the permo triassic transition in spitsbergen δ13corg chemostratigraphy fe and s geochemistry facies fauna and trace fossils new 13 c org analyses of two boundary sections between the late permian kapp starostin formation and the early triassic vardebukta formation of western spitsbergen confirm field evidence that their contact is a conformable one thus contrary to previous reports some spitsbergen sections contain a complete record of the environmental and faunal changes during the crisis interval of the end permian mass extinction no environmental deterioration is recorded in the late permian until near the end of the terminal changxingian stage whereupon the abundant siliceous sponge fauna of the kapp starostin formation disappears along with the deep burrowing fauna responsible for the zoophycus trace fossil a low diversity dysaerobic trace fossil assemblage is briefly developed before a transition to finely laminated pyritic facies immediately beneath the permo triassic boundary analysis of the s c ratios from the laminated strata suggests that free h 2 s was present in the water column euxinic conditions even in relatively nearshore settings subject to storm sandstone deposition the mass extinction crisis in spitsbergen is therefore coincident with the extensive development of oxygen poor conditions in the water column and compares closely both in timing and nature with the crisis seen in lower latitude tethyan settings however the subsequent aftermath and recovery in the boreal sections of spitsbergen was more rapid than in tethys thus a shoreface sandstone body within the dienerian stage contains an appreciable diversity of fauna by the standards of the early triassic including bryozoans calcareous algae and deep infaunal bivalves that suggests the marine ecosystem recovery began earliest in higher palaeolatitudes

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

earliest triassic claystone breccias and soil erosion crisis abstract chemostratigraphic methods 13corg for pinpointing the permian triassic boundary in nonmarine rocks of antarctica australia and south africa have drawn attention to unusual claystone breccias at this horizon of the greatest extinction in the history of life on earth these rocks differ from other breccias in having a high proportion of clasts with birefringence microfabrics sepic plasmic fabrics characteristic of soils and can be called sepic pedoliths in the terminology of soil science at many localities earliest triassic sepic pedoliths are thin 5 15 cm beds but some fill shallow paleochannels and pinch out laterally other non marine breccias at the permian triassic boundary are dominated by fragments of coal pedogenic carbonate nodules and deeply weathered volcanic rock fragments earliest triassic sepic pedoliths record an unusually severe and widespread episode of soil erosion associated with forest dieback at the permian triassic boundary comparable sepic pedoliths are found in debris flows after clear cutting of forests in western oregon today studies of these modern deposits show that sepic soil peds do not withstand weathering for more than a few months such clayey clasts are held together mainly by roots and fungi which decay rapidly in soils and streams these modern analogs demonstrate that terminal permian soil erosion was rapid and profound sepic pedoliths are also known at other times of mass extinction such as the triassic jurassic boundary but are not yet known before the devonian advent of trees and forested clayey soils

evidence for rapid precipitation of calcium carbonate in south china at the beginning of early triassic abstract anachronistic facies are sedimentary features and fabrics that are very common in the early history of the earth but mainly occur following mass extinctions during the phanerozoic anachronistic facies are typically found in carbonates commonly have a microbial origin and reflect an unusual oceanic chemistry the aftermath of the end permian mass extinction is one of the periods when anachronistic facies were common and occur in sedimentary rocks from around the world in south china different types of anachronistic facies appear in an orderly succession over time microbialites are often the first anachronistic sediments that formed after the end permian mass extinction in shallow platform settings and are subsequently followed by oolites and oncolites which are sometimes intercalated with vermicular limestones because different types of anachronistic facies represent different depositional environments this succession pattern in the strata records the evolution of marine environments following the end permian mass extinction based on sedimentological analysis of the yangjiawan section hunan province south china this study suggests that the transition from microbialite to oolitic limestone was associated with a rise of sea level and an increase in hydrodynamic energy the shift from oolite to oncolite reflects a sustained rapid rise of sea level the occurrence of vermicular limestone is considered to be the product of an ephemeral restricted environment anachronistic facies reach a thickness of 75 m at the yangjiawan section while over nearly the same time interval argillaceous limestone reaches a thickness of only 40 cm of beds 27 29 at the global stratotype section and point gssp section at meishan in zhejiang province this difference in thickness indicates strongly elevated sedimentation rates in shallow water platform settings after the end permian mass extinction high rates of carbonate precipitation are indicative of calcium carbonate supersaturation within shallow watermasses which may have resulted from the upwelling of alkaline anoxic deep waters accompanied by high rates of evaporation as a consequence of extremely high temperatures at the time nevertheless it is the global sea level rise in the early triassic that provided the accommodation space necessary for the precipitation of the great thickness of anachronistic carbonate sediments at the yangjiawan section

