climate warming in the latest permian and the permian triassic mass extinction high resolution oxygen isotope records document the timing and magnitude of global warming across the permian triassic p tr boundary oxygen isotope ratios measured on phosphate bound oxygen in conodont apatite from the meishan and shangsi sections south china decrease by 2 in the latest permian translating into low latitude surface water warming of 8 c the oxygen isotope shift coincides with the negative shift in carbon isotope ratios of carbonates suggesting that the addition of isotopically light carbon to the ocean atmosphere system by siberian traps volcanism and related processes resulted in higher greenhouse gas levels and global warming the major temperature rise started immediately before the main extinction phase with maximum and harmful temperatures documented in the latest permian meishan bed 27 the coincidence of climate warming and the main pulse of extinction suggest that global warming was one of the causes of the collapse of the marine and terrestrial ecosystems in addition very warm climate conditions in the early triassic may have played a major role in the delayed recovery in the aftermath of the permian triassic crisis

timing of recovery from the end permian extinction geochronologic and biostratigraphic constraints from south china four volcanic ash beds bracket the early middle triassic boundary as defined by conodont biostratigraphy in a stratigraphic section in south china high precision u pb dates of single zircons allow us to place the early to middle triassic olenekian anisian boundary at 247 2 ma magnetic reversal stratigraphy allows global correlation the new dates constrain the early triassic interval characterized by delayed biotic recovery and carbon cycle instability to 5 m y this time constraint must be considered in any model for the end permian extinction and subsequent recovery

stromatolites near the permian triassic boundary in chongyang hubei province south china a geobiological window into palaeo oceanic fluctuations following the end permian extinction abstract stromatolites just after the end permian extinction are exceptionally well developed in the chongyang area of hubei province south china the stromatolites include endolithic coccoidal microbes and exhibit three growth forms columnar layered pseudo columnar and columnar each located in different stratigraphic horizons the columnar type is the most conspicuous and provides key information on the mode of their construction in this paper we describe the mega to microscopic features of these stromatolites together with interpretations of their construction the columnar type typically comprises alternations of lighter and darker laminae with intercalations of dense micritic laminae the lighter laminae are composed of fine to coarse calcite cement and fine dolomite whereas the darker laminae are composed of micrite and microspar endolithic coccoids are sporadic in these laminae in contrast the dense micritic laminae consist of micrite with abundant endolithic coccoids accentuating the laminae of stromatolites the columnar stromatolites were formed under deteriorating conditions after the end permian mass extinction as follows 1 the alternating development of lighter and darker laminae due to the colonization of different microbial communities in lower energy shallow to deep subtidal settings 2 carbonate precipitation within each microbial community through microbial metabolic activity and degradation of extracellular polymeric substances eps leading to the alternations of lighter and darker laminae 3 episodic interruption of the growth of the lighter and darker laminae by endolithic coccoidal activity and 4 high levels of endolithic activity accompanied by the precipitation of carbonate within boreholes to produce the dense micritic laminae in contrast the columnar layered and pseudo columnar types comprise alternations of lighter and darker laminae composed mainly of fine to coarse calcite cement fine dolomite micrite peloids and microspar with sporadic endolithic coccoids the dense micritic laminae are absent or rare in these stromatolites these types were essentially produced by the repetition of processes 1 and 2 documented in the columnar type the finely alternating laminae of these stromatolites are therefore the product of the repeated initiation and cessation of growth of relevant microbial communities in response to changing environmental conditions the stromatolites were formed immediately after the end permian extinction and persisted intermittently throughout the early triassic the chongyang stromatolites are undoubtedly some of the best developed stromatolites near the permian triassic boundary and retain a high resolution record of microbial successions and palaeo oceanic perturbations immediately following the end permian extinction

the terrestrial end permian mass extinction in south china abstract the end permian mass extinction reflects the most severe life crisis during the phanerozoic and was associated with major global environmental changes however the consistency of the time and pattern of the terrestrial and marine extinctions remains controversial in this paper we presented detailed analyses of the high resolution biostratigraphical and geochemical data from terrestrial sections in south china our analyses show that the transitional kayitou formation actually recorded the process of terrestrial mass extinction as evidenced by the mass disappearance of the gigantopteris megaflora in the lower part the dramatic reduction in abundance of palynomorphs in the middle and the last occurrences of plant remains and abundant charcoal fossils in the uppermost part it is associated with a distinct negative shift of 13corg beginning in the middle part of the formation which is correlative with that in the top of bed 26 at the marine meishan section in addition the kayitou formation is characterized by a distinct shift of lithofacies of fresh lake swamp or river flat environment from olive grey black mudstone siltstone fine to coarse sandstone in the lower part to gradually increasing maroon rocks to purely maroon mudrocks with poorly sorted breccia calcic palaeosols and calcareous nodules in the lowest part of the dongchuan formation which indicates a dramatic collapse of soil system associated with rapid deforestation and climatic warming and drying in the coastal area the kayitou formation contains marine beds with the typical permian triassic mixed faunas and floras which are correlative with the latest changhsingian marine mixed fauna 1 at meishan the kayitou formation also recorded a distinct transgression that began in the latest changhsingian all above phenomena suggest that the kayitou formation is actually the witness of the terrestrial end permian mass extinction and it is mostly or entirely of latest changhsingian permian rather than triassic age

productivity or preservation the factors controlling the organic matter accumulation in the late katian through hirnantian wufeng organic rich shale south china abstract the wufeng organic rich shale is widespread in the upper yangtze platform and it is one of the most advantageous shale gas producers in china its deposition commenced with the onset of the boda warming event in the late katian and terminated at the hirnantian glacial maximum the depositional mechanism of the wufeng formation was poorly understood owing to its relatively thin thickness being interpreted as the result of organic matter om accumulation in a shelf setting under anoxic conditions this study integrated detailed geochemical analyses based on the core samples from three boreholes which are located in the outer middle and inner shelf of the upper yangtze platform in order to investigate the depositional environments during the deposition of the wufeng formation geochemical redox proxies mo ef u ef and v cr and productivity proxies p baxs sixs indicate that the deposition of the wufeng formation was associated with four intervals wf1 to wf4 each characterized by its unique geochemical features related to sea level fluctuations black siliceous mudstones deposited during wf1 and wf2 are relatively organic lean due to low productivity less favorable preservation conditions and terrestrial dilution whereas black siliceous mudstone deposited during wf3 and wf4 is organic rich due to high paleoproductivity and conducive preservation conditions the geochemical proxies cd mo co x mn associated with the modern upwelling settings were replicated in the wufeng formation revealing that the outer shelf of the upper yangtze platform was dominated by persistent upwelling the upwelling driven primary productivity is considered as the first order control for the om enrichment at the outer shelf of the upper yangtze platform seasonal upwelling may influence the middle shelf of the upper yangtze platform where both primary productivity and preservation played essential roles in the om accumulation in contrast the om accumulation at the inner shelf was fundamentally driven by good preservation conditions

oceanic redox evolution across the end permian mass extinction at shangsi south china abstract the end permian mass extinction epme was the most severe extinction event of the phanerozoic to investigate oceanic redox conditions around the epme we conducted a series of geochemical analyses including iron speciation trace element geochemistry total organic carbon toc and nitrogen isotopes of kerogen 15nkero around the epme at the shangsi section south china three intervals with different redox conditions can be distinguished based on iron speciation during the first interval early and middle changhsingian bottom waters were pervasively euxinic in the second interval late changhsingian and the epme bottom water fluctuated between oxic and anoxic but non sulfidic conditions with the oxic mode becoming increasingly predominant over time during the third interval following the epme bottom waters appeared to have been consistently anoxic although again not pervasively euxinic this redox history is supported by enrichments in the authigenic fraction of redox sensitive elements these relatively high 15nkero values 1 0 corresponding with changhsingian euxinia suggest reducing bottom waters did not impinge on the photic zone the shift to values near 0 within and above the epme indicates an ecological expansion of diazotrophs stratigraphic trends of nixs cdxs pxs and toc indicate that primary productivity was highest in the first interval coinciding with euxinic bottom water then decreased during the lower part of interval 2 and remained at low level through the remainder of the studied section the temporal relationship between redox condition and primary productivity suggests that euxinia was supported by high productivity and carbon export in the early changhsingian the expansion of n2 fixation coincides closely with the previously documented warming of the ocean surface at shangsi and may be related to reduced oceanic circulation and suppressed vertical mixing the temporal distribution of deepwater anoxia and euxinia suggests that they were not primary causes for the extinction of benthos at shangsi

progressive environmental deterioration in northwestern pangea leading to the latest permian extinction stratigraphic records from northwestern pangea provide unique insight into global processes that occurred during the latest permian extinction lpe we examined a detailed geochemical record of the festningen section spitsbergen a stepwise extinction is noted as starting with 1 loss of carbonate shelly macrofauna followed by 2 loss of siliceous sponges in conjunction with an abrupt change in ichnofabrics as well as dramatic change in the terrestrial environment and 3 final loss of all trace fossils we interpret loss of carbonate producers as related to shoaling of the lysocline in higher latitudes in relationship to building atmospheric co 2 the loss of siliceous sponges is coincident with the global lpe event and is related to onset of high loading rates of toxic metals hg as co that we suggest are derived from siberian trap eruptions the final extinction stage is coincident with redox sensitive trace metal and other proxy data that suggest onset of anoxia after the other extinction events these results show a remarkable record of progressive environmental deterioration in northwestern pangea during the extinction crises

the beginning of the buntsandstein cycle early middle triassic in the catalan ranges ne spain sedimentary and palaeogeographic implications abstract the early middle triassic siliciclastic deposits of the catalan ranges ne spain are dominated by aeolian sediments indicating a predominance of arid climate during this time span in sharp contrast with the coeval fluvial sediments found in the castilian branch of the iberian ranges 300 km to the sw the ne sw oriented catalan basin evolved during the middle late permian as the result of widespread extension in the iberian plate this rift basin was bounded by the pyrenees ebro and montalban oropesa highs the permian early triassic age sediments of the catalan basin were deposited in three isolated subbasins montseny garraf prades separated by intrabasinal highs but linked by transversal nw se oriented faults the three subbasins show evidence of diachronic evolution with different subsidence rates and differences in their sedimentary records the buntsandstein sedimentary cycle started in the late early triassic smithian spathian in the central and southern domains garraf and prades with conglomerates of alluvial fan origin followed by fluvial and aeolian sandstones source area of the fluvial sediments was nearby paleozoic highs to the north and west in contrast with the far away source areas of the fluvial sediments in the iberian ranges to the sw these fluvial systems were interacting with migrating aeolian dune fields located towards the s which developed in the shadow areas behind the barriers formed by the paleozoic highs these highs were separating the subbasins under arid and semi arid climate conditions the dominating winds came from the east where the westernmost coast of the tethys sea was located and periods of water run off and fields of aeolian dunes development alternated some of the fluvial systems were probably evaporating as they were mixed into the interdune areas never reaching the sea from the end of the smithian to the spathian the catalan basin and neighbour peri tethys basins of the present day southern france sardinia and minorca islands constituted a geographical arch where arid and semi arid conditions represented an extension of the prevailed arid and hyper arid conditions in surrounding areas of the variscan belt harsh climatic conditions in this area prevented the life recovery in the aftermath of the permian triassic extinction event until the early anisian when more humid climate allowed for the colonisation of the area by plants amphibians and reptiles the boundary between desert areas and semi arid and or seasonal climate domains during the smithian spathian in sw europe can be precisely established in ne iberia between the catalan ebro region and the castilian branch of the iberian ranges to the sw

