Latest Permian Mass Extinction Research Articles

Early Triassic (Griesbachian) spheroids in Beibei, Chongqing, Southwestern China: Characteristics, cause and implications for palaeo‐oceanic conditions

Following the latest Permian mass extinction (LPME), abundant unusual sedimentary features and fabrics were widely distributed in Early Triassic carbonate platforms. As a unique type of carbonate grain, spheroids from the Lower Triassic are infrequently reported, yet differ significantly from giant ooids and oncoids. Griesbachian micritic spheroids are well preserved in the Lower Triassic Feixianguan Formation at the Baimiaozi (BMZ) outcrop in Beibei, Chongqing, southwestern China. These spheroids (diameter: 3.9–10.8 mm) were in a marl layer interbedded with massive oolites. They were deposited in the wave troughs of ripple marks comprising micritic clots, sparry calcite, clay minerals, organic matter and pyrite. A microbial spheroid origin is implied based on the coccoidal microbes (coccoid‐like microspherules and bacterial clump‐like microspherules), numerous pyrite framboids (indications suggest the presence of many sulphate‐reducing bacteria and the high iron content in seawater can promote nitrogen‐fixing cyanobacteria proliferation) and microbial‐derived microspherules. The dark‐coloured matrix between the spheroids primarily included microcrystalline calcite, clay minerals, organic matter and metazoan fossils. The spherical and ellipsoidal shapes of the spheroids suggested rapid accretion and lithification. As a unique carbonate depositional mode, Greisbachian spheroids may have been recorded for a palaeo‐ocean with dysoxic and calcium carbonate supersaturation shortly after the LPME.

Early Triassic (Griesbachian) Deposits of High-Energy Events at the Northwestern Upper Yangtze Region, China

Following the latest Permian mass extinction (LPME), the ocean experienced turbulent conditions due to elevated temperatures during the Griesbachian (Early Triassic). These adverse conditions resulted in a prolonged delay in biotic recovery. However, the current understanding of the sedimentological responses of the ocean at that time to these adverse conditions remains incomplete. The Griesbachian harsh ocean conditions led to the formation of abnormal carbonate rocks (known as anachronistic facies) all around the world. These facies were influenced by a combination of environmental conditions, biotic factors, and actualistic sedimentological processes (e.g., waves and currents, sedimentation). However, the role of actualistic sedimentological processes in forming anachronistic facies during the Griesbachian has been underemphasized in the existing studies. In this research, we examine calcirudite beds, such as flat-pebble conglomerates, from Member 1 of the Feixianguan Formation across multiple sections, including Shangsi, Yudongzi, Dagouli, and Jianfeng in the Upper Yangtze Region. Our analysis is grounded in field investigations, thin-section observations, and the study of triggering mechanisms and formation processes. We identified and described five calcirudite beds (S1–S5) in the Shangsi section, two beds (D1–D2) in the Dagouli section, one at Jianfeng (J1), and one (Y1) in the Yudongzi section. Bed S1 features matrix-supported flat pebbles with a normal grading, interpreted as the result of a debris flow mass-transport process. Beds S2, S3, D1, and J1 contain large mud rip-up clasts, ooids, and bioclasts, suggesting a potential link with tsunami backwash. Beds S4, D2, and Y1 display hummocky cross-stratification and ‘chrysanthemum-shaped’ flat pebbles, indicating storm influence. The presence of vermicular limestones in Bed S5 suggests harsh marine environmental conditions. Collectively, this evidence suggests that high-energy oceanic conditions, including tsunamis and frequent storms, potentially influenced Early Triassic biotic recovery.

