, based on <strong>the</strong> plate tectonic <strong>the</strong>ory <strong>of</strong> <strong>the</strong> new global tectonics, was<br />
shown by Kanmera and Nishi (1983) and Sano and Kanmera (1988). They con<br />
sidered that <strong>the</strong> <strong>Akiyoshi</strong> organic reef was developed on a seamount <strong>of</strong> basaltic rock<br />
and <strong>the</strong>n accreted to <strong>the</strong> terrigenous sediments <strong>of</strong> <strong>the</strong> Permian Tsunemori Formation
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 5<br />
at <strong>the</strong> end <strong>of</strong> <strong>the</strong> Middle Permian.<br />
The following palaeontological and geological contributions are important for<br />
establishment <strong>of</strong> <strong>the</strong> biostratigraphy and comprehension <strong>of</strong> <strong>the</strong> accretionary process<br />
<strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>: Fujii (1972); Fujii and Mikami (1970); Haikawa<br />
(1986, 1988); Haikawa and M. Ota (1978, 1983); Hasegawa (1967); Hashimoto<br />
(1979); Ichikawa (1984, 1990); Kawano (1960); Kimura, Hayami and Yoshida<br />
(1991); Matsusue (1986, 1988); Miura (1987); Nakamura and M. Ota (1974);<br />
Nishida (1971); Nishida and Kyuma (1982, 1984); M. Ota (1971); M. Ota,<br />
Toriyama, Sugimura and Haikawa (1973); N. Ota, Sugimura and M. Ota (1969);<br />
Sakagami (1964a, b); Sakagami and Sugimura (1978, 1983); Sano, Iijima and<br />
Hattori (1987); Sano and Kanmera (1991a, b, c, d); Sugimura (1972, 1974, 1985);<br />
Sugimura and M. Ota (1971, 1980); Sugiyama (1984); Uchiyama, Sano and<br />
Kanmera (1986); Ueno (1991a, b, c); Yanagida (1962, 1965, 1968, 1973, 1979,<br />
1983); Yanagida, M. Ota and Nagai (1977); Yamagiwa and M. Ota (1963).<br />
-II. Middle Carboniferous to Lower Permian biostratigraphic units in <strong>the</strong><br />
<strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong><br />
The fusulinacean biostratigraphy <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> has been<br />
treated as a standard <strong>of</strong> <strong>the</strong> Japanese Carboniferous and Permian. Recently, <strong>the</strong><br />
chronostratigraphic units <strong>of</strong> <strong>the</strong> Middle Carboniferous and Lower Permian have been<br />
very <strong>of</strong>ten discussed in <strong>the</strong> world to confirm <strong>the</strong> exact boundary between <strong>the</strong> Carbon<br />
iferous and Permian. The Middle Carboniferous to Lower Permian biostratigraphic<br />
units in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> also have been discussed by many workers,<br />
such as, Ozawa (1923), Kobayashi (1935, 1941), Sugiyama (1939), Toriyama<br />
(1954a, b), Hasegawa (1958, 1963, 1988), Murata (1961), M. Ota (1968, 1977),<br />
Ueno (1989), Ishii (1990), Ozawa and Kobayashi (1990), Watanabe (1991), and<br />
Y. Ota and M. Ota (1993).<br />
In case <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> region, it is well known that <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong><br />
<strong>Group</strong> was formed as an organic reef complex and that <strong>the</strong>re is a great variation in<br />
<strong>the</strong> bi<strong>of</strong>acies and lith<strong>of</strong>acies. Consequently, in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong>, <strong>the</strong> fusulina<br />
cean assemblages <strong>of</strong> <strong>the</strong> same age <strong>of</strong>ten show different constituents with different types<br />
<strong>of</strong> <strong>the</strong> limestone, suggesting different paleoenvironments (M. Ota, 1977). Therefore,<br />
it is indispensable to carefully discern <strong>the</strong> paleoenvironment in <strong>the</strong> <strong>Akiyoshi</strong> organic<br />
reef complex to establish <strong>the</strong> standard fusulinacean zones in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong><br />
<strong>Group</strong>. A number <strong>of</strong> stratigraphic units <strong>of</strong> <strong>the</strong> same age with different leading fossils<br />
are known in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. It is understood that <strong>the</strong> complicated<br />
state <strong>of</strong>zonation might be caused by differences <strong>of</strong> <strong>the</strong> original habitats <strong>of</strong> biota in <strong>the</strong><br />
organic reef complex. For instance, Ozawa and Kobayashi (1990) proposed 47<br />
fossil zones in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. However, <strong>the</strong>se zones are generally<br />
not mappable and some fossils are not included in <strong>the</strong>se zones (e.g. Sugiyama and<br />
Haikawa, 1993). These finely distinguished zones, appear to be reasonable, how-
6 Yasuhiro Ota<br />
ever <strong>the</strong>y are sometimes not practical. A careful examination <strong>of</strong> <strong>the</strong> lateral and<br />
vertical distributions and transitions in <strong>the</strong> bi<strong>of</strong>acies and lith<strong>of</strong>acies is required so as<br />
not to disregard <strong>the</strong> original habitats <strong>of</strong> biota in <strong>the</strong> various types <strong>of</strong> limestones.<br />
Watanabe (1991) discussed <strong>the</strong> inflated schwagerinids and proposed some phy<br />
logenetic lineages and datum levels among <strong>the</strong>m. His proposals are very interesting<br />
and logical. The inflated schwagerinids are well known in world wide distribution.<br />
Therefore <strong>the</strong>y are very useful for international correlation. For establishing <strong>the</strong><br />
chronostratigraphic units, <strong>the</strong> reconstruction <strong>of</strong> <strong>the</strong> evolutionary trend <strong>of</strong> <strong>the</strong> inflated<br />
schwagerinids is indispensable. On <strong>the</strong> o<strong>the</strong>r hand, <strong>the</strong> inflated schwagerinids are<br />
also known to occur in specialized environments <strong>of</strong> deposition, that show apparently<br />
imbalanced distribution <strong>of</strong> <strong>the</strong>m, near <strong>the</strong> Carboniferous and Permian boundary<br />
(Ross, 1964). Therefore, special attention and examination <strong>of</strong> <strong>the</strong> constituents <strong>of</strong> <strong>the</strong><br />
inflated schwagerinids are essential to establish <strong>the</strong> standard <strong>of</strong> both logical and<br />
practical chronostratigraphic units in <strong>the</strong> local area. Details <strong>of</strong> examination and<br />
comparison <strong>of</strong> <strong>the</strong> biostratigraphic units are discussed in <strong>the</strong> following chapters.<br />
Research on <strong>the</strong> chronostratigraphic units near <strong>the</strong><br />
Carboniferous-Permian boundary<br />
The chronostratigraphic divisions <strong>of</strong> <strong>the</strong> Carboniferous and Permian have been<br />
discussed for many years in and outside Japan. The definition <strong>of</strong><strong>the</strong> Carboniferous-<br />
Permian boundary has received special attention. As <strong>the</strong> Carboniferous-Permian<br />
boundary is an intersystem boundary, defining <strong>the</strong> boundary means to establish <strong>the</strong><br />
datum position in <strong>the</strong> rock sequences and this is essential for worldwide correlation.<br />
The name Carboniferous was derived from <strong>the</strong> coal bearing beds (Coal Mea<br />
sures) in England, whereas that <strong>of</strong> <strong>the</strong> Permian originated from <strong>the</strong> region <strong>of</strong> Perm,<br />
Russia. The Upper Carboniferous in England is mainly composed <strong>of</strong> terrigenous<br />
sediments. The Lower Permian in Russia, on <strong>the</strong> o<strong>the</strong>r hand, mainly comprises ma<br />
rine sediments. Therefore, it is not easy to confirm <strong>the</strong> boundary between <strong>the</strong> Car<br />
boniferous and Permian and to make intercontinental correlations <strong>of</strong> <strong>the</strong> Upper<br />
Carboniferous to Lower Permian successions. In general <strong>the</strong> Carboniferous-Per<br />
mian boundary is defined by marine sediments and fossils, which should be effective<br />
for <strong>the</strong> world wide correlation. From historical view points, <strong>the</strong> boundary should be<br />
defined in Russia. However, <strong>the</strong> Carboniferous and Permian boundary has been left<br />
ambiguously even in <strong>the</strong> type area. Therefore, it is true that many workers continue<br />
to apply <strong>the</strong>ir own definition.<br />
Here, careful considerations are summarized in three cases, relating to <strong>the</strong><br />
boundary problems.<br />
(1). The first case is <strong>the</strong> incompatibility caused by treating <strong>the</strong> stratigraphic<br />
boundary as <strong>the</strong> chronostratigraphic boundary. This consideration has resulted<br />
from regarding faunal elements <strong>of</strong> different ages as being <strong>of</strong> <strong>the</strong> same age.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 7<br />
(2). The second case is <strong>the</strong> confusion caused by applying <strong>the</strong> personal defini<br />
tion <strong>of</strong> each worker for <strong>the</strong> Carboniferous and Permian boundary even in Russia.<br />
This trouble is also due to a key fossil which was chosen for defining <strong>the</strong> Carbonifer<br />
ous-Permian boundary in spite <strong>of</strong> <strong>the</strong> inexact state <strong>of</strong> its taxonomic position.<br />
(3). The third case is shown by applying <strong>the</strong> evolutionary stage <strong>of</strong> a fossil for<br />
defining <strong>the</strong> boundary. There are also some problems, because it is difficult to con<br />
firm <strong>the</strong> key fossil for defining <strong>the</strong> Carboniferous-Permian boundary.<br />
As mentioned above, each case includes complicated and unsolved problems,<br />
and arguments about <strong>the</strong> definition <strong>of</strong> <strong>the</strong> Carboniferous-Permian boundary have<br />
continued since Murchison first introduced <strong>the</strong> Permian in 1841.<br />
Some proposals are introduced as follows.<br />
According to Rauser and Shchegolev (1979), <strong>the</strong> Carboniferous-Permian<br />
boundary has been studied intensively since Murchison, and <strong>the</strong> highest stratig<br />
raphic unit in <strong>the</strong> Carboniferous, namely, <strong>the</strong> top <strong>of</strong> "Schwagerina" Horizon was<br />
widely recognized as marking <strong>of</strong> <strong>the</strong> Carboniferous-Permian boundary. However,<br />
after <strong>the</strong> Asselian Stage was established by Ruzhencev, some paleontologists argued<br />
that <strong>the</strong> Carboniferous-Permian boundary should lie at <strong>the</strong> base <strong>of</strong> <strong>the</strong> Asselian,<br />
namely, at <strong>the</strong> base<strong>of</strong> <strong>the</strong> "Schwagerina" Horizon. Definitions <strong>of</strong> <strong>the</strong> boundary <strong>of</strong> <strong>the</strong><br />
Carboniferous and Permian boundary have been summarized as follows.<br />
1. Put <strong>the</strong> boundary between <strong>the</strong> Carboniferous and Permian at <strong>the</strong> base <strong>of</strong> <strong>the</strong><br />
Daixina sokensis Zone <strong>of</strong> <strong>the</strong> Gzhelian.<br />
2. Make <strong>the</strong> base <strong>of</strong> <strong>the</strong> Asselian <strong>the</strong> boundary between <strong>the</strong> Carboniferous and<br />
Permian.<br />
3. Put <strong>the</strong> boundary at <strong>the</strong> base <strong>of</strong> <strong>the</strong> upper fusulinacean zone in <strong>the</strong> Asselian,<br />
(<strong>the</strong> base <strong>of</strong> Nenetsky Horizon).<br />
4. Place <strong>the</strong> boundary at <strong>the</strong> top <strong>of</strong> <strong>the</strong> Asselian (Table 1).<br />
Rui and Zhang (1987) summarized <strong>the</strong> Carboniferous-Permian boundary in <strong>the</strong><br />
world. According to <strong>the</strong>m, six proposals for <strong>the</strong> Carboniferous-Permian boundary<br />
were shown even in Russia as follows.<br />
1. The Carboniferous-Permian boundary is at <strong>the</strong> base <strong>of</strong> <strong>the</strong> Daixina sokensis<br />
Zone in <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Gzhelian Stage.<br />
2. The base <strong>of</strong> <strong>the</strong> Daixina bosbylauensis-Daixina robusla Zone is <strong>the</strong> Car<br />
boniferous-Permian boundary.<br />
3. The basal part <strong>of</strong> <strong>the</strong> Asselian Stage in Russia, namely, <strong>the</strong> Schwagerina<br />
vulgaris-Schwagerina fusiformis Zone is <strong>the</strong> lowest part <strong>of</strong> <strong>the</strong> Permian.<br />
4. The basal part <strong>of</strong> <strong>the</strong> Schwagerina sphaerica-Pseud<strong>of</strong>usulina firma Zone <strong>of</strong> <strong>the</strong><br />
upper part <strong>of</strong> <strong>the</strong> Asselian, namely, <strong>the</strong> lowest part <strong>of</strong> <strong>the</strong> Nenet Horizon is <strong>the</strong> lowest<br />
part <strong>of</strong> <strong>the</strong> Permian.<br />
5. The Carboniferous-Permian boundary is between <strong>the</strong> top <strong>of</strong> <strong>the</strong> Asselian and<br />
<strong>the</strong> base <strong>of</strong> <strong>the</strong> Sakmarian, namely, between <strong>the</strong> Schwagerina sphaerica-Pseud<strong>of</strong>usulina<br />
firma Zone and <strong>the</strong> Pseud<strong>of</strong>usulina moelleri-Pseud<strong>of</strong>usulina uralica Zone.
Yasuhiro Ota<br />
Table 1.<br />
Correlation <strong>of</strong> <strong>the</strong> Carboniferous and Permian boundary among <strong>the</strong> main pro<br />
vinces (after Rauser and Shcheoolev, 1979).<br />
Russian<br />
Platform &Ural<br />
Camlc<br />
Alps<br />
USA<br />
W.Texas<br />
New<br />
Mexfoo<br />
Kuma<br />
Zone<br />
Formation<br />
Zone<br />
si<br />
1<br />
m<br />
Hi<br />
nil<br />
ft<br />
l!<br />
C3<br />
ii<br />
6. The Carboniferous-Permian boundary is at <strong>the</strong> boundary between <strong>the</strong><br />
Artinskian and Sakmarian (Table 2).<br />
In USA Beede and Kniker (1924) considered that "Schwagerina" was a good<br />
index fossil and its earliest occurrence mightbe safely regarded as revealing <strong>the</strong> basal<br />
part <strong>of</strong> <strong>the</strong> Permian. They proposed that "<strong>the</strong> zone <strong>of</strong> Schwagerina" (=Pseudo<br />
schwagerina <strong>of</strong> modern usage) should be recognized as <strong>the</strong> base <strong>of</strong> <strong>the</strong> Permian. Ac<br />
cording to <strong>the</strong> Permian Subcommittee <strong>of</strong> <strong>the</strong> National Research Council's Committee<br />
on Stratigraphy (Dunbar, Chairman) (1960), <strong>the</strong> U.S. Geological Survey <strong>of</strong>ficially<br />
recognized <strong>the</strong> Permian as a system in 1941. But it was uncertain until 1951 wheth<br />
er <strong>the</strong> Wolfcampian Series was "Permian". It is common that American geologists<br />
usually put <strong>the</strong> base <strong>of</strong> <strong>the</strong> Pseudoschwagerina Zone as <strong>the</strong> base <strong>of</strong> <strong>the</strong> Permian. They
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I<br />
Table 2. Different levels proposed for <strong>the</strong>Carboniferous-Permian boundary in Russia (after<br />
Rui and Zhang, 1987).<br />
Official Carboniferous - Permian boundary in Russia<br />
(Russian Platformand Ural)<br />
Horizon<br />
Zone<br />
Rybakov. 1962<br />
Lurryak. 1962<br />
Lever), 1986<br />
Barkhatova,<br />
1970<br />
Raiser. 1960<br />
RertOnger.<br />
1969: Koar. 1884<br />
Movsrtovich. 1S66<br />
Ruzherchev<br />
and<br />
Sarycheva,<br />
196S<br />
Irgjn<br />
Burtsyev<br />
Parafusulinalutugtni<br />
Pseud<strong>of</strong>usulina ccncavutas<br />
Permian<br />
Styertttamak<br />
Pseud<strong>of</strong>usulina urdalensis<br />
Pseud<strong>of</strong>usulina vemeuSi •<br />
Psf. uraBca<br />
Pseud<strong>of</strong>usulina moeBeri<br />
£<br />
Psf.<br />
moeBeriZ.<br />
Schwagerina sphaerica -<br />
Pseud<strong>of</strong>usulina firma<br />
Nenet<br />
Horizon<br />
Carboniferous<br />
Sokotiegor<br />
Schwagerina moelleri•<br />
Pseud<strong>of</strong>usulina fecunda<br />
Schwagerina vulgaris •<br />
SfusHbrmis<br />
S. vulgaris.<br />
S. fusttcnnlsZ.<br />
Dah&ia<br />
bosbyt&u<strong>of</strong>tsls<br />
D. robust* Z<br />
Carboniferous<br />
Carboniferous<br />
Daixina sokensis<br />
Daixina<br />
sokensisZ.<br />
JiguHtespgulensis<br />
Carboniferous<br />
have <strong>the</strong> opinion that <strong>the</strong> base <strong>of</strong> <strong>the</strong> Permian in <strong>the</strong> U.S. is essentially equivalent<br />
to <strong>the</strong> same horizon <strong>of</strong> <strong>the</strong> Russia (Fig. 2). Ross (1984) summarized Carbonifer<br />
ous-Permian fusulinaceans <strong>of</strong> North America and concluded that <strong>the</strong> base <strong>of</strong> <strong>the</strong><br />
Asselian in <strong>the</strong> Russian type locality, namely, <strong>the</strong> base <strong>of</strong> <strong>the</strong> zone with large, inflated<br />
schwagerinids, was presently widely recognized as <strong>the</strong> base <strong>of</strong> <strong>the</strong> lowest Permian<br />
faunal zone by many invertebrate paleontologists in North America, Japan and south<br />
ern Europe. Wilde (1984) also published on <strong>the</strong> Carboniferous-Permian boundary<br />
and he discussed this problem from <strong>the</strong> viewpoint <strong>of</strong> fusulinacean taxonomy. He<br />
also remarked that <strong>the</strong> Carboniferous-Permian boundary had been drawn at <strong>the</strong> base<br />
<strong>of</strong> <strong>the</strong> Asselian Stage in Russia. In addition, he recognized <strong>the</strong> boundary as equiva<br />
lent to <strong>the</strong> middle Wolfcampian unconformity, identified in <strong>the</strong> type section <strong>of</strong> <strong>the</strong><br />
Wolfcampian in <strong>the</strong> United States (Figs. 3, 4).<br />
In China, Rui and Zhang (1987) reviewed <strong>the</strong> current situations <strong>of</strong> <strong>the</strong> Car<br />
boniferous-Permian boundary. According to <strong>the</strong>m, before 1970, Chinese workers<br />
traditionally regarded <strong>the</strong> top <strong>of</strong> <strong>the</strong> Pseudoschwagerina Zone in <strong>the</strong> Maping (Chuanshan)<br />
Formation as <strong>the</strong> upper most <strong>of</strong> <strong>the</strong> Carboniferous, and <strong>the</strong> lower part <strong>of</strong> <strong>the</strong><br />
Chihsia Formation, namely, <strong>the</strong> Schwagerina tschernyschewi Zone or <strong>the</strong> Misellina<br />
Subzone <strong>of</strong><strong>the</strong> Parafusulina Zone as <strong>the</strong> lower most <strong>of</strong><strong>the</strong> Permian. In 1981, Rui Lin<br />
found <strong>the</strong> "Carboniferous" (traditional Chinese sense)-Permian mixed fusulinacean
10 Yasuhiro Ota<br />
U Jl i t i L ii<br />
UJ 4<br />
CD<br />
c<br />
a 1-<br />
1<br />
co<br />
z<br />
Pseud<strong>of</strong>usulina<br />
<<br />
Q. a.<br />
•V*<br />
<<br />
/ 'seudoschif/agerina<br />
<<br />
.3<br />
_i<br />
§<br />
Schubertella<br />
Schwdgerina<br />
ir<br />
ii ,, -J-<br />
LeptoWffc/tes<br />
"<br />
Parasch vagerina<br />
f<br />
w<br />
c<br />
a<br />
c<br />
UJ<br />
CD 9 o<br />
<<br />
r-<br />
CO<br />
<br />
Pseudoi usulinella<br />
z<br />
<<br />
"1<br />
Dunba inella<br />
> 5 Tr/fii ;/fes<br />
>.<br />
a: V<br />
CO ><br />
c<br />
c<br />
' f<br />
a><br />
a<br />
© z<br />
•9 <<br />
3<br />
rr<br />
O<br />
CO<br />
CO<br />
Eowaeringella<br />
1<br />
'<br />
Fig. 2. Approximate ranges <strong>of</strong> important fusulinacean genera near <strong>the</strong> Virgilian-Wolfcam<br />
pian boundary in <strong>the</strong> Big Hatchet Mts. (after Wilde, 1984; Rui and Zhang, 1987).<br />
fauna in <strong>the</strong> section <strong>of</strong> <strong>the</strong> "Carboniferous" to Permian continuous sediments above<br />
<strong>the</strong> uppermost Pseudoschwagerina Zone or <strong>the</strong> Robustoschwagerina schellwieni Zone <strong>of</strong><br />
Permian age. This sequence seems to represent <strong>the</strong> Liangshan Member, and Rui<br />
advocated that <strong>the</strong> lower boundary <strong>of</strong> <strong>the</strong> Permian should be placed below this<br />
limestone sequence. Afterwards, some workers supplemented and revised <strong>the</strong><br />
definition on <strong>the</strong> traditional boundary. At present 18 main proposals for <strong>the</strong><br />
Chinese Carboniferous-Permian boundary are known (Rui and Zhang, 1987).<br />
These Chinese proposals have been continuously discussed and <strong>the</strong>y are put into six<br />
main opinions about <strong>the</strong> definition <strong>of</strong> <strong>the</strong> Carboniferous-Permian boundary (Table<br />
3).<br />
1. Putting <strong>the</strong> boundary between <strong>the</strong> Carboniferous and Permian at <strong>the</strong> top <strong>of</strong><br />
Schwagerina Zone, is known as <strong>the</strong> traditional boundary in China and used for more<br />
than 40 years. In short, <strong>the</strong> boundary is compared with <strong>the</strong> top <strong>of</strong> <strong>the</strong> Pseudo<br />
schwagerina Zone or <strong>the</strong> Sphaeroschwagerina Zone, namely <strong>the</strong> top <strong>of</strong> <strong>the</strong> Maping<br />
Formation or <strong>the</strong> Chuanshan Formation, correlated with <strong>the</strong> boundary between <strong>the</strong>
Fig. 3. Correlation <strong>of</strong> Carboniferous-Permian fusulinid zones between Russia and U. S. A. (after Wilde, 1984).<br />
c<br />
Q.<br />
E<br />
s<br />
cr)<br />
c<br />
co<br />
CD<br />
Q_<br />
CD<br />
Q<br />
c<br />
eg<br />
'c<br />
CO<br />
c<br />
c<br />
CD<br />
Q_<br />
u.<br />
0<br />
Q.<br />
Q.<br />
J3_<br />
O<br />
RUSSIA<br />
U. S. A.<br />
Robustoschwagerina tumida, Parafusulina<br />
Pseud<strong>of</strong>usulina ex gr. vulgaris - kraffti<br />
11<br />
Robustoschwagerina stanislavi<br />
Parafusulina, Skinnerella<br />
Robustoschwagerina ex gr. tumidiformis<br />
10<br />
Pseudoschwagerina<br />
Chalaroschwagerina, Monodixodina<br />
CD<br />
Q_<br />
Schwagerina sphaerica<br />
Preparafusulina<br />
1CD<br />
i<br />
Cuniculinella<br />
o<br />
Pseudoschwagerina robusta<br />
Schwagerina moelleri<br />
2<br />
8<br />
Pseudoschwagerina robusta<br />
Schwagerina vulgaris - fusiformis<br />
Pseudoschwagerina uddeni<br />
Occidentoschwagerina<br />
Daixina<br />
Triticites - Schwagerina<br />
ui<br />
Jigulites<br />
Triticites - Schwagerina<br />
c<br />
o<br />
n<br />
i_<br />
CO<br />
O<br />
k_<br />
CD<br />
Q.<br />
Q.<br />
D<br />
CD<br />
Rauserites stuckenbergi<br />
Triticites<br />
ohioensis - articus - irregularis<br />
Montiparus<br />
Obsoletes - Protriticites<br />
Triticitesbeedei - moorei - plummeri<br />
Dunbarinella, Waeringella, Rauserites<br />
Kansanella<br />
Triticites ohioensis<br />
Triticites planus<br />
Eotriticites<br />
Eowaeringella
12 Yasuhiro Ota<br />
4. Possible alternate correlation <strong>of</strong>fusulinid zones, Russia-USA (after Wilde, 1984).<br />
Asselian and Sakmarian Stages.<br />
2. The Carboniferous-Permian boundary should be drawn at <strong>the</strong> base <strong>of</strong> <strong>the</strong><br />
Pseudoschwagerina morsei- Robustoschwagerina xiaodushanica Zone, namely, <strong>the</strong> lowermost<br />
part <strong>of</strong> <strong>the</strong> Mapingian, characterized by <strong>the</strong> first appearance <strong>of</strong> <strong>the</strong> rapidly evolving<br />
pseudoschwagerinids (Zhou et ai, 1987, Fig.5).<br />
3. The base <strong>of</strong> <strong>the</strong> Montiparus Zone is regarded as <strong>the</strong> lowest part <strong>of</strong> <strong>the</strong><br />
Permian. The Montiparus Zone is characterized by <strong>the</strong> first appearance <strong>of</strong> <strong>the</strong><br />
kerio<strong>the</strong>ca in <strong>the</strong> wall microstructure (Zhang, 1984, Figs. 6, 7).<br />
4. The Carboniferous-Permian boundary should be placed between <strong>the</strong> Late<br />
Carboniferous Nephelophyllum-Pseudotimania assemblage Zone and <strong>the</strong> Early Permian<br />
Kepingophyllum assemblage Zone, namely between <strong>the</strong> Shazitang Formation and <strong>the</strong><br />
Longyin Formation <strong>of</strong> <strong>the</strong> Longyin section in Guizhou. However, Rui and Zhang<br />
(1987) noticed that <strong>the</strong> lowest part <strong>of</strong><strong>the</strong> Kepingophyllum assemblage Zone was higher<br />
than <strong>the</strong> base <strong>of</strong> <strong>the</strong> Pseudoschwagerina Zone.<br />
5. The lowest part <strong>of</strong> <strong>the</strong> Pseud<strong>of</strong>usulina moelleri Zone and <strong>the</strong> Protopopanoceras<br />
Zone in <strong>the</strong> Longyin section <strong>of</strong> Guizhou, is correlated with <strong>the</strong> lowest Sakmarian in<br />
Russia and it is regarded as <strong>the</strong> lowest <strong>of</strong><strong>the</strong> Permian. According to Ruiand Zhang<br />
(1987), this consideration <strong>of</strong> <strong>the</strong> Carboniferous and Permian boundary is ambiguous,<br />
because <strong>the</strong> Pseud<strong>of</strong>usulina moelleri Zone contains Sphaeroschwagerina and o<strong>the</strong>r charac<br />
teristic elements <strong>of</strong> <strong>the</strong> Asselian Stage.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I<br />
13<br />
Table 3.<br />
Different levels proposed to <strong>the</strong> Carboniferous-Permian boundary in China (after<br />
Rui and Zhang, 1987).<br />
Locality Lower Permian Upper Carboniferous<br />
Nanjing Mis<br />
Chen, 1934,Sheng.1962<br />
Chinling Range<br />
Wang etaL 1973<br />
Nanjing hits<br />
Wang,1978<br />
Puan,Guizhou<br />
Wuetal., 1979<br />
Yangel al.,1983<br />
Sou<strong>the</strong>rnJiang<br />
Yu.1981<br />
Yangzistratigraphic province<br />
Rui,1981<br />
South China<br />
Sheng., 1982<br />
Puan,Guizhou<br />
Zhang, el al, 1982<br />
Longlin, Guanga<br />
Long, 1982<br />
Longlin, Guangxi<br />
Huang, 1984<br />
Sou<strong>the</strong>rn Hunan<br />
Zhou, 1982<br />
Nanjing hBis<br />
Zhang, 1983<br />
Southwestern Guizhou<br />
Wuetal., 1983<br />
Puan,Guizhou<br />
Zhang, 1983<br />
Qinling Range<br />
Ding etal., 1983<br />
South China<br />
Wu, etal., 1984<br />
South China<br />
Zhang, 1985<br />
Luodan, Guizhou<br />
Xiong etal, 1985<br />
Swine <strong>Limestone</strong> Member<br />
Chuanshan Fra<br />
MdaudaeZ 1 S. tschemyschewi Z PseudoschwaaerinaZ 1 TriMesZ<br />
YaziFra<br />
SanBchongFm.<br />
MiseSlmaZ. PamuinaZ PseudoschwacsrhaZ 1 TriMesZ<br />
L Permian<br />
Upper CarbonSerous<br />
Swine L Mem.<br />
ChuanshanFm.<br />
M. daudae Z .Sphaeroschwagerina moelleri Z 1 TriMesZ<br />
Lower Permian<br />
Upper CarbonSerous<br />
ChBisia Fm. LiangshanFra Baomoshan Fra Longyin Fra I Shazitang Fm.<br />
Robust,<br />
Sphaeroschwagerina Z<br />
schellwieniZ Sph. domerosa ISph. constans<br />
Triticites Z<br />
Lower Permian"<br />
UpperCarboniferous<br />
ChhsiaFm.<br />
ChuanshanFm.<br />
Parawenl Z 1Chuanshan. Z 1<br />
Chftsia Stage<br />
MapingStage<br />
Misellina Z PseudoschwaaerinaZ. 1 TriMesZ<br />
ChBisia Stage<br />
Maping Stage<br />
M. daudaeZ 1Schwagerina tschemyschewi Z Pseudosc wagerina Z I Triticites Z<br />
Lower Permian<br />
Upper Carboniferous<br />
Chihsia Stage Longyin Fm Shazitang Fra<br />
MiseSna daudae Zone Pseud<strong>of</strong>usulna moelleriZone Ps-ZelliaZ TriMesZ<br />
ChBisia Fra ChannmoFra Mapina Fm<br />
Misellina,<br />
Pseud<strong>of</strong>usul'ina inusilata-<br />
Paratusulina Robustoschwagerina Z Pseudoschwagerina Z TriMesZ<br />
ChihsiaFm. LortfinStaae Maping Stage<br />
Misellina Z Pamtina- Nagatoella {Daivasies Pseudoschwagerina Z | Triticites Z<br />
ChBisia F.<br />
Chuanshan Fm<br />
M. daudaeZ Staffollal S.cushmaniZ Pseudoschwagerina Z<br />
ChBisia Fra Swine <strong>Limestone</strong> Fm. Chuanshan Fra<br />
M. daudae Z Darvasites oidinatus Z Sphaeroschwagerina moelleri Z Triticites Z<br />
Proposal 1 Lower Permian U.Carb.<br />
M daudae<br />
Bed<br />
M.<br />
Rob.<br />
Psl.-<br />
Rob.<br />
Rob.<br />
schellwieni Q.<br />
Psl. moelleri-<br />
Psl. fusiormis<br />
j<br />
1 N «£<br />
TriMesZ<br />
Proposal 2 Lower Permian U.Carb.<br />
Lower Permian<br />
UpperCarboniferous<br />
ChBisia Fm. Uanoshan Fm. Baomoshan Fm Longyin Fm. | Shazitang Fm.<br />
Rob.<br />
schellwieni Z<br />
Sphmoschwaaerina Z.<br />
Sph. domerosa\ Sph. constans<br />
Lower Permian<br />
UpperCarbonSerous<br />
YaziFra
14<br />
Yasuhiro Ota<br />
U<br />
J0.F<br />
si<br />
I<br />
1. Protriticites subschwagerinoides Zone<br />
2. Triticites montiparus Zone<br />
3. Triticites schwageriniformis Zone<br />
4. Triticites dictyophorvs Zone<br />
5. Triticites shikhanensis compactus Zone<br />
6. fteudaschwagerina mo/sej -<br />
Robustoschwagerina xiaodushanica Zone<br />
7. fteudoschwagerina parabeedei -<br />
Sphaeroschwagerina sphaerica Zone<br />
8. fteudoschwagerina robusta -<br />
Zellia chengkungensis Zone<br />
9. Pseud<strong>of</strong>usulina vulgaris -<br />
laxifusulina iniqua zone<br />
10. Chalaroschwagerina tumentis Zone<br />
11. Pamirinachinlingensis Zone<br />
Fig. 5. Composite stratigraphic section, showing fusulinacean faunas near <strong>the</strong> Carbonifer<br />
ous-Permian boundary at Xiaodushan, Guangnan, Easter Yunnan (after Zhou et al.,<br />
1987).<br />
6. The top <strong>of</strong> <strong>the</strong> Baomoshan Formation, namely <strong>the</strong> Robustoschwagerina Zone is<br />
correlated with <strong>the</strong> base <strong>of</strong> Artinskian Stage and it is regarded as <strong>the</strong> lowest part <strong>of</strong><br />
<strong>the</strong> Permian in China.<br />
In Japan, <strong>the</strong> definition <strong>of</strong> <strong>the</strong> Carboniferous-Permian boundary also has been<br />
discussed for a long time in several important provinces by many workers. The<br />
author presents some recent considerations on this problem, by some workers in <strong>the</strong><br />
<strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>.<br />
Toriyama (1954a, b, 1958) divided <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> into <strong>the</strong><br />
following seven fusulinacean zones in descending order.<br />
Yabeina Zone<br />
Neoschwagerina Zone<br />
Parafusulina Zone<br />
Pseudoschwagerina Zone<br />
Fusulinella Zone<br />
Projusulinella Zone<br />
Millerella Zone<br />
He subdivided <strong>the</strong> Pseudoschwagerina Zone into two subzones, <strong>the</strong> upper, <strong>the</strong><br />
Pseud<strong>of</strong>usulina vulgaris Subzone and <strong>the</strong> lower, <strong>the</strong> Triticites simplex Subzone. Then
South Ural<br />
Zone<br />
Paralusulina<br />
Parafusulina<br />
soSdissima,<br />
concessa,<br />
schellwieni<br />
Psl. urdalensis<br />
Psl. callosa,<br />
Psl. vemeuilis,<br />
Psl. moelleri<br />
Sph.<br />
sphaerica- Psf.<br />
firma<br />
Sph<br />
moelleri-<br />
Psf. fecunda<br />
Psf. vulgaris•<br />
Psf. fusiformis<br />
D. sokensis<br />
T. jigulensis<br />
T. siuckenbergi<br />
T. acutus •<br />
T. ardicus<br />
Montiparus<br />
montiparus<br />
£<br />
USA<br />
Texas<br />
Zone<br />
Paralusulina<br />
Pseudo<br />
schwagerina •<br />
Monodixodina,<br />
Pseudo<br />
schwagerina -<br />
Triticites,<br />
Triticites-<br />
Schwagerina<br />
Triticites<br />
ventricosus,<br />
Triticites<br />
cullomenensis,<br />
Triticites<br />
Irregularis<br />
O<br />
South China<br />
Nor<strong>the</strong>ast<br />
Japan<br />
Southwest<br />
RUSSIA<br />
Darvas <strong>of</strong> Central Asia Transcaucas<br />
Zone<br />
Zone<br />
Zone<br />
Stage<br />
Zone<br />
Zone<br />
J<br />
Misellina<br />
Nanklnella • Paralusulina<br />
M. claudiae<br />
M. bngjinensis - M. prima<br />
Monodiexodina<br />
matsubaishi<br />
Neoschwagerina<br />
§ simplex-<br />
Cancellina<br />
Bolorian<br />
Misellina<br />
parvicostata<br />
M. dyhrenfurthi<br />
\Chalaroischwagerina<br />
Kungurian<br />
Pseudotusutina<br />
acmeZ.<br />
Darvasites<br />
Nagatoella<br />
Robustoschwagerina schellwieni<br />
(or StatiellarichZone)-<br />
Kepingophyllum<br />
Pseudolusulina<br />
Misellina<br />
Pseudoiusulina<br />
Yakhtashian<br />
Sakmarian<br />
Chalaro<br />
schwagerina<br />
vulgaris-<br />
Pamirina<br />
Robusto<br />
schwagerina<br />
schellwieni •<br />
Parasch mira<br />
Artinskian<br />
Sakmarian<br />
Sphaeroschwagerina<br />
Monodiexodina<br />
Sph. sphaerica<br />
Psl. firma<br />
£<br />
Pseudo<br />
schwagerina<br />
Asselian<br />
Sph.moelleri -<br />
Psf. fecunda<br />
Asselian<br />
Pseudoschwagerina range Zone<br />
Ps. vulgaris -<br />
P& fusitormis<br />
Orenburgian<br />
D. sokensis<br />
Orenburgian<br />
Triticites<br />
Montiparus range Zone<br />
Triticites<br />
Gzhelian<br />
Kasimovian<br />
T. jigulensis<br />
T. siuckenbergi<br />
T. ecutus -<br />
T. ardicus<br />
Montiparus<br />
montiparus<br />
Gzhelian<br />
Kasimovian<br />
Fig. 6. Assemblage zones <strong>of</strong> <strong>the</strong> Permian representative fossils in South<br />
(after Zhang, 1984).<br />
China and <strong>the</strong> international correlation
16<br />
Yasuhiro Ota<br />
The first session <strong>of</strong><br />
stratigraphic conference<br />
China<br />
The second session <strong>of</strong><br />
stratigraphic conference<br />
Zhang(1984)<br />
Central Asia area<br />
<strong>of</strong> USSR<br />
JC c<br />
Ox<br />
Palae<strong>of</strong>usulina<br />
s>§<br />
Palae<strong>of</strong>usulina<br />
.C c<br />
OR<br />
Palae<strong>of</strong>usulina<br />
Dorashamian<br />
Palae<strong>of</strong>usulina<br />
Codon<strong>of</strong>usiella<br />
Codon<strong>of</strong>usiella<br />
Codon<strong>of</strong>usiella<br />
Dzhulfian<br />
Codon<strong>of</strong>usiella<br />
Yabeina<br />
Yabeina<br />
Yabeina<br />
Midiyan<br />
Yabeina<br />
Neoschwagerina<br />
Neoschwagerina<br />
Neoschwagerina<br />
Murgabian<br />
Neoschwagerina<br />
Cancellina<br />
Cancellina<br />
Cancellina<br />
Kubergandian<br />
Cancellina<br />
Bolorian<br />
Misellina<br />
Misellina<br />
Misellina<br />
Misellina<br />
o>2><br />
Pseudo<br />
fusulina<br />
Yakhtashian<br />
Chalaro<br />
schwagerina<br />
Pseudo<br />
schwager<br />
ina<br />
Robusto<br />
schwager<br />
ina<br />
Pseudo<br />
schwager<br />
ina<br />
Robusto<br />
schwager<br />
ina<br />
Sphaero<br />
schwager<br />
ina<br />
Sakmarian<br />
Robusto<br />
schwagerina<br />
Asselian<br />
"Schwagerina"<br />
Triticites<br />
Triticites<br />
&<br />
Pseudo<br />
schwager<br />
ina<br />
Orenburgian<br />
Daixina<br />
Triticites<br />
Montiparus<br />
Gzhelian<br />
Triticites<br />
Kasimovian<br />
T.-Montiparus<br />
Moscovian<br />
03 C<br />
£1<br />
Fusulina<br />
Fusulina<br />
Fusulina<br />
Fusulina<br />
Fig. 7. Stratigraphic development <strong>of</strong> fusuhnaceans (after Zhang, 1984).
