paleoecology and geochemistry of early triassic spathian microbial mounds and implications for anoxia following the end permian mass extinction large microbialite mounds 1 2 m in height have previously been reported from two units within the spathian section of the virgin limestone member of the moenkopi formation at lost cabin spring nevada united states previous investigations led to the interpretation that the mounds were formed under anoxic and alkaline conditions that suppressed metazoan grazers and delayed the biotic recovery from the end permian mass extinction here we report low organic carbon and total sulfur abundances throughout the section that suggest that anoxia was not prevalent during deposition we also report that the upper mound bearing unit contains stromatolitesponge patch reefs in which mutual encrustation between stromatolites and sponges contributed to the building of a reef framework the stromatolite sponge patch reefs contain discrete burrows within stromatolitic laminations suggesting that there was suffi cient oxygen for grazing during the formation of the upper unit mounds the enhanced ecological complexity of the upper unit mounds leads us to conclude that the mounds represent the transition to biotic recovery following the end permian mass extinction

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

oil fields a source of heat flow data abstract a method of calculating terrestrial heat flow from oil fields is evaluated by reviewing its application to twelve petroliferous basins three of them in brazil and nine in indonesia in each well terrestrial heat flow was calculated by multiplying the temperature gradient obtained by commonly used procedures by the effective thermal conductivity the latter was calculated from quick thermal conductivity measurements on core samples by a transient hot wire method and from the lithologic log typically in each basin the conductivity of about 300 core specimens was measured and logs of 50 150 wells were examined in each formation penetrated by a well the total thickness of each rock type such as shale sandstone etc was determined from the composite lithologic log the harmonic mean of the thermal conductivity of a formation in the well was computed from these thicknesses and the average values of the conductivities of the rock types measured on cores collected from that formation the conductivity of the well is the harmonic mean of the conductivities of the formations the average precision of the determination of formation conductivity can be expressed as the 95 limits divided by the average value for twelve basins this measure of precision for formation conductivities averages 3 6 and the average precision of the conductivity of a basin is 2 0 on the same basis the precision of the determination of the temperature gradient in a basin averages 4 7 and that of the heat flow 5 8 expressing the variability of the geothermal quantities in a basin determined at discrete locations as the standard deviation divided by the average value we get for the mean variability in the twelve basins 6 7 for conductivity 15 0 for the gradient and 16 4 for the heat flow the variability must come in part from natural causes in general at the present level of accuracy no correlation between anomalous heat flow and the occurrence of oil in a basin was found values of thermal conductivity of sedimentary rocks and their variation with depth are useful in calculating paleotemperatures the magnitude of the mean heat flows of the basins is normal 63 mw m2 for the jurassic basins of the stable continental margin of brazil and somewhat elevated in the tertiary basins of indonesia north of the sunda trench subduction zone the values decreasing from 130 mw m2 in central sumatra to 70 mw m2 in eastern kalimantan future improvements in the procedures for determining conductivity might possibly bring out local anomalies in heat flow that might be caused by vertical seepage of water this would support the hydraulic theory of accumulation of oil and gas

early middle triassic stromatolites from the luoping area yunnan province southwest china geobiologic features and environmental implications abstract an early middle triassic stromatolite deposit is documented from the guanling formation of the luoping area yunnan sw china the luoping stromatolite shows five types of constructional microbial forms in various magnifications 1 typical stratified columnar structures up to 20 cm high with crinkled laminae dark coloured laminae 1 mm thick are composed of upright filamentous tubes averagely 29 4 m in diameter showing a vertical growth fabric 2 laminoid fenestrae 0 5 1 mm wide and 3 prostrate filaments which are reflected by strong fluorescence in sharp contrast to dolomite cement in fluorescent images 4 rod like aggregates 4 6 18 m in diameter composed of minute dolomite rhombs are very common in stromatolitic laminae they resemble present day cyanobacterial trichome and thus may represent putative fossilized cyanobacteria 5 moreover small pits coccoid like spheroids calcified biofilms and fibrous structures are also common in stromatolitic laminae the last two may represent calcified extracellular polymeric substances eps that contributed to the development and lithification of stromatolites authigenic quartz grains are common and may also have involved biological processes in stromatolite formation of these microbial functional groups driving accretion and lithification processes of stromatolite documented in literature both lithified cyanobacteria oxygenic phototrophs and possible sulfate reducing bacteria srb which induced microbial formation of dolomite and contributed to the accretion of the luoping stromatolite are suggestive of biogenic origin the luoping stromatolite differs from the permian triassic boundary microbialites ptbms in having abundant filamentous structures and growing in an oxic marine environment both sedimentary facies analysis and abundant fossilized cyanobacteria may indicate proliferation of oxygenic phototrophs in a normal oxic habitat during the middle anisian early middle triassic a period when hospitable environments coupled with biotic diversification prevailed in south china and set an agenda for the full recovery of marine ecosystems in middle late anisian however the post extinction stromatolites and other anachronistic facies are not necessarily indicative of anoxic or oxic conditions and their environmental settings are much more complex than previously thought

