Capitanian Mass Extinction Research Articles

Coupled volcanic activity and marine anoxia in the Upper Yangtze region prior to the Capitanian mass extinction

The Capitanian mass extinction was a severe biotic crisis in geological history. To present more evidence for this event, this study acquired geochemical data from shelf-margin facies deposits in the Upper Yangtze region, China (i.e., the Shangsi section; the third member of the Maokou Formation [Mao III Member] prior to the Capitanian mass extinction). A significant Hg anomaly is associated with the negative δ13Ccarb excursion in the Mao III Member, suggesting a link to the volcanic activity of the Emeishan large igneous province (ELIP). With increasing water depth, enhanced marine anoxia and stronger water column stratification existed, as evidenced by both organic and inorganic geochemical proxy data. This suggests a possible oceanographic change in response to ELIP volcanism. We propose a three-stage model for the coupled volcanic–climatic–oceanic variations in the Upper Yangtze region during the early Capitanian and the volcanism associated with the ELIP was a potential driving mechanism of the environmental changes and biotic crisis. The ELIP volcanism could have caused the widespread marine anoxia along the continental margin, due to climate warming and the release of nutrient elements. The significant water column stratification and basin restriction were enhanced by climate warming, which would have resulted in expansion of oxygen minimum zones into shelf habitats. This coincided with a decrease in the fusulinacean foraminiferal assemblages and calcareous algae in the Shangsi section. The enhanced marine anoxia and intensified water column stratification may have had a direct role in the death of these organisms. Therefore, widespread marine anoxia/euxinia driven by volcanic activity and climate warming resulted from the ELIP eruption could finally led to the Capitanian biotic crisis.

Widespread marine euxinia along the western Yangtze Platform caused by oxygen minimum zone expansion during the Capitanian mass extinction

The development of widespread marine anoxic and/or euxinic conditions has been proposed as a likely driver of the mid-Capitanian mass extinction. However, the driving mechanisms and spatiotemporal evolution of anoxia/euxinia remain poorly constrained. In order to decipher changes in marine redox conditions and their possible influence on the mid-Capitanian biotic crisis, we applied multiple geochemical indicators to three sections across a shelf-to-basin transect in the Middle Permian Kuhfeng and Lower Yinping formations of the Lower Yangtze Basin, South China. Our integrated Fe speciation and redox-sensitive trace element data suggest that euxinic waters dynamically coexisted at intermediate depths on the western margin of the Yangtze Platform, with oxygenated surface waters and ferruginous deeper waters providing compelling evidence for a redox structure similar to an oxygen minimum zone (OMZ). The synthesis of a five-stage spatiotemporal evolution of redox conditions, coupled with changes in upwelling and hydrographic restriction, indicates particularly intensified euxinia and an expanded OMZ across the shelf-basin transect during the middle Capitanian. Long-lasting anoxia-euxinia was likely maintained by enhanced phosphorus cycling, with sluggish ocean circulation due to collapsed upwelling and enhanced restriction under climate warming intensifying the euxinic conditions. Through a comparison of available global data, we infer that widespread anoxia-euxinia was prevalent in the middle Capitanian due to expanded OMZ conditions. Expanded anoxia and euxinia in shelf and slope environments occurred concurrently with an ongoing biotic crisis suggesting that these redox changes were a contributory factor.

The Emeishan large igneous province eruption triggered coastal perturbations and the Capitanian mass extinction: Insights from mercury in Permian bauxite beds

