anomalous early triassic sediment fluxes due to elevated weathering rates and their biological consequences analysis of 16 marine permian triassic boundary sections with a near global distribution demonstrates systematic changes in sediment fluxes and lithologies in the aftermath of the end permian crisis sections from continent margin and platform settings exhibit higher bulk accumulation rates bars and more clay rich compositions in the griesbachian earliest triassic relative to the changhsingian latest permian these patterns which largely transcend regional variations in tectonic setting sequence stratigraphic factors and facies are hypothesized to have resulted from a substantial average 7 increase in the flux of eroded material from adjacent land areas owing to accelerated rates of chemical and physical weathering as a function of higher surface temperatures increased acidity of precipitation and changes in landscape stability tied to destruction of terrestrial ecosystems this sediment surge may have been a contributory factor to the latest permian marine biotic crisis as well as to the delayed recovery of early triassic marine ecosystems owing to the harmful effects of siltation and eutrophication contemporaneous deep sea sections show no increases in sediment flux across the permian triassic boundary owing to their remoteness from continental siliciclastic sources and location below the paleo carbonate compensation depth

anoxic vs dysoxic events reflected in sediment geochemistry during the cenomanian turonian boundary event cretaceous in the umbria marche basin of central italy abstract one of the most spectacular expressions of global oceanic anoxic events oaes of the cretaceous is the livello bonarelli of central italy deposited during the cenomanian turonian boundary event ctbe or oae2 at around 93 5 ma at furlo in the umbria marche basin in italy the bonarelli consists of approximately 1 m of c org rich shales interbedded with radiolarian rich layers and contrasts sharply with the extensive over and underlying siliceous limestones several minor c org rich intervals herein termed black levels average thickness 4 5 cm are interbedded within the scaglia bianca beneath the bonarelli x ray fluorescence and icp ms analyses show that these sediments consist of different mixing systems with three end members 1 sio 2 caco 3 scaglia bianca 2 average shale caco 3 black levels and 3 average shale sio 2 bonarelli given the sharp lithologic contacts and the little geochemical mixing between the groups these are thought to represent rapid switching events between sedimentary modes major element concentrations are generally low except for si and p owing to dilution by silica up to 96 and carbonates as al normalised ratios for elements such as ti or zr taken as proxies for higher energy environments are close to average shale values excess sio 2 is most likely linked to biogenic processes rather than quartz element al ratios of ti mg k rb and zr are fairly constant pointing to a mostly homogeneous source area the black levels and bonarelli are characterised by lower mg al ratios compared to the scaglia bianca sediments suggesting variability in chlorite input which could be linked with short term sea level drops indicated by ti al ratios the bonarelli sediments are severely depleted in mn which is indicative of oxygen depleted bottom water conditions and an open marine environment while the black levels appear to have been deposited in a much more restricted setting a model involving partial physical isolation of the furlo site by a sill coupled to omz variations by extra basinal forcing mechanisms is proposed to account for these conflicting data based on re mo ratios the bonarelli sediments were deposited under varying oxygen depletion levels from suboxic to anoxic while re mo ratios in the black levels show deposition under less oxygen deficient conditions most minor elements many of them redox sensitive or sulphide residing are strongly enriched in the c org rich sediments further documenting the absence of oxygen and potential availability of hydrogen sulphide in the water column at times while high zn concentrations suggest elevated submarine hydrothermal activity during this time interval ba is also present in very high concentrations up to 1 4 with an average weighed concentration of 0 6 for the entire bonarelli and is probably indicative of high paleoproductivity in this area this is further supported by high p concentrations hinting at nutrient availability at this site

experimental determination of the compositional limits of immiscibility in the system cacl2h2oco2 at high temperatures and pressures using synthetic fluid inclusions abstract using the synthetic fluid inclusion method the temperature pressure and compositional limits of fluid immiscibility in the binary system cacl 2 h 2 o have been determined at 600 and 700 c at pressures between 1 and 2 kbar the limits of the immiscible regions were determined by observation of two different inclusion types in the samples and by measurements of the depression of ice melting temperatures the region of immiscibility in this system extends to much higher pressures than that of the nacl h 2 o system with similar compositional ranges a similar study was done on the cacl 2 h 2 o co 2 system at 500 600 and 700 c at pressures of 1 1 5 2 and 3 kbar in the ternary system the presence of two different inclusion types and the measurement of clathrate melting temperatures were used to delineate the compositional regions of immiscibility the presence of co 2 extends the regions of immiscibility shown in the binary system study to much higher pressures tie lines in the two phase regions were determined by measuring the homogenization temperatures of co 2 vapor and liquid phases and the volume ratios of inclusion bubble to total inclusion in vapor rich type inclusions the locations of these tie lines indicate that the cacl 2 is heavily partitioned towards the more liquid rich phase the experimental results show that with even relatively small amounts of a divalent salt such as cacl 2 immiscibility can exist to very high temperatures and pressures from these results immiscibility should be a very common phenomenon in geologic processes ranging from sedimentary to quite high grade metamorphic environments and that it should have a very important effect on reactions between hydrothermal fluids and rocks and the resulting mineral assemblages

synthetic fluid inclusions vii re equilibration of fluid inclusions in quartz during laboratory simulated metamorphic burial and uplift p t conditions inferred from fluid inclusions in metamorphic rocks often disagree with the values predicted from mineral equilibria calculations these observations suggest that inclusions formed during early stages of regional metamorphism continue to re equilibrate during burial and subsequent uplift in response to differential pressure p t conditions accompanying burial and uplift were experimentally simulated by initially forming pure h2o inclusions in quartz at elevated temperatures and pressures and then re equilibrating the inclusions in the presence of a 20 wt nacl solution such that final confining pressures ranged from 5 kbar above to 4 kbar below the initial internal pressure of the inclusions at the temperature of re equilibration in all samples re equilibrated at confining pressures below the internal pressure some inclusions were formed that had compositions of 20 wt nacl and densities in accord with the final p t conditions additionally some inclusions were observed to contain fluids of intermediate salinities between 0 and 20 wt nacl densities of these inclusions were also consistent with formation at the re equilibration p t conditions the remainder of the fluid inclusions observed in these samples contained pure h2o and their homogenization temperatures corresponded to densities intermediate between the initial and final p t conditions in short term experiments 7 days where the initial internal overpressure exceeded 1 kbar no inclusions were found that contained the original density and none were found to have totally re equilibrated instead most h2o inclusions re equilibrated until their internal pressures were between 750 and 1500 bars above the confining pressure regardless of the initial pressure differential in a long term experiment 52 days inclusions re equilibrated at a lower confining pressure than the initial internal pressure displayed homogenization temperatures corresponding to a range in final internal pressures between 0 kbar i e total re equilibration and 1 2 kbar above the confining pressure in experiments where the confining pressure during re equilibration exceeded the initial internal pressure densities of pure h2o inclusions increased to values intermediate between the initial and final p t conditions additionally these inclusions were generally surrounded by a three dimensional halo of smaller inclusions also of intermediate density resulting in a texture similar to that previously ascribed to decrepitation from internal overpressure in extreme cases where confining pressures were 4 5 kbar above the initial pressure the parent inclusion almost completely closed leaving only the three dimensional array of small 5 m inclusions the outline of which may be several times the volume of the original inclusion groups of such inclusions closely resemble textures commonly observed in medium to high grade metamorphic rocks inclusions containing 10 and 42 wt nacl solutions trapped at 600 c and 3 kbar were re equilibrated at 600 c and 1 kbar for 5 days in dry argon to evaluate the importance of h2o diffusion as a mechanism of lowering the inclusion bulk density salinities of re equilibrated inclusions obtained from freezing point depressions and halite dissolution temperatures indicate that original compositions were preserved density changes similar to those previously described were noted in these experiments in inclusions showing no visible microfractures therefore density variations observed in inclusions in this study re equilibrated under rapid deformation conditions are considered to result from a change in the inclusion volume without significant loss of contents by diffusion or leakage

sedimentary mercury enrichments as a marker for submarine large igneous province volcanism evidence from the mid cenomanian event and oceanic anoxic event 2 late cretaceous oceanic anoxic event 2 oae 2 during the cenomanian turonian transition 94 ma was the largest perturbation of the global carbon cycle in the mid cretaceous and can be recognized by a positive carbon isotope excursion in sedimentary strata although oae 2 has been linked to large scale volcanism several large igneous provinces lips were active at this time e g caribbean high arctic madagascan ontong java and little clear evidence links oae 2 to a specific lip the mid cenomanian event mce 96 ma identified by a small 1 positive carbon isotope excursion is often referred to as a prelude to oae 2 however no underlying cause has yet been demonstrated and its relationship to oae 2 is poorly constrained here we report sedimentary mercury hg concentration data from four sites three from the southern margin of the western interior seaway and one from demerara rise in the equatorial proto north atlantic ocean we find that in both areas increases in mercury concentrations and hg toc ratios coincide with the mce and the oae 2 however the increases found in these sites are of a lower magnitude than those found in records of many other mesozoic events possibly characteristic of a marine rather than atmospheric dispersal of mercury for both events combined the new mercury data presented here are consistent with an initial magmatic pulse at the time of the mce with a second greater pulse at the onset of oae 2 possibly related to the emplacement of lips in the pacific ocean and or the high arctic

