cosmic impact event in lake sediments from central europe postdates the laacher see eruption and marks onset of the younger dryas abstractthe younger dryas yd climate episode 12 850 11 650 calendar years before present cal bp is an event recorded widely across the northern hemisphere we conducted multiple analyses at

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

de glauconiarum origine the glauconitic facies is widespread on present day continental shelves from 50 s to 65 n and at water depths between 50 and 500 m and is in particularly great abundance on the upper slope and outer shelf between 200 and 300 m it is also common in many ancient rocks of post late precambrian age it occurs as sand to pebble sized essentially green particles granular facies but also as a surface coating on particles and hardgrounds and as a diffuse impregnation film and diffuse facies we suggest the replacement of the term glauconite which has been interchangeably used to designate a morphological form and a specific mineral by glaucony facies and glauconitic smectite and glauconitic mica as end members of the glauconitic mineral family the widely accepted model of burst and hower for glauconitization requires a degraded micaceous 2 1 layer lattice structure parent clay mineral however detailed analysis of numerous samples of recent glaucony reveals that such a parent substrate is exceptional the model therefore requires modification generally the parent material is carbonate particles argillaceous kaolinitic faecal pellets infillings of foraminiferal tests various mineral grains and rock fragments that pass gradually into the commonly occurring green grains we show that the process of glauconitization is achieved by de novo authigenic growth of automorphous crystallites in the pores of the substrate accompanied by progressive alteration and replacement of the substrate it is this two fold evolution that causes the verdissement of granular substrates macrofossils and hardgrounds the authigenic mineral is an iron rich and potassium poor glauconitic smectite while new smectites are growing into the remaining pore space the earlier smectites are modified by incorporation of potassium producing decreasingly expandable minerals with a non expandable glauconitic mica as the end member this mineralogical diversity of the glauconitic mineral family explains the highly variable physical and chemical properties of glaucony four categories nascent little evolved evolved and highly evolved glaucony are distinguished glauconitization appears to be controlled by a delicate balance between degree of physical confinement of a particle and the amount of ionic exchange between the micro environment and ambient open marine sea water the optimum conditions for glauconitization are those of semi confinement as a result the interior of a grain is more glauconitized than its less confined periphery similarly for identical substrate types large grains 500 m provide more favourable substrates for glauconitization than lesser confined small grains on a larger scale the formation of glaucony is governed by the availability of iron and potassium and the balance between detrital influx and winnowing low accumulation rates expose grains to the open marine environment for sufficiently long times 105 106 years for highly evolved glaucony

carbon isotope stratigraphy across the permian triassic boundary a review abstract the palaeozoic mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon isotope excursion at the permian triassic p t boundary well known from a plethora of marine and continental sediments potential causes for this negative 13 c trend and their links to the latest permian mass extinction have been intensively debated in the literature in order to draw conclusions regarding causation a general 13 c curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background the most important features of the p t carbon isotope trend are the following the 4 7 13 c decline lasting 500 000 years is gradual and began in the changhsingian at the stratigraphic level of the c bachmanni zone the decreasing trend is interrupted by a short term positive event that starts at about the latest permian low latitude marine main extinction event horizon eh indicating that the extinction itself cannot have caused the negative carbon isotope excursion after this short term positive excursion the 13 c decline continues to a first minimum at about the p t boundary a subsequent slight increase is followed by a second occasionally two peaked minimum in the lower and middle i isarcica zone the negative carbon isotope excursion was most likely a consequence of a combination of different causes that may include 1 direct and indirect effects of the siberian trap and contemporaneous volcanism and 2 anoxic deep waters occasionally reaching very shallow sea levels a sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon isotope trend is questionable at least for the time span a little below the eh and somewhat above the p t boundary

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

on the causes of mass extinctions the temporal link between large igneous province lip eruptions and at least half of the major extinctions of the phanerozoic implies that large scale volcanism is the main driver of mass extinction here we review almost twenty biotic crises between the early cambrian and end cretaceous and explore potential causal mechanisms most extinctions are associated with global warming and proximal killers such as marine anoxia including the early middle cambrian the late ordovician the intra silurian intra devonian end permian and early jurassic crises many but not all of these are accompanied by large negative carbon isotope excursions supporting a volcanogenic origin most post silurian biocrises affected both terrestrial and marine biospheres suggesting that atmospheric processes were crucial in driving global extinctions volcanogenic atmospheric kill mechanisms include ocean acidification toxic metal poisoning acid rain and ozone damage and consequent increased uv b radiation volcanic darkness cooling and photosynthetic shutdown each of which has been implicated in numerous events intriguingly some of the most voluminous lips such as the oceanic plateaus of the cretaceous were emplaced with minimal faunal losses and so volume of magma is not the only factor governing lip lethality the missing link might be continental configuration because the best examples of the lip extinction relationship occurred during the time of pangaea many of the proximal kill mechanisms in lip extinction scenarios are also potential effects of bolide impact including cooling warming acidification and ozone destruction however the absence of convincing temporal links between impacts and extinctions other than the chicxulub cretaceous example suggests that impacts are not the main driver of extinctions with numerous competing extinction scenarios and the realisation that some of the purported environmental stresses may once again be driving mass extinction we explore how experimental biology might inform our understanding of ancient extinctions as well as future crises

griesbachian earliest triassic palaeoenvironmental changes in the salt range pakistan and southeast china and their bearing on the permo triassic mass extinction abstract facies and faunal analysis from pakistan and china show that the permo triassic mass extinction of marine invertebrate faunas was associated with a spectacularly rapid griesbachian transgression which lead to the widespread establishment of deep water anoxic and dysoxic conditions the extinction event was thus caused by habitat loss due to the extensive development of inhospitable conditions the initial griesbachian transgression in pakistan produced extensive shallow normal marine conditions in which permian holdover taxa were able to survive until the development of dysaerobic facies in the late griesbachian the exceptionally complete sections of china show a three phased deepening and extinction event beginning in the latest permia by the late griesbachian a variety of dysaerobic and anaerobic facies were developed in all the regions studied several of these contain evidence for minimal sulphate reducing activity suggesting that marine productivity and thus organic matter flux to the sediments was very low in early triassic seas