Limited change in silicate chemical weathering intensity during the Permian–Triassic transition indicates ineffective climate regulation by weathering feedbacks

Vast emissions of volcanogenic greenhouse gases resulted in rapid global warming during the latest Permian mass extinction (LPME, ∼252 Ma), the impact of which on continental chemical weathering conditions was complex. Here, we compile Chemical Index of Alteration (CIA) records from 25 terrestrial and 12 marine sections with a near-global paleogeographic distribution to reconstruct the evolution of chemical weathering intensity of silicates during the LPME. This compilation shows that the CIA profiles, except those from the Australian Sydney and Bowen basins of the high-latitude Southern Hemisphere, exhibit either indiscernible changes or decreases through the LPME interval, contrary to previous inferences of increased silicate chemical weathering intensity. The lack of major changes in silicate chemical weathering intensity is further supported by the near uniformity of clay mineral assemblages through the LPME interval, with only minor increases of illite and chlorite and, if present, decreases in kaolinite content in some terrestrial sections. We infer a shift from dominantly transport-limited to kinetic-limited weathering regimes, likely caused by environmental climate factors such as widespread devegetation, river-flow changes (i.e., toward flashier and more intense discharge), and aridification during the earliest Triassic that effectively reduced water availability on land for water/rock reactions. Combined with limited changes in chemical weathering fluxes from previous estimates, our data imply possibly ineffective climate regulation by silicate chemical weathering at a (near-)global scale, despite high erosion rates, amid the intense global warming that followed the LPME.

Ostracodal evolution during the Permian–Triassic transition at the Youping section of the Nanpanjiang Basin

The Permian–Triassic mass extinction has been considered the largest bio-crisis of the Phanerozoic, with more than 90% of marine species extinct. Previous studies showed that ostracods suffered various extinction patterns in different localities and were relatively enriched in the lowermost Triassic shallow marine microbialites. Multiple hypotheses have been put forward to explore the reasons for this phenomenon. Abundant ostracod fossils were collected from the microbialite-bearing Youping section in the Nanpanjiang Basin. 45 species in 22 genera from Wujiaping Formation increased dramatically to 104 species in 33 genera from the microbialites of basal Luolou Formation. However, Ostracods from the Youping section suffered severe extinction during the second phase of the Permian–Triassic crisis, i.e., the earliest Triassic mass extinction (ETME), rather than the first phase, i.e., the latest Permian mass extinction (LPEM). In addition, the Sørenson coefficient has been used to examine the similarity of faunal associations among different sections of the Permian–Triassic transitional beds. There was no significant differences for ostracods between microbialites and non-microbialites sections based on similarity analysis. Thus, we proposed that “Shallow marine refuge” hypothesis could explain the high diversity and high abundance of ostracods of the Permian–Triassic transitional beds. Besides, ostracods showed remarkable geographical differentiation at both regional and global scales during the Permian–Triassic transitional beds and were presumably controlled by geographical isolation.

Mercury evidence from southern Pangea terrestrial sections for end-Permian global volcanic effects

The latest Permian mass extinction (LPME) was triggered by magmatism of the Siberian Traps Large Igneous Province (STLIP), which left an extensive record of sedimentary Hg anomalies at Northern Hemisphere and tropical sites. Here, we present Hg records from terrestrial sites in southern Pangea, nearly antipodal to contemporaneous STLIP activity, providing insights into the global distribution of volcanogenic Hg during this event and its environmental processing. These profiles (two from Karoo Basin, South Africa; two from Sydney Basin, Australia) exhibit significant Hg enrichments within the uppermost Permian extinction interval as well as positive Δ199Hg excursions (to ~0.3‰), providing evidence of long-distance atmospheric transfer of volcanogenic Hg. These results demonstrate the far-reaching effects of the Siberian Traps as well as refine stratigraphic placement of the LPME interval in the Karoo Basin at a temporal resolution of ~105 years based on global isochronism of volcanogenic Hg anomalies.