cadmium isotopic evidence for increasing primary productivity during the late permian anoxic event abstract earth s most extreme extinction event near the end of the late permian decimated more than 90 of all extant marine species widespread and intensive oceanic anoxia almost certainly contributed to the catastrophe though the driving mechanisms that sustained such conditions are still debated of particular interest is whether water column anoxia was a consequence of a stagnant ocean or if it was controlled by increases in nutrient supply primary productivity and subsequent heterotrophic respiration testing these competing hypotheses requires deconvolving sedimentary bottom water redox conditions from changes in surface water productivity in marine sediments we address this issue by studying marine shales from east greenland and the mid norwegian shelf and combining sedimentary redox proxies with cadmium isotopic analyses sedimentary nitrogen isotopic data pyrite framboid analyses and organic and inorganic shale geochemistry reveal sulfidic conditions with vigorous upwelling and increasingly anoxic conditions with a strengthening upwelling in the greenland and norwegian sections respectively detailed analysis of sedimentary metal budgets illustrates that cd is primarily associated with organic carbon and records primary geochemical signatures thus enabling reconstruction of surface water nutrient utilization cadmium isotopic analyses of the authigenic shale fraction released by inverse aqua regia digestion yield an average cd 114 110 of 0 15 0 01 2 se n 12 rel nist srm 3108 indicative of incomplete surface water nutrient utilization up section the constant degree of nutrient utilization combined with strong upwelling requires increasing primary productivity and not oceanic stagnation to balance the larger nutrient fluxes to both study sites during the development of the late permian water column anoxia overall our data illustrate that if bottom water redox and upwelling can be adequately constrained cd isotopic analyses of organic rich sediments can be used to provide valuable information on nutrient utilization and therefore past productivity

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

crocetane a potential marker of photic zone euxinia in thermally mature sediments and crude oils of devonian age abstract crocetane an irregular c 20 isoprenoid in sediments generally associated with gas hydrate settings is a molecular indicator for the anaerobic oxidation of methane green sulfur bacteria gsb are the main source for specific aromatic carotenoids e g isorenieratane in sedimentary environments and are molecular indicators of photic zone euxinia pze the present study comprises a detailed molecular and isotopic study of crocetane and gsb derived carotenoids in devonian sediments of the western canada sedimentary basin wcsb covering a range of thermal maturities in addition a series of oils generated from devonian source rocks of the basin have been analysed for crocetane crocetane was found in ten sediments from the wcsb and in seven devonian wcsb crude oils its abundance was found to increase with thermal maturity whereas the components derived from c 40 derived carotenoids decrease steadily we were not able to identify 2 6 10 15 19 pentamethylicosane pmi neither in the duvernay formation sediments nor in the wcsb crude oils consistent with previous findings the preferred proposed natural product precursor for crocetane is thus gsb derived carotenoids this is corroborated by their similar structural features and the 13 c value of combined crocetane and phytane in these samples however contributions from other carotenoids cannot be fully excluded crocetane can provide evidence for pze conditions in highly mature samples and crude oils of devonian age

anaerobic methane oxidation and a deep h2s sink generate isotopically heavy sulfides in black sea sediments the main terminal processes of organic matter mineralization in anoxic black sea sediments underlying the sulfidic water column are sulfate reduction in the upper 2 4 m and methanogenesis below the sulfate zone the modern marine deposits comprise a ca 1 m deep layer of coccolith ooze and underlying sapropel below which sea water ions penetrate deep down into the limnic pleistocene deposits from 9000 years bp sulfate reduction rates have a subsurface maximum at the so42 ch4 transition where h2s reaches maximum concentration because of an excess of reactive iron in the deep limnic deposits most of the methane derived h2s is drawn downward to a sulfidization front where it reacts with fe iii and with fe2 diffusing up from below the h2s fe2 transition is marked by a black band of amorphous iron sulfide above which distinct horizons of greigite and pyrite formation occur the pore water gradients respond dynamically to environmental changes in the black sea with relatively short time constants of ca 500 yr for so42 and 10 yr for h2s whereas the fes in the black band has taken ca 3000 yr to accumulate the dual diffusion interfaces of so42 ch4 and h2s fe2 cause the trapping of isotopically heavy iron sulfide with 34s 15 to 33 at the sulfidization front a diffusion model for sulfur isotopes shows that the so42 diffusing downward into the so42 ch4 transition has an isotopic composition of 19 close to the 23 of h2s diffusing upward these isotopic compositions are however very different from the porewater so42 43 and h2s 15 at the same depth the model explains how methane driven sulfate reduction combined with a deep h2s sink leads to isotopically heavy pyrite in a sediment open to diffusion these results have general implications for the marine sulfur cycle and for the interpretation of sulfur isotopic data in modern sediments and in sedimentary rocks throughout earth s history

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

synthetic h2oco2 fluid inclusions in spontaneously nucleated forsterite enstatite and diopside hosts the method and applications abstract synthetic h2o co2 fluid inclusions have been produced in forsterite diopside and enstatite hosts during the spontaneous nucleation and growth of these phases at t 800 980 c and p 6100 7800 bars via the reactions 2 trem 18h 2 o 4 diopside 3 forsterite 5si oh 4 2h 2 o 1 trem 3h 2 o 2 diopside 3 enstatite si oh 4 2h 2 o 2 the inclusions are large 10 40 m abundant and commonly of regular shape making them ideal as standards for microthermometric and spectroscopic analyses the technique provides the opportunity to study fluid inclusion trapping mechanisms and their potential effect on inclusion chemistry the fluid inclusions exhibit a small degree of compositional scatter about the ambient composition deviations between the ambient and inclusion composition increase for experiments performed in the presence of low 3 8 c thermal gradients along the capsule length this observation suggests that compositional heterogeneities may develop in the absence of fluid convection in the capsule the effect on the inclusion composition however does not exceed 3 mol in xco2 for all inclusions studied the advantages of this technique are 1 it provides a means of producing fluid inclusions of known compositions in hosts other than quartz and 2 inclusion formation is relatively slow allowing ample time for the p t x fluid conditions of the run to equilibrate the disadvantages are that the small grains produced can be difficult to work with and the host producing reactions are viable over a relatively narrow range of p t x fluid conditions

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

the permo triassic extinction the end permian mass extinction brought the palaeozoic great experiment in marine life to a close during an interval of intense climatic tectonic and geochemical change improved knowledge of latest permian faunas coupled with recent advances in isotopic studies and biostratigraphy have greatly enhanced our understanding of the events of 250 million years ago and have begun to provide answers to many questions about the causes of extinction

cretaceous oceanic anoxic event 2 triggered by a massive magmatic episode oceanic anoxic events oaes were episodes of widespread marine anoxia during which large amounts of organic carbon were buried on the ocean floor under oxygen deficient bottom waters oae2 occurring at the cenomanian turonian boundary about 93 5 myr ago is the most widespread and best defined oae of the mid cretaceous although the enhanced burial of organic matter can be explained either through increased primary productivity or enhanced preservation scenarios the actual trigger mechanism corresponding closely to the onset of these episodes of increased carbon sequestration has not been clearly identified it has been postulated that large scale magmatic activity initially triggered oae2 refs 4 5 but a direct proxy of magmatism preserved in the sedimentary record coinciding closely with the onset of oae2 has not yet been found here we report seawater osmium isotope ratios in organic rich sediments from two distant sites we find that at both study sites the marine osmium isotope record changes abruptly just at or before the onset of oae2 using a simple two component mixing equation we calculate that over 97 per cent of the total osmium content in contemporaneous seawater at both sites is magmatic in origin a approximately 30 50 fold increase relative to pre oae conditions furthermore the magmatic osmium isotope signal appears slightly before the oae2 as indicated by carbon isotope ratios suggesting a time lag of up to approximately 23 kyr between magmatism and the onset of significant organic carbon burial which may reflect the reaction time of the global ocean system our marine osmium isotope data are indicative of a widespread magmatic pulse at the onset of oae2 which may have triggered the subsequent deposition of large amounts of organic matter

comparison of chemical procedures for re isotopic measurements by n tims abstract precise and accurate measurements of the isotopic composition of rhenium re in geologic samples are of paramount importance for the successful application of the re os geochronometer two methods for chemical isolation of re are used in the geochronology community column chemistry using anion exchange resin and solvent solvent extraction using a sodium hydroxide acetone mixture despite their ubiquitous application a systematic comparison of these two methods is missing here we compare re isotopic data on a variety of samples sulfides hydrocarbons shales and in house standard solutions that were processed by both chemical methods measured 185re 187re ratios for both methods have similar precision and overlap within the propagated long term analytical reproducibility of 1 for samples that yield moderate to strong intensities 50 mv on the weaker re mass in contrast measured 185re 187re ratios for most samples that yield less intense re signals

sedimentary fractionations between al ti and zr and the genesis of strongly peraluminous granites sedimentary sorting produces alternating shales and sandstones with complementary chemistries the preferential partitioning of quartz and zircon in the coarse grained fraction of the sediments results in a strong fractionation between sio 2 zr and other components al 2 o 3 tio 2 as a consequence shales may be defined chemically as having higher al 2 o 3 sio 2 and tio 2 zr ratios than their source rocks sandstones have the opposite characteristics and vary in composition according to the maturity of their source and the intensity of sorting processes most sedimentary suites display a good correlation between al 2 o 3 sio 2 and tio 2 zr this result is used to evaluate an average bulk composition for recent clastic materials and to model their composition on a ternary al ti zr diagram because the al 2 o 3 tio 2 ratio of igneous rocks is highly sensitive to magmatic differentiation igneous and sedimentary trends crosscut in the al ti zr di