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

mercury deposition through the permo triassic biotic crisis abstract a 6 7 million year record of marine sedimentation through the permo triassic biotic crisis shows notable shifts in mercury concentrations that varied over an order of magnitude 0 002 to 0 116 g g mercury concentrations correlate strongly with total organic carbon showing both parallel increasing and decreasing trends over geologic time scales results suggest that changes in bioproductivity strongly influence mercury sequestration into marine sediment this may provide insight to potential marine response to modern anthropogenic hg loading and supports models that suggest enhanced bioproductivity that due to recent climate has increased hg sequestration over time

lithofacies and depositional mechanisms of the ordovician silurian wufeng longmaxi organic rich shales in the upper yangtze area southern china the ordovician silurian organic rich shales in the wufeng and longmaxi formations are widespread in southern china and are the most important shale gas producers in china the shales display varying total organic carbon content ranging from 0 2 to 6 and are composed of black siliceous mudstone shelly limestone siliceous clay rich mudstone gray silty shaly interlaminated mudstone gray argillaceous mudstone and calcareous or dolomitic mudstone detailed stratigraphic correlation of these formations was achieved and a high resolution sequence stratigraphy was constructed based on the integration of well log data mineralogical geochemical and petrophysical analyses the wufeng formation and the guanyinqiao bed were interpreted to be a condensed section with four cycles of sea level fluctuation the longmaxi formation consists of three members the long 1 member was interpreted to be a third order depositional sequence that can be subdivided into a transgressive systems tract an early highstand systems tract and a late highstand systems tract within the constructed isochronal stratigraphic framework the characteristics and genetic mechanism of different shale lithofacies were studied the deposition of black siliceous mudstone of high total organic carbon in the wufeng formation and the long 1 transgressive systems tract was likely influenced by volcanic activity the guanyinqiao shelly limestone or calcareous mudstone was associated with the ordovician silurian transition when glaciation and mass extinction took place the gray silty shaly interlaminated mudstone of moderate total organic carbon in the long 1 early highstand systems tract was the product of bottom flow intrusion the deposition of gray argillaceous mudstone and calcareous or dolomitic mudstone with low total organic carbon in the long 1 late highstand systems tract resulted from enhanced terrigenous input from peripheral uplifts the distribution pattern of different lithofacies varies greatly in the upper yangtze area and this difference is a result of dissimilar sediment provenances and variable hydraulic restriction levels that were controlled by basin geometry a better understanding of the distribution pattern and depositional history of the wufeng and longmaxi formations might provide guidance for future profitable shale gas exploration

sources of sr and s in aluminum phosphate sulfate minerals in early middle triassic sandstones iberian ranges spain and paleoenvironmental implications for the west tethys aluminum phosphate sulfate aps minerals formed during early diagenesis in relation to acid meteoric waters are the main host of sr and s in the early middle triassic continental sandstones of the iberian ranges east of the iberian peninsula the sources of these elements and the effects of paleoenvironmetal changes on these sources and on the formation of aps minerals during early middle triassic times were established on the basis of sr and s isotopic analyses the s and sr data d34s v cdt 11 to 14 and 87sr 86sr 0 7099 0 7247 respectively can be interpreted as resulting from mixing of different sources strontium was sourced from the dissolution of pre existing minerals like k feldspar and clay minerals inherited from the source areas causing high radiogenic values however the isotopic signal must also be influenced by other sources such as marine or volcanic aerosol that decreased the total 87sr 86sr ratios marine and volcanic aerosols were also sources of sulfur but the d34s was lowered by dissolution of pre existing sulfides mainly pyrite pyrite dissolution and volcanic aerosols would also trigger the acid conditions required for the precipitation of aps minerals aps minerals in the study area are found mainly in the canizar formation olenekian aegian which has the lowest 87sr 86sr ratios the lower abundance of aps minerals in the eslida formation aegian pelsonian may indicate change in the acidity of pore water towards more alkaline conditions while the increased 87sr 86sr ratios imply decreased sr input from volcanic activity and or marine aerosol inputs during anisian times therefore the decrease in abundance of aps minerals from the early to middle triassic and the variations in the sources of sr and s are indicative of changes in paleoenvironmental conditions during the beginning of the triassic period these changes from acid to more alkaline conditions are also coincident with the first appearance of carbonate paleosols trace fossils and plant fossils in the upper part of the canizar formation and more in the overlying eslida formation and mark the beginning of biotic recovery in this area the presence of aps minerals in other european basins of the western tethys such as the german basin the paris basin and the southeastern france and sardinia basins could thus also indicate that unfavorable environmental conditions caused delay in biotic recovery in those areas in general the presence of aps minerals may be used as an indicator of arid acidic conditions unfavorable to biotic colonization

extreme euxinia just prior to the middle triassic biotic recovery from the latest permian mass extinction abstract the greatest mass extinction on earth occurred 252 million years ago during the latest permian complete biotic recovery characterized by a return to pre extinction diversity levels took an extraordinarily long time ca 5 10 6 yr probably because harsh conditions developed repeatedly during the early triassic here we show the recurrence of euxinic conditions during the early triassic and the development of especially severe such conditions during the late early triassic just prior to full biotic recovery from the mass extinction dibenzothiophenes and carotenoids accumulated in upper lower triassic sediments from south china located on the western margin of the paleotethys ocean among these chlorobactane a biomarker for green pigmented green sulfur bacteria and okenane a biomarker for purple sulfur photosynthetic bacteria were identified in upper early triassic samples both compounds were detected in limestone micrite and we therefore infer that planktonic green and purple sulfur bacteria were the sources of these carotenoids and that their presence indicates photic zone euxinia at the time of deposition concentrations of redox sensitive elements m v and u relative to that of al and the u th ratio progressively increased during the late early triassic the euxinic conditions represented by the carotenoids and the elements were likely caused by a combination of locally shallow restricted conditions and global environmental oscillations such as those related to global warming during the late early triassic the presence of these biomarkers together with the increase in the abundance of redox sensitive elements relative to al and the u th suggests that euxinic conditions could be one of the causes for the delayed recovery of marine communities in the paleotethys ocean after the latest permian mass extinction event

onset development and cessation of basal early triassic microbialites betm in the nanpanjiang pull apart basin south china block abstract new investigations in the nanpanjiang basin indicate that the onset of the iconic microbialites associated with the paleozoic mesozoic boundary was early triassic in age bathymetry water agitation oxygenation light penetration and clastic load are shown to have exerted a direct control on the growth of microbialites carbonate supersaturation is also required for the deposition of the microbialites bathymetric control is further corroborated by the inheritance of the topography of a latest permian pull apart basin into early triassic times with a distribution of basal early triassic microbialites betm restricted to uplifted blocks and the accumulation of carbonaceous black shales in adjacent troughs the geographically most extensive nanpanjiang betm bloomed on a large nw se trending uplifted block exceeding 12 000 km 2 luolou platform centered on northwestern guangxi post triassic displacements along the youjiang fault obscure the paleogeographic relation of betm exposed west of this fault triassic foraminifers occur in the basal most betm episode which is locally bracketed by high energy grainstones made of reworked permian foraminifers therefore the permian triassic boundary ptb is within the unconformity that separates the late permian heshan fm from the basal most betm where accommodation space was sufficient up to five event surfaces are associated with the unconformity microfacies analysis supports chemical dissolution but did not reveal evidence for subaerial erosion although intercalated grainstone made of permian foraminifers indicate reworking chemical dissolution and mechanical erosion both conceivably contributed to the genesis of the unconformity the upward shift from tabulated to domical microbial build ups is accompanied by accumulation of coquinoid lenses between domes which indicates deepening of the luolou platform betm the main drowning resulting from both regional tectonic subsidence and a global sea level rise led to the cessation of the betm that were buried under predominant fine siliciclastics any concomitant change in sea water chemistry appears unlikely

timing of the early triassic carbon cycle perturbations inferred from new u pb ages and ammonoid biochronozones based on analyses of single thermally annealed and chemically abraded zircons a new high precision u pb age of 251 22 0 20 ma is established for a volcanic ash layer within the kashmirites densistriatus beds of early smithian age early triassic from the luolou formation northwestern guangxi south china this new date together with recalculated uncertainties of previous u pb ages from the same section m ovtcharova h bucher u schaltegger t galfetti a brayard j guex new early to middle triassic u pb ages from south china calibration with ammonoid biochronozones and implications for the timing of the triassic biotic recovery earth planet sci lett 243 2006 463 475 allows constraining the time framework of the early triassic and leads to an estimated duration of i ca 0 7 0 6 my for the smithian and ii a maximal duration of ca 1 4 0 4 my for the griesbachian dienerian time interval the new u pb age considerably reduces the absolute age gap comprised between the permian triassic boundary and the spathian late early triassic the new age framework provides the basis for the calibration of a new carbonate carbon isotope and ammonoid records of the early triassic luolou fm which in turn are of high significance for global correlations and for carbon cycle modeling this calibration indicates that the most significant and fastest early triassic carbon isotope perturbations occur between the earliest smithian and the early spathian thus spanning a time interval of about 1 my whatever caused these carbon cycle shifts of high intensity and short duration there is evidence for connections between these fluctuations the pulsate recovery of ammonoids and conodonts as well as climate changes