Multiple drivers and lineage-specific insect extinctions during the Permo–Triassic

The Permo–Triassic interval encompasses three extinction events including the most dramatic biological crisis of the Phanerozoic, the latest Permian mass extinction. However, their drivers and outcomes are poorly quantified and understood for terrestrial invertebrates, which we assess here for insects. We find a pattern with three extinctions: the Roadian/Wordian (≈266.9 Ma; extinction of 64.5% insect genera), the Permian/Triassic (≈252 Ma; extinction of 82.6% insect genera), and the Ladinian/Carnian boundaries (≈237 Ma; extinction of 74.8% insect genera). We also unveil a heterogeneous effect of these extinction events across the major insect clades. Because extinction events have impacted Permo–Triassic ecosystems, we investigate the influence of abiotic and biotic factors on insect diversification dynamics and find that changes in floral assemblages are likely the strongest drivers of insects’ responses throughout the Permo–Triassic. We also assess the effect of diversity dependence between three insect guilds; an effect ubiquitously found in current ecosystems. We find that herbivores held a central position in the Permo–Triassic interaction network. Our study reveals high levels of insect extinction that profoundly shaped the evolutionary history of the most diverse non-microbial lineage.

High temperature methane emissions from Large Igneous Provinces as contributors to late Permian mass extinctions

Methane (CH4) emissions induced by Large Igneous Provinces have the potential to contribute to global environmental changes that triggered mass extinctions in Earth’s history. Here, we explore the source of methane in gas samples from central Sichuan Basin, which is within the Emeishan Large Igneous Province (ELIP). We report evidence of high methane formation temperatures (between 249−17/+19 and 256−20/+22 °C) from clumped methane measurements and mantle-derived signatures of noble gases, which verify that oil-cracked CH4 and pyrobitumen are by-products within the reservoirs, associated with hydrothermal activity and enhanced heating by the ELIP. We estimate the volume of oil-cracked CH4 induced by the ELIP and argue that CH4 emissions would have been sufficient to initiate global warming prior to the end of the Permian. We also suggest that similar emissions from oil-cracked CH4 associated with the Siberian Traps Large Igneous Province may also have contributed to the end-Permian mass extinction significantly.

Биогенные структуры терригенных отложений пограничного пермо-триасового интервала Южного Верхоянья, Республика Саха (Якутия)

The article describes biogenic structures (trace fossils and bioturbation) of clastic rocks within the Permian-Triassic boundary interval in the Tiryakh-Kobyumeh section (Southern Verkhoyanye). The section is built by interbedding marine sandstones and siltstones, and is associated with the Late Permian mass extinction event. Most of the strata contain a variety of biogenic structures. Different taxonomic compositions of trace fossils and high bioturbation of Permian rocks indicate dense habitation of the basin bottom. In the Lower Triassic deposits, diversity of trace fossils sharply decreases as well as the degree of bioturbation. In the lower part of the Nekuchan suite's Triassic deposits, an interval of horizontally stratified rocks without bioturbation interbedded with rocks bioturbated by stratum has been identified. The interval is overlaid with highly bioturbated deposits, which indicates a rapid recovery of biodiversity after the Permian mass extinction.

Marine redox evolution and organic accumulation in an intrashelf basin, NE Sichuan Basin during the Late Permian

The Late Permian oceanic redox conditions are suggested to have had a causal relationship with the latest Permian mass extinction (LPME); however, the tempo-spatial variations of marine redox conditions which could have controlled environmental context of the LPME and organic accumulation remain loosely constrained. Here, we selected an organic-rich Lopingian succession deposited in an intrashelf basin, NE Sichuan Basin, SW China. To document the coeval oceanic changes, we present multiple geochemical proxies, including iron speciation, (major and trace) element contents, mercury (Hg) contents, total organic carbon contents (TOC) and carbonate carbon isotopic composition. Four intervals (I-IV) of discrete redox conditions were identified based on Fe–Mo–U–V datasets, revealing the evolutions from oxic to euxinic, and further to ferruginous conditions. Meanwhile, the primary productivity increased, then decreased in these intervals. The euxinic water wedge appeared in parallel with the high primary productivity and enrichment of organic matter, and advanced upslope and retreated downslope dynamically in the pace of sea-level rise and fall. In this case, marine redox variations were related to interactions of eustatic changes, organic decomposition, paleogeographic setting, upwelling currents, terrigenous input and volcanic activities. Compared with previous studies from other continents, it seems that the Paleo-Tethys was more anoxic and stagnant than Neo-Tethys and Panthalassa during the Late Permian, due to paleogeographic contexts and the more restricted oceanic circulation. In general, the prominent marine anoxia prevailed in the moderate water depth, and predated the major pulse of the LPME in several sections, which implies that anoxia may have not acted as the direct “killing mechanism” of this event.

