Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

This review forms the preface of a special issue dealing with Environmental stresses and biotic responses during the Palaeozoic-Mesozoic transition, and develops an improved understanding of the sequence of catastrophe events associated with the Permian-Triassic (P–Tr) transition in particular. The 16 papers that comprise this special issue mostly focus on the Paleo-Tethys and Panthalassia regions, and enable us to recognize seven distinct phases of biotic and environmental evolution that may be precisely correlated between marine and terrestrial environments. Phase 1 represents the normal marine environments and biota that existed at 252.104 Ma, prior to the onset of major environmental perturbation. Phase 2 is marked by the onset of a negative carbon (δ¹³Ccarb) isotopic excursion, and coincides with a significant decline in radiolarian diversity, the collapse of communities in shallow metazoan reefs and deep-water settings, and the loss of rainforests on land (including the disappearance of Gigantopteris flora). Phase 3 is characterized by a pulse of biodiversification on the eve of the end-Permian extinction (EPE). Phase 4 comprises the EPE event itself, dated to 251.941 Ma, and coincides with an extreme episode of widespread anoxia, biodiversity loss, community structural collapse, and volatile volcanic eruptions. Phase 5 is marked by the renewed onset of oxic conditions in all oceanic environments except those in microbialite-rich shallow platform settings where abundant pyrite framboids signal dysoxia. Phase 6 includes the earliest Triassic extinction (ETE) event, dated to 251.880 Ma, and associated with euxinic to anoxic conditions and ocean acidification. An extended phase of deoxygenation and acidification returned to the marine settings during Phase 7, possibly driving a calcium crisis. The terrestrial extinction event (Phase 2) probably commenced c. 60 kyrs (in South China) or 370 kyrs (in Sydney basin) before the marine P–Tr extinction, the latter consisting of two distinct events (Phases 4 and 6), spaced c. 60 kyr apart, each being marked by both a carbon isotope excursion and ecologic collapse. The environmental changes associated with these three extinction phases in the ocean and on land can be attributed to the effects of volcanic emissions (e.g., CO2, SO2, halogens and metals) during the eruption of the Siberian Traps Large Igneous Province and convergent margin volcanism related to Tethyan tectonics.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

ResearchGate has not been able to resolve any citations for this publication.
Article
Full-text available
The Permian-Triassic mass extinction severely depleted biodiversity, primarily observed in the body fossil of well-skeletonized animals. Understanding how whole ecosystems were affected and rebuilt following the crisis requires evidence from both skeletonized and soft-bodied animals; the best comprehensive information on soft-bodied animals comes from ichnofossils. We analyzed abundant trace fossils from 26 sections across the Permian-Triassic boundary in China and report key metrics of ichnodiversity, ichnodisparity, ecospace utilization, and ecosystem engineering. We find that infaunal ecologic structure was well established in the early Smithian. Decoupling of diversity between deposit feeders and suspension feeders in carbonate ramp-platform settings implies that an effect of trophic group amensalism could have delayed the recovery of nonmotile, suspension-feeding epifauna in the Early Triassic. This differential reaction of infaunal ecosystems to variable environmental controls thus played a substantial but heretofore little appreciated evolutionary and ecologic role in the overall recovery in the hot Early Triassic ocean.
Article
Full-text available
Redox variations across the Permian‐Triassic boundary (PTB) have long been debated, especially during the proliferation of PTB microbialites. Here, we report redox fluctuations across the PTB to evaluate links between the two based on pyrite framboid analysis from basin to platform settings in South China. During the end‐Permian extinction, abundant framboids indicate a widespread anoxia that was likely a direct cause of extinction. In the earliest Triassic (Hindeodus parvus conodont zone), pyrite framboids were absent in ramp to basin and shallow, nonmicrobialite platform sections. In contrast, the coeval microbialites yield abundant framboids indicative of dysoxia. The fact that framboids were only confined to PTB microbialites and absent in other habitats indicates that microbe bloom may have stimulated dysoxic watermass and triggered the framboid growth within microbe aggregates. Thus, microbialites were not built in reducing settings, but instead, microbial proliferation caused local, dysoxia within shallow oxygenated platforms after the extinction.
Article
Full-text available
The sources of isotopically light carbon released during the end-Triassic mass extinction remain in debate. Here, we use mercury (Hg) concentrations and isotopes from a pelagic Triassic-Jurassic boundary section (Katsuyama, Japan) to track changes in Hg cycling. Because of its location in the central Panthalassa, far from terrigenous runoff, Hg enrichments at Katsuyama record atmospheric Hg deposition. These enrichments are characterized by negative mass independent fractionation (MIF) of odd Hg isotopes, providing evidence of their derivation from terrestrial organic-rich sediments (Δ 199 Hg < 0‰) rather than from deep-Earth volcanic gases (Δ 199 Hg~0‰). Our data thus provide evidence that combustion of sedimentary organic matter by igneous intrusions and/or wildfires played a significant role in the environmental perturbations accompanying the event. This process has a modern analog in anthropogenic combustion of fossil fuels from crustal reservoirs.
Article
Full-text available
The Siberian Traps large igneous province (STLIP) is commonly invoked as the primary driver of global environmental changes that triggered the end-Permian mass extinction (EPME). Here, we explore the contributions of coeval felsic volcanism to end-Permian environmental changes. We report evidence of extreme Cu enrichment in the EPME interval in South China. The enrichment is associated with an increase in the light Cu isotope, melt inclusions rich in copper and sulfides, and Hg concentration spikes. The Cu and Hg elemental and isotopic signatures can be linked to S-rich vapor produced by felsic volcanism. We use these previously unknown geochemical data to estimate volcanic SO2 injections and argue that this volcanism would have produced several degrees of rapid cooling before or coincident with the more protracted global warming. Large-scale eruptions near the South China block synchronous with the EPME strengthen the case that the STLIP may not have been the sole trigger.
Article
Full-text available
Extreme warming at the end-Permian induced profound changes in marine biogeochemical cycling and animal habitability, leading to the largest metazoan extinction in Earth’s history. However, a causal mechanism for the extinction that is consistent with various proxy records of geochemical conditions through the interval has yet to be determined. Here we combine an Earth system model with global and local redox interpretations from the Permian/Triassic in an attempt to identify this causal mechanism. Our results show that a temperature-driven increase in microbial respiration can reconcile reconstructions of the spatial distribution of euxinia and seafloor anoxia spanning the Permian–Triassic transition. We illustrate how enhanced metabolic rates would have strengthened upper-ocean nutrient (phosphate) recycling, and thus shoaled and intensified the oxygen minimum zones, eventually causing euxinic waters to expand onto continental shelves and poison benthic habitats. Taken together, our findings demonstrate the sensitive interconnections between temperature, microbial metabolism, ocean redox state and carbon cycling during the end-Permian mass extinction. As enhanced microbial activity in the ocean interior also lowers subsurface dissolved inorganic carbon isotopic values, the carbon release as inferred from isotope changes in shallow subsurface carbonates is likely overestimated, not only for this event, but perhaps for many other carbon cycle and climate perturbations through Earth’s history. Warming-enhanced microbial respiration can explain marine anoxia patterns across depth, a key driver of the end-Permian mass extinction, according to biogeochemical modelling and geochemical proxy records.
Article
Full-text available
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.
Article
Full-text available
Rapid climate change was a major contributor to the end-Permian extinction (EPE). Although well constrained for the marine realm, relatively few records document the pace, nature, and magnitude of climate change across the EPE in terrestrial environments. We generated proxy records for chemical weathering and land surface temperature from continental margin deposits of the high-latitude southeastern margin of Gondwana. Regional climate simulations provide additional context. Results show that Glossopteris forest-mire ecosystems collapsed during a pulse of intense chemical weathering and peak warmth, which capped ~1 m.y. of gradual warming and intensification of seasonality. Erosion resulting from loss of vegetation was short lived in the low-relief landscape. Earliest Triassic climate was ~10–14 °C warmer than the late Lopingian and landscapes were no longer persistently wet. Aridification, commonly linked to the EPE, developed gradually, facilitating the persistence of refugia for moisture-loving terrestrial groups.
Article
Full-text available
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.
