shallow marine carbon and oxygen isotope and elemental records indicate icehouse greenhouse cycles during the early jurassic 1 for much of the mesozoic record there has been an inconclusive debate on the possible global significance of isotopic proxies for environmental change and of sequence stratigraphic depositional sequences we present a carbon and oxygen isotope and elemental record for part of the early jurassic based on marine benthic and nektobenthic molluscs and brachiopods from the shallow marine succession of the cleveland basin uk the invertebrate isotope record is supplemented with carbon isotope data from fossil wood which samples atmospheric carbon new data elucidate two major global carbon isotope events a negative excursion of 2 at the sinemurian pliensbachian boundary and a positive excursion of 2 in the late pliensbachian the sinemurian pliensbachian boundary event is similar to the slightly younger toarcian oceanic anoxic event and is characterized by deposition of relatively deepwater organic rich shale the late pliensbachian strata by contrast are characterized by shallow marine deposition oxygen isotope data imply cooling locally for both events however because deeper water conditions characterize the sinemurian pliensbachian boundary in the cleveland basin the temperature drop is likely of local significance in contrast a cool late pliensbachian shallow seafloor agrees with previous inference of partial icehouse conditions both the large scale long term and small scale short duration isotopic cycles occurred in concert with relative sea level changes documented previously from sequence stratigraphy isotope events and the sea level cycles are concluded to reflect processes of global significance supporting the idea of an early jurassic in which cyclic swings from icehouse to greenhouse and super greenhouse conditions occurred at timescales from 1 to 10 ma

tracing euxinia by molybdenum concentrations in sediments using handheld x ray fluorescence spectroscopy hhxrf abstract elevated molybdenum mo contents in organic rich sediments are indicative of deposition from an anoxic and sulfide rich euxinic water column this can be used for tracing past euxinic conditions in ancient oceans from sedimentary archives conventional analytical detection of elevated molybdenum levels is however expensive and cannot be directly performed in the field here we show that handheld x ray absorption spectroscopy hhxrf on both rock powders and rock surfaces provides a powerful tool for laboratory or field based geochemical characterization of mo content and the tracing of euxinic depositional conditions we further present a sedimentary mo database compiled from over 300 globally distributed modern marine sites to show that modern euxinic marine basins are characterized by molybdenum enrichment 25 ppm relative to average crust 1 5 ppm and river suspended matter 3 ppm only mn oxide rich deposits from oxygenated deep sea settings match such high mo enrichments but these are easily distinguished from mo rich sediments from the continental shelves hence past and present organic rich sediments enriched in mo are indicative of at least intermittent water column euxinia we analyzed the molybdenum content of powdered and homogenized samples of holocene miocene triassic jurassic ordovician and cambrian age by hhxrf and inductively coupled plasma mass spectrometry icpms we further analyzed 2 certified nist standard references nist 2781 with mo 47 ppm and nist 2702 with mo 10 ppm for analytical control analytical precision 1 after 30 120 and 300 seconds of measuring time was 4 2 and 1 ppm with a respective detection limit of 11 5 3 ppm 3 noise level the data were accurate to within the given precision 1 after a daily calibration to samples covering a range of mo concentrations from 0 to 30 ppm hand held xrf equipment also allows mo measurements directly on fresh rock surfaces both in the field and under laboratory conditions rock samples from a cambrian drill core closely match icpms obtained mo concentrations from homogenous powders of the same rocks collectively our data show that hhxrf as a quick and reliable method for the precise and accurate quantification of molybdenum concentrations in both rock powders and at fresh rock surfaces the non destructive nature of the hhxrf measurements is combined with low per sample analytical costs minor sample preparation and easy applicability in the field

organic carbon isotopic record across the triassic jurassic boundary in austria and its bearing on the cause of the mass extinction carbon isotope analyses of total organic carbon across the triassic jurassic boundary in the classic section of kendelbach austria show that a positive excursion in 13c values of organic carbon in the boundary marl correlates with a negative excursion in 13c values in carbonates in this section the change in isotope values is inferred to be the result of diagenesis with no evidence of any primary change that could relate to bioproductivity this and other evidence do not support the claim that there was a fall in productivity associated with the end triassic mass extinction possibly caused by bolide impact

anomalies in global carbon cycling and extinction at the triassic jurassic boundary evidence from a marine c isotope record this study investigates whether the end triassic biotic crisis was coupled with a perturbation of the marine c isotope budget the marine c isotope signature serves as a proxy of the marine carbon reservoir and ultimately of the global c cycle a continuous shallow water marine limestone succession from the western southern alps bergamasc alps northern italy provides information on the end triassic biotic crisis and on the evolution of the marine carbon reservoir across the triassic jurassic t j boundary the established carbonate c isotope curve is marked by a negative c isotope pulse coinciding with the disappearance of the end triassic benthic faunal assemblage and a widespread rhaetian carbonate platform drowning event the negative spike is followed by a positive c isotope excursion starting at the palynological t j transition the negative c isotope pulse may have resulted from the sudden release of gas hydrates the positive isotope excursion records a global change in organic carbon burial rates probably in response to elevated atmospheric co2 levels at a time of massive volcanic activity in the central atlantic magmatic province high co2 levels were responsible for the end triassic biocalcification crisis carbonate platform collapse and possibly the sudden release of methane from gas hydrate

terrestrial and marine extinction at the triassic jurassic boundary synchronized with major carbon cycle perturbation a link to initiation of massive volcanism mass extinction at the triassic jurassic tr j boundary occurred about the same time 200 ma as one of the largest volcanic eruptive events known that which characterized the central atlantic magmatic province organic carbon isotope data from the uk and greenland demonstrate that changes in flora and fauna from terrestrial and marine environments occurred synchronously with a light carbon isotope excursion and that this happened earlier than the tr j boundary marked by ammonites in the uk the results also point toward synchronicity between extinctions and eruption of the first central atlantic magmatic province lavas suggesting a causal link between loss of taxa and the very earliest eruptive phases the initial isotopic excursion potentially provides a widely correlatable marker for the base of the jurassic a temporary return to heavier values followed but relatively light carbon dominated the shallow oceanic and atmospheric reservoirs for at least 600 k y

barremian danian chemostratigraphic sequences of the cauvery basin india implications on scales of stratigraphic correlation abstract chemostratigraphic concepts postulate that distinct chemozones could be recognized from rock records to help correlate geographically separated strata many studies have upheld this view but were limited to classic boundaries such as cenomanian turonian or cretaceous tertiary only a few elements and isotopic compositions were made use in such studies an attempt to recognize chemozones of barremian danian strata of the cauvery basin south india through whole rock chemistry had revealed many complex signals and depositional events as expressed by bulk geochemical profiles the signals indicate major shift in sedimentation pattern from dynamic depocenter to stable depositional conditions during santonian varying sensitivities of different elements towards prevalent depositional conditions are also inferred trends of geochemical composition indicated domination of single depositional control all through the depositional history basinal configuration that limited terrestrial sediment source and episodic influx of detrital materials presence of distinct change in whole rock geochemistry across geochronological and lithostratigraphic boundaries is deciphered through a statistical tool anova these results demonstrate that visual delineation of chemozones in a long ranging rock record would be tenuous and has to be exercised with caution

satellite gravity and the mass balance of the antarctic ice sheet changes in the earth s gravity field with time have important applications to a broad range of disciplines any process that involves a large enough horizontal redistribution of mass either within the earth or on or above its surface is potentially detectable in particular when ice sheets grow or shrink gravity changes as mass is redistributed in the solid earth and between the oceans and the ice sheets the sources of global sea level rise about 2 mm a 1 over the last century and in particular the contribution of the antarctic ice sheet thereto are not well understood gravity measurements can help to diminish this uncertainty the technology currently exists to measure gravity with high accuracy by a dual satellite mission in which the distance between the satellites is precisely monitored we estimate from recent studies that temporal changes in the gravity field as determined by a satellite gravity mission lasting 5 years at an orbital height of 400 km would be sensitive to changes in the overall mass of the antarctic ice sheet to a precision corresponding to better than 0 01 mm a 1 of sea level change however the effects of three other phenomena that could each produce a temporally varying gravity signal with characteristics comparable to that caused by a change in antarctic ice postglacial rebound inter annual variability in snowfall and atmospheric pressure trends also need to be evaluated postglacial rebound could be partly separated from ice mass changes with the aid of global positioning system campaigns and numerical models of rebound that use improved determinations of mantle viscosity also provided by the gravity mission determination of inter annual ice mass changes will be aided by measurements of moisture flux divergence around the perimeters of the ice sheets and direct observations of inter annual changes by the gravity satellite itself the removal of pressure effects over antarctica will become more effective as the number of automatic weather stations in the interior of the continent increases even after corrections are made for these factors the uncertainties they cause limit the accuracy in the determination of the contribution of the antarctic ice sheet to sea level change to about 0 5 mm a 1 however there is a strong complementarity between gravity measurements and the surface height measurements that will be produced by nasa s laser altimeter mission early next century together they should be able to determine that contribution to an accuracy of about 0 1 mm a 1

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

the organic carbon isotopic and paleontological record across the triassic jurassic boundary at the candidate gssp section at ferguson hill muller canyon nevada usa we present new litho bio and chemostratigraphic data from the triassic jurassic t j boundary section at ferguson hill muller canyon nevada usa this section is a candidate for the base of the hettangian stage and thus the t j boundary our measurements yield a 19 m thickness for the muller canyon member of the gabbs formation we recognize the triassic jurassic boundary using the first appearance of agerchlamys and place it 9 6 m above the boundary between the muller canyon member and the subjacent mount hyatt member with the first occurrence of the ammonite psiloceras tilmanni occurring 0 9 m above this our organic carbon isotope record from this section shows two excursions toward lighter values one at the t j boundary and the second in the lower parts of the jurassic sunrise formation these results are significantly different from a prior report on light stable isotopes from this section

a new rhaetian δ13corg record carbon cycle disturbances volcanism end triassic mass extinction ete abstract the links between large scale volcanism carbon cycle perturbations and the biotic crises at the end triassic extinction event ete are not well understood the ete seems to be marked by three carbon isotope excursions cies likely triggered by different eruptive phases of the central atlantic magmatic province camp these three cies appear to occur during the late rhaetian close to the triassic jurassic boundary tjb but the relative timing connecting the volcanism carbon perturbations and extinctions is still subject to debate resulting from i the difficulties in long distance biostratigraphic correlations of rhaetian successions due to the step like extinction pattern characterizing the ete and to the lack of globally correlatable key fossil group s across the system boundary ii the limit of coverage of available 13c profiles to the system boundary interval rather than the entire rhaetian iii the inherent difficulties in correlating cies without clear biostratigraphic markers here we present a 13corg curve from the lombardy basin which covers for the first time the entire rhaetian using this chemostratigraphy we propose two possible correlations option 1 and option 2 with other late rhaetian to early hettangian successions worldwide these two possible correlations rely on a combination of paleontological ammonoids pollens conodonts lithostratigraphic and geochemical constraints option 2 in particular has important implications for the causality and geochronology of the ete events by suggesting that the sharp negative peak usually considered to be the initial cie in the lombardy might represent a carbon perturbation within the negative trend of the main cie this implies that a reconsideration of the succession of biotic events occurring during this time interval is required