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I<br />
17<br />
AKIYOSHI LIMESTONE GROUP<br />
Y.OZAWA<br />
(1923)<br />
S. HANZAWA<br />
(1941)<br />
R. TORIYAMA<br />
(1953-1957)<br />
ll<br />
I<br />
Sumatrina<br />
annae<br />
Yabeina<br />
Sumatrina<br />
Neoschwagarina<br />
Verbeekina<br />
subzone<br />
Yabeina<br />
sniraiwensis<br />
Neoschwagerina iperina |<br />
dowillei<br />
c<br />
CO<br />
is<br />
Pseud<strong>of</strong>usulina<br />
ambigua<br />
ParafusuSna<br />
Verbeekina<br />
verbeeki<br />
Neoschwagarina<br />
craticulifera<br />
CD<br />
Q_<br />
<<br />
Pseud<strong>of</strong>usulina<br />
japonica<br />
Paralusulina<br />
lutugini<br />
Parafusulina<br />
Paraschwagerina<br />
Parafusulina<br />
kaerimizensis<br />
Pseud<strong>of</strong>usulina<br />
Pseudoschwagerina<br />
ojomotosa<br />
Pseudoschwagerina<br />
Pseud<strong>of</strong>usulina<br />
vulgaris<br />
SI<br />
Pseudoschwagerina<br />
muong<strong>the</strong>nsis<br />
Schwagerina<br />
Quasffusutina<br />
Triticites<br />
Triticites simplex<br />
c<br />
2<br />
"c<br />
Ctf<br />
><br />
CO<br />
c<br />
c<br />
CD<br />
Q.<br />
£<br />
Q =<br />
L<br />
Fusulinella<br />
bocki<br />
Lonsdaleia<br />
(foriforms<br />
NagatophyBum<br />
satoi<br />
Fusulinella'<br />
biconica<br />
Pr<strong>of</strong>usulinelta<br />
beppensis<br />
MillereOa sp. a<br />
Fig. 8. The fusulinacean zones <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (after Toriyama, 1958).
18 Yasuhiro Ota<br />
he correlated <strong>the</strong> base <strong>of</strong> Pseudoschwagerina Zone (including Triticites simplex Subzone)<br />
with <strong>the</strong> base <strong>of</strong> Sakmarian in Russia, Wolfcampian in North America and<br />
Sakamotozawan in Japan (Fig. 8).<br />
Hasegawa (1958, 1963) divided <strong>the</strong> <strong>Akiyoshi</strong> limestone <strong>Group</strong> into eight zones.<br />
Of <strong>the</strong>m, Pr<strong>of</strong>usulinella, Fusulina-Fusulinella and Yabeina-Lepidolina Zones were almost<br />
<strong>the</strong> same as those by Toriyama (1954a, b, 1958), but he subdivided Pseudoschwagerina<br />
Zone into an upper, <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Subzone and a lower, <strong>the</strong><br />
Triticites simplex Subzone. At that time, he did not clearly indicate <strong>the</strong> Carbonifer<br />
ous-Permian boundary. However, he noticed <strong>the</strong> Mg-rich and oolitic limestones in<br />
<strong>the</strong> lower part <strong>of</strong> Pseudoschwagerina Zone.<br />
Murata (1961) divided <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> into eight foraminiferal<br />
zones. He put <strong>the</strong> Carboniferous-Permian boundary below <strong>the</strong> base <strong>of</strong> <strong>the</strong> Pseudo<br />
schwagerina Zone, where <strong>the</strong> subfamily, Schwagerininae first appeared, and <strong>the</strong><br />
genera, Fusulinella, Fusulina and Beedeina disappeared.<br />
M. Ota (1968, 1977) established 21 fossil zones (Table 4). He considered <strong>the</strong><br />
Carboniferous-Permian boundary below <strong>the</strong> Triticites simplex Zone.<br />
Minato, Kato, Nakamura, Niikawa and Hasegawa (1984) gave a review on<br />
studies <strong>of</strong> <strong>the</strong> Carboniferous-Permian boundary in Japan and mentioned that <strong>the</strong><br />
Table 4. Biostratigraphic zones <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (after M. Ota, 1977).<br />
Geologic age Name <strong>of</strong><strong>the</strong> fossil zone Symbol Thickness<br />
C<br />
CO<br />
E<br />
Q_<br />
Late Lepldollna multiseptata shlraiwensis Zone Puo +25m<br />
Middle<br />
Early<br />
Colania douvillei Zone<br />
Verbeekina verbeekl Zone<br />
Neoschwagerina craticullfera Zone<br />
Afghanellaschenckl Zone<br />
Parafusulina kaerimlzensis Zone<br />
Misellina daudiae Zone<br />
Pseud<strong>of</strong>usulina ambigua Zone<br />
Pseud<strong>of</strong>usulina vulgaris Zone<br />
Pseudoschwagerina (P.) muong<strong>the</strong>nsis Zone<br />
Triticites simplex Zone<br />
PmS<br />
Pm y<br />
PmjS<br />
Pma2<br />
Pma1<br />
PIS<br />
Ply<br />
PI/5<br />
Pla2<br />
Plal<br />
40m<br />
20m<br />
25m<br />
15m<br />
25m<br />
20m<br />
40m<br />
50m<br />
20m<br />
±50m<br />
Late Triticites (s. 1.) matsumotoi Zone Cua 20m<br />
CO<br />
2<br />
*^<br />
'c<br />
o<br />
.a<br />
I—<br />
CO<br />
O<br />
Middle<br />
Early<br />
Beedeina akiyoshiensis Zone<br />
Fusulinella biconica Zone<br />
<strong>Akiyoshi</strong>ella ozawalZone<br />
Pr<strong>of</strong>usulinella beppensis Zone<br />
Pseudostaftella antiqua Zone<br />
Millerellayowarensts Zone<br />
Nagatophyllum satol Zone<br />
Zahrentoldes sp. Zone<br />
Marginalia toriyama! Zone<br />
Cmy<br />
Cm 3<br />
Cm a 3<br />
Cm a 2<br />
Cma1<br />
CIS<br />
Cly<br />
CI0<br />
CI a<br />
±30m<br />
-80m<br />
20m<br />
20m<br />
20m<br />
60m<br />
70m<br />
40m<br />
80m
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 19<br />
relationship between <strong>the</strong> Lower Permian and Carboniferous deposits in Japan is<br />
variable from place to place (Fig. 9).<br />
Ozawa and Kobayashi (1990) reexamined <strong>the</strong> fusulinacean zones <strong>of</strong> <strong>the</strong><br />
<strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, and drew <strong>the</strong> Carboniferous-Permian boundary between<br />
<strong>the</strong> Daixina robusta-"Pseudoschwagerina" minatoi Zone and <strong>the</strong> "Sphaeroschwagerina" fusiformis<br />
Zone. Ozawa, Kobayashi and Watanabe (1990) established <strong>the</strong> new genus<br />
"Carbonoschwagerina" with Pseudoschwagerina morikawai Igo as <strong>the</strong> type species. They<br />
remarked that this genus represents Carboniferous age. They placed <strong>the</strong> Carbonif<br />
erous-Permian boundary at <strong>the</strong> same horizon as Ozawa and Kobayashi (1990).<br />
Watanabe (1991) emphasized <strong>the</strong> same opinion that <strong>the</strong> Carboniferous-Permian<br />
boundary should be placed under <strong>the</strong> Sphaeroschwagerina fusiformis Zone.<br />
Fig. 9.<br />
Correlation <strong>of</strong> <strong>the</strong> Upper Carboniferous and <strong>the</strong> Lower Permian in Japan (after<br />
Minato et al., 1984).<br />
<strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> near <strong>the</strong> Carboniferous-<br />
Permian boundary in <strong>the</strong> three different areas<br />
-1-1. <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> Jigoku-dani area<br />
The first area investigated, Jigoku-dani, is located in <strong>the</strong> northwestern <strong>of</strong> <strong>the</strong><br />
<strong>Akiyoshi</strong> Plateau(s. s.). This area topographically consists <strong>of</strong>a deep valley with NE-
20 Yasuhiro Ota<br />
SW trend, ranging from about 200 m to 350 m in altitude and well-developed karst<br />
topography. M. Ota (1977) confirmed <strong>the</strong> following fusulinacean zones in this area:<br />
Fusulinella biconica Zone, Triticites simplex Zone, Pseud<strong>of</strong>usulina vulgaris Zone and<br />
Pseud<strong>of</strong>usulina ambigua Zone. The <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> in this area is consid<br />
ered to have originally accumulated in a lagoonal sedimentary environment within<br />
<strong>the</strong> <strong>Akiyoshi</strong> organic reef complex and is geologically inverted in structure. How<br />
ever, in this area, fusulinacean zones such as <strong>the</strong> Beedeina akiyoshiensis Zone, Triticites<br />
(s. 1.) matsumotoi Zone, and Pseudoschwagerina muong<strong>the</strong>nsis Zone <strong>of</strong> <strong>the</strong> generalized<br />
fusulinacean zones <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (M. Ota, 1977) have not been<br />
confirmed yet and elements <strong>of</strong> <strong>the</strong> fusulinacean fauna have remained unknown.<br />
Topography <strong>of</strong> <strong>the</strong> Jigoku-dani area is characterized by <strong>the</strong> limestone lapie field<br />
and it is difficult to confirm <strong>the</strong> exact localities <strong>of</strong> <strong>the</strong> collected materials. Therefore,<br />
<strong>the</strong> author selected some traverses to measure with <strong>the</strong> name <strong>of</strong>JI (JI Traverse 1-5)<br />
and collected materials along <strong>the</strong> traverses. Materials from localities 300 to 788 are<br />
mainly discussed here (Fig. 10).<br />
<strong>Limestone</strong>s in <strong>the</strong> Jigoku-dani area are generally massive. They are white to<br />
gray white, but pardy dark brown in color. The dark brown color is considered to<br />
be caused by <strong>the</strong> secondary alteration, but <strong>the</strong> genesis needs to be carefully studied.<br />
The limestones in this area are ordinarily composed <strong>of</strong> micrite, with some intercalat<br />
ing limestone with sparry calcite cements. Frame building organisms <strong>of</strong> reef en<br />
vironment are almost absent. These features suggest that <strong>the</strong> limestones in <strong>the</strong><br />
Jigoku-dani area were mostly accumulated under a low energy lagoon sedimentary<br />
environment.<br />
Based on <strong>the</strong> microscopic study <strong>of</strong> <strong>the</strong> collected specimens, 56 fusulinacean spe<br />
cies including two subspecies among 23 genera are discriminated (Table 5). Dis<br />
tribution <strong>of</strong> <strong>the</strong>se fusuhnaceans and distinction <strong>of</strong> lith<strong>of</strong>acies are illustrated in Fig. 11.<br />
Distribution <strong>of</strong> <strong>the</strong> characteristic fusuhnaceans and <strong>the</strong> fusulinacean zones along five<br />
traverses, JI Traverse 1-5 are shown in Fig. 12. Fur<strong>the</strong>rmore, <strong>the</strong> detailed distribu<br />
tion <strong>of</strong> <strong>the</strong> fusulinacean species and <strong>the</strong> lith<strong>of</strong>acies along each traverse are shown in<br />
Figs. 13 and 14, respectively.<br />
From <strong>the</strong>se examinations, nine zones including seven subzones were recognized<br />
in <strong>the</strong> Jigoku-dani area (Table 6). The representative fusuhnaceans <strong>of</strong> <strong>the</strong> proposed<br />
zones and <strong>the</strong> thickness <strong>of</strong> each zone measured along each traverse are shown in<br />
Table 7.<br />
From <strong>the</strong> distribution <strong>of</strong> <strong>the</strong>se fusulinacean zones, it is confirmed that <strong>the</strong><br />
<strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> in this area has <strong>the</strong> general strike <strong>of</strong> N10°W, dipping to<br />
ward SW with angles <strong>of</strong> 10 to 20 degrees. Fur<strong>the</strong>rmore, <strong>the</strong> older fusulinacean zones<br />
are recognizable at higher topographical locations than <strong>the</strong> younger ones along <strong>the</strong><br />
western slope <strong>of</strong> <strong>the</strong> valley, and <strong>the</strong>refore limestones in this area apparently exhibit an<br />
inverted succession. In addition, <strong>the</strong>se limestones are mainly composed <strong>of</strong> micrite<br />
without <strong>the</strong> frame builders <strong>of</strong> organic reefs. They are considered to have accumu-
Fig. 10. The first investigated area, Jigoku-dani, showing survey traverses: JI Traverse 1-5 and <strong>the</strong>ir cardinal<br />
points.<br />
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22 Yasuhiro Ota<br />
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Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 23<br />
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Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I<br />
25<br />
JI Traverse 5<br />
JI Traverse 3<br />
1 JI Traverse 1<br />
JI Traverse 4<br />
110m<br />
Fig. 12. Distribution <strong>of</strong> <strong>the</strong> characteristic fusulinacean species (shown by <strong>the</strong> locality numbers) and<br />
<strong>the</strong> fusulinacean zones (1-9) along <strong>the</strong> JI Traverse 1-5.<br />
The following numbers are used for fusulinacean zones: 1. Fusulinella biconica Zone; 2. Fusulina cf.<br />
shikokuensis Zone; 3. Obsoletes obsoletus Zone; 4. Montiparus sp. A Zone; 5. Triticites yayamadakensis<br />
Zone; 6. Schwagerina () cf. satoi Zone; 7. Pseudoschwagerina muong<strong>the</strong>nsis Zone; 8. Pseud<strong>of</strong>usulina<br />
vulgaris globosa Zone; 9. Pseud<strong>of</strong>usulina aff. ambigua Zone. The characteristic fusuhnaceans with<br />
localities are as follows: 332, Pseudoschwagerina muong<strong>the</strong>nsis (Deprat); 387, Schwagerina () cf. satoi<br />
(Ozawa); 392, 439, 569, 605, Triticites yayamadakensis Kanmera; 454, 554, Montiparus () sp. A;<br />
461, Fusulinella biconica (Hayasaka); 465, Fusulinella cf. obesa Sheng; 468, Protriticites toriyamai<br />
Ota; 477, 633, Obsoletes obsoletus (Schellwien); 489, 538, Protriticites matsumotoi (Kanmera); 517,<br />
Pseud<strong>of</strong>iisulinella hidaensis (Kanuma); 520, Protriticites masamichii Ota; 578, Schwagerina sp. A; 663,<br />
Montiparus sp. A; 686, Triticites yayamadakensis evectus Kanmera; 723, Pseud<strong>of</strong>usulina () sp. A; 729,<br />
Pseudoschwagerina sp.; 736, Paraschwagerina sp.; 766, Pseud<strong>of</strong>usulina aff. ambigua (Deprat).
26<br />
Yasuhiro Ota<br />
Fig. 13-1. JI Traverse 1.<br />
13. Distribution <strong>of</strong> <strong>the</strong> characteristic fusulinacean<br />
species (shown by <strong>the</strong> locality numbers) and <strong>the</strong><br />
fusulinacean zones (1-9) along <strong>the</strong> JI Traverse 1-5.<br />
The following numbers are used for fusulinacean<br />
zones: 1. Fusulinella biconica Zone; 2. Fusulina cf.<br />
shikokuensis Zone; 3. Obsoletes obsoletus Zone; 4. Monti<br />
parus sp. A Zone; 5. Triticites yayamadakensis Zone; 6.<br />
Schwagerina () cf. satoi Zone; 7. Pseudoschwagerina<br />
muong<strong>the</strong>nsis Zone; 8. Pseud<strong>of</strong>usulina vulgaris globosa<br />
Zone; 9. Pseud<strong>of</strong>usulina a(T. ambigua Zone.
d5'<br />
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ftrcniffna cf* ih&oJttieaiit<br />
Protrtticttts tnxoustotot<br />
FksoUseiia ef. oka '<br />
PtmtiiScixts MiyKBtl I<br />
Obs<strong>of</strong>eta obmlems<br />
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S4<br />
Obsakta obsoSctw \<br />
ProtrWctXJ mMBumoal<br />
ProaiOcttajrtBltklll<br />
Momtpam (I) sp. A'<br />
IMtkfttscf.otai<br />
7Wdc)»»fcJcfawij'<br />
TWtktet ct bona<br />
7HUcteiw»m«ftitfmto eveclm<br />
ScAmijeriai ip. A<br />
7W(idKirazaJ4(<br />
7WiJi4ies blcoojrax '<br />
TMdcttes •&. dapla<br />
mtkintytymMctikmilj'<br />
THtfcftwcf. i»eraii<br />
QtfHifuja/ins sp. B<br />
32<br />
en t3><br />
FxudafmuIlBM (J) sp. A<br />
7Wclcftcs cf. pje»rfrtt/ntplcx<br />
fteacfafcl»«m«ilia ip.'<br />
fsnxf«r/n«i(trbia muanftbenllj<br />
Amscfcw«faiai sp.<br />
ftrtxfoAuuttu vcfeirti fjcboia'<br />
fteuct<strong>of</strong>tnaUai afl. imAtfm<br />
Acuda/uRtttn cf. vuCjirfs s.«.<br />
o
28 Yasuhiro Ota<br />
.irrestone<br />
with<br />
Locally rriaite<br />
matrix<br />
Urrestone<br />
with<br />
rr.:r;.:<br />
matrix<br />
Lines;one<br />
with<br />
sparry<br />
calcrte<br />
cement<br />
Blackand<br />
dark<br />
brown<br />
color<br />
limestone<br />
Subzone<br />
Zone<br />
jrrfistonc<br />
with<br />
Locally rriaite<br />
matrix<br />
300<br />
Lirestone<br />
with<br />
micritic<br />
matrix<br />
<strong>Limestone</strong><br />
with<br />
sparry<br />
calate<br />
cerrent<br />
BlackanT<br />
dark<br />
brown<br />
color<br />
limestone<br />
Subzone<br />
Zone<br />
::•:•::•::•<br />
5-3<br />
304<br />
•::•:•:•::•:•:<br />
306<br />
V-'<br />
r/,<br />
4jl<br />
ice<br />
5-2<br />
"31<br />
sir<br />
m<br />
4«<br />
316<br />
317<br />
319<br />
7<br />
i®<br />
410<br />
s<br />
21 :••:•:••: :<br />
322<br />
323<br />
324<br />
325<br />
37-i<br />
41/<br />
—28~<br />
'•::.••<br />
419<br />
5-1<br />
3X<br />
422<br />
534"<br />
;.;....<br />
311<br />
313<br />
318<br />
436<br />
360<br />
•~~<br />
440<br />
y.i<br />
:•:•:•:•••:•:•<br />
445 1<br />
446<br />
:':•:•:<br />
4<br />
361<br />
~ss~<br />
6<br />
354<br />
~356—<br />
—370<br />
457<br />
3<br />
461<br />
375<br />
376<br />
Fig. 14-1. JI Traverse 1. Loc. 388 (upper<br />
most <strong>of</strong> <strong>the</strong> left column) continues to Loc.<br />
387 (lowermost <strong>of</strong> <strong>the</strong> right column).<br />
375<br />
"383 -<br />
-%:•-<br />
Fig. !•!. Distribution <strong>of</strong> lith<strong>of</strong>acies along <strong>the</strong> JI Traverse 1-5.<br />
The following numbers arc used for fusulinacean zones: 1. Fusulinella biconica Zone, 2.<br />
Fusulina cf. shikokuensis Zone: 2-1. Fusulina cf. obesaSubzone, 2-2. Pseud<strong>of</strong>usulinella hidaensis<br />
Subzone, 3. Obsoletes obsoletus Zone: 3-1. Protriticites loriyamai Subzone, 3-2. Protriticites<br />
matsumotoi Subzone, 4. Montiparus sp. A Zone, 5. Triticites yayamadakensis Zone: 5-1.<br />
Triticites saurini Subzone, 5-2. Schwagerina sp. A Subzone, 5-3. Triticites biconkus Subzone,<br />
6. Schwagerina () cf. satoi Zone, 7. Pseudoschwagerina muong<strong>the</strong>nsis Zone, 8. Pseud<strong>of</strong>usulina<br />
vulgaris globosa Zone, 9. Pseud<strong>of</strong>usulina aff. ambigua Zone.
. .<br />
.<br />
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. Part I 29<br />
L rrescne<br />
with<br />
Locally rriaite<br />
matrix<br />
.. rrestc-e<br />
with<br />
rrtcritic<br />
matrix<br />
<strong>Limestone</strong><br />
with<br />
sparry<br />
catate<br />
cerrent<br />
Black and<br />
dark<br />
brown<br />
color<br />
Imestone<br />
Subzone<br />
Zone<br />
Lirrestone<br />
with<br />
Locally rriaite<br />
matrix<br />
<strong>Limestone</strong><br />
with<br />
rriaitic<br />
matrix<br />
Linesone<br />
with<br />
sparry<br />
calate<br />
cement<br />
Backano<br />
dark<br />
brown<br />
color<br />
Imestone<br />
Subzone<br />
Zone<br />
615<br />
.<br />
564 | wmm<br />
553<br />
613<br />
5-3<br />
561<br />
560 :-<br />
"••«.••••—<br />
,,,,7,7,",',",",.,<br />
559<br />
4<br />
607<br />
555 l<br />
605<br />
603<br />
1<br />
601<br />
3-2<br />
5-2<br />
5<br />
:•:•:•: :-<br />
3<br />
595<br />
585<br />
3-1<br />
5/9<br />
578<br />
5//<br />
576 • : ::••:•:•<br />
5/5 • : ::-:-:::-:-:<br />
57; :•:::.<br />
5-1<br />
2-2<br />
2-1<br />
2<br />
570<br />
559<br />
Fig. 11-3. JI Traverse 3 (Loc. 569 to Loc.<br />
616, right column). Loc. 568 (upper<br />
most <strong>of</strong> <strong>the</strong> left column) continues to Loc.<br />
569 (lowest <strong>of</strong> <strong>the</strong> right column).<br />
1<br />
Fig. 14-3. JI Traverse 3 (Loc. 509 to Loc.<br />
568. left column).<br />
<strong>Limestone</strong><br />
with<br />
Locality rriaite<br />
matrrx<br />
<strong>Limestone</strong><br />
with<br />
micritic<br />
matrix<br />
<strong>Limestone</strong><br />
with<br />
sparry<br />
calate<br />
cerrent<br />
Backand<br />
dark<br />
brawn<br />
color<br />
irrestone<br />
Subzone<br />
Zone<br />
Lirrestone<br />
with<br />
Locally rriaite<br />
matrrx<br />
Lirrestone<br />
with<br />
rriaitic<br />
matrix<br />
Lirrestone<br />
with<br />
sparry<br />
calate<br />
cement<br />
Biackand<br />
dark<br />
brown<br />
color<br />
rrestrjr.e<br />
Subzone<br />
Zone<br />
•:.-:•:-•.-:•-:•:<br />
.:•:::•::<br />
4/4<br />
4/3<br />
4/2<br />
4/1<br />
4/0<br />
3<br />
483<br />
3<br />
2-2<br />
2<br />
Fig. 14-2. JI Traverse 2 (Loc. 464 to Loc.<br />
479, left column).<br />
i<br />
459<br />
iX<br />
506<br />
507<br />
•••:<br />
•<br />
2-1<br />
2<br />
Fig. 14-2. JI Traverse 2 (Loc. 507 to Loc.<br />
•180, right column).
