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

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

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

early hettangian benthic planktonic coupling at doniford sw england palaeoenvironmental implications for the aftermath of the end triassic crisis abstract this paper presents a high resolution micropalaeontological study integrated with geochemical and sedimentological analyses of the triassic jurassic tr j transition at the doniford section sw england our analyses indicate the renewal of surface carbonate production in the blue lias formation early hettangian after the end triassic mass extinction based on the high abundance of surface carbonate producers schizosphaerellids which occurred in phase with development at sea floor of calcareous hyaline benthic foraminifers we deduce that a benthic pelagic coupling resulted in both the initial restoration of the biological carbonate pump and also a more efficient export production the presence of monospecific phytoplankton assemblages and benthic foraminiferal assemblages typical of poorly oxygenated environments suggest that the environmental stress continued after the end triassic maximal perturbation complete environmental recovery was prevented by a succession of alternating dysaerobic and anoxic phases that favoured the deposition of black shale sediments the hypothesis of a methane release mechanism as a trigger for the global carbon cycle perturbation and greenhouse conditions during the early jurassic is discounted based on evidence from the decoupled carbon isotope records of carbonate and organic matter apart from local control of a high amplitude sea level change across the tr j boundary the succession and nature of events at doniford are consistent with a scenario of global environmental and biotic changes triggered by the physical and chemical effects of the central atlantic magmatic province camp volcanism a super greenhouse climate in the aftermath of the end triassic mass extinction appears to be the results of the combination of the long term co2 accumulation in the atmosphere system due to the camp volcanic activity as well as the inefficiency of the biological pump due to reduced export production

changes in terrestrial floras at the triassic jurassic boundary in europe abstract one of the biggest mass extinctions took place at the triassic jurassic boundary it affected both marine and terrestrial ecosystems and caused the disappearance of many animal taxa mostly marine ones its influence on floral changes has been widely discussed with arguments offered for the sudden mass extinction of plants over vast areas or alternatively for slow less extensive changes the aim of this study was to statistically verify changes in terrestrial plant composition during the tjb in europe and to examine the type and extent of these changes data from polish localities an interesting new addition to the floristic data from the tjb were compared with those from other selected localities in europe the database contains 311 macroflora taxa from 106 localities 16 polish in 13 countries grouped into 29 regions and 571 microflora taxa from 105 localities 29 polish in 11 countries grouped into 37 regions the analysed data cover the period from the anisian to the toarcian stages range based metrics for diversity dynamics were calculated to show trends in floral changes during the studied time interval the focus being on the tjb due to strong disproportions in the number of localities and occurrences the rhaetian and the hettangian stages were overrepresented the warm and humid climate of those stages promoted plant diversity and led to the formation of numerous broad floodplains conducive to the preservation of remains e g in coal the patterns established by the raw data analyses were also assessed by applying a sampling standardisation procedure our results based on accurate data from poland and the rest of europe confirm and visualize a scenario in which there were no significant changes in terrestrial plant composition at the tjb hierarchical clustering suggests that local habitat conditions are the key factor in the grouping of localities with similar floristic composition and that differences between floras are not associated with the time dimension stages

correlating the end triassic mass extinction and flood basalt volcanism at the 100 ka level new high precision u pb geochronology from volcanic ashes shows that the triassic juras sic boundary and end triassic biological crisis from two independent marine stratigraphic sections correlate with the onset of terrestrial fl ood volcanism in the central atlantic mag matic province to 150 ka this narrows the correlation between volcanism and mass extinc tion by an order of magnitude for any such catastrophe in earth history we also show that a concomitant drop and rise in sea level and negative 13 c spike in the very latest triassic occurred locally in 290 ka such rapid sea level fl uctuations on a global scale require that global cooling and glaciation were closely associated with the end triassic extinction and potentially driven by central atlantic magmatic province volcanism

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

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

a middle late triassic ladinian rhaetian carbon and oxygen isotope record from the tethyan ocean abstract we obtained bulk sediment 18o and 13c data from biostratigraphically constrained tethyan marine sections at aghia marina greece guri zi albania and brumano and italcementi quarry italy and revised the published chemostratigraphy of the pizzo mondello section italy we migrated these records from the depth to the time domain using available chronostratigraphic tie points generating ladinian rhaetian 13c and 18o records spanning from 242 to 201 ma the 18o record seems to be affected by diagenesis whereas the 13c record appears to preserve a primary signal and shows values increasing by 1 in the ladinian followed by an 0 6 decrease across the ladinian carnian boundary followed by relatively constant but oscillatory carnian values punctuated by a negative excursion at 233 ma in the early carnian a second negative excursion at 229 5 ma across the early late carnian boundary and a positive excursion at 227 ma across the carnian norian boundary the norian record is characterized by a long term decreasing trend and a negative excursion at 216 ma rapid increases and decreases in 13c have been observed in the rhaetian but these may be at least in part due to mixing of different sources of carbonate carbon with different 13c values our triassic 13c record has been compared to data from the literature and a composite 13c record spanning the last 242 myr of earth s history has been generated this composite record shows a sequence of dated 13c trends and events that can be used for stratigraphic correlation as well as for a better understanding of the global carbon cycle in the mesozoic cenozoic