the trace metal content of recent organic carbon rich sediments implications for cretaceous black shale formation organic carbon rich sediments are enriched in several redox sensitive and stable sulfide forming trace metals tm and form an important sink in global tm cycles in today s ocean such sediments are deposited in coastal upwelling areas like those in the gulf of california off peru or off the namibian coast and euxinic basins like the black sea in an attempt to distinguish both environments by their specific tm patterns some important conclusions may be drawn 1 the tm enrichment seen in both environments broadly is rather similar 2 upwelling sediments are often enriched in cd and p and depleted in co and mn 3 sapropels have a tendency towards higher enrichments in ba and mo s re as cu ni sb and fe reflecting the strong sulfidation in an anoxic water column 4 upwelling systems cover a broad range of environmental settings where the steepness of the slope the proximity of h2s to the sediment seawater interface and the intensity of bio accumulation and regeneration play an important role for tm accumulation 5 the tm content of anoxic basins is mainly controlled by tm availability in the water column and sedimentation rate 6 enhanced bio productivity is the main switch turning an oxygenated into an anoxic environment cretaceous black shales oae 2 exhibit tm signatures of both coastal upwelling areas and sapropels the strong enrichments in cd mo tl v cu ni bi and sb demonstrate that bio accumulation and presence of h2s in the water column and associated sulfidation processes persisted during this time interval in large parts of the proto atlantic the usefulness of ba as a paleoproductivity proxy is obscured by diagenesis the extreme accumulation in ag and zn requires either an additional tm source for instance hydrothermal input or a different tm seawater composition during the cretaceous the geochemical data suggest that the major driving force for the widespread occurrence of c t black shales seems to be the increase in volcanic activity and associated co2 input throughout the cretaceous the ocean atmosphere system operated in a mode different from today during this time interval after conversion of the nutrient co2 into organic matter the system switched back into the normal operational mode

synthetic fluid inclusions in natural quartz i compositional types synthesized and applications to experimental geochemistry synthetic fluid inclusions having a wide range of geologically applicable compositions in the c o h s na k ca cl cu fe system have been formed by healing fractures in inclusion free natural quartz and by precipitating new quartz overgrowths on an original seed crystal inclusion types synthesized include 1 1 liquid rich pure h2o inclusions of primary and secondary origin 2 2 pure h2o inclusions with the critical density 3 3 liquid rich inclusions containing undersaturated aqueous solutions of nacl or kcl or cacl2 or mixtures of the three salts 4 4 h2o nacl inclusions containing halite daughter minerals 5 5 h2o nacl kcl inclusions containing halite and sylvite daughter minerals 6 6 h2o co2 inclusions of various compositions containing liquid h2o and either co2 vapor or co2 liquid or both at 25 c 7 7 h2o co2 nacl inclusions containing an aqueous phase liquid and vapor co2 and halite at 25 c 8 8 c o h inclusions containing liquid h2o a co2 ch4 liquid phase and graphite daughter minerals at 25 c 9 9 h2o nacl inclusions that contain a chalcopyrite daughter mineral and 10 10 inclusions representing trapping of the coexisting immiscible fluids in the h2o nacl h2o co2 nacl and na c o h systems the inclusions exhibit uniform phase ratios at room temperature and the temperatures of various phase changes within individual inclusions agree with those predicted from experimental and theoretical data indicating that the inclusion fluid has the same composition and density as the parent solution these miniature autoclaves thus may be used to study various problems related to fluid inclusion research to calibrate analytical equipment used to study natural inclusions and to study phase equilibria solubility and pvt relations of a variety of chemical systems

subsidence rates and urban damages in alluvial dolines of the central ebro basin ne spain in the central ebro basin alluvial dolines develop on quaternary materials overlying neogene evaporites this process is very active analysing aerial photographs of different years important differences can be observed since the 1970s when the urbanisation of the area took place karst processes have damaged many buildings and infrastructures from the dates of construction and the repair of a number of buildings and pavements we calculate subsidence rates 12 120 mm year moreover we decided to monitor for around 4 years three dolines developed on urban areas to determine their subsidence behaviour a water level device with an error of 2 3 mm was utilised for this purpose the subsidence rates so obtained are 64 5 39 and 21 mm year which fit with the previous data from repaired zones

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

source and significance of selected polycyclic aromatic hydrocarbons in sediments hovea 3 well perth basin western australia spanning the permian triassic boundary abstract stable carbon isotopic data for polycyclic aromatic hydrocarbons pahs chrysene and triphenylene benzo e pyrene 9 methylphenanthrene in sediments of comparable thermal maturity from a petroleum drill core hovea 3 well perth basin western australia spanning the largest mass extinction event in the past 500 million years permian triassic boundary are consistent with an algal kerogen source in the basal triassic as opposed to a combustion and or higher plant source in the underlying permian sediments the 13c values of extractable pahs are less negative in the permian inertinitic interval 24 7 to 29 2 than the triassic sapropelic interval 30 to 33 3 a strong correlation is evident between 13c of individual pahs 13c of kerogen and rock eval pyrolysis hydrogen index providing unequivocal evidence that pah 13c is mainly controlled by organic matter type abundant algal derived pahs in basal triassic sediments may be a global feature the lack of coal globally in the basal triassic sediments is also consistent with this observation the early triassic coal gap appears to coincide with the global extinction of peat forming plants at the end of the permian coal did not reappear until the middle triassic and permian levels of plant diversity and thick peat deposits did not recover until the late triassic the pah isotopic data support the contention that a global anoxic event at the end of the permian period contributed to the gradual worldwide asphyxiation and ultimate extinction of many marine and terrigenous organisms

enhanced recycling of organic matter and os isotopic evidence for multiple magmatic or meteoritic inputs to the late permian panthalassic ocean opal creek canada abstract the geochemical record for the permian triassic boundary in northern latitudes is essential to evaluation of global changes associated with the most profound extinction of life on earth we present inorganic and organic geochemical data and re os isotope systematics in a critical stratigraphic interval of pre and post extinction upper permian lower triassic sediments from opal creek western canada paleolatitude of 30 n we document significant and long lived changes in panthalassa seawater chemistry that were initiated during the first of four magmatic or meteoritic inputs to late permian seawater evidenced by notable decreases of os isotopic ratios upsection geochemical signals indicate establishment of anoxic bottom waters shortly after regional transgression reinitiated sedimentation in the late permian euxinic signals are most prominent in the upper permian sediments with low organic carbon and high sulfur contents and gradually wane in the lower triassic the observed features may have been generated in a strongly euxinic ocean in which high bacterioplankton productivity sustained prolific microbial sulfate reduction in the sediment and or water column providing hydrogen sulfide to form pyrite this scenario requires nearly complete anaerobic decomposition of predominantly labile marine organic matter om without the necessity for a complete collapse of primary marine productivity similar geochemical variations could have been achieved by widespread oxidation of methane by sulfate reducers after a methanogenic burst in the late permian both scenarios could have provided similar kill mechanisms for the latest permian mass extinction despite the moderate thermal maturity of the section om in all studied samples is dominantly terrestrial and or continentally derived recycled and refractory ancient om we argue that as such the quantity of the om in the section mainly reflects changes in terrestrial vegetation and or weathering and not in marine productivity at opal creek a pyrite layer and

correlating terrestrial signatures from biomarker distributions δ13c and palynology in fluvio deltaic deposits from nw australia triassic jurassic abstract a multidisciplinary study using molecular and organic isotope geochemistry petrology and palynology has been used to establish palaeoenvironmental conditions of fluvio deltaic deposits from the delambre 1 well western australia triassic jurassic changes in higher plant biomarker distributions correlate with 1 brackish water environments 2 major changes in composition of spore and pollen assemblages 3 variations in types of sedimentary facies and 4 stable carbon isotopic composition of higher plant biomarkers these changes are all consistent with the occurrence of climatic shifts in northwestern australia during triassic jurassic periods established by parrish j t bradshaw m t brakel a t mulholland s m totterdell j m yeates a n 1996 palaeoclimatology of australia during the pangean interval palaeoclimates 1 241 281 the combustion marker benzo e pyrene is abundant in samples that contain pollen from falcisporites australis the decline of f australis and the rapid emergence of assemblages dominated by corollina spp at the end of the triassic marks a rapid pollen spore extinction event at the triassic jurassic boundary there is an increase in relative abundance of the higher plant biomarkers cadalene and simonellite in a prodeltaic facies the 13 c values of between 26 9 and 24 9 for retene are consistent with a source from class i conifer resinites and relate to samples abundant in araucariacian conifers in the early middle jurassic where facies are characterized as pro distal deltaic

guidelines for evaluating petroleum source rock using programmed pyrolysis rock eval pyrolysis is used to rapidly evaluate the petroleum generative potential and thermal maturity of rocks accurate conclusions require programs every 30 60 ft 9 18 m understanding of interpretive pitfalls and supporting data such as visual kerogen vitrinite reflectance and elemental analyses the generative potential of coals is commonly overestimated by pyrolysis and is best determined by elemental analysis and organic petrography most coals show high s2 s3 5 and low hi values 300 mg hc g toc migrated oil and mud additives which alter rock eval data can sometimes be removed by special processing for immature rocks bimodal s2 peaks and pi values over 0 2 indicate contamination pyrolysis downgrades organic poor clay rich rocks which show lower hi and higher tmax values than isolated kerogen because of adsorption of pyrolyzate on the clays tmax values for small s2 peaks 0 2 mg hc g toc are unreliable tmax is affected by maturation organic matter type contamination and the mineral matrix s3 is sensitive to inorganic and adsorbed carbon dioxide and to instrumentation problems acidification of carbonate rich samples and proper maintenance improves s3 measurement constant sample weights 100 mg are recommended below a threshold weight tmax increases by up to 10 c and other parameters decrease organic rich samples which overload the detector can be diluted with carbonate detector linearity is determined by pyrolyzing various weights of an organic rich rock