pyrite framboid evidence for oxygen poor deposition during the permian triassic crisis in kashmir abstract the khunamuh formation of the guryul ravine section in kashmir provides one of the most detailed deep water records of the end permian mass extinction in perigondwanan palaeolatitudes examination of pyrite framboid size distributions and sediment microfabric reveals a distinct change in the uppermost permian strata from nonlaminated pyrite free silty mudstones to finely laminated silty shales rich in framboidal pyrite around 1 m above the base of the formation the size frequency distribution of the framboids is identical to populations from severely oxygen restricted modern depositional environments this change to dysoxic benthic conditions coincides with the rapid demise of diverse permian brachiopod and bryozoan assemblages thus the link between extinction and anoxia is clearly seen at guryul ravine and it provides an interesting contrast to other perigondwanan sections developed in shallower water where both the onset of anoxia and the extinction occurred somewhat later in the earliest triassic

permian triassic sedimentology of jameson land east greenland incised submarine channels in an anoxic basin the presence of deeply erosive conglomeratic sandstone filled channels around the permian triassic p tr boundary in east greenland has been widely cited as evidence for a major late permian eustatic lowstand facies analysis of such channels and their associated strata in fact suggests that they record part of an intrinsic style of basinal deposition that persisted into early triassic time their origin can be explained without the need to invoke eustatic sea level fall active faulting and hinterland elevation is envisaged to have generated powerful sediment gravity flows that were capable of submarine erosion of fine grained unconsolidated strata stacked turbidite sandstone filled lenses also occur beneath fan delta sandbodies and probably record infill of channels or chutes cut into the subaqueous slopes of such deltas shale successions developed between the incised channel locations record complete p tr transitions in which a rapid onset of anoxic deposition is seen in latest permian time this is the local manifestation of a global anoxic event unusual aspects of the lower triassic sequence in greenland include the presence of well oxygenated intervals stromatolite bioherms and red algae

periodic black auroral patches at the dawnside dipolarization front during a substorm 1 periodic black auroral patches were observed in the canadian postmidnight sector by ground based all sky cameras during an auroral substorm the aurora consisted of several black patches of 50 km 1 in longitude scales that appeared along the equatorward edges of the proton auroras over a 3 h local time segment from gillam to sanikiluaq ground stations 15 min after the auroral intensification occurred in alaska to the best of our knowledge this type of black auroras has never been reported before although the surrounding luminous auroras evolve into the well known torch structures later in situ observations by the themis satellites three of which were close to being magnetically conjugate in the plasma sheet as well as ground based proton auroral observations show that a dipolarization front and associated dawnward ion flows propagated eastward at poleward of the black patches coinciding with their appearance the flow motions of auroras observed poleward of the black patches are possibly generated by decelerations of dawnward ion flow because of the consistency of both durations and positions we speculate based on manifestations of high pressure regions in dipolarized flux tubes the pressure driven interchange instability formed a beading shape periodic black patches of field aligned currents the black auroral patches developed into torch structures after the flow disappearance indicating the dawnward flows might stabilize and limit the instability within a narrow l shell where the pressure gradient is directed earthward and flows cannot enter we conclude that the periodic black patches arise as a consequence of a relaxation process of enhanced plasma pressure near the inner boundary of the plasma sheet during a substorm

intrabasin variability of the carbon isotope record across the permian triassic transition sverdrup basin arctic canada abstract a major late paleozoic depocentre the sverdrup basin canadian high arctic has been largely left out of the latest permian extinction debate as early workers presumed middle to late permian strata were absent basin scale sequence stratigraphic and chemostratigraphic correlations indicate late permian strata are only missing on the basin margins where they were removed by sub triassic erosion whereas continuous deposition is recorded in the basin centre the varying degree of sub triassic erosion has significant impact on the carbon isotope record across the latest permian extinction event where both the apparent rate and magnitude of carbon isotope shift vary as a function of basin position the intrabasin variability in apparent 13corg shift across the event is equivalent to that observed globally in contrast to the abrupt isotope shifts recorded on the basin margin similar to many records reported globally the basin centre section shows a systematic shift associated with the latest permian extinction the earth likely underwent a prolonged period of increasing environmental stress leading up to the event

the early toarcian oceanic anoxic event in the external subbetic southiberian palaeomargin westernmost tethys geochemistry nannofossils and ichnology abstract the analysis of macroinvertebrates trace fossils calcareous nannofossils and geochemistry from pliensbachian to lower toarcian deposits of the subbetic southern spain allows us to interpret the incidence of the toarcian oceanic anoxic event t oae in the boundary between the tethys and the hispanic corridor trace fossils from the marl limestone rhythmite upper pliensbachian to lower toarcian indicate an oxygenated bottom a dark marly interval occurs above a fossil rich condensed surface with a negative excursion of 18o interpreted as evidence of the early toarcian transgression and a climate warming the carbon cycle perturbation is recorded by decreasing caco3 content and the negative excursion of 13c at the base of the serpentinum zone njt 6 nannofossil zone the barren interval for nektonic and benthic organisms at the beginning of the serpentinum zone confirms the oxygen restricted conditions in the sea floor environmental conditions were unfavourable for the development of calcareous nannoplankton as attested by the drop in absolute abundances the deep photic zone seemed to be particularly hostile to phytoplankton as shown by the decrease in relative abundance of the deep dweller mitrolithus jansae related to shoaling of the oxygen minimum zone in the water column increasing values of redox sensitive elements and total organic carbon as well as the record of pyrite framboids

simulating permian triassic oceanic anoxia distribution implications for species extinction and recovery the biggest mass extinction in the phanerozoic at the end of the permian has been associ ated with oceanic changes but the exact dynamics are still debated intensifi ed stratifi cation widespread anoxia chemocline excursions and large scale ocean overturn events have all been invoked as contributors to the extinction in this study the effects of possible changes in environmental conditions such as an increase in nutrient input or dust fl uxes into the ocean or an intensifi cation of the biological pump on permian triassic ocean chemistry are inves tigated series of sensitivity experiments were performed with a fully coupled climate carbon cycle model none of the forcings alone generates extensive low oxygen conditions in the deep sea these are only simulated by an intense eutrophication in combination with an enhanced biological pump but still confi ned to the central panthalassic tethys and the eastern boreal oceans our fi ndings support the conclusions from a recent geochemical study of a japanese deep panthalassa section that around the permian triassic boundary the oxygen minimum zone expanded considerably while the deep panthalassa remained ventilated the warming induced increase in low oxygen conditions within the water column aggravated adverse exist ing conditions and likely contributed to the extinction peak upwelling of toxic water was probably regionally confi ned and hence not the main cause for the end permian marine and terrestrial mass extinction widespread deep sea anoxia generated by a strong increase in weathering and the related enhanced nutrient input into the oceans is probably closely linked to the delayed recovery of species in the early triassic