Article
Full-text available
The Earth has been beset by many crises during its history, and yet comparing the ecological impacts of these mass extinctions has been difficult. Key questions concern the kinds of species that go extinct and survive, how communities rebuild in the post-extinction recovery phase, and especially how the scaling of events affects these processes. Here, we explore ecological impacts of terrestrial and freshwater ecosystems in three mass extinctions through the mid-Phanerozoic, a span of 121 million years (295–174 Ma). This critical duration encompasses the largest mass extinction of all time, the Permian–Triassic (P–Tr) and is flanked by two smaller crises, the Guadalupian–Lopingian (G–L) and Triassic–Jurassic (T–J) mass extinctions. Palaeocommunity dynamics modelling of 14 terrestrial and freshwater communities through a long sedimentary succession from the lower Permian to the lower Jurassic in northern Xinjiang, northwest China, shows that the P–Tr mass extinction differed from the other two in two ways: (i) ecological recovery from this extinction was prolonged and the three post-extinction communities in the Early Triassic showed low stability and highly variable and unpredictable responses to perturbation primarily following the huge losses of species, guilds and trophic space; and (ii) the G–L and T–J extinctions were each preceded by low-stability communities, but post-extinction recovery was rapid. Our results confirm the uniqueness of the P–Tr mass extinction and shed light on the trophic structure and ecological dynamics of terrestrial and freshwater ecosystems across the three mid-Phanerozoic extinctions, and how complex communities respond to environmental stress and how communities recovered after the crisis. Comparisons with the coeval communities from the Karoo Basin, South Africa show that geographically and compositionally different communities of terrestrial ecosystems were affected in much the same way by the P–Tr extinction.
Article
Full-text available
Teratological spores and pollen are widespread in sediments that record the Permian- Triassic mass extinction. The malformations are thought to be the result of extreme environmental conditions at that time, but the mutagenic agents and the precise timing of the events remain unclear. We examined the abundance of teratological sporomorphs and metal concentrations in a Permian-Triassic tropical peatland succession of southwestern China. We find a significant peak of spore tetrads of lycopsid plants (as much as 19% of all sporomorphs) coeval with increases in Cu and Hg concentrations above the main terrestrial extinction interval, which marks the loss of Permian Gigantopteris forests, increased wildfire activity, and the disappearance of coal beds. Thus, in tropical peatlands, mutagenesis affected only surviving plants. Mutagenesis was likely caused by metal toxicity, linked to increased Hg and Cu loading, but was not itself a direct cause of the terrestrial crisis.
Article
Full-text available
Enhanced regional subduction-related volcanism in the South China craton concurrent with Siberian Traps large igneous province magmatism was a likely contributor to major biotic and environmental stresses associated with the Permian-Triassic boundary (ca. 252 Ma) mass extinction. However, the timing, intensity, and duration of this regional volcanic activity remain uncertain. We analyzed mercury (Hg) concentrations in three widely separated marine sections in the South China craton (Shangsi, Ganxi, and Chaohu) as well as Hg isotopic compositions in one section (Shangsi) from the Upper Permian (Changhsingian) through the lowermost Triassic (Induan) in order to track volcanic inputs. Four mercury enrichment (ME) intervals, dating to the lowermost Changhsingian (ME1), mid-Clarkina changxingensis zone (ME2), upper C. changxingensis to lower C. yini zones (ME3), and latest Permian mass extinction (LPME) interval (ME4), were recognized on the basis of elevated Hg/total organic carbon ratios. These records provide evidence of strong volcanism in the Tethyan region starting ∼2 m.y. before the LPME, whereas only the ME4 event is recorded in extra-Tethyan sections. Mercury isotopes support the inference that pre-LPME Hg peaks were related to regional subduction-related volcanism, and that Hg emissions at the LPME were the result of Siberian Traps large igneous province intrusions into organic-rich sediments. This study demonstrates the feasibility of distinguishing flood-basalt from subduction-related volcanic inputs on the basis of marine sedimentary Hg records.
Article
Full-text available
The role of ocean anoxia as a cause of the end-Triassic marine mass extinction is widely debated. Here, we present carbonate-associated sulfate d34S 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 (<1 millimolar), a common feature of many Phanerozoic deoxygenation events. We propose that sulfate scarcity preconditions oceans for the development of anoxia during rapid warming events by increasing the benthic methane flux and the resulting bottom-water oxygen demand.
Article
Full-text available
Records suggest that the Permo–Triassic mass extinction (PTME) involved one of the most severe terrestrial ecosystem collapses of the Phanerozoic. However, it has proved difficult to constrain the extent of the primary productivity loss on land, hindering our understanding of the effects on global biogeochemistry. We build a new biogeochemical model that couples the global Hg and C cycles to evaluate the distinct terrestrial contribution to atmosphere–ocean biogeochemistry separated from coeval volcanic fluxes. We show that the large short-lived Hg spike, and nadirs in δ²⁰²Hg and δ¹³C values at the marine PTME are best explained by a sudden, massive pulse of terrestrial biomass oxidation, while volcanism remains an adequate explanation for the longer-term geochemical changes. Our modelling shows that a massive collapse of terrestrial ecosystems linked to volcanism-driven environmental change triggered significant biogeochemical changes, and cascaded organic matter, nutrients, Hg and other organically-bound species into the marine system.
Article
Full-text available
The Permian-Triassic mass extinction is widely attributed to the global environmental changes caused by the eruption of the Siberian Traps. However, the precise temporal link between marine and terrestrial crises and volcanism is unclear. Here, we report anomalously high mercury (Hg) concentrations in terrestrial strata from southwestern China, synchronous with Hg anomalies in the marine Permian-Triassic type section. The terrestrial sediments also record increased abundance of fossil charcoal coincident with the onset of a negative carbon isotope excursion and the loss of tropical rainforest vegetation, both of which occurred immediately before the peak of Hg concentrations. The organic carbon isotope data show an ∼5‰–6‰ negative excursion in terrestrial organic matter (bulk organic, cuticles, and charcoal), reflecting change in atmospheric CO2 carbon-isotope composition coincident with enhanced wildfire indicated by increased charcoal. Hg spikes provide a correlative tool between terrestrial and marine records along with carbon isotope trends. These data demonstrate that ecological deterioration occurred in tropical peatlands prior to the main marine mass extinction.
Article
Full-text available
The current model for the end-Permian terrestrial ecosystem crisis holds that systematic loss exhibited by an abrupt turnover from the Daptocephalus to the Lystrosaurus Assemblage Zone (AZ; Karoo Basin, South Africa) is time equivalent with the marine Permian–Triassic boundary (PTB). The marine event began at 251.941 ± 0.037 Ma, with the PTB placed at 251.902 ± 0.024 Ma (2σ). Radio-isotopic dates over this interval in the Karoo Basin were limited to one high resolution ash-fall deposit in the upper Daptocephalus AZ (253.48 ± 0.15 (2σ) Ma) with no similar age constraints for the overlying biozone. Here, we present the first U-Pb CA-ID-TIMS zircon age (252.24 ± 0.11 (2σ) Ma) from a pristine ash-fall deposit in the Karoo Lystrosaurus AZ. This date confirms that the lower exposures of the Lystrosaurus AZ are of latest Permian age and that the purported turnover in the basin preceded the end-Permian marine event by over 300 ka, thus refuting the previously used stratigraphic marker for terrestrial end-Permian extinction.
Article
Full-text available
The Permian-Triassic mass extinction is widely attributed to the global environmental changes caused by the eruption of the Siberian Traps. However, the precise temporal link between marine and terrestrial crises and volcanism is unclear. Here, we report anomalously high mercury (Hg) concentrations in terrestrial strata from southwestern China, synchronous with Hg anomalies in the marine Permian-Triassic type section. The terrestrial sediments also record increased abundance of fossil charcoal coincident with the onset of a negative carbon isotope excursion and the loss of tropical rainforest vegetation, both of which occurred immediately before the peak of Hg concentrations. The organic carbon isotope data show an ~5‰–6‰ negative excursion in terrestrial organic matter (bulk organic, cuticles, and charcoal), reflecting change in atmospheric CO2 carbon-isotope composition coincident with enhanced wildfire indicated by increased charcoal. Hg spikes provide a correlative tool between terrestrial and marine records along with carbon isotope trends. These data demonstrate that ecological deterioration occurred in tropical peatlands prior to the main marine mass extinction.
Article
Full-text available
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.
