Search

Abstract Immediately after the latest Permian mass extinction, bivalve faunas colonized the Permian-Triassic Transitional Beds (PTTB), especially in littoral clastic facies of South China. The Permian-Triassic (P-Tr) transitional bivalve fauna is composed of holdovers, long-term survivors and newly evolved taxa, and characterized by moderate diversity and high dominance. However, the taxonomy and ecology of this bivalve fauna of littoral clastic facies have not been well understood, especially in comparison with offshore marine records. This paper presents a study on a P-Tr transitional bivalve fauna from five sections of littoral clastic facies in southwestern China, and as such it contributes to a better knowledge of the ecological processes of benthic communities during the P-Tr transition. In total, 20 species in 13 genera of bivalves are identified from the PTTB in the lower part of the Kayitou Formation and the basal part of the Feixianguan Formation of the five sections. Cluster analysis suggests that the transitional bivalve fauna could be further divided into two successive communities (early and late communities), and each is composed of five assemblages. Promyalina – Neoschizodus community (early community) is characterized by presence of holdover taxa, high taxonomic diversity and evenness, and more abundant shallow infaunal suspension feeders. In Pteria community (late community), taxonomic diversity and evenness are much lower, and stationary epifaunal suspension feeders boost at the expense of shallow infaunal suspension feeders compared with the Promyalina – Neoschizodus community. Furthermore, the Promyalina – Neoschizodus community shows a clear spatial variation along environmental gradient from brackish lagoon to shallow marine settings, while the Pteria community is more uniform and homogeneous laterally. The Promyalina – Neoschizodus community in the studied region is of latest Permian age while the Pteria community should belong to the earliest Triassic. Consequently, a significant taxonomical and ecological turnover of bivalve communities occurred between the Promyalina – Neoschizodus community and the Pteria community during the extinction interval in southwestern China. Highlights • A highly diverse P-Tr transitional bivalve fauna colonized the clastic facies • The transitional bivalve fauna is subdivided into two (early and late) communities. • The two bivalve communities differ in taxonomy, ecology and distribution patterns • A significant turnover of bivalve communities occur in the P-Tr transitional beds [ABSTRACT FROM AUTHOR]

Abstract Shallow carbonate platforms exhibit major changes in faunal composition and facies types during the latest Permian and earliest Triassic. Although the microbialites that developed following the latest Permian mass extinction (LPME) have attracted wide attention, temporal variations in shallow-platform facies and faunas prior to the LPME have been less thoroughly studied. Here, we analyze diversity patterns and variation in skeletal composition in three Upper Permian sections from isolated carbonate platforms of the Nanpanjiang Basin. In addition to the well-known transition from fossil-rich Upper Permian limestones to fossil-poor Permian-Triassic boundary (PTB) microbialites, these sections exhibit several distinct changes that predate the LPME. First, foram faunas show a shift from non-fusulinid-dominated to fusulinid-dominated communities in the <1-m interval below the LPME horizon of each section, reflecting a shallowing trend over ~20–30 kyr preceding the mass extinction. Second, a "foram gap" and concurrent "detrital event" are observed below the LPME in all three sections, recording a rapid influx of detrital siliciclastics that predated the mass extinction by <60 kyr. These features reflect a degree of marine environmental instability prior to the end-Permian mass extinction. The sudden influx of siliciclastics may represent an early perturbation to terrestrial ecosystems linked to incipient Siberian Traps magmatism, resulting in secondary effects in marine environments through increased sediment yields. Highlights • Analysis of carbonate microfacies and foraminifer abundances in three P-Tr sections (Wengna, Taiping, Lung Cam) • Environmental instability on carbonate platforms of Nanpanjiang Basin, South China up to 60 kyr preceding mass extinction • A discrete episode of detrital siliciclastic influx to carbonate platforms initiated major pre-extinction faunal changes. • Shift to fusulinid-dominated foram assemblages at ~20–30 kyr prior to mass extinction owing to platform shallowing • Pre-extinction perturbations possibly caused by terrestrial ecosystem deterioration and increased subaerial erosion. [ABSTRACT FROM AUTHOR]

Abstract Correlation between marine and continental Permian-Triassic (P-Tr) strata is crucial for full understanding of the nature of this global extinction event, but it has proved difficult to achieve. Here, we show that two sections in South China and North China record similar mixed continental-marine biota in the post-extinction stratigraphic interval, including conchostracans, plants, insects, marine bivalves and lingulid brachiopods. In addition, the continental P-Tr mass extinction was represented by a sharp decrease in the diversity and abundance of the Gigantopteris flora in South China, but eliminated the Palaeozoic-type conifer flora and herbivorous pareiasaurs in North China. These mixed continental-marine biota provide the biological evidence for stratigraphic correlation between marine and continental P-Tr transitional beds in South China and North China, especially the co-occurrence of the Pteria - Towapteria - Eumorphotis bivalve assemblage and the Euestheria gutta -bearing conchostracan fauna or Euestheria gutta - Magniestheria mangaliensis - Palaeolimnadiopsis vilujensis conchostracan assemblage. We propose that these specific marine bivalve and continental conchostracan assemblages could be considered as markers of P-Tr transitional beds in marine-continental siliciclastic settings. Highlights • We report two P-Tr boundary sections from South China and North China. • A similar mixed marine and terrestrial biota were collected from the two sections. • The mixed terrestrial-marine biota preserved in the post-extinction stratigraphic interval. • The PTTB was marked by the specific bivalve and conchostracan assemblage. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Graphite discs from Cryogenian Nantuo Formation in Shennongjia area of South China. • Nantuo Graphite discs are detrital in origin. • They were likely sourced from metamorphic basement of Kongling terrane. • Shennongjia and Kongling terranes were both parts of Yangtze block by Cryogenian. Abstract The tectonic history of the Yangtze block of South China prior to the Ediacaran Period has been a matter of debate. In particular, the tectonic history of the Shennongjia terrane in the central-northern margin of the Yangtze block is poorly understood, and the tectonic relationship between the Shennongjia terrane and the Huangling massif (exposed in the Huangling anticline) is unclear. Previous researchers have reported U-Pb dates of detrital zircons and Nd isotopic compositions of clastic rocks from Cryogenian successions in the Shennongjia terrane to identify ancient crustal remnants and the provenance of clastic sediments, and to constrain the age and crustal evolution of the Yangtze block. Here, we describe abundant graphite discs from silty mudstone of the Cryogenian Nantuo Formation in the Shennongjia area of the Yangtze block. These graphite discs are opaque, ∼23–171 μm in size, and highly reflective. Most are abraded or rounded, although some show hexagonal crystalline morphology. Their Raman spectra are distinct from those of indigenous carbonaceous material (CM) in the sedimentary matrix from the Nantuo Formation at the same locality. Raman CM geothermometric analysis indicates that graphite discs experienced a maximum metamorphic temperature of nearly 600 °C, which is inconsistent with the relatively low metamorphic grade of the host rock. These observations indicate that the graphite discs are of detrital origin, most likely derived from high-grade metamorphic rocks in the basement of the Yangtze block (e.g., the Archean-Paleoproterozoic Kongling terrain in the core of the Huangling anticline), consistent with the hypothesis that the Shennongjia region was a part of Yangtze block by the end of the Cryogenian Period. [ABSTRACT FROM AUTHOR]

