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Permian–Triassic boundary microbialites (PTBMs) are organosedimentary carbonates formed immediately after the end-Permian mass extinction. All those reported PTBMs constrained by convincing conodont biozones are present stratigraphycally not higher than the Hindeodus parvus zone and most of them are dominated by thrombolites. This paper provides the first record of a brief, but spectacular development of stromatolite-dominated PTBMs within the basal Isarcicella isarcica conodont zone of the earliest Triassic from the Xikou section of South Qinling Block that was at the margin of the North China Block during the Permian–Triassic transition and was geographically separated from the major occurrence of post-extinction microbialites in the South China Block. This stromatolite cap overlies a 3.7-m-thick oolitic limestone and is composed of a lower 0.2-m-thick bed and an upper 0.5-m-thick bed, separated by a 0.2-m-thick greyish green siliciclastic mudstone. These two stromatolite beds mainly consist of columnar stromatolites with subordinate domal stromatolites. The intercolumn and interstitial spaces within the stromatolites are filled with oolitic grainstones. At the microscopic scale, laminoid structures in stromatolites comprise wavy, millimetric-domical and tangled laminae. The increased grain and fossil contents and/or bioturbation in the domical and tangled laminae indicate that the formation of these laminae is likely related to an increase in the populations and the disruptions by benthic metazoans, as well as an influx of sediment grains. The δ13Ccarb values fluctuate between 2‰ and 3‰ in the uppermost Permian strata; a distinct negative shift of 1.9‰ occurs at the topmost oolitic grainstone, just below the lower stromatolite bed, and the lowest value of −0.1‰ is located at the base of the upper stromatolite bed. The stratigraphic succession from stromatolites to thrombolites of the PTBMs may represent a transgressive succession and/or a transient ecosystem recovery immediately after the end-Permian mass extinction. The thrombolites-dominated PTBMs mainly developed in near-equator shallow marine geographic locations, and stromatolite-dominated PTBMs mainly developed at higher latitude settings, which probably indicates that a relatively lower diversity and abundance of marine benthic metazoans existed at higher latitudes after the end-Permian mass extinction.

We report the first discovery of Lower Triassic Clarkina assemblages: four natural conodont assemblages from Lower Triassic pelagic black claystones of the North Kitakami Belt in northeastern Japan (Akkamori section). The fossils were obtained from the 2.5-m horizon level above the black claystone base, which is assigned to the end-Permian mass-extinction event. This horizon has been dated to the earliest Triassic (Griesbachian) by the occurrence of Hindeodus parvus, which is the index species for the base of the Triassic, in the same and subjacent horizons. These four fossil assemblages include a paired segminiplanate-formed P1 element, which was identified as the genus Clarkina, and have fully or partially preserved the original components of conodont elements. The most complete assemblage among them includes 15 distinctive elements, namely S0 and pairs of M, S1, S2, S3, S4, P1, and P2. It is noteworthy that these fossil assemblages preserve probable impressions of ‘eyes,’ which were replaced by aggregations of silicate, phosphate, and sulphide minerals. The occurrence of several sets of fossils that retain the original positioning of the conodonts' elemental apparatuses, as well as the original presence of soft tissue, may be attributed to the process by which the conodonts' bodies were transported to the deep seafloor, and by which the activity of agents of decomposition was inhibited in near-abiotic sediments under anoxic conditions in the pelagic deep sea during the earliest Triassic.

The Kamura section, located in the Chichibu Belt of Kyushu Island in southern Japan, contains a succession of uppermost Permian to Upper Triassic shallow-marine atoll sediments from the mid-Panthalassic Ocean. In the present study, carbonate microfacies, conodont biostratigraphy, and carbonate carbon isotopes were analyzed, making it possible to construct a detailed biochronological framework for the Triassic of the central Panthalassic region. A total of 14 conodont zones are recognized from the uppermost Changhsingian to the upper Norian. The Lower Triassic contains the Hindeodus parvus, Isarcicella isarcica, and H. postparvus zones (Griesbachian), the Neospathodus dieneri Zone (Dienerian), and the Novispathodus ex gr. waageni-Parachirognathus Zone (Smithian), while no evidence of the upper Lower Triassic Spathian substage was recovered at Kamura. The overlying Middle Triassic section consists of the Chiosella ex gr. timorensis-Cratognathus, ‘Paragondolella’ ex gr. alpina-Pg. ex gr. excelsa, Budurovignathus hungaricus, and B. mungoensis zones, followed in the Upper Triassic by the Quadralella tadpole-Gladigondolella malayensis, Q. lobata-Q. carpathica, Primatella cf. orchardi-Pr. permica, Epigondolella rigoi-‘Pg.’ hallstattensis, and E. ex gr. bidentata-Norigondolella steinbergensis zones. The exact stratigraphic intervals present at Kamura were refined through intercalibration of the conodont biozonation data with its δ13Ccarb profile, which shows a characteristic series of negative and positive excursions that correspond to well-established global reference profiles. The Permian–Triassic boundary is placed 0.20 m above the Mitai-Kamura formation contact (a reference datum corresponding to the end-Permian extinction horizon, = 0 m) based on the first appearance of H. parvus, and the Olenekian–Anisian boundary is placed 17.60 m above the reference datum based on the first appearance of Ch. ex gr. timorensis. Kamura carbonates were assigned to six fabric types and 17 microfacies. The microfacies succession records a deepening immediately following the end-Permian mass extinction, a strong shallowing during the mid to late Smithian, development of an unconformity spanning the entire Spathian, and minor sea-level fluctuations during the Middle and Late Triassic. The Spathian unconformity is attributed to a eustatic fall related to a sharp cooling event at or close to the Smithian–Spathian boundary that exposed the Kamura atoll. The subsequent resumption of shallow-marine sedimentation in the earliest Middle Triassic was probably due to continued thermal subsidence of the oceanic crustal basement beneath the atoll. The present work is the most complete analysis to date of the conodont biostratigraphic, carbon isotope chemostratigraphic, and eustatic records of the Triassic System in the central Panthalassic Ocean and should serve as a regional reference standard in the future.

Molybdenum isotopes are considered to be a promising paleoredox proxy in reducing facies for evaluating either global-ocean redox conditions (given quantitative Mo uptake) or local redox conditions (given non-quantitative Mo uptake). Here, we examine the Mo-isotopic composition of black to gray shales from the Permian-Triassic boundary (PTB) section at Chaohu, eastern China, in order to assess the utility of this proxy under a range of paleoredox conditions. We evaluated local redox conditions using a combination of redox-sensitive trace-element concentrations (Mo, U) and FeT/Al ratios, recognizing six intervals of more reducing conditions at the PTB and Induan-Olenekian boundary (IOB), in the mid-Smithian, at the Smithian-Spathian boundary (SSB), and in the mid- and upper Spathian. These six intervals are associated with variably weak to moderate enrichments of Mo, and they show variable shifts away from background δ98Mo values of ca. −0.4 to +0.1‰ (recording detrital Mo-isotopic compositions) toward δ98Mo values as high as +2.3 ± 0.2‰. Based on an analysis of local redox proxies versus δ98Mo as well as of sample-to-sample variance in δ98Mo values, we conclude that only one of the six reducing intervals in the study section is likely to record contemporaneous seawater δ98Mo (as a result of quasi-quantitative Mo uptake), i.e., the interval from the Hindeodus typicalis conodont Zone close to the PTB, for which δ98Mo values of +2.3 ± 0.2‰ suggest average global-ocean redox conditions similar to those of the modern ocean. For the remaining five reducing intervals, non-quantitative Mo uptake led to Mo-isotope signatures reflecting local, mostly suboxic redox conditions. The highest Mo concentrations (17–23 ppm) were yielded by the mid- and upper Spathian intervals, and the lack of concurrent U enrichment in the mid-Spathian interval suggests the local operation of a Mn-Fe particulate shuttle, an inference that is consistent with its relatively low δ98Mo values (0 ± 0.3‰). The lack of evidence for strong oceanic anoxia in the South China Craton following the PTB crisis may have been a factor in the relatively rapid recovery of marine ecosystems in this region during the Early Triassic. The present contribution serves as a case study of the application of Mo-isotopes as a paleoredox proxy in low-[Mo] sediments, which requires a careful assessment of the relative importance of global versus local redox influences based on additional proxies and evaluation criteria.

We present recent study results of the Lower Triassic conodont succession from the Ganxi and Jianshi areas of Enshi city, western Hubei Province, South China, which were situated on a carbonate ramp at the northeastern margin of the Upper Yangtze Platform. Therein, the uppermost Permian to Lower Triassic succession is well exposed and yielded abundant conodonts. A total of nine conodont zones are differentiated: (1) Clarkina yini Zone, (2) Clarkina meishanensis Zone, (3) Hindeodus changxingensis Zone, (4) Hindeodus parvus Zone, (5) Hindeodus postparvus Zone, (6) Clarkina planata Zone, (7) Neoclarkina aff. discreta Zone, (8) Neospathodus dieneri Zone, and (9) Novispathodus waageni Zone. The Ns. dieneri M1, Ns. dieneri M2, and Ns. dieneri M3 Subzones have also been distinguished within the Ns. dieneri Zone, and the Nv. waageni eowaageni and Nv. waageni waageni Subzones are recognizable within the Nv. waageni Zone in Jianshi. Most of the zones occur in succession, but the C. planata Zone is a local ecozone reflecting deeper water biofacies during H. postparvus Zone time. In the Jianshi section, the Permian–Triassic boundary is placed at Bed 136-2 based on the appearance of Hindeodus parvus immediately above the disappearance of Changhsingian taxa, while the Induan–Olenekian boundary (IOB) is drawn at Bed 225 + 40 cm based on the first appearance of Nv. waageni eowaageni within the upper range of the Ns. dieneri Zone indices. The Enshi conodont zones overall correlate well with those recognized elsewhere in South China and worldwide.

