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Understanding spatial variation in origination and extinction can help to unravel the mechanisms underlying macroevolutionary patterns. Although methods have been developed for estimating global origination and extinction rates from the fossil record, no framework exists for applying these methods to restricted spatial regions. Here, we test the efficacy of three metrics for regional analysis, using simulated fossil occurrences. These metrics are then applied to the marine invertebrate record of the Permian and Triassic to examine variation in extinction and origination rates across latitudes. Extinction and origination rates were generally uniform across latitudes for these time intervals, including during the Capitanian and Permian–Triassic mass extinctions. The small magnitude of this variation, combined with the possibility of its attribution to sampling bias, cautions against linking any observed differences to contrasting evolutionary dynamics. Our results indicate that origination and extinction levels were more variable across clades than across latitudes.

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.

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.

The largest mass extinction since the advent of animals occurred during the Permian-Triassic (P-Tr) transition, ca. 252 Ma, and is commonly attributed to the eruption of the Siberian Traps large igneous province. However, the direct killing mechanism is still debated. In this study, we investigated marine redox conditions of the intermediate water column that most organisms inhabit with special attention to the time interval before the onset of the mass extinction. The carbon isotope composition of carbonate and organic carbon (δ13Ccarb and δ13Corg) as well as the nitrogen isotope composition of bulk nitrogen (δ15N) were analyzed in four P-Tr boundary sequences (Zhongli, Jianshi, Ganxi, and Chaotian sections), which record a transect from a shallow water carbonate platform to a deep water, lower ramp slope in South China. δ13Ccarb shows a distinct negative shift in all sections and displays a clear, 2–4‰, decreasing gradient accompanying an increase in water depth both before and after the mass extinction. A distinct negative shift in δ15N is observed in the shallow water Zhongli section, whereas a minor negative shift is present in the three deeper water sections. Before the mass extinction, the δ15N values from shallow water sections are higher than those from deeper waters. The low δ15N values close to 0‰ in deeper water sections suggest that microbial nitrogen fixation was the predominant source of biologically available nitrogen before the onset of the mass extinction. Thus, the water depth- dependent gradient in δ13Ccarb and δ15N suggests that an oxygen-deficient intermediate water column was already present before the mass extinction. The uniform δ15N values around 0‰ accompanying the onset of the mass extinction reveal that anoxic intermediate waters expanded into shallow waters. Meanwhile, the distinct positive shift in δ13Corg observed in upper ramp slope sections, i.e., the Jianshi and Ganxi sections, suggests that a euxinic photic zone was at least episodically present in the earliest Triassic. The temporal coincidence between the expansion of intermediate water column anoxia and the onset of the P-Tr mass extinction supports the hypothesis that marine anoxia was a direct killing mechanism.

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.

The abundance of dolomitic strata in the geological record contrasts with the general rarity of locations where dolomite forms today, a discrepancy that has long posed a problem for their interpretation. Recent culture experiments show that dolomite can precipitate at room temperature, raising the possibility that many ancient dolomites may be of syngenetic origin. We compiled a large geodata set of secular variations in dolomite abundance in the Phanerozoic, coupled with compilations of genus richness of marine benthic invertebrates and sulfur-isotope variations in marine carbonates. These data show that dolomite abundance is negatively correlated to genus diversity, with four dolomite peaks occurring during mass extinctions. Dolomite peaks also correspond to the rapid increase in sulfur-isotope composition (δ34S), an indicator of enhanced sulfate reduction, in anoxic oceans. These results confirm that variations in dolomite abundance during the Phanerozoic were closely linked with changes in marine benthic diversity, with both in turn related to oceanic redox conditions.