—<br />
30 Yasuhiro Ota<br />
jrreacne<br />
with<br />
Locally rriaite<br />
matrix<br />
<strong>Limestone</strong><br />
with<br />
micrrtic<br />
matrix<br />
<strong>Limestone</strong><br />
with<br />
sparry<br />
caldte<br />
cerrent<br />
Biackand<br />
dark<br />
brown<br />
color<br />
limestone<br />
Subzone<br />
Zone<br />
Locality<br />
«<br />
Lirrestone<br />
with<br />
rriaite<br />
matrix<br />
Lirrestone<br />
with<br />
micritic<br />
matiix<br />
<strong>Limestone</strong><br />
with<br />
sparry<br />
calorie<br />
cerrent<br />
Bac.K ar,a<br />
dark<br />
brown<br />
color<br />
limestone<br />
Subzone<br />
Zone<br />
",<br />
h;<br />
7a<br />
705<br />
704<br />
9<br />
5<br />
771<br />
698 • •:•••:•-: "<br />
" W<br />
•:•:-•:•:•:••:•.<br />
•<br />
763<br />
/60<br />
685<br />
684<br />
•:.-3<br />
756<br />
690<br />
679<br />
678<br />
8<br />
4<br />
669<br />
-••:•:• •: •<br />
<br />
665<br />
664<br />
663<br />
662<br />
661<br />
660 •: ::•:•:• • •:•<br />
659<br />
• ••:•.-.. .,• ..<br />
657<br />
.••.-•••••••;,<br />
655 ..:•:•: .<br />
731<br />
726<br />
725<br />
7<br />
6<br />
•:•:•::•.•:•:•<br />
. •<br />
615<br />
648 •:•:••:-:•:••:•:•••:••:•<br />
32<br />
3<br />
5<br />
.:•••:•.•<br />
643<br />
642<br />
611<br />
616<br />
638<br />
63/<br />
/14<br />
Fig. 14—5.<br />
788).<br />
JI Traverse 5 (Loc. 713 to Loc.<br />
6a 3-1<br />
:'.'<br />
631<br />
630<br />
659<br />
(27<br />
£5<br />
22<br />
2<br />
620<br />
618<br />
2-1<br />
1<br />
Fig. 11—1.<br />
712).<br />
JI Traverse 4 (Loc. 617 to Loc.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 31<br />
Table 6. Fusulinacean zones in ascending order recognized in<br />
<strong>the</strong> Jigoku-dani area.<br />
Fusulinacean zones in <strong>the</strong> Jigoku-dani area<br />
9. Pseud<strong>of</strong>usulina aff. ambigua Zone<br />
8. Pseud<strong>of</strong>usulina vulgaris globosa Zone<br />
7. Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
6. Schwagerina () cf. satori Zone<br />
5. Triticites yayamadakensis Zone<br />
5-3. Triticites biconicus Subzone<br />
5-2. Schwagerina sp. A Subzone<br />
5-1. Triticites saurini Subzone<br />
4. Montiparus sp. A Zone<br />
3. Obsoletes obsoletus Zone<br />
3-2. Protriticites matsumotoi Subzone<br />
3-1. Protriticites loriyamai Subzone<br />
2. Fusulina cf. shikokuensis Zone<br />
2-2. Pseud<strong>of</strong>usulinella hidaensis Subzone<br />
2-1. Fusulinella cf. obesa Subzone<br />
1. Fusulinella biconica Zone<br />
lated in a relatively low energy lagoon environment within <strong>the</strong> <strong>Akiyoshi</strong> organic reef<br />
complex. Distributions <strong>of</strong> fusulinacean zones are shown in Fig. 15 and <strong>the</strong> cross<br />
sections along A-A', B-B' and C-C, are respectively indicated in Fig. 16.<br />
The detailed characters <strong>of</strong> each fusulinacean zone are given as follows.<br />
1. Fusulinella biconica Zone.<br />
The Fusulinella biconica Zone is <strong>the</strong> oldest in <strong>the</strong> Jigoku-dani area and is exposed<br />
in <strong>the</strong> highest part <strong>of</strong><strong>the</strong> western slope <strong>of</strong> this area. The thickness is estimated to be<br />
about 2 m + . This zone is typified by <strong>the</strong> occurrence <strong>of</strong> Fusulinella biconica (Hayasaka).<br />
<strong>Limestone</strong>s have a general NE strike and dip gently to northwest, but occa<br />
sionally dip toward <strong>the</strong> sou<strong>the</strong>ast. They are mainly composed <strong>of</strong> micritic limestones<br />
with intercalation <strong>of</strong> limestones with sparry calcite cements.<br />
2. Fusulina cf. shikokuensis Zone<br />
The Fusulina cf. shikokuensis Zone conformably overlies <strong>the</strong> Fusulinella biconica Zone<br />
and is defined by <strong>the</strong> occurrence <strong>of</strong> Fusulina cf. shikokuensis Ishii. This zone is<br />
subdivided into two subzones, <strong>the</strong> lower, <strong>the</strong> Fusulinella cf. obesa Subzone and <strong>the</strong><br />
upper, <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Subzone.<br />
2-1. Fusulinella cf. obesa Subzone.<br />
The Fusulinella cf. obesa Subzone is characterized by <strong>the</strong> occurrences <strong>of</strong> Fusulinella<br />
cf. obesa Sheng in association with Fusulinella cf. shikokuensis Ishii.<br />
<strong>Limestone</strong>s <strong>of</strong> this
Table 7. Representative fusuhnaceans in <strong>the</strong> proposed zones and <strong>the</strong> thickness <strong>of</strong> each zone measured along <strong>the</strong><br />
surveyed traverses.<br />
Representative fusuhnaceans <strong>of</strong> each zone in <strong>the</strong> Jigoku-dani area Thickness<br />
9. Pseud<strong>of</strong>usulina aff. ambigua Zone (766-788)<br />
Ji Route 1 Ji Route 3 JI Route 3 Ji Route 4 Ji Route 6<br />
Pseud<strong>of</strong>usulina aff. amd&ua[766(16)], Psf. cf. vulgaris b.b.[766(6)]. 42+m,<br />
83m,<br />
(736-766)<br />
17m,<br />
(729-736)<br />
11m,<br />
(723-729)<br />
8. Pseud<strong>of</strong>usulina vulgaris globosa Zone<br />
Pseud<strong>of</strong>usulina vulgarisglobosa [738d>2, 755(l)-3, 763(2>-3],<br />
Paraschwagerina spp.[786(2), 756(2), 756(8). 759(1)-1].<br />
7. Pseudoschuagerlna muong<strong>the</strong>nsis Zone<br />
StaffeUamoelleri,Schubertettakingi, SchwagerinaokafuJiiT.S12o.-2], S. primigena[313f\, S. cf. prtncefw[312fj,<br />
5. sp. A[3S2(2e>7], S. sp. B[S32D2], S. sp. C[311a, 317D],5. sp. D[382b-1], S. (7)aff. Au«fc«ft«wfa[S08c-l),<br />
Pseudoschwagerlnamuong<strong>the</strong>nsisVlSUli-l, 332(la)-3], Ps. sp.[729(1)1. Ps. (7) sp.[800d-b].<br />
6. Schwagerina () <strong>of</strong>. satoi Zone<br />
Ozawainella <strong>of</strong>f. magna, NankineUa sp. A Sehubertella lata, Triticites hayderuT379d], 7. michiae[379p],<br />
7. cf. o6ai[S78d-2], 7. cf. pseudosimplex[311 B.-2, 725(1)], 7. aff. stoyrf«:[379c-l], 7. aff. ai»uAii[37Sa-l],<br />
Schwagerina cf. «to&ais[836a-2,S86e, 336d], S. ()cf. «atoi[387d2], "Pseud<strong>of</strong>usulina "cf. oacca[336b-3],<br />
'Psf.' aff. /iwfbnni»[8791-2] Psf. () sp. A[360a, 387c-A 723], Rwos<strong>of</strong>u3ulinaarclicalS4Ba-l, 354a-2].<br />
5. Triticites yayamadakensis Zone<br />
5-8. Triticites oiconlcus subzone<br />
Quasifusullna sp. B[890c-1, 614(1)],Triticites biconicw>[392b-l, 392b-2], 7. cf. iso«nji5[608d],<br />
7. AuroJu>a*/uM392a-2], 7. yayamadakensis [392a-3. S92A-1. 605b-ll.<br />
5-2. Schwagerina sp. A snbxono<br />
Triticites biconicus,7. aff. simp/«x(586d], 7. su«u&f[581c-3], 7. yayamadakensislBSl}),<br />
Schwagerina sp. A[578(6). 586b-2, 586i-l], 5. sp. B.<br />
5-1. Triticites saurinl subzone<br />
Triticites cf. oonus[569k], 7. hidensisl421e.-l), 7. mfcAtae[694-(4)], 7. 8auniuT403a-3, 403b, 429a, 429b,<br />
433a-l], 7. aff. simplex, T. yayamadakensis[489b, 569d], 7. yayamadakensis evectus [694(18), 569'(1), 686(1),<br />
687(b)-l].<br />
4. Montiparus sp. A Zone<br />
Quasifusulinalongissima[675(2), 675(4>2], Quasifusulina sp. A(675(3)], Montiparussp. A[663(l), 676(1), 679(1)],<br />
M () sp. A[464a. 554(1)]. Triticiteshidensis. 7. cf. otai. 7. saurtro[673(8)l.<br />
3. ObeoUtee obsoletus Zone<br />
3-2. Protriticites matsumotoi subzone<br />
Obsoletes obsoletus[469a7, 637(b)], Protriticites matsumotoli4S9c, 538a, 634(1)], Pwt yano£Wai[540a],<br />
Quasifusulinoides () sp. [639(1)1.<br />
3-1. Pr<strong>of</strong>rtficltee toriyamal subzone<br />
Obsoletes obsoletus[4Tla, 532a. 633-1], Protriticites masamichUlBWa), Prot loriyamai [468c].<br />
2. Fusulina <strong>of</strong>. shikokuensis Zone<br />
2-2. Pseud<strong>of</strong>usulinella hidaensis subzone<br />
Pseud<strong>of</strong>usulinella fcdae/w»[492(2)-2, 517a. 517b], Fusulina ct.shikokuensis[492&-l, 492b].<br />
2-1. Fusulinella <strong>of</strong>. <strong>of</strong>reso subzone<br />
Fusulina ct. shikokuensts[62U2)],<br />
Fusulinella cf. ©4e*a[465a, 467a].<br />
2. Fusulinella biconica Zone<br />
Fusulinella biconica[461a, 618a-l].<br />
32+m,<br />
(332-300)<br />
76m,<br />
(387-332)<br />
15m,<br />
(392-387) 32+m,<br />
109m,<br />
(439-392)<br />
34m,<br />
(454-439)<br />
9m,<br />
(454-477)<br />
2m<br />
(481-477)<br />
2+m,<br />
(462-461)<br />
8m,<br />
(465-468)<br />
44+m,<br />
(489-507)<br />
(605-616)<br />
43m,<br />
(578-605)<br />
15m,<br />
(569-578)<br />
20m,<br />
(554-569)<br />
31m,<br />
(538-554)<br />
63m,<br />
(520-538)<br />
2m,<br />
(517-520)<br />
72m,<br />
(686-723)<br />
24m,<br />
(663-686)<br />
14m,<br />
(634-663)<br />
lm,<br />
(633-634)
Fig. 15. Distribution <strong>of</strong> fusulinacean zones in <strong>the</strong>Jigoku-dani area.<br />
The following numbers are used for fusulinacean zones: 1. Fusulinella biconica Zone; 2. Fusulina cf. shikokuensis<br />
Zone; 3. Obsoletes obsoletus Zone: 1. Montiparus sp. A Zone; 5. Triticites yayamadakensis Zone; 6. Schwagerina () cf.<br />
Mtoi Zone; 7. Pseudoschwagerina muong<strong>the</strong>nsis Zone; 8. Pseud<strong>of</strong>usulina vulgaris globosa Zone; 9. Pseud<strong>of</strong>usulina aff.<br />
ambigua Zone.<br />
n
34<br />
Yasuhiro Ota<br />
350m<br />
300m<br />
250m .<br />
5. Triticites yayamadakensis Zone<br />
6. Schwagerina () cf. saroi Zone<br />
7. Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
8. Pseud<strong>of</strong>usulina<br />
vulgaris globosa Zone<br />
9. Pseud<strong>of</strong>usulina<br />
aff. ambigua Zone<br />
200m<br />
A<br />
1:1<br />
1. Fusulinella biconica Zone<br />
350m<br />
300m<br />
2. Fusulina cf. shikokuensis Zone<br />
J v' 3. Obsoletes obsoletus Zone<br />
Montiparus sp. A Zone<br />
£- S. Triticites yayamadakensis Zone<br />
250m.<br />
200m'<br />
B<br />
6. Schwagerina ()<br />
t cf. satoi Zone<br />
7. Pseudoschwagerina<br />
/ muong<strong>the</strong>nsis Zone<br />
1:1 a-<br />
350m<br />
2. Fusulina cf. shikokuensis Zone<br />
^ 3. Obsoletes obsoletus Zone<br />
300m<br />
.4. Montiparus sp. A Zone<br />
250m<br />
^<br />
5. Triticites yayamadakensis Zone<br />
200m<br />
C<br />
iiic<br />
Fig. 16.<br />
Cross sections along A-A', B-B' and C-C in <strong>the</strong> Jigoku-dani area.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 35<br />
subzone strike N10°W, gently dipping toward southwest. They are composed <strong>of</strong><br />
micritic constituents, but limestones with sparry calcite cements are intercalated at<br />
<strong>the</strong> basal part<strong>of</strong>this subzone. Additionally, limestones <strong>of</strong>black to dark brown color<br />
occur in this basal horizon, though <strong>the</strong> origin <strong>of</strong> <strong>the</strong> black to dark brown limestones<br />
has not been determined.<br />
2-2. Pseud<strong>of</strong>usulinella hidaensis Subzone.<br />
The base <strong>of</strong> <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Subzone is marked by <strong>the</strong> first occur<br />
rence <strong>of</strong> Pseud<strong>of</strong>usulinella hidaensis (Kanuma) and this diagnostic species is associated<br />
with Fusulina cf. shikokuensis Ishii. <strong>Limestone</strong>s <strong>of</strong> this subzone are estimated to be 2<br />
m in thickness, and have a general NW strike and gentle dip toward <strong>the</strong> southwest.<br />
They are characterized by micrite, but are partly intercalated by limestones with <strong>the</strong><br />
sparry calcite cements.<br />
3. Obsoletes obsoletus Zone.<br />
The diagnostic species <strong>of</strong> <strong>the</strong> Obsoletes obsoletus Zone is Obsoletes obsoletus (Schellwien).<br />
In <strong>the</strong>Jigoku-dani area, this zone is recognized as an interval from <strong>the</strong> hori<br />
zon with <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Obsoletes or <strong>the</strong> genus Protriticites, to <strong>the</strong><br />
horizon with Montiparus () sp. A or Montiparus sp. A. It is subdivided into two subzones,<br />
<strong>the</strong> lower, <strong>the</strong> Protriticites toriyamai Subzone with primitive species <strong>of</strong> Protriticites,<br />
and <strong>the</strong> upper, <strong>the</strong> Protriticites matsumotoi Subzone characterized by Protriticites matsu<br />
motoi (Kanmera).<br />
3-1. Protriticites toriyamai Subzone.<br />
In this subzone, primitive species <strong>of</strong> Protriticites, such as Protriticites toriyamai Ota<br />
and Protriticites masamichii Ota, are associated with <strong>the</strong> diagnostic species, Obsoletes<br />
obsoletus (Schellwien). These primitive species <strong>of</strong> Protriticites are very important to<br />
determine <strong>the</strong> upper limit <strong>of</strong> <strong>the</strong> Middle Carboniferous. This subzone was named<br />
after <strong>the</strong> characteristic occurrences <strong>of</strong> Protriticites toriyamai Ota. Maximum thickness<br />
<strong>of</strong> this zone is estimated as 63 m. <strong>Limestone</strong>s <strong>of</strong> this zone have a wide variety <strong>of</strong><br />
matrices from micrites to sparry calcites though <strong>the</strong>y are somewhat coarser in grain<br />
size. Black to dark brown limestones previously mentioned are observed in this<br />
zone.<br />
3-2. Protriticites matsumotoi Subzone.<br />
The Protriticites matsumotoi Subzone is defined by <strong>the</strong> first occurrence <strong>of</strong> Protriticites<br />
matsumotoi (Kanmera). The o<strong>the</strong>r constituent species <strong>of</strong> this subzone are Obsoletes<br />
obsoletus (Schellwien), Protriticites yanagidai Ota and Quasifusulinoides () sp. This<br />
zone has an estimated maximum thickness <strong>of</strong> about 31 m. <strong>Limestone</strong>s <strong>of</strong> this subzone<br />
strike NW and have a gentle dip toward <strong>the</strong> southwest. This zone is mostly<br />
limestones with micrite matrix, but those with sparry calcite cements are intercalated<br />
in <strong>the</strong> lower part <strong>of</strong> this subzone. The grains <strong>of</strong> sparry calcite cements are ra<strong>the</strong>r<br />
coarse in size.<br />
Black to dark brown limestones are common in this zone.<br />
4. Montiparus sp. A Zone.<br />
The Montiparus sp. A Zone is characterized by <strong>the</strong> occurrence <strong>of</strong> Montiparus sp. A.
36 Yasuhiro Ota<br />
However, limestones along some traverses, did not yield Montiparus sp. A, but were<br />
characterized by Montiparus () sp. A. Montiparus () sp. A is closely similar to<br />
Montiparus sp. A, except for some features. <strong>Limestone</strong>s <strong>of</strong> this zone are estimated to<br />
be about 34 m in maximum thickness. They generally show a NW strike, dipping<br />
toward southwest direction, with an occasional NE strike, dipping toward northwest<br />
direction. The main constituent <strong>of</strong> limestones is micrite. Black to dark brown<br />
limestones are also present in this zone. The following fusuhnaceans also occur in<br />
this zone: Quasifusulina longissima (Moller), Quasifusulina sp. A, Triticites hidensis Igo,<br />
Triticites cf. obai Toriyama, and Triticites saurini Igo.<br />
5. Triticitesyayamadakensis Zone.<br />
The Triticites yayamadakensis Zone is defined by <strong>the</strong> occurrence <strong>of</strong> Triticites<br />
yayamadakensis Kanmera. In <strong>the</strong> Jigoku-dani area, Triticites yayamadakensis Kanmera<br />
is easily recognized, and is a good index fossil. The estimated thickness <strong>of</strong> this zone<br />
is 124m. This zone is subdivided into <strong>the</strong> following three subzones by characteristic<br />
fusuhnaceans in ascending order.<br />
5-1. Triticites saurini Subzone.<br />
This subzone is characterized by abundance <strong>of</strong> Triticites saurini Igo. The base <strong>of</strong><br />
this zone is demarcated by <strong>the</strong> first occurrence <strong>of</strong> Triticitesyayamadakensis Kanmera or<br />
Triticites yayamadakensis evectus Kanmera. The following fusuhnaceans are also in<br />
association with Triticites cf. bonus Chen and Wang, T. hidensis Igo, T. michiae<br />
Toriyama, T. aff. simplex (Schellwien).<br />
Triticites yayamadakensis evectus was first described by Kanmera (1958) from <strong>the</strong><br />
Yayamadake <strong>Limestone</strong>, Kyushu, Japan. He pointed out <strong>the</strong> difference <strong>of</strong> <strong>the</strong><br />
stratigraphic horizon between Triticites yayamadakensis yayamadakensis Kanmera and<br />
Triticitesyayamadakensis evectus Kanmera. However, <strong>the</strong> difference was not confirmed<br />
in <strong>the</strong> Jigoku-dani area. The thickness <strong>of</strong> this subzone attains 15 m at most. Lime<br />
stones <strong>of</strong> this subzone show general strike <strong>of</strong> about N14°W and dip about 18° toward<br />
SW. <strong>Limestone</strong>s are mainly composed <strong>of</strong> micritic matrices, and black to dark brown<br />
limestones are intercalated in some horizons.<br />
5-2. Schwagerina sp. A Subzone.<br />
The Schwagerina sp. A Subzone is characterized by <strong>the</strong> occurrence <strong>of</strong> Schwagerina<br />
sp. A and Triticitesyayamadakensis Kanmera. The lowest boundary <strong>of</strong> this subzone is<br />
demarcated by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Schwagerina. The occurrence <strong>of</strong><br />
Schwagerina sp. A was also ascertained from <strong>the</strong> AK Traverse in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>dai<br />
Museum <strong>of</strong> Natural History and this species possibly has a wide distribution in<br />
<strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. The general strike and dip <strong>of</strong> limestones in this subzone<br />
are unknown. However, from <strong>the</strong> conformable relationship with <strong>the</strong> underlying<br />
limestones, <strong>the</strong>y are common to those <strong>of</strong> <strong>the</strong> underlying subzone. Fur<strong>the</strong>rmore, <strong>the</strong><br />
limestone sequence <strong>of</strong> this subzone intercalates limestones with sparry calcite cements<br />
as were seen in <strong>the</strong> underlying Triticites saurini Subzone. <strong>Limestone</strong>s <strong>of</strong> this subzone<br />
yield <strong>the</strong> following fusuhnaceans such as Triticites biconicus Toriyama, Triticites aff.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 37<br />
simplex (Schellwien), Triticites suzukii (Ozawa), and Schwagerina sp. B.<br />
5-3. Triticites biconicus Subzone.<br />
The Triticites biconicus Subzone is characterized by <strong>the</strong> abundant occurrences <strong>of</strong><br />
Triticitesyayamadakensis Kanmera and <strong>the</strong> characteristicoccurrence <strong>of</strong> Triticites biconicus<br />
Toriyama. Therefore, <strong>the</strong> fusulinacean constituents <strong>of</strong> this subzone clearly distin<br />
guish <strong>the</strong>m from those <strong>of</strong> o<strong>the</strong>r subzones. Triticitesyayamadakensis Kanmera from this<br />
subzone has a ra<strong>the</strong>r advanced form, such as larger shell and thicker spiro<strong>the</strong>ca, than<br />
those in <strong>the</strong> lower horizon. <strong>Limestone</strong>s <strong>of</strong> this subzone have a general strike <strong>of</strong> about<br />
N10°W and gently dip to <strong>the</strong> south ward. The basal part <strong>of</strong> this subzone mainly<br />
consists <strong>of</strong> limestones with sparry calcite cements. Matrices <strong>of</strong> limestones gradually<br />
change from sparry calcites to micrites upward in <strong>the</strong> section. However, <strong>the</strong><br />
uppermost part <strong>of</strong> this subzone contains coarse grains <strong>of</strong> fossil fragments <strong>of</strong> frame<br />
builders. In <strong>the</strong> Jigoku-dani area, this zone is <strong>the</strong> upper limit <strong>of</strong> distribution <strong>of</strong> black<br />
to dark brown limestones. The following fusuhnaceans are recognized in this<br />
subzone: Quasifusulina sp. B, Triticites cf. isaensis Toriyama and Triticites kuroiwaensis<br />
Toriyama.<br />
6-1. Schwagerina () cf. satoi Zone.<br />
The lowest part <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi Zone is defined by <strong>the</strong> horizon from<br />
<strong>the</strong> first occurrence <strong>of</strong> Schwagerina () cf. satoi (Ozawa) or Pseud<strong>of</strong>usulina () sp. A to<br />
<strong>the</strong> first occurrence <strong>of</strong> Pseudoschwagerina muong<strong>the</strong>nsis (Deprat) or Pseudoschwagerina sp.<br />
The estimated thickness <strong>of</strong> this zone is 76 m. The following fusuhnaceans are also<br />
recognized in this zone: Ozawainella aff. magna Sheng, Nankinella sp. A, Schubertella lata<br />
Lee and Chen, Triticites haydeni (Ozawa), T. michiae Toriyama, T cf. obai Toriyama,<br />
T. cf. pseudosimplex Chen, T. aff. simplex (Schellwien), T. aff. suzukii (Ozawa),<br />
Schwagerina cf. stabilis (Rauser), "Pseud<strong>of</strong>usulina" cf. bacca Morikawa and Isomi, "Psf"<br />
aff.fusiformis (Schellwien), and Rugos<strong>of</strong>usulina arctica (Schellwien).<br />
The fusulinacean index fossil, Schwagerina () cf. satoi (Ozawa) resembles <strong>the</strong><br />
specimen that was first described as Schellwienia satoi by Ozawa (1925). As it has<br />
been already pointed out by Ozawa (1925) and Toriyama (1958), Schwagerina<br />
satoi (Ozawa) is intermediate in form between Schwagerina and Pseudoschwagerina.<br />
Schwagerina () cf. satoi (Ozawa) from <strong>the</strong> Jigoku-dani area also has an intermediate<br />
form between Schwagerina and Pseudoschwagerina morikawai Igo and <strong>the</strong> present form is<br />
similar to <strong>the</strong> microspheric form <strong>of</strong> Pseudoschwagerina. The question whe<strong>the</strong>r <strong>the</strong><br />
present species is referable to <strong>the</strong> inflated schwagerinids is uncertain. This species,<br />
however, is very important for regional correlation. Fusuhnaceans <strong>of</strong> this zone are<br />
distinguished from those <strong>of</strong> <strong>the</strong> underlying zone by <strong>the</strong>ir ra<strong>the</strong>r advanced forms in<br />
having larger shell, and thicker spiro<strong>the</strong>ca. Weakly developed phreno<strong>the</strong>cae occur<br />
in some specimens. The phreno<strong>the</strong>cae are generally observed in Pseud<strong>of</strong>usulina, but<br />
<strong>the</strong> present specimens are found in a lower horizon than <strong>the</strong> horizon <strong>of</strong> Pseud<strong>of</strong>usulina<br />
as known before in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. More detailed studies are<br />
required to solve <strong>the</strong> problem <strong>of</strong> <strong>the</strong> "Pseud<strong>of</strong>usulina" Horizon.
38 Yasuhiro Ota<br />
<strong>Limestone</strong>s <strong>of</strong> this zone are mainly composed <strong>of</strong> micritic matrices. However,<br />
<strong>the</strong> upper part <strong>of</strong> <strong>the</strong> underlying zone contains some fragments <strong>of</strong>fossils <strong>of</strong> reef frame<br />
builders. No evidence <strong>of</strong> change in lith<strong>of</strong>acies <strong>of</strong> <strong>the</strong> lower Triticites biconicus Subzone<br />
to <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi Zone suggest a remarkable hiatus.<br />
7. Pseudoschwagerina muong<strong>the</strong>nsis Zone.<br />
The lowest part <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Zone in <strong>the</strong> Jigoku-dani area<br />
is marked by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Pseudoschwagerina, namely, Pseudo<br />
schwagerina muong<strong>the</strong>nsis (Deprat) or Pseudoschwagerina sp. In <strong>the</strong> Jigoku-dani area,<br />
well preserved specimens <strong>of</strong> Pseudoschwagerina were not obtained. Along <strong>the</strong> AK<br />
Traverse near <strong>the</strong> <strong>Akiyoshi</strong>-dai Museum <strong>of</strong> Natural History, microspheric forms <strong>of</strong><br />
Pseudoschwagerina are obtained from a stratigraphically slightly lower position com<br />
pared with that <strong>of</strong> <strong>the</strong> megalospheric forms. Along <strong>the</strong> nor<strong>the</strong>rn JI Traverse, JI<br />
Traverse 5, <strong>the</strong> microspheric form <strong>of</strong> Pseudoschwagerina also occurs in a lower horizon<br />
about 2 m below <strong>the</strong> megalospheric form. However, along <strong>the</strong> o<strong>the</strong>r JI Traverses,<br />
<strong>the</strong> microspheric form has not yet been confirmed. Therefore, <strong>the</strong> boundary on <strong>the</strong><br />
underlying zone is tentatively drawn between <strong>the</strong> horizons <strong>of</strong> microspheric form <strong>of</strong><br />
Pseudoschwagerina sp. and megalospheric form <strong>of</strong> Pseudoschwagerina muong<strong>the</strong>nsis (De<br />
prat). The estimated maximum thickness <strong>of</strong> this zone is 32 m-K <strong>Limestone</strong>s in<br />
<strong>the</strong> lower part <strong>of</strong> this zone, consist <strong>of</strong> ra<strong>the</strong>r coarse constituents and intraclasts. The<br />
upper part <strong>of</strong> <strong>the</strong> underlying Schwagerina () cf. satoi Zone is dominated by micritic<br />
limestones. The changes <strong>of</strong> lith<strong>of</strong>acies is present between <strong>the</strong> upper part <strong>of</strong><br />
Schwagerina () satoi Zone and <strong>the</strong> lowest part <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis<br />
Zone. However, each zone is conformably distributed with nearly <strong>the</strong> same strike<br />
and dip. Therefore, a visible gap is not assumed between <strong>the</strong> two zones in <strong>the</strong> field.<br />
On <strong>the</strong> o<strong>the</strong>r hand, limestones gradually become micritic in texture as <strong>the</strong> stratigra<br />
phy is studied from <strong>the</strong> lower to <strong>the</strong> upper part in <strong>the</strong> present zone. This means that<br />
<strong>the</strong> energy <strong>of</strong> <strong>the</strong> environment decreased.<br />
The recognized species <strong>of</strong> this zone are as follows: Staffella moelleri Ozawa,<br />
Schubertella kingi Dunbar, Schwagerina okafujii Toriyama, Schwagerina primigena Nogami,<br />
Schwagerina cf. princeps (Ehrenberg), Schwagerina sp. A, Schwagerina sp. B, Schwagerina<br />
sp. C, Schwagerina sp. D, Schwagerina () aff. kueichihensis (Chen), Pseud<strong>of</strong>usulina regularis<br />
(Schellwien) and Pseudoschwagerina () sp.<br />
8. Pseud<strong>of</strong>usulina vulgaris globosa Zone.<br />
The Pseud<strong>of</strong>usulina vulgaris globosa Zone is characterized by <strong>the</strong> abundant occur<br />
rence <strong>of</strong> Pseud<strong>of</strong>usulina vulgaris globosa (Schellwien) and <strong>the</strong> association <strong>of</strong> Paraschwagerina<br />
sp. In this zone <strong>the</strong> author could not directly determine <strong>the</strong> strike and<br />
dip <strong>of</strong> <strong>the</strong> limestone. The present zone is considered to conformably overlie <strong>the</strong><br />
Pseudoschwagerina muong<strong>the</strong>nsis Zone. <strong>Limestone</strong>s in this zone are estimated to be at<br />
most 83 m in thickness. They are characterized by micritic texture. However, <strong>the</strong><br />
lowest part <strong>of</strong> this zone is composed <strong>of</strong> sparry calcite cements with ra<strong>the</strong>r coarse<br />
grains. The grain size <strong>of</strong> limestones near <strong>the</strong> top <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 39<br />
Zone is micritic. The changes <strong>of</strong> lith<strong>of</strong>acies are present between <strong>the</strong> top <strong>of</strong> <strong>the</strong><br />
Pseudoschwagerina muong<strong>the</strong>nsis Zone and <strong>the</strong> lowest part <strong>of</strong> this zone.<br />
9-1. Pseud<strong>of</strong>usulina aff. ambigua Zone.<br />
The Pseud<strong>of</strong>usulina aff. ambigua Zone is <strong>the</strong> youngest zone, characterized by <strong>the</strong><br />
occurrence <strong>of</strong> Pseud<strong>of</strong>usulina aff. ambigua (Deprat). The index fossil, Pseud<strong>of</strong>usulina<br />
aff. ambigua (Deprat), is closely similar to Fusulina ambigua <strong>of</strong> Deprat (1913), and<br />
Pseud<strong>of</strong>usulina ambigua by Toriyama (1958). However, <strong>the</strong> present species differs<br />
from <strong>the</strong> above species in having a larger proloculus. More specimens are necessary<br />
to determine <strong>the</strong> specific position. Distribution <strong>of</strong> this zone is restricted near <strong>the</strong><br />
bottom <strong>of</strong>Jigoku-dani along <strong>the</strong> nor<strong>the</strong>rn slope. The estimated thickness is 42 m at<br />
least. This zone is characterized by ra<strong>the</strong>r coarse limestones. Near <strong>the</strong> boundary<br />
between <strong>the</strong> underlying zone and <strong>the</strong> present one, <strong>the</strong> limestones with sparry calcite<br />
cements intercalate with somewhat coarse grained varieties. The limestones gradu<br />
ally decrease in grain size from <strong>the</strong> lower to <strong>the</strong> upper, and <strong>the</strong>y become micritic in<br />
texture. However, <strong>the</strong>y change to limestones with sparry calcite cements near <strong>the</strong><br />
top <strong>of</strong> this zone.<br />
-1-2. Correlation<br />
The Carboniferous and Permian chronostratigraphic units have been examined<br />
in Japan for a long time and <strong>the</strong> Middle Carboniferous and Lower Permian<br />
biostratigraphic units and <strong>the</strong>ir boundaries are currently being debated around <strong>the</strong><br />
world. In <strong>the</strong> <strong>Akiyoshi</strong> region, <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> has been studied<br />
since Ozawa (1923) and many important studies <strong>of</strong> Japanese Carboniferous and<br />
Permian geology were carried out <strong>the</strong>re, for example, <strong>the</strong> establishment <strong>of</strong> <strong>the</strong><br />
fusulinacean specific zones <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (Toriyama, 1958), <strong>the</strong><br />
paleoenvironmental investigation <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> as an organic reef<br />
complex (M. Ota, 1968), <strong>the</strong> examination on <strong>the</strong> geologic history <strong>of</strong> <strong>the</strong> lowest to<br />
lower part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> in <strong>the</strong> nor<strong>the</strong>astern part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong><br />
Plateau (Yanagida, et al. 1971), and <strong>the</strong> establishment <strong>of</strong> <strong>the</strong> local standard <strong>of</strong> <strong>the</strong><br />
biostratigraphic units in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (M. Ota, 1977). Recently,<br />
<strong>the</strong> Middle Carboniferous and Lower Permian biostratigraphic units were actively<br />
discussed and some important results were reported, namely, by Hasegawa (1988),<br />
Ueno (1989), Ozawa and Kobayashi (1990), Ishii (1990), Watanabe (1991) and Y.<br />
Ota and M. Ota (1993). The refinement <strong>of</strong> <strong>the</strong> fusulinacean zones will contribute<br />
not only for making clear <strong>the</strong> stratigraphic transition <strong>of</strong> fusuhnaceans, but also for<br />
establishing <strong>the</strong> phylogeny <strong>of</strong> fusuhnaceans. In addition, <strong>the</strong> regional examination<br />
<strong>of</strong> <strong>the</strong> chronostratigraphic units with sedimentological analysis requires careful at<br />
tention.<br />
In <strong>the</strong> investigated area, nine fusulinacean zones including seven subzones were<br />
discriminated. The older limestones are successively exposed in topographically<br />
higher positions along <strong>the</strong> slope <strong>of</strong>Jigoku-dani without any remarkable hiatus. The
Ishii (1990)<br />
Rob, schellwieni z.<br />
Chalaroschwagerina<br />
vulgaris z.<br />
'*. muong<strong>the</strong>nsis on£tA< z.<br />
Sph. fusiformis z.<br />
T. hidensis z.<br />
T. exsculptusz.<br />
T.yayamadakcnsis~<br />
iVot<br />
(Prot) matsumotoi z.<br />
P. kuriltiensis z.<br />
,F. ohtanii z.<br />
B. higoensis z.<br />
PsfUaT<br />
FUa. simplicata z.<br />
Fig. 17. Correlation among <strong>the</strong> Middle Carboniferous to Early Permian biostratigraphic units established in <strong>the</strong><br />
different areas <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> and relevant sections.<br />
Watanabe (1991)<br />
Rob.<br />
schellwieni schellwieni •<br />
Psf. vulgaris vulgaris Z.<br />
Rob. scheUwieni<br />
pamirica • S. krotowi Z.<br />
Parasch.<br />
akiyoshiensis Z.<br />
5. globulusjaponials<br />
Ps. miharanoensis Z.<br />
Alp. saigusai •<br />
Ps. cf. robusta Z.<br />
Sph. pavlooi<br />
Ps muong<strong>the</strong>nsis Z.<br />
Sph. fusiformis Z.<br />
"Ps." minatoi Z.<br />
"Ps * morikawai Z.<br />
S .msatoiZ.<br />
M.<br />
matsumotoi inflatus Z.<br />
Ob. oo3oieiu«Z.<br />
Jigoku-dani area<br />
Pseud<strong>of</strong>usulina<br />
aff. ambigua Z.<br />
Pseud<strong>of</strong>usulina<br />
vulgaris globosa Z.<br />
AKarea<br />
Ota and Ota<br />
Psf. vulgaris Z.<br />
M. Ota (1977)<br />
PsTambtgua]<br />
Psf. vulgaris Z.<br />