global ocean redox variations across the smithian spathian boundary linked to concurrent climatic and biotic changes abstract the smithian spathian boundary ssb was an interval characterized by a major global carbon cycle perturbation climatic cooling from a middle late smithian boundary hyperthermal condition and a major setback in the recovery of marine necto pelagic faunas from the end permian mass extinction although the ssb has been linked to changes in oceanic redox conditions key aspects of this redox variation e g duration extent and triggering mechanisms and its relationship to coeval climatic and biotic changes remain unresolved here we report a high resolution middle smithian to middle spathian u isotope 238u record based on marine carbonates of the zuodeng south china and jesmond british columbia sections to investigate the timing and global extent of ocean redox variation across the ssb our 238u record reveals values similar to or slightly heavier than modern seawater 0 39 during the middle smithian a rapid negative shift to highly negative values during the early late smithian a positive shift at the ssb and a rapid shift back to more negative values in the early middle spathian a simple u isotope mass balance modeling suggests that the global area of anoxic seafloor expanded strongly during the late smithian and the early middle spathian covering 11 of total seafloor area but that it contracted sharply during the ssb 2 the redox pattern documented by our 238u record shows a good first order correspondence to tropical sea surface temperature sst data for the smithian spathian in particular peak anoxia coincided with the middle late smithian boundary hyperthermal event and diminished anoxia with a pronounced decline in ssts at the ssb the temporal correlation between anoxia and low biodiversity levels of many marine clades e g conodonts and ammonoids during the late smithian indicates that oceanic anoxia may have played a role in the ssb biocrisis

carbon isotopic shift and its cause at the wuchiapingian changhsingian boundary in the upper permian at the zhaojiaba section south china evidences from multiple geochemical proxies abstract the late permian environmental change connecting the guadalupian lopingian g l middle upper permian boundary mass extinction and the permain triassic p tr boundary mass extinction has attracted more and more attentions a significant negative shift for carbon isotope had been found at the wuchiapingian changhsingian w c boundary in the upper permian recently however the cause s of this negative excursion is still unknown to resolve this problem we analyzed the bulk organic carbon isotope total organic carbon toc content pyritic sulfur spy content major element concentrations and molecular organic biomarkers in the wujiaping and dalong formations in the upper permian from the zhaojiaba section in western hubei province south china our results show that 1 there was a significant negative excursion in organic carbon isotopes at the w c boundary and again a negative excursion at the top of changhsingian stage 2 the significant negative excursion at the w c boundary was probably a global signal and mainly caused by the low primary productivity and 3 the negative carbon isotope excursion at the top of changhsingian was probably caused by the siberian traps eruptions a decline in oceanic primary productivity at the w c boundary probably represents a disturbance of the marine food web leading to a vulnerable ecosystem prior to the p tr boundary mass extinction

paleophysiology and end permian mass extinction physiological research aimed at understanding current global change provides a basis for evaluating selective survivorship associated with permo triassic mass extinction comparative physiology links paleontological and paleoenvironmental observations supporting the hypothesis that an end permian trigger most likely siberian trap volcanism touched off a set of physically linked perturbations that acted synergistically to disrupt the metabolisms of latest permian organisms global warming anoxia and toxic sulfide probably all contributed to end permian mass mortality but hypercapnia physiological effects of elevated pco2 best accounts for the selective survival of marine invertebrates paleophysiological perspectives further suggest that persistent or recurring hypercapnia global warmth also played a principal role in delayed triassic recovery more generally physiology provides an important way of paleobiological knowing in the age of earth system science 2007 elsevier b v all rights reserved

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

records of terrestrial sulfur deposition from the latest permian coals in sw china abstract different sulfur fractions of low sulfur average 0 11 coals from the latest permian in southwestern china were analyzed isotopically at a high vertical resolution to examine the ramifications for potential terrestrial extinction mechanisms at the permo triassic boundary s org organic sulfur accounts for 87 of the total sulfur content on average while s py pyritic sulfur is very low 13 of the total sulfur content and ca 0 01 of the whole sample weight and relatively constant throughout the profile except for some insignificant additions in clay rich layers these indicate the possible differential contribution of local diagenesis during the early stages of peat accumulation the 34 s org values have a relatively narrow range from 1 5 to 7 6 while the 34 s py values have a wider range from 0 8 to 34 1 suggesting that pyrite was possibly formed in different stages and that there was negligible bacterial contribution to the primary organic sulfur fraction thus the organic sulfur signal in the coal is largely sourced from the original plant material and records temporal variations in the isotopic composition of the sulfur input to the coal forming environment the stratigraphically lower coal b3 has 34 s org values around 4 while the stratigraphically higher coal b2 which is closer to the permian triassic boundary has clearly higher 34 s org values ranging from 5 3 to 7 6 this change is most likely due to increased marine sulfate aerosol inputs into the coal forming peatland caused by coastline retreat during late permian transgression importantly there is no evidence in these discrete intervals of coal formation to indicate a dominant role of atmospheric inputs of isotopically lighter sulfur from either h 2 s released from euxinic oceans or volcanic so 2 this militates against theories that implicate such sources of sulfur in terrestrial extinction mechanisms at the end permian

changes in the global carbon cycle occurred as two episodes during the permian triassic crisis coeval records of ocean atmosphere and terrestrial change are crucial to understanding the pattern and causes of global mass extinction across the permian triassic boundary ptb however relationships among changes in different settings remain largely unclear primarily due to the challenges associated with the correlation among disparate records here we compare marine carbon isotopic records with marine and terrestrial environmental and biotic events recorded in sediments from the meishan ptb section of south china time scaled carbonate carbon isotopes exhibit two gradual major shifts across the ptb at meishan and these are duplicable elsewhere around the tethys ocean the two shifts are associated with two episodes of enhanced terrestrial weathering indicated by an increased abundance of 13 c enriched moretanes relative to hopanes and an elevated abundance of black carbon fragments key marine events previously reported for the ptb including photic zone euxinia faunal mass extinction and cyanobacterial expansion also occur as two episodes coinciding with both of the progressive shifts to negative 13 c values and enhanced weathering the temporal sequence of the duplicable events suggests that the biotic crisis was a consequence of prolonged and episodic changes in the marine and continental systems and argues against an extraterrestrial impact as the main cause

permian triassic boundary ptb in the lower yangtze region southeastern china a new discovery of deep water archive based on organic carbon isotopic and u pb geochronological studies abstract the lower yangtze region of southeastern china is an important area for the study of permian triassic boundary ptb in this region many well known ptb sections e g meishan have been investigated widely and extensively however these sections are dominantly in shallow water settings and data from deep water areas are lacking to fill the gap we conducted a field survey recently and found a deep water ptb section with relatively continuous deposition using integrated organic carbon isotopic and u pb geochronological studies this well exposed and fresh section is located at niushan xuancheng city anhui province 90 km west of the well known meishan section which is the ptb global boundary stratotype section and point the organic carbon isotope curve of the section contains three positive excursions pcies and two negative excursions ncies which can be well correlated with other ptb sections as well as with wuchiapingian changhsingian boundary wcb sections worldwide they archive the original ptb and wcb signatures further u pb dating of magmatic zircons in volcanic ashes validates this new finding i e the ptb interval between 252 49 0 76 ma and 251 74 0 77 ma carbon isotopes of ptb sections in south china reflect the regional paleogeography the two ncies ncie 2 and ncie 3 across the ptb transition are most likely caused by widespread large scale volcanic activity in contrast the ncie 1 near the wcb is possibly related to an increase in the productivity of organic matter as a result of transgression and a change in the organic matter type from terrigenous to marine

cyanobacterial blooms tied to volcanism during the 5 m y permo triassic biotic crisis comment 40 ar 39 ar ages obtained on volcanic ash layers from south china and volcanic rocks of the siberian traps st respectively xie et al argue that the volcanism associated with the st is predominantly younger than the p tr boundary age xie et al note that the majority of st 40 ar 39 ar ages e g reichow et al 2009 are similar to u pb zircon ages for two triassic boundaries and consequently that st volcanism was likely responsible for the prolonged stress in the early triassic ecosystems however the suggested age correlation is fl and the purpose of this comment is to challenge the comparison based on ages obtained by different methodologies and demonstrate that one of the conclusions drawn by xie et al is invalid ar

global warming and the end permian extinction event proxy and modeling perspectives abstract the mass extinction event that occurred at the close of the permian period 252 million years ago represents the most severe biodiversity loss in the ocean of the phanerozoic the links between the global carbon cycle climate change and mass extinction are complex and involve a whole range of often inter related geochemical biological ecologic and climatic factors it has become widely accepted that the end permian mass extinction was associated with a global warming event because the age of the siberian trap eruption a potentially massive source of carbon dioxide coincides within error with the extinction event however geologic data that are in support of this global warming event are relatively sparse the chain of events and the causal relationship between the eruption of siberian traps and mass extinction is not well established global warming in particular has only been reported from limited proxy data and climate models for which the pco2 in the atmosphere just before and during the end permian extinction event is poorly known this study critically assesses both the proxy climate data and the existing paleoclimate simulations with the goals of assessing our current understanding of the link between mass extinction and climate change and providing some guidance for future studies proxies indicate that prior to the end permian extinction event tropical sea surface temperatures ranged from 22 to 25 c and possible pco2 values ranged from 500 to 4000 ppm before the extinction event during the peak extinction tropical temperatures rose up to 30 c while pco2 perhaps increased up to 8000 ppm climate models that use different pre event pco2 values show similar amount of co2 doubling to replicate the observed carbon isotope excursions we find that the temperature anomaly during the end permian extinction is consistent with 1 5 doublings of atmospheric pco2 and that the implied climate sensitivity is 5 6 c within the upper range of values produced by climate models

