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

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

paired carbon isotopic analysis of ordovician bulk carbonate δ 13 c carb and organic matter δ 13 c org spanning the great ordovician biodiversification event abstract paired measurements of bulk carbonate 13ccarb organic matter 13corg and their difference 13c can be used to estimate changes in isotopic fractionation through time as a function of o2 co2 in the atmosphere however because local scale processes can also affect 13c it is essential to compare sections from widely separated water masses here we present new 13corg data from ordovician carbonate rocks from the great basin oklahoma and appalachian basin and compare with published 13ccarb records from these sections and paired 13c values from other carbonate successions around north america these new data complement previous studies that focused on upper ordovician 13ccarb excursions and now provide a composite ordovician 13corg record new lower ordovician tremadocian stage 13corg data range from ca 26 to 28 decreasing throughout the lower middle ordovician floian dapingian stages to ca 29 to 31 13corg values remain at their lowest throughout the sandbian and are similar to other published upper ordovician sandbian katian 13corg data from north america 13c values from well preserved intervals generally vary between 26 to 28 throughout the lower to middle ordovician tremadocian to early darriwilian but increase to 31 during the mid late darriwilian and mid sandbian similar to published data from younger late ordovician positive 13c excursions known as the guttenberg gice and hirnantian hice events the overall 13c trend shows a 3 increase throughout the early middle ordovician and coincides with a previously interpreted period of ocean cooling and some of the earliest pulses of global biodiversity of marine invertebrates and planktonic organisms modeling studies predict that pco2 decreased during this time suggesting that the effect of pco2 on 13c may have been overwhelmed by other controls such as an in increase in po2 or a higher o2 co2 ratio during this biodiversification event

an alternative model for positive shifts in shallow marine carbonate 13c and 18o positive shifts in global seawater d 13 cdic are related to changes in the ratio of organic relative to inorganic carbon burial in oceanic basins whereas factors such as climatic cooling and the accumulation of polar ice are known to cause positive shifts in d 18 o here an alternative model is proposed for the formation of local positive isotope shifts in shallow marine settings the model involves geochemically altered platform top water masses and the effects of early meteoric diagenesis on carbonate isotopic composition both mechanisms are active on modern sub tropical carbonate platforms and result in low carbonate d 13 ca ndd 18 o relative to typical oceanic values during high amplitude transgressive events the impact of isotopically light meteoric fluids on the carbonate geochemistry is much reduced and 13 c depleted platform top water mixes with open oceanic water masses having higher isotope values both factors are recorded as a transient increase in carbonate 13 c and 18 o relative to low background values these processes must be taken into consideration when interpreting the geochemical record of ancient epeiric seas

duration of and decoupling between carbon isotope excursions during the end triassic mass extinction and central atlantic magmatic province emplacement abstract changes in 13 c carb and 13 c org from marine strata occur globally in association with the end triassic mass extinction and the emplacement of the central atlantic magmatic province camp during the break up of pangea as is typical in deep time the timing and duration of these isotopic excursions has remained elusive hampering attempts to link carbon cycle perturbations to specific processes here we report 13 c carb and 13 c org from late triassic and early jurassic strata near levanto peru where intercalated dated ash beds permit temporal calibration of the carbon isotope record both 13 c carb and 13 c org exhibit a broad positive excursion through the latest triassic into the earliest jurassic the first order positive excursion in 13 c org is interrupted by a negative shift noted in many sections around the world coincident with the extinction horizon our data indicate that the negative excursion lasts 85 25 kyrs longer than inferred by previous studies based on cyclostratigraphy a 260 80 kyr positive 13 c org shift follows during which the first jurassic ammonites appear the overall excursion culminates in a return to pre perturbation carbon isotopic values over the next 1090 70 kyrs via chronologic isotopic and biostratigraphic correlation to other successions we find that 13 c carb and 13 c org return to pre perturbation values as camp volcanism ceases and in association with the recovery of pelagic and benthic biota however the initiation of the carbon isotope excursion at levanto predates the well dated camp sills from north america indicating that camp may have started earlier than thought based on these exposures or that the onset of carbon cycle perturbations was not related to camp

the triassic jurassic ecostratigraphic transition in the lombardian alps italy abstract three paleoenvironmental phases and two declines in diversity characterize the late triassic to early jurassic history of the lombardian platforms the first phase of late triassic time choristoceras zone consists of 1 5 m thick shallowing upward subtidal cycles of molluscan coralline and echinoderm wackestone and packstone of the zu limestone biotic and ecostratigraphic characteristics such as typical rhaetavicula contorta fauna and facies allow correlation to the kossen formation of the northern calcareous alps the second phase of latest triassic time upper choristoceras zone consists of shallow restricted marine or peritidal carbonates of the chonchodon formation dominated by barren lime mudstone and dolostone algal laminites and oolitic grainstone the zu conchodon transition predates the triassic jurassic boundary and represents the first and most severe diversity decline for the lombardian fauna corresponding to a fall in sea level where observed the upper and lower contacts of the conchodon formation are conformable and do not constitute sequence boundaries as suggested by some workers the lower jurassic psiloceras zone sedrina limestone marks the beginning of the third phase with the onset of transgression and return of normal marine conditions typical microfacies include molluscan echinoderm and sponge wackestone and packstone with abundant anomuran microcoprolites the second diversity decline occurred at or just above the triassic jurassic boundary at the conchodon sedrina transition where the remaining restricted marine forms disappeared with the transgression anoxia was not a factor in this decline in diversity although other mechanisms in addition to sea level change cannot be discounted

toarcian oceanic anoxic event an assessment of global causes using belemnite c isotope records from black shales markingthe toarcian oceanic anoxic event t oae the first explanation envisions recycling of dissolved inorganiccarbon dic with a light isotopic signature into the photic zone from the lower levels of a salinity stratifiedwater mass essentially requiring a regional paleoceanographic driver of the carbon cycle the second involvesthe rapid and massive dissociation of methane from gas hydrates that effectively renders the t oae a globalperturbation of the carbon cycle we present c isotope records from belemnites d

correlation of early cretaceous carbon isotope stratigraphy and platform drowning events a possible link the early cretaceous carbonate carbon isotope record is marked by three positive high amplitude 1 5 excursions each covering time spans of more than 106 years they are of late valanginian hauterivian and early and late aptian age in a case study along a transect across the western tethys ocean we identified a coincidence between 13c excursions black shale formation and widespread carbonate platform drowning events we conclude that the 13c excursions reflect a change in partitioning of carbon between the organic and carbonate carbon sinks which was triggered by climate induced ecological changes in cretaceous pelagic and neritic environments episodes of intensified greenhouse climate conditions led to an increase in weathering erosion and runoff rates and to elevated nutrient transfer rates from continents into oceans the resulting increase in oceanic nutrient levels favoured marine phytoplankton production and black shale deposition while conditions for carbonate producing biotas became unfavourable partial choking of carbonate production along river influenced coasts resulted in widespread carbonate platform drowning during times of sea level rise in the valanginian and aptian widespread contemporaneous black shale deposits and drowned carbonate platforms therefore reflect the contrasting response of the marine organic and carbonate carbon pumps to nutrient enhanced phytoplankton productivity the change in marine carbon partitioning is mirrored in a shift of the 13c record towards more positive values the transition to the 13c peak values lasted up to several hundred thousand years the peaks of the excursions also covering a time span of up to several hundred thousand years reflect a new stabilisation of the carbon partitioning between carbonate and organic carbon sinks a renewed intensification of carbonate sedimentation under mesotrophic conditions was facilitated by stabilisation of the sea level rise at a high level decreasing 13c values record increasing carbonate carbon burial rates at constant or decreasing organic carbon accumulation rates these changes contributed to the stabilisation of the marine carbon budget and the global carbon cycle up to millions of years after its initial perturbation

