Permian Triassic Boundary Interval Research Articles

Early Permian and Permian–Triassic boundary interval conodonts from the Central Qiangtang metamorphic belt, northern Tibet, and their paleobiogeographic and paleoclimatic implications

The >500-km-long Central Qiangtang metamorphic belt (CQMB), northern Tibet, offers valuable materials for studying the tectonic evolution and paleobiogeography of the Qiangtang Block. In this study, two conodont faunas (the Mesogondolella and Clarkina–Hindeodus–Isarcicella faunas) are reported for the first time, from the Jiaomuri area of the CQMB. The Mesogondolella fauna, including M. siciliensis, M. qiangtangensis, and?M. sp., is from the exotic limestone blocks at the Jiaomuchaka 2 and Jiangaizangbu sections, indicating a late Kungurian age (Cisuralian, Early Permian). A total of 20 conodont species from five genera are identified and two conodont biozones are established in the Clarkina–Hindeodus–Isarcicella fauna at the Jiaomuchaka 1 section. In addition, the Borinella nepalensis horizon is also recognized at the present section. Based on the conodont succession, the Permian–Triassic boundary (PTB) is temporarily placed between the Clarkina yini and Isarcicella staeschei zones. The late Kungurian Mesogondolella fauna belongs to a transitional zone between the warm- and cool-water conodont provinces and is slightly different from faunas in the southwestern part of the South Qiangtang Block (SQB). A potential explanation for this phenomenon is that the SQB may have undergone anticlockwise rotation during northward-drifting, and warm-water currents along the northern peri-Gondwanan margin may have played a crucial role in conodont distribution. The absence of coeval cool-water Vjalovognathus and M. idahoensis in the CQMB and the southern part of the SQB suggests a weak paleobiogeographical affinity with the Lhasa Block, eastern Myanmar, and Western Australia. In the Clarkina–Hindeodus–Isarcicella fauna of the PTB interval, the co-existence of the endemic species C. sosioensis and warm-water Iranognathus may indicate that the SQB drifted to equatorial regions and had a close relationship with Iran. In addition, the existence of Borinella confirms that the genus preferred relatively cool-water habitats in the Induan–Olenekian boundary (IOB) interval.

Pre-shortening reconstruction of the adria microplate: Balanced and restored cross-sections through the Southern Apennines–Dinarides (Central Mediterranean Sea)

The Adria plate and/or microplate has accommodated the differential eastward motion of Africa, Europe-Iberia, since the Jurassic times, and the subsequent convergence between Africa and Eurasia from Middle Cretaceous onwards. Its complex tectonic deformation, responsible of the development of the opposing Apennines and Dinarides thin- and thick-skinned fold and thrust belts, remains poorly constrained, fueling an ongoing debate on the original position of Adria, its pre-compressional continental width, and crustal structure. Here we tackle these uncertainties by analyzing and integrating published structural cross-sections, subsurface data and 2D lithospheric numerical models to build a 758 km long regional balanced and restored cross-sections along a SW-NE transect through the Southern Apennines and Southern Dinarides. Employing the line length method for the sedimentary cover and assuming the preservation of the pre-Triassic continental crustal area, we reconstruct the pre-compressional continental width of Adria. The unfolding of the sedimentary cover along the SW-NE cross-section results in an undeformed continental Adria microplate width of approximately 1050 km, slightly under previous estimations (1175 to 1670 km). The minimum total shortening results in 291 km: 148 km across the Southern Apennines and 143 km across the Southern Dinarides. We then calculate the Adria microplate continental crustal thickness during Middle-Late Jurassic time assuming local isostatic balance, obtaining 23 km for the eastern and central Adria sectors, based on shallow water carbonate sequences. In contrast, the western Adria sector at the Southern Apennines results in a restored pre-Triassic continental crustal thickness of only 7 km, suggesting that the middle and lower crustal layers in this sector may have been partially removed, possibly by mantle delamination during Neogene to Quaternary collisional processes. The results strongly support that the Adria microplate was located to the east of the Pelagian Basin and formed part of the African Plate around the Permian–Triassic boundary interval.