Hg Isotopes and Enhanced Hg Concentration in the Meishan and Guryul Ravine Successions: Proxies for Volcanism Across the Permian-Triassic Boundary

High-resolution organic carbon isotope (δ13C), Hg concentration and Hg isotopes curves are presented for the Permian-Triassic boundary (PTB) sections at Guryul Ravine (India) and Meishan D (China). The total organic carbon (TOC)-normalized Hg concentrations reveal more intense environmental changes at the Latest Permian Mass Extinction (LPME) and the earliest Triassic Mass Extinction (ETME) horizons coinciding with majorδ13C shifts. To highlight palaeoredox conditions we used redox-sensitive elements and Rare Earth Element distribution. At Meishan, three Hg/TOC spikes (I, II, and III) are observed. Spike I remains after normalization by total aluminum (Al), but disappears when normalized by total sulfur (TS). Spike III, at the base of Bed 26, corresponds with excursions in the Hg/TS and Hg/Al curves, indicating a change in paleoredox conditions from anoxic/euxinic in the framboidal pyrite-bearing sediments (Bed 26) to oxygenated sediments (Bed 27). At Guryul Ravine, four Hg/TOC spikes were observed: a clear spike I in Bed 46, spike II at the base of the framboidal pyrite-rich Bed 49, spike III at the PTB, and spike IV at the LPME horizon. Some of these Hg/TOC spikes disappear when TS or Al normalization is applied. The spike I remains in the Hg/TS and Hg/Al curves (oxic conditions), spike II only in the Hg/TS curve (anoxic/euxinic), and spikes III and IV only in Hg/Al curves (oxic). In both sections, Hg deposition was organic-matter bound, the role of sulfides being minor and locally restricted to framboidal pyrite-bearing horizons. Positive mass-independent fractionation (MIF) for Hg odd isotopes (odd-MIF) was observed in pre-LPME samples, negative values in the LPME–PTB interval, and positive values above the ETME horizon. Most Hg-isotope patterns are probably controlled by the bathymetry of atmospheric Hg-bearing deposits. The source of Hg can be attributed to the Siberian Traps Large Igneous Province (STLIP). In the LPME-PTB interval, a complex of STLIP sills (Stage 2) intruded coal-bearing sediments. The negativeδ202Hg, the mercury odd-MIF Δ201Hg patterns, and the Δ199Hg–Hg plot in both sections are compatible with volcanic mercury deposition. Our study shows the strength of Hg/TOC ratios as paleoenvironmental proxy and as a tool for stratigraphic correlation.

Upwelling-induced organic matter enrichment of the Upper Permian Dalong Formation in the Sichuan Basin, SW China and its paleoenvironmental implications