volcanism co2 and palaeoclimate a late jurassic early cretaceous carbon and oxygen isotope record a composite tethyan late jurassic early cretaceous carbon and oxygen isotope curve is presented c isotope data provide information on the evolution and perturbation of the global carbon cycle o isotope data are used as a palaeotemperature proxy in combination with palaeontological information the resulting trends in climate and in palaeoceanography are compared with biocalcification trends and oceanographic conditions favouring or inhibiting biocalcification positive c isotope anomalies in the valanginian and aptian correlate with episodes of increased volcanic activity regarded as a source of excess atmospheric carbon dioxide a major warming pulse accompanies the aptian but not the valanginian c isotope event the observed change in early aptian temperatures could have triggered the destabilization of sedimentary gas hydrates and the sudden release of methane to the biosphere as recorded as a distinct negative carbon isotope pulse preceding the positive excursion both c isotope anomalies are accompanied by biocalcification crises that may have been triggered by p co 2 induced changes in climate and in surface water chemistry elevated nutrient levels in river influenced coastal waters and in upwelling regions further weakened marine calcification these conditions contrast with normal trophic conditions prevailing in the latest jurassic and favouring biocalcification the c and o isotope curves record a stable mode of carbon cycling and stable temperatures we conclude that biocalcification is mostly triggered and inhibited by co 2 conditions in the atmosphere ocean system

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

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

chronology of the central atlantic magmatic province implications for the central atlantic rifting processes and the triassic jurassic biotic crisis abstract the central atlantic magmatic province camp is among the largest igneous provinces on earth emplaced synchronously with or just prior to the triassic jurassic t j boundary ca 200 ma in great part due to the controversial connection between the occurrence of camp and the events of the t j boundary the demand for better constraints on the duration and eruptive chronology of this province has increased more than 100 new 40 ar 39 ar ages have been published in the last 15 years with more than half of these in the last 3 years a careful review and selection of available ages as well as the publication of 16 new ages from the carolinas newark basin usa french guyana and morocco are presented judicious selection yields a total of 58 accepted age determinations for camp magmatism ranging from 202 to 190 ma covering every part of the camp a more complete picture develops with intrusive camp magmatism commencing as early as 202 ma extrusive activity initiated abruptly 200 ma reaching peak volume and intensity around 199 ma on the african margin the main period of camp magmatism is confirmed as brief but is suggested to consist of at least two phases over 1 5 ma with magmatism commencing along the africa north american margins and slightly later along the south american margin two volumetrically minor but distinctive magmatic peaks centered at 195 and 192 ma are mirrored in data from all three continents and highlighted by our statistical approach models describing rifting and thermal input and magma production on these timescales are explored despite significant advances in our understanding of the chronology of camp more data of better quality and broader geographical coverage are needed to completely characterize the evolution of the camp and infer its geodynamic origin in addition lack of a well defined t j boundary age as well as the absence of a relevant basis for comparison between u pb and 40 ar 39 ar data for this time period remain limiting factors to unambiguously linking camp in time with the events of the t j boundary

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

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

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

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

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

mesozoic c cycle perturbations and climate evidence for increased resilience of the cretaceous biosphere to greenhouse pulses the mesozoic c isotope record traces the history of the global carbon cycle major perturbations of the carbon cycle triggered by extraordinary volcanic activity are recorded in negative spikes cou

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

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

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

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

the nonmarine triassic jurassic boundary in the newark supergroup of eastern north america abstract for the last three decades the position of the triassic jurassic boundary tjb in nonmarine strata has largely been based on its palynostratigraphic placement just below the oldest basalts of the central atlantic magmatic province camp in the newark supergroup of eastern north america this boundary however is demonstrably older than the tjb as it is defined in marine strata thus the palynostratigraphic change used to place this tjb in the newark most resembles a late norian change in the european section and does not correspond to any palynological event at the marine defined tjb conchostracan biostratigraphy suggests that the tjb is in the newark extrusive zone above the oldest camp basalt and vertebrate biostratigraphy is consistent with this placement of the tjb radioisotopic ages indicate that the tjb defined in marine strata is no older than 200 ma but the oldest camp basalts of the newark supergroup consistently yield ages averaging about 201 ma magnetostratigraphic correlation of the newark section to the tjb section at st audrie s bay in england also indicates that the onset of camp volcanism in the newark supergroup is older than the marine tjb correlations based on carbon and osmium isotopes are also consistent with this correlation thus all data indicate that the tjb in the newark supergroup is above the lowest camp basalt in the newark extrusive zone correct placement of the tjb in the newark supergroup allows key nonmarine and marine events to be sequenced across the tjb indicating the following succession of events crurotarsan thecodont extinction the palynofloral turnover in the newark the first camp eruptions the extinctions of rhaetian ammonites and conodonts and the first appearance of jurassic psiloceratid ammonites

