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

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

mechano chemical interactions in sedimentary rocks in the context of co2 storage weak acid weak effects abstract due to the corrosive nature of dissolved co2 the potential short or long term alteration of rock properties represents a major issue in several sites where natural co2 circulation is observed as well as in reservoirs targeted for storage of anthropogenic co2 to date this has been primarily studied from a transport chemical perspective with laboratory evidence of microstructural modifications together with the consequences for flow properties compared to the transport chemical aspects the mechanical chemical aspects have been less investigated though it is to be expected that mechanical properties e g elastic properties failure parameters and time dependent mechanical behaviour could potentially be affected in a similar manner to hydraulic parameters yet since co2 is a weak acid the ph drop is expected to be moderate with a likely lower limit close to 4 0 the buffering of ph by calcite minerals present in most reservoirs targeted for storage may further limit the ph drop as well as confining it to a localized rock volume around the injection well this leads to the question of the magnitude and time spatial scales of chemically mediated mechanical processes during co2 sequestration the authors propose to address this issue by reviewing recent laboratory based studies restricted to sedimentary rocks namely reservoir rocks carbonate or sandstone intact or fractured caprocks and fault rocks key findings include the following 1 the short term impact on the elastic and inelastic behaviour of intact caprocks remains limited 2 shear strength weakening is likely to be respectively low and low to moderate for shale clay rich and anhydrite rich faults but without modifying slip stability in either case 3 the largest impact is located within carbonate reservoirs but with a broad range of reported responses depending on hydrodynamic conditions closed or open and on dissolution regime uniform or channelling and 4 creep experiments confirm that co2 induced dissolution may enhance long term compaction of carbonate reservoirs but the magnitude of acceleration varying from non significant to 50 times depends to a large extent on site specific conditions grain size ph temperature effective stress state etc which renders any direct extrapolation from laboratory to reservoir scale difficult finally some directions for future research studies are discussed

ultrasonic velocity and attenuation during co2 injection into water saturated porous sandstone measurements using difference seismic tomography we undertook laboratory based seismic measurements with dense sensor array at ultrasonic frequencies during the injection of co2 into a water saturated sandstone specimen the resulting high quality seismic data enabled detailed determination of the relative velocity and attenuation coefficient of the compressional wave using difference seismic tomography which directly inverses time lapse changes in rock properties from time lapse changes in observed data co2 migration and water displacement were clearly mapped using tomographic images of relative velocity and the attenuation coefficient the final and largely stabilised volume fraction of co2 in the pore space of the sample is about 30 40 on average the p velocity fell by 7 5 12 and 14 5 and the attenuation coefficient q 1 increased by factors of 3 3 2 7 and 3 7 as a result of the replacement of water with co2 during the injection of gaseous liquid and supercritical co2 respectively as a function of gas saturation both the velocity and attenuation data are in good agreement with results obtained using the white and dutta ode model for partial saturation indicating that viscous losses due to fluid diffusion are of significant importance for compressional waves travelling at ultrasonic frequencies in porous rocks

comments on the role of marine sediment burial as a repository for anthropogenic co2 in a recent letter to this journal smith and mackenzie 1991 emphasized the role of near shore environments such as bays and estuaries as being the principal locus for the enhanced burial of organic matter due to anthropogenically derived nutrient inputs to the oceans i commend them for this because of the relative lack of attention given to near shore environments by much of the biogeochemical and ocanographic community it is along continental margins and not in the pelagic ocean where most organic matter as well as most sediment is buried from an extensive review of the sediment literature i have shown berner 1982 that principal organic carbonburial on a global basis occurs in deltas and other continental margin environments a large proportion of the organic c may be of terrestrial origin although the average carbon content of the surficial portions of deltaic and continental shelf muds is only about 0 75 c the large mass of sediment carrying this small carbon percentage adds up to a very large burial rate the riverine flux of suspended sediment to the oceans has been estimated e g milliman and meade 1983 milliman and syvitski 1992 to be between 12 000 and 25 000 tg 102grams per year and most of this sediment is deposited at present on or near the continental shelves at 0 75 c this amounts to anannual carbon burial rate of 90 190 tg c burial rates in other environments such as offshore upwelling zones of high productivity or the vast pelagic realms of the oceans do not come close to matching these rates if one is to look for a locus for the burial of excess carbon from fossil fuel burning and deforestation the place to look is near the continents

