end permian extinction and subsequent recovery of the ophiuroidea echinodermata a worldwide stratigraphical survey of late palaeozoic and early mesozoic ophiuroids echinodermata reveals unique extinction and recovery patterns during and after the end permian mass extinction event the ophiuroidea suffered the loss of all palaeozoic genera however this clade profited greatly from the event by undergoing a significant increase in species number in the postextinction oceans although both sampling and taphonomic biases may have affected ophiuroid diversity changeover patterns across the permian triassic p tr transition to some extent both biases cannot explain adequately the abrupt increase in species numbers and geographically wide distributions of ophiuroids in the early triassic oceans the ophiuroidea recovery follows erwin s model of a logistic increase in diversity beginning immediately after the end of the mass extinction without the survival interval morphological innovation i e emergence of advanced canal systems diversification of life habitats and biogeographical dispersal over the palaeotethyan and gondwanan regions enabled the ophiuroidea to occupy efficiently vacant ecospace created by the end permian extinction enabling the clade to recover and radiate in the early triassic oceans previously reported ophiuroids from the upper permian to lower triassic of china are also taxonomically revised these ophiaulaxoides bijieensis feng huangzhishania gulinensis feng ophiolepis shanxiensis yang and ophioderma schistovertebrata yang were described from the lower triassic while aganaster qingchangensis feng and syntomospina kaiyangensis feng came from the upper permian

petrologic and zircon u pb geochronological characteristics of the pelitic granulites from the badu complex of the cathaysia block south china abstract the recognition of the indosinian orogeny in the south china block has been controversial and difficult because of strong weathering and thick cover high temperature ht and high pressure hp metamorphic rocks related to this orogeny were considered to be absent from this orogenic belt until the recent discovery of eclogite and granulite facies meta igneous rocks occurring as lenses within the meta sedimentary rocks of the badu complex however metamorphic state of these meta sedimentary rocks is still not clear besides there have been no geochronological data of ht pelitic granulites previously reported from the badu complex this paper presents petrographic characteristics and zircon geochronological results on the newly discovered kyanite garnet gneiss pyroxene garnet gneiss and the ht pelitic granulites sillimanite garnet gneiss mineral assemblages are garnet sillimanite ternary feldspar plagioclase quartz biotite for the ht pelitic granulite kyanite ternary feldspar garnet sillimanite plagioclase quartz biotite for the kyanite garnet gneiss and garnet biotite pyroxene plagioclase ternary feldspar quartz for the pyroxene garnet gneiss respectively decompressional coronas around garnet grains can be observed in all these pelitic rocks typical granulite facies mineral assemblages and reaction textures suggest that these rocks experienced hp granulite facies metamorphism and overprinted decompression along a clockwise p t loop results from integrated u pb dating and ree analysis indicate the growth of metamorphic zircons from depleted heavy ree sources 100 50 chondrite compared with detrital zircons derived from granitic sources typically 1000 chondrite metamorphic zircons in hp granulite exhibit no or subdued negative eu anomalies which perhaps indicate zircon overgrowth under eclogite facies conditions the zircon overgrowth ages range from 250 to 235 ma suggesting that hp granulite eclogite to granulite facies metamorphism of these supracrustal rocks occurred in the early middle triassic based on the presence of hp granulite facies pelitic rocks it is inferred that significant underthrusting was involved during the indosinian orogeny which introduced these supracrustal rocks to lower crustal levels

a newly discovered earliest triassic chert at gaimao section guizhou southwestern china abstract 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

early triassic seawater sulfate drawdown abstract the marine sulfur cycle is intimately linked to global carbon fluxes atmospheric composition and climate yet relatively little is known about how it responded to the end permian biocrisis the largest mass extinction of the phanerozoic here we analyze carbonate associated sulfate cas from three permo triassic sections in south china in order to document the behavior of the c s cycle and its relationship to marine environmental changes during the mass extinction and its aftermath we find that 34 s cas varied from 9 to 44 at rates up to 100 myr 1 during the griesbachian smithian substages of the early triassic we model the marine sulfur cycle to demonstrate that such rapid variation required drawdown of seawater sulfate concentrations to 4 mm and a reduction in its residence time to 200 kyr this shorter residence time resulted in positive covariation with 13 c carb due to strong coupling of the organic carbon and pyrite burial fluxes carbon and sulfur isotopic shifts were associated with contemporaneous changes in climate marine productivity and microbial sulfate reduction rates with negative shifts in 13 c carb and 34 s cas linked to warming decreased productivity and reduced sulfate reduction sustained cooling during the spathian re invigorated oceanic overturning circulation reduced marine anoxia and limited pyrite burial as seawater sulfate built to higher concentrations during the spathian the coupling of the marine c and s cycles came to an end and a general amelioration of marine environmental conditions set the stage for a recovery of invertebrate faunas variation in seawater sulfate during the early triassic was probably controlled by climate change possibly linked to major eruptive phases of the siberian traps