detection and prediction of warm season midtropospheric vortices by the rapid update cycle the authors perform a statistical and dynamical analysis of midtropospheric mesoscale vortices captured by analyses from the rapid update cycle version 2 ruc 2 during the period 1 may to 31 august 1999 a total of 203 vortices meeting conditions of an automated algorithm were found of these 86 were observed to form within organized convection and were termed mesoscale convective vortices mcvs mcvs were favored over a broad area from eastern colorado and western nebraska to the mississippi river valley essentially collocated with the loci of organized convection the remaining 117 vortices termed dry vortices clustered in the immediate lee of the rocky mountains and over the southeastern united states vortices arising from convection had considerably greater intensity and longevity than dry vortices they were roughly five times more likely to be involved with the triggering of new convection a relationship was found between intensity and longevity such that there appears to be a maximum vortex lifetime that can be estimated from its maximum intensity vortices arising from convection had markedly greater humidity and water vapor mixing ratio underneath their centers compared to dry vortices consistent with many dry vortices having a topographic origin and mcvs arising from organized convection parameters such as horizontal scale background vertical wind shear and horizontal deformation were not systematically related to intensity or longevity prediction of mesoscale vortices by the ruc 2 was examined for a subsample of all cases in general the ruc 2 was able to predict the evolution of vortices once analyzed but had virtually no skill at predicting 12 h in advance the formation of the vortices however forecasts of organized convection should still benefit from accurate predictions of long lived vortex tracks

triggers of permo triassic boundary mass extinction in south china the siberian traps or paleo tethys ignimbrite flare up abstract assessment of the synchroneity between the siberian traps and the permo triassic boundary ptb mass extinction has led to the proposition that the siberian flood volcanism was responsible for the severest biotic crisis in the phanerozoic however recent studies suggest that the siberian traps may have postdated the main extinction horizon in this paper we demonstrate using stratigraphy a time and intensity coincidence between ptb volcanic ash and the main extinction horizon geochemistry of the ptb volcanic ashes in five sections in south china indicates that they were derived from continental magmatic arc zircons extracted from the ptb volcanic ashes have negative e hf t 12 9 to 2 0 and 18 o 6 8 to 10 9 consistent with an acidic volcanism and a crustal derived origin and therefore exclude a genetic link between the ptb mass extinction and the siberian traps on the basis of spatial variation in the number of the ptb volcanic ash layers and the thickness of the ash layers in south china we propose that the ptb volcanic ash may be related to paleo tethys continental arc magmatism in the kunlun area ignimbrite flare up related to rapid plate subduction during the final assemblage of the pangea super continent may have generated a volcanic winter which eventually triggered the collapse of ecosystem and ultimately mass extinction at the end of the permian the siberian traps may have been responsible for a greenhouse effect and so have been responsible for both a second pulse of the extinction event and early triassic ecological evolution

evidence for recurrent early triassic massive volcanism from quantitative interpretation of carbon isotope fluctuations abstract carbon cycle disturbance associated with mass extinction at the end of the permian period continued through the early triassic an interval of approximately 5 million years coincidence of carbon cycle stabilization with accelerated middle triassic biotic recovery suggests a link between carbon cycling and biodiversity but the cause of early triassic carbon isotope excursions remains poorly understood previous modeling studies have focused exclusively on the initial negative excursion in 13c across the permian triassic boundary and have not addressed the cycles of positive and negative excursions observed through the early triassic this study uses a simple carbon cycle box model to investigate potential causes underlying the series of early triassic carbon isotope excursions and to assess possible relationships between isotope excursions and coeval patterns of carbonate deposition according to the model introduction of carbon with the isotope composition of volcanic co2 produces small negative carbon isotope excursions followed by larger and more protracted positive excursions positive excursions result because increased pco2 causes warming enhancing marine anoxia and associated regeneration of phosphate and thus allowing greater productivity in addition carbonate weathering is more sensitive than organic carbon weathering to changes in atmospheric pco2 and climate causing an increase in the overall 13c composition of weathered carbon therefore the full early triassic record of negative and positive carbon isotope excursions can only be accounted for within the model by several pulses of carbon release characterized by varying mixtures of organic and mantle isotope compositions thermal metamorphism of coal and carbonate rocks in the crust of the siberian craton during eruption of the siberian traps flood basalts provides the most plausible mechanism for such a carbon release scenario if multiple episodes of co2 release account for early triassic carbon cycle instability regardless of their precise trigger then cessation of co2 release is likely to explain acceleration of biotic recovery early in the middle triassic

fine grained volcanic hydrothermal sedimentary rocks in permian lucaogou formation santanghu basin nw china implications on hydrocarbon source rocks and accumulation in lacustrine rift basins abstract subaqueous volcanic hydrothermal field is a complex hybrid geological system where sediments originated from volcanic hydrothermal lacustrine terrestrial and biotic sources are mixed recent petrological studies on such sediments have indicated a potential relationship between volcanic hydrothermal activities and oil generation and accumulation here we explore the mechanisms of sedimentation and oil accumulation in well laminated organic rich fine grained sedimentary rocks in permian lucaogou formation deposited in the lacustrine santanghu rift basin nw china we conducted petrographic carbon and oxygen isotopic and organic geochemical analyses of fifty four core samples from three wells forty eight samples from well w1 two from w2 four from w3 designed for tight oil exploration four main observations and interpretations are 1 the fine grained sediments are a mixture of volcanic hydrothermal detrital feldspar grains authigenic quartz crystals and primary lacustrine dolomite forming interbedded tuffaceous shale and dolostone 2 authigenic quartz crystals were precipitated from acidic hydrothermal fluids whereas fine grained angular alkaline feldspars were derived from subaqueous volcanic eruption 3 the toc content and oil generation potential increase with increased mixing of feldspars and carbonate minerals hence the dolomite bearing tuffaceous shale and tuffaceous dolostone are the best source rocks and 4 the fine grained sedimentary rocks are interpreted as a subaqueous volcanic hydrothermal deposit that controls the source potential the sedimentary processes of an ancient sediment hosted geothermal system and its implications on hydrocarbon source rocks and accumulation were first identified algal bloom induced by subaqueous eruptions is the main cause for episodic deposition of organic matter and extreme heterogeneity in both lithofacies and source rock distribution the results suggest that cone shaped buildups on seismic sections which were formed by volcanic hydrothermal deposits and contain highly mixed feldspar and carbonate sediments are the best hydrocarbon reservoirs and demonstrate a strong relationship between volcanic hydrothermal activities and hydrocarbon accumulation in an extensional tectonic setting

record of the end permian extinction and triassic biotic recovery in the chongzuo pingguo platform southern nanpanjiang basin guangxi south china abstract 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

biogeochemical formation of calyx shaped carbonate crystal fans in the subsurface of the early triassic seafloor abstract the kuh e dena sedimentary section in iran developed on the southwestern margin of the neotethys ocean the fossil and bioturbation lean early triassic section late dienerian to early smithian is typified by finely laminated calcareous shales that are interbedded with laterally extending carbonate beds which are mostly composed of calyx shaped carbonate crystal fans the calyxes consist of fibrous crystals that apparently formed within the subseafloor in soft water saturated sediment by displacive growth rare earth element and yttrium patterns indicate that calyx shaped crystals precipitated from anoxic pore waters biomarker patterns of the carbonate beds reveal major input of lipids from prokaryotes that typically occur within layered benthic microbial mats i e cyanobacteria anoxygenic phototrophic bacteria sulphate reducing bacteria and methanogenic archaea along their length the fibrous crystals of the calyxes reveal a trend of increasing 13 c carb values from 2 7 to 3 3 suggesting that archaeal methanogenesis affected the carbonate pool apart from the putative benthic prokaryotes molecular fossils of halophilic most likely planktic archaea were detected in the carbonate beds low pristane to phytane ratios 0 8 and the presence of halophilic archaea are in accord with the lack of bioclasts and bioturbation which likely reflects increased salinities the former presence of a benthic microbial mat with cyanobacteria underlain by anoxygenic phototrophic bacteria sulphate reducing bacteria and methanogenic archaea is in accordance with studies on living microbial mats in hypersaline low oxygen marine environments the early triassic subseafloor seems to have been a sink for carbon driven by biologically induced formation of secondary diagenetic carbonate

high resolution carbon isotope changes in the permian triassic boundary interval chongqing south china implications for control and growth of earliest triassic microbialites abstract high resolution 13 c carb analysis of the permian triassic boundary ptb interval at the laolongdong section beibei near the city of chongqing south china encompasses the latest permian and earliest triassic major facies changes in the south china block scb microbialites form a distinctive unit in the lowermost 190 cm above the top of the changhsing formation latest permian at laolongdong comparable to a range of earliest triassic sites in low latitudes in the tethyan area the data show that declining values of 13 c carb well known globally began at the base of the microbialite high positive values 3 to 4 ppt of 13 c carb in the late permian are interpreted to indicate storage of 12 c in the deep waters of a stratified ocean that was released during ocean overturn in the earliest triassic contributing to the distinctive fall in isotope values this interpretation has been stated by other authors and is followed here the 13 c carb curve shows fluctuations within the microbialite unit which are not reflected in the microbialite structure comparisons between microbialite branches and adjacent micritic sediment show little difference in 13 c carb demonstrating that the microbialite grew in equilibrium with surrounding seawater the early triassic microbialites are interpreted to be a response to upwelling of bicarbonate rich poorly oxygenated water in low latitudes of tethys ocean consistent with current ocean models for the ptb interval however the decline of 13 c carb may be due to a combination of processes including productivity collapse resulting from mass extinction return of deep water to ocean surface oxidation of methane released from methane hydrate destabilisation and atmospheric deterioration nevertheless build up of bicarbonate rich anoxic deep waters may be expected as a result of the partial isolation of tethys due to continental geography release of bicarbonate rich deep water by ocean upwelling in the earliest triassic may have been an inevitable consequence of this combination of circumstances

large perturbations of the carbon cycle during recovery from the end permian extinction high resolution carbon isotope measurements of multiple stratigraphic sections in south china demonstrate that the pronounced carbon isotopic excursion at the permian triassic boundary was not an isolated event but the first in a series of large fluctuations that continued throughout the early triassic before ending abruptly early in the middle triassic the unusual behavior of the carbon cycle coincides with the delayed recovery from end permian extinction recorded by fossils suggesting a direct relationship between earth system function and biological rediversification in the aftermath of earth s most devastating mass extinction