facies changes across the triassic jurassic boundary in nevada usa a combination of data from litho and biofacies and gamma ray spectrometry indicates an upward marine shallowing in the late rhaetian succession of nevada followed by deepening in the early hettangian which conforms well to a regression transgression couplet of the sort associated with many marine mass extinctions this pattern can be discerned widely across the world most notably in north and south america and in europe suggesting the operation of eustatic control of sea level a global fall being followed by a rise

orbital forcing in a stochastic resonance model of the late pleistocene climatic variations applying a number of simplifying assumptions we have used a zero dimensional energy balance climate model ebm of the budyko sellers type to investigate the degree to which the climatic variability of the late pleistocene can be explained by the mechanism of stochastic resonance as a logical extension of an earlier version of this model we have included a more complete representation for the orbital forcings to show that a reasonably good agreement with the paleoclimatic record can be obtained this zerodimensional ebm is appealing because of its simplicity and its ability to reproduce some of the most striking qualitative features of the observed climatic variability with a very limited number of parameters several of which can be derived from either the observations or general circulation model gcm simulations of ice age conditions

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

time calibration of triassic jurassic microfloral turnover eastern north america abstract palynological data from the newark basin of the newark supergroup reveal a spike in the spore pollen ratio at the triassic jurassic boundary this spore spike is coincident with a 60 regional extinction of the palynoflora and approximately synchronous with terrestrial vertebrate extinctions orbitally controlled sedimentary cycles allow stratigraphic sections to be calibrated in time constraining the duration of the microfloral turnover to an interval of 21 ky the geologically brief palynofloral break is similar to cretaceous tertiary boundary fern spikes these data support a triassic jurassic boundary impact extinction scenario

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

effect of sub core scale heterogeneities on acoustic and electrical properties of a reservoir rock a co2 flooding experiment of brine saturated sandstone in a computed tomography scanner the effect of sub core scale heterogeneity on fluid distribution pattern and the electrical and acoustic properties of a typical reservoir rock was studied by performing drainage and imbibition flooding tests with co2 and brine in a laboratory moderately layered rothbach sandstone was used as a test specimen two core samples were drilled one perpendicular and the other parallel to the layering to allow injection of fluids along and normal to the bedding plane during the test 3d images of fluid distribution and saturation levels were mapped by an industrial x ray ct scanner together with simultaneous measurement of electrical resistivity ultrasonic velocities as well as amplitudes the results showed how the layering and the flooding direction influenced the fluid distribution pattern and the saturation level of the fluids for a given fluid saturation level the measured changes in the acoustic and electrical parameters were affected by both the fluid distribution pattern and the layering orientation relative to the measurement direction the p wave amplitude and the electrical resistivity were more sensitive to small changes in the fluid distribution patterns than the pwave velocity the change in amplitude was the most affected by the orientation of the layering and the resulting fluid distribution patterns in some instances the change due to the fluid distribution pattern was higher than the variation caused by the change in co2 saturation as a result the gassmann relation based on uniform or patchy saturation pattern was not suitable to predict the p wave velocity variation overall the results demonstrate the importance of core imaging to improve our understanding of fluid distribution patterns and the associated effects on measured rock physics properties

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

palaeogeographical significance of the triassic jurassic unconformity in the north iberian basin sierra del moncayo spain abstract field work carried out on the lower jurassic i e hettangian lower pliensbachian of the north iberian basin sierra del moncayo spain including the mapping of unconformities and sedimentary units as well as the facies analysis has allowed us to recognize two episodes in the sedimentary evolution of the basin a lower one hettangian in age includes sediments deposited during the period of extensional tectonic activity which involved the formation of half graben basins by normal listric faults sedimentary breccias and rudites located mainly at the edges of the half grabens are derived from the erosion of blocks uplifted during the triassic in the depocenter of the half grabens which show most subsidence these breccias pass into thick dolomitic and evaporitic successions deposited in sabkha environments under negligible marine influence the later episode sinemurian and lower pliensbachian in age consists of shallow marine carbonate units deposited in a low angle ramp setting evaporite accumulation took place during phases of relative lowstand of sea level i e lowstand systems tract when the basin was cut ooff from open marine conditions whereas the carbonate sediments mainly represent transgressive and highstand systems tracts in the iberian basin the lowstand episode during the hettangian was mainly induced by the breakup of the upper triassic ramp which favoured the isolation from open marine conditions of several subsident sub basins in addition it should be noted that the hettangian is considered as a lowstand sea level episode in some of the proposed global eustatic cycle charts so that a eustatic component may also be postulated for the isolation of the basin at this time the infilling of the hettangian half grabens left an even topography which was flooded during the sinemurian sea level rise leaving shallow carbonate deposits the results presented here give new information on the paleogeography of northeast iberia at the triassic jurassic boundary in the context of the opening of the western margin of the tethys