FIRST REPORT ON THE UPPERMOST PERMIAN OSTRACODS FROM THE MASORE SECTION (EXTERNAL DINARIDES), SLOVENIA

The ostracod assemblages from the Upper Permian and Permian-Triassic transitional strata of the Masore section in the External Dinarides (Slovenia) were studied. Altogether 13 genera and 20 species of the orders Palaeocopida, Platycopida and Podocopida are identified and illustrated. All recovered ostracods belong to shallow marine taxa. The older fauna from the uppermost Permian and the younger fauna from the Permian-Triassic boundary strata are distinguished. The obtained fauna from the Permian Bellerophon Formation corresponds to the “benthonic ostracod Eifelian Mega-assemblage” occupying the shelf sea floors. This study presents the first report of ostracod faunas from the uppermost Permian and Permian-Triassic boundary interval of Slovenia. The recovered ostracod fauna display a distinct faunal change and yield important paleobiogeographic implications as it reveals similarity with stratigraphical equivalent faunas from some other neighboring localities in the western Paleotethys, such as Bulla in Italy, Komirić in Serbia, and the Bükk Mountains in Hungary.

End-Permian marine ecosystem collapse was a direct consequence of deforestation: Evidence from the Kockatea Shale of the Perth Basin, Western Australia

The end-Permian mass extinction event resulted in devastated continental biomes, desolated land, and toxic waters. Anoxia led to widespread extinctions in marine ecosystems, affecting most oceanic clades. In this paper, the palynofacies of the marine Kockatea Shale, Western Australia, was studied in drill cores Hovea-3 and Redback-2, with the aim of linking changes in the marine and continental realms across the Permian–Triassic boundary interval in Australia. We show that the post-extinction ‘Dead Zone’ of the Frazer Beach Member of the Sydney Basin, eastern Australia, whose base is dated to 252.10 ± 0.06 Ma, directly correlates to the lower part of the Kockatea Shale in the Perth Basin, the so-called Inertinitic Interval. We demonstrate that the extinction of Permian Glossopteris forests observed in the Perth Basin had an immediate impact on the marine faunas due to the massive buildup of organic matter, leading to euxinia in the photic zone and ultimately pushing the marine faunas to an ecological extinction. The last lingering occurrence of marine invertebrates of Permian aspect occur in layers that may tentatively mark the Permian–Triassic boundary, positioned just below the appearance of Triassic floras of the Kraeuselisporites saeptatus Zone (equivalent to the Lunatisporites pellucidus Zone). A striking feature at the base of the Early Triassic Sapropelic Interval of the Hovea Member is the sudden and synchronous appearances of anomalously abundant acritarchs and lycophyte spores, alongside the mass occurrence of the bivalve Claraia, allowing correlation with the rise of the eastern Australian post-extinction pioneer floras in the Early Triassic. This demonstrates a significant lag time between the recovery of the terrestrial versus the marine pioneer biota in high-latitude Gondwana, with a significant delay for the faunal recovery.

Integrated biochemostratigraphy of the Permian-Triassic boundary interval and Lower Triassic succession in the eastern Cimmerian continent (Baoshan block, West Yunnan, southwest China)

The records of extreme biotic and environmental crises have been well documented worldwide from Permian-Triassic successions. However, the Cimmerian continent, a Gondwana-derived continental terrane/block strip, has received insufficient attention in terms of its eastern part including the Baoshan block. Here, we report an integrated conodont biostratigraphic zonation and carbon isotope profile from the Permian-Triassic boundary (PTB) beds and Lower Triassic succession of the Baoshan block. The conodont faunas obtained from the dolomitized Hewanjie Formation at the Dajianshan section are dominated by Hindeodus and Isarcicella species. Representatives of Eurygnathodus and the Ellisoniidae are also present. Five conodont zones are recognized in ascending order: the Hindeodus parvus Zone, the Isarcicella staeschei Zone, the Isarcicella isarcica Zone, the Hindeodus postparvus Zone, and the Eurygnathodus costatus Zone. The carbon isotope curve exhibits two pulses of negative excursion around the PTB. In general, both the conodont zones and the carbon isotope profile correlate well with those from other well-documented sections in the world. The Permian-Triassic boundary, extinction horizons and Induan-Olenekian boundary are calibrated in terms of conodont and carbon isotopic data. In addition, conodont biofacies analyses show that the depositional water-depth was shallow in general, as indicated by the lack of gondolellids and neospathodids and the presence of ellisonids and Eurygnathodus.

