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Finely preserved fossil assemblages (lagerstätten) provide crucial insights into evolutionary innovations in deep time. We report an exceptionally preserved Early Triassic fossil assemblage, the Guiyang Biota, from the Daye Formation near Guiyang, South China. High-precision uranium-lead dating shows that the age of the Guiyang Biota is 250.83 +0.07/–0.06 million years ago. This is only 1.08 ± 0.08 million years after the severe Permian-Triassic mass extinction, and this assemblage therefore represents the oldest known Mesozoic lagerstätte found so far. The Guiyang Biota comprises at least 12 classes and 19 orders, including diverse fish fauna and malacostracans, revealing a trophically complex marine ecosystem. Therefore, this assemblage demonstrates the rapid rise of modern-type marine ecosystems after the Permian-Triassic mass extinction.

The rapid and accurate taxonomic identification of fossils is of great significance in paleontology, biostratigraphy, and other fields. However, taxonomic identification is often labor-intensive and tedious, and the requisition of extensive prior knowledge about a taxonomic group also requires long-term training. Moreover, identification results are often inconsistent across researchers and communities. Accordingly, in this study, we used deep learning to support taxonomic identification. We used web crawlers to collect the Fossil Image Dataset (FID) via the Internet, obtaining 415,339 images belonging to 50 fossil clades. Then we trained three powerful convolutional neural networks on a high-performance workstation. The Inception-ResNet-v2 architecture achieved an average accuracy of 0.90 in the test dataset when transfer learning was applied. The clades of microfossils and vertebrate fossils exhibited the highest identification accuracies of 0.95 and 0.90, respectively. In contrast, clades of sponges, bryozoans, and trace fossils with various morphologies or with few samples in the dataset exhibited a performance below 0.80. Visual explanation methods further highlighted the discrepancies among different fossil clades and suggested similarities between the identifications made by machine classifiers and taxonomists. Collecting large paleontological datasets from various sources, such as the literature, digitization of dark data, citizen-science data, and public data from the Internet may further enhance deep learning methods and their adoption. Such developments will also possibly lead to image-based systematic taxonomy to be replaced by machine-aided classification in the future. Pioneering studies can include microfossils and some invertebrate fossils. To contribute to this development, we deployed our model on a server for public access at www.ai-fossil.com.

Studies from the terrestrial facies indicate that the life and environment experienced a similar and interrelated process on land and in water through the great Permian-Triassic transition, that is, the quick temperature rising in the latest Permian associated with the great end-Permian mass extinction, a subsequent prolonged superhigh temperature throughout the Early Triassic with extensive red sediments and extremely barren fossils, and the climate returning to normal during the Middle Triassic with the reconstruction of the Mesozoic ecosystems. However, the refined integrative study on the Permian-Triassic stratigraphy and fossil and depositional records from North China displays some inconsistency of the biotic and environmental events through the great Paleozoic-Mesozoic transition. For instance, the red beds and related arid climatic indicators such as paleosols show the temperature rising through the mid-late Permian. The Permo-Triassic mass extinction on land looks clearly prior to the major marine crisis whereas the major changeover of the depositional systems, i.e. the river system transforming from meandering to braided rivers, obviously lagging behind. The recovery of animals recorded from trace fossils happened in the late Early Triassic while the plants showed a gradual reconstruction of the Mesophytic communities during the Middle-Late Triassic.