sudden productivity collapse associated with the triassic jurassic boundary mass extinction the end triassic mass extinction is one of the five most catastrophic in phanerozoic earth history here we report carbon isotope evidence of a pronounced productivity collapse at the boundary coincident with a sudden extinction among marine plankton from stratigraphic sections on the queen charlotte islands british columbia canada this signal is similar to though smaller than the carbon isotope excursions associated with the permian triassic and cretaceous tertiary events

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

evaluating compositional turnover of brachiopod communities during the end triassic mass extinction northern calcareous alps removal of dominant groups recovery and community reassembly abstract this study highlights the role of large scale physical perturbations in mediating biotic replacements and shows that an environmental disturbance at the triassic jurassic t j boundary correlates with abrupt and substantial changes in the composition of brachiopod communities disturbance changed the phylogenetic structure of early jurassic brachiopod communities owing to a removal of higher taxa that were abundant in the late triassic a replacement of brachiopod communities through the rhaetian in the kossen basin northern calcareous alps related to a combination of habitat tracking and immigration local extinction events indicates a high compositional turnover this turnover is of local nature only because early rhaetian communities migrated or tracked their habitats beyond the kossen basin and persisted through to the late rhaetian in other regions a siliciclastic interval that is several meters thick with rare brachiopods dated as the earliest hettangian marks the extinction survival interval this interval is coeval with a negative carbon isotope anomaly implying a correlation with global perturbation of carbon cycle a rapid brachiopod recovery is indicated by a presence of several distinct communities in late early and middle hettangian that show onshore offshore differentiation and beta diversity comparable to pre extinction levels analyses of similarities demonstrate that 1 the compositional turnover of brachiopod communities on generic level at the t j boundary r 0 83 is substantially higher than turnovers between the rhaetian zones r 0 28 0 57 and between the hettangian zones r 0 28 0 53 and 2 the turnover at superfamily level at the t j boundary accounts for differential composition of rhaetian and hettangian communities a global extinction of athyridoid spondylospiroid and dielasmatoid superfamilies characterized by high community level abundances during the late triassic led to a new assembly of jurassic brachiopod communities from surviving superfamilies in addition to persisting rhynchonellids and zeillerioids hettangian brachiopod communities were dominated by terebratuloids spiriferinoids and pennospiriferinoids these superfamilies were characterized in the late triassic by low community level abundance we argue for tracking the phylogenetic structure of communities across mass extinction events because a measurement of the turnover in community level abundance of higher taxa can be highly relevant for estimating the ecologic impact of mass extinctions taxonomic extinction rate metrics or diversity measures can be depressed by surviving taxa that do not re attain their pre extinction community level abundance

triassic jurassic boundary events inferred from integrated stratigraphy of the csővar section hungary abstract processes and causes of biotic and environmental change at the triassic jurassic transition remain controversial partly because of a scarcity of triassic jurassic boundary sections studied in detail continuous marine strata spanning the boundary are exposed at cs var hungary where new integrated stratigraphic data were obtained from multidisciplinary investigations to help reconstruct the end triassic and early jurassic events boundary strata are predominantly slope to basinal carbonates deposited in a periplatform basin the position of the system boundary is constrained by radiolarian foraminiferan conodont and ammonoid biostratigraphy pronounced radiolarian turnover is observed between assemblages assigned to the late rhaetian globolaxtorum tozeri zone and the early hettangian canoptum merum zone benthic foraminifera suffered lesser extinction successive conodont faunas of the latest rhaetian misikella posthersteini and misikella ultima zones record a marked drop in diversity and abundance but sporadic survivors persist into the earliest hettangian the extinction is also recorded in a reduction of biogenic components in carbonates decline of benthic and planktic biota is followed by a negative 13ccarb excursion of up to 6 that is composed of short term fluctuations revealed by dense sampling carbon and oxygen isotope ratios are positively correlated in the lower part of the section and appear to reflect primary variations drivers of the stable isotope trends are interpreted as warming in excess of 10 c and concomitant episodic short term perturbations of the global carbon cycle possibly due to methane release from gas hydrate dissociation induced by rapid climatic events the main biotic and isotopic events occurred within a single sedimentary cycle but sea level does not appear to have exerted a critical influence on these changes the triassic jurassic boundary crisis appears a short but not instantaneous event

assessing the record and causes of late triassic extinctions accelerated biotic turnover during the late triassic has led to the perception of an end triassic mass extinction event now regarded as one of the big five extinctions close examination of the fossil record reveals that many groups thought to be affected severely by this event such as ammonoids bivalves and conodonts instead were in decline throughout the late triassic and that other groups were relatively unaffected or subject to only regional effects explanations for the biotic turnover have included both gradualistic and catastrophic mechanisms regression during the rhaetian with consequent habitat loss is compatible with the disappearance of some marine faunal groups but may be regional not global in scale and cannot explain apparent synchronous decline in the terrestrial realm gradual widespread aridification of the pangaean supercontinent could explain a decline in terrestrial diversity during the late triassic although evidence for an impact precisely at the boundary is lacking the presence of impact structures with late triassic ages suggests the possibility of bolide impact induced environmental degradation prior to the end triassic widespread eruptions of flood basalts of the central atlantic magmatic province camp were synchronous with or slightly postdate the system boundary emissions of co2 and so2 during these eruptions were substantial but the contradictory evidence for the environmental effects of outgassing of these lavas remains to be resolved a substantial excursion in the marine carbon isotope record of both carbonate and organic matter suggests a significant disturbance of the global carbon cycle at the system boundary release of methane hydrates from seafloor sediments is a possible cause for this isotope excursion although the triggering mechanism and climatic effects of such a release remain uncertain d 2003 elsevier b v all rights reserved

