phytoplankton associations of the anisian peri tethys basin central europe evidence of basin evolution and palaeoenvironmental change abstract anisian lower muschelkalk phytoplankton associations of the nw tethys shelf and the northern peri tethys basin are characterized by acritarchs and prasinophytes stratigraphical and lateral variations in the distribution pattern of these phytoplankton groups were analyzed in key sections of the central basin germany the southern gate areas switzerland poland and the northwestern tethys shelf hungary with the aim to infer palaeoenvironmental changes related to the basin evolution stratigraphically maximum abundance of marine phytoplankton is recognized during phases of maximum flooding laterally a dominance of different phytoplankton groups within these intervals is documented in the central part of the basin prasinophytes reach 80 percent of the total plankton association sediments of the basin margin the gate areas and proximal shelf show high amounts of acritarchs ranging from 76 to 95 these signatures clearly reflect the basin evolution of the anisian lower muschelkalk peri tethys basin and the interaction between a restricted intracratonic basin and an open ocean generally the peri tethys basin is characterized by a stratified water column with oxygen depleted bottom waters and maximum abundance of prasinophytes during phases of transgression cooler waters from the shelf flood the restricted basin displayed in the acritarch dominated phytoplankton associations of the shelf and gate areas marginal parts of the basin are generally well oxygenated and dominated by acritarchs within the acritarch assemblage veryhachium spp is characteristic of the marginal and central parts of the basin whereas micrhystridium spp dominates shelf deposits and sediments of the gate areas respectively the present study highlights the significance of different phytoplankton associations in basin analysis and high resolution sequence stratigraphy

late guadalupian to lopingian permian carbon and strontium isotopic chemostratigraphy in the abadeh section central iran abstract the abadeh section well exposed in the hambast valley in central iran has long been one of the most extensively studied sections because of its continuous carbonate dominated strata from lower permian to lower triassic however biostratigraphy and correlation with the equivalent sequences in other regions remain controversial in this paper both carbon isotope excursion 13 c carb and strontium isotope ratio 87 sr 86 sr based on bulk carbonate samples have been measured to serve as chemostratigraphical proxies to estimate the three different chronostratigraphical boundaries in the lopingian at the abadeh section including the permian triassic event pteb the guadalupian lopingian glb and the wuchiapingian changhsingian boundaries wcb these three boundaries are important for understanding the marine biological evolution around this critical interval based on the 13 c excursions the rising trend of 87 sr 86 sr and the value around 0 7073 and the occurrence of microbialite beds the permian triassic event boundary bed 25 at the meishan section is suggested at 0 5 m below the base of the main microbialite bed the glb is suggested at 46 5 m based on the position of the minor 13 c carb negative depletion coupled with the values between 0 7069 and 0 7070 of 87 sr 86 sr and its beginning point of the rising trend which is above the lowest value 0 7068 of 87 sr 86 sr ratio in the paleozoic the relationship between section thickness and their high resolution depositional age projecting age is interpolated for the whole lopingian using locally weighted regression scatter plot smoother lowess of strontium isotopic ratio based on the negative 13 c excursion and the value 0 7072 of 87 sr 86 sr ratio the wcb is estimated at 1 m above the lithologic boundary between unit 6 and unit 7 much lower than the boundary defined by previous conodont biostratigraphy but similar to other index fossils this boundary is projected as ca 254 6 ma in 87 sr 86 sr age projecting model and is close to zircon u pb dating age from south china

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

a carbon isotopic study of an end permian mass extinction horizon bulla northern italy a negative δ13c shift prior to the marine extinction palaeontological data from the permian triassic bulla section northern italy demonstrate a rapid extinction at this site this occurs after a negative carbonate carbon isotope d 13 ccarb shift consistent with two other northern italian sites val badia and tesero however conclusion goes against recent reporting that the extinction occurs before the d 13 ccarb shift we agree that the shift occurs after the extinction at jameson land east greenland a high latitude palaeolocation however all other sections show the shift before or coincident with the extinction we suggest that the simplest explanation is a coeval shift in carbonate carbon isotope shifts and it follows that the extinction was not this suggests that the end permian extinction crept from region to region it also suggests that the marine extinction occurred first in high northern latitudes

sequencing events across the permian triassic boundary guryul ravine kashmir india abstract the permian triassic boundary ptb section at guryul ravine kashmir india comprises a 100 m thick apparently conformable succession of mixed siliciclastic carbonate sediments deposited in a deep shelf or ramp setting this section although long important in debates concerning placement of the ptb has not previously been the focus of an integrated chemostratigraphic study in the present study samples from a 20 m thick interval straddling the ptb were analyzed for major and trace element concentrations toc tic rees and organic 13c 15n to investigate contemporaneous environmental changes the guryul ravine section exhibits a sequence of discrete events that provide potentially important information about the character and cause s of the ptb two transient negative c isotopic excursions within the upper changxingensis zone predate the late permian event horizon lpeh i e the global mass extinction event by 200 400 kyr and are associated with the onset of a major eustatic rise and with secondary extinction peaks these excursions may record minor environmental disturbances prior to the main end permian crisis supporting an intrinsic mechanism such as volcanism and climate change rather than an extrinsic mechanism such as a bolide impact the onset of a large 4 0 to 4 5 sustained negative c isotope shift marks the lpeh which is located at the zewan khunamuh formation contact 260 cm below the biostratigraphically defined ptb the guryul ravine section exhibits a stepwise extinction pattern with the largest peak between the lpeh and ptb and a secondary peak just above the ptb a pattern similar to that observed in the meishan d gssp

shaking a methane fizz seismicity from the araguainha impact event and the permian triassic global carbon isotope record abstract the late permian and early triassic periods are marked by large fluctuations in the carbon isotope record but the source s of the disturbance to the global carbon cycle and the link to the end permian mass extinction are widely debated this contribution explores the possible isotopic effects of an impact event into the hydrocarbon rich rocks of the parana karoo basin recent u pb and 40ar 39ar dating of the 40 km araguainha impact structure of central brazil reveals an age of 254 7 2 5 ma 2 error for this event the calculated energy 105 106 mt of tnt equivalent released by this impact is less than threshold values of 107 108 mt tnt equivalent for global mass extinctions thus the araguainha crater is unlikely to have been the cause of the end permian biotic crisis however the combined seismic effects from the impact itself and the post impact collapse of the 20 25 km diameter transient crater to its present 40 km diameter would result in large magnitude earthquakes mw 9 3 10 5 and tsunamis in the shallow marine parana karoo basin slope failure and sediment liquefaction are predicted to have occurred within a 700 3000 km radius of the crater causing large scale release of methane from organic rich sediments of this basin including the oil shale horizons of the irati formation new geological evidence for seismicity in the parana basin at the time of impact is presented together with a compilation of existing carbon isotope data from the parana basin which demonstrate a widespread pattern of disturbance consistent with the release of methane these two datasets suggest that both seismicity and methane release took place within ca 1000 km of the impact site with mass balance calculations suggesting ca 1600 gt of methane were released into the atmosphere at this time methane release at this scale would have significant climate effects and would contribute to a sharp

platinum element group variations at the permo triassic boundary in kashmir and british columbia and their significance abstract the end permian marks the greatest extinction in the geological record but there is no consensus on whether it was caused by terrestrial or extraterrestrial factors platinum group elements pge can readily separate extraterrestrial from terrestrial sources and the few studies so far from china and europe indicate terrestrial sources for the pge we report here detailed pge analyses of two expanded sections from the late permian northern and southern hemispheres that allow separate events to be distinguished and confirm a terrestrial source for the pge these sources are either contemporaneous seawater or older basaltic volcanics associated with the sections and the pge were precipitated by a possible combination of development of anoxia in the oceans and post depositional redistribution the pge content in sections at the permo triassic boundary is the result of geochemical and lithological control on metal precipitation that is found in many other black shales throughout geological time

high organic carbon content and a decrease in radiolarians at the end of the permian in a newly discovered continuous pelagic section a coincidence article i nfo the greatest mass extinction occurred at the end of the permian most records of the mass extinction are not from pelagic sediments but from shallow marine and terrestrial sediments although several pelagic sections that span the end permian mass extinction have been found these sections contain few index fossils and are often discontinuous because of small faults we found the index fossils albaillella cf triangularis radiolaria in siliceous claystone beds hindeodus parvus conodont in the overlying black claystone beds and neospathodus cf cristagalli and ns waageni conodont in the subsequent siliceous claystone beds in akkamori section 2 in northern japan these fossils suggest that this section ranges from the late permian to the early triassic including the early induan and olenekian stages furthermore the lithological changes in the section i e starting from bedded chert through siliceous claystone and black claystone to siliceous claystone are concordant with those of well known permian triassic pelagic sequences in japan there is no gap between each lithofacie of the akkamori section 2 critical lithological continuity between upper permian siliceous claystone beds and uppermost permian to lowermost triassic black claystone beds of the akkamori section 2 was recognized by observing hand polished specimens and thin sections such paleontological and sedimentological evidence implies that the akkamori section 2 is a continuous pelagic section that records the end permian mass extinction event the carbonaceous black claystone beds have high total organic carbon toc concentrations 1 06 3 31 wt suggesting oceanic anoxia at least deep and probably stable primary productivity a decrease in radiolarian abundance from 26 563 to 0 27 20 specimens cm 2 coincided with an increase in toc content from 0 01 0 16 to 1 06 3 31 wt at the boundary of the siliceous claystone and the overlying black claystone beds near the top of the permian implying that radiolarian extinction occurred at the end of the permian coinciding with oceanic anoxia although toc contents decreased in the early olenekian smithian radiolarian abundance did not increase at that time indicating that radiolarian recovery was delayed by n1 5 m y

the interplay between massive volcanism and the local environment geochemistry of the late permian mass extinction across the sydney basin australia abstract the isotopic geochemical and physical characteristics of the late permian mass extinction have been identified and assessed from terrestrial sections across the sydney basin eastern australia these new data are used to both correlate the extinction event across the basin and elucidate its cause two stratigraphically well constrained cores were examined one each from the northern and southern regions of the sydney basin both sections show uninterrupted transitions from the last permian coal to a carbonaceous shale overlain by siltstones mudstones sandstones and shales whose mineralogical and physical characteristics are consistent with non marine origins these non marine origins are also broadly supported by elemental data carbon isotopic data were the primary means for identifying the stratigraphic position of the late permian mass extinction across the basin the data show that the mass extinction occurred as an interval with the form of a closely spaced double negative 13corg excursion within 1 m of the top of the last permian coal a feature previously unrecognised in the basin this result is supported by coincident excursions in 15n and 34spyrite the first measurements of their kind for the late permian mass extinction in the sydney basin the interrelationships between the c n and s isotopic data concentrations and elemental ratios together with major trace and rare earth element concentrations ratios and statistical analyses show severe environmental disruption occurred at the time of the extinction event with die off of terrestrial vegetation and the injection of sulphate into the water column consistent with massive volcanism geochemical evidence also shows however that local conditions have the potential to disrupt the late permian mass extinction signature and hence the data need to be interpreted carefully