upper lower triassic stromatolite from anhui south china geobiologic features and paleoenvironmental implications abstract widespread stromatolites and other microbialite deposits characterize lower triassic marine successions worldwide this study documents a stromatolite deposit 1 1 m thick from the upper spathian lower triassic of the susong area south china the stromatolite comprises distinct laminated domes in the basal part and columns at the upper part dark laminae are loosely spaced and interlayered with thicker light colored laminae diffusive dark colored laminae are composed of peloidal micrite that grade locally into microclotted structures and yield copies of bacteria clump like and coccoid like spheroid aggregates the former are characterized by cloudy micrite nuclei rimmed by coarse grained euhedral sparry calcite crystals while the latter are comprised of solid calcite crystal nuclei coated with rather thin micrite envelopes the cloudy micrite nuclei resemble bacteria clump like structures observed in present day travertine both the coccoid like spheroids and bacteria clump like structures are surrounded by coarse grained euhedral calcite crystals suggesting a similar accretion mechanism both spherical structures therefore could be crucial in the accretion of the susong stromatolite the laminated microclotted structures are interpreted as the result of variation in timing of lithification relative to the timing of the decay of microbes micro analysis also unravels the common occurrence of authigenic micro quartz crystals in association with fe bearing illite clay minerals in the stromatolite columns their coalescing nature with each other together with the associated pyrite grains strongly support the formation of micro quartz crystals from microbial reduction of an fe bearing smectite precursor by sulfate reducing bacteria a comparison of the susong stromatolite with its counterparts from the upper lower triassic strata in dajiang south china reveals many similarities in stromatolite microstructures suggesting that a harsh euxinic anoxic environment resulting in the bloom of sulfate reducing bacteria most likely extended into the latest spathian in south china

early triassic recovery of the brachiopod faunas from the end permian mass extinction a global review abstract brachiopod faunas in lower triassic deposits from spitzbergen primorye of russia japan mangyslak of kazakhstan alpine europe the caucasus the middle east the himalaya south china new zealand and western usa are taxonomically and stratigraphically reviewed they comprise survivors of the end permian extinction and taxa originating in the early triassic origination of the mesozoic type taxa represents the recovery of early triassic brachiopods the initial recovery of brachiopod faunas began in the late griesbachian and the time interval between the end of extinction and the onset of the recovery of brachiopods is much shorter than previously suspected the early triassic recovery of brachiopod faunas is characterized by widespread brachiopod dispersal multiprovincialism and the presence of rare lazarus genera at that time taxonomic selectivity of the recovery brachiopod faunas favors the rhynchonellids the re population of post extinction brachiopods varies geographically there is a preference for regions either previously barren of latest permian taxa or regions where the pre extinction changhsingian and surviving brachiopods are very rare this unique biogeographic selectivity is probably partly responsible for the impoverished nature of brachiopod faunas in the triassic even mesozoic oceans five intervals of extinction survival survival recovery recovery dispersal and radiation are recognized based on variations in brachiopod faunas from the latest permian to the early triassic a dramatic reduction in brachiopod diversity at the end permian mass extinction is followed by several stepwise declines in diversity in the survival interval the time during which the surviving brachiopods are dominated by geographically widespread generalist faunas that adapted to a wide variety of environments the survival interval was followed by a slow re population of new lineages dominated by progenitor taxa