The end-Permian mass extinction, the largest biological crisis in Earth history, is currently understood in the context of Siberian Traps volcanism introducing large quantities of greenhouse gases to the atmosphere. We reconstructed the late Permian to Middle Triassic atmospheric CO2 record by applying the carbonate paleosol pCO2 barometer to soil carbonates from sections in northwest China (Xinjiang Province), north China (Henan and Shanxi Provinces), Russia (South Ural foreland basin), South Africa (Karoo Basin), and the United Kingdom (Dorset). Atmospheric pCO2 shows an approximate 4-fold increase from mean concentrations of 412–919 ppmv in the late Permian (Changhsingian) to maximum levels between 2181 and 2610 ppmv in the Early Triassic (late Griesbachian). Mean CO2 estimates for the later Early Triassic are between 1261–1936 ppmv (Dienerian) and 1063–1757 ppmv (Spathian). Significantly lower concentrations ranging from 343 to 634 ppmv are reconstructed for the latest Early to Middle Triassic (Anisian). In parallel to the reconstructed rise in greenhouse gas levels, low-latitude sea surface temperatures (SST) increased by 7–10 °C, from 25–28 °C to >35 °C (Joachimski et al., 2020). With the decrease in pCO2 in the late Spathian to Anisian, SSTs decreased as well (Sun et al., 2012). Thus, pCO2 as well as SSTs persisted at high levels for almost 5 m.y. In contrast, pCO2 reconstructed using the photosynthetic carbon isotope fractionation suggest much lower atmospheric pCO2 (e.g. Shen et a. 2022), inconsistent with significant warming, while modeling studies suggest up to a 13-fold increase in pCO2 (e.g. Cui et al. 2021). Most important, the 5 m.y. long episode of elevated pCO2 suggests that negative feedback mechanisms such as silicate weathering, the most effective mechanism by which to extract CO2 from the atmosphere and to buffer Earth’s climate, were not effective enough to reduce atmospheric pCO2 to pre-crisis levels. Instead, marine authigenic clay formation (i.e., reverse weathering) may have been an important component of the global carbon cycle keeping atmospheric pCO2 at elevated levels during this critical time interval. References: Cui et al. 2021, PNAS, V. 118, No.37, e201470118; Joachimski et al. 2020, GSA Bull., 132, 427-443; Shen et al. 2022, Nat. Geosc., 15, 839-844; Sun et al. 2012, Science, 338, 366-370.

The Permian–Triassic was a major transition in the evolution of life in the earth history, when happened the greatest mass extinction during the Phanerozoic and an unusually prolonged or delayed recovery. Most studies have been carried in the marine facies while very few in the continental facies. On land, plants play a great role in the interaction of climate and terrestrial ecosystems. Here we present a regional case of stepwise recovery of vegetation in North China. Prior to the Permian–Triassic mass extinction, the voltzialean conifer forest community dominated in the Changhsingian. Consequently, the extinction event wiped out of the voltzialean conifer forest community, probably conciding with the extension of the red beds. The first post-crisis flora was an Induan herbaceous lycopsid community, succeeded by the Pleuromeia–Neocalamites shrub marsh community. A pteridosperm shrub woodland community dominated for a short time in the late Early Triassic along with the reappearance of insect herbivory. In the early Middle Triassic, gymnosperm forest communities gradually rose to predominate in both uplands and lowlands along with other diverse plant communities, indicating the beginning of the establishment of the Mesophytic Flora. In the late Middle Triassic–Late Triassic, it was occupied by the Danaeopsis–Symopteris flora and the opportunism elements gradually were replaced by the advanced taxa, which represents the complete establishment of the Mesophytic Flora.

In terrestrial settings, the Permo-Triassic mass extinction is commonly linked to major changes in sedimentological and climatic conditions that include a switch from meandering to braided fluvial systems and increased aridity. We examined the predominantly terrestrial strata of North China to reveal that, on the contrary, there was little substantial sedimentological change during the Permo-Triassic mass extinction. The crisis level occurs in the upper Sunjiagou Formation, where a range of environments, including low-sinuosity rivers, distally terminating alluvial fans, and mud-dominated coastal plains are recorded. A major sedimentological change occurred slightly higher, within the lowest Triassic, and involved a switch to braided fluvial and shallow lacustrine/fluviodeltaic conditions of the Liujiagou Formation. Later in the Early Triassic, fine-grained, playa lake, and alluvial plain facies became widespread (Heshanggou Formation). Paleosols are present throughout the basin fill and record a transition from Aridisols and Vertisols in the Late Permian to Inceptisols in the Early Triassic followed by gleyed Aridisols, Vertisols, and Inceptisols later in the Early Triassic. Previously reported aeolian facies from Lower Triassic strata were not encountered in this study and were unlikely to have occurred given the prevalence of lacustrine and fluvial conditions at this time. Overall, the North China Basin experienced an increase in seasonal rainfall in the latest Permian and a base-level rise that introduced marine conditions into the southwest of the basin. During the Early Triassic, seasonal or interannual rainfall was frequent, with strong evaporation in a hot climate. Overall, substantial sedimentological changes occurred in the terrestrial Permo-Triassic environments of North China, but despite earlier claims from studies in North China and elsewhere, there was no abrupt transition in fluvial styles around the Permo-Triassic mass extinction.