late triassic and early jurassic palaeogeographic evolution and depositional cycles of the western tethys iberian platform system eastern spain deposition of upper triassic and lower jurassic sediments on the iberian platform system took place in a post rift intraplate basin which formed part of the western tethys shelf nevertheless there is evidence for the tensional reactivation of a network of faults with associated magmatic activity early jurassic palaeogeographic reconstructions based on over 70 sections and 9 oil wells reveal the presence of a series of highs and lows depocentres two main highs referred to as the el maestrazgo high in the east and the la mancha high in the west where condensed sections were deposited were mainly controlled by syndepositional faults the main depocentres were situated between these two highs areas in a northwest trending belt in the central northern and southern areas despite partial fault control development of some early jurassic depocentres appears to be mainly controlled by thermal contraction of the lithosphere following triassic main rifting pulse the upper triassic lower jurassic succession of the iberian platform system was deposited during four transgressive and regressive cycles of 12 to 6 my duration the lowermost cycle lj 1 started in late norian and lasted until the sinemurian the second cycle lj 2 started in the sinemurian and ended in the pliensbachian davoei zone and can be subdivided into two minor cycles lj2 1 and lj2 2 the cycle lj 3 started with an extensive upper pliensbachian davoei zone transgression whereas the top of its regressive cycle is dated to the toarcian variablilis zone within cycle lj 3 three cycles can be distinguished maximum deepening was reached during the bifrons zone and active volcanism took place along the teruel and caudiel faults the transgressive phase of the cycle lj 4 started in the thouarsense zone and extended up to the insigne zone its regressive phase developed during the upper toarcian pseudoradiosa and aalensis zones and part of the aalenian opalinum and murchisonae zones this cycle can be subdivided in two minor cycles with their transgressive peaks occurring during the insigne zone and the aalensis zone respectively palaeogeographically this corresponds with the expansion of the marginal carbonate platforms over hemipelagic deposits the top of the cycle corresponds to a major unconformity with regional emersion during the aalenian murchisonae zone

fluids and frequency dependent seismic velocity of rocks summary compressional and shear velocities of rocks are dependent on frequency and this dispersion may be significant even within the seismic band the amount and position of dispersion will be largely a function of fluid properties distribution and motion in the pores velocities are thus directly coupled to rock permeability and pore compliance propagation often will be in the high frequency regime even at a few tens of hertz static or low frequency models such as gasmann will fail under such conditions in addition biot theory will not correctly model wave propagation in many cases

transgressive regressive cycles and jurassic palaeogeography of northeast iberia abstract a correlation and sequence stratigraphy study of jurassic successions has been carried out in the main sedimentary basins of northeast iberia i e asturias basque cantabrian and iberian basins based on the identification of transgressive regressive cycles the development and palaeogeographic evolution of the epicontinental carbonate platforms of northeast iberia were largely controlled by major tectonic activity at three main intervals at the beginning of the jurassic in the lower middle jurassic transition and during the uppermost jurassic respectively during early jurassic times northeast iberia was the site of a single and large carbonate ramp opened to the north this carbonate ramp suffered a progressive drowning evolving from an inner to hemipelagic ramp systems with the local development of suboxic environments in the deepest areas located to the north during the middle jurassic different open carbonate platforms were formed including the development of swells in intermediate areas during the upper jurassic the outer ramp areas were progressively moving to the east iberian basin and the ammonite faunas showing a markedly tethyan affinity thereafter three first order t r cycles bounded by major discontinuities associated with significant time gaps are identified they extend respectively from the latest rhaetian to the early aalenian from the middle aalenian to the early oxfordian and from the early oxfordian to the late berriasian major transgressive peaks occurred at the middle toarcian bifrons zone at the late bajocian upper niortense and garantiana zones and at the mid kimmeridgian divisum zone each of the first order cycles includes four second order t r cycles cycles 1 1 1 4 are identified in the northern basins cycles 2 1 2 4 display some differences in age of transgressive peaks from one basin to another cycles 3 1 3 4 are mainly identified in the iberian basin the correlation with other separated boreal and thethysian basins demonstrates that the number and age of t r cycles varies from one basin to another and are mainly controlled by the local or regional tectonic development the transgressive peaks may reflect episodes of eustatic rise during the jurassic however their different age from one basin to another is explained by different subsidence evolution