mesozoic climates and oceans a tribute to hugh jenkyns and helmut weissert the study of past greenhouse climate intervals in earth history such as the mesozoic is an important relevant and dynamic area of research for many sedimentary geologists geochemists palaeontologists and climate modellers the mesozoic sedimentary record provides key insights into the mechanics of how the earth system works under warmer conditions providing examples of natural climate change and perturbations to ocean chemistry including anoxia that are of societal relevance for understanding and contextualizing ongoing and future environmental problems furthermore the deposition of widespread organic carbon rich sediments black shales during the mesozoic means that this is an era of considerable economic interest in july 2015 an international group of geoscientists attended a workshop in ascona switzerland to discuss all aspects of the mesozoic world and to celebrate the four decade long contributions to our understanding of this fascinating era in earth history made by hugh jenkyns university of oxford and helmut weissert eth zurich this volume of sedimentology arose from that meeting and contains papers inspired by and co authored by hugh and helmi here a brief introduction to the volume is provided that reviews aspects of hugh and helmi s major achievements contextualizes the papers of the thematic issue and discusses some of the outstanding questions and areas for future research this article is protected by copyright all rights reserved

triassic jurassic atmospheric co2 spike i question the claim by tanner et al 1 that atmospheric co2 levels remained constant across the triassic jurassic boundary on the grounds of problems with stratigraphic completeness and contamination with atmospheric methane because methanogenic ch4 has a light isotope composition and oxidizes readily to co2 methane clathrate dissociation and oxidation events cannot be detected by palaeobarometers that use the carbon isotope composition of palaeosol carbonate

uniquely extensive seismite from the latest triassic of the united kingdom evidence for bolide impact a 2 4 m thick seismite in places overlain by a previously unreported tsunamite can be traced across 250 000 km 2 of the outcrop and subcrop of the latest triassic rhaetian cotham member of the penarth group united kingdom an extent unique for the british phanerozoic its consistent thickness intensity of deformation and preferred orientations of slump fold axes indicate a seismic event of m 10 with an epicenter 600 km w or nw of central britain the magnitude of the event is incompatible with known terrestrial mechanisms fault volcano but is consistent with a major bolide impact a short but unknown interval separates the top of the cotham member seismite from major geochemical and biotic perturbations associated with the end triassic extinction although a direct link between the seismite and these other events remains equivocal the exceptional extent of mega seismites such as this may prove a useful indicator of previously undocumented bolide impacts

mass extinctions and sea level changes abstract review of sea level changes during the big five mass extinctions and several lesser extinction events reveals that the majority coincide with large eustatic inflexions the degree of certainty with which these eustatic oscillations are known varies considerably thus the late ordovician and end cretaceous extinctions are associated with unequivocal major regressions demonstrated from numerous widespread regions in contrast the multiple high frequency sea level changes reported for the frasnian famennian crisis based on the supposed depth preferences of conodont taxa have little support from sequence stratigraphic analyses which reveals the interval to be one of highstand the end permian mass extinction has long been related to a severe first order lowstand of sea level newell n d 1967 revolutions in the history of life geol soc am spec pap 89 63 91 based primarily on the widespread absence of latest permian ammonoid markers but field evidence reveals that the interval coincides with a major transgression newell s hypothesis that marine extinctions are related to shelf habitat loss during severe regression remains tenable for the end guadalupian and end triassic extinction events but not for other crises rapid high amplitude regressive transgressive couplets are the most frequently observed eustatic changes at times of mass extinction with the majority of extinctions occurring during the transgressive pulse when anoxic bottom waters often became extensive the ultimate cause of the sea level changes is generally unclear a glacioeustatic driving mechanism can only be convincingly demonstrated for the end ordovician and end devonian events at other times it is speculated that they may relate to the widespread regional doming and subsequent collapse caused by the impingement of superplumes and ultimate eruption on the base of the lithosphere

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

upper kellwasser carbon isotope excursion pre dates the f f boundary in the upper devonian lennard shelf carbonate system canning basin western australia abstract here we report four high resolution carbon isotope records in addition to trace element data for the frasnian famennian f f boundary interval in the lennard shelf carbonate system of the canning basin western australia this region lacks the characteristic black shale horizons associated with the global late devonian kellwasser extinction events yet still exhibits a trend in carbon isotope character similar to what has been reported from elsewhere in the world two positive 13c excursions with 3 4 amplitudes enrichments in select trace element ratios suggest that both excursions are related to periods of oxygen deprivation and perhaps increased biological productivity given the continuous and stratigraphically expanded nature of lennard shelf sections together with high density sampling constrained by both conodont biostratigraphy and magnetostratigraphy we observe that the upper kellwasser isotope excursion maximum 13c values and associated trace element enrichments occur distinctly lower than the f f boundary level these results have implications for the paleoenvironmental conditions leading up to the late devonian mass extinction in terms of ocean chemistry and circulation patterns this data set allows for a rare detailed look at the temporal relationship between the kellwasser events and the f f boundary and constrains the pattern of carbon isotope perturbations at the intra zonal scale