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

trace fossil evidence for restoration of marine ecosystems following the end permian mass extinction in the lower yangtze region south china abstract unlike the high abundance low diversity macrofaunas that characterize many early triassic benthic palaeocommunities ichnofossils were relatively common in the aftermath of the end permian mass extinction worldwide ichnofossils therefore are a good proxy for ecosystem recovery after the end permian biotic crisis this paper documents 14 ichnogenera and one problematic form from lower triassic successions exposed in the lower yangtze region south china post extinction ichnodiversity remained rather low throughout the griesbachian early smithian period and abruptly increased in the late smithian however several lines of evidence including extent of bioturbation burrow size trace fossil complexity and tiering levels indicate that diversification of ichnotaxa in the late smithian did not signal full marine ecosystem recovery from the permian triassic p tr mass extinction marine ichnocoenoses did not recover until the late spathian in south china the marginal sea provided hospitable habitats for tracemakers to proliferate in the aftermath of the end permian mass extinction

environmental instability prior to end permian mass extinction reflected in biotic and facies changes on shallow carbonate platforms of the nanpanjiang basin south china abstract shallow carbonate platforms exhibit major changes in faunal composition and facies types during the latest permian and earliest triassic although the microbialites that developed following the latest permian mass extinction lpme have attracted wide attention temporal variations in shallow platform facies and faunas prior to the lpme have been less thoroughly studied here we analyze diversity patterns and variation in skeletal composition in three upper permian sections from isolated carbonate platforms of the nanpanjiang basin in addition to the well known transition from fossil rich upper permian limestones to fossil poor permian triassic boundary ptb microbialites these sections exhibit several distinct changes that predate the lpme first foram faunas show a shift from non fusulinid dominated to fusulinid dominated communities in the

unusual shallow marine matground adapted benthic biofacies from the lower triassic of the northern paleotethys implications for biotic recovery following the end permian mass extinction abstract we report two shallow marine ichnofauna bivalve microbial mat biofacies from the lower triassic xiahuancang formation of the southern qilian area qinghai province northwestern china which was located at moderate high paleolatitudes on the northern margin of the paleotethys ocean paleoenvironmental analyses show that members i and ii of the xiahuancang formation represent a shoreface and a lower shoreface to offshore transition setting respectively biofacies 1 recognized from member i is characterized by a diverse ichnofauna including deep tiers of rosselia and diplocraterion claraia dominated bivalves and microbially induced sedimentary structures misss biofacies 2 in succeeding member ii is dominated by a diverse ichnofauna epifaunal and shallow infaunal bivalves and wrinkle structures primary co occurrences preservational features and palimpsest or crosscutting relationships of all components within the biofacies indicate that microbial mats bivalves and trace makers actively interacted with one another during deposition they largely represent contemporaneous biotic associations microbial mats are interpreted to have grown under well oxygenated conditions after storm deposition due to the association of deep tiering infauna and diverse epifauna as well as well developed cross stratification and the top layer of microbial mats could serve as an oasis for metazoans microbial mats not only proliferated in harsh environments but also coexist with epifauna and deep tiering infauna in well oxygenated settings following the end permian crisis their occurrences in the early triassic are unrelated to environmental stresses which are coincident with their sedimentologic record from other geological time intervals apparently the southern qilian ichnofauna bivalve microbial mat biofacies with juxtaposed epifauna infauna and miss or wrinkle related microbial mats represents a matground adapted benthic metazoan ecosystem in the earliest triassic which provided sufficient oxygen food and other hydrodynamic conditions hospitable for metazoans and ecosystems to recover and reached a fairly high level recovery stage 3 in a tough time when most biotas suffered biotic depletion and environmental stress the biotic components in unique biofacies may represent a phase shift community in siliciclastic settings during the early triassic

nanpanjiang basin a window on the tectonic development of south china during triassic assembly of the southeastern and eastern asia abstract as the largest siliciclastic sink in the south china block the triassic nanpanjiang basin is generally thought of as a foreland basin related to indosinian collision between the south china and indochina blocks our basin analysis spanning an eight years period provides details of lopingian to middle triassic stratigraphic fill and tectonic subsidence of the basin field observation and sedimentological analyses reveal that the basin was not filled by a monotonous turbidite system and suggest instead the development of five primary depositional units constituted by deep water turbidite systems mass transport deposits condensed drapes shallow water isolated carbonate platforms and volcano volcaniclastic rocks the stratigraphic completeness of the basin the coexistence of widespread but localized carbonate platforms within axially filled deep water basin tectonically generated cyclothems of transverse mass transport deposits along intrabasinal faults and basin fill of extrusive rocks of bimodal composition together apparently call in question the claim that crustal shortening prevailed during the late permian to pre norian triassic patterns of basin fill differential tectonic subsidence and very high subsidence rate of the region adjacent to master fault are more closely match the pattern expected for extensional to transtensional basin in a back arc setting the crustal extension in the southwestern south china was not consistent with hypothesized indosinian collision between south china and indochina blocks but more likely developed in response to northwestward subduction of the paleo pacific plate our results combined with regional considerations lead to a new model for the triassic tectonic evolution of south china during triassic assembly of the southeastern and eastern asia

