multi scale characterisation of coastal sand aquifer media for contaminant transport using x ray computed tomography to be able to predict contaminant transport in groundwater an accurate conceptual and physical understanding of aquifer properties at multiple scales is required in this study physical and hydraulic properties of a coastal sand aquifer were derived using micro and macro x ray computed tomography xct techniques qualitative and quantitative data improved conceptualisation of the aquifer structure at micro and macro scale at the macro scale 50 mm diameter by 1 500 mm long core xct images of undisturbed drill core identified coarse grained laminae not obvious to the naked eye of increased porosity and permeability variations in mineral assemblage and particulate organic matter distribution within the core micro xct analysis 16 mm diameter cores of the three main aquifer layers provided quantitative micro scale data on permeability porosity grain pore and throat size distribution statistics and grain sphericity ratios of mean pore to grain diameter were 0 65 0 75 and ratios of mean throat to mean grain diameter were 0 2 multiple permeability and porosity values were derived from micro domains 4 35 mm3 within each micro xct core permeability values varied between and within micro xct core samples reflecting the heterogeneity at the millimetre core scale in these sediments sphericity values were similar for all three layers average 0 4 which reflected sem observations of the semi spherical nature of the dominant quartz and feldspar grains the results of this study indicate that models based on the assumptions of homogeneity in depositional structure below centimetre scale may not suitably address factors affecting flow and transport of contaminants

data resolution matrix and model resolution matrix for rayleigh wave inversion using a damped least squares method inversion of multimode surface wave data is of increasing interest in the near surface geophysics community for a given near surface geophysical problem it is essential to understand how well the data calculated according to a layered earth model might match the observed data a data resolution matrix is a function of the data kernel determined by a geophysical model and a priori information applied to the problem not the data a data resolution matrix of high frequency 2 hz rayleigh wave phase velocities therefore offers a quantitative tool for designing field surveys and predicting the match between calculated and observed data we employed a data resolution matrix to select data that would be well predicted and we find that there are advantages of incorporating higher modes in inversion the resulting discussion using the data resolution matrix provides insight into the process of inverting rayleigh wave phase velocities with higher mode data to estimate s wave velocity structure discussion also suggested that each near surface geophysical target can only be resolved using rayleigh wave phase velocities within specific frequency ranges and higher mode data are normally more accurately predicted than fundamental mode data because of restrictions on the data kernel for the inversion system we used synthetic and real world examples to demonstrate that selected data with the data resolution matrix can provide better inversion results and to explain with the data resolution matrix why incorporating higher mode data in inversion can provide better results we also calculated model resolution matrices in these examples to show the potential of increasing model resolution with selected surface wave data

forcing mechanisms for mid cretaceous black shale formation evidence from the upper aptian and lower albian of the vocontian basin se france calcareous nannoplankton palynomorph benthic foraminifera and oxygen isotope records from the supraregionally distributed niveau paquier early albian age oceanic anoxic event 1b and regionally distributed niveau kilian late aptian age black shales in the vocontian basin se france exhibit variations that reflect paleoclimatic and paleoceanographic changes in the mid cretaceous low latitudes to quantify surface water productivity and temperature changes nutrient and temperature indices based on calcareous nannofossils were developed the nutrient index strongly varies in the precessional band whereas variations of the temperature index reflect eccentricity since polar ice caps were not present during the mid cretaceous these variations probably result from feedback mechanisms within a monsoonal climate system of the mid cretaceous low latitudes involving warm humid and cool dry cycles a model is proposed that explains the formation of mid cretaceous black shales through monsoonally driven changes in temperature and evaporation precipitation patterns the lower albian niveau paquier which has a supraregional distribution formed under extremely warm and humid conditions when monsoonal intensity was strongest bottom water ventilation in the vocontian basin was diminished probably due to increased precipitation and reduced evaporation in regions of deep water formation at low latitudes surface water productivity in the vocontian basin was controlled by the strength of monsoonal winds the upper aptian niveau kilian which has a regional distribution only formed under a less warm and humid climate than the niveau paquier low latitude deep water formation was reduced to a lesser extent and or on regional scale only the threshold for the formation of a supraregional black shale was not reached the intensity of increases in temperature and humidity controlled whether black shales developed on a regional or supraregional scale at least in the vocontian basin the increased preservation of organic matter at the sea floor was more significant in black shale formation than the role of enhanced productivity

high resolution carbon isotope records of the aptian to lower albian from se france and the mazagan plateau dsdp site 545 a stratigraphic tool for paleoceanographic and paleobiologic reconstruction high resolution carbon isotope stratigraphy is established for the aptian to lower albian of the vocontian basin se france and correlated to the carbon isotope record of the mazagan plateau dsdp site 545 the carbon isotope stratigraphy of the vocontian basin is proposed as a standard reference curve for the aptian to lower albian due to the completeness and high temporal resolution of the stratigraphic succession the good biostratigraphical time control and the frequent occurrence of regional to global black shale horizons including oceanic anoxic events 1a oae 1a of the lower aptian and oae 1b of the lower albian the carbon isotope record appears better suited for long distance short term correlation of different marine and terrestrial environments than biostratigraphy because of the synchroneity of carbon isotope signals in a range of sediment types however the combination of both biostratigraphy and carbon isotope stratigraphy provides an effective tool to reconstruct biotic change and paleoceanography and to correlate regional to global black shale horizons in different marine environments this combined approach allows us to ascertain the synchroneities or diachroneities of first and last appearances of biostratigraphic marker species based on the demonstrated diachroneity of important biostratigraphic markers of the aptian albian boundary the globally observed break point between the end of the uppermost aptian positive carbon isotope excursion and the onset of the pronounced negative shift of 13c values is an alternative criterion the distinctive structure and amplitudes of the carbon isotope record are observed in both the inorganic and organic carbon and can therefore be recognized in all marine and terrestrial environments of the aptian to lower albian

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

laterally constrained inversion of ground roll from seismic reflection records seismic reflection data contain surface waves that can be processed and interpreted to supply shear wave velocity models along seismic reflection lines the coverage of seismic reflection data allows the use of automated multifold processing to extract high quality dispersion curves and experimental uncertainties in a moving spatial window the dispersion curves are then inverted using a deterministic laterally constrained inversion to obtain a pseudo 2d model of the shear wave velocity a monte carlo global search inversion algorithm optimizes the parameterization when the strategy is used with synthetic and field data consistent final models with smooth lateral variations are successfully retrieved this method constitutes an improvement over the individual inversion of single dispersion curves

late cretaceous carbon isotope stratigraphy in europe correlation and relations with sea level and sediment stability abstract upper cretaceous upper cenomanian to lower coniacian stable carbon isotope stratigraphy of german hemipelagic marls borehole dresden blasewitz pelagic carbonates quarries salzgitter salder and sohlde and of two turonian to santonian pelagic sections in the northern alpine helvetic zone supplemented by published carbon isotope data kent southern england gubbio italy are used for correlations of northern temperate boreal and tethyan sections general carbon isotopic trends are different in pelagic and hemipelagic carbonates probably in response to the input of terrestrial organic carbon to the inner shelf carbon reservoir including sediments the global component in the carbon isotope stratigraphy is best recorded in pelagic carbonates sufficient biostratigraphic control is present to correlate all sections across facies boundaries and between the two biogeographic provinces hiatuses produce breaks in the gradual carbon isotopic trends and their duration can be estimated relative to complete sections a broad 13c minimum straddles the turonian coniacian boundary at the proposed boundary stratotype salzgitter salder with its center about 0 5 1 m below the biostratigraphic reference level first occurrence of c rotundatus fiege sensu troger non fiege increases and maxima of pelagic 13c values occur during phases of sediment accumulation decreasing pelagic 13c values and minima characterise phases of sediment erosion the amplitudes of these stratigraphic fluctuations may indicate the intensity of sediment reworking changes in the sediment accumulation erosion ratio and accompanied carbon isotopic variation may be related to short term sea level fluctuations and their effect on fine grained sediment stability

