carbon isotopes stratigraphy and environmental change the middle upper cambrian positive excursion spice in port au port group western newfoundland canada in many basins upper cambrian carbonate successions display intervals with a positive carbon isotope excursion cie of up to 5 in north america this marks the boundary between the sauk ii iii super sequences a steptoean positive carbon isotope excursion spice locality previously identified in the port au port peninsula western newfoundland has been revisited and an additional potential spice locality found in both locations a cie is found to be associated with a prominent bioherm and sandstone layer within a sequence of carbonate rocks at march point columnar stromatolites occur whereas at felix cove thrombolites can be seen in the latter the sandstone immediately overlies the thrombolites coincident with the cie whereas at march point a dolomitized grainstone occurs above the stromatolites the sandstone at this locality post dates the cie although lower than the spice in some localities a positive cie is present in both sections march point 1 1 and felix cove 1 8 additional

facies and architectural element analysis of a meandering fluvial succession the permian warchha sandstone salt range pakistan abstract the 30 to 155 m thick early permian artinskian warchha sandstone of the salt range pakistan is a conglomerate sandstone and claystone succession within which seven lithofacies types gt st sp sr sh fl and fm occur in a predictable order as repeated fining upward cycles common sedimentary structures in the conglomerates and sandstones include planar and trough cross bedding planar lamination soft sediment deformed bedding compound cosets of strata with low angle inclined bounding surfaces and lags of imbricated pebbles structures in the finer grained facies include desiccation cracks raindrop imprints caliche nodules and bioturbation groups of associated facies are arranged into nine distinct architectural elements channels gravel bars sandy bedforms downstream and laterally accreting barforms sand sheets crevasse splays levees floodplain units and shallow lakes which is consistent with a fluvial origin for the succession the types of architectural elements present and their relationship to each other demonstrate that the warchha sandstone preserves a record of a meandering river system that drained the northern margin of gondwanaland the dominance of fine grained floodplain facies over gravel grade channel base facies and the widespread occurrence of large scale lateral accretion elements supports the interpretation of a high sinuosity meandering fluvial system in which channel bodies accumulated via the lateral accretion of point bars but in which the active channels covered only a small part of a broad floodplain at any time instant although the regional and temporal distribution of these deposits is complex in broad terms the lower part is dominated by stacked multistorey channel bodies whereas single storey channel elements isolated in abundant fine grained floodplain deposits dominate the middle and upper parts of the formation

cretaceous tertiary and permian triassic boundary events compared abstract the cretaceous tertiary k t and permian triassic p tr events differ in many more aspects than they are similar this alone makes it unlikely that they are parts of a common web of periodic mass extinction events mee unlike the k t most mee have no ir anomalies and where in the comparatively complete section of the p tr at gartnerkofel austria weak ir concentrations are found their ratios to siderophile elements co ni cr are far less than chondritic in contrast ratios to chalcophile elements as sb zn never approach chondritic even in k t peaks and locality differences suggest local depositional processes that may also affect the siderophiles profiles of isotopes 13ccarb 87 sr 86 sr and possibly 18ocarb across these boundaries also differ radically whereas the k t profile of surface ocean 18ocarb has been shown to be mainly a drop in primary productivity the p tr profile is interpreted at least in part to be a consequence of a large and accelerating oxidation of previously stored corg with greatly differing consequences for climate these and other differences of proximate forcings for these two mee lead us to a hypothesis that such external exigencies were ever intermittently and severally with us but were effective only when the biotic web had already internally unravelled in some crucially strained patch gaia became antigaia

the guadalupian permian kamura event in european tethys article i nfo in order to document paleoenvironmental conditions of the equatorial western paleo tethys during the late middle permian prior to the end guadalupian mass extinction chemostratigraphic analysis using stable carbon isotopes was conducted for the guadalupian rocks at brusane in the velebit mtn central croatia by analyzing 72 carbonate samples of the capitanian upper guadalupian velebit formation we found an interval with unusually high 13 ccarb values 4 to 6 in the ca 150 m thick yabeina fusuline zone the present find clarifies that the primary productivity and burial rate into the sediments were considerably high during the capitanian in westernmost paleo tethys this chemostratigraphic signal is properly correlated with the kamura event detected in a mid panthalassan paleo atoll limestone in japan the present results identify the capitanian kamura event for the first time in european paleo tethys on the opposite side of the globe from the mid panthalassan paleo seamount and prove the global context of the event as well as its utility in chemostratigraphic correlation in order to enhance bioproductivity on a global scale the increase in nutrient supply is inevitable in addition to riverine run off from pangea active oceanic circulation in particular upwelling of deep sea water enriched in nutrients was likely vital both in panthalassa and paleo tethys the extinction of some guadalupian fauna in particular photosymbiotic community large tested fusulines large bivalves rugose corals was likely related to a temporary cooling coupled with eutrophication in low latitude shallow marine environments of paleo tethys and panthalassa

identification of tsunami deposits considering the tsunami waveform an example of subaqueous tsunami deposits in holocene shallow bay on southern boso peninsula central japan abstract this study proposes a tsunami depositional model based on observations of emerged holocene tsunami deposits in outcrops located in eastern japan the model is also applicable to the identification of other deposits such as those laid down by storms the tsunami deposits described were formed in a small bay of 10 20 m water depth and are mainly composed of sand and gravel they show various sedimentary structures including hummocky cross stratification hcs and inverse and normal grading although individually the sedimentary structures are similar to those commonly found in storm deposits the combination of vertical stacking in the tsunami deposits makes a unique pattern this vertical stacking of internal structures is due to the waveform of the source tsunamis reflecting 1 extremely long wavelengths and wave period and 2 temporal changes of wave sizes from the beginning to end of the tsunamis the tsunami deposits display many sub layers with scoured and graded structures each sub layer especially in sandy facies is characterized by hcs and inverse and normal grading that are the result of deposition from prolonged high energy sediment flows the vertical stack of sub layers shows incremental deposition from the repeated sediment flows mud drapes cover the sub layers and indicate the existence of flow velocity stagnant stages between each sediment flow current reversals within the sub layers indicate the repeated occurrence of the up and return flows the tsunami deposits are vertically divided into four depositional units tna to tnd in ascending order reflecting the temporal change of wave sizes in the tsunami wave trains unit tna is relatively fine grained and indicative of small tsunami waves during the early stage of the tsunami unit tnb is a protruding coarse grained and thickest stratified division and is the result of a relatively large wave group during the middle stage of the tsunami unit tnc is a fine alternation of thin sand sheets and mud drapes deposited from waning waves during the later stage of the tsunami unit tnd is deposited during the final stage of the tsunami and is composed mainly of suspension fallout cyclic build up of these sub layers and depositional units cannot be explained by storm waves with short wave periods of several to ten seconds common in small bays

the end permian mass extinction a rapid volcanic co2 and ch4 climatic catastrophe abstract the end of the permian was a time of crisis that culminated in the earth s greatest mass extinction there is much speculation as to the cause for this catastrophe here we provide a full suite of high resolution and coeval geochemical results trace and rare earth elements carbon oxygen strontium and clumped isotopes reflecting ambient seawater chemistry and water quality parameters leading up to the end permian crisis preserved brachiopod low mg calcite based seawater chemistry supplemented by data from various localities documents a sequence of interrelated primary events such as coeval flows of siberian trap continental flood basalts and emission of carbon dioxide leading to warm and extreme greenhouse conditions with sea surface temperatures sst of 36 c for the late permian although anoxia has been advanced as a cause for the mass extinction most biotic and geochemical evidence suggest that it was briefly relevant during the early phase of the event and only in areas of upwelling but not a general cause instead we suggest that renewed and increased end permian siberian trap volcanic activity about 2000 years prior to the extinction event released massive amounts of carbon dioxide and coupled with thermogenic methane emissions triggered extreme global warming and increased continental weathering eventually these rapidly discharged greenhouse gas emissions less than 1000 years before the event ushered in a global hothouse period leading to extreme tropical ssts of 39 c and higher based on these sea surface temperatures atmospheric co 2 concentrations were about 1400 ppmv and 3000 ppmv for the late and end permian respectively leading up to the mass extinction there was a brief interruption of the global warming trend when sst dropped concurrent with a slight but significant recovery in biodiversity in the western tethys it is possible that emission of volcanic sulfate aerosols resulted in brief cooling just after the onset of intensified warming during the end of the permian after aerosol deposition global warming resumed and the biotic decline proceeded and was accompanied by suboxia in places of the surface ocean which culminated in the greatest mass extinction in earth history

geochemistry of central tethyan upper permian and lower triassic strata abadeh region iran nearly 2 km of upper permian to lower triassic limestones are exposed in the hambast mountain abadeh region iran lime mud matrix and most bioclasts of permian age are recrystallized into large calcite crystals and contain 600 4000 ppm sr suggesting a probable aragonite precursor low bulk rock 18 o values 7 to 10 pdb and recrystallized textures are also indicative of diagenetic alteration within the murghabian and abadehian two gradual upward increases in carbonate and organic matter 13 c compositions each roughly 3 pdb in magnitude are documented both are attributed to increased organic productivity and sequestration of organic matter in sediments within the julfian and across the permian triassic p t boundary two sharp upward decreases in carbonate and organic matter 13 c values each 4 pdb in magnitude are observed both are best explained by mixing of a deep water mass having low 13 c values and a shallow water mass having high 13 c compositions early triassic 13 c values initially low 1 pdb increase to 3 pdb within 100 m above the p t boundary variations in 13 c compositions of carbonate and organic matter and changes in 13 c 13 ccar 13 corg indicate that early triassic 13 c values were controlled by productivity cycles

thickness and grain size distribution of the 2004 indian ocean tsunami deposits in periya kalapuwa lagoon eastern sri lanka abstract in this paper we describe the sedimentary characteristics of the 2004 indian ocean tsunami deposits in and around periya kalapuwa lagoon sri lanka periya kalapuwa is a coastal lagoon of about 13 km 2 area and has an average depth of about 1 m it is separated from the indian ocean by coastal barrier sand dunes of up to 9 m elevation through which two inlet channels open the lagoon to the ocean this region was hit by three waves during the 2004 indian ocean tsunami the second wave was largest 4 6 m and entered the lagoon not only via the two inlet channels but also by flowing over the sand dunes erosive scars were found on the sand dunes adjacent to the two inlets twenty seven core samples along with trenching and hand auger data show that the tsunami deposits are 9 cm thick on average up to 35 cm in the lagoon and up to 66 cm on the shore and are composed mainly of medium sand mean grain size 1 06 with low mud content 0 61 wt which is similar to the composition of sand from near the erosive scars in the sand dunes mean grain size 0 94 but different from the lagoon deposits mean grain size 1 68 mud content 4 7 wt the distribution of the tsunami deposits was limited to within about 1 km from each inlet the tsunami deposits become thinner and finer grained with increasing distance from the inlets most of the tsunami deposits are massive but some show sedimentary structures single or multiple graded bedding structures parallel laminations defined by layers of heavy minerals and muddy laminations our observations and analyses suggest that the tsunami deposits were formed mainly from sand eroded from sand dunes near the two inlets we estimated the total volume of tsunami sediments to be 83 000 m 3 by assuming that the sediments of the tsunami deposits were supplied only by erosion of sand dunes from near the two inlets this is equivalent to erosion of 83 m 3 of sand per meter of sand dune traversed by the tsunami wave

patterns of early post depositional and burial cementation in distal shallow marine sandstones upper cretaceous kenilworth member book cliffs utah usa there is a limited understanding of the spatial linkage between cementation processes in shoreface coastal plain successions and those operating in distal offshore successions to address this an integrated sedimentological sequence stratigraphic and diagenetic study was undertaken on a distal shallow marine succession the upper cretaceous kenilworth member book cliffs utah usa laterally extensive carbonate cement is the most volumetrically significant diagenetic feature it constitutes up to 55 vol of the distal lower shoreface sandstone and sandy siltstone units beneath major flooding surfaces during rising relative sea level major flooding events resulted in low sedimentation which extended residence time of sediments in early diagenetic zones and promoted enhanced cementation beneath these boundaries carbonate for early calcite cements was probably derived from sulphate reduction marine water and oxidation of organic matter stable isotopic composition of later ankerite 18o 11 9 to 6 0 vdpb 13c 4 5 to 0 3 vdpb suggests precipitation during progressive burial c 1 7 to 3 4 km 72 to 122 c from evolved marine fluids the carbonate and other mineralizing solutes were derived increasingly with burial from decarboxylation of organic matter and clay mineral transformations in adjacent siltstones and shales these interbedded overlying and underlying facies provided an important source of mineralizing solutes that influenced the extent of pervasive cementation during burial the combination of stratigraphic and lithofacies control resulted in laterally extensive cements that differ to shoreface successions although are similar in form to those described for many offshore mudstone dominated successions limited early concretionary ferroan dolomite beneath the expression of the sequence boundary and some flooding surfaces however suggests cementation by meteoric fluids at times of relative sea level lowstand similar processes have been demonstrated in more proximal successions in the book cliffs