quantitative stratigraphic correlation of the lower triassic in south china based on conodont unitary associations abstract 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

halogens cl br and i geochemistry in middle triassic carbonates implications for salinity and diagenetic alteration of i ca mg ratios abstract as an important family of elements halogens cl br and i have been widely used to study geological processes particularly in high temperature environments showing great prospects either in fundamental or in applied studies however little work has been conducted for sedimentary and low temperature diagenetic environments re construction although these elements have the potential in theory here we perform a pilot study on this issue using a case study of middle triassic marine dolomitization in south china our results show that the average cl concentrations in limestone dolomitic limestone calcitic dolomite and dolomite are 88 3 ppm 114 7 ppm 121 3 ppm and 142 9 ppm respectively and the corresponding br concentrations are 1 15 ppm 1 42 ppm 1 59 ppm and 2 13 ppm respectively both the concentrations of cl and br increased with the increasing dolomitization degree the increasing tendency of cl and br is similar to the seawater evaporation trajectory before halite precipitation indicating that dolomitization occurs in fluids with elevated salinity meanwhile the difference of cl br ratios between our carbonate samples and seawater may be ascribed to the input of terrestrial water which has variable cl br ratios as for the concentration of i the mean values sharply decreased from 0 36 ppm in limestone to 0 13 ppm in dolomitic limestone samples and it further lowered to 0 09 ppm and 0 08 ppm in calcitic dolomite and dolomite samples respectively the calculated i ca mg ratios in limestones vary between 0 05 and 0 58 mol mol with an average value of 0 29 mol mol indicating that limestone formed in open ocean oxygen minimum zone omzs or anoxic basin environment the average i ca mg ratio decreases from 0 29 mol mol in limestone to 0 06 mol mol in dolomite serving as an important case that dolomitization decreases i ca mg ratios of carbonates rocks halogens in carbonates therefore have promising potential for investigating the sedimentary and diagenetic environments of carbonate rocks

tectonics and history of the andaman sea region abstract the andaman sea is an active backarc basin lying above and behind the sunda subduction zone where convergence between the overriding southeast asian plate and the subducting australian plate is highly oblique the effect of the oblique convergence has been formation of a sliver plate between the subduction zone and a complex right lateral fault system the late paleocene collision of greater india and asia with approximately normal convergence started clockwise rotation and bending of the northern and western sunda arc the initial sliver fault which probably started in the eocene extended through the outer arc ridge offshore from sumatra through the present region of the andaman sea into the sagaing fault with more oblique convergence due to the rotation the rate of strike slip motion increased and a series of extensional basins opened obliquely by the combination of backarc extension and the strike slip motion these basins in sequence are the mergui basin starting at 32 ma the conjoined alcock and sewell rises starting at 23 ma east basin separating the rises from the foot of the continental slope starting at 15 ma and finally at 4 ma the present plate edge was formed alcock and sewell rises were separated by formation of the central andaman basin and the faulting moved onshore from the mentawai fault to the sumatra fault system bisecting sumatra

conodont biostratigraphy across the permian triassic boundary at the dawen section great bank of guizhou guizhou province south china implications for the late permian extinction and correlation with meishan 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