massive volcanism at the permian triassic boundary and its impact on the isotopic composition of the ocean and atmosphere abstract bulk carbonate and conodonts from three permian triassic p t boundary sections at guryul ravine kashmir abadeh central iran and pufels bula bulla italy were investigated for 13 c and 18 o carbon isotope data highlight environmental changes across the p t boundary and show the following features 1 a gradual decrease of 4 to more than 7 starting in the late permian changhsingian c bachmanni zone with two superimposed transient positive excursions in the c meishanensis h praeparvus and the m ultima s mostleri zones 2 two 13 c minima the first at the p t boundary and a higher occasionally double minimum in the lower i isarcica zone it is unlikely that the short lived phenomena such as a breakdown in biological productivity due to catastrophic mass extinction a sudden release of oceanic methane hydrates or meteorite impact s could have been the main control on the latest permian carbon isotope curve because of its prolonged 0 5 ma duration gradual decrease and the existence of a 1 positive shift at the main extinction horizon the p t boundary 13 c trend matches in time and magnitude the eruption of the siberian traps and other contemporaneous volcanism suggesting that volcanogenic effects such as outgassed co 2 from volcanism and even more thermal metamorphism of organic rich sediments as the likely cause of the negative trend

organic geochemistry across the permian triassic transition at the idrijca valley western slovenia abstract bulk and molecular stable c isotopic compositions and biomarker distributions provide evidence for a diverse community of algal and bacterial organisms in the sedimentary organic matter of a carbonate section throughout the permian triassic p tr transition at the idrijca valley western slovenia the input of algae and bacteria in all the upper permian and lower scythian samples is represented by the predominance of c15 c22 n alkanes odd c number alkylcyclohexanes c27 steranes and substantial contents of c21 c30 acyclic isoprenoids the occurrence of odd long chain n alkanes c22 c30 and c29 steranes in all the samples indicate a contribution of continental material the decrease of corg and ccarb contents increase of rock eval oxygen indices and 13c enrichment of the kerogen suggest a decrease in anoxia of the uppermost permian bottom water the predominance of odd c number alkylcycloalkanes c27 steranes and c17 n alkanes with 13c values 30 and 13c enrichment of the kerogens in the lowermost scythian samples are evidence of greater algal productivity this increased productivity was probably sustained by a high nutrient availability and changes of dissolved co2 speciation associated to the earliest triassic transgression a decrease of corg content in the uppermost scythian samples associated to a 13c depletetion in the carbonates up to 4 and individual n alkanes up to 3 4 compared to the upper permian samples indicate lowering of the primary productivity algae cyanobacteria and or higher degradation of the organic matter

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

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

mantle plume the invisible serial killer application to the permian triassic boundary mass extinction the earth experienced a severe mass extinction at the permian triassic boundary ptb about 252 million years ago this biological catastrophe was accompanied by major changes in geochemical composition of the atmosphere and ocean and the appearance of sedimentary features which had not occurred since the precambrian time the eruption of the largest continental flood basalt the siberian traps overlapped this mass killing many hypotheses have been proposed but no definitive conclusion currently exits here we present characteristics of three sections from iran and china and propose that an active mantle plume initiated a series of processes which led to the mass mortality and produced major sedimentological mineralogical and geochemical changes observed in the transition from the paleozoic to the mesozoic the injection of mantle plume related igneous dike swarms into the continental margin facilitated the release of massive amounts of ch 4 primarily from the dissociation of marine gas hydrates and secondarily from the maturation of organic rich sediments and fracturing of hydrocarbon reservoirs the bulk of the ch 4 was aerobically oxidized in the water column producing dissolved co 2 with low 13 c values this co 2 saturated seawater became acidic to the point of dissolution of shelf carbonates promoting precipitation of siliciclastic rich strata in the transition from the permian to the triassic methane derived co 2 also lowered carbon isotopic composition of seawater leading to the observed decline in 13 c composition of organic and inorganic marine carbon at the ptb gas charged oceans released large volumes of co 2 and ch 4 into the atmosphere which created a severe global warming the end permian inferno causing the release of additional ch 4 from the dissociation of polar gas hydrates these events lowered 13 c compositions of terrestrial carbon simultaneously feeder dikes from the mantle plume formed the siberian traps flood basalt marine mass extinction was the result of a change in seawater composition due to the injection and oxidation of ch 4 in the water column causing low ph high concentrations of co 2 ca 2 and hco 3 and low co 3 2 values combined with a hot seawater temperature these changes made calcification of marine organisms difficult and produced major physiological crisis including reduced metabolic rates high sensitivity to environmental stress and hampered growth and reproduction terrestrial mass extinction can be attributed to severe global warming and soil acidification produced by increased atmospheric co 2 acid rain that was generated by so 2 derived from the siberian trap eruption and loss of habitat cessation of the plume activity during early triassic stopped the release of ch 4 into the ocean and terminated continental flood basalt eruption ending the environment of death on land and in sea the cut off of co 2 production in the ocean instantly increased carbonate saturation of seawater resulting in extensive seafloor cementation it also resulted in the deposition of marine carbonates by microbial activities in the hostile post extinction environment from the trigger to recovery the perturbation which included the end permian mass mortality could have lasted for at least 2 myr several major mass extinctions of the phanerozoic are temporally accompanied by flood basalt eruptions so far these two events have been interpreted in a cause and effect relation flood basalt eruption causes mass extinction this study proposes that flood basalts and their time correlative biological crises are themselves the consequence of a complex perturbation caused by mantle plume activities if so major disturbances in the near surface of the earth are ultimately controlled by changes in the mantle the physical sedimentological observations presented here combined with previous paleontological evidence cast doubt on other interpretations which use geochemical variables numerical modeling biomarkers and ce anomaly to suggest that late permian ocean was anoxic all the way to the photic zone

an ecologic explanation for the permo triassic carbon and sulfur isotope shifts the boundary between late permian and early triassic stratigraphic sequences is characterized by the onset of a marked shift in the isotopic composition of both marine carbonates and sulfates the abrupt 3 decrease in the carbon isotope ratio of carbonates and the more gradual 5 increase in the sulfur isotope ratio of sulfates can be explained by changes in the nature of the earth s ecosystems induced by the massive permo triassic extinctions we propose that the continental ecosystem responsible for the preservation and burial of organic matter during permian time was disrupted and that the relatively efficient marine food web of permian time was replaced by a less efficient system which allowed for a greater fraction of the marine organic matter to reach the seafloor these changes were reflected by a major shift in the depositional environment for the reduced component of material accumulating in sediments during the permian organic carbon burial on the continents dominated whereas during the triassic deposition of organic carbon on the seafloor dominated allowing sulfides to become an important component of the reduced phase

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

comparison of organic and inorganic carbon isotope patterns across the frasnian famennian boundary abstract the carbon isotopic composition of organic matter is reported for two frasnian famennian boundary sections from the rheinische schiefergebirge germany during the late frasnian 13 c org values commonly range from 27 5 to 26 highest 13 c org values around 24 are encountered immediately above and below the kellwasser horizons all samples from the kellwasser horizons are depleted in 13 c org by 2 5 to 4 7 this depletion is explained by a higher proportion of biomass derived from isotopically depleted chemoautotrophic bacteria a comparison of the positive 13 c excursions shows that the 13 c org shifts precede the 13 c carb shifts by some 10 5 years consequently 13 c values document a shift towards lower values below the upper kellwasser horizon a contribution of terrestrial organic matter as well as a thermal alteration of the 13 c org signals do not provide compelling explanations for the earlier 13 c org shift increases in primary productivity or carbon burial rate will change the co 2 aq content of surface waters affect the carbon isotope fractionation during photosynthetic carbon uptake and thus enrich organic carbon in 13 c however both processes cannot account for the earlier onset of the 13 c org shift because the 13 c carb record should document the resulting 13 c enrichment in surface waters as well a reduction in the calcium carbonate precipitation rate due to the global extinction of the reef ecosystem may have played an important role in reducing the co 2 aq content of surface waters without changing the isotopic composition of surface waters whether this process or other factors such as a rise in sea surface temperature or a change in the phytoplankton association account for the earlier onset of the positive shift in the 13 c org curve must be determined by further studies that may be able to confirm the global significance of the reported 13 c org pattern in frasnian famennian boundary sections from other parts of the globe

the 2002 denali fault earthquake alaska a large magnitude slip partitioned event the mw moment magnitude 7 9 denali fault earthquake on 3 november 2002 was associated with 340 kilometers of surface rupture and was the largest strike slip earthquake in north america in almost 150 years it illuminates earthquake mechanics and hazards of large strike slip faults it began with thrusting on the previously unrecognized susitna glacier fault continued with right slip on the denali fault then took a right step and continued with right slip on the totschunda fault there is good correlation between geologically observed and geophysically inferred moment release the earthquake produced unusually strong distal effects in the rupture propagation direction including triggered seismicity

conodont biostratigraphic control on transitional marine to non marine permian triassic boundary sequences in yunnan guizhou china the recovery of conodonts associated with ash beds and magnetostratigraphy in the key zhongzhai section near langdai liuzhi guizhou province provides precise and definitive control on the position of the permian triassic boundary in the transition from marine to non marine facies of western guizhou and eastern yunnan provinces of southwestern china in the zhongzhai section the boundary interval consists of a lower limestone 20 cm thick that contains fragments of hindeodus sp and clarkina sp this is overlain by a 50 cm thick black shale bed containing an abundant brachiopod fauna but only a single conodont fragment this bed is in turn overlain by a 23 cm thick limestone that contains clarkina meishanensis merrillina ultima hindeodus changxingensis h praeparvus and h eurypyge directly over this limestone is a 5 cm thick ash bed followed by a 10 cm thick black shale which is overlain by a second upper ash bed that is 3 cm thick on top of the upper ash bed is a 20 cm thick silty limestone containing an abundant dwarf conodont fauna dominated by hindeodus and containing h parvus but also including clarkina tulongensis the permian triassic boundary is placed at the level of the black shale located between the two ash beds 2007 elsevier b v all rights reserved

low oxygen levels in earliest triassic soils an earliest triassic methane postapocalyptic greenhouse following the permian triassic p t extinction event was proposed on the basis of evidence of deeply weathered paleosols at high latitudes with features of low latitude soils and low stomatal index values of seed fern leaves reexamination of distinctive phyllosilicates unique to a single stratigraphic level in paleosols located just above the isotopically defined permian triassic boundary in australia and antarctica furnishes additional tests of this hypothesis illite is the dominant clay mineral in earliest triassic paleosols from antarctica but the paleosols also contain conspicuous green nodules of coarsely crystalline berthierine examples from the geologic record and from experimental studies indicate that the formation of berthierine is restricted to reducing conditions the occurrence of this unusual mineral in soils may indicate soil oxygen consumption by the influx of atmospheric methane to form carbon dioxide which in turn warmed the earliest triassic giving rise to a postapocalyptic greenhouse