late quaternary paleoproductivity and deep water circulation in the eastern south atlantic ocean evidence from benthic foraminifera abstract two late quaternary sediment cores from the northern cape basin in the eastern south atlantic ocean were analyzed for their benthic foraminiferal content and benthic stable carbon isotope composition the locations of the cores were selected such that both of them presently are bathed by north atlantic deep water nadw and past changes in deep water circulation should be recorded simultaneously at both locations however the areas are different in terms of primary production one core was recovered from the nutrient depleted walvis ridge area whereas the other one is from the continental slope just below the coastal upwelling mixing area where present day organic matter fluxes are shown to be moderately high recent data served as the basis for the interpretation of the late quaternary faunal fluctuations and the paleoceanographic reconstruction during the last 450 000 years nadw flux into the eastern south atlantic ocean has been restricted to interglacial periods with the strongest dominance of a nadw driven deep water circulation during interglacial stages 1 9 and 11 at the continental margin high productivity faunas and very low epibenthic 13c values indicate enhanced fluxes of organic matter during glacial periods this can be attributed to a glacial increase and lateral extension of coastal upwelling the long term glacial interglacial paleoproductivity cycles are superimposed by high frequency variations with a period of about 23 000 yr enhanced productivity in surface waters above the walvis ridge far from the coast is indicated during glacial stages 8 10 and 12 during these periods cold nutrient rich filaments from the mixing area were probably driven as far as to the southeastern flank of the walvis ridge

benthic foraminiferal response to variations in surface water productivity and oxygenation in the northern arabian sea abstract a benthic foraminiferal record of 120 000 year obtained from the base of the oxygen minimum zone omz at a site in the northern arabian sea was studied quantitative benthic foraminiferal data were compared with palaeoproductivity indices corg and globigerina bulloides and indices for bottom water oxygen concentration pteropod preservation index mo al v al and mn al the benthic foraminiferal record revealed two distinct assemblages that show variations in the precession frequency band a high diversity low equitability assemblage proliferates in isotopic stages 1 4 and 5 and has been interpreted to reflect relatively oxygenated bottom water conditions this assemblage shows a strong covariance with minima in summer monsoon productivity a low diversity low equitability fauna typically with a few species showing high dominances is considered to reflect low bottom water oxygen conditions related to eutrophic surface water conditions dominating species in this assemblage are bolivinids buliminids and globobuliminids this assemblage dominates during precession driven maxima in summer surface water productivity and also during isotopic stages 2 and 3 we suggest that an intensified and colder glacial winter ne monsoon led to increased winter production which superimposed on the precession driven changes in surface water productivity resulted in overall poorly oxygenated bottom water during glacial stages 2 and 3 a promising proxy for tracing winter productivity in the northern arabian sea is the planktonic foraminifer globigerina falconensis the benthic foraminiferal species rotaliatinopsis seminvoluta in particular is prolific under glacial conditions

cretaceous oceanic anoxic events and radially elongated chambered planktonic foraminifera paleoecological and paleoceanographic implications chamber elongation is a recurring morphological character in cretaceous and cenozoic planktonic foraminiferal evolution suggesting that the clavate body plan takes advantage through particular environmental conditions cretaceous planktonic foraminifera bearing radially elongated chambers become repeatedly a consistent component of assemblages in correspondence with the deposition of remarkable organic layers that record the effects of oceanic anoxic events oaes due to this apparent correspondence chamber elongation has been recently interpreted as an adaptation to low oxygen levels in the upper water column the paleoceanographic significance of planktonic foraminifera with radially elongated chambers remains however unclear we investigated in great detail the distribution and abundance of elongated chambered planktonic foraminifera in an interval of about 40 myr across the cretaceous oaes in different well dated sections the increased abundance of planktonic foraminifera with elongated chambers can be a markedly evident feature across the faraoni the selli and the bonarelli oaes however each event shows its own peculiarities remarkably the first radiation of the cretaceous elongated chambered morphotypes just predates the latest hauterivian faraoni event the selli event records the greatest diversification number of species of the group bearing elongated chambers however this was a period of great diversification in the planktonic foraminifera this evidence may suggest that radiation of these forms was driven by more than upper water column anoxia per se e g increased upper water column stratification greater productivity and or greater seasonality the albian oae1b oae1c and oae1d display the lowest abundance and diversity of this group conversely according to the available data the first appearances of the species muricohedbergella simplex and of the genus schackoina occur close to the oae1b and oae1d respectively in the italian record the relative abundance of radially elongated chambered forms appears to be larger before the onset of the bonarelli event with respect to the selli event the pattern involving this group across the bonarelli event appears more regular thus indicating that the onset and the end of the oae2 depend on very powerful global factors and are less influenced by local aspects we speculate that the relative abundance of planktonic foraminifera with radially elongated chambers may be proportional to the strength of the environmental perturbation related to the oaes thus reinforcing the idea that the ecological perturbation related to the oae2 was more severe for the former several lines of evidence suggest that water oxygenation could not have been the single controlling factor governing the development of elongate chambers the role of availability of food and the nature of food has been so far probably underestimated it is most likely that an interplay of several influential physical chemical and ecological factors i e dissolved oxygen concentration temperature salinity nutrients type of food trace elements was responsible for such a morphological adaptation we document linkages between the distribution abundance morphometric changes and evolution of the cretaceous radially elongated chambered planktonic foraminifera and the major igneous geological geochemical climate nutrification and biotic events and biocalcification trends

colloid deposition on non ideal porous media the influences of collector shape and roughness on the single collector efficiency 1 the transport of groundwater colloids e g bacteria viruses clay particles is governed in part by the rate at which the colloids strike and adhere to aquifer mineral grains we report results of coupled flow and transport simulations that reveal how changes in mineral grain shape and surface roughness influence the single collector contact efficiency t a parameter of colloid filtration theory that quantifies the frequency of colloid collisions with the surface of a mineral grain collector our analyses indicate that the sensitivity of t to variations in collector shape and roughness depends on colloid size and suggests that quantitative descriptions of colloid transport through real aquifers will in some cases require nontraditional approaches that are not limited by the simplifying assumptions of smooth spherical collectors

a review of seismic geophysical testing in iran for building near surface velocity models abstract it has long been understood that the near surface structure of the earth affects several aspects of civil engineering practice particularly in seismic applications therefore the implementation of a competent subsurface exploration program not only addresses the need for comprehensive site characterization but also reduces the devastating consequences of seismic activities typical geotechnical practice for subsurface exploration has often relied on a combination of drilling in situ testing such as standard penetration testing and cone penetration testing and laboratory testing of field samples however geophysical techniques have been developed over the years to evaluate near surface velocity models as a proxy for subsurface stiffness in seismic applications in this regard seismic geophysical methods such as refraction reflection downhole and crosshole testing spectral analysis of surface waves sasw and multichannel analysis of surface waves masw have continued to receive increase

effect of precessional insolation changes on cretaceous climate and cyclic sedimentation the often striking presence of cyclical beddings has frequently been noted in cretaceous marine sediment deposits in many instances these beddings appear to have periodicities similar to those of the earth s orbit i e its precession obliquity and eccentricity variations in the primary deposition of ocean sediments are strongly linked to atmosphere land ocean interactions we report a set of numerical experiments using an atmospheric general circulation model that are designed to examine the sensitivity of mid cretaceous climate to insolation changes due to the precessional cycle we restrict attention to a single orbital parameter because most limestone black shale bedded sequences were deposited at low latitudes where precessional insolation variations predominate we varied systematically the precessional index between the maximum positive and negative values calculated over the last 2 m y and used mid cretaceous paleogeographic and paleotopographic reconstructions and zonally symmetric sea surface temperatures based on earlier work by barron and washington surface wetness and albedo values appropriate for grassland were prescribed uniformly over all land regions to capture the seasonality of precession we employed both perpetual january and perpetual july simulations changes in surface heating due to the imposed insolation anomalies resulted in a strong basically linear response of monsoonal circulations dominated by changes over the northern hemisphere the hydrologic cycle shows a significant response over many regions the low latitude proto south atlantic region varies from a strong net sink for water vapor excess precipitation to a strong source excess evaporation over the precession cycle this variation is consistent with an alternation between a stagnant stratified ocean basin with anoxic bottom water and an evaporative basin that produces bottom water that is warm saline and oxygenated the portion of the tethys ocean that overlays the limestone black shale sequences now found in present day italy does not exhibit comparable behavior but the reconstruction of orography and basin boundaries in this region is less known the simulations show however that as the monsoonal flow over south proto asia intensifies water vapor evaporated in this part of tethys is prevented from crossing the proto alps into the interior of the continent thereby remaining in the tethian drainage basin as a result central proto asia shifts between arid and moist conditions with precessional variations the water vapor budget over northeast africa varies systematically from zero seasonality to a marked wet dry seasonal cycle the deposition of eolian material can be inferred from a combination of continental aridity favorable mean wind directions and significant wind variances in our experiments the mean surface and upper winds often show a systematic response to precession but surface wind variances show a systematic response only in isolated regions our simulations do not provide a simple mechanism to explain the cyclicity in eolian deposition that has been reported for north central tethys