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

transient metazoan reefs in the aftermath of the end permian mass extinction microbes were thought to be the dominant reef constructors following the end permian mass extinction sponge microbe reef deposits formed in the early triassic from the western united states suggest that instead metazoan reef building continued immediately following the extinction wherever marine conditions allowed

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

sudden and extreme hyperthermals low oxygen and sediment influx drove community phase shifts following the end permian mass extinction abstract we present a correlated record of carbon isotope geochemistry and sedimentological analysis for the lower triassic werfen formation from the italian dolomites macro and mid sized fossil diversity ecology and climate sensitivity are included to provide an integrated account of the benthic response to paleoenvironmental change novel communities developed in the wake of the mass extinction during pervasive fluctuations in environmental conditions in the sedimentary sequences of the werfen formation of the italian dolomites microbialites microconchids foraminifera and ubiquitous flat clams formed a complex community within the first 500 000 years later increased sea surface temperatures and inundation of the seafloor with siliciclastic sediments favored infaunal bivalves and microgastropods persistent trends in the environment can produce directional often irreversible community shifts defined here as phase shifts phase shifts in ecosystem structure can be driven by environmental shifts across threshold boundaries to produce an abrupt and dramatic novel community composition a phenomenon readily observed during the early triassic previously described disaster forms including flat clams microconchids foraminifera and microbialites are re envisioned as a phase shift community we hypothesize that the unique persistent and reoccurring microbialite and mid sized fauna assemblages observed during the initial recovery from the end permian mass extinction and re appearing throughout the early triassic typify a phase shift community in the smithian infaunal bivalves and microgastropods represent a second phase shift community developed in response to a persistent directional rise in sea surface temperatures and enhanced sediment influx we compare and contrast phase shifts with other models for ecosystem recovery including trophic competition and earth system succession

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

pioneer reef communities within a middle triassic anisian to upper triassic carnian mixed carbonate siliciclastic ramp system from the star peak group south canyon central nevada abstract reef patterns change drastically between the late paleozoic and early mesozoic due to the effects of the end permian mass extinction reef communities follow an ecological transition from the stabilization stage in the anisian to the colonization stage in the carnian through norian to the final diversification and domination stages in the norian through the rhaetian most eastern panthalassa reef studies focused on documenting framework supported reef structures elevated from the seafloor during the late triassic diversification stage however to fully understand reef development we also need to record the precursor stages here we examine field based and microfacies data using a sequence stratigraphic lens to develop a quantitative assessment of non skeletal and skeletal carbonate grains our results indicate that a reef mound and biostromes developed during an overall transgressive sequence due to substrate cementation caused by flooding events although taxonomic differences between biostromes and the reef mound change through time we conclude that these taxonomic changes do not record true first occurrence data instead these fossil accumulations probably occurred due to random chance of larval recruitment even though the reef types found here preserve similar taxa that have been shown to promote high reef growth e g calcified demosponges calcareous algae and bivalves low reef growth structures are found at our site thus reefs containing large amounts of micrite built by low growing binding and encrusting organisms typify this middle and upper triassic section confirming that this section records the colonization stage of reef recovery