Article
Full-text available
During the earliest Triassic microbial mats flourished in the photic zones of marginal seas, generating widespread microbialites. It has been suggested that anoxic conditions in shallow marine environments, linked to the end-Permian mass extinction, limited mat-inhibiting metazoans allowing for this microbialite expansion. The presence of a diverse suite of proxies indicating oxygenated shallow sea-water conditions (metazoan fossils, biomarkers and redox proxies) from microbialite successions have, however, challenged the inference of anoxic conditions. Here, the distribution and faunal composition of Griesbachian microbialites from China, Iran, Turkey, Armenia, Slovenia and Hungary are investigated to determine the factors that allowed microbialite-forming microbial mats to flourish following the end-Permian crisis. The results presented here show that Neotethyan microbial buildups record a unique faunal association due to the presence of keratose sponges, while the Palaeotethyan buildups have a higher proportion of molluscs and the foraminifera Earlandia. The distribution of the faunal components within the microbial fabrics suggests that, except for the keratose sponges and some microconchids, most of the metazoans were transported into the microbial framework via wave currents. The presence of both microbialites and metazoan associations were limited to oxygenated settings, suggesting that a factor other than anoxia resulted in a relaxation of ecological constraints following the mass extinction event. It is inferred that the end-Permian mass extinction event decreased the diversity and abundance of metazoans to the point of significantly reducing competition, allowing photosynthesis-based microbial mats to flourish in shallow-water settings and resulting in the formation of widespread microbialites.
Article
Full-text available
Thrombolite and stromatolite habitats are becoming increasingly recognized as important refuges for invertebrates during Phanerozoic Oceanic Anoxic Events (OAEs); it is posited that oxygenic photosynthesis by cyanobacteria in these microbialites provided a refuge from anoxic conditions (i.e., the “microbialite refuge” hypothesis). Here we test this hypothesis by investigating the distribution of ~34, 500 benthic invertebrate fossils found in ~100 samples from microbialite succession that developed following the latest Permian mass extinction event on the Great Bank of Guizhou (South China), representing microbial (stromatolites and thrombolites) and non-microbial facies. The stromatolites were the least taxonomically diverse facies and the thrombolites also recorded significantly lower diversities when compared to the non-microbial facies. Based on the distribution and ornamentation of the bioclasts within the thrombolites and stromatolites, the bioclasts are inferred to have been transported and concentrated in the non-microbial fabrics, i.e., cavities around the microbial framework. Therefore, many of the identified metazoans from the post-extinction microbialites are not observed to have been living within a microbial mat. Furthermore, the lifestyle of many of the taxa identified from the microbialites was not suited for, or even amenable to, life within a benthic microbial mat. The high diversity of oxygen dependent metazoans in the non-microbial facies on the Great Bank of Guizhou, and inferences from geochemical records, suggests that the microbialites and benthic communities developed in oxygenated environments, which disproves that the microbes were the source of the oxygenation. Instead, we posit that microbialite successions represent a taphonomic window for exceptional preservation of the biota, similar to a Konzentrat-Lagerstätte, which has allowed for diverse fossil assemblages to be preserved during intervals of poor preservation.
Article
Full-text available
The latest Permian mass extinction, the most devastating biocrisis of the Phanerozoic, has been widely attributed to eruptions of the Siberian Traps Large Igneous Province, although evidence of a direct link has been scant to date. Here, we measure mercury (Hg), assumed to reflect shifts in volcanic activity, across the Permian-Triassic boundary in ten marine sections across the Northern Hemisphere. Hg concentration peaks close to the Permian-Triassic boundary suggest coupling of biotic extinction and increased volcanic activity. Additionally, Hg isotopic data for a subset of these sections provide evidence for largely atmospheric rather than terrestrial Hg sources, further linking Hg enrichment to increased volcanic activity. Hg peaks in shallow-water sections were nearly synchronous with the end-Permian extinction horizon, while those in deep-water sections occurred tens of thousands of years before the main extinction, possibly supporting a globally diachronous biotic turnover and protracted mass extinction event.
Article
The Permian-Triassic mass extinction (PTME) strongly devastated marine ecosystems, and, consequently, sponges, especially the reef-building clades, suffered dramatic losses in biodiversity. The Early Triassic therefore was believed to be an evolutionary gap for sponges. Microbialites spread over shallow marine carbonate settings across the entire low-latitude Tethys region following the PTME and occupied the ecospace that the pre-extinction metazoan reefs left. Here, we report putative keratose sponge consortia from the microbialites near the Permian-Triassic boundary in the Xiushui, Laolongdong, and Dongwan sections, South China. The putative keratose sponges exhibit vermiform, filamentous textures forming maze-like networks. Within the keratose sponge-microbial fabrics, the calcified sponge skeleton might firm the overall framework of microbialite, promoting construction of the sponge-microbial build-ups. The coeval occurrence of putative keratose sponges in both eastern Palaeotethys and central Neotethys regions indicates that sponges may have widely spread and played important roles in constructing metazoan-microbial reefs in earliest Triassic. Besides, several characteristics are conducive to keratose sponge surviving the stressful environments after the PTME. Global dataset shows that keratose sponges mostly confined to tropic and temperate zones. Keratose sponges overall flourished in coincidence with occurrence abundance peaks of microbial reefs during the Phanerozoic history, and they seem to be particularly abundant and widespread in the Cambrian-Ordovician, Late Devonian and the aftermath of the end-Permian mass extinction.
Article
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. At the Permian–Triassic boundary (252 million years ago), a series of environmental crises triggered by the Siberian Traps eruptions caused the extinction of 81–94% of marine species and 70% of terrestrial vertebrate families. This Review discusses the relationships between volcanism, environmental perturbations and ecosystem collapse at the Permian–Triassic boundary. The Permian–Triassic mass extinction (252 million years ago) substantially reduced global biodiversity, with the extinction of 81–94% of marine species and 70% of terrestrial vertebrate families.Sedimentary, palaeontological and geochemical records of the mass extinction indicate that a cascade of environmental changes caused the extinction.The environmental changes can be linked (and attributed to) the effects of volcanic emissions (for example, CO2, SO2, halogens and metals) during the eruption of the Siberian Traps Large Igneous Province.The inferred volcanically driven environmental perturbations include: global warming, oceanic anoxia, oceanic acidification, ozone reduction, acid rain and metal poisoning.The crisis on land probably started about 60–370 thousand years before that in the ocean, indicating the different response times of terrestrial and marine ecosystems to volcanism, but the reasons for the earlier terrestrial crisis remain poorly understood. The Permian–Triassic mass extinction (252 million years ago) substantially reduced global biodiversity, with the extinction of 81–94% of marine species and 70% of terrestrial vertebrate families. Sedimentary, palaeontological and geochemical records of the mass extinction indicate that a cascade of environmental changes caused the extinction. The environmental changes can be linked (and attributed to) the effects of volcanic emissions (for example, CO2, SO2, halogens and metals) during the eruption of the Siberian Traps Large Igneous Province. The inferred volcanically driven environmental perturbations include: global warming, oceanic anoxia, oceanic acidification, ozone reduction, acid rain and metal poisoning. The crisis on land probably started about 60–370 thousand years before that in the ocean, indicating the different response times of terrestrial and marine ecosystems to volcanism, but the reasons for the earlier terrestrial crisis remain poorly understood.
Article
Emplacement of the Central Atlantic Magmatic Province (CAMP) is thought to have triggered global environmental changes and the end-Triassic mass extinction (ETE). However, the mechanisms linking volcanism and environmental change are unclear. Here we provide new insight into these linkages by measuring the abundance of both sedimentary five- to six-ring polycyclic aromatic hydrocarbons (PAHs) and mercury from strata deposited in shallow marine environments across the ETE at the GSSP Kuhjoch section in Austria and St. Audrie's Bay section in the UK. To contextualize these data, we report results from laboratory experiments measuring the production of SO2 and CO2 during heating of limestone and mudstone. ETE sediments record parallel enrichments of mercury and five- to six-ring PAHs, which could have been produced by intrusive magma (mainly sills) and lava flows during the early stage of the CAMP emplacement; these data indicate a direct link between massive gas emission from sill contact metamorphism and the ETE. The fraction of coronene – a highly condensed six-ring PAH that requires greater energy to form compared to smaller PAHs – accumulated in the sediments during these initial volcanic events is low, and it coincides with the terrestrial plant turnover and initial marine extinction. Coronene increases to medium values coinciding with the final marine extinction level. Our heating experiments of typical carbonate and mudstone materials show that relatively low temperature heating (>350 °C) by sills releases massive amounts of SO2 on a 100 yr time scale, whereas higher temperature heating (500–600 °C) forms more CO2 on the same time scale. The combination of our end-Triassic geochemical data and laboratory results implies that low heating by sills caused SO2-dominated gas emission to the stratosphere and low CO2 emission, inducing global cooling that could have precipitated the mass extinction. The subsequent increase in coronene content indicates higher volcanic temperature that would have volatilized CO2 rich gas; the consequence was a switch to greater CO2 release and long-term (>10⁵ yr) global warming.
