Latest Permian Mass Extinction Research Articles

A Smithian (Early Triassic) ichnoassemblage from Lichuan, Hubei Province, South China: Implications for biotic recovery after the latest Permian mass extinction

A late Smithian ichnoassemblage is reported from the Lower Triassic succession from the Lichuan section, western Hubei Province, South China. This ichnoassemblage comprises 13 ichnogenera, which include simple, horizontal traces (Cochlichnus, Cosmorhaphe, Didymaulichnus, Gordia, Circulichnis, and Planolites), vertical traces (Arenicolites, Laevicyclus), oblique- or horizontal branching traces (Palaeophycus), slightly complex burrow networks (Thalassinoides, and Treptichnus), and grazing traces (Cosmorhaphe and Gyrochorte). These traces are also categorized into fodinichnia, domichnia, pascichnia, and repichnia ethologic types, suggesting a fairly high degree of behavioral complexity. Of these, the fodinichnia traces are most abundant. The ichnoassemblage horizons usually have rather high ichnofabric indices (ii), reaching ii 4–5. Bedding plane coverage is up to 70–90%, resulting in high bedding plane bioturbation index as well (BPBI 4–5). The Lichuan ichnoassemblage traces have mean and maximum diameters of 4.8mm and 9mm, respectively (n=342). The traces penetrate to a depth of up to 30mm into the sediment, with an average depth of penetration of 15mm, indicating third to fourth tiering levels (3–4). Overall, the Lichuan ichnofauna shows an abrupt increase in ichnodiversity, burrow width, behavioral complexity, and ecologic tiering level, which are indicative of recovery stages of 2–3 in the late Smithian. When compared to five coeval ichnoassemblages from other sections in South China (Yashan, Susong, Daxiakou, Gaimao, and Tianshengqiao) and coeval ichnoassemblages from elsewhere (northern Italy, Western Australia, western US), the Lichuan trace-fossil assemblage reaches similar level of diversity during this time interval. Paleoenvironmental analysis indicates that the late Smithian recovery pulse is typically confined to the offshore transition setting, whereas more distal zones record much lower levels of recovery. Therefore, time and environmental conditions were the two crucial factors controlling the rate and degree of recovery of trace-making organisms in the aftermath of the latest Permian mass extinction.

Oceanic environmental changes on a shallow carbonate platform (Yangou, Jiangxi Province, South China) during the Permian-Triassic transition: Evidence from rare earth elements in conodont bioapatite

Paleoceanic environmental stresses (e.g., expanded anoxia, elevated siliciclastic fluxes) are thought to have been important factors in the latest Permian mass extinction (LPME). Here, we investigate changes in redox conditions and siliciclastic fluxes during the Permian-Triassic transition in South China through in-situ analysis of the rare earth element (REE) composition of albid crowns of single conodont elements measured using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). For comparison, we also analyzed REEs in the sediment matrix enclosing the conodonts (i.e., whole-rock samples). The study locale (Yangou) was located on a shallow carbonate platform on the eastern margin of the Yangtze Platform to minimize the influence of detrital siliciclastics and, thus, enhance the chances of recovering a hydrogenous (seawater-sourced) REE signal.The analyzed conodonts exhibit REE patterns consistent with mixed hydrogenous (seawater) and lithogenous (siliciclastic) sources, with specimens from below the LPME horizon showing dominantly hydrogenous influences (Y/Ho >50) and those from above the LPME horizon showing dominantly lithogenous influences (Y/Ho <50). Locally elevated Ce/Ce* ratios and U concentrations in pre-LPME conodonts suggest an episodic shoaling of the oceanic chemocline, causing incursions of suboxic to anoxic seawaters onto the shallow Yangou carbonate platform. Chemical index of alteration (CIA) values increase sharply at the LPME, suggesting increased rates of continental erosion and a relative increase in chemical over physical weathering, possibly as a consequence of globally elevated temperatures. The present case study confirms that conodonts from relatively clean, low-clay (Al <0.5%) carbonate facies can potentially preserve original seawater REE signatures.