sedimentary organic matter characterization of the triassic jurassic boundary gssp at kuhjoch austria abstract the triassic jurassic t j boundary interval coincides with enhanced extinction rates in the marine realm and pronounced changes in terrestrial ecosystems on the continents it is further marked by distinct negative excursions in the 13corg and 13ccarb signature that may represent strong perturbations of the global carbon cycle we present integrated geochemical stable isotope and palynological data from the kuhjoch section the global boundary stratotype section and point gssp for the base of the jurassic northern calcareous alps austria we show that the initial carbon isotope excursion cie coinciding with the marine extinction interval and the formation of black shales in the western tethys eiberg basin is marked by only minor changes in kerogen type which is mainly of terrestrial origin increased total organic carbon toc concentrations of 9 at the first half of the initial cie coincide with hydrogen index hi values of over 600 mg hc g toc the high correlation with r2 0 93 between hi values and terrestrial cheirolepidiaceaen conifer pollen suggests a terrestrial source for the hydrogen enriched organic compounds the lack of major changes in source of the sedimentary organic matter suggests that changes in the 13corg composition are genuine and represent true disturbances of the global c cycle the sudden decrease in total inorganic carbon tic concentrations likely represents the onset of a biocalcification crisis it coincides with a 4 5 negative shift in 13corg values and possibly corresponds to the onset of camp related volcanic activity the second half of the initial cie is marked by the dramatic increase of green algae remains in the sediment the simultaneous increase of the corg ntot ratio suggests increased marine primary production at the final stage of black shale formation

correlation of the triassic jurassic boundary in england and austria an attempt is made to fix the triassic jurassic boundary at the classic locality of st audries bay somerset by reference to biostratigraphy in conjunction with lithostratigraphy utilizing comparison with the more fully marine sequence of the kendelbach gorge in austria the boundary is placed at the base of the blue lias formation

structural complexity at and around the triassic jurassic gssp at kuhjoch northern calcareous alps austria one of the key requirements for a global stratotype section and point gssp is the absence of tectonic disturbance the gssp for the triassic jurassic system boundary was recently defined at kuhjoch northern calcareous alps austria new field observations in the area of the triassic jurassic boundary gssp site demonstrate that the overturned tight and almost upright karwendel syncline was formed at semibrittle deformation conditions confirmed by axial planar foliation tight to isoclinal folds at various scales were related to a tectonic transport to the north brittle faulting occurred before and after folding as confirmed by tilt tests the rotation of structural data by the average bedding foliation is ubiquitous in the incompetent units including the kendlbach formation at the gssp a reverse fault inferred to be formed as a normal fault before folding crosscuts the gssp sections results in the partial tectonic omission of the schattwald beds and thus makes it impossible to measure a complete and continuous stratigraphic section across the whole kendlbach formation based on these observations the kuhjoch sections do not fulfil the specific requirement for a gssp regarding the absence of tectonic disturbances near boundary level

biogeochemical constraints on the triassic jurassic boundary carbon cycle event 1 the end triassic mass extinctions represent one of the five most severe biotic crises in earth history yet remain one of the most enigmatic ongoing debate concerns the environmental effects of the central atlantic magmatic province camp eruptions and their linkage with the mass extinction event across the triassic jurassic boundary there is conflicting paleo evidence for changes in atmospheric pco2 during the extrusion of the camp basalts studies on sediments from european and pacific localities have however identified a substantial negative isotopic anomaly up to 3 5 across the tr j boundary providing an important indicator of changes in the operation of the ancient global carbon cycle we sought to explain the paleo evidence by utilizing a carbon cycle model for the hothouse world of the end triassic that emphasizes the chemical weathering of silicate and carbonate rocks and the ocean carbonate chemistry we find that volcanic co2 outgassing fails to fully account for either a sufficient rise in atmospheric pco2 indicated by the stomata of fossil leaves or the sedimentary isotopic fingerprint instead the scenario that best fits all of the geologic evidence is a positive feedback loop in which warming due to a buildup of volcanically derived co2 triggers destabilization of seafloor methane hydrates and the catastrophic release of ch4 palfy et al 2001 we calculate that this carbon cycle perturbation was huge involving the release of 8000 9000 gt c as co2 during the camp basaltic eruptions and 5000 gt c as ch4 in the model the initial isotopic excursion is assumed to take place over 70 kyr while complete reequilibration of the ocean atmosphere system with respect to co2 is accomplished over 700 1000 kyr our results thus provide a preliminary theoretical explanation for the bioevents estimated pco2 changes and isotopic excursions observed in marine and continental sediments at this time

a new correlation of triassic jurassic boundary successions in nw europe nevada and peru and the central atlantic magmatic province a time line for the end triassic mass extinction abstract understanding the end triassic mass extinction event 201 36 ma requires a clear insight into the stratigraphy of boundary sections which allows for long distance correlations and correct distinction of the sequence of events however even after the ratification of a global stratotype section and point global correlations of tjb successions are hampered by the fact that many of the traditionally used fossil groups were severely affected by the crisis here a new correlation of key tjb successions in europe u s a and peru based on a combination of biotic palynology and ammonites geochemical 13 c org and radiometric u pb ages constraints is presented this new correlation has an impact on the causality and temporal development during the end triassic event it challenges the hitherto used standard correlation which has formed the basis for a hypothesis that the extinction was caused by more or less instantaneous release of large quantities of light carbon methane to the atmosphere with catastrophic global warming as a consequence the new correlation instead advocates a more prolonged scenario with a series of feedback mechanisms as it indicates that the bulk of the hitherto dated high titanium quartz normalized volcanism of the central atlantic magmatic province camp preceded or was contemporaneous to the onset of the mass extinction in addition the maximum phase of the mass extinction which affected both the terrestrial and marine ecosystems was associated with a major regression and repeated enhanced earthquake activity in europe a subsequent transgression resulted in the formation of hiati or condensed successions in many areas in europe later phases of volcanic activity of the camp producing low titanium quartz normalized and high iron quartz normalized basaltic rocks continued close to the first occurrence of jurassic ammonites and the defined tjb during this time the terrestrial ecosystem had begun to recover but the marine ecosystem remained disturbed

palynostratigraphy and vegetation history of the triassic jurassic transition in east greenland we present a palynological study of a terrestrial triassic jurassic tr j c 200 ma boundary section at astartekloft east greenland we have generated a new palynostratigraphic scheme and vegetation history for this locality and have integrated these with existing carbon isotope records samples for palynological analysis were collected from precisely the same stratigraphic horizons as plant macrofossils and samples used for geochemical analyses our results highlight four local sporomorph assemblage zones that are compositionally distinct from each other at astartekloft the extremely low abundance of classopollis pollen in all samples and the pronounced decline of ricciisporites tuberculatus during the late rhaetian are notable features of the sporomorph record of tr j vegetation at astartekloft correlation of astartekloft and a marine tr j boundary section at st audrie s bay uk provides no support for the idea that extinction and diversity loss in terrestrial ecosystems preceded biotic change in marine ecosystems at the tr j instead the available data support suggestions that the onset of the tr j biotic crisis was synchronous in terrestrial and marine environments peak extinction among plants at astartekloft occurred relatively late in the sequence of events across the tr j and may represent a response to long term cumulative effects of volcanism at this time supplementary material plates of selected sporomorphs recovered from astartekloft and a full pollen diagram are available at www geolsoc org uk sup18553

carbon isotope geochemistry of the frasnian famennian transition abstract carbon isotope records for inorganic and total organic carbon toc as well as for individual organic biomarkers show two positive excursions in the late frasnian with comparable shape and amplitude in 13c the positive shifts in 13c can be correlated with the deposition of the kellwasser horizons the inorganic carbon isotope excursions are explained by an enhanced organic carbon burial that is expected to lower the concentration of oceanic dissolved co2 toc 13c values do not exhibit a larger shift than that recorded by inorganic carbon 13c values this is unexpected since a decrease in the dissolved co2 concentration should result in lower carbon isotope fractionation during photosynthesis ep 13c values of presumed algal biomarkers low molecular weight n alkanes pristane phytane although offset by 2 5 exhibit essentially identical records as toc and confirm this unexpected result it is proposed that high atmospheric and oceanic co2 concentrations during the devonian resulted in maximum photosynthetic fractionation any change in the co2 concentration would thus not affect ep as such 13c of primary organic carbon and 13ccarb will exhibit parallel excursions the data imply that carbon isotopes and the relationship between ep and co2 will not be effective to study changes in pco2 levels during the devonian since co2 concentrations were too high

the end triassic mass extinction record of williston lake british columbia abstract triassic jurassic boundary sections on the shore of lake williston british columbia record a spectrum of depositional environments from the western canadian continental margin a primarily deep water anoxic record of deposition indicated by v v ni v cr th u indices and pyrite framboid and facies data is seen throughout the late triassic early jurassic norian hettangian interval in a section at black bear ridge abundant monotis bivalve populations in norian strata are interpreted to have lived on the seabed during transient oxygenation events that punctuated the background anoxic conditions monotis went extinct around the norian rhaetian boundary and the deep water assemblages are subsequently dominated by thin shelled pectinids an intra rhaetian sea level fall generated a major hiatus in the proximal black bear ridge section whilst distinctive lowstand strata were developed in the more distal and more complete ne parle pas point and pardonet creek sections these consist of shallow water phosphatic ooid sand facies that contain diverse bivalves the majority of the infaunal bivalves but not the epifaunal ones disappeared at the acme of the regression this is the end triassic mass extinction event and it occurred shortly before a terminal triassic flooding event this transgressive event is associated with a rapid negative shift of 13corg values interpreted to be the initial isotope excursion of hesselbo et al hesselbo s p robinson s a surlyk f piasecki s 2002 terrestrial and marine extinction at the triassic jurassic boundary synchronized with major carbon cycle perturbation a link to initiation of massive volcanism geology 30 251 254 the rhaetian record of williston lake thus records an extinction of shallow water infaunal bivalves during a lowstand prior to the development of a transgressive record that is associated with a major negative c isotope