Article
As one of the most important intervals in Earth life evolution, the latest Permian to earliest Triassic witnessed the greatest mass extinction and most profound recovery of marine biotas. In this period, gondolellid conodonts went through a major faunal turnover and morphologic change marked by platform reduction during the late Griesbachian to Dienerian. However, the details of this morphologic change process remain poorly known. The resultant Dienerian segminate conodonts also display remarkable morphologic variations related to growth, which has caused a great deal of confusion in taxonomy. Ontogenetic and phylogenetic studies are believed to be essential in understanding the developmental process and evolution of organisms and thus will be helpful for improving taxonomic definitions and revealing temporal changes of morphology. Here, based on abundant and well-preserved specimens from the Salt Range and Surghar Range of northwestern Pakistan, we described in detail the morphologic variants and reconstructed the ontogenetic series for seven stratigraphically important Griesbachian-Dienerian conodonts belonging to Clarkina, Neoclarkina, Neospathodus, and Sweetospathodus. A further Dienerian key species Eurygnathodus costatus is also included in discussion based on the work of Lyu et al. (2020). The phylogenetic relationships among these taxa were reconstructed by means of cladistic approach. Some important evolutionary trends were recognized. Morphometric data including element length, platform width and denticle number were collected based on global occurrences and were plotted to illustrate the ontogenetic trajectory. Comparisons of ontogenetic trajectories revealed complex heterochronic patterns for platform growth. The reduction of platform may result from progenesis and neoteny in late Griesbachian Neoclarkina species and further from postdisplacement of the flange in Dienerian segminate conodonts. The Dienerian Neospathodus lineage may represent a paedomorphosis of the flange, whereas the lineage of Sw. kummeli–Eu. costatus was probably characterized by a peramorphosis of the platform through acceleration.
Article
The end-Permian mass extinction (EPME) severely impacted global biodiversity. Extinction selectivity of biotas behaved differently in various environmental settings, and biotic variations before, during, and after the EPME on the shallow platform remain unclear. This paper describes a new microbialite near the Permian-Triassic (P-Tr) boundary (PTB) from the Xiejiacao section, South China. The PTB microbialite comprises thrombolite and dendrolite fabrics and yields abundant columnar cyanobacteria and various microspheroids. Abundant metazoan fossils, including conodonts, foraminifers, ostracods, gastropods, ammonoids, brachiopods, and ophiuroids, are reported from the uppermost Permian bioclastic limestone, PTB microbialite (PTBM), and lowest Triassic strata in Xiejiacao. Stratigraphic occurrences of these taxa display a two-fold decline pattern of the end-Permian mass extinction, calibrating to the base and top of the PTB microbialite and corresponding to the first extinction phase (EP1) and second extinction phase (EP2) of the EPME, respectively. This two-fold extinction pattern is also reinforced by fossil fragment components of various clades through the P-Tr transition in Xiejiacao. Updated dataset of metazoan fossil records from 25 PTBM sections in South China is also compiled, and it shows the two-fold declines in biodiversity. The dominance role of foraminifers in the latest Permian faunas switched to ostracods in the PTB microbialite after EP1, and then to bivalves after EP2. Proportions of infaunal, stationary, and omnivore forms declined continuously across the EP1 and EP2, while pelagic, fast-moving, suspension-feeding, and predatory taxa underwent stepwise increases across these two extinctions. Proportions of epifaunal, slow-moving, and deposit-feeding taxa increased after EP1 but decreased after EP2. This might be associated with the extinction of brachiopods and, the immigration, and the proliferation of mollusks (bivalves, gastropods, and ammonoids). The metazoan fossil dataset of all PTBM sections across South China refutes the taphonomic window hypothesis and the refuge scenario, instead, supports that the post-extinction unique palaeoceanographic conditions in microbial ecosystems may have been beneficial to diversification of the PTBM faunas. The dataset of the stratigraphic distributions of all PTBM taxa in all palaeoenvironmental settings across South China shows that the drastic decline in biodiversity of the PTBM faunas during the cessation of microbialite was not due to facies control on fossil preservation, but closely related to the biotic extinction in EP2 of the EPME.
Article
The Guryul Ravine section in Kashmir, northern India is an important reference section for global Lower Triassic stratigraphy. Once a candidate Global Stratotype Section and Point (GSSP) for the Permian-Triassic Boundary (PTB), the section has attracted intense attention for the PTB beds, but few studies have concerned the entire Lower Triassic stratigraphy. As one of the most continuous marine Lower Triassic successions on the northern margins of Gondwana, the Guryul Ravine section provides an important conodont biostratigraphic yardstick for worldwide correlations. This study presents recent results of the Lower Triassic conodont zonation from the Guryul Ravine section. A total of 6500 elements including 1600 P1 elements were recovered. Ten conodont zones were recognized from the Griesbachian to Spathian: Hindeodus parvus, Isarcicella staeschei, Clarkina planata, Neoclarkina krystyni, Neospathodus dieneri, Ns. pakistanensis, Novispathodus waageni, Scythogondolella mosheri, Nv. pingdingshanensis, and Nv. abruptus – Nv. brevissimus zones. The PTB is placed within Bed 52 in Unit E2, 80 cm above the base of Unit E2, based on the first occurrence (FO) of H. parvus. The Induan–Olenekian boundary (IOB) is tentatively placed at the base of Member G according to the positive maximum δ¹³Ccarb values, but it could be slightly higher based on conodonts. The Smithian-Spathian boundary (SSB) is drawn at the top of Member H based on the FO of Nv. pingdingshanensis and the carbon mdpt(N3-P3). Several conodont taxa are newly recognized near the top of the study section where the conodont fauna is dominated by segminiplanate elements of the Neogondolellinae. Many of these age-diagnostic species have been identified in other sections around the world, and their occurrence in Guryul Ravine supports their potential for worldwide correlation. The conodont sequence erected from the study section corresponds well to those of South China (e.g. Meishan) and elsewhere worldwide. The newly established conodont zonation from Kashmir provides a high precision time-frame to consider biotic evolution and environmental change during the Early Triassic, a crucial period of Earth history.
Article
The end-Permian mass extinction (EPME) has been linked with the widespread development of oxygen-poor oceanic conditions. However, information on the spatial extent of anoxia in the Panthalassa super-ocean has been limited. This study reports oceanic redox records from a deep-sea chert succession (the Waiheke 1 section, WHK 1, New Zealand) that was located in southern mid-latitudes of Panthalassa. High-resolution carbon isotope (δ13C) correlation between Waiheke and the Permian-Triassic boundary (PTB) type section indicates that the EPME is recorded in a thin black claystone interbedded between siliceous mudstone beds at WHK 1. Pyrite-dominated enrichment in highly reactive iron, coupled with elevated U/Al and Mo/Al ratios, are prevalent through this black claystone bed and the overlying Permo-Triassic transition strata, suggesting the development of euxinic water column conditions. Similar redox variations across the EPME horizon have been reported from other Panthalassic deep-sea PTB sections. Comparison with these PTB sections indicates that euxinic conditions were widespread in low-latitude regions of the Panthalassan ocean, and such conditions developed earlier than in mid-latitude settings, up to 100,000 years before the EPME. This suggests there was a gradual expansion of ocean anoxia from low to middle-high latitude regions during the Permo-Triassic transition. The extent of ocean anoxia resulted in a decrease in the seawater inventory of redox sensitive trace metals (e.g., Mo), which is evident in the earliest Triassic strata of the studied section and other PTB sections. Panthalassic anoxia during the EPME coincides with extreme climate warming and the associated effects (e.g., changes in ocean circulation, marine eutrophication intensified by terrestrial weathering) were likely critical triggers for ocean deoxygenation.