early triassic induan olenekian conodont biostratigraphy global anoxia carbon isotope excursions and environmental perturbations new data from western australian gondwana the early triassic induan olenekian stage boundary dienerian smithian sub stage boundary has been identified at a depth of 2719 25m in the petroleum exploration well senecio 1 located in the northern perth basin western australia conodont faunas represent three conodont zones in ascending order the neospathodus dieneri zone the neospathodus waageni eowaageni zone and the neospathodus waageni waageni zone the induan olenekian dienerian smithian boundary is placed at the base of the neospathodus waageni eowaageni zone equivalent to the first appearance of neospathodus ex gr waageni utilised elsewhere and adopted by the iugs ics triassic subcommission to define the base of the olenekian bulk kerogen 13c carbon isotopes define a positive peak of c 4 per mille that essentially coincides with the induan olenekian boundary as seen in proposed global stratotype sections and points gssps in south china and spiti india demonstrating the global utility of this level for correlation an anoxic zone is recognised in the lower part of the senecio 1 core and the upper limit of this zone is dated as late induan late dienerian temporal and spatial mapping of marine anoxia and dysoxia globally demonstrates that pulses of dysoxia anoxia affected shallow marine zones at different times in different locations dysoxia anoxia in the shallow marine environment appeared in the latest permian at the extinction level later than in the deep marine environment and appears to be largely restricted to the induan griesbachian and dienerian and early olenekian smithian temporally and geographically restricted upwelling of an oxygen minimum zone into the ocean surface layer due to environmental perturbations including extreme global warming increased terrestrial chemical weathering intensity and continental erosion sea level rise and changes in marine nutrient inventories and productivity rates is interpreted as a likely cause of observed variation in shallow marine dysoxia anoxia in the early triassic

global correlations of mid early triassic events the induan olenekian boundary in the dolomites italy abstract the dolomites southern alps italy are a reference area for research on the end permian mass extinction and its early triassic aftermath the effects on shallow marine benthic biota are recorded in the werfen formation a thick mixed carbonate siliciclastic sedimentary succession only in its lower griesbachian and upper spathian parts this formation is bio chronologically constrained by means of conodonts and ammonoids whilst no significant bioevent occurs in its middle part this represents an impediment to the biochronologic recognition of the induan olenekian boundary iob the bulla pufels val gardena succession is a key section for the p t boundary and early triassic for global correlation due to the abundance of studies on biostratigraphy mostly on conodonts magnetostratigraphy and chemostratigraphy carried out there by stratigraphers of various nationalities recent chemostratigraphic studies have permitted the recognition of some carbon isotope positive peaks the strongest of which is considered to approximate the iob however various authors have reached different conclusions on the position of the maximum peak and thus on the iob location this leads to important stratigraphic consequences for the calibration of conodont biostratigraphy the critical revision of the traditional stratigraphic units litho and biostratigraphy under evaluated in most of the recent literature and magneto chemo and sequence stratigraphic units allowed herein an integrated stratigraphic scale for the bulla pufels section to be proposed this contribution highlights the mid early triassic dolomites record for regional and global correlations the most significant results attained herein regard the different lithostratigraphic subdivisions of the middle werfen formation and its consequences on the position of the iob with respect to the conodont and bivalve biostratigraphy and sequence stratigraphic units the upper part of the section is attributed herein to the gastropod oolite member which is represented by the lithozone a a predominant supratidal episode and the lower part of the subtidal lithozone b between the lithozones a and b a sequence boundary of 3th order sc2 sc3 is located the maximum carbon isotope excursion is near this boundary which therefore approximates the iob in the dolomites this proposal suggests a dienerian age for the fo of the conodont pachycladina obliqua which occurs about 60 m below the stage boundary no significant biotic event either for molluscs or conodonts occurred across this stage boundary

detrital provenance of early mesozoic basins in the jiangnan domain south china paleogeographic and geodynamic implications abstract detrital provenance analysis is an effective way to understand paleogeographic change and geodynamics in this paper we present petrological whole rock geochemical and detrital zircon u pb geochronological analysis of early and middle jurassic terrestrial clastic rocks in the jingdezhen basin and the huangshan basin in the jiangnan domain south china petrology and whole rock geochemistry show that the source rocks are dominated by intermediate to acid component the chemical index of alteration ranges from 69 to 86 suggesting a moderate weathering history for the source rocks the early middle jurassic sediments in the jingdezhen and huangshan basins were mostly sourced from magmatogenic greywackes and felsic magmatic rocks respectively detrital zircons have seven age peaks at 240 ma 430 ma 1390 ma 1880 ma 2500 ma 3200 ma and 788 999 ma a wide peak provenance analysis indicates that the source rocks are in the jiangnan domain the northwest zhejiang basin and the wuyishan domain combining these with previous results and paleocurrent directions we infer that the ne trending wuyishan and xuefengshan domains and the nearly e w jiangnan domain and nanling tectonic belt were orogenic uplifts and watersheds during the late triassic to middle jurassic the early mesozoic geodynamics in the south china block was related to the westward subduction of the paleo pacific plate and the northward continent continent collision following the closure of the paleo tethys ocean