The organic-rich siliceous rock was developed worldwide during the Late Permian which contains plenty of information about paleoenvironment. This study reveals the vertical variation in organic matter enrichment of the Upper Permian Dalong Formation in the northern Sichuan Basin, which was related to the expansion of the Paleo-Tethys Ocean induced transgression and upwelling in the northern continental margin of the Upper Yangtze. The Dalong Formation was divided into three units from bottom to top on the basis of lithology and organic matter abundance: the lower calcareous mudstone (Unit A), the middle organic-rich siliceous shales (Unit B), and the upper marlstones (Unit C), with average TOC contents of 4.09%, 6.72%, and 1.20%, respectively. The Unit A was deposited at the early stage of the transgression under seasonal upwelling settings with moderate paleoproductivity evidenced by the moderate-high Cd/Mo ratios and concentration of P, Cu and Zn. The Unit B shows extremely high Cd/Mo ratios and Ni concentration indicating the perennial upwelling and high paleoproductivity induced by the extensive transgression. The Unit C was deposited under similar hydrographic conditions with the Unit A but lower paleoproductivity due to the effect of the latest Permian mass extinction. In addition, the redox conditions varied with the paleoproductivity and positive correlations between P and redox proxies (e.g. VEF, NiEF, ZnEF and CuEF) were observed (the Unit A: moderate paleoproductivity and suboxic-anoxic conditions, the Unit B: high productivity and anoxic-euxinic conditions, the Unit C: low-moderate productivity and oxic-suboxic conditions), which indicate that nutrients brought to primary producers by the upwelling during the transgression stimulate blooms and accelerate the consumption of oxygen leading to the anoxic-euxinic bottom water conditions. During the transgression, differences in types and strength of the upwelling result in the variation of paleoproductivity and redox conditions, and thus the organic matter abundance.

Mercury fluxes record regional volcanism in the South China craton prior to the end-Permian mass extinction

Abstract 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.

Late Permian–Early Triassic environmental changes recorded by multi-isotope (Re-Os-N-Hg) data and trace metal distribution from the Hovea-3 section, Western Australia

The temporal coincidence between the Late Permian mass extinction (LPME) and the emplacement of Siberian Trap basalts suggests a causal link between the two events. Here, we discuss stratigraphic changes of organic and inorganic (including isotopic) geochemical properties of marine sediments across the Permian–Triassic boundary (PTB) in the Hovea-3 core, Western Australia, a key PTB section in the southern Neo-Tethys ocean. These data are compared with published data from the Meishan section, southern China, and from the Opal Creek section in western Canada, providing a view of Tethys and Panthalassa changes at the PTB. Trace metal and N-isotopic data, together with organic matter properties suggest that anoxic conditions were established prior to the LPME, intensified close to the LPME, and continued with photic-zone euxinia into the Early Triassic. For the Hovea-3 section, Re-Os ages confirm Changhsingian (253.5 ± 1.4 Ma) deposition of the dated interval sampled immediately below the stratigraphic level characterized by major lithological and isotopic changes. Evaluation of Re-Os, N, and Hg elemental and isotopic data for Hovea-3 suggests that anoxic conditions in the latest Permian were generally unrelated to direct magmatic contributions. A major increase in the initial Os isotopic ratio of Lower Triassic shales suggest an ~8× increase in the Early Triassic continental runoff, based on moderately conservative assumptions for end-members contributing Os to the Permian–Triassic ocean. Comparison to other PTB sections confirms a global signal of increasing Re/Os ratios in the Late Permian, and major and long-lived changes in the isotopic composition of the post-extinction ocean. A distinct peak in Hg concentrations carrying a volcanic isotopic signature, also identified in other PTB sections, likely represents a major pulse of Siberian Trap volcanism. This Hg peak in the Hovea-3 section, however, is detected above the stratigraphic level containing multiple other widely recognized and more permanent geochemical changes. Therefore, direct volcanic inputs to the Permian–Triassic Ocean likely post-date the LPME in this Western Australian section.