regional and global changes around the triassic jurassic boundary reflected in the late norian hettangian history of the apennine basins abstract palaeogeographic restorations for the late triassic and early jurassic of the west mediterranean area show that significant facies changes occurred in this period the study of three basinal successions in the northern central and southern apennines indicates that changes in ecological conditions occurred at the same time in different palaeogeographic and geodynamic domains the early mesozoic evolution of the apennines is controlled by the opening of two oceans the ionian east mediterranean tethys to the south east and the alpine ocean to the north west the lagonegro basin in the southern apennines was the northern continental margin of the ionian tethys from the triassic while the la spezia basin in the northern apennines became part of the south eastern continental margin of the alpine ocean in the middle late jurassic the third studied basin mt camicia basin in the gran sasso central apennines was an intra platform basin from the early norian up to the late hettangian early sinemurian during the norian hettangian period these basins were not directly connected to each other being separated by wide carbonate platforms and show different evolutionary trends stratigraphic studies in these successions place the triassic jurassic boundary in 6 8 m thick intervals with anoxic facies in the three basins relevant facies changes are also recorded in the late norian in the northern apennines the sedimentation of sulphate evaporites ended being replaced by the rhaetavicula contorta facies whilst in the southern apennines lagonegro basin the deposition of radiolarites began the end of evaporite accumulation can be explained by a climate change from arid to humid conditions and it is also probably linked to an extensional phase preceding the jurassic rifting of the alpine ocean and may therefore have a regional significance nevertheless it corresponds to the spread of the r contorta facies into other parts of southern europe from france to germany and austria the beginning of radiolaritic sedimentation in the lagonegro basin could be related to the rise of atmospheric co2 content linked to volcanic activity in the ionian ridge these facies changes reflect changes of environmental conditions that caused the decline of some fossil associations favoring the development of opportunistic forms e g triasina hantkeni the end triassic extinction coupled with an anoxic episode in all the examined basins immediately preceded a new environmental change documented by the recovery of the carbonate platforms with oolitic facies and different associations the evolution of all these basins suggests that geodynamics were probably responsible for regional events and that at certain moments development reflected global effects as a response to new connections between formerly different domains the central atlantic magmatic province camp volcanism considered as one of the possible causes for the end triassic mass extinction would have had even greater importance if coupled with the volcanism linked to the rifting of the ionian tethys

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

strontium isotope profiles of triassic jurassic boundary sections in england and austria strontium isotope profiles are provided from the austrian salzkammergut and south west england two of the best available marine sections across the triassic jurassic boundary the results in the english section have been affected by diagenesis but the austrian results are excellent and demonstrate that in favorable circumstances trust worthy sr isotope results can be obtained from pure or nearly pure limestones and oxygen isotope data provide the best means of obtaining an independent check although the triassic jurassic boundary was marked by significant sea level changes this is not reflected in the sr isotope results which show no change across the boundary in contrast to what has been claimed for the cretaceous tertiary and permian triassic boundaries

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

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

phosphogenesis carbon isotope stratigraphy and carbonate platform evolution along the lower cretaceous northern tethyan margin we distinguish three different stages in the evolution of the tithonian late jurassic to aptian early cretaceous northern tethyan carbonate platform 1 carbonate production in the coral oolite mode late tithonian to early valanginian early barremian to early aptian 2 carbonate production in the crinoid bryozoan mode early valanginian haute rivian late aptian and 3 platform retrogradation and destruction condensation and phosphogenesis that is platform drowning early valanginian to early hauterivian middle hauterivian late hauterivian to early barremian early to early late aptian and latest aptian to earliest albian transitions from the coral oolite mode to the crinoid bryozoan mode and consequently to platform drowning may have been driven by increases in nutrient levels on the shelf phases of relative sea level rise in times of carbonate production in the coral oolite mode are named constructive because of the observed platform regeneration following phases of widespread emersion during late sea level highstands in contrast phases of relative sea level rise in times of platform drowning are termed destructive the 13 c stratigraphies obtained from valanginian hauterivian and aptian albian hemipelagic successions beyond the platform correlate well with the early cretaceous pelagic 13 c record positive excursions in the pelagic 13 c record correspond in time to episodes of platform drowning this suggests the existence of a coupling mechanism between changes in the global carbon cycle and platform drowning in our view the early cretaceous crises in carbonate platform growth were the consequence of reinforced greenhouse conditions which may have been triggered by episodes of extensive flood basalt volcanism strong greenhouse conditions may have induced the following chain of feedback mechanisms enabling the biosphere to return to normal conditions climate warming sea level rise accelerated water cycle intensified weathering nutrient mobilization platform destruction increased productivity increased phosphogenesis and carbon burial weakened greenhouse conditions

multiple negative carbon isotope excursions during the carnian pluvial episode late triassic abstract the carnian pluvial episode was a phase of global climatic change and biotic turnover that occurred during the early late triassic in marine sedimentary basins the arrival of huge amounts of siliciclastic sediments the establishment of anoxic conditions and a sudden change of the carbonate factory on platforms marked the carnian pluvial episode the sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as for example an extinction among ammonoids and conodonts in the ocean and a turnover of the vertebrate fauna and the flora on land multiple negative carbon isotope excursions were recorded during the carnian pluvial episode in both organic matter and marine carbonates suggesting repeated injection of 13c depleted co2 into the ocean atmosphere system but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood we here review the existing carbon isotope records and present new data on the carbon isotope composition of organic carbon in selected sections of the western tethys realm that record the entire carnian pluvial episode new ammonoid conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections the results provide biostratigraphically constrained composite organic carbon isotope curves for the carnian which sheds light on the temporal and causal links between the main carbon isotope perturbations and the distinct environmental and biotic changes that mark the carnian pluvial episode the carbon isotope records suggest that a series of carbon cycle perturbations possibly recording multiple phases of volcanic activity during the emplacement of the wrangellia large igneous province disrupted carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years

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

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

carbon isotope record of the early jurassic toarcian oceanic anoxic event from fossil wood and marine carbonate lusitanian basin portugal thetoarcianoceanicanoxicevent oae intheearlyjurassic 183maago wascharacterizedbywidespreadnear synchronous deposition of organic rich shales in marine settings as well as perturbations to several isotopic systems characteristically two positive carbon isotope excursions in a range of materials are separated by an abrupt negative shift carbon isotope profiles from toarcian fossil wood collected in england and denmark have previously been shown to exhibit this large drop 7 i n 13 c values interpreted as due to an injection of isotopically light co2 into the ocean atmosphere system however the global nature of this excursion has been challengedonthebasisofcarbon isotopedatafromnektonicmarinemolluscs belemnites whichexhibitheavierthanexpectedcarbonisotope values here we present new data principally from fossil wood and bulk carbonate collected at centimetre scale from a hemipelagic section at peniche coastal portugal this section is low in organic carbon average toc 0 5 and the samples should not have suffered significant diagenetic contamination by organic carbon of marine origin the carbon isotope profile based on wood shows two positive excursions separated by a large and abrupt negative excursion which parallels exactly the profile based on bulk carbonate samples from the same section albeit with approximately twice the amplitude 8 in wood versus 3 5 in carbonate these data indicate thatthe negative carbon isotope excursion affected the atmosphereand by implication the global ocean as well the difference in amplitude between terrestrial organic and marine carbonate curves can be explained by greater water availability in the terrestrial environment during the negative excursion for which there is independent evidence from marine osmiumisotope records and plausibly changes in atmospheric co2 content for which independent evidence is also available the peniche succession is also notable for the occurrence of re deposited sediments their lowest occurrence coincides with the base of the negative excursionandtheirhighestoccurrencecoincideswithitstop thus slopeinstabilityandsedimentsupplycouldhavebeenstronglylinked to the global environmental perturbation an association that may misleadingly simulate the effects of sea level fall