nannofossils and superplumes the early aptian nannoconid crisis a group of calcareous nannoplankton named nannoconids experienced a crisis in the early aptian and recovered only later in the late aptian after a period of virtual absence although no extinctions occurred the widespread nature of the nannoconid crisis suggests a global causal factor this crisis is recorded within the chiastozygus litterarius nannofossil and globigerinelloides blowi planktonic foraminiferal zones postdates magnetic chronozone m0 by approximately 300 kyr and precedes the oceanic anoxic subevent 1a and associated 13c anomaly by some 40 100 kyr selective dissolution and anoxia cannot explain the crisis because nannoconids are dissolution resistant forms and their crisis clearly precedes the deposition of anoxic sediments at least 1 m y prior to the nannoconid crisis the onset of a nannoplankton speciation event may be the response of nannofloras to a major rise in relative sea level the nannoconid crisis seems to be synchronous with the early aptian volcanic eruptions in the pacific ocean hence calcareous nannoplankton were severely affected by the superplume volcanic episode the coccolithophorid bloom nannoconid crisis was possibly induced by the excessive co2 levels in the atmosphere and or caused by changes in nutrient content of oceanic surface waters fertility was enhanced by rapid turnover of nutrients due to the abnormal volcanic activity and accelerated transfer of nutrients from the continents into the oceans under warm and humid conditions of the mid cretaceous greenhouse climate the nannoconid crisis may represent a competition between phytoplankton groups for nutrients or more likely competition between different calcareous nannoplankton the biologic affinity and mode of life of nannoconus are unknown because there is no modern analog of this genus however comparison of lower cretaceous nannofossil assemblages with modern nannoplankton cummunities suggests that nannoconids like extant florisphaera profunda possibly inhabited the lower photic zone concentrations of nutrients in the upper euphotic zone may have triggered blooms of coccolithophorids and nannoconid depletion this model implies that the nannoconid crisis is the result of an abrupt major change in the structure of surface waters caused directly or indirectly by the superplume the adjustments of the biosphere to the new paleoceanographic and climatic conditions required some 40 100 kyr before changing into abnormally high primary productivity and deposition of organic carbon rich sediments with dinoflagellates outcompeting nannoplankton

marine and terrestrial sedimentation across the t j transition in the north german basin abstract the global mesozoic sea level rise contributed to the stepwise flooding of the central european basin ceb across the t j transition and transformed the ceb from a late triassic inland playa to an early jurassic semi enclosed inland sea the calibration of sections from north germany and thuringia using high resolution palynomorph and ammonite biostratigraphy contributes to the improved temporal and spatial resolution of this decisive period the herein proposed deltoidospora concavisporites dc zone placed between the rhaetian ricciisporites polypodiisporites rp zone and the hettangian pinuspollenites trachysporites zone marks the transitional zone of overlapping rhaetian and hettangian palynomorphs in brackish marine brackish and terrestrial environments of the north german basin ngb thus the dc zone enables the identification of the t j transition in the ngb following a short term ingression in the late norian corollina porcellispora subzone the first rhaetian transgression contributed to substantial marine terrestrial facies shifts the diachronous transgressive onlap of brackish marine strata culminated in a first rhaetian maximum flooding in the upper corollina enzonalasporites zone to lower rhaetipollis limbosporites rl zone after a regressive maximum in the middle rl zone the next transgression culminated in a second rhaetian maximum flooding in the upper rl zone following the end triassic regression herein assigned to the upper rp zone the diachronous transgressive onlap of marine shales marks the change to marine jurassic environments the herein proposed deltoidospora concavisporites dc zone placed between the rhaetian ricciisporites polypodiisporites rp zone and the hettangian pinuspollenites trachysporites zone marks the transitional zone of overlapping rhaetian and hettangian palynomorphs in brackish marine brackish and terrestrial environments of the north german basin ngb thus the dc zone enables the identification of the t j transition in the ngb at the western gate of the ceb the onset of marine hettangian strata with ammonites dated as the p erugatum biohorizon at st audrie s bay postdates the base hettangian gssp by 250 kyr from there to thuringia the diachronous onlap of marine hettangian strata with ammonites herein dated as the p plicatulum biohorizon took place over 100 kyr the first jurassic maximum flooding is dated as the interval of the p psilonotum to p plicatulum biohorizons lower planorbis zone rhaetian hettangian 3rd order sequences of the ceb correlate with contemporaneous sequences described from tethyan and peri tethyan basins pointing to circum tethyan eustatic cycles the 4th order sequences are evident in the rhaetian hettangian but only a set of rhaetian 4th order sequences can be correlated in the ngb so far

stability of atmospheric co2 levels across the triassic jurassic boundary the triassic jurassic boundary 208 million years ago is associated with widespread extinctions in both the marine and terrestrial biota the cause of these extinctions has been widely attributed to the eruption of flood basalts of the central atlantic magmatic province this volcanic event is thought to have released significant amounts of co2 into the atmosphere which could have led to catastrophic greenhouse warming but the evidence for co2 induced extinction remains equivocal here we present the carbon isotope compositions of pedogenic calcite from palaeosol formations spanning a 20 myr period across the triassic jurassic boundary using a standard diffusion model we interpret these isotopic data to represent a rise in atmospheric co2 concentrations of about 250 p p m across the boundary as compared with previous estimates of a 2 000 4 000 p p m increase the relative stability of atmospheric co2 across this boundary suggests that environmental degradation and extinctions during the early jurassic were not caused by volcanic outgassing of co2 other volcanic effects such as the release of atmospheric aerosols or tectonically driven sea level change may have been responsible for this event

co2 and the end triassic mass extinction the end of the triassic period was marked by one of the largest and most enigmatic mass extinction events in earth s history1 and with few reliable marine geochemical records terrestrial sediments offer an important means of deciphering environmental changes at this time tanner et al 2 describe an isotopic study of mesozoic fossil soils which suggests that the atmospheric concentration of carbon dioxide pco2 across the triassic jurassic boundary was relatively constant within 250 p p m v but this is inconsistent with high resolution evidence from the stomatal characters of fossil leaves3 here i show that the temporal resolution of the fossil soil samples may have been inadequate for detecting a transient rise in pco2 i also show that the fossil soil data are consistent with a large increase in pco2 across the triassic jurassic boundary when variations in the stable carbon isotope denoted as 13c in terrestrial plant leaves are taken into account these factors suggest that the linkage between pco2 global warming and the end triassic mass extinction remains intact