The upper Ediacaran Miaohe Member (∼551 Ma) in South China contains exceptionally preserved macroscopic carbonaceous compression fossils that provide a crucial view of the marine ecosystem shortly before the Cambrian explosion. However, these fossils were previously known only from one locality near the Miaohe Village on the northern bank of the Yangtze River. It was puzzling that equivalent strata a short distance away contained no fossils, raising questions about the environmental, ecological and taphonomic restriction of these fossils. Here, we describe macroscopic fossils from the Miaohe Member at three new localities to the north and north-west of Miaohe Village. These fossils are taxonomically similar to those from Miaohe Village, and include mostly benthic multicellular algae, a few putative metazoans and several morphologically simple problematic taxa. Twenty-seven species are described, including one new genus (Maxiphyton gen. nov.) and six new species (Baculiphyca brevistipitata sp. nov., Doushantuophyton? laticladus sp. nov., Enteromorphites magnus sp. nov., Konglingiphyton? laterale sp. nov., Maxiphyton stipitatum sp. nov. and Sinocylindra linearis sp. nov.). Insofar as the new localities represent shallower palaeoenvironments than Miaohe Village in the late Ediacaran, the new fossils expand the palaeoenvironmental distribution of macrofossils in the Miaohe Member. Most of the new fossils are preserved as carbonaceous compressions through kerogenization, but pyritization and aluminosilicification also played an important role. This confirms the taphonomic model that there is a continuous preservational gradient among kerogenization, pyritization and aluminosilicification. This taphonomic window provides a glimpse of the late Ediacaran marine ecosystem and complements the cast-mould preservation that accounts for the much-celebrated Ediacara-type soft-bodied macrofossils. [ABSTRACT FROM AUTHOR]

The Triassic rocks are widespread in China, and both marine and terrestrial strata are well developed. The Triassic stratigraphic architecture of China is very complex in both spatial variation of the so-called "South Marine and North Continental", i.e. the southern areas of China occupied mostly by marine facies while the northern China by terrestrial facies during the Triassic Period, and temporal transition of the "Lower Marine and Upper Continental", i.e. the lower part of the Triassic System composed mainly of marine facies and the upper part of terrestrial strata especially in South China. Although the Global Stratotype Section and Point (GSSP) of the Permian-Triassic boundary is located in South China, the Triassic of China except for some marine Lower-Middle Triassic depositions shows significantly local characteristics and is hardly correlated with the global chronostratigraphic chart. Consequently, the Triassic of China contains not only the international research hotspots but also difficult points in stratigraphic study. This paper aims to present a brief review of the Triassic in China, including chronostratigraphy, biostratigraphy, magnetostratigraphy and chemostratigraphy, and summarize an integrated Triassic stratigraphic framework of China. Accordingly, a stratigraphic correlation is proposed for the lithostratigraphic sequences among the three tectono-paleogeographic stratigraphic regions. The comprehensive study indicates that ammonoids are the classic index fossils in Triassic biostratigraphy but conodonts are more advantageous in the study and definition of the Triassic chronostratigraphic boundaries. China still has the potential to optimize the GSSPs of the Induan-Olenekian boundary and Olenekian-Anisian boundary. The correlation of the Permian-Triassic boundary between marine and terrestrial facies might be achieved with the help of the Permian-Triassic "transitional bed" and its related biotic and environmental events in association with the biostratigraphic study of conchostracan, vertebrate and plant fossils. In addition, the carbon isotopes have been proved to be one of the powerful methods in marine Triassic stratigraphic study, whereas the oxygen and strontium isotopes may be additional important bridges to establish the correlation between the marine and terrestrial strata, but as yet lacking of relevant studies in terrestrial strata. Considering the most stratigraphic intervals of the Triassic and the terrestrial Triassic in China are difficult to be correlated to the global chart, the proposed Chinese (regional) Triassic chronostratigraphic chart of marine and terrestrial stages would be of importance to the study of Chinese Triassic stratigraphy and related aspects, but the stages must be conceptually in line with international standards and studied as soon as possible in order to finalize the definition. [ABSTRACT FROM AUTHOR]

Forty-four well-preserved specimens of Kouphichnium , a typical limuloid (horseshoe crab) trackway, are reported and systematically studied for the first time from continental Upper Permian to Lower Triassic successions in North China. A new ichnotaxonomic system of Kouphichnium is proposed according to the ichnotaxobase of limuloid trackways, including simple foot imprints (T), pusher imprints (P), median impressions (M) and genal spine impressions (GS). In total, one ichnogenus and six ichnospecies are recognized, one of which is new: Kouphichnium liulinensis sp. nov. Ichnogenus Paramphibius is regarded as a synonym of Kouphichnium and the diagnoses of ichnogenus Kouphichnium and its two early ichnospecies, i.e. type ichnospecies Kouphichnium lithographicum Oppel, and Kouphichnium didactylum Willard, are revised. A morphological-palaeoethological pattern is proposed in reference to these ichnospecies from the continental Upper Permian to Lower Triassic successions in North China. These six ichnospecies are assigned to six types in the new ichnotaxonomic system and the locomotion rates of each type can be ranked by the possible speed index λ. The size of trackmaker is estimated from the external width of the trackway, and it shows a drastic decrease from the Late Permian to Early Triassic, followed by a gradual increase in the Early Triassic. This size variation of trackmakers (limuloids) during the Permian-Triassic transition, especially the drastic drop, probably reflects the intensive environmental stress during the biotic crisis. In addition, the analysis of the sizes of pusher imprints (P) from certain well-preserved trackways suggests a potential sexual dimorphism of limuloids. [ABSTRACT FROM AUTHOR]

After the end-Permian mass extinction, genus Claraia (Bivalvia) was the most abundant and most noticeable fossil during the survival and recovery stage. However, the reasons for the proliferation of Claraia are still debated. This paper describes a new Griesbachian (Early Triassic) mollusc fauna from deep-water settings in South China in the aftermath of end-Permian mass extinction. This fauna yielded five bivalve species in two genera (Claraia griesbachi, C. wangi, C. stachei, C. radialis, and Promyalina putiatinensis) and two ammonoid species (Ophiceras sp. and Ussuridiscus sp.) and could be assigned to the Claraia wangi-C. griesbachi assemblage zone, indicating a Middle-Late Griesbachian Age. The bivalves were dominated by Claraia griesbachi and were featured by articulated Claraia fossils. As Claraia was epibyssate, it was an excellent autochthonous fauna. While the shallow and deep marine water became dysoxic to anoxic globally, as indicated by recent studies of the early Early Triassic, we suggest the genus Claraia could tolerate dysoxic and/or anoxic conditions and its proliferation could be attributed to its physiological features which were adapted to the stressed environment. The wide distribution of Claraia was probably related to its planktonic larval stage. Where the larva of Claraia could have been transported by ocean flow and increased its potential for long-distance dispersal. In addition, Claraia was a significant disaster and opportunistic taxon during the Early Triassic based on observations in South China. [ABSTRACT FROM AUTHOR]

Evidence for microbial mats has been reported repeatedly from marine Lower Triassic rocks, but scarcely mentioned in post-mass extinction terrestrial facies. Here, we report from the terrestrial Lower Triassic Liujiagou Formation in North China the presence of five kinds of microbially induced sedimentary structures (MISS) or sedimentary surface textures, including “old elephant skin” textures, wrinkle structures, palimpsest ripples, “ Manchuriophycus ” structures and sand cracks. Terrestrial microbial communities that produced these MISS adapted not only to periodically desiccated conditions, but also to the storm-dominated palaeoenvironments in the Liujiagou Formation. The Permian–Triassic mass extinction (PTME) in North China is marked by the die-off of plants, disappearance of coal beds, extinction of pareiasaurs among tetrapods, decreased bioturbation levels and a dramatic change of sedimentary systems through the Sunjiagou Formation. The Sunjiagou Formation recorded the turnover from an ever-wet to a progressively drier and hotter climate and it spans the PTME in North China. Following this mass extinction, MISS became much more common and widespread, suggesting that the mass extinction provided favourable biological and environmental conditions for the development of the MISS in terrestrial ecosystems, especially the decreased bioturbation intensity and grazing pressure associated with increased temperature and climatic drying. In the upper part of the Liujiagou Formation and overlying Heshanggou Formation, the disappearance of MISS coupled with increased bioturbation might indicate an improvement of terrestrial ecosystems and the beginning of the Triassic biotic recovery. However, as the investigation of MISS in space and time through the geological record is in its early stages, further geobiologic and geochemical studies, as well as high-precision isotopic dating from Permian–Triassic terrestrial successions, are needed to fully reveal the timing and pattern of the Early Triassic terrestrial ecosystem reconstruction. [ABSTRACT FROM AUTHOR]