end permian mass extinction in the oceans an ancient analog for the twenty first century the greatest loss of biodiversity in the history of animal life occurred at the end of the permian period 252 million years ago this biotic catastrophe coincided with an interval of widespread ocean anoxia and the eruption of one of earth s largest continental flood basalt provinces the siberian traps volatile release from basaltic magma and sedimentary strata during emplacement of the siberian traps can account for most end permian paleontological and geochemical observations climate change and perhaps destruction of the ozone layer can explain extinctions on land whereas changes in ocean oxygen levels co2 ph and temperature can account for extinction selectivity across marine animals these emerging insights from geology geochemistry and paleobiology suggest that the end permian extinction may serve as an important ancient analog for twenty first century oceans

lower triassic deep sea carbonate precipitates from south tibet china abstract sea floor carbonate precipitates scps commonly seen in pre cambrian strata were widely developed during the permian triassic mass extinction and the early triassic recovery interval most scps are found in shallow water facies with few scps reported from deep sea settings here we document lower triassic deep sea scps from turbidite deposits exposed at the xiukang section south tibet china the scps only occur within thin bedded silty limestones that are embedded in dark grey shale parallel aligned mud cobbles rounded micritic intraclasts and micro erosional surfaces are commonly seen in these planar laminated limestones that contain abundant radiolarians and thin shelled bivalves indicating deposition in a deep basin via turbidity currents the deep sea scps which are comprised of bladed calcite crystals display a weak vertical 13c variation with the overlying matrix and a uniform element distribution and consequently have a homogenous cathodoluminescence pattern suggesting rapid precipitation in the open ocean followed by a quick burial which led to minimal diagenetic effects on the scps we propose a new hypothesis that rapid carbonate precipitation resulted from mixing driven by the turbidity current that introduced shallow seawater to the deep seawaters with a high alkalinity based on this model the turbidity currents during the early triassic might serve as a potential role in the connection between the oxic surface oceans and the euxinic deep oceans

early triassic environmental dynamics and microbial development during the smithian spathian transition lower weber canyon utah usa the early triassic biotic recovery following the end permian mass extinction is well documented in the smithian spathian thaynes group of the western usa basin this sedimentary succession is commonly interpreted as recording harsh conditions of various shallow marine environments where microbial structures flourished however recent studies questioned the relevance of the classical view of long lasting deleterious post crisis conditions and suggested a rapid diversification of some marine ecosystems during the early triassic using field and microfacies analyses we investigate a well preserved early triassic marine sedimentary succession in lower weber canyon utah usa the identification of microbial structures and their depositional settings provide insights on factors controlling their morphologies and distribution the lower weber canyon sediments record the vertical evolution of depositional environments from a middle smithian microbial and dolosiliciclastic peritidal system to a late smithian early spathian bioclastic muddy mid ramp the microbial deposits are interpreted as microbially induced sedimentary structures miss that developed either 1 in a subtidal mid ramp where microbial wrinkles and chips are associated with megaripples characterizing hydrodynamic conditions of lower flow regime or 2 in protected areas of inter to subtidal inner ramp where they formed laminae and domal structures integrated with other published data our investigations highlight that the distribution of these microbial structures was influenced by the combined effects of bathymetry hydrodynamic conditions lithology of the substrat physico chemical characteristics of the depositional environment and by the regional relative sea level fluctuations thus we suggest that local environmental factors and basin dynamics primarily controlled the modalities of microbial development and preservation during the early triassic in the western usa basin

rapid marine recovery after the end permian mass extinction event in the absence of marine anoxia a new early triassic marine fauna is described from the central oman mountains the fauna is griesbachian in age on the basis of abundant conodonts and ammonoids and was deposited in an oxygenated seamount setting off the arabian platform margin it is the first griesbachian assemblage from a well oxygenated marine setting and thus provides a test for the hypothesis that widespread anoxia prevented rapid recovery the earliest griesbachian parvus zone contains a low diversity benthic fauna dominated by the bivalves promyalina and claraia a similar level of recovery characterizes the immediate postextinction interval worldwide however the middle upper griesbachian sedimentary rocks isarcica and carinata zones contain an incredibly diverse benthic fauna of bivalves gastropods articulate brachiopods a new undescribed crinoid echinoids and ostracods this fauna is more diverse and ecologically complex than the typical middle to late griesbachian faunas described from oxygen restricted settings worldwide the level of postextinction recovery observed in the oman fauna is not recorded elsewhere until the spathian these data support the hypothesis that the apparent delay in recovery after the end permian extinction event was due to widespread and prolonged benthic oxygen restriction in the absence of anoxia marine recovery is much faster