A major discrepancy for the age of the Selong Group from middle Cisuralian (Early Permian) to Changhsingian resulted from previous reports of Sakmarian, Kungurian and Guadalupian (Middle Permian) conodonts and Lopingian (Late Permian) brachiopods. Recently, Cisuralian and Guadalupian conodonts were reported again from the Selong Group and the basal part of the Kangshare Formation at the Selong section, but the age discrepancy remains. We present our conodont materials based on large samples collected from the Selong Group and our interpretation based on identifications using a sample population approach. Three conodont zones are recognized in our re-investigation of the upper part of the Selong Group. They include the Vjalovognathus sp., the Mesogondolella hendersoni, and the M. sheni zones, in ascending order. These zones are overlain by the basal Triassic Hindeodus parvus Zone and the Otoceras woodwardi Zone. Our reassessment of conodonts reported by previous studies from Selong and nearby sections suggest that all specimens consistently point to a Lopingian age; the upper part of the Selong Group is latest Changhsingian in age based on the presence of Clarkina orchardi and Mesogondolella sheni. Previously reported early Cisuralian and Guadalupian conodonts are misidentified using a form species concept. A hiatus may be present at the erosional surface between the Selong Group and the Waagenites Bed of the basal part of the Kangshare Formation. However, the hiatus is minimal because conodont and brachiopod assemblages above and below this surface are very similar, and it results from a latest Changhsingian transgression just before the extinction that follows a global latest Changhsingian regression. There is a distinct rapid end-Permian mass extinction at Selong within the Waagenites Bed, as indicated by the disappearances of all benthic brachiopods, rugose corals and Permian bryozoans. The burst of Clarkina species in the Waagenites Bed and throughout the entire Lower Triassic at Selong is interpreted as a southward migration of equatorial conodont animals associated with the rapid global warming beginning at the end of the Permian. The cool- or cold-water species of Mesogondolella, in the upper part of the Selong Group and the basal part of the Kangshare Formation, are representative of the uppermost Permian in the bipolar/bi-temperate cold-water province and are not reworked from the underlying Selong Group or any other unknown Cisuralian or Guadalupian deposits.

The Guryul Ravine section in Kashmir, northern India is an important reference section for global Lower Triassic stratigraphy. Once a candidate Global Stratotype Section and Point (GSSP) for the Permian-Triassic Boundary (PTB), the section has attracted intense attention for the PTB beds, but few studies have concerned the entire Lower Triassic stratigraphy. As one of the most continuous marine Lower Triassic successions on the northern margins of Gondwana, the Guryul Ravine section provides an important conodont biostratigraphic yardstick for worldwide correlations. This study presents recent results of the Lower Triassic conodont zonation from the Guryul Ravine section. A total of 6500 elements including 1600 P1 elements were recovered. Ten conodont zones were recognized from the Griesbachian to Spathian: Hindeodus parvus, Isarcicella staeschei, Clarkina planata, Neoclarkina krystyni, Neospathodus dieneri, Ns. pakistanensis, Novispathodus waageni, Scythogondolella mosheri, Nv. pingdingshanensis, and Nv. abruptus – Nv. brevissimus zones. The PTB is placed within Bed 52 in Unit E2, 80 cm above the base of Unit E2, based on the first occurrence (FO) of H. parvus. The Induan–Olenekian boundary (IOB) is tentatively placed at the base of Member G according to the positive maximum δ13Ccarb values, but it could be slightly higher based on conodonts. The Smithian-Spathian boundary (SSB) is drawn at the top of Member H based on the FO of Nv. pingdingshanensis and the carbon mdpt(N3-P3). Several conodont taxa are newly recognized near the top of the study section where the conodont fauna is dominated by segminiplanate elements of the Neogondolellinae. Many of these age-diagnostic species have been identified in other sections around the world, and their occurrence in Guryul Ravine supports their potential for worldwide correlation. The conodont sequence erected from the study section corresponds well to those of South China (e.g. Meishan) and elsewhere worldwide. The newly established conodont zonation from Kashmir provides a high precision time-frame to consider biotic evolution and environmental change during the Early Triassic, a crucial period of Earth history.

Investigation of the end-Permian mass extinction (EPME) has been greatly facilitated by high-resolution conodont biostratigraphic studies. To date, however, a detailed biostratigraphic framework has been lacking for shallow-marine successions of the Tethys region. In the present study, we analyzed carbonate microfacies, conodont biostratigraphy, and carbonate carbon isotopes of the Yangou Quarry section, a shallow-marine EPME succession that accumulated on an isolated carbonate bank on the northern margin of the Yangtze Platform. Microfacies analysis yielded four facies and 8 microfacies that record a seawater deepening immediately following the EPME. Ooids were abundantly produced during the EPME and earliest Triassic mass extinction (ETME) but were replaced by microbial mats, algae, bivalves, and brachiopods during an earliest Triassic transgression. A total of three conodont zones are recognized from the uppermost Changhsingian to the lowermost Griesbachian, in ascending order, the Hindeodus praeparvus Zone, H. parvus Zone, and Isarcicella staeschei Zone. The EPME and PTB (Permian-Triassic boundary) horizons are marked by the first occurrences of H. praeparvus at 6.18 m and H. parvus at 6.57 m, respectively, above the base of the section. The conodont biostratigraphic framework of the Yangou Quarry section was refined through intercalibration with its δ13Ccarb profile. This section records two discrete negative carbon isotope excursions (CIEs) that are correlative with the EPME and ETME horizons, and that can be correlated with similar CIEs at Meishan D and other PTB sections globally. Our study provides the first integrated, high-resolution biochemostratigraphic framework for a shallow-marine PTB succession in the eastern Tethys region, which will facilitate paleoenvironmental studies of similar facies elsewhere as well as correlations with deeper-water facies.

The Permian Period is punctuated by Earth system changes unlike any other in geological history. The start of the Permian witnessed the termination of the Late Paleozoic Ice Age, followed by the climatic transition from icehouse to greenhouse conditions. The Guadalupian-Lopingian (Middle-Late Permian) was characterized by two biocrises associated to volcanisms: (i) the end-Guadalupian crisis and (ii) the end-Permian mass extinction. Seawater Sr isotope (87Sr/86Sr) records can shed light on the evolution of the Permian Earth system. The Permian 87Sr/86Sr record suffers from a number of issues including low resolution and potential diagenetic alteration. In this paper, we summarize the existing Permian 87Sr/86Sr records and focus on the current challenges. We also present a new, high-resolution Permian 87Sr/86Sr curve derived from pristine brachiopod shells based on data resulting from careful diagenetic screening. Our new record shows that the 87Sr/86Sr of seawater decreased continuously from the earliest Permian to the middle Capitanian (late Guadalupian), with the lowest ratio of 0.706832 registered in the Colania douvillei-Kahlerina pachiytheca Zone. Subsequently, 87Sr/86Sr ratios increased from the late Capitanian to the latest Permian and reached a ratio of 0.707167 just 0.8 m below the first occurrence of the Hindeodus parvus. We employed a stochastic oceanic box model to explore the potential drivers of the Permian seawater Sr isotope record. Our results support that changes in the hydrothermal input, rather than changes in continental weathering intensity, are the most likely controlling factor for the observed variations in Permian seawater 87Sr/86Sr. Therefore, we suggest that the marine hydrothermal system (and hence ocean basin dynamics and deep-sea temperatures) may have been the driver of the pronounced decreasing 87Sr/86Sr trend across the Permian.

The Permian–Triassic boundary (PTB) is defined by the conodont Hindeodus parvus at Meishan section D in the palaeotropical Tethyan region, where basal Triassic ammonoids are rare and poorly preserved. Here we describe some basal Early Triassic ammonoids from the lower part of the Kangshare Formation at the Qubu section in the Mt. Everest area in southern Tibet, China. Our study recognizes three distinct ammonoid zones, the Otoceras woodwardi, Ophiceras tibeticum, and Ambites zones in ascending order. The occurrence of Otoceras, a key basal Triassic taxon, is here documented for the first time in this area. The first occurrence of Triassic conodonts at Qubu indicates that the PTB is not higher than the level 0.81 m above the base of the dolomite unit of the Kangshare Formation, and the first occurrence of the ammonoid Otoceras woodwardi is 0.89 m higher up at the section. At Qubu, the Griesbachian–Dienerian boundary is placed between the Ophiceras tibeticum Zone and the Ambites Zone. Our work represents a valuable addition for the construction of a high resolution of Griesbachian and Dienerian ammonoid biozonations in southern Tibet and provides a framework for the basal Triassic correlation in the Mt. Everest area.

Understanding the timing and correlation of significant global events in Earth history is facilitated by the Global Boundary Stratotype Section and Point (GSSP) concept, along with multi-proxy correlation techniques. As an example, the Permian–Triassic boundary (PTB) GSSP is used herein to correlate three PTB successions in east and southeast Asia. The PTB is defined using the First Appearance Datum (FAD) of the conodont Hindeodus parvus at the Meishan D section in China. By definition then, Meishan D is the only section on Earth where the FAD of H. parvus represents the beginning of the Triassic, at ~ 251.88 Ma, and thus the end of the Permian. Therefore, when correlating strata in any other section back to the PTB using biostratigraphic data, the local Lowest Observed Occurrence Point (LOOP) of H. parvus will probably not equate precisely to the defined FAD GSSP level (the PTB) for the beginning of the Triassic at Meishan D. The Graphic Correlation method, applied to PTB sites in China and Vietnam, is used herein to demonstrate that LOOPs of H. parvus in other successions are not equivalent in time to the PTB FAD. The LOOP and Highest Observed Occurrence Point (HOOP) for conodont data at two other successions studied, Huangzhishan in China, and Lung Cam in Vietnam, are used to determine the approximate level where the Triassic begins in these successions, resulting in high-resolution correlation among the sections and correlation back to the PTB GSSP level. It is demonstrated that when critical biostratigraphic data are missing, multiple proxy correlation techniques, geochemical, geophysical and, in some regional instances, unique lithostratigraphic information such as coeval ash beds, can be used to aid in locating the boundary in successions that are not the defining GSSP. LOOP and HOOP data are used to establish a Line of Correlation to differentiate between a defining PTB H. parvus FAD versus the H. parvus LOOP in secondary successions, and to project the PTB FAD into secondary sections to define the PTB at these localities. In addition, the timing of H. parvus arrivals at these sections is used to establish rough dispersal rates and patterns in the region.

