numerical investigation of debris materials prior to debris flow hazards using satellite images abstract the volume of debris flows occurred in mountainous areas is mainly affected by the volume of debris materials deposited at the valley bottom quantitative evaluation of debris materials prior to debris flow hazards is important to predict and prevent hazards at midnight on 7th august 2010 two catastrophic debris flows were triggered by the torrential rain from two valleys in the northern part of zhouqu city nw china resulting in 1765 fatalities and huge economic losses in the present study a depth integrated particle method is adopted to simulate the debris materials based on 2 5 m resolution satellite images in the simulation scheme the materials are modeled as dry granular solids and they travel down from the slopes and are deposited at the valley bottom the spatial distributions of the debris materials are investigated in terms of location volume and thickness simulation results show good agreement with post disaster satellite images and field observation data additionally the effect of the spatial distributions of the debris materials on subsequent debris flows is also evaluated it is found that the spatial distributions of the debris materials strongly influence affected area runout distance and flow discharge this study might be useful in hazard assessments prior to debris flow hazards by investigating diverse scenarios in which the debris materials are unknown

lower triassic peritidal cyclic limestone an example of anachronistic carbonate facies from the great bank of guizhou nanpanjiang basin guizhou province south china abstract most shallow marine sections described from the lower triassic formed in mixed carbonate siliciclastic systems shallow marine limestones from an isolated carbonate platform the great bank of guizhou in the nanpanjiang basin south china provide a unique opportunity to examine a pure peritidal carbonate depositional system the platform had a low relief bank profile in the early triassic with oolite shoals at the margin shallow subtidal and peritidal deposits in the interior and pelagics debris flow deposits and turbidites on gentle basin margin slopes interior strata are 265 m thick beginning in the lowermost triassic with renalcis biostromes followed by lime mudstone oolite and cyclic peritidal limestone the cyclic limestone is olenekian in age 164 m thick and contains up to 83 cycles parasequences parasequences are 0 2 7 4 m thick and typically shallow upward from subtidal oolite grainstone and skeletal packstone facies followed by renalcis reef mounds or biostromes and capped by intertidal flaser bedded ribbon rock the skeletal packstone and reef mounds contain a low diversity biota of cyanobacteria echinoderms bivalves gastropods lingulid brachiopods spirorbids and ostracodes ribbon rock contains alternating lime mud and fine peloidal packstone and grainstone laminae scour surfaces ripple cross lamination lime mud drapes and minor prism cracks parasequence stacking patterns exhibit gradual increase and decrease of parasequence thickness defining a third order sequence boundary and several 4th order parasequence sets that correlate between interior sections parasequence stacking patterns similar to those of lower palaeozoic green house sequences and different from ice house sequences the lower triassic platform interior parasequences represent an anachronistic facies in that they are strikingly similar to the common renalcis mound ribbon rock parasequences of the lower palaeozoic and different from other permo triassic parasequences e g capitan shelf parasequences or loferites facies similarities such as renalcis mounds and flaser bedded intertidal ribbon rock reflect anomalous oceanic conditions resulting in low biodiversity and low intensity of bioturbation after the end permian extinction similarities in parasequence stacking patterns reflect low amplitude high frequency sea level fluctuations resulting from green house conditions common to the early palaeozoic and early triassic

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

composition and structure of microbialite ecosystems following the end permian mass extinction in south china after the end permian mass extinction microbialites were widespread in the shallow marine environments in south china diverse microbialites are characteristic of the early triassic carbonate sequences their stratigraphic range is rather short just across the permian triassic p tr boundary and defined by conodonts n meishanensis h changxingensis and h parvus zones thus the p tr microbialites grew immediately after the first episode of the end permian mass extinction coinciding with the beginning of the conodont n meishanensis zone and ceased their growth at the beginning of the conodont i staeschei zone which occurred just before the second episode of the end permian crisis at meishan they include three main types stromatolites thrombolites and dendrites in south china the presence of abundant microbial remains of coccoid type and renalcis like microbes strengthens the previous view that the p tr microbialites are biogenic both cyanobacteria and other microbes have participated to construct the microbial ecosystems the thrombolite communities are dominated by the renalcis like microbes and foraminifers and also contain ostracods microgastropods and microconchids the stromatolite communities are dominated by coccoidal microbes with minor constituents of other undetermined microbes metazoans are rare the dendrolite assemblage contains few identifiable microfossils most of microbialite communities have a high abundance low diversity community structure characteristic of marine communities after the end permian mass extinction some metazoans of either opportunists or disaster forms dwelled in this special ecosystem the microbialite builders formed the primary producer communities and constructed the lowest level ecosystem structure the lower level ecosystem proliferated due to the collapse of the higher level of ecosystem structure characterized by benthic shelly and predator communities in the end permian crisis