palaeotethys seawater temperature rise and an intensified hydrological cycle following the end permian mass extinction abstract the end permian mass extinction has been associated with severe global warming main stage volcanism of the siberian traps occurred at or near the extinction interval and has been proposed as a likely greenhouse catalyst in this study a high resolution 18o record is established using diagenetically resistant apatite of conodonts and low mg calcite of brachiopods from stratigraphically well constrained permian triassic p tr boundary successions in northwestern iran a new evaluation is made for previously published conodont 18o values from south china and revised palaeotemperatures are presented together with new data from wuchiapingian to griesbachian sections in iran 18o data from p tr sections in iran document tropical sea surface temperatures sst of 27 33 c during the changhsingian with a negative shift in 18o starting at the extinction horizon translating into a warming of ssts to over 35 c the results are consistent with re calculated ssts of the south chinese sections warming was associated with an enhanced hydrological cycle involving increased tropical precipitation and monsoonal activity in the tethys sea global warming intensification of the hydrological cycle and associated processes vertical water column stratification eutrophication and subsequent local anoxia may all have facilitated an extinction event

globally enhanced hg deposition and hg isotopes in sections straddling the permian triassic boundary link to volcanism abstract mercury hg toc spikes from eight permian triassic boundary ptb sections in this study display patterns similar to each other across the so called extinction interval as well as strong variation in sedimentation rates from section to section mercury may have been originated from the synchronous magmatism of the siberian traps large igneous province stlip at the gssp in meishan china hg toc peaks were observed in the latest permian mass extinction interval lpme and early triassic mass extinctions etme the successions at hovea 3 australia ursula creek canada idrijca slovenia rizvanusa croatia exhibit hg toc peaks at the lpme and ptb the rizvanusa section displays one peak at the etme horizon zal and abadeh iran successions at the lpme and etme horizons while misci seres tyrol italy section shows an enrichment at the lpme the largest hg toc peaks at the lpme ptb and etme are perhaps linked to the beginning of stage 2 extrusive hiatus of the siberian traps lip the meaning of the hg toc spike between the lpme event and the ptb in seven of these sections is fuzzy in the 202hg mdf vs 201hg mif cross plot the majority of samples from the extinction interval appear within the volcanic emission box and a few samples plot in the sediment soil peat box hg isotope signatures resulted from mixing processes of volcanic and normal marine sediment hg generating four horizontal trends whose 201hg shows negligible to no variation less terrigenous hg influx was noticed in the sections closer to the stlip rizvanusa idrijca and seres misci all in europe in which 201hg mif is close to zero marked influence occurs in sections far distant from the stlip meishan ursula creek and hovea 3 that exhibit negative 201hg mif the two sections from iran at intermediate distance from the stlip exhibit the highest positive 201hg values abadeh section and the lowest negative 201hg values zal section a 199hg mif vs hg n ng 1 cross plot suggests that volcanic hg has been contaminated by normal marine source hg influx in these sections helping to shape two major curved trends the negative c isotope excursions and hg toc enrichments in the studied sections are nearly coeval and this supports the hypothesis of synchronism between the permian triassic transition biotic crises lpme and etme and the start of the stage 2 of the siberian traps sill intrusion style of magmatism

upper boundary of the pacific plate subducting beneath hokkaido japan estimated from scsp phase abstract three dimensional geometry of the upper boundary of the pacific plate subducting beneath hokkaido japan was obtained using the scsp phase the phase converted from scs s wave reflected at the core mantle boundary to p wave at the plate boundary taking the advantage of a dense seismic network hi net recently deployed across the japanese islands we applied several seismic array analyses to the recorded waveform data for a large nearby deep earthquake in order to enhance very weak scsp signals in the original records at first we set up five blocks for the region in plate dip directions after aligning the travel times of scs and stacking seismograms among stations in a given sub block perpendicular to each dip direction we searched for the optimal plate model i e two dimensional geometry of the upper boundary for each block the model was parameterized by seven depth grids and seismograms were stacked based on the travel time of scsp as a time lag of each sub block so that the optimal model would yield the maximum spectral energy of scsp after stacking this model parameter search was conducted using ray tracings of scsp with a reference velocity model and a non linear inversion scheme neighbourhood algorithm the optimal model of each block was combined each other by cubic spline interpolation in order to construct an overall three dimensional geometry of the upper boundary of the plate next we performed the frequency wavenumber f k spectral analysis to refine the above result assuming each station as a reference point we made beam output from records of its adjacent stations as a function of wavenumber vector k x k y and frequency the peak of its power spectrum was considered to represent the wavenumber vector of scsp that is azimuth of arrival and slowness so that we can estimate the position and depth of the corresponding scs scsp conversion in the frequency range from 0 5 to 1 5 hz we could estimate the conversion points for 21 stations or hypothetical arrays and revised the geometry of the upper boundary obtained by the non linear stacking approach in the previous step the final plate model was compared with the distribution of intraplate earthquakes in the pacific plate this comparison clearly reveals that the upper seismic zone merges with the lower from 150 to 200 km in depth deviating systematically away from the upper boundary where the boundary is slightly bumped in a convex manner

permian triassic extinction organic δ13c evidence from british columbia canada the permian triassic p t extinction is documented geochemically in a marine sequence deposited in a basinal setting at williston lake northeastern british columbia by using elemental and isotopic organic geochemical data from well preserved sedimentary rocks the 13 c values of kerogens in the rocks exhibit a sudden shift at the p t boundary from latest permian values of 29 1 pdb to a minimum of 32 6 2 m above the p t boundary and then back to the permian value 4 m above the p t boundary after considering various factors we conclude that reduced surface water primary productivity following the p t mass extinction is largely responsible for the observed 13 c shift the abruptness of the 13 c shift in a sequence of continuous deposition argues that the strong pulse of extinction at the p t boundary was sudden rather than gradual marine primary productivity did not recover until at least 50 to 100 ka after the time of the p t boundary so a higher atmospheric p co 2 in the earliest triassic may have resulted from buildup of dissolved co 2 owing to reduced photosynthetic carbon demand in the surface water

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

rapid and synchronous collapse of marine and terrestrial ecosystems during the end permian biotic crisis a newly studied permian triassic p tr boundary section in jameson land east greenland contains an abundant and well preserved marine fauna as well as terrestrial palynomorphs for the first time it is possible to compare the biotic crises of the marine and terrestrial realms using the same samples from the same section the sediments record a negative excursion in 13 c carb values of 8 9 and in 13 c org values of 10 11 the presence of the conodont hindeodus parvus combined with the 13 c carb record enables correlation with the proposed global stratotype section at meishan this shows that the greenland section is the most expanded p tr section known collapse of the marine and terrestrial ecosystems took between 10 and 60 k y it took a further few hundred thousand years for the final disappearance of permian floral elements collapse of the terrestrial and marine ecosystems began at the same stratigraphic level and preceded the sharp negative excursion in the 13 c record

resolving original signatures from a sea of overprint the geochemistry of the gungri shale upper permian spiti valley india abstract the geochemistry of black shales can faithfully record paleoenvironmental conditions however the original geochemical signatures are obscured by post depositional events such as diagenesis and weathering resolving the relative influence of these processes on the geochemistry of shales requires a combination of geochemical and chemometric chemical statistics approaches to data analysis that identify the sources of variance in major and trace element geochemistry the permian gungri shale kuling group at attargoo spiti valley himachal pradesh india is a gray to black shale capped unconformably by an iron rich pebble sand layer ferruginous layer marking ostensibly the permian triassic boundary high resolution analysis of the gungri at attargoo 3 cm intervals reveals a geochemical record complicated by low grade metamorphism diagenesis and modern weathering using multivariate chemometric techniques e g principal component analysis we identified variance in the geochemical record associated with the original detrital and depositional conditions we also identified 4 beds within the gungri that mark depositional events which may correlate to those identified in other pt sections e g guryul ravine kashmir identification of sources of variance allowed us to identify geochemical signatures that can be used for paleooceanographic reconstruction the attargoo section records a sequence of discrete events including transient iron enrichments attributed to euxinic depositional conditions and late diagenetic formation of siderite and regression condensation surfaces associated with pulsed transgression regression towards the uppermost permian our results show that chemometric analysis of geochemical data enables the resolution of paleoenvironmental conditions in shales impacted by post depositional alteration

magnetostratigraphic correlations of permian triassic marine to terrestrial sections from china abstract we have studied three permian triassic pt localities from china as part of a combined magnetostratigraphic 40ar 39ar and u pb radioisotopic and biostratigraphic study aimed at resolving the temporal relations between terrestrial and marine records across the permo triassic boundary as well as the rate of the biotic recovery in the early triassic the studied sections from shangsi sichuan province langdai guihzou province and the junggar basin xinjiang province span marine paralic and terrestrial pt environments respectively each of these sections was logged in detail in order to place geochronologic paleomagnetic geochemical conodont and palynologic samples within a common stratigraphic context here we present rock magnetic paleomagnetic and magnetostratigraphic results from the three localities at shangsi northern sichuan province we sampled three sections spanning permo triassic marine carbonates magnetostratigraphic results from the three sections indicate that the composite section contains at least eight polarity chrons and that the pt boundary occurs within a normal polarity chron a short distance above the mass extinction level and a reversed to normal r n polarity reversal furthermore the onset of the illawarra mixed interval lies below the sampled section indicating that the uppermost permian changhsingian and at least part of the wuchiapingian stages postdate the end of the kiaman permo carboniferous reversed superchron at langdai guizhou province we studied magnetostratigraphy of pt paralic mudstone and carbonate sediments in two sections the composite section spans an r n polarity sequence section mean directions pass a fold test at the 95 confidence level and the section mean poles are close to the mean pt pole for the south china block based on biostratigraphic constraints the r n transition recorded at langdai is consistent with that at shangsi and demonstrates that the pt boundary occurred within a normal polarity chron a short distance above the mass extinction level in the southern junggar basin xinjiang province in northwest china we determined the magnetostratigraphy of three sections of a terrestrial sequence normal and reversed polarity directions are roughly antipodal and magnetostratigraphies from the three sections are highly consistent combined bio and magneto stratigraphy used to correlate this sequence to other pt sequences suggests that the previously proposed biostratigraphic pt boundary in the junggar sections was most likely misplaced by earlier workers suggesting that further work is necessary to confidently place the pt boundary there