The Capitanian mass extinction occurring at the mid-Capitanian to the Guadalupian–Lopingian boundary (GLB; ca. 262–257 Ma) was temporally coincident with the eruption of the Emeishan large igneous province (LIP). Recent observation of Hg anomalies at the GLB at shelf and slope/basinal settings demonstrated a possible causal link between the Capitanian extinction and the Emeishan LIP eruption. However, Hg records of the GLB at coastal settings remain uninvestigated, limiting our knowledge of global impact of the Emeishan LIP and its role in the Capitanian mass extinction. Here we report new datasets of Hg concentrations, Hg isotopes and organic carbon isotopes in two coastal shallow-water sections in the Guangxi region, SW China. Elevated Hg/TOC ratios (up to 3330 and 221 ppb/wt%, respectively) and near-zero to positive Δ199Hg values (−0.04‰ to +0.26‰) were observed across the GLB in the two sections, indicative of extensive volcanic Hg input to the ocean via wet Hg(II) deposition. A negative δ13Corg excursion (2.5‰) coincides with widespread marine anoxia, peak Emeishan LIP magmatism, Hg/TOC anomalies, sea-level rise, and the Capitanian mass extinction. The temporal link between these phenomena suggests that the Emeishan LIP was a key driver of the climate/ocean dynamics, global ecosystems, and the formation of bauxite beds during the GLB.

Vertebrate tracks from the Permian of Gonfaron (Provence, Southern France) and their implications for the late Capitanian terrestrial extinction event

The Guadalupian was a key epoch for the evolution of tetrapod faunas. It includes the earliest unambiguous occurrences of therapsids and stereospondyls (groups that later became dominant in terrestrial and freshwater environments, respectively) and the late Capitanian mass extinction event. The low-latitude faunas from this time interval, where sufficiently dated, comprise rare tetrapod body fossils whereas the most complete records are provided by ichnoassociations, especially coming from the Provence basins of France. In this paper, we revise the tetrapod ichnoassociation from the Pélitique Formation of the Le Luc Basin of Provence, identifying the following tetrapod ichnotaxa: Batrachichnus salamandroides (temnospondyls/lepospondyls), Capitosauroides talus comb. nov. (therocephalian therapsids), Dicynodontipus isp. (cynodont therapsids), Varanopus isp. (bolosaurian parareptiles), Hyloidichnus bifurcatus (captorhinomorph eureptiles) and Rhynchosauroides isp. (neodiapsid eureptiles). According to our revised ichnotaxonomy and stratigraphic correlations, we date the Pélitique Formation as late Capitanian and assign its tetrapod ichnoassociation to the newly defined Association V (Dicynodontipus sub-biochron of the Erpetopus biochron). The Pélitique Formation ichnoassociation shows a typical composition for a post-dinocephalian extinction ichnofauna, as shown by preliminary multivariate statistics on Guadalupian–Lopingian tetrapod ichnoassociations. It is similar to the contemporaneous skeletal faunas described from the mid- to high-latitude sites of Russia and South Africa and is arguably the earliest evidence of post-dinocephalian extinction recovery at low-latitudes. Our results confirm the global and abrupt impact of the late Capitanian terrestrial mass extinction and the subsequent recovery in the low-latitude realm. This extinction was probably time-equivalent with a global benthic marine mass extinction, and both events may have been linked to climatic perturbation caused by the Emeishian volcanic activity in China, which reached its peak around 260 Ma.

Mass extinction or extirpation: Permian biotic turnovers in the northwestern margin of Pangea

Abstract The Capitanian (Middle Permian) mass extinction event, prior to and separate from the end-Permian mass extinction, has been suggested as a severe biotic crisis comparable to the big five mass extinctions of the Phanerozoic. However, there is still controversy about its global significance. In particular, this purportedly disastrous event in the Capitanian was mostly documented in the eastern Tethys, especially South China and Japan, whereas its extent in higher latitudinal regions remains unclear. A few recent studies have reported biostratigraphic and chemostratigraphic evidence for the Capitanian extinction at the northwestern marginal shelf of Pangea, including in the Kapp Starostin Formation in Spitsbergen. However, we here report a different result from these previous studies based on a study of abundant brachiopod fossils collected from eight geological sections that represent the same formation in western and central Spitsbergen, Arctic Norway. Our biostratigraphic investigation recognizes a total of five brachiopod assemblages from the type section of the Kapp Starostin Formation at Festningen in Spitsbergen. The most striking biotic change in species composition is observed at the interval between the lowermost Vøringen Member (late Artinskian) and its overlying member (Kungurian) of the Kapp Starostin Formation in Spitsbergen, which makes it much earlier than the Capitanian. A similar faunal shift at the same stratigraphic interval is also observed from bryozoan-based biostratigraphic data. This faunal turnover could be linked to a significant climatic shift (cooling) along the northwestern margin of Pangea during the Artinskian−Kungurian. Specifically, it is inferred that a climatic perturbation (cooling) likely drove the extirpation (emigration) of marine faunas out of Spitsbergen and dispersal eastward into some lower latitudinal and climatically more habitable areas. Our result indicates that the Capitanian interval in Spitsbergen does not record a catastrophic event that corresponds to the Capitanian mass extinction in Tethyan regions but rather marks gradual faunal transitions throughout the Middle to Late Permian. This faunal transition, driven by continuous cooling, was accompanied by major changes in regional lithology, which suggest a degree of local environmental control, especially in the changes of substrate and water depth, on the composition of the benthic faunas. The Wegener Halvø and Schuchert Dal Formations (Lopingian) in central East Greenland contain a diverse brachiopod fauna that is comparable to that of the post-Vøringen Member in Spitsbergen. This implies that the brachiopods in the northwestern marginal shelf of Pangea did not suffer a severe mass extinction in the Capitanian; instead, many of them migrated southward with the development of the Zechstein seaway.