Hasegawa (1988)<br />
Psf. vulgaris aubz.<br />
Ueno (1989)<br />
Psf. ex. gr. vulgaris z.<br />
Ozawa and Kobayashi<br />
(1990)<br />
Psf. vulgaris Z.<br />
Pseudoschwagerina<br />
muong<strong>the</strong>nsis Z.<br />
Ps muong<strong>the</strong>nsis Z.<br />
75<br />
IPs.) muong<strong>the</strong>nsis Z.<br />
Pseudoschwagerina Z.<br />
Alp. () fusiformis z.<br />
Dutkevttchia<br />
spUndidaZ<br />
Ps. n. «p. Z.<br />
Ps miharanoensis Z.<br />
Ps. muong<strong>the</strong>nsis Z.<br />
'Sph." fusiformis Z.<br />
Schwagerina ()<br />
cf. satoi Z.<br />
T. simplex Z.<br />
T. simplex Z.<br />
T. simplex subz.<br />
T. simple<br />
Dx. cf. robusta •<br />
"Ps" minatoi Z.<br />
Triticites<br />
yayamadakensis Z.<br />
S. tp. A Z.<br />
TT<<br />
Yj. " morikawai Z.<br />
T.(R.)stuckenbergiZ.<br />
T. (JR.) paraarctieus Z.<br />
T.exsculptusZ.<br />
T.yayamadakensis~Z~<br />
Montiparus sp. A Z.<br />
Obsoletes obsoletus Z~.<br />
Fusulina,<br />
ef. shikokuensis Z.<br />
M. sp. A Z.<br />
Qfdsx,.AZ.<br />
Prot. matsumotoi Z.<br />
Psflla. hidaensis Z.<br />
T. (s. 1.) matsumotoi Z.<br />
fl. akiyoshiensis Z.<br />
T. matsumotoi subz.<br />
'At toriyamai z.<br />
«!•ot sp. z.<br />
Beedeina<br />
akiyoshiensis z.<br />
M. matsumotoi Z.<br />
M. montiparus -<br />
Qfd. ohtanii Z.<br />
Trot<br />
subschwagerinoides Z.<br />
Ob. obsoletus Z.<br />
P^Ua hidaensis Z.<br />
fffa. paemtoooefct Z.<br />
fl. akiyoshiensis Z. *<br />
Psflla. UoiZ.<br />
Fusulinella biconica Z.<br />
Fusulinella biconica Z.<br />
Fusulinella biconica Z.<br />
FUa. taishakuensis~<br />
FUa. biconica z.<br />
FUa. biconicaZ.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 41<br />
following fusulinacean zones are successively discriminated from <strong>the</strong> top to <strong>the</strong><br />
bottom along <strong>the</strong> slope: 1. Fusulinella biconica Zone, 2. Fusulina cf. shikokuensis Zone:<br />
Fusulinella cf. obesa Subzone, Pseud<strong>of</strong>usulinella hidaensis Subzone, 3. Obsoletes obsoletus<br />
Zone: Protriticites toriyamai Subzone, Protriticites matsumotoi Subzone, 4. Montiparus sp. A<br />
Zone, 5. Triticites yayamadakensis Zone: Triticites saurini Subzone, Schwagerina sp. A<br />
Subzone, Triticites biconicus Subzone, 6. Schwagerina () cf. satoi Zone, 7. Pseudoschwager<br />
ina muong<strong>the</strong>nsis Zone, 8. Pseud<strong>of</strong>usulina vulgaris globosa Zone, and 9. Pseud<strong>of</strong>usulina aff.<br />
ambigua Zone.<br />
In this chapter, <strong>the</strong> author presents a correlation chart (Fig. 17) <strong>of</strong> each zone in<br />
<strong>the</strong> Jigoku-dani area with Middle Carboniferous to Early Permian biostratigraphic<br />
units established by workers in different areas <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>.<br />
1. Fusulinella biconica Zone.<br />
The Fusulinella biconica Zone was characterized by <strong>the</strong> occurrence <strong>of</strong> Fusulinella<br />
biconica (Hayasaka). This zone was first introduced by Toriyama (1954a) with<br />
chronostratigraphic position <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>an Series for this zone. According to M.<br />
Ota (1977), <strong>the</strong> lower part <strong>of</strong> Fusulinella biconica Zone is characterized by ra<strong>the</strong>r<br />
primitive species <strong>of</strong> Fusulinella, namely, Fusulinella simplicata Toriyama. Fusulinella<br />
biconica (Hayasaka) typified <strong>the</strong> middle part <strong>of</strong> <strong>the</strong> zone and Fusulinella itoi Ozawa,<br />
<strong>the</strong> upper part. Ueno (1989) divided <strong>the</strong> Fusulinella Zone into <strong>the</strong> following two<br />
zones, <strong>the</strong> lower, <strong>the</strong> Fusulinella biconica Zone and <strong>the</strong> upper, <strong>the</strong> Fusulinella taishakuensis<br />
Zone. In Jigoku-dani, <strong>the</strong> Fusulinella biconica Zone is definitively located at <strong>the</strong> top <strong>of</strong><br />
<strong>the</strong> slope <strong>of</strong> <strong>the</strong> Jigoku-dani area, but <strong>the</strong> Fusulinella taishakuensis Zone was not con<br />
firmed in this area. This zone corresponds to Fusulinella Zone in o<strong>the</strong>r areas.<br />
2. The Fusulina cf. shikokuensis Zone is characterized by <strong>the</strong> first occurrence <strong>of</strong><br />
subfamily Fusulininae, especially by Fusulina cf. shikokuensis Ishii.<br />
This zone is divided into two subzones, <strong>the</strong> lower, <strong>the</strong> Fusulinella cf. obesa Subzone,<br />
and <strong>the</strong> upper, <strong>the</strong> Pseud<strong>of</strong>usulina hidaensis Subzone. The Fusulinella cf. obesa<br />
Subzone, is characterized by Fusulinella cf. obesa Sheng. This subzone probably<br />
corresponds to <strong>the</strong> Kurikian Series that was proposed by Kanmera (1952) from <strong>the</strong><br />
fusulinacean biostratigraphy <strong>of</strong> <strong>the</strong> Yayamadake <strong>Limestone</strong> in <strong>the</strong> outer zone <strong>of</strong><br />
Kyushu. Fur<strong>the</strong>rmore, this subzone is stratigraphically correlative with <strong>the</strong> Beedeina<br />
akiyoshiensis Zone by M. Ota (1977). According to him, <strong>the</strong> Beedeina akiyoshiensis<br />
Zone is typically developed in <strong>the</strong> Shishide-dai area, <strong>the</strong> nor<strong>the</strong>astern part <strong>of</strong><br />
<strong>Akiyoshi</strong>-dai with distinguishable litho- and bi<strong>of</strong>acies from <strong>the</strong> subjacent zone. In<br />
Jigoku-dani, limestones <strong>of</strong> this subzone do not contain reef building organisms and<br />
are considered to have accumulated in a lagoonal environment within <strong>the</strong> <strong>Akiyoshi</strong><br />
organic reef complex. Beedeina akiyoshiensis (Toriyama) has not been found yet.<br />
The difference <strong>of</strong> <strong>the</strong> fusulinacean assemblage seems to be dependent on <strong>the</strong> dif<br />
ference <strong>of</strong> <strong>the</strong> bio- and lith<strong>of</strong>acies <strong>of</strong> limestones.<br />
This subzone is correlated to <strong>the</strong><br />
Fusulina Zone elsewhere.<br />
The upper subzone, <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Subzone, is characterized by <strong>the</strong>
42 Yasuhiro Ota<br />
occurrence <strong>of</strong> Pseud<strong>of</strong>usulinella hidaensis (Kanuma). This zone was first introduced by<br />
Ozawa and Kobayashi (1990) in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. However, at<br />
present, <strong>the</strong> occurrence <strong>of</strong> this species is confined to particular areas. In <strong>the</strong> Jigokudani<br />
area, Pseud<strong>of</strong>usulinella hidaensis (Kanuma) is found in some localities, but its<br />
distribution could not be traced widely. This subzone is probably correlated with<br />
<strong>the</strong> upper part <strong>of</strong> <strong>the</strong> upper Fusulina-Fusulinella Zone.<br />
3. Obsoletes obsoletus Zone<br />
The Obsoletes obsoletus Zone is defined by <strong>the</strong> occurrence <strong>of</strong> Obsoletes obsoletus<br />
(Schellwien). This zone is subdivided into two subzones, <strong>the</strong> lower Protriticites<br />
toriyamai Subzone and <strong>the</strong> upper Protriticites matsumotoi Subzone.<br />
The lower, Protriticites toriyamai Subzone comprises primitive species <strong>of</strong> Protriti<br />
cites, namely Protriticites toriyamai Ota and Protriticites masamichii Ota. This subzone<br />
seems to be also characterized by <strong>the</strong> first appearance <strong>of</strong> very finely perforated walls<br />
in genus. Distribution <strong>of</strong> this subzone is restricted in its stratigraphic distribution.<br />
The Protriticites toriyamai Subzone is considered to be <strong>the</strong> basal zone <strong>of</strong> <strong>the</strong> Hikawan<br />
that was first introduced at Hikawa Valley, Kyushu, by Kanmera (1952). Addi<br />
tionally, this subzone is equivalent to <strong>the</strong> lower part <strong>of</strong> Obsoletes-Protriticites Zone or<br />
Obsoletes Zone in o<strong>the</strong>r areas.<br />
The upper, Protriticites matsumotoi Subzone is characterized by <strong>the</strong> occurrence <strong>of</strong><br />
Protriticites matsumotoi (Kanmera) with Obsoletes obsoletus (Schellwien). The basal<br />
boundary <strong>of</strong> <strong>the</strong> Protriticites matsumotoi Subzone with <strong>the</strong> underlying Protriticites tori<br />
yamai Subzone is marked by <strong>the</strong> first occurrence <strong>of</strong> Protriticites matsumotoi (Kanmera).<br />
Protriticites matsumotoi (Kanmera) was first described by Kanmera (1955) under <strong>the</strong><br />
generic name <strong>of</strong> Triticites (s. 1.) and this species is a diagnostic one <strong>of</strong> <strong>the</strong> Hikawan.<br />
Here, <strong>the</strong> author treats this species as <strong>the</strong> genus Protriticites by its having <strong>the</strong><br />
"Protriticites-tyot wall" only in <strong>the</strong> outer volution. This subzone may be equivalent<br />
to a lower part <strong>of</strong> Hikawan and <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Obsoletes-Protriticites Zone, and<br />
can be correlated with <strong>the</strong> Triticites (s. 1.) matsumotoi Zone by M. Ota (1977). In <strong>the</strong><br />
AK area and some o<strong>the</strong>r regions, <strong>the</strong> occurrence <strong>of</strong> <strong>the</strong> genus Quasifusulinoides was<br />
reported from <strong>the</strong> upper part <strong>of</strong>Protriticites Zone and/or <strong>the</strong> overlying strata. In <strong>the</strong><br />
Jigoku-dani area, however, <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> present subzone yields Quasifusuli<br />
noides () sp., but no well-preserved specimen <strong>of</strong> Quasifusulinoides were obtained. The<br />
upper part <strong>of</strong>this zone is possibly correlative with <strong>the</strong> Quasifusulinoides Zone in o<strong>the</strong>r<br />
areas.<br />
4. Montiparus sp. A Zone.<br />
The Montiparus sp. A Zone is characterized by <strong>the</strong> occurrence <strong>of</strong> <strong>the</strong> genus<br />
Montiparus, and <strong>the</strong> basal boundary <strong>of</strong> this zone is drawn by <strong>the</strong> first occurrence <strong>of</strong><br />
Montiparus sp. A or Montiparus () sp. A. The upper limit <strong>of</strong> this zone is defined by<br />
<strong>the</strong> first occurrence <strong>of</strong> Triticites yayamadakensis Kanmera and T.yayamadakensis evectus<br />
Kanmera. The genus Montiparus was first introduced by Rozovskaya (1948) as a<br />
subgenus <strong>of</strong> Triticites (s. 1.) with <strong>the</strong> name <strong>of</strong> Triticites montiparus Ehr. em. Moell.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 43<br />
Davydov (1990) showed <strong>the</strong> phylogenetic line <strong>of</strong> Protriticites-Montiparus-Rauserites. In<br />
<strong>the</strong> Jigoku-dani area, continuation <strong>of</strong> <strong>the</strong> limestone sequence is confirmed without<br />
any remarkable hiatus from <strong>the</strong> Protriticites matsumotoi Subzone to <strong>the</strong> Montiparus sp. A<br />
Zone. This generic transition from <strong>the</strong> genus Protriticites to <strong>the</strong> genus Montiparus in<br />
<strong>the</strong> above phylogenetic line is acceptable in <strong>the</strong> Jigoku-dani area. Therefore it is<br />
possible to establish <strong>the</strong> datum level by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Montiparus.<br />
This zone probably corresponds to <strong>the</strong> Montiparus Zone or <strong>the</strong> lower part <strong>of</strong> Triticites<br />
(s. 1.) Zone.<br />
5. Triticitesyayamadakensis Zone.<br />
The Triticites yayamadakensis Zone is characterized by <strong>the</strong> occurrence <strong>of</strong> Triticites<br />
yayamadakensis Kanmera. This zone is subdivided into three subzones, <strong>the</strong> lower, <strong>the</strong><br />
Triticites saurian Subzone, <strong>the</strong> middle, <strong>the</strong> Schwagerina sp. A, and <strong>the</strong> upper, <strong>the</strong><br />
Triticites biconicus Subzone. The diagnostic species <strong>of</strong> this zone, Triticites yayama<br />
dakensis Kanmera was described from <strong>the</strong> Yayamadake <strong>Limestone</strong> (Kanmera, 1955).<br />
Therefore, <strong>the</strong> Triticitesyayamadakensis Zone in <strong>the</strong> Jigoku-dani area is correlated to <strong>the</strong><br />
Triticites yayamadakensis Zone <strong>of</strong> <strong>the</strong> upper Hikawan Series (Kanmera, 1952; Tori<br />
yama 1967).<br />
The representative species <strong>of</strong> <strong>the</strong> lower, <strong>the</strong> Triticites saurini Subzone, is Triticites<br />
saurini Igo first reported from Fukuji, Hida Massif, central Japan (Igo, 1957). This<br />
species has a shell <strong>of</strong> large size with highly complicated septa and well-developed<br />
chomata. In <strong>the</strong> Jigoku-dani area, this species is associated with Triticites yayama<br />
dakensis evectus Kanmera that was originally reported from a horizon higher than that<br />
<strong>of</strong> Triticites yayamadakensis yayamadakensis Kanmera. Therefore, a slight doubt on <strong>the</strong><br />
stratigraphic position <strong>of</strong> this subzone still remains. More detailed examinations <strong>of</strong><br />
<strong>the</strong> fusulinacean constituents <strong>of</strong> this subzone are necessary to confirm <strong>the</strong> exact<br />
stratigraphic position.<br />
The middle part <strong>of</strong> this zone, <strong>the</strong> Schwagerina sp. A Subzone, is characterized by<br />
<strong>the</strong> abundant occurrence <strong>of</strong> Schwagerina sp. A. Outside <strong>the</strong> Jigoku-dani area, this<br />
subzone is also confirmed along <strong>the</strong> AK Traverse. The boundary with <strong>the</strong> lower<br />
subzone is defined by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Schwagerina. Therefore, <strong>the</strong><br />
basal boundary <strong>of</strong> this subzone possibly coincides with lower to middle part <strong>of</strong> <strong>the</strong><br />
Triticites-Schwagerina Zone(s. s.).<br />
The upper subzone, <strong>the</strong> Triticites biconicus Subzone, is discriminated by predomi<br />
nance <strong>of</strong> Triticites biconicus Toriyama. In <strong>the</strong>Jigoku-dani area, <strong>the</strong> present subzone<br />
is distributed over <strong>the</strong> Schwagerina sp. A Subzone. This subzone also contains Triti<br />
cites yayamadakensis Kanmera in association with Triticites biconicus Toriyama. Triti<br />
cites yayamadakensis from this subzone is very similar to Triticites ozawai originally<br />
described by Toriyama (1958) and Schellwienia montipara (Ehrenberg) by Ozawa<br />
(1925), respectively from <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>. Triticites yayamadakensis<br />
from this subzone has an intermediate form between <strong>the</strong> above two species. On <strong>the</strong><br />
o<strong>the</strong>r hand, Triticites ozawai Toriyama was reported from <strong>the</strong> Triticites simplex Zone in
44 Yasuhiro Ota<br />
<strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (M. Ota, 1977). Summarizing <strong>the</strong>se evidences, <strong>the</strong><br />
Triticites biconicus Subzone possibly corresponds to <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Triticites<br />
simplex Zone(M. Ota, 1977). These three subzones, are correlative with <strong>the</strong> middle<br />
and upper part <strong>of</strong> <strong>the</strong> Triticites simplex Zone (M. Ota, 1977).<br />
6. Schwagerina () cf. satoi Zone.<br />
The lower boundary <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi Zone is tentatively drawn by<br />
<strong>the</strong> first occurrence <strong>of</strong> Schwagerina () cf. satoi (Ozawa) and Pseud<strong>of</strong>usulina () sp. A.<br />
The distinguishing species, Schwagerina () cf. satoi (Ozawa) from <strong>the</strong> Jigoku-dani<br />
area has an intermediate form between <strong>the</strong> inflated schwagerinids, e.g. Pseudo<br />
schwagerina, and not inflated ones, and this species is very important for correlation.<br />
This zone also contains <strong>the</strong> following fusuhnaceans: Ozawainella aff. magna Sheng,<br />
Nankinella sp. A, Schubertella lata Lee and Chen, Triticites haydeni (Ozawa), Triticites<br />
michiae Toriyama, Triticites cf. obai Toriyama, Triticites cf. pseudosimplex Chen, Triticites<br />
aff. simplex (Schellwien), Triticites aff. suzukii (Ozawa), Schwagerina cf. stabilis<br />
(Rauser), "Pseud<strong>of</strong>usulina" cf. bacca Morikawa and Isomi, "Pseud<strong>of</strong>usulina" aff. fusi<br />
formis (Schellwien) and Rugos<strong>of</strong>usulina arctica (Schellwien). In comparison with<br />
fusuhnaceans <strong>of</strong> <strong>the</strong> underlying zone, those <strong>of</strong> this zone are characterized by having<br />
advanced forms, such as larger shell and thicker spiro<strong>the</strong>ca. It is apparent that<br />
fusulinacean diversity rapidly increased in <strong>the</strong> Schwagerina () cf. satoi Zone. In<br />
addition, coarse grained limestones with fragments <strong>of</strong> reef frame builders are inter<br />
calated near <strong>the</strong> boundary between <strong>the</strong> present zone and <strong>the</strong> underlying zone. The<br />
changes <strong>of</strong> lith<strong>of</strong>acies and faunas are present near <strong>the</strong> basal boundary <strong>of</strong> <strong>the</strong> present<br />
zone. On <strong>the</strong> o<strong>the</strong>r hand, this zone is also characterized by <strong>the</strong> appearance <strong>of</strong> <strong>the</strong>se<br />
fusuhnaceans that possess <strong>the</strong> phreno<strong>the</strong>cae typically recognized in <strong>the</strong> genus<br />
Pseud<strong>of</strong>usulina. Degree <strong>of</strong> <strong>the</strong> development is weak, but <strong>the</strong> phreno<strong>the</strong>cae can be<br />
observed in some specimens. Summarizing <strong>the</strong>se facts, <strong>the</strong> author tentatively<br />
correlates <strong>the</strong> basal boundary <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi Zone with <strong>the</strong> appearance<br />
<strong>of</strong> "Pseud<strong>of</strong>usulina" or <strong>the</strong> basal boundary <strong>of</strong> <strong>the</strong> Daixina Zone.<br />
7. Pseudoschwagerina muong<strong>the</strong>nsis Zone.<br />
The Pseudoschwagerina muong<strong>the</strong>nsis Zone is demarcated from <strong>the</strong> underlying zone<br />
by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Pseudoschwagerina. This lower boundary possibly<br />
coincides with <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> inflated schwagerinids. However, Schwager<br />
ina () cf. satoi (Ozawa) in <strong>the</strong> underlying zone has <strong>the</strong> intermediate form between<br />
Schwagerina and Pseudoschwagerina. Therefore, <strong>the</strong> basal boundary <strong>of</strong> this zone is<br />
drawn by using fusuhnaceans with typically inflated shell. In <strong>the</strong> Jigoku-dani area,<br />
<strong>the</strong>y are represented by Pseudoschwagerina muong<strong>the</strong>nsis (Deprat) and Pseudoschwagerina<br />
sp. Unfortunately, well-preserved materials <strong>of</strong> Pseudoschwagerina have not been<br />
obtained from <strong>the</strong> Jigoku-dani area, and as a result <strong>the</strong> detailed stratigraphic dis<br />
cussion <strong>of</strong> this zone is very hard to make clear. However, an obtained sagittal<br />
section <strong>of</strong> <strong>the</strong> microspheric form <strong>of</strong> Pseudoschwagerina sp. is closely similar to that <strong>of</strong><br />
Pseudoschwagerina morikawai Igo from <strong>the</strong> AK area in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>-dai Muse-
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 45<br />
um. Outside <strong>the</strong> microspheric form <strong>of</strong> Pseudoschwagerina, <strong>the</strong> megalospheric form <strong>of</strong><br />
Pseudoschwagerina muong<strong>the</strong>nsis (Deprat) was obtained from a slightly higher horizon<br />
than that <strong>of</strong> <strong>the</strong> former along <strong>the</strong> JI Traverse 5. This stratigraphic relationship,<br />
however, was not confirmed in o<strong>the</strong>r traverses. This zone can be correlated with <strong>the</strong><br />
strata containing Pseudoschwagerina and typical inflated schwagerinids. Besides,<br />
limestones near <strong>the</strong> lowest boundary <strong>of</strong> this zone are composed <strong>of</strong> ra<strong>the</strong>r coarse<br />
limestones with sparry calcite cements. Conspicuous changes <strong>of</strong> lith<strong>of</strong>acies from <strong>the</strong><br />
top <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi Zone to <strong>the</strong> basal part <strong>of</strong> <strong>the</strong> Pseudoschwagerina<br />
muong<strong>the</strong>nsis Zone are apparently observed as stated previously. The facies change<br />
seems to be closely related to <strong>the</strong> appearance <strong>of</strong> <strong>the</strong> genus Pseudoschwagerina. From<br />
<strong>the</strong> above facts, <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Pseudoschwagerina becomes an<br />
excellent marker for <strong>the</strong> correlation <strong>of</strong> <strong>the</strong> basal part <strong>of</strong> <strong>the</strong> Lower Permian. In<br />
Japan, <strong>the</strong> Lower Permian is represented by <strong>the</strong> Sakamotozawan Series in Sakamotozawa<br />
and Nagaiwa areas, with <strong>the</strong> Kitakami massif as <strong>the</strong> type locality. Toriyama<br />
(1963) proposed two subzones for <strong>the</strong> Sakamotozawan, namely <strong>the</strong> lower Pseudo<br />
schwagerina morikawai Subzone and <strong>the</strong> upper Pseud<strong>of</strong>usulina vulgaris Subzone. Accord<br />
ing to Kanmera and Mikami (1965a, b), <strong>the</strong> basal part <strong>of</strong> <strong>the</strong> Sakamotozawan Series<br />
is absent at <strong>the</strong> type locality. Therefore, <strong>the</strong> definition <strong>of</strong> <strong>the</strong> Sakamotozawan Series<br />
has become ambiguous. However, <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Zone possibly<br />
corresponds to <strong>the</strong> lower part <strong>of</strong> Sakamotozawan Series that was defined as <strong>the</strong> lower<br />
Permian by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> genus Pseudoschwagerina.<br />
8. Pseud<strong>of</strong>usulina vulgaris globosa Zone.<br />
The Pseud<strong>of</strong>usulina vulgaris globosa Zone is characterized by <strong>the</strong> abundance <strong>of</strong><br />
Pseud<strong>of</strong>usulina vulgaris globosa (Schellwien). The lower part <strong>of</strong> this zone in Jigokudani<br />
area comprises Paraschwagerina spp. <strong>Limestone</strong>s <strong>of</strong> this zone mostly consist <strong>of</strong><br />
micritic matrices, but those near <strong>the</strong> base and top <strong>of</strong> this zone comprise sparry calcite<br />
cements with coarse grains. Change <strong>of</strong> lith<strong>of</strong>acies from <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> under<br />
lying Pseudoschwagerina muong<strong>the</strong>nsis Zone to <strong>the</strong> present zone is obvious, but <strong>the</strong><br />
limestone sequence containing Paraschwagerina sp. and Pseud<strong>of</strong>usulina vulgaris globosa<br />
(Schellwien) seems to represent a nearly complete succession. The present zone is<br />
correlated with Pseud<strong>of</strong>usulina vulgaris Zone in o<strong>the</strong>r areas. This zone possibly cor<br />
responds to <strong>the</strong> upper or middle part <strong>of</strong> <strong>the</strong> Sakamotozawan Series.<br />
9. Pseud<strong>of</strong>usulina aff. ambigua Zone.<br />
The Pseud<strong>of</strong>usulina aff. ambigua Zone is defined by <strong>the</strong> first occurrence <strong>of</strong><br />
Pseud<strong>of</strong>usulina aff. ambigua (Deprat). Distribution <strong>of</strong> this zone is restricted to <strong>the</strong><br />
bottom <strong>of</strong> Jigoku-dani, and <strong>the</strong>refore <strong>the</strong> detailed characters are not observed. The<br />
representative species <strong>of</strong> this zone is Pseud<strong>of</strong>usulina aff. ambigua (Deprat). This<br />
species is closely similar to Pseud<strong>of</strong>usulina ambigua <strong>of</strong> Deprat (1913), but it differs from<br />
<strong>the</strong> latter species in having a slightly larger proloculus and a more developed<br />
phreno<strong>the</strong>cae. In <strong>the</strong> Jigoku-dani area, Pseud<strong>of</strong>usulina aff. ambigua (Deprat) is<br />
associated with Pseud<strong>of</strong>usulina cf. vulgaris s. s. (Schellwien), which is similar to
46 Yasuhiro Ota<br />
Pseud<strong>of</strong>usulina vulgaris <strong>of</strong> Schellwien (1909) and also resembles Chalaroschwagerina<br />
infiata <strong>of</strong> Skinner and Wilde (1965). This zone is tentatively compared with <strong>the</strong><br />
strata containing <strong>the</strong> genus Chalaroschwagerina, but its precise stratigraphic position is<br />
unknown. In <strong>the</strong> <strong>Akiyoshi</strong> region, Toriyama (1954a, b, 1957, 1958) first divided<br />
Parafusulina Zone into <strong>the</strong> lower Pseud<strong>of</strong>usulina ambigua Subzone and <strong>the</strong> upper<br />
Parafusulina kaerimizensis Subzone. The present zone possibly corresponds to <strong>the</strong><br />
previous Pseud<strong>of</strong>usulina ambigua Zone in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>.<br />
-1-3. Conclusion<br />
In <strong>the</strong> Jigoku-dani area, <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> is characterized by <strong>the</strong><br />
following paleontological and lithological compositions and <strong>the</strong> author's studies led to<br />
<strong>the</strong> following conclusions.<br />
Biostratigraphically, limestones in this area are divided into <strong>the</strong> nine fusulina<br />
cean zones including seven subzones, ranging from <strong>the</strong> Middle Carboniferous to <strong>the</strong><br />
Lower Permian. They are as follows in ascending order: 1. Fusulinella biconica Zone,<br />
2. Fusulina cf. shikokuensis Zone, 2-1. Fusulinella cf. obesa Subzone, 2-2. Pseud<strong>of</strong>usu<br />
linella hidaensis Subzone, 3. Obsoletes obsoletus Zone, 3-1. Protriticites toriyamai Subzone,<br />
3-2. Protriticites matsumotoi Subzone, 4. Montiparus sp. A Zone, 5. Triticites yayama<br />
dakensis Zone, 5-1. Triticites saurini Subzone, 5-2. Schwagerina sp. A Subzone, 5-3.<br />
Triticites biconicus Subzone, 6. Schwagerina () cf. satoi Zone, 7. Pseudoschwagerina<br />
muong<strong>the</strong>nsis Zone, 8. Pseud<strong>of</strong>usulina vulgaris globosa Zone, 9. Pseud<strong>of</strong>usulina afT. ambigua<br />
Zone.<br />
The above listed zones are easily traceable in this area and indicate that <strong>the</strong>se<br />
limestones are structurally inverted.<br />
Lithologically, limestones in this area have micritic matrices without biolithites.<br />
Sedimentary environment <strong>of</strong> limestones is considered to be lower energy environ<br />
ments like a lagoon within <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex. Additionally, any<br />
remarkable stratigraphical gap, such as <strong>the</strong> lack <strong>of</strong> an important fossil zone, was not<br />
confirmed through <strong>the</strong> fusulinacean zones. This evidence indicates that <strong>the</strong> lagoonal<br />
limestones in <strong>the</strong> area were continuously accumulated through <strong>the</strong> Middle Carbon<br />
iferous and Lower Permian.<br />
In <strong>the</strong> Jigoku-dani area, Pseudoschwagerina muong<strong>the</strong>nsis Zone is defined by <strong>the</strong> first<br />
occurrence <strong>of</strong> <strong>the</strong> inflated schwagerinids: pseudoschwagerinids, namely, <strong>the</strong> genus<br />
Pseudoschwagerina. The inflated schwagerinids including <strong>the</strong> genus Pseudoschwagerina<br />
are supposed to be planktonic during a part <strong>of</strong> <strong>the</strong>ir life cycle (Ross, 1982) and have<br />
world-wide distribution. Therefore, <strong>the</strong>y are apparently excellent index fossils and<br />
are <strong>the</strong> most useful for <strong>the</strong> correlation <strong>of</strong> <strong>the</strong> Lowest Permian. The genus Pseudo<br />
schwagerina is known from some characteristic lith<strong>of</strong>acies, such as <strong>the</strong> biohermal lime<br />
stones (Ross, 1964). For regional correlation, <strong>the</strong> associated fossils are indispensable<br />
for determining <strong>the</strong> age and paleoenvironment. In this paper, <strong>the</strong> author prefers to<br />
correlate <strong>the</strong> limestones <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Zone to <strong>the</strong> Lowest
Fusulinacean Biostradgraphy <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 47
48 Yasuhiro Ota<br />
Permian by taking <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> inflated schwagerinids (pseudo<br />
schwagerinids) into consideration.<br />
-II-1. The second investigated AK area<br />
The second investigated AK area is located in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>-dai Museum<br />
<strong>of</strong> Natural History. The details <strong>of</strong> <strong>the</strong> stratigraphy and paleontology in this area<br />
have already been described by Y. Ota and M. Ota (1993). Here, <strong>the</strong> author<br />
reexamines <strong>the</strong> results <strong>of</strong> <strong>the</strong> investigation <strong>of</strong> <strong>the</strong> AK area, to compare with those <strong>of</strong><br />
<strong>the</strong> Jigoku-dani area.<br />
The selected area represented by AK Traverse is in <strong>the</strong> normal sequence <strong>of</strong> <strong>the</strong><br />
<strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> (M. Ota, 1977). This traverse was established along <strong>the</strong><br />
general trend, NE-SW (Fig. 18). The author had thin sections from rock samples <strong>of</strong><br />
56 localities and reexamined <strong>the</strong> bi<strong>of</strong>acies and lith<strong>of</strong>acies.<br />
-II-2.<br />
Results <strong>of</strong> <strong>the</strong> investigations<br />
-2-(l). Bi<strong>of</strong>acies and Lith<strong>of</strong>acies<br />
The limestones are divided into two types by <strong>the</strong>ir color in <strong>the</strong> field. The first<br />
type is characterized by white limestone whereas <strong>the</strong> second one is black to dark gray<br />
color limestone. The former is subdivided into micrite, limestones with <strong>the</strong> sparry<br />
calcite cements and intermediate micritic limestone with micrite and sparry calcite<br />
cements. Dunham's classification (Dunham, 1962) <strong>of</strong> limestone is used for <strong>the</strong><br />
present study. In <strong>the</strong> classification he emphasized that <strong>the</strong> limestone texture is<br />
important for <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> energy condition. According to his classification,<br />
limestones along AK Traverse are recognized as <strong>the</strong> alternation <strong>of</strong> those <strong>of</strong> micritic<br />
matrices and sparry calcite cements. In addition <strong>the</strong> black to dark brown color<br />
limestones occur at AK 9, AK 11 and AK 12.<br />
The distribution <strong>of</strong>sedimentary facies<br />
is shown in Fig. 19.<br />
Grain components consisting <strong>of</strong> abundant fusuhnaceans and phylloid algae were<br />
obtained from many localities in this area, and coarse grained limestones containing<br />
fragments <strong>of</strong> crinoids and bryozoans were interbedded in this limestone sequence<br />
(Fig. 20).<br />
Summarizing <strong>the</strong>se facts, <strong>the</strong> sedimentary environment <strong>of</strong> this area is recon<br />
structed as <strong>the</strong> environment near an marginal lagoon within <strong>the</strong> <strong>Akiyoshi</strong> organic reef<br />
complex.<br />
-2-(2). Analysis <strong>of</strong> fusulinaceans along AK Traverse<br />
Almost all localities along AK Traverse yield many fusulinaceans. Lists <strong>of</strong> <strong>the</strong><br />
identified fusulinaceans on AK Traverse and <strong>the</strong> composite stratigraphic sections<br />
with typical fusulinaceans are shown in Table 8 and Figs. 21, 22. On <strong>the</strong> basis <strong>of</strong><br />
<strong>the</strong> fusulinaceans along AK Traverse, each horizon <strong>of</strong> this limestone sequence was<br />
characterized by <strong>the</strong> following fusulinacean subfamilies.<br />
AK 1-AK 6: Fusulinellinae
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I<br />
49<br />
LEGEND<br />
Micrite Matrix<br />
Micritic Matrix<br />
Sparry Calcite<br />
Cements<br />
Black to Dark Brown<br />
Color <strong>Limestone</strong><br />
Fig. 19.<br />
Distribution <strong>of</strong> sedimentary facies along <strong>the</strong> AK Traverse.
