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

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

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

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

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

ammonoid diversity and disparity track episodes of chaotic carbon cycling during the early mesozoic episodes of mass extinction represent the largest events of biodiversity loss known in the geologic record and may provide tests of biodiversity ecosystem stability hypotheses here we present the first correlation between ammonoid diversity and disparity and ecosystem stability as represented by stable carbon isotopic records spanning the end permian through end triassic mass extinctions ammonoid generic richness from a single biogeographic realm shows that nearly all taxa disappeared coincident with major carbon isotopic shifts to lighter values the intervals following these two major mass extinctions were characterized by multiple positive negative couplets of chaotic carbon cycling and were composed of low richness ammonoid faunas characterized by higher proportions of passively floating non swimming morphotypes than before or after in contrast richness was highest during intervals of stable carbon isotope values we propose that these chaotic carbon episodes reflect the breakdown of functional redundancy in the ecosystem and that the post extinction carbon cycle did not stabilize until redundancy was restored

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

volcanism and deep ocean acidification across the end triassic extinction event abstract the end triassic extinction event marks one of the big five mass extinction events of the phanerozoic the ultimate cause of the extinction is considered to be volcanic activity at the central atlantic magmatic province camp yet the underlying nature of global environmental changes that accompanied the biotic turnover remains elusive here we present chemical and mineralogical studies across the end triassic extinction level of the deep sea chert sequence inuyama japan depleted hematite content normalized by terrigenous material predated the end triassic extinction level with significant rock color change from brick red to purple which is consistent with the rock magnetic records of hematite reported this suggests the loss of authigenic hematite possibly due to the acidification of bottom water and the underlying sediment pore water this timing is consistent with the initial eruption of camp volcanism suggesting a catastrophic release of greenhouse gases as a cause of deep ocean acidification across the end triassic extinction interval mgo al2o3 fe2o3 al2o3 and al2o3 sio2 increased with change in color from purple to dusty red this trend became close to those of weathered camp basalts in arid area implying that it became the considerable source of aeolian dust in cherts after the end triassic extinction event these temporal relations support the synchrony among the initial eruption of camp deep ocean acidification and the end triassic extinction similar rock color changes of cherts might have potential information for the volcanisms and deep ocean acidification in other geologic events

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

a major perturbation of the carbon cycle before the ghaub glaciation neoproterozoic in namibia prelude to snowball earth 1 a large 11 15 negative shift in 13c is observed in shallow water carbonates directly beneath neoproterozoic glacial deposits or correlative disconformity in northwest namibia ascribed to a snowball earth reproducibility and stratigraphic concordance of this anomaly in 16 sections across the ancient continental shelf support a primary origin and field relations show it predates the fall in sea level associated with the ghaub glaciation we crudely estimate the duration of the isotopic shift as 0 6 106 years from a simple thermal subsidence model similar or larger 13c anomalies are found directly beneath neoproterozoic glacial units in australia canada china scotland and svalbard after considering conventional interpretations for negative 13c anomalies we conclude that a prolonged methane release to the atmosphere is most consistent with the timescale magnitude and geological context of the anomaly in namibia counterintuitively an anomalous methane flux that is sustained for 100s kyr may be consistent with a snowball glaciation

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

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

late quaternary evolution of coastal sand barriers port stephens myall lakes area central new south wales australia abstract the geomorphic and stratigraphic history of six coastal embayments has been studied in the vicinity of newcastle new south wales n s w australia in order to determine modes of deposition and the degree to which marine and estuarine deposits can be correlated and dated each embayment possesses its own distinctive suite of landforms ranging from those dominated by coastal dunes to those in which beach ridges occur in four of the bays dual sand barriers comprising an inner barrier and an outer barrier provide the framework for correlation between embayments six stages are recognized in the deposition of late quaternary sediments in this area i pre last interglacial involving accumulation of separate composite units consisting of estuarine clays and transgressive dune complexes ii last interglacial stage during which inner barriers were formed iii last glacial reworking of barrier and dune sands by westerly winds iv postglacial marine transgression during which the outer barriers were initiated v mid holocene stage following cessation of sea level rise ca 6000 6500 yr b p on this coast and involving progradation of outer barriers in some embayments and vi late holocene episodic eolian reworking of dune complexes and outer barriers the relatively high wave and wind energy as well as the tectonic setting of the central n s w coast results in somewhat different geomorphic histories from barrier island coasts in north america and europe