an overview of laboratory apparatuses to measure seismic attenuation in reservoir rocks intrinsic wave attenuation at seismic frequencies is strongly dependent on rock permeability fluid properties and saturation however in order to use attenuation as an attribute to extract information on rock fluid properties from seismic data experimental studies on attenuation are necessary for a better understanding of physical mechanisms that are dominant at those frequencies an appropriate laboratory methodology to measure attenuation at seismic frequencies is the forced oscillation method but technical challenges kept this technique from being widely used there is a need for the standardization of devices employing this method and a comparison of existing setups is a step towards it here we summarize the apparatuses based on the forced oscillation method that were built in the last 30 years and were used to measure frequency dependent attenuation in fluid saturated and or dry reservoir rocks under small strains 10 8 10 5 we list and discuss important technical aspects to be taken into account when working with these devices or in the course of designing a new one we also present a summary of the attenuation measurements in reservoir rock samples performed with these apparatuses so far

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

characterisation and multifaceted anisotropy assessment of corvio sandstone for geological co2 storage studies we present a comprehensive characterisation of the physical mineralogical geomechanical geophysical and hydrodynamic properties of corvio sandstone this information together with a detailed assessment of anisotropy is needed to establish corvio sandstone as a useful laboratory rock testing standard for well constrained studies of thermo hydro mechanical chemical coupled phenomena associated with co2 storage practices and for geological reservoir studies in general more than 200 core plugs of corvio sandstone 38 1 and 50 mm diameters 2 1 length to diameter ratio were used in this characterisation study with a rock porosity of 21 7 1 2 dry density 2036 32 kg m 3 and unconfined compressive and tensile strengths of 41 3 28 and 2 3 0 14 mpa respectively geomechanical tests show that the rock behaves elastically between 10 and 18 mpa under unconfined conditions with associated young s modulus and poisson s ratio of 11 8 2 8 gpa and 0 34 0 01 gpa respectively permeability abruptly decreases with confining pressure up to 10 mpa and then stabilises at 1 md ultrasonic p and s wave velocities vary from about 2 8 3 8 km s 1 and 1 5 2 4 km s 1 respectively over confining and differential pressures between 0 1 and 35 mpa allowing derivation of associated dynamic elastic moduli anisotropy was investigated using oriented core plugs for electrical resistivity elastic wave velocity and attenuation permeability and tracer injection tests corvio sandstone shows weak transverse isotropy symmetry axis normal to bedding of 10 for velocity and 20 for attenuation

laboratory measurements of the effect of fluid saturation on elastic properties of carbonates at seismic frequencies abstract a significant portion of the world s hydrocarbon reserves are found in carbonate reservoirs yet analysis of the petrophysical properties of these reservoirs is associated with a number of challenges some of these challenges stem from physical and chemical interactions between the carbonate rock matrix and pore fluids which can affect elastic properties of the rock hence the study of the pore fluid effects on the elastic properties of carbonates is important for understanding a change of the field performance properties of carbonate reservoir caused by fluid movements during hydrocarbon extraction in producing fields in this laboratory study we investigate the applicability of gassmann s model for predictions of the elastic moduli of water and hydrocarbon saturated savonnieres limestone and the influence of partial water saturation on elastic and anelastic properties of the rock we present the results of two sets of laboratory experiments on the savonnieres oolitic limestone where we i evaluate the effect of full water and n decane saturation on elastic moduli and attenuation at seismic 0 1 hz 120 hz and ultrasonic 0 5 mhz frequencies and ii quantify the dependence of elastic moduli and extensional attenuation on water saturation at two seismic frequencies of 1 hz and 10 hz we demonstrate that the change in the bulk modulus of limestone fully saturated either with n decane or water is in agreement with gassmann s fluid substitution theory whereas the shear modulus is noticeably reduced the measurements with partial saturation show that the bulk modulus decreases with increasing water saturation to a lesser extent than the young s and shear moduli our results show that extensional attenuation in the samples with closed boundaries is insignificant under dry and fully saturated conditions but is influenced greatly by the liquid content when saturation is between 0 and 20 or 95 and 100