extinction dissolution and possible ocean acidification prior to the cretaceous paleogene k pg boundary in the tropical pacific abstract biotic perturbations and changes in ocean circulation during the maastrichtian stage of the latest cretaceous raise questions about whether the biosphere was preconditioned for the end cretaceous mass extinction of calcareous plankton a brief acme of inoceramid clams at 71 ma on shatsky rise in the tropical north pacific was followed by their extinction during the mid maastrichtian event at 70 1 ma associated with an abrupt warming of deep waters this was later followed by an interval of intense dissolution beginning 67 8 ma at odp site 1209 2387 m the late maastrichtian dissolution interval was initially gradual and is characterized by a low planktic benthic p b ratio highly fragmented planktic foraminifera mostly an absence of larger taxa low abundances of smaller taxa extremely low planktic foraminiferal numbers and low planktic foraminiferal and nannofossil species richness a partial recovery in carbonate preservation and calcareous plankton simple diversity began 250 kyr prior to the k pg boundary associated with the incursion of a younger more enriched 13c deep water mass although total abundances of planktic foraminifera in the sediment remained a tiny fraction of their earlier maastrichtian values a second brief dissolution event occurred 200 kyr before the boundary evidenced by renewed increase in planktic fragmentation but without a decrease in p b ratio our data show that changing deep water masses coupled with reduced productivity and associated decrease in pelagic carbonate flux was responsible for the first 1 6 myr dissolution interval while deccan traps volcanism may have caused surface ocean acidification 200 kyr prior to the k pg mass extinction event

record of environmental changes in the triassic jurassic boundary interval in the zliechov basin western carpathians abstract the fatra and kopieniec formations in the zliechov basin comprise a record of several environmental crises that may have contributed to the global triassic jurassic t j boundary events the diversity of the benthic fauna decreases at the base of the transition beds the uppermost member of the fatra formation this assemblage comprises many species that do not appear in younger strata in cycle 13 of the fatra formation stable isotope excursions correspond to significant lithological changes in the sequence the negative 13 c excursion is correlated with a positive 18 o peak and the beds containing the excursion are overlain by a thin layer with unusual lithological and mineral composition this layer is composed of small calcitized microspheres showing complex alteration during diagenesis the origin of this layer traceable over tens of kilometres is problematic impact ejecta volcanic glass or altered aragonitic particles an increase in terrigenous sediment recorded by sandy beds in the uppermost part of the fatra formation indicates increased run off a sharp lithological boundary between the fatra and the kopieniec formations marks a sudden termination of carbonate sedimentation followed by deposition of the boundary clay the negative 13 c anomaly recognized in this succession may correspond to the isotopic signature at the t j boundary which has been described from many sections in the world

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

major perturbation in sulfur cycling at the triassic jurassic boundary stable sulfur isotopes from the reduced sulfur fraction of late triassic early jurassic marine sediments at kennecott point in british columbia canada show evidence for a major perturbation in sulfur cycling coincident with a major carbon cycle perturbation in the wake of a mass extinction event at the triassic jurassic boundary the 34 s of reduced sulfur shifts from values consistent with open system bacterial sulfate reduction 30 to values higher than any previously reported for early jurassic sulfates 20 and consistent with complete utilization of sulfate and rayleigh fractionation in a closed system we suggest that this isotopic shift was initiated by declining seawater sulfate concentration due to evaporite deposition in nascent atlantic rift zones and enhanced by a local mechanism such as a decoupling of the zone of sulfate reduction from the sulfate supply due to a catastrophic increase in the flux of land derived sediments reaching the sea in the wake of massive terrestrial plant die off during the triassic jurassic mass extinction

disentangling the hettangian carbon isotope record implications for the aftermath of the end triassic mass extinction 1 this study provides an organic carbon stable isotope 13corg record calibrated with detailed ammonite biostratigraphy following the end triassic biological crisis precise correlation between this crucial fossil group and the 13corg record is key to understanding feedbacks between biological and environmental events following mass extinction the latest triassic and hettangian 13corg record shows several negative and positive excursions the end triassic negative shift coinciding with the mass extinction interval is followed by a positive excursion in the earliest hettangian psiloceras spelae beds which marks the onset of recovery in the marine ecosystem this positive trend is interrupted by a second negative 13corg excursion in the p pacificum beds related to a minor ammonite extinction event this pattern of the 13corg curve culminates in the uppermost hettangian angulata zone major positive excursion this indicates that both the ecosystem and the carbon cycle remained in a state of perturbation for at least 2 ma although the recovery of some pelagic taxa already began at the base of jurassic the early and late hettangian positive 13corg excursions have been confused in several recent papers here we show that during the hettangian there are indeed two distinct positive 13corg excursions phases of anoxia and further pulses of central atlantic magmatic province volcanism during the hettangian might have inhibited the full recovery for that interval of time the main liasicus angulata organic positive cie carbon isotope excursion during the late hettangian might be related to gradual decreasing of pco2 due to protracted high organic burial and coincides with a second phase of recovery as indicated by a pulse of ammonoid diversification

palaeoenvironmental interpretation of a triassic jurassic boundary section from western austria based on palaeoecological and geochemical data a section spanning the triassic jurassic boundary is described from near the village of loruns in the vorarlberg region of western austria at loruns the uppermost triassic is characterised by bedded carbonates of the kossen formation supporting a stenotopic fauna indicative of a shallow sub tidal environment of normal marine salinity the triassic jurassic boundary may be represented as a sequence boundary developed on top of a 1 1 m thick red mudstone of the lower schattwald shale which is interpreted to have been deposited in a marginal marine environment possibly a mud flat above the boundary beds the upper schattwald shale is characterised by thin bedded marl and dark limestone beds with an earliest hettangian macrofauna dominated by epifaunal filter feeding bivalves including ostreids mytilids and oxytomids which suggest a shallow subtidal salinity controlled environment typical of an interplatform lagoon carbonate production rejuvenated in the later early hettangian with development of the loruns oolite a shallow subtidal oolitic and oncolitic unit bearing echinoderms indicative of normal marine conditions low thu ratios from the remainder of the section are a result of reduced thorium in carbonate rich sediments and not from authigenic uranium in anoxic sediments in the boundary beds evidence for marine anoxia or dysoxia is absent where thu values determined by gamma ray spectrometry are above 5 the negative excursion in 13c and positive excursion in 18o in the boundary beds may be due to secondary geochemical effects due to organic diagenesis or the precipitation of caliche during paleosol development alternatively the excursions may reflect a primary geochemical signal recording short term decline in primary productivity comparison in 18o and 13c values between the kossen formation and lorfus oolite indicate no significant long term geochemical changes are evident in the section and suggest that any environmental perturbations were restricted to the boundary beds and possible sequence boundary

massive dissociation of gas hydrate during a jurassic oceanic anoxic event in the jurassic period the early toarcian oceanic anoxic event about 183 million years ago is associated with exceptionally high rates of organic carbon burial high palaeotemperatures and significant mass extinction heavy carbon isotope compositions in rocks and fossils of this age have been linked to the global burial of organic carbon which is isotopically light in contrast examples of light carbon isotope values from marine organic matter of early toarcian age have been explained principally in terms of localized upwelling of bottom water enriched in 12c versus 13c refs 1 2 5 6 here however we report carbon isotope analyses of fossil wood which demonstrate that isotopically light carbon dominated all the upper oceanic biospheric and atmospheric carbon reservoirs and that this occurred despite the enhanced burial of organic carbon we propose that as has been suggested for the late palaeocene thermal maximum some 55 million years ago the observed patterns were produced by voluminous and extremely rapid release of methane from gas hydrate contained in marine continental margin sediments