Article
The Permian−Triassic mass extinction was the most severe biotic crisis of the past 540 million years, eliminating 80–90% of species in the ocean and ~ 70% of land-based vertebrate families. Researchers have debated whether terrestrial vegetation collapse occurred before or after the marine extinction, or if they were synchronous. We analyzed the ratios of normal alkanes of terrestrial plant origin to total normal alkanes (terrestrial plant index) as well as those of pristane to phytane, which are affected by terrestrial plant inflow and ocean redox, in shallow marine, terrestrial lagoon, and central deep-ocean sedimentary rocks from China, Italy, India, and Japan to elucidate the terrestrial vegetation history. Interpretation of pristane/phytane ratios was conducted through comparison with other seawater redox indices. Both proxies indicate that two terrestrial vegetation collapses occurred, before and at the end-Permian marine extinction in the coastal sea environment, followed by the complete plant devastation, and a subsequent terrestrial vegetation proto-recovery in the earliest Triassic. The two proxies showed opposite patterns in a terrestrial lagoon setting section, and those from a central deep-ocean setting indicate that little terrestrial plant material reached the central ocean. These differing responses of the pristane/phytane ratios among geographical settings are consistent with natural phenomena, indicating that the method proposed in this study results in valid reconstruction of vegetation changes. Cyanobacterial blooms occurred from the end-Permian vegetation collapse until after the massive plant-soil erosion, suggesting that terrestrial ecosystem disturbance caused deterioration of the environment for eukaryotic algae in the coastal sea and terrestrial lagoon.
Article
The narrow active temperature ranges of ectothermic tetrapods can be used as proxies for reconstructing paleoclimates. Here we deduce the climatic preferences of major Permo-Triassic tetrapod groups based on their known geographic distributions, the critical thermal limits of living tetrapods, and paleoclimate information from other sources. The resulting preferred temperature sequence of amniotes places most Triassic archosauromorphs at the high end of the spectrum, with preferred temperatures over 32 °C in some cases, followed by captorhinids, pareiasaurs, procolophonids, cynognathian cynodonts, dicynodonts (excluding Lystrosaurus), Proterosuchus fergusi, and finally Lystrosaurus at the lowest preferred temperature. The poleward distribution of Permian Lystrosaurus marks the border of cool temperate climates, whereas Triassic Lystrosaurus delineates the border of the arid zone. Most temnospondyls indicate the availability of perennial water sources. Captorhinids and pareiasaurs preferred dry climates, whereas dicynodonts preferred wetter conditions. Based on current evidence, central Pangea transitioned from an arid zone to a tropical zone during the late Olenekian.
Article
The Rhynchonellida is a major group of brachiopods that survived the “big five” mass extinctions and flourished after the Permian/Triassic (P/Tr) crisis. However, phylogenetic and character evolution in the Rhynchonellida across the P/Tr transition is poorly understood. In view of the widespread homoplasy across this order, we employ a tip-dated Bayesian analysis to reconstruct phylogenetic relationships for late Permian–Triassic rhynchonellides. The same data were also analyzed using three other methods: undated Bayesian, equal-weighting, and implied-weighting parsimony. Compared with trees generated by other methods, those constructed by tip-dating best account for the homoplasy in this group and are closer to previous assumptions on the evolution of this order. Based on the analyses of multiple trees, the major increase in lineage richness occurred in the Early and early Middle Triassic. Also, richness in the Anisian almost reached the highest level seen in the Triassic. According to fossil records, a pronounced reduction in shell size and in the development of ornamentation occurred after the P/Tr extinction, which is largely due to the loss of large and highly sculptured genera and the diversification of small-sized and weakly ornamented genera. Ancestral-state estimation of shell size and development of ornamentation, coupled with comparisons of other characters, indicate that the Early–Middle Triassic mature “small-sized taxa” may have characters displayed by juveniles of their ancestors. This suggests that for these genera, paedomorphosis was possibly a strategy to survive and diversify in the harsh environment after the P/Tr extinction.
Article
Abundant conodont faunas from the subsurface of British Columbia, Canada, allow the correlation of Lower and Middle Triassic strata with outcrop sections in British Columbia, the Canadian Arctic and the western USA, as well as recording the previously recognized radiation of neogondolellin conodonts in the early Spathian. Twenty-eight samples collected from the Progress Hz Caribou D-040-H/094-G-07 and Progress Hz Laprise A-082-I/094-G-01 wells yielded more than 1100 conodont specimens, representing twenty-nine pectiniform species belonging to fourteen genera. These faunas enable the recognition of the Dienerian–Smithian, Smithian–Spathian, and Spathian–Anisian boundaries in these wells. Five of the conodont species recognized in the Smithian and Spathian samples are new: Neogondolella n. sp. A, Borinella n. sp. A, Magnigondolella. n. sp. A, Columbitella n. sp. A, and Co. talpa sp. nov. Together with these new segminiplanate species, several other neogondolellin conodonts occur. These faunas are the manifestation in British Columbia of the previously recognized increase in abundance of neogondolellin conodonts in the early Spathian, and they are consistent with hypotheses in which the earliest species of Magnigondolella evolved from Borinella by a progressive fusion of the denticles of the carina. These conodonts help to characterize the events around the globally significant Smithian–Spathian boundary, and to correlate this boundary in North America.
Article
The end Permian mass extinction (EPME) is the greatest among the “Big Five” extinctions of the Phanerozoic, and is believed to have been triggered primarily by the Siberian Traps Large Igneous Province (STLIP). This hypothesis is supported by the temporal correlation of STLIP with the EPME by radiometric ages and Hg enrichments in sedimentary rocks. However, how signatures of volcanic Hg emissions are preserved in sediments, and how this may vary from deep basin to shelf to terrestrial successions, remain unclear. To examine variability in the Hg record in different environments, we systematically measured organic carbon isotopes, Hg concentrations and isotopes, major elements, and total organic carbon (TOC) contents from: 1) a terrestrial section at Chahe, 2) a marine-nonmarine transitional section at Jinzhong both in Guizhou Province, Southwest China. Results show that Hg versus TOC and Hg versus Al exhibit no correlation through the terrestrial section at Chahe, whereas there is positive correlation in the transitional Jinzhong section. These relationships indicate that organic matter and clay minerals would not affect Hg fluctuations on land, but dominates Hg sequestration in transitional settings. Thus, Hg/TOC along with Hg/Al ratios were able to be employed to recognize abnormal Hg deposition in Jinzhong, and Hg concentrations were utilized to examine records of Hg enrichments in Chahe. The studied sections all show synchronous changes between carbon isotopic perturbations and Hg deposition events with first Hg enrichment and associated negative carbon isotopic negative excursion coinciding with terrestrial ecological disturbance and with a second Hg enrichment corresponding to the largest carbon isotopic negative excursion and marine biological crisis. These trends across the Permian-Triassic boundary are also observed in other 13 sections around the world, indicating a common source that injected massive CO2 and Hg, impacting the global C and Hg cycles. Hg isotope (Δ¹⁹⁹Hg values) of the first peak in Hg concentrations have similar characteristics in the terrestrial Chahe and transitional Jinzhong sections along with other sections (e.g., Shangsi and Chaohu in South China, Guryul Ravine section in India and Buchanan Lake section in Canada), all showing positive values, indicative of predominantly atmospheric-derived volcanic Hg. In contrast, Δ¹⁹⁹Hg values at the second Hg peak, corresponding to the marine extinction horizon in Chahe and Jinzhong, are negative. This relationship indicates an elevated involvement of terrestrial sourced Hg into the terrestrial or nearshore aquatic realm due to increased weathering after the collapse of terrestrial ecosystem. Our study suggests that the STLIP could have two pulses of volatile eruptions that released massive CO2 and Hg, resulting in two pulses of Hg enrichments coupled with negative carbon isotopic excursions coinciding with end Permian terrestrial and marine extinction events.