the carbon isotope shift at the permian triassic boundary in the southern alps is gradual carbon isotope ratios in marine carbonate rocks have been shown to shift at some of the time boundaries associated with extinction events for example cretaceous tertiary1 and ordovician silurian2 the permian triassic boundary the greatest extinction event of the phanerozoic3 is also marked by a large 13c depletion4 5 new carbon isotope results from sections in the southern alps show that this depletion did not actually represent a single event but was a complex change that spanned perhaps a million years during the late permian and early triassic these results suggest that the permian triassic p tr extinction may have been in part gradual and in part stepwise 6 7 but was not in any case a single catastrophic event

carbon isotope stratigraphy across the permian triassic boundary a review abstract the palaeozoic mesozoic transition is marked by distinct perturbations in the global carbon cycle resulting in a prominent negative carbon isotope excursion at the permian triassic p t boundary well known from a plethora of marine and continental sediments potential causes for this negative 13 c trend and their links to the latest permian mass extinction have been intensively debated in the literature in order to draw conclusions regarding causation a general 13 c curve was defined after consideration of all available datasets and with due reference to the biostratigraphic background the most important features of the p t carbon isotope trend are the following the 4 7 13 c decline lasting 500 000 years is gradual and began in the changhsingian at the stratigraphic level of the c bachmanni zone the decreasing trend is interrupted by a short term positive event that starts at about the latest permian low latitude marine main extinction event horizon eh indicating that the extinction itself cannot have caused the negative carbon isotope excursion after this short term positive excursion the 13 c decline continues to a first minimum at about the p t boundary a subsequent slight increase is followed by a second occasionally two peaked minimum in the lower and middle i isarcica zone the negative carbon isotope excursion was most likely a consequence of a combination of different causes that may include 1 direct and indirect effects of the siberian trap and contemporaneous volcanism and 2 anoxic deep waters occasionally reaching very shallow sea levels a sudden release of isotopically light methane from oceanic sediment piles or permafrost soils as a source for the negative carbon isotope trend is questionable at least for the time span a little below the eh and somewhat above the p t boundary

assessing the fidelity of marine vertebrate microfossil δ18o signatures and their potential for palaeo ecological and climatic reconstructions abstract conodont biogenic apatite has become a preferred analytical target for oxygen isotope studies investigating ocean temperature and palaeoclimate changes in the palaeozoic despite the growing application in geochemically based palaeoenvironmental reconstructions the paucity or absence of conodont fossils in certain facies necessitates greater flexibility in selection of robust oxygen bearing compounds for analysis vertebrate microfossils teeth dermal denticles spines offer a potential substitute for conodonts from the middle palaeozoic vertebrate bioapatite is particularly advantageous given a fossil record extending to the present with representatives across freshwater to fully marine environments thus widening the scope of oxygen isotope studies on bioapatite however significant tissue heterogeneity within vertebrates and differential susceptibility of these tissues to diagenetic alteration have been raised as potential problems affecting the reliability of the oxygen isotope ratios as palaeoclimatic proxies well preserved vertebrate microfossils and co occurring conodont fossils from the upper devonian and lower carboniferous of the lennard shelf canning basin western australia were analysed using bulk gas isotope ratio mass spectrometry girms and in situ secondary ion mass spectrometry sims methodologies with the latter technique allowing investigation of specific tissues within vertebrate elements the 18oconodont results may be interpreted in terms of palaeolatitudinally and environmentally sensible palaeo salinity and temperature and provide a baseline standard for comparison against vertebrate microfossil 18o values despite an absence of obvious diagenetic modification girms of vertebrate denticles yielded 18o values depleted in 18o by 2 4 relative to co occurring conodonts sims analysis of dentine tissues exhibited significant heterogeneity while hypermineralised tissues in both scales and teeth produced 18o values comparable with those of associated conodonts the susceptibility of permeable phosphatic fossil tissues to microbial activity fluid interaction and introduction of mineral precipitates post formation is demonstrated in the dentine of vertebrate microfossils which showed significant heterogeneity and consistent depletion in 18o relative to conodonts the hypermineralised tissues present in both teeth and scales appear resistant to many diagenetic processes and indicate potential for palaeoclimatic reconstructions and palaeoecological investigations

complementary constraints from carbon 13c and nitrogen 15n isotopes on the glacial ocean s soft tissue biological pump a three dimensional process based model of the ocean s carbon and nitrogen cycles including 13c and 15n isotopes is used to explore effects of idealized changes in the soft tissue biological pump results are presented from one preindustrial control run pictrl and six simulations of the last glacial maximum lgm with increasing values of the spatially constant maximum phytoplankton growth rate max which accelerates biological nutrient utilization mimicking iron fertilization the default lgm simulation without increasing max and with a shallower and weaker atlantic meridional overturning circulation and increased sea ice cover leads to 280 pg more respired organic carbon corg storage in the deep ocean with respect to pictrl dissolved oxygen concentrations in the colder glacial thermocline increase which reduces water column denitrification and with delay nitrogen fixation thus increasing the ocean s fixed nitrogen inventory and decreasing 15nno3 almost everywhere this simulation already fits sediment reconstructions of carbon and nitrogen isotopes relatively well but it overestimates deep ocean 13cdic and underestimates 15nno3 at high latitudes increasing max enhances corg and lowers deep ocean 13cdic improving the agreement with sediment data in the model s antarctic and north pacific oceans modest increases in max result in higher 15nno3 due to enhanced local nutrient utilization improving the agreement with reconstructions there models with moderately increased max fit both isotope data best whereas large increases in nutrient utilization are inconsistent with nitrogen isotopes although they still fit the carbon isotopes reasonably well the best fitting models reproduce major features of the glacial 13cdic 15n and oxygen reconstructions while simulating increased corg by 510 670 pg compared with the preindustrial ocean these results are consistent with the idea that the soft tissue pump was more efficient during the lgm both circulation and biological nutrient utilization could contribute however these conclusions are preliminary given our idealized experiments which do not consider changes in benthic denitrification and spatially inhomogenous changes in aeolian iron fluxes the analysis illustrates interactions between the carbon and nitrogen cycles as well as the complementary constraints provided by their isotopes whereas carbon isotopes are sensitive to circulation changes and indicate well the three dimensional corg distribution nitrogen isotopes are more sensitive to biological nutrient utilization

wuchiapingian early lopingian permian global brachiopod palaeobiogeography a quantitative approach abstract a global presence absence database of 212 wuchiapingian early lopingian permian brachiopod genera from 30 stations is analysed by cluster analysis nonmetric multidimensional scaling and minimum spanning tree to document the global palaeobiogeographical patterns five core groups are revealed by the quantitative analysis and interpreted as representing five marine biotic provinces they are the cathaysian tropical western tethyan tropical himalayan warm temperate austrazean cold temperate and greenland svalbard provinces cold temperate the cathaysian province is composed of many isolated or semi isolated islands situated in the palaeotethys whereas the other four provinces occurred mainly on the continental shelves of pangea the western tethyan province along the western coast of the palaeotethys the himalayan province on the northern margin of gondwanaland the austrazean province along the southeastern margin of gondwanaland and the greenland svalbard province on the northern margin of pangea in addition nonmetric multidimensional scaling helped to identify key biogeographic determinants latitude related thermal gradient appears to have accounted for most of the variance in the data geographic distance and ocean circulation may have also played a major but subordinate role in the delineation and or enhancement of some of the provinces comparison with early and middle permian global marine provincialism indicates that marine biotic provinces had significantly reduced during the lopingian late permian in the lead up to the end permian mass extinction

sedimentary heterogeneity and petrophysical characterization of barremian tsunami and barrier island inlet deposits the aliaga outcrop as a reservoir analogue galve sub basin eastern spain abstract the present study examined two sandstone deposits in the aliaga outcrop as a reservoir analogue over a distance of 200 m long and attempted to establish a correlation between sand facies and the petrophysical properties of the sandstones in order to investigate the reservoir heterogeneity the aliaga reservoir analogue represents the upper part of camarillas fm deposited during the barremian synrift phase of the galve sub basin iberian basin spain it is characterized by a transitional sedimentary interval from sandy dominant deposits to carbonate dominant deposits which were deposited under the same palaeoenvironmental conditions in relation to systems of back barrier sedimentation the description of the aliaga outcrop provided here consists of lithological descriptions of two sandstone deposits a tsunami and a barrier island inlet at both mesoscopic decimetres to tens of metres and microscopic scales millimetres to centimetres both deposits recognized at the basin scale were described in terms of sand grain size sand sorting and cementation further cores were drilled along outcrop to collect samples for porosity and permeability measurements both sandstone reservoirs are the result of different sedimentary processes that determined facies characteristics as the different petrophysical properties observed in these deposits consequently the sedimentary process controls the heterogeneity of the sandstones facies and thus the sand heterogeneity controls the distribution of the petrophysical properties the classification of sand facies in terms of sand sorting seems to be more appropriate for describing sand heterogeneity accordingly petrophysical parameters in both deposits were also influenced by sand sorting the sand facies and petrophysics heterogeneity of the described deposits can be hierarchically ordered first order heterogeneity is related to the basin scale second order heterogeneity is related to genesis and the conditions of sediment deposition and third order heterogeneity is related to synsedimentary faults and or post sedimentation events

time dependent onshore tsunami response abstract while bulk measures of the onshore impact of a tsunami including the maximum run up elevation and inundation distance are important for hazard planning the temporal evolution of the onshore flow dynamics likely controls the extent of the onshore destruction and the erosion and deposition of sediment that occurs however the time varying dynamics of actual tsunamis are even more difficult to measure in situ than the bulk parameters here a numerical model based on the non linear shallow water equations is used to examine the effects variations in the wave characteristics bed slope and bottom roughness have on the temporal evolution of the onshore flow model results indicate that the onshore flow dynamics vary significantly over the parameter space examined for example the flow dynamics over steep smooth morphologies tend to be temporally symmetric with similar magnitude velocities generated during the run up and run down phases of inundation conversely on shallow rough onshore topographies the flow dynamics tend to be temporally skewed toward the run down phase of inundation with the magnitude of the flow velocities during run up and run down being significantly different furthermore for near breaking tsunami waves inundating over steep topography the flow velocity tends to accelerate almost instantaneously to a maximum and then decrease monotonically conversely when very long waves inundate over shallow topography the flow accelerates more slowly and can remain steady for a period of time before beginning to decelerate these results indicate that a single set of assumptions concerning the onshore flow dynamics cannot be applied to all tsunamis and site specific analyses may be required

a unique 4000 year long geological record of multiple tsunami inundations in the augusta bay eastern sicily italy abstract we present the geological evidence for a 4000 year long record of multiple tsunami inundations along the coast of the augusta bay eastern sicily and discuss its implications the research was carried out through a multi theme approach which benefited from an extraordinarily long historical record that we used to guide detailed geomorphologic and geologic surveys coring campaigns and laboratory analyses two sites named the augusta hospital and priolo reserve were selected and investigated in detail along the 25 km long coastline of augusta bay we found evidence for six possibly seven tsunami deposits three of them may be tentatively associated with the 1693 and 365 ad ionian sea historical tsunamis and the 3600 bp santorini event the other three possibly four deposits are evidence for unknown paleo inundations dated at about 650 770 ad 600 400 bc and 975 800 bc at augusta hospital site and 800 600 bc at priolo reserve site we use these ages to extend further back the historical record of tsunamis available for this coastal area the exceptional number of tsunami deposits found with this study allowed us to derive an average geologic tsunami recurrence interval in the augusta bay of about 600 years for the past 4 ka conversely the historical tsunami data for the past millennium suggest an average tsunami recurrence interval of about 250 years this difference in the average recurrence intervals suggests that only the strongest inundations may leave recognizable geological signatures at the investigated sites i e the evidence for the 1908 and 1169 tsunamis is missing but also that the geomorphological setting of the site and its erosional depositional history are critical aspects for the data recording thus an average recurrence interval derived from the geological record should be considered as a minimum figure the identification and age estimation of tsunami deposits represent a new and independent contribution to tsunami scenarios and modeling for coastal hazard assessment in civil protection applications furthermore our study cases provide new elements on tsunami deposit recognition related to exceptionally large events that occurred in the aegean sea

fault controlled and stratabound dolostones in the late aptian earliest albian benassal formation maestrat basin e spain petrology and geochemistry constrains this study was developed under the exxonmobil fc2 alliance fundamental controls on flow in carbonates the authors wish to thank exxonmobil production company and exxonmobil upstream research company for providing funding the views in this article by sherry l stafford are her own and not necessarily those of exxonmobil this research was supported by the sedimentary geology research group of the generalitat de catalunya 2014sgr251 we would like to thank andrea ceriani and paola ronchi for their critical and valuable reviews and associated editor piero gianolla for the editorial work