climate of the supercontinent pangea numerous climate models predict that the geography of the supercontinent pangea was conducive to the establishment of a megamonsoonal circulation in general geologic evidence supports the hypothesis of a megamonsoon that reached maximum strength in the triassic pangea in the late carboniferous had widespread peat formation in what is now central and eastern north america and europe and relatively dry conditions on the colorado plateau the equatorial region of the continent became drier through the end of the carboniferous by the permian the equatorial region of pangea was dry and indicators of aridity and rainfall seasonality became more widespread wind directions from colorado plateau eolian sandstones are consistent with an increasing influence of monsoonal circulation at this time in the triassic climate in the colorado plateau region became relatively wet though still seasonal and the few eolian sandstones indicate a major shift in wind direction at that time in addition sedimentation

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

an experimental study of acoustic responses on the injection of supercritical co2 into sandstones from the otway basin quantitative knowledge of the acoustic response of rock from an injection site on supercritical co2 scco2 saturation is crucial for understanding the feasibility of time lapse seismic monitoring of co2 plume migration a suite of shaley sandstones from the injection interval of the crc 2 well otway basin australia is tested to reveal the effects of supercritical co2 injection on acoustic responses co2 is first injected into dry samples flushed out with brine and then injected again into brine saturated samples such a suite of experiments allows us to obtain acoustic velocities of the samples for a wide range of co2 brine saturations from 0 to 100 on injection of scco2 into brine saturated samples the rocks exhibit a decrease of compressional velocities by about 7 with the increase of co2 saturation from 0 to a maximum of about 50 anisotropy of the shaley sandstones from the otway basin must be taken into account as the difference in the velocities normal and parallel to bedding is comparable with the perturbation due to co2 injection and the samples of different orientations exhibit transition from gassmann hill to gassmann wood bound at different scco2 saturations changes of the dry samples before and after the co2 injection if any are not traceable by acoustic methods

are changes in time lapse seismic data due to fluid substitution or rock dissolution a co2 sequestration feasibility study at the pohokura field new zealand seismic methods are commonly used to monitor the subsurface when carbon dioxide co2 is injected into a reservoir besides fluid saturation and pressure changes co2 water mixtures may cause rock alteration in this petrophysical study we compare the elastic property changes due to fluid replacement and those due to mineral dissolution for carbonate cemented sandstones at the pohokura field new zealand we quantify the effects of fluid substitution from fully brine to fully supercritical co2 saturation and carbonate cement dissolution on the seismic signatures of the reservoir rocks by combining laboratory results petrographic analyses and geophysical well log data we conclude that elastic property changes due to mineral dissolution are significantly greater than those due to fluid substitution alone the northern part of the pohokura field has coarser grained sandstones which experience the largest changes in wave speeds our hypothesis is that these changes result from carbonate cement dissolution in the presence of co2 water sandstone reactions if time lapse seismic data were to be acquired in this field the northern area could show p wave velocity reductions of up to 20 and a 131 7 increase in seismic amplitude from a brine saturated rock to an altered fully co2 saturated rock in comparison the southern part of the field where sandstones are mostly fine grained we expect a p wave velocity decrease of 6 if such dissolution process took place finally we show that the elastic properties of the reservoir rocks can be described with the constant cement model the model is used to predict that the dissolution process reduces the volume of grain contact cement on average from 2 5 to 1 75 of the total rock mineral volume our analysis suggests that changes to the rock frame which includes carbonate minerals cannot be ignored for a co2 injection scenario

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

pore throat sizes in sandstones tight sandstones and shales pore throat sizes in siliciclastic rocks form a continuum from the submillimeter to the nanometer scale that continuum is documented in this article using previously published data on the pore and pore throat sizes of conventional reservoir rocks tight gas sandstones and shales for measures of central tendency mean mode median pore throatsizes diameters are generally greater than2 mm in conventionalreservoir rocks range from about 2 to 0 03 mm in tight gas sandstones and rangefrom0 1to0 005 mminshales hydrocarbonmolecules asphaltenes ring structures paraffins and methane form another continuum ranging from 100 a 0 01 mm for asphaltenes to 3 8 a 0 00038 mm for methane the pore throat size continuum provides a useful perspective for considering 1 the emplacement of petroleum in consolidated siliciclastics and 2 fluid flow through fine grained source rocks now being exploited as reservoirs