growth and demise of permian biogenic chert along northwest pangea evidence for end permian collapse of thermohaline circulation abstract the permian chert event pce was a 30 ma long episode of unusual chert accumulation along the northwest margin of pangea and possibly worldwide the onset of the pce occurred at about the sakmarian artinskian boundary in the sverdrup basin canadian arctic where it coincides with a maximum flooding event the ending of high frequency high amplitude shelf cyclicity the onset of massive biogenic chert deposition in deep water distal areas and a long term shift from warm to cool water carbonate sedimentation in shallow water proximal areas a similar and coeval shift is observed from the barents sea to the northwestern usa a landward and southward expansion of silica factories occurred during the middle and late permian at which time warm water carbonate producers disappeared completely from the northwest margin of pangea biotically impoverished and increasingly narrow cold water carbonate factories characterised by non cemented bioclasts of sponges bryozoans echinoderms and brachiopods were then progressively replaced by silica factories by late permian time little carbonate sediments accumulated in the barents sea and in the sverdrup basin where the deep to shallow water sedimentary spectrum was occupied by siliceous sponge spicules by that time biogenic silica sedimentation was common throughout the world silica factories collapsed in the late permian abruptly bringing the pce to an end in northwest pangea the end permian collapse of the pce was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions chert deposition resumed in the distal oceanic areas during the early middle triassic anisian after a 8 10 ma interruption early triassic chert gap the conditions necessary for the onset expansion and zenith of the pce were provided by the thermohaline circulation of nutrient rich cold waters along the northwestern and western margin of pangea and possibly throughout the world oceans these conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area created a nutrient and oxygen rich environment favouring siliceous biogenic productivity established cold sea floor conditions hindering silica dissolution while increasing calcium carbonate solubility and provided conditions adverse to organic and inorganic carbonate production the northwest margin of pangea was for nearly 30 ma bathed by cold waters presumably derived from the seasonal melting of northern sea ice the assumed engine for thermohaline circulation this process started near the sakmarian artinskian boundary intensified throughout middle and late permian time and ceased suddenly in latest permian time it led to oceanic conditions much colder than normally expected from the palaeolatitudes and the influence of cold northerly derived water was felt as far south southern nevada the demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warmer marine environment accompanied by sluggish circulation and perhaps a reduced input of dissolved silica to the ocean complete thawing of northern sea ice would have ended thermohaline circulation and led to warm and sluggish oceanic conditions inimical to the production accumulation and preservation of biogenic silica

brachiopod miniaturization and its possible causes during the permian triassic crisis in deep water environments south china abstract brachiopod miniaturization is both the reduction in size of individuals of a species over time and where one brachiopod fauna dominated by larger individuals was replaced by a brachiopod fauna dominated by smaller individuals over time this paper investigates this phenomenon prior to and during the end permian crisis in a deep water setting in south china based on precise measurements of brachiopod body size and on the abundance and diversity of brachiopod species the process of miniaturization near the permian triassic boundary in deep water environments is characterized by 1 larger species including martinia sp costatumulus dongpanensis and anidanthus mucronata reduced in average body size and abundance over time towards the end permian brachiopod extinction event 2 small species including attenuatella mengi and spinomarginifera semicircridge showed a mixed response with either no size change or a reduction in average body size while these species increased in abundance over time indicating they were less sensitive to the stressed environmental setting 3 both the total abundance and the diversity of this brachiopod fauna decreased over time towards the end permian crisis regression an increased input of terrestrial material and productivity decline are considered to all have contributed to brachiopod miniaturization based on the biotic replacement and changes in sea water chemistry among these factors the fall in sea level is perhaps the primary factor and led to a decline in productivity and an increased input of terrestrial material into the marine setting

some aspects of the permian triassic boundary ptb and of the possible causes for the biotic crisis around this boundary abstract the first appearance datum fad of hindeodus parvus is an excellent datum very close to the base of the otoceras woodwardi zone priority base of the triassic for the first time it allows an exact correlation of the ptb in all marine facies and faunal realms the following features of the extinction and recovery patterns near the ptb are most important for the search for causes of the ptb biotic crisis 1 most strongly affected were the siliceous plankton radiolarians and the warm water benthos and nekton 2 most of the cold water faunas were not significantly affected 3 the recovery of the warm water benthos and siliceous plankton occurred only after an unusually long time during the late olenekian and middle triassic 4 the productivity of the terrestrial plants dropped strongly and the recovery was mainly in the upper olenekian and in the middle triassic 5 several terrestrial extinction events occurred at different levels within the upper permian considerable before the marine ptb at or close to the fad of lystrosaurus no extinction event in the terrestrial faunas can be observed 6 terrestrial faunal elements that survived the dzhulfian dorashamian extinctions were able to survive some months of extreme climatic conditions by hibernation like life stages vertebrates or by dry and freezing resistant eggs conchostracans 7 about 50 of the genera that disappeared at the ptb re appeared in the olenekian middle triassic interval lazarus taxa or in this time interval genera appeared that had undoubtedly evolved from genera that had disappeared at the ptb and 8 the ptb is preceded by mass occurrences of marine and continental fungi and the fungal spike ends abruptly a little before the ptb a scenario for the ptb biotic crisis is elaborated that takes into consideration the real not interpolated diversity patterns of different marine and continental fossil groups the exact correlation of bioevents in different faunal realms and facies the strong biotic crisis in the tethyan warm water faunas in contrast to the much weaker biotic event in cold water faunas the severe dzhulfian dorashamian climate in many parts of the world caused by the continent ocean configuration and by siberian trap volcanism the cooling of the boreal area by the northward drift of pangaea that interrupted the exchange of warm water benthos between the tethys and western north america during the guadalupian the extinction event at the guadalupian lopingian boundary that restricted most of the affected warm water faunas to the tethys the importance of lower scythian anoxia that reached an unusually shallow level and above all the effects of the contemporaneous huge volcanic events about 250 m y ago on the siberian platform and in the eastern tethys that caused a 3 6 months lasting volcanic winter with strong cooling in low latitudes followed by a strong global warming

deev jahi model of the permian triassic boundary mass extinction a case for gas hydrates as the main cause of biological crisis on earth the smoking gun revealing the secrets of the end permian mass mortality is a unique 1 2 m thick layer consisting of 5 20 cm long crystals of calcite that occurs precisely at the permian triassic boundary ptb in iran armenia turkey and china this layer is interpreted as synsedimentary abiotic seafloor cement indicative of precipitation from a highly carbonate supersaturated seawater its 13 c composition 13 c 0 pdb is 4 to 5 pdb lower than the typical upper permian values 4 to 5 pdb suggesting the involvement of massive amounts of gas hydrate ch 4 13 c 60 pdb the temporal coincidence of the cement layer with the ptb suggests that the process that promoted seafloor cementation was also responsible for the biological crisis a cementation model is developed based on accumulation dissociation cycle of gas hydrates which also explains the mass extinction at the ptb the upper permian accumulation period of gas hydrates ended abruptly adjacent to the ptb and the dissociation event began releasing 3 2 to 4 7 10 18 g ch 4 into the ocean oxidation of ch 4 in the water column created a seawater that was charged with co 2 an oceanic acid bath and had lower than normal o 2 content but not anoxic this oceanic acid bath first dissolved suspended fine grained carbonate particles and small calcareous organisms followed by extensive dissolution of platform carbonates raising ca 2 and hco 3 concentrations of seawater when the release of ch 4 declined the acid bath ocean became a soda ocean precipitating massive amount of seafloor cements observed globally at the ptb the study suggests that prior to cement precipitation the ptb ocean was charged with co 2 warm had low oxygen high ca 2 and high hco 3 concentrations these conditions collectively created stressful conditions causing the marine mass mortality the leakage of ch 4 to the atmosphere produced a super hot climate resulting in the biological devastation on land the proposed kill mechanism is developed on the basis of the physical clue the cement layer left behind by the killing process the change in ocean chemistry the accumulation dissociation cycles of gas hydrates also explain the 13 c pattern of marine carbonates and the periodicity of mass extinction events during the phanerozoic accumulation periods were long 5 to 20 my providing favorable conditions for ecosystem development pardeess phase the dissociation events were short and catastrophic 10 to 500 ky causing low oxygenation super hot climate and biological devastation doozakh phase it appears that most mass extinctions of the phanerozoic have been related to the internal working of the earth system during the phanerozoic methane has played the role of the deev jahi a female demon in persian mythology whose task is to attack the earth every so often to kill life on land and in sea

tempo of the end permian event high resolution cyclostratigraphy at the permian triassic boundary the permian triassic p t boundary is marked by the most severe mass extinction in the geologic record high resolution cyclostratigraphy on a 10 4 yr scale across the p t boundary in a core from the carnic alps austria revealed significant cycles in the ratio 40 10 4 7 2 3 m identified with milankovitch cycles of 412 100 40 20 k y eccentricity 1 and 2 obliquity and precession wavelet analysis indicates continuity of deposition across the boundary with an average accumulation rate of 10 cm k y the dramatic faunal changes at the p t boundary can be constrained within an interval of 60 k y possibly 8 k y with the accompanying sharp negative global carbonisotope shift within 30 k y suggesting a catastrophic cause

fungal event and palynological record of ecological crisis and recovery across the permian triassic boundary the end of the permian period was marked by the most severe mass extinction in the geologic record detailed quantitative study of pollen and spores from shallow marine deposits spanning the permian triassic p tr boundary in israel reveals a sequence of palynological ecological stages reflecting a major crisis among land plants the disappearance of the gymnosperm dominated palynoflora of the late permian lueckisporites virkkiae zone is recorded at a claystone horizon containing almost exclusively abundant fungal remains and carbonized terrestrial plant debris this fungal spike is followed by a zone dominated by marine acritarchs and a succession showing ecological recovery with abundantlycopodsporesandeventualreappearanceofbisaccategymnospermpolleninthe earlytriassic thelatestpermianproliferationoffungiisrecognizableworldwideandcan be correlated with other paleontological and geochemical markers of a global ecological disaster

climate simulation of the latest permian implications for mass extinction life at the permian triassic boundary ca 251 ma underwent the largest disruption in earth s history paleoclimatic data indicate that earth was significantly warmer than present and that much of the ocean was anoxic or euxinic for an extended period of time we present results from the first fully coupled comprehensive climate model using paleo geography for this time period the coupled climate system model simulates warm high latitude surface air temperatures related to elevated carbon dioxide levels and a stagnate global ocean circulation in concert with paleodata indicating low oxygen levels at ocean depth this is the first climate simulation that captures these observed features of this time period

remote triggering of deep earthquakes in the 2002 tonga sequences it is well established that an earthquake in the earth s crust can trigger subsequent earthquakes but such triggering has not been documented for deeper earthquakes models for shallow fault interactions suggest that static permanent stress changes can trigger nearby earthquakes within a few fault lengths from the causative earthquake1 2 3 whereas dynamic transient stresses carried by seismic waves may trigger earthquakes both nearby and at remote distances4 5 6 7 8 here we present a detailed analysis of the 19 august 2002 tonga deep earthquake sequences and show evidence for both static and dynamic triggering seven minutes after a magnitude 7 6 earthquake occurred at a depth of 598 km a magnitude 7 7 earthquake 664 km depth occurred 300 km away in a previously aseismic region we found that nearby aftershocks of the first mainshock are preferentially located in regions where static stresses are predicted to have been enhanced by the mainshock but the second mainshock and other triggered events are located at larger distances where static stress increases should be negligible thus suggesting dynamic triggering the origin times of the triggered events do not correspond to arrival times of the main seismic waves from the mainshocks and the dynamically triggered earthquakes frequently occur in aseismic regions below or adjacent to the seismic zone we propose that these events are triggered by transient effects in regions near criticality but where earthquakes have difficulty nucleating without external influences