morphometric response of late aptian planktonic foraminiferal communities to environmental changes a case study of paraticinella rohri at poggio le guaine central italy abstract the aptian albian boundary interval represents a pivotal time of pronounced climate ocean changes associated with oceanic anoxic event 1b oae 1b that seriously influenced marine pelagic ecosystems the sedimentary successions record the first and most significant species turnover in the evolutionary history of planktonic foraminifera consisting of the selective extinction disappearance of large aptian species and resulting in inter specific size reduction the post extinction dwarfing as in the lilliput effect in the earliest albian assemblages in this study we investigate how the planktonic foraminifera respond to crucial environmental stress and if any intra specific decrease in test size predate the extinction pre extinction dwarfing paraticinella rohri was chosen as the most representative of the aptian planktonic foraminiferal taxa and its test size evolution was compared with the high resolution record of redox and productivity geochemical proxies through the uppermost aptian lowermost albian pelagic succession of poggio le guaine central italy our geochemical data document long term fluctuations characteristic of a system with transitions among different states oligotrophic mesotrophic eutrophic and oxic dysoxic anoxic the strong correlation of the large test size changes of pa rohri during its total range with higher productivity increased baexcess concentrations suggests that the trophic regime was the key factor controlling robust abundance and size variability in this taxon the progressive increase in surface water fertility during the late aptian offered optimum ecological conditions for planktonic foraminifera that increased in abundance size and specific diversity after the transient anoxic 113 jacob sub event smaller to dwarfed specimens of pa rohri and depauperate planktonic foraminifera assemblages faced high selective pressures due to more oligotrophic conditions transition to a more eutrophic ocean in the latest aptian irreversibly eroded their resilience and aptian dwarfed k strategist taxa became extinct the planktonic foraminifera turnover has been therefore the result of an irreversible and drastic regime shift toward a more eutrophic ecosystem that promoted the thriving of small sized opportunistic disaster planktonic foraminiferal species and the siliceous radiolaria

three hundred eighty thousand year long stable isotope and faunal records from the red sea influence of global sea level change on hydrography stable isotope and faunal records from the central red sea show high amplitude oscillations for the past 380 000 years positive 18o anomalies indicate periods of significant salt buildup during periods of lowered sea level when water mass exchange with the arabian sea was reduced due to a reduced geometry of the bab el mandeb strait salinities as high as 53 and 55 are inferred from pteropod and benthic foraminifera 18o respectively for the last glacial maximum during this period all planktonic foraminifera vanished from this part of the red sea environmental conditions improved rapidly after 13 ka as salinities decreased due to rising sea level the foraminiferal fauna started to reappear and was fully reestablished between 9 ka and 8 ka spectral analysis of the planktonic 18o record documents highest variance in the orbital eccentricity obliquity and precession bands indicating a dominant influence of climatically driven sea level change on environmental conditions in the red sea variance in the precession band is enhanced compared to the global mean marine climate record specmap suggesting an additional influence of the indian monsoon system on red sea climates

carbon and oxygen isotope stratigraphy of the early cretaceous carbonate platform of pădurea craiului apuseni mountains romania a chemostratigraphic correlation and paleoenvironmental tool abstract stable c and o isotope records were obtained from carbonate rocks spanning the hauterivian to cenomanian interval collected in several sections from the carbonate platform of p durea craiului apuseni mountains romania in the absence of some key biostratigraphic marker species stable isotopes were applied as a tool for stratigraphic correlation and dating the composite 13c and 18o curves for the early cretaceous shows variable conditions with large positive and negative excursions and provide information on past environmental changes the hauterivian and the barremian limestones blid formation display lower 13c values 2 8 to 2 9 relative to the aptian albian deposits 2 6 to 5 4 ecleja valea m gurii and v rciorog formations the red detrital formation albian cenomanian is characterized by a highly variable distribution of the 13c values 3 5 to 3 9 based on the similarities between the c isotope curve established in p durea craiului and from other sections in the tethyan and the pacific regions two major oceanic anoxic events characterized by 13c positive excursions were clearly recognized the first is the oae1a event early aptian in the upper part of the ecleja formation and the valea m gurii formation the second is the oae1b event late aptian albian in the upper part of the v rciorog formation and in the subpiatr member the position of the aptian albian boundary is estimated to be at the upper part of the v rciorog formation immediately after the beginning of the 13c positive excursion the 13c data show major negative excursions during the barremian blid formation early aptian ecleja formation and late aptian v rciorog formation the o isotope variation pattern 10 2 to 2 1 is consistent with progressively warming temperatures during the early barremian followed by a cooling period a subsequent warming period culminated in the early aptian a significant cooling phase corresponds to the late aptian and early albian and the climate cooled again during the late albian and into the early cenomanian stage the data provide a better understanding of the early cretaceous sedimentation cycles in p durea craiului and create a more reliable framework for regional correlations

mid cretaceous oceanic anoxic events in the pacific ocean revealed by carbon isotope stratigraphy of the calera limestone california usa the paleoceanographic history of the pacific ocean during the mid cretaceous is poorly constrained due to the loss of much of the contemporaneous pacific seafloor to subduction and difficulties in recovering chert rich sediments by ocean drilling pelagic sediments that were originally deposited in the pacific ocean but that have been subsequently accreted during subduction potentially provide an alternative paleoceanographic archive this study presents micropaleontological and carbon isotope data from the calera limestone part of the classic franciscan complex exposed in permanente quarry central california usa in the three stratigraphic sections studied pelagic limestones with low organic carbon contents are the dominant lithology however two stratigraphic intervals are recognized that contain organic carbon and these date to the early aptian and late albian early cenomanian these time intervals correspond to two mid cretaceous oceanic anoxic events oaes early aptian oae1a equivalent to the selli level and late albian oae1d equivalent to the breistroffer event it is well established that both of these events were associated with significant carbon isotope excursions which are also shown to exist in the calera limestone the record of oae1a from the calera limestone complements ocean drilling records by providing further evidence for variability in the sedimentary and stratigraphic record of this event the carbon isotope data from the late albian early cenomanian provide the first detailed chemobiostratigraphic record of this period for the pacific ocean confirming that environmental change occurred at this time in the pacific possibly related to oae1d

paleoenvironmental changes across the mid cenomanian event in the tropical atlantic ocean demerara rise odp leg 207 inferred from benthic foraminiferal assemblages abstract this study is based on cenomanian sediments of ocean drilling program odp sites 1258 and 1260 from demerara rise leg 207 western tropical atlantic off suriname 1000 and 500 m paleo water depth respectively studied sediments consist of laminated black shales with toc values between 3 and 18 and include the mid cenomanian event mce a positive carbon isotope excursion predating the well known oceanic anoxic event 2 oae 2 benthic foraminiferal assemblages of the continuously eutrophic environment at demerara rise are characterized by low diversities 9 species per sample and large fluctuations in abundances indicating oxygen depletion and varying organic matter fluxes dominant species at both sites are bolivina anambra gabonita levis gavelinella dakotensis neobulimina albertensis praebulimina prolixa and tappanina cf laciniosa benthic foraminiferal assemblages across the mce show a threefold pattern 1 stable ecological conditions below the mce interval indicated by relatively high oxygenation and fluctuating organic matter flux 2 decreasing oxygenation and or higher organic matter flux during the mce with decreasing benthic foraminiferal numbers and diversities site 1258 and a dominance of opportunistic species site 1260 and 3 anoxic to slightly dysoxic bottom water conditions above the mce as indicated by very low diversities and abundances or even the absence of benthic foraminifera slightly dysoxic conditions prevailed until oae 2 at demerara rise a comparison with other atlantic ocean and tethyan sections indicates that the mce reflects a paleoceanographic turning point towards lower bottom water oxygenation at least in the proto north atlantic ocean and in the tethyan and boreal realms this general trend towards lower oxygenation of bottom waters across the mce is accompanied by ongoing climate warming in combination with rising sea level and the development of vast shallow epicontinental seas during the middle and late cenomanian these changes are proposed to have favoured the formation of warm and saline waters that may have contributed to intermediate and deep water masses at least in the restricted proto north atlantic and tethyan ocean basins poor oxygenation of the late cenomanian sediments and the changes in benthic foraminiferal assemblages across the mce