permian triassic boundary interval in the abadeh section of iran with implications for mass extinction part 1 sedimentology the uppermost permian strata of the abadeh section in iran consist of 56 m of skeletal limestone abadehian that grades upward into 18 m of grey bioturbated lime mudstone djulfian which in turn grades upward to 18 m of red nodular wackestone dorashamian containing an abundant pelagic fauna the overlying lowermost triassic includes two enigmatic layers at its base immediately above the boundary is a 1 m thick layer of inorganically precipitated synsedimentary carbonate cement the cement is composed of 10 20 cm long crystals oriented either perpendicular to the bedding or as dome shaped features resembling botryoids about 0 5 m of wackestone overlies the cement layer the second layer is a 1 5 m thick grainstone overlying the cement horizon and consists of recrystallised spherical grains ooids or peloids the remainder of unit a is composed of 100 m of grey bioturbated to nodular lime mudstone the lithofacies succession of the uppermost permian is interpreted to represent deposition under increasing water depth related to rising of relative sea level which led to drowning of the carbonate platform to below storm wave base sedimentologic characteristics lithology wide distribution and slow sedimentation rates indicate that strata immediately below the permian triassic p t boundary dorashamian interval were deposited in deep oxygenated waters the enigmatic lowermost triassic synsedimentary carbonate cement and grainstone layers are interpreted to have been deposited in shallow waters indicating a rapid and major drop in relative sea level at the end of permian time in this area followed by a relative sea level rise during the earliest triassic precipitation of synsedimentary cement immediately above the p t boundary in iran and elsewhere south china suggests a global change in ocean chemistry one possible explanation is that dissolved calcium and bicarbonate concentrations in seawater increased sufficiently to promote spontaneous carbonate precipitation a rare event in the phanerozoic but common during precambrian time alternatively a massive heating event could have resulted in co2 degassing and decreases in oceanic carbonate solubility both leading to inorganic synsedimentary carbonate precipitation inorganic precipitation of synsedimentary carbonate cement may indicate that biochemical production of carbonate was halted due to the p t boundary events our study indicates that shallow and moderately deep waters during the latest permian were well oxygenated in the open ocean setting of the central tethys sea in iran therefore p t mass extinction scenarios that invoke upon widespread marine anoxia should be viewed with caution

conodont diversity and evolution through the latest permian and early triassic upheavals abstract a study of latest permian and early triassic multielement conodonts identifies eight steps in their evolutionary history during an interval when earth s biosphere was highly stressed these steps are 1 gradual decline of families and genera through the changhsingian up to the late griesbachian 2 conodont biofacies change and extinction of tethyan endemic species close to the permian triassic boundary ptb 3 faunal turnover with extinction and origination in the late griesbachian 4 initial radiation in gondolellids and diversification in apparatuses during the dienerian 5 explosive radiation in the early middle smithian 6 major extinction in the late smithian 7 major radiation early in the spathian 8 gradual turnover and decline in the late spathian through early anisian conodontophorids were reduced from five families at the beginning of the changhsingian to three by the ptb and to two late in the griesbachian from the changhsingian to the late griesbachian there was a single multielement apparatus represented in the gondolellidae whereas by the olenekian there were at least twelve given absolute age constraints the conodont recovery in the aftermath of the ptb was extraordinary conodont evolution during the dienerian remains obscure but was very significant in terms of changes in multielement apparatuses in spite of induan extinctions generic diversity generally increased from the ptb up to the late smithian in terms of species genera and multielement apparatuses the acme of triassic conodonts was in the middle smithian and the biggest extinction was in the late smithian after this extinction generic and apparatus diversity quickly returned to high levels marking a significant spathian recovery gradual decline characterized the late spathian and persisted into the early anisian a synthetic summary of the temporal distribution and proposed relationships amongst all known lower triassic conodonts provide an improved foundation for biostratigraphic and biochronologic studies extinction and radiation trends correlate well with sea level changes and sequence boundaries faunal turnovers correspond to lowstands in the late griesbachian late smithian and late spathian and radiations correspond to transgressions in the early griesbachian early smithian and early spathian the trends also correlate with perturbations in the carbon cycle with lower triassic 13c minima corresponding to extinction and faunal turnover and positive values generally occurring during radiations however middle triassic recovery of marine benthos follows a positive maxima and an overall decline in conodont diversity new taxa borinella chowadensis b megacuspa neogondolella griesbachensis and n mongeri are described