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

sea level change and facies development across potential triassic jurassic boundary horizons sw britain the late triassic to early jurassic aged succession of sw britain the penarth and lower lias groups comprises mudstone sandstone and limestone strata deposited in a variety of marine to non marine environments faunal and floral characteristics of these successions have led to the proposal that one location in sw england st audrie9s bay should serve as the global stratotype section and point gssp for the base of the hettangian stage and thus for the triassic jurassic tr j boundary the sections of sw britain have also been used previously to infer sea level change history and relate this to potential kill mechanisms associated with the tr j boundary mass extinction chemostratigraphic biofacies and lithofacies data are used here to suggest alternative models of sea level change in relation to possible tr j boundary horizons in the sections of sw britain a sea level lowstand surface of erosion is inferred to occur within the cotham member of the lilstock formation a unit deposited in an environment that was often subaerially exposed in contrast to previous interpretations the top surface of the overlying langport member here inferred to be deposited on a carbonate ramp of depositional or tectonic origin represents a drowning event of at least regional extent all horizons regarded as plausible levels at which to place the tr j boundary based on fossil distributions lie within strata deposited during relative sea level rise however it is doubtful whether the higher horizons proposed to mark the boundary faithfully record times of true biotic change on a global scale and additionally there is no positive evidence that sea level fall had any relation to the genesis of proposed tr j marker horizons it is unlikely that sea level fall played a significant role in the tr j boundary extinctions in either a local or a global context

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

carbon and nitrogen isotope disturbances and an end norian late triassic extinction event major perturbations of organic carbon and nitrogen isotope ratios from a norian rhaetian late triassic boundary section in british columbia coincide with an extinction of the dominant deep water invertebrate fauna of the late triassic monotids and most ammonoids the carbon isotope excursion is attributed to the development of widespread oceanic stagnation that favored organic rich shale deposition the coincident nitrogen isotope excursion suggests that progressively more nitrate limited productivity forced a change to nitrogen fixing cyanobacteria populations as ocean stagnation created nutrient starved conditions the biotic crisis and geochemical events of the norian rhaetian boundary predate the latest rhaetian end triassic mass extinction thus the late triassic interval was marked by more than one extinction event

biosedimentology of the early jurassic post extinction carbonate depositional system central high atlas rift basin morocco this study documents a liassic example of the long ranging effects of mass extinction on carbonate systems biohistoric constraints inherent in the liassic carbonate depositional system are deciphered from normal marine sub tidal deposits of the central high atlas rift basin morocco through hettangian sinemurian to early toarcian times the integration of results from the analysis of lithofacies depositional geometries microfacies macrobenthos carbonate build ups carbon and oxygen stable isotopes and rare earth element yttrium distribution patterns allows the intrinsic or biohistoric control on the central high atlas deposits to be separated from extrinsic factors such as basin development and palaeoclimate the survival interval in the aftermath of the end triassic mass extinction persisted until the early sinemurian indicated by a severely depleted carbonate system impoverished in skeletal organisms a tectonic pulse at the early to late sinemurian boundary interval caused a basin widening with immigration of a marine fauna however until the latest sinemurian macdonelli subzone of the raricostatum zone the deposits were dominated by filter feeding benthic heterotrophs sponges brachiopods polychaetes and crinoids during this stage primary production within the enlarged basin must have been largely planktonic and there was a net flux of organic matter to the sea floor oxygen minimum zone a regional radiation of organic walled phytoplankton is inferred to explain the selective success of the filter feeding community and the occurrence of sponge mounds thus significant effects of the end triassic mass extinction are still present during the late sinemurian through almost the entire pliensbachian a highly productive shoal rimmed carbonate platform existed it developed subsequent to tectonic reorganization and a marine recirculation event radiolarian facies 13c 1 1 strongly negative ce anomaly photosymbiotic sediment producers mainly large bivalves now state the success of specialists and environmental equilibrium conditions in the latest pliensbachian the climax stage was reached with the development of a coralgal reef rimmed carbonate platform the liassic carbonate depositional system experienced a terminal multicausal early toarcian drowning event during which most of the large bivalves became extinct