The Middle Permian was marked by a major biotic crisis, in the Capitanian, and the termination of the long-lasting Gondwanan glaciation, which began in the Carboniferous. Eruption of the Emeishan large igneous province (ELIP) in South China may have been linked with this event and contemporary changes of ocean circulation. However, causal mechanisms linking the extinction with potential ELIP-climate-ocean co-variations remain poorly constrained. Here we have examined these themes by studying a deep-water section on the margin of the South China continent (lower Yangtze platform margin) region. Our results show chemical weathering increased from the Roadian to the Capitanian suggesting a change from a warm-humid to a hot-humid climate. This trend was enhanced at the time of ELIP eruption in the middle Capitanian. Using the Cd/Mo and Co x Mn proxies reveals that a strong coastal upwelling system with anoxic (but not euxinic) conditions and moderate-high productivity persisted for at least 10 m.y. on the Yangtze Platform margin. However, it abruptly collapsed in the middle Capitanian and then shifted to a relatively restricted but nutrient-enriched system with increased productivity and intensified anoxia. Climate warming slightly precedes these changes, making it likely that it was a primary trigger. Not only does warming slow down ocean circulation, it also promotes the delivery nutrients to the ocean through accelerated continental weathering. All contributed to the intensification and expansion of ocean anoxia-euxinia which occurred immediately prior to the Capitanian biotic crisis. Large-scale volcanic activity of the ELIP likely triggered these decoupled climate-ocean changes. An upwelling regime was re-established in the late Capitanian flowing a cooling that may have been caused by chemical weathering of the Emeishan flood basalts.

The latitudinal diversity gradient (LDG) is recognized as one of the most pervasive, global patterns of present-day biodiversity. However, the controlling mechanisms have proved difficult to identify because many potential drivers covary in space. The geological record presents a unique opportunity for understanding the mechanisms which drive the LDG by providing a direct window to deep-time biogeographic dynamics. Here we used a comprehensive database containing 52,318 occurrences of marine fossils to show that the shape of the LDG changed greatly during the Permian-Triassic mass extinction from showing a significant tropical peak to a flattened LDG. The flat LDG lasted for the entire Early Triassic (∼5 My) before reverting to a modern-like shape in the Middle Triassic. The environmental extremes that prevailed globally, especially the dramatic warming, likely induced selective extinction in low latitudes and accumulation of diversity in high latitudes through origination and poleward migration, which combined together account for the flat LDG of the Early Triassic.

The foreshore at Redcar hosts the oldest Jurassic succession exposed on the Yorkshire-Cleveland Coast but has received little attention since the late nineteenth century. Temporary removal of beach sands by winter storms early in 2018 allowed for a sedimentological and palaeontological study of a nearly 60 m-thick foreshore section. The rocks are latest Hettangian to Early Sinemurian in age (Early Jurassic) and comprise five coarsening-upward cycles (parasequences) that grade from mudstones through siltstones into Gryphaea-rich shell beds. Ammonites are reasonably common along with a diverse benthos that includes abundant bivalves (e.g. Gryphaea, Cardinia, Luciniola, Plagiostoma and Oxytoma) and rarer serpulids, gastropods, foraminifera and solitary corals. In the upper part of the section thicker-shelled taxa are commonly bored by cirripedes and bryozoans. Despite relatively high benthic diversity and intense bioturbation, pyrite framboids are common with size distributions suggesting deposition under a moderately oxygen-restricted water column. The Redcar succession post-dates the end-Triassic mass extinction by as much as 4 Ma and the diverse marine assemblages indicate that recovery was substantially complete by this time.

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.

The climatic and environmental impact of exclusively volcanic CO2 emissions is assessed during the main effusive phase of the Central Atlantic Magmatic Province (CAMP), which is synchronous with the end-Triassic mass extinction. CAMP volcanism occurred in brief and intense eruptive pulses each producing extensive basaltic lava flows. Here, CAMP volcanic CO2 injections into the surface system are modelled using a biogeochemical box model for the carbon cycle. Our modelling shows that, even if positive feedback phenomena may be invoked to explain the carbon isotope excursions preserved in end-Triassic sedimentary records, intense and pulsed volcanic activity alone may have caused repeated temperature increases and pH drops, up to 5 °C and about 0.2 log units respectively. Hence, rapid and massive volcanic CO2 emissions from CAMP, on a similar scale to current anthropogenic emissions, severely impacted on climate and environment at a global scale, leading to catastrophic biotic consequences.