paleo oxygenation in tertiary epeiric seas evidence from dinoflagellate cysts the dinoflagellate cyst record from an epeiric setting in the oligocene of southwest germany exhibits major changes associated with variations in paleo oxygenation inferred from benthic foraminifera dinoflagellate cyst diversity and equitability strongly decline in the case of extreme oxygen depletion the relative abundance of the dinoflagellate cyst thalassiphora pelagica inversely correlates with the availability of benthic oxygen the t pelagica spectrum consists of different morphotypes which are considered to represent different stages within the cystal part of the t pelagica life cycle following the concept of benedek and gocht the distribution of these morphotypes is also linked to oxygen availability horizons with highest t pelagica abundances are characterized by the occurrence of t pelagica specimens representing an early stage in cyst formation a model is proposed that uses t pelagica as a proxy to assess oxygenation both at the sediment surface and in the water column the occurrence of t pelagica specimens representing an early stage in cyst formation is interpreted to reflect the extension of oxygen depletion upwards into the water column because t pelagica is an easily recognized globally distributed element of paleogene and early neogene dinoflagellate cyst assemblages the application of this model may be of importance in the reconstruction of paleo oxygenation in epeiric settings from these times its sensitivity to changes in benthic oxygenation can be as high as if not higher than that of the approach based on foraminifera moreover it is applicable to decalcified sediments

evolution patterns of radiolaria and organic matter variations a new approach to identify sea level changes in mid cretaceous pelagic environments the relation between sea level changes plankton productivity and evolution as well as the occurrence of anoxic sediments provides an interesting avenue of paleooceanographic research in this context we examined mid cretaceous radiolarian faunas carbonate isotopic and organic matter type data of deep sea drilling project and ocean drilling program cores from the north atlantic and samples from outcrops of the western tethys from central and northern italy former studies indicate that an expansion of the oxygen minimum zone caused plankton extinctions at the cenomanian turonian boundary an expanded oxygen minimum zone would destroy deeper habitats of planktic foraminifera causing the extinction of deeper dwelling forms although this model is well established for the cenomanian turonian boundary not much is known about the causes of extinctions and radiations during the entire mid cretaceous aptian turonian we demonstrate that the dimension of the oxygen minimum zone which depends on the relative sea level and the corresponding nutrient supply causes the complex pattern of evolution and radiation of planktic protozoa and the sedimentation of black shales in the mid cretaceous this new depositional model allows correlation of micropaleontologic data and different types of black shales in the pelagic realm within a sequence stratigraphic framework

formation of the late aptian niveau fallot black shales in the vocontian basin se france evidence from foraminifera palynomorphs and stable isotopes abstract we present paleoceanographic models for the formation of the marlstone facies and the most prominent black shale intervals of the late aptian niveau fallot black shale succession from the vocontian basin se france in the lower part of the succession the composition of benthic foraminiferal assemblages of the niveau fallot 2 and 2 black shales suggests an enhanced burial of organic matter due to more eutrophic conditions and resulting low oxygen conditions at the seafloor in the upper part of the succession including niveau fallot 3 and 4 a third order sea level fall indicated by a decrease in the stable carbon isotope values may have resulted in a reduced water mass exchange between the vocontian basin and the western tethyan ocean this may have led to dysoxic conditions at the seafloor of the vocontian basin and may have favored the formation of organic rich sediments as shown by benthic foraminiferal assemblages decreased evaporation however is proposed as the most important mechanism causing a restriction of deep water formation within the basin which finally led to the formation of the niveau fallot 3 and 4 black shales based on our investigations the formation of the niveau fallot black shales was caused by different factors the most prominent ones include sea level fluctuations increasing productivity and changes in precipitation and evaporation rates furthermore niveau fallot 3 can probably be correlated with the thalmann black shale event in california and a dark horizon at the mazagan plateau dsdp site 545

changes in southern ocean bottom water environments associated with the middle eocene climatic optimum meco abstract the middle eocene climatic optimum meco was a 650 kyr long interval of pronounced warmth superimposed on the long term eocene cooling trend we investigate benthic foraminiferal assemblage and fossil fish tooth cerium anomaly variability from ocean drilling program odp site 738 in the indian sector of the southern ocean southern kerguelen plateau to assess changes in bottom water chemistry and effects on benthic foraminiferal ecosystems the studied section spans 41 9 to 38 4 ma encompassing the meco as well as extensive pre meco and post meco intervals we report a marked faunal turnover at 40 4 ma 200 kyrs after the onset of the meco at 40 6 ma from an assemblage dominated by epifaunal benthic foraminifera to an infaunal dominated assemblage the infaunal domination persisted until the termination of the meco at 39 95 ma thereafter the pre meco assemblage returned this change is attributed to an increase in export productivity associated with the warming possibly caused by an increase in continental runoff or the influence of a more eutrophic surface water mass superimposed on the change in tropic state the ce ce record shows a positive excursion during the 100 kyrs long meco peak warming at around 40 05 ma indicative of a decrease in bottom water oxygen content synchronously infaunal benthic foraminifera drop briefly in abundance hence we suggest that the peak warming is associated with bottom water oxygen depletion potentially caused by elevated productivity and or a transient influence of an older oxygen depleted water mass

middle late cretaceous climate of the southern high latitudes stable isotopic evidence for minimal equator to pole thermal gradients a detailed 18 o and 13 c stratigraphy has been generated from analysis of well preserved albian early maastrichtian foraminifera from deep sea drilling project dsdp sites 511 and 327 falkland plateau 58 s 62 s paleolatitude in the southern south atlantic and cenomanian and coniacian santonian foraminifera from dsdp site 258 naturaliste plateau 58 s paleolatitude in the southern indian ocean these results when combined with previously published maastrichtian stable isotope data from ocean drilling program odp site 690 weddell sea 65 s paleolatitude provide new insight into the climatic and oceanographic history of the southern high latitudes during middle late cretaceous time the planktonic foraminifer 18 o curves reveal a gradual warming of surface waters from the albian through the cenomanian followed by extremely warm surface waters from the turonian through the early campanian long term cooling of surface waters began in the late early campanian and continued through the end of the maastrichtian the benthic foraminifer 18 o record generally parallels changes in the oxygen isotopic curves defined by shallow dwelling planktonic foraminifera the vertical oxygen and carbon isotopic gradients were relatively low during the albian cenomanian high from the turonian early campanian and then low during the late campanian and maastrichtian foraminiferal oxygen isotopic data from published sources and this study are averaged for each site corrected for latitudinal changes in salinity based on modern day surface water values and plotted versus paleolatitude for the late albian coniacian santonian and late maastrichtian differences between lowand high latitude surface water paleotemperatures are estimated at 14 c during the late albian and late maastrichtian but the coniacian santonian reconstruction reveals only a 0 4 c latitudinal temperature gradient uncertainty regarding cretaceous salinity gradients and possible diagenetic alteration of 18 o values introduce error into our estimates of paleolatitudinal thermal gradients however apparent low equator to pole temperature differences could indicate much higher poleward heat transport than at present