lower silurian stromatolites in shallow marine environments of the south china block guizhou province china and their palaeoenvironmental significance this study was supported by national natural science foundation of china granted no 41072002 41372022 xdb10010503 and 41521061

investigating the effects of micro texture and geo mechanical properties on the abrasiveness of volcanic rocks abstract the abrasiveness of rocks is a fundamental rock property that affects sawing and cutting performance wear of tunnel boring machine tbm heads the cerchar abrasiveness index cai test is a commonly used procedure to define rock abrasivity this paper investigates the relationship between quantitative mineralogical and petrographic data and cai values for some selected volcanic rocks in addition the research examines the relationship between physical e g effective porosity and p wave velocities and mechanical e g uniaxial compressive strength ucs brazilian tensile strength bts young s modulus e properties including brittleness values and cai values quantitative mineralogical and petrographic analyses reveal the variations in micro textural properties as defined by different groundmass phenocryst ratios analyses also suggest that the dimensions of opaque minerals and plagioclase feldspar apparently have individual effects on cai values additionally the combined effects of grain size and primary types of constituent minerals have a significant on cai values additionally results of physical and mechanical tests indicate that as p wave velocities increase cai values increase the increasing values of ucs bts and e cause cai values to increase significantly however only one of three brittleness values was found to have a considerable relationship with cai values this research demonstrates the importance of evaluating the micro textural variations and the combined effects of micro texture physical properties and mechanical properties on the cai values of volcanic rocks

the unusual sedimentary rock record of the early triassic a case study from the southwestern united states abstract sedimentary systems as well as the earth s biota changed dramatically following the end permian mass extinction this global sedimentological transformation is reflected in the widespread occurrence of flat pebble conglomerates subtidal wrinkle structures microbialites and carbonate seafloor fans in various lower triassic sections as a case study a facies analysis of the lower triassic virgin limestone member of the moenkopi formation and the middle and upper members of the union wash formation southwestern united states was conducted and all unusual facies were documented within a palaeoenvironmental framework the occurrence of the flat pebble conglomerates and wrinkle structures is significant because these reflect a long term reduction in vertical bioturbation in the case of the subtidal microbialites and carbonate seafloor fans their formation is linked to an increase in alkalinity the presence of these facies in the uppermost lower triassic strata of the southwestern united states indicates that reduced levels of infaunal bioturbation as well as and perhaps a consequence of unusual ocean chemistry extended for 5 6 million years after the end permian mass extinction suggesting that depositional environments as well as the biota were significantly affected by the extinction event

tsunami induced conglomerates in miocene upper bathyal deposits chita peninsula central japan abstract the tsubutegaura conglomeratic tsunamiites occur in the middle section of the miocene storm related sand silt alternation system in the chita peninsula central japan deposition of the system in the upper bathyal environment in a bay and synsedimentary seismic activity has been elucidated by palaeontological palaeogeographical and sedimentological studies two coupled units each built up by a conglomerate layer with an overlying sandstone layer and the alignment of lenticular sedimentary bodies are exceptional in this sequence some typical lenticular bodies confined within sedimentary troughs consist of a boulder bearing conglomerate layer and calcareous sandstone layer of the lower couple and another conglomerate layer of the upper couple the tuffaceous sandstone layer of the upper couple is distributed more widely than the other lithologies the framework gravels in the coupled conglomerates form a clast supported fabric and are quite notably monomictic the clasts are angular and imbricated partly forming peculiar gravel clusters due to traction current transportation conspicuous laminations develop in the coupled sandstone layers antidunes with chute and pool structure in the upper couple sandstone layer indicate deposition from an upper flow regime current on the other hand the calcareous composition of the lower couple sandstone layer reveals shallow water provenance thixotropic deformations and diastasis cracks in the siltstone bed immediately beneath the layers of the couples show that a severe earthquake tremor and a rapid change of water pressure occurred just before the deposition of the tsunamiites submarine debris flows due to collapse of a fault scarp in a shallow bank and the ensuing wash by two pulses of the tsunami induced ebb current comprise the scenario for the formation of the tsubutegaura conglomeratic tsunamiites