Permian strata from the Tieqiao section (Jiangnan Basin, South China) contain several distinctive conodont assemblages. Early Permian (Cisuralian) assemblages are dominated by the genera Sweetognathus, Pseudosweetognathus and Hindeodus with rare Neostreptognathodus and Gullodus. Gondolellids are absent until the end of the Kungurian stage—in contrast to many parts of the world where gondolellids and Neostreptognathodus are the dominant Kungurian conodonts. A conodont changeover is seen at Tieqiao and coincided with a rise of sea level in the late Kungurian to the early Roadian: the previously dominant sweetognathids were replaced by mesogondolellids. The Middle and Late Permian (Guadalupian and Lopingian Series) witnessed dominance of gondolellids (Jinogondolella and Clarkina), the common presence of Hindeodus and decimation of Sweetognathus. Twenty main and seven subordinate conodont zones are recognised at Tieqiao, spanning the lower Artinskian to the middle Wuchiapingian Stage. The main (first appearance datum) zones are, in ascending order by stage: the Sweetognathus (Sw.) whitei, Sw. toriyamai, and Sw. asymmetrica n. sp. Zones for the Artinskian; the Neostreptognathodus prayi, Sw. guizhouensis, Sw. iranicus, Sw. adjunctus, Sw. subsymmeticus and Sw. hanzhongensis Zones for the Kungurian; the Jinogondolella (J.) nankingensis Zone for the Roadian; the J. aserrata Zone for the Wordian; the J. postserrata, J. shannoni, J. altudaensis, J. prexuanhanensis, J. xuanhanensis, J. granti and Clarkina (C.) hongshuiensis Zones for the Capitanian and the C. postbitteri Zone and C. transcaucasica Zone for the base and middle of the Wuchiapingian. The subordinate (interval) zones are the Pseudosweetognathus (Ps.) costatus, Ps. monocornus, Hindeodus (H.) gulloides, Pseudohindeodus ramovsi, Gullodus (G.) sicilianus, G. duani and H. excavates Zones. In addition, three new species, Gullodus tieqiaoensis n. sp., Pseudohindeodus elliptica n. sp. and Sweetognathus asymmetrica n. sp. are described. Age assignments for less common species (e.g., G. duani, H. catalanoi and Pseudosweetognathus monocornus etc.) are reassessed based on a rich conodont collection.

The well-exposed stratigraphic sequences on the Great Bank of Guizhou (GBG) in South China provide important information for the understanding of various environmental settings during the Permian-Triassic mass extinction and the subsequent recovery, including one of the oldest Triassic marginal reef complexes, which is viewed as an important indicator of biotic recovery following the end-Permian mass extinction. Here we report a systematic conodont study on a newly exposed Lower-Middle Triassic section, the Mingtang section, at the margin of the GBG to provide more data for the time scale of the post-extinction recovery. Twenty-four species in 11 conodont genera are identified and assigned to Hindeodus parvus , Neoclarkina discreta , Neospathodus dieneri , Novispathodus waageni , Neospathodus triangularis - Triassospathodus homeri , Chiosella timorensis , Nicoraella germanica , and Nicoraella kockeli zones in ascending order. These zones correlate well with the conodont successions in South China and over the world. The Induan-Olenekian boundary can be well defined by the first occurrence of Novispathodus waageni in the lower-middle part of the Luolou Formation, while the Early-Middle Triassic boundary was placed at 0.2 m below the top of the Luolou Formation according to the first occurrence of Chiosella timorensis . These conodont data suggest that the Tubiphytes -reef began to recover in the Bithynian (early Middle Triassic), later than benthonic organisms such as foraminifers and calcareous algae.

The biochronological characterization of the Permian–Triassic boundary (PTB) is here improved by means of conodont unitary associations zones (UAZs). The selected data set comprises the six best documented sections in South China, including the Meishan global stratotype section and point of the PTB. This new biochronological zonation has a much higher accuracy than previous schemes, which were based on continuous interval zones. We show how traditional interval zones around the PTB in South China suffer from diachronous boundaries that cross each other as the result of sampling effort (intensity and density) and of geographical or ecological exclusion of zonal index taxa, inclusive of the first occurrence of the base Triassic index species Hindeodus parvus . Our quantitative and robust approach produces a discrete sequence comprising six UAZs. In the closest agreement with the position of the PTB in Meishan, the PTB falls here in the interval of separation between UAZ 2 and UAZ 3 . In Meishan, this interval of separation corresponds to the stratigraphic interval above bed 25 and below bed 27, which also includes the formational boundary between the Changhsing and the Yinkeng formations. We provide a new and independent support for this placement by showing that it correlates with the main turnover of conodont species within the analysed time interval. As previously documented, the main extinction interval ranged from bed 25 to bed 28 in Meishan, which are here assigned to UAZ 2 and to UAZ 4 , respectively. Therefore, the main extinction episode is not of end-Permian age but straddles the PTB. Previous claims for two distinct extinction pulses bracketing the PTB in South China were based on traditional conodont interval zones and are not supported by the new UA zonation. The oldest Triassic UAZ 3 is identified by the characteristic species Hindeodus pisai and by any of the ten characteristic pairs of species Neogondolella zhejiangensis or Neogondolella tulongensis associated with Hindeodus changxingensis , Hindeodus parvus , Neogondolella planata , Neogondolella taylorae or Isarcicella huckriedei . Separate analyses of anchignathodontids and neogondolellids sub-data sets show that the base of the Triassic is unambiguously defined by the occurrences of the characteristic species H. changxingensis , Isarcicella prisca , and I. huckriedei in shallow-water settings, and of two characteristic species, N. planata and N. taylorae , in deep-water settings. Moreover, we document uncoupled diversity trends across the PTB for each of these two clades. A substantial diversification phase of anchignathodontids spans the interval from UAZ 3 to UAZ 5 . It is followed by a drastic (50%) reduction of the number of species between UAZ 5 and UAZ 6 . On the other hand, neogondolellids show a protracted extinction from UAZ 4 to UAZ 6 . In South China, correlations are proposed for the microbialite-bearing sections and deeper-water PTB sections. The UA method also highlights which parts of the conodont record are still insufficiently documented for reliable correlations. Biochronological correlations with Meishan and its U–Pb radio-isotopic ages allow inferring a maximal duration of 61 ± 48 ka for the gap at the base of the Triassic microbial limestone at Dajiang, a time interval that also corresponds to the duration of the main extinction episode in Meishan.

In many tropical shallow water regions the end-Permian mass extinction event occurs at the top fossiliferous packstone beds and is immediately followed by the development of microbialite facies. Both the age and redox conditions of the microbialite have been debated and both factors are addressed here in a study of the Gaohua section (Cili County, Hunan Province, China): specifically the size distribution of pyrite framboids and high-resolution conodont biostratigraphy. The framboids populations show a broad size range with examples up to 30 microns in diameter, and indicating dysoxic but not anoxic depositional conditions. More intense dysoxia is recorded in interbedded laminated micrites but not beds of giant ooids. Both the Hindeodus parvus zone and Isarcicella isarcica zones were established with the microbialite beds being confined to the H. parvus zone. Therefore, the formation of microbialite postdates the end Permian main mass extinction and records oxygen-poor conditions even in a shallow-water setting such as Gaohua section at Cili.

We report herein new Permian conodont data from the strata of the La Cueva Limestone and the Mina Mexico Formation in central Sonora. These data allow us to characterize the biostratigraphy of the southwestern Laurentian Permian successions and the last stage of the Ouachita-Marathon-Sonora orogen in northwestern Mexico. We studied three sections in central Sonora, which cover the stratigraphic contact between both formations. In the Las Rastras Section (LRS), we recognized a conodont association that includes Neostreptognathodus exsculptus sensu Henderson and McGugan, Sweetognathus “whitei”, Sw. subsymmetricus, and Hindeodus aff. H. minutus at its base and Sw. subsymmetricus, Hindeodus aff. H. gulloides, Gullodus tieqiaoensis, and Mesogondolella siciliensis at its top. These conodonts date the upper part of the La Cueva Limestone as latest early to earliest late Kungurian and the lower part of the Mina Mexico Formation as late Kungurian in the LRS. In the Sierra Martinez 1 and 2 sections (SMS-1 and SMS-2), located 7 km to the east of the LRS, the conodont association points to an age corresponding to the latest early to earliest middle Kungurian for both La Cueva Limestone and Mina Mexico Formation. This association is represented by the species Ns. exsculptus sensu Henderson and McGugan and Sw. subsymmetricus. The stratigraphic contact between both formations has been interpreted as the beginning of the autochthonous deformation of the Laurentian platform. This new conodont data allows us to associate this event to the latest early–earliest middle Kungurian in SMS-1 and SMS-2, and to the late Kungurian in the LRS showing a diachrony between these localities. This diachrony may be related to the continental oblique collision of Laurentia against Gondwana that resulted in progressively younger basins westward along the Ouachita-Marathon-Sonora orogen. This diachrony can also be due to the configuration of the subsiding Mina Mexico foredeep, which would have produced a non-coeval contact in the areas closer to the thrust front and those located far from it.

Conodont biostratigraphic and high-precision U-Pb isotope data are presented for the Permian-Triassic transition in three limestone hills, Gua Bama, Gua Panjang and Gua Sei, in the Malay Peninsula. Gua Bama yielded conodonts representating the Clarkina orientalis, Clarkina wangi and Clarkina subcarinata zones and the Wuchiapingian-Changhsingian stage boundary is identified for the first time in Malaysia. The Wuchiapingian subspecies Hindeodus julfensis wardlawi Kozur is elevated to species level, H. wardlawi, and evolved to the Changhsingian species Hindeodus julfensis Sweet and then Hindeodus changxingensis Wang. Distinguishing features and a new phylogeny of species of the genera Hindeodus and Isarcicella in the Late Permian-Early Triassic are presented. A new CA-TIMS high-precision U-Pb age of 253.70 ± 0.06 Ma for zircon from a tuff layer 6.5 m above the Wuchiapingian-Changhsingian boundary and in the lower part of the Clarkina subcarinata zone is reported. Conodont faunas from Gua Panjang represent the Clarkina changxingensis-Hindeodus praeparvus, Clarkina yini-Clarkina zhangi, and Hindeodus parvus zones and the PTB is placed at approximately 12 m in the studied 19 m thick sequence. Three tuff layers in the lower part of Gua Panjang contain zircon grains with CA-TIMS U-Pb ages of 252.23 ± 0.07 Ma, 252.47 ± 0.12 Ma and 252.16 ± 0.16 Ma (maximum age), respectively. Conodont faunas from Gua Sei represent the Upper Permian (Changhsingian) Clarkina hauschei - Hindeodus latidentatus Zone and the basal Triassic lower Induan (Griesbachian) Hindeodus parvus and Isarcicella staeschei zones. The PTB is placed at 30 m above the base of the Gua Sei sequence.