Large carbon cycle perturbations associated with the Middle Permian (Capitanian) mass extinction have been widely reported, but their causes and timing are still in dispute. Low resolution carbon isotope records prior to this event also limit the construction of a Middle Permian chemostratigraphic framework and global or local stratigraphic correlation, and hence limit our understanding of carbon cycle and environmental changes. To investigate these issues, we analyzed the 13Corg values from the Middle Permian chert-mudstone sequence (Gufeng Formation) in the Lower Yangtze deep-water basin (South China) and compared them with published records to build a chemostratigraphic scheme and discuss the underlying environmental events. The records show increased δ13Corg values from late Kungurian to early Guadalupian, followed by a decrease to the late Wordian/early Capitanian. The early-mid Capitanian was characterized by elevated δ13Corg values suggesting the presence of the “Kamura Event”: an interval of heavy positive values seen in the δ13Ccarb record. We propose that these heavy Capitanian δ13C values may be a response to a marked decline in chemical weathering rates on Pangea and associated reduction in carbonate burial, which we show using a biogeochemical model. The subsequent negative δ13C excursion seen in some carbonate records, especially in shallower-water sections (and in a muted expression in organic carbon) coincide with the Capitanian mass extinction may be caused by the input of isotopically-light carbon sourced from the terrestrial decomposition of organic matter.

Until recently, the biotic crisis that occurred within the Capitanian Stage (Middle Permian, ca. 262 Ma) was known only from equatorial (Tethyan) latitudes, and its global extent was poorly resolved. The discovery of a Boreal Capitanian crisis in Spitsbergen, with losses of similar magnitude to those in low latitudes, indicated that the event was geographically widespread, but further non-Tethyan records are needed to confirm this as a true mass extinction. The cause of this crisis is similarly controversial: While the temporal coincidence of the extinction and the onset of volcanism in the Emeishan large igneous province in China provides a clear link between those phenomena, the proximal kill mechanism is unclear. Here, we present an integrated fossil, pyrite framboid, and geochemical study of the Middle to Late Permian section of the Sverdrup Basin at Borup Fiord, Ellesmere Island, Arctic Canada. As in Spitsbergen, the Capitanian extinction is recorded by brachiopods in a chert/limestone succession 30–40 m below the Permian-Triassic boundary. The extinction level shows elevated concentrations of redox-sensitive trace metals (Mo, V, U, Mn), and contemporary pyrite framboid populations are dominated by small individuals, suggestive of a causal role for anoxia in the wider Boreal crisis. Mercury concentrations—a proxy for volcanism—are generally low throughout the succession but are elevated at the extinction level, and this spike withstands normalization to total organic carbon, total sulfur, and aluminum. We suggest this is the smoking gun of eruptions in the distant Emeishan large igneous province, which drove high-latitude anoxia via global warming. Although the global Capitanian extinction might have had different regional mechanisms, like the more famous extinction at the end of the Permian, each had its roots in large igneous province volcanism.

Microbially induced sedimentary structures (MISS) are reportedly widespread in the Early Triassic and their occurrence is attributed to either the extinction of marine grazers (allowing mat preservation) during the Permo-Triassic mass extinction or the suppression of grazing due to harsh, oxygen-poor conditions in its aftermath. Here we report on the abundant occurrence of MISS in the Lower Triassic Blind Fiord Formation of the Sverdrup Basin, Arctic Canada. Sedimentological analysis shows that mid-shelf settings were dominated by deposition from cohesive sand-mud flows that produced heterolithic, rippled sandstone facies that pass down dip into laminated siltstones and ultimately basinal mudrocks. The absence of storm beds and any other “event beds” points to an unusual climatic regime of humid, quiet conditions characterized by near continuous run off. Geochemical proxies for oxygenation (Mo/Al, Th/U, and pyrite framboid analysis) indicate that lower dysoxic conditions prevailed in the basin for much of the Early Triassic. The resultant lack of bioturbation allowed the development and preservation of MISS, including wrinkle structures and bubble textures. The microbial mats responsible for these structures are envisaged to have thrived, on sandy substrates, within the photic zone, in oxygen-poor conditions. The dysoxic history was punctuated by better-oxygenated phases, which coincide with the loss of MISS. Thus, Permo-Triassic boundary and Griesbachian mudrocks from the deepest-water settings have common benthos and a well-developed, tiered burrow profile dominated by Phycosiphon. The presence of the intense burrowing in the earliest Triassic contradicts the notion that bioturbation was severely suppressed at this time due to extinction losses at the end of the Permian. The notion that Early Triassic MISS preservation was caused by the extinction of mat grazers is not tenable.