stromatolites of the lower triassic union wash formation ca evidence for continued post extinction environmental stress in western north america through the spathian abstract recent studies have documented the complexity of biotic recovery from the permian triassic mass extinction by revealing that recovery began quickly in some regions while the biota in other areas continued to suffer as the result of widespread harsh environmental conditions throughout much of the early triassic period examination of lower triassic rocks from the southwestern u s has produced a variety of sedimentologic and biotic evidence that point to persistent environmental stress following the extinction specifically anoxic alkaline waters in the deep ocean and possible high carbon dioxide levels in the surface ocean and have also documented trends in the long suffering biota present in that region the shoaling facies of the upper member of the union wash formation at the cerro gordo ca usa locality contain stratiform stromatolites that suggest harsh environmental conditions in the area may have lingered until the late spathian latest early triassic the stromatolites are laterally extensive some layers persist for at least 1 km and typically exhibit planar to wavy laminations with some development of small domes up to 10 cm in height a shallow subtidal depositional environment is suggested by evidence of eroded or planed surfaces within the stromatolites as well as channelization of the stromatolites and the occurrence of ooids and coated grains within the interval the stromatolites documented here occur stratigraphically higher than previously documented inorganic calcium carbonate precipitates from the union wash formation e g woods a d bottjer d j corsetti f a 2007 calcium carbonate seafloor precipitates from the outer shelf to slope facies of the lower triassic smithian spathian union wash formation california u s a sedimentology and palaeobiologic significance palaeogeography palaeoclimatology palaeoecology 252 281 290 woods a d bottjer d j mutti m morrison j 1999 lower triassic large seafloor carbonate cements their origin and a mechanism for the prolonged biotic recovery from the end permian mass extinction geology 27 645 648 and microbialites from the virgin limestone e g schubert j k bottjer d j 1992 early triassic stromatolites as post mass extinction disaster forms geology 20 883 886 pruss s b bottjer d j 2004 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 palaeogeography palaeoclimatology palaeoecology 211 127 137 therefore these stromatolites may represent the last known occurrence of anachronistic facies and associated unusual palaeoceanographic conditions in eastern panthalassa following the permian triassic mass extinction

time specific aspects of facies state of the art examples and possible causes abstract the term time specific facies tsf was introduced to the scientific community by the late otto h walliser to refer to unique facies typical of particular narrow intervals some of which were related to bioevents in some senses however the concept was recognized much earlier and is even engrained in the very names of some geologic periods the concept of time specific facies is expanded slightly herein to include distinctive or unique regional to global characteristics of the sedimentary record that characterize particular intervals of geologic time the recognition of time specific and widespread processes in the sedimentary record is a critical step in unraveling the interplay between processes of differing scale these range from very short term but widespread facies that overlap with event deposits to general facies types that may persist for intervals up to 10s of millions of years in duration this paper briefly summarizes the history of development of the tsf concept provides examples to illustrate a few of the key aspects of time specific facies and offers a few tentative explanations for this phenomenon among the factors that control tsfs abrupt changes in redox conditions and early diagenetic mineralization sedimentary condensation often associated with abrupt sea level change altered climate and paleoceanography and biotic evolution and extinction seem to be most critical and permit a preliminary genetic classification of tsfs inevitably however many tsfs reflect multiple effects and some remain largely unexplained

microbially induced sedimentary structures misss from the lower triassic kockatea formation northern perth basin western australia palaeoenvironmental implications abstract like microbialites microbially induced sedimentary structures misss are commonly observed in siliciclastic and mixed carbonate siliciclastic settings in the lower triassic and are represented by several morphological types including wrinkle structures however their origin and their role in the early triassic ecosystem recovery is currently a hot topic of debate herein we report and describe abundant wrinkle structures from the smithian kockatea shale formation of northampton area in the perth basin western australia on the basis of detailed field observations as well as petrographic and sem examinations of rock thin sections the surficial morphologies of wrinkles are characterized by closely spaced crests and ridges on the upper bedding surfaces together with other forms such as pitted bulges and reticulated ridges detailed petrologic analysis revealed that the smithian wrinkle structures from the northern perth basin possess a distinct vertical profile 1 cross stratified lamianted sandstone 2 alternating laminated layers and sandstone 3 laminated layers and 4 wrinkled layers in an ascending order the wrinkled layers are overlain by thin shale laminated layers beneath wrinkled surfaces comprise densely packed pronounced wavy laminae mica flakes in laminations show a preferred alignment parallel to bedding under sem imaging suggesting the binding and trapping of the former presence of a microbial matground these evidences support that the early triassic wrinkle structures from the smithian kockatea formation are biogenic in origin close association of both trace and body fossils with the wrinkle structure bearing layers is interpreted to indicate the presence of a matground ecosystem in which some small gastropods and various trace making animals lived possibly taking the habitat as a refuge the global temporal and spatial occurrences of early triassic miss were tabulated and analyzed revealing a wide range of palaeoenvironmental distributions and the seemingly selected association between metazoans and certain miss as to why only some misss have been found together with metazoans remains as an open question it will require further investigation especially with regard to the specific type of microbes that had built the microbial matground ecosystems and their interplay with the hosted metazoans in the aftermath of the end permian mass extinction

