Early Triassic lingulidae and associated marine faunas in south China

The survival strategies of Early Triassic Lingulidae fauna and its associated shallow marine faunas across the end-Permian mass extinction 250 million years ago are discussed. Three new genera and nine new species are erected. A comprehensive database of all Lingulidae species through the Late Devonian to Present is also constructed.

New early Triassic Lingulidae (Brachiopoda) genera and species from South China

Two new genera, Sinolingularia gen. nov. and Sinoglottidia gen. nov., together with three new species, Sinolingularia huananensis gen. et sp. nov., Sinolingularia yini gen. et sp. nov. and Sinoglottidia archboldi gen. et sp. nov., are described on the basis of a large collection of well-preserved specimens from several sections straddling the Permian - Triassic boundary in South China.

Early Triassic (early Olenekian) life in the interior of East Gondwana: Mixed marine-terrestrial biota from the Kockatea Shale, Western Australia

A new terrestrial-marine assemblage from the lower beds of a thin outcrop section of the Kockatea Shale in the northern Perth Basin, Western Australia, contains a range of fossil groups, most of which are rare or poorly known from the Lower Triassic of the region. To date, the collection includes spinose acritarchs, organic-cemented agglutinated foraminifera, lingulids, minute bivalves and gastropods, ammonoids, spinicaudatans, insects, austriocaridid crustaceans, actinopterygians, a temnospondyl-like mandible, plant remains, and spores and pollen. Of these groups, the insects, crustaceans and macroplant remains are recorded for the first time from this unit. Palynomorphs permit correlation to nearby sections where conodonts indicate an early Olenekian (Smithian) age. The locality likely represents the margin of an Early Triassic shallow interior sea with variable estuarine-like water conditions, at the southwestern end of an elongate embayment within the East Gondwana interior rift-sag system preserved along the Western Australian margin. Monospecific spinose acritarch assemblages intertwined with amorphous organic matter may represent phytoplankton blooms that accumulated as mats, and suggest potentially eutrophic surface waters. The assemblage represents a mixure of marine and terrestrial taxa, suggesting variations in water conditions or that fresh/brackish-water and terrestrial organisms were transported from adjacent biotopes. Some of the lower dark shaly beds are dominated by spinicaudatans, likely indicating periods when the depositional water body was ephemeral, isolated, or subjected to other difficult environmental conditions. The biota of the Kockatea Shale is insufficiently known to estimate biotic diversity and relationships of individual taxa to their Permian progenitors and Triassic successors, but provides a glimpse into a coastal-zone from the interior of eastern Gondwana. Specialist collecting is needed to clarify the taxonomy of many groups, and comparisons to other Lower Triassic sites are required to provide insights into the pattern of biotic decline and recovery at the end-Permian crisis.

Early Triassic disaster and opportunistic foraminifers in South China

Survival and recovery are important dynamic processes of biotic evolution during major geological transitions. Disaster and opportunistic taxa are two significant groups that dominate the ecosystem in the aftermath of mass extinction events. Disaster taxa appear immediately after such crises whilst opportunists pre-date the crisis but also bloom in the aftermath. This paper documents three disaster foraminiferal species and seven opportunistic foraminiferal species from Lower Triassic successions of South China. They are characterized by extreme high abundance and low diversity and occurred occasionally in Griesbachian, Smithian and Spathian strata. The characteristics (small size, simple morphology) and stratigraphic ranges of these groups suggest that r-selection is a commonly used strategy for survivors to cope with either harsh post-extinction conditions and/or environments lacking incumbents.