Article
Wrinkle structures have occurred on our planet for 3.2 billion years. They, therefore, if proved to be biogenic origin, could represent one of oldest life forms on Earth. Such distinct microbial mats were commonly present in the Precambrian, and were also widespread in shallow marine siliciclastic settings in the Cambrian and aftermath of major Phanerozoic mass extinctions, but their interactions with metazoans remain varied. Here, I reassess abundant wrinkle structures which were documented previously from the Lower Triassic successions of two moderate-high latitudinal localities, the southern Qilian basin of west China, and the northern Perth Basin of Western Australia in both northern and southern hemispheres. Wrinkle structures commonly occurred at the interface between a fine sandstone bed and an overlying siltstone or mudstone bed. Both burrowing and shelly benthos were sporadically distributed in wrinkle structures, contrasting with the biomass in non-wrinkled layers. Although wrinkle structures may be preserved in well‑oxygenated habitable habitats together with diverse benthos, they proliferated during anoxic transient periods or when storm-influenced sediments were deposited. The co-occurrence of wrinkle structures with trace fossils and benthos such as bivalves reflects an animal-sediment interaction, instead of an animal-mat interaction, and caution therefore should be made when documenting the interactions between microbes and metazoans in fossil records. Grazing activities by both infaunal deposit-feeders and bivalves were absent on the wrinkled surfaces, while horizontal burrows and infaunal bivalves cross-cut and disrupted the wrinkled surfaces, implying that trace fossils post-dated the formation of the wrinkle structures, and the organisms mainly exploited in buried microbial mats. The distribution of trace fossils and benthos on wrinkled surfaces from these two studied localities do not support the concept of microbial refugia or the preferential preservational window hypotheses. MISS including wrinkle structures and microbialites have been documented from both low- and high-latitude regions, and their relatively sparse occurrences in moderate- to high-paleolatitudes regions may be due to sampling bias. The proliferation of microbes such as cyanobacteria in the aftermath of the mass extinction was not related to selectivity of climate zones and seawater temperature in shallow marine settings.
Article
Investigation of the end-Permian mass extinction (EPME) has been greatly facilitated by high-resolution conodont biostratigraphic studies. To date, however, a detailed biostratigraphic framework has been lacking for shallow-marine successions of the Tethys region. In the present study, we analyzed carbonate microfacies, conodont biostratigraphy, and carbonate carbon isotopes of the Yangou Quarry section, a shallow-marine EPME succession that accumulated on an isolated carbonate bank on the northern margin of the Yangtze Platform. Microfacies analysis yielded four facies and 8 microfacies that record a seawater deepening immediately following the EPME. Ooids were abundantly produced during the EPME and earliest Triassic mass extinction (ETME) but were replaced by microbial mats, algae, bivalves, and brachiopods during an earliest Triassic transgression. A total of three conodont zones are recognized from the uppermost Changhsingian to the lowermost Griesbachian, in ascending order, the Hindeodus praeparvus Zone, H. parvus Zone, and Isarcicella staeschei Zone. The EPME and PTB (Permian-Triassic boundary) horizons are marked by the first occurrences of H. praeparvus at 6.18 m and H. parvus at 6.57 m, respectively, above the base of the section. The conodont biostratigraphic framework of the Yangou Quarry section was refined through intercalibration with its δ¹³Ccarb profile. This section records two discrete negative carbon isotope excursions (CIEs) that are correlative with the EPME and ETME horizons, and that can be correlated with similar CIEs at Meishan D and other PTB sections globally. Our study provides the first integrated, high-resolution biochemostratigraphic framework for a shallow-marine PTB succession in the eastern Tethys region, which will facilitate paleoenvironmental studies of similar facies elsewhere as well as correlations with deeper-water facies.
Article
The end-Triassic mass extinction (ETME) is considered to be one of the five most severe extinction events in Earth history and caused the disappearance of ca. 80% of all species. The terrestrial ecosystems were also greatly affected by this extinction, but the severity of the land plant diversity loss is not well understood. Ferns are once a principal component of the terrestrial ecosystem from the late Paleozoic/early Mesozoic era and colonizers taxa commonly found in disturbed environments. In this study, we investigated the diversity and ecology of fern during the Triassic-Jurassic (Tr–J) transition in the Sichuan Basin of South China and focused for the first time on the impact of the end-Triassic mass extinction event on the fern communities. We assembled fern fossil records in 16 localities from the Rhaetian Xujiahe (XJH) Formation to the lowermost Jurassic Zhenzhuchong (ZZC) Formation. Our results indicate that no obvious mass extinctions of macro-microflora of ferns but a clear species turnover was recorded at ETME in the Sichuan Basin, reflected an appropriate response of plants in places far away from CAMP volcanism. The paleoecological analysis based on macroflora and microflora in the Sichuan Basin shows a warm and humid condition of tropical-subtropical climate during Rhaetian followed by an increase of specific dry-resistant taxa, indicating a dryer environment at the Earliest Jurassic. Additionally, multivariate statistical approaches (principal coordinates analysis, cluster analysis, network analysis) for fern macro-remains and spores data in the southeastern Sichuan Basin infer that the members of XJH and ZZC Formation cluster in three groups, corresponding to their environmental conditions, determined by humidity and temperature.
Article
Increasing evidence shows that the recovery of marine ecosystems after the Permian/Triassic mass extinction (PTME) was coupled with environmental amelioration. Recently, abundant insects and complete trophic structures were unraveled from the Ladinian (late Middle Triassic) in the Ordos basin, central China, deciphering recovery of lacustrine ecosystem from the PTME. Coeval environmental settings, however, remain unclear. In the Ordos basin, the Ladinian succession is dominated by black organic-matter-rich shales of the Chang 7 Member of the Yanchang Formation, and their depositional environments and palaeo-productivity are reconstructed based on major and trace element concentrations, pyrite framboid size and morphology, and total organic carbon (TOC) contents. High values of TOC and phosphorous (P) concentrations, as well as more enrichment of trace-metal elements such as Copper (Cu) and zinc (Zn) all indicate a rather high primary productivity. Such a high productivity during the deposition of the Chang 73 sub-member is also reinforced by and the presence of abundant organic-matter-enrich laminae in black shales and the diverse chrysophytes, as well as intensive occurrence of tuff layers and possible hydrothermal fluids. Analyses of framboidal pyrite size and morphology as well as Corg/P ratio and trace-metal elements such as molybdenum (Mo) and uranium (U), indicate the dysoxic to oxic conditions in water columns of the Ordos lake during the late Middle Triassic. The Ladinian-Carnian cooling likely promoted the occurrence of dissolved oxygens in the lake. As a result, although the massive black shales of the Chang 73 sub-member were deposited and suggest a rather high primary productivity, they also indicate slightly oxygen-poor to oxygenated conditions of water columns, which are inductive for lacustrine biota to inhabit, and also offer hospitable habitats for freshwater lake ecosystems to recover from the PTME.
Article
The Smithian negative C-isotope excursion was one of the major perturbations of the global carbon cycle following the end-Permian mass extinction event. Profound oceanographic and biological changes occurred during the Smithian, but the mechanism driving the negative C-isotope excursion and its links with marine environmental and biotic changes remain poorly constrained. Here, we use high-resolution paired C-isotope records from the early Smithian to the early Spathian in the Jiarong section, South China, to investigate the origin of the carbon cycle perturbation and its relationship with contemporaneous environmental changes. The paired C-isotope data reveal parallel negative excursions in both δ¹³Ccarb and δ¹³Corg during the Smithian that can be correlated globally. The global Smithian negative C-isotope excursion shows a good first-order correspondence with global transgression and anoxia. The results of numerical box modeling suggest that the Smithian negative C-isotope excursion could have been generated by increased organic carbon oxidation in response to the upward movement of anoxic bottom waters during transgression. The oxidative decay of organic carbon is primarily fueled by the consumption of oxygen and sulfate in the atmosphere and ocean system. Hence, we use the model to quantify the oxidants consumption rate that could be required to simulate the global Smithian negative C-isotope excursion through organic carbon oxidation. The modeling results show that the organic carbon oxidation during the Smithian could have generated a high demand for oxidants in the ocean, leading to the expansion of anoxia. Our study provides quantitative constraints on the causal link between the Smithian negative C-isotope excursion and widespread anoxia. The nadir of the Smithian negative C-isotope excursion coincided with the severe loss of biodiversity, suggesting that the expansion of anoxia in response to the transgressive upward movement of anoxic waters may have driven the late Smithian extinction. Hence, it could be one of the causes of the prolonged Early Triassic biotic recovery.