low frequency source characteristics of the great 1960 chilean earthquake the low frequency nature of the great 1960 chilean earthquake the earth s largest recorded event is characterized and a source model composed of three events with a combined seismic moment of 5 5 1023 n m and a duration of 1500 s is presented the results show conclusively that large scale slip which is only observed at low frequencies preceded the main shock complex amplitude measurements of normal mode data in the band 1 0 5 0 mhz recorded at eight vertical component stations comprise the data set in this band the earthquake source is assumed to be described by a line source propagating at a constant rupture velocity the data set is the basis for a sequence of least squares inversions to determine the seismic moment rupture velocity spatial slip distribution and the temporal slip function the data are best explained by a source model that begins 1150 s before the main shock with an event of moment 1 9 1023 n m and rise time of 300 s a main shock with moment of 3 2 1023 n m and for which most of the low frequency energy was released beginning about 50 s after the short period origin time and an event 350 s later with moment of 0 4 1023 n m the uncertainty in the moment estimate of the great 1960 chilean earthquake is about 50 and is due primarily to the probable range of fault plane dip which is not well constrained at this time

reconstruction of atmospheric co2 concentration during the late changhsingian based on fossil conifers from the dalong formation in south china abstract a single species of fossil conifer with well preserved cuticles from multiple layers of the dalong formation in two sections in duanshan town guizhou province southwest china has been used to reconstruct palaeo atmospheric pco2 the age of these layers can be dated back to the late changhsingian latest permian corresponding to the clarkina changxingensis and clarkina yini conodont zones two calibration approaches were employed in this study using the stomatal ratio method the pco2 curves of the two sections showed matching trends with levels decreasing in the middle of the profiles and similar ranges at ca 340 510 ppm and ca 300 440 ppm similar values ca 360 520 ppm yet with wider error ranges were obtained when the mechanistic model proposed by franks et al in 2014 was applied to one of the sections our values are lower than the mean pco2 values from coeval palaeosols but partly overlap with them when error ranges are taken into consideration thus more independent studies are needed to evaluate the discrepancies between the two proxy methods the low atmospheric co2 concentrations in this study suggest a cool climate rather than extensive glaciation for the brief period of late changhsingian which is supported by the oxygen isotope record of conodont apatite and a major restructuring of late permian flora and fauna

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

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

late permian to early triassic environmental changes in the panthalassic ocean record from the seamount associated deep marine siliceous rocks central japan abstract in order to infer the late late permian to early early triassic environmental changes in a pelagic realm of the panthalassic ocean the stratigraphic variations of toc wt and 13corg of the ptb siliceous rock section 3 5 m in thickness were examined the study section crops out in the mino terrane central japan and consists of the upper upper permian chert changhsingian and lower lower triassic induan black claystone intermittently with thin chert beds the succession is reconstructed as sediments on the lower slope of a mid panthalassic seamount the major extinction event of permian radiolarians mee occurs at the top of the changhsingian chert our analysis shows that the toc content is markedly higher in the induan black claystone than the changhsingian chert toc values rapidly increase across the ptb the onset of the increase in toc values corresponds to mee the rapid and profound increase in toc values implies the sudden onset of oceanic anoxia as well as the rapid increase in primary production at the ptb 13corg values are generally higher in the changhsingian chert than the induan claystone and chert the stepwise drop of 13corg values characterizes their excursion of the study section the largest scale drop occurs prior to mee the minimum 13corg value is recorded at the base of the induan claystone the flux of 13c depleted gasses related to the siberian traps could have significantly contributed to the marked drop of 13corg values due to the weakened ocean circulation under the predominant condition of global warming oceanic anoxia suddenly took place at the end of the permian the anoxic condition in the surface layer was the most likely kill mechanism for permian radiolarians the anoxic condition persisted into the induan but was intermittently weakened the episodic relaxation of the anoxic condition in the induan resulted in intermittent and transient blooming of radiolarians and deposition of radiolarian chert with lowered toc values these biotic and depositional records of the study section imply the mid panthalassic ocean was under the more hospitable conditions favored by the earlier recovery of radiolarians relative to the tethys ocean and pangean marginal seas

large scale deformation in the india asia collision constrained by earthquakes and topography analysis of earthquake focal mechanisms allows division of the india asia collision into kinematic domains that strongly correlate with topography these kinematic domains indicate strain partitioning dominated by oblique slip deformation the kunlun and south tibetan fault systems mark discontinuities in the strain field and bound the high flat topography of the plateau which deforms by transtension the northern and southern margins of tibet deform by transpression or contraction and are topographically steep correlations between seismicity and topography are due to mohr coulomb wedge mechanics at the northern and southern plateau margins which produce naturally steep surface slopes whereas the flat interior and eastern margin of the tibetan plateau is underlain by viscous crust which supports subdued topography further muted by cenozoic basin fill these data indicate that the long wavelength topography of the india asia collision is controlled by seismically caused surface displacements which are linked to deep crustal deformation mechanics

a permian triassic boundary section at quinn river crossing northwestern nevada and implications for the cause of the early triassic chert gap on the western pangean margin the upper permian lower triassic quinn river formation in northwestern nevada was previously thought to represent an incomplete permian triassic boundary sequence owing to an inferred disconformable relationship between permian radiolarian and spicule rich chert and overlying triassic siltstone petrographic and geochemical studies demonstrate that the siltstone is in fact a radiolarian bearing early authi genic dolomicrite with both the chert and dolomicrite deposited conformably in deep water chert production declined or ceased in the late permian and reappeared in the spathian forming a widespread chert gap in permian triassic sequences given the conformable lithofacies relationships deep water depositional setting new radiolarian data extending ranges of key taxa and the presence of the global chert gap sedimentation in the quinn river formation was apparently continuous across the permian triassic boundary this represents the first permian triassic boundary section in the united states portion of the north american cordillera and one of the few deep water sections worldwide organic carbon isotope stratigraphy of the quinn river formation displays multiple excursions through sediments of wuchiapingian anisian age with a negative excursion 1 54 m above the chert shale transition likely representing the permian triassic boundary the multiple excursions in the organic carbon record verify studies of the carbonate carbon record in china that suggest instability in the isotopic record throughout the early triassic and demonstrate that the permian triassic boundary isotope excursion was not an isolated event stratigraphic variation in redox sensitive trace metals indicates that seawater became less oxic slightly before the chert shale transition in turn impacting siliceous sponge communities and creating the widespread chert gap the distinctive dolomicrites in the quinn river formation represent a widespread lithofacies deposited in many localities during the late permian early triassic and express early authigenic formation of dolomite via microbial sulfate reduction in organic rich low oxygen environments

anatomy of a mass extinction sedimentological and taphonomic evidence for drought induced die offs at the permo triassic boundary in the main karoo basin south africa abstract the southern part of the karoo basin of south africa contains a near complete stratigraphic record of the permo triassic boundary ptb isotope and magneto stratigraphy confirm that these predominantly fluvial strata are approximately the same age as zircon dated marine ptb sections 252 mya by august 2013 our team had found 579 in situ vertebrate fossils mostly of the clade therapsida in ptb exposures at three widely separated locations in the southern karoo basin biostratigraphic ranges of the various taxa found in each of the sections reveal three separate phases of die off within the same roughly 75 metre thick stratigraphic interval displaying the same sequence of sedimentary facies interpreted as indicative of climatic drying increased seasonality and the onset of an unpredictable monsoon type rainfall regime the three phases of an inferred ecologically stepped mass extinction are phase 1 45 m 30 m below ptb datum brought on by lowered watertables which led to loss of shallow rooting groundcover in the more elevated proximal floodplain areas and the disappearance of the smaller groundcover grazing herbivorous dicynodonts and their attendant small carnivores phase 2 20 0 m below ptb datum is the main extinction that occurs in massive maroon grey mudrock culminating in an event bed of laminated reddish brown siltstone mudstone couplets this facies reflects progressively unreliable rainfall leading to vegetation loss in proximal and distal floodplain areas the larger tree browsing herbivores and their attendant carnivores are confined to watercourses before finally disappearing phase 3 25 30 m above ptb datum occurs in massive maroon siltstone facies with evidence of climatic aridity including the accumulation of mummified carcasses buried by windblown dust all of the surviving permian taxa disappear within 30 m of the ptb temporal resolution based on accretion rates and pedogenic maturity of each stratigraphic section reveals that phase 1 and phase 2 die offs lasted 21 000 and 33 000 years separated by a short period of 7000 years where no disappearances are recorded and this was followed by 50 000 years of stasis for the final extinction phase lasting only 8000 years that removed all the permian survivor taxa we propose that the recorded disappearances are real rather than preferential preservation failure and that they represent drought induced die offs moving progressively up the food chain as the terrestrial ecosystem collapsed the latter mostly likely caused by volcanogenic greenhouse gas emissions and rapid global warming

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

δ18o and δ13c of permian brachiopods a record of seawater evolution and continental glaciation abstract two hundred sixty four 18 o and 13 c values of permian articulate brachiopod shells were analyzed and 81 of these values were characterized as well preserved and biostratigraphically well defined these were then utilized for construction of baseline oxygen and carbon isotope curves for the permian interval in addition 21 13 c whole rock values are reported for the wordian and capitanian the early permian asselian to artinskian times are characterized by 2 5 decrease in oxygen isotope values from 0 7 to 3 3 v pdb this is attributed to a 4 7 c increase in temperature in the southern urals concomitant with the retreat of the permo carboniferous ice sheets and return of the 18 o depleted melt water into the oceans the late permian samples from iran jolfa at kuh e ali bashi and china meishan yield 18 o values and presumably temperatures similar to those that followed the termination of the large scale glaciation in the lower permian in between the upper kungurian to capitanian samples from the delaware basin guadalupe mountains are enriched in 18 o at 1 5 to 3 we have no definitive explanation for these data but tentatively suggest that the anomaly can potentially be a result of evaporative enrichment of seawater in 18 o due to intracratonic arid setting of the basin the 18 o enriched nature of the zechstein samples 1 2 to 2 5 on the other hand is in all probability a reflection of the high evaporation rates in the zechstein sea the permian interval is characterized by a relatively constant 13 c at about 4 the exceptions are again the brachiopods from the delaware basin guadalupe mountains which show 1 6 increase in the guadalupian to values of up to 5 9 in the wordian a tentative explanation as in the case of oxygen is based on the proposition that the semi enclosed delaware basin was likely stratified with sequestration of the 13 c depleted carbon to the deeper water layers and a complementary 13 c enrichment in the upper oxygenated layer the coeval open ocean water dic may have been similar to that of the remainder of the permian interval at 4 as indicated by whole rock carbonate samples from oman sicily and iran in the latest permian the trend mimics the well known 13 c drop at the permian triassic boundary

permian triassic boundary magnetostratigraphy from the southern alps italy palaeomagnetic investigations of permian triassic boundary sections in the dolomites provided a magnetostratigraphy for the uppermost part of the permian bellerophon formation to the lower triassic werfen formation magnetite was the dominant magnetic component in most of the samples while the presence of hematite was characteristic for the tesero horizon which is regarded as the immediate permian triassic boundary layer the palaeomagnetic results are consistent with earlier studies of permian and triassic sediments and volcanites in the southern alps the mean characteristic remanence directions indicate deposition and remanence acquisition at a shallow northerly palaeolatitude and a counterclockwise rotation a zone of reversed polarity occurs at the top of the permian sequence and a polarity change from reverse to normal polarity shortly above the base of the werfen formation the onset of a tectonically controlled sedimentary cycle marks the beginning of the basal triassic normal polarity zone which corresponds to most of griesbachian time the record of geomagnetic polarity across the permian triassic boundary confirms the apparent continuity as found by sedimentologic biostratigraphic investigations which emphasise a gradual lithic transition with no evidence for a time gap at the boundary