abundance anomalies of aromatic biomarkers in the permian triassic boundary section at meishan china evidence of end permian terrestrial ecosystem collapse several aromatic biomarkers detected in solvent extracts and kerogen pyrolysates from samples of the global stratotype section and point gssp for the permian triassic boundary at meishan china show distinctive relative abundance anomalies that may be related to the end permian biotic crisis on land enrichment of dibenzofuran homologues across the permian triassic boundary may corroborate the concept of excessive soil erosion following loss of rooted vegetation enrichment of alkylphenol entities occurs just below the main marine mass extinction horizon and prior to the characteristic end permian 13c decline the alkylphenols were probably derived from lignin and may provide a molecular record of dieback of woody vegetation highly decreased relative abundances of dibenzothiophenes could be indicative of excessive supply of fe2 it is suggested that fe2 was land derived and may have originated from soils in addition to the permian triassic boundary interval biomarker abundance anomalies also occur around the wuchiapingian changhsingian boundary in the basal part of the meishan section

u mo ratios and δ98 95mo as local and global redox proxies during mass extinction events abstract when used in conjunction with trace metal redox proxies the use of u mo ratios and 98 95 mo values can considerably enhance the interpretation of ocean oxygenation trends both locally and globally this is illustrated with studies from two biogenic chert dominated records of mass extinction the ordovician silurian boundary and the late permian in sections from the yangtze block in south china the latest ordovician mass extinction is well known to coincide with oxygenation episode in the hirnantian stage here revealed by trace metal proxies v v ni v cr ni co that show it sandwiched between anoxic euxinic black shales the predominantly anoxic euxinic ordovician silurian strata provide a record of seawater 98 95 mo values that are seen to gradually rise during the interval from 0 5 to 1 0 the exception to the 98 95 mo stability is the datum of the slight negatively 98 95 mo associated with decreasing of v cr and v v ni ratio suggesting the hirnantian oxygenation event the upper permian chert succession at shangsi reveals an overall better ventilated record in which the best oxygenated strata show the highest u mo values that is interpreted as relative enrichment of u in suboxic conditions at a few levels anoxic euxinic conditions show the 98 95 mo values to be 2 close to modern values implying that latest permian oceans were as well ventilated as those today the well known end permian oceanic anoxic event is therefore suggested to only develop at the end of this period

an integrated biomarker isotopic and palaeoenvironmental study through the late permian event at lusitaniadalen spitsbergen abstract the largest extinction of the phanerozoic occurred near the permian triassic p tr boundary some 252 ma ago several scenarios and drivers have been proposed for this event here we report for the first time an integrated study comprising sedimentological data biomarker distributions abundances and selected stable carbon and hydrogen isotopes along with bulk isotopes 34spyrite 13ccarb 13corg for a late permian section from lusitaniadalen spitsbergen norway sedimentological and geochemical data support a marine transgression and collapse of the marine ecosystem in the late permian strong evidence for waxing and waning of photic zone euxinia throughout the late permian is provided by chlorobiaceae derived biomarkers including 13c data and 34spyrite implying multiple phases of h2s outgassing and potentially several pulses of extinction a rapid decrease in abundance of various land plant biomarkers prior to the marine collapse event indicates a dramatic decline of land plants during the late permian and or increasing distance from palaeoshoreline as a consequence of sea level rise changes in d of selected biomarkers also suggest a change in source of organic matter om or sea level rise we also found biomarker and isotopic evidence for a phytoplanktonic bloom triggered by eutrophication as a consequence of the marine collapse compound specific isotope analyses csia of algal and land plant derived biomarkers as well as 13c of carbonate and bulk om provide strong evidence for synchronous changes in 13c of marine and atmospheric co2 attributed to a 13c depleted source the source could be associated with isotopically depleted methane released from the melting of gas clathrates and or from respired om due to collapse of the marine ecosystem

global climate perturbations during the permo triassic mass extinctions recorded by continental tetrapods from south africa several studies of the marine sedimentary record have documented the evolution of global climate during the permo triassic mass extinction by contrast the continental records have been less exploited due to the scarcity of continuous sections from the latest permian into the early triassic the south african karoo basin exposes one of the most continuous geological successions of this time interval thus offering the possibility to reconstruct climate variations in southern laurasia from the middle permian to middle triassic interval both air temperature and humidity variations were estimated using stable oxygen 18op and carbon 13cc isotope compositions of vertebrate apatite significant fluctuations in both 18op and 13cc values mimic those of marine records and suggest that stable isotope compositions recorded in vertebrate apatite reflect global climate evolution in terms of air temperature oxygen isotopes show an abrupt increase of about 8 c toward the end of the wuchiapingian this occurred during a slight cooling trend from the capitanian to the permo triassic boundary ptb at the end of the permian an intense and fast warming of 16 c occurred and kept increasing during the olenekian these thermal fluctuations may be related to the emeishan south china and siberian volcanic paroxysms that took place at the end of the capitanian and at the end of the permian respectively vertebrate apatite 13cc partly reflects the important fluctuations of the atmospheric 13c values the differences with marine curves being likely due to the evolution of local humidity both the oxygen and carbon isotope compositions indicate that the ptb was followed by a warm and arid phase that lasted 6 ma before temperatures decreased during the late anisian toward that of the end permian environmental fluctuations occurring around the ptb that affected both continental and marine realms with similar magnitude likely originated from volcanism and methane release

assimilated observations of thermospheric winds the aurora and ionospheric currents over alaska we present simultaneous measurements of thermospheric winds auroral emissions and ionospheric currents over alaska obtained from four separate instruments thermospheric f region wind maps were recorded by an all sky imaging fabry perot spectrometer located at poker flat and observing at 630 0 nm auroral images at 557 7 nm were obtained from the low resolution visible imager on board the polar satellite white light all sky auroral images were recorded by ground based all sky cameras located in alaska at poker flat 65 07 n 212 34 e and at kaktovik 70 06 n 217 24 e finally the east west component of the ionospheric f region plasma convection was inferred using the alaskan meridian chain of magnetometers montage images of these four data sets are presented projected onto a geographic map of the alaskan region we examine a 10 hour period during the alaskan local nighttime of february 10 1997 these montages illustrate a close relationship between spatial structures occurring in the aurora in the ionospheric plasma convection and in the f region wind field latitudinal shear of the geomagnetic zonal wind often observed in the premidnight time sector was seen to be associated with both the equatorward and poleward boundaries of the discrete aurora we focus particularly on a period commencing just after 0900 ut when a strong shear in the zonal wind was observed to sweep southward across alaska after magnetic midnight the wind field was dominated by the emergence of the cross polar jet from the polar cap this overwhelmed any wind features associated with local auroral processes