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

a microbialite carbonate crust at the permian triassic boundary in south china and its palaeoenvironmental significance a 1 m thick carbonate crust layered and commonly domal caps crinoidal limestones on reef complexes of the top permian changxing formation in the huaying mountains eastern sichuan china the crust s stratigraphic level lies at a sharp change in facies and is overlain by poorly fossiliferous laminated micrites and shales of the lower triassic feixianguan formation the crust therefore appears to coincide with the end permian extinction event although the dating of the strata is currently imprecise the crust is composed mostly of digitate carbonate locally thrombolitic with remnant lobate fabric and resembles microbialites but is mostly recrystallised and a microbial origin is unconfirmed it is enclosed in micrite with pyrite crystals ostracode and other shell debris the crust is absent from interreef areas previous interpretations of karstification and calcrete formation are not upheld and the facies were deposited under water overlying sediments are low energy with abundant ferroan calcite and pyrite reflecting anoxia associated with rising sea level various interpretations of the crust are possible 1 it was organic and microbia grew preferentially on topographic highs of reef tops 2 microbia were a disaster biota in the absence of grazers 3 microbia took advantage of favourable conditions for calcification associated with a rapidly rising environmental co2 content during the late permian 4 the crust was an inorganic precipitate associated with co2 rich water microbial crusts are rare after the cambrian but whether this crust is organic or not its presence in these strata reinforces the view that oceanic atmospheric conditions in the permian triassic boundary interval were unusual

age and timing of the permian mass extinctions u pb dating of closed system zircons the age and timing of the permian triassic mass extinction have been difficult to determine because zircon populations from the type sections are typically affected by pervasive lead loss and contamination by indistinguishable older xenocrysts zircons from nine ash beds within the shangsi and meishan sections china pretreated by annealing followed by partial attack with hydrofluoric acid result in suites of consistent and concordant uranium lead u pb ages eliminating the effects of lead loss the u pb age of the main pulse of the extinction is 252 6 0 2 million years synchronous with the siberian flood volcanism and it occurred within the quoted uncertainty

the spatial nearshore offshore distribution of latest permian phytoplankton from the yangtze block south china abstract in order to analyze the spatial paleoecological distribution of the organic walled microphytoplankton in the late permian five sections from the yangtze block south china displaying different sediment facies types from neritic to offshore paleoenvironments including basinal facies have been investigated palynologically based on the diversity and relative abundance of acritarch species and genera the new data from the permian provide similar patterns as those described from other geological periods 1 low diversities with 2 to 4 acritarch species occur in nearshore environments whereas the higher diversities more than ten acritarch species appear in the offshore environments 2 at the generic level the genera leiosphaeridia reduviasporonites and micrhystridium are distributed widely from nearshore facies corresponding to shallow water environments to offshore facies corresponding to deeper water settings whereas some genera such as dictyotidium and veryhachium have a narrower distribution occurring on the continental shelf and towards the basin indicating open marine environments 3 the genus schizosporis only occurs around the permian triassic boundary ptb when the sea level declined probably indicating nearshore environments with shallow water settings 4 at the specific level the species micrhystridium breve displaying short spines and leiosphaeridia minutissima are indicative of neritic facies whereas the other species of micrhystridium and veryhachium with longer spines e g micrhystridium stellatum and veryhachium hyalodermum and leiosphaeridia microgranifera indicate more open marine environments big spherical acritarch species over 80 m in diameter such as dictyotidium reticulatum indicate shallow water environments and 5 in the ptb strata the relative abundance of the enigmatic reduviasporonites interpreted by some authors as a fungal spore is not higher than 14 in every sample indicating that a spike of reduviasporonites does not occur in the yangtze area reduviasporonites chalastus 40 m in length obviously dominates in shelf environments of shallow water whereas the smaller reduviasporonites catenulatus 15 m in length are more common in deeper water

global oolite deposits across the permian triassic boundary a synthesis and implications for palaeoceanography immediately after the end permian biocrisis abstract 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

mixed biogenic and hydrothermal quartz in permian lacustrine shale of santanghu basin nw china implications for penecontemporaneous transformation of silica minerals the cycling of various isomorphs of authigenic silica minerals is a complex and long term process a special type of composite quartz qc grains in tuffaceous shale of permian lucaogou formation in the sediment starved volcanically and hydrothermally active intracontinental lacustrine santanghu rift basin nw china is studied in detail to demonstrate such processes samples from one well in the central basin were subject to petrographic elemental chemical and fluid inclusion analyses about 200 qc bearing laminae are 0 1 2 mm and mainly 1 mm thick and intercalated within tuffaceous shale laminae the qc grains occur as framework grains and are dispersed in igneous feldspar dominated matrix suggesting episodic accumulation the qc grains are bedding parallel uniform in size 100 s m elongate and radial in crystal pattern suggesting a biogenic origin qc grains are composed of a core of anhedral microcrystalline quartz and an outer part of subhedral mega quartz grains whose edges are composed of small euhedral quartz crystals indicating multiple episodic processes of recrystallization and overgrowth abundance of al and ti in quartz crystals and estimated temperature from fluid inclusions in qc grains indicate that processes are related to hydrothermal fluids finally the qc grains are interpreted as original silica precipitation in microorganism algae cysts which were reworked by bottom currents and altered by hydrothermal fluids to recrystalize and overgrow during penecontemporaneous shallow burial it is postulated that episodic volcanic and hydrothermal activities had changed lake water chemistry temperature and nutrient supply resulting in variations in microorganic productivities and silica cycling the transformation of authigenic silica from amorphous to well crystallized had occurred in a short time span during shallow burial

cyanobacterial blooms tied to volcanism during the 5 m y permo triassic biotic crisis reply we welcome the comment from reichow and saunders 2011 1 and are glad that they agree with our main conclusion on the relationship among cyanobacterial blooms volcanism and carbon isotope excursions across the permian triassic boundary xie et al 2010 2 they do challenge however

shallow marine dysoxia across the permian triassic boundary evidence from pyrite framboids in the microbialite in south china abstract the end permian mass extinction resulted in the collapse of reef ecosystems and the subsequent formation of microbialites in shallow carbonate platforms in south china large quantities of pyrite framboids are preserved in the microbialites but absent in the underlying skeletal limestone indicating an abrupt shift in water column redox conditions in association with the shallow marine faunal mass extinction detailed study of size distributions of 1374 pyrite framboids found in 9 horizons in laolongdong section in chongqing municipality south china were performed to evaluate this shift in paleo redox condition of the shallow marine environment pyrite framboids in the microbialite average 8 41 m in size comparable with those from modern sediments underlying dysoxic water columns this infers that dysoxic waters in the latest permian might have expanded to reach the shallow marine environments in south china mean diameters of pyrite framboids from mudstones overlying the microbialite are 7 63 m 7 68 m likely indicating continuing intensification of oxygen deficiency in the bottom waters microgastropods ostracods and some foraminifers which survived and flourished in the microbialite almost disappeared during the mudstone deposition possibly reflecting a consequence of oxygen depletion

petrologic and geochemical evidence for the formation of organic rich siliceous rocks of the late permian dalong formation lower yangtze region southern china abstract black shales are economically and scientifically important because they are commonly associated with high quality hydrocarbon source rocks and metal accumulations formed during periods of abrupt environmental change organic rich siliceous rocks of the late permian dalong formation developed extensively within middle upper yangtze region western yangtze platform however the formation mechanism of its formation in the lower yangtze region eastern yangtze platform remains a subject of debate due to a lack of outcrop exposure petrologic mineralogic and geochemical data are presented for three sections of the dalong formation within the lower yangtze region geochemical ratios including v v ni v cr ni co u th and v sc suggest that the dalong formation was deposited in an oxygen poor environment the elevated concentration of mo 100 ppm further suggests that free h2s existed in the bottom water which was favorable for the accumulation of large amounts of organic matter mo toc ratios reveal that water flow in the lower yangtze basin was moderately to strongly restricted during deposition of the dalong formation flow within the upper middle parts of the yangtze basin was also restricted suggesting that northern marginal basins on the yangtze platform formed part of a single ocean during the late permian i e changhsingian cherts of the dalong formation reflect high primary productivity similar to that of modern day upwelling zones which increased the amount of organic matter these results combined with previous work suggest that the long term oxygen poor conditions during deposition of the dalong formation were caused by restricted water circulation in a unique paleogeographic environment characterized by low latitude and submarine paleo highlands such settings of low latitude characterized by tropical climate favored the growth of siliceous zooplankton in the zones with submarine paleo highlands having created topographic barriers to water circulation restricted bottom water flow and oceanic anoxia during the late permian were likely the main controls on the accumulation of organic rich rocks elevated nutrient levels caused by frequent oceanic upwelling along the western margin of the south china craton and global volcanism at this time facilitated siliceous organism productivity

late early triassic microbial reefs of the western united states a description and model for their deposition in the aftermath of the end permian mass extinction abstract research in the western united states to reinvestigate and characterize the previously reported stromatolites of the latest early triassic spathian virgin limestone member of the moenkopi formation has shown that these microbial build ups formed patch reef mounds detailed field analysis of these reef mounds and the surrounding beds has established that they attained 1 2 m of topographic relief above the seafloor a petrographic study of these microbial mounds illustrates that they consisted of microbial fabrics as well as voids with early marine cements and formed in the absence of in situ metazoans these reef mounds formed during the aftermath of the end permian mass extinction that spanned the early triassic due to the devastation of marine metazoans at this extinction the early triassic has often been deemed a reef gap because no metazoan reefs are found at this time whereas colonial metazoan reefs are globally absent from lower triassic strata microbial build ups similar to these described from the western united states have been found in south china armenia southern turkey and greenland a regional early permian to late early triassic unconformity exists in the study region however analysis of these microbial reefs within a global context suggests that conditions favouring microbial reef development must have existed as long as 4 8 m y after the end permian mass extinction a depositional model of these microbial mounds indicates that flooding of the shelf with anoxic and or co2 rich deep waters may have fostered their occurrence

evolution of oceanic redox conditions during the permo triassic transition evidence from deepwater radiolarian facies abstract the 90 biodiversity loss among marine invertebrate species during the end permian mass extinction the most severe phanerozoic biocrisis has been attributed to widespread oceanic anoxia superanoxia recent studies of the lithofacies inorganic geochemistry and biomarkers of permian triassic boundary ptb sections have yielded an inferred pattern of oceanic redox changes that is complex and sometimes inconsistent in this contribution we review the ecology of radiolarians an important microzooplankton group during the permo triassic transition and consider its implications for contemporaneous changes in paleoceanographic conditions our analysis shows that 1 late permian radiolarian faunas were cosmopolitan with different orders having specific depth preferences i e albaillellarians favoring deeper waters and spherical forms entactinarians and spumellarians shallower waters 2 deep water taxa declined earlier than shallow water taxa 3 many paleozoic type taxa survived into the early triassic but went extinct during a second crisis in the dienerian dead clade walking followed by the appearance or expansion of mesozoic type taxa during the olenekian and 4 the survival of paleozoic type taxa during the early triassic was greater at higher paleolatitudes than in the tropics these observations are consistent with a first order redox control on radiolarian faunal distributions specifically a shallowing and poleward expansion of the oceanic oxygen minimum zone during the ptb crisis the consequent adaptation of some deepwater taxa to shallower environments resulted in early triassic radiolarian faunas in continental basins becoming more similar to those in pelagic settings enhanced survival of paleozoic type taxa in high latitude regions indicates that the main stressor on permo triassic radiolarian communities was reduced oceanic oxygen levels stronger in the tropics rather than climatic warming stronger at the poles