Article
The value of taxonomy as a tool in palaeoenvironmental analysis depends on accuracy of determination of relevant taxa; in cases where taxa present unresolved problems of distinction (identification uncertainty and overlap), difficulties may exist in their application in facies studies. A prime example is found in ostracods of the Permian–Triassic boundary interval, considered here in sequences from south China. Low-latitude shallow-marine carbonate facies in the immediate aftermath of the end-Permian extinction (EPE) have common widespread microbialite biostromes containing abundant shelly fossils including ostracod assemblages not found elsewhere, stimulating the earlier idea that the microbialite was a refuge from stressors of extinction. These assemblages are dominated by the Family Bairdiidae that are mostly smooth-shelled ostracods notoriously difficult to resolve into sub-familial taxonomic units. Studies of ostracod taxonomy require a careful approach of integrating cornerstone aspects of their biology such as ontogenetic development and sexual dimorphism to disentangle taxonomically discrete groups. These significant difficulties of taxonomic resolution have a knock-on impact on application of the faunas in facies analysis; several studies remain open to interpretation because of these issues. Resolution of ostracod taxonomy is critical to the refuge hypothesis, because ostracods (mostly as complete closed carapaces, including juveniles and adults) accumulated in the microbialite; thus shell morphology is critical to analysis of ostracods in the microbialites so understanding the taxonomy is vital. The microbialites comprise two main facies where ostracods are abundant: (1) layers consisting of microbial components and intervening micrite; (2) uncommon shell-rich lenses of packstone-grainstone fabric between microbial layers. The refuge hypothesis is considered unlikely by some authors, who instead interpret the microbialites as a taphonomic window for imported ostracod shell preservation. However, post-extinction microbialite sheets are extensive on shallow marine carbonate platforms in Tethys and show little evidence of physical damage. We deduce that, instead of a taphonomic window, the well-preserved ostracod assemblages lived on the microbialite, and that the ‘refuge hypothesis’ remains viable. The concepts discussed in this study may be applicable to other fossil groups where taxonomic problems are acute.
Article
Combustion-derived polycyclic aromatic hydrocarbons (PAHs) are frequently used as molecular proxies for wildfire in recent and ancient sediments. Here, we document the abundances of four hydrocarbon compounds, i.e., phenanthrene (Phe), benzo[e]pyrene (BeP), benzo[ghi]perylene (Bpery), and coronene (Cor), across the Permian–Triassic boundary (PTB) in five marine sections of South China. High values of PAHs are present below the end-Permian mass extinction (EPME) horizon, from the Clarkina changxingensis Zone to the Clarkina yini Zone, suggesting strong perturbations to terrestrial ecosystems predating the marine crisis. PAHs peaked in the uppermost C. yini Zone, correlative with the EPME, reflecting simultaneity of the most severe phases of the terrestrial and marine crises. The proxy records document suitable climatic conditions for wildfires (high pO2) throughout the P-Tr transition. The results of the present study are also significant in validating the utility of BeP, Bpery, Cor, and BeP/Phe as proxies for terrestrial wildfires in deep-time marine successions.
Article
Extreme greenhouse warming in the latest Permian played a key role in the largest animal extinction event ever recorded in Earth history. The extinction was likely triggered by volcanic eruptions that dramatically increased atmospheric CO2 levels and pushed the Earth system into a lethally hot greenhouse state with stratified, anoxic and more acidic oceans. These conditions intensified a few million years later during the middle/late Smithian Thermal Maximum (STM), and a further biodiversity loss occurred during the subsequent cooling across the Smithian-Spathian boundary (SSB). The marine carbonate factory is expected to have changed during this period, but relevant studies are still lacking. Here, we report calcium isotopic data of bulk carbonate rocks (δ44/40Cacarb) from two marine carbonate sections (Jiarong and Shitouzhai) in South China, showing ~0.5–0.7‰ positive shift of δ44/40Cacarb coupled to a ~ 4–6‰ positive shift of δ¹³Ccarb from the middle Smithian to the early Spathian. Box modeling of the marine Ca cycle yielded two scenarios (i.e., constant and variable δ44/40Caseawater) that can produce a ~0.5‰ positive shift of δ44/40Cacarb: (1) A local mineralogical shift in primary carbonate mineralogy at both sites from 80% aragonite to 80% calcite, or (2) a >10× increase of global carbonate burial flux. The former is consistent with a ~20-50-fold rise of Ca/Mg ratios and ~10-50-fold decrease of Sr/Ca ratios in the study sections, and the latter fits well with massive carbonate deposition globally during the early Spathian. Oceanic overturn and upwelling of alkaline deep waters during SSB climatic cooling is proposed as the main reason for the increase in carbonate burial flux. Thus, the SSB transition marks an important step in the recovery of the marine fauna after the end-Permian mass extinction triggered by climatic cooling, ocean ventilation, and a pronounced rise in marine carbonate deposition on continental shelves.
Article
The Carnian Pluvial Episode (CPE) was a dramatic climatic event during the early Late Triassic. The CPE has been recognized worldwide and is marked by the termination of carbonate platform successions and by pronounced negative δ 13 C excursions (denoted as the CPE excursion). The onset of the CPE has been proposed to be linked with the volatile eruption of the Wrangellia Large Igneous Province (W-LIP). However, this extreme climatic event remains disputed in terms of its precise global correlation, timing of onset, duration, and global magnitude. We compiled a database of 13 conodont biozone-controlled stable-isotope reference sections throughout the Tethyan region. After a reexamination of previously published conodont taxonomy from each section, the statistics on the conodont assemblages/zones yield a global set of 17 high-resolution conodont Unitary Association Zones (UAZs) spanning the entire Carnian successions. A set of age-tie points placed an age model on this global UAZ scale. We added paired δ 13 C carb and δ 13 C org data from two sections in South China to other records in this global database, and then normalized all carbon-isotope datasets. A pronounced negative δ 13 C carb excursion with a magnitude of −2 ± 0.5‰ (from an average of ~3‰ to ~1‰) is evident in these normalized trends and is recognized around the entire Tethys realm. The CPE excursion coincides with conodont UAZ-4 (~234 Ma) through UAZ-8 (within the Mazzaella carnica and Paragondolella praelindae zones, Julian2) and has a duration of ca. 1.5 Myr. We note that an apparent delayed onset of the CPE excursion in South China relative to elsewhere in the Tethys as suggested by previous studies may have been an artifact caused by incomplete conodont-stratigraphic records and/or irregularities in taxonomic identification. A carbon and phosphorus cycle model highlight the strong relationship between the eruption of the W-LIP and CPE excursion; however, the estimated amount of CO 2 volatiles released by the W-LIP would directly account for only ~25% of the total amount of light-carbon required to explain the combined magnitude and duration of the global CPE excursion.
Article
The end-Triassic mass extinction was one of the big five crises of the fossil record. It affected diverse marine groups, including bivalves, brachiopods, ostracods, calcareous algae, radiolarians, and tetrapods and coincided with major changes in palynological assemblages. The rapidity of the event has long been debated and here we show that it can be resolved into two distinct, short-lived extinction pulses separated by a several hundred-thousand-year interlude phase. Detailed collecting in the British Isles shows the first extinction in the lower Cotham Member eliminated many bivalves and ostracods. This event has been previously considered as the end-Triassic mass extinction horizon, however a second extinction is also seen at the top of the Langport Member after a phase of recovery marked by diversity increase. This younger crisis caused the loss of further bivalves, ostracods and the last of the conodonts. The two phases of marine extinctions coincide with marked turnovers amongst palynofloral assemblages with the interlude phase manifest as a fern spore-dominated interval (the Polypodiisporites polymicroforatus abundance interval). Correlation of Triassic-Jurassic boundary sections (and their associated extinction record) in Europe has been controversial. The most parsimonious correlation scheme assumes that a brief, high amplitude negative excursion of δ¹³Corg values, seen at the level of the first extinction phase in the UK, is manifest in other European sections in the same way. Alternative correlation schemes require complex scenarios with extinction occurring in some areas as recovery is happening elsewhere. In Europe, the first extinction coincides with regression whilst the second occurs at a flooding surface marked by the spread of anoxia. The extinction history of the terminal Triassic crisis is remarkably similar to that seen during other extinction events (end-Ordovician, Permo-Triassic, Toarcian) and suggests that, if the ultimate driver of these crises – large igneous province eruptions – is the same, then they show the same “double-punch” eruption history separated by a more benign interval of a few hundred-thousand-year duration.
Article
The end-Permian mass extinction (EPME) profoundly shaped shallow marine ecosystems. Although much has been learned about this event based on the body-fossil record, the global infaunal response to the EPME, as represented by ichnofossils, is much less understood. Here we analyze secular changes in ichnodiversity and ichnodisparity from the late Permian to the Middle Triassic based on a global trace-fossil data set. Results show that, in contrast to the body-fossil record, late Permian global ichnodiversity and ichnodisparity maintained their level until the Griesbachian, followed by a sharp loss in the Dienerian. Notably, the Griesbachian shows an unusual dominance of shallower tiers. The discrepancy between the body- and trace-fossil record is interpreted to be the result of the resurgence of widespread microbial matgrounds in the Griesbachian that aided the preservation of surface, semi-infaunal, and shallow-tier ichnofossils. Our study shows that the EPME strongly affected the sediment mixed layer, allowing the preservation of shallower tier trace fossils. The disappearance of the mixed layer in the earliest Triassic may have enhanced pyrite burial in sediments and inhibited its further re-oxidation, therefore impacting sea water sulfate concentrations.