Research on the Permian-Triassic boundary (PTB) along the northern margins of Pangaea (exposed today in the Arctic region) has been heavily reliant on field observations, where data resolution was consequently determined by outcrop condition and accessibility. Core drilling in central Spitsbergen allowed for a near-complete recovery of two ~90 m cores through the PTB. Analyses of the core and nearby outcrops include stratigraphic logging and sampling, XRF scanning, petrography, biostratigraphy, isotope geochemistry, and geochronology. The First Appearance Datum (FAD) of H. parvus in Svalbard places the base of the Triassic ca. 4 m above the base of the Vikinghøgda Formation, and ca. 2.50 m above the End-Permian Mass Extinction (EPME) and its associated sharp negative δ13C. The PTB therefore falls within the Reduviasporonites chalastus Assemblage Zone in Svalbard. Precise U-Pb TIMS dating of two zircon crystals in a tephra layer just above the first documented Hindeodus parvus in Svalbard gives an age of 252.13 ± 0.62 Ma. High-resolution palaeoenvironmental proxies, including Si/kcps (kilo counts per second), Zr/Rb, K/Ti, Fe/K, and V/Cr, indicate a transition towards a more arid climate in the earliest Triassic, contemporaneous with prolonged bottom-water dysoxic/anoxic conditions, following an increase in volcanic activity in the Late Permian. Statistical analysis of Zr/Rb, K/Ti and V/Cr elemental ratios suggests that the system was impacted by long-eccentricity (400 kyr) cyclicity. The δ13C excursion in organic carbon (δ13Corg) record signals a large negative carbon isotope excursion (CIE) associated with the mass extinction event, but also records a second, smaller negative CIE ca. 22 m above this interval. This younger δ13Corg excursion correlates to similar CIEs in the Dienerian (late Induan) records of other sections, notably in the Tethys Ocean, which have been interpreted as recording a small biotic crisis during the post-extinction recovery. Evidence of this negative CIE in Spitsbergen suggests that the Dienerian crisis may have been global in extent. The negative δ13Corg values are associated with evidence for dysoxia or anoxia in the core, and the occurrence of tephra layers in the same interval suggests a possible connection between the Dienerian crisis and a discrete episode of volcanic activity. A new high-resolution stratigraphic and palaeoenvironmental record spanning the End-Permian Mass Extinction and its aftermath in central Spitsbergen, Svalbard publishedVersion

Unitary Association Method (UAM) analyses of conodont faunas from 28 sections spanning the biggest Phanerozoic end-Permian mass extinction and significant global environmental and ecosystem perturbations during the succeeding Early Triassic are presented. Based on 72 conodont species, 26 Unitary Association Zones (UAZs) are established for the latest Permian to earliest Middle Triassic of South China. These UAZs provide quantitative high-resolution tools to correlate sequences in the Early Triassic of South China and to compare and test high-resolution conodont biostratigraphy based on interval conodont zones developed over the past three decades. Our quantitative analyses provide insights on ongoing debates relating to the First Appearance Datum (FAD) of the conodont Hindeodus parvus which is used to place and subsequently correlate the “Golden Spike” defining the base of the Triassic (Permian-Triassic Boundary) at the base of Bed 27c at the GSSP Meishan D Section. Previous proposals that suggested potential earlier occurrences of H. parvus below its FAD at Meishan section are not supported by our results. In deep water sections, the First Occurrence (FO) of H. parvus lies at the base of UAZ 5 at the Bianyang section while it lies within UAZ 6 at the Meishan section. This indicates that the earliest occurrence of H. parvus in South China is in the Bianyang section but this conclusion needs further testing due to the reliance on “spot” data by the UAM. Anomalously high occurrences of Hindeodus in the Mingtang section (close to the Bianyang section) further suggests that the Bianyang-Mingtang area may have provided a temporally extended habitable zone for anchignathodontid conodonts. Stage boundaries currently proposed or established using interval conodont zones locate within or between UAZs and are difficult to correlate with carbon isotope curves. UAZs are useful in helping to define GSSPs by recognizing which correlations are most robust and in the selection of the most appropriate species and level for GSSPs.

New collecting at a biostratigraphically highly-resolved deep-water section in South China, reveals a brief (a few tens of thousands of years) but measurable delay in extinction timing relative to contemporaneous, shallower water sections. Foraminifers and conodonts in the Bianyang section show a sharp extinction at the top of Hindeodus changxingensis Zone, whilst in shallower sections, such as the well-known Meishan GSSP location, these taxa have a major extinction pulse at the top of the preceding Clarkina yini Zone. The main end-Permian extinction coincides with the onset of a negative carbon isotope excursion whilst the deep-water extinctions occur around the lowpoint of the carbon isotope curve. Rapidly increasing surface water temperatures, and the effects of deep-water anoxia were all important during the crisis although it is noteworthy that regression and extinction also show a close temporal link.

The Permian–Triassic mass extinction (PTME) is not only a dramatic loss in biodiversity and major change in ecosystem structures, but also coincided with the formation of abundant unusual sedimentary structures. Of these, ooids were widespread in shallow marine carbonate settings during the Permian–Triassic (P–Tr) transition, and giant ooids occurred more frequently at this critical period than any time during the Phanerozoic. Global review of 43 oolite-bearing Permian–Triassic boundary (PTB) sections with reliable biostratigraphic controls indicates that ooids occurred mostly in coincidence with the latest Permian extinction (LPE) and its immediate aftermath. Ooids became widespread over extensive regions just after the LPE during the interval corresponding to the conodont Hindeodus changxingensis Zone. They persisted into the earliest Triassic until the conodont Isarcicella isarcica Zone. In addition, oolites are often found in association with microbialites in low-latitude shallow-marine settings. Proliferation of ooids over the P–Tr transition indicates an extensive range of warm waters with high level of carbonate saturation state that prevailed in the oceans during that time. The latest Permian ooids were usually small (0.3 to 0.7 mm in diameter), aragonitic, poorly preserved and recrystallized, while moderately to well-preserved morphology, bimineralic, and oversized forms usually occurred in the I. isarcica Zone of the earliest Triassic and afterwards. Widespread aragonitic ooids in the end of the Permian reinforce the scenario that an “aragonite sea” period may have resulted in the dramatic losses of skeletal organisms that precipitated low-Mg calcite and hampered their recovery in the aftermath. The anomalous primary mineralogy of Lower Triassic ooids implies that previously assumed stable seawater composition during the Early Triassic needs to be revaluated.

During and after the end Permian mass extinction terrestrial and marine biota underwent major changes and reorganizations. The latest Permian and earliest Triassic is also characterized by major negative carbon isotope shifts reflecting fundamental changes in the carbon cycle. The present study documents a high-resolution bulk organic carbon isotope record and palynofacies analysis spanning the latest Permian–earliest Triassic of East Greenland. An almost 700 meter thick composite section from Kap Stosch allowed discriminating 6 chemostratigraphic intervals that provide the basis for the correlation with other coeval records across the world, and for the recognition of basin wide transgressive–regressive events documenting tectonic activity during the opening of the Greenland–Norway Basin. The identification of the main factors that influenced the organic carbon isotope signal during the earliest Triassic (Griesbachian to Dienerian) was possible due to the combination of bulk organic carbon isotope, palynofacies and Rock-Eval data. Two negative carbon isotopic shifts in the Kap Stosch record can be correlated with negative shifts recorded in coeval sections across the globe. A first negative shift precedes the base of the Triassic as defined by the first occurrence of the conodont Hindeodus parvus in the Meishan reference section, and the second one coincides with the suggested Griesbachian–Dienerian boundary. This new organic carbon isotope record from the extended Kap Stosch section from the Boreal Realm documents regional and global carbon cycle signals of the interval between the latest Palaeozoic and the onset of the Mesozoic.

The conodont genera Hindeodus and Streptognathodus are reported for the first time within the Carboniferous–Permian transition in the northern high latitudes of the Paren' River, Omolon Massif, NE Russia. Several fossil groups, including brachiopods, bivalves, scaphopods and microgastropods were found to be prolific in the invertebrate-dominated bioherms. These bioherms occur within predominantly siliciclastic sequences with extremely poor fauna, whereas in the studied bioherms the diversity of the bivalves and brachiopods exceeded observed diversity elsewhere in coeval facies in NE Russia. The bioherms are biostratigraphically constrained as uppermost Pennsylvanian to lowermost Cisuralian based on ammonoids. The very unusual peak of bivalve and brachiopod diversity and the occurrence of conodonts that require minimum sea water temperatures of at least 10–12 °C indicate a short lived, but significant warming event at that time, at least of provincial significance. This event most likely corresponds with a short-lived warming event recently discovered in the east of the southern hemisphere, in Timor and Australia. Thus, the event is possibly of global significance.

The chronostratigraphy of Guandao section has served as the foundation for numerous studies of the end-Permian extinction and biotic recovery in south China. Guandao section is continuous from the Permian–Triassic boundary to the Upper Triassic. Conodonts enable broad delineation of stage and substage boundaries and calibration of foraminifer biostratigraphy as follows. Changhsingian–Griesbachian: first Hindeodus parvus, and first appearance of foraminifers Postcladella kalhori and Earlandia sp. Griesbachian–Dienerian: first Neospathodus dieneri, and last appearance of foraminifer P. grandis. Dienerian–Smithian: first Novispathodus waageni and late Dienerian first appearance of foraminifer Hoyenella ex gr. sinensis. Smithian–Spathian: first Nv? crassatus and last appearance of foraminifers Arenovidalina n. sp. and Glomospirella cf. vulgaris. Spathian–Aegean: first Chiosella timorensis and first appearance of foraminifer Meandrospira dinarica. Aegean–Bithynian: first Nicoraella germanica and first appearance of foraminifer Pilammina densa. Bithynian–Pelsonian: after last Neogondolella regalis, prior to first Paragondolella bulgarica and first appearance of foraminifer Aulotortus eotriasicus. Pelsonian–Illyrian: first Pg. excelsa and last appearance of foraminifers Meandrospira? deformata and Pilamminella grandis. Illyrian–Fassanian: first Budurovignathus truempyi, and first appearance of foraminifers Abriolina mediterranea and Paleolituonella meridionalis. Fassanian–Longobardian: first Bv. mungoensis and last appearance of foraminifer A. mediterranea. Longobardian–Cordevolian: first Quadralella polygnathiformis and last appearance of foraminifers Turriglomina mesotriasica and Endotriadella wirzi. The section contains primary magnetic signature with frequent reversals occurring around the Permian–Triassic, Olenekian–Anisian, and Anisian–Ladinian boundaries. Predominantly normal polarity occurs in the lower Smithian, Bithynian, and Longobardian–Cordevolian. Predominantly reversed polarity occurs in the upper Griesbachian, Induan–Olenekian, Pelsonian and lower Illyrian. Reversals match well with the GPTS. Large amplitude carbon isotope excursions, attaining values as low as −2.9‰ δ13C and high as +5.7‰ δ13C, characterize the Lower Triassic and basal Anisian. Values stabilize around +2‰ δ13C through the Anisian to Carnian. Similar signatures have been reported globally. Magnetic susceptibility and synthetic gamma ray logs show large fluctuations in the Lower Triassic and an overall decline in magnitude of fluctuation through the Middle and Upper Triassic. The largest spikes in magnetic susceptibility and gamma ray, indicating greater terrestrial lithogenic flux, correspond to positive δ13C excursions. High precision U–Pb analysis of zircons from volcanic ash beds provide a robust age of 247.28 ± 0.12 Ma for the Olenekian–Anisian boundary at Guandao and an age of 251.985 ± 0.097 Ma for the Permian–Triassic boundary at Taiping. Together, the new U–Pb geochronology from the Guandao and Taiping sections suggest an estimated duration of 4.71 ± 0.15 Ma for the Early Triassic Epoch.