Oxygen restricted conditions were widespread in European shelf seas after the end-Triassic mass extinction event and they are reported to have hindered the recovery of marine benthos. Here we reconstruct the redox history of the Early Jurassic Blue Lias Formation of southwest Britain using pyrite framboid size analysis and compare this with the recovery of bivalves based on field and museum collections. Results suggest widespread dysoxia punctuated by periods of anoxia in the region, with the latter developing frequently in deeper water settings. Despite these harsh conditions, initial benthic recovery occurred rapidly in the British Jurassic, especially in shallowest settings, and shows no relationship with the intensity of dysoxia. A stable diversity was reached by the first recognised ammonite zone after the end-Triassic mass extinction. This contrasts with the deeper-water, more oxygen-poor sections where the diversity increase was still continuing in the earliest Sinemurian Stage, considerably longer than previously reported. Similar recovery rates are seen amongst other groups (brachiopods and ammonites). Oxygen-poor conditions have been suggested to delay recovery after the Permo-Triassic mass extinction, but this is not the case after the end-Triassic crisis. We suggest that this was because the European dysoxia was only a regional phenomenon and there were plenty of well-ventilated regions available to allow an untrammelled bounce back.

The aftermath of end-Permian mass extinction was marked by a ∼5 million year interval of poorly-understood, extreme environments that likely hindered biotic recovery. Contemporary nitrogen isotope variations are considered, using a new conceptual model, to support a scenario that shows intensive nitrate-removal processes gradually depleted the global oceanic nitrate inventory during long-lasting oceanic anoxia. Enhanced nitrogen fixation shifted the oceanic nitrogenous nutrient (nutrient-N) inventory to an ammonium-dominated state. Ammonium is toxic to animals and higher plants but fertilizes algae and bacteria. This change in ocean chemistry could account for the intense and unexplained losses of nektonic taxa and the proliferation of microbial blooms in the Early Triassic. The transition from a nitrate ocean to an ammonium ocean was accompanied by a decrease in respiration efficiency of organisms and a shrinking oceanic nutrient-N inventory, ultimately leading to generally low productivity in the Early Triassic oceans. These unappreciated nutrient changes during episodes of prolonged ocean anoxia may be the key life-limiting factor at such times.

The nature of Phanerozoic carbonate factories is strongly controlled by the composition of carbonate-producing faunas. During the Permian–Triassic mass extinction interval there was a major change in tropical shallow platform facies: Upper Permian bioclastic limestones are characterized by benthic communities with significant richness, for example, calcareous algae, fusulinids, brachiopods, corals, molluscs and sponges, while lowermost Triassic carbonates shift to dolomicrite-dominated and bacteria-dominated microbialites in the immediate aftermath of the Permian–Triassic mass extinction. However, the spatial–temporal pattern of carbonates distribution in high latitude regions in response to the Permian–Triassic mass extinction has received little attention. Facies and evolutionary patterns of a carbonate factory from the northern margin of peri-Gondwana (palaeolatitude ca 40°S) are presented here based on four Permian–Triassic boundary sections that span proximal, inner to distal, and outer ramp settings from South Tibet. The results show that a cool-water bryozoan-dominated and echinoderm-dominated carbonate ramp developed in the Late Permian in South Tibet. This was replaced abruptly, immediately after the Permian–Triassic mass extinction, by a benthic automicrite factory with minor amounts of calcifying metazoans developed in an inner/middle ramp setting, accompanied by transient subaerial exposure. Subsequently, an extensive homoclinal carbonate ramp developed in South Tibet in the Early Triassic, which mainly consists of homogenous dolomitic lime mudstone/wackestone that lacks evidence of metazoan frame-builders. The sudden transition from a cool-water, heterozoan dominated carbonate ramp to a warm-water, metazoan-free, homoclinal carbonate ramp following the Permian–Triassic mass extinction was the result of the combination of the loss of metazoan reef/mound builders, rapid sea-level changes across Permian–Triassic mass extinction and profound global warming during the Early Triassic.