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

a new high resolution stratigraphic and palaeoenvironmental record spanning the end permian mass extinction and its aftermath in central spitsbergen svalbard abstract research on the permian triassic boundary ptb along the northern margins of pangaea exposed today in the arctic region has been heavily reliant on field observations where data resolution was consequently determined by outcrop condition and accessibility core drilling in central spitsbergen allowed for a near complete recovery of two 90 m cores through the ptb analyses of the core and nearby outcrops include stratigraphic logging and sampling xrf scanning petrography biostratigraphy isotope geochemistry and geochronology the first appearance datum fad of h parvus in svalbard places the base of the triassic ca 4 m above the base of the vikinghogda formation and ca 2 50 m above the end permian mass extinction epme and its associated sharp negative 13c the ptb therefore falls within the reduviasporonites chalastus assemblage zone in svalbard precise u pb tims dating of two zircon crystals in a tephra layer just above the first documented hindeodus parvus in svalbard gives an age of 252 13 0 62 ma high resolution palaeoenvironmental proxies including si kcps kilo counts per second zr rb k ti fe k and v cr indicate a transition towards a more arid climate in the earliest triassic contemporaneous with prolonged bottom water dysoxic anoxic conditions following an increase in volcanic activity in the late permian statistical analysis of zr rb k ti and v cr elemental ratios suggests that the system was impacted by long eccentricity 400 kyr cyclicity the 13c excursion in organic carbon 13corg record signals a large negative carbon isotope excursion cie associated with the mass extinction event but also records a second smaller negative cie ca 22 m above this interval this younger 13corg excursion correlates to similar cies in the dienerian late induan records of other sections notably in the tethys ocean which have been interpreted as recording a small biotic crisis during the post extinction recovery evidence of this negative cie in spitsbergen suggests that the dienerian crisis may have been global in extent the negative 13corg values are associated with evidence for dysoxia or anoxia in the core and the occurrence of tephra layers in the same interval suggests a possible connection between the dienerian crisis and a discrete episode of volcanic activity

changes in biomarker abundances and sulfur isotopes of pyrite across the permian triassic p tr schuchert dal section east greenland abstract in this study we report on biomarker abundances through parts of the permian triassic boundary ptb of schuchert dal east greenland that contains rich marine faunal records and excellent terrestrial palynological records biomarker abundances and sulfur isotopes are used to correlate the series of events including changes in element cycling and associated redox conditions of the ocean surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on earth during a mass extinction episode the upper schuchert dal formation contains a low diversity palynological assemblage ascribed to arborescent cordiaite conifer pteridosperm vegetation samples from this pre collapse interval are characterised by high abundances of dibenzofuran dbf dibenzothiophene dbt and biphenyl since these compounds have similar base structures and show comparable abundance curves it is plausible that they probably derive from a common source we propose that phenolic compounds of lignin of the woody plants present during this period could be the source for dbf dbt and biphenyl the redox conditions during this period of time also support the formation of dbf and dbt just above the extinction interval there is a dramatic decrease in the abundances of dbf and dbt which occurs at the same time as a sudden change in the stable sulfur isotopic composition 34s of pyrite indicating a change in redox conditions from oxic to anoxic euxinic conditions 34s values leading up to the extinction are highly depleted in the heavy sulfur isotope about 40 vs vcdt whilst shortly after the extinction interval much more positive isotope values are observed about 25 an inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections it is suggested that two processes are operating closely here 1 changes in redox conditions and 2 extinction and or transgression accounting for the absence of woody material

climate changes caused by degassing of sediments during the emplacement of large igneous provinces most mass extinctions during the last 500 m y coincide with eruptions of large igneous provinces lips the cretaceous tertiary extinction was synchronous with the deccan flood volcanism the permian triassic extinction with the eruption of the enormous siberian traps and the end guadalupian extinction with the emeishan volcanic province the causal link remains disputed however and many lips apparently had no significant impact on the biosphere here we show that a key control on the destructive consequences of lip emplacement is the type of sedimentary rock in basins beneath the flood basalts contact metamorphism around intrusions in dolomite evaporite coal or organic rich shale generates large quantities of greenhouse and toxic gases co 2 ch 4 so 2 which subsequently vent to the atmosphere and cause global warming and mass extinctions the release of sediment derived gases had a far greater impact on the environment than the emission of magmatic gases

frequent euxinia in southern neo tethys ocean prior to the end permian biocrisis evidence from the spiti region india abstract in this study we reconstruct water column oxygen availability during the deposition of late permian shales wuchiapingian to approximately early changhsingian using the geochemistry and morphology of sedimentary pyrite fes2 deposition of the shales occurred prior to the end permian mass extinction within the southern neo tethys ocean spiti region himachal pradesh india we found that the variability of pyritic sulfur to organic carbon spyr corg and the pyritic sulfur isotopic composition 34spyr did not record changes in oxygen availability at spiti sections this was due to the removal of original pyritic sulfur by modern oxidative weathering and diagenetic pyrite formation which overwhelmed the original 34spyr values however pyrite framboid size distributions was a reliable recorder of paleoredox conditions the degree of oxygen limitation varied with multiple transient euxinic events interrupting a predominantly oxic dysoxic trend near the top of the gungri formation upper member approximately late wuchiapingian to early changhsingian these transient euxinic intervals provide important insight and regional evidence of environmental stress and instability in the southern neo tethys well prior to the end permian mass extinction

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

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

no abrupt change in redox condition caused the end permian marine ecosystem collapse in the east greenland basin abstract multiple observations have revealed that environmental disturbances may have been linked to the end permian mass extinction and delayed biotic recovery biogeochemical constraints on the temporal and spatial changes of oceanic redox chemistry during the permian triassic interval are essential to evaluate global significance of previous hypotheses and to improve our understanding of extinction and recovery processes to investigate redox ocean chemistry change associated with the end permian extinction and subsequent delayed biotic recovery we examine framboidal pyrites as well as sulfur isotopic compositions of pyrites from the east greenland basin the size distributions of framboidal pyrites in sediments from a continuous section across the permian triassic boundary reveal that sulfidic conditions in water columns were established about 0 7 m above the extinction event in the east greenland basin our detailed examination of framboidal pyrites challenges a leading hypothesis that euxinia in the photic zone caused the end permian ecosystem collapse we identify several positive and negative s isotopic shifts before and after the extinction event and demonstrate that a positive s isotopic shift is not indicative of an abrupt change of redox chemistry in water columns in contrast to previous claims the integration of isotope and framboidal pyrite data provides a nearly continuous record of ocean chemistry evolution and new insights into the end permian extinction and delayed biotic recovery in the east greenland basin