anachronistic facies and carbon isotopes during the end permian biocrisis evidence from the mid tethys kisejin iran abstract late permian mass extinction lpme research has focused primarily on tethyan sections because it is believed that these successions are more complete than those from other localities and provide a more comprehensive record of the largest most devastating extinction event in earth history the kisejin section a previously undocumented mid tethyan upper permian lower triassic succession located in the central iran plate the kisejin section contains a continuous permian triassic sequence with only small breaks in sedimentation and was examined in order to determine sedimentologic biostratigraphic and carbon isotopic trends across the permian triassic transition abnormal anachronistic carbonates developed in the study area following the lpme and include microbialites edgewise conglomerates sparitic microspheres and microbially coated grains microbialites occur as thrombolites stromatolites and as agglutinated forms renalcis type calcimicrobes are documented for the first time from permian triassic boundary microbialites ptbms of iran coated grains fall into two groups and include pre ptbm ooids which are dense and cloudy and possibly microbial in origin and post ptbm cortoids with destructive and constructive micrite envelopes latest permian conodonts h praeparvus m ultima coupled with carbon isotopic values place the permian triassic boundary within the lowermost thrombolite unit about 2 1 m above the boundary between the nessen formation and the elika formation and indicate that microbialite growth began during the latest permian our study of this previously unknown section shows that unlike other well known ptb sections from iran the microbialite pattern is complicated and is more similar to ptbm successions from turkey in addition we note a similarity between the unusual facies of the kisejin section and those of eastern tethyan sections from china i e sparry microspheres and renalcis type calcimicrobes these unusual facies have not been previously reported from other well known iranian sections including julfa and abadeh which are thick and have been extensively studied

marine diagenesis of lower ordovician carbonate sediments dumugol formation korea cementation in a calcite sea abstract the lower ordovician dumugol formation exhibits many features that indicate early lithification such as calcite nodules hardgrounds mud mounds and intraclasts detailed observations of these early lithified features reveal that rapid marine cementation was instrumental in their formation marine lithification took place in a low energy subtidal environmental that was influenced by intermittent storms marine cements include syntaxial overgrowth bladed calcite fibrous calcite and fine crystalline equant calcite cements syntaxial overgrowths precipitated on echinoderm grains and contributed to rapid marine lithification of echinoderm bearing sediments bladed fibrous and fine crystalline equant calcite cements precipitated in locally suitable sites but their occurrence is limited and thus played a minor role in marine lithification microcrystalline calcites also precipitated in lime mud rich fine grained sediments and participated in rapid marine lithification of the dumugol sediments the absence of aragonite allochems and cement and the predominance of calcite cement suggest that the dumugol sea was undersaturated with respect to aragonite but supersaturated with respect to calcite which is indicative of a calcite sea

early triassic disaster and opportunistic foraminifers in south china survival and recovery are important dynamic processes of biotic evolution during major geological transitions disaster and opportunistic taxa are two significant groups that dominate the ecosystem in the aftermath of mass extinction events disaster taxa appear immediately after such crises whilst opportunists pre date the crisis but also bloom in the aftermath this paper documents three disaster foraminiferal species and seven opportunistic foraminiferal species from lower triassic successions of south china they are characterized by extreme high abundance and low diversity and occurred occasionally in griesbachian smithian and spathian strata the characteristics small size simple morphology and stratigraphic ranges of these groups suggest that r selection is a commonly used strategy for survivors to cope with either harsh post extinction conditions and or environments lacking incumbents

trace fossils and the aftermath of the permo triassic mass extinction evidence from northern italy abstract the duration of early triassic anoxia in the carbonate ramp settings of the werfen formation dolomites northern italy has been constrained using ichnofabric and sedimentological data this includes fine lamination and abundant pyrite framboids commonly reworked into lags by storm events the anoxic event spanned the entire griesbachian stage and extended from deep waters into extraordinarily shallow water settings evidence for oxygen deficiency can be found in mid and inner ramp facies the extent and duration of this event may at least partially explain the magnitude of the permo triassic mass extinction normal benthic conditions returned rapidly in the dienerian stage and pervasively bioturbated distal ramp facies testify to the ventilation of the deeper water areas of the region in post griesbachian times a post mass extinction radiation is not particularly well displayed in either trace fossil or body fossil diversity compilations from the dolomites moderate low levels of trace fossil diversity are maintained throughout the post griesbachian werfen formation whilst the body fossil data shows a moderate increase from the mid smithian stage there is thus a curious lag period spanning the dienerian to mid smithian when environmental conditions were apparently normal but the marine fauna failed to show any recovery