litho bio and chemostratigraphy across the cenomanian turonian boundary oae 2 in the vocontian basin of southeastern france the oceanic anoxic event 2 oae 2 was one of at least two large oceanic anoxic events during the cretaceous period and it is characterized in the stratigraphic record by double positive peaks in the 13c curves of carbonate and organic carbon since the positive 13c shift is believed to have resulted from massive burial of isotopically depleted organic carbon generated globally in anoxic oceanic environments the positive 13c shift tend to coincide with widespread deposition of organic rich sediments in the case of oae 2 however the organic rich horizons do not accord exactly with the two intervals with positive 13c shifts at many sites such as pueblo tarfaya eastbourne and gubbio e g tsikos h jenkyns h c walsworth bell b petrizzo m r forster a kolonic s erba e premoli silva i baas m wagner t sinninghe dameste j s 2004 carbon isotope stratigraphy recorded by the cenomanian turonian oceanic anoxic event correlation and implications based on three key localities journal of the geological society london 161 711 719 the thomel level of the cenomanian turonian c t boundary in the vocontian basin southeastern france accumulated during the oae 2 and it is marked by frequent intercalations of black shale and organic rich marl detailed litho bio and chemostratigraphy analyses across the c t boundary in the vocontian basin indicate that the 13ccarbonate profile fluctuation across the thomel level corresponds well with changes in lithofacies total organic carbon toc and calcium carbonate caco3 abundance positive 13c excursions within the oae 2 correlate with basal and middle parts of the thomel level that are characterized by high toc low caco3 and predominantly contain organic rich sediments such as black shale and dark gray marl on the other hand negative 13c intervals within the oae 2 correspond with lower and upper parts of the thomel level that consist of marly limestone and limy marl with low toc and high caco3 values since the fluctuation of redox conditions during thomel level deposition in the vocontian basin coincides well with the global carbon burial rate indicated by its 13c profile the thomel level could be an ideal candidate for the reference section of the oae 2

retrieving lateral variations from surface wave dispersion curves surface wave analysis is usually applied as a 1d tool to estimate v s profiles here we evaluate the potential of surface wave analysis for the case of lateral variations lateral variations can be characterized by exploiting the data redundancy of the ground roll contained in multifold seismic data first an automatic processing procedure is applied that allows stacking dispersion curves obtained from different records and which retrieves experimental uncertainties this is carried out by sliding a window along a seismic line to obtain an ensemble of dispersion curves associated to a series of spatial coordinates then a laterally constrained inversion algorithm is adopted to handle 2d effects although a 1d model has been assumed for the forward problem solution we have conducted different tests on three synthetic data sets to evaluate the effects of the processing parameters and of the constraints on the inversion results the same procedure applied to the synthetic data was then tested on a field case both the synthetic and field data show that the proposed approach allows smooth lateral variations to be properly retrieved and that the introduction of lateral constraints improves the final result compared to individual inversions

mid cretaceous ocean circulation results from model sensitivity studies a series of ocean general circulation model gcm experiments for mid cretaceous continental paleogeography with atmospheric forcing prescribed from atmospheric gcm experiments are utilized to investigate the nature of the mid cretaceous ocean circulation the experiments illustrate a tethys system of clockwise currents and predominant eastward flow in marked contrast with earlier reconstructions this result is apparently robust for changes in bathymetry and in the degree of planetary warmth changes in sea level have the largest potential to produce alternative circulation characteristics two major current systems outside of tethys dominate the model simulation the site of bottom water formation is the north pacific however in a sensitivity experiment for a warmer climate the eastern tethys became a site of deep water formation

long and short term hydroclimatic variabilities in the aptian tethys clues from the orbital chronostratigraphy of evaporite rich beds in the apennine carbonate platform mt faito southern italy abstract the stratigraphic signature of the global late aptian cooling episode and sea level lowstand has been investigated in the mt faito section of the apennine carbonate platform apcp of southern italy several meter scale fine grained limestone intervals with abundant quartz pseudomorphs after anhydrite and minor calcite pseudomorphs after gypsum are present in the middle upper gargasian straddling the marly orbitolina level a regional key marker correlative with part of the fallot oceanic anoxic event the evaporite rich intervals were deposited in a mudflat saltern setting and together with frequent transgressive shallow marine interlayers alternate quite regularly with lacustrine paralic or very shallow marine deposits suggestive of overall wetter conditions three to five couplets of cyclic arid wet phases are thus identified their timing and duration determined by an original cyclostratigraphically constrained age model tuned with the astrochronology from deep water tethyan reference sections suggest fluctuating hydroclimatic conditions arid semiarid vs wet phases over time scales as brief as 100 and 400 ky they are considered to reflect astronomically induced latitudinal migrations of intertropical climate belts a secular climate shift from arid to humid conditions supra regionally correlatable across the upper gargasian of the tethyan realm is dated at 118 1 my it corresponds to the onset of persistent lacustrine deposits on the partially emerged apcp and of abundant river borne supply of siliciclastics along the opposing tethyan margin the observed climate fluctuations occurred during a major apcp subaerial exposure which lasted for 4 4 my precise supra regional correlations suggest that the platform exposure was glacioeustatic in origin and coeval with a long lived late aptian cooling episode which interrupted the mid cretaceous greenhouse biostratigraphic and astrochronological tuning from the apcp indicates that the glacioeustatic lowstand terminated in the earliest albian just above the o reicheli key marker

further examples of archaeal derived hydrocarbons in mid cretaceous oceanic anoxic event oae 1b sediments abstract biomarker and total organic carbon toc analyses were carried out on laminated black shales and massive marls from the goguel level oae1a and the paquier and kilian levels oae1b of the vocontian basin of southeast france toc content was high ca 3 8 throughout the goguel the paquier and kilian levels archaeal derived hydrocarbons such as 2 6 15 19 tetramethylicosane tmi and 2 6 10 15 19 pentamethylicosane pmi were present in the oae1b sediments as reported previously kuypers m m m blokker p erbacher j kinkel h pancost r d schouten s sinninghe damste j s 2001 massive expansion of marine archaea during a mid cretaceous oceanic anoxic event science 293 92 94 however we did not detect these archaeal biomarkers in the goguel level confirming that the prevalence of archaea producing tmi and pmi was restricted to oae1b

palaeoceanographic differences of early late aptian black shale events in the vocontian basin se france abstract a high resolution study focussing on the distribution of calcareous nannofossils and carbon isotopes was carried out to improve the understanding of mid cretaceous black shale formation the studied interval of the early late aptian is characterized by two major black shale couplets the niveau noire 4 nn4 and niveau noire calcaire 2 nnc2 of the serre chaitieu section in the vocontian basin se france breheret 1997 this interval occurs within a long term negative carbon isotope excursion of 1 5 following the early aptian oceanic anoxic event 1a oae1a in contrast to the local nn4 black shales the black shales of nnc2 are of regional significance and occur at the end of the major negative carbon isotope excursion of the early late aptian time equivalent black shales are suggested to be coeval with black shales found in the western tethys and atlantic ocean herrle et al 2004 calcareous nannofossil analyses and carbon isotopes indicate higher surface water productivity mesotrophic warmer surface water and higher sea level during the formation of the nn4 black shales in contrast the formation of the nnc2 black shales took place during a cooler phase lower surface water productivity and lower sea level a sea level fall may cause a restriction of water mass exchange between the open marine western tethys and the vocontian basin this resulted in a longer residence time of the bottom water decreased ventilation and less mixing of surface waters and thus enhanced preservation of organic matter at the sea floor our results indicate that the black shale formation of nn4 and nnc2 was caused by different processes such as increased surface water productivity and enhanced preservation of organic matter at the sea floor thus we emphasize the role of different forcing factors which control the formation of local and regional black shales the most important factors are sea level fluctuations increasing productivity and changes in precipitation and evaporation rates

stability of the astronomical frequencies over the earth s history for paleoclimate studies the expected changes over the past 500 million years in the principal astronomical frequencies influencing the earth s climate may be strong enough to be detectable in the geological records and such effects have been inferred in several cases calculations suggest that the shortening of the earth moon distance and of the length of the day back in time induced a shortening of the fundamental periods for the obliquity and climatic precession from 54 to 35 41 to 29 23 to 19 and 19 to 16 thousand years over the last half billion years at the same time the precessional constant increased from 50 to 61 arc seconds per year the changes in the frequencies of the planetary system due to its chaotic motion are much smaller their influence on the changes of the periods of climatic precession obliquity and eccentricity of the earth s orbit around the sun can be neglected eccentricity periods used for quaternary climate studies may therefore be considered to have been more or less constant for pre quaternary times