erosional truncation of uppermost permian shallow marine carbonates and implications for permian triassic boundary events on shallow marine carbonate buildups in south china turkey and japan uppermost permian skeletal limestones are truncated by an erosional surface that exhibits as much as 10 cm of topography including overhanging relief sedimentary facies microfabrics carbon isotopes and cements together suggest that erosion occurred in a submarine setting moreover biostratigraphic data from south china demonstrate that the surface postdates the uppermost permian sequence boundary at the global stratotype section and truncates strata within the youngest known permian conodont zone the occurrences of similar truncation surfaces at the mass extinction horizon on carbonate platforms across the global tropics each overlain by microbial buildups and their association with a large negative excursion in 13 c further suggest a causal link between erosion of shallow marine carbonates and mass extinction previously proposed to account for marine extinctions the hypothesis of rapid carbon release from sedimentary reservoirs or the deep ocean can also explain the petrographic observations rapid unbuffered carbon release would cause submarine carbonate dissolution accounting for erosion of uppermost permian skeletal carbonates and would be followed by a pulse of high carbonate saturation explaining the precipitation of microbial limestones containing upwardgrowing carbonate crystal fans models for other carbon release events suggest that at least 5 10 18 g of carbon released in 100 k y would be required of previously hypothesized permian triassic boundary scenarios thermogenic methane production from heating of coals during siberian traps emplacement best accounts for petrographic characteristics and depositional environment of the truncation surface and overlying microbial limestone as well as an associated carbon isotope excursion and physiologically selective extinction in the marine realm

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

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

pyrite framboids in the permian triassic boundary section at meishan china evidence for dysoxic deposition pyrite framboid evidence from the permian triassic global stratotype at meishan china indicates the late permian mass extinction is closely associated with a dramatic decline of benthic oxygen levels sizes and abundances of the framboids were determined from acid residues and in situ on polished sections of the samples the framboids are abundant in the thin pyrite lamina on the top of bed 24e the upper layer of bed 24 and beds 25 26 and 29 rare in bed 24e and bed 28 but absent in bed 27 they have narrow size distributions with average diameters from 4 6 mu m to 8 7 mu m which are similar to those formed under anoxic dysoxic conditions the abundances and mean diameters of the pyrite framboids indicate redox conditions of deposition changing from upper dysoxia bed 24e and lower dysoxia pyrite lamina beds 25 and 26 to oxygenation bed 27 and again to upper dysoxia bed 28 and lower dysoxia bed 29 our discovery confirms a worldwide dysoxic marine event during the permian triassic transition suggestive of a direct relationship with the permian triassic marine mass extinction c 2007 elsevier b v all rights reserved

an extensive survey of dayside diffuse aurora based on optical observations at yellow river station by using 7 years optical auroral observations obtained at yellow river station magnetic latitude 76 24 n at ny alesund svalbard we performed the first extensive survey for the dayside diffuse auroras ddas and acquired observational results as follows 1 the ddas can be classified into two broad categories i e unstructured and structured ddas the unstructured ddas are mainly distributed in morning and afternoon but the structured ddas predominantly occurred around the magnetic local noon mln 2 the unstructured ddas observed in morning and afternoon present obviously different properties the afternoon ones are much stable and seldom show pulsating property 3 the ddas are more easily observed under geomagnetically quiet times 4 the structured ddas mainly show patchy stripy and irregular forms and are often pulsating and drifting the drifting directions are mostly westward with speed 5 km s but there are cases showing eastward or poleward drifting 5 the stripy ddas are exclusively observed near the mln and most importantly their alignments are confirmed to be consistent with the direction of ionospheric convection near the mln 6 a new auroral form called throat aurora is found to be developed from the stripy ddas based on the observational results and previous studies we proposed our explanations to the ddas we suggest that the unstructured ddas observed in the morning are extensions of the nightside diffuse aurora to the dayside but that observed in the afternoon are predominantly caused by proton precipitations the structured ddas occurred near the mln are caused by interactions of cold plasma structures which are supposed to be originated from the ionospheric outflows or plasmaspheric drainage plumes with hot electrons from the plasma sheet we suppose that the cold plasma structures for producing the patchy ddas are in lumpy and are more likely from the plasmaspheric drainage plumes the cold plasma structure for producing the stripy ddas should be in wedge like and is generated by conveying the cold plasmas from lower l shell toward higher l shell with magnetospheric convection and that for producing the irregular ddas is resulted from deforming the wedge like structure by disturbance the throat aurora is supposed to be projection of a newly opened flux of reconnection in addition we also found that structured ddas correspond to structured electron precipitations in the ionosphere which implies that the cold plasma structures in the magnetosphere are magnetically mapped to the ionosphere and act as a duct for producing the structured ddas we argue that we have presented some new observational results about dda in this paper which will be useful for fully understanding the ddas

latest permian to early triassic basin to shelf anoxia in the sverdrup basin arctic canada a combined sequence stratigraphic and geochemical study of the latest permian extinction event in nw pangea provides new insight into the onset and extension of basin anoxia onto the adjacent shallow shelf the latest permian transgression in the sverdrup basin of arctic canada initiated prior to onset of deep water anoxia and continued past the latest permian extinction event deep water anoxia initiated after the shelf was flooded in mid to late changhsingian time requiring a much more rapid and much greater vertical rise in the chemocline than that associated with relative sea level supporting the chemocline upward excursion model our work also extends evidence of global euxinc conditions to nw pangea euxinic conditions developed just prior to the main extinction event and we suggest that this was associated with a significant pyrite rain out event which stripped bio essential nutrients from anoxic seawater prior to the main disruption of the global carbon cycle as recorded by shifts in the carbon isotope record

changes in productivity and redox conditions in the panthalassic ocean during the latest permian the gujo hachiman section in central japan provides a rare window into environmental conditions within the panthalassic ocean which encompassed more than half the earth s surface at 251 ma the section is characterized by a sharp transition from green gray organicpoor cherts to black siliceous shales in the uppermost permian normalization to the clay fraction demonstrates that apparent increases in the concentrations of organic matter and trace metals above this transition were due primarily to the loss of a diluent biogenic radiolarian silica fl ux and only secondarily to a small shift toward more reducing bottom waters in the black shale pyrite abundance increases by a factor of 30 and is dominated by framboidal grains of probable syngenetic origin these observations suggest that the expansion of lowoxygen conditions within the panthalassic ocean was focused within the oxygen minimum zone rather than at the seafl oor such a pattern implies that 1 changes in nutrient fl uxes and primary productivity rates rather than stagnation of oceanic circulation were a key factor infl uencing oceanic redox conditions around the permian triassic boundary and 2 large regions of the panthalassic ocean underwent only limited redox changes providing potential refugia for marine taxa that survived into the triassic