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

mapping mud content and median grain size of north sea sediments a geostatistical approach abstract sediment grain size is well known for its influence on biogeophysical processes and hence grain size parameter maps important elements in an integrated ecological modelling strategy in this study a large database was compiled from legacy data on grain size parameters and distributions in north sea surface sediments the database was analysed by means of non linear regression to enable a consistent quantification of various grain size parameters in a second step multivariate geostatistics kriging were employed to predict the spatial distribution of percentage mud content and median grain size in the north sea with a resolution of 1 1 nautical miles the results show that incorporation of secondary information in the interpolation led to a physically more realistic representation of large scale patterns compared to deterministic approaches an evaluation of map confidence however suggests only minor differences in the quality obtained by different kriging techniques it appears that the data density and distribution are not an issue when it comes to performance instead insufficient metadata constrain the assessment and harmonisation of data sets and introduce uncertainty into the predictions

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

phanerozoic large igneous provinces lips heatt haline euxinic acidic thermal transgression episodes and mass extinctions abstract the phanerozoic consists of three mutually exclusive climate states icehouse greenhouse and hothouse the greenhouse is the default state representing 70 of the phanerozoic it is characterized by a weak thermal mode pole driven deep water formation with little or no continental sea ice and weakly oxic cool water sinking near the poles nitrogen limitation characterizes greenhouse oceans in which ammonium may be the dominant bioavailable form of nitrogen the steady state greenhouse default must be forced to produce either of the other two states continent continent collision produces the intense chemical weathering that draws down atmospheric co2 and results in the icehouse state that comprises 20 25 of the phanerozoic icehouses have ice caps in contact with the ocean that produce icebergs and foster sea ice formation sea ice formation fills the ocean with highly oxic phosphorus limited icewater except for a thin layer of warm surface water in the tropics of the 23 most conspicuous mass extinctions of the phanerozoic including the late ediacaran 4 are associated with ice volume related regressions and 3 are problematic we suggest that the other 16 mass extinctions occurred when greenhouse climate was forced to hothouse climate large igneous provinces lips can trigger the heatt haline euxinic acidic thermal transgression mechanism which can force greenhouse climate to a hothouse climate state the rapid voluminous co2 emissions of lips cause a series of events that result in very slow but pronounced haline mode circulation mid latitude driven deep water formation that produces warm saline bottom water at very dry hot subtropical and middle latitudes this water upwells at the poles causing warm and moist equable climate hothouse development promotes deep sea anoxia that is generated in concert with co2 buildup and warming the spread of anoxia favors reduced nitrogen over nitrate and limited iron dust curtails nitrogen fixation this leads to dominance of primary productivity by primitive green algae and or cyanobacteria progression to euxinia that reaches the photic zone severely curtails primary productivity via poisoning even as availability of usable nitrogen plummets the result is eukaryotic mass extinction we suggest that the 16 phanerozoic mass extinctions referred to above resulted at least in part from the heatt process evidence for this relationship at 11 of the most severe extinctions is convincing data sets for the other 5 are strongly suggestive of heatt related mass extinction but do not yet have enough documentation to reliably characterize them as heatt episodes