Controls on regional marine redox evolution during Permian-Triassic transition in South China

Although oceanic anoxia is regarded as a leading cause of the Permian-Triassic boundary (PTB) mass extinction, its timing, extent, and underlying causes remain unclear. Here, we conducted a high-resolution Fe-S-C-Mo geochemical study of the entire Changhsingian and lowermost Induan succession in a carbonate-ramp setting at Ganxi, western Hubei Province, South China. Six stratigraphic units representing discrete redox intervals were identified based on integrated Fe-S-C-Mo data. Units I–III are of latest Wuchiapingian to early Changhsingian age, with Units I and III characterized by euxinia and Unit II by uncertain redox conditions. Unit IV, of mid-Changhsingian age, records a gradual transition from euxinic to ferruginous conditions. Units V and VI, spanning the latest Permian mass extinction (LPME) to earliest Triassic interval, were deposited under dominantly ferruginous conditions punctuated by both euxinic and oxic episodes. Redox variations at Ganxi were controlled by contemporaneous oceanographic changes in the upper oceanic thermocline region: (i) euxinia in Units I and III may record elevated marine productivity (as suggested by mean organic carbon accumulation rates, or OCAR, of 6.5 and 5.1mg/cm2/kyr, respectively) that was possibly related to upwelling; (ii) the euxinic-to-ferruginous transition from Unit IV to Units V–VI can be attributed to a combination of reduced sulfate availability and rising terrigenous iron inputs (mean Fe of 1.7% and 3.9%, respectively, for Units V–IV and VI compared to 1.0% for Units I–III); and (iii) transient intervals of euxinia in Units V and VI were facilitated by enhanced sulfate fluxes related to episodic volcanism during this interval. An integration of the redox data from Ganxi with previously published data from the Shangsi and Xiakou sections suggests that enhanced weathering fluxes were most likely the key factor controlling the marine redox transition from euxinic to ferruginous conditions during the latest Permian across the South China region.

Global-ocean redox variation during the middle-late Permian through Early Triassic based on uranium isotope and Th/U trends of marine carbonates

Abstract Uranium isotopes (238U/235U) in carbonates, a proxy for global-ocean redox conditions owing to their redox sensitivity and long residence time in seawater, exhibit substantial variability in the Daxiakou section of south China from the upper-middle Permian through the mid-lower Triassic (∼9 m.y.). Middle and late Permian ocean redox conditions were similar to that of the modern ocean and were characterized by improving oxygenation in the ∼2 m.y. prior to the latest Permian mass extinction (LPME), countering earlier interpretations of sustained or gradually expanding anoxia during this interval. The LPME coincided with an abrupt negative shift of &amp;gt;0.5‰ in δ238U that signifies a rapid expansion of oceanic anoxia. Intensely anoxic conditions persisted for at least ∼700 k.y. (Griesbachian), lessening somewhat during the Dienerian. Th/U concentration ratios vary inversely with δ238U during the Early Triassic, with higher ratios reflecting reduced U concentrations in global seawater as a consequence of large-scale removal to anoxic facies. Modeling suggests that 70%–100% of marine U was removed to anoxic sinks during the Early Triassic, resulting in seawater U concentrations of &amp;lt;5% that of the modern ocean. Rapid intensification of anoxia concurrent with the LPME implies that ocean redox changes played an important role in the largest mass extinction event in Earth history.