an abrupt extinction in the middle permian capitanian of the boreal realm spitsbergen and its link to anoxia and acidification the controversial capitanian middle permian 262 ma extinction event is only known from equatorial latitudes and consequently its global extent is poorly resolved we demonstrate that there were two severe extinctions amongst brachiopods in northern boreal latitudes spitsbergen in the middle to late permian separated by a recovery phase new age dating of the spitsbergen strata belonging to the kapp starostin formation using strontium isotopes and d 13 c trends and comparison with better dated sections in greenland suggests that the first crisis occurred in the capitanian this age assignment indicates that this middle permian extinction is manifested at higher latitudes redox proxies pyrite framboids and trace metals show that the boreal crisis coincided with an intensification of oxygen depletion implicating anoxia in the extinction scenario the widespread and near total loss of carbonates across the boreal realm also suggests a role for acidification in the crisis the recovery interval saw the appearance of new brachiopod and bivalve taxa alongside survivors and an increased mollusk dominance resulting in an assemblage reminiscent of younger mesozoic assemblages the subsequent end permian mass extinction terminated this late permian radiation

towards field bounds on rock mass failure criteria abstract various rock mass failure criteria are being validated against field performance as part of a large research program into the geotechnical risk of concrete gravity dams the project has sought rock structures which may contribute to providing either upper or lower bounds to various failure criteria and therefore the emphais has been on finding sites with high quality field and laboratory data the first two sites investigated have been chichester dam foundation and nattai north escarpment failure both in new south wales australia the paper summarises the existing information for both cases each case has been analysed using the distinct element method the results of these analyses allow the field occurrence to be compared with the commonly used hoek brown empirical rock mass failure criterion as expected the bounds on the various failure criteria are very broad and care must be taken when placing any reliance on any particular criterion

catastrophic soil erosion during the end permian biotic crisis organic geochemical analyses of sedimentary organic matter from a marine permian triassic transition sequence in northeastern italy reveal a significant influx of land derived diagenetic products of polysaccharides this unique event reflects massive soil erosion resulting from destruction of land vegetation due to volcanogenic disturbance of atmospheric chemistry the excessive supply of soil materials to the oceans provides a direct link between terrestrial and marine ecological crises suggesting that ecosystem collapse on land could have contributed to the end permian marine extinctions

pyrite framboid study of marine permian triassic boundary sections a complex anoxic event and its relationship to contemporaneous mass extinction size analysis of pyrite framboids has been undertaken on epicontinental permian triassic boundary sections throughout the world in order to evaluate the intensity and duration of anoxia mid paleolatitude sections from the margins of the boreal spitsbergen greenland and neotethyan oceans western australia reveal intense anoxia throughout the permian triassic boundary interval with euxinic conditions frequently developing and dysoxia encountered even in relatively shallow water settings above storm wave base at equatorial paleolatitudes weakly oxygenated dysoxic conditions are widely developed in a broad range of water depths including those shallow enough to produce oolite deposition although euxinia was rare western and eastern tethyan locations re veal a complex and unstable redox history anoxia in the hindeodus praeparvus zone was replaced by oxygenated facies in the permian triassic boundary interval h changxingensis to h parvus zones oxygen poor deposition returned during the succeeding isarcicella isarcica zone the more persistent and intense development of oxygen restriction in cooler water mid paleolatitude sections argues against warming and dissolved oxygen decline as the key cause of permian triassic bound ary anoxia in higher paleolatitudes the ben thic invertebrate extinctions occurred during a prolonged phase of oxygen poor deposition while in equatorial tethyan locations benthic losses occurred at the end of the fi rst anoxic phase in the late h praeparvus zone

adaptive strategies and environmental significance of lingulid brachiopods across the late permian extinction abstract linguliform brachiopods are traditionally considered a conservative group which seems to pass through the late permian extinction without any significant loss and even appear to thrive immediately after the extinction peak in the southern alps lingulids are very common in the post extinction mazzin member early induan of the werfen formation sparse occurrences are also known in the overlying siusi and gastropod oolite members late induan and early olenekian in age respectively the recent discovery of well preserved specimens from a pre extinction bed of the bellerophon formation changhsingian has permitted a detailed comparative analysis mostly based on the interior characters preserved in the lingulid succession from across the extinction beds the following effects on the lingulid populations have been analyzed i change in taxonomic assessment ii adaptive strategies during the surviving and recovery phases and iii environmental proxy connected with the killing mechanisms of the late permian extinction the pre extinction individuals belong to lingularia cf smirnovae biernat and emig a species that is characterized by large sized shells with a short lophophoral cavity the post extinction populations belong to different species and probably even to a different genus the first post extinction population early induan with small sized shells and long lophophoral cavity has been referred to lingularia yini peng and shi it records the most severe effects of the late permian extinction on the marine ecosystems the late induan olenekian lingularia borealis bittner with large sized shells and long lophophoral cavity appears during the first phase of the triassic biotic recovery the main adaptive strategies of lingularia yini in comparison with the permian species include i shell miniaturization ii increasing of the lophophoral cavity surface respiratory surface and iii increasing of shell width length ratio these modifications are interpreted as adaptations towards warming and hypoxia two main killing mechanisms of the marine biota the recovery species lingularia borealis maintains a large lophophoral cavity indicating an adaptation towards predominant low oxygenated bottom marine waters the appearance and the great abundance of lingularia yini in the mazzin member early induan represent a proxy of dysaerobic conditions which determined the appearance of the second phase of the lilliput biota characterized by the definitive disappearance of the rhynchonelliform brachiopods and calcareous algae in the southern alps