early triassic calcimicrobial mounds and biostromes of the nanpanjiang basin south china stanley s model 1988 proposed that a permiantype reef fauna survived the early triassic reefless period in yet undiscovered refuges in the ancestral pacific ocean and then reappeared as the builders of middle triassic reefs flugel 1994 in contrast suggested that the middle triassic reefbuilding fauna are not holdovers from the permian but bear only a superficial resemblance to permian fossils recent publications reflect a consensus that the early triassic lacked reefs and reef mounds although some authors acknowledged the possibility that reef like structures may have existed in poorly explored areas such as south china and russia senowbari daryan et al 1993 flugel 1994 it is shown herein that calcimicrobial framework mounds and biostromes existed in the early triassic in the nanpanjiang basin of south china organic framework in this paper refers to a three dimensional biologically constructed network of calcified fossils that forms a rigid mass and supports an interconnected network of internal cavities that were open during accumulation although the calcimicrobial frameworks discussed herein are much smaller than frameworks of modern metazoan reefs the term framestone is more appropriate for these fabrics than other reef rock terms such as bindstone or bafflestone embry and klovan 1971 these calcimicrobial mounds and biostromes are important as the first organic framestones documented from the early triassic

lithofacies architecture and reservoir heterogeneity of tidal dominated platform marginal oolitic shoal an analogue of oolitic reservoirs of lower triassic feixianguan formation sichuan basin sw china abstract the yudongliang outcrop located in the northern part of the sichuan basin nicely exposes oolitic shoal complexes of the lower triassic feixianguan formation the outcrop is an analogue for the subsurface longgang and yuanba gas fields and other permo triassic reservoirs with dolomitized and nondolomitized oolite dominated grainstone bodies as the main producing zones based on five measured sedimentological sections and petrographic and petrophysical analysis of 200 plugs the architecture of the reservoir bodies has been reconstructed in detail and placed within a high frequency sequence stratigraphic framework the studied interval belongs to the highstand system tract hst of a single composite sequence and comprises three shallowing upward high frequency sequences which consist from base to top of oncoid peloid ooid grain dominated packstone cross bedded ooid grainstone dolograinstone fenestra laminated dolomite and crystalline dolomite the internal architecture of the oolitic shoal is the result of complex tidal dominated hydrodynamics facies and diagenetic partitioning with each high frequency sequence are the primary controls on pore types and reservoir properties original lithofacies texture and subsequent cementation resulted in interbedded thin effective reservoirs and permeability barriers that created a complex internal architecture of reservoir bodies the shapes of reservoir bodies generally follow those of the lithofacies but with the addition of intercalated thin flow barriers

environmental controls on marine ecosystem recovery following mass extinctions with an example from the early triassic abstract the recovery of marine ecosystems following a mass extinction event involves an extended interval of increasing biotic diversity and ecosystem complexity the pace of recovery may be controlled by intrinsic ecosystem or extrinsic environmental factors here we present an analysis of changes in marine conditions following the end permian mass extinction with the objective of evaluating the role of environmental factors in the protracted 5 myr long recovery of marine ecosystems during the early triassic specifically our study examines changes in weathering productivity and redox proxies in three sections in south china chaohu daxiakou and zuodeng and one in northern india mud our results reveal 1 recurrent environmental perturbations during the early triassic 2 a general pattern of high terrestrial weathering rates and more intensely reducing marine redox conditions during the early griesbachian late griesbachian mid smithian and more weakly the mid spathian 3 increases in marine productivity during the aforementioned intervals except for the early griesbachian and 4 stronger and more temporally discrete intervals of environmental change in deepwater sections chaohu and daxiakou relative to shallow and intermediate sections zuodeng and mud our analysis reveals a close relationship between episodes of marine environmental deterioration and a slowing or reversal of ecosystem recovery based on metrics of biodiversity within community alpha diversity infaunal burrowing and ecosystem tiering we infer that the pattern and pace of marine ecosystem recovery was strongly modulated by recurrent environmental perturbations during the early triassic these perturbations were associated with elevated weathering and productivity fluxes implying that nutrient and energy flows were key influences on recovery more regular secular variation in deepwater relative to shallow water environmental conditions implies that perturbations originated at depth i e within the oceanic thermocline and influenced the ocean surface layer irregularly finally we compared patterns of environmental disturbance and ecosystem recovery following the other four big five phanerozoic mass extinctions to evaluate whether commonalities exist in general the pace of ecosystem recovery depends on the degree of stability of the post crisis marine environment