the impact of the central atlantic magmatic province on climate and on the sr and os isotope evolution of seawater abstract there is a wide range of geochemical sedimentological and palaeontological evidence suggesting that the interval at the end of the triassic and the beginning of the jurassic some 200 ma ago was a time of major environmental change the supercontinent pangaea began to rift eustatic sea level rose and there was a mass extinction in marine and terrestrial biota the eruption of at least 3 10 6 km 3 of basaltic lavas that comprise the central atlantic magmatic province camp also took place at that time and was intimately associated with the onset of rifting of pangaea emplacement of this large igneous province occurred within a relatively very short period of perhaps no more than 1 ma although relatively little of camp now remains the original province was extremely large extending from present day nova scotia to bolivia and from central southern usa to morocco of major relevance to the environmental impact of the camp was its relatively rapid emplacement and its original location across the equator recent advances in our understanding of the weathering of silicate rocks and in particular of fresh basaltic rocks have highlighted the importance of the weathering process in influencing environmental change in this contribution we examine the details of the seawater sr and os isotope records that span the triassic jurassic boundary in order to understand the nature and course of environmental change at that time correlation of sr isotope data from mainland europe and the uk shows that the rapid rate of decrease in the 87 sr 86 sr ratio of seawater which had started in the early rhaetian late triassic came to an end in the late rhaetian close to the triassic jurassic boundary at that time the 187 os 188 os ratio of seawater had also decreased to particularly low values in the late rhaetian the seawater 87 sr 86 sr ratio rapidly increased from 0 70765 to 0 70775 and then it and the seawater 187 os 188 os ratio both remained approximately constant for the duration of the hettangian the first 3 ma of the jurassic apart from a transient excursion to radiogenic os isotope values i e high 187 os 188 os ratios near the triassic jurassic boundary the unradiogenic 187 os 188 os ratio of seawater during the hettangian is interpreted as reflecting a major perturbation to global weathering patterns that was caused by the rapid weathering and erosion of the camp immediately after its emplacement we suggest that the rapid increase of seawater 87 sr 86 sr ratios in the late rhaetian and the approximately constant 87 sr 86 sr ratios throughout the hettangian were caused by the input of a large amount of additional radiogenic sr to the oceans which was likely to have been derived from a readily weathered lithology such as carbonate or evaporite at the start of the sinemurian the 87 sr 86 sr ratio of seawater began to decrease while at the same time the 187 os 188 os ratio of seawater increased to more radiogenic values we interpret the trends in the seawater sr and os isotope compositions at the start of the sinemurian as evidence that much of the camp had been removed by chemical weathering by which time the camp had ceased to have a major influence on earth s environment the patterns of change in the seawater sr and os isotope records that occurred in the latest triassic and earliest jurassic show many similarities with those that took place in the pliensbachian toarcian 183 ma ago overlapping the eruption of the karoo ferrar igneous province in both cases the seawater sr and os isotope records indicate that there was a relatively very brief interval during which rates of continental weathering increased greatly the similarities in the responses of the seawater sr and os isotope records at those times strongly suggest that the eruption and subsequent erosion of basaltic large igneous provinces have played a major role in defining the course of environmental change in the past

time variability of the earth s gravity field hydrological and oceanic effects and their possible detection using grace the grace satellite mission scheduled for launch in 2001 is designed to map out the earth s gravity field to high accuracy every 2 4 weeks over a nominal lifetime of 5 years changes in the gravity field are caused by the redistribution of mass within the earth and on or above its surface grace will thus be able to constrain processes that involve mass redistribution in this paper we use output from hydrological oceanographic and atmospheric models to estimate the variability in the gravity field i e in the geoid due to those sources we develop a method for constructing surface mass estimates from the grace gravity coefficients we show the results of simulations where we use synthetic grace gravity data constructed by combining estimated geophysical signals and simulated grace measurement errors to attempt to recover hydrological and oceanographic signals we show that grace may be able to recover changes in continental water storage and in seafloor pressure at scales of a few hundred kilometers and larger and at timescales of a few weeks and longer with accuracies approaching 2 mm in water thickness over land and 0 1 mbar or better in seafloor pressure

late triassic to early jurassic palaeogeography and eustatic history in the nw tethyan realm new insights from sedimentary and organic facies of the csővar basin hungary abstract sedimentary and organic facies of a continuous late triassic early jurassic toe of slope to basin succession of the ne transdanubian range n hungary was studied in order to reconstruct the palaeogeographical and eustatic evolution of the cs var basin an intraplatform basin of the nw neotethys margin characteristic facies successions point to sea level changes of different hierarchies cyclic patterns inferred to result from orbital eccentricity forcing are also reflected in the stratigraphical distribution of sedimentary organic matter furthermore both palaeontological and isotope data document drastic climatic changes around the triassic jurassic boundary detecting sea level changes leads to a more accurate interpretation of the late triassic palaeogeographic setting and evolution of the transdanubian range s carbonate platform our integrated sedimentological and palynological data suggest a complex topography and dynamic sea level history which contradicts a previous model of broad uniform platform setting and lack of any major drowning and emersion events during the late triassic

palaeoenvironmental significance of carbon and oxygen isotope stratigraphy of marine triassic jurassic boundary sections in sw britain abstract carbon isotope stratigraphy is a useful tool for stratigraphic correlation especially for strata deposited during major perturbations of the carbon cycle that affected the marine terrestrial and atmospheric reservoirs for the triassic jurassic boundary effectively defined by a first order mass extinction major fluctuations in carbon isotope values have been well documented but these datasets have generally been derived from bulk rock samples hence the extent to which features of the isotopic curve reflect diagenetic alteration or changing proportions of constituent materials is unconstrained here carbon and oxygen isotope data are presented from well preserved oyster shells liostrea comprising low magnesium calcite a mineral species relatively resistant to diagenetic alteration samples were obtained from lavernock point glamorgan wales a coastal section close to a candidate stratotype for the base of the jurassic at st audrie9s bay somerset england the carbon isotope signature from st audrie9s bay previously defined on the basis of analysis of bulk organic matter is confirmed by our new data major features are 1 the upper part of an initial9 negative isotope excursion in the lowest part of the section followed by 2 a pronounced positive excursion and 3 an extended main9 negative isotope excursion in the highest part of the section the data confirm that the carbon isotope stratigraphy previously documented from bulk organic matter in sw england records the chemical composition of the contemporaneous seawater bulk carbonates sampled over the same interval near lyme regis england show similar trends to those from oyster calcite in the lower part of the study section but there are more 13 c depleted values up section these lower values probably result from an admixture of primary and diagenetic carbonate palaeotemperatures calculated from oxygen isotope values from lavernock point oyster shells are relatively cool at the beginning of the positive carbon isotope excursion and increased by up to 10 c during the main negative carbon isotope excursion the new results are compatible with the view that positive carbon isotope excursions correspond to times of low atmospheric carbon dioxide content whereas negative carbon isotope excursions correspond to times of high atmospheric carbon dioxide content as is also found to be the case during the early jurassic toarcian oceanic anoxic event the mg ca and sr ca ratios and 18 o of investigated liostrea hisingeri show no correlation supporting data from modern bivalves that indicate that incorporation of mg and sr is controlled mainly by factors other than temperature

changing co2 conditions during the end triassic inferred from stomatal frequency analysis on lepidopteris ottonis goeppert schimper and ginkgoites taeniatus braun harris abstract end triassic fluctuations in atmospheric carbon dioxide co2 concentration were reconstructed by the use of stomatal frequency analysis on a single plant species the seedfern lepidopteris ottonis goeppert schimper stomatal index showed no distinct intra and interpinnule variation which makes it a suitable proxy for past relative co2 changes records of decreasing stomatal index and density from the bottom to the top of the rhaetian hettangian wustenwelsberg section bavaria germany indicate rising co2 levels during the triassic jurassic transition additionally stomatal frequency data of fossil ginkgoalean leaves ginkgoites taeniatus braun harris suggest a maximum palaeoatmospheric co2 concentration of 2750 ppmv for the latest triassic

an organic record of terrestrial ecosystem collapse and recovery at the triassic jurassic boundary in east greenland abstract terrestrial ecosystem collapse at the end of the triassic period coincided with a major mass extinction in the marine realm and has been linked to increasing atmospheric carbon dioxide global warming and fire activity extractable hydrocarbons in samples from the fluvial triassic jurassic boundary section at astartekloft east greenland were analyzed to investigate the molecular and isotopic organic record of biotic and environmental change during this event carbon isotopic compositions of individual plant wax lipids show a 4 negative excursion coinciding with peak extinction and a further decrease of 2 coinciding with peak p co 2 as estimated from the stomatal indices of fossil gingkoales an increase of 30 in the hydrogen isotopic compositions of the same plant wax lipids coincides with ecosystem collapse suggesting that the biotic crisis was accompanied by strong hydrologic change concentrations of polycyclic aromatic hydrocarbons related to combustion also increase together with abrupt plant diversity loss and peak with fossil charcoal abundance and maximum plant turnover supporting the role of fire in terrestrial extinctions anomalously high concentrations of a monoaromatic diterpenoid related to gymnosperm resin derivatives and similar to dehydroabietane occur uniquely in samples from the boundary bed indicating that environmental stress factors leading to peak plant extinction stimulated increased resin production and that plant resin derivatives may be effective biomarkers of terrestrial ecosystem stress

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

nitrogen isotope record of a perturbed paleoecosystem in the aftermath of the end triassic crisis doniford section sw england 1 the triassic jurassic transition tj is characterized by successive perturbations of the carbon cycle during a time of biotic disruption as recorded by the carbon isotopic composition of organic matter 13corg the nitrogen isotopic composition of sedimentary organic matter 15norg constitutes a key parameter to explore the functioning of the ecosystem during carbon cycle perturbations and biological crises because it provide information on seawater redox conditions and or nutrient cycling here we report the first continuous 15norg record across the tj transition at the doniford bay section bristol channel basin uk combined with 13corg kerogen typology and carbon 13cmin and oxygen 18omin isotopic composition of bulk carbonates the end triassic is characterized by a major negative excursion both in 13corg and 13cmin very low toc total organic carbon wt and high 15norg values associated with a sea level lowstand a second 13corg negative excursion occurs during the lower hettangian this interval is characterized by phases of carbonate production increase alternated with phases of exceptional accumulations of type i organic matter up to 12 associated with lower 15norg and 13corg this alternation likely reflects a succession of nutrient input increase to the basin leading to enhanced productivity and eutrophication which promoted a primary production driven by organic walled prokaryotic organisms the following om export increase generates anaerobic conditions within the basin these events occur between periods of relatively good seawater column ventilation and nutrient recycling boosting the carbonate producer recovery ecosystems remain perturbed in the bristol channel basin during the aftermath of the end triassic crisis

carbon and oxygen isotope records from the southern eurasian seaway following the triassic jurassic boundary parallel long term enhanced carbon burial and seawater warming abstract fossil shells of benthos and nektobenthos have been shown to be faithful recorders of seawater carbon and oxygen isotope geochemistry and thus also useful to track the relationship between carbon cycle and palaeotemperature in this study we present an extensive dataset from lower jurassic hettangian and lower sinemurian mollusc and brachiopod hard parts collected from biostratigraphically well calibrated uk coastal outcrops bristol channel and hebrides basins these basins lay palaeogeographically in the southern part of the laurasian seaway that connected the tethys and boreal oceans all samples have been subject to screening for diagenesis on the basis of elemental composition light microscopy and sem observations in the case of some localities within the hebrides basin alteration by hydrothermal systems around paleogene intrusions has led to re setting of carbonate oxygen isotopes but the original carbon isotope values from the shells are largely preserved above the prominent and apparently short lived 3 per mil 13ccarb amplitude positive carbon isotope excursion cie that occurs immediately above the triassic jurasic t j boundary in the tilmanni ammonite biozone a pronounced negative cie the so called main negative cie spans the entire hettangian stage at the hettangian sinemurian boundary and through the lower sinemurian the carbon isotope values of the skeletal carbonate again trend towards progressively more positive values but representing a time of several million years the heaviest 13ccarb values of about 4 3 per mil are evident towards the top of the lower sinemurian and are comparable with values observed from the tilmanni zone and from the lower toarcian higher in the jurassic this long term positive hump which confirms trends derived from bulk organic matter carbon isotope records is supporting evidence of prolonged enhanced organic carbon burial that is inferred to have occurred in the extensive system of lacustrine and marine rifts that traversed a fragmenting pangaea after emplacement of the central atlantic magmatic province in parallel oxygen isotope values of the skeletal carbonate show a continuous downward trend from the lower part of the hettangian 1 per mil 18ocarb in the planorbis zone to the top of the lower sinemurian 2 5 per mil 18ocarb in the higher turneri zone oxygen isotope values may be interpreted as due to gradually increasing palaeotemperature and or addition of a meteoric or cryospheric water component in the case of the laurasian seaway palaeoceanographic and palaeoecological considerations point towards a dominant palaeotemperature signal consequently any atmospheric carbon dioxide drawdown effect on global palaeotemperatures as suggested by progressively increasing 13ccarb values and assuming a constant silicate weathering sink was more than counterbalanced in the seaway by regional processes that led to significantly warmer bottom water temperatures