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

mapping the upper mantle three dimensional modeling of earth structure by inversion of seismic waveforms a method is presented for the inversion of waveform data for the three dimensional distribution of seismic wave velocities the method is applied to data from the global digital networks international deployment of accelerometers global digital seismograph network the selected data set consists of some 2000 seismograms corresponding to 53 events and 870 paths the moment tensors of the earthquakes are determined through an iterative procedure which minimizes the corrupting influence of lateral heterogeneity a global model is constructed for shear wave velocity expanded up to degree and order 8 in spherical harmonics and described by a cubic polynomial in depth for the upper 670 km of the earth s mantle although no a priori information is incorporated the model predictions reproduce much of what is known about the dispersion of mantle waves for example high phase velocities for shields low velocities at ridges and a strong degree 2 pattern for rayleigh waves since the method makes use of complete waveforms overtone data are also included it is shown that the model is reproducible in that substantially the same model can be constructed from each half of the total data set considered independently the model shows that shields and ridges are major features in the depth interval 25 250 km the ridges of the southern pacific and the larger shields persist to 350 km but the southeast indian rise is underlain by a high velocity anomaly at this depth as is much of the mid atlantic ridge at 450 650 km the major features are a broad region of high velocities incorporating south america much of the south atlantic and parts of west africa a broad region of low velocities in the central and eastern pacific high velocities in the western pacific and a low velocity anomaly beneath the red sea and the gulf of aden in the absence of a crustal correction degrees 2 and 3 show a high positive correlation with the geoid paradoxically this is largely destroyed when the distribution in crustal thickness is taken into account spherical harmonic degrees 4 7 show a significant negative correlation

high resolution terrestrial permian triassic eventostratigraphic boundary in western guizhou and eastern yunnan southwestern china the adjoining area of western guizhou and eastern yunnan provinces in southwest china is an ideal place to investigate the feasibility of correlating marine and nonmarine permian triassic boundary ptb sequences as it contains outcrop sections of shallow marine marginal marine or paralic and terrestrial ptb sections all in close geographic proximity this paper documents for the first time multiple stratigraphic data from several well preserved terrestrial ptb sections in the area and attempts to use these data to define locate and correlate the ptb in the area a study of the spores and pollen and vegetation types across the terrestrial ptb sections in the study area suggests three distinct evolutionary stages across the boundary stage 1 xuanwei formation is characterised by late permian or paleozoic type ferns and pteridosperms 85 0 with a few gymnosperms 15 0 stage 2 is marked by an abrupt drop of sporopollen elements of late permian aspects coupled with the appearance of fungal spores and limited early triassic palynomorphs stage 3 top xuanwei formation and kayitou formation is dominated by gymnosperm pollen 58 8 of clearly early triassic aspect although still retaining limited ferns and pteridosperms the three biotic stages seem to well correspond with the changing trend of the 13corg curves from the same sections which is characterized by a sharp drop just before the ptb followed by a short term partial recovery across the boundary and then succeeded by a gradual decline after the ptb in the early triassic combining evidence from eventostratigraphic i e the succession of boundary clay beds biostratigraphic using both macroplants and palynomorphs and chemostratigraphic i e organic carbon isotope excursion signals we propose that a high resolution ptb succession closely correlatable to its marine counterpart at the meishan section in eastern china is recognisable at the terrestrial ptb sections in the western guizhou eastern yunnan area in southwest china

geochemical consequences of the permian triassic mass extinction in a non marine succession sydney basin australia abstract the identification of the permian triassic boundary ptb and permian triassic mass extinction event ptme in eastern australia is based primarily on palynological and plant fossil evidence with limited 13 c org data from the northern part of the sydney basin consequently the ptb in the sydney basin has been placed at the top of the last permian coal measures here we report carbon and nitrogen isotopic data together with major element trace element and mineralogical data for a continuous non marine permian triassic p tr section from the southern sydney basin the ptme is identified by a negative shift in 13 c org of 3 8 occurring approximately 1 m above the bulli coal seam lack of correlation between 13 c org and toc indicates that the isotopic signature has not been affected by contamination or diagenetic processes the interrelationships between c n and s data indicate severe environmental disruption and increased weathering at the time of the extinction event with die off of terrestrial vegetation and the injection of sulphuric acid into the water column positive excursions in ni cr and co are coincident with the negative 13 c org shift and are most consistent with a reduction in oxygen availability due to a major volcanic eruption

uranium depletion across the permian triassic boundary in middle east carbonates signature of oceanic anoxia we present a geochemical profile through a 445 m 1459 9 ft section of shallow water carbonate platform strata in the upper part of the khuff formation the permian triassic boundary ptb is recognized in this section based on the immediately preceding negative shift in bulk rock carbonate carbon isotope composition equivalent to the end permian extinction horizon combined with biostratigraphic control from nearby wells these strata show an abrupt and long lasting decrease in bulk rock uranium u content coincident with the carbon isotope shift because of low siliciclastic content and the consequently low potassium and thorium of these carbonates the decrease in u is clearly reflected in the total gamma ray gr profile recorded by wire line logging published log curves show similar distinctive gr profiles throughout a large area of the middle east indicating that u depletion across the ptb is a regional characteristic this feature cannot be explained as diagenetic and is not related to the organic matter content of the host sediments but it is suggested to reflect the global depletion of u in earliest triassic seawater caused by the abrupt onset of deep ocean anoxia and the resulting increase in u precipitation in oxygen poor sediments this explanation carries the implication that similar u depletion should be characteristic of lowermost triassic carbonates from shallow water oxygenated settings worldwide analogous signatures of u depletion should also have developed in shallow water carbonates deposited contemporaneously with episodes of deep ocean anoxia during other periods of geological time these predictions can be tested by high accuracy u profiling of other well characterized carbonate successions potentially yielding a new approach for tracking the degree of oceanic circulation throughout earth s history

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

an experiment in systematic study of global seismicity centroid moment tensor solutions for 201 moderate and large earthquakes of 1981 data from the global digital seismograph network were used to obtain centroid moment tensor solutions using the method of dziewonski et al 1981 results were obtained for 201 earthquakes ranging in seismic moment from 7 1023 to 3 1027 dyne cm the wide dynamic range of the sro asro stations allows us to investigate using the same algorithm series of events among which the smallest and the largest may differ in moment by a factor as large as 1000 among the events studied is a particularly interesting series in january 1981 off the island of honshu the main shock was preceded by three foreshocks and followed by four aftershocks all falling within the range of our analysis there is an indication that the source mechanism changes with the size of the event statistical analysis of the results for all earthquakes reveals that the half duration of shallow and intermediate events is approximated by 1 6 10 8 m01 3 the shifts in origin time for deep focus earthquakes are indicative of the general complexity of these events which depends only weakly on the seismic moment the extreme departures from a double couple mechanism seem to depend both on the moment and on the focal depth while for shallow earthquakes these departures decrease from a maximum at about 1025 dyne cm with increasing moment the reverse appears to be true with respect to deep focus earthquakes shallow earthquakes north of new guinea and along the solomon islands show systematic and substantial departures from the double couple mechanism

stable carbon isotope stratigraphy across the permian triassic boundary in shallow marine carbonate platforms nanpanjiang basin south china a distinct negative 13c excursion is documented in two permian triassic sections heping and taiping in shallow marine carbonate platform deposits in the nanpanjiang basin south china these sections span from the changhsingian to the dienerian and are characterized by a distinct marine boundary facies change from massive skeletal lime packstone in the changhsingian to distinctive calcimicrobial framestone in the griesbachian hindeodus parvus zone the 13corg and 13ccarb excursions occur directly after the onset of the calcimicrobial framestone herein termed the permian triassic boundary event and before the first occurrence of h parvus the isotope shifts are associated with a sharp drop in species abundance and diversity and coincide with a decrease in total organic carbon toc content the shift towards depleted values in 13corg and 13ccarb at the permian triassic boundary event together with low toc contents persists throughout the griesbachian h parvus zone these data document a corresponding negative shift of 13corg and 13ccarb values and low toc contents with the onset of growth of calcified microbial framestones a postextinction disaster facies immediately below the base of the griesbachian h parvus zone based on paleontological evidence the first occurrence of the disaster facies follows the extinction event which implies that the 13c depleted values above this facies postdate the event this suggests that two separate events had to account for the initiation of the extinction and the 13c excursion however the consequences that led to the negative isotopic shift might be linked to the intriguing recovery lag of early triassic ecosystems based on data from ptb sections worldwide of a greater 13c offset in high compared with low latitudes we propose that methane eruptions from thermal destabilization of high latitude clathrate deposits may have led to the negative 13c shift and may have caused long term adverse ecological conditions

anomalous hopane distributions at the permian triassic boundary meishan china evidence for the end permian marine ecosystem collapse abstract molecular and carbon isotopic geochemistry of hopanes in marine sediments of the meishan section in changxing county zhejiang province of china were studied to reveal biotic and environmental changes across the permian triassic boundary ptb and the wuchiapingian changhsingian boundary wcb the hopane distribution at the ptb is characterized by high ratios of moretane hopane tm ts tm c 30 hopane c 31 c 32 hopane and hopane sterane this hopane distribution is anomalous for these marine sediments but it is typical of coal measure strata and soils two possible genetic mechanisms for such an anomaly are suggested 1 these hopanes were terrigenous and most probably originated from acidified soil and peat this mechanism implies that the marine primary production and aerobic bacteria production at the ptb were extremely low 2 this hopane distribution was possibly caused by freshening and acidification of the upper water column during the end permian to early triassic marine stagnation and stratification this hopane anomaly which coincides with the end permian mass extinction and carbon isotope excursion may signal the end permian mass extinctions and marine and terrigenous ecosystem collapse the 13 c enriched hopanes with the fingerprint of typical anoxic marine shales coupled with an n c 15 n c 17 dominated distribution of n alkanes strongly indicate that the organic matter around the wcb at meishan originated mainly from cyanobacteria the corresponding positive 13 c carbonate and higher total organic carbon and hydrocarbon index hi values strongly suggest that high marine primary production and marine anoxia caused by intermittent cyanobacterial blooms resulted in the local mass extinction at meishan