early hettangian ammonites and radiolarians from the queen charlotte islands british columbia and their bearing on the definition of the triassic jurassic boundary abstract the triassic jurassic boundary t j boundary interval is one of the most important but poorly understood intervals in the phanerozoic here we fully document the ammonite and radiolarian successions at several sites in the queen charlotte islands qci british columbia eleven ammonite taxa are described and eighteen radiolarian taxa are discussed with the radiolarian genus tipperella described as new type species t kennecottensis n sp there are two continuous t j boundary sections in the qci one is located at kennecott point on graham island section i the other on the southeastern shore of kunga island section iii a second section at kennecott point contains fossils of early hettangian age only section ii radiolarian faunas include taxa from the upper rhaetian globolaxtorum tozeri zone in the two continuous sections and the lower hettangian canoptum merum zone in all three sections in each section the lowest hettangian fossils are radiolarians and a few collections contain rare rhaetian holdovers these mixed faunas may equate with the lowest hettangian ammonite zone the spelae zone of the north american succession the upper portion of section i contains a sparse ammonite fauna which indicates an early hettangian age this section has also provided carbon isotope data with a negative excursion spanning the t j boundary section ii contains a more diverse early hettangian ammonite assemblage that permits correlation of the upper portion of this section with the lower hettangian minutus zone section iii has been previously proposed as a potential basal hettangian global stratotype section and point gssp in addition to an outstanding radiolarian fauna the section contains moderately diverse early hettangian ammonites that permit correlation of the lower portion of the section with the minutus and pacificum zones and the upper portion with the lower hettangian polymorphum zone this section has previously provided a u pb date of 199 6 0 3 ma from 3 6 m below the t j boundary currently there are four candidates and no ideal gssp for the basal hettangian a section in new york canyon nevada has also been proposed as a potential gssp this section is easily accessible and provides a virtually complete ammonoid succession but lacks geochronology and microfossils the section on kunga island in the qci provides geochronologic data and excellent radiolarian constraints in essence the sections at kunga island in the qci and new york canyon in nevada are complementary close correlations between the two sections are possible using ammonite faunas we suggest the section from nevada be designated as holostratotype for the basal hettangian and the qci section be designated as a parastratotype to improve recognition of this interval

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

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

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

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

carbon and nitrogen isotope disturbances and an end norian late triassic extinction event comment and reply comment sephton et al 2002 1 reported a complex isotopic event marked by a positive 13corg excursion and an initially positive 15norg excursion from a triassic jurassic boundary succession at black bear ridge williston lake northeastern british columbia corresponding to the level of

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

response of the marine infauna to triassic jurassic environmental change ichnological data from southern england abstract the trace fossil record through the triassic jurassic boundary interval is examined at three sites in central and southern england st audrie s bay somerset pinhay bay devon and long itchington warwickshire the lower pre planorbis beds of the blue lias formation record low ichnotaxonomic diversity low bioturbation intensity small burrow diameters and an absence of deep tier bioturbation the stepwise reappearance of ichnotaxa following this interval is similar at the three sites suggesting similar rates of recovery in the benthic marine ecosystem and highlighting the potential contribution of these trace fossils to stratigraphic correlation mass extinction in the late triassic is increasingly linked to the emplacement of the central atlantic magmatic province camp timing of the onset of camp volcanism in the uk is currently imperfectly known but potentially occurred within either the westbury formation or the lilstock formation if the onset of camp was within the lilstock formation the modestly diverse trace fossil assemblage of the langport member of the lilstock formation suggests that emplacement of camp had little lasting effect on the marine benthos in central and southern england the decline in benthic activity recorded in the pre planorbis beds appears to be unrelated to the onset of camp and any associated environmental change it is more likely related to an episode of marine anoxia an episode of marine anoxia also provides a suitable causal mechanism for the reduction of infaunal tiering