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

seawater temperature and carbon isotope variations in belemnites linked to mass extinction during the toarcian early jurassic in central and northern spain comparison with other european sections the early toarcian mass extinction marks one of the critical events in the history of the earth many of these events have been linked to important climate changes two sections of the toarcian showing high resolution ammonite based biostratigraphy are studied in central and northern spain stable isotope datasets based on the analysis of 192 diagenetically screened belemnite calcite and 41 bulk carbonates allowed the construction of 13c curves and a 18o based palaeotemperature comparison of the extinction pattern with other sections in europe and northern africa shows that the early toarcian mass extinction boundary occurred at the tenuicostatum serpentinum transition and that the organic rich facies linked to the oceanic anoxic event and the associated negative 13c excursion are diachronous from a latest pliensbachian cooling interval a first increment of seawater temperature averaging about 4 5 c started around the pliensbachian toarcian boundary and developed during the earliest toarcian tenuicostatum biochron marking the beginning of the main extinction interval from the tenuicostatum serpentinum transition up to the bifrons biochron a rise in seawater temperature averaging 5 7 c to 7 8 c was recorded this warming interval which started rapidly and which seems to be synchronous at least in western europe is considered one of the main factors responsible for mass extinction for some authors this rapid warming was probably due to a massive injection of greenhouse gases into the atmosphere but it does not seem to be recorded in belemnite calcite and the origin of these possible gases is largely debated in the literature additional isotope excursions were found in the studied sections in spain during the middle and late toarcian a negative 13cbel excursion has been recorded at the latest bifrons biochron above this shift the illustris vitiosa subzones thermal peak which represents a 2 3 c t could be linked to one of the tectonomagmatic activity peaks recorded in the karoo basin a renewal in the ammonite and brachipod faunas coincident with this climatic change has been recognized in nw europe and western tethys an interesting thermal peak has also been detected in belemnites of the insigne subzone t is in the order of 3 c and in both sections the thermal peak is included into a 13cbel negative excursion of about 1 5 relative synchrony with the new age for the karoo main magmatic activity 178 180 ma indicates that the 13c negative anomaly and the warming interval could be caused by the release of volcanogenic greenhouse gases at this short interval noteworthy changes in the abundance and diversity of the recorded assemblages in several faunal groups of nw europe and tethys are observed the uppermost levesquei subzone thermal peak has only been recognized in the deposits of the section located in central spain and coincides with a positive 13c excursion

the paleocene eocene carbon isotope excursion in higher plant organic matter differential fractionation of angiosperms and conifers in the arctic abstract a study of upper paleocene lower eocene p e sediments deposited on the lomonosov ridge in the central arctic ocean reveals relatively high abundances of terrestrial biomarkers these include dehydroabietane and simonellite derived from conifers gymnosperms and a tetra aromatic triterpenoid derived from angiosperms the relative percentage of the angiosperm biomarker of the summed angiosperm conifer biomarkers was increased at the end of the paleocene eocene thermal maximum petm different when observed with pollen counts which showed a relative decrease in angiosperm pollen stable carbon isotopic analysis of these biomarkers shows that the negative carbon isotope excursion cie during the petm amounts to 3 for both conifer biomarkers dehydroabietane and simonellite comparable to the magnitude of the cie inferred from marine carbonates but significantly lower than the 4 5 of the terrestrial c29 n alkane m pagani n pedentchouk m huber a sluijs s schouten h brinkhuis j s sinninghe damste g r dickens and the iodp expedition 302 expedition scientists 2006 arctic s hydrology during global warming at the paleocene eocene thermal maximum nature 442 671 675 which is a compound sourced by both conifers and angiosperms conspicuously the angiosperm sourced aromatic triterpane shows a much larger cie of 6 and suggests that angiosperms increased in their carbon isotopic fractionation during the petm our results thus indicate that the 4 5 c29 n alkane cie reported previously represents the average cie of conifers and angiosperms at this site and suggest that the large and variable cie observed in terrestrial records may be partly explained by the variable contributions of conifers and angiosperms the differential response in isotopic fractionation of angiosperms and conifers points to different physiological responses of these vegetation types to the rise in temperature humidity and greenhouse gases during the petm

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

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

a tale of two extinctions converging end permian and end triassic scenarios the end permian c 252 ma and end triassic c 201 ma mass extinction events are commonly linked to the emplacement of the large igneous provinces of the siberia traps and central atlantic magmatic province respectively accordingly scenarios for both extinctions are increasingly convergent and cross fertilization of ideas has become important here we present a synthesis of extinction scenarios based on a critical assessment of the available palaeontological sedimentological geochemical and geophysical evidence how similar were the extinction events what gaps exist in our understanding and how can a comparison of the events enhance our understanding of each event individually our focus is on the most important proximate kill mechanisms including climate change and atmospheric pollution increased soil erosion weathering and runoff forest dieback and the spread of pathogens and ocean temperature changes anoxia and acidification there is substantial evidence to suggest that very similar kill mechanisms acted upon late permian as well as late triassic ecosystems strengthening the hypothesis that the ultimate causes of the mass extinction events were similar

isotopic chemostratigraphy across the early middle frasnian transition late devonian on the south polish carbonate shelf a reference for the global punctata event abstract the coupled high resolution carbon isotope data from whole rock limestone and organic matter samples of the transitans early frasnian punctata and the earliest hassi zones middle frasnian from the south polish carbonate shelf successions reveal the presence of a large multi part 13 c excursion one of the largest known carbon cycle disturbance of devonian period this early middle frasnian e mf 13 c perturbation consists of two positive excursions a minor event i and a major event iii and two negative shifts events ii and iv the major positive excursion up to 5 begins near the e mf boundary and the onset of middlesex transgressive anoxic event the latter broader scale positive 13 c perturbation correlates with the worldwide punctata event documented across eastern and western laurussia as well as northern gondwana the large magnitude of the punctata isotopic event paired with negligible biotic effects is similar to the silurian biogeochemical perturbations but contrasts markedly with the younger kellwasser events the distinctive protracted about 1 ma e mf 13 c variations may be only partly explained by escalated sea water exchange between epeiric seas and the anoxic open ocean during successive transgressive pulses very high 13 c plateau values of the punctata event correspond to a positive 87 sr 86 sr shift as well as elevated clastic input proxies and magnetic susceptibility suggesting altogether that delivery of tectonically promoted land derived nutrients to marine basins was a key factor stimulating the biogeochemical perturbation extreme increases in primary productivity and enhanced organic matter burial in restricted deeper basinal settings would promote a gradual drawdown in surface water as well as atmospheric p co 2 and consequently a climatic cooling by 5 c as indicated by the high resolution 18 o phosphate record