A silicified Early Triassic marine assemblage from Svalbard

Understanding how the marine biosphere recovered from the late Permian mass extinction event is a major evolutionary question. The quality of the global fossil record of this interval is, however, somewhat poor due to preservational, collection and sampling biases. Here we report a new earliest Induan (Hindeodus parvus Zone) marine assemblage from the Deltadalen Member of the Vikinghøgda Formation, central Spitsbergen, which fills a critical gap in knowledge. The fully silicified fossils comprise the oldest silicified assemblage known from the Triassic and provide critical new systematic data. For its age, the assemblage is exceptionally diverse with 14 species of bivalves and gastropods, as well as conodonts and ammonoids. Four new bivalve species (Austrotindaria antiqua, A. svalbardensis, Nucinella taylori and N. nakremi) and one new gastropod species (Glabrocingulum parvum) are described, and five families are recorded in the Induan for the first time. Some of the common and globally widespread Early Triassic taxa, such as Unionites, are also present, and their exceptional preservation reveals key morphological characters that are documented for the first time. Taxonomic and ecological revisions based on these new data suggest that shallow-infaunal deposit-feeders were a dominant component of pre-Spathian benthic communities. The gastropods and bivalves all possessed a planktotrophic larval stage, which may have been a particular advantage in the wake of the late Permian mass extinction.http://zoobank.org/urn:lsid:zoobank.org:pub:3EBCAEF3-27C2-4216-9F18-89F195FA534F

Estimates of the magnitudes of major marine mass extinctions in earth history

Procedures introduced here make it possible, first, to show that background (piecemeal) extinction is recorded throughout geologic stages and substages (not all extinction has occurred suddenly at the ends of such intervals); second, to separate out background extinction from mass extinction for a major crisis in earth history; and third, to correct for clustering of extinctions when using the rarefaction method to estimate the percentage of species lost in a mass extinction. Also presented here is a method for estimating the magnitude of the Signor-Lipps effect, which is the incorrect assignment of extinctions that occurred during a crisis to an interval preceding the crisis because of the incompleteness of the fossil record. Estimates for the magnitudes of mass extinctions presented here are in most cases lower than those previously published. They indicate that only ∼81% of marine species died out in the great terminal Permian crisis, whereas levels of 90-96% have frequently been quoted in the literature. Calculations of the latter numbers were incorrectly based on combined data for the Middle and Late Permian mass extinctions. About 90 orders and more than 220 families of marine animals survived the terminal Permian crisis, and they embodied an enormous amount of morphological, physiological, and ecological diversity. Life did not nearly disappear at the end of the Permian, as has often been claimed.

Heterogeneous volcanism across the Permian–Triassic Boundary in South China and implications for the Latest Permian Mass Extinction: New evidence from volcanic ash layers in the Lower Yangtze Region

Volcanism has been suggested to have occurred widely in South China across the Permian–Triassic boundary (PTB); this has important implications for understanding the cause of the Latest Permian Mass Extinction (LMPE). However, few volcanic deposits have been reported in the Lower Yangtze Region and the extent of volcanism is uncertain. Herein we report new discoveries of intensive volcanism in this region for the first time, as evidenced by multiple (n>20) and thick (3–5cm) claystones (volcanic ash layers, K-bentonite) found in three deep-water outcrops in Xuancheng city, southern Anhui Province. Detailed petrographic and geochemical analyses of the ash layers were conducted to understand their origin and implications for the cause of the LPME, including X-ray diffraction, scanning electronic microscopy, energy dispersive spectroscopy, and whole-rock geochemistry. The petrological and mineralogical results show that the claystones contain clastic minerals indicative of a volcanic origin, such as zircon, analcites, pentagonal dodecahedral pyrite, and micro-spherules. The whole-rock geochemical data of the claystones suggest that the source rock of the ash layers was intermediate–acidic rhyodacite. The claystones are different from previously known claystones in the Middle–Upper Yangtze regions, indicating the occurrence of chemically heterogeneous volcanism in South China at the PTB.