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

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

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

geochronological constraints on post extinction recovery of the ammonoids and carbon cycle perturbations during the early jurassic abstract this paper presents the first quantitative study of the early jurassic recovery of ammonoids after the end triassic mass extinction based on detailed u pb id tims isotope dilution thermal ionization mass spectrometry geochronology from ash bed zircons placed within a clear phylogenetical and biochronological framework at the subzonal and species level this study was triggered by the discovery of a rich peruvian succession of ammonites deposited concomitantly with an unusually large number of ash beds two major phases of rediversification are observed during the psiloceras spelae and angulaticeras zones that correspond to positive peaks in the 13corg curve providing a possible link between biodiversity and the global carbon cycle in the case of the post extinction recovery the development of the earliest hettangian ammonites occurs within the genus psiloceras which begins with the occurrence of p spelae and then explodes into worldwide development of smooth psiloceratids of the psiloceras planorbis group s l this rapid biodiversification likely occurred less than 100 ka after the end triassic crisis the genus psiloceras occupied all the possible ecological niches worldwide from the pacific deep waters to the nw european shallow deposits and also in some rare tethyan occurrences like at germig in tibet this global dispersion allowed the differentiation of the group in several major phyla the schlotheimiidae discamphiceratinae arietitidae and lytocerataceae which were the roots of all other jurassic and cretaceous ammonites

rising atmospheric co2 as a possible trigger for the end triassic mass extinction the end triassic mass extinction one of the five largest extinctions in earth history was a severe catastrophe in which 80 of all species were wiped out the cause of the extinction is controversial but any mechanism must account for mass extinction in both marine and terrestrial environments one smoking gun the eruption of the central atlantic magmatic province camp has prompted the hypothesis that co2 degassing to the atmosphere may have induced an environmental catastrophe at the end triassic in this study we use a numerical coupled ocean atmosphere climate model of the late triassic to determine environmental stresses associated with a rapid increase in atmospheric co2 a series of sensitivity experiments with co2 levels that bracket estimated end triassic pco2 estimates 2 8 pre industrial levels predict extreme environmental conditions on land increasing co2 from 2 to 8 pre industrial levels causes an increase in the number and severity of hot days and days without precipitation an exponential increase in continental area experiencing hot days and enhanced seasonal fluctuation in the ocean wind driven circulation decreases and meridional overturning diminishes by a factor of 4 leading to enhanced ocean stratification a three box model of the deep ocean predicts a decline of 85 mol l in deep ocean oxygen concentration with a 4 fold increase in atmospheric co2 consequently while terrestrial organisms would have been subject to severe heat and water stress marine fauna would have experienced oxygen deprivation additional sensitivity experiments indicate that variations in milankovitch orbital parameters may further contribute to faunal stress by intensifying continental heating and seasonal fluctuations in sum model results predict that rising atmospheric co2 would have significantly impacted both marine and continental environments providing a link between turnover on land and ocean during the late triassic

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

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

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

carbon and nitrogen isotope disturbances and an end norian late triassic extinction event comment and reply reply we thank hall and pitaru for their comments and look forward to the publication of their work on the ammonites of the black bear ridge section this will undoubtedly provide much needed details on this important triassic jurassic boundary section however for now the information they provide

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

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

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

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

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

a 70 million year astronomical time scale for the deep sea bedded chert sequence inuyama japan implications for triassic jurassic geochronology abstract the astronomical time scale ats has provided high resolution geochronology however the early mesozoic ats is still under construction partly due to the lack of continuous pelagic sequences of the early mesozoic here we present ca 70 myr long ats constructed from the early mesozoic deep sea bedded chert sequence exposed in the inuyama area central japan the sedimentary rhythms of bedded chert display a full range of climatic precession related cycles 20 kyr cycle as a chert shale couplet and 100 405 2000 to 4000 and 10 000 kyr cycles as chert bed thickness variation the newly established ats inuyama ats is tuned by 405 kyr eccentricity cycle and is anchored at the end triassic radiolarian extinction level as 201 4 0 2 ma this inuyama ats gives ages consistent with the radiometric ages projected to the inuyama deep sea sequence using biostratigraphy and carbon isotope stratigraphy the inuyama ats provides the age constraints for the triassic and jurassic stage boundaries which support the long norian option of muttoni et al 2004 because the deep sea bedded chert sequence covers a long time interval before the cretaceous the ats for the bedded chert will serve as a template for the astrochronology of mesozoic and older ages