theoretical simulation of the evolution of methane hydrates in the case of northern south china sea since the last glacial maximum the distribution and inventory of gas hydrates in a region is determined by the sediment characteristics methane supply and evolution of the reservoir in recent decades the geo environmental constraints and sources of methane have been intensively investigated and numerous experimental and numerical simulation tools have been developed to evaluate the inventory of hydrates however information regarding the evolution of hydrate reservoirs remains limited this study developed a simulator to theoretically model the evolution of specific reservoirs since the last glacial maximum lgm the lgm was a recent cold epoch that occurred approximately 18 000 years ago since the lgm the earth s climate system has experienced a continuous increase of surface temperature and rising sea level given a sufficient supply of methane and a transport system hydrates may form in marine sediments if sea level rises or melt if the temperature increases a one dimensional simulator that represents the sediment was developed and uses the current hydrate profiles as the initial conditions and reliable paleoenvironmental data obtained in sites located in the northern shelf of the south china sea scs as boundary conditions two types of hydrate profiles were reversely simulated till the lgm 1 a gaussian profile which was observed in the shenhu area and 2 a trapezoidal profile which was observed in the dongsha area scs the evolution and past quantities of local hydrate reservoirs were estimated the model results demonstrated that shallow 500 700 m below the seafloor or mbsf moderate saturation 50 pore volume or v v hydrate deposits will form if they are subjected to recent climate changes the inventory of hydrates in the nscs increased by only 0 7 over the past 18 000 years under various scenarios a sensitivity analysis was performed to identify the most pertinent parameters that control the formation and dissociation of hydrates including the grain size temperature gradient and deposition depth the distribution and depth of the reservoir were determined to be the most critical factors in the evolution of the studied hydrates

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

events around the triassic jurassic boundary in northern and eastern spain a review abstract more than 20 successions containing the triassic jurassic t j boundary were studied in five of the major geological units of spain the data are from outcrop cored boreholes and interpreted well logs a consistent 3 4 13 c org isotope excursion starting in the rhaetian and continuing in the hettangian was recorded in asturias climate changes in the t j transition show a warming episode in the early hettangian other climate changes are indicated by an increase in hygrophytic miospores above the t j boundary this reflects a more humid episode at the beginning of the hettangian the messejana dyke in southeastern iberia is part of the central atlantic magmatic province camp co 2 outgassing related to extensive magmatic activity in the camp is thought to be one of the possible factors responsible for the end triassic mass extinction no major sea level changes or unconformities were recorded at the t j boundary only in the asturias area was there a well defined shallow carbonate platform during the t j transition the other areas of eastern and northern spain were occupied by coastal playas and sabkhas that developed in arid climatic conditions the biotic crisis around the t j boundary is reflected in the palynomorph record in asturias seven species do not persist beyond the late rhaetian and only six appeared in the triassic jurassic transition however 22 taxa appeared in the early hettangian

evolution of the marine stable carbon isotope record during the early cretaceous a focus on the late hauterivian and barremian in the tethyan realm abstract in order to improve our understanding of the relationships between the late hauterivian oceanic anoxic faraoni event contemporaneous platform drowning along the northern tethyan margin and global environmental change in general we established high resolution 13 c and 18 o curves for the late hauterivian and the entire barremian stage these data were obtained from whole rock carbonate samples from the veveyse de ch tel saint denis section switzerland the fiume bosso section and the nearby gorgo a cerbara section central italy and the angles section barremian stratotype france we observe an increase of 0 3 in mean 13 c values within sediments from the middle hauterivian subsaynella sayni ammonite zone to the hauterivian barremian boundary 13 c values remain essentially stable during the early barremian during the latest early barremian and most of the late barremian 13 c values increase slowly until the imerites giraudi zone and the latest barremian is characterized by a negative trend in 13 c values with minimal values at the barremian aptian boundary during the earliest aptian 13 c mean values start to rise again and attain 2 25 we interpret the evolution of the 13 c record as resulting from the interaction between changes in the carbon cycle in the tethyan basin and the adjacent platforms and continents in particular changes towards warmer and more humid conditions on the continent and coeval phases of platform drowning along the northern tethyan margin may have contributed to enhance the oceanic dissolved inorganic carbon dic reservoir which may have pushed the 13 c record towards more negative values and exerted a general attenuation on the 13 c record from this may have come the general change from a heterozoan to a photozoan carbonate platform community which influenced the evolution in 13 c values by increasing the export of aragonite and diminishing export of dissolved organic carbon into the basins

additive effects of acidification and mineralogy on calcium isotopes in triassic jurassic boundary limestones the end triassic mass extinction coincided with a negative 13c excursion consistent with release of 13c depleted co2 from the central atlantic magmatic province however the amount of carbon released and its effects on ocean chemistry are poorly constrained the coupled nature of the carbon and calcium cycles allows calcium isotopes to be used for constraining carbon cycle dynamics and vice versa we present a high resolution calcium isotope 44 40ca record from 100 m of marine limestone spanning the triassic jurassic boundary in two stratigraphic sections from northern italy immediately above the extinction horizon and the associated negative excursion in 13c 44 40ca decreases by 0 8 in 20 m of section and then recovers to preexcursion values coupled numerical models of the geological carbon and calcium cycles demonstrate that this 44 40ca excursion is too large to be explained by changes to seawater 44 40ca alone regardless of co2 injection volume and duration less than 20 of the 44 40ca excursion can be attributed to acidification the remaining 80 likely reflects a higher proportion of aragonite in the original sediment based largely on high concentrations of sr in the samples our study demonstrates that coupled models of the carbon and calcium cycles have the potential to help distinguish contributions of primary seawater isotopic changes from local or diagenetic effects on the 44 40ca of carbonate sediments differentiating between these effects is critical for constraining the impact of ocean acidification during the end triassic mass extinction as well as for interpreting other environmental events in the geologic past