floral changes across the triassic jurassic boundary linked to flood basalt volcanism one of the five largest mass extinctions of the past 600 million years occurred at the boundary of the triassic and jurassic periods 201 6 million years ago the loss of marine biodiversity at the time has been linked to extreme greenhouse warming triggered by the release of carbon dioxide from flood basalt volcanism in the central atlantic ocean in contrast the biotic turnover in terrestrial ecosystems is not well understood and cannot be readily reconciled with the effects of massive volcanism here we present pollen spore and geochemical analyses across the triassic jurassic boundary from three drill cores from germany and sweden we show that gymnosperm forests in northwest europe were transiently replaced by fern and fern associated vegetation a pioneer assemblage commonly found in disturbed ecosystems the triassic jurassic boundary is also marked by an enrichment of polycyclic aromatic hydrocarbons which in the absence of charcoal peaks we interpret as an indication of incomplete combustion of organic matter by ascending flood basalt lava we conclude that the terrestrial vegetation shift is so severe and wide ranging that it is unlikely to have been triggered by greenhouse warming alone instead we suggest that the release of pollutants such as sulphur dioxide and toxic compounds such as the polycyclic aromatic hydrocarbons may have contributed to the extinction

marine osmium isotope record across the triassic jurassic boundary from a pacific pelagic site the triassic jurassic t j boundary ca 200 ma represents one of the major mass extinction events of the phanerozoic however the cause of this event remains controversial because of a paucity of geological evidence in this study we present an isotopic record of osmium extracted from a bedded chert succession across the t j boundary in the kurusu section of japan deposited within a paleo pacific panthalassa deep basin the data show a gradual decrease in seawater 187 os 188 os values during the rhaetian followed by a sharp increase in the latest rhaetian and a subsequent stable phase across the t j boundary the decreasing trend of 187 os 188 os values during the rhaetian indicates a gradual increase in the relative supply rate of unradiogenic os from the mantle associated with emplacement of the central atlantic magmatic province the subsequent shift toward radiogenic values reflects an increased supply of radiogenic os due to enhanced continental weathering this interval marks more negative isotopic values of organic carbon the onset of radiolarian faunal turnover and conodont extinctions indicating that the rapid increase in continental weathering rate was closely linked to the perturbation of the carbon cycle and the t j biotic crisis

milankovitch scale palynological turnover across the triassic jurassic transition at st audrie s bay sw uk abstract a high resolution palynological study of the triassic jurassic boundary in the st audrie9s bay section revealed a palynofloral transition interval with four pronounced spore peaks in the lilstock formation regular cyclic increases in palynomorph concentrations can be linked with periods of increased runoff and correspond to the orbital eccentricity cycle spore peaks can be related to precession induced variations in monsoon strength an implication is that the initial carbon isotope excursion lasted for at least 20 ka emergence during deposition of the cotham member had an influence on one of the peaks which is dominated by spore producing pioneer plants e g horsetails and liverworts there is no compelling evidence of a global end triassic spore spike that by analogy with the k t boundary fern spike could be related to a catastrophic mass extinction event climate change is a more plausible mechanism to explain the increased amount of spores supplementary material an alphabetical list of palynomorphs identified in the st audrie9s bay section is available at http www geolsoc org uk sup18406

climate since ad 1510 on dyer plateau antarctic peninsula evidence for recent climate change a 480 year record of the oxygen isotope ratios dust content chemical species and net accumulation from ice cores drilled in 1989 90 on dyer plateau in the antarctic peninsula is presented the continuous analyses of small sub annual samples reveal well preserved annual variations in both sulfate content and 18o thus allowing an excellent time scale to be established this history reveals a recent pronounced warming in which the last two decades have been among the warmest in the last five centuries furthermore unlike in east antarctica on dyer plateau conditions appear to have been fairly normal from ad 1500 to 1850 with cooler conditions from 1850 to 1930 and a warming trend dominating since 1930 reconstructed annual layer thicknesses suggest an increase in net accumulation beginning early in the 19th century and continuing to the present this intuitive conflict between increasing net accumulation and depleted 18o cooler climate in the 19th century appears widespread in the peninsula region and challenges our understanding of the physical relationships among moisture sources air temperatures and snow accumulation the complex meteorological regime in the antarctic peninsula region complicates meaningful interpretation of proxy indicators and results in a strong imprint of local high frequency processes upon the larger scale climate picture

environmental changes across the triassic jurassic boundary and coeval volcanism inferred from elemental geochemistry and mineralogy in the kendlbachgraben section northern calcareous alps austria the end triassic extinction ete one of the five largest phanerozoic mass extinctions is associated with rapid and severe environmental change but existing data permit alternative models of causation volcanism in the central atlantic magmatic province camp has been proposed as the main trigger but direct evidence for this linkage is scarce to help constrain scenarios for the ete and other triassic jurassic boundary tjb events we obtained a temporally highly resolved multidisciplinary dataset from the kendlbachgraben section in the northern calcareous alps in austria the section belongs to the same paleogeographic unit eiberg basin and share similar stratigraphy with the recently selected base jurassic global stratotype section and point at kuhjoch micromineralogic study of the topmost bed of the rhaetian k ossen formation revealed pseudomorphs of altered euhedral pyroxene and amphibole crystals their well faceted morphology is consistent with their origin from distal mafic volcanic ash fallout spherical grains were also observed in the same bed likely representing clay altered volcanic glass clay minerals of this bed include lowto medium charged smectite and mg vermiculite both typical alteration products of mafic rocks the same bed yielded a rare earth element pattern that differs from all other levels in an enrichment of heavy rees hinting at some minor contribution from mafic magmatic material these features from a layer that was deposited very near to the tjb are interpreted as direct evidence of camp volcanism coeval or immediately preceding the ete and the initial negative carbon isotope anomaly the kaolinite dominated clay mineral spectrum of the overlying boundary mudstone records intensive weathering under hot and humid greenhouse conditions redox sensitive minor and trace elements do not support the development of widespread anoxia in the studied section although pyrite is common in several layers framboid size indicates formation within a reductive zone below the sediment water interface rather than in an anoxic water column our data provide a direct link between uppermost triassic marine strata and camp derived material they support scenarios where camp volcanism induced climate and other environmental change which in turn triggered the ete and that is also reflected in the carbon isotope anomalies 2012 elsevier b v all rights reserved

redox conditions and nitrogen cycling during the triassic jurassic transition a new perspective from the mid panthalassa abstract we determined redox sensitive element concentrations along with 15ntn values from the triassic jurassic shales interbedded within deep sea cherts at the katsuyama section sw japan to clarify the redox and related nitrogen cycle conditions in mid panthalassa during the tjb biotic crisis focusing particularly on the linkages with camp volcanism slight enrichments of mn and mo across the tjb suggest a vertically expanded mid panthalassic omz above a well oxygenated deep ocean moreover high resolution 15ntn records during the triassic jurassic transition exhibit a negative nitrogen isotope excursion nnie just above the tjb relative to the previously reported negative carbon isotope excursion ncie across the tjb the nnie can be divided into two intervals negative interval 1 ni 1 during the ncie and ni 2 after the ncie the nnie can be explained as an interval of nitrate rich conditions reflecting an oxic panthalassic ocean during the triassic jurassic transition our geochemical dataset provides new insights into environmental perturbations in mid panthalassia during the tjb biotic crisis 1 a vertically expanded omz and decreased primary productivity owing to global warming caused by camp volcanism across the tjb resulted in an increased nitrate concentration during the ni 1 and 2 eutrophic nitrate rich conditions developed in mid panthalassa during the ni 2 due to the enhanced continental weathering and deep water upwelling significantly our results are the first to demonstrate that the omzs were expanded not only in the shallow marine regions but also in pelagic sites across the tjb suggesting that the globally expanded omzs can be regarded as a crucial driver for the tjb biotic crisis

global perturbations of carbon cycle during the triassic jurassic transition recorded in the mid panthalassa abstract to examine environmental changes in the biosphere during the triassic jurassic transition with a particular focus on the global carbon cycle related to central atlantic magmatic provinces camp volcanism in the mid panthalassa we established stratigraphic 13 c org variations using rhaetian late triassic to hettangian early jurassic shales interbedded within deep sea cherts in the katsuyama section in the mino tanba belt sw japan high resolution record of rhaetian to hettangian 13 c org values in the mid panthalassa contain three distinct negative carbon isotopic excursions ncies before and across the triassic jurassic boundary tjb the rhaetian ncie1 and ncie2 show a deviation of 5 0 from ca 24 0 to ca 29 0 whereas ncie3 across the tjb shows a 3 5 deviation from ca 23 5 to ca 27 0 our newly obtained ncies in the deep mid panthalassa can be correlated with the 13 c org records in the shallow marine tethyan regions i e precursor initial and main cies suggesting that three ncies in the tethys and mid panthalassa likely reflected the global perturbations of the carbon cycle three ncies before and across the tjb can be interpreted as the consequence of the multiple camp volcanic episodes i e the release of thermogenic methane from organic rich sediments by camp intrusive rocks for ncie1 and large scale volcanically derived carbon species for ncie2 and ncie3 in addition progressive increase of atmospheric p co 2 throughout three ncies was possibly attributed to accumulation of volcanically derived co 2 from multiple camp eruptions which resulted in the development of ocean acidification across the tjb on the other hand in view of the oxic conditions in the deep mid panthalassa during three ncies the development of coeval oceanic anoxic euxinic conditions was restricted solely to shallow marine regions therefore ocean acidification together with localized shallow marine anoxia acted as environmental stresses on the biosphere which eventually resulted in the severe biotic crisis at the end of the triassic

late pleistocene and holocene melting history of the antarctic ice sheet derived from sea level variations abstract spatial and temporal variations of the late pleistocene and holocene sea levels provide important constraints on the melting history of the major ice sheets in this study we have examined the sea level variations at eight sites along the coast of antarctica to investigate the melting history of antarctic ice sheet complexes comparisons of sea level variations between observations and predictions due to glacio hydro isostatic adjustment suggest that the ice thicknesses removed from the last glacial maximum lgm around the weddell sea are significantly thicker than those around the ross embayment sea level observations also indicate that climap derived models predict too much relative sea level change and that consequently ice mass change along the coast has to be scaled down improvement of the late pleistocene antarctic ice model is required to evaluate more accurate predictions of present day geophysical observables associated with this history thus these more accurate predictions can then be subtracted from observables and the residual field can be analyzed to constrain ongoing mass changes from the ice sheet we therefore predicted present day geophysical observables such as the rate of change of solid surface gravity and crustal movement these geophysical observables based on the ice models constructed from observed sea level variations are significantly different from those based on previous models on the other hand detailed sea level observations around syowa indicate the existence of a sea level highstand of about 10 m around 40 kyr bp to investigate these sea level observations we have performed preliminary numerical calculations comparisons between these observations and predictions indicate the synchronous melting of the northern and southern ice sheets suggesting a strong link between the melting histories of both polar ice sheets

