n Alas - Alaska Division of Geological & Geophysical Surveys - State ...

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Most speclmens represent detached leaflets or partial
fronds; some, still problematic, may be stems. The
speclmans are preserved mostly as impressions, although
a few have adherent areas of codified organic
residue. Foliar outlines are weU defined in most spec
lmens; more importantly, the veins of some specimens
were originally stout enough that they remain In clear
relief. Thus, regardless of their generally inferior
preservation, the fossils retain enougf, chcuacteristic
features that the following forms are recognizable:
1. Pecopteris spp.: This complex of fernlike foliage
is common in Pennsylvanian and Permian sedimentary
rocks and constitutes a dornInant element
in many of the coal floras. It Is also conspicuous
in the Alaskan flora; hall or more of the
determinable specimens are pecopterids. Three
species are apparently present. Most of the
specimens are referable to the common species
- P. arboremens Schlotheim (fig. 62A). The specimen
shown in figure 828 may, with reasonable
assurance, be referrer to &. hemitelloides
Brongniart. A third species, P. unita Brongniart,
is represented by the frond fragment shown in
figures 62E and 621.
2. Cyclopteroid pinnules (figs. 625 622): The five
specimens representing this generaljzed morpho-
lwc format are not generically identifiable be-
cause of their fragmentary condition. In the
absence of demonstrable apical parts, generic
identification of these basal fragments is at
best, speculative; possibly they are Cyclopteris
Brongniart, aaropteridlum Zalessky, or
Cardioneura Zalessky.
3. Zamiopteris sp.: The speclmens shown in figures
62G through 621 represent the most remarkable
element in the Alaskan essemblage. These are
long linear or linear-lanceolate sy mrnetrical and
petiolate leaves with entire margins, acute
apices, open venation, and e resernblance to
Glossopteris foliage in general outline. The
leaves are clearly within the circumscription of
the genus Zamiopteris Schmalhausen (1 879),
originally described on the basis of leaves (Z.
lmopteroides Schmalhausen) from Permian
fock near Ssuka, U.S.S.R. Subsequently, at letkit
20 species have been described, one from Korea
and the others from the U.S.S.R., all character-
istically Permian. The most recent account of
.amio teris (Zimina, 1977) records several
*e Lower and Uppw Permian of the
Par Bastern floral province, near Vladlvostok.
A few indeterminate specimens make up the
remainder of the collection, all narrow linear frag-
ments with more or less parallel ribbing. One quite
(2 by 28 em) fragment may be an unusual
zamiopterid element; another fragment, with feint but
seemingly regular parallel ribbing, possibly represents
a cordaitean leaf fragment. There is no evidence of
lepidophy tes or arthrophytes.
These fossils, which represent the Eirst post-
Mississippian Paleozoic plants found In Alaska, add Bn
important element to the sparse pre-Cenozoic paleo-
botanic history of the State. Furthermore, they are
crltlcal h geologic dating of the conglomerate of
Mount Dall because of the rarlty of fossils in that
unit. The pecopterids are stratlgraphically long
ranging (Middle Pennsylvanian to Per mian) but are
doubtless youwer than Missjsslppian, and the material
of Pecopteris in the Mmkan eallection has an
intmestingly close resemblance to what probably Is a
superfluous species, E. niamdensis Z d w , most
recently reported by Fefiilova (1973,, p. 88, pl. 23) from
the Permian of the Pechora basm, U.S.S.R. The
cyclopteroid specimens are not stratigraphically defiiitive
because they resemble long-ranging late Paleozoic
texa with approximateIy the same vertical disbibutions
as those of the pecoptetids concerned here.
The ALaskan specimens of Zamiopteris, however, serve
as a common stratigraphic denominator because the
occurrence of thLs genus is restricted to rocks of
Perrnjan age in Siberla, where It occurs mainly Ln the
upper pert of the Lower Permlan and the lower put of
the Upper Permian (S. V. Meyen, oral commun., 1979).
Thus, the evidence favors a Permian age assignment
for the Alaskan plant fossils. The zalniopterid
specimens were previously mlsinterpreted as cordaitean
leaves, and a Pennsylvanian age was assigned
to the conglomerate of Mount Dall (Reed and Nekon,
1977, 1980; Reed and others, 1979). This age was also
applied by Dutro end Jones (1979) in a report discussing
Carboniferous strata in Alaska. The recognition of
Zamlopteris, however, necessitates nsslgnrnent of the
'plant-bearing beds of the conglomerate of Mount Dall
to the Permian. Pending the collection of larger, more
varied assemblages, it seems judioious to regard the
present material as no younger than Early Permian.
These Alaskan plants are of fucther interest in
that they are the first North American flora of
Permian ye known north of the Dunkard basin bat
epprox 40 N.). As shown in figure 63, only a few
areas that yield Permian plants are known h North
America; these areas are concentrated chiefly in the
Southwestern United States, where three distinct
Permian flord provinces are recognized (Read and
Mamay, 1964, each on the basis of a single chmacteristic
genus (m, Glenopteris, and Supaid.
The geographically isolated Akkan flora shares 6
strong pecopterid element with those North American
floras far to the south. However, by vlrtue of its distinguishing
component-Zamiopterb-the Alaskan flora
clearly constitutes an eastwwd extension of the
Permian flora of Angaraland, the greater part of
northeastern Asia. It now seems reasonable to anticjpate
the discovery, in Alaska and, possibly, at more
southerly North American sites, of additional Permian
taxa characteristic of the hgara flora.
Geographic proximity of the Alaskan plant
occurrence to East Asia contributes to the aceurnulation
of widely cited evidence for Paleozoic unity of
the major landmasses and subsequent drifting of the
continents. Long ago, White (1912, p. 513-519)
commented on the presence of Chinese and UraLian
elements in the Permian floras of the Southwestern
United States and speculated regarding plant mipation
from Chlna to North America by way of "the north
Pacific (Alaskan) route." Interestingly, White WBS then
referring obliquely to a "supercontinentn ("* * since
the land migration of the Chinese types could hardly
have been accomplished Without the aid of essential
continuity of environmental conditions * * In), In
which Bast Asia and western Alaska were joined, substantially
as later depicted in the Wegenerian Pangaea