from rifting to drifting tectonic evolution of the south alpine upper crust from the triassic to the early cretaceous abstract the tectonic evolution of the south alpine rifted margin is discussed on the base of four palinspastic upper crustal profiles extension related to the movements between adria and europe began in the norian after variscan orogeny late carboniferous to middle permian orogenic collapse and continental scale wrenching from the late triassic to the early liassic stretching was mostly limited to the lombardian basin during this time extension was mainly controlled by four major listric faults symmetrically centred around the late carboniferous early permian collio grabens smaller faults which also started in the norian were progressively de activated during the late triassic after the middle liassic faulting in the lombardian basin gradually ceased and the site of extension shifted westwards i e towards the future site of crustal separation extension was then controlled by a set of west dipping normal faults oceanic crust was formed not later than 157 ma the overall extension along the profile which had a final length of 290 km was 52 km which corresponds to a stretching factor of 1 22 for the whole length of the preserved margin the strain rate is ca 1 10 16 s the sedimentation history suggests that the extension of the south alpine margin was a continuous process from the norian to the middle jurassic the changes in tectonic pattern are related to progressive hardening of the lithospheric segment undergoing slow extension

extinction trajectories of benthic organisms across the triassic jurassic boundary abstract we analysed diversity and abundance patterns of benthic organisms across the triassic jurassic t j boundary based on the paleobiology database pbdb which compiles palaeontological collection data on a global scale while sepkoski s sepkoski j j jr 2002 a compendium of fossil marine animal genera bulletins of american paleontology 363 1 563 compendium on the stratigraphic ranges of marine animal genera suggests that the dominant macrobenthic groups of the late triassic experienced significant extinctions prior to the t j boundary a significant end triassic extinction peak is evident from pbdb s data this rhaetian extinction peak is found in both an analysis of the raw data of stratigraphic ranges and a sample standardized analysis of occurrence data 41 of all mesobenthic and macrobenthic genera crossing the norian rhaetian boundary became extinct within the rhaetian although this rate suffices to characterize the end triassic extinction as a true mass extinction against a middle triassic to middle jurassic background significantly reduced rhaetian origination rates add to the strong diversity depletion in the earliest jurassic as for other mass extinctions evidence for selective extinction is meagre when the analysis is limited to the boundary interval alone and when focused on taxonomic and ecological characteristics of individual genera when taxa are separated by environmental preferences however several determinants of extinction risk become evident suggesting that reef dwellers had a significantly higher extinction risk than level bottom dwellers taxa with an inshore preference were more strongly affected than offshore taxa taxa preferring carbonate substrates were more strongly hit than taxa preferring siliciclastic substrates and taxa preferentially inhabiting low latitudes had higher extinction rates than taxa more common at intermediate and high latitudes much of this selectivity is not independent and also seen in the intervals of background extinctions suggesting that the end triassic mass extinction represents an intensification of background extinctions but not a qualitatively different macroevolutionary regime one possible exception is related to preferences for depositional environments suggesting a selective rhaetian extinction in reefs and inshore settings

palaeoecology of the late triassic extinction event in the sw uk a high resolution palaeoecological study of the shelly invertebrate macrofauna across two marine triassic jurassic boundary sections in the uk st audrie9s bay and lavernock point is presented loss of taxonomic richness occurs in the upper westbury formation to lower lilstock formation late rhaetian but if sample size is taken into account there is little convincing evidence of a catastrophic marine extinction there is however good evidence for significant palaeoecological change in the benthic marine ecosystem at this time the immediate post event recovery interval in the upper lilstock formation is characterized by assemblages of low abundance low diversity high dominance and low evenness body sizes of taxa that survived the event and originated afterwards were low until the later hettangian recovery to higher abundance higher diversity and higher evenness is recorded in the psiloceras planorbis zone recovery of the benthic ecosystem in the aftermath of the late triassic event was disrupted by marine anoxia and shows additional similarities to the much slower recovery that followed the late permian event the pattern of body size changes recorded in the shelly fossil record closely matches that of the trace fossil record shell thickness trends do not support a biocalcification crisis during the late triassic biotic event