The link between the Permian–Triassic mass extinction (252 million years ago) and the emplacement of the Siberian Traps Large Igneous Province (STLIP) was first proposed in the 1990s. However, the complex cascade of volcanically driven environmental and biological events that led to the largest known extinction remains challenging to reconstruct. In this Review, we critically evaluate the geological evidence and discuss the current hypotheses surrounding the kill mechanisms of the Permian–Triassic mass extinction. The initial extrusive and pyroclastic phase of STLIP volcanism was coeval with a widespread crisis of terrestrial biota and increased stress on marine animal species at high northern latitudes. The terrestrial ecological disturbance probably started 60–370 thousand years before that in the ocean, indicating different response times of terrestrial and marine ecosystems to the Siberian Traps eruptions, and was related to increased seasonality, ozone depletion and acid rain, the effects of which could have lasted more than 1 million years. The mainly intrusive STLIP phase that followed is linked with the final collapse of terrestrial ecosystems and the rapid (around 60 thousand years) extinction of 81–94% of marine species, potentially related to a combination of global warming, anoxia and ocean acidification. Nevertheless, the ultimate reasons for the exceptional severity of the Permian–Triassic mass extinction remain debated. Improved geochronology (especially of terrestrial records and STLIP products), tighter ecological constraints and higher-resolution Earth system modelling are needed to resolve the causal relations between volcanism, environmental perturbations and the patterns of ecosystem collapse.

Massive carbon dioxide (CO 2 ) emissions are widely assumed to be the driver of the end-Permian mass extinction (EPME). However, the rate of and total CO 2 released, and whether the source changes with time, remain poorly understood, leaving a key question surrounding the trigger for the EPME unanswered. Here, we assimilate reconstructions of atmospheric P co 2 and carbonate δ 13 C in an Earth system model to unravel the history of carbon emissions and sources across the EPME. We infer a transition from a CO 2 source with a thermogenic carbon isotopic signature associated with a slower emission rate to a heavier, more mantle-dominated volcanic source with an increased rate of emissions. This implies that the CO 2 degassing style changed as the Siberian Traps emplacement evolved, which is consistent with geochemical proxy records. Carbon cycle feedbacks from terrestrial ecosystem disturbances may have further amplified the warming and the severity of marine extinctions.

The global pattern of plant evolution through the Permian−Triassic mass extinction is uncertain, and the extent to which land plants were affected is debated. Detailed studies undertaken at a regional scale can help evaluate this floral transition, and thus we provide a detailed account of floral evolution from the Permian to Middle Triassic of North China based on new paleobotanical data and a refined biostratigraphy. Five floral transition events are identified from before, during, and after the Permian−Triassic crisis, including the disappearance of the gigantopterid flora (associated with loss of coal deposits), the end-Permian mass extinction of Paleophytic taxa, and gradual recovery in the Triassic with the stepwise appearance of the Mesophytic vegetation. The record begins with a Cisuralian gigantopterid-dominated rainforest community, and then a Lopingian walchian Voltziales conifer-ginkgophyte community that evolved into a voltzialean conifer-pteridosperm forest community. The last is associated with a change amongst terrestrial vertebrates from the Jiyuan fauna to a pareiasaur-dominated fauna, found in red beds that lack coal deposits due to arid conditions. The disappearance of the voltzialean conifer forest community may represents the end-Permian mass extinction of plants although it could also be a consequence of the non-preservation of plants in sedimentary red-beds. The first post-crisis plants are an Induan herbaceous lycopsid community, succeeded by the Pleuromeia-Neocalamites shrub marsh community. A pteridosperm shrub woodland community dominated for a short time in the late Early Triassic along with the reappearance of insect herbivory. Finally, in the Middle Triassic, gymnosperm forest communities gradually rose to dominance in both uplands and lowlands along with other diverse plant communities, indicating the establishment of the Mesophytic Flora.