50 Yasuhiro Ota<br />
LEGEND<br />
DEBRIS LIMESTONE<br />
INCLUDING<br />
CRINOIDS AND BRYOZOANS<br />
FUSULINACEAN LIMESTONE<br />
PHYLLOID ALGAL LIMESTONE<br />
DASYCLADACEAN ALGAL LIMESTONE<br />
LIMESTONE CONGLOMERATE<br />
9 10 20 30 7<br />
Fig. 20.<br />
Route map showing <strong>the</strong>representative bi<strong>of</strong>acies and lith<strong>of</strong>acies <strong>of</strong> limestones along<br />
<strong>the</strong> AK Traverse.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 51<br />
Table 8.<br />
Distribution <strong>of</strong> <strong>the</strong> fusulinacean species in <strong>the</strong> AK area.<br />
S^S; 5>PWeS ^Locality t J ^4in!!11 0/o»03 111 45fi 7fi01 H22!22"Z3 3456 790 333 2 4_ 3*44 71 _ 3
.<br />
Psflls. hidaensis '/..<br />
>><br />
**<br />
row<br />
—i L<br />
Protriticites matsumotoi/.. Qfd. sp. A Z. Montiparus sp. A Z.<br />
> ><br />
CD<br />
o<br />
ro co o ^<br />
f<br />
Schwagerina sp. A Z. T. simplex /..<br />
>><br />
n n c/> •5*<br />
re •n<br />
pi<br />
5<br />
-1<br />
5C re<br />
9<br />
v:<br />
o 8 v:<br />
n<br />
T.<br />
U &j<br />
s 7-<br />
3<br />
re<br />
2<br />
ps<br />
X<br />
0
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I<br />
53<br />
AK30.<br />
AK29.<br />
Pseud<strong>of</strong>usulina vulgaris<br />
s. str. (Schellwien)<br />
I<br />
AK2a<br />
Pseud<strong>of</strong>usulina vulgaris<br />
globosa (Schellwien)<br />
Schwagerina stablis (Rauser)<br />
AK27.<br />
AK2&<br />
Pseudoschwagerina PseudoSchwaaerina sp Pseudoschwagerina<br />
morikawai Igo rseuoosenwagenna sp. muong<strong>the</strong>nsis (Deprat)<br />
Triticites ellipsoidalis Toriyama<br />
Rugsochusenella () sp.<br />
AK23.<br />
AK22<br />
,5<br />
AK21<br />
AK20<br />
AK19<br />
5M<br />
AKia<br />
1mm<br />
Fig. 21-2.<br />
(Continued).
.-i<br />
Yasuhiro Ota<br />
AK34. SSiS<br />
Pseud<strong>of</strong>usulina sp.<br />
AK33<br />
AK3J<br />
Sphaeroschwagerina () sp.<br />
AK31.<br />
AK3a<br />
5__3<br />
Schwagerina<br />
globulus japonicus Watanabe<br />
1mm<br />
5M<br />
Fig. 21-3.<br />
(Continued).<br />
discriminated in ascending order.<br />
1. Pseud<strong>of</strong>usulinella hidaensis Zone<br />
2. Protriticites matsumotoi Zone (s. 1.)<br />
2-(2). Quasifusulinoides sp. A Zone<br />
2-(l). Protriticites matsumotoi Zone (s. s.)<br />
3. Montiparus sp. A Zone<br />
4. Triticites simplex Zone (s. 1.)<br />
4-(2). Triticites simp/ex Zone (s. s.)<br />
4-(l). Schwagerina sp. A Zone<br />
5. Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
6. Pseud<strong>of</strong>usulina vulgaris Zone<br />
The occurrence <strong>of</strong> <strong>the</strong>se fusulinaceans and <strong>the</strong> limestone lithology support <strong>the</strong><br />
conclusion that AK Traverse is composed <strong>of</strong> two nearly complete depositional se<br />
quences. The first sequence is recognized within AK 1 to AK 35, whereas <strong>the</strong><br />
second sequence is recognized within AK 35 to AK 56.<br />
The maximum thickness <strong>of</strong> each zone within <strong>the</strong> sequences is shown in Table 9.<br />
Each zone is characterized by <strong>the</strong> following diagnostic fusulinaceans and stratig<br />
raphic features (Fig. 23) in ascending order.<br />
1. Pseud<strong>of</strong>usulinella hidaensis Zone<br />
The Pseud<strong>of</strong>usulinella hidaensis Zone is characterized by <strong>the</strong> occurrence <strong>of</strong> Pseud<strong>of</strong>u-
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part 1<br />
55<br />
AK48<br />
AK47<br />
Triticites ozawai Toriyama<br />
Triticites michiae Toriyama<br />
AK46-<br />
AK45<br />
AK44<br />
AK41.<br />
AK40.<br />
AK39<br />
Quasifusulina sp.<br />
AK38.<br />
AK37J<br />
AK36.<br />
Montiparus () sp. Protriticites Protriticites<br />
matsumotoi matsumotoi<br />
(Kanmera) (Kanmera)<br />
AK35<br />
Triticites () all. Obsoletes Obsoletes sp. Montiparus () sp.<br />
yayamadakensis obsoletus<br />
evectus Kanmera (Schellwien)<br />
5M<br />
1mm<br />
Fig. 22-1.<br />
The composite stratigraphic section in <strong>the</strong> AK area (Second sequence).
56<br />
Yasuhiro Ota<br />
AK56. ;<br />
Schwagerina stabilis (Rauser)<br />
AK55.;<br />
x4<br />
Ozawainella sp.<br />
Schwagerina cf. compact (White)<br />
i<br />
AK54.1<br />
Schwagerina stabilis (Rauser)<br />
AK53.3<br />
Schwagerina () sp.<br />
AK52j<br />
AK5tt<br />
AK50. 2<br />
AK49.1<br />
5M<br />
AK48. i<br />
x4 N - x4 ^55* x4<br />
Schubertella kingi Dunbar and Skinner Ozawainella sp.<br />
1mm<br />
Fig. 22-2.<br />
(Continued).
Fusulinacean <strong>Biostratigraphy</strong><strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 57<br />
Table 9.<br />
The maximum thickness <strong>of</strong> each zone in <strong>the</strong> AK area.<br />
Fusulinacean zone<br />
Thickness<br />
6. Pseud<strong>of</strong>usulina vulgaris Zone (AK27-29) 13m<br />
5. Pseudoschwagerina muong<strong>the</strong>nsis Zone (AK25-27) (AK52-56) 11 m 34+ m<br />
4. Triticites simplex Zone (s. 1.)<br />
4-(2). Triticites simplex Zone (s. s.) (AK 18-25) (AK46-52) 35 m 42 m<br />
4-(l). Schwagerina sp. A Zone (AK15-18) (AK41-46) 16m 20 m<br />
3. Montiparus sp. A Zone (AK9-10, AK12-15) (AK37-41) 14m 12m<br />
2. Protriticites matsumotoi Zone (s. 1.)<br />
2-(2). Quasifusulinoides sp. A. Zone (AK8-9, AK11) 4 m<br />
2-(l). Protriticites matsumotoi Zone (s. s.) (AK6-8) 13m<br />
1. Pseud<strong>of</strong>usulinella hidaensis Zone (AK1-6) 34+m<br />
sulinella hidaensis (Kanuma) and <strong>the</strong> associated Fusulinella sp.<br />
sists <strong>of</strong> white micrite limestone.<br />
This zone mainly con<br />
2. Protriticites matsumotoi Zone (s. 1.)<br />
The Protriticites matsumotoi Zone (s. 1.) is characterized by <strong>the</strong> occurrence <strong>of</strong><br />
Protriticites matsumotoi (Kanmera). This zone is subdivided into two zones, namely,<br />
<strong>the</strong> lower, <strong>the</strong> Protriticites matsumotoi Zone (s. s.) characterized by Protriticites matsumotoi<br />
(Kanmera), and <strong>the</strong> upper, <strong>the</strong> Quasifusulinoides sp. A Zone, characterized by<br />
Quasifusulinoides sp. A. The genus Quasifusulinoides was not confirmed from <strong>the</strong><br />
second sequence in AK Traverse. The Quasifusulinoides Zone reported by Ueno<br />
(1989) is supposed to be restricted. Therefore, Quasifusulinoides sp. A. Zone is<br />
tentatively discriminated and it is included in <strong>the</strong> Protriticites matsumotoi Zone (s. 1.) be<br />
cause <strong>the</strong> main fusulinacean constituents <strong>of</strong> <strong>the</strong> present two zones belong to Fusu<br />
linellinae and Fusulininae.<br />
2-(l). Protriticites matsumotoi Zone (s. s.)<br />
The Protriticites matsumotoi Zone (s. s.) yields Obsoletes obsoletus (Schellwien),<br />
Protriticites matsumotoi (Kanmera) and Triticites () aff.yayamadakensis evectus Kanmera.<br />
Triticites () aff. yayamadakensis evectus Kanmera resembles <strong>the</strong> Late Carboniferous<br />
Triticitesyayamadakensis evectus Kanmera from <strong>the</strong> Yayamadake <strong>Limestone</strong>, Kumamoto<br />
Prefecture in general shape. However, <strong>the</strong> stratigraphic horizon <strong>of</strong> <strong>the</strong> present spe<br />
cies is higher than those <strong>of</strong> <strong>the</strong> closely related ones from Jigoku-dani and Yayama<br />
dake, because <strong>the</strong> present species is associated with Obsoletes obsoletus (Schellwien).<br />
The limestones with <strong>the</strong>se species commonly have limestones with micritic ma<br />
trices. <strong>Limestone</strong>s with sparry calcite cements are distributed near <strong>the</strong> lower<br />
boundary <strong>of</strong> <strong>the</strong> Protriticites matsumotoi Zone (s. s.). There is a tendency <strong>of</strong> increased<br />
micritic matrices toward <strong>the</strong> upper part <strong>of</strong> this zone.
58 Yasuhiro Ota<br />
Zone<br />
Pseud<strong>of</strong>usulina vulgaris Zone<br />
Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
Triticites simplex Zone (s. 1.)<br />
Triticites simplex Zone (s. s.)<br />
Schwagerina sp. A Zone<br />
Species<br />
Pseud<strong>of</strong>usulina vulgaris s. s. (Schellwien),<br />
Pseud<strong>of</strong>usulina vulgaris globosa (Schellwien),<br />
Pseud<strong>of</strong>usulina sp., Sphaeroschwagerina () sp.,<br />
Triticites complicatus Rozovskaya<br />
Pseudoschwagerina muong<strong>the</strong>nsis (Deprat),<br />
Pseudoschwagerina morikawai Igo,<br />
Pseudoschwagerina sp.,<br />
Triticites ellipsoidalis Toriyamai,<br />
Schwagerina cf. compacts (White),<br />
Schwagerina stabilis (Rauser),<br />
AugosochuseneJ/a () sp.,<br />
Schubertella kingi Dunbar and Skinner<br />
Triticites cf. secalicus (Say),<br />
Triticites ozawaiToriyama,<br />
Triticites michiaeToriyama,<br />
Trinities cf. paraarcticus Rauser,<br />
Schubertella kingi Dunbar and Skinner,<br />
OzawaineHa sp.<br />
Triticites biconicusToriyama,<br />
Triticites cf. saurini Igo,<br />
Triticites ozawaiToriyama,<br />
Triticites exsculptus Igo,<br />
Triticites sp. B,<br />
Triticites sp.C,<br />
Schwagerina sp. A,<br />
Quasifusulina sp. A, Quasifusulina sp.,<br />
Ozawainella sp.<br />
Montiparus sp. A Zone Triticites sp. A,<br />
Triticites () sp.,<br />
Sciitvageriiiaf) sp. A,<br />
Montiparus sp. A,<br />
Montiparus () sp. A,<br />
Protriticites matsumotoi (Kanmera)<br />
fro(ritrcires matsumoroi Zone (s. 1.)<br />
Quasifusulinoides sp. A Zone<br />
Protriticites matsumotoi Zone(s. s.)<br />
Pseud<strong>of</strong>usulinella hidaensis Zone<br />
Quasifusulinoides sp. A<br />
Quasifusulinoides sp.<br />
Triticites () aff. yayamadakensis evectus Kanmera,<br />
ft-otrific/res matsumotoi (Kanmera),<br />
Ohso/eres obsoletus (Schellwien)<br />
Pseud<strong>of</strong>usulinella hidaensis (Kanuma)<br />
Fig. 23.<br />
Fusulinacean zones and <strong>the</strong> faunal elements <strong>of</strong> each zone in <strong>the</strong> AK area.<br />
2-(2). Quasifusulinoides sp. A Zone<br />
The Quasifusulinoides sp. A Zone is discriminated by <strong>the</strong> first occurrence <strong>of</strong><br />
Quasifusulinoides sp. A. This zone is only confirmed in <strong>the</strong> first sequence in AK Tra<br />
verse with a maximum thickness <strong>of</strong> about 4 m.<br />
3. Montiparus sp. A Zone<br />
The diagnostic species <strong>of</strong> this zone is Montiparus sp. A, and <strong>the</strong> associated fossils<br />
are as follows: Protriticites matsumotoi (Kanmera), Montiparus () sp. A, Schwagerina ()<br />
sp. A, Triticites sp. A, and Triticites () sp. In this zone limestones with sparry calcite<br />
cements gradually change to micritic in <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> section. Protriticites<br />
matsumotoi (Kanmera) was found in limestones with sparry calcite cements in <strong>the</strong><br />
lower part <strong>of</strong> <strong>the</strong> present zone. The occurrence <strong>of</strong> Protriticites matsumotoi (Kanmera)<br />
which is <strong>the</strong> diagnostic species <strong>of</strong> <strong>the</strong> underlying zone probably reveals that<br />
Protriticites matsumotoi (Kanmera) and o<strong>the</strong>r associated species are derived from <strong>the</strong>
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 59<br />
underlying limestones.<br />
4. Triticites simplex Zone (s. 1.)<br />
The Triticites simplex Zone (s. 1.) is characterized by <strong>the</strong> occurrence <strong>of</strong> Triticites<br />
and Schwagerina, comparing with <strong>the</strong> Triticites-Schwagerina Zone (s. s.).<br />
4-(l). Schwagerina sp. A Zone<br />
The Schwagerina sp. A Zone is characterized by <strong>the</strong> predominance <strong>of</strong> Schwagerina<br />
sp. A. The lower boundary <strong>of</strong> this zone in <strong>the</strong> first sequence in AK Traverse is<br />
drawn at <strong>the</strong> horizon characterized by <strong>the</strong> occurrence <strong>of</strong> Triticites exsculptus Igo,<br />
Triticites ozawai Toriyama and Triticites cf. saurini Igo, whereas that <strong>of</strong> this zone in <strong>the</strong><br />
second sequence is tentatively drawn at <strong>the</strong> horizon where Quasifusulina sp. occurs<br />
and lith<strong>of</strong>acies change from limestones with micrite matrices to those with sparry<br />
calcite cements.<br />
Schwagerina sp. A is similar to Rugos<strong>of</strong>usulina sp. A reported by Hasegawa (1988).<br />
However, <strong>the</strong> former is distinguished from <strong>the</strong> latter by its very weak rugosity <strong>of</strong> wall.<br />
The specific constituents <strong>of</strong> this zone are as follows: Ozawainella sp., Quasifusulina sp.<br />
A, Quasifusulina sp., Triticites biconicus Toriyama, Triticites exsculptus Igo, Triticites<br />
ozawaiToriyama, Triticites cf. saurini Igo, Triticites sp. B and Triticites sp. C.<br />
The lower part <strong>of</strong> <strong>the</strong> present zone is predominant in limestones with sparry<br />
calcite cements and <strong>the</strong>se contain Schwagerina sp. A. <strong>Limestone</strong>s with micrite matrices<br />
increase toward <strong>the</strong> upper part <strong>of</strong> this zone.<br />
4-(2). Triticites simplex Zone (s. s.)<br />
In <strong>the</strong> AK area, Triticites simplex (Schellwien) was not confirmed. However,<br />
<strong>the</strong> specific assemblages <strong>of</strong> fusulinaceans identify <strong>the</strong>m as members <strong>of</strong> Triticites simplex<br />
Zone (s. s.), which is equivalent to <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Triticites simplex Zone (s. 1.)<br />
(M. Ota, 1977). The following fusulinaceans are common in this zone: Ozawainella<br />
sp., Schubertella kingi Dunbar and Skinner, Schubertella sp., Schwagerina sp., Triticites<br />
michiae Toriyama, Triticites ozawai Toriyama, Triticites cf. secalicus (Say) and Triticites<br />
cf. paraarcticus Rauser. This zone mainly consists <strong>of</strong> limestones with micritic matri<br />
ces. <strong>Limestone</strong>s with sparry calcite cements appear and are interbedded with <strong>the</strong><br />
micritic ones in <strong>the</strong> upper part <strong>of</strong> this zone. The energy condition <strong>of</strong> <strong>the</strong> depositional<br />
environment is considered to have shifted from lower to higher.<br />
5. Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
The Pseudoschwagerina muong<strong>the</strong>nsis Zone is characterized by <strong>the</strong> occurrence <strong>of</strong><br />
Pseudoschwagerina muong<strong>the</strong>nsis (Deprat) and <strong>the</strong> lower boundary <strong>of</strong> this zone is defined<br />
by <strong>the</strong> first appearance <strong>of</strong> Pseudoschwagerina (Pseudoschwagerina morikawai Igo). Along<br />
<strong>the</strong> first sequence <strong>of</strong> AK Traverse, Pseudoschwagerina morikawai Igo, <strong>the</strong> microspheric<br />
form first occurs at a horizon about 8 m lower than that <strong>of</strong> Pseudoschwagerina muongth<br />
ensis (Deprat), <strong>the</strong> megalospheric form. However, Pseudoschwagerina muong<strong>the</strong>nsis<br />
(Deprat) is associated with Pseudoschwagerina morikawai Igo at AK 26. Fur<strong>the</strong>rmore,<br />
<strong>the</strong> boundary <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Zone with <strong>the</strong> underlying zone was<br />
formerly drawn by <strong>the</strong> first occurrences <strong>of</strong> Pseudoschwagerina [Pseudoschwagerina
60 Yasuhiro Ota<br />
muong<strong>the</strong>nsis (Deprat)], including megalospheric and microspheric forms. There<br />
fore, <strong>the</strong> base <strong>of</strong> <strong>the</strong> present Pseudoschwagerina muong<strong>the</strong>nsis Zone is demarcated by <strong>the</strong><br />
first occurrence <strong>of</strong> <strong>the</strong> inflated schwagerinid, Pseudoschwagerina. Along <strong>the</strong> second<br />
sequence, Pseudoschwagerina was not found, but <strong>the</strong> zone was recognized from a hori<br />
zon (AK 52), where advanced fusulinaceans occurred.<br />
<strong>Limestone</strong>s <strong>of</strong> <strong>the</strong> first sequence yield <strong>the</strong> following fusulinaceans: Pseudo<br />
schwagerina muong<strong>the</strong>nsis (Deprat), Pseudoschwagerina morikawai Igo, Pseudoschwagerina<br />
Fig. 24. Distribution <strong>of</strong> fusulinacean zones in <strong>the</strong> AK area (modified from Hasegawa,<br />
1992).
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 61<br />
sp., Rugosochusenella () sp., Triticites ellipsoidalis Toriyama and Schwagerina stabilis<br />
(Rauser). The second sequence yields Schwagerina stabilis (Rauser), Schwagerina cf.<br />
compacta (White), Schwagerina () sp., Schubertella kingi Dunbar and Skinner, and<br />
Ozawainella sp.<br />
This zone is, as a whole, composed <strong>of</strong> micritic limestones except for <strong>the</strong> upper<br />
part. <strong>Limestone</strong>s across <strong>the</strong> boundary between <strong>the</strong> present zone and <strong>the</strong> underlying<br />
zone along <strong>the</strong> first sequence change upward from those with sparry calcite cements<br />
to micritic. <strong>Limestone</strong>s along <strong>the</strong> second sequence, however, are mainly composed<br />
<strong>of</strong> micritic limestones on both sides <strong>of</strong> <strong>the</strong> boundary. <strong>Limestone</strong>s with sparry calcite<br />
cements are common in <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> present zone. They suggest a relative<br />
ly high energy environment and yield abundant Schwagerina, such as Schwagerina<br />
stabilis (Rauser). The lack <strong>of</strong> limestones with sparry calcite cements near <strong>the</strong> lower<br />
boundary <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Zone in <strong>the</strong> second sequence, probably<br />
suggest that <strong>the</strong>se micritic limestones were accumulated in an environment in which<br />
<strong>the</strong> inflated schwagerinids, i.e. Pseudoschwagerina, could not exist.<br />
6. Pseud<strong>of</strong>usulina vulgaris Zone<br />
The Pseud<strong>of</strong>usulina vulgaris Zone in <strong>the</strong> AK area is characterized by <strong>the</strong> diagnostic<br />
species, Pseud<strong>of</strong>usulina vulgaris (Schellwien), and <strong>the</strong> following associated species,<br />
Triticites complicatus Rozovskaya, Sphaeroschwagerina () sp., Pseud<strong>of</strong>usulina vulgaris<br />
globosa (Schellwien) and Pseud<strong>of</strong>usulina sp. This zone is characterized by limestones<br />
with <strong>the</strong> micritic matrices.<br />
From distribution <strong>of</strong> <strong>the</strong> zones (Fig. 24), it has become clear that <strong>the</strong> succession<br />
<strong>of</strong> AK Traverse consists <strong>of</strong> two nearly complete limestone sequences, possibly<br />
separated by <strong>the</strong> NE- SW fault (shown by Ozawa and Kobayashi, 1990).<br />
-II-3.<br />
Correlation<br />
-3-(l). Correlation (Within Japan)<br />
In this chapter <strong>the</strong> author presents <strong>the</strong> tentative correlation <strong>of</strong> fusulinacean zones<br />
<strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> <strong>of</strong> <strong>the</strong> AK area and a reference proposal for <strong>the</strong><br />
subdivision <strong>of</strong> <strong>the</strong> Middle Carboniferous and Lower Permian fusulinacean zones<br />
(shown in Fig. 17).<br />
1. Pseud<strong>of</strong>usulinella hidaensis Zone<br />
The characteristic species <strong>of</strong> this zone is Pseud<strong>of</strong>usulinella hidaensis (Kanuma),<br />
originally described by Kanuma (1953) as Wedekindellina () hidaensis. Ozawa and<br />
Kobayashi (1990) first treated this species under <strong>the</strong> generic name <strong>of</strong> Pseud<strong>of</strong>usulinella<br />
and established <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Zone with <strong>the</strong> diagnostic species. The<br />
phylogenetic trend <strong>of</strong> Pseud<strong>of</strong>usulinella was studied by Ozawa (1967) and Wilde<br />
(1971). According to Kanuma (1953), this species has a small elongate fusiform<br />
shell with a straight axis <strong>of</strong> coiling, inflated central area, bluntly pointed poles and<br />
slightly concave lateral slopes. In addition chomata are large and massive, and<br />
axial fillings are well developed. Wedekindellina Dunbar and Henbest, 1933 is char-
62 Yasuhiro Ota<br />
acterized by its elongated small shell, and well developed axial fillings and four lay<br />
ered wall with perforations. To <strong>the</strong> contrary, Pseud<strong>of</strong>usulinella Thompson, 1951 has a<br />
spiro<strong>the</strong>ca composed <strong>of</strong> a tectum and diaphano<strong>the</strong>ca with very minute but distinct<br />
pores. The massive chomata in <strong>the</strong> center <strong>of</strong> <strong>the</strong> shell cover <strong>the</strong> lower surfaces <strong>of</strong><br />
spiro<strong>the</strong>ca to give it <strong>the</strong> appearance <strong>of</strong> spiro<strong>the</strong>ca <strong>of</strong> four layers as found in Fusulinella<br />
and Fusulina. Pseud<strong>of</strong>usulinella is distinguished from Fusulinella by its younger occur<br />
rences than <strong>the</strong> latter and by having different features <strong>of</strong> <strong>the</strong> wall and axial fillings.<br />
From its general shapes and features, <strong>the</strong> obtained specimen should be referable to<br />
Pseud<strong>of</strong>usulinella hidaensis (Kanuma). The Pseud<strong>of</strong>usulinella hidaensis Zone <strong>of</strong> <strong>the</strong> author<br />
is correlated with <strong>the</strong> same zone by Ozawa and Kobayashi (1990). In this inves<br />
tigated AK Traverse, Beedeina akiyoshiensis (Toriyama) which is <strong>the</strong> diagnostic species<br />
<strong>of</strong> <strong>the</strong> Beedeina akiyoshiensis Zone (M. Ota, 1977) was not confirmed. Hence it is<br />
very difficult to directly correlate <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Zone with <strong>the</strong> Beedeina<br />
akiyoshiensis Zone. Never<strong>the</strong>less <strong>the</strong> present zone corresponds to <strong>the</strong> Beedeina<br />
akiyoshiensis Zone based on biostratigraphic relationship between <strong>the</strong> present zone and<br />
<strong>the</strong> underlying and overlying zones. Ueno (1989) recognized <strong>the</strong> Beedeina akiyoshi<br />
ensis Zone between <strong>the</strong> upper, Fusulinella taishakuensis Zone and <strong>the</strong> lower, Protriticites<br />
sp. Zone. According to him, only Pseud<strong>of</strong>usulinella sp. (sp. nov.) was reported from<br />
Protriticites sp. Zone. Ueno (1991b) reported that Pseud<strong>of</strong>usulinella (Kanmeraia)<br />
praeantiqua Nassichuk and Wilde was found in <strong>the</strong> uppermost part <strong>of</strong> <strong>the</strong> Protriticites<br />
sp. Zone and <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Quasifusulinoides toriyamai Zone (Ueno, 1989), but<br />
<strong>the</strong> detailed relationships between <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Zone and <strong>the</strong>se zones<br />
are not clear. However, Fusulinella biconica Zone is correlative with <strong>the</strong> Fusulinella<br />
biconica Zone <strong>of</strong> Hasegawa (1988) and Ozawa and Kobayashi (1990). On <strong>the</strong><br />
o<strong>the</strong>r hand, <strong>the</strong> Fusulinella taishakuensis Zone was first introduced by Okimura (1987)<br />
and is characterized by <strong>the</strong> occurrence <strong>of</strong> Fusulinella taishakuensis established by Sada<br />
and Yokoyama (1970). The Fusulinella taishakuensis Zone is associated with <strong>the</strong><br />
following fusulinaceans: Fusulinella biconica (Hayasaka), Fusulinella simplicata Tori<br />
yama, Fusulinella bocki Moller and Fusulinella subsphaerica Toriyama. Judging from<br />
<strong>the</strong> constituents <strong>of</strong> <strong>the</strong> preceding zones, <strong>the</strong> Fusulinella taishakuensis Zone and <strong>the</strong><br />
Fusulinella biconica Zone (Ueno, 1989) correspond to <strong>the</strong> Fusulinella biconica Zone (M.<br />
Ota, 1977).<br />
2. Protriticites matsumotoi Zone (s. 1.)<br />
2-(l). Protriticites matsumotoi Zone (s. s.)<br />
Protriticites matsumotoi (Kanmera) is <strong>the</strong> diagnostic species <strong>of</strong> this zone. This<br />
species was described by Kanmera (1955) as a representative species <strong>of</strong> Hikawan<br />
Series and is known as a primitive species <strong>of</strong> this genus. In well preserved speci<br />
mens <strong>of</strong> Protriticites matsumotoi (Kanmera), <strong>the</strong> spiro<strong>the</strong>ca <strong>of</strong> <strong>the</strong> third to <strong>the</strong> fourth<br />
and occasionally <strong>the</strong> fifth volutions appear to be composed <strong>of</strong> four layers. The<br />
spiro<strong>the</strong>cal characters closely resemble those <strong>of</strong> Fusulinella Moller. In mature<br />
specimens, <strong>the</strong> spiro<strong>the</strong>ca <strong>of</strong> <strong>the</strong> fifth to mature volutions have a clearly discernible
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 63<br />
kerio<strong>the</strong>ca. The classification <strong>of</strong> Triticites (s. 1.) and its evolution have been discussed<br />
since Rozovskaya (1948) classified Triticites (s. 1.) into four subgenera, Triticites (s.<br />
s.), Montiparus, Rauserites and Jigulites. Some considerations concerned with <strong>the</strong>ir<br />
several variations are present. One variation is <strong>the</strong> "Protriticites-type wall". Rauser<br />
and Fursenko (1959) described <strong>the</strong> wall structure <strong>of</strong> Protriticites that it is perforated<br />
and composed <strong>of</strong> four-layers in <strong>the</strong> inner volutions and three-layers in outer ones,<br />
namely a tectum, pro<strong>the</strong>ca and outer tectorium. The same structure <strong>of</strong> Protriticites<br />
was also noticed by Loeblich and Tappan (1988). Sheng, Zhang and Wang<br />
(1988) also confirmed that <strong>the</strong> inner spiro<strong>the</strong>ca <strong>of</strong> Protriticites were composed <strong>of</strong> four<br />
layers like Fusulinella, but <strong>the</strong> outer spiro<strong>the</strong>ca were composed <strong>of</strong> a tectum and <strong>the</strong><br />
inner and outer tectoria. They also mentioned that Protriticites was an intermediate<br />
form between Fusulinella and Triticites (s. s.). Rozovskaya (1950) clearly illustrated<br />
<strong>the</strong> kerio<strong>the</strong>cal wall in Protriticites. Putrya (1948) remarked on <strong>the</strong> complicated wall<br />
<strong>of</strong> Protriticites in his original description <strong>of</strong> <strong>the</strong> genus. He noticed that it is composed<br />
<strong>of</strong> a tectum, diaphano<strong>the</strong>ca and two tectoria. Fur<strong>the</strong>rmore, he noticed that <strong>the</strong><br />
diaphano<strong>the</strong>ca, tectoria and chomata possess <strong>the</strong> structure <strong>of</strong> fine alveoli, and <strong>the</strong><br />
coarser ones are recognizable in <strong>the</strong> inner tectorium. In <strong>the</strong> outermost whorl <strong>the</strong><br />
alveolers structure reaches diaphano<strong>the</strong>ca. Davydov (1990) proposed <strong>the</strong> lineage<br />
from Protriticites to Rauserites, through Montiparus. According to him, <strong>the</strong> inner<br />
tectorium which is considered as a characteristic feature <strong>of</strong> Montiparus is only present<br />
in <strong>the</strong> inner whorls where <strong>the</strong> kerio<strong>the</strong>cal wall is not present. Summarizing<br />
preceding evidence, it is noticed that Protriticites has <strong>the</strong> inner tectorium in <strong>the</strong> outer<br />
volution and if we recognize <strong>the</strong> inner tectorium in outer volution <strong>of</strong> a specimen, <strong>the</strong>n<br />
it might belong to Protriticites. Triticites (s. 1.) matsumotoi by Kanmera (1955) has a<br />
Protriticites-type wall only in <strong>the</strong> outer volutions. Based on <strong>the</strong>se facts, <strong>the</strong> author<br />
treats this species under Protriticites. Hasegawa (1988) treated this species as <strong>the</strong><br />
diagnostic species <strong>of</strong> <strong>the</strong> Triticites matsumotoi Subzone. According to hisopinions, this<br />
species has very primitive features <strong>of</strong> Triticites (s. 1.). Additionally, <strong>the</strong> fauna <strong>of</strong> <strong>the</strong><br />
Triticites (s. 1.) matsumotoi Zone is missing in some areas. The fauna <strong>of</strong> <strong>the</strong> Triticites<br />
simplex Zone directly overlies <strong>the</strong> Fusulinella-Fusulina Zone in some cases. Therefore,<br />
he interpreted that Protriticites was able to migrate to <strong>the</strong> place where a fusulinacean<br />
favorable environment appeared in <strong>the</strong> early stage. Recently, a primitive-Triticites<br />
(s. 1.) fauna, including Protriticites, was reported from <strong>the</strong> <strong>Akiyoshi</strong> region and some<br />
o<strong>the</strong>r districts. Hence, <strong>the</strong> author correlated <strong>the</strong> Protriticites matsumotoi Zone (s. s.)<br />
with limestones, bearing species <strong>of</strong> primitive Triticites (s. 1.).<br />
The present Protriticites matsumotoi Zone (s. s.) corresponds to <strong>the</strong> Triticites (s. 1.)<br />
matsumotoi Zone (M. Ota, 1977), <strong>the</strong> Triticites matsumotoi Zone (Hasegawa, 1988) and<br />
<strong>the</strong> Protriticites sp. Zone (Ueno, 1989). Fur<strong>the</strong>rmore it is correlative with <strong>the</strong><br />
Obsoletes obsoletus Zone (Watanabe, 1991) and <strong>the</strong> Protriticites (P.) matsumotoi Zone<br />
(Ishii, 1990).