trends in depth and extent of bioturbation in cambrian carbonate marine environments western united states cambrian carbonate strata of the great basin deposited below fairweather wave base but above mean storm wave base inner shelf and below mean storm wave base but above maximum storm wave base middle shelf were examined for extent and depth of bioturbation data indicate that initial extensive colonization of marine infaunal habitats occurred between tommotian and atdabanian time throughout the remaining 65 m y of cambrian time bioturbation increased although depth of bioturbation remained relatively constant at less than 6 cm during this time the amount of bioturbation in the inner shelf was greater than that in the middle shelf

geochemical evidence from bio apatite for multiple oceanic anoxic events during permian triassic transition and the link with end permian extinction and recovery abstract a detailed 20 myr redox history of permian to triassic oceans changhsingian to carnian stages has been constructed using ce anomaly ce and th u ratios from conodont albid crown apatite material the results show that the well established phenomenon of intense ocean anoxia coincident with the end permian mass extinction is faithfully recorded in conodont ce and th u data extending this conodont redox record shows that end permian anoxia persisted possibly into the earliest dienerian stage and that two intense oceanic anoxic events also occurred later in the early triassic earliest smithian earliest spathian and middle spathian followed by a weaker manifestation of anoxia in the anisian stage seen in ce data marine benthic radiation following the end permian mass extinction began after the smithian earliest spathian anoxic event suggesting a suppression of evolution prior to this due to these inimical conditions the failure of the middle spathian anoxic event to retard the evolutionary rebound implies shallow shelf seas remained well ventilated at this time even if the oceans did not other attributes of the early triassic record also closely coincide with redox fluctuations phases of anoxia intensification saw the proliferation of microbial carbonates and major negative carbon isotope swings that can be attributed to chemocline shallowing causing alkalinity pulses and enrichment in light remineralised carbon and or indicate a trigger meachnaims related to increased fluxes of light c from siberian volcanic sources

microbial mats in the terrestrial lower triassic of north china and implications for the permian triassic mass extinction abstract evidence for microbial mats has been reported repeatedly from marine lower triassic rocks but scarcely mentioned in post mass extinction terrestrial facies here we report from the terrestrial lower triassic liujiagou formation in north china the presence of five kinds of microbially induced sedimentary structures miss or sedimentary surface textures including old elephant skin textures wrinkle structures palimpsest ripples manchuriophycus structures and sand cracks terrestrial microbial communities that produced these miss adapted not only to periodically desiccated conditions but also to the storm dominated palaeoenvironments in the liujiagou formation the permian triassic mass extinction ptme in north china is marked by the die off of plants disappearance of coal beds extinction of pareiasaurs among tetrapods decreased bioturbation levels and a dramatic change of sedimentary systems through the sunjiagou formation the sunjiagou formation recorded the turnover from an ever wet to a progressively drier and hotter climate and it spans the ptme in north china following this mass extinction miss became much more common and widespread suggesting that the mass extinction provided favourable biological and environmental conditions for the development of the miss in terrestrial ecosystems especially the decreased bioturbation intensity and grazing pressure associated with increased temperature and climatic drying in the upper part of the liujiagou formation and overlying heshanggou formation the disappearance of miss coupled with increased bioturbation might indicate an improvement of terrestrial ecosystems and the beginning of the triassic biotic recovery however as the investigation of miss in space and time through the geological record is in its early stages further geobiologic and geochemical studies as well as high precision isotopic dating from permian triassic terrestrial successions are needed to fully reveal the timing and pattern of the early triassic terrestrial ecosystem reconstruction

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

anoxia as a cause of the permian triassic mass extinction facies evidence from northern italy and the western united states facies faunal and geochemical evidence from the permian triassic boundary sediments of the dolomites and idaho indicates a major anoxic event in the earliest triassic in both regions the basal beds consist of finely laminated micrites with common syngenetic pyrite the only fauna consists of occasional bedding plane assemblages of lingula or clacaria a typical lower dysaerobic assemblage this is a level where previous studies have shown a major negative carbon isotope excursion and a cerium anomaly in the dolomites the pyritic micrite directly overlies strata containing a diverse and typically permian marine fauna of algae foraminifers including fusulinids and articulate brachiopods implying an abrupt extinction in contradiction to many previous views sequence stratigraphic analysis of the dolomite boundary sediments reveals a minor sequence boundary in the late permian followed by extremely rapid transgression leading to the development of the relatively deep water pyritic micrite a maximum flooding surface at the permo triassic boundary a further pulsed deepening in the lower griesbachian recorded in both the dolomites and idaho lead to the widespread establishment of dysaerobic facies it is clear that most of the extinctions occurred at the erathem boundary although the subsequent failure of the marine benthos to fill the empty ecospace in the ensuing griesbachian may have been due to the widespread development of dysaerobic conditions