Petrography and geochemistry of the Permian-Triassic boundary interval, Kangjiaping section, South China: Implication for the drastic marine environment change

The Permian-Triassic transitional interval exposed well at Kangjiaping section, northwestern Hunan, South China, contains microbialites, oolitic and oncolitic limestones intercalated with vermiculate micritic limestones in the Lower Triassic overlying the uppermost Permian bioclastic limestones, which provides an excellent opportunity to study the environmental changes after the end-Permian mass extinction (EPME) and the origins and environmental significance of these various anomalous sediments. In this paper, we describe in detail the petrographic and geochemical characteristics of these anomalous sediments, together with the reconstruction of the marine environment after the EPME. The continental margin weathering was significantly enhanced after the EPME, indicated by the higher concentrations of terrigenous minerals, Th, Sc, Sr, and rare earth elements in the Lower Triassic carbonates than in the uppermost Permian bioclastic limestones. Indicators such as V/(V + Ni) and Ni/Co ratios suggest that the oxygen content of shallow seawater significantly decreased after the EPME. While, most samples from the Kangjiaping section preserve a negative cerium anomaly, indicating the shallow seawater was still oxygenated both before and after the EPME. In addition, the abnormally rapid carbonate precipitation rate indicates a supersaturation state with respect to calcium carbonate in the shallow seawater after the EPME, but the depth and salinity of seawater and climate indicated by different microfacies are still different. Under the setting of a rapid transgression after the EPME, the microbialites first deposited on the platform with the exclusion of grazers at the beginning of the Early Triassic, followed by the oncolites formed when the climate turned humid with a relative sea-level rise. The oolites were primarily deposited in an arid climate with a relative sea-level fall, and the salinity and hydrodynamics of seawater controlled the ooids’ grain sizes. In contrast, the (vermiculate) micritic limestones were mainly formed in a humid climate with a relative sea-level rising and more terrigenous inputs. Therefore, the periodic relative sea-level fluctuation and arid-humid climate alternations play a vital role in the evolution and repeat stacking of various microfacies in the Kangjiaping section.

Paleomagnetism and Cyclostratigraphy of the Permian-Triassic Boundary Interval of the Staroe Slukino Section, Vladimir Region

Paleomagnetism and Cyclostratigraphy of the Permian-Triassic Boundary Interval of the Staroe Slukino Section, Vladimir Region

Paleomagnetism and Cyclostratigraphy of the Permian-Triassic Boundary Interval of the Staroe Slukino Section, Vladimir Region

The paper presents the results of paleomagnetic, rock magnetic, and cyclostratigraphic studies of continental red beds that compose the Permian-Triassic boundary interval of the Staroe Slukino section in the Vladimir Region, Russia. Based on the directions of the characteristic components of the natural remanent magnetization of the studied rocks in the sampled stratum, the intervals of normal and reverse polarity related to the regional magnetozones r2RnP, r3RnP, and N3P-T were identified. Within the r3RnP zone, there is an interval of anomalous paleomagnetic directions, which has similar characteristics to those identified earlier in the coeval intervals of the Nedubrovo, Zhukov Ravine, and Okskiy Siyezd sections. Revising the biostratigraphy allows us to assume that the two zones of anomalous paleomagnetic directions in the composite magnetic polarity scale of the upper Permian of the Russian Platform are a reflection of the same epoch of an anomalous geomagnetic field configuration. It is estimated by the cyclostratigraphic method that the studied 16 m interval of the Staroe Slukino section took 900±20 thousand years to accumulate, which limits the duration of the geomagnetic field anomalous state near the Permian-Triassic boundary to ~110 000 years. A new Permian-Triassic (~252 Ma) paleomagnetic pole of the East European Platform is calculated: plat = 36.3°; plong = = 155.0°; dp/dm = 2.8°/4.8°.

Calcareous algae and foraminifers across the Permian-Triassic boundary interval (uppermost Bellerophon Formation and basal Werfen Formation) in the Dolomites (South Tyrol – Trentino, Italy)

Calcareous algae and foraminifers across the Permian-Triassic boundary interval (uppermost Bellerophon Formation and basal Werfen Formation) in the Dolomites (South Tyrol – Trentino, Italy)

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.