Marine Early Triassic Osteichthyes from Spiti, Indian Himalayas

A new, marine osteichthyan (bony fish) fauna from the Early Triassic of northern India is presented. The material was collected in situ at localities within Pin Valley (Lahaul and Spiti District, Himachal Pradesh, India) and is dated as middle-late Dienerian (one specimen possibly earliest Smithian). The new ichthyofauna includes a lower jaw of the predatory basal ray-finned fish Saurichthys, a nearly complete specimen of a parasemionotid neopterygian (cf. Watsonulus cf. eugnathoides), as well as further articulated and disarticulated remains (Actinopterygii indet., Actinistia indet.), and thus comprises the most complete Triassic fish fossils known from the Indian subcontinent. Saurichthys is known from many Triassic localities and reached a global distribution rapidly after the Late Permian mass extinction event. Parasemionotidae, a species-rich family restricted to the Early Triassic, also achieved widespread distribution during this epoch. Comparison of the Spiti material with other parasemionotid species reveals similarities with Watsonulus eugnathoides from Madagascar. However, taxonomic ambiguities within Parasemionotidae prevent a specific attribution of the Spiti specimen. The new material also includes an isolated actinistian urohyal exhibiting morphology distinct from any previously described urohyal. Marine Dienerian black shale deposited on continental shelves are common not only in the Himalayas but also in other geographic regions. Anoxic depositional settings provide ideal preservational conditions for vertebrate fossils, suggesting that additional ichthyofaunas could still be discovered in marine Dienerian strata of other localities. The study of Early Triassic fish assemblages, including the presented one, is fundamental for our understanding of the great osteichthyan diversification after the Late Permian mass extinction event.

The oldest post-Palaeozoic Crinoid and Permian-Triassic origins of the Articulata (Echinodermata).

The Crinoidea are the most primitive class of living echinoderms, and suffered a severe crisis during the Late Permian mass extinction event. All post-Palaeozoic crinoids, including living species, belong to the Articulata, and morphological and recent molecular studies demonstrate that they form a monophyletic clade. The Articulata originated from Palaeozoic cladid crinoids, but the nature and timing of their origination remains obscure. Problems with understanding the origin and early evolution of the Articulata have arisen because the Permian-Triassic crinoid fossil record is particularly poor. We report on a new genus and species from the earliest Triassic, which is the oldest known post-Palaeozoic articulate crinoid and fundamentally alters our understanding of the early evolution of the Articulata. Prior to this study, the most primitive post-Palaeozoic articulate was thought to be Holocrinus of the order Isocrinida. Unexpectedly, the new taxon belongs to the order Encrinida, which reveals a previously hidden diversity of crinoids in the earliest Triassic. Its discovery implies either a dramatic radiation of crinoids in the immediate post-extinction aftermath, when environmental conditions were at their most severe, or a pre-extinction origin of the crown group articulates and survival of multiple lineages.

Episodic euxinia in the Changhsingian (late Permian) of South China: Evidence from framboidal pyrite and geochemical data

A multiproxy study of a new Upper Permian–Lower Triassic section (Xiaojiaba) in Sichuan Province, China, documents large changes in marine productivity, redox conditions and detrital input prior to the latest Permian mass extinction. Marine productivity, as proxied by total organic carbon content (TOC), biogenic SiO2, and excess barium, displays a long-term decline through most of the Changhsingian stage (late late Permian), culminating in very low values around the Permian–Triassic boundary. Concurrently, redox proxies including pyrite framboid, δ34Spy, Moauth and Uauth, and Corg/P document a shift from suboxic to dysoxic/oxic conditions that was interrupted by several episodes of benthic euxinia, and detrital siliciclastic proxies (Al, Hf, Nb, and REEs) suggest an increased flux of weathered material from land areas. The long-term changes in productivity, redox conditions, and terrigenous detrital fluxes were probably caused by a regional sea-level fall across the South China Craton. On the other hand, the brief euxinic episodes occurring during the late Permian had oceanographic causes, probably related to the transient upward expansion of the chemocline at the top of the oceanic oxygen-minimum zone. These euxinic episodes may have been harbingers of the more widespread anoxia that developed concurrently with the latest Permian mass extinction and that may have played a major role in triggering the largest biotic crisis of the Phanerozoic.