Taxonomy, phylogeny and stratigraphical ranges of middle Permian pareiasaurs from the Karoo Basin of South Africa

Pareiasaurs were relatively abundant, globally-distributed, herbivorous parareptiles of the mid to late Permian. The basal-most forms, all members of the Bradysauria, are restricted to the Guadalupian (mid-Permian) of South Africa and went extinct in the late Capitanian near the top of the Tapinocephalus Assemblage Zone. Currently four species are recognized in this group: Bradysaurus seeleyi, B. baini, Embrithosaurus schwarzi and Nochelesaurus alexanderi. These taxa have been poorly defined historically and based on a limited number of specimens, leaving the taxonomic diversity of the group open to doubt and limiting their utility in biostratigraphy. Here, we present our fourth and final contribution to improve the understanding of this group by providing a taxonomical and phylogenetic review, updated stratigraphical ranges, and updated diagnoses for each taxon within Bradysauria. Bradysaurus seeleyi is synonymized with Bradysaurus baini, resulting in three valid mid-Permian pareiasaur taxa: Bradysaurus baini, Embrithosaurus schwarzi and Nochelesaurus alexanderi. Our cladistic analysis of cranial and postcranial characters supports the monophyly of Bradysauria with five synapomorphies. Embrithosaurus schwarzi is recovered as the sister taxon to a clade containing Bradysaurus baini and Nochelesaurus alexanderi. By identifying 157 pareiasaur specimens in fossil collections we show that the Bradysauria are stratigraphically restricted to the Abrahamskraal Formation of the Beaufort Group and suggest a staggered appearance. Bradysaurus baini is first to appear, followed by Nochelesaurus alexanderi, and lastly by Embrithosaurus schwarzi. All three taxa perished during the Capitanian mass extinction, and have their highest occurrences near the top of the Abrahamskraal Formation.

Surface-wave tomography of the Emeishan large igneous province (China): Magma storage system, hidden hotspot track, and its impact on the Capitanian mass extinction

AbstractLarge igneous provinces (LIPs) are commonly associated with mass extinctions. However, the precise relations between LIPs and their impacts on biodiversity is enigmatic, given that they can be asynchronous. It has been proposed that the environmental impacts are primarily related to sill emplacement. Therefore, the structure of LIPs' magma storage system is critical because it dictates the occurrence and timing of mass extinction. We use surface-wave tomography to image the lithosphere under the Permian Emeishan large igneous province (ELIP) in southwestern China. We find a northeast-trending zone of high shear-wave velocity (Vs) and negative radial anisotropy (Vsv > Vsh; v and h are vertically and horizontally polarized S waves, respectively) in the crust and lithosphere. We rule out the possibilities of rifting or orogenesis to explain these seismic characteristics and interpret the seismic anomaly as a mafic-ultramafic, dike-dominated magma storage system of the ELIP. We further propose that the anomaly represents a hidden hotspot track that was emplaced before the ELIP eruption. A zone of higher velocity but less-negative radial anisotropy, on the hotspot track but to the northeast of the eruption center in the Panxi region, reflects an elevated proportion of sills emplaced at the incipient stage of the ELIP. Liberation of poisonous gases by the early sill intrusions explains why the mid-Capitanian global biota crisis preceded the peak ELIP eruption by 2–3 m.y.