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

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

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

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

a two phase end triassic mass extinction abstract the end triassic mass extinction was one of the big five crises of the fossil record it affected diverse marine groups including bivalves brachiopods ostracods calcareous algae radiolarians and tetrapods and coincided with major changes in palynological assemblages the rapidity of the event has long been debated and here we show that it can be resolved into two distinct short lived extinction pulses separated by a several hundred thousand year interlude phase detailed collecting in the british isles shows the first extinction in the lower cotham member eliminated many bivalves and ostracods this event has been previously considered as the end triassic mass extinction horizon however a second extinction is also seen at the top of the langport member after a phase of recovery marked by diversity increase this younger crisis caused the loss of further bivalves ostracods and the last of the conodonts the two phases of marine extinctions coincide with marked turnovers amongst palynofloral assemblages with the interlude phase manifest as a fern spore dominated interval the polypodiisporites polymicroforatus abundance interval correlation of triassic jurassic boundary sections and their associated extinction record in europe has been controversial the most parsimonious correlation scheme assumes that a brief high amplitude negative excursion of 13corg values seen at the level of the first extinction phase in the uk is manifest in other european sections in the same way alternative correlation schemes require complex scenarios with extinction occurring in some areas as recovery is happening elsewhere in europe the first extinction coincides with regression whilst the second occurs at a flooding surface marked by the spread of anoxia the extinction history of the terminal triassic crisis is remarkably similar to that seen during other extinction events end ordovician permo triassic toarcian and suggests that if the ultimate driver of these crises large igneous province eruptions is the same then they show the same double punch eruption history separated by a more benign interval of a few hundred thousand year duration

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

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

dynamics of wind driven upwelling and relaxation between monterey bay and point arena local regional and gyre scale controls 1 in north and central california equatorward winds drive equatorward flows and the upwelling of cold dense water over the shelf during the midspring and summer upwelling season when the winds temporarily weaken the upwelling flows between point reyes and point arena relax becoming strongly poleward over the shelf analytical and numerical models are used to describe the effect of alongshore variability of winds bathymetry and basin scale pressure gradients on the strength of upwelling and its relaxation alongshore winds weaken to the south of point reyes and the shelf becomes narrower from point reyes to monterey bay both of these lead to reduced upwelling at and to the north of point reyes causing an alongshore gradient of temperature and density on the shelf these alongshore gradients lead to an along isobath pressure gradient over the shelf that drive the relaxation flows a simple analytical model is used to explain the dynamics magnitude and structure of the relaxation flows the modeling also suggests that the depth of origin of the upwelled waters and thus their temperature is controlled by the along isobath pressure gradient that exists over the continental slope this along slope pressure gradient is also responsible for the california undercurrent in this region this pressure gradient is not generated in a model of the californian coast extending from 32 n to 42 n and integrated for several months suggesting it is caused by dynamics whose spatial or temporal scales are larger than the californian coast and or longer than several months

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

a review of the broad pattern of jurassic sea level changes and their possible causes in the light of current knowledge abstract an assessment is made of the current state of research into jurassic sea level changes based on new insights into depositional patterns in relation to these changes and new stratigraphic information from several widely separated regions across the world the bearing of this information on alternative models respectively involving sea level rise interrupted by stillstands or falls is then evaluated the gross pattern appears to be one of more or less gradual rise of sea level through the period interrupted by episodes of comparative stillstand rather than eustatic fall and several episodes of significant regression are shown to be the result of regional tectonics major episodes of eustatic rise took place in the early hettangian early sinemurian early pliensbachian early toarcian early and late bajocian middle callovian and late oxfordian to kimmeridgian a significant episode of rapid and very extensive regression possibly global took place at the end of the triassic but other regressive episodes in the late aalenian bathonian late oxfordian kimmeridgian and tithonian are clearly only regional in extent there is no evidence for glacioeustasy and most if not all of the regional or global changes recognised can readily be related to plate tectonics the events at the triassic jurassic boundary seem to be the result of mantle plume activity centred on the central atlantic region

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

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

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

the late rhaetian transgression in southern sweden regional and global recognition and relation to the triassic jurassic boundary palynological investigations of rhaetian outcrops and drillcores in combination with subsurface data from wells in scania southern sweden have revealed the presence of marine dinoflagellate cysts in sedimentary strata that were previously considered to have been deposited in a mainly terrestrial environment two distinct dinocyst events are identified one older event where persistent rare to common occurrences of rhaetogonyaulax rhaetica and lunnomidinium scaniense indicates deposition in shallow marine and marginal marine environments this lunnomidinium interval is preceded and succeeded by assemblages with rare to common r rhaetica and can be correlated with the mid to late rhaetian r rhaetica zone it is associated with spore pollen assemblages of the mid rhaetian rhaetipollis limbosporites zone the younger event the r rhaetica maximum interval is characterised by mass occurrence of r rhaetica with less common or absent dapcodinium priscum in association with a dark grey to black mudstone shale the introduction of d priscum in association with the over whelming abundance of r rhaetica allows correlation with the transition between the r rhaetica zone and the succeeding d priscum zone and signals fully marine conditions the r rhaetica maximum interval is associated with spore pollen assemblages of the late rhaetian ricciisporites polypodiisporites zone and is in sweden succeeded both lithostratigraphically and palynostratigraphically by the t j transition the r rhaetica maximum interval corresponds to a late rhaetian maximum flooding event that took place in a shallow gently sloping embayment that covered the danish basin area during the late triassic early jurassic this maximum flooding event can be recognised in late rhaetian strata from different parts of the northern hemisphere it is an important temporal constraint on the t j boundary as it is associated with the disappearance of triassic marine faunas appears to coincide with the onset of the main pulse of camp volcanism immediately precedes the initial carbon isotope excursion and the global sea level drop that characterises the t j transition