northern hemisphere climate control on the environmental dynamics in the glacial black sea lake abstract the marine isotope stage mis 3 stands out due to its abrupt changes from cold and dry stadials to warm and humid interstadials the so called dansgaard oeschger cycles that also affected temperature and rainfall in the black sea region this study is based on a gravity core from the southeastern se black sea that covers the last glacial lake stage from 64 to 20 ka bp by using the composition of major and trace elements in the sediments terrestrial plant derived n alkane flux and sr ca from benthic ostracods we reconstruct the variability of riverine and aeolian input salinity and productivity in the se black sea region in response to the northern hemisphere climate oscillations during colder and drier stadials the aeolian input increased relative to the riverine discharge potentially due to southward shifted and or stronger westerly winds and due to changes in the vegetation cover an evaporation exceeding freshwater supply by rainfall and rivers possibly caused higher salinity and a lower lake level the environmental status during mis 4 and 2 is very much comparable with the stadial conditions during mis 3 during warmer and more humid interstadials lower salinity and presumably positive lake level changes most likely resulted from increased precipitation and river discharge this likely increased primary productivity through an augmented nutrient supply lowest average salinities are suggested for the middle part of mis 3 in response to enhanced meltwater from the disintegrating fennoscandian ice sheet and or by generally more humid conditions

the marine osmium isotope record over the past decade the marine osmium isotope record has been developed into a new tracer in palaeoceanographic research several analytical developments particularly in the past few years have significantly increased our ability to study the behaviour of osmium in the surficial environment the 187os 188os and osmium concentration of seawater river water rain and hydrothermal vent fluids have been measured directly recently the behaviour of osmium in estuaries critical for estimating the marine residence time of osmium has been studied our knowledge of the surficial osmium cycle has thus significantly improved in addition reconstructions of past variations in the marine 187os 188os recently have been extended back into the mesozoic this review attempts to summarize our current understanding of the marine osmium system present and past the 187os 188os of seawater during the cenozoic to first order mimics the marine 87sr 86sr record it is therefore tempting to interpret both records as reflecting increased input of radiogenic osmium and strontium resulting from enhanced continental weathering regulated by climatic tectonic processes however the marine osmium isotope system differs fundamentally from the marine strontium isotope system this review emphasizes three important differences first large impacts are capable of resetting the 187os 188os to unradiogenic values without significantly affecting the marine strontium system second organic rich sediments are characterized by high 187re 188os resulting 187os 188os ingrowth trajectories are similar to the average slope of the cenozoic 187os 188os seawater record trends towards more radiogenic 187os 188os seawater therefore can be caused by weathering of organic rich sediments at a constant rate third the marine residence time of osmium is sufficiently short to capture short periodic glacial interglacial fluctuations that are inaccessible to the buffered marine strontium isotope system this offers the opportunity to discriminate between high frequency climatic and low frequency tectonic forcing

delineating vulnerability of karst aquifers using hydrochemical tracers in southwestern china karst groundwater is particularly vulnerable to contamination long term hydrochemistry auto monitoring combined with laboratory analyses has shown that the chemograph demonstrates changes in the system in order to determine the primary groundwater vulnerability a relationship between hydrochemical changes and the origin of vulnerability in six karst spring catchments in southwestern china is discussed the reason and physical meaning of the hydrochemical changes in the spring are explained based on tracer tests and physical chemical process in the s31 spring the results prove that the hydrochemical changes show the origin of vulnerability and also can be its expression generally autogenic recharge in bare karst is concentrated in epikarst zone forming bypass flow and shaft flow which causes dilution of ca2 the chemograph reflects the percentage of concentrated and diffuse recharge the higher the ratio of concentrated recharge the higher the grade of groundwater vulnerability due to ca2 hco3 sec ph and temperature in water can change for kinds of reasons during their transport more karst systems with variable natural and human factors are discussed protective layer allogenic water recharge and transform of surface stream and subterranean river can change the origin shape of hydrochemical curve under this circumstance more indicators need to be monitored especially contaminant related ions such as nitrate in order to clearly understand the contribution of concentrated and diffuse recharge to water chemistry after comparing the traditional groundwater vulnerability assessment and the methods based on hydrochemical change rainfall protective layer epikarst transient storage and karst network should be more concerned when the work is done auto monitoring of karst is more and more popular in southwestern china therefore it is suggested that the hydrochemical methods should be used as a primary expression of vulnerability giving a direct reference for karst water management

mo total organic carbon covariation in modern anoxic marine environments implications for analysis of paleoredox and paleohydrographic conditions 1 sedimentary molybdenum mo s has been widely used as a proxy for benthic redox potential owing to its generally strong enrichment in organic rich marine facies deposited under oxygen depleted conditions a detailed analysis of mo s total organic carbon toc covariation in modern anoxic marine environments and its relationship to ambient water chemistry suggests that 1 mo s while useful in distinguishing oxic from anoxic facies is not related in a simple manner to dissolved sulfide concentrations within euxinic environments and 2 patterns of mo s toc covariation can provide information about paleohydrographic conditions especially the degree of restriction of the subchemoclinal water mass and temporal changes thereof related to deepwater renewal these inferences are based on data from four anoxic silled basins the black sea framvaren fjord cariaco basin and saanich inlet and one upwelling zone the namibian shelf representing a spectrum of aqueous chemical conditions related to water mass restriction in the silled basin environments increasing restriction is correlated with a systematic decrease in mo s toc ratios from 45 5 for saanich inlet to 4 5 1 for the black sea this variation reflects control of mo s by mo aq which becomes depleted in stagnant basins through removal to the sediment without adequate resupply by deepwater renewal the basin reservoir effect the temporal dynamics of this process are revealed by high resolution chemostratigraphic data from framvaren fjord and cariaco basin sediment cores which exhibit long term trends toward lower mo s toc ratios following development of water column stratification and deepwater anoxia mo burial fluxes peak in weakly sulfidic environments such as saanich inlet owing to a combination of greater mo aq availability and enhanced mo transport to the sediment water interface via fe mn redox cycling and are lower in strongly sulfidic environments such as the black sea and framvaren fjord these observations demonstrate that at timescales associated with deepwater renewal in anoxic silled basins decreased sedimentary mo concentrations and burial fluxes are associated with lower benthic redox potentials i e more sulfidic conditions these conclusions apply only to anoxic marine environments exhibiting some degree of water mass restriction e g silled basins and are not valid for low oxygen facies in open marine settings such as continent margin upwelling systems

terrestrial sources as the primary delivery mechanism of mercury to the oceans across the toarcian oceanic anoxic event early jurassic abstract this study evaluates the utility of sedimentary mercury hg contents as a proxy for fingerprinting ancient massive volcanism which is often associated with biogeochemical perturbations herein we present new hg geochemical data from anoxic marine basins across the toarcian oceanic anoxic event t oae 183 ma as a test of the complex hg cycle the t oae was likely initiated by the main eruptive phase of the karoo ferrar large igneous province which caused a subsequent cascade of environmental perturbations and resulting mass extinction at present the leading interpretation of sedimentary hg anomalies has been volcanogenic outgassing as the primary source our study and compilation results suggest however that hg toc anomalies were restricted to shallow water and or proximal environments while deep water more distal depositional settings document no significant hg related anomalies furthermore asynchronous stratigraphic deviations in hg enrichments favor terrestrially sourced materials and local redox variability rather than direct volcanogenic emissions as a primary control mechanism additionally hg isotope signatures from our only study site documenting an hg anomaly are also consistent with a terrestrial hg origin during the t oae therefore our results suggest that hg anomalies in the geological record need to be re evaluated as a smoking gun proxy that only infers volcanogenic inputs

distribution patterns of the elements in the ocean a synthesis the observed partition patterns of elements between a marine solid phase e g pelagic clays deep sea manganese nodules seamount manganese crusts and plankton and seawater can be to the first approximation explained by the james and healy adsorption model except for ce co mn pb and tl which are concentrated in the solid phase through oxidative uptake processes in other words the composition of seawater is mainly controlled by the compositions of source materials i e the crustal igneous rocks and primary magmatic volatiles and the physicochemical principles regulating the adsorption processes of various chemical species in seawater onto oceanic pelagic clays

osmium isotope evidence for the regulation of atmospheric co2 by continental weathering the long term stability of earth9s climate throughout the phanerozoic stands in marked contrast to the dramatic fluctuations that have taken place on time scales as short as a few years reflecting the high efficiency of longer term climate regulation through negative feedbacks a fundamental mechanism is thought to involve control of co 2 in the ocean atmosphere system through continental weathering although unambiguous high resolution data supporting this hypothesis have hitherto not been available organic rich mud rocks from yorkshire england which were deposited during the toarcian oceanic anoxic event ca 181 ma early jurassic contain evidence of an exceptionally large excursion in the 187 os 188 os ratio of contemporaneous seawater from 0 4 to 1 0 the most likely explanation for this excursion is that it resulted from a transient increase in global continental weathering rates of 400 800 the os isotope excursion coincided with a well documented global 13 c excursion of 6 that affected all the major biospheric reservoirs of the time higher mean global temperatures caused global chemical weathering rates to increase substantially while in turn chemical weathering was very effective in reducing the elevated levels of atmospheric co 2 and the high temperatures to preexcursion levels