geologic factors controlling co2 storage capacity and permanence case studies based on experience with heterogeneity in oil and gas reservoirs applied to co2 storage a variety of structural and stratigraphic factors control geological heterogeneity inferred to influence both sequestration capacity and effectiveness as well as seal capacity structural heterogeneity factors include faults folds and fracture intensity stratigraphic heterogeneity is primarily controlled by the geometry of depositional facies and sandbody continuity which controls permeability structure the permeability structure in turn has implications for co2 injectivity and near term migration pathways whereas the long term sequestration capacity can be inferred from the production history examples of gulf coast oil and gas reservoirs with differing styles of stratigraphic heterogeneity demonstrate the impact of facies variability on fluid flow and co2 sequestration potential beach and barrier island deposits in west ranch field in southeast texas are homogeneous and continuous in contrast seeligson and stratton fields in south texas examples of major heterogeneity in fluvial systems are composed of discontinuous channel fill sandstones confined to narrow sinuous belts these heterogeneous deposits contain limited compartments for potential co2 storage although co2 sequestration effectiveness may be enhanced by the high number of intraformational shale beds these field examples demonstrate that areas for co2 storage can be optimized by assessing sites for enhanced oil and gas recovery in mature hydrocarbon provinces

late pleistocene barrier island development reconstructed from genetic classification and timing of erosional surfaces paleo tokyo bay japan abstract formative processes of a retrogradational barrier island system and associated transgressive erosional surfaces are reconstructed from the upper pleistocene kioroshi formation developed in paleo tokyo bay japan the kioroshi formation provides high quality sedimentary records of a preserved barrier island system three volcanic ash beds intercalated in the formation provide a high resolution chronostratigraphic framework the barrier island system of the kioroshi formation developed in a glacio eustatically forced sea level cycle during oxygen isotope stages 6 to 5e in the early stage of the transgression paleo tokyo bay was non barred and was exposed to the pacific ocean affected by open ocean wave processes shoreface erosion in such a non barred environment developed a wave ravinement surface rs1 rs1 overlies incised valley fill deposits formed in the earliest stage of the transgression and is overlain by shoreface deposits that are further overlain by embayment deposits such as lagoonal and flood tidal delta deposits formed during succeeding barrier development during the later stage of the same transgression associated with the formation and landward migration of the barrier chain tidal currents in tidal inlet and flood tidal deltas became active and a tidal ravinement surface trs was formed trs is developed on the base of tidal inlet and flood tidal delta deposits furthermore shoreface erosion on the open ocean side of the barrier chain eroded underlying embayment deposits and formed a secondary wave ravinement surface rs2 a chronostratigraphic surface in embayment deposits defined by a volcanic ash bed intersects trs and is eroded by rs2 this relationship together with associated facies architecture indicates diachroneity of the formation of these marine erosional surfaces associated with the retrogradational barrier island system

seawater strontium isotopic perturbation at the permian triassic boundary west spitsbergen and its implications for the interpretation of strontium isotopic data brachiopod shell samples from the kapp starostin formation west spitsbergen provide evidence for a large and rapid drop in seawater strontium isotopic ratios close to the permian triassic boundary the strontium isotopic shift is associated with similarly dramatic declines in carbon and oxygen isotope curves recorded in the same samples this pattern can be explained by a paleoceanographic model that we have proposed previously a model in which there is replacement of a largely stagnant stratified ocean by a vigorously mixed one at the permian triassic boundary

extensional fault control on the sedimentation patterns in a continental rift basin el castellar formation galve sub basin spain in the galve sub basin the sedimentary record of the upper hauterivian lower barremian el castellar formation is divided into two stages by a marlstone interval with gypsum stage 1 shows a great variety of subenvironments and facies alluvial palustrine and lacustrine whereas in stage 2 an extensive shallow carbonate lake developed sedimentation was controlled by a system of south dipping ene wsw listric normal faults laterally bounded by nnw sse steeper transfer faults faults controlled sedimentation from a basin scale basin margins and main characteristics and evolution of sediments to a regional and a local scale thickness and facies distribution of the synrift series as well as the location and evolution of lakes and minor alluvial fans the changes between stages 1 and 2 are related to the passing from an independent movement of faults to the movement of all the extensional faults as a whole at a sole detachment level the interval with gypsum was caused by underground water flow changes associated with the interrelation and connection of the faults in the transition period these changes have been correlated with the transition from the rift initial stage to the rift climax stage which took place in the hauterivian barremian transition

numerical models of tsunami sediment transport current understanding and future directions abstract researchers who study tsunami deposits share common ultimate goals of their work which are to better assess the magnitude information of paleotsunamis and to contribute to the assessment of future tsunami risks numerical modeling of tsunami sediment transport is an important piece of interdisciplinary research that fills the gap between geological studies and practical utilization of tsunami deposits forward and inverse numerical models that address tsunami transport of sand and boulders have been developed over the last two decades forward models are capable of delineating the time evolution of tsunami hydrodynamics sediment transport and the resulting morphological changes associated with erosion and deposition inverse models estimate tsunami characteristics such as flow speed and depth from deposits numerical modeling can be used not only to quantify paleotsunamis but also to enhance our understanding of tsunami sedimentology and hydrodynamics to make progress towards the ultimate goal of improved tsunami risk assessment development of an in depth mutual understanding between modelers and geologists of the advantages limitations and uncertainties in both numerical modeling and geological records is an important challenge

heterogeneity patterns of quaternary glaciofluvial gravel bodies sw germany application to hydrogeology abstract the architecture of sedimentary bodies determines the heterogeneity of many aquifers thus for environmental risk assessment and quantification of clean up efficiencies determination of the spatial distribution of hydraulic properties is required in this study outcrop analogues of glaciofluvial gravel bed deposits are used for a process based analysis of sedimentary heterogeneities which in turn are transformed into hydraulic parameters three scales of heterogeneities are distinguished a the lithofacies scale is formed by unique transport and depositional processes that form the fundamental building blocks hydrofacies types b the depositional element scale shows distinct geometrical characteristics internal structure and bounding surfaces and determines the local distribution of lithofacies and hence the correlation structure of permeabilities c the architectural scale of gravel bodies is formed by the stacking of depositional elements which is controlled by the dynamics of aggrading paleofluvial systems comparison of numerous gravel pits in sw germany revealed three major architectural patterns of glaciofluvial gravel bodies that can be distinguished statistically by the preservation of depositional elements as well as the frequency of lithofacies types the facies analysis results in three conceptual facies models of proglacial river systems which are regionally classified as main intermediate and minor discharge types based on calculated and laboratory measured hydraulic properties of the various lithofacies types detailed outcrop wall maps were digitized into polygons of defined hydrofacies types by using the gis system arc info the two dimensional fields of hydraulic properties were then transferred into a numerical model of groundwater flow modeling results clearly illustrate that the three heterogeneity patterns of gravel bodies also have distinguishable hydraulic response characteristics

geological characteristics and spatial distribution of paleo inlet channels beneath the outer banks barrier islands north carolina usa abstract nearly 200 km of high resolution ground penetrating radar gpr data were acquired along the outer banks barrier island system of north carolina usa gpr data combined with lithofacies and biofacies data reveal multiple depositional facies including inlet channel flood tide delta overwash peat and inner shelf previously undocumented paleo inlet channels constitute a significant portion of the shallow geologic framework between oregon inlet and cape hatteras gpr data reveal the complex stratigraphy associated with multiple sequences of cut and fill within inlet channels two types of paleochannels non migrating and migrating were classified based on geometry and fill patterns sediments and foraminifera collected from vibracores were correlated to gpr data to define the regional shallow stratigraphic framework channel fill facies are characterized by clinoform packages sometimes bounded by erosional surfaces indicating variable sediment transport directions from the ocean and sound sides channels are incised into older flood tide delta deposits corresponding to older inlet activity when barriers existed further seaward flood tide delta deposits are capped with marsh peat and overwash units migrating inlet facies occur under the widest portions of the island whereas narrow portions of the island are underlain by the non migrating inlet facies or flood tide delta overwash facies this geologic geomorphic relationship is attributed to the successional stage of island evolution during transgression and sediment transport processes associated with the different inlet types the radar facies lithofacies and biofacies provide a comprehensive dataset that will permit more precise identification of barrier island facies in the geologic record

facies and petrophysical modelling of a thick lower cretaceous tsunami deposit in e spain up scaling from sample to outcrop scales abstract the tsunami deposit up to 3 m thick of the cretaceous camarillas formation in the galve sub basin eastern spain is characterized by a large lateral extent 35 km 2 and facies uniformity consisting in fine to coarse subarkosic arkosic sandstones at the scale of outcrop observation different lithofacies were distinguished and related to sedimentation processes sand facies distribution conditioned the facies heterogeneity at both mesoscopic or outcrop scales 10 1 10 1 m scale and sample scale 10 3 10 2 m the sample features were up scaled to that of a facies model using probability functions and variograms as well as to outcrop scale data geometry and size of facies distribution and it showed a good correlation with the facies distribution at the outcrop porosity is strongly correlated to permeability and the pairs of porosity and permeability values fall into the global hydraulic element ghes 5 so that they can be up scaled into reservoir models in terms of hydraulic properties from data analysis no apparent link between sand sorting and porosity and permeability values was observed the petrophysical models which were independent of facies models were up scaled taking into account the porosity and permeability values from sample data and the statistical analysis of their distribution along the outcrop the permeability model was carried out as a function of porosity by applying a linear relation which simplified the modelling process and discarded permeability uncertainties linked to facies distribution in the deposit in spite of different source data the petrophysical models show a distribution of lower and higher values that resembles the facies model consequently our modelling results clearly suggest the link of facies type and their grain size distributions with the petrophysical properties into the deposit consistency between facies and petrophysical models and outcrop scale observations make it possible to extrapolate to other deposits related to similar sedimentary processes

development of a largely anoxic stratified ocean and its temporary massive mixing at the permian triassic boundary supported by the sulfur isotopic record systematic sulfur isotope data for whole rock sulfides have been obtained from the chert dominated continuous pelagic sedimentary sequences spanning the permian triassic p tr boundary at tenjinmaru in the chichibu terrane and at sasayama in the tanba terrane in japan the p tr boundary is characterized by the occurrence of siliceous shales in association with a carbonaceous black mudstone which is similar in appearance to the worldwide distributed cretaceous tertiary k t boundary claystone the observed data clearly demonstrate a significant bimodalism the 34s 32s ratios with respect to cdt are generally low throughout the middle permian ca 39 to 25 0 and show a remarkable increase beginning in the lower upper permian and persisting into the lower triassic ca 20 to 2 0 with a temporary and drastic negative shift down to roughly the same isotopic level as in the middle permian just at the suspected p tr boundary ca 41 to 23 0 interestingly the mode of isotopic excursion across the p tr boundary is in striking contrast to that across the k t boundary which was recently described at kawaruppu in hokkado japan the apparent extent of fractionation with respect to contemporaneous seawater sulfate in the high 34s 32s group lies within the range of 25 10 0 which is quantitatively equivalent to the currently confirmed range of kinetic isotope effect during bacterial dissimilatory sulfate reduction and that in the low 34s 32s group mostly exceeds this range giving the values typically in the range of 45 10 0 which is similar to what is generally observed in the present day oceanic sediments the present data would provide strong evidence for the development of a largely stagnant anoxic stratified ocean which presumably began to form in the lower upper permian and persisted into the lower triassic and for a brief episode of its temporary massive mixing just at the suspected p tr boundary such an oceanic oxic anoxic history may account to some extent for the relatively high enrichments of chalcophile elements in basal triassic sediments in the world and add a significant constraint to the current arguments on the cause and consequence of the terminal permian mass extinction

a brachiopod calcite record of the oceanic carbon and oxygen isotope shifts at the permian triassic transition the permian triassic p t mass extinction was the most dramatic of all such events but its cause has thus far remained elusive1 3 carbon and oxygen isotope analyses may offer clues to this puzzle because their results identify major changes in the earth s exosystem4 5 several studies have already dealt with carbon and oxygen isotope records at the p t transition2 6 11 but we present here empirical data derived from the brachiopod shell calcite whose isotope composition generally corresponds to that of the sea water in which the animals lived originally12 15 these data allow us to assess quantitatively the magnitude of changes in the earth s exosystem during that critical time interval

a thick tethyan multi bed tsunami deposit preserving a dinosaur megatracksite within a coastal lagoon barremian eastern spain abstract a thick multiple bed tsunami deposit consisting of sandstones and conglomerates has been discovered and investigated in the camarillas formation 130 6 128 4 ma barremian age in eastern spain the tsunami deposit is interbedded within red mudstones deposited in mud flats of a back barrier system it crops out along 7 km in length and at its base a great number of dinosaur tracks assigned to sauropods ornithopods and theropods have been preserved as natural casts then constituting an exceptional regional megatracksite associated with tsunami deposits on the basis of sedimentological features and the lateral and vertical architecture of the involved lithofacies up to five couplets of inflow backflow deposits formed by a tsunami wave train have been recognized overlying the tracks although sedimentation mainly took place during backflow currents inflows led to the removal of sand from a fronting barrier island and the rip up of lagoonal carbonate and clay pebbles depositing them in the protected back barrier lagoon its unusually great thickness is interpreted among others as being the result of the filling of the previous low topography of the back barrier lagoon