environmental change during the triassic jurassic boundary interval of an equatorial carbonate platform sedimentology and chemostratigraphy of the ghalilah formation united arab emirates abstract the sedimentology and chemostratigraphy 13ccarb 13corg sr concentrations of the triassic jurassic tr j boundary interval has been investigated in detail in sections of the ghalilah formation exposed in wadi ghalilah wadi milaha and wadi naqab northeastern united arab emirates the sequence of events recorded across the tr j boundary interval in ras al khaimah reflects significant environmental change that can ultimately be related to camp volcanism uppermost triassic limestones of the sumra member rich in coral calcareous sponges and large size bivalves are interbedded with siliciclastic mudstones and deposited in an open lagoonal environment these are abruptly followed by oolites with intercalated calcareous mudstones of the sakhra member that are devoid of macrofossil thrombolitic microbialites that occur in the lowermost sakhra member are interpreted to reflect the demise of hypercalcifying marine biota during the tr j boundary interval the oolites of the sakhra member are capped by a subaerial exposure surface followed by peritidal deposits of the shuba member the available sparse biostratigraphic data of the ghalilah formation are critically discussed and support a position of the tr j boundary at the base of the sakhra member a negative excursion in 13corg occurs in the upper sumra member and possibly correlates with the late triassic spelae carbon isotope event the 13ccarb and 13corg values increase across the boundary interval and an extended positive excursion in 13ccarb occurs in the oolites of the sakhra member sr concentrations increase in the bioclastic limestones of the uppermost sumra member and peak in the oolites of the upper sakhra member high sr concentrations also occur at correlative stratigraphical levels in the lombardy basin italy and are interpreted as an early hettangian seawater signal reflecting the global scale reduction of biological aragonite precipitation and an increased continental weathering flux

a new chronology for the end triassic mass extinction article i nfo the transition from the triassic to jurassic period initiating the age of the dinosaurs approximately 200 ma is marked by a profound mass extinction with more than 50 genus loss in both marine and continental realms this event closely coincides with a period of extensive volcanism in the central atlantic magmatic province camp associated with the initial break up of pangaea but a causal relationship is still debated the triassic jurassic t j boundary is recently proposed in the marine record at the first occurrence datum of jurassic ammonites post dating the extinction interval that concurs with two distinct perturbations in the carbon isotope record the continental record shows a major palynological turnover together with a prominent change in tetrapod taxa but a direct link to the marine events is still equivocal here we develop an accurate chronostratigraphic framework for the t j boundary interval and establish detailed trans atlantic and marine continental correlations by integrating astrochronology paleomagnetism basalt geochemistry and geobiology we show that the oldest camp basalts are diachronous by 20 kyr across the atlantic ocean and that these two volcanic pulses coincide with the end triassic extinction interval in the marine realm our results support the hypotheses of phanerozoic mass extinctions resulting from emplacement of large igneous provinces lips and provide crucial time constraints for numerical modelling of triassic jurassic climate change and global carbon cycle perturbations

distribution of iridium and associated geochemistry across the triassic jurassic boundary in sections at kuhjoch and kendlbach northern calcareous alps austria abstract samples from strata spanning the triassic jurassic boundary at the gssp at kuhjoch and at kendlbachgraben were studied by naa xrf and combustion analysis to determine ir levels and associated geochemistry the results are compared to previously determined carbon isotope stratigraphy at these sections ir concentrations in the limestones of the kossen formation at kuhjoch are very low

the asynchronous disappearance of conodonts new constraints from triassic jurassic boundary sections in the tethys and panthalassa abstract the end triassic extinction event ete has been recognized in numerous sections worldwide and it is usually marked by three negative carbon isotope excursions ncies named precursor p ncie initial i ncie and main m ncie negative carbon isotope excursions these three ncies are significant characteristics of this time interval and they are likely related to the emplacement of the central atlantic magmatic province camp that is considered the main trigger of the ete stable carbon isotope excursions commonly related to biotic turnovers and extinctions play an important role in stratigraphic correlations particularly around the triassic jurassic boundary tjb this time interval records the disappearance of conodonts elements of a feeding apparatus belonging to marine organisms that populated the paleozoic early mesozoic seas and which became extinct across the tjb so far the interpretation of conodont extinction has remained ambiguous as the timing of its last occurrence was debated which in turn hindered our understanding of the main cause s that could have led to their disappearance here we present and compare integrated data of nine tjb sections from different areas tethys and panthalassa and different depositional environments i e shallow vs deep water or proximal vs distal shelf each of these sections record both the last occurrences of latest triassic conodont taxa and pronounced changes in the carbon isotopic composition of organic matter across the tjb interval our analysis of chemo and integrated biostratigraphic correlation suggests that the final extinction of the taxon conodonta was asynchronous

geochemical consequences of intense pulse like degassing during the onset of the central atlantic magmatic province the triassic jurassic boundary tjb ismarked by one of the five largestmass extinctions of the phanerozoic and the eruption of a large igneous province the central atlanticmagmatic province camp the tjb is characterized by a carbonate production crisis by negative excursions in the carbon isotopic ratio of buried organic matter and by successive peaks in atmospheric co2 herewe use the numerical model geoclimto explore the possible connections between the camp emplacement and the observed carbon cycle perturbations different degassing scenarios linked to the camp eruption are explored we show that the emission of realistic amounts of co2 that follow a geologically constrained degassing scenario as short termpeaks less than 10 ka leads to successive decrease in carbonate production as observed in the geological record we also calculate the evolution of carbon isotopes and show that our model reproduces the amplitude of the isotopic excursion with a volcanic degassing of co2 characterized by a carbon isotopic composition of 20 such low values could be associated to carbon pools of light isotopic composition located at the transition zone cartigny p 2010 earth and planetary science letters v 296 p 329 339 and not necessarily to biogenicmethane release finally themodel predicts a succession of short term co2 rises with an amplitude in close agreement with available proxy based reconstructions

triassic jurassic organic carbon isotope stratigraphy of key sections in the western tethys realm austria the late triassic period is recognized as one of the five major mass extinctions in the fossil record all these important intervals in earth history are associated with excursions in c isotope records thought to have been caused by perturbations in the global carbon cycle the nature and causes of c isotopic events across the triassic jurassic t j transition however are poorly understood we present several new high resolution organic c isotope records from the eiberg basin austria including the proposed global boundary stratotype section and point gssp for the base of the jurassic the triassic jurassic boundary interval in these records is characterized by the initial and main negative organic carbon isotope excursions cie of up to 8 the initial and main cies are biostratigraphically constrained by first and last occurrences of boundary defining macro and microfossils e g ammonites high resolution c isotope records appear to be an excellent correlation proxy for this period in the eiberg basin pyrolysis analysis demonstrates increased hydrogen index hi values for organic matter coinciding with the initial cie terrestrial organic matter influx and mass occurrences of green algae remains may have influenced the c isotope composition of the sedimentary organic matter this may have contributed to the extreme amplitude of the initial cie in the eiberg basin

the quest for chron e23r at partridge island bay of fundy canada camp emplacement postdates the end triassic extinction event at the north american craton the partridge island stratigraphic section at the bay of fundy maritime canada reveals a continental sedimen tary succession with the end triassic mass extinction level closely followed by basalts of the central atlantic magmatic province camp new paleomagnetic data show that a short reverse magnetic polarity chron correlative to e23r of the newark geomagnetic polarity time scale gpts is present below the extinction event organic carbon isotope data and basalt geochemistry further indicate that the onset of camp emplacement in the bay of fundy was roughly synchronous with emplacement in the newark basin but slightly postdates the oldest camp volcanism in morocco by 20 ka these re sults confirm the potential for long distance camp correlations based on geochemical trace elements indicate substantiate provincialism of latest triassic palynoflora and suggest a very concise period 100 ka of camp emplacement in the northern atlantic region resume la section stratigraphique de l ile partridge dans la baie de fundy maritimes canada revele une succession se dimentaire continentale dans laquelle le niveau d extinction massive de la fin du trias est suivi de pres par des basaltes de la province magmatique centre atlantique camp de nouvelles donnees paleomagnetiques montrent qu un chrone de breve inversion de polarite magnetique correle a e23r de l echelle de temps geomagnetique de polarite de newark est present sous l evenement d extinction des donnees d isotopes du carbone organique et la geochimie des basaltes indiquent de plus que le debut de la mise en place de la camp dans la baie de fundy a ete passablement contemporain avec la mise en place du bassin newark mais cette mise en place a eu lieu peu de temps apres le plus ancien volcanisme camp au maroc soit environ 20 ka ces resultats confirment le potentiel de correler la camp sur de longues distances en se basant sur des ele ments traces geochimiques ils indiquent et valident le provincialisme de la plus recente palynoflore du trias et suggerent une tres courte periode 100 ka pour la mise en place de la camp dans la region de l atlantique nord traduit par la redaction

antarctic elevation change from 1992 to 1996 satellite radar altimeter measurements show that the average elevation of the antarctic ice sheet interior fell by 0 9 0 5 centimeters per year from 1992 to 1996 if the variability of snowfall observed in antarctic ice cores is allowed for the mass imbalance of the interior this century is only 0 06 0 08 of the mean mass accumulation rate

stratigraphy and palaeoenvironmental analysis of the triassic jurassic transition in the western southern alps northern italy abstract high resolution stratigraphic studies were carried out on the rhaetian hettangian succession of the bergamasc alps western southern alps italy in order to characterise the stratigraphic and palaeoenvironmental evolution of the lombardian succession across the triassic jurassic t j boundary the t j boundary in the bergamasc alps is sandwiched between the rhaetian carbonate ramp succession of the zu limestone formation and the malanotte formation a new lithostratigraphic unit introduced in this paper deposited during relative sea level rise in the earliest hettangian the zu limestone is organised into subtidal mixed shale carbonate asymmetric cycles documenting the regional evolution from a distal to a proximal depositional environment of an articulated homoclinal carbonate ramp the malanotte formation lacks cyclicity and shows thin bedding and a dominant micritic facies documenting the subtidal evolution of a relatively homogenous outer carbonate ramp environment the microfloral associations record a gradual evolutionary change at the t j boundary whereas the biocalcifying communities appear to be severely affected by the end triassic biotic crisis