The Late Capitanian Mass Extinction of Terrestrial Vertebrates in the Karoo Basin of South Africa

The Beaufort Group of the main Karoo Basin of South Africa records two major extinction events of terrestrial vertebrates in the late Palaeozoic. The oldest of these has been dated to the late Capitanian and is characterized by the extinction of dinocephalian therapsids and bradysaurian pareiasaurs near the top of Tapinocephalus Assemblage Zone. Faunal turnover associated with the extinction of dinocephalians is evident in vertebrate faunas from elsewhere in Pangaea but it can be best studied in the Karoo Basin, where exposures of the upper Abrahamskraal and lower Teekloof formations allow continuous sampling across the whole extinction interval. Here we present field data for several sections spanning the Capitanian extinction interval in the southwestern Karoo and discuss recent work to establish its timing, severity, and causes. A large collections database informed by fieldwork demonstrates an increase in extinction rates associated with ecological instability that approach that of the end-Permian mass extinction, and shows significant turnover followed by a period of low diversity. Extinctions and recovery appear phased and show similarities to diversity patterns reported for the end-Permian mass extinction higher in the Beaufort sequence. In the Karoo, the late Capitanian mass extinction coincides with volcanism in the Emeishan Large Igneous Province and may have been partly driven by short-term aridification, but clear causal mechanisms and robust links to global environmental phenomena remain elusive.

Biostratigraphy of the Tapinocephalus Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

Abstract The Tapinocephalus Assemblage Zone is the second oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup), biostratigraphically positioned between the underlying Eodicynodon and overlying Endothiodon assemblage zones. It is characterised by a rich fossil tetrapod assemblage comprising basal members of most therapsid clades, but particularly dinocephalians such as Moschops capensis and basal pareiasaurs such as Bradysaurus in co-occurrence with the pylaecephalid dicynodonts Robertia and Eosimops. It corresponds to the upper two thirds of the Abrahamskraal Formation, is Capitanian (Guadalupian) in age, and reaches a maximum thickness of around 1500 m. The biozone is here separated into two subzones: a lower Eosimops – Glanosuchus Subzone and an upper Diictodon – Styracocephalus Subzone. The contact between the two subzones is defined by the first appearance of Diictodon feliceps, which closely corresponds to the base of the Moordenaars Member. The uppermost part of the biozone contains the Capitanian mass extinction and the low diversity fauna in its immediate aftermath. The zone is terminated by the first appearance of Endothiodon bathystoma.

Biostratigraphy of the Endothiodon Assemblage Zone (Beaufort Group, Karoo Supergroup), South Africa

Abstract The Endothiodon Assemblage Zone is the third oldest tetrapod biozone of the Beaufort Group (Adelaide Subgroup, Karoo Supergroup). It is situated between the underlying Tapinocephalus and overlying Cistecephalus assemblage zones and in the southwestern part of the basin corresponds to the majority of the Poortjie and Hoedemaker members of the Teekloof Formation. It is characterised by the dicynodont genus Endothiodon, especially in the lower part of assemblage zone, and records early ecosystem recovery from the Capitanian mass extinction. It also contains the lowest occurrence in the Karoo Basin of cynodont therapsids, eutherocephalians, bidentalian dicynodonts, and diapsids. The biozone reaches a maximum thickness of around 250 m in the southwestern part of the basin. We propose a two-fold subdivision into a lower Lycosuchus - Eunotosaurus Subzone (equivalent to the upper two-thirds of the former Pristerognathus Assemblage Zone) and an upper Tropidostoma - Gorgonops Subzone (equivalent to the former Tropidostoma Assemblage Zone), with the contact defined by the first appearance of Tropidostoma dubium. The Endothiodon Assemblage Zone is terminated by the first appearance of Aulacephalodon bainii.