the marine phosphorus cycle phosphorus introduced to the ocean must ultimately be removed if a steady state is to be maintained over geologic time aeolian input is insignificant and there is evidently no hydrothermal contribution rivers dominate p input to the ocean the fluvial p flux is poorly quantified due to the interactions of two factors 1 man s influence on river nutrient fluxes and 2 inherent complexities in understanding the biological and inorganic associations of p in estuarine and coastal waters our best estimate of the natural or pre man p input flux is about 10 x 10 sup 9 moles p cm sup 2 ocean surface year of the identified flux of phosphorus to the sediments about 90 percent is in the form of biogenic debris or its regeneration products the burial of phosphatic fish debris is negligible p removal by direct reaction of phosphate in seawater with sea floor basalts during mid ocean ridge hydrothermal circulation is insignificant p removal by processes such as sorption on clay surfaces or formation of authigenic fe and al phosphate phases is presently unquantified and remains a serious uncertainty in the phosphorus cycle the identified sources and sinks approximately balance yielding a residence time for p in the oceans of about 10 sup 5 yrs

tsunami sedimentary facies deposited by the storegga tsunami in shallow marine basins and coastal lakes western norway sedimentary successions in small coastal lakes situated from 0 to 11 m above the 7000 year bp shoreline along the western coast of norway contain a distinctive deposit very different from the sediments above and below the deposit is interpreted to be the result of a tsunami inundating the coastal lakes an erosional unconformity underlies the tsunami facies and is traced throughout the basins with most erosion found at the seaward portion of the lakes the lowermost tsunami facies is a graded or massive sand that locally contains marine fossils the sand thins and decreases in grain size in a landward direction above follows coarse organic detritus with rip up clasts here termed organic conglomerate and finer organic detritus the tsunami unit generally fines and thins upwards the higher basins 6 11 m above the 7000 year shoreline show one sand bed whereas basins closer to the sea level 7000 years ago may show several sand beds separated by organic detritus these alternations in the lower basins may reflect repeated waves of sea water entering the lakes in basins that were some few metres below sea level at 7000 years bp the tsunami deposit is more minerogenic and commonly present as graded sand beds but also in some of these shallow marine basins organic rich facies occur between the sand beds the total thickness of the tsunami deposit is 20 100 cm in most studied sites an erosional and depositional model of the tsunami facies is developed

inflow and outflow facies from the 1993 tsunami in southwest hokkaido abstract we describe in detail the sedimentary facies provenance and grain size distributions of the 1993 tsunami deposits in the lower reaches of usubetsu river only two lithofacies were recognized a gravel lobe facies glf and a sand sheet facies ssf the gravel lobe facies was deposited rapidly by a hydraulic jump in contrast the sand sheet facies which contains both current ripples and dunes was deposited by a traction current under subcritical flow conditions we identified four stratigraphic units unit 1 unit 2 unit 3 and unit 4 in ascending order we interpreted units 1 and 2 as having been deposited by the inflow and outflow events of the first run up and units 3 and 4 by the inflow and outflow events of the second run up respectively units 3 and 4 were more widely distributed and coarser grained than units 1 and 2 because the second run up was larger than the first run up furthermore unit 4 was more widely distributed than unit 3 because the outflow eroded the inflow deposits grain size distributions of the inflow and outflow deposits were clearly different unit 4 deposits had a peak at 2 5 phi p 1 population in contrast unit 3 deposits had a bimodal distribution with peaks at 0 5 1 5 phi p 2 population and at 2 5 phi p 1 population a comparison of the tsunami deposits with other sedimentary deposits near the study area showed that the tsunami deposits were mainly derived from the seabed at depths below 5 5 m in the offshore area where the marine sands are about 2 2 5 phi in size and thus are the source of the p 1 population the p 2 population is derived from coarse 0 5 2 phi fluvial materials eroded during the tsunami run up according to our calculations benthic foraminiferal tests were entrained from the comparatively deep seabed at depths up to 100 m during the tsunami run up and included in the tsunami deposits

sandstone body and shale body dimensions in a braided fluvial system salt wash sandstone member morrison formation garfield county utah excellent three dimensional exposures of the upper jurassic salt wash sandstone member of the morrison formation in the henry mountains area of southern utah allow measurement of the thickness and width of fluvial sandstone and shale bodies from extensive photomosaics the salt wash sandstone member is composed of fluvial channel fill abandoned channel fill and overbank flood plain strata that were deposited on a broad alluvial plain of low sinuosity sandy braided streams flowing northeast a hierarchy of sandstone and shale bodies in the salt wash sandstone member includes in ascending order trough cross bedding fining upward units mudstone intraclast conglomerates single story sandstone bodies basal conglomerate abandoned channel fill multistory sandstone bodies and overbank flood plain heterolithic strata trough cross beds have an average width thickness ratio w t of 8 5 1 in the lower interval of the salt wash sandstone member and 10 4 1 in the upper interval fining upward units are 0 5 3 0 m thick and 3 11 m wide single story sandstone bodies in the upper interval are wider and thicker than their counterparts in the lower interval based on average w t linear regression analysis and cumulative relative frequency graphs multistory sandstone bodies are composed of two to eight stories range up to 30 m thick and over 1500 m wide w t 50 1 and are also larger in the upper interval heterolithic units between sandstone bodies include abandoned channel fill w t 33 1 and overbank flood plain deposits w t 70 1 understanding w t ratios from the component parts of an ancient sandy braided stream deposit can be applied in several ways to similar strata in other basins for example to 1 determine the width of a unit when only the thickness is known 2 create correlation guidelines and maximum correlation lengths 3 aid in interpreting the controls on fluvial architecture and 4 place additional constraints on input variables to stratigraphic and fluid flow modeling the usefulness of these types of data demonstrates the need to develop more data sets from other depositional environments

impact of synsedimentary metre scale normal fault scarps on sediment gravity flow dynamics an example from the gres d annot formation se france abstract synsedimentary faults result in the direct interaction between tectonic and sedimentary processes at similar spatio temporal scales sedimentological analysis of sediment laden gravity flows in the northern part of the gres d annot formation sanguiniere sub basin col de la moutiere tete ronde has revealed the presence of fault scarps of metre scale height these synsedimentary fault scarps were sufficient to disturb the sediment gravity flow dynamics resulting in i a strong variation of the erosive behaviour of a concentrated flow and ii the transformation of a strongly stratified laminar hyperconcentrated flow into a turbulent flow in short distance less than 500 m these disturbances develop without the flows being deviated by the fault scarps but produce great facies heterogeneity the least homogeneous facies mixing sand and clay being localized on the upstream obstacle side the most homogeneous massive sand downstream

geochemistry of late permian to early triassic pelagic cherts from southwest japan implications for an oceanic redox change major trace and rare earth element abundances were determined for the southwestern japanese pelagic chert sequence from the early late permian to early early triassic to investigate a redox change in deep sea pelagic environments before and at the permo triassic boundary ptb 251 ma the sequence was primarily deposited in the deep sea of the superocean panthalassa and then was accreted to japan in the middle jurassic a remarkable lithostratigraphic change from red chert to siliceous carbonaceous claystone through gray chert is observed in this sequence constituent elements for these sedimentary rocks are essentially derived from two sources 1 an ancient seawater via biogenic mainly radiolarian hydrothermal and authigenic materials and 2 an average shale like terrigenous material the present measurement demonstrates significant stratigraphic changes of the ce cenon ter value estimated ce anomaly value of non terrigenous component recalculated by subtraction of terrigenous rees from bulk rees and the mn te sample mn te paas value excess mn component other than terrigenous one te terrigenous elements including ti al nb hf th paas post archean average australian shale in the permian chert the ce cenon ter values increase from 0 2 to 1 and the mn te sample mn te paas values decrease up section suggesting that the redox condition of deep sea open ocean changed from oxic to suboxic in an interval of approximately 10 myr the fe te sample fe te paas and mn te sample mn te paas values of carbonaceous claystone near or at the ptb are less than unity suggesting that reductive dissolution of iron and manganese occurred under an anoxic condition this supports the idea of the ptb oceanic anoxia in the superocean panthalassa the present data suggest that the anoxic condition prevailed in the deep sea pelagic regions for an extremely long period much more than 10 myr from the middle late permian to early early triassic this long term development of widespread oceanic anoxia may have been linked to the greatest mass extinction of the phanerozoic

a facies geological test of stable isotope interpretation of the upper permian depositional environment in west spitsbergen lithofacies analysis of two transgressive sequences within the kapp starostin formation upper permian west spitsbergen indicates considerable differences in seawater chemistry between their depositional environments the onshore part of the sequence represented in the voringen and svenskeegga members is largely calcareous with allochthonous and corroded siliceous materials in contrast in the equivalent sequence within the hovtinden member silica is ubiquitous whereas carbonate materials include mainly corroded bioclasts these differences are consistent with predictions of the oceanographic model of overfed and hungry oceans proposed previously on the basis of carbon and oxygen stable isotope analysis

a new high resolution stratigraphic and palaeoenvironmental record spanning the end permian mass extinction and its aftermath in central spitsbergen svalbard abstract research on the permian triassic boundary ptb along the northern margins of pangaea exposed today in the arctic region has been heavily reliant on field observations where data resolution was consequently determined by outcrop condition and accessibility core drilling in central spitsbergen allowed for a near complete recovery of two 90 m cores through the ptb analyses of the core and nearby outcrops include stratigraphic logging and sampling xrf scanning petrography biostratigraphy isotope geochemistry and geochronology the first appearance datum fad of h parvus in svalbard places the base of the triassic ca 4 m above the base of the vikinghogda formation and ca 2 50 m above the end permian mass extinction epme and its associated sharp negative 13c the ptb therefore falls within the reduviasporonites chalastus assemblage zone in svalbard precise u pb tims dating of two zircon crystals in a tephra layer just above the first documented hindeodus parvus in svalbard gives an age of 252 13 0 62 ma high resolution palaeoenvironmental proxies including si kcps kilo counts per second zr rb k ti fe k and v cr indicate a transition towards a more arid climate in the earliest triassic contemporaneous with prolonged bottom water dysoxic anoxic conditions following an increase in volcanic activity in the late permian statistical analysis of zr rb k ti and v cr elemental ratios suggests that the system was impacted by long eccentricity 400 kyr cyclicity the 13c excursion in organic carbon 13corg record signals a large negative carbon isotope excursion cie associated with the mass extinction event but also records a second smaller negative cie ca 22 m above this interval this younger 13corg excursion correlates to similar cies in the dienerian late induan records of other sections notably in the tethys ocean which have been interpreted as recording a small biotic crisis during the post extinction recovery evidence of this negative cie in spitsbergen suggests that the dienerian crisis may have been global in extent the negative 13corg values are associated with evidence for dysoxia or anoxia in the core and the occurrence of tephra layers in the same interval suggests a possible connection between the dienerian crisis and a discrete episode of volcanic activity

mesozoic extensional tectonics stratigraphy and crustal evolution during the alpine cycle of the eastern iberian basin abstract sequence stratigraphy subsidence analysis and the integration of the basin fill data allow to the identification of four successive evolutionary stages in the basins of the eastern iberian margin during mesozoic extension 1 triassic rift late permian hettangian 2 early and middle jurassic postrift sinemurian oxfordian 3 late jurassic and early cretaceous rift kimmeridgian middle albian and 4 late cretaceous postrift late albian maastrichtian the present day crustal structure of the eastern iberian range and evidence of its evolution are deduced from the analysis of a new gravity map and other geophysical data a regional gravity low along the iberian range is interpreted in terms of crustal thickening beneath the orogen as a result of the collision between the ebro block and the iberian plate during the paleogene the boundary between these blocks coincides with a magnetic lineament that is interpreted as an inherited signature of the thinning that occurred during mesozoic extension a geodynamic scenario for the crustal evolution of the eastern part of the iberian peninsula based on the evaluation of mesozoic extensional tectonics and an analysis of the available geophysical data includes three main successive evolutionary stages 1 1 mesozoic crustal thinning 2 2 paleogene crustal thickening 3 3 neogene crustal thinning based on new geological and geophysical arguments this study offers an alternative and a more complete geodynamic history of the eastern iberian basins related to the evolution of the iberian plate and the central north atlantic

morphodynamics of the barrier inlet system west central florida the barrier inlet system along the gulf coast of peninsular florida has one of the most diverse morphologies of any barrier system in the world the delicate balance between tidal and wave generated processes on this low energy coast permits only slight changes in either of these processes to result in significant and rapidly developing morphologic responses some of these responses are the result of natural phenomena such as hurricanes opening tidal inlets closure of inlets due to longshore transport of sediment and changes in the availability of sediment tidal prism is the primary factor in controlling inlet morphology and is greatly influenced by anthropogenic activities in the backbarrier area human activity has also modified the coast in many ways over the past several decades beginning with the construction of the first causeways in the 1920s the various modifications by development have resulted in important morphodynamic changes in the barrier inlet system these include hardening the coast on the beach and at inlets dredging and filling in backbarrier environments and construction of fill type causeways connecting the islands to the mainland construction of seawalls and jetties has inhibited normal coastal processes examples include the downdrift erosion at blind pass and big sarasota pass construction of fill type causeways between the barriers and the mainland has created artificial tidal divides that reduce the tidal prism at some inlets thereby resulting in instability or closure such as blind pass and dunedin pass this is further exacerbated by dredge and fill construction that reduces tidal prism by reducing the area of open water in the backbarrier dredging of the intracoastal waterway also results in a negative impact on selected inlets by channeling tidal flux away from some inlets impacts of these changes inhibit the barrier inlet environments from responding to open coast processes