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

shallow water redox conditions from the permian triassic boundary microbialite the rare earth element and iodine geochemistry of carbonates from turkey and south china redox sensitive elements serve as useful proxies of the oxygenation state of ancient environments but their interpretation may not always be straightforward to evaluate the inherent complexities rare earths and yttrium rey iodine and major element concentrations are determined in two carbonate sections spanning the permian triassic p tr transition in demirtas turkey and cili south china we use major oxides to identify non seawater rey sources such as siliciclastics fe oxides phosphates and diagenetic fluids additionally we employ y ho ratio la anomaly and light rare earth element depletion to identify which samples preserve a seawater like reysn distribution in contrast to past interpretations we find that the p tr boundary microbialites in both sections contain rey signatures indicative of deposition in an oxic environment these boundary microbialites have their base at the extinction horizon and are widespread within the tethyan region in the cili section the underlying permian limestone also preserves a seawater like rey signature with a negative ce anomaly this indicates that the water column was oxygenated both before and after the extinction event the permian limestone in the demirtas section does not preserve a seawater like reysn distribution so the absence of a ce anomaly cannot be used to distinguish prevailing redox conditions during deposition however in these samples we find the presence of a diverse permian benthic community sufficient to identify deposition in an oxic environment the geochemical evidence for a continuously oxic environment during the deposition of the boundary microbialite presented in this study strongly supports work done using ostracods as redox indicators within the boundary microbialite in south china the microbialite has been proposed as a disaster facies in part resulting from the exclusion of grazers although anoxia is one of the suggested mechanisms for the exclusion of grazers we find that it is not supported by geochemical and biotic evidence

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

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

elevated atmospheric co2 and the delayed biotic recovery from the end permian mass extinction excessive co2 in the earth ocean atmosphere system may have been a significant factor in causing the end permian mass extinction co2 injected into the atmosphere by the siberian traps has been postulated as a major factor leading to the end permian mass extinction by facilitating global warming widespread ocean stratification and development of anoxic euxinic and co2 rich deep waters a broad incursion of this toxic deep water into the surface ocean may have caused this mass extinction although previous studies of the role of excessive co2 have focused on these bottom up effects emanating from the deep ocean top down effects of increasing atmosphere co2 concentrations on ocean surface waters and biota have not previously been explored passive diffusion of atmospheric co2 into ocean surface waters decreases the ph and caco3 saturation state of seawater causing a physiological and biocalcification crisis for many marine invertebrates while both bottom up and top down mechanisms may have contributed to the relatively short term biotic devastation of the end permian mass extinction such a top down physiological and biocalcification crisis would have had long term effects and might have contributed to the protracted 5 to 6 million year long delay in biotic recovery following this mass extinction earth s modern marine biota may experience similar top down co2 stresses if anthropogenic input of atmosphere ocean co2 continues to rise

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

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

evidence for sulfidic deep water during the late permian in the east greenland basin a detailed study of the size distribution of framboidal pyrites in the black shales of the upper permian ravnefjeld formation was performed to evaluate the redox state of the late permian ocean in contrast to framboidal pyrites in bioturbated sediments the smaller and less variable size distribution of pyrite framboids in the laminated shales of the ravnefjeld formation provides persuasive evidence for sulfidic h 2 s rich bottom water conditions in the east greenland basin however the s isotope compositions of both pyrite populations show a similar distribution the widespread 3 4 s values of pyrites 41 2 to 28 2 in the black shales of the ravnefjeld formation indicate a large fractionation up to 52 7 relative to seawater sulfate and may record different pathways of sulfur cycling in sulfidic water columns as well as within sediments the new data from the east greenland basin indicate that environmental stress such as widespread sulfidic conditions could have caused the biotic crisis in the late permian