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

gradual onset of anoxia across the permian triassic boundary in svalbard norway the permian triassic extinction event is considered to be the most devastating environmental crisis of the phanerozoic with many coinciding factors involved the role of marine anoxia during the extinction is still poorly understood in this study a boreal permian triassic boundary ptb section from svalbard norway has been investigated with the aim of better understanding the timing and nature of local marine anoxia onset and extinction events across the ptb the section comprises the kapp starostin and vikinghogda formations 13corg values indicate the ptb is located within the lower part of the vikinghogda formation lag deposits at the top of the kapp starostin formation indicate a marine hiatus and ensuing transgression during the late permian shortly before the extinction event implying concurrence of major ecological changes and sea level rise pyrite framboid size distributions and total organic carbon toc were used to evaluate bottom water oxygen conditions and show that changes in bottom water redox conditions and extinction are clearly linked oxic to dysoxic bottom water conditions prevailed during deposition of kapp starostin formation sediments and changed to anoxic to euxinic conditions above the formation boundary the onset of anoxia is not abrupt but rather shows a gradual increase within the kapp starostin formation during the late permian the tipping point where bottom waters reach a long term state of anoxia to euxinia coincides with the final extinction event though changes in biotic assemblages at the top of the kapp starostin formation indicate a marine ecosystem crisis prior to this oxygen depletion in the boreal region as seen in our study section and correlating to greenland and arctic canada seems to be consistently more severe than in lower latitude settings

synchrony and causal relations between permian triassic boundary crises and siberian flood volcanism the permian triassic boundary records the most severe mass extinctions in earth9s history siberian flood volcanism the most profuse known such subaerial event produced 2 million to 3 million cubic kilometers of volcanic ejecta in approximately 1 million years or less analysis of 40 ar 39 ar data from two tuffs in southern china yielded a date of 250 0 0 2 million years ago for the permian triassic boundary which is comparable to the inception of main stage siberian flood volcanism at 250 0 0 3 million years ago volcanogenic sulfate aerosols and the dynamic effects of the siberian plume likely contributed to environmental extrema that led to the mass extinctions

sedimentary evolution and environmental history of lake van turkey over the past 600 000 years the lithostratigraphic framework of lake van eastern turkey has been systematically analysed to document the sedimentary evolution and the environmental history of the lake during the past ca 600 000 years the lithostratigraphy and chemostratigraphy of a 219 m long drill core from lake van serve to separate global climate oscillations from local factors caused by tectonic and volcanic activity an age model was established based on the climatostratigraphic alignment of chemical and lithological signatures validated by 40ar 39ar ages the drilled sequence consists of ca 76 lacustrine carbonaceous clayey silt ca 2 fluvial deposits ca 17 volcaniclastic deposits and 5 gaps six lacustrine lithotypes were separated from the fluvial and event deposits such as volcaniclastics ca 300 layers and graded beds ca 375 layers and their depositional environments are documented these lithotypes are i graded beds frequently intercalated with varved clayey silts reflecting rising lake levels during the terminations ii varved clayey silts reflecting strong seasonality and an intralake oxic anoxic boundary for example lake level highstands during interglacials interstadials iii caco3 rich banded sediments which are representative of a lowering of the oxic anoxic boundary for example lake level decreases during glacial inceptions iv caco3 poor banded and mottled clayey silts reflecting an oxic anoxic boundary close to the sediment water interface for example lake level lowstands during glacials stadials v diatomaceous muds were deposited during the early beginning of the lake as a fresh water system and vi fluvial sands and gravels indicating the initial flooding of the lake basin the recurrence of lithologies i to iv follows the past five glacial interglacial cycles a 20 m thick disturbed unit reflects an interval of major tectonic activity in lake van at ca 414 ka bp although local environmental processes such as tectonic and volcanic activity influenced sedimentation the lithostratigraphic pattern and organic matter content clearly reflect past global climate changes making lake van an outstanding terrestrial archive of unprecedented sensitivity for the reconstruction of the regional climate over the last 600 000 years

palaeogeographical influence on late eocene biosiliceous sponge rich sedimentation southern western australia late eocene nearshore shallow marine environments within the bremer and western eucla basins of southern western australia were characterized by the thick deposition of spongolite and spiculite deposits epibenthic sponge communities dominated estuaries and topographically complex basin margin embayments archipelagos while cool water carbonates with up to 10 sponges accumulated in open shelf environments the transition from a biosiliceous to calcareous epibenthos was related to the degree of palaeogeographical protection within basement protected embayments there was an offshore gradation from shoreface spongolite and pure spiculite to a muddy spiculite facies towards central embayment areas calcareous fossils are rare throughout embayment facies but rapidly increase in more open outer archipelago areas this depositional relationship occurred along 2000 km of the late eocene southern australian coastline palaeogeographical protection from strong currents acted in concert with 1 a planar low gradient inland topography with sluggish run off supplying fine grained sediment nutrients and abundant dissolved silica and 2 a microtidal setting weak to moderate swells and opposing wind and coriolis surface current forcing which inhibited water exchange between embayments estuaries and the open shelf this situation led to an embayment water chemistry that encouraged prolific sponge growth calcareous spiculites record the mixing front between these embayment waters and normal open shelf waters supporting cool water carbonates

a depositional and sequence stratigraphic model for cold water spiculitic strata based on the kapp starostin formation permian of spitsbergen and equivalent deposits from the barents sea this article summarizes the lithostratigraphy of two sections through the kapp starostin formation on spitsbergen having contrasting distal and proximal depositional settings these outcrop sections are compared with an approximately age equivalent spiculitic unit penetrated in two exploration wells 800 km to the southeast on the finnmark platform eight main facies associations comprise these strata including limestones matrix rich matrix poor and mudstone siliciclastics shale and sandstone spiculite dark tight and light colored porous and phosphatized surfaces a sequence stratigraphic model is proposed wherein siliciclastic limestone intervals represent lowstands of relative sea level and the spiculites are mainly highstand deposits based on this model seven depositional cycles sequences are recognized in the distal high accommodation locality on spitsbergen akseloya four in the proximal locality dickson land and two on the finnmark platform a speculative model for correlation between these localities is presented wherein lateral amalgamation of sequences due to landward pinch out of some lowstand intervals results in recognition of fewer sequences in areas of lower accommodation on both dickson land and the finnmark platform an upward change in spiculite lithology from dark tight to light porous is shown and dickson land also shows an upward change in siliciclastic lithology from shale to glauconitic sandstone these changes record a long term shoaling trend approaching the permian triassic boundary this model provides a basis for interpreting the basin scale begin page 2062 distribution of lithofacies and predicting the occurrence of porous zones representing potential hydrocarbon reservoirs

episodic euxinia in the changhsingian late permian of south china evidence from framboidal pyrite and geochemical data abstract a multiproxy study of a new upper permian lower triassic section xiaojiaba in sichuan province china documents large changes in marine productivity redox conditions and detrital input prior to the latest permian mass extinction marine productivity as proxied by total organic carbon content toc biogenic sio 2 and excess barium displays a long term decline through most of the changhsingian stage late late permian culminating in very low values around the permian triassic boundary concurrently redox proxies including pyrite framboid 34 s py mo auth and u auth and c org p document a shift from suboxic to dysoxic oxic conditions that was interrupted by several episodes of benthic euxinia and detrital siliciclastic proxies al hf nb and rees suggest an increased flux of weathered material from land areas the long term changes in productivity redox conditions and terrigenous detrital fluxes were probably caused by a regional sea level fall across the south china craton on the other hand the brief euxinic episodes occurring during the late permian had oceanographic causes probably related to the transient upward expansion of the chemocline at the top of the oceanic oxygen minimum zone these euxinic episodes may have been harbingers of the more widespread anoxia that developed concurrently with the latest permian mass extinction and that may have played a major role in triggering the largest biotic crisis of the phanerozoic