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

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

close up of the end permian mass extinction horizon recorded in the meishan section south china sedimentary elemental and biotic characterization and a negative shift of sulfate sulfur isotope ratio abstract the permian triassic p tr boundary beds of the meishan section south china have been re studied in detail based on complete samples across the p tr transition under the microscope the end permian mass extinction horizon is calibrated to a 12 mm stratal interval the top being 19 mm below the top of bed 24e of the changhsing formation this abrupt disappearance of skeletal fragments of major benthos characterizes the end permian extinction event suggesting a catastrophic event an abrupt decrease in the 34s 32s ratios of seawater sulfate is confirmed to coincide with the end permian event horizon the sulfur isotope event is thought to have been caused by an overturn of a stratified ocean dominated by h2s implying coincidence of the oceanic mixing and the mass extinction coincident siberian flood volcanism may have triggered a long term 103 years cooling leading an ocean mixing a presumed comet impact to the ocean could have directly caused ocean mixing and the mass extinction

association of 34s depleted pyrite layers with negative carbonate δ13c excursions at the permian triassic boundary evidence for upwelling of sulfidic deep ocean water masses 1 a marine permian triassic boundary ptb section at nhi tao vietnam contains a series of at least 9 pyritic horizons characterized by concurrent decreases in pyrite s 34spy and carbonate c isotopic compositions 13ccarb the first and largest of the events that precipitated these pyritic horizons was coincident with the late permian mass extinction while subsequent events were generally smaller and occurred at quasiperiodic intervals of 20 to 30 ka a near complete lack of organic carbon to drive bacterial sulfate reduction in sediment pore waters among other considerations argues against a diagenetic control for these relationships rather the covariant patterns documented herein are most easily explained as the product of recurrent upwelling of anoxic deep ocean waters containing 34s depleted hydrogen sulfide and 13c depleted dissolved inorganic carbon the sulfide 34s record of the study section represents a mixture of a small amount of isotopically heavy authigenic pyrite formed via in situ bacterial sulfate reduction with a generally larger quantity of isotopically light syngenetic pyrite precipitated within the water column during upwelling episodes although upwelling of toxic deepwaters has been invoked in earlier studies as a mechanism for the late permian marine mass extinction this is the first study to 1 document patterns of pyrite 13ccarb covariation that strongly support upwelling as a major process at the ptb and 2 provide evidence of multiple quasiperiodic upwelling events that may reflect reinvigoration of global ocean overturn following a prolonged interval of late permian deep ocean stagnation

altered river morphology in south africa related to the permian triassic extinction the permian triassic transition in the karoo basin of south africa was characterized by a rapid and apparently basin wide change from meandering to braided river systems as evidenced by preserved sedimentary facies this radical changeover in river morphology is consistent with geomorphic consequences stemming from a rapid and major die off of rooted plant life in the basin evidence from correlative nonmarine strata elsewhere in the world containing fluvial permian triassic boundary sections suggests that a catastrophic terrestrial die off of vegetation was a global event producing a marked increase in sediment yield as well as contributing to the global 13 c excursion across the permian triassic boundary

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

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

terrestrial marine teleconnections in the collapse and rebuilding of early triassic marine ecosystems abstract the latest permian mass extinction lpe just prior to the permian triassic boundary at 252 ma resulted in the disappearance of 90 of skeletonized marine taxa and the replacement of the paleozoic fauna by the modern fauna in the immediate aftermath of the extinction shallow marine ecosystems were dominated by microbial communities and diminutive disaster taxa lilliput faunas and the post crisis period in general was characterized by high abundance low diversity marine communities occupying a reduced ecological space the recovery of marine ecosystems was a protracted process lasting throughout the 5 myr long early triassic some clades failed to recover and subsequently went extinct dead clades walking while others recovered only to suffer secondary crises during the early triassic profound environmental changes accompanied these biotic developments deep oceans experienced sustained hypoxia or anoxia for at least several million years following the boundary event anoxia was also widespread in shallow marine areas especially at the time of the lpe but it was more episodic and abated more rapidly than in the deep ocean making it an unlikely factor in the delayed recovery of early triassic marine ecosystems the development of anoxia was due at least in part to a sharp temperature rise following the lpe but may have been stimulated by changes in marine nutrient inventories and productivity rates as well these conditions may have been the result of a concurrent increase in subaerial weathering rates that was sustained into the early triassic in addition to increasing nutrient fluxes to marine areas rapid weathering caused a massive influx of sediment to shallow marine systems subjecting marine biotas to siltation stress this scenario implies close teleconnections between terrestrial and marine environments during the permian triassic boundary crisis with perturbations of the terrestrial realm contributing to the marine crisis