During the end-Permian mass extinction and subsequent Early-Middle Triassic recovery, a series of environmental changes occurred and were accompanied by morphological and ecological responses. This study presents a shell-size analysis study of Upper Permian through lower Middle Triassic bivalve fossils from South China to discover their ecological and environmental implications. With a dataset of over 4900 bivalve specimens from published monographs and our own collections, shell length and shell height are measured and analyzed with a substage-stage binned scale. The mean and median sizes of bivalve shells show a significant Lilliput effect in the immediate aftermath of the end-Permian mass extinction. However, both epifaunal and infaunal bivalves grew larger quickly during the late Griesbachian, indicating a quick rebound of bivalve shell size. The temporal variations in bivalves in South China were mainly controlled by biotic and abiotic factors, e.g., physiological adaptation, changing competition, predatory pressure, and climatic and oxygen changes. • Bivalves suffered a significant Lilliput effect during the Permian-Triassic crisis. • The body size rebound of bivalves occurred during the middle-late Griesbachian. • The Lilliput effect of bivalves was resulted from severe environmental factors. • The quick recovery of bivalves' body-size was mainly controlled by biotic factors. [ABSTRACT FROM AUTHOR]

The well-exposed stratigraphic sequences on the Great Bank of Guizhou (GBG) in South China provide important information for the understanding of various environmental settings during the Permian-Triassic mass extinction and the subsequent recovery, including one of the oldest Triassic marginal reef complexes, which is viewed as an important indicator of biotic recovery following the end-Permian mass extinction. Here we report a systematic conodont study on a newly exposed Lower-Middle Triassic section, the Mingtang section, at the margin of the GBG to provide more data for the time scale of the post-extinction recovery. Twenty-four species in 11 conodont genera are identified and assigned to Hindeodus parvus , Neoclarkina discreta , Neospathodus dieneri , Novispathodus waageni , Neospathodus triangularis - Triassospathodus homeri , Chiosella timorensis , Nicoraella germanica , and Nicoraella kockeli zones in ascending order. These zones correlate well with the conodont successions in South China and over the world. The Induan-Olenekian boundary can be well defined by the first occurrence of Novispathodus waageni in the lower-middle part of the Luolou Formation, while the Early-Middle Triassic boundary was placed at 0.2 m below the top of the Luolou Formation according to the first occurrence of Chiosella timorensis . These conodont data suggest that the Tubiphytes -reef began to recover in the Bithynian (early Middle Triassic), later than benthonic organisms such as foraminifers and calcareous algae. [ABSTRACT FROM AUTHOR]

The Lilliput effect following the Permian–Triassic mass extinction and its aftermath has been documented in a variety of marine animal groups, but it is less known in terrestrial and freshwater invertebrates. Here we present new investigations of the size variations of terrestrial ostracods of the genus Darwinula based on fossil records from a Permian–Triassic section on the northern limb of the Dalongkou Anticline section in Northwest China. Quantitative analyses reveal that ostracod test sizes decreased sharply through the terrestrial Permian–Triassic mass extinction interval. The Lilliput effect in terrestrial ostracods is characterized by the extinction of large taxa and the rise of small-sized and elongate new forms, coupled with the dramatic loss of conchostracans, charophytes, and the blooming of lycopod spores. The size decrease in terrestrial ostracods, following the biotic crisis through the Permian–Triassic interval, was probably triggered by several interacting events, including global warming, anoxia, and enhanced sediment input following acid rain and wildfire. [ABSTRACT FROM AUTHOR]

In South China, the Changhsingian brachiopods are extraordinarily abundant and diverse, comprising 468 species in 144 genera. However, approximately 91% of brachiopod species were eliminated during the Permian–Triassic (P–Tr) mass extinction event. Brachiopods in the aftermath of the P–Tr mass extinction were extremely rare, with only one opportunistic taxon, Lingulida, occasionally found in the Griesbachian and Smithian at a high abundance. Species-diversity of articulated brachiopods in the early Griesbachian, late Griesbachian, Dienerian, and Smithian are 35, 3, 2, and 0, respectively. Although a few of Mesozoic-type species occurred in the Griesbachian, Dienerian and Smithian, a marked diversification of brachiopods occurred in the Spathian and early Anisian and was characterised by 9 and 17 Mesozoic-type species, respectively. The diversification of brachiopods in the Spathian and early Anisian coincides with the contemporaneous expansion of the refuge zone, suggesting that the improvement of marine environmental conditions (e.g., lethally hot temperature and anoxic seawater) played a key role in brachiopod recovery after the P–Tr mass extinction. [ABSTRACT FROM AUTHOR]

The Lower Triassic Daye and Jialingjiang formations of the Three Gorges area (South China) record the recovery interval of benthic tracemaking invertebrates following the P–Tr mass extinction. A total of 17 ichnospecies in 14 ichnogenera are documented from Smithian and Spathian strata. Our trace fossil data, in combination with previously published studies, show that ichnodiversity in the Middle Yangtze region increased markedly in the early Spathian. Trace fossils in the Smithian are dominated by simple, small, horizontal burrows, including Didymaulichnus and Planolites , whereas Spathian trace fossils are diverse and abundant with moderate–high bioturbation levels and complex burrow networks, such as Thalassinoides . Both burrow sizes and penetration depths increased gradually from the early Spathian to the middle–late Spathian, implying a gradual recovery pattern for benthic ecosystems. Early Triassic ichnofossils are characterised by aspects of opportunistic behaviour (e.g., low-to-moderate ichnodiversity, low-to-moderate bioturbation, small burrow widths, and shallow tiering), suggesting stressed environmental conditions. The recovery tempo and pattern of ichnocoenoses in South China is likely structured by temporal and spatial changes of the refuge zone in the Early Triassic. [ABSTRACT FROM AUTHOR]

Various environmental changes were associated with the Permian-Triassic mass extinction at 252.2 Ma. Diverse unusual sediments and depositional phenomena have been uncovered as responses to environmental and biotic changes. Lithological and detailed conodont biostratigraphic correlations within six Permian-Triassic boundary sections in South China indicate rapid fluctuations in carbonate deposition. Four distinct depositional phases can be recognized: (1) normal carbonate deposition on the platform and slope during the latest Permian; (2) reduced carbonate deposition at the onset of the main extinction horizon; (3) expanded areas of carbonate deposition during the Hindeodus changxingsensis Zone to the H. parvus Zone; and (4) persistent mud-enriched carbonate deposition in the aftermath of the Permian-Triassic transition. Although availability of skeletal carbonate was significantly reduced during the mass extinction, the increase in carbonate deposition did not behave the same way. The rapid carbonate depositional changes, presented in this study, suggest that diverse environmental changes played key roles in the carbonate deposition of the Permian-Triassic mass extinction and onset of its aftermath. An overview of hypotheses to explain these changes implies enhanced terrestrial input, abnormal ocean circulation and various geobiological processes contributed to carbonate saturation fluctuations, as the sedimentary response to large volcanic eruptions. [ABSTRACT FROM AUTHOR]