64 Yasuhiro Ota<br />
2-(2). Quasifusulinoides sp. A Zone<br />
The Quasifusulinoides sp. A Zone is characterized by <strong>the</strong> occurrence <strong>of</strong> Quasifusuli<br />
noides. The occurrence <strong>of</strong> this zone is restricted and thus it is included in <strong>the</strong><br />
Protriticites matsumotoi Zone (s. 1.) on <strong>the</strong> basis <strong>of</strong> its confined distribution and <strong>the</strong><br />
stratigraphic relationship between <strong>the</strong> overlying and underlying zones. Ueno (1989)<br />
established <strong>the</strong> Quasifusulinoides toriyamai Zone and this zone is correlated with <strong>the</strong><br />
Quasifusulinoides sp. A Zone. The present zone may be also equivalent to <strong>the</strong> lower<br />
part <strong>of</strong> <strong>the</strong> Montiparus montiparus-Quasifusulinoides ohtanii Zone (Ozawa and Kobayashi,<br />
1990) and <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Obsoletes obsoletus Zone (Watanabe, 1991). In <strong>the</strong><br />
Jigoku-dani area, well-preserved Quasifusulinoides do not occur, but Quasifusulinoides ()<br />
sp. was obtained from <strong>the</strong> Protriticites matsumotoi Subzone. Therefore, <strong>the</strong> present<br />
Quasifusulinoides sp. A Zone probably corresponds to <strong>the</strong> Protriticites matsumotoi Subzone<br />
<strong>of</strong> <strong>the</strong> Jigoku-dani area.<br />
3. Montiparus sp. A Zone<br />
This datum level is defined by <strong>the</strong> occurrence <strong>of</strong> Montiparus. As mentioned<br />
before, Montiparus was first introduced as a subgenus in four subgenera <strong>of</strong> Triticites (s.<br />
1.) with Triticites montiparus Ehr. em. Moell. as <strong>the</strong> type species by Rozovskaya<br />
(1948). However, <strong>the</strong> variations and definitions <strong>of</strong> Montiparus are ambiguous, and<br />
some disagreements about <strong>the</strong> genus are present. Wilde (1984) treated Montiparus<br />
Rozovskaya, 1948 as a synonym <strong>of</strong> Schwagerina montipara (Ehrenberg, 1854) emend.<br />
Dunbar and Skinner, 1936, and proposed <strong>the</strong> new name <strong>of</strong> Eotriticites. In short,<br />
Montiparus has historically two different types and thus <strong>the</strong> definition <strong>of</strong> Montiparus is<br />
unclear. The obtained specimens should be referred to Montiparus Rozovskaya,<br />
1948 with <strong>the</strong> following type species, Triticites (Montiparus) montiparus Rozovskaya,<br />
1948=Fusulina montipara Ehrenberg emend. Moller, 1878. Montiparus sp. A is a<br />
diagnostic species <strong>of</strong> <strong>the</strong> Montiparus sp. A Zone.<br />
The Montiparus sp. A Zone is also associated with Protriticites matsumotoi (Kan<br />
mera), Montiparus () sp. A, Schwagerina () sp. A, Triticites sp. A and Triticites () sp.<br />
This zone is correlated with <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Triticites simplex Zone (M. Ota,<br />
1977), because Triticites in <strong>the</strong> present zone has a relatively primitive form. More<br />
over, this zone probably corresponds to <strong>the</strong> upper Montiparus montiparus-Quasifusuli<br />
noides ohtanii Zone and <strong>the</strong> Montiparus matsumotoi Zone (Ozawa and Kobayashi, 1990),<br />
<strong>the</strong> Triticites yayamadakensis Zone (Ishii, 1990) and <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Triticites<br />
simplex Zone (Hasegawa, 1988).<br />
4. Triticites simplex Zone (s. 1.)<br />
4-(l). Schwagerina sp. A Zone<br />
The Schwagerina sp. A Zone is distinguished by <strong>the</strong> characteristic occurrence <strong>of</strong><br />
Schwagerina sp. A. This zone is associated with occurrences <strong>of</strong> <strong>the</strong> following species:<br />
Triticites biconicus Toriyama, Triticites exsculptus Igo, Triticites ozawai Toriyama,<br />
Triticites cf. saurini Igo, Triticites sp. B, Triticites sp. C, Quasifusulina sp. A, Quasifusulina<br />
sp. and Ozawainella sp. Zhang (1991) placed <strong>the</strong> Triticites-Schwagerina Zone under
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 65<br />
Pseudoschwagerina Zone and reported <strong>the</strong> first occurrence <strong>of</strong> Schwagerina in <strong>the</strong> lower<br />
part <strong>of</strong> <strong>the</strong> Triticites siuckenbergi Zone. Kanmera, Ishii and Toriyama (1976) also<br />
established <strong>the</strong> Schwagerina Zone under <strong>the</strong> Pseudoschwagerina Zone. The present<br />
Schwagerina sp. A Zone corresponds to Triticites-Schwagerina Zone (s. s.) and is tenta<br />
tively correlated with <strong>the</strong> lower parts <strong>of</strong> <strong>the</strong> Triticites simplex Zone (M. Ota, 1977) and<br />
<strong>the</strong> Triticites yayamadakensis Zone in <strong>the</strong> Jigoku-dani area.<br />
4-(2). Triticites simplex Zone (s. s.)<br />
The specific constituents <strong>of</strong> <strong>the</strong> Triticites simplex Zone (s. s.) are as follows:<br />
Ozawainella sp., Schubertella kingi Dunbar and Skinner, Schubertella sp., Schwagerina sp.,<br />
Triticites michiae Toriyama, Triticites ozawai Toriyama, Triticites cf. paraarcticus Rauser<br />
and Triticites cf. secalicus (Say). Unfortunately, Triticites simplex (Schellwien) was<br />
not collected in this investigation. However, judging from <strong>the</strong> coexisted fusulina<br />
ceans, <strong>the</strong> specific assemblage corresponds to that <strong>of</strong> <strong>the</strong> upper part <strong>of</strong> Triticites simplex<br />
Zone (M. Ota, 1977). It is also similar to those from <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Triticites<br />
yayamadakensis Zone to Schwagerina () cf. satoi Zone <strong>of</strong> <strong>the</strong> Jigoku-dani area. In<br />
addition, <strong>the</strong> Triticites simplex Zone (s. s.) is correlated with <strong>the</strong> upper part <strong>of</strong> <strong>the</strong><br />
Triticites hidensis Zone (Ishii, 1990), <strong>the</strong> Triticites (Rauserites) paraarcticus and Triticites<br />
(Rauserites) siuckenbergi Zones (Ozawa and Kobayashi, 1990), <strong>the</strong> upper part <strong>of</strong> <strong>the</strong><br />
Triticites simplex Zone (Hasegawa, 1988) and <strong>the</strong> upper Triticites "simplex" Zone<br />
(Ueno, 1989).<br />
5. Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
The Pseudoschwagerina Zone was formerly divided into two subzones by Toriyama<br />
(1954a), namely <strong>the</strong> lower Triticites simplex Subzone and <strong>the</strong> upper Pseud<strong>of</strong>usulina<br />
vulgaris Subzone (Toriyama, 1954a). Hasegawa (1963) subdivided <strong>the</strong> Pseudo<br />
schwagerina Zone into two subzones, <strong>the</strong> lower, <strong>the</strong> Triticites simplex Subzone and <strong>the</strong><br />
upper, <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Subzone. The Pseudoschwagerina muong<strong>the</strong>nsis<br />
Subzone was treated as <strong>the</strong> Pseudoschwagerina (P.) muong<strong>the</strong>nsis Zone, and <strong>the</strong> Triticites<br />
simplex Subzone as <strong>the</strong> Triticites simplex Zone by M. Ota (1977). The datum level <strong>of</strong><br />
this zone is formerly demarcated by <strong>the</strong> first occurrence <strong>of</strong> inflated schwagerinids, i.e.<br />
Pseudoschwagerina muong<strong>the</strong>nsis (Deprat), including megalospheric and microspheric<br />
forms. Therefore, <strong>the</strong> lowest part <strong>of</strong> <strong>the</strong> present zone in <strong>the</strong> AK area coincides with<br />
<strong>the</strong> occurrence <strong>of</strong> Pseudoschwagerina morikawai Igo. Many fusulinacean workers have<br />
studied before on <strong>the</strong> inflated schwagerinids and <strong>the</strong>ir paleoecology and paleobiogeography.<br />
Studies on <strong>the</strong>ir provinciality were also presented by Ross (1962,<br />
1963a, 1964, 1967, 1982) and Gobbett (1973). Ross (1982) mentioned that several<br />
genera among <strong>the</strong> schwagerinids were probably planktonic during a part <strong>of</strong> <strong>the</strong>ir life<br />
cycles. Ross (1962, 1963a, 1964, 1967) examined <strong>the</strong>ir evolution, migrations and<br />
dispersal in detail. Ross (1967, 1973) pointed out <strong>the</strong> difference <strong>of</strong> each province<br />
based on <strong>the</strong> paleobiogeographic separation <strong>of</strong> fusulinid faunas and also discussed <strong>the</strong><br />
lineage <strong>of</strong> Protriticites. A lineage with Montiparus-Obsoletes-Triticites was confirmed<br />
only in <strong>the</strong> Eurasian- Arctic province. Whereas only Triticites was recognized at <strong>the</strong>
66 Yasuhiro Ota<br />
same stratigraphic positions in Mid-continent province. Ross (1962, 1963a, 1964)<br />
classified <strong>the</strong> pseudoschwagerinids into eight complexes and he discussed <strong>the</strong>ir<br />
details. From <strong>the</strong>se studies, he concluded that <strong>the</strong> greatest diversity <strong>of</strong> <strong>the</strong>m took<br />
place in <strong>the</strong> Tethyan seaway in later Wolfcampian time. On <strong>the</strong> o<strong>the</strong>r hand,<br />
Gobbett (1973) discussed Pseudoschwagerina as a cosmopolitan genus. As mentioned<br />
above, it is very effective to use <strong>the</strong> datum level defined by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong><br />
inflated schwagerinids for accurate global correlation. Rui and Zhang (1987) also<br />
noticed that pseudoschwagerinids might be used for global correlation, owing to <strong>the</strong>ir<br />
rapid evolution and global distribution. The correlation <strong>of</strong> <strong>the</strong> Pseudoschwagerina<br />
Zone has been discussed by many authors, such as Hanzawa (1942), Hayasaka and<br />
Minato (1954), Fujimoto (1959), Fomichev (1960), Kahler (1961), Rauser (1965)<br />
and Lapkin and Kats (1990). Although <strong>the</strong> inflated schwagerinids show global<br />
distribution, <strong>the</strong>ir occurrence seems to be restricted to somewhat coarser sediments.<br />
Evidences for this was given by Ross (1964). Therefore, examination <strong>of</strong> <strong>the</strong>ir<br />
accompanying fossils is indispensable for accurate correlation. The present zone is<br />
correlated with <strong>the</strong> Pseudoschwagerina (P.) muong<strong>the</strong>nsis Zone (M. Ota, 1977), and <strong>the</strong><br />
Pseudoschwagerina muong<strong>the</strong>nsis Zone in <strong>the</strong> Jigoku-dani area. The lower boundary <strong>of</strong><br />
this zone approximately coincides with those <strong>of</strong> <strong>the</strong> Sphaeroschwagerina fusiformis Zone<br />
(Ishii, 1990, Watanabe, 1991), <strong>the</strong> "Sphaeroschwagerina" fusiformis Zone (Ozawa and<br />
Kobayashi, 1990) and <strong>the</strong> Alpinoschwagerina ()fusiformis Zone (Ueno, 1989).<br />
6. Pseud<strong>of</strong>usulina vulgaris Zone<br />
The base <strong>of</strong> this zone is marked by <strong>the</strong> occurrence <strong>of</strong> <strong>the</strong> diagnostic species,<br />
Pseud<strong>of</strong>usulina ex. gr. vulgaris (Schellwien). Several studies <strong>of</strong> <strong>the</strong> systematics <strong>of</strong><br />
Pseud<strong>of</strong>usulina have been carried out internationally. Davydov (1988a, b) examined<br />
in detail <strong>the</strong> origin and development <strong>of</strong> <strong>the</strong> pseud<strong>of</strong>usulinids. However, discussions<br />
on <strong>the</strong> systematics, classification and stratigraphic significance <strong>of</strong> <strong>the</strong> pseud<strong>of</strong>usu<br />
linids still continue. Zhang (1983, 1991) discriminated "Pseud<strong>of</strong>usulina Bed" under<br />
<strong>the</strong> Pseudoschwagerina Zone, and correlated this bed with lower Daixina sokensis Zone.<br />
According to him, Pseud<strong>of</strong>usulina stratigraphically occurs in a bed lower than that<br />
bearing Pseudoschwagerina. Rauser (1951) recognized <strong>the</strong> Pseud<strong>of</strong>usulina Horizon<br />
beneath <strong>the</strong> Schwagerina Horizon in association with primitive species <strong>of</strong> Triticites. In<br />
<strong>the</strong> "Pseud<strong>of</strong>usulina Horizon", <strong>the</strong> earliest pseud<strong>of</strong>usulinids, i.e. Pseud<strong>of</strong>usulina krotowi<br />
(Schellwien) and Pseud<strong>of</strong>usulina paragregaria Rauser occur. Naoumova and Rauser<br />
(1964) reported <strong>the</strong> occurrence <strong>of</strong> two different types <strong>of</strong> <strong>the</strong>se Pseud<strong>of</strong>usulina from<br />
different stratigraphic horizons. Because <strong>of</strong> different reports, <strong>the</strong> correlation <strong>of</strong> <strong>the</strong><br />
Pseud<strong>of</strong>usulina Zone is very difficult. An urgent task is <strong>the</strong> clarification <strong>of</strong> <strong>the</strong> origin<br />
and phylogeny <strong>of</strong> Pseud<strong>of</strong>usulina.<br />
The present Pseud<strong>of</strong>usulina vulgaris Zone corresponds to <strong>the</strong> Pseud<strong>of</strong>usulina vulgaris<br />
Zone (M. Ota, 1977), <strong>the</strong> Pseud<strong>of</strong>usulina vulgaris Subzone (Hasegawa, 1988), <strong>the</strong><br />
Pseud<strong>of</strong>usulina ex. gr. vulgaris Zone (Ueno, 1989), <strong>the</strong> Chalaroschwagerina vulgaris Zone<br />
(Ishii, 1990), <strong>the</strong> Paraschwagerina akiyoshiensis-Pseud<strong>of</strong>usulina firm Zone, <strong>the</strong> Robusto-
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 67<br />
schwagerina schellwieni pamirica-Schwagerina krotowi Zone and <strong>the</strong> Robustoschwagerina<br />
schellwieni schellwieni-Pseud<strong>of</strong>usulina vulgaris vulgaris Zone (Watanabe, 1991), and <strong>the</strong><br />
Dutkevitchia splendida Zone and Pseud<strong>of</strong>usulina vulgaris Zone (Ozawa and Kobayashi,<br />
1990).<br />
-3-(2). Correlation (International)<br />
In this chapter, tentative correlation between <strong>the</strong> investigated AK area and <strong>the</strong><br />
reference sections is examined. The name <strong>of</strong> <strong>the</strong> Carboniferous is derived from<br />
England, and <strong>the</strong> name <strong>of</strong> Permian from "Perm" to <strong>the</strong> west <strong>of</strong> <strong>the</strong> Ural Mountains.<br />
The Carboniferous and Permian Systems were established in different areas with<br />
different facies. There is so far no consensus <strong>of</strong> <strong>the</strong> definition <strong>of</strong> <strong>the</strong> boundary<br />
between <strong>the</strong> two systems. Therefore, each worker has applied his own definition to<br />
each stratigraphical division. Even in <strong>the</strong> stratotype, several proposals for its<br />
division are present. Because <strong>of</strong> this situation, <strong>the</strong> refinement <strong>of</strong> biostratigraphic<br />
units and accurate international correlation <strong>of</strong> <strong>the</strong> Upper Carboniferous and Lower<br />
Permian seems to be difficult and chaotic.<br />
The following zones along AK Traverse are tentatively correlated with <strong>the</strong><br />
biostratigraphic units in <strong>the</strong> reference sections (Fig. 25).<br />
1. Pseud<strong>of</strong>usulinella hidaensis Zone<br />
This zone is characterized by Pseud<strong>of</strong>usulinella hidaensis (Kanuma). It is accom<br />
panied by Fusulina sp. Although Ozawa and Kobayashi (1990) first introduced <strong>the</strong><br />
Pseud<strong>of</strong>usulinella hidensis Zone, this zone is not confirmed in many areas. The<br />
Pseud<strong>of</strong>usulinella hidaensis Zone is correlative with <strong>the</strong> bed over <strong>the</strong> Fusulinella Zone.<br />
Wilde (1971, 1975, 1984) classified Pseud<strong>of</strong>usulinella into four specific groups (<strong>Group</strong><br />
I: elongate-fusiform species with perched chomata, <strong>Group</strong> II: small, very slenderfusiform<br />
species with perched chomata, <strong>Group</strong> III: intermediate, thickly fusiform<br />
species with perched chomata, <strong>Group</strong> IV: large, thickly fusiform species with massive<br />
chomata). Pseud<strong>of</strong>usulinella hidaensis (Kanuma) probably belongs to <strong>Group</strong> I: Species<br />
with elongate-fusiform shell with perched chomata. This zone is possibly correlated<br />
with his Zone A and Zone 1 (Wilde, 1984). Ross (1984) noticed that Pseud<strong>of</strong>usu<br />
linella is sometimes accompanied by lower Permian Schwagerina, and <strong>the</strong>se species <strong>of</strong><br />
Pseud<strong>of</strong>usulinella may be relicts <strong>of</strong> <strong>the</strong>ir Carboniferous ancestors. Gobbett (1973)<br />
emphasized that Pseud<strong>of</strong>usulinella belongs to an element <strong>of</strong> <strong>the</strong> boreal fauna and <strong>the</strong><br />
occurrence is confined to <strong>the</strong> Lower Permian. Rui, Ross and Nassichuk (1991)<br />
discussed <strong>the</strong> paleobiogeography <strong>of</strong> late Moscovian (Desmoinesian) age and discrim<br />
inated four climatic zones and fusulinacean provinces. They mentioned that both<br />
Wedekindellina and Pseudoendothyra are representative <strong>of</strong> <strong>the</strong> Arctic province, whereas<br />
Beedeina, Fusulina, and Neostaffella are characteristic genera <strong>of</strong> <strong>the</strong> Tethyan province.<br />
Beedeina was not found along AK Traverse and JI Traverse, and <strong>the</strong> problem <strong>of</strong> <strong>the</strong><br />
faunal province <strong>of</strong> <strong>the</strong> Pseud<strong>of</strong>usulinella hidaensis Zone and its detailed stratigraphic<br />
position continues to be unclear. However, this zone is possibly correlated with <strong>the</strong><br />
preceding Fusulina-Beedeina Zone and <strong>the</strong> bed under <strong>the</strong> Zone 1 and Zone A by Wilde
68 Yasuhiro Ota<br />
(1984).<br />
2. Protriticites matsumotoi Zone (s. 1.)<br />
This zone is characterized by <strong>the</strong> occurrence <strong>of</strong> Protriticites matsumotoi (Kanmera).<br />
The upper part <strong>of</strong> this zone in <strong>the</strong> first sequence contains Quasifusulinoides sp. A. The<br />
distribution <strong>of</strong> Quasifusulinoides sp. A is definite, so <strong>the</strong> present zone is tentatively<br />
subdivided into two zones <strong>the</strong> lower, <strong>the</strong> Protriticites matsumotoi Zone (s. s.) and <strong>the</strong><br />
upper, <strong>the</strong> Quasifusulinoides sp. A Zone.<br />
2-(l). Protriticites matsumotoi Zone (s. s.)<br />
This zone is defined by <strong>the</strong> occurrence <strong>of</strong> characteristic species, Protriticites<br />
matsumotoi (Kanmera). This zone is correlative with beds <strong>of</strong> o<strong>the</strong>r areas, bearing<br />
Protriticites. Davydov (1990) showed a lineage <strong>of</strong> Fusulinella- Protriticites-Montiparus-<br />
Rauserites and established <strong>the</strong> Protriticites pseudomontiparus-Obsoletes obsoletus Zone over<br />
<strong>the</strong> Fusulinella bocki-Fusulina eopulchra-Fusulina cylindrica Zone. The Protriticites matsumo<br />
toi Zone is correlated with <strong>the</strong> Protriticites pseudomontiparus Zone (Davydov, 1990) from<br />
<strong>the</strong> associated fusulinaceans, such as Obsoletes obsoletus (Schellwien). Ross and<br />
Ross (1985b, 1988) recognized <strong>the</strong> Obsoletes obsoletus Zone under <strong>the</strong> Quasifusulinoides-<br />
Protriticites pseudomontiparus Zone. Ozawa and Kobayashi (1990) also discriminated<br />
<strong>the</strong> Obsoletes obsoletus Zone under <strong>the</strong> Protriticites subschwagerinoides Zone in <strong>the</strong> <strong>Akiyoshi</strong><br />
<strong>Limestone</strong> <strong>Group</strong>. In <strong>the</strong> AK area, Obsoletes obsoletus (Schellwien) was found<br />
within <strong>the</strong> biohorizon <strong>of</strong> <strong>the</strong> first appearance <strong>of</strong> Protriticites matsumotoi (Kanmera).<br />
Watanabe (1991) established <strong>the</strong> Obsoletes obsoletus Zone which is correlative with <strong>the</strong><br />
Protriticites matsumotoi Zone (s. 1.). Davydov (1990) proposed that <strong>the</strong> boundary<br />
between <strong>the</strong> Middle and Upper Carboniferous should be drawn at <strong>the</strong> biohorizon<br />
which is characterized by <strong>the</strong> first appearance <strong>of</strong> Protriticites. Rauser and Shcherbovich<br />
(1974) drew <strong>the</strong> boundary between <strong>the</strong> Moscovian and Kassimovian Stage at<br />
<strong>the</strong> lower boundary <strong>of</strong> <strong>the</strong> Protriticites Zone. Ross and Ross (1985b, 1988) recognized<br />
<strong>the</strong> Fusulina cylindrica-Protriticites ovoides Zone under <strong>the</strong> Obsoletes obsoletus Zone.<br />
The present Protriticites matsumotoi Zone (s. s.) is correlative with <strong>the</strong> lower part <strong>of</strong><br />
<strong>the</strong> Protriticites pseudomontiparus-Obsoletes obsoletus Zone (Leven, 1979, 1980a, 1981;<br />
Leven and Shcherbovich, 1978; Winkler, 1990), <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Eowaeringella<br />
Zone (Wilde, 1984), <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Quasifusulinoides, Eowaeringella, Oketaella<br />
Zone (Ross and Ross, 1985b, 1987, 1988), <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Protriticites sub<br />
schwagerinoides Zone (Zhou et al., 1987), <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Protriticites-Obsoletes<br />
assemblage Zone (Zhang, 1983, 1991) and <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Obsoletes-Montiparus<br />
Subzone (Ding et al., 1991).<br />
2-(2). Quasifusulinoides sp. A Zone<br />
This zone is tentatively defined by <strong>the</strong> first occurrence <strong>of</strong> Quasifusulinoides. The<br />
name Quasifusulinoides was first introduced as Fusulina ex. gr. quasifusulinoides- Quasi<br />
fusulinoides- Quasifusulina in <strong>the</strong> table <strong>of</strong> M. -Maklay, Rauser and Rozovskaya<br />
(1958). After <strong>the</strong>n, Quasifusulinoides was described by Rauser and Fursenko (1959)<br />
with Pseudotriticites fusiformis Rozovskaya, 1952 as <strong>the</strong> type species. Chen (1963)
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 69<br />
and Nikitina (1969) treated Quasifusulinoides as a subgenus <strong>of</strong> Fusulina. M. -Maklay<br />
(1963) considered this genus as a synonym <strong>of</strong> Pseudotriticites. According to Thomp<br />
son (1964), <strong>the</strong> difference between Quasifusulina Chen, 1934 and Quasifusulinoides<br />
cannot be recognized. Sheng, Zhang and Wang (1988) noticed that Quasifusuli<br />
noides should be included in Fusulina. Rozovskaya (1975) treated Quasifusulinoides as<br />
a valid name, and Pseudotriticites as a synonym <strong>of</strong> Fusulina. Ueno (1991b) stated that<br />
Quasifusulinoides could be distinguished from Fusulina by its wall with fine perforation<br />
and its younger stratigraphic occurrence than <strong>the</strong> latter. Ginkel and Villa (1991)<br />
agreed to treat Quasifusulinoides as Fusulina (Quasifusulinoides). In short, <strong>the</strong> differ<br />
ences between Fusulina and Quasifusulinoides were treated as those <strong>of</strong> subgeneric level.<br />
Collected specimens <strong>of</strong> Quasifusulinoides sp. A from AK Traverse have advanced wall<br />
with tectum, "pro<strong>the</strong>ca" and inner tectorium, and <strong>the</strong> wall structure is similar to that<br />
<strong>of</strong> <strong>the</strong> genus Fusulina. Thus Quasifusulinoides is considered to belong to Fusulininae.<br />
Fur<strong>the</strong>rmore, <strong>the</strong> stratigraphic occurrence is higher than that <strong>of</strong> Fusulina, because<br />
Quasifusulinoides sp. A was found above <strong>the</strong> level <strong>of</strong> <strong>the</strong> first appearance <strong>of</strong> Protriticites<br />
matsumotoi (Kanmera). As <strong>the</strong> distribution <strong>of</strong> this zone is narrow and restricted,<br />
detailed correlation is difficult. However, Davydov (1990) noticed <strong>the</strong> coccurrence<br />
<strong>of</strong> Quasifusulinoides with Fusulinella and Protriticites, and he proposed <strong>the</strong> boundary<br />
between <strong>the</strong> Middle and Upper Carboniferous at a level <strong>of</strong> <strong>the</strong> first appearance <strong>of</strong><br />
Protriticites. Therefore, this zone is correlative with <strong>the</strong> Protriticites pseudomontiparus-<br />
Obsoletes obsoletus Zone. Ross and Ross (1985b, 1987, 1988) recognized <strong>the</strong> Quasifusu<br />
linoides Zone and Protriticites pseudomontiparus Zone over <strong>the</strong> Obsoletes obsoletus Zone in<br />
N. W. Europe, Moscow Basin and sou<strong>the</strong>rn Ural. The present Quasifusulinoides sp.<br />
A Zone is correlated with <strong>the</strong> above Quasifusulinoides Zone and Protriticites pseudomonti<br />
parus Zone, and more probably with <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Protriticites pseudomontiparus-<br />
Obsoletes obsoletus Zone <strong>of</strong> Russia (Leven, 1980a, b, 1981; Leven and Shcherbovich,<br />
1978; Winkler, 1990), <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Eowaeringella Zone <strong>of</strong> U. S. A. (Wilde,<br />
1984), <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Quasifusulinoides, Eowaeringella, Oketaella Zones <strong>of</strong> <strong>the</strong><br />
southwestern United State (Ross and Ross, 1985b, 1987, 1988), <strong>the</strong> upper part <strong>of</strong> <strong>the</strong><br />
Protriticites subschwagerinoides Zone <strong>of</strong> South China (Zhou et al., 1987), <strong>the</strong> upper part<br />
<strong>of</strong> <strong>the</strong> Protriticites-Obsoletes assemblage Zone summarized by Zhang (1983, 1991), and<br />
<strong>the</strong> middle part <strong>of</strong> <strong>the</strong> Obsoletes-Montiparus Zone <strong>of</strong> North China (Ding et al., 1991).<br />
3. Montiparus sp. A Zone<br />
The Montiparus sp. A Zone is characterized by <strong>the</strong> occurrence <strong>of</strong> Montiparus, and<br />
correlated with <strong>the</strong> Montiparus Zone in o<strong>the</strong>r areas. Zhang (1984) divided <strong>the</strong><br />
Permian in South China into <strong>the</strong> following three stages, based on <strong>the</strong> fusulinacean<br />
wall structure.<br />
(1). Pre-kerio<strong>the</strong>ca stage (Fusulina: Dalan Stage).<br />
(2). Kerio<strong>the</strong>ca stage (Montiparus, Triticites, Pseudoschwagerina, Sphaeroschwagerina,<br />
Robustoschwagerina: a. Mapingian Stage; Pseud<strong>of</strong>usulina: b. Xiangzhongian Stage;<br />
Misellina: c. Qixian Stage; Cancellina, Neoschwagerina, Yabeina: d. Maokouan Stage).