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

the end permian regression in south china and its implication on mass extinction abstract records of more than 20 permian triassic boundary ptb sections from south china show that widespread end permian regression took place in whole south china timing of the low ebb of this regression was pinpointed to the clarkina meishanensis and hindeodus changxingensis zones biostratigraphic and paleogeographic studies at conodont zonation level reveal that the yangtze carbonate platform and isolated small carbonate platforms in the hunan guizhou guangxi hgg basin experienced sedimentary hiatus during these two zones which lasted about 50 100 kya meanwhile the basinal areas namely the northern marginal basin of yangtze platform and the hunan guizhou guangxi basin have continuous conodont zonation with silicious and ashbed deposits the basinal areas show two negative 13c shifts during the ptb interval from clarkina yini zone to isarcicella isarcica zone while on the platforms there is usually only one negative shift because the early shift at c meishanensis zone was lost during hiatus the end permian regression and successive rapid transgression taking place at the ptb casted important effects to the pattern and process of the ptb mass extinction the depositional hiatus hitherto underestimated will necessitate reassessment of some interpretations on the causes and results of that extinction

permian triassic boundary interval as a model for forcing marine ecosystem collapse by long term atmospheric oxygen drop ecological traits of reefs across the permian triassic boundary interval coincide with a modeled decline of atmospheric oxygen throughout the permian period selective extinction and recovery patterns within the reef system are observed both at the end of the middle permian end guadalupian and at the permian triassic boundary the end guadalupian event selectively affected corals and broke down the cool water carbonate factory sponges however were largely unaffected and bloomed in reefs toward the end of the permian the end permian total destruction of the metazoan reef system only left behind poorly diverse microbial communities the temporal reef patterns are thus similar to spatial patterns of modern benthic communities approaching oxygen minimum zones this observation suggests that a decline in oxygen concentrations was at least partly involved in the destruction of reefs even where there is no direct evidence of oceanic anoxia

de compaction of porous viscoelastoplastic media solitary porosity waves buoyancy driven flow in deformable porous media is important for understanding sedimentary compaction as well as magmatic and metamorphic differentiation processes here mathematical analysis of the viscoplastic compaction equations is used to develop an understanding of the porosity wave instability and its sensitivity to the choice of rheological model the conditions of propagation size speed and shape of the porosity waves depend strongly on the properties of the solid rock frame whereas most of the previous studies on porosity waves were focused on viscous or viscoelastic mode here we consider the ability of a solid matrix to undergo simultaneous plastic rate independent and viscous rate dependent deformation in parallel plastic yielding is identified as a cause of compaction decompaction asymmetry in porous media this is known to lead to a strong focusing of porous flow speed and amplitude of a porosity wave are given as functions of material parameters and a volume of a source region formulation is applicable to fluid flow in sedimentary rocks where viscous deformation is due to pressure solution as well as in deep crustal or upper mantle rocks deforming in a semibrittle regime

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

the permian triassic boundary at nhi tao vietnam evidence for recurrent influx of sulfidic watermasses to a shallow marine carbonate platform the permian triassic boundary at nhi tao cao bang province vietnam was sampled in a 7 5 m thick outcrop section at high resolution 5 cm intervals for chemostratigraphic and magnetic susceptibility analysis the section consists entirely of slightly argillaceous limestone representing shallow marine facies of the jinxi platform one of several large carbonate platforms within the nanpanjiang basin located on the southern margin of the south china craton upper permian strata beds 1 7 are mainly dark gray cherty fossiliferous wackestones and packstones containing a diverse open marine fauna whereas uppermost permian and lower triassic strata beds 9 and higher are medium gray calcimicrobial framestones containing rare macrofossils these facies are separated by a 12 cm thick oolitic pisolitic grainstone bed 8 that coincides with the disappearance of most late permian faunal elements as well as with the first appearance of various geochemical anomalies that continue into the lower triassic part of the section this late permian event horizon is characterized by 1 an abrupt decline in total organic carbon to near zero values 2 the onset of a sustained decline in carbonate 13c and 3 the first of eight concentration peaks in pyrite sulfur significantly each sulfide peak is associated with lower pyrite 34s values as well as with the onset of a negative carbonate 13c excursion or the acceleration of an excursion already in progress these chemostratigraphic relationships are consistent with multiple episodes of upwelling of sulfidic 34s and 13c depleted deep ocean waters onto the jinxi platform the first upwelling event was the most intense and caused a drastic reduction in primary productivity and the demise of the late permian fauna subsequent episodes were less intense but may have contributed to a delay in recovery of early triassic marine ecosystems a ten fold increase in magnetic susceptibility in bed 9 may record the influx of fine detrital particles following destruction of terrestrial ecosystems and massive soil erosion the terrestrial signal of the end permian catastrophe thus follows the marine signal with a 12 cm lag which may reflect the time of transit of soil derived particles across the nanpanjiang basin suggesting that the marine and terrestrial crises in the nhi tao region occurred more or less synchronously these observations suggest a model in which renewal of global ocean overturn followed a prolonged interval of deep ocean stagnation during the late permian with upwelling intensity modulated by short term 20 kyr climate cyclicity