heterogeneous volcanism across the permian triassic boundary in south china and implications for the latest permian mass extinction new evidence from volcanic ash layers in the lower yangtze region abstract volcanism has been suggested to have occurred widely in south china across the permian triassic boundary ptb this has important implications for understanding the cause of the latest permian mass extinction lmpe however few volcanic deposits have been reported in the lower yangtze region and the extent of volcanism is uncertain herein we report new discoveries of intensive volcanism in this region for the first time as evidenced by multiple n 20 and thick 3 5 cm claystones volcanic ash layers k bentonite found in three deep water outcrops in xuancheng city southern anhui province detailed petrographic and geochemical analyses of the ash layers were conducted to understand their origin and implications for the cause of the lpme including x ray diffraction scanning electronic microscopy energy dispersive spectroscopy and whole rock geochemistry the petrological and mineralogical results show that the claystones contain clastic minerals indicative of a volcanic origin such as zircon analcites pentagonal dodecahedral pyrite and micro spherules the whole rock geochemical data of the claystones suggest that the source rock of the ash layers was intermediate acidic rhyodacite the claystones are different from previously known claystones in the middle upper yangtze regions indicating the occurrence of chemically heterogeneous volcanism in south china at the ptb

volcanically induced environmental change at the permian triassic boundary xiakou hubei province south china related to west siberian coal field methane releases a detailed geochemical investigation of the permian triassic boundary in a carbonate ramp setting at xiakou south china provides new insights regarding the role of volcanism in the largest mass extinction in earth history the xiakou section records 9 intervals of volcanic activity some producing up to 25 cm thick composite ash layers during the latest permian and earliest triassic each volcanic episode coincided with major changes in marine environments the largest changes occurred in conjunction with volcanic interval vi 4 correlative with the latest permian mass extinction during which 1 the oceanic oxygen minimum zone expanded as shown by framboidal pyrite flux 2 marine productivity declined sharply as shown by multiple productivity proxies and 3 climate conditions became more humid as shown by increased clay fluxes the mechanism by which volcanic eruptions forced marine environmental changes may be inferred from the relationship between ash layer thickness and the magnitude of the associated negative c isotope excursion the most likely connection is through volcanogenic methane release to the atmosphere possibly as a result of magmatic intrusions into the west siberian coal basin triggering increases in global temperature and humidity these climate changes in turn resulted in stronger oceanic stratification oxygen minimum zone expansion and a decline in marine productivity the xiakou section is important in demonstrating links between volcanism and the marine environment during the permian triassic transition interval

early triassic stromatolites as post mass extinction disaster forms aftermaths of mass extinctions have been thought to be characterized by relaxation of ecological constraints accompanied by increased prominence of opportunistic generalists such taxa termed disaster forms have been shown to increase dramatically in range and abundance after several mass extinction events the cambrian ordovician stromatolite decline in normal marine level bottom environments has been explained as a direct or indirect consequence of increases in ecological constraints such as greater levels of predation and or bioturbation of microbial communities caused by early paleozoic benthic invertebrate evolution and diversification thus one would predict that in post ordovician strata stromatolites might appear in normal marine level bottom environments as disaster forms in the aftermaths of mass extinction particularly devastating to the benthic biota such as during early triassic time mounded stromatolites are present in two beds up to 1 5 m thick of the lower triassic spathian virgin limestone member moenkopi formation in the southwestern spring mountains of nevada stromatolites from level bottom normal marine subtidal environments have also been described from other lower triassic strata in north america europe and asia these stromatolites unusual in level bottom normal marine settings may have developed locally during the long aftermath 4 5 m y of the permian triassic mass extinction because of partial relaxation of the ecological constraintsmore that typically restricted them from unstressed subtidal normal marine level bottom environments less

reconstruction of early triassic ocean redox conditions based on framboidal pyrite from the nanpanjiang basin south china abstract widespread oceanic anoxia has been implicated as an important factor in the ptb permian triassic boundary mass extinction and the delayed recovery of early triassic marine ecosystems an investigation of framboidal pyrite in the bianyang section nanpanjiang basin south china suggests that euxinia dysoxia peaked during the induan late smithian to earliest spathian and late spathian these anoxic episodes show a relationship albeit imperfect to major episodes of climatic warming during the early triassic that were associated with intensified oceanic stratification reduced marine productivity and organic carbon sinking fluxes as well as diminished burial fluxes of organic carbon and reduced sulfur in contrast intervals of better oxygenated marine conditions were associated with episodes of relative climatic cooling during the early to middle smithian and mid spathian the degree of ventilation of the thermocline region in particular had a profound effect on marine biotas with intervals of improved ventilation resulting in increased global diversity among ammonoids and conodonts and increased local abundance of foraminifera in the nanpanjiang basin these observations suggest that oceanic redox fluctuations played an important role in the delayed recovery of early triassic marine ecosystems and specifically that episodic expansion of oceanic oxygen minimum zones omzs resulted in repeated setbacks to the recovery process a pattern that persisted until the late spathian

are early triassic extinction events associated with mercury anomalies a reassessment of the smithian spathian boundary extinction abstract high concentrations of mercury possibly connected with widespread volcanism of the siberian traps have previously been associated with the smithian spathian early triassic boundary ssb in the sverdrup basin tethyan sections in india and china as well as with a shallow water record in western spitsbergen we confirm this hg toc anomaly in the deeper water record at wallenbergfjellet central spitsbergen however both paleontological age control and carbon isotopes indicate that the hg anomaly occurred mainly within strata of middle smithian age therefore this hg anomaly is unlikely to be directly and causally related to mechanisms contributing to the late smithian global extinction of nektonic faunas the toc and trace element data suggest generally more oxygenated conditions during the smithian compared to the spathian which is at odds with the hypothesis that oxygen depletion may have been a global kill mechanism for the ssb extinction further work is needed to assess if precise timing and paleogeographic distribution of anoxia shows any consistent pattern or not during the smithian and spathian the very abrupt lower limb of the positive carbon isotope excursion cie and the coarser grain size immediately below the boundary between the lusitaniadalen member and the vendomdalen member indicate a substantial stratigraphic gap of latest smithian age a previously neglected signal shared with many other boreal ssb sections ammonoid age control also indicates that the onset of the late smithian gap in the high latitudes was earlier than in the tropics the gradual end of the positive cie contrasts with the frequent spike shape observed in tropical shelf records and is definitively earliest spathian in age the middle smithian hg anomaly in the boreal record is only visible in the hg toc values and is associated with a possible shift in organic matter type from terrestrial to marine in the case of spitsbergen this suggests that the middle smithian hg toc anomaly in spitsbergen may not unequivocally originate from volcanism and calls for additional caution before interpreting hg spikes as a volcanic proxy

the formation of microbial metazoan bioherms and biostromes following the latest permian mass extinction abstract after the latest permian mass extinction event microbial mats filled the ecological niche previously occupied by metazoan reefs resulting in widespread microbialites this study focuses on the lipid biomarker molecular fossil and invertebrate fossil records from neotethyan platform margin sections to understand microbial metazoan bioherm formation here we find that early griesbachian thrombolitic and stromatolitic microbialites from curuk dag turkey and kuh e surmeh iran contain abundant lipid biomarkers representing input from cyanobacteria anoxygenic phototrophic bacteria sulfate reducing bacteria and halophilic archaea the biomarker inventory suggests that the microbialites were constructed by cyanobacteria dominated microbial mats biomarkers of halophilic archaea are interpreted to reflect input from the water column suggesting that the neotethys experienced at least episodically hypersaline conditions we also demonstrate that bacteria possible keratose sponges up to 50 of the carbonate is represented by the possible sponges and microconchids lived synergistically to form microbial metazoan bioherms in the immediate aftermath of the extinction along the western margin of the neotethys abundant fossils of oxygen dependent invertebrates i e microconchids bivalves gastropods brachiopods and ostracods and foraminifers were also found within these bioherms the presence of invertebrates in conjunction with abundant molecular fossils of cyanobacteria indicates an oxygenated water column even though the presence of the biomarker isorenieratane in microbialites may considered as evidence for euxinic conditions in the water column its absence in the background sediments rather points to a source organism belonging to the mat community the new finding of bioherms built in part by metazoans suggests that reef ecosystems underwent a major turnover across the extinction event and shortens the metazoan reef gap to just the uppermost changhsingian during the early triassic therefore reefal ecosystems were able to recover in oxygenated settings since the earliest griesbachian albeit in an impoverished state

molecular and petrographic indicators of redox conditions and bacterial communities after the f f mass extinction kowala holy cross mountains poland abstract pyrite framboid diameter analysis and organic geochemistry of the triangularis crepida boundary section at kowala holy cross mountains poland imply suboxic to oxic and sporadically euxinic bottom waters during the lower famennian in addition morphological web like structures typical for microbial mats as well as the recognition of 2 methylhopanes and monomethyl alkane cyanobacteria biomarkers is evidenced of microbial activity after the global frasnian famennian f f extinction event the presence of cyanobacterial mats also suggests suboxic to oxic environments and at the same time photic bottom water conditions however isorenieratane and its derivatives were detected in almost all samples the presence of this well known biomarker of green sulfur bacteria implies that euxinic conditions were present in the upper part of the water column at least intermittently or that temporal euxinia occurred in the water column presence of euxinic conditions is confirmed by the occurrence of small sized pyrite framboids which were particularly dominant in the lower part of the section the shift towards low 13 c values in both micritic limestones and in sedimentary organic matter seen at the beginning of the period of diminished photic zone might reflect an influx of newly respired co 2 to surface waters caused by enhanced respiration at depth after the f f transition in the checiny zbrza basin