Early Triassic temperatures were some of the hottest of the Phanerozoic, sea-surface temperatures approached 40°C, with profound consequences for both the sedimentology and faunal distributions in the oceans. However, the impact of these temperatures in terrestrial settings is unclear. This study examines shallow lacustrine sediments from the Lower Triassic succession of North China. These consist of diverse fluvial to shallow lacustrine sandstones and also spectacular, coarse conglomerates composed of diverse, intraformational clasts reworked from the interbedded sediments. The conglomerate beds can show inverse grading and high angle, flat-pebble imbrication in their lower part and vertically orientated flat pebbles in their upper part. The cobbles include cemented and reworked conglomerate intraclasts and sandstone concentrically-laminated concretions that record multi-step histories of growth and reworking, pointing to rapid cementation of the sandy lake bed (likely facilitated by high temperatures). The conglomerates record frequent, high-energy events that were capable of brecciating a lithified lake bed and transporting cobbles in wave-influenced sediment-gravity flows. Initially, powerful oscillatory flows brecciated and deflated the lake bed and subsequently helped to sustain turbulence during short-distance lateral flow. It is possible that hurricanes, originating from the adjacent hyper-warm, Palaeo-Tethyan Ocean travelled into the major lakes of the North China continent during the Early Triassic.

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.

Climate change is a critical factor affecting biodiversity. However, the quantitative relationship between temperature change and extinction is unclear. Here, we analyze magnitudes and rates of temperature change and extinction rates of marine fossils through the past 450 million years (Myr). The results show that both the rate and magnitude of temperature change are significantly positively correlated with the extinction rate of marine animals. Major mass extinctions in the Phanerozoic can be linked to thresholds in climate change (warming or cooling) that equate to magnitudes >5.2 °C and rates >10 °C/Myr. The significant relationship between temperature change and extinction still exists when we exclude the five largest mass extinctions of the Phanerozoic. Our findings predict that a temperature increase of 5.2 °C above the pre-industrial level at present rates of increase would likely result in mass extinction comparable to that of the major Phanerozoic events, even without other, non-climatic anthropogenic impacts., The linkage between temperature change and extinction rates in the fossil record is well-known qualitatively but little explored quantitatively. Here the authors investigate the relationship of marine animal extinctions with rate and magnitude of temperature change across the last 450 million years, and identify thresholds in climate change linked to mass extinctions.

Queuing behaviour has been documented in marine arthropods from Cambrian to modern oceans. It was previously hypothesized that this behaviour provided energy savings through hydrodynamic drafting, with trilobites in following positions hypothesized to produce less drag than those leading. In this study, we evaluate the hydrodynamics of queuing behaviour in the Devonian trilobite Trimerocephalus chopini using computational fluid dynamics. The results show that the drag forces of the trilobites following in the queue were substantially lower than those produced by the leader (~65–79% lower at velocities of 0.5–2 cm s−1). Drag reduction was positively correlated with the movement speed of the trilobites, but decreased with increasing distance from the leader, and there was essentially no drag reduction at all for the first following trilobite when the following distance was greater than about six times its body length. This agrees with fossil evidence preserving trilobites in queues in close proximity to each other. The results also show that drag reduction was still significant (~86.8% at 2 cm s−1) even for the longest queues preserved in the fossil record. Our findings support the hypothesis that the queuing behaviour of trilobites was an adaptation for reducing hydrodynamic drag. This drag reduction effect compensated for the energy cost of movement, which would have been particularly advantageous during migration.

