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and in the southern Karoo Basin, carbonate
nodular horizons. A change in colour of the
mudstones from green-grey to red-brown
takes place at the palaeontologically defined
boundary. Variations in the major and trace
element abundance profiles are usually limited
to the carbonate nodular horizons, besides the
overall effects of weathering. Bulk carbon
isotopic studies of the Commando Drift Dam
section revealed a negative δ 13 C bulk excursion
(background values of −15 to −20‰, with
total extent of excursion to −24.9‰) 2 cm
below the palaeontological boundary, followed
by a gradual recovery and then another
decrease in values leading towards the palaeomagnetic
boundary. Above this boundary
recovery to less negative δ 13 C bulk values (ca.
−18‰) occurs. The organic carbon record
from the Commando Drift Dam (southern Karoo
Basin) and Injusiti (eastern Karoo Basin)
oscillates between −26.1 and −28.9‰, which
is comparable to previous studies of different
sections in the southern Karoo Basin. The
magnitude of both the bulk and organic carbon
isotopic variation can be interpreted to indicate
a number of inputs (due to the fluctuating
values) of organic carbon. The carbon isotope
data for carbonates in the Injusiti section are
different from the results on carbonates from
other studies, but more work to expand this
dataset is necessary. The palynological studies
on the Commando Drift Dam section reveal
the presence of a low diversity flora composed
principally of bryophytes, lycophytes, and
gymnosperms. These forms, including several
Late Permian key-species, are traces of the
surviving plants enduring after the major extinction-pulse.
The presence of fungal palynomorphs
and dearth of pollen/spores related
to photosynthetic plants some metres above
the palaeontological P–Tr boundary demonstrate
similarities to the pattern of floral extinction
at the Cretaceous–Palaeogene (K–Pg)
boundary. The timing of vertebrate extinctions
in the Karoo Basin has so far not been determined,
but the 252.5 Ma age for a single zircon
crystal from Commando Drift Dam dated
here gives a maximum constraint on the age of
the event bed, which is in agreement with the
accepted age of the boundary. No evidence for
impact-produced microdeformation features
were found in quartz grains from either the
Wapadsberg or Commando Drift Dam sections.
Also, siderophile element data (including
platinum group element (PGE) concentrations)
do not support the possible presence of
a meteoritic component at the boundary. Thus,
a link between impact and P–Tr extinction is
not indicated by the results of this study.
2008010457
华 南 广 西 来 宾 - 合 山 二 叠 系 生 物 地 层 和 岩 相
= Biostratigraphy and lithofacies of the Permian
System in the Laibin–Heshan area of
Guangxi, South China. ( 英 文 ). Shen
Shuzhong; Wang Yue; Henderson C M; Cao
Changqun; Wang Wei. palaeoworld, 2007,
16(1-3): 120-138
The Laibin–Heshan area is probably a
unique area containing a suitable marine reference
for the entire Permian system. Various
fossils, sedimentary characteristics, lithofacies
and palaeoenvironments including near shore,
distal shelf, slope, and basin are developed.
The Permian system in the Laibin–Heshan
area is composed of the Maping, the Chihsia,
the Maokou, the Heshan/Wuchiaping and the
Talung formations in ascending order. The
Maping Formation is characterized by restricted
shoal or intertidal facies and ranges
from the Late Carboniferous Kasimovian to
Early Permian Artinskian. The Chihsia Formation
(Artinskian–Kungurian) and the Maokou
Formation (Roadian–Capitanian) represent
a slope carbonate environment and a
transgressive interval. By the end of the Guadalupian,
the Permian sea was reduced to the
confines of the Laibin area in South China and
nearshore massive crinoid limestone was deposited,
representing the most continuous marine
deposits across the Guadalupian–
Lopingian boundary. The Lopingian sequence
in the Laibin–Heshan area reflects an independent
transgression–regression system. During
the Wuchiapingian basinal or slope phase,
siliceous siltstone and chert and carbonates
were deposited. During the Changhsingian,
the Laibin–Heshan area subsided rapidly, accumulating
about 600 m of limestone, tuffaceous
sandstone, shale, siltstone before the
basin was drained and terrestrial clastics with
coal-seams developed. The end of the
Changhsingian reflected the initial stage of the
rapid transgression of the Triassic forthcoming
supercycle. Limestone with latest Permian
benthic faunas developed during the last stage
of the Permian, which were immediately replaced
by the nektic ammonoid and bivalvedominated
faunas in the earliest Triassic.
2008010458
意 大 利 南 阿 尔 卑 斯 二 叠 纪 地 层 和 大 地 构 造
评 述 = A stratigraphic and tectonic review of
the Italian Southern Alpine Permian. ( 英 文 ).
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