The Permian–Triassic boundary section at Baghuk Mountain, Central Iran: carbonate microfacies and depositional environment

Sections at Baghuk Mountain, 45 km NNW of Abadeh (Central Iran), have excellent exposures of fossiliferous marine Late Permian to Early Triassic sedimentary successions. Detailed bed-by-bed sampling enables the analysis of microfacies changes of three successive rock units across the Permian–Triassic boundary. The Late Permian Hambast Formation is mainly the result of biogenic carbonate production. Its carbonate microfacies is dominated by biogen-rich and bioturbated nodular limestones, indicating a well-oxygenated aphotic to dysphotic environment. The biogen-dominated carbonate factory in the Permian ceased simultaneously with the main mass extinction pulse, which is marked by a sharp contact between the Hambast-Formation and the overlaying Baghuk Member (= ‘Boundary Clay’). The clay and silt deposits of the Baghuk Member with some carbonate beds show only a few signs of bioturbation or relics of benthic communities. The Early Triassic Claraia Beds are characterised by a partly microbially induced carbonate production, which is indicated by frequent microbialite structures. The depositional environment does not provide evidence of large amplitude changes of sea level or subaerial exposure during the Permian–Triassic boundary interval. The deposition of the Baghuk Mountain sediments took place in a deep shelf environment, most of the time below the storm wave base.

Shell microstructures of latest Permian Rugosochonetidae (Brachiopoda): evidence from SEM‐ and CT‐scanned shell materials

Microscopic perforations in brachiopod shells, such as endopunctae, pseudopunctae, extropunctae, aditicules and epipunctae, have various biological functions. Based on excellently preserved material, aditicules are found to be widely developed in the Fusichonetes and Neochonetes, and setae-bearing aditicules are shown to exist in rugosochonetid brachiopods for the first time. SEM and Micro-CT images show that aditicules obliquely insert into the primary layer and are arranged in a single column along the crest of a costellae. The setae are supposed to play a role in triggering the closure of shells by sensing dangers, preventing large particles from entering the inner cavity and helping to increase the water pressure by forming a functional siphon. The SEM and Micro-CT images also show that papillae are solid cones on the inner surface of the shell, and the density of papillae varies over different regions of the shell surface, and with environment. The variation in density of the papillae is most likely related to diverse functions in the ‘filtering system’. In the marginal area, the small and densely spaced papillae can prevent intermediate and fine particles from entering the mantle cavity, whereas the large and sparse papillae in the mid-valve can trap fine particles. In this study, these two microstructures are interpreted as a sediment ‘filtering system’ in Fusichonetes and Neochonetes, which is corroborated by the predominant occurrence of these genera in shallow-water clastic shelves and deep-water siliceous basins across the Permian–Triassic boundary interval in South China.

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.

Deep-water osmium-isotope record of the Permian–Triassic interval from Niushan, China reveals potential delayed volcanic signal post the mass extinction

The end Permian mass extinction event is one of the most severe biotic crisis of the Phanerozoic. The trigger of this event has been widely linked to massive volcanic activity associated with the Siberian Traps Large Igneous Province through the application of multiple geochronological (e.g., UPb and ArAr dating) and geochemical proxies (e.g., C, Hg, Zn, Os, etc.). Of these proxies, a few osmium (187Os/188Os) records are available for near-shore/shallow water depositional settings (e.g., Meishan, China; Opal Creek, Canada), which suggest multiple episodes of volcanism before, during and after the mass extinction event. Here, we present a new initial 187Os/188Os (Osi) stratigraphy across the deep-water Niushan Permian–Triassic boundary interval section of South China that reveals a single unradiogenic Os-isotope shift (from ~0.6 to 0.3) after the end Permian mass extinction event interval, which is interpreted to be related to volcanic activity. Above the unradiogenic excursion, a radiogenic shift to ~1.1 is detected across the Permian–Triassic boundary at Niushan that is correlative to the radiogenic Osi shift observed in the Meishan section. This increase in Os-isotope values is taken to reflect enhanced continental weathering. Both the unradiogenic and radiogenic excursions in the deep-water Niushan section are smaller in magnitude compared with the Os isotope profiles from more shallow-water sections of Meishan and Opal Creek. Our data suggest investigations of multiple sections across a variety of depositional environments may yield a more comprehensive understanding of the scale of the global perturbations related to volcanism and continental weathering intensity of the Permian–Triassic boundary interval.