Flood basalt volcanism represented by the Kalkarindji Province (Australia) is temporally associated with a trilobite mass extinction at the Cambrian Series 2 – Series 3 boundary, providing one of the oldest potential links between volcanism and biotic crisis in the Phanerozoic. However, the relative timing of flood basalt volcanism (Kalkarindji Province, Australia) and the trilobite extinctions, first recorded in North America, is not known. Mercury (Hg) enrichment in the sedimentary record provides a potential proxy for volcanism which may facilitate improved chronologies of eruption and extinction. Here we report mercury records for three sections from mid-shelf strata of the Great Basin (western USA) that straddle the Series 2 – Series 3 boundary. One section (Oak Springs Summit, NV) features a Hg enrichment at the start of the extinction interval, but mercury anomalies are also present at lower levels. These older anomalies may record either earlier phases of Kalkarindji volcanism, eruptions in other locations, or may be the result of sedimentary and/or diagenetic processes affecting the Hg record. In the Carrara Formation at Emigrant Pass, CA, the precise extinction horizon is not well defined, but a carbon isotope anomaly (the Redlichiid-Olenellid Extinction Carbon isotope Event; ROECE) provides a stratigraphic tie point to the Oak Springs Summit section. At Emigrant Pass, Hg enrichments precede the ROECE interval and are absent in the inferred extinction zone. The Pioche Formation at Ruin Wash, NV, lacks Hg enrichment at the extinction horizon but contains older enrichments. The inconsistent Hg records between the three sections demonstrate that factors controlling Hg accumulation and preservation in marine sedimentary environments are not yet fully understood. The effects of redox fluctuations may complicate one-to-one association of sedimentary Hg enrichments and massive volcanism at the Cambrian Series 2 – Series 3 boundary and elsewhere in the geologic record.

Two Permian-Triassic boundary (PTB) sections (Pojue and Dala) are well exposed in an isolated carbonate platform (Napo Platform) on the southwestern margin of the Nanpanjiang Basin, South China. These sections provide an insight into the transition across the PTB and a detailed investigation of the conodont biostratigraphy and inorganic carbon isotopes is presented. The PTB at the Pojue Section is placed at the base of Bed 10B (a dolomitized mudstone found below a microbialite horizon), defined by the first occurrence of Hindeodus parvus. At the Dala Section, four conodont zones occur. They are, in ascending order, the Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone and Clarkina planata Zone. Comparison with the Pojue Section suggests the PTB at Dala also occurs at the base of dolomitized mudstone below a microbialite horizon, although the first occurrence of Hindeodus parvus is near the top of a microbialite bed: an occurrence that is also seen in other platform sections. The succeeding microbialite beds developed during the ongoing PTB mass extinction phase. This time was characterized by low carbon isotope values, and a microbialite ecosystem that provided a refuge for selected groups (bivalves, ostracods and microgastropods) that were likely tolerant of extremely high temperatures.

Significance The Carnian Stage of the Triassic Period marks one of the most significant intervals of the past 250 My. Within the space of ∼2 My, the world’s biota underwent major changes with dinosaurs becoming the notable incumbents. These events coincide with a remarkable interval of intense rainfall known as the Carnian Pluvial Episode (CPE). Here, we show, in a detailed record from a lake in North China, that the CPE can actually be resolved into four distinct events, each one driven by a discrete pulse of intense volcanism associated with enormous releases of carbon dioxide into the atmosphere. These triggered a major intensification of the hydrological cycle and led to lake eutrophication., The Late Triassic Carnian Pluvial Episode (CPE) saw a dramatic increase in global humidity and temperature that has been linked to the large-scale volcanism of the Wrangellia large igneous province. The climatic changes coincide with a major biological turnover on land that included the ascent of the dinosaurs and the origin of modern conifers. However, linking the disparate cause and effects of the CPE has yet to be achieved because of the lack of a detailed terrestrial record of these events. Here, we present a multidisciplinary record of volcanism and environmental change from an expanded Carnian lake succession of the Jiyuan Basin, North China. New U–Pb zircon dating, high-resolution chemostratigraphy, and palynological and sedimentological data reveal that terrestrial conditions in the region were in remarkable lockstep with the large-scale volcanism. Using the sedimentary mercury record as a proxy for eruptions reveals four discrete episodes during the CPE interval (ca. 234.0 to 232.4 Ma). Each eruptive phase correlated with large, negative C isotope excursions and major climatic changes to more humid conditions (marked by increased importance of hygrophytic plants), lake expansion, and eutrophication. Our results show that large igneous province eruptions can occur in multiple, discrete pulses, rather than showing a simple acme-and-decline history, and demonstrate their powerful ability to alter the global C cycle, cause climate change, and drive macroevolution, at least in the Triassic.