glacio eustatic sea level control on red sea salinity previous studies of the red sea demonstrated that glacial surface and bottom water salinities in the basin were significantly higher than at present the very low abundance of planktonic foraminifera the so called aplanktonic zone during the last glacial indicates that surface water conditions approached or exceeded the tolerance limits of this plankton group1 2 glacial sediments are also characterized by high concentrations of magnesian calcite3 4 dolomite3 inorganically precipitated aragonite4 5 and benthic foraminifera typical of hypersaline environments3 6 additional evidence from oxygen isotope records of planktonic2 7 and benthic foraminifera8 9 as well as pteropods2 demonstrate that glacial interglacial contrasts in the red sea have an amplitude much larger than typically observed in open ocean records here we use both oxygen isotope data and a fractional overmixing model to estimate the impact of the most recent 18 000 yr bp pleistocene glacio eustatic sea level lowering on red sea salinity we estimate that during the last glacial maximum surface salinities in the central red sea were more than 10 0 higher than at present deep water salinities were also higher during the last glaciation and remained unusually high through deglaciation the combination of very high bottom salinities and the onset of pluvial conditions during deglaciation in the red sea region prevented ventilation of red sea bottom waters and resulted in the accumulation of organic rich sediments

constrained 1d joint inversion of seismic surface waves and p refraction traveltimes we present a joint inversion scheme that couples p wave refraction and seismic surface wave data for a layered subsurface an algorithm is implemented with a damped least squares approach the estimated parameters are s and p wave velocities and layer thicknesses while densities are assumed constant during inversion the coupling is both geometric and physical layer thicknesses are the same for sand p wave velocity profiles and p wave velocities enter in both forward algorithms sensitivity analysis performed on synthetic data reveals that surface wave dispersion curves can be sensitive also to p wave velocity of some layers especially for poisson s ratio values smaller than about 0 35 allowing synergic resolution of this parameter applications on both synthetic and field data show that the proposed approach mitigates the hidden layer problem of seismic refraction and leads to more accurate results than individual inversions also for surface waves additional constraints on the objective function on a priori poisson s ratio values allow unrealistic and not admissible vp and vs values to be avoided such constraints were applied in one field case considering the a priori information available about water table depth it is also shown that estimation of porosity can help the selection of the proper constraint on a priori poisson s ratio

warm tropical ocean surface and global anoxia during the mid cretaceous period the middle of the cretaceous period about 120 to 80 myr ago was a time of unusually warm polar temperatures1 repeated reef drowning in the tropics2 and a series of oceanic anoxic events oaes that promoted both the widespread deposition of organic carbon rich marine sediments and high biological turnover3 4 5 6 7 8 the cause of the warm temperatures is unproven but widely attributed to high levels of atmospheric greenhouse gases such as carbon dioxide7 8 9 10 11 12 in contrast there is no consensus on the climatic causes and effects of the oaes with both high biological productivity and ocean stagnation being invoked as the cause of ocean anoxia3 4 5 6 7 8 here we show using stable isotope records from multiple species of well preserved foraminifera that the thermal structure of surface waters in the western tropical atlantic ocean underwent pronounced variability about 100 myr ago with maximum sea surface temperatures 3 5 c warmer than today this variability culminated in a collapse of upper ocean stratification during oae 1d the breistroffer event a globally significant period of organic carbon burial that we show to have fundamental stratigraphically valuable geochemical similarities to the main oaes of the mesozoic era our records are consistent with greenhouse forcing being responsible for the warm temperatures but are inconsistent both with explanations for oaes based on ocean stagnation and with the traditional view reviewed in ref 12 that past warm periods were more stable than today s climate

abyssal recolonization by benthic foraminifera after the cenomanian turonian boundary anoxic event in the north atlantic abstract benthic foraminiferal assemblages of distinctive taxonomic composition occur at the top of benthic fossil free black shales which correspond to the anoxic event at the cenomanian turonian boundary in the north atlantic abyssal dsdp odp sites 386 398 603 and 641 these assemblages consist of minute thin walled agglutinated foraminifera with low specific diversity of 2 to 4 species variable abundance and dominance of few taxa haplophragmoides rhizammina and glomospira the species are inferred to be opportunistic able to survive in low oxygen environments and to be pioneers recolonizing the seafloor after cessation of bottom water anoxia most species are characterized by test morphologies with high surface volume ratios and single layered wall structures with loosely agglutinated grains and small amounts of organic cement for agglutination these features are best observed in material from odp hole 641 a which has exceptional foraminiferal preservation because of its shallow burial depth the successive appearance of benthic foraminifera after the anoxic event is probably controlled by the continuous reoccurrence of more oxygenated bottom and interstitial water conditions with the final development of oxic bottom water conditions in the turonian a rapid radiation of deep water agglutinated foraminifera occurred in the north atlantic

campanian maastrichtian intermediate to deep water changes in the high latitudes benthic foraminiferal evidence 1 during the latest cretaceous cooling phase a positive shift in benthic foraminiferal 18o values lasting about 1 5 myr 71 5 70 ma can be observed at a global scale campanian maastrichtian boundary event cmbe this 18o excursion is interpreted as being influenced by a change in intermediate to deep water circulation or by temporal build up of antarctic ice sheets here we test whether benthic foraminiferal assemblages from a southern high latitudinal site near antarctica odp site 690 are influenced by the cmbe if the 18o transition reflects a change in intermediate to deep water circulation from low latitude to high latitude water masses then this change would result in cooler temperatures higher oxygen concentration and possibly lower organic matter flux at the seafloor resulting in a major benthic foraminiferal assemblage change if however the 18o transition was mainly triggered by ice formation no considerable compositional difference in benthic foraminiferal assemblages would be expected our data show a separation of the studied succession into two parts with distinctly different benthic foraminiferal assemblages species dominating the older part 73 0 70 5 ma tolerate less bottom water oxygenation and are typical components of low latitude assemblages in contrast the younger part 70 0 68 0 ma is characterized by species that indicate well oxygenated bottom waters and species common in high latitude assemblages we interpret the observed change in benthic foraminiferal assemblages toward a well oxygenated environment to reflect the onset of a shift from low latitude toward high latitude dominated intermediate to deep water sources this implies that a change in oceanic circulation was at least a major component of the cmbe

cenomanian turonian composite δ13c curve for western and central europe the role of organic and inorganic carbon fluxes abstract detailed 13 c stratigraphies have been published recently for several cenomanian turonian pelagic sections of southern england and the lower saxony basin of germany the observed changes in the 13 c record provide a useful tool for high resolution stratigraphic correlation and are used here to create a composite cenomanian turonian 13 c curve in a time related framework a best fit curve to 673 carbon isotope data is provided using the lowess regression scatterplot smoother the long term trend of the smoothed composite 13 c profile varies on time scales of 10 6 years and shows stable 13 c values through the lower cenomanian an increase in the middle and upper cenomanian with a major positive excursion around the cenomanian turonian boundary and a decrease through the lower and middle turonian short term fluctuations vary on time scales of 10 5 years and dominated the 13 c signal in the higher middle and upper turonian changes of the cenomanian turonian 13 c record have commonly been explained by variations in the organic carbon flux to the sedimentary reservoir in response to eustatic sea level change however mass balance consideration suggests also an influence of carbonate production and burial rate on the 13 c signal enhanced inorganic carbon burial increased the ratio of the inorganic to organic carbon fluxes and shifted the 13 c 12 c ratio to more negative values this pattern may be observed in the early and middle turonian 13 c long term record and correlates with the spatial expansion of pelagic carbonate deposits in epicontinental seas short term 13 c variations could be either a directly response to short term sea level changes reflecting local conditions in the european epicontinental sea or could represent changes in oceanic 12 c storage in response to the varying intensity of thermohaline circulation

major element analysis of cyclic black shales paleoceanographic implications for the early cretaceous deep western tethys lower cretaceous sediments are frequently characterized by a well expressed cyclicity while the processes influencing environments above the carbonate compensation depth ccd are reasonably well understood almost nothing is known about the deep ocean cretaceous sub ccd sediments from the tethys and atlantic oceans typically show rhythmic black green shale successions to gain insight into the nature of these black green shale cycles we performed detailed geochemical analyses x ray fluorescence rock eval and reactive iron analysis on a 3 m long section of latest aptian age the major element distribution of the analyzed shale sequence indicates a periodic change from a high productivity and well oxygenated green shale mode to a low productivity oxygen deficient black shale mode it is proposed here that the preservation of organic matter was dependent on the strength of salinity driven deepwater generation furthermore the data show that the corg content covaries with changes in the detrital composition therefore we hypothesize that tethyan deepwater circulation was sensitive to changes in the monsoonal system time series analysis suggests that these changes are periodic in nature although we are currently unable to prove that the dominant periodicity is related to the precession component of the milankovitch frequencies