Magmatic duration of the Emeishan large igneous province: Insight from northern Vietnam

AbstractThe eruption of Emeishan lava in southwestern China and northern Vietnam is considered to be a contributing factor to the Capitanian mass extinction and subsequent global cooling event, but the duration of volcanism is uncertain. The difficulty in assessing the termination age is, in part, due to the lack of high-precision age data for late-stage volcanic rocks. The Tu Le rhyolite of northern Vietnam is the most voluminous silicic unit of the Emeishan large igneous province (ELIP) and is spatially associated with the Muong Hum and Phan Si Pan hypabyssal plutons. Chemical abrasion–isotope dilution–thermal ionization mass spectrometry U-Pb dating of zircons from the Tu Le rhyolite (257.1 ± 0.6 Ma to 257.9 ± 0.3 Ma) and Muong Hum (257.3 ± 0.2 Ma) and Phan Si Pan (256.3 ± 0.4 Ma) plutons yielded the youngest high-precision ages of the ELIP yet determined. The results demonstrate that Emeishan lavas erupted over a period of ∼6 m.y,. with plutonism ending shortly thereafter. Thus, it is possible that Emeishan volcanism contributed to global cooling into the middle Wuchiapingian. It appears that these rocks represent a distinct period of ELIP magmatism, as they are young and were emplaced oblique to the main north-south–trending Panxi rift.

Middle Permian organic carbon isotope stratigraphy and the origin of the Kamura Event

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.

Impacts of basin restriction on geochemistry and extinction patterns: A case from the Guadalupian Delaware Basin, USA

Geochemical data from carbonates often constrain the nature of environmental change during biotic turnover events. Many ancient carbonates, however, formed in geographically-isolated basins subject to local environmental factors, resulting in varying extinction rates between open ocean and restricted settings. It follows that high-resolution data from restricted basins may help unravel poorly-understood biotic crises such as the Mid-Capitanian extinction, which had especially high extinction rates in restricted settings.This study examines factors controlling salinity, stratification, and oxygenation in the Capitanian (Middle Permian) Delaware Basin, USA. Elemental and carbon isotope measurements from time-equivalent strata reveal differences between shallow- and deep-water masses, pointing to local controls such as stratification and de-oxygenated bottom water. Basinal dolomites and evaporites mark periods of elevated salinity tied to sea-level lowstands, which correspond with turnovers in fusulinid and brachiopod communities. Faunal turnover in the Delaware Basin demonstrates a fundamental attribute of restricted basins: water chemistry is often tightly coupled to physical process such as sea level change. We suggest that the relationships among sea level fluctuations, chemical changes, and biotic turnover may explain why the Capitanian mass extinction was more severe in isolated basins than the open ocean.

Mercury evidence from the Sino-Korean block for Emeishan volcanism during the Capitanian mass extinction

AbstractA prominent large negative δ13Corg excursion and a coeval notable spike in mercury (Hg)/total organic carbon ratio are observed in the middle–upper Permian Gohan Formation in central Korea, located in the eastern Sino-Korean block (SKB), which may represent the Capitanian mass extinction event. The SKB was separated from the South China block by the eastern Palaeo-Tethys Ocean. This finding from the SKB supports the widespread Hg loading to the environment emitted from the Emeishan volcanic eruptions in SW China. This study demonstrates that the Hg cycle was globally perturbed in association with global carbon cycle perturbation that occurred during the Capitanian Extinction.