the permian triassic boundary in western slovenia idrijca valley section magnetostratigraphy stable isotopes and elemental variations stable isotope analyses of carbonate 13ccarb and total organic carbon toc 13corg together with geochemical analyses of 54 major minor and trace elements and magnetic susceptibility measurements were carried out on whole rock samples of the undisturbed permian triassic p tr limestone boundary sequence in the idrijca valley w slovenia at the p tr boundary there is a 0 8 cm thick clayey marl layer ptb showing a characteristic magnetic susceptibility pulse and considerable enrichment in most major minor and trace elements the p tr transition is characterized by 1 an abrupt decrease in sedimentation rate from 32 to 5 cm 100 ka 2 a well known prominent negative excursion of 13ccarb and 13corg reflecting global perturbations in the carbon cycle and 3 the drastic disappearance of typically upper permian marine fauna although the shape of the 13ccarb curve indicates gradual long term change across the p tr boundary the sharp negative 13corg anomaly within an interval from 30 cm below to 6 cm above the boundary suggests an interruption of those gradual processes our observations for selected redox sensitive elements mo u v and zn abundances for organic carbon and sulphur and the rare earth elements ree distribution in the boundary sequence as well as the shape of the ce ce curve suggest that oceanic anoxia was typical of the upper permian and that the transition to oxygenated conditions occurred at the p tr boundary oxygenation at the p tr transition is coincidental with the terminal phase of the upper permian marine regression the shape of the ce ce curve indicates that the redox environmental conditions changed again in the earliest triassic resulting once more in oxygen deficient conditions

geochemistry of central tethyan upper permian and lower triassic strata abadeh region iran nearly 2 km of upper permian to lower triassic limestones are exposed in the hambast mountain abadeh region iran lime mud matrix and most bioclasts of permian age are recrystallized into large calcite crystals and contain 600 4000 ppm sr suggesting a probable aragonite precursor low bulk rock 18 o values 7 to 10 pdb and recrystallized textures are also indicative of diagenetic alteration within the murghabian and abadehian two gradual upward increases in carbonate and organic matter 13 c compositions each roughly 3 pdb in magnitude are documented both are attributed to increased organic productivity and sequestration of organic matter in sediments within the julfian and across the permian triassic p t boundary two sharp upward decreases in carbonate and organic matter 13 c values each 4 pdb in magnitude are observed both are best explained by mixing of a deep water mass having low 13 c values and a shallow water mass having high 13 c compositions early triassic 13 c values initially low 1 pdb increase to 3 pdb within 100 m above the p t boundary variations in 13 c compositions of carbonate and organic matter and changes in 13 c 13 ccar 13 corg indicate that early triassic 13 c values were controlled by productivity cycles

stable isotope and trace element stratigraphy across the permian triassic transition a redefinition of the boundary in the velebit mountain croatia article i nfo stable isotopes of carbonates 13 ccarb 18 ocarb organic matter 13 corg 15 norg and major trace and rare earth element ree compositions of marine carbonate rocks of late permian to early triassic age were used to establish the position of the permian triassic boundary ptb at two continuous sections in the velebit mountain croatia the chosen sections rizvanusa and brezimenjaca are composed of two lithostratigraphic units the upper permian transitional dolomite and the overlying sandy dolomite the contact between these units characterized by the erosional features and sudden occurrence of ooids and siliciclastic grains was previously considered as the chronostratigraphic ptb the sandy dolomite is characterized by high content of non carbonate material up to 30 wt insoluble residue originated from erosion of the uplifted hinterland a relatively rich assemblage of permian fossils including geinitzina globivalvulina hemigordius b ioclasts of gastropods ostracods and brachiopods was found for the first time in sandy dolomite 5 m above the lithologic boundary in the rizvanusa section a rather abrupt negative 13 ccarb excursion in both sections appears in rocks showing no recognizable facies change within the sandy dolomite 2 at rizvanus aa nd 1 2 at brezimenjaca 11 m and 0 2 m above the lithologic contact respectively this level within the lower part of the sandy dolomite is proposed as the chemostratigraphic ptb in the rizvanus as ection the 13 corg values decline gradually from 25 in the upper permian to 29 in the lower triassic the first negative 13 corg

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

timing of mammal like reptile extinctions across the permian triassic boundary in south africa the rate timing and pattern of change in different regions and paleoenvironments are critical for distinguishing among potential causes for the permian triassic p t extinction carbon isotopic stratigraphy can provide global chronostratigraphic control we report a large 13 c excursion at the p t boundary and no long term permian 13 c trends for samples from the interior of pangea stratigraphic gaps between available samples limit the resolution of our 13 c curve but the excursion is within a 15 m thick zone of overlap between permian and triassic taxa sedimentological and taphonomic observations demonstrate that this 15 m interval does not represent geologically instantaneous deposition together these data support a rapid and globally synchronous p t event but suggest that it occurred over a geologically resolvable interval of time

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

the buday ah formation sultanate of oman a middle permian to early triassic oceanic record of the neotethys and the late induan microsphere bloom abstract the middle permian to lower triassic buday ah section exposed in the oman mountains is the first deep sea section to be described in the neotethys the oceanic sediments were deposited along the southern tethys margin in the newly formed hawasina basin it is one of the few places where true tethyan permian radiolarites are exposed that allow the documentation of ccd evolution through time the succession begins as oceanic crust pillow basalt with red ammonoid rich pelagic limestone occurring both above and within inter pillow cavities the new occurrence of clarkina postbitteri hongshuiensis indicates a late capitanian age for the carbonate the sharp change to overlying late capitanian to changhsingian radiolarite reflects rapid subsidence about 10 myrs after initial continental breakup that resulted in the formation of the neotethys ocean new conodonts indicate that the permian triassic boundary succession occurs in the first platy lime mudstone beds above a changhsingian siliceous to calcareous shale unit the platy lime mudstone beds include an upper griesbachian bloom of calcite filled spheres radiolarians that marks a potential world wide event new conodonts indicate an early olenekian age for overlying grey papery limestone that are devoid of both macrofossils and trace fossils indicating that recovery from the late permian extinction has not yet progressed within this deep water environment 13 c org isotope values have not been disturbed and they show a negative shift just below the permian triassic transition and a second one at the parvus zone level above the buday ah succession may represent the most distal and probably deepest permian and lower triassic depositional sequence within the basin

collisions with ice volatile objects geological implications a qualitative treatment abstract an aperiodic collision of the earth with extra terrestrial ice volatile bodies is proposed as a mechanism to produce rapid changes in the geologic record due to the volatile nature of these bodies evidence for their impacts particularly in the ocean might be subtle and best seen as spikes in the geochemical or fossil record against normal background differing effects would result depending on the site of the major break up of the object in the atmosphere on land or in the ocean this paper focuses on the effects of adding material to the seas oceans and atmosphere the treatment is largely qualitative however mass balance calculations were used to estimate the relative mass needed to affect changes in a variety of reservoirs although actual impactors probably have a variable composition the effects of water c n and s containing objects are discussed in the atmosphere effects could include increased rain acidity increased levels of nutrients and enhanced greenhouse warming cooling oceanic effects might include increased oceanic productivity nitrogen containing objects as a result of increased chemical weathering and or greenhouse effects increased temperatures coupled with enhanced productivity could result in wider spread oceanic anoxia or altered calcite aragonite stability possible examples of such impacts from the geologic record and potential biotic effects are given

the triassic isotope record a variety of stable isotope measurements have been found useful in studying processes of environmental change measurements of d 13 c d 18 o d 34 s and 87 sr 86 sr all can provide infor mation about the conditions of the water column in which sediment deposition occurred but the most widely applied of these is d 13 c the carbon isotope record for the triassic system is a complex one a pronounced negative excursion begins below the base of the triassic system and continues into the basal triassic the succeeding 4 to 6 ma lower triassic interval is marked by isotopic instability with positive and negative excursions continuing through the basal middle triassic in contrast to the lower triassic most of the middle and upper triassic display relative isotopic stability with rising values of d 13 c likely reflecting environmental recov ery and increasing storage of organic carbon in terrestrial environments the uppermost triassic is marked by a pronounced negative excursion near the system boundary that has been linked to significant biotic turnover the causes of the various excursions remain under investigation particularly those at the system boundaries with outgassing during volcanic activity changes in productivity ocean anoxia and seafloor methane releases all suggested as mechanisms both for perturbing the global carbon cycle and for forcing biotic extinction

u pb zircon geochronology and tempo of the end permian mass extinction the mass extinction at the end of the permian was the most profound in the history of life fundamental to understanding its cause is determining the tempo and duration of the extinction uranium lead zircon data from late permian and early triassic rocks from south china place the permian triassic boundary at 251 4 0 3 million years ago biostratigraphic controls from strata intercalated with ash beds below the boundary indicate that the changhsingian pulse of the end permian extinction corresponding to the disappearance of about 85 percent of marine species lasted less than 1 million years at meishan a negative excursion in 13 c at the boundary had a duration of 165 000 years or less suggesting a catastrophic addition of light carbon

global seismicity of 2002 centroid moment tensor solutions for 1034 earthquakes abstract centroid moment tensor solutions are presented for 1034 earthquakes that occurred during 2002 the solutions are obtained using the method of dziewonski et al dziewonski a m chou t a woodhouse j h 1981 determination of earthquake source parameters from waveform data for studies of global and regional seismicity j geophys res 86 2825 2852 and applying corrections for aspherical earth structure represented by the whole mantle shear velocity model sh8 u4l8 of dziewonski and woodward dziewonski a m woodward r l acoustic imaging at the planetary scale in emert h harjes h p eds acoustical imaging vol 19 plenum press new york 1992 pp 785 797 the model of anelastic attenuation of durek and ekstrom durek j j ekstrom g 1996 a radial model of anelasticity consistent with long period surface wave attenuation bull seism soc am 86 144 158 is used to predict the decay of the waveforms the focal mechanisms of the largest or otherwise significant earthquakes of 2002 are reviewed

anomalous earthquakes associated with nyiragongo volcano observations and potential mechanisms abstract a series of five unusual earthquakes 4 6 m 5 3 has been recently located near nyiragongo volcano d r congo in the western rift valley of the east african rift despite their moderate size these earthquakes do not appear in global seismicity catalogs but were located using long period surface waves primarily recorded on the global seismographic network three of the events occurred in the week following the january 2002 eruption of nyiragongo while the final two occurred in 2003 and 2005 respectively and are not linked to a major eruption at nyiragongo or its neighboring volcano nyamuragira several common techniques were used to investigate the characteristics of these seismic sources in the context of the volcanic activity of the region the frequency content of the five anomalous earthquakes was compared to that from local events found in global catalogs and the newly detected earthquakes were shown to be slow events being greatly depleted in frequencies above 0 1 hz each of the newly detected earthquakes was modeled by a series of forces and by a centroid moment tensor a deviatoric moment tensor was shown to provide a better fit to the data the newly detected earthquakes are highly non double couple in nature each having a large compensated linear vector dipole component of the moment tensor drawing on models based on similar observations from other active volcanoes we propose that the earthquakes are caused by slip on non planar faults beneath the volcano we suggest a mechanism in which these newly detected earthquakes are generated by the collapse of the roof of a shallow magma chamber along an inward dipping cone shaped ring fault diking events which result in magma evacuation from shallow magma chambers could trigger such earthquakes our results provide new constraints on the dynamics of the poorly understood magma system beneath nyiragongo an active volcano that is a significant threat to life and property