40ar 39ar dating and geochemistry of tholeiitic magmatism related to the early opening of the central atlantic rift tholeiitic effusive and intrusive magmatism from iberia morocco algeria and mali related to the early opening of the central atlantic rift was dated by the 40ar 39ar step heating method four plateau ages ranging from 203 7 2 7 to 197 1 1 8 ma were obtained on plagioclase from dykes from the taoudenni area mali and two lava flows from morocco the messejana dyke iberia which previously yielded discrepant conventional kar dates did not furnish any 40ar 39ar plateau dates however there is a clear inverse relationship between apparent age and k ca ratio for gas fractions from a plagioclase separate proportional to the alteration degree which combined with dates obtained on amphibole biotite and pyroxene allows us to determine an age of around 200 ma for this body these data and those obtained on the foum zguid morocco and the ksi ksou algeria dykes give evidence of a brief magmatic event between 206 and 195 ma ago which affected a large area ca 2500 km long trace element modelling shows that most of these formations originated from a homogeneous enriched source material such a brief magmatic episode related to the opening of a continental rift is in agreement with findings in other magmatic provinces e g the deccan traps and the red sea rift precisely dated by the 40ar 39ar method as well

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

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

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

new early jurassic tetrapod assemblages constrain triassic jurassic tetrapod extinction event the discovery of the first definitively correlated earliest jurassic 200 million years before present tetrapod assemblage fundy basin newark supergroup nova scotia allows reevaluation of the duration of the triassic jurassic tetrapod extinction event present are tritheledont and mammal like reptiles prosauropod theropod and ornithischian dinosaurs protosuchian and sphenosuchian crocodylomorphs sphenodontids and hybodont semionotid and palaeonisciform fishes all of the families are known from late triassic and jurassic strata from elsewhere however pollen and spore radiometric and geochemical correlation indicate an early hettangian age for these assemblages because all typical triassic forms are absent from these assemblages most triassic jurassic tetrapod extinctions occurred before this time and without the introduction of new families as was previously suggested by studies of marine invertebrates this pattern is consistent with a global extinction event at the triassic jurassic boundary the manicouagan impact structure of quebec provides dates broadly compatible with the triassic jurassic boundary and following the impact theory of mass extinctions may be implicated in the cause

measurements of the elastic and anelastic properties of sandstone flooded with supercritical co2 the aim of this study was to investigate the effects of supercritical co2 scco2 injection on the elastic and anelastic properties of sandstone at seismic and ultrasonic frequencies we present the results of the low frequency and ultrasonic experiments conducted on water saturated sandstone donnybrook western australia flooded with scco2 the sandstone was cut in the direction perpendicular to a formation bedding plane and tested in a hoek triaxial pressure cell during the experiments with scco2 the low frequency and ultrasonic systems and the pump dispensing scco2 were held at a temperature of 42 c the elastic parameters obtained for the sandstone with scco2 at seismic 0 1 hz 100 hz and ultrasonic 0 5 mhz frequencies are very close to those for the dry rock the extensional attenuation was also measured at seismic frequencies for the dry water saturated and scco2 injected sandstones the applicability of gassmann s fluid substitution theory to obtained results was also tested during the experiments

a new seismic wave attenuation module to experimentally measure low frequency attenuation in extensional mode abstract a seismic wave attenuation module is developed to experimentally measure the attenuation in extensional mode qe 1 and the young s modulus of copper jacketed 60 mm long and 25 4 mm in diameter samples in a gas medium paterson rig the new module is suitable for natural rock samples and was tested under confining pressure up to 50 mpa and room temperature the module is designed to operate at a strain 10 6 for which rocks behave linearly to calculate attenuation both the applied force and the bulk shortening of the sample are measured employing linear variable differential transformers this technique allows measuring samples with a high degree of heterogeneity attenuation at low seismic frequencies 10 2 102 hz is obtained for rocks at dry and various saturation conditions we present a series of measurements on berea sandstone in a room dry condition and saturated with different fluids water and glycerine solutions with viscosities of 10 cp and 22 cp respectively at a confining pressure of 10 mpa and with a pore pressure of 1 mpa the accuracy of the attenuation data expressed as a phase shift is 0 0019 rad