Paleomagnetic Secular Variation Constraints on the Rapid Eruption of the Emeishan Continental Flood Basalts in Southwestern China and Northern Vietnam

AbstractEstimating the duration of magma eruptions using isotopic dating methods is difficult because of the intrinsic errors of the technique regarding the dated materials (such as zircon). However, the long‐term variation of the geomagnetic field recorded by lava flows can be used to estimate the net duration of an eruption sequence. The Emeishan basalts at Dongchuan, with a thickness of 630 m, yielded a reliable characteristic remanent magnetization of normal polarity and which passed the fold test (Tauxe & Watson, 1994, https://doi.org/10.1016/0012-821X(94)90006-X). Stratigraphic and magnetostratigraphic correlations of the Emeishan basalts in the Dongchuan section with other sections indicate that the eruption of the Emeishan basalts at Dongchuan spans the entire normal polarity zone in the early stage of the Emeishan large igneous province. A flow‐by‐flow analysis of geomagnetic directions of the Emeishan basalts at Dongchuan indicates that four directional groups and fifteen individual lava directions were recorded, with a net duration (excluding quiescent intervals) of no more than 3100 years. The averaged site directions from the Emeishan basalts with normal polarity conforming to a geocentric axial dipole direction indicate that this interval is longer than 104–105 years. In addition, a magnetostratigraphic study indicates that the normal polarity interval recorded by the Emeishan basalts was shorter than 2–20 × 104 years. Thus, the total duration of the normal polarity stage of the Emeishan large igneous province was roughly 105 years. There is a possible relationship between the rapid eruption and the Late Capitanian mass extinction (259.8 ± 0.4 Ma, Henderson et al., 2012).

Stable isotope record implicates aridification without warming during the late Capitanian mass extinction

The late Capitanian mass extinction (~260millionyears ago) represents one of the greatest biotic perturbations of the Phanerozoic and was the earliest mass extinction to affect terrestrial tetrapods and ecosystems. In the past, this extinction has been largely associated with taxonomic loss and ecological restructuring in marine environments but more recently it has also been recognised in terrestrial ecosystems. Though various environmental mechanisms have been proposed for the former, little evidence has yet been presented for the cause of terrestrial extinctions. We determined the stable oxygen and carbon isotope compositions of dentine apatite from twenty-eight specimens of the dicynodont therapsid Diictodon feliceps, to investigate the potential role of climate in driving terrestrial tetrapod extinctions. Studied specimens were recovered from a 270m stratigraphic interval constraining the peak in tetrapod extinction rates in the uppermost Abrahamskraal Formation in the well-sampled main Karoo Basin of South Africa. Our results demonstrate a positive excursion of δ13C values coinciding with the extinction peak that is followed by a return to pre-extinction δ13C values, suggesting a local increase in aridity at the time of the extinction. For the same time interval, the δ18O values did not demonstrate statistically significant changes, suggesting constant temperature in the South African paleoenvironment. This unusual increase in aridity but not in temperature has been interpreted as the possible result of orogenesis in the Cape Fold Mountain source along the southern margin of Gondwana.

Contrasting geochemical signatures on land from the Middle and Late Permian extinction events

AbstractThe end of the Palaeozoic is marked by two mass‐extinction events during the Middle Permian (Capitanian) and the Late Permian (Changhsingian). Given similarities between the two events in geochemical signatures, such as large magnitude negative δ13C anomalies, sedimentological signatures such as claystone breccias, and the approximate contemporaneous emplacement of large igneous provinces, many authors have sought a common causal mechanism. Here, a new high‐resolution continental record of the Capitanian event from Portal Mountain, Antarctica, is compared with previously published Changhsingian records of geochemical signatures of weathering intensity and palaeoclimatic change. Geochemical means of discriminating sedimentary provenance (Ti/Al, U/Th and La/Ce ratios) all indicate a common provenance for the Portal Mountain sediments and associated palaeosols, so changes spanning the Capitanian extinction represent changes in weathering intensity rather than sediment source. Proxies for weathering intensity chemical index of alteration, ∆W and rare earth element accumulation all decline across the Capitanian extinction event at Portal Mountain, which is in contrast to the increased weathering recorded globally at the Late Permian extinction. Furthermore, palaeoclimatic proxies are consistent with unchanging or cooler climatic conditions throughout the Capitanian event, which contrasts with Changhsingian records that all indicate a significant syn‐extinction and post‐extinction series of greenhouse warming events. Although both the Capitanian and Changhsingian event records indicate significant redox shifts, palaeosol geochemistry of the Changhsingian event indicates more reducing conditions, whereas the new Capitanian record of reduced trace metal abundances (Cr, Cu, Ni and Ce) indicates more oxidizing conditions. Taken together, the differences in weathering intensity, redox and the lack of evidence for significant climatic change in the new record suggest that the Capitanian mass extinction was not triggered by dyke injection of coal‐beds, as in the Changhsingian extinction, and may instead have been triggered directly by the Emeishan large igneous province or by the interaction of Emeishan basalts with platform carbonates.