aptian anoxia in the pacific basin marine strata of aptian age in the pacific basin include two distinct levels that represent episodes during which sediments rich in organic carbon were deposited both episodes lasted less than 1 m y as revealed in strata deposited atop submerged topographic highs one unusually widespread episode of early aptian age 117 5 ma correlates with coeval units in europe and thus is analogous to the cenomanian turonian oceanic anoxic event in its short duration and wide geographic extent the second episode of late aptian age 116 5 ma is restricted to allochthonous pelagic deposits in the franciscan complex of california these results support the concept of widespread and narrowly synchronous anoxic events further they show that organic carbon deposition in the pacific basin took place in intermediate water oxygen minimum zones and thus differed in the mode of deposition and hence paleoceanography from that in other middle cretaceous ocean basins

the barremian and aptian stepwise development of the oceanic anoxic event 1a oae 1a crisis integrated benthic and planktic high resolution palaeoecology along the gorgo a cerbara stratotype section umbria marche basin italy abstract the barremian and aptian were times of global plate reconfiguration and profound changes in the ocean climate system culminating in the worldwide deposition of lower aptian black shale layers oae 1a based on high resolution lithostratigraphic and micropaleontological analyses precursor conditions and timing of the anoxia are here reconstructed along a 33 06 m thick section in the proposed barremian aptian boundary gssp stratotype at gorgo a cerbara umbria marche basin italy a non uniform history of benthic foraminiferal diversification is interrupted by the selli level oae 1a and by three turnover points for both benthic and planktic organisms each highlighted by prominent breaks in lithology and outcrop morphology the first two points at 1 1 myr and 20 50 kyr prior to the onset of the oae 1a correspond respectively to the nannoconid bathypelagic calcareous nannofossils decline and crisis events and separate a pelagic limestone chert claystone lithological cycles of the uppermost maiolica formation showing frequencies reminiscent of orbital eccentricity and containing an oligotrophic barremian benthic and planktic assemblage dominated by k selected nannoconids and rhizammina b greenish grey cherty marls of the lowermost marne a fucoidi formation associated to declining sedimentation rates and eutrophic early aptian assemblages dominated by radiolarians and lituolid benthic foraminifera and c anoxic radiolarites and shales of the carbonate free selli level high magnitude and frequency assemblage fluctuations occur between the nannoconid crisis 25 cm below the lowermost oae 1a black shale layer and the selli level base with suggestions of bottom water acidification at 800 kyr after the oae 1a end a third turnover point in the basal reddish member of the marne a fucoidi highlights middle aptian assemblages characterized by a bloom of early macroperforate planktic foraminifera hedbergella spp and appearances of new benthic species marking a shift towards better oxygenation oae 1a oxygen and pelagic carbonate factory crises are here suggested to have been step wise and linked to global warming conditions

stable isotope composition of late cretaceous benthic foraminifera from the southern south atlantic biological and environmental effects abstract the stable carbon and oxygen isotope composition of different benthic foraminiferal species of the latest campanian and earliest maastrichtian from ocean drilling project hole 690c weddell sea southern south atlantic 1800 m paleowater depth have been investigated the total range of measured isotope values of all samples exceeds 4 for 13c and 1 1 for 18o carbon isotope values of proposed deep infaunal species are generally similar or only slightly lower when compared to proposed epifaunal to shallow infaunal species interspecific differences vary between samples probably reflecting temporal changes in organic carbon fluxes to the sea floor constantly lower 13c values for pullenia marssoni and pullenia reussi suggest the deepest habitat for these species the strong depletion of 13c values by up to 3 within lenticulinids may be attributed to a deep infaunal microhabitat strong vital effects or different feeding strategy when compared to other species or modern lenticulinids the mean 18o values reveal a strong separation of epifaunal to shallow infaunal and deep infaunal species epifaunal to shallow infaunal species are characterized by low 18o values deep infaunal species by higher values this result possibly reflects lower metabolic rates and longer life cycles of deep infaunal species or the operating of a pore water co32 effect on the benthic foraminiferal stable isotopes pyramidina szajnochae shows an enrichment of oxygen isotopes with test size comprising a total of 0 6 between 250 and 1250 m shell size although 13c lacks a corresponding trend these data likely represent the presence of changes in metabolic rates during ontogenesis these results demonstrate the general applicability of multi species stable isotope measurements of pristine cretaceous benthic foraminifera to reconstruct past microhabitats and to evaluate biological and environmental effects on the stable isotope composition

a case study of seismic zonation in municipal areas an earthquake of 7 4 magnitude in august 1999 caused major loss of life and severe damage within the municipality of izmit 170 km southeast of istanbul figure 1 a survey of the damaged buildings was made by the municipal authorities shortly after the earthquake the municipal government decided to conduct a pilot seismic zonation project to determine whether the cause of the damage was poor construction materials and methods or weak soil conditions in this project we investigated the soil conditions with two objectives in mind 1 to estimate the seismic model of the soil column at each district to determine the geotechnical earthquake engineering parameters and 2 to map active faults within the municipal area

effect of lateral heterogeneity in the soil column on shear wave velocity estimation by rayleigh wave inversion we conducted elastic wavefield modeling of shot gathers using soil column models with vertical and lateral velocity variations to study the dispersive behavior of rayleigh waves and the effect of lateral heterogeneity on the accuracy of rayleigh wave inversion for shear wave velocity estimation we also conducted a field experiment over an alluvial valley with soil column that thins out in the direction orthogonal to the valley axis from the model and field experiments we found that the dispersion characteristics of rayleigh waves are greatly influenced by the geometry of and lateral heterogeneities within the soil column nevertheless estimation of shear wave velocities within a soil column with lateral heterogeneity by rayleigh wave inversion is sufficiently robust and accurate for geotechnical applications

field characterization and data integration to define the hydraulic heterogeneity of a shallow granular aquifer at a sub watershed scale providing a sound basis for aquifer management or remediation requires that hydrogeological investigations carried out to understand groundwater flow and contaminant transport be based on representative data that capture the heterogeneous spatial distribution of aquifer hydraulic properties this paper describes a general workflow allowing the characterization of the heterogeneity of the hydraulic properties of granular aquifers at an intermediate scale of a few km2 the workflow involves characterization and data integration steps that were applied on a 12 km2 study area encompassing a decommissioned landfill emitting a leachate plume and its main surface water receptors the sediments composing the aquifer were deposited in a littoral sublittoral environment and show evidence of small scale transitional heterogeneities cone penetrometer tests cpt combined with soil moisture and electrical resistivity smr measurements were thus used to identify and characterize spatial heterogeneities in hydraulic properties over the study area site specific statistical relationships were needed to infer hydrofacies units and to estimate hydraulic properties from high resolution cpt smr soundings distributed all over the study area a learning machine approach was used due to the complex statistical relationships between colocated hydraulic and cpt smr data covering the full range of aquifer materials application of this workflow allowed the identification of hydrofacies units and the estimation of horizontal hydraulic conductivity vertical hydraulic conductivity and porosity over the study area the paper describes and discusses data acquisition and integration methodologies that can be adapted to different field situations while making the aquifer characterization process more time efficient and less labor intensive

anoxia vs productivity what controls the formation of organic carbon rich sediments and sedimentary rocks discussion the prevailing explanation for the origin of organic rich sediments and rocks invokes deposition under conditions of anoxia however recent research suggests that high primary production and not water column anoxia provides the first order control on the accumulation of organic rich facies in the modern oceans oxygen minima do not appear to have any direct effect on carbon accumulation in continental margin or marginal sea environments sediments accumulating in the modern black sea the type euxinic basin are not particularly enriched in organic matter despite the presence of an anoxic water column although a sapropel containing extremely high carbon concentrations was deposited during the holocene at a time when the basin was oxic results of a recently published co pled ocean atmosphere model indicate that during the cretaceous thermohaline and surface circulation in the oceans was similar to or more intense than modern conditions despite the overall equable climate such conditions confound the idea that circulation in the cretaceous atlantic for example was punctuated by oceanic anoxic events brought about by more sluggish circulation sporadic temporal and spatial increases in primary production reflecting changes in the behavior and or state of the ocean atmosphere system constitute a more tenable explanation for the occurrence of modern and quaternary carbon rich sediments and cretaceous black shales consequently the fundamental control on the accumulation of carbon rich facies in the oceans and marginal seas is not the presence or absence of anoxia