Upper lower triassic stromatolite from Anhui, South China: geobiologic features and paleoenvironmental implications

Widespread stromatolites and other microbialite deposits characterize Lower Triassic marine successions worldwide. This study documents a stromatolite deposit, 1.1. m thick, from the upper Spathian (Lower Triassic) of the Susong area, South China. The stromatolite comprises distinct laminated domes in the basal part and columns at the upper part. Dark laminae are loosely spaced and interlayered with thicker light colored laminae. Diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures, and yield copies of bacteria clump-like and coccoid-like spheroid aggregates. The former are characterized by cloudy, micrite nuclei rimmed by coarse-grained, euhedral sparry calcite crystals, while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes. The cloudy, micrite nuclei resemble bacteria clump-like structures observed in present-day travertine. Both the coccoid-like spheroids and bacteria clump-like structures are surrounded by coarse-grained euhedral calcite crystals, suggesting a similar accretion mechanism. Both spherical structures therefore could be crucial in the accretion of the Susong stromatolite. The laminated/microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes. Micro-analysis also unravels the common occurrence of authigenic micro-quartz crystals in association with Fe-bearing illite clay minerals in the stromatolite columns. Their coalescing nature with each other, together with the associated pyrite grains, strongly support the formation of micro-quartz crystals from microbial reduction of an Fe-bearing smectite precursor by sulfate reducing bacteria. A comparison of the Susong stromatolite with its counterparts from the upper Lower Triassic strata in Dajiang, South China reveals many similarities in stromatolite microstructures, suggesting that a harsh, euxinic-anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest Spathian in South China.

Integrated Sr isotope variations and global environmental changes through the late permian to early late triassic

New ⁸⁷Sr/⁸⁶Sr data based on 127 well-preserved and well-dated conodont samples from South China were measured using a new technique (LA-MC-ICPMS) based on single conodont albid crown analysis. These reveal a spectacular climb in seawater ⁸⁷Sr/⁸⁶Sr ratios during the Early Triassic that was the most rapid of the Phanerozoic. The rapid increase began in Bed 25 of the Meishan section (GSSP of the Permian-Triassic boundary, PTB), and coincided closely with the latest Permian extinction. Modeling results indicate that the accelerated rise of ⁸⁷Sr/⁸⁶Sr ratios can be ascribed to a rapid increase (>2.8×) of riverine flux of Sr caused by intensified weathering. This phenomenon could in turn be related to an intensification of warming-driven runoff and vegetation die-off. Continued rise of ⁸⁷Sr/⁸⁶Sr ratios in the Early Triassic indicates that continental weathering rates were enhanced >1.9 times compared to those of the Late Permian. Continental weathering rates began to decline in the middle-late Spathian, which may have played a role in the decrease of oceanic anoxia and recovery of marine benthos. The ⁸⁷Sr/⁸⁶Sr values decline gradually into the Middle Triassic to an equilibrium values around 1.2 times those of the Late Permian level, suggesting that vegetation coverage did not attain pre-extinction levels thereby allowing higher runoff.

Global brachiopod palaeobiogeographical evolution from Changhsingian (Late Permian) to Rhaetian (Late Triassic)

Previous studies suggest that the end-Permian mass extinction caused a dramatic drop of marine biodiversity near the Permian-Triassic boundary. However, it is unclear how profoundly this severe extinction might have changed the global provincialism, and how global provincialism responded to the protracted process of this extinction and subsequent recovery through the Triassic. In this paper, we carried out quantitative time-series analyses of global brachiopod palaeobiogeography over a timespan of nine consecutive stages/substages from the latest Permian Changhsingian to the latest Triassic Rhaetian based on a global brachiopod database of 483 genera and 2459 species from 1425 localities. Our results suggest that the extinction resulted in a global 'biogeographical eclipse' in the ensuing Early Triassic Griesbachian and Dienerian times in that neither biogeographic realm nor province could be recognized. It was characterized by an extreme low-diversity, mostly dwarfed and nearly globally distributed brachiopod fauna, coupled with persistently high sea surface temperature and a flattened global latitudinal thermal gradient. Global provincialization emerged again during the Olenekian at province level and reached its peak stage during the Carnian when three realms and six provinces were clearly recognized. Global provincialism became weakened again in the latest Triassic Rhaetian, marked by three general realms, but no province distinguished. Our analyses suggest that both palaeolatitude-related thermal gradient and the presence of Pangea (a profound geographic barrier) were most effective in explaining the spatial patterns. In addition, oceanic currents along the northwestern coast of Pangea also played an important (albeit regional) role in linking southern North and Central America brachiopod faunas with those of the Boreal Realm. This study also revealed that the brachiopod biodiversity center moved northwards over the studied interval, accompanied and hence accountable for by the northward drift of a large number of tectonic blocks in the Palaeotethys and Neotethys during the Triassic.