the topographic state of fluvially conditioned mountain ranges abstract the topography of mountain ranges reflects the competition of constructive and destructive processes driven by tectonics and climate respectively there is a vital debate whether the topography of individual orogens reflects stages of growth steady state or decay that is fueled by the million year time scales hampering direct observations on landscape evolution the superposition of various process patterns and the complex interactions among different processes hence there is a demand for sophisticated analysis tools to extract constraints on the long term evolution of orogens from their topography we review the field of orogen scale landscape evolution from a numerical perspective summarize the most prominent modelling concepts and their implications for the fluvially driven development of mountain topography and finally evaluate their applicability for understanding real world orogens following the concept of equilibrium a state where uplift rates are balanced by erosion rates and topography remains steady over time the erosional long term response of rivers and hillslopes can be mathematically formalised by the stream power and mass diffusion equations respectively based on a simple 1 dimensional model consisting of two rivers separated by a watershed we explain the influence of uplift rate and rock erodibility on steady state channel profiles and show the time dependent development of the channel drainage divide system dynamic drainage network reorganisation adds additional complexity and its effect on topography is explored on a two dimensional model river capture events and drainage divide migrations as expression of the ongoing drainage network reorganisation cause changes in topography until a stable network topology and hence full topographic steady state is achieved the long time spans needed for this drainage network optimization suggest that orogens on earth may never reach full topographic steady state in real world orogens we find evidence for premature mature and decaying topography as well as relief rejuvenation by analysing slope elevation distributions and trace the expression of crustal strain distorting drainage networks by applying the transform we conclude that modern concepts of landscape evolution allow sophisticated analyses of real world orogens but emphasize that unambiguous results are mostly derived from regions dominated by a limited number of interacting processes such as mountain ranges with limited or no glacial imprint this results in a high demand for techniques to disentangle the complex topography of real world orogens into the signals resulting from the individual land shaping processes

sulfur isotopic evidence for chemocline upward excursions during the end permian mass extinction the latest permian was a time of major change in ocean chemistry accompanying the greatest mass extinction of the phanerozoic to examine the nature of these changes samples from two well studied marine sections that span the permian triassic boundary have been analyzed the meishan and shangsi sections located in southern china isotopic analysis of the carbonate associated sulfate in these samples provides a detailed record of several isotopic shifts in 34scas approaching and across the ptb ranging from 30 to 15 vcdt with repeated asynchronous fluctuations at the two locations we interpret the patterns of isotopic shifts in conjunction with other data to indicate a shallow unstable chemocline overlying euxinic deep water which periodically upwelled into the photic zone these chemocline upward excursion events introduced sulfide to the photic zone stimulating a bloom of phototrophic sulfur oxidizing bacteria we hypothesize that elemental sulfur globules produced by these organisms and 34s depleted pyrite produced in the euxinic water column were deposited in the sediment later oxidation led to incorporation as cas this created the large changes to the 34scas observed in the latest permian at these locations

a unique permian triassic boundary section from the neotethyan hawasina basin central oman mountains in the wadi wasit area central oman mountains dienerian breccias are widespread these breccias consist mostly of guadalupian reefal blocks often dolomitised and some rare small sized blocks of lowermost triassic bivalve bearing limestones a unique block with a size of about 200 m3 including permian and earliest triassic faunas has been studied in detail the so called wadi wasit block consists of three major lithological units a basal unstratified grey limestone is rich in various reef building organisms rugose corals calcareous sponges stromatoporoids and has been dated as middle permian it is disconformably overlain by well and thin bedded light grey to yellowish coloured limestones rich in molluscs two major lithologies coquina limestone respectively bioclastic limestone unit characterise the shelly limestones their contact seems gradual these two units are well dated they are of griesbachian age and contain three conodont zones the parvus zone the staeschei zone and the sosioensis zone and two ammonoid zones the ophiceras tibeticum zone and an unnamed interval the third unit consists of a grey marly limestone containing neospathodus kummeli basal dienerian it is the first record of well dated basal triassic sediments in the arabian peninsula the coquina limestone is dominated by the bivalve promyalina with some claraia and eumorphotis this bivalve association is interpreted as a pioneering opportunistic assemblage towards the top of the bioclastic limestone unit the faunal diversity increases and contains probably more than 20 taxa of bivalves microgastropods crinoids brachiopods ammonoids echinoid spines ostracods and conodonts the generic diversity of this biofacies exceeds by far any other griesbachian assemblage known our data give new evidence for the geodynamical history for the distal carbonate shelf bordering the hawasina basin a break in the sedimentation characterises the late permian the basal triassic shows a steady transgression and the breccias may record a distinct gravitational collapse of platform margins linked with sea level low stand at the end of induan time late dienerian basal smithian 13ccarb isotopic analyses were performed and yield typical permian values of around 4 for the reefal limestone with a strong negative shift across the permian triassic boundary during the griesbachian values shift positively from 0 5 to 3 1 parallel to an increase in faunal diversity and probably primary productivity the detailed faunal analysis and the discovery of an unexpected diversity give us a new understanding of the recovery of the early triassic marine ecosystem