Both the duration and severity of deep-water anoxic conditions across the Permian-Triassic mass extinction (PTME) are controversial. Panthalassa Ocean circulation models yield varying results, ranging from a well-ventilated deep ocean to rapidly developing northern-latitude, but not southern-latitude, anoxia in response to Siberian Traps–driven global warming. To address this uncertainty, we examined a southern-paleolatitude pelagic record. Trace metal and pyrite framboid data suggest bottom-water euxinic conditions developed in the southern Panthalassa Ocean at the PTME, coincident with enhanced volcanic activity indicated by Hg geochemistry. While a global ocean euxinic event at the PTME placed extraordinary stress on marine life, southern surface waters appear to have recovered more quickly as radiolarian populations returned several million years before they did in northern Panthalassa.

The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate δ34S data from sections spanning the Late Triassic–Early Jurassic transition, which document synchronous large positive excursions on a global scale occurring in ~50 thousand years. Biogeochemical modeling demonstrates that this S isotope perturbation is best explained by a fivefold increase in global pyrite burial, consistent with large-scale development of marine anoxia on the Panthalassa margin and northwest European shelf. This pyrite burial event coincides with the loss of Triassic taxa seen in the studied sections. Modeling results also indicate that the pre-event ocean sulfate concentration was low (

Records of sulfur cycling during mass extinction events increasingly show that they are associated with rapid shifts in the sulfur isotope composition of seawater indicative of low concentrations of ocean sulfate [1-4]. These events are also often associated with the spread of anoxic conditions in the marine realm. We propose a feedback mechanism whereby the production of methane in marine sediments increases in proportion to decreasing sulfate and consumes bottom water oxygen, thus acting as a positive feedback on spread of anoxic waters. This can be further amplified via increased weathering or recycled fluxes of phosphate enhancing productivity [e.g. 5], the effects of increasing temperature on the rate of methanogenesis and the additional suppression of marine sulfate via increased pyrite burial.We propose that sulfate drawdown occurs prior to climate forcing and other extinction drivers imposed by large igneous province (LIP) eruption. The likely mechanism for the drawdown of sulfate prior to these extinction is the removal of sulfate from the oceans as gypsum in evaporite deposits. Several large mid-Phanerozoic mass extinctions have clear evidence of increased evaporite deposition prior to, or approximately coincidental with LIP eruption and extinction.If this idea is correct, the biological impact of a LIP will partly depend on the sulfate status of the ocean at the time of its eruption, and may at least partly explain the observation that whilst many mass extinctions are associated temporally with a LIP, not all LIPs seem to cause mass extinctions.1. Newton, R.J., et al., Geology, 2011. 39(1): p. 7-10.2. Song, H., et al., Geochimica et Cosmochimica Acta, 2014. 128(0): p. 95-113.3. Witts, J.D., et al., Geochimica et Cosmochimica Acta, 2018. 230: p. 17-45.4. He, T., et al., Science Advances, 2020. 6(37): p. eabb6704.5. Schobben, M., et al., Nature Geoscience, 2020.

The deep-water record of marine anoxia across the Permo-Triassic mass extinction (PTME) is highly controversial; both the length of time and severity of anoxic conditions are uncertain. Panthalassa Ocean circulation models show varying results, ranging from a well-ventilated deep ocean to rapidly developing northern, but not southern, latitude anoxia in response to Siberian Traps driven global warming. To address this uncertainty we examined a southern paleo-latitude pelagic record. Trace metal and pyrite framboid data show bottom water euxinc conditions developed in the southern Panthalassa Ocean at the PTME, coincident with enhanced volcanic activity indicated by Hg geochemistry. While a global deep-ocean euxinic event at the PTME placed extraordinary stress on marine life, southern surface waters appear to have recovered more quickly as radiolarian populations return several million years before they do in northern Panthalassa.

The Permo–Triassic Boundary (PTB) marks a time of profound climatic change. Near the PTB (~252 Ma), the largest known mass extinction occurred with more than 90% of marine species and 70% of terrestrial species became extinct. The mass extinction is linked to a massive warming event at the PTB, where tropical regions became too hot for survival ofspecies. The increase in atmospheric CO2 during the Permian and the PTB is mainly attributed to the decrease of chemically weatherable fresh silicate rock due to orogenesis, and the CO2 released in the atmosphere from the Siberian Traps. In this study, we use the UK Met Office fully coupled HadCM3L General Circulation Model (GCM) to perform Permo-Triassic climate simulations with different atmospheric CO2 values that encompass most of the estimates of atmospheric CO2 concentration during this time, to provide more insights about the climate changes during the end Permian – early Triassic. Specifically, we focus on: a) the spatial extension of dry conditions/lethally hot temperatures under different CO2 conditions, b) the seasonal surface temperature difference and precipitation changes at higher latitudes and c) the effects of increased atmospheric CO2 on the large-scale wind and monsoonal circulation.