major environmental change and bonebed genesis prior to the triassic jurassic mass extinction we present new geochemical and sedimentological data from marginal marine strata of penarth bay south wales uk to elucidate the origin of widespread but enigmatic concentrations of vertebrate hard parts bonebeds in marine successions of rhaetian age late triassic sedimentological evidence shows that the phosphatic constituents of the bonebeds were subjected to intense phosphatization in shallow current dominated settings and subsequently reworked and transported basinward by storms interbedded organic rich strata deposited under quiescent and poorly oxygenated conditions record enhanced phosphorus regeneration from sedimentary organic matter into the water column and probably provided the main source of phosphate required for heavy bonebed clast phosphatization the stratigraphically limited interval showing evidence for oxygen depletion and accelerated p cycling coincides with a negative 4 organic carbon isotope excursion which possibly reflects supra regional changes in carbon cycling and clearly predates the initial isotope excursion characterizing many triassic jurassic boundary strata our data indicate that rhaetian bonebeds are the lithological signature of profound climatically driven changes in carbon cycling and redox conditions and support the idea of a multi pulsed environmental crisis at the end of the triassic possibly linked to successive episodes of igneous activity in the central atlantic magmatic province supplementary material sample positions data table and a detailed stratigraphic log from the upper triassic of penarth bay south wales uk are available at http www geolsoc org uk sup18510

lithogeochemical patterns around pb zn mineralizations in dinantian carbonate rocks of eastern belgium the lithogeochemical distribution patterns of mg sr na zn pb fe mn k corg organic matter and ir insoluble residue in the dinantian limestones and dolomites from the eastern part of belgium have been studied dinant and verviers synclinorium comparison of geochemical data of non mineralized strata revealed higher background values in the strata of the verviers synclinorium where pb zn mineralizations occur in this area a relation may exist with the metallogenetic district herve vesdre theux district proposed by dejonghe 1985b however the higher background values also could relate to the more restricted sedimentation conditions in the verviers synclinorium as opposed to the more open marine conditions in the dinant synclinorium the influence of mineralization on the geochemistry of limestones is limited and unpredictable in dolomites however the effect can be important in these rocks the lithogeochemical distribution of zn pb and mn can be subdivided into three populations i e a regional background a local high background and a halo population the higher trace element concentrations in the halo population is caused by the existence of disseminated sulfide minerals sphalerite galena and pyrite and zn bearing goethite mainly pseudomorphs after pyrite and mn oxides the sulfides relate to the ore emplacement in the local high background only the zn bearing oxides occur their presence and thus the development of the local high background relates to weathering processes

isotopic evidence bearing on late triassic extinction events queen charlotte islands british columbia and implications for the duration and cause of the triassic jurassic mass extinction stable isotope analyses of late triassic to earliest jurassic strata from kennecott point in the queen charlotte islands british columbia canada shows the presence of two distinct and different organic carbon isotope anomalies at the norian rhaetian and rhaetian hettangian triassic jurassic stage boundaries at the older of these boundaries which is marked by the disappearance of the bivalve monotis the isotope record shows a series of short lived positive excursions toward heavier values strata approaching this boundary show evidence of increasing anoxia at the higher boundary marked by the disappearance of the last remaining triassic ammonites and over 50 species of radiolarians the isotopic pattern consists of a series of short duration negative anomalies the two events separated by the duration of the rhaetian age comprise the endtriassic mass extinction while there is no definitive evidence as to cause the isotopic record does not appear similar to that of the impact caused cretaceous tertiary boundary extinction d 2004 published by elsevier b v

middle permian organic carbon isotope stratigraphy and the origin of the kamura event abstract large carbon cycle perturbations associated with the middle permian capitanian mass extinction have been widely reported but their causes and timing are still in dispute low resolution carbon isotope records prior to this event also limit the construction of a middle permian chemostratigraphic framework and global or local stratigraphic correlation and hence limit our understanding of carbon cycle and environmental changes to investigate these issues we analyzed the 13corg values from the middle permian chert mudstone sequence gufeng formation in the lower yangtze deep water basin south china and compared them with published records to build a chemostratigraphic scheme and discuss the underlying environmental events the records show increased 13corg values from late kungurian to early guadalupian followed by a decrease to the late wordian early capitanian the early mid capitanian was characterized by elevated 13corg values suggesting the presence of the kamura event an interval of heavy positive values seen in the 13ccarb record we propose that these heavy capitanian 13c values may be a response to a marked decline in chemical weathering rates on pangea and associated reduction in carbonate burial which we show using a biogeochemical model the subsequent negative 13c excursion seen in some carbonate records especially in shallower water sections and in a muted expression in organic carbon coincide with the capitanian mass extinction may be caused by the input of isotopically light carbon sourced from the terrestrial decomposition of organic matter

mass balance of the antarctic ice sheet the antarctic contribution to sea level rise has long been uncertain while regional variability in ice dynamics has been revealed a picture of mass changes throughout the continental ice sheet is lacking here we use satellite radar altimetry to measure the elevation change of 72 of the grounded ice sheet during the period 1992 2003 depending on the density of the snow giving rise to the observed elevation fluctuations the ice sheet mass trend falls in the range 5 85gt yr 1 we find that data from climate model reanalyses are not able to characterise the contemporary snowfall fluctuation with useful accuracy and our best estimate of the overall mass trend growth of 27 29 gt yr 1 is based on an assessment of the expected snowfall variability mass gains from accumulating snow particularly on the antarctic peninsula and within east antarctica exceed the ice dynamic mass loss from west antarctica the result exacerbates the difficulty of explaining twentieth century sea level rise

a biocalcification crisis at the triassic jurassic boundary recorded in the budva basin dinarides montenegro volcanic activity in the central atlantic magmatic province resulting in an increased flux of co 2 so 2 and ch 4 into the oceans and atmosphere has been proposed as one of the mechanisms causing the biotic crisis at the triassic jurassic boundary oceanic uptake of co 2 due to extreme greenhouse conditions should have had an impact on ocean chemistry and the position of the calcite compensation depth in this study we chose two pelagic sections from the budva basin as archives for paleoceanographic change across the triassic jurassic boundary in deep water settings our record represents the first documentation of a sudden termination of carbonate deposition across the triassic jurassic boundary in a pelagic deep water environment based on radiolarian biostratigraphy the system boundary is placed at the sharp lithological contact between two pelagic formations the upper triassic limestones and lower jurassic siliceous limestones alternating with shales a rapid drop of carbonate content from 90 to less than 10 occurred contemporaneous with a negative anomaly in the stable carbon isotope record measured in both bulk carbonate 1 3 and bulk organic matter 1 1 the abrupt reduction of carbonate content in the budva basin was the result of either increased carbonate dissolution causing shoaling of the calcite compensation depth or reduced carbonate input due to biocalcification crisis both nonexclusive scenarios support the hypothesis of decreased ocean saturation with respect to calcium carbonate which could be a direct consequence of increased co 2 so 2 and ch 4 fluxes

carbon isotope anomaly and other geochemical changes at the triassic jurassic boundary from a marine section in hungary most mass extinctions are linked with carbon isotope excursions implying that biotic crises are coupled with changes in the global carbon cycle the isotopic evolution during the end triassic extinction is far less documented than that for the other major phanerozoic extinctions here we report a sharp and short lived 23 5 excursion in carbon isotope values for carbonate d 13 ccarb corresponding to a 22 excursion in the isotopic composition of marine organic matter d 13 corg and other geochemical

sedimentology carbon isotope stratigraphy and micropalaeontology of the rhaetian zlambach formation implications for the dachstein carbonate platform development northern calcareous alps austria abstract middle to late rhaetian toe of slope to basin deposits zlambach formation of the northern calcareous alps in the tethyan realm have been studied with respect to depositional palaeoenvironments and chemo and sequence stratigraphy using high resolution stable isotope and x ray fluorescence measurements microfacies and microfossil analysis our results show that the zlambach formation represents a regressive transgressive succession which includes one 3rd order and two 4th order depositional sequences as well as several subordinate sedimentary cycles reflecting variations of calciturbidite input from the dachstein platform due to minor sea level fluctuations we present the first high resolution 13ccarb record for the middle and upper rhaetian interval of the west tethyan open marine realm the data show in contrast to earlier suggestions that growth and progradation of the dachstein carbonate platform margin was continuous until the early choristoceras marshi ammonoid zone upper rhaetian in the late c marshi zone the hallstatt basin was affected by significant environmental perturbations as recorded by a 1 0 ccarb negative excursion followed by a 1 3 positive excursion and contemporaneous fluctuations in benthic microfossil abundance and diversity the occurrence of comparable carbon isotope excursions in the late c marshi zone of intraplatform basinal deposits of the northern calcareous alps suggests that these perturbations were of a higher significance than previously thought these isotope excursions could be related to regional ecologic changes such as the late rhaetian termination of the dachstein platform margin growth

multiple phases of carbon cycle disturbance from large igneous province formation at the triassic jurassic transition the end triassic mass extinction ca 201 4 ma coincided with a major carbon cycle perturbation based on an 5 6 negative excursion in 13 c toc total organic carbon records both events coincided directly with the onset of massive flood basalt volcanism in the central atlantic magmatic province camp organic carbon isotope data from the western tethys ocean austria and the germanic basin uk and germany however demonstrate earlier disruption of the global carbon cycle preceding camp eruptions a 2 3 late rhaetian precursor negative excursion in marine and continental 13 c toc records is matched by a negative perturbation in 13 c leaf data suggesting multiple events of rhaetian atmospheric 13 c depletion intruding dike and sill systems preceding camp eruptive volcanic activity may have released 3000 7000 gt of isotopically light carbon as thermogenic methane from subsurface organic rich strata this possibly caused an end triassic atmospheric p co 2 increase and reduced ecosystem stability before the actual onset of eruptive volcanic activity in the camp region we present a model that identifies three phases of disturbances in global biogeochemical cycles related to the formation of this large igneous province

an extended organic carbon isotope record across the triassic jurassic boundary in the queen charlotte islands british columbia canada abstract new lithologic and organic carbon isotope data are presented for the triassic jurassic boundary section at kennecott point queen charlotte islands british columbia canada the previously reported late norian to earliest hettangian record is extended by over 130 m and three new isotopic features are revealed the record now shows a negative offset in baseline carbon isotope values from approximately 29 in the late norian to 31 in the hettangian this offset is accompanied by the previously reported 2 negative excursion at the triassic jurassic boundary and a 5 positive excursion in the early hettangian there is a significant long term negative isotopic trend in the hettangian interval of the section which may be due to camp volcanism the positive excursion is attributed to a decline in bio calcification as well as changes in microbial ecology both related to the mass extinction at the triassic jurassic boundary

extremely elevated co2 concentrations at the triassic jurassic boundary abstract although progress has been made in recent years in reconstructing the environmental conditions at the triassic jurassic boundary tjb published records of atmospheric co 2 concentrations have been of low resolution and or based on multi taxon estimates this is addressed here by reconstructing co 2 concentrations across the tjb using stomatal frequencies of four phylogenetically and ecologically distinct plant groups from two depositionally geographically and taphonomically separate boundary sections in east greenland and northern ireland with stomatal proxy methods and regression analysis the resulting co 2 records then are compared with an additional existing tjb record from a geological section in sweden the final results indicate that pre tjb rhaetian the co 2 concentration was approximately 1000 ppm that it started to rise steeply pre boundary and had doubled to around 2000 2500 ppm at the tjb the co 2 concentration then remained elevated for some time post boundary before returning to pre tjb levels in the hettangian these results are in very good accordance with published c isotope fire and leaf dissection records and clearly indicate steeply rising and lingering co 2 concentration at the tjb