uranium depletion across permian triassic boundary in persian gulf and its implications for paleooceanic conditions abstract high resolution uranium analyses as well as oxygen carbon and strontium isotopes data through permian triassic boundary ptb in the marine sections of three offshore wells in persian gulf are illustrated in this paper a decreasing trend in u content from upper permian strata toward the ptb is recorded in all wells such a trend could not be adequately explained by the facies changes diagenetic events salinity variations dolomitization or total organic carbon toc content of the samples distinct and negative uranium anomalies coincide with the onset of the carbon isotope shifts which might indicate influx of anoxic waters the th u ratios below the ptb in the studied sections are mainly less than 2 reinforcing this possibility reducing conditions associated with the anoxia would have gradually increased the rate of u fixation on the deep sea floor resulting in low u concentration in the shallow water carbonates a negative 18o shift of about 4 could be seen at the ptb in all studied wells such excursion indicates a meteoric diagenesis below the boundary also abnormally higher 87sr 86sr ratios below the ptb indicate significant input of radiogenic 87sr during subaerial exposures at the end of permian this palaeoexposure surface is also reflected in depleted oxygen isotope values of this interval biostratigraphic studies also show that some important guide forms of late permian are absent in studied wells that could be due to several factors including non sedimentation subaerial exposure and erosion thus a near surface meteoric realm or emergent surface could be considered for the ptb in studied wells

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

anachronistic facies from a drowned lower triassic carbonate platform lower member of the alwa formation ba id exotic oman mountains abstract the lower member of the alwa formation lower olenekian found within the ba id exotic in the oman mountains sultanate of oman consists of ammonoid bearing pelagic limestones that were deposited on an isolated drowned carbonate platform on the neotethyan gondwana margin the strata contain a variety of unusual carbonate textures and features including thrombolites frutexites bearing microbialites that contain synsedimentary cements matrix free breccias surrounded by isopachous calcite cement and fissures and cavities filled with large botryoidal cements thrombolites are found throughout the study interval and occur as 0 5 1 0 m thick lenses or beds that contain laterally laterally linked stromatactis cavities the frutexites bearing microbialites occur less frequently and also form lenses or beds up to 30 cm thick the microbialites may be laminated and often developed on hardgrounds in addition the frutexites bearing microbialites also contain synsedimentary calcite cement crusts and botryoids typically frutexites bearing microbialites low level of calcium carbonate supersaturation associated with anoxic conditions and deposition below a stable chemocline formed the results of this study point to continued environmental stress in the region during the early triassic that likely contributed to the uneven recovery from the permian triassic mass extinction

carbonate ramp to deeper shale shelf transitions of an upper cambrian intrashelf basin nolichucky formation southwest virginia appalachians the nolichucky formation 0 300 m thick formed on the cambrian pericratonic shelf in a shallow intrashelf basin bordered along strike and toward the regional shelf edge by shallow water carbonates and by nearshore clastics toward the craton lateral facies changes from shallow basinal rocks to peritidal carbonates suggest that the intrashelf basin was bordered by a gently sloping carbonate ramp peritidal facies of the regional shelf are cyclic upward shallowing stromatolitic carbonates these grade toward the intrashelf basin into shallow ramp cross bedded ooid and oncolitic intraclast grain stones that pass downslope into deeper ramp subwave base ribbon carbonates and thin limestone conglomerate ribbon limestones are layers and lenses of trilobite packstone parallel and wave ripple laminated quartzose calcisiltite and lime mudstone arranged in storm generated fining upward sequences 1 5 cm thick that may be burrowed shallow basin facies are storm generated upward coarsening and upward fining sequences of green calcareous shale with open marine biota parallel to hummocky laminated calcareous siltstone and intraformational flat pebble conglomerate there are also rare debris flow paraconglomerate 10 60 cm thick and shaly packstone wackestone with trace fossils glauconite horizons and erosional surfaces hardgrounds a 15 m thick tongue of cyclic carbonates within the shale package contains subtidal digitate algal bioherms which developed during a period of shoaling in the basin understanding the nolichucky facies within a ramp to intrashelf basin model provides a framework for understanding similar facies which are widely distributed in the lower palaeozoic elsewhere the study demonstrates the widespread effects of storm processes on pericratonic shelf sedimentation finally recognition of shallow basins located on pericratonic shelves is important because such basins influence the distribution of facies and reservoir rocks whose trends may be unrelated to regional shelf edge trends