New hybodontiform and neoselachian sharks from the Lower Triassic of Oman

Elasmobranchs are reported for the first time from Lower Triassic deposits in Oman. The well-preserved remains consist of isolated teeth, dermal denticles and fin spines, recovered from conodont residues. The low-palaeolatitude sections consist of Lopingian–Olenekian shallow and pelagic carbonates in exotics, olistoliths and breccia blocks that have been redeposited in younger allochthonous strata of the Hawasina Basin throughout the Oman Mountains at Jabal Safra (olistoliths within the Jurassic Guwayza Formation, Olenekian), as well as at Wadi Alwa (exotic Alwa Formation, Lopingian–Olenekian) and Wadi Wasit Block (slope breccia in the Al Jil Formation, Induan), both of which occur in the Ba'id region. The recovered fauna contains a small number of pre-existing genera, but is mainly composed of new hybodont and neoselachian taxa. They are identified as: Omanoselache halli Koot & Cuny sp. nov., cf. Omanoselache sp., Safrodus tozeri Koot & Cuny gen. et sp. nov. and Polyfaciodus pandus Koot & Cuny gen. et sp. nov., based on the majority of the recovered dental remains. Spine fragments are identified as cf. Amelacanthus sp. This fauna represents the second published record of neoselachian teeth from the Induan and the most extensive record from the Lower Triassic in terms of abundance and diversity. The fauna is dominated by Neoselachii, whereas other Early Triassic faunas are hybodont-dominated, and histological study of the neoselachian enameloid significantly adds to our knowledge of the early stages of their evolution. All described taxa are new to the Oman fossil record and that of western Neotethys, apart from Omanoselache and Amelacanthus, which have been recognized from Wordian deposits, and Omanoselache is the second genus from Oman known to have survived the late Permian mass extinction. The level of faunal diversity recognized here is comparable to other Early Triassic faunas but is much reduced compared to the Wordian pre-extinctions fauna.http://zoobank.org/urn:lsid:zoobank.org:pub:E82E8BC2-1743-4883-B27B-3564DAAF2DF1

87Sr/86Sr stratigraphy from the Early Triassic of Zal, Iran: Linking temperature to weathering rates and the tempo of ecosystem recovery

Research Article| September 01, 2014 87Sr/86Sr stratigraphy from the Early Triassic of Zal, Iran: Linking temperature to weathering rates and the tempo of ecosystem recovery Alexa R.C. Sedlacek; Alexa R.C. Sedlacek 1Department of Earth Science, University of Northern Iowa, 121 Latham Hall, Cedar Falls, Iowa 50614, USA2School of Earth Sciences, Ohio State University, Columbus, Ohio 43210, USA Search for other works by this author on: GSW Google Scholar Matthew R. Saltzman; Matthew R. Saltzman 2School of Earth Sciences, Ohio State University, Columbus, Ohio 43210, USA Search for other works by this author on: GSW Google Scholar Thomas J. Algeo; Thomas J. Algeo 3Department of Geology, University of Cincinnati, Cincinnati, Ohio 45221, USA Search for other works by this author on: GSW Google Scholar Micha Horacek; Micha Horacek 4BLT Wieselburg, Research Center Francisco-Josephinum, Rottenhauser Strasse 1, 3250 Wieselburg, Austria5Department of Lithospheric Research, Althanstrasse 14, Vienna University, 1090 Vienna, Austria Search for other works by this author on: GSW Google Scholar Rainer Brandner; Rainer Brandner 6Institute of Geology and Paleontology, University of Innsbruck, Innrain 52, 6020 Innsbruck, Austria Search for other works by this author on: GSW Google Scholar Kenneth Foland; Kenneth Foland 2School of Earth Sciences, Ohio State University, Columbus, Ohio 43210, USA Search for other works by this author on: GSW Google Scholar Rhawn F. Denniston Rhawn F. Denniston 7Department of Geology, Cornell College, Mount Vernon, Iowa 52314, USA Search for other works by this author on: GSW Google Scholar Geology (2014) 42 (9): 779–782. https://doi.org/10.1130/G35545.1 Article history received: 05 Feb 2014 rev-recd: 17 Jun 2014 accepted: 28 Jun 2014 first online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Alexa R.C. Sedlacek, Matthew R. Saltzman, Thomas J. Algeo, Micha Horacek, Rainer Brandner, Kenneth Foland, Rhawn F. Denniston; 87Sr/86Sr stratigraphy from the Early Triassic of Zal, Iran: Linking temperature to weathering rates and the tempo of ecosystem recovery. Geology 2014;; 42 (9): 779–782. doi: https://doi.org/10.1130/G35545.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract Recovery from the Late Permian mass extinction was slowed by continued environmental perturbations during the Early Triassic. Rapid fluctuations of the Early Triassic marine carbonate carbon isotope record indicate instability in the global carbon cycle, and recent δ18Oapatite studies link elevated temperatures to the prolonged biotic recovery. High temperatures potentially caused enhanced continental weathering that was detrimental to marine ecosystems, but linking weathering rates to temperature has proven difficult. One proxy for weathering is the 87Sr/86Sr of marine carbonate; we present here an 87Sr/86Sr record from an upper Permian–lower Triassic succession near Zal, Iran, that is coupled to a δ13Ccarbonate record. An increase in the rate of 87Sr/86Sr rise from the Dienerian to the Smithian may be linked to elevated continental weathering rates caused by warming during the Smithian. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