Article
The end-Permian mass extinction (EPME; ca. 252 Ma) led to profound changes in lacustrine ecosystems. However, whether or not post-extinction recovery of lacustrine ecosystems was delayed has remained uncertain, due to the apparent rarity of Early and Middle Triassic deep perennial lakes. Here we report on mid–Middle Triassic lacustrine organic-rich shales with abundant fossils and tuff interlayers in the Ordos Basin of China, dated to ca. 242 Ma (around the Anisian-Ladinian boundary of the Middle Triassic). The organic-rich sediments record the earliest known appearance, after the mass extinction, of a deep perennial lake that developed at least 5 m.y. earlier than the globally distributed lacustrine shales and mudstones dated as Late Triassic. The fossil assemblage in the organic-rich sediments is diverse and includes plants, notostracans, ostracods, insects, fishes, and fish coprolites, and thus documents a Mesozoic-type, trophically multileveled lacustrine ecosystem. The results reveal the earliest known complex lacustrine ecosystem after the EPME and suggest that Triassic lacustrine ecosystems took at most 10 m.y. to recover fully, which is consistent with the termination of the "coal gap" that signifies substantial restoration of peat-forming forests.
Article
The end-Permian mass extinction (EPME; ca. 251.94 Ma) is the most severe mass extinction in the geological record. Detailed paleobiological investigations show a very rapid EPME event, and recently published δ²³⁸U data show a large negative excursion and thus a massive shift to globally expanded anoxia at the main extinction phase in the latest Permian. The negative shift in δ²³⁸U is in correlation with a globally characterized negative δ¹³C excursion near the Permian-Triassic boundary (PTB). In some highly expanded PTB carbonate sections, however, there are two distinct negative δ¹³C excursions whereas uranium isotopes (δ²³⁸U) from such sections have not yet been examined, leaving a gap in the understanding of the global perturbations of marine redox conditions immediately following the EPME. Here, we present a new δ²³⁸U study of syn-depositional dolostones from a well-characterized and highly expanded drill core, which recorded two pronounced negative δ¹³C excursions across the PTB, from the Carnic Alps, Austria. This drill core extends 331-meters across the PTB and provides a unique opportunity to explore the detailed timing, duration, and extent of marine redox chemistry changes before, during, and immediately after the EPME. Our new δ²³⁸U record shows two negative shifts, which are correlated with the two negative δ¹³C excursions. The first negative δ²³⁸U excursion preceding the EPME confirms the recently published δ²³⁸U records from across the EPME and support that syndepositional marine dolostones can record δ²³⁸U trends of seawater similar to that of limestones. Modeling of uranium isotope cycling in the latest Permian and earliest Triassic oceans suggests two distinct stages of expanded marine anoxia separated by a brief interval (∼100 kyr) of reoxygenation across the PTB. The first anoxic episode lasted for ∼ 60 kyr while anoxic seafloor area expanded to cover >18% of the entire seafloor, coeval with the main EPME horizon, agreeing with marine anoxia as a proximate kill mechanism for the EPME. The second anoxic event was less intense compared to the first anoxic pulse but sustained for a longer duration. A global modeling of coupled C, P, and U cycles show that two pulses of volcanic carbon injection that drives global warming and increased phosphorus weathering rate can reasonably reproduce our data to match two phases of anoxia. The model also demonstrates that the loss of terrestrial vegetation in the EPME is crucial to generating an intervening interval of oxygenated ocean. Our new study adds to a growing body of evidence that the global marine redox conditions underwent rapid oscillations during the EPME event and continued afterward, which may have played a central role in delaying the marine ecosystem recovery in the Early Triassic.
Article
A finer record of biodiversity We have pressing, human-generated reasons to explore the influence of environmental change on biodiversity. Looking into the past can not only inform our understanding of this relationship but also help us to understand current change. Paleontological records depend on fossil availability and predictive modeling, however, and thus tend to give us a picture with large temporal jumps, millions of years wide. Such a scale makes it difficult to truly understand the action of environmental forces on ecological processes. Enabled by a supercomputer, Fan et al. used machine learning to analyze a large marine Paleozoic dataset, creating a record with time intervals of only ∼26,000 years (see the Perspective by Wagner). This fine-scale resolution revealed new events and important details of previously described patterns. Science , this issue p. 272 ; see also p. 249
Article
The Smithian-Spathian boundary (SSB) transition was recently identified as a major biocrisis on the road to marine ecosystem recovery following the end-Permian mass extinction. Marine anoxia is hypothesized to have played an important role in the SSB biocrisis. However, an understanding of the relationship of this biocrisis to contemporaneous marine redox conditions has been hampered by limited knowledge of the timing, duration, and extent of anoxia during the Smithian-Spathian (S-S) transition. Here, we present a high-resolution carbonate U-isotope record from the Jiarong section of South China that spans the mid-Smithian to mid-Spathian interval. This record shows persistent negativeδ²³⁸U values (averaging −0.56‰) in the late Smithian, followed by a rapid positive shift (from −0.78‰ to −0.10‰) across the SSB, and then a more gradual shift back to lower δ²³⁸U values in the early to mid-Spathian. U isotope mass balance modeling suggests that the global area of anoxic seafloor expanded strongly during the late Smithian and the early to mid-Spathian but contracted sharply during the S-S transition. This redox pattern shows an excellent correspondence to previously published tropical sea-surface temperature (SST) records, with peak oceanic anoxia coinciding with the Smithian Thermal Maximum (STM) and diminished anoxia during a pronounced global cooling event at the SSB. Although paleontological records commonly do not distinguish between terminations during the late Smithian and SSB, we hypothesize that the SSB biocrisis, which was marked by sharp diversity losses among conodonts, ammonoids, and other marine invertebrates, was primarily associated with the STM, in which case oceanic anoxia is likely to have been a major stressor of mid-Olenekian marine biotas.
Article
Permian-Triassic boundary sections from Armenia were studied for carbon isotopes of carbonates as well as oxygen isotopes of conodont apatite in order to constrain the global significance of earlier reported variations in the isotope proxies and elaborate the temporal relationship between carbon cycle changes, global warming and Siberian Trap volcanism. Carbon isotope records of the Chanakhchi and Vedi II sections show a 3–5‰ negative excursion that start in the Clarkina nodosa (C. yini) conodont Zone (latest Permian) with minimum values recorded in Hindeodus parvus to Isarcicella isarcica conodont zones (earliest Triassic). Sea surface temperatures (SST) reconstructed from oxygen isotopes of conodont apatite increase by 8–10 °C over an extrapolated time interval of ∼39 ka with the onset of global warming occurring in the C. iranica (C. meishanensis) Zone of the latest Permian. Climate warming documented in the Armenian sections is comparable to published time-equivalent shifts in SST in Iran and South China suggesting that this temperature change represents a true global signature. By correlating the Armenian and Iranian section with the radiometrically well-dated Meishan GSSP (Global Stratotype Section and Point) section (South China), the negative shift in δ13C is estimated to have occurred 12–128 ka prior to the onset of global warming. This temporal offset is unexpected given the synchrony in changes in atmospheric CO2 and global temperature as seen in Pleistocene ice core records. The negative δ13C excursion is explained by the addition of emission of isotopically light CO2 and CH4 from thermogenic heating of organic carbon-rich sediments by Siberian Trap sill intrusions. However, the observed time lag in the δ13C and δ18O shifts questions the generally assumed cause-effect relationship between emission of thermogenically produced greenhouse gases and global warming. The onset of temperature rise coincides with a significant enrichment in Hg/TOC (total organic carbon) ratios arguing for a major volcanic event at the base of the extinction interval. Whether global warming was a major factor for the Late Permian mass extinction depends on the duration of the extinction interval. Warming only starts at the base of the extinction interval, but with the extinction encompassing a time interval of 60 ± 48 ka, global climate warming in conjunction with temperature-related stressors as hypoxia and reduced nutrient availability may have been one of the major triggers of the most devastating biotic crisis in Earth history.