Multiple sulfur isotope chemostratigraphy across the Permian–Triassic boundary at Chaotian, China: Implications for a shoaling model of toxic deep‐waters

AbstractPrevious studies on multiple sulfur isotopes (32S, 33S, and 34S) in sedimentary pyrite at the end‐Permian suggested a shoaling of anoxic/sulfidic deep‐water contributing to the extinction. This scenario is based on an assumption that the sedimentary sulfur cycle was largely controlled by benthos activity, though a stratigraphic correlation between the sulfur records and ichnofabrics of the sediments at the end‐Permian has not yet been examined. We report the multiple sulfur isotopic composition of pyrite in the Permian–Triassic boundary interval at Chaotian, South China. Our data can be generally explained by a mixing of sulfur in sulfide from two different sources: one produced via sulfate reduction in an open system with respect to sulfate and the other produced in a closed system. In particular, the former with the substantially low δ34S (<−40 ‰) and high ∆33S (up to +0.100 ‰) values was likely produced via water‐mass sulfate reduction or via sulfate reduction in oxic sediments with common burrows. The frequent occurrence of small pyrite framboids (mostly <5 μm in diameter) in the Lopingian (Late Permian) Dalong Formation of deep‐water facies supports the enhanced water‐mass sulfate reduction in an anoxic deep‐water mass. The negative ∆33S values are observed only in the oxic limestones, and no substantial ∆33S change is observed across the extinction horizon despite of the disappearance of bioturbation. Our results are apparently inconsistent with the previous shoaling model. We expand the model and infer that, when the deep‐water was sulfidic and its shoaling rate was high, a substantial amount of hydrogen sulfide (H2S) was supplied onto the shelf via the shoaling; that resulted in the positive ∆33S value of the bulk sediments. The observed ∆33S variation on a global scale suggests a substantial variation in H2S concentration and/or in upwelling rate of shoaling deep‐waters during the Permian–Triassic transition.

Regime Shifts in an Early Triassic Subtropical Ecosystem

The Early Triassic was one of the most remarkable time intervals in Earth History. To begin with, life on Earth had to face one of the largest subaerial volcanic degassing, the Siberian Traps, followed by a plethora of accompanying environmental hazards with pronounced and repeated climatic changes. These changes not only led to repeated and, for several marine nektonic clades, intense extinction events but also to significant changes in terrestrial ecosystems. The Early Triassic terrestrial ecosystems of the southern subtropical region (Pakistan) are not necessarily marked by abrupt extinction events but by extreme shifts in composition. Modern ecological theories describe such shifts as catastrophic regime shifts. Here, the applicability of modern ecological theories to these past events is tested. Abrupt shifts in ecosystems can occur when protracted changing abiotic drivers (e.g. climate) reach critical points (thresholds or tipping points) sometimes accentuated by stochastic events. Early Triassic terrestrial plant ecosystem changes stand out from the longer term paleobotanical records because changes of similar magnitude have not been observed for many millions of years before and after the Early Triassic. To date, these changes have been attributed to repeated severe environmental perturbations, but here an alternative explanation is tested: the initial environmental perturbations around the Permian–Triassic boundary interval are regarded here as a main cause for a massive loss in terrestrial ecosystem resilience with the effect that comparatively small-scale perturbations in the following ∼5 Ma lead to abrupt regime shifts in terrestrial ecosystems.

Episodic dolomitizations driven by sea-level fluctuations in the Permian–Triassic boundary interval: a case study from a dolomitized Changhsingian reef, Shitouzhai section, South China

The strata exposed in Shitouzhai section, Ziyun region, on the south margin of Yangtze Platform, consists the transaction from Changhsingian reef carbonates (Bed 1) to Griesbachian micritic carbonates (Bed 4). Beds 2–3, which are sandwiched by Bed 1 and Bed 4, are massive layers of fine-crystalline dolostones. The boundary between Bed 1 and Bed 2 is defined by the subaerial exposure related to the end-Permian regression, whereas the Permian–Triassic Boundary (PTB) is emplaced within Bed 3. The dolostones from Bed 1 have 271–493 ppm Sr, 182–1970 ppm Fe and 328–597 ppm Mn. Their dolomites are entirely low-Ca calcian dolomite (LCD, 55 mol% CaCO3) and lesser amounts of LCD, with δ13C of + 2.67‰ to + 3.34‰, δ18O of − 2.53‰ to − 0.66‰. These geochemical attributes point to two phases of dolomitization. Phase 1 is associated with the end-Permian regression and caused partial dolomitization of porous zones in Bed 1. Phase 2 is penecontemporaneous dolomitization associated with the transgression following the end-Permian regression, and responsible for the dolostones of Beds 2–3. This phase stopped when the Early Griesbachian regression exposed Beds 2–3 and led to dedolomitization in these dolostones. The linkage between diagenesis and sea-level changes indicates that dolomitizations and dedolomitization are “regional events”, to which other Permian–Triassic boundary carbonates can refer.