Widespread oceanic anoxia has been implicated as an important factor in the PTB (Permian Triassic boundary) mass extinction and the delayed recovery of Early Triassic marine ecosystems. An investigation of framboidal pyrite in the Bianyang section (Nanpanjiang Basin, South China) suggests that euxinia/dysoxia peaked during the Induan, late Smithian to earliest Spathian and late Spathian. These anoxic episodes show a relationship, albeit imperfect, to major episodes of climatic warming during the Early Triassic that were associated with intensified oceanic stratification, reduced marine productivity and organic carbon sinking fluxes, as well as diminished burial fluxes of organic carbon and reduced sulfur. In contrast, intervals of better-oxygenated marine conditions were associated with episodes of relative climatic cooling during the early to middle Smithian and mid-Spathian. The degree of ventilation of the thermocline region, in particular, had a profound effect on marine biotas, with intervals of improved ventilation resulting in increased global diversity among ammonoids and conodonts and increased local abundance of foraminifera in the Nanpanjiang Basin. These observations suggest that oceanic redox fluctuations played an important role in the delayed recovery of Early Triassic marine ecosystems, and, specifically, that episodic expansion of oceanic oxygen-minimum zones (OMZs) resulted in repeated setbacks to the recovery process, a pattern that persisted until the late Spathian. [ABSTRACT FROM AUTHOR]

A detailed magnetostratigraphic study, linked to a new latest Permian U–Pb ID-TIMS age, was undertaken on the continental Shichuanhe section (SCH) in North China in order to provide a magnetic polarity scale for the Late Permian–early Middle Triassic interval. Tilt-corrected mean directions of the characteristic remanent magnetization pass the reversal test and correspond to a site paleolatitude of 18.1°N during the Early Triassic, consistent with previous results from the North China Block. The magnetostratigraphy shows close similarity with previous studies, allowing interregional correlations with both marine and non-marine records. Normal magnetozone SCH3n, constrained by an absolute age of 252.21 ± 0.15 Ma from an ash bed 3.5 m below its base, is unambiguously correlated to the earliest Triassic normal magnetochron LT1n. Our newly established magnetostratigraphic framework and published carbon-isotope chemostratigraphy, indicate that the Permian–Triassic Boundary is ca. 8 m above the base of SCH3n (within the middle part of the Sunjiagou Formation) at SCH. The overlying reverse polarity dominated interval (SCH3r–SCH5r) ranges to the middle Liujiagou Formation, and straddles an interval from the mid-Griesbachian to mid-Smithian. The base of the Olenekian is provisionally located in the lower part of the Liujiagou Formation, near the base of magnetozone SCH5n. The succeeding thick normal magnetozone SCH6n persists into the upper Heshanggou Formation, with the inferred Smithian–Spathian boundary located in the upper part of the Liujiagou Formation. The transition from reverse magnetozone SCH6r to the overlying normal magnetozone SCH7n, coincides with a clear erosional contact with the base of the Ermaying Formation. Consequently, magnetozone SCH7n is matched to the Early Anisian magnetochron MT3n, with the Olenekian–Anisian boundary interval missing. Our new timescale provides additional magnetostratigraphic constraints on the timing of the terrestrial ecological crisis in North China, which is found to lie within reverse magnetozone SCH2r (equivalent with reverse magnetochron LP3r), a level some 270 ± 150 kyrs before the main marine extinction, that falls in the overlying normal magnetochron LT1n. • Late Permian–Middle Triassic terrestrial geomagnetic polarity timescale from N. China. • Integrated magnetostratigraphy, CA-ID-TIMS age, chemostratigraphy and sedimentology. • New stratigraphic framework for marine-terrestrial correlation. • Terrestrial crisis in N. China preceded the marine extinction by over 270 ± 150 Kyrs. [ABSTRACT FROM AUTHOR]

A Permian-Triassic (P-Tr) boundary section of continuous carbonate facies, which well recorded the biotic and environmental processes through the great P-Tr transition in the shallow non-microbialite carbonate facies, has been studied in Yangou, Leping County, Jiangxi Province. The P-Tr sequence is well correlated with the Meishan section according to the conodont biostratigraphy and the excursion of carbon isotopes. A series of high-resolution thin-sections from the P-Tr boundary carbonate rocks at the Yangou section are studied to explore the interrelation between environmental change and biological evolution during the transitional time. Six microfacies have been identified based upon the observation of the thin-sections under a microscope on the grains and matrix and their interrelation. Combined with the data of fossils and carbon isotopes, Microfacies 4 (MF-4), coated-grain-bearing foraminifer oolitic sparitic limestone, and Microfacies 6 (MF-6), dark shelly micritic limestone, should be the different responses to the two episodes of mass extinction and environmental events that can be correlated throughout South China and even over the world. The oolitic limestone of MF-4 is the first finding from the latest Permian strata in South China and it might be a proxy of an unusual environmental condition of high pCO, low sulfate concentration and of microbial blooming in the aftermath of the latest Permian mass extinction. The micritic limestone of MF-6 containing rich micro-gastropods and ostracods probably represents the blooming event of disaster taxa in the earliest Triassic environment. The microfacies analysis at the Yangou section can well reveal the episodic process of the biological evolution and environmental change in the shallow non-microbialite carbonate facies throughout the great P-Tr transition, thus the Yangou section becomes an important complement to the Meishan section. [ABSTRACT FROM AUTHOR]

Ocean anoxia has been widely implicated in the Permian-Triassic extinction. However, the duration and distribution of the ocean anoxia remains controversial. In this study, the detailed redox changes across the Permian-Triassic boundary (PTB) in the shallow platform interior at Great Bank of Guizhou (GBG) has been reconstructed based on the high-resolution microfossil composition and multiple paleo-redox proxies. The shallow platform is characterized by low sulfur (total sulfur (TS) and pyrite sulfur (S)) concentrations, low S/TOC ratios, and low DOP values before the mass extinction, representing oxic conditions well. Following the mass extinction, the shift of multiple geochemical proxies, including high S/TOC ratios and DOP values, indicates dysoxic-anoxic conditions in shallow ocean. Furthermore, we reconstruct the transition of the redox conditions of Nanpanjiang Basin: the intense volcanic eruptions, which release huge CO and SO before the mass extinction, provoke the temperature rising and the collapse of terrestrial ecosystem. As a result, the increased weathering influx causes the carbon isotopic negative excursion and the expansion of the ocean oxygen minimum zone (OMZ). When the OMZ expanded into the photic zone, the episodic HS release events enhance the pyrite burial at Dajiang section. Thus, intense volcanic eruptions, temperature increase, and oceanic hypoxia together lead to the PTB extinction. Recent studies show high temperature might be the key mechanism of the PTB extinction. In addition, this study confirms that the microbialites were formed in the dysoxic-anoxic shallow water. [ABSTRACT FROM AUTHOR]

Abstract: Late Permian Changhsingian bivalves in South China are very abundant and diverse in nearshore, inner shelf, outer shelf, and deep basin facies. All reported data of both bivalve genera and species from the Permian–Triassic boundary strata of South China have been systematically collected and studied for understanding the evolutionary process of various bivalve groups in different environments through the great Permian–Triassic transition. At the genus level, bivalves show an extinction rate of 50% in the first phase of the Permian–Triassic crisis, though only 9.1% in the second phase. There appears to be no selection of extinction in life-style, feeding type or habitat among bivalves from South China through the crisis. There is no significant difference in the extinction rates between epifaunal and infaunal bivalve genera in all environments. Suspension feeders showed moderate extinction rates, while no deposit feeders went extinct at the genus level. In addition, infaunal bivalves were not at more risk of extinction than epifaunal forms. A combination of ocean anoxia and high seawater temperatures might have contributed to the mass extinction among bivalves during the Permian–Triassic crisis. [Copyright &y& Elsevier]