structural and stratigraphical constraints on the kinematics history of the southern tan lu fault zone during the mesozoic anhui province china abstract the tan lu fault zone tlfz extends in a nne ssw direction for more than 2000 km in eastern china it has been considered either as a major sinistral strike slip fault as a suture zone or as a normal fault we have conducted a structural analysis of the southern segment of this fault zone stlfz in the anhui province the ages triassic to palaeocene of the formations affected by the faults have been re appraised taking into account recent stratigraphical studies to better constraint the ages of the successive stages of the kinematics of the stlfz subsequently the kinematics of the faults is presented in terms of strain stress fields by inversion of the striated fault set data finally the data are discussed in the light of the results obtained by previous workers we propose the following history of the stlfz kinematics during the mesozoic at the time of collision a nne orientated tan lu margin probably connected two margins located north of the dabie and sulu collision belts during the middle late triassic the scb has been obliquely subducted below the ncb along this margin which has acted as a compressional transfer zone between the dabie and sulu continental subduction zones the stlfz has been initiated during the early jurassic and has acted as a sinistral transform fault during the jurassic following which the ncb scb collision stopped a nw trending extension related to metamorphic domes was active during the basal early cretaceous 135 130 ma it has been followed by a nw se compression and a ne sw tension during the middle late early cretaceous 127 to 105 ma possibly 95 ma at that time the tlfz was a sinistral transcurrent fault within the eastern part of the asian continent during the late cretaceous palaeocene the stlfz was a normal fault zone under a wnw ese tension

the lower triassic of south china abstract the permian triassic boundary of south china has been well known and well studied for decades but what is relatively less noticed is that there are also many excellent marine lower triassic sequences in the region covering various paleogeographic lithofacies this paper presents an outline of the various lower triassic stratigraphic sequences in south china and provides a reference to the application of the lower triassic subdivision and stages the early triassic marine basin of south china is subdivided into five sedimentary provinces cathaysia lower yangtze upper yangtze youjiang and lijiang provinces each province has an interrelated distribution of lithofacies and stratigraphy the lower triassic biostratigraphic sequences of bivalves ammonoids and conodonts are summarized in the various sedimentary facies and provinces of south china the chinese twofold subdivision of the lower triassic is primarily demonstrated as well in this paper

upper ocean turbulence during a westerly wind burst a comparison of large eddy simulation results and microstructure measurements the response of the upper ocean to westerly wind forcing in the western equatorial pacific was modeled by means of large eddy simulation for the purpose of comparison with concurrent microstructure observations the model was initialized using currents and hydrography measured during the coupled ocean atmosphere response experiment coare and forced using measurements of surface fluxes over a 24 h period comparison of turbulence statistics from the model with those estimated from concurrent measurements reveals good agreement within the mixed layer the shortcomings of the model appear in the stratified fluid below the mixed layer where the vertical length scales of turbulent eddies are limited by stratification and are not adequately resolved by the model model predictions of vertical heat and salt fluxes in the entrainment zone at the base of the mixed layer are very similar to estimates based on microstructure data

early triassic estuarine depauperate cruziana ichnofacies from the sichuan area of south china and its implications for the biotic recovery in brackish water settings after the end permian mass extinction abstract new ichnological data from the lower triassic induan dongchuan formation longmendong south china record the recovery interval of marginal marine communities following the end permian mass extinction here we document six ichnogenera from the upper part of the dongchuan formation of dienerian early triassic age in the longmendong area sichuan province south china these are cylindrichnus diplocraterion palaeophycus planolites siphonichnus and teichichnus illustrating a depauperate cruziana ichnofacies facies analysis suggests that the depauperate cruziana ichnofacies is present in deposits recording the transition from fluvial to tide dominated estuarine settings compilation of worldwide brackish water ichnofaunas from permian average alpha ichnodiversity 6 2 to triassic average alpha ichnodiversity 5 5 suggests that no significant ichnodiversity decrease took place in these settings as a result of the mass extinction and further implies that the impact of the mass extinction may have been less severe in marginal marine settings ichnofaunas in pre and post extinction marginal marine environments are remarkably similar and tend to be dominated by facies crossing ichnotaxa e g diplocraterion palaeophycus planolites produced by opportunistic faunas