Evidence for volcanism and weathering during the Permian-Triassic mass extinction from Meishan (South China) osmium isotope record

The Permian–Triassic mass extinction event is the most severe biotic crisis during the Phanerozoic. The trigger of this event has been widely linked with massive volcanic activity associated with the Siberian Traps Large Igneous Province. However, the direct link is still lacking to fully understand the event. In this study, we apply osmium isotope (187Os/188Os, or Osi) stratigraphy across the Permian–Triassic boundary interval in the Meishan section of South China. The Os isotope stratigraphy reveals multiple shifts to more unradiogenic 187Os/188Os composition that are interpreted to reflect pulses of volcanism across the mass extinction interval. Additionally, a shift to a more radiogenic 187Os/188Os composition is also found immediately above the mass extinction interval, which is taken to reflect the enhanced weathering of the continental crust in response to greenhouse gas release into the atmosphere and the associated hyperthermal.

Permian–Triassic extinction pattern revealed by foraminifers and geochemical records in the central Persian Gulf, southern Iran

Permian–Triassic boundary (PTB) foraminifers are studied from the upper part of the Dalan Formation and the base of the Kangan Formation in four wells (A, B, E, F) on and near the Qatar Arc, Persian Gulf, Iran. Isotope studies including δ13C and δ18O values from wells B and E and 87Sr/86Sr ratios in wells (B, E, and F) have also been carried out to possibly provide a high-resolution extinction pattern of foraminifers in the PTB interval. The latter has been thoroughly investigated in Iran, Turkey, South China, Vietnam, Slovenia, Carnic Alps and Bükk Mountains, Kashmir, Greenland, and Serbia. The distribution of the last appearance of foraminiferal genera from the PTB interval in all of the wells is very similar featuring a stepwise extinction from 3 to 2 m before the boundary and compares to that observed in some of the sections from elsewhere, i.e., South China, Vietnam, Slovenia, and Serbia. The δ13C value in wells B and E shows a negative shift at the base of a thrombolite unit immediately after the considered PTB, and another negative shift at about 11 m below it in well E. The thrombolite unit is assumed as earliest Triassic, but questionable with no supportive conodonts. The δ18O isotope values in wells B and E demonstrate the same negative upward trend due to dysoxic or anoxic conditions in the end-Permian oceans. The uniform reduction without any sharp incline in the δ18O profile suggests concurrent global warming. The highest 87Sr/86Sr ratio fluctuations in wells B, E, and F coincide with the appearance of thrombolites. Changes in the profiles of carbon, oxygen, and strontium isotopes close to the PTB in wells B, E, and F seem to correspond to lithofacies variations from limestone to dolostone and a reduction in foraminiferal diversity. These changes substantiate a clear perturbation in the marine environmental and global geochemistry elements through the PTB interval. The δ13C, δ18O and 87Sr/86Sr values obtained from the studied wells are comparable to those in other PTB stratigraphic sections in the Paleo-Tethyan region.

Proxy evidence from the Gartnerkofel-1 core (Carnic Alps, Austria) for hypoxic conditions in the western Tethys during the end-Permian mass-extinction event

The most severe mass extinction in the Phanerozoic in the latest Permian Period (251.9 Ma), has been attributed to environmental effects related to the massive coeval Siberian flood-basalt eruptions. A potential causal link between the eruptions and the marine extinctions arises from lethal global warming from greenhouse-gas emissions and the resulting development of widespread hypoxic conditions in the warm oceans. The 331-m Gartnerkofel-1 core (Carnic Alps, Austria) penetrated the Permian-Triassic boundary interval in a western Tethys shallow carbonate-ramp setting. We calculated U/Th ratios and element-enrichment factors (for U, Cr, V, Co, and Ni) using the previously published raw elemental data from the core. These redox-sensitive proxy calculations provide evidence for an ~60-ky long episode of anoxic to euxinic ocean conditions in the shallow western Tethys at the time of the abrupt end-Permian mass extinction (EPME). Subsequent fluctuating dysoxic conditions were coincident with a negative excursion of δ13Ccarb that is estimated to have lasted ~450 ky in the earliest Triassic at the GK-1 site. These findings in a high-deposition-rate section support previous reports of widespread anoxia in the western Tethys, and in the oceans in general, coincident with the EPME and its aftermath.