an evaporite based high resolution sulfur isotope record of late permian and triassic seawater sulfate abstract variations in the sulfur isotope composition of dissolved marine sulfate through time reflect changes in the global sulfur cycle and are intimately related to changes in the carbon and oxygen cycles a large shift in the sulfur isotope composition of sulfate at the permian triassic boundary has been recognized for long time and a number of studies were carried out to understand the causes and significance of this shift however data for the middle and late triassic are very sparse and the stratigraphic evolution of the sulfur isotope composition of seawater is poorly constrained due to the small number of samples analyzed and or due to the limited stratigraphic intervals studied moreover in the last few years the triassic timescale has significantly changed due to a wealth of new radiometric and stratigraphic data in this study we show that for the late permian and the triassic it is possible to obtain a precise reconstruction of the evolution of the sulfur cycle for parts of it at sub million year resolution by analyzing exclusively gypsum and anhydrite deposits we base our reconstruction on new data from the middle and late triassic evaporites of northern switzerland and literature data from evaporites from germany austria italy and the middle east we propose a revised correlation between the well dated marine tethyan sections in northern italy and the evaporites from northern switzerland and from the germanic basin calibrated to the newest radiometric absolute age scale this new correlation allows for a precise dating of the evaporites and constructing a composite sulfur isotope evolution of seawater sulfate from the latest permian lopingian epoch to the norian we show that a rapid positive shift of approximately 24 at the permian triassic boundary can be used to constrain seawater sulfate concentrations in the range of 2 6 mm thus higher than previous estimates but with less rapid changes finally we discuss two possible evolution scenarios for the middle triassic negative shift to values of 15 that subsequently remain constant during the late triassic

late permian early triassic environmental changes recorded by multi isotope re os n hg data and trace metal distribution from the hovea 3 section western australia abstract the temporal coincidence between the late permian mass extinction lpme and the emplacement of siberian trap basalts suggests a causal link between the two events here we discuss stratigraphic changes of organic and inorganic including isotopic geochemical properties of marine sediments across the permian triassic boundary ptb in the hovea 3 core western australia a key ptb section in the southern neo tethys ocean these data are compared with published data from the meishan section southern china and from the opal creek section in western canada providing a view of tethys and panthalassa changes at the ptb trace metal and n isotopic data together with organic matter properties suggest that anoxic conditions were established prior to the lpme intensified close to the lpme and continued with photic zone euxinia into the early triassic for the hovea 3 section re os ages confirm changhsingian 253 5 1 4 ma deposition of the dated interval sampled immediately below the stratigraphic level characterized by major lithological and isotopic changes evaluation of re os n and hg elemental and isotopic data for hovea 3 suggests that anoxic conditions in the latest permian were generally unrelated to direct magmatic contributions a major increase in the initial os isotopic ratio of lower triassic shales suggest an 8 increase in the early triassic continental runoff based on moderately conservative assumptions for end members contributing os to the permian triassic ocean comparison to other ptb sections confirms a global signal of increasing re os ratios in the late permian and major and long lived changes in the isotopic composition of the post extinction ocean a distinct peak in hg concentrations carrying a volcanic isotopic signature also identified in other ptb sections likely represents a major pulse of siberian trap volcanism this hg peak in the hovea 3 section however is detected above the stratigraphic level containing multiple other widely recognized and more permanent geochemical changes therefore direct volcanic inputs to the permian triassic ocean likely post date the lpme in this western australian section

high resolution δ13ccarb chemostratigraphy from latest guadalupian through earliest triassic in south china and iran large carbon cycle perturbations are associated with the end permian mass extinction and subsequent recovery but late permian lopingian carbon cycle dynamics prior to the mass extinction event remain poorly documented here we present a high resolution 13ccarb chemostratigraphic framework from latest guadalupian to earliest triassic time calibrated with high resolution conodont biostratigraphy and high precision geochronology we observe two large negative excursions in 13ccarb the first in uppermost guadalupian strata and the second at the end of the changhsingian stage and between these events distinctive excursions from the middle wuchiapingian to the early changhsingian the end changhsingian excursion represents a major reorganization of the global carbon cycle associated with the end permian mass extinction however the extent to which the end guadalupian and wuchiapingian changhsingian boundary excursions result from local versus global controls remains unresolved regardless of their underlying causes these three excursions provide chemostratigraphic markers for global correlation of lopingian strata

global mercury cycle during the end permian mass extinction and subsequent early triassic recovery abstract the end permian mass extinction epme at 252 ma was the most severe extinction in the phanerozoic marine ecosystems devastated by the epme had a highly prolonged recovery and did not substantially recover until after the smithian spathian substage boundary ssb of the lower triassic 5 to 9 ma after the epme while the siberian traps large igneous province stlip has been invoked as the driver of the mass extinction there remains controversy as to the cause of the protracted early triassic recovery although renewed stlip volcanism has been suggested these previous studies though have drawn conclusions based on geochemical records of sediments deposited in northern latitude settings to investigate the relationship between stlip and extinction recovery processes on a global base we examined mercury chemostratigraphy including mercury concentrations and isotopes from high southern latitude and equatorial sections that span the late permian changhsingian to early triassic spathian substage successions the guryul ravine section kashmir in northern india and the chaohu section in southern china organic and inorganic carbon isotope data define the epme horizon in the chaohu section and the ssb in the guryul ravine section respectively hg toc values are dramatically elevated approaching the epme horizon and maintain high values until the lower isarcicella isarcica conodont zone the base of which is believed to be the end of the mass extinction in the stratigraphically overlying beds hg toc generally displays lower values with slight fluctuations through the two sections these fluctuations are likely related to the increased terrestrial hg influx associated with strong chemical weathering in the early triassic as shown by a positive correlation between the contents of hg and al and by less positive 199 hg values in early triassic samples our data presenting the first southern hemisphere hg record from guryul ravine in combination with previous results indicates that anomalous high mercury deposition at the epme occurred globally the generally positive 199 hg values at this time reflects atmospheric derived hg consistent with a volcanic hg source which we suggest indicates global impact of stlip eruption in contrast there is no evidence for a global hg toc anomaly during the protracted early triassic biotic recovery suggesting that potentially renewed stlip volcanism had only a northern hemisphere influence on the global hg cycle this more limited impact may still have played a role in the delayed early triassic recovery

definition of new trace metal proxies for the controls on organic matter enrichment in marine sediments based on mn co mo and cd concentrations abstract trace metal enrichments in sedimentary deposits are of prime interest because they are governed by processes that also control the production and preservation of organic matter consequently trace metals have been used in reconstructions of the palaeo depositional environment of organic rich deposits but most of these studies have primarily focused on hydrographically restricted basins and the response of trace metals to changing redox conditions whereas the role of trace metals in the nutrient cycle and primary productivity in upwelling settings remains relatively unexplored in this study we present a comprehensive database of published trace metal concentration data in modern organic rich deposits from a variety of marine settings scrutiny of the compiled dataset has resulted in the development of novel trace metal based proxies that allow the distinction between two marine end member depositional settings that are associated with enhanced organic carbon burial open marine settings on the continental margin associated with upwelling e g namibian margin and hydrographically restricted marginal marine basins e g black sea it is shown that high cd mo values are typical for sediments from continental margin upwelling settings whereas co and mn concentrations expressed as co mn values are high in samples from hydrographically restricted marine basins the cd mo ratios are thought to track the relative importance of productivity versus preservation with high values in productivity driven systems attributed to the transfer of cd to the sediments from re mineralised plankton biomass co mn values on the other hand are believed to reflect the supply and reactive behaviour of co and mn and can be used to assess circulation patterns in the water column and the relative contribution of deep versus surface river water influx to the basin it is demonstrated that the combined use of the cd mo and co mn proxies provides a highly effective way to distinguish modern recent marine sedimentary environments which holds promise for its use in palaeo environmental reconstructions

a potential biomarker for the permian triassic ecological crisis abstract a unique biomarker a c33 n alkylcyclohexane n heptacosylcyclohexane which strongly increases in abundance within the extinction interval of the end permian ecological crisis is here reported from the key permian triassic p tr marine section in greenland prior to this study this compound had been known from early triassic organic rich marine rocks and oils from the northern perth basin western australia for two decades we have identified the compound in high relative abundance in 29 samples from p tr marine sections from two separate paleogeographic localities from laurasia and gondwana relative concentrations of the c33 n alkylcyclohexane show similar changes to the relative abundances of extinct spinose acritarchs veryhachium and micrhystridium indicating that the source organism of the c33 n alkylcyclohexane is associated with the depositional environments facies in which the acritarchs are identified these organisms probably formed the cornerstone of the unique marine ecosystem that thrived in the extinction aftermath in the early triassic ocean