The microfacies and sedimentary responses to the mass extinction during the Permian-Triassic transition at Yangou Section, Jiangxi Province, South China

A Permian-Triassic (P-Tr) boundary section of continuous carbonate facies, which well recorded the biotic and environmental processes through the great P-Tr transition in the shallow non-microbialite carbonate facies, has been studied in Yangou, Leping County, Jiangxi Province. The P-Tr sequence is well correlated with the Meishan section according to the conodont biostratigraphy and the excursion of carbon isotopes. A series of high-resolution thin-sections from the P-Tr boundary carbonate rocks at the Yangou section are studied to explore the interrelation between environmental change and biological evolution during the transitional time. Six microfacies have been identified based upon the observation of the thin-sections under a microscope on the grains and matrix and their interrelation. Combined with the data of fossils and carbon isotopes, Microfacies 4 (MF-4), coated-grain-bearing foraminifer oolitic sparitic limestone, and Microfacies 6 (MF-6), dark shelly micritic limestone, should be the different responses to the two episodes of mass extinction and environmental events that can be correlated throughout South China and even over the world. The oolitic limestone of MF-4 is the first finding from the latest Permian strata in South China and it might be a proxy of an unusual environmental condition of high pCO2, low sulfate concentration and of microbial blooming in the aftermath of the latest Permian mass extinction. The micritic limestone of MF-6 containing rich micro-gastropods and ostracods probably represents the blooming event of disaster taxa in the earliest Triassic environment. The microfacies analysis at the Yangou section can well reveal the episodic process of the biological evolution and environmental change in the shallow non-microbialite carbonate facies throughout the great P-Tr transition, thus the Yangou section becomes an important complement to the Meishan section.

Extreme euxinia just prior to the Middle Triassic biotic recovery from the latest Permian mass extinction