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

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

two pulses of extinction during the permian triassic crisis over 90 of marine species were lost during the end permian extinction fossil data show that the crisis in china was marked by two distinct phases of marine extinction separated by a 180 000 year recovery period

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

paleoredox biotic and sulfur isotopic changes associated with the end permian mass extinction in the western tethys abstract detailed cm scale s toc total organic carbon 34ssulfide and pyrite morphological analysis of the permian triassic boundary beds at the bulla section northern italy suggests that marine waters at this site saw the influx of two dysoxic euxinic intervals that mark the end permian extinction event this suggests reduced oxygen conditions and the presence of h2s is the cause of the end permian extinction the bulla section also shows three troughs in 34ssulfate of which the latter two coincide with the dysoxic euxinic intervals this suggests that the latter two 34ssulfate troughs are the result of h2s oxidation in surface waters but the first trough is the result of a different mechanism we propose that h2s was oxidized in another region either to low 34ssulfate water or elemental s which then moved to the bulla area at the balvany section hungary there are two 34ssulfate troughs near the extinction and no evidence of euxinia a similar mechanism to the first bulla 34ssulfate trough is proposed with the suggestion that these waters were also depleted in oxygen in order to effect the extinction at balvany

complete biotic and sedimentary records of the permian triassic transition from meishan section south china ecologically assessing mass extinction and its aftermath abstract the meishan section south china is the global stratotype section and point gssp for the permian triassic boundary ptb and is also well known for the best record demonstrating the permian triassic mass extinction ptme all over the world this section has also been studied using multidisciplinary approaches to reveal the possible causes for the greatest phanerozoic biocrisis of life on earth many important scenarios interpreting the great dying have been proposed on the basis of data from meishan nevertheless debates on biotic extinction patterns and possible killers still continue this paper reviews all fossil and sedimentary records from the permo triassic p tr transition based on previously published data and our newly obtained data from meishan and assesses ecologically the ptme and its aftermath to determine the biotic response to climatic and environmental extremes associated with the biocrisis eight updated conodont zones clarkina yini clarkina meishanensis hindeodus changxingensis clarkina taylorae hindeodus parvus isarcicella staeschei isarcicella isarcica and clarkina planata zones are proposed for the ptb beds at meishan major turnover in fossil fragment contents and ichnodiversity occurs across the boundary between bed 24e 5 and bed 24e 6 suggesting an extinction horizon in a thin stratigraphic interval the irregular surface in the middle of bed 27 is re interpreted as a firmground of glossifungites ichnofacies rather than the previously proposed submarine dissolution surface or hardground surface both fossil fragment contents and ichnodiversity underwent dramatic declines in beds 25 26a coinciding with metazoan mass extinction fossil fragment content ichnodiversity and all ichnofabric proxies including burrow size tiering level bioturbation level indicate that the p tr ecologic crisis comprises two discrete stages coinciding with the first and second phases of the ptme in meishan ecologic crisis lagged behind biodiversity decline during the ptme pyrite framboid size variations suggest that depositional redox condition was anoxic to euxinic in the latest changhsingian became euxinic in beds 25 26a turned dysoxic in bed 27 then varied from euxinic to anoxic through most of the griesbachian the 9 c increase in seawater surface temperature from bed 24e to bed 27 at meishan seems to result in dramatic declines in biodiversity and fossil fragment contents in beds 25 26a but had little effect on all ecologic proxies both metazoans and infauna seem not to have been affected by the pre extinction anoxic euxinic condition the anoxic event associated with the ptme may have occurred in a much shorter period than previously thought and is only recorded in beds 25 26a at meishan fossil fragment contents ichnofaunas ichnofabrics and pyrite framboid size all show that no signs of oceanic acidification and anoxia existed in bed 27 the early griesbachian anoxia may have resulted in rarity of ichnofauna and metazoans in the lower yinkeng formation in which the ichnofauna is characterized by small simple horizontal burrows of planolites and metazoan faunas are characterized by low diversity high abundance opportunist dominated communities the rapid increase of 9 c in sea surface temperature and a short anoxia or acidification coincided with the first pulse biocrisis while a prolonged and widespread anoxia probably due to a long period of high seawater temperate condition may be crucial in mortality of most organisms in the second pulse ptme marine ecosystems started to recover coupled with environmental amelioration in the late griesbachian