Intensified chemical weathering during Early Triassic revealed by magnesium isotopes

Marine ecosystem recovery after the latest Permian mass extinction (LPME) was a protracted process during the Early Triassic (∼252–247 Ma) owing to repeated climatic and environmental perturbations. Chemical weathering can supply nutrients to the ocean and may have played an important role in the Early Triassic carbon cycle and biological recovery. However, only limited geochemical records of chemical weathering during the Early Triassic have been presented to date, and the relationship between changes in weathering intensity and the slow recovery of marine ecosystems is effectively unknown. Here, we report magnesium (Mg) isotopic compositions of the siliciclastic components from shallow-marine carbonates in two well-studied Upper Permian-Lower Triassic sections in Iran and South China to track changes in chemical weathering intensity after the LPME. Both sections display a wide range of δ26Mg values (−2.09‰ to +1.10‰ at Zal, −2.30‰ to +0.33‰ at Zuodeng). We identified two distinct stages (I and II) in each section based on δ26Mg values and major elemental ratios. Variations of δ26Mg values in Stage I (Changhsingian to mid-Dienerian) are mainly controlled by mineralogical composition that can obscure weathering signals. By contrast, δ26Mg variations in Stage II (upper Dienerian to upper Spathian) are independent of lithology and inferred to reflect control by chemical weathering intensity. The trends in chemical weathering intensity within Stage II correspond to first-order variations in climate and carbon cycling. Marine ecosystem recovery during the Early Triassic may have been linked to recurrent episodes of intense chemical weathering caused by CO2 degassing and climate warming. This study demonstrates the potential utility of the Mg isotopic compositions of the silicate fraction in marine carbonates as a proxy for chemical weathering intensity, laying the groundwork for general applications of this method to deep-time Earth systems.

Globally enhanced Hg deposition and Hg isotopes in sections straddling the Permian–Triassic boundary: Link to volcanism

Mercury (Hg/TOC) spikes from eight Permian–Triassic boundary (PTB) sections in this study display patterns similar to each other across the so-called extinction interval as well as strong variation in sedimentation rates from section to section. Mercury may have been originated from the synchronous magmatism of the Siberian Traps Large Igneous Province (STLIP).At the GSSP in Meishan, China, Hg/TOC peaks were observed in the latest Permian mass extinction interval (LPME) and Early Triassic mass extinctions (ETME). The successions at Hovea-3 (Australia), Ursula Creek (Canada), Idrijca (Slovenia), Rizvanuša (Croatia) exhibit Hg/TOC peaks at the LPME and PTB. The Rizvanuša section displays one peak at the ETME horizon, Zal and Abadeh (Iran) successions at the LPME and ETME horizons, while Misci/Seres (Tyrol/Italy) section shows an enrichment at the LPME. The largest Hg/TOC peaks at the LPME, PTB and ETME are, perhaps, linked to the beginning of stage 2 (extrusive hiatus) of the Siberian Traps LIP. The meaning of the Hg/TOC spike between the LPME event and the PTB in seven of these sections is fuzzy.In the δ202Hg (MDF) vs Δ201Hg (MIF) cross plot, the majority of samples from the extinction interval appear within the volcanic-emission box and a few samples plot in the sediment/soil/peat box. Hg-isotope signatures resulted from mixing processes of volcanic and normal marine sediment Hg, generating four horizontal trends whose Δ201Hg shows negligible to no variation. Less terrigenous-Hg influx was noticed in the sections closer to the STLIP (Rizvanuša, Idrijca and Seres/Misci, all in Europe) in which Δ201Hg (MIF) is close to zero. Marked influence occurs in sections far distant from the STLIP (Meishan, Ursula Creek and Hovea-3) that exhibit negative Δ201Hg (MIF). The two sections from Iran, at intermediate distance from the STLIP, exhibit the highest, positive Δ201Hg values (Abadeh section) and the lowest, negative Δ201Hg values (Zal section). A Δ199Hg (MIF) vs Hg (n·ng−1) cross plot suggests that volcanic Hg has been contaminated by normal marine source-Hg influx in these sections helping to shape two major curved trends.The negative C-isotope excursions and Hg/TOC enrichments in the studied sections are nearly coeval and this supports the hypothesis of synchronism between the Permian–Triassic transition biotic crises (LPME and ETME) and the start of the stage 2 of the Siberian Traps (sill-intrusion style of magmatism).