The greatest mass extinction on Earth occurred 252million years ago during the latest Permian. Complete biotic recovery, characterized by a return to pre-extinction diversity levels, took an extraordinarily long time (ca. 5×106yr), probably because harsh conditions developed repeatedly during the Early Triassic. Here, we show the recurrence of euxinic conditions during the Early Triassic and the development of especially severe such conditions during the late Early Triassic, just prior to full biotic recovery from the mass extinction. Dibenzothiophenes and carotenoids accumulated in upper Lower Triassic sediments from South China, located on the western margin of the Paleotethys Ocean. Among these, chlorobactane, a biomarker for green-pigmented green sulfur bacteria, and okenane, a biomarker for purple sulfur photosynthetic bacteria, were identified in upper Early Triassic samples. Both compounds were detected in limestone (micrite) and we therefore infer that planktonic green and purple sulfur bacteria were the sources of these carotenoids, and that their presence indicates photic zone euxinia at the time of deposition. Concentrations of redox sensitive elements (M, V, and U), relative to that of Al, and the U/Th ratio, progressively increased during the late Early Triassic. The euxinic conditions represented by the carotenoids and the elements were likely caused by a combination of locally shallow restricted conditions and global environmental oscillations, such as those related to global warming, during the late Early Triassic. The presence of these biomarkers, together with the increase in the abundance of redox sensitive elements relative to Al and the U/Th, suggests that euxinic conditions could be one of the causes for the delayed recovery of marine communities in the Paleotethys Ocean after the latest Permian mass extinction event.

Functional diversity of marine ecosystems after the Late Permian mass extinction event

The Late Permian mass extinction event about 252 million years ago was the most severe biotic crisis of the past 500 million years and occurred during an episode of global warming. The loss of around two-thirds of marine genera is thought to have had substantial ecological effects, but the overall impacts on the functioning of marine ecosystems and the pattern of marine recovery are uncertain. Here we analyse the fossil occurrences of all known benthic marine invertebrate genera from the Permian and Triassic periods, and assign each to a functional group based on their inferred lifestyle. We show that despite the selective extinction of 62–74% of these genera, all but one functional group persisted through the crisis, indicating that there was no significant loss of functional diversity at the global scale. In addition, only one new mode of life originated in the extinction aftermath. We suggest that Early Triassic marine ecosystems were not as ecologically depauperate as widely assumed. Functional diversity was, however, reduced in particular regions and habitats, such as tropical reefs; at these smaller scales, recovery varied spatially and temporally, probably driven by migration of surviving groups. We find that marine ecosystems did not return to their pre-extinction state, and by the Middle Triassic greater functional evenness is recorded, resulting from the radiation of previously subordinate groups such as motile, epifaunal grazers. At least two-thirds of marine genera died out during the end-Permian mass extinction about 252 million years ago. An analysis of extinct and surviving taxa shows no substantial loss in global functional diversity, although there were significant losses in some settings such as tropical reefs.

Functional Diversity of Marine Ecosystems Following the Late Permian Mass Extinction Event

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Comment on: Plankton and productivity during the Permian–Triassic boundary crisis: An analysis of organic carbon fluxes (Algeo et al., 2013, Global and Planetary Change)

Algeo et al. (2013) accumulated a large dataset from the literature together with original data and interpreted them with respect to changes in organic fluxes from the Changhsingian to the Griesbachian. They detect a general increase in deposition of organic material from the Changhsingian to the Griesbachian with the exception of South China, where they identify a decrease in sedimentation of organic matter. They interpret the South China anomaly as a catastrophic decline in bioproductivity in response to the Late Permian Mass Extinction (LPME), whereas the noted general increase is explained by changed ambient environmental conditions (sedimentation rate, ocean oxygenation). We show i) that the dataset utilized by Algeo et al. (2013) contains numerous errors and ii) that the representativeness of some of the data is questionable, limiting the accuracy of the calculations and interpretations in the article. Additionally, we present an alternative interpretation of the data by proposing an exceptional situation in the Changhsingian in South China, seemingly more in agreement with the data than a catastrophic decline in the Griesbachian bioproductivity.