biochronology of triassic bivalves substantial advances by numerous researchers over the past 20 years have made it possible to develop a composite biochronological scheme for the triassic based on the bivalves claraia peribositria enteropleura daonella halobia eomonotis and monotis these bivalves exhibit temporal durations nearly equal to ammonoids and conodonts widely distributed across the tethys panthalassa and boreal regions these bivalves occur in a wide variety of marine facies and water depths but are most notable for their thick shell accumulation in deeper water oxygen deficient environments they were most likely resting or reclining benthos may have housed chemosymbionts and were part of episodic opportunistic palaeocommunities in or near oxygen deficient settings a new biochronological zonation for bivalves is presented that encompasses the entire triassic and is integrated with standard ammonoid schemes the lower triassic is characterized by 2 3 zones of claraia most notably from the eastern tethys representing the entire induan and lower portion of the olenekian later in the olenekian and most notably from the boreal realm species of peribositria included by some workers within bositra provide useful zonal indexes the middle triassic is well represented by enteropleura middle anisian and daonella upper anisian through ladinian in the tethys and north america with significant occurrences through out the circum pacific and boreal realms the upper triassic can be subdivided into 8 13 bivalve zones based on the succession of halobia eomonotis and monotis sensu lato species with best representation in the tethys boreal and eastern panthalassa regions

evaluation of paleomarine redox conditions using mo isotope data in low mo sediments a case study from the lower triassic of south china abstract 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 98mo values of ca 0 4 to 0 1 recording detrital mo isotopic compositions toward 98mo values as high as 2 3 0 2 based on an analysis of local redox proxies versus 98mo as well as of sample to sample variance in 98mo values we conclude that only one of the six reducing intervals in the study section is likely to record contemporaneous seawater 98mo as a result of quasi quantitative mo uptake i e the interval from the hindeodus typicalis conodont zone close to the ptb for which 98mo 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 98mo 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

onset of biotic and environmental recovery from the end permian mass extinction within 1 2 million years a case study of the lower triassic of the meishan section south china abstract paleontological sedimentary and geochemical data obtained from the lower triassic strata of the meishan section south china suggest that onset of biotic recovery coincided with amelioration of paleoceanographic conditions and an increase in ocean productivity the griesbachian meishanorhynchia association from meishan indicates biotic recovery between the recovery stages 1 and 2 both the initial biotic recovery and palaeoceanic environmental amelioration occurred within 1 2 myr after the end permian mass extinction in the late griesbachian

late early triassic climate change insights from carbonate carbon isotopes sedimentary evolution and ammonoid paleobiogeography the late early triassic sedimentary facies evolution and carbonate carbon isotopemarine record 13ccarb of ammonoid rich outer platform settings show striking similarities between the south china block scb and the widely distantnorthern indianmargin nim the studied sections are located within the triassic tethyshimalayan belt losar section himachal pradesh india and the nanpanjiang basin in the south china block jinya section guangxi province respectively carbon isotopes from the studied sections confirm the previously observed carbon cycle perturbations at a time of major paleoceanographic changes in the wake of the end permian biotic crisis this study documents the coincidence between a sharp increase in the carbon isotope composition and the worldwide ammonoid evolutionary turnover extinction followed by a radiation occurring around the smithian spathian boundary based on recent modeling studies on ammonoid paleobiogeography and taxonomic diversity we demonstrate that the late early triassic smithian and spathian was a time of a major climate change more precisely the end smithian climate can be characterized by a warm and equable climate underlined by a flat pole to equator sea surface temperature sst gradient while the steep spathian sst gradient suggests latitudinally differentiated climatic conditions moreover sedimentary evidence suggests a transition froma humid and hot climate during the smithian to a dryer climate fromthe spathian onwards by analogywith comparable carbon isotope perturbations in the latedevonian jurassic andcretaceouswe propose that high atmosphericco2 levels could have been responsible for the observed carbon cycle disturbance at the smithian spathian boundary we suggest that the end smithian ammonoid extinction has been essentially caused by a warm and equable climate related to an increased co2 flux possibly originating froma short eruptive event of the siberian igneous province this increase in atmospheric co2 concentrations could have additionally reduced the marine calcium carbonate oversaturation and weakened the calcification potential of marine organisms including ammonoids in late smithian oceans

milankovitch and sub milankovitch cycles of the early triassic daye formation south china and their geochronological and paleoclimatic implications 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 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 13 c shift from high 13