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

volcanism impact and mass extinctions incredible or credible coincidences massive continental volcanism and or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years the end permian end cretaceous and end triassic extinctions however reevaluation of the frequency of bolide impacts and plume related flood basalt provinces indicates that both types of event occur much more frequently than mass extinctions and so in isolation may not be responsible for the largest extinctions furthermore the kill mechanisms associated with either flood basalts or impacts do not appear to be sufficiently powerful to cause worldwide collapse of ecosystems leading to the largest mass extinctions contemporaneous flood basalts and bolide impact may be prerequisites for the largest mass extinctions we present a statistical analysis of the probability of coincidence between volcanism and impact and show that three random coincidences of these events in the last 300 m y are likely no causal relationship between impact and volcanism is necessary the lesser mass extinctions on the other hand may not require juxtaposition of two such catastrophic events such coincidences occurring on more than three occasions during the last 300 m y become increasingly unlikely d 2004 elsevier b v all rights reserved

triassic environments climates and reptile evolution abstract a consideration of all the available data on triassic vertebrate faunas and their stratigraphic location reveals a relatively sudden extinction event among the last of the mammal like reptiles and the herbivorous rhynchosaurs in the norian of the upper triassic this event was apparently quickly followed by the radiation of the dinosaurs also in the norian this conclusion suggests that competition was not the main factor in the initial success of the dinosaurs but opportunistic radiation following the extinction of major reptile groups a global review of triassic sedimentary facies shows that there were climatic and floral changes towards the end of the triassic it is envisaged that increasing aridity in the later triassic resulting from plate motions and particularly affecting gondwanaland and southwestern laurasia brought about floral changes and then the reptile extinctions with the rapid evolution of new floras of conifers and bennettitaleans the dinosaurs came to dominate all terrestrial faunas within the space of only a few million years

pangaean climates megamonsoons of the megacontinent the climate for a highly idealized geographic representation of the megacontinent of pangaea corresponding to the period 250 200 m y ago is explored using a low resolution atmospheric general circulation model that is coupled to a static mixed layer ocean of constant depth with a provision for sea ice formation and decay soil moisture is included as a predicted variable on the continent because there are large uncertainties about key factors that might influence the pangaean climate sensitivity experiments are used to examine the climate for two different mean elevations 0 and 1000 m two different snowcover prescriptions and two different levels of implied greenhouse heating and solar luminosity modern co2 concentration and modern solar luminosity fivefold increase in modern co2 concentration and a 1 decrease in modern solar luminosity in all of the experiments the large bipolar land masses of laurasia and gondwanaland joined near the equator in the west and separated by the tethys sea in the east exhibit extreme continentality with hot summers cold winters and large scale summer and winter monsoon circulations year round or seasonal aridity is simulated for all but the eastern coastal regions the tropical western coast and the regions poleward of 40 latitude the simulated climate of the idealized pangaean continent has many features that correspond qualitatively with geologic evidence for tropical warmth and aridity in the late permian and triassic however the model results serve mainly to indicate the importance of various climate forming factors geography topography heating detailed comparisons will require new experiments with better models and more accurate geologic boundary conditions

laboratory seismic monitoring of supercritical co2 flooding in sandstone cores using the split hopkinson resonant bar technique with concurrent x ray computed tomography imaging abstract accurate estimation of co2 saturation in a saline aquifer is essential for the monitoring of supercritical co2 injected for geological sequestration because of strong contrasts in density and elastic properties between brine and co2 at reservoir conditions seismic methods are among the most commonly employed techniques for this purpose however the relationship between seismic p wave velocity and co2 saturation is not unique because the velocity depends on both wave frequency and the co2 distribution in rock in the laboratory we conducted measurements of seismic properties of sandstones during supercritical co2 injection seismic responses of small sandstone cores were measured at frequencies near 1 khz using a modified resonant bar technique split hopkinson resonant bar method concurrently saturation and distribution of supercritical co2 in the rock cores were determined via x ray ct scans changes in the determined velocities generally agreed with the gassmann model however both the velocity and attenuation of the extension wave young s modulus or bar wave for the same co2 saturation exhibited differences between the co2 injection test and the subsequent brine re injection test which was consistent with the differences in the co2 distribution within the cores also a comparison to ultrasonic velocity measurements on a bedded reservoir rock sample revealed that both compressional and shear velocities and moduli were strongly dispersive when the rock was saturated with brine further large decreases in the velocities of saturated samples indicated strong sensitivity of the rock s frame stiffness to pore fluid