co variation of nitrogen isotopes and redox states through glacial interglacial cycles in the black sea abstract in all aquatic environments nitrogen cycling within the water column is strongly influenced by oxygen we hypothesize that the nitrogen isotopic composition 15 n of organic matter deposited in the sediments is a proxy for the redox state of the water column at the time of deposition we tested the hypothesis by measuring the bulk sedimentary 15 n values in a drill core from the black sea a basin that alternates between oxic less saline conditions and anoxic marine conditions on glacial interglacial time scales we reconstructed these changes in black sea redox conditions using sedimentary 15 n total organic carbon toc total nitrogen tn redox sensitive metals and micropaleontological data from a deep sea core dsdp site 380 the sedimentary data reveal that during the transitions between oxic and anoxic conditions 15 n values increased relative to the preceding and succeeding quasi steady state oxic and anoxic periods the results indicate that the reciprocal transitional states from anoxic to oxic conditions were accompanied by intense denitrification during the quasi stable oxic and anoxic states characterized by glacial fresh water and interglacial marine conditions nitrification and complete nitrate utilization respectively dominate the nitrogen cycle while other factors may influence the 15 n record our results support the hypothesis that the variations in nitrogen isotopic composition of organic matter are strongly influenced by changes in redox state in the black sea subphotic zone on glacial interglacial time scales and can be explained by a relatively simple model describing the effects of oxygen on the microbial processes that drive the nitrogen cycle in marine ecosystems our model suggests that the nitrogen isotopic composition of marine sediments on geological time scales can be used to reconstruct the redox state of the overlying water column

evidence for wildfire in the meishan section and implications for permian triassic events polynuclear aromatic hydrocarbons pahs and black carbon bc in sediments are powerful tools in the identification of the combustion process throughout geologic history in this study combustion derived pahs and bc were carefully investigated in sediments from the global stratotype section and point of the permian triassic p tr boundary in meishan china quantitative analyses of combustion derived pahs and bc demonstrate anomalously high concentrations in the boundary event beds that coincide with the mass extinction horizon the prevalence of parent polynuclear aromatics e g phenanthrene in pahs together with non metric multidimensional scaling analysis confirms that the pahs are mainly derived from vegetation burning instead of having a coal and or oil origin bc detected in sediment occurs in various forms from large irregular charcoal particles to fine aciniform soot with an equivalent reflectance of up to 3 5 the results strongly suggest that a wildfire occurred during the p tr boundary which served as one of the possible triggers of mass extinction on land the wildfire occurrence indicates that the o2 concentration of the atmosphere during or before the p tr mass extinction was probably 17 the temporal coincidence of the mass extinction with intensive volcanic eruption marine anoxia and wildfire events in the region of the meishan section provides new insight into the mechanisms of the p tr biotic crisis our results show that wildfires could have played an important role in the collapse of the ecosystem in the meishan p tr events

isotopic signatures of mercury contamination in latest permian oceans sedimentary records from the northwest margin of pangea and the tethys show anomalously high hg levels at the latest permian extinction boundary background 202 hg values are consistent with normal marine conditions but exhibit negative shifts coincident with increased hg concentrations hg isotope mass independent fractionation 199 hg trends are consistent with volcanic input in deep water marine environments in contrast nearshore environments have 199 hg signatures consistent with enhanced soil and or biomass input we hypothesize that the deep water signature represents an overall global increase in volcanic hg input and that this isotope signature is overwhelmed in nearshore locations due to hg from terrestrial sources high productivity nearshore regions may have experienced stressed marine ecosystems due to enhanced hg loading

paleo redox conditions during oae 2 reflected in demerara rise sediment geochemistry odp leg 207 abstract cretaceous black shales deposited under severe oxygen depletion are carriers of proxy signals for paleoenvironmental conditions using high resolution patterns of iron and sulfur speciation stable sulfur isotope discrimination and trace element enrichment from black shale sequences of sites 1258 and 1260 we identified alterations of the depositional environment during the cenomanian turonian boundary event oae 2 in the southern north atlantic odp leg 207 demerara rise changes in redox conditions are suggested by high ratios of reactive to total iron which indicate that pyrite was formed both in the water column and within the sediment this corresponds to euxinic paleoenvironmental conditions with at least temporarily free dissolved sulfide in the water column a situation similar to the modern deep black sea in addition besides fixation of sulfide as iron sulfide organic matter acted as an important sulfur trap during early diagenesis stable sulfur isotope fractionation went through a minimum within the oae 2 interval indicating enhanced sulfur isotope discrimination during highest burial of organic matter om potentially due to lower burial efficiency of reduced sulfur and or a higher contributions from the oxidative part of the sulfur cycle e g in the water column or the surface sediments elevated fe al and co al values within the cenomanian turonian interval confirm euxinic conditions but at the same time require a zone where reducing but non sulfidic conditions prevail allowing reductive fe and co mobilization in oxygen depleted nearshore sediments the existence of an expanded oxygen minimum zone omz is demonstrated by extremely low mn al ratios a change in the trace metal tm inventory of seawater is postulated from a decline in seawater derived tm enrichment because hypoxic or even euxinic environments form an important sink for tm the enlargement of euxinic depositional areas at the global onset of black shale deposition during oae 2 have likely led to a drawdown of the seawater tm reservoir

environmental and engineering problems of karst geology in china karst terrane is generally regarded as a fragile and vulnerable environment its underground drainage system can aggrevate both drought and flood problems the lack of filtration in an underground conduit makes waste disposal more difficult and the lack of soil cover in bare karstland can enhance deforestation moreover karst terranes are quite often haunted by a series of engineering problems such as water gushing into mines or transportation tunnels leakage from reservoirs and failure of building foundations in china there are more than 200 cases of karst collapse which include many thousands of individual collapse points some of these are paleo and natural collapses but most of them are modern collapses induced by human activities and they have caused serious damage many factors such as geologic structure overburden thickness and character lithologic features of karstified rock and intensity of karstification are related to development and distribution of modern collapses however china s karst is mainly developed in pre triassic old phase hard compact carbonate rock consequently most modern collapses have occurred only in the overlying soil so it is understandable that the fluctuation of the water table in the underlying karstified strata plays an important role in the process of collapse nevertheless there are different explanations as to how the groundwater activities can induce collapse

significance of δdkerogen δ13ckerogen and δ34spyrite from several permian triassic p tr sections for the first time we report d of kerogen dkerogen for three permian triassic p tr sequences hovea 3 perth basin western australia jameson land east greenland and lusitaniadalen spitsbergen we have compared dkerogen with 13c of kerogen 13ckerogen and 34s of total reduced inorganic sulfur tris essentially pyrite 34spyrite of all the sections and for one sample set with 13c of carbonate 13ccarbonate to establish i similarities between the sections and ii evaluate whether these signals are local and or global stable isotope shifts occur for all three sample sets either at the p tr transition western australia or coinciding with the marine ecosystem collapse spitsbergen and east greenland dkerogen reflects organic matter om kerogen type and is not sensitive to the low level of thermal maturation reliable palaeoenvironmental information in terms of the use of d can therefore only be obtained for the p tr transition from hydrogen compound specific isotope analyses csia of biomarkers nabbefeld et al 2010b the negative shifts in 13ccarbonate primary and 13ckerogen are attributed to the release of 13c depleted carbon into the atmosphere whereas the isotopic excursions in 34spyrite relate to palaeoredox changes however the global coincidence in timing of the shifts in dkerogen 34spyrite and 13ckerogen suggests a relation between the sulfur carbon and hydrogen cycles the negative shifts in 13ccarbonate primary are in general attributed to the release of 13c depleted source of carbon into the oceans and atmosphere whereas 13ckerogen can reflect the latter in certain cases but can also be superimposed by varying sources of om kerogen type isotopic excursions in 34spyrite relate to global changes in the palaeoredox conditions that affect sulfur cycling in the ancient seas

pattern of marine mass extinction near the permian triassic boundary in south china the meishan section across the permian triassic boundary in south china is the most thoroughly investigated in the world a statistical analysis of the occurrences of 162 genera and 333 species confirms a sudden extinction event at 251 4 million years ago coincident with a dramatic depletion of 13ccarbonate and an increase in microspherules

hot acidic late permian seas stifle life in record time abstract the end of permian time 252 251 ma hosts the largest mass extinction in earth history yet events heralding this global catastrophe remain intensely disputed we present a chemostratigraphic marker the 187re 188os ratio which soars to unprecedented levels approaching the permo triassic boundary these ratios are tied to profound trace element changes and a precise re os time record at 252 ma preserved in black shales from east greenland and the mid norwegian shelf within a 36 meter shale section an 80 fold increase in re concentrations two fold for os signals seawater conditions that became increasingly inhospitable to life unwavering initial 187os 188os ratios of 0 6 preclude mafic volcanism and meteorite impact as the direct cause of late permian anoxia we argue that extraordinarily high 187re 188os ratios are the hallmark of simultaneously rising ocean temperature and acidity leading to loss of oxygen and the stifling of life in latest permian time