A new genus of Rhynchonellid Brachiopod from the Lower Triassic of South China and Implications for timing the recovery of Brachiopoda after the end-Permian mass extinction

A new genus, Meishanorhynchia, is proposed based on new material from the Lower Triassic of the Meishan section, South China. It is of a late Griesbachian age based on both associated biozones (ammonoids and
bivalves) and radiometric dates of the intercalated volcanic ash beds. Comparison with both Palaeozoic and Mesozoic-Cenozoic-related genera suggests that it may represent the first radiation of progenitor brachiopods in the aftermath of the end-Permian extinction. The lowest brachiopod horizon that contains the genus is estimated to be about 250.1±0.3 Ma. This implies that the initial stage of recovery of Brachiopoda in the Early Triassic was probably about 1.3±0.3 myr after the major pulse of the end-Permian mass extinction (dated as 251.4±0.3 Ma). This is in agreement with Hallam's expectancy that biotic recovery typically begins within one million years or so of major mass extinctions, in contrast to current views on the end-Permian extinction event which propose that the recovery of most if not all biotic groups in the Early Triassic was severely delayed and only began about five million years after the end-Permian extinction.

High-resolution terrestrial permian-triassic eventostratigraphic boundary in western Guizhou and eastern Yunnan, southwestern China

The adjoining area of western Guizhou and eastern Yunnan Provinces in southwest China is an ideal place to investigate the feasibility of correlating marine and nonmarine Permian–Triassic boundary (PTB) sequences, as it contains outcrop sections of shallow marine, marginal marine (or paralic), and terrestrial PTB sections, all in close geographic proximity. This paper documents for the first time multiple stratigraphic data from several well-preserved terrestrial PTB sections in the area and attempts to use these data to define, locate, and correlate the PTB in the area. A study of the spores and pollen and vegetation types across the terrestrial PTB sections in the study area suggests three distinct evolutionary stages across the boundary: Stage 1 (Xuanwei Formation) is characterised by Late Permian or Paleozoic-type ferns and pteridosperms (85.0%), with a few gymnosperms (15.0%); stage 2 is marked by an abrupt drop of sporopollen elements of Late Permian aspects, coupled with the appearance of fungal spores and limited Early Triassic palynomorphs; stage 3 (top Xuanwei Formation and Kayitou Formation) is dominated by gymnosperm pollen (58.8%) of clearly Early Triassic aspect, although still retaining limited ferns and pteridosperms. The three biotic stages seem to well correspond with the changing trend of the δ13Corg curves from the same sections, which is characterized by a sharp drop just before the PTB, followed by a short term partial recovery across the boundary, and then succeeded by a gradual decline after the PTB in the Early Triassic. Combining evidence from eventostratigraphic (i.e., the succession of boundary clay beds), biostratigraphic (using both macroplants and palynomorphs), and chemostratigraphic (i.e., organic carbon isotope excursion signals), we propose that a high-resolution PTB succession, closely correlatable to its marine counterpart at the Meishan section in eastern China, is recognisable at the terrestrial PTB sections in the western Guizhou–eastern Yunnan area in southwest China.

Significance of Claraia from the late permian of South Guizhou, China

Recently collecte material of two Claraia taxa, Claraia zhiyunica Yang et al, 2001 and Claraia sp. nov. from the Late Permian of South China, are described. Late Permian Claraia species are compared with those from the Early Triassic, and the survival of Claraia across the mass extinction period across the Permian- Triassic boundary (PTB) is discussed.