Jiarong (Huishui County, Guizhou Province, South China) is a key locality for the study of the Early Triassic recovery after the end-Permian mass extinction. The size reduction of conodonts at the Smithian/Spathian transition was first documented in Jiarong, and it is also a locality that contributes to the documentation of the Early Triassic paleo-seawater temperatures. In the Jiarong sections, thirteen conodont zones were identified for the Early Triassic; in ascending order, they are Hindeodus parvus Zone, Hindeodus sosioensis Zone, Clarkina krystyni Zone, Neoclarkina discreta Zone, Neospathodus cristagalli–Eurygnathodus costatus assemblage zone, Novispathodus waageni eowaageni Zone, Novispathodus waageni waageni Zone, Discretella discreta Zone, Pachycladina–Parachirognathus assemblage zone, Novispathodus pingdingshanensis Zone, Icriospathodus collinsoni Zone, Triassospathodus homeri Zone, Triassospathodus triangularis Zone. These conodont zones in the Jiarong sections improve the global correlation of Early Triassic sections and also provide better regional age constraints in an area that is important for studies of recovery from the extinction. Based on the first appearance of Nv. waageni eowaageni, the Induan/Olenekian boundary is recognized at 3.6 m above the base of the Jiarong III Section. The dominance of blade-shaped (segminate) conodonts was replaced by gondola-shaped (segminiplanate) conodonts twice; the first time was in the late Griesbachian, and the second time was in the early Spathian. The dominance of segminiplanate conodonts probably indicates that the deeper seawater environment became more oxygenated during the late Griesbachian and early Spathian for short time intervals, as it is believed that the Griesbachian segminiplanate conodonts favored deeper oxygenated water habitats. A new genus, Spathogondolella gen. nov., and a new species, Spathogondolella jiarongensis sp. nov., have been recognized.

Previous studies suggested rapid evolution of conodonts across the Permian–Triassic boundary (PTB), and the end-Permian mass extinction pattern varies in different sections in South China. Here we document a high-resolution conodont succession from a carbonate facies of the Changhsingian Stage and across the PTB at the Daijiagou section, about 35 km north to Chongqing City, Southwest China. Two genera and twelve species are identified. Seven conodont zones are recognized from the uppermost part of the Lungtan Formation to the lowest Feixianguan Formation. They are the Clarkina liangshanensis , C. wangi , C. subcarinata , C. changxingensis , C. yini , C. meishanensis , and Hindeodus parvus zones in ascending order. Based on the high-resolution biostratigraphical framework at Daijiagou, the end-Permian mass extinction was rapid and it began in the base of the Clarkina meishanensis Zone. Associated with the extinction, a negative excursion of δ 13 C carb started in the middle part of Clarkina yini Zone with a progressive shift of 1.6‰ to the middle part of the Clarkina meishanensis , followed by a sharp shift of 3.51‰ from the Clarkina meishanensis Zone to the Hindeodus parvus Zone. Our study also suggests that the Triassic index species Hindeodus parvus co-occurred with Hindeodus changxingensis and Clarkina zhejiangensis and directly overlies the Clarkina meishanensis Zone at the Daijiagou section. All these data from the Daijiagou section and some previous studies of other sections in Sichuan, Guizhou provinces and Chongqing City suggest that the first occurrences of Hindeodus parvus are slightly earlier than the sharp negative excursion of δ 13 C carb and the FAD at the Meishan GSSP section. We consider that the slight difference of the end-Permian mass extinction, chemostratigraphy and conodont biostratigraphy at Daijiagou and its adjacent areas is most likely subject to different lithofacies, fossil preservation, and the constraint on the stratigraphic resolution rather than a different tempo of the end-Permian mass extinction in a global sense. The whole Changhsingian conodont succession at Daijiagou provides a high-resolution correlation with other equivalent sections in the Palaeotethys. The controversial results of biostratigraphy and chemostratigraphy between the sections investigated in this paper and the Meishan GSSP section also provide some important implications that accurate chronocorrelation requires the evaluation of multiple, varied stratigraphcal signals rather than relying solely on the FAD of the Triassic index species Hindeodus parvus for recognizing the Permian–Triassic boundary (PTB). Growth series of abundant specimens for each species are figured. The taxonomy of some Hindeodus species in the PTB interval is updated.

Records of more than 20 Permian-Triassic Boundary (PTB) sections from South China show that widespread end-Permian regression took place in whole South China. Timing of the low ebb of this regression was pinpointed to the Clarkina meishanensis and Hindeodus changxingensis zones. Biostratigraphic and paleogeographic studies at conodont zonation level reveal that the Yangtze Carbonate Platform and isolated small carbonate platforms in the Hunan–Guizhou–Guangxi (HGG) Basin experienced sedimentary hiatus during these two zones which lasted about 50–100 kya. Meanwhile the basinal areas, namely the Northern Marginal Basin of Yangtze Platform and the Hunan–Guizhou–Guangxi Basin, have continuous conodont zonation with silicious and ashbed deposits. The basinal areas show two negative δ13C shifts during the PTB interval from Clarkina yini zone to Isarcicella isarcica zone, while on the platforms there is usually only one negative shift because the early shift at C. meishanensis zone was lost during hiatus. The end-Permian regression and successive rapid transgression taking place at the PTB casted important effects to the pattern and process of the PTB mass extinction. The depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction.

The Wenbudangsang section is a newly discovered continuous succession of marine carbonates that straddles the Permian–Triassic boundary (PTB), extending from the late Permian to the earliest Triassic (Induan). The section is located in the Wenbudangsang area of Geji County, northern Tibet, and tectonically sits within the northern Gangdise Stratigraphic division. Conodonts are abundant throughout this section, except being comparatively rare and less diverse in the Permian strata below the distinctive PTB Clay Bed. The conodonts are mainly represented by Hindeodus–Isarcicella Pa elements, Neogondolella Pa elements, and ramiform elements, with few Neospathodus Pa elements present at the top of the section. Two conodont zonal successions have thus been determined based on Hindeodus–Isarcicella and Neogondolella species. The Hindeodus–Isarcicella succession includes the uppermost Permian Hindeodus julfensis Zone, Hindeodus praeparvus Zone, and the lowermost Triassic Hindeodus parvus Zone, Isarcicella staeschei Zone, Isarcicella isarcica Zone, and Hindeodus postparvus Zone. The Neogondolella succession consists of the upper Permian Neogondolella changxingensis–Neogondolella deflecta–Neogondolella postwangi Zone, Neogondolella yini–Neogondolella zhangi Zone, Neogondolella meishanensis Zone, the Neogondolella taylorae Zone that crosses the PTB, and the lowermost Triassic Neogondolella krystyni Zone and Neogondolella prediscreta n. sp. Zone. The top of the section is defined by the Neospathodus kummeli Zone and Neospathodus cristagalli Zone. Two new species, Hindeodus microdentatus n. sp. and N. prediscreta n. sp., are established and described in this paper. The PTB conodont successions recognised in the new Wenbudangsang section have been closely correlated herein with other well-known PTB sections: the GSSP Meishan section of South China, sections in Abadeh in Iran, and sections at Spiti in India. Importantly, the conodont faunas from Wenbudangsang now provide an opportunity to effectively correlate the PTB hindeodid and gondolellid zonal schemes given the high abundance of both assemblages, which is unique to this section.

Meishan Section D with the Wuchiapingian/Changhsingian and Permian/Triassic GSSPs has become the most intensively studied section because it records the whole process of the largest biological extinction during the Phanerozoic. Numerous data including high-precision geochronology, multiple isotope chemostratigraphy, magnetostratigraphy, and high-resolution multiple fossil biostratigraphy have been determined during the last decade. Conodonts are very abundant in the Changhsingian Stage at the Meishan sections and their biostratigraphy together with geochronologic and multiple geochemical data provide a basic temporal framework to calibrate the end-Permian mass extinction and realize global correlation between sections at Meishan and those in other regions of the world. However, major discrepancies exist in various previous studies of conodonts from the Meishan sections. Many different authors have documented very different species ranges based on different concepts and approaches of taxonomy. We here employ a sample population approach to revise and refine the high-resolution conodont biostratigraphic framework for the Changhsingian Stage and end-Permian mass extinction interval across the Permian–Triassic boundary (PTB) at the Meishan sections. Eight zones are recognized from the latest Wuchiapingian to the basal Triassic. They are, in ascending order, the Clarkina longicuspidata Zone in the uppermost Wuchiapingian; the Clarkina wangi Zone, Clarkina subcarinata Zone, Clarkina changxingensis Zone, Clarkina yini Zone, Clarkina meishanensis Zone, Clarkina zhejiangensis–Hindeodus changxingensis Zone in the Changhsingian Stage, and the Hindeodus parvus Zone in the basal Triassic. Conodont evolutionary lineages for the whole Changhsingian are also tentatively established. All species are described in detail and growth series of different specimens for valid species are figured as completely as possible. The temporal relationship of each conodont zone with geochemical excursions, geochronologic calibration and magnetostratigraphical polarity zones are provided, which is critical to understand the tempo of the end-Permian mass extinction.

New conodont samples have been systematically collected at high stratigraphic resolution from the upper part of the Longtan Formation through to the lower part of the Yelang Formation at the Zhongzhai section, southwestern Guizhou Province, South China, in an effort to verify the first local occurrence of Hindeodus parvus in relation to the Permian–Triassic boundary at this section. The resampled conodont fauna from the Permian–Triassic boundary interval comprises five identified species and two undetermined species in Hindeodus and Clarkina . Most importantly, the first local occurrence of Hindeodus parvus is found for the first time from the bottom of Bed 28a, 18 cm lower than the previously reported first local occurrence of this species at this section. Considering the previously accepted PTB at the Zhongzhai section, well calibrated by conodont biostratigraphy, geochronology and carbon isotope chemostratigraphy, this lower (earlier) occurrence of H . parvus suggests that this critical species could occur below the Permian–Triassic boundary. As such, this paper provides evidence that (1) the first local occurrences of H . parvus are diachronous in different sections with respect to the PTB defined by the First Appearance Datum (FAD) of this species at its GSSP section in Meishan, China and that (2) the lower stratigraphic range of H . parvus should now be extended to latest Permian.