mercury anomalies associated with three extinction events capitanian crisis latest permian extinction and the smithian spathian extinction in nw pangea strata of permian early triassic age that include a record of three major extinction events capitanian crisis latest permian extinction and the smithian spathian extinction were examined at the festningen section spitsbergen over the c 12 ma record examined mercury in the sediments shows relatively constant background values of 0 005 0 010 g g 1 however there are notable spikes in hg concentration over an order of magnitude above background associated with the three extinctions the hg total organic carbon toc ratio shows similar large spikes indicating that they represent a true increase in hg loading to the environment we argue that these represent hg loading events associated with enhanced hg emissions from large igneous province lip events that are synchronous with the extinctions the hg anomalies are consistent across the nw margin of pangea indicating that widespread mercury loading occurred while this provides utility as a chemostratigraphic marker the hg spikes may also indicate loading of toxic metals to the environment a contributing cause to the mass extinction events

quantitative biochronology of the permian triassic boundary in south china based on conodont unitary associations abstract 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

diversity and factors controlling widespread occurrence of syn rift ladinian microbialites in the western tethys triassic catalan basin ne spain abstract the fault block carbonate ramps of the ladinian middle triassic catalan basin hosted a wide variety of microbial deposits which formed during a syn rift stage stratigraphical and sedimentological analyses of these microbialites allow us to reconstruct two depositional models for such microbial deposits moreover new insights into the interplay between the intrinsic and extrinsic factors that controlled the widespread development of these microbialites are provided stromatolites ooidal muddy microbial laminites and thrombolites were analyzed on the basis of their geometry lamination and textural attributes these microbialites are distributed over two transgressive regressive sequences and coexisted during the fassanian early ladinian regressive stage later stromatolites and ooidal muddy microbial laminites developed during the longobardian late ladinian transgressive stage three types of lamina couplets reflect distinct accretion processes linked to water chemistry sediment supply and hydrodynamic conditions thrombolite textures were produced by accretionary binding and encrusting processes microbially mediated and pervasive cementation the widespread occurrence of microbial deposits is explained as a consequence of a biogeochemical cascade of events e g anoxic dysoxic seawater conditions volcanic activity upwelling of alkaline waters nutrient concentrations and microbial blooms which promoted favorable conditions for microbial growth in the tethys during the ladinian furthermore in the catalan basin syn rift fault induced subsidence and local water energy gradients exerted an essential role in the distribution of the three types of microbialites through space and time thrombolites were prone to grow in the hanging wall block of a half graben subtidal conditions whereas stromatolites and ooidal muddy microbial laminites flourished preferably in a foot wall block setting intertidal shallow subtidal conditions however the fact that thrombolites exhibit abundant botryoidal and isopachous fibrous marine cements corrosion and significant microbial evidence allow us to hypothesize about the relationship between thrombolite occurrence and hydrothermal fault controlled fluid circulation during the triassic rifting the two depositional models here proposed constitute a step forward the understanding of the platform to basin microbialite heterogeneity during the ladinian furthermore this work sheds new light on the mechanisms that likely promoted microbialite development during a period of major ecological restructuration and complex oceanographic conditions

two episodes of environmental change at the permian triassic boundary of the gssp section meishan abstract high resolution stratigraphic records through the permian triassic boundary ptb interval of the global stratotype section and point gssp at meishan zhejiang province china reveal that the ptb crisis was not a single abrupt catastrophe a bed by bed analysis of environmental and biotic changes makes clear that the crisis can be resolved into two discrete episodes each consisting of three stages a unstably oscillating conditions b peak crisis conditions and c ameliorating conditions the first crisis episode commenced in bed 23 peaked in beds 24e 26 and ameliorated in beds 27 and 28 while the second crisis episode commenced in bed 29 peaked in beds 34 38 and ameliorated in beds 39 and higher the macroscopic mass extinctions happened not at the beginning nor the end of each cycle but at times when the crisis or perturbation of environments began these extinction events do not show detectable feedbacks to concurrent environmental changes in each episode cyanobacteria proliferation postdated the macroscopic extinction while proliferation of green sulfur bacteria predated the environmental crisis causational analysis between environmental and microbial changes show that geomicrobial functional groups exercised pronounced effects on the marine c n s cycles and ocean redox conditions during the ptb crisis it is possible thus that the microbial crises played an important role in strengthening or evening triggering the environmental crisis

phytoplankton acritarch community changes during the permian triassic transition in south china abstract the permian triassic boundary ptb at 252 ma coincided with the largest mass extinction of the phanerozoic previous research on diversity and abundance changes during this event has focused mainly on the terrestrial vertebrate and marine invertebrate records with little attention to date given to the phytoplankton that form the base of the marine trophic web although the fossil record of permian triassic phytoplankton is relatively poor owing to preservational factors sufficient material is now available to evaluate secular changes in acritarch communities through the mass extinction interval in this contribution we evaluate diversity and abundance changes among 8 genera and 25 species of acritarchs including large spherical small spherical long spined and short spined forms ranging from the upper permian clarkina yini to the lower triassic isarcicella isarcica zones in eight sections representing different sedimentary facies of the south china craton acritarchs declined sharply from the latest permian c meishanensis zone to the earliest triassic i staeschei zone with extinctions and abundance changes concentrated at two horizons the first in the latest permian c meishanensis zone bed 25 at meishan d and the second in the earliest triassic i staeschei zone bed 28 at meishan d mirroring the pattern of mortality among marine invertebrates differences in the nature and intensity of these two extinction episodes the second having a relatively larger effect on acritarch community composition suggest that these events may have resulted from different types of environmental perturbations

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

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

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

negative c isotope excursions at the permian triassic boundary linked to volcanism two permian triassic boundary ptb sections from south china provide insights regarding the origin of negative excursions in carbonate and organic carbon isotope records associated with the largest mass extinction in earth history xiakou a carbonate ramp section exhibits delta c 13 carb excursions of up to 2 parts per thousand and xinmin a deep shelf section exhibits delta c 13 org excursions of up to 6 parts per thousand in both sections these excursions are associated with volcanic ash layers and excursion size scales with ash layer thickness these relationships document the direct influence of volcanism on the earth surface carbon cycle during the ptb crisis previous studies of ash layers in south china ptb sections have invoked a source in regional subduction zone volcanism in the eastern tethys but our analysis suggests that these ash layers may represent distal deposits from large scale explosive eruptions of the siberian traps if confirmed by further investigation this hypothesis would have important implications both for kill mechanisms during the ptb crisis as well as for refinement of the eruption history of the siberian traps

mass occurrence of oncoids at the cambrian series 2 series 3 transition implications for microbial resurgence following an early cambrian extinction abstract the traditional lower middle cambrian transition cambrian series 2 series 3 transition is marked by the first major biotic extinction of the phanerozoic eon this biotic crisis has been arguably linked to changes in ocean chemistry and or marine environments but their casual relationships remain controversial to better understand the microbial responses to paleoceanographic changes across this critical transition we have studied the environmental conditions for mass occurrence of oncoids in the western north china platform oncoids at the lower middle cambrian transition form 1 to 3 m thick massive beds show spherical subspherical morphology and contain 8 14 light dark cortical laminar couplets the light laminae are thicker and contain densely intertwined filamentous cyanobacteria that have calcified sheaths and a prostrate growth pattern the dark laminae are thinner and rich in organic matter relics pyrite framboids and heterotrophic bacteria in most oncoids cortical laminae show the same growth orientation for more than five light dark laminar couplets suggesting much less frequent grain overturning than generally thought both light and dark laminae contain well preserved organomineralization fabrics textures including extracellular polymeric substances epss nanoglobules polyhedrons and micropeloids suggesting oncoid formation in shallow marine environments with high alkalinity and active sulfate reduction the presence of pyrite framboids and heterotrophic bacterial relics implies anoxic dysoxic bottom water conditions stratigraphic correlation indicates that time equivalent oncolites and other microbialites are widespread not only in north china but also in other early cambrian successions globally the mass occurrence of oncoids coincides with the kalkarindji large igneous province of australia a prominent negative 13 c excursion roece or redlichiid olenellid extinction carbon isotope excursion a significant increase in 87 sr 86 sr and a large positive shift in 34 s the coincidence of these events suggests that the early cambrian biotic crisis may have been caused by an ocean anoxic event resulting from enhanced volcanic release of co 2 global warming and increased continental weathering preservation of massive oncolites is likely related to decreased metazoan grazing following an early cambrian biotic crisis during which archaeocyathids and many early cambrian trilobite taxa went to extinction the oncoid mass occurrence provides evidence for the resurgence of microbial life in anoxic dysoxic marine shelf environments concomitant with the early cambrian extinction event

marine productivity changes during the end permian crisis and early triassic recovery abstract the latest permian mass extinction lpme coincided with major changes in the composition of marine plankton communities yet little is known about concurrent changes in primary productivity earlier studies have inferred both decreased and increased productivity in marine ecosystems immediately following the end permian crisis here we assess secular and regional patterns of productivity variation during the crisis through an analysis of the burial fluxes of three elemental proxies total organic carbon toc phosphorus p and biogenic barium babio primary productivity rates appear to have increased from the pre crisis late permian through the early triassic in many parts of the world although the south china craton is unusual in exhibiting a pronounced decline at that time most of the 14 permian triassic study sections show concurrent increases in sediment bulk accumulation rates suggesting two possible influences linked to subaerial weathering rate changes 1 intensified chemical weathering resulting in an increased riverine flux of nutrients that stimulated marine productivity and 2 intensified physical weathering leading to higher fluxes of particulate detrital sediment to continental shelves thus enhancing the preservation of organic matter in marine sediments an additional factor especially in the south china region may have been the intensified recycling of bacterioplankton derived organic matter in the ocean surface layer reducing the export flux rather than primary productivity per se the ecosystem stresses imposed by elevated fluxes of nutrients and particulate sediment as well as by locally reduced export fluxes of organic matter may have been important factors in the 2 to 5 million year long delay in the recovery of early triassic marine ecosystems

overflow thermal springs of tuscany italy abstract there are several low temperature geothermal systems spread over a large part of tuscany the italian region containing the high temperature geothermal fields of larderello travale and mt amiata this region is characterized by a main thermal aquifer that is generally confined except in some areas where the aquifier formations outcrop most of the thermal springs of the region are located on the boundaries of these permeable outcrops field observations suggest a diffuse flow conceptual model for these springs as opposed to the commonly accepted models that assume water flow along faults or other isolated channels mathematical models assuming porous medium flow have been used to investigate some of the main characteristics of water circulation in such systems the spring discharge can be supplied entirely by water absorbed into the adjacent permeable outcrops or by water belonging to the regional circulation or by a mixture of the two in different proportions infiltration rate surface morphology and the resistance to water flow in the aquifer away from the permeable outcrops are factors strongly affecting the flow pattern and spring characteristics