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

chemical signals for oxidative weathering predict re os isochroneity in black shales east greenland abstract re and os isotopes in shales are increasingly used for precise and accurate geochronology and for tracking rates of continental weathering in the geologic past moreover trace element compositions of organic rich shales reveal paleoredox conditions and properties of shale organic matter om useful for lithostratigraphic correlations chemical weathering alters the original shale composition and hence may compromise geologic interpretations based on geochemical data here we compare re os isotopes trace elements and om properties in correlative shales from outcrops and nearby drillcore to quantify the effects of weathering we define chemical parameters that distinguish weathered from pristine shale in samples that are macroscopically identical black shale from the ravnefjeld formation in east greenland yields disturbed re os isotope systematics for outcrop samples and highly precise re os isochron ages for drillcore geochemical data show that re os and common os are hosted in the organic matter rather than sulfides re and os both show mobility during weathering combined use of rock eval pyrolysis indices and sulfur contents documents oxidation of both om and pyrite thereby providing a valuable chemical criterion to assess invisible shale weathering further studies on chemically diverse shales will test the widespread application of these criteria as weathering indicators systematic differences in major and trace element content and kerogen quality between weathered and fresh shale samples are used to characterize and quantify weathering effects the character of the om in shales is most telling ravnefjeld data are compared with data from time correlative shales from the mid norwegian shelf georgiev et al 2011 hot acidic late permian seas stifle life in record time earth planet sci lett 310 389 400 to present a strategy for identification of re os isochroneity in advance of re os analytical work our recent compilation and comparison of upper permian shales from widely separated sequences on pangea s margins reveal exceptionally high re os ratios on a global scale we suggest upper permian shales may have significantly influenced the cenozoic e g eocene 187os 188os ratio of seawater on their exposure and weathering

osmium isotope evidence for volcanism across the wuchiapingian changhsingian boundary interval abstract two negative carbon isotope excursions 3 5 6 5 across the wuchiapingian changhsingian boundary wcb are observed globally sections in china canada and iran however the causative mechanism of these excursions is debated here high resolution osmium isotope 187os 188os or osi chemostratigraphy of four globally correlated wcb sections 3 in china meishan shangsi and lianyuan and 1 in canada buchanan lake show two separate osi excursions to less radiogenic compositions that are coincident with the carbon isotope shifts for two of the south china sections lianyuan meishan in contrast only a single osi excursion to less radiogenic compositions coinciding with the earliest changhsingian carbon isotope shift is observed for the shangsi and buchanan lake sections the osi shift is interpreted to reflect increased unradiogenic os input from basaltic magmatism in south china possibly related to the emeishan large igneous province lip however 187os 188os data suggest that only the earliest changhsingian volcanism had global impact on both the ocean and atmosphere the lack of any evidence for a biotic event associated with the wcb therefore may have been due to the more regional rather than global impact of volcanism during the latest wuchiapingian in contrast during the earliest changhsingian volcanism was sufficient to cause a more global signal in the ocean osmium record but was inadequate or too prolonged to drive any significant environmental change volcanism however may have provided the isotopically light carbon that drove the negative carbon isotope excursions across the wcb

cessation of a productive coastal upwelling system in the panthalassic ocean at the permian triassic boundary abstract while the end permian extinction in the marine realm is well known from the tethys ocean it remains little studied in the vast panthalassic ocean opal creek alberta canada is a biostratigraphically continuous permian triassic boundary ptb section that is interpreted to have been deposited in a deep outer shelf setting along the panthalassic western margin of pangaea significant organic carbon and nitrogen isotope excursions precede the extinction of the dominant late permian benthic organisms siliceous sponges geochemical comparison with underlying guadalupian age rocks and analysis of the conodont fauna suggest that the latest permian at opal creek records the shutdown of a productive cold water upwelling ecosystem with a mid water column oxygen minimum followed by the transition to a warm and less vigorously circulating system with a bottom water oxygen minimum the transition from a low diversity cold water conodont fauna in the middle permian to a more diverse latest permian fauna containing equatorial species coincides with a transition from elevated 15n values characteristic of coastal zones with denitrification in a mid water oxygen minimum to more normal marine values a spike in the 13c of organic carbon following a latest permian marine transgression along western pangaea is here attributed to transient increased productivity in the photic zone preceding the main extinction likely related to the synergistic effects of warming increased nutrient runoff and residual upwelling this is followed by an equilibration to lower 13corg values characteristic of a lower productivity regime in the early triassic

geochemical paleoredox indicators in devonian mississippian black shales central appalachian basin usa the degree of anoxia that existed during accumulation of devonian mississippian black shales in central kentucky has been debated widely in this study geochemical data were used to elucidate paleodepositional environments for these units using analyses from ten cores collected from the outcrop belt in central kentucky sulfur carbon and selected trace element relationships were compared the sunbury shale tournasian lower mississippian and the cleveland and huron members of the ohio new albany shale fammenian upper devonian show different relationships between carbon sulfur and trace elements c s fe relationships for the sunbury suggest anoxic possibly even euxinic conditions prevailed during sediment accumulation analysis of c s fe data suggests that the cleveland may have accumulated under anoxic conditions with intermittent dysoxia whereas the huron member may have accumulated under a relatively wide range of conditions from anoxic to dysoxic to possibly oxic these three units exhibit different degrees of trace element enrichment with the approximate order of enrichment relative to an average shale being mo pb zn v ni cu cr co the sunbury shows the highest levels of enrichment followed by the cleveland with the huron showing only slight enrichment for most of these trace elements differing degrees of enrichment may reflect differences in depositional environment during accumulation high mo concentrations in the sunbury generally 200 550 ppm may infer euxinic conditions prevailed during sediment accumulation the cleveland and the huron both show considerably lower mo contents averaging around 100 ppm geochemical ratios including ni co v cr and v v ni also indicate variable paleoredox conditions for these shales based on previously established thresholds v cr and ni co ratios infer at least anoxic conditions during accumulation of the sunbury anoxic to dysoxic conditions during cleveland accumulation and dysoxic to oxic conditions for the huron v v ni ratios tend to indicate consistently lower oxygen regimes than do other paleoredox indicators and this discrepancy is greatest for the huron member it is suggested that thresholds established for paleoredox indicators in previous studies should not be applied strictly but that relative differences in these indicators collectively can infer variations in the degree of anoxia in addition relationships between corg and redox elements may help elucidate the role of anoxia in om accumulation it may be concluded from this study that the devonian mississippian black shales of central kentucky accumulated under variable bottom water conditions at least anoxic conditions prevailed during accumulation of much of the sunbury shale and the upper part of the cleveland member and possibly euxinic conditions for the sunbury bottom water conditions may have been intermittently anoxic and dysoxic during deposition of the lower cleveland during accumulation of the huron member it is likely that conditions ranged from anoxic to dysoxic to marginally oxic possibly being close to normal marine conditions at times during accumulation of the lowermost huron sediments

ammonium ocean following the end permian mass extinction abstract the aftermath of end permian mass extinction was marked by a 5 million year interval of poorly understood extreme environments that likely hindered biotic recovery contemporary nitrogen isotope variations are considered using a new conceptual model to support a scenario that shows intensive nitrate removal processes gradually depleted the global oceanic nitrate inventory during long lasting oceanic anoxia enhanced nitrogen fixation shifted the oceanic nitrogenous nutrient nutrient n inventory to an ammonium dominated state ammonium is toxic to animals and higher plants but fertilizes algae and bacteria this change in ocean chemistry could account for the intense and unexplained losses of nektonic taxa and the proliferation of microbial blooms in the early triassic the transition from a nitrate ocean to an ammonium ocean was accompanied by a decrease in respiration efficiency of organisms and a shrinking oceanic nutrient n inventory ultimately leading to generally low productivity in the early triassic oceans these unappreciated nutrient changes during episodes of prolonged ocean anoxia may be the key life limiting factor at such times

a comparison of thermal maturity parameters between freely extracted hydrocarbons bitumen i and a second extract bitumen ii from within the kerogen matrix of permian and triassic sedimentary rocks abstract in this study we compared various maturity dependent aromatic steroid and triterpenoid hydrocarbon ratios in bitumens that are freely extractable from sedimentary rocks bitumen i with those in second extracts that comprised hydrocarbons closely associated with the kerogen mineral matrix bitumen ii bitumen ii was released through kerogen isolation and demineralisation using hcl and hf h3bo3 the samples studied although of similar age come from different localities they represent a range of facies and two kerogen types ii and iii and all were deposited under marine conditions the results show that the more stable isomers of methylnaphthalene mn and methylphenanthrene mp are relatively more abundant in bitumen ii the difference between the methylnaphthalene ratio mnr of bitumens i and ii when plotted against the ratio of clay to total organic carbon clay toc gives an excellent correlation r2 0 88 the highest clay toc ratio corresponds with the biggest difference in mnr for the respective bitumens consistent with the more stable isomers being preferentially retained within the clay kerogen matrix since the mp isomers are higher in bitumen ii than in bitumen i it was anticipated that their methylphenanthrene index mpi 1 values a commonly used measure of thermal maturity would also be different for most samples the measured mpi 1 in bitumen i is generally higher than that in bitumen ii except for three samples thus showing a bias towards a lower thermal maturity for the second extract the opposite is true of the mp ratio and mnr this may be attributed to the fact that phenanthrene p which is part of the denominator in mpi 1 is more stable than its methylated counterparts steroid and triterpenoid maturity parameters also showed differences between the two extracts with c27 diasterane sterane and ts ts tm being higher in bitumen i only the former parameter is positively correlated with the clay toc ratio suggesting that clay content probably influences the diagenetic transformation of steroid precursors to diasteranes the observed differences between the maturity parameters of bitumen i and bitumen ii may be especially important in sedimentary rocks that contain high percentages of clay minerals

siberian gas venting and the end permian environmental crisis abstract the end of the permian period is marked by global warming and the biggest known mass extinction on earth the crisis is commonly attributed to the formation of the siberian traps large igneous province although the causal mechanisms remain disputed we show that heating of tunguska basin sediments by the ascending magma played a key role in triggering the crisis our conclusions are based on extensive field work in siberia in 2004 and 2006 heating of organic rich shale and petroleum bearing evaporites around sill intrusions led to greenhouse gas and halocarbon generation in sufficient volumes to cause global warming and atmospheric ozone depletion basin scale gas production potential estimates show that metamorphism of organic matter and petroleum could have generated 100 000 gt co2 the gases were released to the end permian atmosphere partly through spectacular pipe structures with kilometre sized craters dating of a sill intrusion by the u pb method shows that the gas release occurred at 252 0 0 4 million years ago overlapping in time with the end permian global warming and mass extinction heating experiments to 275 c on petroleum bearing rock salt from siberia suggests that methyl chloride and methyl bromide were significant components of the erupted gases the results indicate that global warming and ozone depletion were the two main drivers for the end permian environmental crisis we demonstrate that the composition of the heated sedimentary rocks below the flood basalts is the most important factor in controlling whether a large igneous provinces causes an environmental crisis or not we propose that a similar mechanism could have been responsible for the triassic jurassic 200 ma global warming and mass extinction based on the presence of thick sill intrusions in the evaporite deposits of the amazon basin in brazil