Climatic and glacio-eustatic information for the Late Paleozoic Ice Age is often extracted from cyclothems of the Midcontinent of North America. Although it is recognized that these important archives of global climate and environmental change are the result of waxing and waning of Gondwanan glaciers that produced widespread transgressive-regressive events, the relationships of conodont biofacies to changes in water depth, water chemistry, and other environmental parameters remain in dispute. Here, we investigate environmental gradients within the watermass of the Middle Pennsylvanian North American Midcontinent Sea (NAMS) based on geochemical proxies and conodont abundance patterns. To this purpose, we studied the Excello Shale at three geographically widely separated locations representing a ~500-km transect across the Midcontinent Shelf. We analyzed the organic (total organic carbon, carbon isotopes, and organic matter maturity) and inorganic geochemistry (major and trace elements) of the black and gray shale succession, as well as conodont abundance patterns and oxygen isotopic compositions, at 5–10 cm intervals through each study section. Our results suggest that the standard depth-stratification model of conodont biofacies in Pennsylvanian marine systems needs refinement. Although both Gondolella and Idioprioniodus are regarded as deep-water taxa, they differ in their stratigraphic distributions, with Idioprioniodus present through most of the Excello Shale but Gondolella confined to a narrow zone in the middle part. The Gondolella acme was not accompanied by pronounced changes in δ18O or trace-metal enrichment factors, implying that water depths and redox conditions were not the main controls on its distribution. Rather, the Gondolella acme is associated with the regressive condensation surface (RCS) of the core shale, which marks the onset of eustatic fall (renewed Gondwanan glaciation) and breakdown of the NAMS pycnocline. The latter process led to enhanced vertical overturn, mixing nutrients up into the ocean-surface layer and stimulating marine algal productivity, which was probably the trigger for blooms of Gondolella, suggesting that it was an opportunistic taxon. The upper part of the Excello is characterized by divergent δ18O compositions (~1‰ heavier in proximal areas), greater conodont abundance in offshore areas, and the appearance of Hindeodus exclusively in nearshore areas. This pattern suggests that Hindeodus was tolerant of somewhat more saline conditions, which developed during the climatic drying trend that accompanied the onset of the renewed Gondwanan glaciation. Our refined conodont biofacies model thus takes into consideration the effects of variable nutrient levels and watermass salinities in addition to water-depth controls.

article The mass extinction at the end of Permian was followed by a prolonged recovery process with multiple phases of devastation-restoration of marine ecosystems in Early Triassic. The time framework for the Early Triassic geological, biological and geochemical events is traditionally established by conodont biostratigra- phy, but the absolute duration of conodont biozones are not well constrained. In this study, a rock magnetic cyclostratigraphy, based on high-resolution analysis (2440 samples) of magnetic susceptibility (MS) and anhysteretic remanent magnetization (ARM) intensity variations, was developed for the 55.1-m-thick, Early Triassic Lower Daye Formation at the Daxiakou section, Hubei province in South China. The Lower Daye Formation shows exceptionally well-preserved lithological cycles with alternating thinly-bedded mud- stone, marls and limestone, which are closely tracked by the MS and ARM variations. Power spectral, wavelet and amplitude modulation (AM) analyses of the ARM and MS series reveal strong evidence for the presence of Milankovitch to sub-Milankovitch frequencies dominated by precession index signal and 4-5 ka cycles. Cy- cles expressed by variations in MS and ARM were likely controlled by changes in the input of fine-grained detrital magnetite, which in turn may have been driven by astronomically induced changes in monsoon in- tensity in the equatorial eastern Paleotethys during the Early Triassic greenhouse period. On the basis of the 100-ka tuning results, the astronomically constrained duration of the Induan stage is 1.16 Ma, with the Griesbachian and Dienerian substages of 490 ka and 670 ka, respectively. The new astro- nomical time scale also provides time constraints for the conodont and bivalve biozones and the carbonate carbon isotope (δ 13 C) records of the Lower Triassic Daye Formation. Time constraints for the conodont bio- zones include 34 ka for Hindeodus parvus ,2 4 ka forIsarcicella staschei-I. isarcica, 366 ka for Neogondolella planata-Ng. carinata, 66 ka for Neogondolella discreta, 255 ka for Neospathodus kummeli and 415 ka for Neospathodus dieneri. The duration for the negative δ 13 C shift from high δ 13

The Permian–Triassic (PTB) boundary section at Gaimao (Huaxi District, Guiyang, Guizhou Province) records a unique lithological transition between the Permian and Triassic in South China. Thus, bioclastic limestones of the Changxing Formation are overlain by radiolarian-bearing siliceous rocks of the Dalong Formation and ultimately limestone/mudstone alternations of the Shabaowan Formation. Conodont sampling of the section revealed well-preserved elements that enabled a conodont biostratigraphy to be established. The occurrences of Hindeodus julfensis and Hindeodus typicalis in Changxing Formation bioclastic limestone indicate a Late Permian age. Four conodont zones have been established in Dalong and Shabaowan Formations. In ascending order those are the Isarcicella isarcica Zone, Neogondolella (or Clarkina) planata Zone, Neogondolella krystyni Zone and Neospathodus dieneri Zone. The presence of typical Griesbachian conodonts I. isarcica and Isarcicella staeschei in upper Dalong Formation indicates that this formation's radiolarian-bearing siliceous mudrocks are of earliest Triassic age and not restricted to the Permian as previously thought. Thin section analysis reveals that the upper Dalong Formation contains spheroidal radiolarians but not a diverse assemblage of Permian holdover taxa. The new data proves that, following the end-Permian mass extinction of radiolarian, the abundance of these siliceous planktons was maintained at least locally enabling chert deposition to persist. Thus, the Gaimao section provides an exception to the ‘Early Triassic Chert Gap’, the first of its kind in Palaeo-Tethys, and indicates that the end of chert deposition does not always mark the end-Permian mass extinction.

Late Permian conodonts are for the first time reported from Vietnam. Pa, Sa, Sb, Sc and M elements of the Changhsingian conodont species Hindeodus julfensis (Sweet) are reported from a 40 cm thick limestone in the middle part of the Yenduyet Formation near Son La, NW Vietnam. The occurrence of H. julfensis indicates a Changhsingian age that is consistent with an interpreted early Changhsingian age for a brachiopod fauna slightly higher in the sampled section. The Son La section is located in the Song Da Rift Zone and overlies basaltic volcanics considered equivalent to the Emeishan large igneous province basalts that are plume related. The Permian–Triassic boundary in Vietnam is yet to be precisely located biostratigraphically but proxy chemostratigraphic data indicate its likely position in sections at Nhi Tao and Lung Cam, N. Vietnam and correlation with the Global Stratotype Section and Point at Meishan, South China. The recovered conodonts have a Conodont Colour Alteration Index of 5 and have been heated to c. 600 °C but they do not show any evidence of textural alteration due to regional metamorphism such as micro-folding or stretching that would indicate any direct effects of the compressional Indosinian Orogeny.

Large conodont samples (20 kg at most) have been collected from the uppermost Permian and the lowermost Triassic (beds 26–33) at Shangsi, northern Sichuan. These have enabled us to establish parallel hindeodid and gondolellid conodont zones through the section similar to previously recognized in the Meishan section. In ascending order, three newly established gondolellid zones at the Shangsi section are: Neogondolella yini Zone (bed 26), Neogondolella meishanensis Zone (beds 27a–27c), Neogondolella taylorae Zone (beds 28a–29 d). Also in ascending order, four revised or newly established hindeodid zones are: Hindeodus changxingensis Zone (beds 28a–29b) Hindeodus parvus Zone (beds 29c–30a), Isarcicella lobata Zone (beds 30b–31a), Isarcicella isarcica Zone (bed 31b and above). According to the new data, the first occurrence of H. parvus is about 2 m lower than the previously reported horizon. On the basis of both hindeodid and gondolellid taxa, the PTB is placed 22 cm above the base of bed 28a. This conodont zonation of the Shangsi section will help improve correlations of global Permian–Triassic boundary sections.

Several continuous Permian–Triassic boundary (PTB) sections are well exposed in the interior of the Great Bank of Guizhou (GBG) on the east limb of the Bianyang syncline, Luodian County, Guizhou Province, South China. Fourteen conodont taxa are identified, including Clarkina kazi, Clarkina lehrmanni n. sp., Clarkina taylorae, Clarkina zhejiangensis, Hindeodus eurypyge, Hindeodus inflatus, Hindeodus sxlatidentatus, Hindeodus parvus erectus, Hindeodus parvus parvus, Hindeodus postparvus, Hindeodus praeparvus, Hindeodus typicalis, Isarcicella staeschei, and Merrillina ultima based on a detailed study of the Permian-Triassic interval at the Dawen section. The first occurrence (FO) of H. parvus parvus in the lower Daye Formation, at about 7.45 m above the contact surface between the Upper Permian skeletal packstone and a calcimicrobial framestone unit, is correlated with the Permian–Triassic boundary; the occurrence of H. eurypyge, H. praeparvus and M. ultima immediately below and H. postparvus above the interval supports this interpretation. A morphometric analysis of 31 Hindeodus specimens helped distinguish H. parvus erectus from H. parvus parvus and H. postparvus. Correlation with the Meishan section (PTB GSSP) using both conodont biostratigraphy and carbon isotopes, indicates that the major extinction at the two localities is simultaneous and coincides with the top of the skeletal packstone at Dawen. The contact between the skeletal packstone and the calcimicrobialite is very irregular and has previously been interpreted as a dissolution surface and correlated with a surface in the lower part of bed 27 at Meishan. Our results confirm this interpretation and reveal that the dissolution event postdated the extinction.

article i nfo The greatest mass extinction occurred at the end of the Permian. Most records of the mass extinction are not from pelagic sediments, but from shallow-marine and terrestrial sediments. Although several pelagic sections that span the end-Permian mass extinction have been found, these sections contain few index fossils and are often discontinuous because of small faults. We found the index fossils Albaillella cf. triangularis (Radiolaria) in siliceous claystone beds, Hindeodus parvus (Conodont) in the overlying black claystone beds, and Neospathodus cf. cristagalli and Ns. waageni (Conodont) in the subsequent siliceous claystone beds in Akkamori section-2 in northern Japan. These fossils suggest that this section ranges from the late Permian to the Early Triassic, including the early Induan and Olenekian stages. Furthermore, the lithological changes in the section, i.e., starting from bedded chert through siliceous claystone and black claystone to siliceous claystone, are concordant with those of well-known Permian-Triassic pelagic sequences in Japan. There is no gap between each lithofacie of the Akkamori section-2. Critical lithological continuity between Upper Permian siliceous claystone beds and uppermost Permian to lowermost Triassic black claystone beds of the Akkamori section-2 was recognized by observing hand-polished specimens and thin sections. Such paleontological and sedimentological evidence implies that the Akkamori section-2 is a continuous pelagic section that records the end-Permian mass extinction event. The carbonaceous black claystone beds have high total organic carbon (TOC) concentrations (1.06-3.31 wt.%), suggesting oceanic anoxia at least deep and probably stable primary productivity. A decrease in radiolarian abundance from 26-563 to 0.27-20 specimens/cm 2 coincided with an increase in TOC content from 0.01-0.16 to 1.06-3.31 wt.% at the boundary of the siliceous claystone and the overlying black claystone beds near the top of the Permian, implying that radiolarian extinction occurred at the end of the Permian coinciding with oceanic anoxia. Although TOC contents decreased in the early Olenekian (Smithian), radiolarian abundance did not increase at that time, indicating that radiolarian recovery was delayed by N1.5 m.y.