the triassic jurassic boundary event from an equatorial carbonate platform ghalilah formation united arab emirates the ghalilah formation uae provides a complete and continuous equatorial shallow water carbonate sequence through the upper triassic to lower jurassic interval in higher latitudes this interval is frequently associated with widespread ocean acidification evidenced by a lack of carbonates or a hiatus in deposition the data presented here in contrast show evidence for aragonite supersaturation at the triassic jurassic boundary in the equatorial tethys 13 c carb shows a characteristic negative excursion with values as low as 2 8 just below the boundary deposition of fossiliferous limestones in this location persisted into the latest rhaetian through the initial negative carbon isotope excursion supplementary material 13 c carb data from bulk rock and a detailed stratigraphic log with sample locations are available at https doi org 10 6084 m9 figshare c 3277283

inland thinning of the amundsen sea sector west antarctica 1 together with the pine island glacier pig the thwaites tg and smith sg glaciers are the principal drainage systems of the amundsen sea as sector of western antarctica here we use satellite radar altimetry and interferometry to show that a rapid thinning of ice has occurred within the fastest flowing sections of all as outlet glaciers the pattern of thinning extends to distances greater than 150 km inland between 1991 and 2001 the tg and sg thinned by more than 25 and 45 m at their grounding lines and a total of 154 16 km 3 of ice or 0 43 mm of eustatic sea level rise was lost from the as sector glaciers to the ocean we show that the thickness changes may have caused the pig tg and sg to retreat inland by over 8 4 and 7 km respectively in line with independent estimates of grounding line migration

foraminiferal biostratigraphy and sequence stratigraphy of peritidal carbonates at the triassic jurassic boundary karaburun peninsula western turkey abstract continuous shallow marine carbonates spanning the triassic jurassic boundary are exposed in the karaburun peninsula western turkey the studied section tahtaiskele section consists of upper triassic cyclic shallow marine carbonates intercalated with clastics overlain by lower liassic carbonates based on the microfacies stacking patterns three main types of shallowing upward cycles have been recognized cycles are mostly composed of subtidal facies at the bottom intertidal supratidal facies and or subaerial exposure structures at the top the duration of the cycles suggests that cycles were driven by the precessional milankovitch rhytmicity in the sequence stratigraphic frame of the tahtaiskele section 4 sequence boundaries were detected and globally correlated the first sequence boundary is located at the alaunian sevatian boundary nearly coinciding with the first appearance of triasina hantkeni the second falls in the rhaetian corresponding to a major sea level fall which led to the invasion of forced regressive siliciclastic deposits over the peritidal carbonates the third occurs close to the t j boundary and the fourth lies slightly above the base of the jurassic in the studied section extinction survival and recovery intervals have been recognized based on the stratigraphic occurrence patterns of benthic foraminifera and algae foraminifers became nearly totally extinct in the inner carbonate shelves at the triassic jurassic boundary and an interval of approximately 0 5 my passed before the begining of the recovery of jurassic foraminifera

on the onset of central atlantic magmatic province camp volcanism and environmental and carbon cycle change at the triassic jurassic transition neuquen basin argentina abstract the triassic jurassic transition is characterized by the end triassic mass extinction approximately synchronous with the onset of emplacement of the central atlantic magmatic province camp and associated with a major negative carbon isotope excursion cie affecting the ocean atmosphere system here we present new data total organic carbon pyrolysis analysis carbon isotopes from bulk organic matter elemental mercury and other elemental contents from a southern hemisphere triassic jurassic boundary succession in the neuquen basin argentina the end triassic mass extinction there coincides with a relatively small 2 3 negative cie in bulk organic matter and we present a model that suggests that extreme aridity across the western pangaean landmass may have resulted in rather limited terrestrial organic matter flux to the sedimentary realm in eastern panthalassic marine basins hypothetically reducing the magnitude of the observed negative cie in 13ctoc increased deposition of sedimentary hg and hg toc and hg zr in the marine neuquen basin began stratigraphically before the negative cie associated with the end triassic mass extinction and thus before the commencement in north america and africa of camp related basaltic volcanism but possibly coinciding with the early emplacement of camp associated intrusives dykes and sills this relative chronology suggests thermal alteration of intruded country rocks and or intrusive magmatic degassing of hg as potential major sources of elevated hg fluxes to the atmosphere at this time the neuquen basin experienced the development of dysoxic anoxic marine conditions across the triassic jurassic transition enabling increased preservation of organic matter simple mass balance calculations show that enhanced carbon burial rates can explain the inferred evolution of the global exogenic carbon cycle across this time interval

sedimentological palynological and geochemical studies of the terrestrial triassic jurassic boundary in northwestern poland the kamien pomorski ig 1 borehole pomerania nw poland yields a profile through the triassic jurassic t j transition in continental deposits an integrated study of the sedimentology sequence stratigraphy palynology biostratigraphy and geochemistry of these deposits has been carried out on the boundary interval which represents a time of major environmental change two lithological units within the transitional section are distinguished the lower middle rhaetian wielichowo beds of alluvial plain facies which shows evidence of a semi arid climate and the upper rhaetian to lower hettangian zagaje formation lying above a marked erosional sequence boundary composed of mudstone claystone and sandstone deposited in a fluvial lacustrine environment carbon isotope values obtained from palynomaceral separates and thus reflecting isotopic changes in atmospheric co 2 show significant fluctuations through the rhaetian the most conspicuous negative 13 c org excursion is correlated with the rhaetian initial excursion and shows two sub peaks pointing to short term carbon cycle disturbances of lesser magnitude above the initial negative excursion there is a positive excursion followed again by more negative values representing subordinate fluctuation within a positive excursion and is correlated with the t j boundary seventy two miospore taxa have been determined from the studied t j transitional section two major palynological assemblages have been distinguished the lower one typically rhaetian named the cingulizonates rhaeticus limbosporites lundblandii association which corresponds to the rhaetipollis ricciisporites rhaetipollis limbosporites zone and the upper one typically hettangian named the conbaculatisporites mesozoicus dictyophyllidites mortoni cerebropollenites thiergartii association with the age diagnostic pollen c thiergartii which corresponds to the pinuspollenites trachysporites trachysporites heliosporites zone the t j palynofloral turnover occurred in a humid period and is more conspicuous then palynofloral changes observed in greenland the tethyan domain or other parts of ne europe the osmium isotope system is studied herein for the first time from t j continental deposits and shows marked disturbances similar to those measured in marine deposits and attributed to volcanic fallout carbon and osmium isotope correlation and coeval increase in polycyclic aromatic hydrocarbon pah content and darkening of miospores confirm that eruptions of the central atlantic magmatic province camp contributed to the perturbances in climate and crisis in the terrestrial biosphere a series of periodical atmospheric loading by co 2 ch 4 or alternatively by so 2 sulphate aerosols and toxic compounds is inferred to have caused a series of rapid climatic reversals directly influencing the ecosystem and causing the triassic floral crisis a floral turnover period commenced at the initial 13 c excursion with the onset of camp volcanism obtained values of initial 187 os 186 os between 2 905 and 4 873 and very low iridium content about 5 ppt lend no support to a role for an extraterrestrial impact at the t j boundary event the position of the initial negative carbon isotope excursion about 12 m below the t j boundary position of sequence boundaries emergence surfaces and other isotope excursions allow reliable correlation with marine profiles including st audrie9s bay uk csovar hungary and the gssp profile at kuhjoch austria

carbon cycle perturbation in the middle jurassic and accompanying changes in the terrestrial paleoenvironment abstract carbon isotope analyses of fossil wood from the middle jurassic ravenscar group yorkshire ne england reveal a significant excursion toward light isotopic values 13c change of 3 to 4 at about the aalenian bajocian boundary 174 ma a positive carbon isotopic excursion is also shown for the middle bajocian 170 ma but is less clearly defined these isotopic patterns are very similar to the few published marine carbonate records available for this time in particular one based on belemnites from the hebrides basin nw scotland and others from pelagic limestones in italy the similarity of the terrestrial and marine isotope curves is an indication that the observed isotopic signal is a global phenomenon through parts of the ravenscar group the scarborough formation supplementary data from bulk organic carbon and palynofacies analysis confirm that isotopic curves based on bulk analyses may be strongly influenced by the balance of terrestrial versus marine organic matter present in th

palaeoenvironmental changes in the late triassic rhaetian of the northern calcareous alps clues from stable isotopes and microfossils abstract the triassic kossen formation rhaetian in the northern calcareous alps has been studied with respect to oxygen and carbon isotope ratios of brachiopod shells and whole rocks together with the stratigraphic range and ecology of ostracod assemblages in order to detect palaeotemperature changes in the kossen formation and determine their significance for environmental and climatic conditions in the rhaetian sea of the eiberg basin northern calcareous alps for this purpose 60 18 o measurements on 43 articulate brachiopods samples from 8 different horizons were carried out the results indicate a progressive decrease of 2 5 c in seawater bottom temperature in the middle late rhaetian the carbonate microfacies as well as macro and microfossil assemblages indicate a gradual increase of water depth in the eiberg basin and thereby explain the observed bottom water cooling the oxygen isotope data further suggest that the palaeobathymetric temperature gradient in the eiberg basin was rather low indicating that almost no deep water exchange with tethys existed at that time carbon isotopes from brachiopod shells and from bulk carbonates show a trend to heavier values from the hochalm member up to the lowest unit 3 of the eiberg member that parallels oxygen isotopes this positive 13 c trend is interrupted by a sudden 1 5 negative excursion in the late rhaetian late rhaetian event a time span when the oxygen isotopes remain heavy

mercury evidence for pulsed volcanism during the end triassic mass extinction the central atlantic magmatic province camp has long been proposed as having a causal relationship with the end triassic extinction event 201 5 ma in north america and northern africa camp is preserved as multiple basaltic units interbedded with uppermost triassic to lowermost jurassic sediments however it has been unclear whether this apparent pulsing was a local feature or if pulses in the intensity of camp volcanism characterized the emplacement of the province as a whole here six geographically widespread triassic jurassic records representing varied paleoenvironments are analyzed for mercury hg concentrations and hg total organic carbon hg toc ratios volcanism is a major source of mercury to the modern environment clear increases in hg and hg toc are observed at the end triassic extinction horizon confirming that a volcanically induced global hg cycle perturbation occurred at that time the established correlation between the extinction horizon and lowest camp basalts allows this sedimentary hg excursion to be stratigraphically tied to a specific flood basalt unit strengthening the case for volcanic hg as the driver of sedimentary hg toc spikes additional hg toc peaks are also documented between the extinction horizon and the triassic jurassic boundary separated by 200 ky supporting pulsatory intensity of camp volcanism across the entire province and providing direct evidence for episodic volatile release during the initial stages of camp emplacement pulsatory volcanism and associated perturbations in the ocean atmosphere system likely had profound implications for the rate and magnitude of the end triassic mass extinction and subsequent biotic recovery