Abstract: The marine sulfur cycle is intimately linked to global carbon fluxes, atmospheric composition, and climate, yet relatively little is known about how it responded to the end-Permian biocrisis, the largest mass extinction of the Phanerozoic. Here, we analyze carbonate-associated-sulfate (CAS) from three Permo–Triassic sections in South China in order to document the behavior of the C–S cycle and its relationship to marine environmental changes during the mass extinction and its aftermath. We find that δ34SCAS varied from +9‰ to +44‰ at rates up to 100‰Myr−1 during the Griesbachian–Smithian substages of the Early Triassic. We model the marine sulfur cycle to demonstrate that such rapid variation required drawdown of seawater sulfate concentrations to ⩽4mM and a reduction in its residence time to ⩽200kyr. This shorter residence time resulted in positive covariation with δ13Ccarb due to strong coupling of the organic carbon and pyrite burial fluxes. Carbon and sulfur isotopic shifts were associated with contemporaneous changes in climate, marine productivity, and microbial sulfate reduction rates, with negative shifts in δ13Ccarb and δ34SCAS linked to warming, decreased productivity, and reduced sulfate reduction. Sustained cooling during the Spathian re-invigorated oceanic overturning circulation, reduced marine anoxia, and limited pyrite burial. As seawater sulfate built to higher concentrations during the Spathian, the coupling of the marine C and S cycles came to an end and a general amelioration of marine environmental conditions set the stage for a recovery of invertebrate faunas. Variation in seawater sulfate during the Early Triassic was probably controlled by climate change, possibly linked to major eruptive phases of the Siberian Traps. [Copyright &y& Elsevier]

Abstract: Vertical gradients in the δ13C of seawater dissolved inorganic carbon (Δδ13CDIC) can be estimated for paleomarine systems based on δ13Ccarb data from sections representing a range of depositional water depths. An analysis of eight Lower Triassic sections from the northern Yangtze Platform and Nanpanjiang Basin, representing water depths of ~50 to 500m, allowed reconstruction of Δδ13CDIC in Early Triassic seas of the South China craton for seven time slices representing four negative (N) and three positive (P) carbon-isotope excursions: 8.5‰ (N1), 5.8‰ (P1), 3.5‰ (N2), 6.5‰ (P2), 7.8‰ (N3), −1.9‰ (P3), and 2.2‰ (N4). These values are much larger than vertical δ13CDIC gradients in the modern ocean (~1–3‰) due to intensified stratification and reduced vertical mixing in Early Triassic seas. Peaks in Δδ13CDIC around the PTB (N1) and in the early to mid-Smithian (P2–N3) coincided with episodes of strong climatic warming, reduced marine productivity, and expanded ocean anoxia. The Dienerian–Smithian boundary marks the onset of a major mid-Early Triassic disturbance, commencing ~1Myr after the latest Permian mass extinction, that we link to a second eruptive stage of the Siberian Traps. Inhospitable oceanic conditions generally persisted until the early Spathian, when strong climatic cooling caused re-invigoration of global-ocean circulation, leading to an interval of negative Δδ13CDIC values and a sharp increase in δ13Ccarb driven by upwelling of nutrient-rich deepwaters. These developments marked the end of the main eruptive stage of the Siberian Traps. [Copyright &y& Elsevier]

Carbonate carbon isotope ( δC) has received considerable attention in the Permian-Triassic transition for its rapid negative shift coinciding with the great end-Permian mass extinction event. The mechanism has long been debated for such a δC negative excursion through the end-Permian crisis and subsequent large perturbations in the entire Early Triassic. A δC-depth gradient is observed at the Permian-Triassic boundary sections of different water-depths, i.e., the Yangou, Meishan, and Shangsi sections, and such a large δC-depth gradient near the end-Permian mass extinction horizon is believed to result from a stratified Paleotethys Ocean with widespread anoxic/euxinic deep water. The evolution of δC-depth gradient combined with paleontological and geochemical data suggests that abundant cyanobacteria and vigorous biological pump in the immediate aftermath of the end-Permian extinction would be the main cause of the large δC-depth gradient, and the enhanced continental weathering with the mass extinction on land provides a mass amount of nutriment for the flourishing cyanobacteria. Photic zone anoxia/euxinia from the onset of chemocline upward excursion might be the direct cause for the mass extinction whereas the instability of chemocline in the stratified Early Triassic ocean would be the reason for the delayed and involuted biotic recovery. [ABSTRACT FROM AUTHOR]

Series of large conodont samples with 20 species and 3 similar species in 3 genera were collected from the Permian-Triassic (P-T) boundary sequence in a shallow carbonate facies at Yangou (沿沟), Leping (乐平) County, Jiangxi (江西) Province, South China. On the basis of the distributions of the identified species, seven conodont zones have been recognized in ascending order as follows, Neogondolella changxingensis zone, Neogondolella yini zone, Hindeodus changxingensis zone, Neogondolella taylorae zone, Hindeodus parvus zone, Isarcicella staeschei zone, and Isarcicella isarcica zone. The successive occurrences of Hindeodus changxingensis, Neogondolella taylorae and Hindeodus parvus serve as proxies for defining the P-T biostratigraphy boundary at the base of Sub-bed 21-4 of Bed 21 in the Yangou Section. Correlations with the Meishan Section are also discussed in terms of conodont biostratigraphy. Three successive conodont faunal assemblages are grouped through the P-T transitional interval to examine the evolution of conodonts across the great transitional event. [ABSTRACT FROM AUTHOR]

The article focuses on a study which examined the size variation of foraminifers in China and the relationship between the protozoan body sizes and the end-Permian selective extinction. Samples were collected from the Changhsingian and Induan strata at the Meishan Section. Results of the study showed that there was a decline in maximum, mean and minimum sizes of the foraminifers. It also found that foraminiferal test sizes declined in both the genus and species levels.

The article focuses on a study which examined vermicular limestone from the Lower Triassic Daye Formation at the Dalongping Section in Wufeng, Hubei Province, South China. Results of the study showed that micritic limestone has higher element contents than the vermicular limestone. It also found frequent fluctations of sedimentary conditions in the interbeds of micritic and vermicular limestones.

The article focuses on a study which examined brachiopod assemblages from Qingyan, Guizhou Province, China. Specimens of brachiopod were collected from the Qingyan Formation of Anisian. The total number of brachiopod species identified from 21 genera was 31, while seven assemblages were recognized. Results of the study showed that the Diholkorhynchia sinensis dominated the D assemblage. It also observed a stepwise diversification for the brachiopod faunas during the recovery/radiation time.

The cause of the great Permian-Triassic (P-T) boundary mass extinctions remains unknown. A crucial step in identifying the cause involves a precise timing of the mass extinction interval (MEI) in order to reconstruct the pattern of biotic evolution and the chronologic record of potential triggers. Here we present an estimate of the P-T boundary MEI duration based on astronomical tuning of multiple cyclic sedimentary records. Magnetic susceptibility data from Shangsi, southern China, provide evidence for strong 405 k.y. orbital eccentricity forcing throughout the P-T boundary interval. Radioisotope dating combined with 405 k.y. tuning provides an absolute time scale through the P-T boundary interval at unprecedented high resolution. An estimated ~700 k.y. duration for the MEI at Shangsi is supported by eccentricity tuned estimates of four other sections in China and Austria. In addition, at Shangsi, the onset of mass extinction occurred shortly following a coincidence of minima in the observed ~1.5 m.y., 405 k.y., and ~100 k.y. cycles. A change in the magnetic susceptibility response to astronomical forcing occurred just prior to the onset of extinction, with reduced 100-k.y.-scale cyclicity continuing into the Early Triassic for more than 2 m.y. [ABSTRACT FROM AUTHOR]

Abstract: The Middle Triassic Qingyan Formation at its type section, the Qingyan section of Guizhou, Southwest China, yields more than 300 species belonging to 17 fossil groups, which mark the radiation of benthic organisms following the end-Permian mass extinction. This study intends to establish a primary conodont biostratigraphical succession through the Lower and Middle Triassic sequence at Qingyan to provide a time framework for the understanding of the recovery and radiation process from the mass extinction. A total of 30 species in 8 conodont genera are stratigraphically significant and assigned to the Neospathodus dieneri, Neospathodus cristagalli, Neospathodus waageni, Neospathodus homeri, Chiosella timorensis, and Neogondolella cf. bulgarica Zones in ascending order. Most conodont zones correlate well with their counterparts recognized from elsewhere in China and even worldwide. The first appearance of Ns. waageni marks the Induan–Olenekian boundary, which is placed at the lower–middle part of the Luolou Formation, 121.47m above the Permian–Triassic boundary. The Olenekian–Anisian (Early–Middle Triassic) boundary is here defined by the first occurrence of Chiosella timorensis at the base of the Qingyan Formation. Although no conodonts retrieved from the upper Qingyan Formation containing the extraordinarily diverse biota, i.e. the Qingyan Biota, stratigraphical correlation with the neighbouring conodont-bearing sections in Guizhou and the ammonoid zones suggest that the Qingyan Biota has an age of early late Anisian (early–Middle Triassic). [Copyright &y& Elsevier]