70 Yasuhiro Ota<br />
(3). Post-kerio<strong>the</strong>ca stage (Codon<strong>of</strong>iisiella: a. Sanyangian Stage; Palae<strong>of</strong>usulina: b.<br />
Changxingian Stage). Zhang insisted that <strong>the</strong> base <strong>of</strong> <strong>the</strong> Permian System should<br />
be placed at <strong>the</strong> base <strong>of</strong> (2)-a: Mapingian Stage, and it was reasonable to draw <strong>the</strong><br />
boundary based on <strong>the</strong> evolutionary stage, i.e. <strong>the</strong> development <strong>of</strong> kerio<strong>the</strong>ca, and<br />
this was suitable for establishing <strong>the</strong> biostratigraphic boundary. According to<br />
Zhang (1984), <strong>the</strong> most primitive fusulinacean with kerio<strong>the</strong>ca is Montiparus, but he<br />
did not remark on Protriticites. The problems <strong>of</strong> <strong>the</strong> "Protriticites-type wall" still<br />
remain in question. The present zone's leading fossil belongs to Montiparus, and thus<br />
<strong>the</strong> zone is correlative with <strong>the</strong> Lower Permian Mapingian (Zhang, 1984), but <strong>the</strong><br />
correlation based on <strong>the</strong> first appearance<strong>of</strong> kerio<strong>the</strong>ca is very difficult. Ross (1967,<br />
1973) pointed out that <strong>the</strong> rapid evolution <strong>of</strong> fusulinaceans in <strong>the</strong> Eurasian Arctic<br />
province had produced a series <strong>of</strong> early schwagerinid genera such as Protriticites,<br />
Montiparus, Obsoletes and Triticites. Triticites was considered to be <strong>the</strong> only genus <strong>of</strong><br />
this series which had successfully invaded in <strong>the</strong> mid-continent province. In short,<br />
<strong>the</strong> genera Obsoletes, Protriticites and Montiparus are representative <strong>of</strong> <strong>the</strong> Eurasian-<br />
Andean province and <strong>the</strong>refore <strong>the</strong> direct correlation based on <strong>the</strong>se genera is very<br />
difficult among <strong>the</strong> o<strong>the</strong>r different faunal provinces.<br />
The present Montiparus sp. A Zone corresponds to <strong>the</strong> following biohorizons by<br />
Wilde (1984): Zone 2, Triticites planus, Eotriticites; Zone 3, Kansanella, Triticites ohioensis;<br />
Zone 4, Dunbarinella, Triticites beedei- moorei- plummeri, Waeringella, Rauserites}. In<br />
addition <strong>the</strong> following zones by Ross and Ross (1985b, 1987, 1988), probably<br />
correspond to <strong>the</strong> present zone: <strong>the</strong> Kansanella (Lowanella) winterensis and Triticites cf.<br />
ohioensis Zones; <strong>the</strong> Triticites ohioensis, Triticites collus, and Triticites nebraskensis Zones;<br />
<strong>the</strong> Triticites primarius and Kansanella neglecta Zones; <strong>the</strong> Triticites iatensis, Triticites newelli<br />
and Kansanella (Kansanella) joensis Zones; <strong>the</strong> Triticites mcgrewensis and Dunbarinella<br />
Zones <strong>of</strong> <strong>the</strong> southwestern United State. The Montiparus montiparus Zone and <strong>the</strong><br />
Triticites acutus-Triticites quasiarcticus Zone <strong>of</strong>Russia (Winkler, 1990), <strong>the</strong> upper part <strong>of</strong><br />
<strong>the</strong> Montiparus montiparus Zone and <strong>the</strong> overlying Triticites acutus-Triticites quasiarcticus<br />
Zone <strong>of</strong> Russia (Popov et al., 1985; Chuvashov et al., 1986), <strong>the</strong> Montiparus montiparus<br />
Zone and <strong>the</strong> overlying Triticites acutus-Triticites ardicus Zone in Russia (Leven, 1980a,<br />
b, 1981; Leven and Shcherbovich, 1978) are also correlative with <strong>the</strong> present zone.<br />
The Triticites montiparus Zone in South China (Zhang et al., 1987) and <strong>the</strong> Montiparus<br />
range Zone or <strong>the</strong> Triticites acme Zone <strong>of</strong> Zhang (1983, 1991) are tentatively cor<br />
related with <strong>the</strong> present zone.<br />
4. Triticites simplex Zone(s. 1.)<br />
The Triticites simplex Zone (s. 1.) comprises <strong>the</strong> tentatively discriminated two<br />
zones: <strong>the</strong> lower, <strong>the</strong> Schwagerina sp. A Zone, and <strong>the</strong> upper, <strong>the</strong> Triticites simplex Zone<br />
(s. s.).<br />
4-(l).<br />
Schwagerina sp. A Zone<br />
This zone is characterized by <strong>the</strong> abundant occurrence <strong>of</strong> Schwagerina sp. A.<br />
The stratigraphic significance <strong>of</strong> <strong>the</strong> genus Schwagerina was mentioned by many
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 71<br />
authors, for example, Dunbar and Skinner (1936), Dunbar (1958), Ross (1963b),<br />
Skinner and Wilde (1965) and Rauser and Shcherbovich (1970). In 1954,<br />
opinion 213 designated <strong>the</strong> type species <strong>of</strong> Schwagerina sensu Moller, 1877 with<br />
Borelis princeps Ehrenberg, 1842= Ehrenberg, 1854 sensu Dunbar and Skinner,<br />
1936, non Schwagerina moelleri Rauser, 1937= Schwagerina princeps (Ehrenberg) sensu<br />
Moller, 1878. In Japan, many workers use <strong>the</strong> generic name Schwagerina sensu by<br />
Dunbar and Skinner (1936, 1937), but internationally, two types and senses for<br />
Schwagerina are apparently present. In short, two species <strong>of</strong> <strong>the</strong> Schwagerina are used<br />
for <strong>the</strong> type species, namely Schwagerina moelleri Rauser, 1936 = princeps (Ehrenberg,<br />
1942) sensu Moller, 1878, and Schwagerina sensu Moller, 1877, based on <strong>the</strong><br />
reexamination <strong>of</strong> Borelis princeps Ehrenberg by Dunbar and Skinner (1936). Wilde<br />
(1984) maintained that Rugos<strong>of</strong>usulina Rauser, 1938 is a synonym <strong>of</strong> Pseud<strong>of</strong>usulina<br />
Dunbar and Skinner, and numerous workers in C. I. S. had included Schwagerina in<br />
Pseud<strong>of</strong>usulina. Zhang (1991) noticed that <strong>the</strong> first appearance <strong>of</strong> Schwagerina was<br />
recognized at <strong>the</strong> base <strong>of</strong> <strong>the</strong> Triticites stuckenbergi Zone in Russia. Therefore, <strong>the</strong><br />
present Schwagerina sp. A Zone is correlative with <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> Triticites<br />
stuckenbergi Zone. Wilde (1984) correlated <strong>the</strong> Triticites-Schwagerina Zone with a part<br />
<strong>of</strong> Triticites (a part <strong>of</strong> C3b), Rauserites stuckenbergi (C3c), Jigulites (C3d) and Daixina<br />
(C3e). Sheng, Zhang and Wang (1988) regarded Daixina as a synonym <strong>of</strong><br />
Schwagerina sensu Dunbar and Skinner, 1936. From <strong>the</strong>se facts, <strong>the</strong> first appeared<br />
biohorizon <strong>of</strong>Schwagerina probably corresponds to <strong>the</strong> base <strong>of</strong>'<strong>the</strong>Daixinafragilis Zone<br />
(Popov et al., 1985) and <strong>the</strong> Triticites stuckenbergi Zone in <strong>the</strong> o<strong>the</strong>r area. Rauser<br />
(1958) subdivided <strong>the</strong> Triticites arcticus-Triticites acutus Zone under <strong>the</strong> Triticites<br />
stuckenbergi Zone into five units as follows: (1) <strong>the</strong> Triticites irregularis-Fusiella granumoryzae<br />
unit; (2) <strong>the</strong> Triticites acutus- Triticites rossicus unit; (3) <strong>the</strong> Rugos<strong>of</strong>usulina unit; (4)<br />
<strong>the</strong> Triticitesfortissimus unit, and (5) <strong>the</strong> Triticites praeexilis unit. Of<strong>the</strong>m, <strong>the</strong> Triticites<br />
irregularis-Fusellagranum- oryzae unit contains Quasifusulina longissima (Moller). From<br />
<strong>the</strong> similarity between <strong>the</strong> obtained Quasifusulina sp. A and Quasifusulina longissima<br />
(Moller), <strong>the</strong> present Schwagerina sp. A Zone possibly corresponds to <strong>the</strong> upper<br />
Triticites arcticus-Triticites acutus Zone or <strong>the</strong> biohorizon over <strong>the</strong> latter zone. How<br />
ever, Quasifusulina sp. A has a more advanced form than Quasifusulina longissima<br />
(Moller), and <strong>the</strong> first appearance <strong>of</strong> Schwagerina seems to coincide with <strong>the</strong> lower<br />
boundary <strong>of</strong> <strong>the</strong> Triticites siuckenbergi Zone. Taking this evidence into consideration,<br />
<strong>the</strong> Schwagerina sp. A Zone probably corresponds to <strong>the</strong> Triticites stuckenbergi Zone in<br />
o<strong>the</strong>r areas, or Zone 5, <strong>the</strong> lower part <strong>of</strong><strong>the</strong> Triticites-Schwagerina Zone (Wilde, 1984),<br />
or <strong>the</strong> Triticites callosus, Triticites cullomensis and Triticites plummeri Zones (Ross and<br />
Ross, 1985b, 1987, 1988).<br />
4-(2). Triticites simplex Zone (s. s.)<br />
This zone is characterized by <strong>the</strong> following fusulinaceans (M. Ota, 1977):<br />
Triticites simplex (Schellwien), Triticites ozawai Toriyama, Triticites montiparus (Ehren<br />
berg, 1854) sensu Moller, 1878, non Ehrenberg: Fusulina montipara (Moller, 1878)
72 Yasuhiro Ota<br />
sensu Ozawa, 1925, Triticites biconicus Toriyama, Triticites suzukii (Ozawa), Triticites<br />
noinskyi paula Toriyama, Triticites arctica (Schellwien), Quasifusulina longissima (Mol<br />
ler) and Schubertella kingi Dunbar and Skinner. The diagnostic species, Triticites<br />
simplex (Schellwien) was not found along AK Traverse and thus this zone was<br />
divided by <strong>the</strong> o<strong>the</strong>r diagnostic fusulinaceans. In this paper, <strong>the</strong> Triticites simplex<br />
Zone by M. Ota (1977) is divided into three zones, namely, <strong>the</strong> lower, <strong>the</strong> Montiparus<br />
sp. A Zone, <strong>the</strong> middle, <strong>the</strong> Schwagerina sp. A Zone, and <strong>the</strong> upper, <strong>the</strong> Triticites<br />
simplex Zone (s. s.). The Montiparus sp. A Zone probably corresponds to <strong>the</strong> stratigraphically<br />
lower biohorizon, bearing Triticites montiparus sensu Ozawa and Quasifusu<br />
lina longissima (Moller). The Schwagerina sp. A Zone is correlated with <strong>the</strong><br />
biohorizon <strong>of</strong> Triticites biconicus Toriyama. The Triticites simplex Zone (s. s.) corres<br />
ponds to <strong>the</strong> biohorizon<strong>of</strong> Triticites ozawai Toriyama. Therefore, <strong>the</strong> Triticites simplex<br />
Zone (s. s.) in this paper is correlated with <strong>the</strong> upper part <strong>of</strong> <strong>the</strong> Triticites simplex Zone<br />
(M. Ota, 1977), a part <strong>of</strong> <strong>the</strong> Triticites-Schwagerina Zone, <strong>the</strong> upper <strong>of</strong> Zone 5, and 6<br />
(Wilde, 1984), and <strong>the</strong> Triticites subventricosus, Triticites whetstonensis, Schubertella<br />
whetensis Zones, and <strong>the</strong> Leptotriticites americana, Triticites ventricosus, Schwagerina cf.<br />
Schwagerina longissimoidea Zones (Ross and Ross, 1985b, 1987, 1988).<br />
5. Pseudoschwagerina muong<strong>the</strong>nsis Zone<br />
The datum level <strong>of</strong> this zone is well defined by <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong> inflated<br />
schwagerinid, Pseudoschwagerina. This zone is characterized by Pseudoschwagerina<br />
muong<strong>the</strong>nsis (Deprat) and <strong>the</strong> base coincides with <strong>the</strong> biohorizon bearing Pseudo<br />
schwagerina morikawai Igo. Hence, this biohorizon is correlated with that <strong>of</strong> <strong>the</strong> in<br />
flated schwagerinids.<br />
Inflated schwagerinids have been studied by many paleontologists for a long<br />
time. The following important studies on inflated schwagerinids should be men<br />
tioned: Dunbar and Skinner (1936, 1937), Dunbar (1958), Rauser (1959, 1960), M.<br />
-Maklay (1959), Ross (1962, 1963a, b, 1964, 1967, 1972a, 1973, 1982), Tikhvinskiy<br />
(1965), Rauser and Shcherbovich (1958, 1970), Sheng, Wang and Zhong (1984),<br />
Davydov (1984), Leven (1987) and Yang and Hao (1991). Dunbar and Skinner<br />
(1936) defined Schwagerina and established two new genera, namely, Pseudoschwagerina<br />
and Paraschwagerina. Then, <strong>the</strong>y designated Schwagerina uddeni Beede and Kniker,<br />
1924, as <strong>the</strong> type species <strong>of</strong> Pseudoschwagerina and remarked that <strong>the</strong> proloculus <strong>of</strong> this<br />
genus is commonly large, and <strong>the</strong> whorls <strong>of</strong> <strong>the</strong>juvenarium are relatively short and<br />
thickly fusiform (pi. 11, figs. 6 and 7). Original designation <strong>of</strong> Schwagerina uddeni<br />
Beede and Kniker included both microspheric and megalospheric forms. Dunbar<br />
and Skinner (1936, plate 11, figs. 6-7; 1937, plate 50, figs. 1-10; 1937, plate 53, fig.<br />
8) regarded a typical form <strong>of</strong>Pseudoschwagerina uddeni (Beede and Kniker, 1924) sensu<br />
Dunbar and Skinner as a megalospheric form, but Schwagerina uddeni Beede and<br />
Kniker, 1924 originally includes <strong>the</strong> microspheric form also. In <strong>the</strong>ir description,<br />
Dunbar and Skinner (1936) expressed as "commonly large" for <strong>the</strong> proloculus, and<br />
<strong>the</strong>y implicitly recognized <strong>the</strong> existence <strong>of</strong> <strong>the</strong> microspheric form. Such being <strong>the</strong>
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 73<br />
case, it is preferable that Pseudoschwagerina has both <strong>the</strong> two types microspheric and<br />
megalospheric forms. Fur<strong>the</strong>rmore, <strong>the</strong> holotype <strong>of</strong> Pseudoschwagerina was designated<br />
by Thompson (1948) with <strong>the</strong> specimen figured by Beede and Kniker (pi. 6, fig. 1,<br />
axial section <strong>of</strong> microspheric form). M. -Maklay (1959) classified Schwagerinidae<br />
Dunbar and Henbest, 1930 into 10 genera, recognizing Schwagerina Moller, 1877<br />
and establishing new genera, namely Occidentoschwagerina and Sphaeroschwagerina (in<br />
1956, Sphaeroschwagerina was originally proposed by M. -Maklay, but no description<br />
was done.). Rauser and Shcherbovich (1958) recognized both Pseudoschwagerina<br />
Dunbar and Skinner, 1936 and Schwagerina Moller, 1877. Rauser (1959) treated<br />
Pseudoschwagerina Dunbar and Skinner, 1936 as distinct from Schwagerina Moller,<br />
1877 based on <strong>the</strong> form <strong>of</strong> each juvenarium. Rauser (1960) subdivided Schwagerina<br />
Moller, 1878 into five genera, and Zellia Kahler, 1937 into three groups. In<br />
addition, she established <strong>the</strong> new genus Parazellia with Fusulina muong<strong>the</strong>nsis Depart,<br />
1951 (pi. II, fig. 1) as <strong>the</strong> type species. Rauser and Fursenko (1959) also regarded<br />
Schwagerina Moller, 1877 as an independent genus and designated Schwagerina<br />
princeps sensu Moller, 1878 as <strong>the</strong> type species. Rauser and Shcherbovich (1970)<br />
discussed characters <strong>of</strong> Schwagerina Moller, 1877 and <strong>the</strong>y clearly distinguished<br />
Pseudoschwagerina Dunbar and Skinner from Schwagerina Moller.<br />
As mentioned before <strong>the</strong> type species <strong>of</strong> Schwagerina sensu Moller, 1877 is Borelis<br />
princeps Ehrenberg, 1842 without doubt. If Schwagerina moelleri Rauser, 1936 and<br />
Schwagerina moelleri Rauser, 1949 are distinguishable from Schwagerina uddeni Beede<br />
and Kniker, 1924, a new genus will be established for Schwagerina "moelleri" Rauser.<br />
Perhaps, <strong>the</strong> concept <strong>of</strong> <strong>the</strong> above new genus corresponds to that <strong>of</strong> Alpinoschwagerina<br />
Bensh, 1972. However, Alpinoschwagerina Bensh, 1972 is considered to be a synonym<br />
<strong>of</strong> Pseudoschwagerina Dunbar and Skinner, 1936. Sheng, Zhang and Wang (1988)<br />
distinguished Sphaeroschwagerina M. -Maklay, 1959 from Pseudoschwagerina Dunbar<br />
and Skinner, 1936 by its having concave pointed poles and small proloculus.<br />
However, <strong>the</strong>y treated Alpinoschwagerina Bensh as a synonym <strong>of</strong> Sphaeroschwagerina M.<br />
-Maklay, 1959. In addition, <strong>the</strong>y emphasized that Schwagerina in Russia is <strong>the</strong> same<br />
as Pseudoschwagerina Dunbar and Skinner. According to Loeblich and Tappan<br />
(1988), Sphaeroschwagerina can be distinguished from Pseudoschwagerina by its short axis.<br />
To <strong>the</strong> contrary, Alpinoschwagerina, which was established by its having a much<br />
smaller proloculus than that <strong>of</strong> Pseudoschwagerina, practically cannot be distinguished<br />
from Pseudoschwagerina Dunbar and Skinner, 1936. In a word, Alpinoschwagerina rep<br />
resents <strong>the</strong> microspheric form <strong>of</strong> Pseudoschwagerina. On <strong>the</strong> o<strong>the</strong>r hand, Davydov<br />
(1984) studied <strong>the</strong> origin <strong>of</strong> "Schwagerina" and discussed two lineages, Biwaella-<br />
Dutkevichites- Sphaeroschwagerina and Biwaella- Biwaella. Then he proposed <strong>the</strong> sub<br />
family Biwaellinae, and mentioned that <strong>the</strong> taxonomic homonym between "Schwager<br />
ina" and Pseudoschwagerina still continues. Moreover, he pointed out that <strong>the</strong><br />
overestimated "Schwagerina sensu Rauser" should be treated as Sphaeroschwagerina,<br />
which was applied to <strong>the</strong> inflated "Schwagerina" <strong>of</strong> M. -Maklay (1959). Leven
74 Yasuhiro Ota<br />
(1987) noticed that among <strong>the</strong> group <strong>of</strong> "Schwagerina", Occidentoschwagerina, Para<br />
schwagerina, Pseudoschwagerina and Zellia appeared in Asselian time, whereas Robusto<br />
schwagerina in Sakmarian time, and Orientoschwagerina appeared in Murgabian time.<br />
Additionally, he mentioned about <strong>the</strong> origin <strong>of</strong> Schubertellidae Skinner, 1931 and<br />
agreed with <strong>the</strong> Davydov's opinion in 1984, in which schubertellid was regarded as<br />
an ancestor <strong>of</strong> Biwaella. Davydov (1988b) regarded <strong>the</strong> occurrence <strong>of</strong> Schwagerina<br />
sensu Davydov (1988b) as being at <strong>the</strong> lower horizon <strong>of</strong> <strong>the</strong> Daixina (Ultradaixina)<br />
postsokensis Zone.<br />
As a result, <strong>the</strong> collected megalospheric species at AK 26 along AK Traverse<br />
was discriminated as Pseudoschwagerina muong<strong>the</strong>nsis (Deprat) because it has a relative<br />
ly large proloculus, thick spiro<strong>the</strong>ca and inflated outline. Loeblich and Tappan<br />
(1988) and Sheng, Zhang and Wang (1988) also regarded it as Pseudoschwagerina.<br />
In <strong>the</strong> AK area, <strong>the</strong> collected inflated schwagerinids with microspheric proloculus are<br />
closely similar to a variation <strong>of</strong> Pseudoschwagerina morikawai Igo, 1957. Judging from<br />
<strong>the</strong> morphology <strong>of</strong> Pseudoschwagerina, <strong>the</strong> collected specimen was identifiable as<br />
Pseudoschwagerina morikawai Igo. The present Pseudoschwagerina muong<strong>the</strong>nsis Zone is<br />
approximately correlated with <strong>the</strong> biozone between <strong>the</strong> first occurrence <strong>of</strong> inflated<br />
schwagerinids and <strong>the</strong> occurrence <strong>of</strong> typical Pseud<strong>of</strong>usulina in o<strong>the</strong>r areas.<br />
5. Pseud<strong>of</strong>usulina vulgaris Zone<br />
The characteristic species<strong>of</strong> this zone is Pseud<strong>of</strong>usulina vulgaris s. s. (Schellwien,<br />
1909). Internationally, several variations <strong>of</strong> Pseud<strong>of</strong>usulina are present. Naoumova<br />
and Rauser (1964) reported two different types <strong>of</strong> Pseud<strong>of</strong>usulina at different stratigra<br />
phic positions. Rauser (1951) reported a primitive type <strong>of</strong> "Pseud<strong>of</strong>usulina" fauna<br />
from <strong>the</strong> "Pseud<strong>of</strong>usulina Horizon" (C3II) under <strong>the</strong> Schwagerina Horizon (C3III).<br />
According to this, Pseud<strong>of</strong>usulina ex. gr. vulgaris Schellwien, 1908, occurs from an<br />
older horizon than <strong>the</strong> Schwagerina Horizon. Davydov (1988a, b), reexamined<br />
pseud<strong>of</strong>usulinids and discussed <strong>the</strong>ir origin. Zhang (1983, 1991) made <strong>the</strong> bioho<br />
rizon <strong>of</strong> <strong>the</strong> first appearance <strong>of</strong> <strong>the</strong> "Pseud<strong>of</strong>usulina" coincide with <strong>the</strong> lower boundary<br />
<strong>of</strong> <strong>the</strong> Daixina sokensis Zone. If this is so, Pseud<strong>of</strong>usulina appears under <strong>the</strong> Pseudo<br />
schwagerina Zone. Pseud<strong>of</strong>usulina was first established by Dunbar and Skinner (1931)<br />
with Pseud<strong>of</strong>usulina huecoensis Dunbar and Skinner, 1931 as <strong>the</strong> type species. Pseudo<br />
fusulina, at one time, was regarded as a synonym <strong>of</strong> Schwagerina (Dunbar and Skin<br />
ner, 1936). Rauser (1937) proposed <strong>the</strong> new genus Rugos<strong>of</strong>usulina with Alveoli prisca<br />
Ehrenberg em. Moeller as <strong>the</strong> type species. Thompson (1948) designated <strong>the</strong><br />
holotype <strong>of</strong> Pseud<strong>of</strong>usulina huecoensis (plate 1, figure 5, Dunbar and Skinner, 1931).<br />
Rauser (1949) studied Pseud<strong>of</strong>usulina Dunbar and Skinner, 1931 and referred<br />
Fusulina moelleri Schellwien, 1908 to Pseud<strong>of</strong>usulina. Since <strong>the</strong>n, <strong>the</strong> confusion be<br />
tween Pseud<strong>of</strong>usulina and "Schwagerina" has continued. Skinner and Wilde (1965,<br />
1966) revised <strong>the</strong> definition <strong>of</strong> <strong>the</strong> genus Pseud<strong>of</strong>usulina, because <strong>of</strong> <strong>the</strong> existence <strong>of</strong><br />
rugosity in Pseud<strong>of</strong>usulina huecoensis Dunbar and Skinner, 1931. At <strong>the</strong> same time,<br />
<strong>the</strong>y established <strong>the</strong> new genus Chalaroschwagerina characterized by having a distinct
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 75<br />
phreno<strong>the</strong>cae. Rozovskaya (1975) treated Rugos<strong>of</strong>usulina Rauser, 1937 as a valid<br />
genus, but did not recognized Chalaroschwagerina Skinner and Wilde, 1965 because<br />
<strong>the</strong> latter genus was treated as a synonym <strong>of</strong> Pseud<strong>of</strong>usulina Dunbar and Skinner.<br />
Thompson (1964) accepted both Pseud<strong>of</strong>usulina Dunbar and Skinner and Rugos<strong>of</strong>usu<br />
lina Rauser. In Loeblich and Tappan (1988) Rugos<strong>of</strong>usulina Rauser was treated as<br />
a synonym <strong>of</strong> Pseud<strong>of</strong>usulina Dunbar and Skinner, but Chalaroschwagerina Skinner and<br />
Wilde, 1965 was treated as valid. Sheng, Zhang and Wang (1988) also recognized<br />
both Pseud<strong>of</strong>usulina and Chalaroschwagerina as distinct genera. They additionally<br />
commented that Chalaroschwagerina has a special form which is distinct from <strong>the</strong> genus<br />
Pseud<strong>of</strong>usulina. They also pointed out that <strong>the</strong> sense <strong>of</strong> Pseud<strong>of</strong>usulina in Russia was a<br />
mixed one <strong>of</strong> Schwagerina sensu Dunbar and Skinner (1936) and Pseud<strong>of</strong>usulina sensu<br />
Dunbar and Skinner (1931). Consequently, <strong>the</strong> stratigraphic position and defini<br />
tion <strong>of</strong> "Pseud<strong>of</strong>usulina" are ambiguous and its correlation is very difficult at present.<br />
According to Leven (1970), <strong>the</strong> following species are <strong>the</strong> index fusulinaceans <strong>of</strong><br />
Upper Artinskian time: Misellina (Brevaxina) dyhrenfurtki (Dutk.), Darvasites ordinatus<br />
(Chen), Darvasites contractus (Schellw. and Dyhr.), Rugos<strong>of</strong>usulina vulgariformis Kalm.,<br />
Pseud<strong>of</strong>usulina kraffti (Schellw. and Dyhr.) and Pseud<strong>of</strong>usulina fusiformis (Schellw.<br />
and Dyhr.), Pseud<strong>of</strong>usulina exigua (Schellw. and Dyhr.). Thus, <strong>the</strong> upper limit <strong>of</strong><br />
<strong>the</strong> present Pseud<strong>of</strong>usulina vulgaris Zone becomes older than <strong>the</strong> base <strong>of</strong> <strong>the</strong> Upper<br />
Artinskian. Leven (1975) insisted that <strong>the</strong> Sakmarian Stage with robustoschwagerinids<br />
and paraschwagerinids must be assigned to <strong>the</strong> deposits in <strong>the</strong> interval between<br />
<strong>the</strong> lower, <strong>the</strong> Schwagerina Bed and <strong>the</strong> upper, <strong>the</strong> Pseud<strong>of</strong>usulina Bed with Pseud<strong>of</strong>usuli<br />
na vulgaris-Pseud<strong>of</strong>usulina kraffti. Leven (1979) proposed that <strong>the</strong> Bolorian Stage is<br />
divided into <strong>the</strong> upper, <strong>the</strong> Misellina parvicostata Zone and <strong>the</strong> lower, <strong>the</strong> Misellina<br />
dyhrenfurtki Zone. He mentioned that <strong>the</strong> Bolorian species, comparing with <strong>the</strong>ir<br />
immediate ancestors, have larger dimensions, and more intense and regular folding <strong>of</strong><br />
septa and cuniculus. Fur<strong>the</strong>rmore, he concluded that <strong>the</strong> characteristic fusulina<br />
ceans <strong>of</strong> <strong>the</strong> Pseud<strong>of</strong>usulina vulgaris Zone, <strong>the</strong> Pseud<strong>of</strong>usulina fusiformis Zone, and <strong>the</strong><br />
Pseud<strong>of</strong>usulina ambigua Zone (Kanmera and Mikami, 1965a, b), <strong>the</strong> Pseud<strong>of</strong>usulina<br />
ambigua Zone <strong>of</strong> Toriyama (1958) and <strong>the</strong> Pseud<strong>of</strong>usulina kraffti magna Zone, renamed<br />
by Hasegawa (1963), were similar to those which accompanied misellinids in<br />
Darvaz, and fur<strong>the</strong>r more that <strong>the</strong> Parafusulina kaerimizensis Subzone with misellinids<br />
(Nogami, 1961) is probably correlated with <strong>the</strong> Upper Kubergandian Stage. Leven<br />
(1980b) correlated <strong>the</strong> Yakhtashian Stage, named after Mt. Yakhtash in Darvaz with<br />
<strong>the</strong> Pseud<strong>of</strong>usulina vulgaris Subzone (Toriyama, 1958). Leven and Shcherbovich<br />
(1980) pointed out that Pseud<strong>of</strong>usulina vulgaris (Deprat) is a primitive species regarded<br />
as Chalaroschwagerina. From <strong>the</strong>se facts and studies, <strong>the</strong> present Pseud<strong>of</strong>usulina vulgaris<br />
Zone probably corresponds to <strong>the</strong> lower part <strong>of</strong> <strong>the</strong> "Chalaroschwagerina" vulgaris Zone<br />
or <strong>the</strong> biohorizon under <strong>the</strong> latter zone (Leven and Shcherbovich, 1978), and <strong>the</strong><br />
Pseud<strong>of</strong>usulina vulgaris-Laxifusulina iniqua Zone (Zhou et al. 1987), <strong>the</strong> Pseudoschwagerina<br />
convexa, Pseud<strong>of</strong>usulina nelsoni, Schwagerina diversiformis, and Eoparafusulina Zones (Ross
76 Yasuhiro Ota<br />
and Ross, 1985b, 1987, 1988).<br />
-II-4. Conclusion<br />
The investigated AK area was selected in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>-dai Museum <strong>of</strong><br />
Natural History, sou<strong>the</strong>rn part <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> Plateaus (s. s.).<br />
Materials from 56 localities were collected along AK Traverse. 15 genera and<br />
44 species <strong>of</strong> fusulinaceans were described. <strong>Limestone</strong>s on AK Traverse are mainly<br />
composed <strong>of</strong> alternating beds with sparry calcite cements and micritic or micrite<br />
matrices, and are intercalated with <strong>the</strong> black to dark brown colored limestones.<br />
These limestones yield abundant fusulinaceans and algae, and interbedded with <strong>the</strong>m<br />
are ra<strong>the</strong>r coarse limestones containing fragments <strong>of</strong> crinoids and bryozoans. From<br />
<strong>the</strong>se studies, <strong>the</strong> following six zones including tentatively discriminated four zones in<br />
a narrow sense are recognized along AK Traverse: 1. Pseud<strong>of</strong>usulinella hidaensis Zone,<br />
2. Protriticites matsumotoi Zone (s. 1.), 2-(l). Protriticites matsumotoi Zone (s. s.), 2-(2).<br />
Quasifusulinoides sp. A Zone, 3. Montiparus sp. A Zone, 4. Triticites simplex Zone (s. 1.),<br />
4-(l). Schwagerina sp. A Zone, 4-(2). Triticites simplex Zone (s. s.), 5. Pseudoschwagerina<br />
muong<strong>the</strong>nsis Zone, 6. Pseud<strong>of</strong>usulina vulgaris Zone. The distribution <strong>of</strong> <strong>the</strong>se zones<br />
indicates that <strong>the</strong> limestones in this area have a general nor<strong>the</strong>astern strike and <strong>the</strong><br />
younger zones are successively distributed toward <strong>the</strong> northwest. Fur<strong>the</strong>rmore, <strong>the</strong><br />
limestones along AK Traverse are recognizableas <strong>the</strong> alternations <strong>of</strong> limestone <strong>of</strong> two<br />
different sequences, probably caused by a fault <strong>of</strong> NE-SW trend (Ozawa and<br />
Kobayashi, 1990). In addition, <strong>the</strong> tentatively discriminated Quasifusulinoides sp. A<br />
Zone was not identified in <strong>the</strong> second sequence. The lower part <strong>of</strong> <strong>the</strong> overlying<br />
Montiparus sp. A Zone is composed <strong>of</strong> limestones with sparry calcite cements<br />
containing characteristic fusulinaceans similar to those <strong>of</strong> <strong>the</strong> underlying zone,<br />
namely Protriticites matsumotoi (Kanmera). The transitions from Fusulininae or<br />
Fusulinellinae to Schwagerininae are also recognizable between <strong>the</strong> Quasifusulinoides<br />
sp. A Zone or <strong>the</strong> Protriticites matsumotoi Zone (s. s.) and <strong>the</strong> Montiparus sp. A Zone.<br />
Thus, gaps might be present between <strong>the</strong> underlying Protriticites matsumotoi Zone (s. 1.)<br />
and <strong>the</strong> overlying Montiparus sp. A Zone. However, <strong>the</strong>se gaps are interpreted as <strong>of</strong><br />
small scale, because genus level transitions between zones shift gradually as<br />
mentioned above. The recognized fusulinacean zones were attempted to be corre<br />
lated with <strong>the</strong> biostratigraphic zones in <strong>the</strong> reference sections. The inflated<br />
schwagerinids have a worldwide distribution and are very useful for international<br />
correlation <strong>of</strong> <strong>the</strong> Upper Carboniferous to Lower Permian. On AK Traverse, <strong>the</strong><br />
Pseudoschwagerina muong<strong>the</strong>nsis Zone was characterized by <strong>the</strong> occurrence <strong>of</strong> Pseudos<br />
chwagerina muong<strong>the</strong>nsis (Depart) and <strong>the</strong> base <strong>of</strong> this zone was defined by <strong>the</strong> first<br />
occurrence <strong>of</strong> Pseudoschwagerina morikawai Igo. The author tentatively made <strong>the</strong><br />
basal boundary coincide with <strong>the</strong> first occurrence <strong>of</strong> pseudoschwagerinids in o<strong>the</strong>r<br />
areas.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 77<br />
-III-l. The third investigated area, Mt. Maruyama, Mine City, Yamaguchi<br />
Prefecture<br />
The third investigated area, Mt. Maruyama, is located in Mine City, Yamaguchi<br />
Prefecture. In this chapter, <strong>the</strong> author would like to discuss <strong>the</strong> phylogenetic<br />
consideration <strong>of</strong> <strong>the</strong> species relative to Protriticites yanagidai Ota and Protriticites<br />
masamichii Ota from <strong>the</strong> Mt. Maruyama area.<br />
,200m-<br />
Fusulinella simplicata Subzone<br />
(Kyuma and Nishida, 1987)<br />
/<br />
Fusulinella biconica Subzone<br />
(Kyuma and Nishida, 1987)<br />
Yr-~-><br />
Pr<strong>of</strong>usulinella beppensisZone<br />
78 Yasuhiro Ota<br />
The Mt. Maruyama area is underlain by Middle to Upper Carboniferous<br />
limestones, and <strong>the</strong>se limestones generally have a nor<strong>the</strong>ast strike and a northward<br />
dip. Fur<strong>the</strong>rmore, limestones <strong>of</strong> this area are regarded as reef facies deposits and<br />
contain stromatolites and chaetetids (M. Ota, 1968). According to Kyuma and<br />
Nishida (1987), <strong>the</strong> following zones are distributed in ascending order: <strong>the</strong> Pr<strong>of</strong>usu<br />
linella beppensis Zone, <strong>the</strong> Fusulinella simplicata Subzone and <strong>the</strong> Fusulinella biconica<br />
Subzone (Fig. 26).<br />
The author measured <strong>the</strong> section along <strong>the</strong> traverse, namely MA Traverse to<br />
clarify <strong>the</strong> localities <strong>of</strong> <strong>the</strong> collected fusulinids. Locality MA 66 yields <strong>the</strong> following<br />
species: Protriticitesyanagidai Ota, Protriticites masamichii Ota, Protriticites toriyamai Ota<br />
and Protriticites aff. matsumotoi (Kanmera) mainly obtained from limestones with<br />
sparry calcite cements.<br />
<strong>Limestone</strong>s <strong>of</strong> <strong>the</strong> Mt. Maruyama area are composed <strong>of</strong> biomicrite to biomicrudite,<br />
bryozoa-crinoid biosparite, and shell-crinoid biosparrudite. New species <strong>of</strong><br />
goniatites were described in this area (Kyuma and Nishida, 1987). These sedimen<br />
tary features suggest that <strong>the</strong> limestones in this area were formed in a paleoenviron<br />
ment similar to <strong>the</strong> reef core in <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex. <strong>Limestone</strong>s near<br />
Loc. MA 66 seem to have accumulated on a reeffiat <strong>of</strong> a bypass margin between <strong>the</strong><br />
fore reef and open sea, because <strong>the</strong>y yield fragments <strong>of</strong> ammonoids and fusulinaceans<br />
(Y. Ota, 1994).<br />
Form ratio<br />
2.00 .<br />
1.00 4.00<br />
Length<br />
(mm)<br />
Fig.27. Each form ratio <strong>of</strong> <strong>the</strong> length to width. K: Protriticites afT. matsumotoi. M: Protriticites<br />
masamichii. T: Protriticites toriyamai. Y: Protriticitesyanagidai.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 79<br />
-III-2. Phylogenetic Consideration<br />
The collected species, Protriticites yanagidai Ota, Protriticites masamichii Ota,<br />
Protriticites toriyamai Ota and Protriticites aff. matsumotoi (Kanmera), are characterized<br />
by <strong>the</strong>ir small size, compared to <strong>the</strong> known species <strong>of</strong>Protriticites. Each form ratio <strong>of</strong><br />
<strong>the</strong> length to widthis shown in Fig. 27. Of <strong>the</strong>se species, Protriticites toriyamai has <strong>the</strong><br />
smallest size shell. Protriticites yanagidai and Protriticites masamichii are almost <strong>the</strong><br />
same in size. Protriticites aff. matsumotoi is about twice as large as Protriticitesyanagidai<br />
or Protriticites masamichii. Protriticitesyanagidai Ota has a small, fusiform to ellipsoidal<br />
shell, with slightly and irregularly convex lateral slopes and somewhat sharply<br />
pointed poles. The present species is closely similar to Protriticites globulus Putrya,<br />
as <strong>the</strong> type species <strong>of</strong> <strong>the</strong> genus Protriticites. Fur<strong>the</strong>rmore, it resembles Protriticites<br />
matsumotoi, which was first described as Triticites (s. 1.) by Kanmera (1955). There<br />
fore <strong>the</strong> phylogenetic line from Protriticites yanagidai Ota to Protriticites matsumotoi<br />
(Kanmera) is similar to <strong>the</strong> primitive species <strong>of</strong> Triticites (s. 1.). On <strong>the</strong> o<strong>the</strong>r hand,<br />
Protriticites masamichii Ota resembles Montiparus matsumotoi infktus, reported by<br />
Watanabe (1991) in having moderately inflated, oval to subspherical shell.<br />
Fur<strong>the</strong>rmore, this species is similar to <strong>the</strong> illustration <strong>of</strong> Montiparus montiparus shown<br />
by Rozovskaya (1950). Here, Protriticites masamichii Ota and Montiparus matsumotoi<br />
infktus <strong>of</strong> Watanabe (1991) are probably linked toge<strong>the</strong>r with a phylogenetic line<br />
(Fig. 28). From <strong>the</strong>se viewpoints, Protriticites yanagidai is considered to be in a<br />
primitive stage <strong>of</strong> <strong>the</strong> phylogenetic lines towards Protriticites matsumotoi, while Protriti<br />
cites masamichii seems to be a transitional species to Montiparus matsumotoi inflatus.<br />
In <strong>the</strong> investigatedJigoku-dani area, <strong>the</strong> limestones bearing Protriticites masamichii<br />
in <strong>the</strong> Protriticites toriyamai Subzone are successively overlain by limestones with<br />
Protriticites matsumotoi (Kanmera) in <strong>the</strong> Protriticites matsumotoi Subzone. From this<br />
field evidence and <strong>the</strong> morphological affinities, Protriticites matsumotoi is considered to<br />
be derived possibly from <strong>the</strong> primitive species <strong>of</strong> Protriticites, namely Protriticites tori<br />
yamai, Protriticites masamichii and Protriticitesyanagidai. On <strong>the</strong> o<strong>the</strong>r hand, limestones<br />
<strong>of</strong> <strong>the</strong> Protriticites matsumotoi Subzone are successively overlain by limestones with<br />
Montiparus sp. A in <strong>the</strong> Montiparus sp. A Zone at <strong>the</strong> Jigoku-dani area. In <strong>the</strong> AK<br />
area, <strong>the</strong> Protriticites matsumotoi Zone (s. s.) are overlain by <strong>the</strong> Montiparus sp. A Zone<br />
with small gaps, but <strong>the</strong> limestones are in nearly complete succession. Montiparus sp.<br />
A is closely similar to Montiparus matsumotoi inflatus <strong>of</strong> Watanabe (1991). Therefore,<br />
Montiparus sp. A and Montiparus matsumotoi infktus sensu Watanabe are possibly<br />
derived from <strong>the</strong> primitive species <strong>of</strong> Protriticites, but it is uncertain whe<strong>the</strong>r Protriticites<br />
matsumotoi is directly connected with above species <strong>of</strong> Montiparus. Incidentally,<br />
Montiparus matsumotoi inflatus <strong>of</strong> Watanabe (1991) was mainly reported from <strong>the</strong> Omi<br />
<strong>Limestone</strong>, whereas Protriticites matsumotoi is from <strong>the</strong> Yayamadake <strong>Limestone</strong>. The<br />
above speciations and phyletic transitions might have resulted from <strong>the</strong> geographic<br />
isolation between <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong>, <strong>the</strong> Yayamadake and Omi <strong>Limestone</strong>s.<br />
However, <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> yields <strong>the</strong>se fusulinaceans as mentioned above and
80<br />
Yasuhiro Ota<br />
Yayamadake<br />
Geographic Speciation <br />
or<br />
Chronologic speciation 7<br />
Omi<br />
Fig. 28. Phylogenetic consideration. 1. Protriticites yanagidai Y'. Ota. 2. Protriticites globulus<br />
Putrya. 3. Protriticites matsumotoi (Kanmera). 4. Protriticites masamichii Y. Ota. 5, 7.<br />
Montiparus matsumotoi inflatus, reported from Watanabe (1991). 6. Montiparus montiparus<br />
from Rozovskaya (1950). 8. Obsoletes obsoletus (Schellwien).<br />
nearly complete successions <strong>of</strong> limestones from <strong>the</strong> Protriticites Zone to <strong>the</strong> Montiparus<br />
Zone are confirmed without a remarkable hiatus. Hence, <strong>the</strong> above speciations and<br />
phyletic transitions have a great possibility to be <strong>the</strong> result <strong>of</strong> chronological speciation.<br />
Fur<strong>the</strong>rmore, <strong>the</strong> collected species from <strong>the</strong> Mt. Maruyama area have close<br />
affinities with Protriticites praemontiparus Zhou, Sheng and Wang, 1987 and Protriticites<br />
minor Zhou, Sheng and Wang, 1987 from eastern Yunnan, South China. The<br />
fusulinaceans in <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex probably are closely related to<br />
those <strong>of</strong> South China during this period.