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

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

synthetic fluid inclusions in natural quartz ii application to pvt studies synthetic fluid inclusions have been used to determine volumetric properties of h2o and a 20 wt kcl solution from 300 700 c and 1 3 kb comparison of results obtained for h2o with previously published data indicates that the synthetic fluid inclusion technique provides pvt data that are within a few percent of those obtained from conventional pvt studies this technique thus provides a fast relatively simple means of determining pvt properties of many fluids of geologic interest

timing duration and causes for late jurassic early cretaceous anoxia in the barents sea abstract re os isochron ages for black shales of the hekkingen formation in the barents sea constrain the onset 157 7 1 3 ma and termination 138 8 1 0 ma and thereby indicate a long duration 19 myr of widespread jurassic cretaceous anoxia in the arctic integration of these new re os ages with published radiometric ages ammonite biostratigraphy and geomagnetic polarity chrons shows shorter late oxfordian late kimmeridgian and longer berriasian stages relative to estimates in the 2012 and 2016 geological time scales late jurassic anoxia was likely the result of warming climate due to high atmospheric co2 levels from increased oceanic crust production rising temperatures enhanced weathering and nutrient supply increased productivity and slowed ocean circulation before a sea level rise brought anoxic waters onto continental shelves assessment of new and published os and sr isotopic data suggests that prolonged oceanic anoxia required a sustained co2 source from fast spreading rates and or longer subduction zones and spreading ridges to balance large burial of carbon in voluminous upper jurassic and lower cretaceous black shales

an assessment of the accuracy of isochore location techniques for h2o co2 nacl fluids at granulite facies pressure temperature conditions abstract synthetic h 2 o co 2 nacl fluid inclusions with xco 2 compositions ranging from 0 10 0 51 and relative salinities r s wt nacl wt nacl wt h 2 o of 6 to 23 9 wt have been produced in spontaneously nucleated forsterite diopside and orthopyroxene hosts molar volumes of the fluids at the pressure and temperature of formation have been calculated using microthermometric data from the fluid inclusions these p v t data are used to compare the accuracy of published methods of isochore location for h 2 o co 2 nacl fluids at elevated pressures and temperatures the results of these analyses show that isochores calculated with the mrk equation of bowers and helgeson geochim cosmochim acta vol 47 1247 1275 1983 reproduce the trapping pressures and temperatures well for fluids with xco 2 0 3 and up to 23 9 wt nacl for a fluid with xco 2 0 49 and relative salinity of 15 however the agreement is poor for these fluid compositions the observed molar volume is larger than that predicted from the mrk equation of bowers and helgeson and if not corrected will give isochores that are too low in pressure for a given temperature the ideal geometric mixing model of brown and lamb geochim cosmochim acta vol 53 1209 1221 1989 provides less satisfactory results for the fluid compositions studied

biogeochemical evidence for euxinic oceans and ecological disturbance presaging the end permian mass extinction event article i nfo the permian triassic boundary event at 252 2 ma marks the largest extinction of marine fauna in the phanerozoic and there is a wide consensus that the extinction coincided with an intense oceanic anoxic event thestratotypeofthechanghsingianstage preciselyconstrainedbytheptbglobalstratotypesectionandpoint gssp and the gssp for the wuchiapingian changhsingian boundary both at meishan in southern china is well documented in respect to geochronology and the pattern of extinction here we report secular trends in bulk isotopic parameters and lipid biomarkers in a core spanning 214 m of stratigraphic section across the ptb and through the entire changhsingian interval our analysis of these data viewed in the context of relative sea level change and strontium isotopes reveals distinct shifts in paleoenvironmental conditions and profound changes in plankton ecology well before and following the biological extinction event specifically patterns of steroids and triterpenoids indicate a marine plankton community that was heavily dominated by bacteria during the late wuchiapingian middle changhsingian and early griesbachian stages secular trends in aromatic hydrocarbons diagnostic for anoxygenic green sulphur bacteria chlorobiaceae identify periods when euxinic conditions extended into the photic zone during the entire changhsingian stage here also the 15

mercury anomalies across the end permian mass extinction in south china from shallow and deep water depositional environments abstract life on earth suffered its greatest bio crisis since multicellular organisms rose 600 million years ago during the end permian mass extinction coincidence of the mass extinction with flood basalt eruptions in siberia is well established but the exact causal connection between the eruptions and extinction processes in south china is uncertain due to their wide spatial separation and the absence of direct geochemical evidence linking the two the concentration and stable isotope analysis of mercury provides a way to test these links as its concentration is thought to be tied to igneous activity mercury total organic carbon ratios from three permian triassic boundary sections with a well resolved extinction record in south china show elevated values up to 900 ppb wt relative to a background of 199 hg with sustained positive values indicate a predominant atmospheric derived signature of volcanic hg in deep shelf settings of the daxiakou and shangsi sections in contrast the nearshore environment of the meishan section displays a negative 199 hg signature interpreted to be related to terrestrial hg sources such temporal differences in 199 hg values shed new light on hg geochemical behavior in marine settings and also on the kill mechanisms associated with volcanism that were responsible for biotic mortality at the end of the permian

mercury in marine ordovician silurian boundary sections of south china is sulfide hosted and non volcanic in origin abstract mercury hg enrichment in stratigraphic successions is now widely used as a proxy for volcanic inputs often for the purpose of documenting a relationship between large igneous province lip magmatism and ecosystem perturbations earlier studies of hg in ordovician silurian boundary osb sections in south china and laurentia identified transient spikes in hg toc ratios on the basis of which a link between volcanism and the late ordovician mass extinction lome was claimed however hg enrichments must be tested based on normalization to their main host phase and hg toc is a suitable proxy only if hg is mainly complexed by organic matter in the sediment here we demonstrate that hg in three osb sections in south china qiliao yanzhi and jiaoye is overwhelmingly associated with pyrite as shown by r hg ts 0 9 versus r hg toc 199 hg values 0 11 0 03 that are inconsistent with volcanic inputs we therefore infer that previous reports of hg enrichments in osb sections were due to the presence of hg rich sulfides and that hg data from both the present and earlier studies provide no evidence of any volcanic influences on the lome the results of the present study highlight the need for caution in applying the hg proxy for volcanic inputs and the importance of evaluating the main host phase of hg in paleo marine sediments

basinal restriction black shales re os dating and the early toarcian jurassic oceanic anoxic event 1 profiles of mo total organic carbon toc through the lower toarcian black shales of the cleveland basin yorkshire united kingdom and the posidonia shale of germany and switzerland reveal water mass restriction during the interval from late tenuicostatum zone times to early bifrons zone times times which include that of the putative early toarcian oceanic anoxic event the degree of restriction is revealed by crossplots of mo and toc concentrations for the cleveland basin which define two linear arrays with regression slopes ppm of 0 5 and 17 the slope of 0 5 applies to sediment from the upper semicelatum and exaratum subzones this value which is one tenth of that for modern sediments from the black sea mo toc regression slope 4 5 reveals that water mass restriction during this interval was around 10 times more severe than in the modern black sea the renewal frequency of the water mass was between 4 and 40 ka the mo toc regression slope of 17 applies to the overlying falciferum and commune subzones the value shows that restriction in this interval was less severe and that the renewal frequency of the water mass was between 10 and 130 years the more restricted of the two intervals has been termed the early toarcian oceanic anoxic event but is shown to be an event caused by basin restriction local to nw europe crossplots of re os and mo against toc show similar trends of increasing element concentration with increase in toc but with differing slopes together with modeling of 187 os 188 os and d 98 mo the element toc trends show that drawdown of re os and mo was essentially complete during upper semicelatum and exaratum subzone times mo toc regression slope of 0 5 drawdown sensitized the restricted water mass to isotopic change forced by freshwater mixing so that continental inputs of re os and mo via a low salinity surface layer created isotopic excursions of up to 1 3 in d 98 mo and up to 0 6 for 187 os 188 os restriction thereby compromises attempts to date toarcian black shales and possibly all black shales using re os chronology and introduces a confounding influence in the attempts to use d 98 mo and initial 187 os 188 os for palaeo oceanographic interpretation

occurrence and significance of phytanyl arenes across the permian triassic boundary interval abstract phytanyl benzene and phytanyl toluene occur in mudstones from several key permian triassic boundary ptb sections from mid northern palaeolatitudes spitsbergen and eastern greenland as well as mid southern palaeolatitudes western australia the occurrence of these compounds through the different ptb sections is related to the occurrence of the previously identified c33 n alkyl cyclohexane suggesting their parent organism shared a similar unique ecological niche and was associated with the extinction horizon further the lack of these compounds in the carbonate dominated palaeoequatorial global stratotype section and point gssp meishan 1 south china section possibly points to their source being temperature and climate controlled