Abstract: There is growing evidence of the Lilliput effect in the end-Permian mass extinction and its aftermath. However, very little has been published on assessing the Lilliput effect on protozoans in the Early Triassic based on quantitative analysis of a great quantity of samples from outcrop sections. This study investigates foraminiferal test size variations through the Changhsingian to the Olenekian based on fossil records from three outcrop sections in South China. The sharp reduction in foraminifer sizes coincides with the first or main episode of the end-Permian mass extinction. Foraminifers remained small in sizes in the early Induan. Their body sizes increased slowly in the late Induan to Olenekian, but never recovered to the pre-extinction test size levels. The Lilliput effect on foraminifera in the aftermath of the end-Permian crisis is indicated by the extinction of large taxa, decrease in size for surviving taxa and rise of small-sized new forms. Physiological reactions of various foraminifer groups reveal that several defaunation events such as anoxia, ocean acidification, and global warming that prevailed through the Permian–Triassic interval may be responsible for both the end-Permian crisis and the Lilliput effect. [Copyright &y& Elsevier]

The West Pingdingshan Section in Chaohu, Anhui Province, has been extensively studied in recent years and become one of the classic Lower Triassic sequences well-clarified in multiple stratigraphies. Also it is an important section that defines the Smithian-Spathian (S-S) boundary within the Olenekian Stage. The S-S boundary strata at the section are restudied in high-resolution conodont biostratigraphy and carbon isotopes. The refined S-S boundary defined by the FAD of conodont Neospathodus pingdingshanensis is at 30 cm above the base of Bed 52, corresponding to a rapid diversification of conodonts. A sharp positive shift of δC curve co-occurs at the S-S boundary and it can be used as a key reference to define the boundary. The defined S-S boundary position and carbon isotopes curve can be well correlated globally. [ABSTRACT FROM AUTHOR]

Abstract: Unlike the high-abundance, low-diversity macrofaunas that characterize many Early Triassic benthic palaeocommunities, ichnofossils were relatively common in the aftermath of the end-Permian mass extinction worldwide. Ichnofossils therefore are a good proxy for ecosystem recovery after the end-Permian biotic crisis. This paper documents 14 ichnogenera and one problematic form from Lower Triassic successions exposed in the Lower Yangtze region, South China. Post-extinction ichnodiversity remained rather low throughout the Griesbachian–early Smithian period and abruptly increased in the late Smithian. However, several lines of evidence, including extent of bioturbation, burrow size, trace-fossil complexity, and tiering levels, indicate that diversification of ichnotaxa in the late Smithian did not signal full marine ecosystem recovery from the Permian/Triassic (P/Tr) mass extinction. Marine ichnocoenoses did not recover until the late Spathian in South China. The marginal sea provided hospitable habitats for tracemakers to proliferate in the aftermath of the end-Permian mass extinction. [ABSTRACT FROM AUTHOR]

Abstract: The Permian/Triassic (P/Tr) transition is ecologically assessed based on examining 23 shelly communities from five shallow platform, ramp and shelf basin facies Permian–Triassic boundary (PTB) sections in South China. The shelly communities have undergone two major collapses coinciding with the two episodes of the end-Permian mass extinction. The first P/Tr extinction event devastated shelly communities in all types of settings to some extent. The basin communities have been more severely impacted than both platform and ramp communities. The survival faunas have rebounded more rapidly in shallow niches than in relatively deep habitats. The second P/Tr crisis destroyed the survival communities in shallow setting and had little impact on the basin communities in terms of community structures. The early Griesbachian communities are overall low-diversity and high-dominance. The governorship switch from brachiopods to bivalves in marine communities has been facilitated by two pulses of the end-Permian mass extinction and the whole takeover process took about 200ka across the P/Tr boundary. Bivalve ecologic takeover initially occurred immediately after the first P/Tr extinction in shallow water habitats and was eventually completed in all niches after the second P/Tr event. Some post-extinction communities have the irregular rarefaction curves due to the unusual community structures rather than sampling intensities. [ABSTRACT FROM AUTHOR]

In the comment on our paper, Forel and Crasquin (2015) make a number of very strong criticisms that attempt to cast doubt on everything in our study. We thank them for their detailed discussion of our paper, especially the taxonomic and methodological issues and the insightful explanations on the causes of the reduction of ostracod size. However, many of their criticisms are excessive. Our paper focused on the change of ostracod size across the Permian–Triassic boundary according to reliable data, and several probable causes were presented. We accept some of the comments by Forel and Crasquin (2015), but these do not negate the core conclusions of our original paper. [ABSTRACT FROM AUTHOR]

Abstract: Chaohu is located in a deep part of carbonate ramp on the Lower Yangtze Block, which belonged to the low-latitude eastern Tethyan archipelago during the Early Triassic. Fossils were very rich in the Lower Triassic of Chaohu. Bivalves, ammonoids, conodonts were very common throughout the Lower Triassic, while fish fossils were generally rich in some beds of the upper part. It is one of the most typical sections for the Early Triassic chronostratigraphy in the world. Although various fossils had been studied in the 1980s and 1990s, recent studies based upon new and more detailed collections from the Lower Triassic of Chaohu showed that the conodont zonation needs revision. We collected Lower Triassic conodont fossils from continuous sections of the West Pingdingshan, North Pingdingshan and South Majiashan, Chaohu, Anhui Province, and updated zonations were made for each section. Eight conodont zones have been distinguished. They are, in ascending order, Hindeodus typicalis zone, Neogondolella krystyni zone, Neospathodus kummeli zone, Neospathodus dieneri zone, Neospathodus waageni zone, Neospathodus pingdingshanensis zone, Neospathodus homeri zone, and Neospathodus anhuinensis zone. The first occurrence of Neospathodus waageni eowaageni of the N. w. eowaageni subzone (i.e. the base of the N. waageni zone) is suggested as the marker to define the Induan–Olenekian boundary. [Copyright &y& Elsevier]

Abstract: Paleontological, sedimentary and geochemical data obtained from the Lower Triassic strata of the Meishan section, South China, suggest that onset of biotic recovery coincided with amelioration of paleoceanographic conditions and an increase in ocean productivity. The Griesbachian Meishanorhynchia association from Meishan indicates biotic recovery between the recovery stages 1 and 2. Both the initial biotic recovery and palaeoceanic environmental amelioration occurred within 1–2 myr after the end-Permian mass extinction in the late Griesbachian. [Copyright &y& Elsevier]

Abstract: The Lower Triassic, consisting of the Yinkeng Fm., Helongshan Fm. and the lower part of the Nanlinghu Fm., is well developed at the Meishan D Section of Changxing County, Zhejiang Province, South China. Based on detailed study of the conodont biostratigraphy from the interval of the Permian–Triassic boundary and the Lower Triassic in the Meishan D Section, 8 conodont zones are recognized in ascending order as follows: the Neogondolella changxingensis yini–Hindeodus praeparvus Zone (beds 24a–24e, top of the Changxing Fm.), the Neogondolella meishanensis meishanensis–Hindeodus eurypyge Zone (beds 25–27b, base of the Yinkeng Fm.), the Hindeodus parvus Zone (beds 27c–27d, first conodont zone of Triassic, the global index for the base of Triassic), the Isarcicella staeschei Zone (beds 28–29a, lower part of the Yinkeng Fm), I. isarcica Zone (beds 29b–51, lower part of the Yinkeng Fm.), the Neogondolella tulongensis–N planata Zone (beds 52–72, from upper part of the Yinkeng Fm. to lower part of the Helongshan Fm.), the Neospathodus kummeli Zone (beds 73–92, middle part of the Helongshan Fm.), and the Neospathodus cristagalli–N dieneri Zone (beds 93–111, from upper part of the Helongshan Fm. to the base of the Nanlinghu Fm.). At the Meishan D Section, the palynological biostratigraphy is also studied herein. The palynological assemblage of Lundbladispora–Taeniaesporites–Equisetosporites is found in the intervals which contain the conodont Isarcicella isarcica Zone and the lower part of the Neogondolella tulongensis–N. planata Zone. [Copyright &y& Elsevier]