A high-latitude Gondwanan lagerstätte: The Permian permineralised peat biota of the Prince Charles Mountains, Antarctica

The Toploje Member chert is a Roadian to Wordian autochthonous–parautochthonous silicified peat preserved within the Lambert Graben, East Antarctica. It preserves a remarkable sample of terrestrial life from high-latitude central Gondwana prior to the Capitanian mass extinction event from both mega- and microfossil evidence that includes cryptic components rarely seen in other fossil assemblages. The peat layer is dominated by glossopterid and cordaitalean gymnosperms and contains moderately common herbaceous lycophytes, together with a broad array of dispersed organs of ferns and other gymnosperms. Rare arthropod–plant and fungal–plant interactions are preserved in detail, together with a plethora of fungal morphotypes, Peronosporomycetes, arthropod remains and a diverse coprolite assemblage. Comparisons to other Palaeozoic ecosystems show that the macroflora is of low diversity. The fungal and invertebrate–plant associations demonstrate that a multitude of ecological interactions were well developed by the Middle Permian in high-latitude forest mires that contributed to the dominant coal deposits of the Southern Hemisphere. Quantitative analysis of the constituents of the silicified peat and of macerals within adjacent coal seams reveals that whilst silicified peats provide an unparalleled sample of the organisms forming Permian coals, they do not necessarily reflect the volumetric proportions of constituents within the derived coal. The Toploje Member chert Lagerstätte provides a snapshot of a rapidly entombed mire climax ecosystem in the closing stages of the Palaeozoic, but prior to the onset of the protracted crisis that engulfed and overthrew these ecosystems at the close of the Permian.

The mid-Capitanian (Middle Permian) mass extinction and carbon isotope record of South China

Conodont, C isotope and fossil and facies data are presented for the Capitanian (Middle Permian) mass extinction record seen in platform carbonates (Maokou and Wuchiaping formations) of South China, where limestones interdigitate with the volcanic succession of the Emeishan large igneous province. The Maokou Formation provides an extinction record marked by the loss of keriothecal-walled fusulinaceans and a turnover in calcareous algae. In sections within the Emeishan province this crisis occurs at the base of the oldest record of volcanism from the Jinogondolella altudaensis conodont zone (of mid-Capitanian age). Around the periphery of the Emeishan province this extinction level lies within the upper part of the Maokou Formation at a level where platform carbonate deposition was frequently interrupted by thick volcanic ash depositional events. The assemblages of the uppermost Maokou Formation are characterised by typical “Late Permian” taxa although these levels still lie within the Middle Permian (Guadalupian Series). “Disaster” taxa, such as Earlandia and Diplosphaerina are locally prolifically abundant in the aftermath of the mass extinction. The crisis is particularly noteworthy amongst photosynthetic taxa such as calcareous algae and fusulinaceans that probably harboured photosymbionts. Therefore, a kill mechanism involving cooling from explosive volcanism and potentially acid rain from sulphate aerosols appears appropriate. A composite δ 13C carb curve, calibrated against a high-resolution conodont biostratigraphy reveals a major intra-Capitanian negative excursion (of > 5‰) superimposed on typically heavy (4–5‰) Middle Permian values. This curve can also be recognised in Panthalassan seamount carbonates of Japan although this requires reassignment of apparently Upper Permian limestones to the Middle Permian. In both China and Japan the Capitanian mass extinction occurs during the early stage of this major, intra-Capitanian negative excursion. Assuming typical platform carbonate accumulation rates, the records of the Maokou Formation suggest δ 13C carb values fell at ∼ 0.01‰/kyr suggesting a catastrophic origin (such as gas hydrate destabilisation) is unlikely, although a volcanic source is possible.