response of early cretaceous carbonate platforms to changes in atmospheric carbon dioxide levels during the late barremian and early aptian about 120 million years ago intense volcanic degassing and extremely rapid release of methane hydrates contained in marine sediments added high amounts of carbon to the ocean and atmosphere and resulted most probably in rising atmospheric carbon dioxide pressure in order to document the response of the shallow water carbonate producing communities to this pronounced disturbance of the carbon cycle we studied a late barremian to early aptian neritic carbonate succession deposited on the northern tethyan shelf swiss alps the sedimentological and stable carbon and oxygen isotope records of two sections located along a n s transect from proximal to more distal shelf environments were investigated the sediments correspond to outer mid and inner ramp deposits of a homoclinal carbonate ramp vertical facies variations within the two studied sections feature three progradation phases of the platform a highly resolved correlation of the shelf sediments with a pelagic succession from the southern alps northern italy is based on both 13c stratigraphy and biostratigraphy and indicates that the drowning of the helvetic carbonate platform coincided with a pronounced calcification crisis of calcareous nannofossils the biocalcification crisis started before but culminated during the aptian methane event recorded in a negative carbon isotope spike we propose that increased carbon dioxide concentrations in oceans and atmosphere related to volcanic activity and to sudden methane release reduced the marine calcium carbonate oversaturation and the calcification potential of benthic and planktonic organisms carbonate producing shallow water communities on platforms and ramps suffering from additional environmental stress such as extreme temperatures or high nutrient levels could not survive during times of rising sea level and as a consequence carbonate platforms drowned

timing the end triassic mass extinction first on land then in the sea the end triassic marks one of the five biggest mass extinctions but current geologic time scales are inadequate for understanding its dynamics a tuff layer in marine sedimentary rocks encompassing the triassic jurassic transition yielded a u pb zircon age of 199 6 0 3 ma the dated level is immediately below a prominent change in radiolarian faunas and the last occurrence of conodonts additional recently obtained u pb ages integrated with ammonoid biochronology confirm that the triassic period ended ca 200 ma several million years later than suggested by previous time scales published dating of continental sections suggests that the extinction peak of terrestrial plants and vertebrates occurred before 200 6 ma the end triassic biotic crisis on land therefore appears to have preceded that in the sea by at least several hundred thousand years

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

estimating aircraft sar response characteristics and ocean wave spectra in the labrador sea extreme waves experiment the labrador extreme waves experiment lewex was an international effort to assess methods of measuring and modeling the directional aspects of wind generated ocean waves especially their evolution in the presence of rapidly turning winds the author describes data processing methods that have been developed to derive estimates of two dimensional wave height variance spectra from the ocean imagery obtained in lewex by a c band synthetic aperture radar sar system aboard a canadian cv 580 aircraft sar spectra at altitudes of 20000 and 12000 ft are compared for both large approximately 50 degrees and small approximately 25 degrees radar look angles independence spectral estimates from both a surface contour radar and a radar ocean wave spectrometer aboard a nasa aircraft are used to verify the surface wave spectrum

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

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

carbon cycle 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

the end triassic mass extinction a new correlation between extinction events and δ13c fluctuations from a triassic jurassic peritidal succession in western sicily abstract a new 13ccarb curve was obtained from an expanded peritidal succession in western sicily and was used to investigate the relationships between isotopic signatures and biological events on carbonate platforms across the triassic jurassic boundary tjb the resulting curve shows two main negative carbon isotopic excursions cies that fit well with the initial and main cies that are recognized worldwide and linked to the end triassic extinction ete in the studied section the first negative cie marks the disappearance of the large megalodontids which were replaced by small and thin shelled specimens while the main cie corresponds to the last occurrence lo of the megalodontids and approximately 50 m upsection to the total demise of the rhaetian benthic foraminifer community upward the carbon curve shows a positive trend ca 1 and a gradual recovery of the benthic communities after an approximately 10 m thick barren interval populated only by the problematic alga thaumatoporella parvovesiculifera a comparison between the mt sparagio 13ccarb curve and other coeval ccarb and corg curves from carbonate platform ramp and deep basin successions indicates similar isotopic trends however the diverse magnitudes and responses of benthic communities confirm that the carbon cycle perturbations have been globally significant and were influenced by external forces such as camp volcanism the multiphase nature of the extinction pulses could have been caused by local environmental changes related to transgression regression phenomena overall this study adds new data and a new timing to the effect of the acidification process on carbon productivity and benthic communities in different environments across the tjb

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

evolution of early triassic outer platform paleoenvironments in the nanpanjiang basin south china and their significance for the biotic recovery detailed microfacies and paleoenvironmental analyses were conducted through the early triassic interval of the outer platform ammonoid rich series of the nanpanjiang basin luolou formation guangxi province south china extensive investigations on outcrops and on thin sections reveal that the widely reported well diversified latest permian fauna dominated by abundant corals calcareous algae calcareous sponges crinoids brachiopods gastropods ostracods and foraminifera is abruptly replaced by decimated early triassic communities essentially composed of low diversity bivalves microgastropods ostracods and rare foraminifera along with this drastic change in faunal assemblages the recolonization of devastated habitats by calcimicrobial frameworks is observed in the aftermath of the end permian mass extinction calcimicrobialites of griesbachian age are followed by mixed ammonoid and conodont rich carbonate siliciclastic series consisting of dark suboxic laminated mudstones intercalated with organic rich shales of dienerian to late smithian age the carbonate siliciclastic series are interrupted by a brief carbonate episode during the early middle smithian massive carbonate production resumes only from the early spathian onward and persists throughout the spathian the initial deposition of both carbonate episodes is coeval with i re establishment of well oxygenated conditions ii a marked early smithian to extreme early spathian ammonoid conodont diversification iii a significant increase in the skeletal grain diversity and abundance and iv peak carbon isotope values a short interval of black organic rich shales precedes the onset of these two distinct carbonate events which are both marked by a positive carbonate carbon isotope excursion known from other tethyan marine localities the comparison between the early triassic stratigraphic evolution of tethyan outer platform paleoenvironments and platform basin margin settings of the nanpanjiang basin suggests a causal connection between large fluctuations of the global carbon cycle climate shifts sea level changes oxygen availability in the oceans and the biological rediversification in the wake of the end permian biotic crisis