high resolution ammonite and carbon isotope stratigraphy across the triassic jurassic boundary at new york canyon nevada the triassic jurassic boundary is generally considered as one of the major extinctions in the history of phanerozoic the high resolution ammonite correlations and carbon isotope marine record in the new york canyon area allow to distinguish two negative carbon excursions across this boundary with different paleoenvironmental meanings the late rhaetian negative excursion is related to the extinction and regressive phase the early hettangian 13corg negative excursion is associated with a major floristic turnover and major ammonite and radiolarian radiation the end triassic extinction early jurassic recovery is fully compatible with a volcanism triggered crisis probably related to the central atlantic magmatic province the main environmental stress might have been generated by repeated release of so2 gas heavy metals emissions darkening and subsequent cooling this phase was followed by a major long term co2 accumulation during the early hettangian with development of nutrient rich marine waters favouring the recovery of productivity and deposition of black shales

carbon cycle dynamics following the end triassic mass extinction constraints from paired δ13ccarb and δ13corg records 1 constraining the carbon isotopic changes associated with the end triassic mass extinction is key to understanding the causes of the extinction and dynamics of recovery from it yet the pattern and timing of 13c variation surrounding the extinction remain poorly constrained here we present close to 1000 new 13c measurements from six newly sampled sections in italy we observe a sharp negative excursion in 13ccarb coincident with the disappearance of the triassic fauna and two positive excursions above it the negative 13ccarb excursion in these sections does not occur in 13corg suggesting a possible diagenetic origin in contrast the interval of elevated 13c occurs in both carbonate and organic carbon suggesting that it is likely to be a primary feature the positive excursions in the lombardy basin southern alps and mt cefalo southern apennines appear to be time correlative on the basis of their position above the disappearance of characteristically triassic biota however it is less certain that they are time correlative with positive excursions in other sections worldwide as few options exist that honor both bio and chemostratigraphy nonetheless similarity to other events that are interpreted as global as well as carbon cycle considerations suggest that the isotopic enrichment is best interpreted to reflect a shift in the isotope composition of the global surface carbon reservoir our data indicate that perturbation of the global carbon cycle was not confined to the immediate vicinity of the extinction interval but rather persisted for substantial length of geologic time afterwards

new geochemical evidence for the onset of volcanism in the central atlantic magmatic province and environmental change at the triassic jurassic boundary the late triassic early jurassic was a time of major global change however the fundamental processes driving these changes are less than clear we have determined the re and os abundances and os isotope compositions of marine mudrock samples that span the triassic jurassic boundary in the uk and have established that major isotopic and geochemical shifts in the composition of seawater took place in the latest triassic we argue that these shifts were caused by the sudden initiation of widespread igneous activity within the central atlantic magmatic province associated with rifting of the supercontinent pangea the os isotope composition of seawater responded rapidly to these events demonstrating that the seawater os isotope system has great potential in identifying the nature and precise timing of major environmental change

palaeoenvironmental significance of organic facies and stable isotope signatures the ladinian san giorgio dolomite and meride limestone of monte san giorgio switzerland whl unesco the over 600 m thick ladinian carbonate section of monte san giorgio world heritage list united nations educational scientific and cultural organization switzerland including the san giorgio dolomite and the meride limestone was analysed with respect to its sedimentology organic matter content rock eval and palynofacies and stable carbon and oxygen isotope composition application of geochemical proxies and optical data transmitted light microscopy epifluorescence cathodoluminescence and scanning electron microscopy allowed the assessment of the relative sea level trend and the characterization of the organic matter content three main organic matter assemblages were defined according to their composition and stratigraphic position overall results suggest immature organic matter predominantly of marine bacterial origin with an upsection increasing land plant derived contribution forcing factors controlling organic matter accumulation include changes in sea level productivity and runoff which in turn were probably promoted by periods of rainfall following explosive volcanic activity enhanced productivity during sea level highstands is considered to have played a key role in black shale formation under anoxic sulphidic conditions mainly in the besano formation in contrast sea level lowstands coupled with intensified runoff resulted in increased basin restriction and in deposition of laminated limestone mainly under lower dysoxic to anoxic conditions chiefly in the lower meride limestone under the latter conditions benthic microbial activity produced most of the hydrogen rich organic matter contributed to carbonate precipitation and also played a major role in taphonomic control on vertebrate fossil preservation in more general terms the monte san giorgio section proved to be an excellent testing ground making it possible to compare diverse approaches with each other and more specifically to relate optical evidence to geochemical signatures

carbon cycle perturbation and stabilization in the wake of the triassic jurassic boundary mass extinction event 1 the triassic jurassic boundary mass extinction event t j 199 6 ma is associated with major perturbations in the carbon cycle recorded in stable carbon isotopes two rapid negative isotope excursions in bulk organic carbon 13corg occur within the immediate boundary interval at multiple locations and have been linked to the outgassing of 12c enriched co2 from the central atlantic magmatic province in british columbia a positive 13corg excursion of 5 vienna peedee belemnite v pdb spans part or all of the subsequent hettangian stage here we examine the significance of these carbon isotope excursions as records of global carbon cycle dynamics across the t j boundary and test the link between carbon cycle perturbation stabilization and biotic extinction recovery patterns a combination of 13corg and palynological analyses from the late triassic to early jurassic in the mingolsheim core germany suggests that organic carbon isotope variations are best explained as the result of both compositional changes in terrestrial versus marine input and disturbance and recovery patterns of major terrestrial plant groups across the t j boundary a new high resolution 13ccarb record from the val adrara section in the southern alps italy spanning from the uppermost rhaetian through lower sinemurian does not exhibit a negative excursion at the t j boundary but does record a large positive 13ccarb excursion of 4 v pdb in bulk carbonate that begins at the t j boundary and reaches a local maximum at the early late hettangian boundary values then gradually decrease reaching 0 5 at the hettangian sinemurian boundary and remain relatively constant into the early sinemurian complementary 13ccarb data from 4 more sections that span the hettangian sinemurian boundary support carbon cycle stabilization within the upper hettangian our analyses suggest that isotope changes in organic carbon reservoirs do not necessarily require a shift in the global exogenic carbon reservoir and that the positive excursion in the carbonate carbon isotope record is best explained as the combined result of an increase in atmospheric pco2 leading to accelerated carbon cycling decreased skeletal carbonate production and increased organic carbon burial lasting several hundred thousand years the termination of the positive inorganic carbon isotope excursion coincides with the recovery of marine skeletal carbonate producers and coeval changes in terrestrial vegetation and reflects the gradual reduction in pco2 and the stabilization of the global carbon cycle during the sinemurian

stagnation of ice stream c west antarctica by water piracy the dynamic behavior of the west antarctic ice sheet is of interest because of the possibility that it may change and cause rapid sea level rise attention is focused on the fast moving and rapidly responding ice streams that drain the ice sheet one of these ice stream c largely stopped about a century ago and some models for this shutdown postulate negative feedbacks that would tend to stabilize the ice sheet here new data are presented indicating that the slowdown of the ice stream is restricted to its lower part and occurred because of loss of lubrication on localized sticky spots at the bed of the ice stream the increased friction probably arises from a topographic accident of the glacier bed that has directed lubricating water to the neighboring ice stream b together with slow drawdown of the ice sheet rather than from any general stabilizing feedbacks

carbon isotope stratigraphy and palynostratigraphy of the triassic jurassic transition in the tiefengraben section northern calcareous alps austria abstract the end triassic is characterized by enhanced rates of biotic turnover in both the marine and terrestrial realms carbon isotope anomalies have been reported worldwide that may indicate coeval global disturbances in the biogeochemical cycles here we present the results of an integrated study of the palynomorph assemblages and the carbon isotope composition of organic matter in the tiefengraben section near st wolfgang austria carbon isotope values from bulk organic matter show significant fluctuations through the triassic jurassic t j boundary interval with two prominent negative 13 c org excursions an initial negative carbon isotope excursion occurs at the base of the kendlbach formation tiefengraben member pre planorbis beds although triassic ammonoids and conodonts have their highest occurrence at the top of the underlying kossen formation the palynomorph and calcareous microfossil assemblages indicate still a rhaetian age for the lower part of the tiefengraben member high abundance of prasinophytes during the interval of the initial carbon isotope excursion may represent a bloom of green algae that flourished as a result of the disturbance of the marine ecosystems increased spore abundance together with the disappearance of distinctive late triassic pollen types e g ovalipollis rhaetipollis indicate vegetation changes on land that are contemporaneous with the marine biotic crisis a second negative carbon isotope excursion occurs in the middle part of the tiefengraben member based on palynological evidence the t j boundary may be drawn at about this level by the lowest occurrence of cerebropollenites thiergartii the established carbon isotope curve as well as palynostratigraphic and other biostratigraphic events can be correlated with st audrie s bay england

mass balance of polar ice sheets recent advances in the determination of the mass balance of polar ice sheets show that the greenland ice sheet is losing mass by near coastal thinning and that the west antarctic ice sheet with thickening in the west and thinning in the north is probably thinning overall the mass imbalance of the east antarctic ice sheet is likely to be small but even its sign cannot yet be determined large sectors of ice in southeast greenland the amundsen sea embayment of west antarctica and the antarctic peninsula are changing quite rapidly as a result of processes not yet understood

climate change driven black shale deposition during the end triassic in the western tethys abstract several new triassic jurassic boundary sections from the eiberg basin northern calcareous alps austria have been studied at high resolution we present integrated geochemical and biological proxy data from this western tethys shelf basin high resolution correlation of kuhjoch the global boundary stratotype section and point gssp for the base of the jurassic hochalplgraben and tiefengraben shows that the initial and main carbon isotope excursions cie are contemporaneous with first and last occurrences of boundary defining macro and microfossils we focus on the end triassic initial cie at the transition from the limestones of the kossen formation to the marls of the kendlbach formation this change coincides with a dramatically increased influx of conifer cheirolepidiaceae pollen and increased total organic carbon toc values succeeded by an acme of green algae cymatiosphaera we present a model in which increased terrestrial organic matter influx is related to enhanced seasonality and increased erosion of the hinterland reduced salinity of the surface waters led to the mass occurrence of green algae stratification of the water column may have caused anoxic bottom water conditions and black shale deposition during the initial cie at the base of the kendlbach fm

the end triassic negative δ13c excursion a lithologic test abstract the end triassic mass extinction is associated with a large negative carbon isotope excursion which has been interpreted as reflecting the rapid injection of 13 c depleted co 2 or methane associated with the emplacement of the central atlantic magmatic province however in a number of sections in central europe the negative excursion is associated with a carbonate poor lithology and the most isotopically depleted values are associated with the lowest percent carbonate raising the possibility of a lithologic control on 13 c carb here we test the uniqueness of the relationship between the carbonate poor lithology and the 13 c signal by comparing the geochemistry of the extinction marl with two upper triassic carbonate poor beds from lower positions within the same stratigraphic sections we find that the extinction and non extinction marls overlap nearly completely in terms of their carbonate content but differ substantially in their isotopic trends the extinction marl sections show strong depletions in the 13 c and 18 o of carbonate and enrichment in 13 c of bulk organic carbon while the non extinction marls show almost no change in these metrics accordingly the difference in isotopic content must lie in differences inherent to the beds themselves and the circumstances of their deposition and early diagenesis although a range of primary drivers for the isotopic trends is possible an acidification origin for the marl and oceanic origin for the carbon isotope excursion in carbonate are compatible with our data and supported by the broader context of the extinction