VOLCANIC EFFECTS ON MICROPLANKTON DURING THE PERMIAN-TRIASSIC TRANSITION (SHANGSI AND XINMIN, SOUTH CHINA)

The end-Permian mass extinction, the most severe biocrisis in Earth history, has been attributed to major flood basalt volcanism, but direct evidence of volcanic effects on contemporaneous marine biotas is scarce. In this study, we examined the relationship of two components of the microplankton community (acritarchs and radiolarians) to volcanic ash deposits in two deepwater sections from South China (Shangsi and Xinmin). In these sections, each eruptive event was recorded as a volcanic couplet consisting of a pale, 0.1 to 3.0-cm-thick bentonite (altered volcanic ash) overlain by a dark, 0.1- to 1.0-cm-thick, organic-rich mudstone layer. Acritarchs were found in peak abundance in the mudstone overlying each ash layer but were otherwise present only in low concentrations in the background sediment. In contrast, radiolarians were rare in the volcanic couplets but frequently abundant in the background intervals. The thickest volcanic ash layers in both sections are found immediately below and above the latest Permian mass extinction (LPME) horizon. At this level, radiolarians underwent a major regional extinction but acritarchs reached their peak abundance, confirming their role as a disaster taxon. Above the LPME, long-spined and small spherical acritarchs declined more rapidly than short-spined forms. The preference of the short-spined acritarchs for neritic inner-shelf facies may indicate that such areas served as biotic refugia during intervals of extreme environmental stress. We infer that volcanic eruptions during the Permian–Triassic transition had both positive effects (e.g., increased nutrient supply) and negative effects (e.g., metal toxicity, lowered seawater pH, increased turbidity) on marine microplankton communities, the importance of which varied both spatially and temporally.

Volcanically induced environmental change at the Permian–Triassic boundary (Xiakou, Hubei Province, South China): Related to West Siberian coal-field methane releases?

A detailed geochemical investigation of the Permian–Triassic boundary in a carbonate-ramp setting at Xiakou, South China, provides new insights regarding the role of volcanism in the largest mass extinction in Earth history. The Xiakou section records 9 intervals of volcanic activity, some producing up to 25-cm-thick composite ash layers, during the latest Permian and earliest Triassic. Each volcanic episode coincided with major changes in marine environments. The largest changes occurred in conjunction with volcanic interval VI-4, correlative with the latest Permian mass extinction, during which (1) the oceanic oxygen-minimum zone expanded (as shown by framboidal pyrite flux), (2) marine productivity declined sharply (as shown by multiple productivity proxies), and (3) climate conditions became more humid (as shown by increased clay fluxes). The mechanism by which volcanic eruptions forced marine environmental changes may be inferred from the relationship between ash layer thickness and the magnitude of the associated negative C-isotope excursion. The most likely connection is through volcanogenic methane release to the atmosphere, possibly as a result of magmatic intrusions into the West Siberian Coal Basin, triggering increases in global temperature and humidity. These climate changes in turn resulted in stronger oceanic stratification, oxygen-minimum zone expansion, and a decline in marine productivity. The Xiakou section is important in demonstrating links between volcanism and the marine environment during the Permian–Triassic transition interval.

Impacts of a massive release of methane and hydrogen sulfide on oxygen and ozone during the late Permian mass extinction

The largest mass extinction of animals and plants in both the ocean and on land occurred in the late Permian (252Ma), largely coinciding with the largest flood basalt volcanism event in Siberia and an oceanic anoxic/euxinic event. We investigated the impacts of a massive release of methane (CH4) from the Siberian igneous province and the ocean and/or hydrogen sulfide (H2S) from the euxinic ocean on oxygen and ozone using photochemical model calculations. Our calculations indicated that an approximate of 14% decrease in atmospheric O2 levels would have occurred in the case of a large combined CH4 and H2S flux to the atmosphere, whereas an approximate of 8 to 10% decrease would have occurred from the CH4 flux and oxidation of all H2S in the ocean. The slight decrease in atmospheric O2 levels may have contributed to the extinction event. We demonstrate for the first time that a massive release of CH4 from the Siberian igneous province and a coincident massive release of CH4 and H2S did not cause ozone collapse. A collapse of stratospheric ozone leading to an increase in UV is not supported by the maximum model input levels for CH4 and H2S. These conclusions on O2 and O3 are correspondent to every H2S release percentages from the ocean to the atmosphere.