Abstract: The Palaeozoic–Mesozoic transition is characterized not only by the biggest Phanerozoic mass extinction, at the end of Permian, but also a prolonged period of recovery of the biota during the succeeding Early Triassic. The delayed recovery is generally attributed to the effects of extreme environmental conditions on the Early Triassic ecosystem. However, there has been very little study of the cause and mechanism of the environmental conditions that prevailed during the period of extinction and subsequent recovery. Research on the Permian–Triassic boundary and Lower Triassic, especially that on environmental events at the beginning of the Triassic in South China, indicates that the slowness of the recovery may be the result of three factors: (1) extreme environmental conditions that persisted through the transitional period and which were maintained by, for example, intermittent contemporary volcanism; (2) a passive evolutionary and ecologic strategy of the biota, in which r-selection taxa were dominant and K-selection forms insignificant; (3) an immature, poorly functioning ecosystem, which had difficulty in responding to and withstanding extreme environmental changes. According to data from South China, environmental changes were frequent during the Late Permian, and especially serious at the Permian–Triassic boundary. The Late Permian ecosystem was well structured and fully functioning as a result of a long period of steady development during the late Palaeozoic, and was capable of resisting general environmental changes. However, increasingly frequent and probably more extreme environmental events in the latest Permian may have led to a general collapse of this ecosystem and to the mass extinction at the end of the Permian. The Early Triassic ecosystem was immature, functioned poorly, and was unable to respond effectively to environmental changes, so that persisting extreme environmental conditions slowed ecosystem reconstruction considerably, and the recovery of the biota therefore took a relatively long time. The environmental events at the Permian–Triassic boundary might not be significantly different from those at other Phanerozoic transitions, but they consisted of a series of events that occurred at intervals during the transitional period. [Copyright &y& Elsevier]

Calcimicrobialites, which could be correlated to the layer 27 in Meishan section according to the Hindeodus parvus, occur abruptly on the end-Permian mass extinction boundary in South China. Microbialites mainly distribute on the top of reef facies or shallow carbonate platforms, thin-fling into deep facies. All the microbialites discovered are composed of micrite and coarse crystal digitate carbonate or patch carbonate. Microfossils usually dominate in the microbialites, and small gastropods, bivalves and ostracodes can also be found. This fossil assemblage represents a simple but particular remanent biota after the end-Permian mass extinction on the top of reefs or shallow carbonate platforms. Abrupt occurrence of microbialites above the mass extinction boundary is the ecological response to the end-Permian global event in reef or shallow carbonate facies. Many studies have been done on the Permian-Triassic boundary and event in deep water facies sections or middle to lower shelf facies sections. However, the calcimicrobialites in South China are mainly located above reef facies or shallow carbonate platform facies. It will surely be helpful for people to know more about the different responses in different depths of ancient marine environment during the transition between Permian and Triassic by the study of petrology, palaeontology and palaeoecology of the calcimicrobialites. [ABSTRACT FROM AUTHOR]

The Permian–Triassic boundary of South China has been well-known and well-studied for decades, but what is relatively less noticed is that there are also many excellent marine Lower Triassic sequences in the region, covering various paleogeographic lithofacies. This paper presents an outline of the various Lower Triassic stratigraphic sequences in South China and provides a reference to the application of the Lower Triassic subdivision and stages.The Early Triassic marine basin of South China is subdivided into five sedimentary provinces: Cathaysia, Lower Yangtze, Upper Yangtze, Youjiang and Lijiang provinces. Each province has an interrelated distribution of lithofacies and stratigraphy. The Lower Triassic biostratigraphic sequences of bivalves, ammonoids and conodonts are summarized in the various sedimentary facies and provinces of South China. The Chinese twofold subdivision of the Lower Triassic is primarily demonstrated as well in this paper. [Copyright &y& Elsevier]

Discusses the advances in the study of the Lower Triassic conodonts at Meishan Section, Changxing, Zhejiang Province in China. Meishan as the best selection of global stratotype section and point (GSSP) of the Permian and Triassic boundary (PTB); Advantage of Zhejiang Province in competing for the GSSP of PTB.

The article focuses on a study which examined the link between biotic evolution and environmental change in the Early Triassic using the sulfur isotope. Samples of pure carbonate were collected from the Guandao Section in Nanpanjiang basin, South China. Results of the study showed a gradual increase in the sulfur isotopes of carbonate associated sulfate (CAS) in the lower and middle Dienerian and a decline at the end of the Dienerian.

The article examines the recovery history of marine ecosystems following the end-Permian mass extinction in South China. A definition of biotic recovery is provided. It notes that the Lower Triassic of South China is rich in bivalves and ammonoids, as well as fishes and reptiles. Eight localities yielded fossil fishes, while early Triassic reptiles were found in four localities. Information on the paleographic location of these fossils is given.

• Carbonaceous spheroids from Cryogenian Nantuo Formation in Shennongjia area of South China. • Potential abiotic and biotic origins have been discussed. • A definitive conclusion could not be drawn on their nature. • Adds to a growing list of fossil-like structure records in the Cryogenian Period. Black shale of the Cryogenian Nantuo Formation, Shennongjia area, South China contains spheroids which co-occur with fossils of macroalgae. These three-dimensional structures occur sparsely as isolated specimens or abundantly as clusters which show different types of boundaries between individuals. They are generally circular on bedding surfaces and elliptical on transecting sections, and range up to several millimeters in diameter. Both petrographic thin sections and scanning electron microscopy (SEM) reveal that these spheroids are mostly organic carbon in composition and exhibit sharp, well-rounded external margins composed of microcrystalline clay minerals. The carbonaceous nature of these spheroids and different elemental abundances between spheroids and matrix are also confirmed by Raman spectroscopy and energy dispersive X-ray spectroscopy (EDS). Organic carbon isotopic values of individual spheroids range from −28.55‰ to −28.83‰, with an average of −28.72‰, which show indistinguishable δ13C org values with the surrounding sedimentary matrix but exhibit statistically significant difference to those of contemporaneous macroalgae. A range of physical origins for these spheroids—including concretions, fluid escape structures, raindrop impressions, or bubble impressions—are considered and cannot be entirely rejected. Alternatively, biogenic origin is also a possible interpretation from observations of their morphological, mineralogical, geochemical, and sedimentological characteristics. Although their nature remains unresolved, the documentation of these new carbonaceous spheroids from the Nantuo Formation of Shennongjia area adds to a growing list of fossil-like structure records in the Cryogenian Period. [ABSTRACT FROM AUTHOR]