recurrent early triassic ocean anoxia the early triassic record from the smithian stratotype shows that the organic carbon isotope record from northwest pangea closely corresponds to major fluctuations in the inorganic carbon records from the tethys indicating truly global perturbations of the carbon cycle occurred during this time geochemical proxies for anoxia are strongly correlated with carbon isotopes whereby negative shifts in 13 c org are associated with shifts to more anoxic to euxinic conditions and positive shifts are related to return to more oxic conditions rather than by a delayed or prolonged recovery the early triassic is better characterized by a series of aborted biotic recoveries related to shifts back to ocean anoxia potentially driven by recurrent volcanism

permian carboniferous and permian triassic magmatism in the rift zone bordering the tethyan margin of southern pangea magma was emplaced in the india australia rift zone along the tethyan margin during permian carboniferous and permian triassic time permian carboniferous alkalic granite and basaltic and rhyolitic lava flows and tuffs formed at the same time as right lateral transtension of pangea as recorded by the magmatic rocks of neocratonic post variscan europe and post kanimblan eastern australia permian triassic tholeiitic basalt in india alkalic magmatic rocks in oman and rhyolite dolerite and undersaturated alkalic volcanic rocks in western australia preceded and accompanied the early opening of the neo tethys ocean coeval magmatism included the voluminous mid plate siberian traps the emeishan basalt of south china and the peak activity of the magmatic arc along the convergent panthalassan margin the background magmatism probably permitted the siberian traps to trigger the environmental catastrophe at the permian triassic boundary

fluctuations of redox conditions across the permian triassic boundary new evidence from the gssp section in meishan of south china abstract oceanic anoxia has long been considered as one of the main causes for the end permian mass extinction however the results obtained by different researchers are rather divergent from different sections or even on the same section using the same redox proxy this study aims to examine the causes for some of these divergent results using high resolution pyrite framboid sampling at the meishan gssp section in south china detailed microfacies analysis shows that the uppermost late permian strata comprises two significantly different sedimentary facies one characterized by silicious muddy limestone and recognized as representing autochthonous background sediments the other distinguished by bioclastic grainstone interpreted to be allochthonous in origin and have been transported from the nearby platform margin these two different sedimentary facies represent two distinctly different redox conditions together with the facies analysis a statistical analysis of pyrite framboids was carried out to evaluate the redox evolution across the permian triassic boundary abundant framboids with average diameters of about 6 m are found in background sediments beneath the extinction boundary indicating generally anoxic bottom water conditions but this condition was punctuated by transient intervals of rapid oxygenation interpreted to have been caused by intrusion of intermittent turbidity flows our study also showed that anoxic conditions persisted into the immediate aftermath of the mass extinction thereafter it was quickly followed by a relatively long period of oxic conditions with rare framboids however the redox conditions returned to anoxia with abundant pyrite framboids averaging about 5 m in diameter accompanied by a rapid global transgression the oxygenation manifested near the permian triassic boundary coincides with the negative excursion of carbon isotope this would imply that contrary to previous interpretations this great 13c negative excursion was probably not caused by the upwelling of anoxic deep ocean waters

microbial proliferation coinciding with volcanism during the permian triassic transition new direct evidence from volcanic ashes south china abstract coupling with major biotic extinction both widespread microbially mediated deposits and ash beds characterize the permian triassic boundary ptb successions worldwide thus active volcanism through the ptb interval has been proposed to account for contemporary microbial bloom direct evidence however has long been scarce here we present several lines of evidence for microbial proliferation in the ptb ashes from south china petrographic analysis reveals annular granular and tubular bioalteration textures that formed during microbial dissolution of glass and subsequent precipitation annular textures appear as fresh glass shards connected with bands in different thicknesses showing rough and sharp interfaces and are bordered with fibrous textures granular textures are composed of clusters of near spherical bodies ranging in size from 0 05 to 2 m tubular textures occur as straight curved or spiral tunnels excavating into fresh glass their distinctive morphologies microbe analogous sizes and log normal size distributions all indicate a biogenic origin element mapping along alteration fronts shows enrichment of organic carbon and depletion in metabolically significant elements providing further support for their biogenicity besides textural relationships low n k and high c contents as well as pronounced microstructure density variations between different ash beds in same section all suggest that the bioalteration textures are syngenetic with volcanic glass relevant to microfossils rather than recent microbes we interpret the fossilized organic remains e g small coccoid like spheroids rods filaments and thin films as extracellular polymeric substances eps probably produced by microorganisms which might have served as templates for nucleation and played a crucial role in bio mineralization process the diversity of microstructure sizes shapes and organic remains may reflect a complex community of microbes in the ptb ashes we infer that microbial proliferation may contribute to negative c isotope excursions in the ptb ashes microbial blooms in ash beds directly triggered by large scale volcanism may reveal that extreme environmental stresses prevailed during the ptb crisis

stepwise and large magnitude negative shift in δ13ccarb preceded the main marine mass extinction of the permian triassic crisis interval abstract large perturbations to the global carbon cycle occurred during the permian triassic boundary mass extinction the largest extinction event of the phanerozoic eon 542 ma to present controversy concerning the pattern and mechanism of variations in the marine carbonate carbon isotope record of the permian triassic crisis interval ptci and their relationship to the marine mass extinction has not been resolved to date herein high resolution carbonate carbon isotope profiles 13ccarb accompanied by lithofacies were generated for four sections with microbialite taiping zuodeng cili and chongyang in south china to better constrain patterns and controls on 13ccarb variation in the ptci and to test hypotheses about the temporal relationship between perturbations to the global carbon cycle and the marine mass extinction event all four study sections exhibit a stepwise negative shift in 13ccarb during the late permian early triassic with the shift preceding the end permian crisis being larger 3 than that following it 1 2 the pre crisis shifts in 13ccarb are widely correlatable and hence represent perturbations to the global carbon cycle the comparatively smaller shifts following the crisis demonstrate that the marine mass extinction event itself had at most limited influence on the global carbon cycle and that both late permian 13ccarb shifts and the mass extinction must be attributed to some other cause their origin cannot be uniquely determined from c isotopic data alone but appears to be most compatible with a mechanism based on episodic volcanism in combination with collapse of terrestrial ecosystems and soil erosion

cyanobacterial blooms tied to volcanism during the 5 m y permo triassic biotic crisis widespread but episodic deposition of cyanobacterial mats occurred during the 5 m y permo triassic biotic crisis providing a critical record to decipher the long term stressful environmental conditions and thus a linkage with the killer here we document the timing and duration of these blooms indicated by lipid biomarkers and microbialites throughout south china and compare them to the timing of volcanic activity the initial cyanobacterial bloom has the longest duration and is associated with a prominent eu anomaly in southwestern china where the most intensive volcanism has been proposed to occur suggesting a causal relationship subsequent cyanobacterial blooms in the early triassic are associated with known volcanic events in south china and also with the most voluminous siberian flood basalts and with the largest negative carbon isotope excursions thus it appears that volcanic activity has had a significant impact on microbial development in south china south china volcanism around the permian triassic boundary ptb could have played a much larger role in biotic changes of both bacterial and calcified faunal ecosystems than previously thought the well known siberian volcanism is proposed herein on the basis of the current compilation of dating data to protract the early triassic faunal recovery rather than to cause the end permian extinction

framboidal pyrite evidence for persistent low oxygen levels in shallow marine facies of the nanpanjiang basin during the permian triassic transition abstract previous studies suggested that anoxia was a causal factor in the end permian mass extinction epme marked by abrupt enrichment of pyrite framboids in the post epme microbialites of the earliest triassic on shallow platforms and that this dysoxic anoxic phase followed a time of well oxygenated seafloors here we report persistent dysoxia throughout the latest permian and euxinia just before the epme based on a new redox history reconstruction study using framboidal pyrite size distribution as well as sulfur isotopic compositions of pyrites from the taiping section on the pingguo platform in the nanpanjiang basin in china further we show that the epme was followed here by rapid oxygenation not an anoxic incursion this revised redox history might be an unusual localized phenomenon when compared to other platforms or it could be solid sedimentary evidence for redox oscillations outside the bioclast enriched photic zone which broadens our understanding of terrestrial marine ecosystem interactions before and during the epme

could acidity be the reason behind the early triassic biotic crisis on land abstract in recent years there is growing evidence of the importance of the smithian spathian early triassic ecological crisis to explain the delayed recovery of life after the permian triassic boundary mass extinction this study focuses on sedimentary continental rocks of middle permian to middle triassic age from four different peritethys basins in subequatorial latitudes similar distribution patterns of aluminum phosphate sulfate aps minerals contents in these rocks in the four studied basins provide evidence of increased acidity during the smithian spathian transition coinciding with a lack of indicators of organic activity in the same interval thus this period of high acidity on land may have been one of the causes of this biological crisis based on the quantification of aps minerals in the studied sedimentary sequences we propose that it was not until acidity in the environment diminished that biotic recovery was possible aps data may also be useful to interpret other past biotic crises

enhanced nitrogen fixation in the immediate aftermath of the latest permian marine mass extinction the carbon 13 c org and nitrogen 15 n isotopic compositions of bulk organic matter were analyzed in two high resolution permian triassic transitional sections containing microbialite in south china the results from these shallow marine sections show that an abrupt negative shift in 15 n from 3 to 0 occurred immediately after the latest permian mass extinction lpe in both sections concurrent with a distinct negative shift in 13 c org the persistently low values of 15 n suggest that following the lpe microbial nitrogen fixation became the main source of biologically available nitrogen in the nanpanjiang basin and perhaps over a broader region of the eastern paleotethys ocean enhanced n fixation is probably indicative of the prevalence of stratified anoxic water masses characterized by intense denitrification and or anaerobic ammonium oxidation at the time perturbation of the marine nitrogen cycle might have contributed to high temperatures following the main marine mass extinction through the release of the greenhouse gas n 2 o the sharp declines in 15 n and 13 c org may be ascribed to an abrupt change in shallow water microbial communities which differed in composition from contemporaneous deep water communities

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