seismic attenuation in partially saturated berea sandstone submitted to a range of confining pressures using the forced oscillation method we measure the extensional mode attenuation and young s modulus of a berea sandstone sample at seismic frequencies 0 5 50 hz for varying levels of water saturation 0 100 and confining pressures 2 25 mpa attenuation is negligible for dry conditions and saturation levels 80 for saturation levels between 91 and 100 attenuation is significant and frequency dependent in the form of distinct bell shaped curves having their maxima between 1 and 20 hz increasing saturation causes an increase of the overall attenuation magnitude and a shift of its peak to lower frequencies on the other hand increasing the confining pressure causes a reduction in the attenuation magnitude and a shift of its peak to higher frequencies for saturation levels above 98 the fluid pressure increases with increasing confining pressure when the fluid pressure is high enough to ensure full water saturation of the sample attenuation becomes negligible a second series of comparable experiments reproduces these results satisfactorily based on a qualitative analysis of the data the frequency dependent attenuation meets the theoretical predictions of mesoscopic wave induced fluid flow wiff in response to a heterogeneous water distribution in the pore space so called patchy saturation these results show that mesoscopic wiff can be an important source of seismic attenuation at reservoir conditions

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

chemical mechanical coupling observed for depleted oil reservoirs subjected to long term co2 exposure a case study of the werkendam natural co2 analogue field geological storage of co2 is one of the most promising technologies to rapidly reduce anthropogenic emissions of carbon dioxide in order to ensure storage integrity it is important to understand the effect of long term co2 brine rock interactions on the mechanical behaviour of a storage complex as most of these reactions are too slow to reproduce on laboratory timescales we studied a natural co2 analogue reservoir the rot fringe sandstone werkendam field the netherlands 125 135 ma of co2 exposure and its unreacted counterpart we focused on co2 induced mineralogical and porosity permeability changes and their effect on mechanical behaviour of both intact rock and simulated fault gouge overall co2 exposure did not lead to drastic mineralogical changes the co2 exposed material shows a stronger dependence of permeability on porosity which is attributed to differences in diagenesis closed system diagenesis and hydrocarbon emplacement taking place before co2 charging the limited extent of reaction was in part the result of bitumen coatings protecting specific mineral phases from reaction in local mm sized zones displaying significant anhydrite cement dissolution enhanced porosity was observed for most of the reservoir the long term mechanical behaviour after co2 exposure could be described by the behaviour of the unreacted sandstone while these more porous zones had a lower rock strength in addition co2 exposure did not affect the fault friction behaviour and slip is expected to result in stable sliding simple stress path calculations predict that reservoir failure due to depletion and injection is unlikely even for the porous zones nor will fault reactivation occur for realistic injection scenarios

modeling attenuation in reservoir and nonreservoir rock elastic waves attenuate in earth the number of wavelengths over which the amplitude decreases by a factor of ten is 0 733 q where q is the quality factor for vp 3 km s and frequency f 30 hz the wavelength vp f 0 1 km then for q 10 the amplitude decreases by a factor of 10 as the wave travels 0 733 q 0 733 km

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

enhanced deformation of limestone and sandstone in the presence of high fluids 1 geological repositories subject to the injection of large amounts of anthropogenic carbon dioxide will undergo chemical and mechanical instabilities for which there are currently little experimental data this study reports on experiments where low and high 8 mpa aqueous fluids were injected into natural rock samples the experiments were performed in flow through triaxial cells where the vertical and confining stresses temperature and pressure and composition of the fluid were separately controlled and monitored the axial vertical strains of two limestones and one sandstone were continuously measured during separate experiments for several months with a strain rate resolution of 10 11 s 1 fluids exiting the triaxial cells were continuously collected and their compositions analyzed the high fluids induced an increase in strain rates of the limestones by up to a factor of 5 compared to the low fluids injection of high fluids into the sandstone resulted in deformation rates one order of magnitude smaller than the limestones the creep accelerating effect of high fluids with respect to the limestones was mainly due to the acidification of the injected fluids resulting in a significant increase in solubility and reaction kinetics of calcite compared to the limestones the much weaker response of the sandstone was due to the much lower solubility and reactivity of quartz in high fluids in general all samples showed a positive correlation between fluid flow rate and strain rate x ray tomography results revealed significant increases in porosity at the inlet portion of each core the porosity increases were dependent on the original lithological structure and composition the overall deformation of the samples is interpreted in terms of simultaneous dissolution reactions in pore spaces and intergranular pressure solution creep