unusual intraclastic limestones in lower triassic carbonates and their bearing on the aftermath of the end permian mass extinction flat pebble conglomerates were a common carbonate facies in cambrian to early ordovician open marine settings but they become extremely rare in these environments after this time however the early triassic witnessed an anachronistic reappearance of flat pebbles together with other intraclast types in a range of carbonate depositional settings in south china flat pebble conglomerates are encountered in storm dominated platform carbonates to deep basinal settings while prefossilized bivalve intraclasts and flat pebbles are common in mid ramp facies of northern italy the emplacement mechanisms of the intraclast bearing beds appear to have been diverse and to have included basinal turbidity flows and storm generated hyperconcentrated flows true storm beds deposited under combined flow conditions are rare the cause of the widespread early lithification implied by the early triassic intraclasts appears to have been twofold suppression of bioturbation allowing the preservation of thin beds and rapid submarine lithification both features appear to be a response to the widespread development of benthic dysoxia anoxia during and following the end permian mass extinction this event appears to have temporarily recreated the conditions that pertained in cambro ordovician shelf seas flat pebble conglomerates may therefore constitute a proxy indicator of stressed environmental conditions associated with global anoxic dysoxic events

evolutionary models in the early triassic marine realm abstract the relative influences of extrinsic compared to intrinsic drivers of evolutionary change have long been theorized and debated in the fossil record ecological recoveries from mass extinction events present records in which to examine these contrasts competition in a low diversity world reproductive strategy reconstruction of trophic systems and ecological specialization represent possible intrinsic controls on diversification feedback between diversity and abundance shifts of marine organisms with biogeochemical cycling and environmental conditions act as extrinsic controls on recovery process and rate disentangling these evolutionary pressures is a major challenge for understanding evolutionary recovery from mass extinction the end permian mass extinction 251 88 ma represents the largest mass extinction in earth history and led to an extended recovery interval which lasted the duration of the early triassic 4 8 myr and beyond recent analyses suggest that the survivors of the mass extinction were biased toward organisms with higher metabolic rates that were more resilient against the volatile environmental changes that pervaded the early triassic including extreme temperature events low ph and low oxygen conditions we use the early triassic recovery of gastropods echinoids and ammonoids to examine the processes of taxonomic and ecological evolution in response to or in spite of extrinsic environmental perturbations the case studies of benthic gastropods and echinoids when compared to pelagic ammonoids reflect similarities and differences in recovery following the end permian mass extinction gastropods and echinoids exhibit evidence of strong extrinsic environmental limitations which implicate the availability of refugia as a control on recovery low initial taxonomic diversity of survivors may have also limited the evolutionary recovery of both clades abundant and diverse microgastropod assemblages are interpreted as an adaptation to extreme environmental conditions the morphological diversity of disarticulated echinoid spines and plates described in the southwestern united states and examination of phylogenetic ghost lineages hints at a significant hidden diversity of early triassic echinoids ammonoids experienced taxonomic resets but are shown to be resilient to repeated environmental perturbations in the boreal ocean over the duration of the early triassic ammonoids may have adapted to persistent latitudinal temperature gradients and oxygen minimum zones that developed in the early triassic ocean basins

evolution of early triassic outer platform paleoenvironments in the nanpanjiang basin south china and their significance for the biotic recovery detailed microfacies and paleoenvironmental analyses were conducted through the early triassic interval of the outer platform ammonoid rich series of the nanpanjiang basin luolou formation guangxi province south china extensive investigations on outcrops and on thin sections reveal that the widely reported well diversified latest permian fauna dominated by abundant corals calcareous algae calcareous sponges crinoids brachiopods gastropods ostracods and foraminifera is abruptly replaced by decimated early triassic communities essentially composed of low diversity bivalves microgastropods ostracods and rare foraminifera along with this drastic change in faunal assemblages the recolonization of devastated habitats by calcimicrobial frameworks is observed in the aftermath of the end permian mass extinction calcimicrobialites of griesbachian age are followed by mixed ammonoid and conodont rich carbonate siliciclastic series consisting of dark suboxic laminated mudstones intercalated with organic rich shales of dienerian to late smithian age the carbonate siliciclastic series are interrupted by a brief carbonate episode during the early middle smithian massive carbonate production resumes only from the early spathian onward and persists throughout the spathian the initial deposition of both carbonate episodes is coeval with i re establishment of well oxygenated conditions ii a marked early smithian to extreme early spathian ammonoid conodont diversification iii a significant increase in the skeletal grain diversity and abundance and iv peak carbon isotope values a short interval of black organic rich shales precedes the onset of these two distinct carbonate events which are both marked by a positive carbonate carbon isotope excursion known from other tethyan marine localities the comparison between the early triassic stratigraphic evolution of tethyan outer platform paleoenvironments and platform basin margin settings of the nanpanjiang basin suggests a causal connection between large fluctuations of the global carbon cycle climate shifts sea level changes oxygen availability in the oceans and the biological rediversification in the wake of the end permian biotic crisis