global ocean redox variation during the middle late permian through early triassic based on uranium isotope and th u trends of marine carbonates uranium isotopes 238u 235u in carbonates a proxy for global ocean redox conditions owing to their redox sensitivity and long residence time in seawater exhibit substantial variability in the daxiakou section of south china from the upper middle permian through the mid lower triassic 9 m y middle and late permian ocean redox conditions were similar to that of the modern ocean and were characterized by improving oxygenation in the 2 m y prior to the latest permian mass extinction lpme countering earlier interpretations of sustained or gradually expanding anoxia during this interval the lpme coincided with an abrupt negative shift of 0 5 in 238u that signifies a rapid expansion of oceanic anoxia intensely anoxic conditions persisted for at least 700 k y griesbachian lessening somewhat during the dienerian th u concentration ratios vary inversely with 238u during the early triassic with higher ratios reflecting reduced u concentrations in global seawater as a consequence of large scale removal to anoxic facies modeling suggests that 70 100 of marine u was removed to anoxic sinks during the early triassic resulting in seawater u concentrations of 5 that of the modern ocean rapid intensification of anoxia concurrent with the lpme implies that ocean redox changes played an important role in the largest mass extinction event in earth history

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

high frequency fluctuations in redox conditions during the latest permian mass extinction abstract new high resolution geochemical and sedimentological data from fiskegrav east greenland reveal fluctuations in marine redox conditions associated with the final disappearance of bioturbating organisms during the latest permian mass extinction lpme sedimentological observations imply a transgressive episode and associated geochemical evidence for decreasing oxygen availability and the establishment of persistently ferruginous fe 2 rich conditions implies the shoreward migration of oxygen deficient waters the long term decline in dissolved oxygen do availability could have been exacerbated by increasing water temperatures reducing the solubility of oxygen and promoting thermal stratification mixing of the water column could have been further inhibited by freshwater influxes that could have generated salinity contrasts that reinforced thermal stratification enhanced runoff could also have increased the delivery of nutrients to the marine shelf stimulating biological oxygen demand bod during the transition to persistently ferruginous conditions we identify intervals of intermittent benthic meiofaunal recolonization events that we attribute to small transient increases in do availability the mechanism controlling these fluctuations remains speculative but given the possible centennial to millennial scale frequency of these changes we hypothesise that the mid latitude setting of fiskegrav during the late permian was sensitive to changes in atmospheric circulation patterns which may have influenced local precipitation and intermittently modulated some of the processes promoting anoxia

observations of black auroral patches and of their relationship to other types of aurora a morphological study of black patches and newly reported black rings black patches with islands of embedded diffuse aurora was conducted using an archive of low light level all sky and narrow field television camera data the overwhelming majority of black patches and rings drifted eastward poleward of westward drifting pulsating aurora in the early recovery phase of the auroral substorm occasionally black aurora would overlap with pulsating aurora sometimes the pulsations would add to the intensity in the black aurora more than in the surrounding diffuse aurora called veiling one example was documented where the pulsation was purely additive adding to the intensity of the black aurora and the surrounding diffuse aurora equally cases of total veiling suggest an intensity limit possibly associated with the strong pitch angle diffusion limit

late permian to early triassic changes in acritarch assemblages and morphology in the boreal arctic new data from the finnmark platform abstract the late permian extinction interval is in many marine locations characterized by the development of anoxic conditions the finnmark platform is one of few exceptions as sedimentological and palynofacies evidence indicate oxygenated conditions throughout the event changes in acritarch assemblages and morphology were studied in order to better understand the link between acritarchs and environmental conditions the main taxa are of micrhystridium baltisphaeridium and leiospheres while veryhachium and the prasinophytes cymatiosphaera and tasmanites were present in low abundances increased concentrations of acritarchs particularly micrhystridium show that the environmental changes at the start of the extinction event may have resulted in enhanced marine productivity a shift from micrhystridium baltisphaeridium dominance before and during the extinction event to leiosphere dominance after the extinction event indicates a shift towards a more inshore environment the new data are compared with published late permian acritarch records from east greenland china and pakistan a striking difference between the east greenland and finnmark platform which are both expanded upper permian lower triassic sections is that the acritarch record from greenland shows a strong decrease in process length of the acritarch micrhystridium together with a change in the acritarch assemblage this change in morphology was interpreted to represent a decrease in salinity at the site resulting from increased run off the differences between the east greenland and the finnmark records are likely due to their palaeogeographical settings as the east greenland section was located in a narrow and elongated basin which was likely more sensitive to evaporation and run off changes than the finnmark platform

evidence for a diachronous late permian marine crisis from the canadian arctic region a high resolution chemostratigraphic study of a 24 m thick section at west blind fiord on ellesmere island canadian arctic documents stepwise environmental deterioration in the marine sverdrup basin during the late changhsingian late late permian as a result of volcanic disturbances to surrounding landmasses a horizon within the upper lindstrom formation datum a is characterized by increased fe oxyhydroxide fl uxes and weathering intensity as well as modest shifts toward more reducing watermass conditions and higher marine productivity recording an initial disturbance that washed soils into the marine environment the contact between chert of the lindstrom formation and silty shale of the overlying blind fiord formation which is 1 6 m higher and 50 k y younger than datum a records a large increase in detrital sediment fl ux more strongly enhanced marine productivity and a regional extinction of siliceous sponges herein termed the arctic extinction event the horizon equivalent to the latest permian mass extinction of tethyan shallow marine sections is 5 6 m higher and 100 k y younger than the arctic extinction event demonstrating the diachronous nature of the marine biotic and environmental crisis at a global scale it is associated with intensifi ed anoxia and possible changes in phytoplankton community composition in the study section marine environmental deterioration in the sverdrup basin probably triggered by terrestrial ecosystem deterioration and elevated detrital sediment fl uxes was under way by the early part of the late changhsingian well before the onset of main stage siberian traps fl ood basalt volcanism the event sequence at west blind fiord may record the deleterious effects of early stage explosive silicic eruptions that affected the boreal region possibly through deposition of toxic gas and ash within a restricted latitudinal band while having little impact on marine ecosystems in the peri equatorial tethyan region