high resolution terrestrial permian triassic eventostratigraphic boundary in western guizhou and eastern yunnan southwestern china the adjoining area of western guizhou and eastern yunnan provinces in southwest china is an ideal place to investigate the feasibility of correlating marine and nonmarine permian triassic boundary ptb sequences as it contains outcrop sections of shallow marine marginal marine or paralic and terrestrial ptb sections all in close geographic proximity this paper documents for the first time multiple stratigraphic data from several well preserved terrestrial ptb sections in the area and attempts to use these data to define locate and correlate the ptb in the area a study of the spores and pollen and vegetation types across the terrestrial ptb sections in the study area suggests three distinct evolutionary stages across the boundary stage 1 xuanwei formation is characterised by late permian or paleozoic type ferns and pteridosperms 85 0 with a few gymnosperms 15 0 stage 2 is marked by an abrupt drop of sporopollen elements of late permian aspects coupled with the appearance of fungal spores and limited early triassic palynomorphs stage 3 top xuanwei formation and kayitou formation is dominated by gymnosperm pollen 58 8 of clearly early triassic aspect although still retaining limited ferns and pteridosperms the three biotic stages seem to well correspond with the changing trend of the 13corg curves from the same sections which is characterized by a sharp drop just before the ptb followed by a short term partial recovery across the boundary and then succeeded by a gradual decline after the ptb in the early triassic combining evidence from eventostratigraphic i e the succession of boundary clay beds biostratigraphic using both macroplants and palynomorphs and chemostratigraphic i e organic carbon isotope excursion signals we propose that a high resolution ptb succession closely correlatable to its marine counterpart at the meishan section in eastern china is recognisable at the terrestrial ptb sections in the western guizhou eastern yunnan area in southwest china

the isotopic composition of strontium and sulfur in seawater of late permian zechstein age abstract the paleozoic minima of 87 sr 86 sr ratios and 34 s values in seawater are observed in anhydrite layers of the stassfurt a 2 and aller a 4 cycles of evaporation of late permian age in germany these minima were probably caused by extremely low rates of continental runoff and bacterial sulfate reduction thereafter conditions changed suddenly with a steeply increasing supply of radiogenic sr and of nutrients into seawater the latter induced a large growth in the production of organic material in bacterial activity in sediments and in the flow of isotopically heavy sulfur back into the oceans this large change in the cycles of s and sr as well as of c and o within the relatively short zechstein period 2 5 ma reflects a considerable modification of the plate tectonic and environmental conditions shortly before the beginning of the mesozoic era the ochoan deposition in the usa is probably of the same age as the stassfurt leine evaporation in w europe

porosity permeability and textural heterogeneity of reservoir sandstones from the lower cretaceous putaohua member of yaojia formation weixing oilfield songliao basin northeast china abstract with the granulometric analyses mineral composition x ray diffraction xrd analyses porosity and permeability measurements scanning electron microscopy sem observations and mercury porosimetry measurements of the reservoir sandstones from four wells in the weixing oilfield songliao basin ne china the porosity permeability and pore structural heterogeneity features of the putaohua member sandstone of the lower cretaceous yaojia formation have been investigated in this paper the sandstones are mostly characterized by a similar deposition in continental detrital environments with quartz and feldspar taking the majority 97 and argillaceous minerals illite kaolinite and chlorite the minority 3 however their granule size sorting index porosity and permeability vary significantly in contrast to the generality that high porosity permeability often corresponds to large grain sizes and sorting indexes the porosity and permeability here show no good correlations to the grain size and sorting index suggesting the presence of a remarkable textural heterogeneity in terms of sequential change in permeability along the well depth cyclic sedimentation modes have been identified in some sub layers despite the porosity data showing little response to those scenarios this may be ascribed to the sandstone s peculiar intergranular pore structures in which the cementation occurred in pore lining and filling manners to different extents depending on their depositional environments the distributary channel facies tends to have lowest detrital clay content and rather open packed texture in pore lining cementation manner whereas sand sheet facies has pore filling manner the hg porosimetry analytical data are in fairly good agreement with the heterogeneous pore structures observed by sem large sized pores and channels connecting them though only accounting for a low percentage of the total porosity are believed to contribute mostly to the effective permeability in the sandstone reservoir such textural heterogeneities should be closely associated with the dynamic changing sedimentary facies of sandstones in the continental environment

stratified oceans and oxygenation of the late precambrian environment a post glacial geochemical record from the neoproterozoic of w mongolia the late neoproterozoic 750 545 ma was a time of revolutionary environmental change recurrent glaciation and tectonic upheaval which culminated in the evolution of metazoans and animal biomineralization geochemical data are presented for a post glacial 700 ma limestone succession from w mongolia 87 sr 86 sr is used to constrain the timing of early diagenetic exchange stratigraphic trends to high d 13 c carb and d 13 c org mirror sea level fluctuations which we argue is consistent with the hypothesis that late precambrian ocean chemistry was controlled by vertical stratification repeated establishment of stratification 700 545 ma would have led to greater oxygen availability in the surface environment a causal link between this oxygenation and the further evolution of animals is proposed

capitanian late guadalupian permian global brachiopod palaeobiogeography and latitudinal diversity pattern a global database containing 3365 occurrences 821 species and 251 genera of the capitanian late guadalupian permian brachiopod faunas from 24 stations has been analyzed by cluster analysis using the jaccard and otsuka coefficients and the probabilistic index of similarity nonmetric multidimensional scaling and minimum spanning tree two supergroups three groups and six subgroups are revealed and interpreted as representing respectively two biotic realms the palaeoequatorial and gondwanan realms two regions and six provinces an additional realm the boreal realm based on the fauna from spitsbergen also appears recognizable although it also shows considerable similarities with southwestern north america and the northern margin of gondwana as revealed by the statistical analysis the palaeoequatorial realm can be further subdivided into the north america region and the asian tethyan region the six biotic provinces are the cathaysian province in the palaeotethys and mesotethys the greenland svalbard province in the arctic region the austrazean province in eastern australia and new zealand the grandian province in western north america and the two transitional zones the himalayan province in the southern temperate zone and the sino mongolian japanese province in the northern temperate zone polynomial regression analysis and rarefaction analysis indicate that the generic diversities of brachiopod faunas during the capitanian peaked in the palaeoequatorial cathaysian province and the two transitional zones himalayan province and sino mongolian japanese province but fell dramatically in the polar regions the generic diversity of the palaeoequatorial grandian province is apparently lower than in the two transitional zones of temperate palaeolatitudes suggesting that the generic diversity of capitanian brachiopod faunas does not exhibit a strict negative correlation with palaeolatitudes this in turn would suggest that biogeographical determinants such as geographical barriers inhabitable area and ocean currents other than latitude related temperature control may also have played an important role in the dispersal of some brachiopods and the characterization of some local provinces and high diversities the capitanian global brachiopod palaeobiogeography is generally comparable with those in the wuchiapingian and changhsingian but with some notable differences these include 1 that the grandian province of the capitanian in western north america vanished after the end guadalupian regression 2 that the western tethyan province of the lopingian could not be distinguished in the capitanian and 3 that the austrazean province was larger in area than either in the wuchiapingian or in the changhsingian

isotope shifts in the late permian of the delaware basin texas precisely timed by varved sediments closely spaced samples 285 in number of varved sediments from the upper permian in delaware basin texas have been analyzed for 13ccarb 13corg 18ocarb corg ccarb and calcite dolomite 13c records a dramatic rise from 2 8 to 5 7 in only 4400 years detected in three sections across the basin extrapolating smoothly through a 600 year interruption by a local west side of the basin fresh water inflow evidenced by low 18o this continuity and low corg within the basin both indicate that the excess net deposition of corg necessary to generate the rise in 13c took place in the ocean external to the delaware basin correlation with similar records from the zechstein basin suggest that the event was world wide although this poses obvious difficulties for the carbon cycle the rate of rise of 13c and its sustained high level must imply conversions of oxidized carbon to reduced carbon that are very large depending on which reservoirs were involved

lacustrine system evolution during early rifting el castellar formation galve sub basin central iberian chain abstract a detailed sedimentological study of the first synrift deposits recorded in the galve sub basin of ne spain during the early cretaceous aided in the reconstruction of climatic and tectonic influences the el castellar formation is composed of siliciclastics and carbonates unit 1 claystones gypsum and carbonates unit 2 and marls and limestones unit 3 unit 1 facies formed in alluvial and palustrine plains a local alluvial fan and low energy shallow lake subenvironments low energy lacustrine facies characterised unit 2 in contrast palustrine low and high energy lake facies were identified for unit 3 the spatial and temporal distribution of lithofacies representing the several environments were used to propose a general lacustrine system evolution from isolated ponds and marshes to low energy shallow lakes and finally to an extensive high energy lake lake evolution is related to changes in the subsidence pattern from local to basin scale subsidence which was ultimately related to the transition from the initial rift to rift climax stage shallowing upwards lacustrine successions have been interpreted as climatically forced and linked to sediment and water supply both tectonics and climate determined the change from an overfilled to a balanced fill lake basin through time

multidisciplinary high resolution correlation of the permian triassic boundary abstract biostratigraphic correlation of the ten most important permian triassic boundary sections throughout tethys enables establishment of four conodont and ammonoid subdivisions within a stratigraphic interval one to a few metres thick representing less than 1 ma in ascending order they are conodonts clarkina changxingensis c deflecta zone hindeodus typicalis interval isarcicella parva zone and i isarcica zone and ammonoids pseudotirolites pleuronodoceras zone lower otoceras zone upper otoceras zone and ophiceras zone most of them can be traced to north america and the arctic region carbon isotope investigations of 24 sections along tethys and in greenland and spitzbergen confirm the consistency of 13c negative excursions at the permian triassic boundary together with an inconsistent ir anomaly eight sections show that in most cases there is a succession of ir anomaly denoting the end permian catastrophic environment 13c excursion biomass loss extinction p t boundary origination of newcomers potentially capable of intercontinental correlation within that short time interval there is an intercontinental sequence boundary at the top of the permian and a transgressive surface at the p t boundary followed shortly by a maximum flooding surface an intercontinental anoxia event accompanied the transgression three delineations of the mass extinction phases and three population explosions have been recognized and can be more or less correlated in south china and the southern alps radiometric dating of the volcanogenic boundary clays of meishan shangsi and the main stage siberian tunguss traps give an almost identical age of 250 ma thus implying a synchronous interregional volcanic event there are a few palaeomagnetic transforms within the ptb strata thus multidisciplinary research of the p t boundary strata allows subdivision of this short interval into more than ten intercontinentally correlatable parts each subdivision averages less than 100 ka in duration this may be the highest resolution obtained so far in pre cretaceous rocks high frequency milankovitch type cyclic deposits within the p t boundary beds enable correlation of even higher resolution in the lower yangtze area this high resolution is made possible because the p t transition is a time of saltation and catastrophy in geological history causality of the aggregation of events merits further investigation

the late cambrian spice δ13c event and the sauk ii sauk iii regression new evidence from laurentian basins in utah iowa and newfoundland carbon isotope data from upper cambrian sections in three laurentian basins in northern utah central iowa and western newfoundland record a large positive d 13 c excursion spice event of up to 1 5 peak d 13 c ratios are well dated by trilobite collections to the middle of the steptoean stage dunderbergia zone and occur during maximum regression associated with formation of the sauk ii sauk iii subsequence boundary on the north american craton max imum regression was marked by an influx of quartz sand into carbon ate platform settings in all three widely separated basins in northern utah this quartz sand formed a thick sequence known as the worm creek quartzite which marks a conspicuous interruption of carbonate deposition during the middle to late cambrian in the region in west ern newfoundland the thickness of the quartz sand unit is much re duced but still marks a brief shutdown of the carbonate factory that is unique to the cambrian shelf succession of the area in the central iowa area of the cratonic interior an upward shallowing carbonate succession culminates in cross stratified trilobite grainstones at the peak of the spice in dunderbergia zone time and the lowest point on the relative sea level curve is associated with the occurrence of coarse quartz sand derived from the encroaching shoreface although it is difficult to determine precisely the departure from baseline d 13 c that marks the beginning of the spice excursion in the stratigraphic successions analyzed our results are consistent with a rise and subsequent fall in d 13 c tracking a major regressive transgressive event recorded across northern laurentia the correlation of a major d 13 c excursion with regression is similar to that described for the late ordovician for which the pattern has been attributed to either in creased carbonate relative to terrigenous weathering rates as ice sheets covered up organic matter containing silicates at high latitudes or high productivity and organic carbon burial driven by oceanic overturn the lack of known steptoean age ice sheets that could have affected the ratio of carbonate to silicate weathering rates suggests that organic carbon burial was the likely cause of the spice event we suggest that increased weathering and erosion rates during relative sea level fall sauk ii iii increased the burial fraction of organic carbon in an expanded region of fine grained siliciclastic deposits in shelf and upper slope environments during the steptoean