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 81<br />
Consideration<br />
The purpose <strong>of</strong> this study is to reexamine <strong>the</strong> Middle Carboniferous to <strong>the</strong><br />
Lower Permian fusulinacean biostratigraphic units in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>.<br />
The details are shown in <strong>the</strong> previous chapters. Here <strong>the</strong> author would like to<br />
summarize <strong>the</strong> paleontology <strong>of</strong> <strong>the</strong> Jigoku-dani, AK and Mt. Maruyama areas, which<br />
respectively contain <strong>the</strong> characteristic fusulinacean fauna, reflecting slight differences<br />
<strong>of</strong> paleoenvironmental character.<br />
Jigoku-dani area, AK area in front <strong>of</strong> <strong>Akiyoshi</strong>-dai Museum <strong>of</strong> Natural History,<br />
and Mt. Maruyama area were selected and <strong>the</strong> field investigations were carried out.<br />
First investigated area, Jigoku-dani is located in <strong>the</strong> northwestern part <strong>of</strong> <strong>the</strong><br />
<strong>Akiyoshi</strong> Plateau (s. s.). The inverted limestones <strong>of</strong> Middle Carboniferous to <strong>the</strong><br />
Lower Permian are widely distributed in this area. The studies in this area, lead to<br />
<strong>the</strong> following conclusions: The collected materials from <strong>the</strong> measured sections, JI<br />
Traverse comprise 56 fusulinacean species including two subspecies and 23 genera.<br />
From <strong>the</strong> fusulinacean constituents and distinctions <strong>of</strong> lith<strong>of</strong>acies, limestones were<br />
tentatively divided into nine zones including seven subzones from <strong>the</strong> Middle<br />
Carboniferous to <strong>the</strong> Lower Permian. These zones are well traceable in this area.<br />
They are as follows: 1. Fusulinella biconica Zone; 2. Fusulina cf. shikokuensis Zone, 2-1.<br />
Fusulinella cf. obesa Subzone, 2-2. Pseud<strong>of</strong>usulinella hidaensis Subzone; 3. Obsoletes<br />
obsoletus Zone, 3-1. Protriticites toriyamai Subzone, 3-2. Protriticites matsumotoi Subzone;<br />
4. Montiparus sp. A Zone; 5. Triticites yayamadakensis Zone, 5-1. Triticites saurini<br />
Subzone, 5-2. Schwagerina sp. A Subzone, 5-3. Triticites biconicus Subzone; 6.<br />
Schwagerina () cf. satoi Zone; 7. Pseudoschwagerina muong<strong>the</strong>nsis Zone; 8. Pseud<strong>of</strong>usulina<br />
vulgaris globosa Zone; 9. Pseud<strong>of</strong>usulina aff. ambigua Zone. Distribution <strong>of</strong> <strong>the</strong>se zones<br />
indicates that limestones are inverted in structure. They are composed mainly <strong>of</strong><br />
micritic limestones without frame building organisms. The limestone facies suggest<br />
that <strong>the</strong>y were deposited in a relatively low energy environment like a lagoon within<br />
<strong>the</strong> <strong>Akiyoshi</strong> organic reef complex. Fur<strong>the</strong>rmore, <strong>the</strong>y were successively accumu<br />
lated without a remarkable hiatus, because no remarkable faunal break could be<br />
observed in <strong>the</strong> limestone sequence. Considerable facies changes are present near<br />
<strong>the</strong> basal boundaries <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi Zone and <strong>the</strong> Pseudoschwagerina<br />
muong<strong>the</strong>nsis Zone. <strong>Limestone</strong>s near <strong>the</strong> basal boundary <strong>of</strong> <strong>the</strong> Schwagerina () cf. satoi<br />
Zone intercalate fairly coarse grainstones with fragments <strong>of</strong> reef frame builders and<br />
<strong>the</strong> fusulinacean diversity becomes larger across <strong>the</strong> boundary. <strong>Limestone</strong>s near <strong>the</strong><br />
base <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis Zone consist <strong>of</strong> ra<strong>the</strong>r coarse grainstones<br />
with <strong>the</strong> sparry calcite cement. In this paper, <strong>the</strong> author tentatively correlates <strong>the</strong><br />
limestones <strong>of</strong> <strong>the</strong> Jigoku-dani area with Middle Carboniferous to Lower Permian<br />
strata in o<strong>the</strong>r areas <strong>of</strong> Japan and outside Japan by using <strong>the</strong> first occurrence <strong>of</strong> <strong>the</strong><br />
inflated schwagerinids, i.e. Pseudoschwagerina. The inflated schwagerinids are very<br />
useful to correlate <strong>the</strong> Upper Carboniferous and <strong>the</strong> Lower Permian, because <strong>the</strong>y are
82 Yasuhiro Ota<br />
widely distributed in many regions and are assumed to be planktonic during a part <strong>of</strong><br />
<strong>the</strong>ir life cycle. They seem to be excellent index fossils for <strong>the</strong> correlation <strong>of</strong> <strong>the</strong><br />
Upper Carboniferous to <strong>the</strong> Lower Permian. However, <strong>the</strong>y are also known to occur<br />
in distinctive facies, such as biohermal limestones. Therefore, for regional correla<br />
tion, examination <strong>of</strong> <strong>the</strong> associated fossils along with <strong>the</strong> inflated schwagerinids is<br />
indispensable.<br />
The second investigated AK area is located in front <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong>-dai Museum<br />
<strong>of</strong> Natural History. AK Traverse was measured and fossils collected along <strong>the</strong><br />
traverse. From <strong>the</strong> paleontological and lithological viewpoints, <strong>the</strong> following fusu<br />
linacean zones are tentatively discriminated in ascending order: Pseud<strong>of</strong>usulinella<br />
hidaensis Zone, Protriticites matsumotoi Zone (s. s.), Quasifusulinoides sp. A Zone,<br />
Montiparus sp. A Zone, Schwagerina sp. A Zone, Triticites simplex Zone (s. s.),<br />
Pseudoschwagerina muong<strong>the</strong>nsis Zone and Pseud<strong>of</strong>usulina vulgaris Zone. Detailed field<br />
mapping <strong>of</strong> <strong>the</strong> area revealed two limestone sequences cut by a fault <strong>of</strong> nor<strong>the</strong>astern<br />
trend in this area. <strong>Limestone</strong>s appear to have accumulated in a marginal lagoon<br />
environment in <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex.<br />
The Mt. Maruyama area in Mine City, Yamaguchi Prefecture, is <strong>the</strong> third<br />
investigated area. The limestone facies <strong>of</strong> this area indicate that <strong>the</strong> paleoenviron<br />
ment is probably a true reef within <strong>the</strong> organic reef complex. Loc. MA 66 was<br />
examined in detail and <strong>the</strong> following fusulinaceans were identified: Protriticites<br />
yanagidai Ota, Protriticites masamichii Ota, Protriticites toriyamai Ota and Protriticites aff.<br />
matsumotoi (Kanmera). These species are characterized by having ra<strong>the</strong>r small shell,<br />
as compared with <strong>the</strong> known species <strong>of</strong> Protriticites. From <strong>the</strong>ir morphological<br />
characters, two phylogenetic lines were shown among <strong>the</strong> primitive Triticites (s. 1.).<br />
The first line is from Protriticites yanagidai Ota to Protriticites matsumotoi (Kanmera).<br />
The second one is from Protriticites masamichii Ota to Montiparus matsumotoi infktus,<br />
reported by Watanabe (1991). From hypo<strong>the</strong>sis based on <strong>the</strong> morphological<br />
affinities, Protriticites yanagidai seems to be a primitive stage in <strong>the</strong> first line, whereas<br />
Protriticites masamichii is considered to be a transitional species in <strong>the</strong> second line.<br />
The transition from Protriticites masamichii to Protriticites matsumotoi in association with<br />
Protriticites toriyamai is successively confirmed in <strong>the</strong> Protriticites toriyamai Subzone to<br />
<strong>the</strong> Protriticites matsumotoi Subzone in <strong>the</strong> Jigoku-dani area. Therefore, Protriticites<br />
matsumotoi (Kanmera) seems to be linked to <strong>the</strong> above primitive species <strong>of</strong> Protriticites.<br />
Fur<strong>the</strong>rmore, <strong>the</strong> Montiparus sp. A Zone, though small gaps were present, conform<br />
ably overlies <strong>the</strong> Protriticites matsumotoi Subzone or Zone along AK and JI Traverses.<br />
Therefore, <strong>the</strong> relevant species <strong>of</strong> Montiparus sp. A and Montiparus matsumotoi infktus<strong>of</strong><br />
Watanabe (1991) are probably linked to <strong>the</strong> primitive species <strong>of</strong> Protriticites, but it is<br />
doubtful whe<strong>the</strong>r Protriticites matsumotoi (Kanmera) is directly connected with Monti<br />
parus matsumotoi infktus sensu Watanabe, because <strong>of</strong> its morphological characters. In<br />
addition <strong>the</strong>se fusulinaceans are closely similar to Protriticites praemontiparus Zhou,<br />
Sheng and Wang, 1987 and Protriticites minor Zhou, Sheng and Wang, 1987,
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 83<br />
respectively from eastern Yunnan, South China. The examinations <strong>of</strong> <strong>the</strong> fusulina<br />
cean affinities between China and Japan are very important for studying paleobiogeography<br />
during Carboniferous-Permian time.<br />
The tentative divisions <strong>of</strong> <strong>the</strong> fusulinacean zones proposed for <strong>the</strong> Middle<br />
Carboniferous and Lower Permian <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> and <strong>the</strong> relevant<br />
sections are shown in Fig. 17. As mentioned before, it is very difficult to obtain a<br />
consensus on <strong>the</strong> leading and index fusulinaceans <strong>of</strong> each zone even in <strong>the</strong> <strong>Akiyoshi</strong><br />
<strong>Limestone</strong>. This seems to be caused mainly by <strong>the</strong> differences <strong>of</strong> <strong>the</strong> original<br />
habitats and <strong>the</strong> fusulinacean ecological adaptations and has a close relationship with<br />
<strong>the</strong> paleoecology in <strong>the</strong> <strong>Akiyoshi</strong> organic reefcomplex (e.g. M. Ota, 1968; Nagai and<br />
M. Ota 1980; Nagai, 1985). M. Ota (1977) already mentioned that habitat<br />
segregation is observable with <strong>the</strong> fusulinacean distribution in <strong>the</strong> <strong>Akiyoshi</strong> Lime<br />
stone, namely Pseud<strong>of</strong>usulina kraffti magna Toriyama in <strong>the</strong> lagoonal facies and<br />
Pseud<strong>of</strong>usulina ambigua (Deprat) in <strong>the</strong> sand facies <strong>of</strong> <strong>the</strong> reef flat environment.<br />
The following paleoecology studies were well known before. Ross (1961, 1965,<br />
1969, 1972b) tried to establish biostratigraphic zones, by considering <strong>the</strong>ir paleoen<br />
vironment.<br />
He remarked that fusulinaceans lived on <strong>the</strong> surface <strong>of</strong> <strong>the</strong> substratum<br />
and have adapted to <strong>the</strong> influence <strong>of</strong> water conditions, such as temperature, salinity,<br />
currents and turbidity. Ross (1964) suggested that <strong>the</strong> morphological changes were<br />
due to ecological adaptation, for example, <strong>the</strong> inflated schwagerinids occur in specific<br />
rock types, such as patch reef accumulations or bioherms. Tikhvinskiy (1965)<br />
insisted that <strong>the</strong> elongated and fusiform genera <strong>of</strong> Schwagerininae were undoubtedly<br />
bottom dwellers, but some genera with inflated form probably had a planktonic<br />
habit. Menner (1971) criticized <strong>the</strong> above opinions because it was very difficult to<br />
confirm whe<strong>the</strong>r <strong>the</strong> genus "Schwagerina" is planktonic or benthonic. Ross (1972b)<br />
reconstructed <strong>the</strong> isolated bioherms in <strong>the</strong> lower Wolfcampian Neal Ranch Forma<br />
tion, and discussed <strong>the</strong> fusulinacean habitats. According to him, <strong>the</strong> inflated<br />
schwagerinids, including Pseudoschwagerina uddeni (Beede and Kniker), have a<br />
distribution near <strong>the</strong> biohermal buildups and on associated debris aprons. More<br />
over, Ross (1982) insisted that some genera in <strong>the</strong> inflated schwagerinids had a<br />
planktonic phase in <strong>the</strong> life cycle. Ross and Ross (1988) and Seslavinskiy (1991)<br />
made it clear that during late Carboniferous and early Permian time, transgression<br />
shifted to regression. Fur<strong>the</strong>rmore, Ross and Ross (1988) suggested that <strong>the</strong><br />
sedimentary environment from <strong>the</strong> base to upper part <strong>of</strong> <strong>the</strong> Wolfcampian changes<br />
from shelf to basin. Sea level changes may closely relate to <strong>the</strong> worldwide dispersal<br />
<strong>of</strong> <strong>the</strong> inflated schwagerinids.<br />
The sedimentary environments <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> in <strong>the</strong> investi<br />
gated AK Traverse were, as a whole, reconstructed as like a marginal lagoon within<br />
<strong>the</strong> <strong>Akiyoshi</strong> organic reef complex. The Jigoku-dani area is recognizable as a<br />
relatively low energy environment like a lagoon. The Mt. Maruyama area, on <strong>the</strong><br />
contrary, reveals an environment near <strong>the</strong> reef core, according to <strong>the</strong> bi<strong>of</strong>acies and
84 Yasuhiro Ota<br />
lith<strong>of</strong>acies.<br />
Along AK Traverse, well preserved Pseudoschwagerina were obtained from micritic<br />
limestone. The collected specimens <strong>of</strong> Pseudoschwagerina from AK Traverse, are<br />
considered to be preserved in <strong>the</strong> original living position and form. Machiyama and<br />
Kawamura (personal communication), examined <strong>the</strong> biohorizon <strong>of</strong> Pseudoschwagerina<br />
along AK Traverse and concluded that <strong>the</strong> energy level <strong>of</strong> that environment was very<br />
low because <strong>of</strong> abundant occurrence <strong>of</strong> wackestone. In contrast with <strong>the</strong> AK area,<br />
Pseudoschwagerina in <strong>the</strong>Jigoku-dai area rarely occurs in limestones with sparry calcite<br />
cements and is poorly preservation. Under high energy condition, Pseudoschwagerina<br />
seems to be difficult to preserve well, because <strong>of</strong> its thin and not very strong walls.<br />
Pseudoschwagerina in <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex probably chose its habitat in<br />
<strong>the</strong> marginal lagoon environment and sometimes extended into <strong>the</strong> central environ<br />
ment <strong>of</strong> <strong>the</strong> lagoon.<br />
The Triticites-Schwagerina Zone (s. s.) outside <strong>the</strong> <strong>Akiyoshi</strong> region, approximately<br />
corresponds to <strong>the</strong> Triticites yayamadakensis Zone and <strong>the</strong> Triticites simplex Zone along<br />
AK and JI Traverses. These zones in <strong>the</strong> investigated areas are typified by<br />
dominance <strong>of</strong> Triticites (s. s.) and are also characterized by abundance <strong>of</strong> Schwagerina<br />
sp. A along two traverses. Triticites yayamadakensis Kanmera is abundant and easily<br />
traced in <strong>the</strong> Jigoku-dani area, but this species is rare along AK Traverse. Triticites<br />
ozawai Toriyama, a closely related species to Triticitesyayamadakensis Kanmera occurs<br />
along AK Traverse. Fusulinacean constituents <strong>of</strong> <strong>the</strong>se zones along AK and JI<br />
Traverses are slightly different, but <strong>the</strong> above zones also yield many mutual<br />
fusulinaceans.<br />
The Montiparus sp. A Zone is confirmedin both AK and Jigoku-dani areas. The<br />
lower part <strong>of</strong> <strong>the</strong> Montiparus sp. A Zone along AK Traverse is accompanied by <strong>the</strong><br />
underlying diagnostic Protriticites matsumotoi (Kanmera). This species might be<br />
regarded as a member <strong>of</strong> a "ghost fauna" or <strong>the</strong> mixed fauna derived from various<br />
zones, resulting from condensation by sea level changes. Hence, gaps are possibly<br />
present between <strong>the</strong> overlying Montiparus sp. A Zone and <strong>the</strong> underlying Quasifusuli<br />
noides sp. A Zone in <strong>the</strong> Protriticites matsumotoi Zone (s. 1.). Fur<strong>the</strong>rmore, <strong>the</strong> horizon<br />
<strong>of</strong> <strong>the</strong> gaps coincides with <strong>the</strong> biohorizon, changing from Fusulininae or Fusulinell<br />
inae to Schwagerininae. Consequently <strong>the</strong> geological event, suggested by <strong>the</strong> gaps,<br />
is considered to play an important role in <strong>the</strong> transition from Fusulininae or<br />
Fusulinellinae to Schwagerininae. However, Ross (1989) has already pointed out<br />
that <strong>the</strong> time for fusulinacean transitions in such a condensed section is too short to<br />
be reason for <strong>the</strong> evolution <strong>of</strong> fusulinaceans. Therefore, <strong>the</strong> rapid transitions from<br />
Fusulininae or Fusulinellinae to Schwagerininae observed along AK Traverse are<br />
dependent on <strong>the</strong> original evolutionary cause, which fusulinaceans possess ra<strong>the</strong>r<br />
than that caused by paleoenvironmental change. Hasegawa (1963, 1988) discussed<br />
<strong>the</strong> origin <strong>of</strong> <strong>the</strong> black sparry calcite limestone near <strong>the</strong> boundary between <strong>the</strong><br />
Carboniferous and Permian. According to him, <strong>the</strong> datum level <strong>of</strong> <strong>the</strong> lower limits
Fusulinacean <strong>Biostratigraphy</strong> <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 85<br />
<strong>of</strong> <strong>the</strong> black sparry calcite limestone coincides with <strong>the</strong> biohorizon, where <strong>the</strong><br />
Fusulina-Fusulinella fauna extinguishes, and <strong>the</strong> new Triticites (s. 1.) fauna appears.<br />
From its chemical composition, this black to dark brown color limestone is not<br />
dolomitic, and changes <strong>of</strong> sedimentary environments are suggested (Musashino,<br />
Hikabe and Arai, personal communication). It is possible that <strong>the</strong> black to dark<br />
brown color limestone along AK Traverse is <strong>the</strong> product <strong>of</strong> a geological event, that<br />
took place after <strong>the</strong> limestone accumulations <strong>of</strong> <strong>the</strong> Quasifusulinoides sp. A Zone.<br />
The Protriticites matsumotoi Zone in <strong>the</strong> investigated areas was first introduced by<br />
M. Ota (1977) as <strong>the</strong> Triticites (s. 1.) matsumotoi Zone, and is characterized by<br />
primitive species <strong>of</strong> Triticites (s. 1.), such as Protriticites matsumotoi (Kanmera). In<br />
connection with this zone, Minato, Kato, Nakamura, Niikawa and Hasegawa<br />
(1984) reported that Protriticites matsumotoi (Kanmera) was widely found in Southwest<br />
Japan. Hasegawa (1988) also reported that <strong>the</strong> Triticites simplex fauna partly<br />
overlies in occurrence <strong>the</strong> ra<strong>the</strong>r primitive Triticites (s. 1.) fauna, such as Protriticites<br />
matsumotoi fauna. He assumed that <strong>the</strong> primitive Triticites (s. 1.) was probably able to<br />
settle only in <strong>the</strong> area, where conditions suitable for fusulinacean recovery arrived<br />
early in <strong>the</strong> environmental change. Of <strong>the</strong> study areas, AK Traverse and JI<br />
Traverse are supposed to be <strong>the</strong> presumably recovered areas for <strong>the</strong>m, because a<br />
ra<strong>the</strong>r primitive Triticites (s. 1.) fauna, such as Protriticites matsumotoi fauna, was found.<br />
The Fusulina-Fusulinella Zone, comparable with <strong>the</strong> Beedeina akiyoshiensis Zone <strong>of</strong><br />
M. Ota (1977) was not confirmed along AK Traverse and in <strong>the</strong> Jigoku-dani area.<br />
Beedeina akiyoshiensis (Toriyama) is known in limestones with sparry calcite cements,<br />
accumulated in a reef environment. Therefore, it is suggested that Beedeina<br />
akiyoshiensis (Toriyama) originally could not live in a relatively low energy environ<br />
ment like along AK and JI Traverses, where <strong>the</strong> central to marginal lagoon<br />
environment was predominant.<br />
As mentioned above, in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> <strong>the</strong> Middle Carbonifer<br />
ous and Lower Permian fusulinaceans <strong>of</strong> each zone are slightly different in <strong>the</strong>ir com<br />
position in different areas. This fact suggests that some fusulinaceans have distinc<br />
tive habitats different from o<strong>the</strong>rs in <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex. These<br />
distributional characters control <strong>the</strong> local bio-divisions and fusulinacean zonations.<br />
Hence, <strong>the</strong> analysis <strong>of</strong> <strong>the</strong> fusulinacean assemblages, relating to <strong>the</strong>ir special<br />
distribution habitat in <strong>the</strong> <strong>Akiyoshi</strong> organic reefcomplex, is essential to establish <strong>the</strong><br />
detailed biostratigraphic division in <strong>the</strong> future.<br />
The establishment <strong>of</strong>detailed biostratigraphic units is very important for making<br />
clear <strong>the</strong> process <strong>of</strong> formation <strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> organic reefcomplex and is essential to<br />
learning <strong>the</strong> paleogeography <strong>of</strong> Japan in late Paleozoic time. In this connection,<br />
Hill (1973) referred to <strong>the</strong> relation between <strong>the</strong> sedimentary environment <strong>of</strong> <strong>the</strong><br />
organic reef and <strong>the</strong> paleolatitude. In fact, Japanese Islands in late Paleozoic time<br />
was formerly illustrated in many paleogeographic maps nearly at <strong>the</strong> north latitude<strong>of</strong><br />
60° in <strong>the</strong> Arctic region (e.g. Smith et al. 1973; Boucot and Gray, 1980). Taking
86 Yasuhiro Ota<br />
<strong>the</strong> <strong>Akiyoshi</strong> organic reef complex (e.g. M. Ota, 1968; Nagai, 1978, 1979; Sugiyama<br />
and Nagai, 1990) and modern coral reef into consideration, <strong>the</strong> above location <strong>of</strong> <strong>the</strong><br />
late Paleozoic Japanese Islands, including <strong>Akiyoshi</strong> region, is unsuitable with present<br />
knowledge. Ross and Ross (1985a) and Scotese and Mckerrow (1990) showed <strong>the</strong><br />
location <strong>of</strong> <strong>the</strong> Japanese Islands in late Paleozoic time near <strong>the</strong> equator. Their<br />
conclusions agree with <strong>the</strong> results <strong>of</strong> <strong>the</strong> present study.<br />
With regard to <strong>the</strong> changes <strong>of</strong> fusulinacean genera along AK and JI Traverses,<br />
<strong>the</strong> following generic transitions are confirmed: Pseud<strong>of</strong>usulinella- Protriticites-<br />
Montiparus- Triticites (Schwagerina)- Pseudoschwagerina- Pseud<strong>of</strong>usulina. The genus<br />
Pseud<strong>of</strong>usulinella was first introduced by Thompson (1951) and is considered to have<br />
originated from Fusulinella, in <strong>the</strong> Eurasian Arctic faunas at about <strong>the</strong> end <strong>of</strong> late<br />
Carboniferous time (Ross, 1973). According to Rui, Ross and Nassichuk (1991),<br />
<strong>the</strong> Tethyan province, namely tropical and subtropical climatic zones, is marked by<br />
<strong>the</strong> transitional series <strong>of</strong> Fusulinella-Neostaffella-Beedeina-Fusulina fauna. Therefore,<br />
during <strong>the</strong> period <strong>of</strong> <strong>the</strong> Pseud<strong>of</strong>usulinella Zone, corresponding to <strong>the</strong> Fusulina and<br />
Beedeina Zones, <strong>the</strong> <strong>Akiyoshi</strong> organic reef complex was formed in a subtropical and<br />
tropical environment ra<strong>the</strong>r than just an area with a warm temperature. Addi<br />
tionally, <strong>the</strong> faunal transition from <strong>the</strong> Protriticites Zone to <strong>the</strong> Montiparus Zone was<br />
confirmed along AK and JI Traverses. As respects Triticites (s. 1.), many authors,<br />
for examples, Davydov (1990) and Ginkel and Villa (1991) have discussed it<br />
before. The successive transition from Protriticites to Montiparus has been confirmed<br />
in <strong>the</strong> Tethyan province but not in <strong>the</strong> Mid-continent province. Hence, <strong>the</strong> Tethyan<br />
faunal province during <strong>the</strong> time from <strong>the</strong> Protriticites matsumotoi Zone to <strong>the</strong> Montiparus<br />
sp. A Zone seems to have little connection with that <strong>of</strong> <strong>the</strong> Mid-continent faunal<br />
province. The Pseudoschwagerina muong<strong>the</strong>nsis Zoneis characterized by <strong>the</strong> widespread<br />
genus, Pseudoschwagerina. This genus is considered to be planktonic during a part <strong>of</strong><br />
its life cycle. In a strict sense, <strong>the</strong> development <strong>of</strong> <strong>the</strong> Pseudoschwagerina muong<strong>the</strong>nsis<br />
fauna in <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong> possibly has a time lag in comparison with<br />
that <strong>of</strong> Pseudoschwagerina uddeni (Beede and Kniker) in <strong>the</strong> Mid-continental province,<br />
because <strong>the</strong> pseudoschwagerine faunas arose in western NorthAmerica and after that<br />
<strong>the</strong>y dispersed and migrated into <strong>the</strong> Tethys ocean. However, this dispersal time<br />
was short and we can adapt synchronism to <strong>the</strong> migration rapidity <strong>of</strong> Pseudoschwager<br />
ina. This is <strong>the</strong> reason why Pseudoschwagerina is very useful for worldwide correlation.<br />
The next overlying Pseud<strong>of</strong>usulina Zone is characterized by a cosmopolitan genus,<br />
Pseud<strong>of</strong>usulina. However, <strong>the</strong> stratigraphic distribution and definition <strong>of</strong> this zone are<br />
still left in question.<br />
Acknowledgments<br />
The author expresses his grateful thanks to Pr<strong>of</strong>essor Juichi Yanagida, Kyushu<br />
University, who kindly read <strong>the</strong> manuscript and <strong>of</strong>fered many helpful suggestions to
Fusulinacean <strong>Biostratigraphy</strong><strong>of</strong> <strong>the</strong> <strong>Akiyoshi</strong> <strong>Limestone</strong> <strong>Group</strong>, Part I 87<br />
accomplish this study. Cordial thanks are due to Pr<strong>of</strong>essor Hakuyu Okada and<br />
Associate Pr<strong>of</strong>essor Akihiko Matsukuma, Kyushu University, for reading <strong>the</strong><br />
manuscript and <strong>the</strong>ir giving <strong>the</strong> author helpful criticisms and suggestions during <strong>the</strong><br />
course <strong>of</strong> this study. The author also wishes to express his grateful thanks to<br />
Pr<strong>of</strong>essor Kimiyoshi Sada, Hiroshima University, who kindly read <strong>the</strong> manuscript<br />
and provided many suggestions about fusulinaceans. Dr. Kametoshi Kanmera,<br />
Pr<strong>of</strong>essor Emeritus, Kyushu University gave him many valuable comments and<br />
helpful suggestions on <strong>the</strong> fusulinacean paleontology. Dr. Wilbert R. Danner,<br />
Pr<strong>of</strong>essor Emeritus, University <strong>of</strong> British Columbia, kindly read <strong>the</strong> manuscript and<br />
made minor changes in grammar and syntax where needed, and provided useful<br />
comments and suggestions. Dr. Masamichi Ota, Director <strong>of</strong> <strong>the</strong> Kitakyushu<br />
Museum and Institute <strong>of</strong> Natural History critically read <strong>the</strong> manuscript and <strong>of</strong>fered<br />
many valuable comments and helpful suggestions. The author thanks <strong>the</strong> following<br />
persons for <strong>the</strong>ir kind help in giving him facilities in field work and valuable<br />
suggestions; Pr<strong>of</strong>essor Tamio Nishida, Saga University, Assoc. Pr<strong>of</strong>. Koichi Nagai,<br />
Ryukyu University, Assoc. Pr<strong>of</strong>. Testuo Sugiyama, Fukuoka University, Dr.<br />
Kyoichiro Ueda, Curator <strong>of</strong> <strong>the</strong> Kitakyushu Museum and Institute <strong>of</strong> Natural<br />
History, Messrs. Akihiro Sugimura and Takehiko Haikawa, <strong>Akiyoshi</strong>-dai Museum<br />
<strong>of</strong> Natural History and Mrs. Yuko Kyuma, Primary School <strong>of</strong> Nagasaki Prefecture.<br />
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