The end-Permian mass extinction (ca. 252 Ma) represents the most severe biotic crisis of the Phanerozoic, and it was accompanied by profound environmental perturbations, especially to the global carbon cycle, as indicated by sharp negative carbon isotope excursions (CIE) in both carbonates (δ13Ccarb) and organic matter (δ13Corg). To date, carbon isotope records are mostly from marine Permian-Triassic transitional sequences with relatively few high-resolution carbon isotope profiles having been generated for terrestrial facies. Terrestrial Permian-Triassic sequences suitable for high-resolution carbon isotope study are rare globally and are difficult to correlate with better-studied marine sequences. However, carbon isotope records from continental facies are essential to a full understanding of global carbon cycle changes during the Permian-Triassic transition. Here, we present bulk δ13Corg profiles for three terrestrial sections in North China representing Permian-Triassic transitional beds. These profiles exhibit similar patterns of secular variation defining three stages: (1) a pre-CIE interval, (2) a CIE interval, characterized by a rapid negative shift of 1.7‰–2.2‰ within the middle part of the Sunjiagou Formation, and (3) a post-CIE interval. The similarity of the CIE in all three study sections facilitates correlations among them, and its presence in the Permian-Triassic transitional beds suggests that it is equivalent to the negative CIE at the Permian-Triassic boundary in the Meishan global stratotype section and point (GSSP) and in coeval marine and terrestrial sections globally. The end-Permian CIE was probably triggered by a massive release of 13C-depleted carbon from volcanogenic sources leading to elevated atmospheric pCO2, although oceanic sources of CO2 cannot be ruled out at present.

Eleven conodont zones are established for the Lower Triassic of the Motianling section in the Nanpanjiang Basin, South China. Detailed size measurements on 2244 P1 conodont elements demonstrate dynamic size variation patterns during the Early Triassic that are calibrated to the Early Triassic timescale and conodont zonation. Correlation of conodont size variation with various environmental indicators shows that these size changes are primarily controlled by rapidly changing and episodic environmental conditions and ecological recovery in the aftermath of the end-Permian mass extinction. Decreasing size trends occur in the early Griesbachian, late Griesbachian and at the Smithian–Spathian boundary. Episodes of size increase (rebounds) occur in the middle Griesbachian, Induan–Olenekian boundary and middle–late Spathian. The observed temporal size variations indicate that conodont animals were significantly affected by rapidly changing environmental conditions (mainly temperature and redox conditions) during the Early Triassic and recurrent size increases (rebounds) occurred during periods of environmental and climatic amelioration (climatic cooling and oxygenation), demonstrating a complicated recovery history of marine ecosystems in the aftermath of the largest Phanerozoic biotic crisis. Supplementary material: Data for all species are available at https://doi.org/10.6084/m9.figshare.c.4528616

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.

Global warming is inferred to have been one of the main causes of the Permian-Triassic (P-Tr) boundary mass extinction. Although a strong temperature rise in tropical sea-surface temperatures during the latest Permian has been documented, coeval climate changes in terrestrial sections are less well-known. Here, we analyzed multiple weathering indexes (including CIA, CIW, and PIA) for two terrestrial sections in North China (Shichuanhe and Yima), all of which show a major excursion toward higher values (greater weathering intensity) around the end-Permian plant extinction (EPPE). At Shichuanhe, the CIA (chemical index of alteration) increases from 70 to 75 over the interval of 11–36 m, which straddles the EPPE at 33 m, and then decreases from 75 to 71 in the overlying strata. At Yima, CIA increases from 63 to 79 over the interval of 57–68 m, extending up to the EPPE at 68 m, and then gradually decreases from 78 to 72 in the overlying strata. These results imply a strong warming event coupled with intense chemical weathering in soil environments leading up to the end-Permian plant extinction. The decline in CIA values following the EPPE may reflect loss of weathered soils through physical erosion rather than climatic cooling. Estimation of atmospheric temperatures from the CIA data indicate rapid rises at Shichuanhe (from ~11.6 °C to 16.5 °C) and Yima (from 9.3 °C to 18.4 °C) during the end-Permian crisis. The findings in this study are consistent with the hypothesis that a sharp temperature rise caused the extinction of terrestrial organisms during the end-Permian crisis.

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.

Description of the studied borehole, analytical methods, supplemental figure, and data tables.