on traction carpet sedimentation traction carpets are highly concentrated bedload layers that are developed beneath and driven by turbulent overlying flows they have a convex up velocity profile and comprise a lower frictional and an upper collisional region the frictional region having a particle concentration more than 80 of the packed bed is characterized by nearly continuous grain contacts low strain rate and hampered grain segregation on the other hand the collisional region has a particle concentration between 15 and 80 of the packed bed and is characterized by active grain collisions and higher strain rate deposition from the traction carpets occurs via progressive aggradation of the bed rather than via en masse freezing while the downward grain flux from the overlying flow maintains them the thickness of a traction carpet stratum is therefore determined by the cumulative amount of sediment settled during the lifespan of a traction carpet and can be much larger than the thickness of a moving traction carpet inverse grading can be produced in the collisional region by the vertical gradient of dispersive pressure which is related to nonuniform distribution of particles when a thick frictional region develops however the inverse size distribution in the collisional region is poorly recorded in the deposits depositional features of traction carpet strata are therefore determined by the duration of a traction carpet and the thickness ratio of collisional to frictional regions the thickness ratio is further controlled by the applied shear stress sediment fallout rate and grain size generally a collisional region is better developed beneath a highly competent and coarse grained gravelly flow whereas a thick frictional region is developed beneath a heavily sediment laden fine grained sandy flow this explains the more common occurrence of inverse grading in coarse grained deposits

brachiopods as indicators of original isotopic compositions in some paleozoic limestones the original stable isotopic composition of paleozoic marine carbonate rocks is important to establish a baseline for evaluating diagenetic alteration and providing a reliable data base for modeling exogenic geochemical cycles of the elements we have compared the 18 o and 13 c values in the nonluminescent portions of brachiopods with similar published data of whole brachiopods other whole fossils and estimates of original isotopic composition of marine cements the oxygen and carbon isotopic records for each of these paleozoic components show generally good internal consistency significant discrepancies however were noted between results on the different components isotopic and trace element data presented in this study suggest that permo carboniferous whole brachiopods are little altered chemically nonetheless a more reliable but not fool proof approach for obtaining pristine isotopic values is microsampling of least altered regions based on cathodoluminescence in conjunction with staining techniques and elemental analyses the carbon and oxygen isotopic compositions of all components decrease in 18 o and 13 c in geologically older material neither temporal trend is monotonic however oxygen isotopic results suggest an important positive shift in 18 o of about 2 during the early carboniferous whereas the carbon isotope trend shows a major positive shift 2 3 during the mid carboniferous

geochemistry of brachiopods oxygen and carbon isotopic records of paleozoic oceans abstract combined trace element and isotope studies of 319 brachiopods covering the ordovician to permian time span show that 13c and 18o in well preserved specimens varied during the paleozoic the overall 13c secular trend is in accord with the previously published observations but its details are obscured by vital isotopic fractionation effects at generic level nonetheless the results suggest that the negative correlation between marine 13ccarbonate and 34ssulphate deteriorates at time scales of 106 years due to the long residence time and thus slow response of so42 in the ocean for oxygen isotopes all devonian and older specimens have 18o of 4 while the well preserved permian samples have near present day 18o of about 1 pdb this isotopic dichotomy is probably not due to post depositional phenomena salinity or biogenic fractionation effects this leaves open the perennial arguments for a change in 18 o 16 o of sea water versus warmer ancient oceans the present data are difficult to explain solely by the temperature alternative the coincidence of the proposed shift in 18o with the large late paleozoic changes in marine 87 sr 86 sr 13 c 12 c 34 s 32 s and sea level stands argues for a tectonic cause and for a change in 18 o 16 o of sea water although such explanation is difficult to reconcile with global balance considerations and with isotopic patterns observed in alteration products of ancient basalts and ophiolites whatever the precise cause or combination of causes the implications for tectonism and or paleoclimatology are of first order significance

the oxygen and carbon isotope composition of carboniferous fossil components sea water effects the aragonitic molluscs and lime mud of the pennsylvanian buckhorn asphalt deese group of southern oklahoma precipitated calcium carbonate in oxygen and carbon isotopic equilibrium with ambient sea water in addition 18o values indicate that the pelecypods precipitated their shells during the warmer months of the year the coiled nautiloids probably precipitated their shells in the warm surface water and throughout the year for the orthocone nautiloids the 18o values suggest that they precipitated their shells in deeper cooler water the low mg calcite brachiopods of the mississippian lake valley formation of new mexico precipitated shells in oxygen and carbon isotopic equilibrium with ambient sea water the 18o and 13c values of the buckhorn and lake valley faunas in conjunction with other published results suggest that carboniferous sea water was on a average depleted in 18o by 1 5 2 pdb relative to recent sea water however the 13c value of 2 6 2 pdb for average carboniferous sea water is similar to that of recent ocean water early diagenetic alteration of metastable carbonates probably occurs in a meteoric sea water mixing zone in this zone the oxygen and carbon isotopic compositions of these components are increased by about 2 4 pdb over their marine composition

fluvial architecture variations linked to changes in accommodation space rio chico formation late paleocene golfo san jorge basin argentina abstract the upper paleocene rio chico formation is a 50 180 m thick fluvial succession developed in a passive margin setting golfo san jorge basin central patagonia argentina a detailed description and interpretation of outcrops was carried out analyzing exposures from the northern basin margin to the most complete successions at the southern depocenter the unit is characterized by a regional fluvial system that flowed to the south east five main lithofacies associations were defined i active fluvial channels with three sub types braided meandering and low sinuosity ii sheet flood deposits iii proximal floodplain natural levee and crevasse splay iv distal floodplain and v abandoned channels lateral vertical changes in fluvial architecture of the rio chico formation were recognized by variations in preserved thickness fluvial styles geometry of fluvial channels regional paleoflow directions and channel floodplain ratios close to the northern basin margin the fluvial succession is 50 60 m thick composed of braided channels sheet flow deposits and high channel floodplain ratio in a basinward direction the alluvial succession increases to 180 m in thickness the dominant fluvial styles change to low sinuosity and meandering channels and channel floodplain ratio reduces the fluvial architecture of the rio chico formation shows two main depositional trends that resulted from changes in accommodation space across the basin the interpreted break point coincides with the underlying cretaceous basin boundary thus the synsedimentary extensional reactivation of the pre existing tectonic lineament generated differential subsidence delimiting two different accommodation settings

sr and nd isotopes at the prmian triassic boundary a record of climate change abstract we present a detailed curve of seawater 87sr 86sr for the middle permian to triassic based on analyses of conodonts from overlapping sections in the u s a pakistan correlated using conodont biostratigraphy the isotope ratio decreased in the middle permian at an average rate of 0 000062 ma 1 reached a minimum in the capitanian 257 258 ma and increased in the late permian at an average rate of 0 000097 ma 1 the late permian rate of increase was roughly two and a half times greater than the average increase over the past 40 ma and approximately equal to the highest cenozoic rates which occurred over much shorter time intervals modeling results suggest that decreasing middle permian 87sr 86sr ratios were driven by changes in the riverine sr flux to the oceans while increasing ratios in the late permian triassic are attributed to both increased riverine 87sr 86sr and flux the reduced middle permian riverine flux coincides with extreme continental aridity associated with the formation of pangea and recorded by massive evaporite deposits in addition mountains in the equatorial region of pangea may have created a rain shadow thereby minimizing precipitation in regions that currently contribute the bulk of chemical weathering products to the ocean increasing riverine 87sr 86sr in the late permian is suggested by the observation that 143nd 144nd values decrease at the same time however the source of radiogenic sr is not known frequently cited mechanisms for increasing 87sr 86sr in runoff such as glaciations and continent to continent collisions coincide instead with decreasing seawater 87sr 86sr in the middle permian one possible source may have been deep erosion into older orogens associated with a dramatic increase in chemical weathering in the late permian the cause of enhanced weathering appears to have been increased levels of atmospheric co2 with associated global warming and increased humidity proposed sources of co2 include dissociation of gas hydrates and oxidation of organic matter during extreme sea level regression as well as volcanic emissions from siberian traps eruptions continental floral and faunal distributions are consistent with this interpretation as are oceanic 13c patterns and variations in shallow water sediment lithologies

mineralogy and chemistry of the lower pennsylvanian kendrick fauna eastern kentucky 1 trace elements abstract the original calcite and aragonite mineralogy is preserved for the fauna of the lower pennsylvanian kendrick shale of eastern kentucky the brachiopods secreted low mg calcite shells with 2 mole mgco3 the crinoids and rugose corals secreted intermediate mg calcite endoskeletons and exoskeletons with 5 8 mole mgco3 the average sr content of 1140 ppm for the brachiopods 2140 ppm for the crinoids and 1770 ppm for the rugose corals is in accord with their respective mineralogy the mineralogy of the kendrick crinoids is at variance with that of their holocene counterparts which secrete high mg calcite endoskeletons on the other hand the low to intermediate mg calcite mineralogy for the kendrick rugose corals is in accord with observations for other paleozoic rugose corals but is significantly different from the aragonite and or high mg calcite mineralogy of holocene scleractinians and octocorals the kendrick molluscs cephalopods gastropods and pelecypods secreted aragonite skeletons and shells with mg contents of less than 1000 ppm which is analogous to the mg content of the aragonite skeletons and shells of their holocene counterparts however the average sr content of 4040 ppm for the cephalopods 5210 ppm for the gastropods and 4840 ppm for the pelecypods of the kendrick shale is higher by a factor of 2 over the average sr content of their holocene counterparts intermediate mg calcite with 4 8 mole mgco3 is the dominant carbonate phase of the calcareous shale matrix material of the kendrick shale other carbonates constituting the matrix are sedimentary aragonite and low mg calcite this varied carbonate mixture of the matrix material is not corroborated by elemental analysis which by its very nature cannot define the different carbonate phases of bulk rock samples

mantle plume the invisible serial killer application to the permian triassic boundary mass extinction the earth experienced a severe mass extinction at the permian triassic boundary ptb about 252 million years ago this biological catastrophe was accompanied by major changes in geochemical composition of the atmosphere and ocean and the appearance of sedimentary features which had not occurred since the precambrian time the eruption of the largest continental flood basalt the siberian traps overlapped this mass killing many hypotheses have been proposed but no definitive conclusion currently exits here we present characteristics of three sections from iran and china and propose that an active mantle plume initiated a series of processes which led to the mass mortality and produced major sedimentological mineralogical and geochemical changes observed in the transition from the paleozoic to the mesozoic the injection of mantle plume related igneous dike swarms into the continental margin facilitated the release of massive amounts of ch 4 primarily from the dissociation of marine gas hydrates and secondarily from the maturation of organic rich sediments and fracturing of hydrocarbon reservoirs the bulk of the ch 4 was aerobically oxidized in the water column producing dissolved co 2 with low 13 c values this co 2 saturated seawater became acidic to the point of dissolution of shelf carbonates promoting precipitation of siliciclastic rich strata in the transition from the permian to the triassic methane derived co 2 also lowered carbon isotopic composition of seawater leading to the observed decline in 13 c composition of organic and inorganic marine carbon at the ptb gas charged oceans released large volumes of co 2 and ch 4 into the atmosphere which created a severe global warming the end permian inferno causing the release of additional ch 4 from the dissociation of polar gas hydrates these events lowered 13 c compositions of terrestrial carbon simultaneously feeder dikes from the mantle plume formed the siberian traps flood basalt marine mass extinction was the result of a change in seawater composition due to the injection and oxidation of ch 4 in the water column causing low ph high concentrations of co 2 ca 2 and hco 3 and low co 3 2 values combined with a hot seawater temperature these changes made calcification of marine organisms difficult and produced major physiological crisis including reduced metabolic rates high sensitivity to environmental stress and hampered growth and reproduction terrestrial mass extinction can be attributed to severe global warming and soil acidification produced by increased atmospheric co 2 acid rain that was generated by so 2 derived from the siberian trap eruption and loss of habitat cessation of the plume activity during early triassic stopped the release of ch 4 into the ocean and terminated continental flood basalt eruption ending the environment of death on land and in sea the cut off of co 2 production in the ocean instantly increased carbonate saturation of seawater resulting in extensive seafloor cementation it also resulted in the deposition of marine carbonates by microbial activities in the hostile post extinction environment from the trigger to recovery the perturbation which included the end permian mass mortality could have lasted for at least 2 myr several major mass extinctions of the phanerozoic are temporally accompanied by flood basalt eruptions so far these two events have been interpreted in a cause and effect relation flood basalt eruption causes mass extinction this study proposes that flood basalts and their time correlative biological crises are themselves the consequence of a complex perturbation caused by mantle plume activities if so major disturbances in the near surface of the earth are ultimately controlled by changes in the mantle the physical sedimentological observations presented here combined with previous paleontological evidence cast doubt on other interpretations which use geochemical variables numerical modeling biomarkers and ce anomaly to suggest that late permian ocean was anoxic all the way to the photic zone