photic zone euxinia during the permian triassic superanoxic event carbon and sulfur isotopic data together with biomarker and iron speciation analyses of the hovea 3 core that was drilled in the perth basin western australia indicate that euxinic conditions prevailed in the paleowater column during the permian triassic superanoxic event biomarkers diagnostic for anoxygenic photosynthesis by chlorobiaceae are particularly abundant at the boundary and into the early triassic similar conditions prevailed in the contemporaneous seas off south china our evidence for widespread photiczone euxinic conditions suggests that sulfide toxicity was a driver of the extinction and a factor in the protracted recovery

high temperature and low oxygen perturbations drive contrasting benthic recovery dynamics following the end permian mass extinction the end permian mass extinction event was the greatest loss of biodiversity ever experienced on the planet the event is thought to have been triggered by the initiation of the volcanic eruptions of the siberian traps the five million year recovery interval that followed the extinction event was strongly influenced by the environmental effects of sustained volcanic eruptions including extreme temperature events and persistent global and regional oxygen minimum zones the effects of these environmental perturbations on the paleoecological recovery of the benthic marine fauna were studied in two depositional units from the southwestern united states representing two substages during the early triassic recovery the smithian sinbad limestone was influenced by high sea surface temperatures and contains a relatively high diversity fauna that exhibits extremely small body size gastropods that lived in this environment were size limited a possible result of metabolic stress due to extreme temperatures these microgastropods were able to become dominate components of the benthic fauna by occupying niche space vacated by other taxa that were excluded by high temperatures the spathian virgin limestone shows evidence for low oxygen conditions the resulting low diversity benthic fauna had a more ecologically complex community structure than the smithian sinbad limestone including the occupation of epifaunal tiering space by crinoids as the prevalence of aerobic facies increased through time diversity body size and the complexity of faunal interactions also increased suggesting that low oxygen conditions were the limiting factor for the benthic recovery in that region the differences in diversity and community structure between the two units highlight the importance of environmental and temporal differences in driving the recovery patterns of the benthic fauna following the extinction event high temperature events and low oxygen conditions restricted the benthic fauna in different ways but both contributed to the delay in recovery from the end permian mass extinction

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

strontium isotope evolution of late permian and triassic seawater the 87sr 86sr values based on brachiopods and conodonts define a nearly continuous record for the late permian and triassic intervals minor gaps in measurements exist only for the uppermost brahmanian lower part of the upper olenekian and middle norian and only sparse data are available for the late permian these 219 measurements include 67 brachiopods and 114 conodont samples from the tethyan realm as well as 37 brachiopods and one conodont sample from the mid european middle triassic muschelkalk sea the late permian lower triassic interval is characterized by a steep 1 3 10 3 rise from 0 7070 at the base of the dzhulfian to 0 7082 in the late olenekian a rate of change comparable to that in the cenozoic in the mid triassic anisian and ladinian the isotope values fall to 0 7075 followed again by a rise to 0 7081 in the middle late norian the 87sr 86sr values decline again in the late norian sevatian and rhaetian to 0 7076 the sharp rise in the 87sr 86sr values during the late permian early triassic was coincident with widespread clastic sedimentation because of the paucity of tectonic uplifts the enhanced erosion may have been due to intermittent humid phases during mainly an arid interval coupled with the absence of a dense protective land plant cover following the mass extinction during the latest permian the apex of the 87sr 86sr curve at the olenekian anisian boundary coincides with cessation of the large scale clastic sedimentation and also marks the final recovery of land vegetation as indicated by the renewed onset of coal formation in the middle triassic the rising 87sr 86sr values from the middle carnian to the late norian coincide with the uplift and erosion of the cimmeride indosinian orogens marking the closure of the palaeotethys the subsequent rhaetian decline that continues into jurassic pliensbachian toarcian boundary on the other hand coincides with the opening of the vardar ocean and its eastern continuation in the izmir ankara ophiolitic belt samples from the upper muschelkalk are more radiogenic than the global trend this may reflect separation of the basin from the open ocean due to strong meteoric influx from a large land mass in the north the germanic basin became increasing brackish up section in the north and east but because of the high evaporation rates the salt content was not much reduced in the southern and central basin where a rich but increasingly endemic marine fauna survived