Unitary Association Method (UAM) analyses of conodont faunas from 28 sections spanning the biggest Phanerozoic end-Permian mass extinction and significant global environmental and ecosystem perturbations during the succeeding Early Triassic are presented. Based on 72 conodont species, 26 Unitary Association Zones (UAZs) are established for the latest Permian to earliest Middle Triassic of South China. These UAZs provide quantitative high-resolution tools to correlate sequences in the Early Triassic of South China and to compare and test high-resolution conodont biostratigraphy based on interval conodont zones developed over the past three decades. Our quantitative analyses provide insights on ongoing debates relating to the First Appearance Datum (FAD) of the conodont Hindeodus parvus which is used to place and subsequently correlate the "Golden Spike" defining the base of the Triassic (Permian-Triassic Boundary) at the base of Bed 27c at the GSSP Meishan D Section. Previous proposals that suggested potential earlier occurrences of H. parvus below its FAD at Meishan section are not supported by our results. In deep water sections, the First Occurrence (FO) of H. parvus lies at the base of UAZ 5 at the Bianyang section while it lies within UAZ 6 at the Meishan section. This indicates that the earliest occurrence of H. parvus in South China is in the Bianyang section but this conclusion needs further testing due to the reliance on "spot" data by the UAM. Anomalously high occurrences of Hindeodus in the Mingtang section (close to the Bianyang section) further suggests that the Bianyang-Mingtang area may have provided a temporally extended habitable zone for anchignathodontid conodonts. Stage boundaries currently proposed or established using interval conodont zones locate within or between UAZs and are difficult to correlate with carbon isotope curves. UAZs are useful in helping to define GSSPs by recognizing which correlations are most robust and in the selection of the most appropriate species and level for GSSPs. [ABSTRACT FROM AUTHOR]

Ichnological studies are exceptionally important for reconstruction of ecosystems in the aftermath of mass extinctions, but they have only rarely been undertaken from strata deposited in continental settings during the Permian–Triassic transition. This paper systematically documents seventeen ichnogenera and three ichno-types coupled with plant fossils (mainly equisetaceous stems and roots) from the fluvial–lacustrine Late Permian to Middle Triassic Shichuanhe section in North China. These ichnofossils constitute several ichnoassemblages, including resting traces (Lockeia), locomotion traces (Diplichnites , Kouphichnium , Protovirgularia), dwelling traces (Arenicolites , Camborygma , Macanopsis , Palaeophycus , Skolithos), grazing traces (Gordia , Helminthoidichnites , Monomorphichnus) and feeding traces (Planolites , Scoyenia , Spongeliomorpha , Taenidium) and some of them were scarcely reported in the coeval sediments of North China. The ichnological criteria, such as ichnodiversity, intensity of bioturbation, and burrow size and depth, exhibit a significant reduction in the latest Permian rocks, accompanied by simplification of trace maker ethology. These signals initially rebound in the early Early Triassic, when the behavioral generalists opportunistically occupied the empty niches and constructed simple but deep Skolithos. A full reconstruction of continental ecosystems should take place in the late Early Triassic to Middle Triassic, with high ichnodiversity, intensive bioturbation and behavior complexity of trace producers. The small, simple but deep burrows occurring in the early Early Triassic would be the ecological responses of the animals to the lethal heat in the terrestrial facies. • Diverse P-Tr ichnofossils from terrestrial Shichuanhe section in North China • Ichnotaxa reveal extinction and recovery of continental biota in the P-Tr transition • Size reduction and fossorial behavior might be biotic responses to the lethally hot [ABSTRACT FROM AUTHOR]

The Permian–Triassic mass extinction was the largest biotic extinction event in the Phanerozoic and affected both marine and continental life. Marine Permian–Triassic transitional sequences can be correlated in many regions, but this has proved difficult for continental successions. A growing number of studies show that spinicaudatans are some of the most common fossils in continental strata and can be used as index fossils for continental stratigraphic division and correlation. Here we document the morphology and biostratigraphic significance of Euestheria gutta based on well‐preserved fossils from southwestern China. It shows strong intraspecific morphological variation, while the most important feature is the strongly convex larval valve and significant finely pitted to weakly reticulated ornamentation on the growth bands. Evidence from palaeobotany, charcoal, and organic carbon isotopes indicated that the continental mass extinction in southwestern China was marked by the catastrophic loss of tropical rainforest vegetation, enhanced wildfire and a negative carbon isotope excursion (CIE) during the P–Tr transition. Meanwhile, abundant E. gutta first appeared at the onset of the negative CIE and just above the horizon of the loss of macroflora. Based on the global geographic distribution of E. gutta and temporal correlation, we conclude that this species existed from the latest Permian to the earliest Triassic, and the occurrence of E. gutta could be used as an index fossil of the continental mass extinction interval or P–Tr transitional beds. [ABSTRACT FROM AUTHOR]

Abstract Organic-rich black shales in the Upper Permian Dalong Formation are considered excellent source rocks in the western Hubei Basin, South China. However, the mechanisms of organic matter (OM) accumulation remain controversial. Furthermore, the evolution of primary productivity and ocean hypoxia during the Late Permian in the western Hubei Basin is unclear. In this study, we discuss the paleoclimate, paleoceanography, paleoenvironment and the mechanisms of OM accumulation based on geochemical characteristics and pyrite framboid data from drillcore H 1 in Ensi, western Hubei Province. Black shales from the Dalong Formation have high total organic carbon (TOC) contents (2.8–9.3%), while the mudstone samples contain low TOC contents (0.48–1.96%). The weak chemical weathering indicates paleoclimate conditions were relatively cold during black shale deposition, whereas rapid warming occurred during gray mudstone deposition, which may be connected with the Late Permian Changhsingian global climate event. Redox indices, namely, V, U, and Mo concentrations, and the relationship of U EF and Mo EF combined with pyrite framboid data suggest that an anoxic to euxinic environment predominated during black shale accumulation. In contrast, oxic to hypoxic marine conditions pervaded the western Hubei Basin during the deposition of mudstone. The primary productivity indices (Cu/Al and Nixs) suggest that high paleoproductivity occurred in the Late Permian, especially during periods of transgression. However, declining primary productivity with enhanced intensity of chemical weathering may indicate that biological extinction was associated with a rapid increase in temperature during the Late Permian. Negative/positive relationships between the TOC contents and Baxs and Nixs values demonstrate that sulfate was consumed by a higher OM input and OM accumulation was mainly controlled by high primary productivity. The study implies that ocean hypoxia and high primary productivity played important roles in OM accumulation. The depositional model shows that high primary productivity possibly resulted from weathering of volcanic ash from land during transgressions and that intense degradation of OM resulted in an euxinic environment. Highlights • Anoxia and intermittent euxinia occurred during the organic matter accumulation. • Productivity enhanced during superimposed sea level rises. • Increasing temperature and enhanced intensity of chemical weathering caused the reducing primary productivity. • Organic matter accumulation was mainly controlled by the paleoproductivity. [ABSTRACT FROM AUTHOR]

The article proposes an alternative estimate of the duration between the Permian-Triassic (P-T) mass extinction events. Evidence for astronomical forcing was obtained through high-resolution magnetic susceptibility data from the Huangzhishan Section of South China. A ‵700 ka duration was observed between the two extinction events via time series analysis and astronomical calibration. it cites 600-700 ka as the minimum duration between the two P-T extinction events.

Wrinkle structures in rocks younger than the Permian-Triassic (P-Tr) extinction have been reported repeatedly in marine strata, but rarely mentioned in rocks recording land. Here, three newly studied terrestrial P-Tr boundary rock succession in North China have yielded diverse wrinkle structures. All of these wrinkles are preserved in barely bioturbated shore-shallow lacustrine siliciclastic deposits of the Liujiagou Formation. Conversely, both the lacustrine siliciclastic deposits of the underlying Sunjiagou Formation and the overlying Heshanggou Formation show rich bioturbation, but no wrinkle structures or other microbial-related structures. The occurrence of terrestrial wrinkle structures in the studied sections reflects abnormal hydrochemical and physical environments, presumably associated with the extinction of terrestrial organisms. Only very rare trace fossils occurred in the aftermath of the P-Tr extinction, but most of them were preserved together with the microbial mats. This suggests that microbial mats acted as potential oases for the surviving aquatic animals, as a source of food and oxygen. The new finds suggests that extreme environmental stresses were prevalent both in the sea and on land through most of the Early Triassic. [ABSTRACT FROM AUTHOR]