chemostratigraphic and sedimentological framework of the largest negative carbon isotopic excursion in earth history the neoproterozoic shuram formation nafun group oman abstract oman records in its neoproterozoic nafun group huqf supergroup an essentially complete carbonate rich ediacaran succession the nafun group overlies the presumed marinoan rift related fiq member ca 635 ma and ends just below the precambrian cambrian boundary 542 ma tectonic subsidence caused by thermal contraction following fiq aged rifting allowed the preservation of about 1 km of postrift stratigraphy with no major stratigraphic breaks the nafun group above the marinoan cap carbonate hadash formation represents two siliciclastic to carbonate grand cycles both initiated by significant transgressions these cycles comprise the masirah bay khufai formations and the shuram buah formations the khufai shuram boundary is associated with the start of a major carbon isotope perturbation the uppermost ramp carbonates of the khufai formation record a smooth decrease in 13c from about 4 to values around 0 followed by two descending steps across which values plunge to a nadir of 12 in the overlying red siltstones and shales interbedded with thin limestones of the shuram formation this fall in isotopic values is temporally rapid and coincident in both shallow and deep water sections in the time span of a single parasequence the 13c nadir is then followed by 50 million years of monotonic recovery the shuram shift represents the largest 13c inorganic carbon negative excursion in earth history although the snowball earth theory links periods of depleted carbon isotopic ratios with periods of global glaciation the non glaciated context of the shuram formation suggests that the causal relationship between global glaciation and negative carbon isotopic excursions is non unique although the precise mechanism driving this major perturbation of the carbon cycle remains enigmatic the long term remineralization of an isotopically depleted organic carbon reservoir in ocean water is a promising candidate

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

first alkaline magmatism during iberia newfoundland rifting the age and origin of alkaline rocks emplaced into the sediments of the rift related continental lusitanian basin were investigated to constrain earliest magmatic activity occurring prior to oceanic plate formation between iberia and newfoundland the u pb titanite ages are 146 5 1 6 2 sterr 145 3 1 4 and 142 3 1 0 ma and initial pb isotopic ratios of feldspars lie at 18 418 18 978 for 206pb 204pb at 15 594 15 925 for 207pb 204pb and at 37 105 39 216 for 208pb 204pb initial 87sr 86sr ratios measured in the same feldspar fractions lie at 0 705409 0 706462 this episode of magmatic activity lasting for at least 4 2 2 6 myr most likely marks a phase of maximum lithospheric thinning during which zones of weakness were created to allow deep magmas to reach the surface such zones are preferentially re activated palaeozoic faults of the iberian plate the isotope data suggest that the dominant volume of alkaline magmas was generated by partial melting of the metasomatized subcontinental iberian mantle

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

late early triassic climate change insights from carbonate carbon isotopes sedimentary evolution and ammonoid paleobiogeography the late early triassic sedimentary facies evolution and carbonate carbon isotopemarine record 13ccarb of ammonoid rich outer platform settings show striking similarities between the south china block scb and the widely distantnorthern indianmargin nim the studied sections are located within the triassic tethyshimalayan belt losar section himachal pradesh india and the nanpanjiang basin in the south china block jinya section guangxi province respectively carbon isotopes from the studied sections confirm the previously observed carbon cycle perturbations at a time of major paleoceanographic changes in the wake of the end permian biotic crisis this study documents the coincidence between a sharp increase in the carbon isotope composition and the worldwide ammonoid evolutionary turnover extinction followed by a radiation occurring around the smithian spathian boundary based on recent modeling studies on ammonoid paleobiogeography and taxonomic diversity we demonstrate that the late early triassic smithian and spathian was a time of a major climate change more precisely the end smithian climate can be characterized by a warm and equable climate underlined by a flat pole to equator sea surface temperature sst gradient while the steep spathian sst gradient suggests latitudinally differentiated climatic conditions moreover sedimentary evidence suggests a transition froma humid and hot climate during the smithian to a dryer climate fromthe spathian onwards by analogywith comparable carbon isotope perturbations in the latedevonian jurassic andcretaceouswe propose that high atmosphericco2 levels could have been responsible for the observed carbon cycle disturbance at the smithian spathian boundary we suggest that the end smithian ammonoid extinction has been essentially caused by a warm and equable climate related to an increased co2 flux possibly originating froma short eruptive event of the siberian igneous province this increase in atmospheric co2 concentrations could have additionally reduced the marine calcium carbonate oversaturation and weakened the calcification potential of marine organisms including ammonoids in late smithian oceans

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