an analytical solution for transient radial flow through unsaturated fractured porous media this paper presents analytical solutions for one dimensional radial transient flow through horizontal unsaturated fractured rock formation in these solutions unsaturated flow through fractured media is described by a linearized richards equation while fracture matrix interaction is handled using the dual continuum concept although linearizing richards equation requires a specially correlated relationship between relative permeability and capillary pressure functions for both fractures and matrix these specially formed relative permeability and capillary pressure functions are still physically meaningful these analytical solutions can thus be used to describe the transient behavior of unsaturated flow in fractured media under the described model conditions they can also be useful in verifying numerical simulation results which as demonstrated in this paper are otherwise difficult to validate

a global marine sedimentary response to the end permian mass extinction examples from southern turkey and the western united states the end permian mass extinction greatly diminished marine diversity and brought about a whole scale restructuring of marine ecosystems these ecosystem changes also profoundly affected the sedimentary record data presented here attained through facies analyses of strata deposited during the immediate aftermath of the end permian mass extinction southern turkey and at the close of the early triassic southwestern united states in combination with a literature review show that sedimentary systems were profoundly affected by 1 a reduction in biotic diversity and abundance and 2 long term environmental fluctuations that resulted from the end permian crisis lower triassic strata display widespread microbialite and carbonate seafloor fan development and contain indicators of suppressed infaunal bioturbation such as flat pebble conglomerates and wrinkle structures facies considered unusual in post cambrian subtidal deposits our observations suggest that depositional systems too respond to biotic crises and that certain facies may act as barometers of ecologic and environmental change independent of fossil assemblage analyses close investigation of facies changes during other critical times in earth history may serve as an important tool in interpreting the ecology of metazoans and their environment

the paleoenvironmental distribution of phanerozoic wrinkle structures abstract wrinkle structures are microbially induced sedimentary structures that are known to have formed in ancient marine siliciclastic environments this study reviews the sedimentary context and paleoenvironmental distribution of these sedimentary structures throughout three distinct intervals of the phanerozoic the cambrian the post cambrian paleozoic and the lower triassic during these times wrinkle structures are found primarily within two sedimentary environments storm dominated subtidal environments and the intertidal zone subtidal occurrences of wrinkle structures during the post ordovician phanerozoic only appear to occur during intervals of environmental stress while earlier examples from the cambrian and lowermost ordovician likely formed prior to significant increases in extent and depth of bioturbation that hallmark most of the phanerozoic intertidal examples occur regardless of severe environmental stress and may have formed under low levels of bioturbation due to inherent vagaries of a marginal marine setting these environmental preferences appear to be conservative throughout the phanerozoic and may very well extend throughout earth s history

controls on the formation of microbially induced sedimentary structures and biotic recovery in the lower triassic of arctic canada microbially induced sedimentary structures miss are reportedly widespread in the early triassic and their occurrence is attributed to either the extinction of marine grazers allowing mat preservation during the permo triassic mass extinction or the suppression of grazing due to harsh oxygen poor conditions in its aftermath here we report on the abundant occurrence of miss in the lower triassic blind fiord formation of the sverdrup basin arctic canada sedimentological analysis shows that mid shelf settings were dominated by deposition from cohesive sand mud flows that produced heterolithic rippled sandstone facies that pass down dip into laminated siltstones and ultimately basinal mudrocks the absence of storm beds and any other event beds points to an unusual climatic regime of humid quiet conditions characterized by near continuous run off geochemical proxies for oxygenation mo al th u and pyrite framboid analysis indicate that lower dysoxic conditions prevailed in the basin for much of the early triassic the resultant lack of bioturbation allowed the development and preservation of miss including wrinkle structures and bubble textures the microbial mats responsible for these structures are envisaged to have thrived on sandy substrates within the photic zone in oxygen poor conditions the dysoxic history was punctuated by better oxygenated phases which coincide with the loss of miss thus permo triassic boundary and griesbachian mudrocks from the deepest water settings have common benthos and a well developed tiered burrow profile dominated by phycosiphon the presence of the intense burrowing in the earliest triassic contradicts the notion that bioturbation was severely suppressed at this time due to extinction losses at the end of the permian the notion that early triassic miss preservation was caused by the extinction of mat grazers is not tenable