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

carbon isotope evidence for cam photosynthesis in the mesozoic crassulacean acid metabolism cam photosynthesis a flexible adaptation to water stress has not been shown to occur before the pleistocene despite suggestions that cam first evolved in the mesozoic or earlier here we report on multiple 7 positive organic carbon isotope excursions d 13 corg 20 i n late triassic and early jurassic c 200 ma sedimentary rocks from an arid terrestrial ecosystem in south africa these excursions are interpreted as evidence of the episodic domin ance of cam plants in response to heightened aridity in the heartland of gondwana and hint at climatic instability in a greenhouse world

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

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

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

discussion on sea level change and facies development across potential triassic jurassic boundary horizons sw britain tony hallam paul wignall write we welcome the paper by hesselbo et al 2004 for its thorough description and careful evaluation of the environmental significance of an important group of system boundary strata but beg to take issue on a number of key points 1 most importantly while we agree with the evidence of a regressive phase within the cotham member we maintain in marked contrast to their opinion that there was also a sharp regression followed by a rapid transgression at the junction of the langport member of the lilstock formation and blue lias it is pertinent before discussing the evidence in sw england further to take into account the broader european context hallam wignall 1999 with many relevant references cited therein the evidence is especially clear in germany where there was extensive shallowing in the latest rhaetian marked by progradation of sandstone over shales in northern frankonia bavaria fluvial sandstones infill channels incised into late rhaetian marine strata and are overlain by marine hettangian the sea level rise in the earliest hettangian planorbis zone was evidently rapid with the limit of marginal marine sandstones in the eastern part of southern germany being pushed back at the expense of fully marine shales to the maximum extent achieved during the whole hettangian stage both in the north and south of europe a similar pattern of successive sea level fall and rise can be inferred a clear end triassic regressive pulse can be recognized in the danish basin while both in southern sweden and nw poland the upper rhaetian is missing and there is an unconformity at the base of the jurassic in the northern calcaerous alps of austria widespread emergence at the end of the triassic is recognized with the creation of karst surfaces on emergent reef complexes while

elevated atmospheric co2 and the delayed biotic recovery from the end permian mass extinction excessive co2 in the earth ocean atmosphere system may have been a significant factor in causing the end permian mass extinction co2 injected into the atmosphere by the siberian traps has been postulated as a major factor leading to the end permian mass extinction by facilitating global warming widespread ocean stratification and development of anoxic euxinic and co2 rich deep waters a broad incursion of this toxic deep water into the surface ocean may have caused this mass extinction although previous studies of the role of excessive co2 have focused on these bottom up effects emanating from the deep ocean top down effects of increasing atmosphere co2 concentrations on ocean surface waters and biota have not previously been explored passive diffusion of atmospheric co2 into ocean surface waters decreases the ph and caco3 saturation state of seawater causing a physiological and biocalcification crisis for many marine invertebrates while both bottom up and top down mechanisms may have contributed to the relatively short term biotic devastation of the end permian mass extinction such a top down physiological and biocalcification crisis would have had long term effects and might have contributed to the protracted 5 to 6 million year long delay in biotic recovery following this mass extinction earth s modern marine biota may experience similar top down co2 stresses if anthropogenic input of atmosphere ocean co2 continues to rise

episodic photic zone euxinia in the northeastern panthalassic ocean during the end triassic extinction severe changes in ocean redox nutrient cycling and marine productivity accompanied most phanerozoic mass extinctions however evidence for marine photic zone euxinia pze as a globally important extinction mechanism for the end triassic extinction ete is currently lacking fossil molecular biomarker and nitrogen isotopic records from a sedimentary sequence in western canada provide the first conclusive evidence of pze and disrupted biogeochemistry in neritic waters of the panthalassic ocean during the end triassic increasing water column stratification and deoxygenation across the ete led to pze in the early jurassic paralleled by a perturbed nitrogen cycle and ecological turnovers among noncalcifying groups including eukaryotic algae and prokaryotic plankton if such conditions developed widely in the panthalassic ocean pze might have been a potent mechanism for the ete