paleoecology biogeography and evolution of reef ecosystems in the panthalassa ocean during the late triassic insights from reef limestone of the sambosan accretionary complex shikoku japan upper triassic reefs from the panthalassa ocean have been understudied in comparison to their tethyan counterparts and are therefore pivotal to understanding the global reef evolution during the late triassic to fill this gap upper triassic reef limestone from ten localities of the sambosan accretionary complex at shikoku island japan has been investigated biotic assemblages quantitative microfacies analysis and integrated biostratigraphy allow us to characterize two types of reefs those attributed to the ladinian early carnian and those attributed to the late carnian rhaetian at the regional scale our data refine the biostratigraphic framework of the upper triassic sambosan limestone at the global scale multivariate analyses support a strong paleobiogeographic affinity of the western panthalassa reef biota with those of the south tethys ocean during the ladinian carnian and norian rhaetian additionally they indicate connections with east panthalassa reefs during the norian rhaetian

environmental and diagenetic variations in carbonate associated sulfate an investigation of cas in the lower triassic of the western usa an integrated stable isotope elemental and petrographic analysis of early triassic spathian carbonates and evaporites along a proximal to deep environmental transect reveals significant variations in 34s composition of carbonate associated sulfate cas the variations in the 34s of cas are strongly correlated with the ca mg composition of carbonates suggesting that the variations are driven by the degree of dolomitization the 34s of dolostones and evaporites are similar to one another and exhibit lower 34s values than limestones from all localities three hypotheses may explain the differences in 34s between proximal dolostones evaporites and inner middle shelf limestones 1 limestones experienced anaerobic sulfate reduction and subsequent incorporation of 34s enriched sulfate into cas during diagenesis while dolostones did not this is unlikely because of the lack of correlation between 34scas and toc as well as other indicators of diagenesis 2 dolomitization controlled the 34scas in proximal paleoenvironments where the source of the 34s depleted fluids was either continentally derived or the result of rayleigh distillation during evaporite formation and 3 a 34s depth gradient existed during the early triassic such that limestones formed in distal waters are more enriched in 34s versus evaporites and dolostones formed in proximal settings we do not favor this hypothesis because the strong correlation between ca mg and 34scas implies that dolomitization controls the 34scas in these samples results from subtidal well preserved non dolomitized limestones suggest that the 34s of spathian seawater sulfate may have been heavier than previously suggested from analyses of evaporite deposits alone

lower triassic large sea floor carbonate cements their origin and a mechanism for the prolonged biotic recovery from the end permian mass extinction precipitation of inorganic calcium carbonate is a common occurrence in both modern and ancient marine environments however synsedimentary growth of large 5 10 cm crystalline carbonate cements directly onto the sea floor has been thought to be limited to the proterozoic when seawaters were highly oversaturated with calcium carbonate compared to average phanerozoic values outer shelf to slope deposits of the lower triassic union wash formation in east central california deposited in oxygen restricted settings contain crystalline calcium carbonate cements that appear to have grown directly on the sea floor paleoenvironmental analyses indicate that these large calcium carbonate cements grew under conditions that were similar to those proposed for the precipitation of inorganic calcite in the black sea sulfate reduction of organic matter led to an increase in the amount of bicarbonate ion in deep waters and a concomitant increase in co 2 and alkalinity mixing with surface waters led to co 2 degassing and precipitation of cements from waters supersaturated with calcium carbonate the presence of these cements and associated facies thus provides evidence of harsh environmental conditions in the early triassic at the regional level which may have acted in concert with biotic effects of the end permian mass extinction as well as similar deleterious conditions e g shelf anoxia in other regions to produce a prolonged as well as temporally and geographically variable biotic recovery from this mass extinction