Based on the analysis of thousands of conodont specimens from the Permian –Triassic (P–T) transition at Meishan (the GSSP of P–T Boundary) and Shangsi sections in South China, this study investigates the size variation of Hindeodus and Isarcicella P1 elements during the mass extinction interval. The results demonstrate that Hindeodus – Isarcicella underwent 4 episodes of distinct size reduction during the P–T transition at the Meishan Section and 2 episodes of size reduction in the earliest Triassic at Shangsi. The size reductions at Meishan took place at the junctions of beds 24d/24e, 25/26, 27b/27c and 28/29, and at the junctions of beds 28/29c and 30d/31a at Shangsi. The two earliest Triassic size reduction episodes were correlative between the two sections. These changes coincide with some important geological events such as eustatic sea-level changes, anoxic events, carbon isotope oscillations, miniaturization of brachiopods and microbial changes. Through detailed investigation of the palaeoenvironment and the palaeoecology of Hindeodus – Isarcicella , the authors propose that the main causes of the size reduction was a sharp decline of food availability because of the mass extinction and the anoxic event during the P/T transition. The pattern of size reduction supports suggestions that the end-Permian mass extinction was multi-episodal, consisting of 3 extinction events rather than a single catastrophic event.

Chaohu is located in a deep part of carbonate ramp on the Lower Yangtze Block, which belonged to the low-latitude eastern Tethyan archipelago during the Early Triassic. Fossils were very rich in the Lower Triassic of Chaohu. Bivalves, ammonoids, conodonts were very common throughout the Lower Triassic, while fish fossils were generally rich in some beds of the upper part. It is one of the most typical sections for the Early Triassic chronostratigraphy in the world. Although various fossils had been studied in the 1980s and 1990s, recent studies based upon new and more detailed collections from the Lower Triassic of Chaohu showed that the conodont zonation needs revision. We collected Lower Triassic conodont fossils from continuous sections of the West Pingdingshan, North Pingdingshan and South Majiashan, Chaohu, Anhui Province, and updated zonations were made for each section. Eight conodont zones have been distinguished. They are, in ascending order, Hindeodus typicalis zone, Neogondolella krystyni zone, Neospathodus kummeli zone, Neospathodus dieneri zone, Neospathodus waageni zone, Neospathodus pingdingshanensis zone, Neospathodus homeri zone, and Neospathodus anhuinensis zone. The first occurrence of Neospathodus waageni eowaageni of the N. w. eowaageni subzone (i.e. the base of the N. waageni zone) is suggested as the marker to define the Induan–Olenekian boundary.

In order to reveal environmental changes across the Permo-Triassic boundary (PTB), the detailed lithostratigraphy of the PTB interval is analyzed at Chaotian in northern Sichuan, China. The studied section is composed of the Changhsingian (Upper Permian) Dalong Formation and the Induan (Lower Triassic) Feixianguan Formation of a lower-slope facies deposited on the northwestern margin of the Yangtze carbonate platform. The 12-m-thick interval across the PTB consists mainly of bedded carbonates and mudstone, and is lithologically divided into 7 units, i.e., Units A to G, in ascending order. The main extinction horizon of Permian taxa is recognized at the Unit D/E boundary where various fossil metazoans and protists, such as ammonoids, brachiopods, bivalves, conodonts, and radiolarians, rapidly disappeared or became scarce. The complete disappearance of radiolarians at the Unit D/E boundary emphasizes that the PTB extinction affected not only various Late Permian benthic and free-swimming metazoans but also planktonic protozoans. The lowest Induan index conodont Hindeodus parvus first occurs at the base of Unit F, marking the biostratigraphically defined PTB horizon. Unit E composed of unique bedded marl between the main extinction horizon and the first occurrence of Triassic taxon represents a period of strong environmental stresses that suppressed productivity both of silica- and carbonate-secreting organisms. By changing their size, radiolarians reacted most sensitively to the environmental change that already started in the late Changhsingian, appreciably before the final extinction event. The frequent intercalation of rhyo-dacitic tuff beds, particularly in Unit D and the lower part of Unit E across the main extinction horizon, suggests that intermittent felsic volcanism and relevant environmental change may have been responsible for the mass extinction of the Permian taxa and for the prolonged post-extinction lag time before the initial recovery. The frequent ash falls during the late Changhsingian indicate that the volcanism-induced environmental change had already started earlier than the main extinction. All the biological production (carbonate, silica, and organic matter) collapsed at the Unit D/E boundary when the environmental stresses may have passed a critical threshold for maintaining ecological stability. The PTB interval between the extinction and the first appearance of Triassic taxon at Chaotian is ca. 1.4 m thick, apparently almost eight times thicker than that at the Global Stratotype Section and Point of PTB in Meishan (19 cm). The Chaotian section, as well as the neighboring Shangsi section in northern Sichuan, may provide a better chance for high-resolution chemostratigraphic analyses that may allow detection and correlation of subtle environmental changes across the PTB.

The Chongzuo-Pingguo platform is a vast isolated platform, 180 km across, in the southern part of the Nanpanjiang basin. The end-Permian extinction is recorded in conformable sections in the northern part of the platform (Pingguo area). Upper Permian skeletal packstone contains diverse open-marine fossils including Nankinella and Sphaerulina. It is overlain by a 4.6 m thick horizon of calcimicrobial framestone constructed by globular calcified microbial framework similar to Renalcis. The PTB event horizon is interpreted to occur at the top of the packstone, coincident with the abrupt change to calcimicrobial framestone lacking Permian macrofossils. The transition from Hindeodus latidentatus to H. parvus occurs 1 m above the base of the calcimicrobial framestone, marking the conformable biostratigraphic boundary. During the Early Triassic the platform developed as a low-relief bank rimmed with oolite shoals but was bordered by a high-relief, fault-controlled escarpment along its southern margin. Platform interior facies of the Majiaoling and Beisi formations are 900 m thick and consist of thin-bedded lime mudstone, oolite, and dolostone with restricted marine biota in four shallowing-upward packages that define depositional sequences. In the Chongzuo area the platform was terminated at the end of the Early Triassic by burial with up to 1600 m of felsic pyroclastic volcanics and lava flows. Transgression and shallow-marine carbonate sedimentation resumed early in the Middle Triassic followed by drowning in the Bithynian as indicated by a shift to deep-marine carbonate and clastic deposition. In the Pingguo area volcanic deposits are much thinner and only briefly interrupted carbonate accumulation. Here the platform interior drowned during a major back step early in the Middle Triassic (Anisian, Bithynian). Smaller pinnacle platforms of the Guohua Fm., up to 1700 m thick, continued to accumulate above the Early Triassic platform margin and were eventually drowned by the Late Pelsonian. In the Anisian, the pinnacle platforms shifted to sharply defined, reef-rimmed margins with Tubiphytes reefs. The shift coincides with accelerated metazoan biotic recovery in the Anisian. However, the reefs lack metazoan frameworks and are composed almost entirely of Tubiphytes reinforced by large volumes of marine cement. These observations indicate that controls beyond the recovery of framework-building metazoans governed the re-establishment platform-margin reefs in the Middle Triassic.

The Early Triassic paleogeographical setting of the Chaohu section in China was in a deep part of the Yangtze platform and this has resulted in a rather complete Lower Triassic sequence with rich ammonoid and conodont successions. Three Lower Triassic sections, West Pingdingshan, North Pingdingshan and South Majiashan, have been sampled in detail for a systematic conodont study. Eight conodont zones are recognized; in ascending order these are the zones of Hindeodus typicalis , Neogondolella krystyni , Neospathodus kummeli , Neospathodus dieneri , Neospathodus waageni , Neospathodus pingdingshanensis , Neospathodus homeri , and Neospathodus anhuinensis. These are correlated with the sequences in North America and other areas of the world. The succession provides a good basis for the definition of the global stratotype of the Induan–Olenekian boundary (GSSP), which has been proposed at the base of the Neospathodus waageni Zone in West Pingdingshan. Seven new species are introduced: Neospathodus chaohuensis , N. chii , N. concavus , N. eotriangularis , N. pingdingshanensis , N. posterolongatus , N. tongi , a new subspecies N. waageni eowaageni , and three morphotypes of N. dieneri .

A study of latest Permian and Early Triassic multielement conodonts identifies eight steps in their evolutionary history during an interval when Earth's biosphere was highly stressed. These steps are: 1) gradual decline of families and genera through the Changhsingian (up to the late Griesbachian); 2) conodont biofacies change and extinction of Tethyan endemic species close to the Permian–Triassic Boundary (PTB); 3) faunal turnover with extinction and origination in the late Griesbachian; 4) initial radiation in gondolellids and diversification in apparatuses during the Dienerian; 5) explosive radiation in the early–middle Smithian; 6) major extinction in the late Smithian; 7) major radiation early in the Spathian; 8) gradual turnover and decline in the late Spathian through early Anisian. Conodontophorids were reduced from five families at the beginning of the Changhsingian to three by the PTB, and to two late in the Griesbachian. From the Changhsingian to the late Griesbachian, there was a single multielement apparatus represented in the Gondolellidae, whereas by the Olenekian there were at least twelve. Given absolute age constraints, the conodont recovery in the aftermath of the PTB was extraordinary. Conodont evolution during the Dienerian remains obscure but was very significant in terms of changes in multielement apparatuses. In spite of Induan extinctions, generic diversity generally increased from the PTB up to the late Smithian. In terms of species, genera, and multielement apparatuses, the acme of Triassic conodonts was in the middle Smithian, and the biggest extinction was in the late Smithian. After this extinction, generic and apparatus diversity quickly returned to high levels, marking a significant Spathian recovery. Gradual decline characterized the late Spathian and persisted into the early Anisian. A synthetic summary of the temporal distribution and proposed relationships amongst all known Lower Triassic conodonts provide an improved foundation for biostratigraphic and biochronologic studies. Extinction and radiation trends correlate well with sea-level changes and sequence boundaries: faunal turnovers correspond to lowstands in the late Griesbachian, late Smithian, and late Spathian, and radiations correspond to transgressions in the early Griesbachian, early Smithian, and early Spathian. The trends also correlate with perturbations in the carbon cycle, with Lower Triassic δ13C minima corresponding to extinction and faunal turnover, and positive values generally occurring during radiations. However, Middle Triassic recovery of marine benthos follows a positive maxima and an overall decline in conodont diversity. New taxa Borinella chowadensis, B. megacuspa, Neogondolella griesbachensis, and N. mongeri are described.