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

reply to comment on the organic carbon isotopic and paleontological record across the triassic jurassic boundary at the candidate gssp section at ferguson hill muller canyon nevada usa by ward et al 2007

end triassic calcification crisis and blooms of organic walled disaster species the triassic jurassic t j mass extinction event is marked by isotope anomalies in organic 13 corg and carbonate carbon 13 ccarb reservoirs these have been attributed to a rapid 4 fold rise in pco2 as a result of massive flood basalt volcanism and or methane hydrate dissociation here we examine the response of marine photosynthetic phytoplankton to the proposed perturbation in the carbon cycle our high resolution micropalaeontological analysis of t j boundary beds at st audrie s bay in somerset uk provides evidence for a bio calcification crisis that is characterized by 1 extinction and malformation in calcareous nannoplankton and 2 contemporaneous blooms of organic walled green algal disaster species which comprise in one case n70 of the total palynomorph fraction blooms of prasinophytes and acritarchs occur at the onset and in association with a prominent negative shift in 13 corg values close to the first appearance of the early jurassic ammonite psiloceras planorbis across the same interval we obtained palaeotemperature and palaeosalinity estimates from oyster low mg calcite based on mg ca sr ca and 18 o records the results of our palynological and geochemical analyses strongly suggest that shallow marine basins in nw europe during this period became salinity stratified inducing anoxic conditions the t j boundary event shows similarities with the permian triassic p t mass extinction event which was also marked by extensive flood basalt volcanism negative excursions in carbon isotope records a bio calcification crisis the development of shallow marine anoxia and mass abundances of acritarchs in the early triassic this leads us to suggest that the proliferation of green algal phytoplankton may be symptomatic of elevated carbon dioxide levels in the atmosphere and oceans during mass extinction events 2007 published by elsevier b v

the valanginian carbon isotope event a first episode of greenhouse climate conditions during the cretaceous lower cretaceous pelagic carbonates outcropping along the southern alps of northern italy provide a record of tethyan palaeoceanography as well as of low frequency fluctuations in the global carbon cycle the carbonate c isotope stratigraphy established at five selected localities in the southern alps allows an accurate picture to be drawn of the duration and amplitude of the valanginian c isotope event 13c values near 1 25 1 50 determined in berriasian and lower valanginian sediments are replaced by more pdsitive 13c values near 3 in the late valanginian the carbonate c isotope excursion ends in the early hauterivian with values fluctuating between 1 5 and 2 the carbonate c isotope excursion is accompanied by a positive excursion in the total organic carbon c isotope curve the valanginian c isotope excursion identified in tethyan sediments correlates with a c isotope excursion recorded in the western north atlantic in the gulf of mexico and in the central pacific dsdp sites 534 391 535 and 167 by analogy with the aptian stage also marked by a significant positive c isotope excursion the time of positive 13c values is regarded as a time of accelerated carbon cycling coupled with increased burial rates of organic carbon and detrital material in oceanic sediments a warm and humid climate possiblycoupled with a high atmospheric co2 content and a high global sea level may have triggered the acceleration of the global carbon cycling in this case the valanginian c isotope event would reflect a first episode of greenhouse earth conditions during the cretaceous

stable carbon isotopes of wood a clue to palaeoclimate abstract detailed stable carbon isotope and molecular investigations were undertaken on a number of archaeological and fossil wood specimens to provide insights into their use as rigorous independent palaeoclimatic and palaeoenvironmental parameters the isotope data revealed large differences amongst the material with the oldest specimens being least depleted in 13 c although natural variation could account for some of the observed differences the isotope values of the archaeological and tertiary specimens are most probably related to the absolute abundance of polysaccharides present and the degree of lignin alteration the molecular data based on pyrolysis of the antarctic cretaceous conifer specimens revealed only transformed lignin with virtually no intact lignin building blocks 2 methoxyphenols preserved and no evidence of polysaccharides this degree of chemical alteration is suggested here to be one of the main causes for the 13 c enriched values of these conifer specimens these results show the importance of combining detailed molecular information on individual wood components with stable carbon isotope data for palaeoclimatic and palaeoenvironmental studies

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

the nature of the δ13c of periplatform sediments implications for stratigraphy and the global carbon cycle the carbon isotopic composition y 13 c of bulk carbonates obtained from a transect of sites drilled through platform and periplatform sediments of holocene to early miocene age has been compared to ascertain whether changes in the y 13 c can be correlated between sediments of equivalent ages and whether such changes can be related to global changes in the y 13 c of the dissolved inorganic carbon in the oceans over this time period five of the sites were drilled during leg 166 of the ocean drilling project 1003 1007 in a transect ranging from five km to 25 km away from the platform margin and penetrating sediments of holocene to oligocene age that are contained in 17 depositional sequences a q two shallow water sites clino and unda were situated on a extension of the same transect on great bahama bank in a water depth of 10 15 m with the exception of unda and clino the y 13 c of the carbonates ranges from 5x in the younger sequences to 1x in the early miocene in each of the sites the y 13 c is strongly positively correlated with the percentage of aragonite as a consequence the y 13 c of sequences a through f is strongly correlated reflecting the decreasing amount of aragonite with increasing depth in the two platform sites the y 13 c is significantly lower in the younger portions of the cores as a result of the influences of meteoric diagenesis during repeated exposure during the pleistocene although the y 13 c of the individual sequences can be correlated in most instances between the odp holes the changes are not related to global changes in the y 13 c of the oceans which in contrast to the y 13 c of the platform sediments become isotopically lower towards the present day instead variations in the y 13 c appear to be related to varying mixtures of y 13 c rich banktop sediments and pelagic material

calibrating the magnitude of the toarcian carbon cycle perturbation sedimentary rocks recording the toarcian oceanic anoxic event t oae are marked by a negative carbon isotope excursion cie reaching up to 7 and ranking among the largest known in the phanerozoic these records suggest a dramatic perturbation of the carbon cycle that has been linked to the transfer of juvenile carbon from the endogenic to the exogenic reservoirs nevertheless the magnitude of the toarcian cie varies significantly from one substrate to another hence complicating mass balance evaluation of the potential driving mechanisms here we show using high resolution paired records of 13ctotal organic carbon toc and hydrogen index from the denkingen core and dotternhausen quarry germany that the amplitude of the negative cie in marine organic matter is considerably exaggerated by changes in organic matter sourcing our corrected 3 4 cie implies a constant carbon isotope fractionation between organic and carbonate carbon across the t oae and may point to a prominent role of cyanobacteria as organic matter producers during the early jurassic these results also suggest that the difference between inorganic and organic carbon isotope values in marine strata constitutes a poor proxy of pco2 levels across the t oae moreover this corrected 3 4 cie together with evidence for 5 c seawater warming across the t oae point to the input of 25 000 gt c with much more 13c enriched signature than previously modeled our results thus allow reconciling inorganic and organic 13c records of the t oae and have important implications for the evaluation of their causal mechanisms

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

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

coupled climate impacts of the drake passage and the panama seaway tectonically active gateways between ocean basins have modified ocean circulation over earth history today the atlantic and pacific are directly connected via the drake passage which forms a barrier to the time mean geostrophic transport between the subtropics and antarctica in contrast during the warm early cenozoic era when antarctica was ice free the drake passage was closed instead at that time the separation of north and south america provided a tropical seaway between the atlantic and pacific that remained open until the isthmus of panama formed in the relatively recent geological past ocean circulation models have previously been used to explore the individual impacts of the drake passage and the panama seaway but rarely have the two gateways been considered together and most explorations have used very simple atmospheric models here we use a coupled ocean ice atmosphere model gfdl s cm2mc to simulate the impacts of a closed drake passage both with and without a panama seaway we find that the climate response to a closed drake passage is relatively small when the panama seaway is absent similar to prior studies although the coupling to a dynamical atmosphere does increase the temperature change however with a panama seaway closing drake passage has a much larger effect due to the cessation of deep water formation in the northern hemisphere both gateways alter the transport of salt by ocean circulation with the panama seaway allowing fresh pacific water to be imported to the north atlantic and the drake passage preventing the flow of saline subtropical water to the circum antarctic a flow that is particularly strong when the panama seaway is open thus with a panama seaway and a closed drake passage the southern ocean tends to be relatively salty while the north atlantic tends to be relatively fresh such that the deep ocean is ventilated from the circum antarctic ensuing changes in the ocean heat transport drive a bi polar shift of surface ocean temperatures and the intertropical convergence zone migrates toward the warmer southern hemisphere the response of clouds to changes in surface ocean temperatures amplifies the climate response resulting in temperature changes of up to 9 c over antarctica even in the absence of land ice feedbacks these results emphasize the importance of tectonic gateways to the climate history of the cenozoic and support a role for ocean circulation changes in the glaciation of antarctica