The Permian–Triassic mass extinction was marked by a massive release of carbon into the ocean-atmosphere system, evidenced by a sharp negative carbon isotope excursion. Large carbon emissions would have increased atmospheric pCO2 and caused global warming. However, the magnitude of pCO2 changes during the PTME has not yet been estimated. Here, we present a continuous pCO2 record across the PTME reconstructed from high-resolution δ13C of C3 plants from southwestern China. We show that pCO2 increased from 426 +133/−96 ppmv in the latest Permian to 2507 +4764/−1193 ppmv at the PTME within about 75 kyr, and that the reconstructed pCO2 significantly correlates with sea surface temperatures. Mass balance modelling suggests that volcanic CO2 is probably not the only trigger of the carbon cycle perturbation, and that large quantities of 13C-depleted carbon emission from organic matter and methane were likely required during complex interactions with the Siberian Traps volcanism., The Permian–Triassic mass extinction was accompanied by a massive release of carbon into the ocean-atmosphere system, but the magnitude of change is not well known. Here, the authors present a new record of C3 plants from southwestern China which shows that atmospheric pCO2 increased by a factor of six during this event.

Past major biological turnovers are coeval to large injections of CO2 into the atmosphere–ocean system that are often linked to the emplacement of Large Igneous Provinces. The impact of these CO2 pulses on ecosystems is however different at different times, and this difference is contingent on the initial boundary conditions. Here, we show how delayed vegetation recovery from the Permo–Triassic mass extinction (ca. 252 Ma) and continuing amalgamation of Pangaea, determined the style of the Late Triassic Carnian Pluvial Episode (ca. 233 Ma), a global climate change event linked to a major biological turnover and to the emplacement of the Wrangellia LIP. Our new biogeochemical modelling can reproduce changes in C and Sr isotopes only when we assume that high terrestrial productivity recovers in the Carnian, ∼15 Myrs after the Permo–Triassic crisis, consistent with the re-appearance of large coal swamps. In the model, this early Carnian expansion of the terrestrial organic C reservoir results in a drop of atmospheric pCO2 and global temperatures. Furthermore, climate modelling shows how the resulting low pCO2 conditions, coupled to the aridity of Pangaea, made the Carnian Earth system more susceptible to hydrological cycle enhancements following C inputs from coeval volcanism, thus explaining the nature of the Carnian Pluvial Episode.

The Permian–Triassic transition witnessed the extinction of some 90% in the marine realm and 70% taxa on land. Paleoclimate seems to have played a key role in this largest Phanerozoic biodiversity crisis. However, to understand past climatic conditions on land, which display significant spatial variability (e.g., in terms of local temperature and humidity), regional sedimentary records need to be investigated in detail to reconstruct local paleoclimate and inform larger scale models. Here we present a paleosols study of the Permian–Triassic Shichuanhe section in the Shaanxi Province of the central North China Basin. Based on field observation and microscopic study, six types of paleosols have been identified as calcic Inceptisol, vertic Aridisol, gleyed Vertisol, gleyed Inceptisol, calcic Vertisol, and gleyed Aridisol. Fe quasi-coating and calcite hypo-coating disappear in the Early Triassic, taking Fe depleted nodules as major morphological pedofeature. Mean annual precipitation was calculated as 320 ± 147 mm/yr in the latest Permian and 520–680 ± 147 mm/yr in the late Early Triassic. The results suggest local aridity in the latest Permian, and intensified precipitation in the late Early Triassic, contributing to the mass extinction and recovery in its aftermath on land.

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.

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.

Ocean temperature and dissolved oxygen concentrations are critical factors that control ocean productivity, carbon and nutrient cycles, and marine habitat. However, the evolution of these two factors in the geologic past are still unclear. Here, we use a new oxygen isotope database to establish the sea surface temperature (SST) curve in the past 500 million years. The database is composed of 22 796 oxygen isotope values of phosphatic and calcareous fossils. The result shows two prolonged cooling events happened in the Late Paleozoic and Late Cenozoic, coinciding with two major ice ages indicated by continental glaciation data, and seven global warming events that happened in the Late Cambrian, Silurian-Devonian transition, Late Devonian, Early Triassic, Toarcian, Late Cretaceous, and Paleocene-Eocene transition. The SSTs during these warming periods are about 5–30 °C higher than the present-day level. Oxygen contents of shallow seawater are calculated from temperature, salinity, and atmospheric oxygen. The results show that major dissolved oxygen valleys of surface seawater coincide with global warming events and ocean anoxic events. We propose that the combined effect of temperature and dissolved oxygen account for the long-term evolution of global oceanic redox state during the Phanerozoic.