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

a smooth negative shift of organic carbon isotope ratios at an end permian mass extinction horizon in central pelagic panthalassa abstract the end permian mass extinction is associated with a global perturbation in the carbon isotopic composition of carbonates and organic matter but such changes are not well documented from pelagic deep sea sediments one of the most continuous pelagic deep sea permian triassic boundary ptb sections the am 2 section is exposed in the accretionary complexes of japan new data for organic carbon isotope ratios 13corg were obtained from 36 samples from section am 2 the 13corg excursion curve exhibits a negative shift of 2 0 in the low latitude pelagic panthalassic ocean at the end of the permian which coincides with a radiolarian extinction the 13corg values of pelagic deep sea panthalassic sections and those of shallow water sections from panthalassic seamounts exhibit a smooth negative shift that lacks temporary increases like those reported from paleotethyan ptb sections absence of temporary 13corg increases at the ptb in panthalassa may reflect less algal and bacterial blooming in pelagic panthalassa compared to the shallow water paleotethys

carbon sulfur oxygen and strontium isotope records organic geochemistry and biostratigraphy across the permian triassic boundary in abadeh iran pelagic deposits at abadeh represent a complete biostratigraphic record across the permian triassic boundary ptb the presumed water depth during deposition of these sediments was between 60 and 90 m similar to other permian triassic boundary sections the succession at abadeh is characterised by a negative carbon isotope shift of approximately 4 the values start to decrease in the lower c changxingensis c deflecta s l zone reach 0 12 v pdb in the uppermost permian just below the ptb remain low to the early i isarcica zone 0 32 and increase subsequently in the upper i isarcica zone for the time interval of the ptb negative carbon isotope excursion between the c iranica and the i isarcica zones no correlation exists between the 13ccarb and the 18ocarb the above observations argue against the conclusion of heydari et al 2001 that the carbon isotope event at the p t transition is an alteration artefact and not a global signal the decrease in 13ccarb is accompanied by a 5 and potentially up to 10 increase in 34ssss together these features are thought to reflect a complex global event notably the development of widespread anoxic oceans with anoxic bottom layers rising onto the shelves for the carbon isotope drop other factors such as the collapse of ocean primary productivity may also have played a role the 87sr 86sr ratios of dzhulfian seawater show only a minor increase from 0 70705 to 0 70710 reaching 0 70720 in the dorashamian the increase becomes steeper in the early triassic reaching 0 70754 in the n dieneri zone the rise of the strontium isotope values is thought to be related to enhanced continental weathering under humid climatic conditions in the uppermost permian c meishanensis h praeparvus zone and the lack of a dense land vegetation in the early triassic prior to the spathian upper olenekian

δ13c depth profiles from paleosols across the permian triassic boundary evidence for methane release stable carbon isotopic analyses of organic carbon 13 c in individual paleosol profiles from permian triassic sequences of antarctica reveal systematic isotopic variations with profile depth these variations are in many cases analogous to those in modern soils which are functions of redox conditions soil development and degree and type of microbial decay in modern soils these isotopic depth functions develop independently from vegetation changes c 3 versus c 4 vegetation and can be diagnostic of soil orders this study shows that soil intrinsic functions can be preserved in the 13 c values of paleosols as old as 260 ma and constitute valuable data for paleoecological interpretations a large carbon isotopic offset of as much as 10 in whole paleosol profiles across the permian triassic boundary indicates significant changes in the soil biogeochemistry and the soil atmosphere system early triassic paleosols are distinctive in their extremely low 13 c values to 42 and often show an anomalous 13 c depth distribution compared to both permian paleosols and modern soils highly depleted 13 c values as the ones in early triassic paleosols are suggested to be associated with microbial methane oxidation methanotrophy this hypothesis implies increased methane concentrations in the early triassic soil atmosphere system increased atmospheric methane was probably partly responsible for the global carbon isotopic shift documented in marine and terrestrial sediments across the permian triassic boundary

molecular carbon isotope variations in core samples taken at the permian triassic boundary layers in southern china stable carbon isotope composition 13c of carbonate sediments and the molecular biomarker characteristics of a continuous permian triassic pt layer in southern china were studied to obtain geochemical signals of global change at the permian triassic boundary ptb carbonate carbon isotope values shifted toward positive before the end of the permian period and then shifted negative above the ptb into the triassic period molecular carbon isotope values of biomarkers followed the same trend at and below the ptb and remained negative in the triassic layer these biomarkers were acyclic isoprenoids ranging from c15 to c40 steranes c27 dominates and terpenoids that were all significantly more abundant in samples from the permian layer than those from the triassic layer the triassic layer was distinguished by the dominance of higher molecular weight waxy n alkanes stable carbon isotope values of individual components including n alkanes and acyclic isoprenoids such as phytane isop c25 and squalane are depleted in 13c by up to 8 10 in the triassic samples as compared to the permian measured molecular and isotopic variations of organic matter in the pt layers support the generally accepted view of permian oceanic stagnation followed by a massive upwelling of toxic deep waters at the ptb a series of large scale global outgassing events may be associated with the carbon isotope shift we measured this is also consistent with the lithological evidence we observed of white thin clay layers in this region our findings in context with a generally accepted stagnant permian ocean followed by massive upwelling of toxic deep waters might be the major causes of the largest global mass extinction event that occurred at the permian triassic boundary

stable carbon isotope signature in mid panthalassa shallow water carbonates across the permo triassic boundary evidence for 13 c depleted superocean the jurassic accretionary complex in southwest japan contains exotic blocks of the permo triassic limestone primarily deposited on ancient mid oceanic seamounts in an ancient pacific ocean or superocean panthalassa this study examines stable carbon isotope compositions 13ccarb and 13corg of such open ocean shallow water limestone across the permo triassic boundary ptb at kamura and taho in southwest japan the results show an almost identical secular change in 13ccarb values with a remarkable negative spike across the ptb in both sections this confirms for the first time that the mid panthalassa shallow water carbonates are bio and chemo stratigraphically correlated not with previously studied ptb sections from the peripheries of pangea the negative shift in 13ccarb occurs parallel to that of 13corg in both sections and the difference 13c 13ccarb 13corg remains nearly constant throughout the sections this implies that the 13c depleted water should have developed widely probably in a global extent throughout the superocean panthalassa across the ptb these findings suggest that a large input of 12c enriched carbon into the ocean atmosphere system has occurred and may have caused a global environment change probably relating to the greatest mass extinction in the phanerozoic

major perturbation of ocean chemistry and a strangelove ocean after the end permian mass extinction the severe mass extinction of marine and terrestrial organisms at the end of the permian period c 251 ma was accompanied by a rapid 1 ma decrease in sedimentary burial of organic carbon in the early triassic

carbon isotope excursions and microfacies changes in marine permian triassic boundary sections in hungary abstract several permian triassic boundary sections occur in various structural units within hungary these sections represent different facies zones of the western palaeotethys margin the gardony core in the ne part of the transdanubian range typically represents the inner ramp while the balvany section in the bukk mountains of northern hungary represents an outer ramp setting the two sections have different patterns for their 13 c values the balvany section shows a continuous change towards more negative 13 c values starting at the first biotic decline followed by a sharp quasi symmetric negative peak at the second decline the appearance of the 13 c peak has no relationship to the lithology and occurs within a shale with low overall carbonate content indicating that the peak is not related to diagenesis or other secondary influences instead the shift and the peak reflect primary processes related to changes in environmental conditions the continuous shift in 13 c values is most probably related to a decrease in bioproductivity whereas the sharp peak can be attributed to an addition of c strongly depleted in 13 c to the ocean atmosphere system the most plausible model is a massive release of methane hydrate the quasi symmetric pattern suggests a rapid warming cooling cycle or physical unroofing of sediments through slope failure and releasing methane hydrate the gardony 1 core shows a continuous negative 13 c shift starting below the p t boundary however the detailed analyses revealed a sharp 13 c peak in the boundary interval just below the major biotic decline although its magnitude doesn t reach that observed in the balvany section based on careful textural examination and high resolution stable isotope microanalyses we suggest that the suppression of the 13 c peak that is common in the oolitic boundary sections is due to combined effects of condensed sedimentation sediment reworking and erosion as well as perhaps diagenesis

two episodes of 13c depletion in organic carbon in the latest permian evidence from the terrestrial sequences in northern xinjiang china new analyses reveal two intervals of distinctly lower 13c values in the terrestrial organic matter of permian triassic sequences in northern xinjiang china the younger negative 13corg spike can be correlated to the conspicuous and sharp 13c drops both in carbonate carbon and organic carbon near the permian triassic event boundary pteb in the marine section at meishan the geochemical correlation criteria are accompanied by a magnetic susceptibility pulse and higher abundances of distinctive chain like organic fossil remains of reduviasporonites the older negative 13corg spike originates within a latest permian regression significant changes in organic geochemical proxies are recorded in the equivalent interval of the marine section at meishan these include relatively higher concentrations of total organic carbon isorenieratane c14 c30 aryl isoprenoids and lower ratios of pristane phytane that together indicate the onset of anoxic euxinic and restricted environments within the photic zone the massive and widespread oxidation of buried organic matter that induced these euxinic conditions in the ocean would also result in increased concentrations of 13c depleted atmospheric co2 the latest permian environmental stress marked by the older negative 13corg episode can be correlated with the distinct changeover of ostracod assemblages and the occurrences of morphological abnormalities of pollen grains these observations imply that biogeochemical disturbance was manifested on the land at the end of the permian and that terrestrial organisms responded to it before the main extinction of the marine fauna

enhanced deformation of limestone and sandstone in the presence of high fluids 1 geological repositories subject to the injection of large amounts of anthropogenic carbon dioxide will undergo chemical and mechanical instabilities for which there are currently little experimental data this study reports on experiments where low and high 8 mpa aqueous fluids were injected into natural rock samples the experiments were performed in flow through triaxial cells where the vertical and confining stresses temperature and pressure and composition of the fluid were separately controlled and monitored the axial vertical strains of two limestones and one sandstone were continuously measured during separate experiments for several months with a strain rate resolution of 10 11 s 1 fluids exiting the triaxial cells were continuously collected and their compositions analyzed the high fluids induced an increase in strain rates of the limestones by up to a factor of 5 compared to the low fluids injection of high fluids into the sandstone resulted in deformation rates one order of magnitude smaller than the limestones the creep accelerating effect of high fluids with respect to the limestones was mainly due to the acidification of the injected fluids resulting in a significant increase in solubility and reaction kinetics of calcite compared to the limestones the much weaker response of the sandstone was due to the much lower solubility and reactivity of quartz in high fluids in general all samples showed a positive correlation between fluid flow rate and strain rate x ray tomography results revealed significant increases in porosity at the inlet portion of each core the porosity increases were dependent on the original lithological structure and composition the overall deformation of the samples is interpreted in terms of simultaneous dissolution reactions in pore spaces and intergranular pressure solution creep