reconstruction of δ13c of chemocline co2 aq in past oceans and lakes using the δ13c of fossil isorenieratene abstract high abundances of the diaromatic carotenoid isorenieratene derived from photosynthetic green sulfur bacteria chlorobiaceae were found just below the chemocline in an anoxic fjord in norway throughout the annual cycle the stable carbon isotope composition of this carotenoid co varied with the 13c of co2 aq and is independent of the co2 and isorenieratene concentration this constant isotopic fractionation p of isorenieratene versus co2 4 1 was subsequently used in the reconstruction of 13c of co2 at the chemocline in ancient oceans and lakes these reconstructions indicate that 13c of co2 at the chemocline is often influenced by isotopically light co2 formed by remineralization of organic matter this process can depending on the depth and stability of the chemocline also effect the isotopic composition of the phytoplankton and thus isotopic records of sedimentary inorganic and organic carbon

interactions between environmental change and shallow water carbonate buildup along the northern tethyan margin and their impact on the early cretaceous carbon isotope record 1 the evolution of the early cretaceous northern tethyan carbonate platform was not only influenced by changes in sea level detrital influx and surface water temperature but also by changes in trophic levels we distinguish between phases of carbonate production dominated by oligotrophic photozoan communities and by mesotrophic and eventually colder water heterozoan communities superimposed on this bimodal trend in platform evolution were phases of platform demise for which we provide improved age control based on ammonite biostratigraphy the initial phase of these episodes of platform demise corresponds in time to episodes of oceanic anoxic events and environmental change in general on the basis of a comparison between the temporal changes in an early cretaceous ammonite calibrated d 13 c record from southeastern france and coeval changes in the platform record we suggest that the history of carbon fractionation along the northern tethyan margin was not only influenced by changes in the oceanic carbon cycle such as in the rate of production and preservation of organic and carbonate carbon and in the size of the oceanic dissolved inorganic carbon reservoir but it was also influenced by the above mentioned changes in the ecology and geometry of the adjacent carbonate platform phases of photozoan carbonate production induced positive trends in the hemipelagic carbonate d 13 c record phases of heterozoan carbonate production pushed the d 13 c system toward more negative values platform drowning episodes implied an initial increase in d 13 c values followed by a longerterm decrease in d 13 c values

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

parameters determining the carbon isotopic composition of coal and fossil wood in the early miocene oberdorf lignite seam styrian basin austria abstract petrographical and geochemical data of gelified and ungelified fossil wood from the early miocene oberdorf lignite seam styrian basin austria provide evidence that the early diagenetic aerobic degradation of wood by fungi may be followed by further decomposition under reducing conditions by the activity of anaerobic bacteria based on the molecular compositions of terpenoid hydrocarbons the wood fragments in the lignite are identified as gymnosperms this result is corroborated by the mean isotopic composition 13c 24 2 of the macrofossils the isotopic difference between fossil wood and extracted cellulose of most samples 3 9 2 5 is higher than in modern trees which can be explained by the smaller effect of 13c discrimination during decomposition of cellulose when compared with wood the mean carbon isotope values found for gymnosperms and coals 24 2 and 24 7 respectively confirm the results from biomarker analyses indicating that the peat forming vegetation of the oberdorf seam was dominated by gymnosperm taxa minor variation in the relative contributions of gymnosperms and angiosperms to coal deposition is of negligible influence on the isotopic composition of the coals cross correlations between 13c of the coals soluble organic matter yield and the proportions of liptinite macerals of higher plant origin imply that the carbon isotopic composition may be affected by the contents of plant lipids because of their 13c values ranging from 5 to 10 less than whole plant tissue values an isotopic shift of the coals towards more negative values due to the activity of prokaryotes i e anaerobic bacteria in organic matter degradation is proposed the results obtained from the early miocene oberdorf lignite indicate that the carbon isotope ratios of the coals are primarily affected by varying contributions of different parts of whole plant tissue due to their different isotopic and molecular compositions e g epicuticular leaf waxes resins wood and their different decay resistance against the early diagenetic changes involved in organic matter decomposition carbon cycling during anoxic decomposition of plant derived organic matter is assumed to affect the 13c values of coal 13c values of wood and extracted cellulose are affected only to a minor extent

interpreting carbon isotope excursions carbonates and organic matter abstract variations in the carbon isotopic compositions of marine carbonate and organic carbon provide a record of changes in the fraction of organic carbon buried through time and may provide clues to changes in rates of weathering and sources of organic carbon paired carbonate and organic carbon isotope determinations provide a possibility of interpreting not only changes in the global carbon cycle through time but changes in atmospheric pco2 as well interpretations of these types of data are typically rather qualitative a quantitative basis is required to develop a better understanding of changes in the carbon cycle for this purpose we employ a simple model of the global carbon cycle which is subjected to a number of different perturbations each lasting 500 ky i e much longer than the residence times of carbon and phosphorus in the ocean atmosphere system in addition to standard considerations of carbon mass and isotopic fluxes to the ocean atmosphere system from weathering and volcanism and fluxes of organic carbon and carbonate carbon to sediments the model incorporates sensitivity of the photosynthetic carbon isotope effect to changes in pco2 the inclusion of this parameter leads to unexpected carbon isotope responses to forcing that causes increased rates of organic carbon burial a series of simple to more complex simulations illustrates the significant effects of varying differences between the carbon isotopic composition of sedimented carbonate and organic carbon b with constant b a 50 increase in organic carbon burial produces a parallel increase in carbonate and organic carbon isotopic compositions however the same simulation with b responsive to pco2 changes produces an initial parallel 13 c increase but this is followed by an even greater 13 c enrichment in organic carbon because pco2 falls in response to increased organic carbon burial the counterintuitive overall result of the enhanced organic carbon burial event is that the carbonate carbon isotopic composition actually decreases because of the more substantial increase in 13 c org in addition we illustrate the effects on carbon isotopic compositions of the oceanic inorganic carbon reservoir and buried organic matter of a 50 increase in volcanic co2 outgassing a 50 increase in weathering rate with coupled phosphate and riverine carbon flux responses a 50 decrease in shale associated organic carbon weathering a 50 decrease in silicate weathering rate and the possible effects of the rise in abundance of c4 plants in the late miocene to recent we compare the model simulated carbon isotopic responses for some of these experiments to paired carbonate and organic carbon records to illustrate how these records might be interpreted in light of the model response

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