growth and demise of permian biogenic chert along northwest pangea evidence for end permian collapse of thermohaline circulation abstract the permian chert event pce was a 30 ma long episode of unusual chert accumulation along the northwest margin of pangea and possibly worldwide the onset of the pce occurred at about the sakmarian artinskian boundary in the sverdrup basin canadian arctic where it coincides with a maximum flooding event the ending of high frequency high amplitude shelf cyclicity the onset of massive biogenic chert deposition in deep water distal areas and a long term shift from warm to cool water carbonate sedimentation in shallow water proximal areas a similar and coeval shift is observed from the barents sea to the northwestern usa a landward and southward expansion of silica factories occurred during the middle and late permian at which time warm water carbonate producers disappeared completely from the northwest margin of pangea biotically impoverished and increasingly narrow cold water carbonate factories characterised by non cemented bioclasts of sponges bryozoans echinoderms and brachiopods were then progressively replaced by silica factories by late permian time little carbonate sediments accumulated in the barents sea and in the sverdrup basin where the deep to shallow water sedimentary spectrum was occupied by siliceous sponge spicules by that time biogenic silica sedimentation was common throughout the world silica factories collapsed in the late permian abruptly bringing the pce to an end in northwest pangea the end permian collapse of the pce was associated with a major transgression and with a return to much warmer oceanic and continental climatic conditions chert deposition resumed in the distal oceanic areas during the early middle triassic anisian after a 8 10 ma interruption early triassic chert gap the conditions necessary for the onset expansion and zenith of the pce were provided by the thermohaline circulation of nutrient rich cold waters along the northwestern and western margin of pangea and possibly throughout the world oceans these conditions provided an efficient transportation mechanism that constantly replenished the supply of silica in the area created a nutrient and oxygen rich environment favouring siliceous biogenic productivity established cold sea floor conditions hindering silica dissolution while increasing calcium carbonate solubility and provided conditions adverse to organic and inorganic carbonate production the northwest margin of pangea was for nearly 30 ma bathed by cold waters presumably derived from the seasonal melting of northern sea ice the assumed engine for thermohaline circulation this process started near the sakmarian artinskian boundary intensified throughout middle and late permian time and ceased suddenly in latest permian time it led to oceanic conditions much colder than normally expected from the palaeolatitudes and the influence of cold northerly derived water was felt as far south southern nevada the demise of silica factories was caused by the rapid breakdown of these conditions and the establishment of a much warmer marine environment accompanied by sluggish circulation and perhaps a reduced input of dissolved silica to the ocean complete thawing of northern sea ice would have ended thermohaline circulation and led to warm and sluggish oceanic conditions inimical to the production accumulation and preservation of biogenic silica

changes in carbon isotope ratios in the late permian recorded in therapsid tooth apatite the end of the permian witnessed global extinctions of marine and terrestrial fauna1 as marine biogenic carbonate and atmospheric carbon dioxide are in long term isotopic equilibrium changes in carbon isotope ratios in marine carbonate strata should record changes that occurred at that time in atmospheric ratios one might then expect a correlation between 13c 12c ratios in such marine sequences and those in terrestrial records that derive from carbon bearing materials that incorporate atmospheric co2 an example of the latter is fossil tooth apatite from herbivorous fauna correlations of this sort between marine and terrestrial records are however difficult to establish as they rely on particular characteristics of the isotope curves here we show that stable carbon isotope ratios in tooth apatite from diictodon a mammal like reptile in the late permian lower beaufort succession of the south african karoo 260 245 myr show a progressive depletion in 13c that is very similar to trends in marine carbonates from late permian deposits in eurasia2 7 these results suggest that global changes in total biomass occurred towards the end of the permian primary production decreased and continental aridity increased8 leading to a depletion of 13c in atmospheric and oceanic co2

reservoir and aquifer characterization of fluvial architectural elements stubensandstein upper triassic southwest germany this paper aims at a quantitative sedimentological and petrophysical characterization of a terminal alluvial plain system exemplified by the stubensandstein south german keuper basin the study follows the outcrop analogue approach where information derived from outcrops is collected in order to enhance interpretation of comparable subsurface successions quantitative data on sandbody geometries porosities and permeabilities are presented in order to constrain modelling of subsurface sandbodies and permeability barriers for sedimentological characterization the method of architectural element analysis miall a d 1996 the geology of fluvial deposits springer berlin was used and modified to include poroperm facies a special photo technique with a precise theodolite survey was developed to create optically corrected photomosaics for outcrop wall maps from up to 20 000 m2 large outcrops nine architectural elements have been classified and quantified bedload mixed load and suspended load channel fills are separated the petrophysical characterization of the architectural elements integrated porosity and permeability measurements of core plugs with gamma ray measurements along representative sections it could be demonstrated that certain architectural elements show a characteristic poroperm facies four scales of sedimentary cycles have been recognized in the stubensandstein cyclic sedimentation causes changing lithofacies patterns within the architectural elements depending on their position in the sedimentary cycle stratigraphic position exerts only some paleogeographic position exerts significant influence on porosity and permeability of the sandbodies the highest poroperm values were found in proximal areas of the alluvial plain and in middle parts within sedimentary macrocycles the strong internal heterogeneity on the alluvial plain system is important for its reservoir and aquifer characteristics compartments of bedload channel sandstones in medial positions of a stratigraphic cycle represent very good reservoirs or aquifers the seals or aquicludes are formed by extensive floodplain claystones lacustrine sediments paleosols and suspended load deposits strongly cemented zones of sandstones represent aquitards

18o16o and 13c12c in lower paleozoic articulate brachiopods implications for the isotopic composition of seawater three hundred and eleven articulate brachiopods with extensive geographic coverage spanning the cambrian to silurian stratigraphic interval were analyzed for oxygen and carbon isotopic composition cambrian samples have 18o 7 ordovician samples 2 4 and silurian samples 1 9 confirming the previously established trend towards lighter isotopic compositions with increasing age throughout the lower paleozoic forty nine best preserved ordovician and silurian samples were identified based on scanning electron microscopy and trace element analysis they were found to bracket the isotopic compositions of over 85 of specimens from these stratigraphic intervals supporting widespread preservation of the isotopic signal some latest ordovician and lower ludlovian samples associated with shale sequences are apparently enriched in 18o these are interpreted as an environmental phenomenon perhaps related to water temperature and glaciation a number of silurian samples of varying genera and stratigraphic levels are highly enriched in 13c up to 6 some are shale related but some are associated with carbonate bearing basins these are also thought to represent near original compositions but a single environmental cause is unknown the present data show that luminescence is not a decisive criterion for evaluating the degree of brachiopod preservation whole shell values were isotopically similar to their nonluminescent portions for both oxygen and carbon

carbon cycle changes of the zechstein sea isotopic transition zone in the marl slate the carbon isotope composition of carbonate rocks is one parameter used to study the carbon sulphur and oxygen cycles through geological time1 2 the understanding of these interrelated cycles is important in quantitative flux modelling of sedimentary rocks the carbon isotope composition in the large reservoir of dissolved carbonate in ocean water is a result of mass balance between the amount of carbon in the reduced organic reservoir and the oxidized carbonate reservoir at any given stage the reduced carbon reservoir preferentially sequesters 12c owing to biological fractionation processes any change in the removal ratio of oxidized reduced carbon will be reflected by the change of the 13c value of the oceanic carbonate system here we present a detailed study of the change in 13c which took place at the base of the upper permian zechstein sequence

relating small scale sedimentary structures and permeability in a cross bedded aquifer summary the objective of this study is to investigate the relation between small scale sedimentary structures and permeability in the brussels sands formation an early middle eocene shallow marine sand deposit in central belgium that constitutes a major groundwater source in the region a field campaign was carried out consisting of field observations of the sedimentary structures and in situ measurements of air permeability the sedimentary structures were interpreted sketched digitally photographed and measured in a representative outcrop additionally a total of 2750 cm scale air permeability measurements were carried out in situ analysis of the spatial distribution of sedimentary structures and permeability shows that clay rich sedimentary features such as bottomsets and distinct mud drapes exhibit a different statistical and geostatistical permeability distribution compared to the other lithofacies in the cross bedded sands spatial analysis of the air permeability data shows that permeability anisotropy in the cross bedded lithofacies is dominated by the foreset lamination orientation these results show that small scale sedimentary heterogeneity strongly influences the local spatial distribution of the hydraulic properties and results in permeability heterogeneity and stratification that would produce anisotropy in upscaled permeability values

isotope signatures associated with early meteoric diagenesis the environments in which carbonate diagenesis proceeds have been documented in previous studies of holocene and late pleistocene sediments and limestones on barbados west indies variations in the carbon and oxygen isotopic composition of limestones produced during early freshwater diagenesis have been observed in this study to occur in specific patterns six potentially useful patterns emerge when one views stable isotope data within a stratigraphic framework 1 the subaerial exposure surface is characterized by strongly 12c enriched limestones 13c compositions of underlying limestones grow progressively heavier with increasing depth 2 the subaerial exposure surface may also be marked by slight 18o enrichment 3 an abrupt shift in 18o values may differentiate sediments above the exposure surface from those below 4 sediments altered in the marine meteoric mixing zone may be characterized by positive covariance between their 18o and 13c compositions 5 the vadose phreatic boundary may be marked by a sharp increase in 13c values in the seaward portions of a fresh groundwater system and 6 samples contemporaneously altered in a single fresh groundwater system within an areally restricted region should display a narrow range of 18o and a wide range of 13c compositions analysis of samples from five palaeozoic and mesozoic formations which contained petrographic evidence of early freshwater diagenesis showed that isotope patterns similar to those observed in barbados limestones have been preserved in rocks as old as mississippian these isotope patterns could prove to be useful for identifying diagenetically induced porosity trends in carbonate rocks they might be used to identify limestones diagenetically altered in meteoric environments to identify mixing zone cements and dolomites and to trace the regional and vertical distributions of early meteoric groundwater systems in ancient carbonate formations

lithological heterogeneity in a back barrier sand island implications for modelling hydrogeological frameworks abstract sediment mineralogy quartz grain surface textures grain size analysis bore hole logging and ground penetrating radar are combined to develop a three dimensional stratigraphic model of a back barrier sand island in southeast queensland australia the island consists of an unconsolidated sedimentary pile above an erosional bounding surface at the top of the underlying bedrock the stratigraphy is complex recording the shift in depositional environments from fluvio deltaic to strandplain via estuarine stages of evolution the back barrier island deposits are correlated with the stratigraphy of the adjacent coastal plain to the west and the barrier island to the east extrapolation of optically stimulated luminescence dates obtained from the barrier island combined with direct dating of the back barrier island sediments is used to constrain the depositional age and chronology of the back barrier island stratigraphy the modern depositional environment evolved from a chenier plain into a barrier island system by the flooding of an interdune swale and development of a shore parallel back barrier tidal lagoon the lithological heterogeneity of the back barrier island succession was controlled by the presence of a bedrock incised palaeovalley and changes in relative sea level sedimentary facies associations constrain the spatial distribution of hydraulic properties controlled by lithological heterogeneity post depositional alteration horizons are integrated with the facies model to account for the effects of weathering and diagenesis on hydraulic behaviour the derived hydrostratigraphy describes a vertically stacked dual aquifer island groundwater system consisting of a semi confined palaeovalley aquifer overlain by an unconfined strand plain aquifer hydrostratigraphic analysis based on sedimentary facies associations integrated with post depositional alteration characteristics reveals great complexity of groundwater systems within small island settings the facies modelling approach employed in this study more accurately estimates the distribution of lithological heterogeneity and the associated variations in hydraulic properties in the sedimentary pile

causes and consequences of extreme permo triassic warming to globally equable climate and relation to the permo triassic extinction and recovery permian waning of the low latitude alleghenian variscan hercynian orogenesis led to a long collisional orogeny gap that cut down the availability of chemically weatherable fresh silicate rock resulting in a high co2 atmosphere and global warming the correspondingly reduced delivery of nutrients to the biosphere caused further increases in co2 and warming melting of polar ice curtailed sinking of o2 and nutrient rich cold brines while pole to equator thermal gradients weakened wind shear and associated wind driven upwelling lessened further diminishing productivity and carbon burial as the earth warmed dry climates expanded to mid latitudes causing latitudinal expansion of the ferrel circulation cell at the expense of the polar cell increased coastal evaporation generated o2 and nutrient deficient warm saline bottom water wsbw and delivered it to a weakly circulating deep ocean warm deep currents delivered ever more heat to high latitudes until polar sinking of cold water was replaced by upwelling wsbw with the loss of polar sinking the ocean was rapidly filled with wsbw that became increasingly anoxic and finally euxinic by the end of the permian rapid incursion of wsbw could have produced 20 m of thermal expansion of the oceans generating the well documented marine transgression that flooded embayments in dry hot pangaean mid latitudes the flooding further increased wsbw production and anoxia and brought that anoxic water onto the shelves release of co2 from the siberian traps and methane from clathrates below the warming ocean bottom sharply enhanced the already strong greenhouse increasingly frequent and powerful cyclonic storms mined upwelling high latitude heat and released it to the atmosphere that heat trapped by overlying clouds of its own making suggests complete breakdown of the dry polar cell resulting rapid and intense polar warming caused or contributed to extinction of the remaining latest permian coal forests that could not migrate any farther poleward because of light limitations loss of water stored by the forests led to aquifer drainage adding another 5 m to the transgression non peat forming vegetation survived at the newly moist poles climate feedback from the coal forest extinction further intensified warmth contributing to delayed biotic recovery that generally did not begin until mid triassic but appears to have resumed first at high latitudes late in the early triassic current quantitative models fail to generate high latitude warmth and so do not produce the chain of events we outline in this paper future quantitative modeling addressing factors such as polar cloudiness increased poleward heat transport by deep water and its upwelling by cyclonic storms and sustainable mid latitude sinking of warm brines to promote anoxia warming and thermal expansion of deep water may more closely simulate conditions indicated by geological and paleontological data