Oceanic anoxia through the late Permian Changhsingian Stage in the Lower Yangtze region, South China: Evidence from sulfur isotopes and trace elements

The late Permian oceanic anoxic event is suggested to have had a causal relationship with the Latest Permian Mass Extinction (LPME); however, the nature of spatio-temporal variations in the anoxic event prior to the LPME remains poorly known. Here we provided new constraints on this issue based on high-resolution geochemical analyses of sulfur isotopes and trace elements in the Niushan section (nearby the Meishan section) of the Lower Yangtze region, South China. Results show that the entire Upper Permian Changhsingian in the study area can be divided into five intervals according to organic carbon isotope evolutionary trend. From the bottom to top, the water was oxic (interval I) to anoxic with sporadically euxinic condition (interval II) to primarily suboxic (interval III) to anoxic with frequently euxinic condition (interval IV), to a transient euxinic event (interval VEH) under dysoxic/oxic conditions (interval V). Multiple productivity proxies (total organic carbon, Cuxs, and Znxs) suggest that the primary productivity may have experienced a stable low (interval I), then was enhanced but with strong fluctuations (interval II), followed by a transient sharp decline (interval III), and was then subsequently relatively high with small fluctuations (interval IV), and finally experienced a gradual decline with occasional peaks (interval V) through the time interval represented by the Niushan section. The relationship between redox changes and paleoproductivity supports that a redox-stratified late Permian Ocean was present in the eastern Tethys region. Combined with previous results in South China, we propose that all the deep-water sections in the northern marginal basin of the Yangtze Platform (NMBY) might display similar trends, indicating that the NMBY was part of a single paleo-ocean system during the Changhsingian, although the Niushan section records more severely euxinic benthic water. The transient euxinic event during interval extinction horizon (VEH) can be well correlated with other sections worldwide, suggesting that the end-Permian marine anoxia in the Niushan section represents a global signal. The extinction horizon accompanied by a single euxinic episode in this study provides further evidence for the LPME having been caused by widespread anoxia. The bio-environmental evolutionary history of this continuous deep-water section will help us to better evaluate the data for the nearby shallow-water Meishan section.

Mercury evidence of intense volcanic effects on land during the Permian-Triassic transition

Abstract The Siberian Traps large igneous province (STLIP) was the likely trigger for the ca. 252 Ma latest Permian mass extinction (LPME), but direct evidence for global volcanic effects on land remains rare. Here, we used mercury (Hg) enrichments, a proxy for ancient volcanic activity, to assess volcanic inputs to two terrestrial Permian-Triassic boundary (PTB) sections that were separated by thousands of kilometers and represent different latitudinal zones—the peri-equatorial Lubei section (South China craton) and the high-latitude (40–60°N) Dalongkou section (Junggar terrane). Both sections exhibit strong Hg enrichment within a discrete (≤40 m) stratigraphic window representing the LPME. At Lubei, this interval is also characterized by negative mass-independent fractionation (MIF) of odd Hg isotopes, consistent with massive volcanogenic and/or terrestrial Hg inputs. These findings are significant in documenting Hg spikes and negative MIF excursions near the PTB in terrestrial sections for the first time, providing evidence of the global influence of the STLIP, as well as in demonstrating at high stratigraphic resolution its synchronicity with the PTB negative carbon-isotope excursion (CIE), supporting a common global cause for these anomalies.

Siberian Trap volcanism, global warming and the Permian-Triassic mass extinction: New insights from Armenian Permian-Triassic sections

AbstractPermian-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.

Facies selectivity of benthic invertebrates in a Permian/Triassic boundary microbialite succession: Implications for the "microbialite refuge" hypothesis.

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 froma 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, that is, 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.

Evidence for a prolonged Permian\u2013Triassic extinction interval from global marine mercury records

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.