The Lower Triassic, consisting of the Yinkeng Fm., Helongshan Fm. and the lower part of the Nanlinghu Fm., is well developed at the Meishan D Section of Changxing County, Zhejiang Province, South China. Based on detailed study of the conodont biostratigraphy from the interval of the Permian–Triassic boundary and the Lower Triassic in the Meishan D Section, 8 conodont zones are recognized in ascending order as follows: the Neogondolella changxingensis yini–Hindeodus praeparvus Zone (beds 24a–24e, top of the Changxing Fm.), the Neogondolella meishanensis meishanensis–Hindeodus eurypyge Zone (beds 25–27b, base of the Yinkeng Fm.), the Hindeodus parvus Zone (beds 27c–27d, first conodont zone of Triassic, the global index for the base of Triassic), the Isarcicella staeschei Zone (beds 28–29a, lower part of the Yinkeng Fm), I. isarcica Zone (beds 29b–51, lower part of the Yinkeng Fm.), the Neogondolella tulongensis–N planata Zone (beds 52–72, from upper part of the Yinkeng Fm. to lower part of the Helongshan Fm.), the Neospathodus kummeli Zone (beds 73–92, middle part of the Helongshan Fm.), and the Neospathodus cristagalli–N dieneri Zone (beds 93–111, from upper part of the Helongshan Fm. to the base of the Nanlinghu Fm.). At the Meishan D Section, the palynological biostratigraphy is also studied herein. The palynological assemblage of Lundbladispora–Taeniaesporites–Equisetosporites is found in the intervals which contain the conodont Isarcicella isarcica Zone and the lower part of the Neogondolella tulongensis–N. planata Zone.

Detailed conodont biostratigraphy of the Permian–Triassic boundary (PTB) interval was analyzed at the fossiliferous Chaotian section in northern Sichuan, China. The PTB interval at Chaotian is composed of the uppermost Permian mudstone/limestone of the Dalong Formation and the lowermost Triassic marl/limestone of the Feixianguan Formation both representing deep basinal facies. The PTB interval is enriched in ammonoids and conodonts, and is divided into 6 conodont zones including 1) Clarkina changxingensis changxingensis–C. subcarinata Assemblage Zone, 2) C. postwangi–C. sp. B Assemblage Zone, 3) C. taylorae–C. zhejiangensis–C. changxingensis yini Assemblage Zone, 4) barren intra-zone, 5) Hindeodus parvus Zone, and 6) Isarcicella Zone in ascending order. The first four zones correspond to the Changhsingian, whereas the latter two to the Lower Induan (Griesbachian). The first occurrence (FO) of H. parvus in the lowermost Feixianguan Formation is regarded as the conodont biostratigraphic boundary. From the uppermost Dalong Formation, various taxa of the genus Clarkina occurred abundantly, and suddenly disappeared at the top of the Dalong Formation, therefore, the top of the Dalong Formation is interpreted as a horizon of the eventostratigraphic boundary. On the basis of conodont zones, the Chaotian section is correlated with the Shangsi and Meishan (GSSP of the PTB) sections in South China, and the Zal section in Iran.

This study documents the Permian–Triassic Boundary in the Žiri area of western Slovenia. A paleontological study of the Lukac section, northwest of Žiri, resulted in the recovery of a variety of microfossils. This report documents the conodont fauna recovered from the section. This is the first report of the Hindeodus–Isarcicella population in Slovenia and it provides important new biostratigraphic data for the definition of the Permian–Triassic Boundary. Hindeodus parvus has been recovered, and its first appearance in the lowermost Werfen Formation indicates the base of the Triassic Period. Based on the conodont taxa H. parvus, Hindeodus typicalis, Hindeodus sp., Isarcicella isarcica, Isarcicella lobata, Isarcicella staeschei, Isarcicella turgida, and Isarcicella sp. A, at least three faunas can be distinguished, and they make possible a worldwide correlation.

The recovery of conodonts associated with ash beds and magnetostratigraphy in the key Zhongzhai Section, near Langdai, Liuzhi, Guizhou Province, provides precise and definitive control on the position of the Permian–Triassic boundary in the transition from marine to non-marine facies of western Guizhou and eastern Yunnan Provinces of southwestern China. In the Zhongzhai Section the boundary interval consists of a lower limestone, 20 cm thick, that contains fragments of Hindeodus sp. and Clarkina sp. This is overlain by a 50 cm thick black shale bed containing an abundant brachiopod fauna, but only a single conodont fragment. This bed is in turn overlain by a 23 cm thick limestone that contains Clarkina meishanensis, Merrillina ultima, Hindeodus changxingensis, H. praeparvus and H. eurypyge. Directly over this limestone is a 5 cm thick ash bed followed by a 10 cm thick black shale, which is overlain by a second, upper, ash bed that is 3 cm thick. On top of the upper ash bed is a 20 cm thick silty limestone containing an abundant dwarf conodont fauna, dominated by Hindeodus, and containing H. parvus but also including Clarkina tulongensis. The Permian–Triassic boundary is placed at the level of the black shale located between the two ash beds. © 2007 Elsevier B.V. All rights reserved.

Large conodont samples have been collected from the uppermost Permian and lowermost Triassic (beds 24–29) at the Meishan section — the Global Stratotype Section and Point (GSSP) for the Permian–Triassic Boundary. This new information revises the ranges of some important conodont species in this section. For the first time, usable numbers of Neogondolella specimens have been found from the basal-most Triassic, enabling the establishment of parallel hindeodid and gondolellid zonations through the same section over this interval. In ascending order, the refined hindeodid zones are as follows: Hindeodus latidentatus Zone (bed 24a), Hindeodus praeparvus Zone (24b–26), Hindeodus changxingensis Zone (27a–b), Hindeodus parvus Zone (27c), Isarcicella staeschei Zone (27d–28), Isarcicella isarcica Zone (bed 29 and above). Three revised and newly established Neogondolella zones are proposed. In ascending order these are as follows: Neogondolella yini Zone (bed 24 and below), Neogondolella meishanensis Zone (25–26), Neogondolella taylorae Zone (27a and above). Neogondolella taylorae —a proposed earliest Triassic marker species, first appears in bed 27a, just below specimens of Hindeodus cf. parvus in bed 27b. Three successive conodont faunal assemblages are identified through the Permian–Triassic transitional interval.

The marine conodont fossil species, Hindeodus changxingensis Wang, that has a distinctive morphology, is restricted to a very narrow stratigraphic interval essentially from the Permian–Triassic extinction event through the internationally recognized boundary and into the very earliest Triassic. The species is geographically widespread in the Tethyan Region, from Italy to South China, and serves as a characteristic index fossil to reliably identify this short but critical interval that encompasses the greatest mass extinction of life on earth and the boundary between the Paleozoic and Mesozoic Eras. © 2007 Nanjing Institute of Geology and Palaeontology, CAS. Published by Elsevier Ltd. All rights reserved.

The conodont succession and stratigraphic events around the Permian–Triassic boundary (PTB) have been investigated in detail in the open sea deposits of Iran (Abadeh and Shahreza in central Iran, and Jolfa and Zal in northwestern Iran). This investigation produced a very detailed conodont zonation from the Clarkina nodosa Zone up to the Isarcicella isarcica Zone. All significant events have been accurately located and dated within this zonation, and the duration of most of these conodont zones has been calculated by cross-correlation with continental lake deposits that display obvious Milankovitch cyclicity. The unusually short duration of all conodont zones in the interval from the C. nodosa up to the Hindeodus parvus Zone indicates that there was persistent high ecological stress during this time interval. Most of the conodont zones can be accurately correlated with South China. In the interval from the C. hauschkei Zone to the H. parvus Zone, even correlation with the Arctic is possible. Within three thin stratigraphic intervals, the Changhsingian (Dorashamian) warm water conodont fauna of the C. subcarinata lineage is replaced by a cool water fauna with small H. typicalis, rare Merrillina sp., and cool water Clarkina that have very widely spaced denticles. The uppermost cool water fauna horizon comprises the lower C. zhangi Zone and can be accurately correlated with continental beds by recognition of a short reversed magnetozone below the long uppermost Permian–lowermost Triassic normal magnetozone. In Iran and Transcaucasia, this short reversed zone comprises the upper C. changxingensis–C. deflecta Zone and most of the C. zhangi Zone. Its top lies 50 cm below the top of the Paratirolites Limestone (s.s.) in the Dorasham 2 section, which is at the beginning of the upper quarter of the C. zhangi Zone. In the Germanic Basin, this short palaeomagnetic interval comprises the lower and the basal part of the upper Fulda Formation. On the Russian Platform, the Nedubrovo Formation belongs to this short reversed magnetic interval. In its upper part (corresponding to the top of the lower C. zhangi Zone, see above) there is a fallout of mafic tuffs from the Siberian Trap event that originated about 3000 km away in eruption centres in the Siberian Tungusska Basin. In the Germanic Basin and in Iran, this horizon contains volcanic microsphaerules. Thus, a direct correlation can be made between the immigration of a cool water fauna into the tropical realm and an exceptionally strong interval of explosive activity during the Siberian Trap volcanic episode. These faunal changes are the same as those found at the base of the Boundary Clay, suggesting that a short cooling event at this horizon also was due to intense volcanism. Additional influence by a bolide impact cannot be excluded. Most of the events in the interval from the C. nodosa up to the I. isarcica Zone (upper Changhsingian to middle Gangetian) in the Iranian sections can be also observed in other marine sections (e.g., in Meishan) and even in continental sections of the Germanic Basin. Of particular significance is the fact that, in the investigated Iranian sections, the PTB lies either in red sediments or in light grey sediments (as in Abadeh) that contain an ostracod fauna indicative of highly oxygenated bottom waters. Therefore, anoxia cannot be the reason for the PTB extinction event in this region, even though anoxia does cause locally or regionally elsewhere an overprint on the extinction event.