Throughout Earth’s history, the coincidence in time between Large Igneous Province eruptions and mass extinctions points out a potential causality, where volcanic degassing may drive the global-scale climatic and environmental changes leading to biotic crises. The volcanic activity of the Central Atlantic Magmatic Province (CAMP, ca. 201 Ma), one of Earth’s most voluminous Large Igneous Provinces, is synchronous with the end-Triassic mass extinction event, among the most severe extinctions during the Phanerozoic. Combining different in situ analytical techniques (optical microscopy, confocal Raman microspectroscopy, EMP, SEM-EDS, and NanoSIMS analyses), bubble-bearing melt inclusions within basaltic rocks revealed the abundance of CO2 (up to 1.0 wt.%) in CAMP magmas [1]. Gaseous CO2 and solid elemental C, alternatively preserved by gas exsolution bubbles within melt inclusions mainly hosted in clinopyroxene crystal clots, represent direct evidence for large amounts of volcanic CO2 (up to 105 Gt) emitted into Earth’s surface during the entire CAMP activity [1]. The entrapment conditions of these melt inclusions within clinopyroxene aggregates constrain the degassed CO2 to a mantle and/or lower-middle crustal origin, indicating a deep source of carbon which may favour rapid and intense CAMP eruption pulses. Each magmatic pulse may have injected CO2 into the end-Triassic atmosphere in amounts similar to those projected for the anthropogenic emissions during the 21st century [1]. Therefore, volcanic CO2 degassed during CAMP eruptions likely contributed to end-Triassic global warming and ocean acidification with catastrophic consequences for the biosphere. [1] Capriolo et al. (2020), Nat. Commun. 11, 1670.

Studying the long-term evolution of nutrient cycles and their interaction with other biogeochemical cycles is essential to understand Earth’s history. Marine nutrient cycling forms a key control on the cycling of carbon and oxygen in the bio- and geospheres. Here, we focus on phosphorus, which is the ultimate limiting nutrient on geological timescales and a potential driver of past intervals of marine anoxia/euxinia. Despite its importance, obtaining direct information on spatial and temporal variations in marine phosphorus concentrations has proved challenging. Recent work has demonstrated the potential for calcium carbonate-associated phosphorus in corals to record water-column phosphorus (e.g., LaVigne et al., 2008; 2010). Building on this approach, we are investigating the use of other calcitic fossils as a proxy for water column phosphorus concentration, focussing on belemnites, an extinct group of nektic molluscs.We have developed and optimised a method to quantify phosphorus in the belemnite rostrum, and initially applied this method to samples from the upper Sinemurian to the Toarcian in the Lower Jurassic. During this time there were major climatic and environmental events in the latest Pliensbachian and early Toarcian, which are thought to have been driven by large scale volcanism of the Karoo-Ferrar Large Igneous Provinces (LIP). Of particular interest are an icehouse event during the Pliensbachian, and a warming event during the Toarcian which coincided with widespread ocean anoxia (the Toarcian Ocean Anoxic Event [TOAE]) and a second order mass extinction event (the Early Toarcian Mass Extinction).We will present P/Ca results from method development tests and collections of belemnites from the Sinemurian to the Toarcian from a number of sites in the European Epicontinental Sea (EES). Pilot data show similar trends in belemnite phosphorus concentrations at different sites in the EES, including a sharp peak during the TOAE. We will also discuss the impact of inter-species variation on belemnite phosphorus concentrations, as well as internal variability in phosphorus concentrations in individual belemnites, to determine the potential impact of these variables on the reconstruction of water column phosphorus concentrations. LaVigne, M., Field, M. P., Anagnostou, E., Grottoli, A. G., Wellington, G. M., Sherrell, R. M. (2008). Skeletal P/Ca tracks upwelling in Gulf of Panamá coral: Evidence for a new seawater phosphate proxy. Geophysical Research Letters 35.LaVigne, M., Matthews, K. A., Grottoli, A. G., Cobb, K. M., Anagnostou, E., Cabioch, G., Sherrell, R. M. (2010). Coral skeleton P/Ca proxy for seawater phosphate: Multi-colony calibration with a contemporaneous seawater phosphate record. Geochimica et Cosmochimica Acta 74: 1282–1293.