facies controls on the distribution of diagenesis and compaction in fluvial deltaic deposits abstract the upper triassic lower jurassic are formation comprising the deeper reservoir in the heidrun field offshore mid norway consists of fluvial channel sandstones fch floodplain fines ff and sandy and muddy bay fill sediments sbf mbf deposited in an overall transgressive fluvial to lower delta plain regime the formation has been investigated to examine possible sedimentary facies controls on the distribution of cementation and compaction based on petrography and sem micro probe analyses of core samples related to facies associations and key stratigraphic surfaces the most significant authigenic minerals are kaolinite calcite and siderite kaolinite and secondary porosity from dissolution of feldspar and biotite are in particular abundant in the fluvial sandstones the carbonate minerals show complex compositional and micro structural variation of pure siderite sid i mg siderite sid ii fe dolomite ankerite and calcite displaying decreasing fe from early to late diagenetic carbonate cements an early diagenetic origin for siderite and kaolinite is inferred from micro structural relations whereas pore filling calcite and ankerite formed during later diagenesis the fe dolomite probably related to mixing zone dolomitization from increasing marine influences and a regional correlatable calcite cemented layer has been related to a flooding event porosity values in non cemented sandstone samples are generally high in both fch and sbf facies associations averaging 27 differential compaction between sandstone and mudstone has a ratio of up to 1 2 and with lower values for mbf we emphasize the role of eogenetic siderite cementation in reducing compactability in the fine grained coal bearing sediments most prominent in mbf facies this has implications for modeling of differential compaction between sandstone and mudstones deposited in fluvial deltaic environments

permian gondwanaland paleoenvironment inferred from carbon and oxygen isotope records of brachiopod fossils from sydney basin southeast australia abstract the 13 c and 18 o records of permian fossil brachiopods with biostratigraphical age control from southeastern australia have been constructed to investigate the high latitude paleoenvironment of gondwanaland all samples were thin sectioned and examined using petrographic and cathodoluminescence microscopy for evaluating shell preservation elemental compositions of select brachiopod shells were measured using electron probe microanalysis to further evaluate shell preservation within these intervals the average 13 c values of the best preserved non luminescent nl portion of the brachiopod shells are all greater than 5 1 with the highest value 7 0 at lower wandrawandian siltstone late kungurian these carbon isotope values are similar to those of contemporaneous tropical eastern pangea russian platform but heavier than those of western pangea north america the oxygen isotope difference between brachiopods of high southern latitudes and low latitudes fluctuated during early to middle permian the mean 18 o values of the high latitude nl brachiopod shells were more positive than those of the low latitudes in early sakmarian 0 3 early late artinskian 1 1 late kungurian 1 0 roadian 0 2 and wordian 0 7 comparable to those of tropical western pangea in early artinskian 2 1 and early kungurian 2 5 and more negative than those of tropical western pangea in late late artinskian 3 9 assuming the oxygen isotope value for permian seawater in southeast australia was 1 the calculated oxygen isotope temperatures were mostly between 12 c and 16 c reflecting southeast australia s cool high latitude temperature conditions higher apparent oxygen isotope temperatures for the upper pebbly beach formation 29 c late late artinskian berriedale limestone 21 c early artinskian and snapper point formation 22 c early kungurian may be attributed to a combination of warmer climate and lower seawater 18 o in this region

diagenetic history and hydrocarbon potential of upper permian carbonate buildups wegener halvo area jameson land basin east greenland 1 the upper permian of jameson land includes two carbonate sequences the karstryggen and wegener halvo formations the karstryggen formation contains hypersaline carbonates and localized evaporites that were heavily weathered and dissected prior to deposition of the overlying strata the overlying wegener halvo formation represents an abrupt and extensive marine inundation over the underlying karstified karstryggen surface bryozoan brachiopod algal cement buildups of the wegener halvo formation are localized on karstic highs and show up to 150 m of depositional relief in situ mound core deposits are flanked by allodapic limestones which pass laterally into intermound calcareous shales the diagenetic histories of the core and flank facies are very different core facies porosity was intially obliterated by marine cements but repeated meteoric exposure altered unstable core facies constituents this alteration produced extensive secondary porosity through grain and cement leaching with local collapse brecciation flank strata however underwent little sea floor diagenesis and low permeability and mineralogically stable grain composition protected these strata from meteoric alteration early cementation and stabilization of core strata led to minimal burial diagenetic porosity loss uncemented flank beds however underwent profound mechanical and chemical compaction during this stage thus at the time of hydrocarbon generation distal flank beds had less than 2 porosity coarse upper flank beds had 5 10 remnant primary porosity and core facies deposits had 8 12 secondary pore space hydrocarbons generated from surrounding marine shales charged many of the bioherms with oil subsequent fracturing and hydrothermal fluid flow however flushed hydrocarbons and filled pores with ferroan calcite barite fluorite galena and baroque dolomite this heating and flushing is thought to have been especially intense in the wegener halvo region thus more basinal areas may still have reservoirs containing significant oil in equivalent upper permian limestones if as is likely the sea level changes affecting the greenland permian were eustatic then this study may provide significant clues to porosity development throughout the largely unexplored northern zechstein basin and the arctic basin of the barent sea this study also provides some important connections to the probably time equivalent guadalupian carbonate reservoir rocks of west texas new mexico and wyoming

reply to the comment by s t petsch on carbon isotope ratios of phanerozoic marine cements re evaluating global carbon and sulfur systems

the role of diagenesis and depositional facies on pore system evolution in a triassic outcrop analogue se spain abstract this study aims at unravelling the diagenetic history and its effect on the pore system evolution of the triassic redbeds exposed in se spain tibem 1 an outcrop analogue of the tagi trias argilo greseux inferieur reservoir berkine ghadames basin algeria similar climatic base level and tectonic conditions of aforementioned alluvial formations developed analogue fluvial facies stacking patterns furthermore interplay of similar detrital composition and depositional facies in both formations resulted in analogue early diagenetic features petrographic observations indicate lithic subarkosic floodplain facies and subarkosic braidplain facies compositions which are considered suitable frameworks for potential reservoir rocks primary porosity is mainly reduced during early diagenesis through moderate mechanical compaction and formation of k feldspar overgrowth gypsum dolomite and phyllosilicate cements early mesodiagenesis is testified by low chemical compaction and quartz cementation telodiagenetic calcite filling fractures and k feldspar dissolution determined the final configuration of analysed sandstones mercury injection capillary pressure technique reveals overbank deposits in the floodplain as the least suitable potential reservoirs because of their lowest open porosity op k k 95 md and greater thickness and lateral continuity so being considered the best potential reservoir the accurate estimation of tibem microscale attributes can provide important input for appraisal and enhanced oil recovery performance in tagi and in others reservoirs consisting on similar fluvial sandy facies

carbon isotopes as biogeochemical recorders of life over 3 8 ga of earth history evolution of a concept ever since pioneering studies in the late 1930s had shown that the conversion of inorganic carbon into biogenic substances entails sizeable redistributions of the stable carbon isotopes biologically mediated 13c 12c fractionations have come to be recognized as a common corollary of biochemical reactions meanwhile it is firmly established that the universal bias in favour of 12c characterizing biological materials primarily derives from a kinetic isotope effect that is imposed on the first carbon fixing enzymatic carboxylation reaction in the primary metabolism of co2 fixing autotrophic organisms this preference for 12c has turned out to be one of the most enduring relics of the ordered state of the biological precursor substances that may be preserved in fossil organics over billions of years with the currently known sedimentary record at hand it can be stated with confidence that biological carbon isotope fractionations have persisted throughout 3 8 ga of recorded earth history indicating that microbial prokaryotic and archaeoprokaryotic ecosystems had been prolific already on the archean earth while for the time span 3 5 ga the isotopic evidence is unequivocal the information encoded in the preceding record is commonly blurred by a metamorphic overprint this holds particularly for the metasediments of the 3 8 ga old isua supracrustal belt of west greenland which apart from widespread metasomatism have suffered amphibolite grade metamorphism it is known that 13c 12c exchange occurs in organic kerogenous rock constituents during both amphibolite and granulite facies metamorphism if a second carbon partner is available as either fluids or carbonate with isotopic re equilibration often only partially achieved due to the sluggish kinetics of the exchange reaction thermodynamic equilibria predict however that 13c 12c ratios in kerogen and graphite increase during this process hence high t exchange equilibria are always bound to drive 13c values in positive direction the lowermost values encountered being consequently the least exchanged and most pristine with the lowest values of reduced graphitic carbon obtained in early isua studies falling into the range 22 to 28 pdb we had straightforward evidence since the late 1970s that carbon constituents with the isotopic composition of biogenic matter were indeed present in the pre metamorphic isua suite it was therefore by no means surprising that the results of recent isotope work performed on apatite hosted carbonaceous microdomains in isua banded iron formation utilizing advanced techniques of instrumental microanalysis had prompted similar conclusions hence the mainstream of the sedimentary carbon isotope record can be best interpreted as the geochemical manifestation of the isotope discriminating properties of the principal co2 fixing reactions s in biological carbon assimilation suggesting an extreme degree of evolutionary conservatism in the biochemistry of autotrophic carbon fixation as a consequence biological modulation of the geochemical carbon cycle had been established at least 3 8 ga ago having been fully operative by the time of formation of the earth s oldest sediments

relating lithofacies to hydrofacies outcrop based hydrogeological characterisation of quaternary gravel deposits abstract a considerable part of today s drinking water supplies in europe and north america rely on clean groundwater from gravelly valley aquifers of quaternary age the sedimentary architecture the distribution of lithofacies and of architectural elements in such heterogeneous deposits are of fundamental importance for the analysis of groundwater flow and contaminant transport as the aquifers are not directly accessible for observation representative outcrop analogues were used to study the sedimentology on a local scale conventional sedimentological classification schemes were adapted for the purpose of hydrogeological evaluations measurements of hydraulic properties were then used to define a set of 5 hydrofacies from 23 possible sediment lithofacies a digital photographic mapping procedure was developed to allow fast data acquisition in the field the sedimentologically interpreted outcrops were stored in a gis style database and thus allow the output for further sedimentological or hydrogeological analysis

barrier island aggradation via inlet migration mustang island texas abstract after establishing its present location around 9 5 ka mustang island aggraded stacking over 20 m of barrier island sand in the same location throughout mustang island s history tidal inlets shifted within nearly the same location from 7 5 ka to the present leaving 10 15 m thick deposits of clean well sorted quartz sand deposited within only a few centuries these deposits lack some of the sedimentary features normally associated with tidal inlets such as tidal couplets and shell hash the lack of such features is attributed to the uniform nature of the deposits cut by the inlets during the island s relatively long period of aggradation mustang island was able to maintain an aggradation character throughout most of the holocene due to the sediment eroded from three sources pleistocene headlands the transgressive colorado river delta of texas and the ois 3 shoreline of the central texas shelf each of these sources was exposed to waves and accompanying longshore drift during the island s early history when sea level rose quickly but was flooded or capped by transgressive muds by the time sea level rise slowed during the middle holocene

environmental and physiological influences on isotopic and elemental compositions of brachiopod shell calcite implications for the isotopic evolution of paleozoic oceans abstract brachiopods from the demissa bed middle devonian hamilton group biologically regulated the incorporation of mg sr and na into their shell calcite significant taxonomic differences in the elemental contents of three species athyris spiriferoides mediospirifer audacula and mucrospirifer mucronatus may be related to differences in calcification processes in contrast no significant difference or vital effects were observed between the isotopic values of mediospirifer audacula and athyris spiriferoides from erie 18o 0 03 p 0 949 13c 0 76 p 0 083 and genessee counties 18o 0 39 p 0 471 13c 0 06 p 0 854 this suggests that these brachiopods did not exert a biological control over their isotopic compositions and that their shell calcites reflect ambient physicochemical conditions isotopic compositions in unaltered shell calcites of brachiopods from genessee county which was close to the basin depocentre are heavy for carbon 13c x 5 01 pdb and oxygen 18o x 2 85 pdb compared to the species sampled at the basin s edge erie county 13c x 2 79 pdb 18o x 3 83 pdb there is a significant separation in isotopic values between the deeper and shallower water brachiopods of the basin 18o 0 98 p 0 0005 13c 2 22 p 0 0005 the 18o variation suggests a temperature salinity change with water depth whereas the change in 13c composition probably records an enrichment depletion of organic matter with water depth this observation has significant implications for paleozoic ocean isotopic evolution studies because many global changes in marine 18o and 13c are based on isotopic shifts of similar magnitude