Based on a study of 49 conodont and 57 geochemical samples from the Upper Triassic, carbonate-dominated Dengdengqiao Formation, Qinling Basin, China, the Carnian conodonts and carbon isotope records are first reported. Two genera and four species have been identified amongst 87 conodont elements: Mosherella praebudaensis, Mo. longnanensis sp. nov., Mo. sp., and “Misikella” longidentata. The presence of Mo. praebudaensis indicates that the lower part (bed 2) of the formation is attributable to the Julian (lower Carnian) substage. A radiolarian fauna identified in a previous study belongs to the upper Carnian, but the sampling horizon is unclear. The δ13Ccarb curve shows a ∼1.8‰ negative excursion beginning from upper part of bed 3, but its stratigraphic location is uncertain. The Dengdengqiao Formation is clearly at least partly of Carnian age but could include younger strata. The abundant calcareous algae at the section is probably due to some transport rather than preserved in site. The unusual ecosystem with rare marine organisms may reflect long-term stressful and unfavorable conditions at Dengdengqiao.

Summary The Late Permian mass extinction is the largest mass extinction of whole geological history, followed by a prolonged life recovery expending the early Triassic. To better understand the recovery pattern of primary productivity through Permo-Triassic intervals and its longer-term changes in early Triassic, we applied biomarkers to reveal the community evolutions of marine primary producers. Our results indicate a possible rapid recovery of eukaryotic primary producers after the extinction during Griesbachian-Dienerian.

We investigate the influence of smooth and ribletted shark skin on a turbulent boundary layer flow. Through laser Doppler anemometry (LDA) the role of riblets in combination with the shark skin denticle is established for the first time. Our results show that smooth denticles behave like a typical rough surface when exposed to an attached boundary layer. Drag is increased for the full range of tested dimensionless denticle widths, w + ≈ 25–80, where w + is the denticle width, w, scaled by the friction velocity, u τ , and the kinematic viscosity, ν. However, when riblets are added to the denticle crown we demonstrate there is a significant reduction in drag, relative to the smooth denticles. We obtain a modest maximum drag reduction of 2% for the ribletted denticles when compared to the flat plate, but when compared to the smooth denticles the difference in drag is in excess of 20% for w + ≈ 80. This study enables a new conclusion that riblets have evolved as a mechanism to reduce or eliminate the skin friction increase due to the presence of scales (denticles). The combination of scales and riblets is hydrodynamically efficient in terms of skin-friction drag, while also acting to maintain flow attachment, and providing the other advantages associated with scales, e.g. anti-fouling, abrasion resistance, and defence against parasites.

Oxygen deprivation and hydrogen sulfide toxicity are considered potent kill mechanisms during the mass extinction just before the Permian–Triassic boundary (~251.9 million years ago). However, the mechanism that drove vast stretches of the ocean to an anoxic state is unclear. Here, we present palaeoredox and phosphorus speciation data for a marine bathymetric transect from Svalbard. This shows that, before the extinction, enhanced weathering driven by Siberian Traps volcanism increased the influx of phosphorus, thus enhancing marine primary productivity and oxygen depletion in proximal shelf settings. However, this non-sulfidic state efficiently sequestered phosphorus in the sediment in association with iron minerals, thus restricting the intensity and spatial extent of oxygen-depleted waters. The collapse of vegetation on land immediately before the marine extinction changed the relative weathering influx of iron and sulfate. The resulting transition to euxinic (sulfidic) conditions led to enhanced remobilization of bioavailable phosphorus, initiating a feedback that caused the spread of anoxic waters across large portions of the shelf. This reconciles a lag of >0.3 million years between the onset of enhanced weathering and the development of widespread, but geographically variable, ocean anoxia, with major implications for extinction selectivity. Phosphorus remobilized from seafloor sediments due to a reduced influx of iron-oxide from land led to widespread anoxia during the end-Permian mass extinction, according to palaeoredox and phosphorus speciation proxy records from Svalbard.