site amplification assessment in the east corinth gulf using 3d finite difference modeling and local geophysical data elastic 3d wave field simulations were performed in the seismically active region of eastern gulf of corinth in the area of loutraki city a new methodology was tested with the aim of performing multiple simulations for a large variety of realistic sources located around the study area by employing 3d finite difference modeling using matrix operations for the calculation of the spatial velocity and stress derivatives the new methodology was proven to be quite efficient in simulating the near surface 3d site effect of the study area by greatly minimizing the simulation time thus allowing the use of 3d finite difference modeling for a large number of simulations the complex geological features of the study area were obtained by performing multiple passive masw surveys within the busy urban area of loutraki by processing the acquired geophysical data a highly inhomogeneous near surface velocity structure in the study area was obtained and was implemented in the 3d wave field simulations the near surface amplification that is caused by the 3d subsurface structure was proven to be highly significant for the area of loutraki with high spectral amplification compared to the amplification that is caused by an equivalent 1d model in the area the dominant frequencies of the spectral amplification for the 3d model were also confirmed by processing hvsr measurements that were also taken in the area finally we also investigated how the propagation direction affects the near surface amplification

terrestrial record of methane hydrate dissociation in the early cretaceous reconstruction of changing c isotopic composition of early cretaceous atmospheric co2 from fossilized c3 vascular land plant tissue revealed a brief and striking negative excursion d 25 in atmospheric d 13 c followed by a rapid positive compensation d 15 during the aptian ca 117 ma mass balance calculations show that dissociation of a small amount of methane gas hydrate is the most tenable cause of the negative excursion this would also result in an increased co2 o2 mixing ratio as o2 is consumed during ch4 oxidation to co2 spurring the exponential phase of angiosperm biogeographic expansion

middle cretaceous reef collapse linked to ocean heat transport biologically defined fluctuations in cretaceous tropical reef boundaries of the caribbean region record a dynamic rather than stable environmental history these fluctuations may be related to major thermal changes resulting from ocean heat transport with simultaneous poleward movement of surface and subsurface waters on sea level highstands the superheated middle cretaceous tropics cooled the reef line contracted diversity decreased and reef ecosystems collapsed leading to mass extinction geologic data qualitatively test and support the hypothesis of enhanced cretaceous ocean heat transport formulated from general circulation models in these models four times the present day atmospheric concentration of co 2 and twice the present day model value of ocean heat transport cooled the superheated tropics and provided the best match to the distribution of inferred middle cretaceous temperature data these dynamic changes suggest an important role for large scale disturbance in the evolution of tropical ecosystems

massive expansion of marine archaea during a mid cretaceous oceanic anoxic event biogeochemical and stable carbon isotopic analysis of black shale sequences deposited during an albian oceanic anoxic event 112 million years ago indicate that up to 80 weight percent of sedimentary organic carbon is derived from marine nonthermophilic archaea the carbon 13 content of archaeal molecular fossils indicates that these archaea were living chemoautotrophically their massive expansion may have been a response to the strong stratification of the ocean during this anoxic event indeed the sedimentary record of archaeal membrane lipids suggests that this anoxic event marks a time in earth history at which certain hyperthermophilic archaea adapted to low temperature environments

carbon and oxygen isotope stratigraphy of the english chalk and italian scaglia and its palaeoclimatic significance a detailed carbon and oxygen isotope stratigraphy has been generated from upper cretaceous coastal chalk sections in southern england east kent culver cliff isle of wight eastbourne and seaford head sussex norfolk coast and the british geological survey bgs trunch borehole norfolk data are also presented from a section through the scaglia facies exposed near gubbio italian apennines wherever possible the sampling interval has been one metre or less both the chalk and scaglia carbon isotopic curves show minor positive excursions in the mid cenomanian mid and high turonian basal coniacian and highest santonian lowest campanian there is a negative excursion high in the campanian in chalk sections that span that interval the well documented cenomanian turonian boundary spike is also well displayed as is a broad positive excursion centred on the upper coniacian a number of these positive excursions correlate with records of organic carbon rich deposition in the atlantic ocean and elsewhere the remarkable similarity in the carbon isotope curves from england and italy enables cross referencing of macrofossil and microfossil zones and pinpoints considerable discrepancy in the relative positions of the turonian coniacian and santonian stages the oxygen isotope values of the various chalk sections although showing different absolute values that are presumably diagenesis dependent show nonetheless a consistent trend the east kent section which is very poorly lithified indicates a warming up to the cenomanian turonian boundary interval then cooling thereafter regional organic carbon burial documented for this period is credited with causing drawdown of co 2 and initiating climatic deterioration inverse greenhouse effect data from other parts of the world are consistent with the hypothesis that the cenomanian turonian temperature optimum was a global phenomenon and that this interval represents a major turning point in the climatic history of the earth

nonlinear refraction traveltime tomography a few important issues for performing nonlinear refraction traveltime tomography have been identified they include the accuracy of the traveltime and raypath calculations for refraction the physical information in the refraction traveltime curves and the characteristics of the refraction traveltime errors consequently we develop a shortest path ray tracing method with an optimized node distribution that can calculate refraction traveltimes and raypaths accurately in any velocity model we find that structure ambiguity caused by short and long rays in the seismic refraction method may influence the inversion solution significantly therefore we pose a nonlinear inverse problem that explicitly minimizes the misfits of the average slownesses ratios of traveltimes to the corresponding ray lengths and the apparent slownesses derivatives of traveltimes with respect to distance as a result we enhance the resolution as well as the convergence speed to regularize our inverse problem we use the tikhon

warm saline bottom water in the ancient ocean considerable isotopic evidence indicates that oceanic bottom water was much warmer in the geological past a simple convection model driven by multiple turbulent buoyant plumes and observations of present deep water formation have led to the development of a theory for the formation of warm saline bottom water it is suggested that changes in the size and configuration of marginal seas in net evaporation zones due to lithospheric plate motions and eustatic sea level change caused these seas to become sources of warm saline bottom water evidence from the palaeotemperature record and palaeogeography during the late cretaceous is used to reinforce the hypothesis climatic and chemical consequences of the formation of warm saline bottom water are discussed

latest cenomanian earliest turonian low oxygen tolerant benthonic foraminifera a case study from the sergipe basin n e brazil and the western anglo paris basin southern england abstract distinctive sedimentological geochemical isotopic and micropalaeontological response characterise the nature of sediments deposited under hypoxic anoxic bottom conditions during the latest cenomanian to earliest turonian of most of the world s basins the composition of the biota is a direct response to overall environmental conditions the recognition of distribution patterns of low oxygen tolerant microfauna is therefore of primary importance in evaluating and reconstructing the regional palaeoceanographic settings where such events took place a case study is presented from two coeval stratigraphic sequences the sergipe basin northeastern brazil and the western anglo paris basin southern england the associated benthonic foraminiferal assemblages from oxygen depleted environments consist mostly of opportunistic r selected species basic patterns in community trophic structures appear to have primarily dictated the composition of the biota the assemblages from outer shelf to upper slope oxygen depleted environments are commonly characterised by 1 low diversity 2 limited intraspecific variation 3 predominance c 40 60 of the total foraminiferal assemblage of epifaunal deposit feeding plano concavo convex trochospiral calcareous hyaline morphotypes gavelinellids conorboidids rosalinids and bagginids 4 variable numbers c 10 30 of infaunal bacterial detrital scavengers tapered and elongate morphotypes turrilinids bolivinids buliminellids fursenkoinids polymorphinids and caucasinids 5 epifaunal shallow infaunal deposit feeding lenticular morphotypes coiled vaginulinids c 5 19 6 variable numbers c 10 30 of agglutinated specimens lituolids discamminids eggerellids textulariids trochamminids ammodiscids tritaxiids and valvulinids and 7 dominance about 60 80 of minute c 100 200 m in maximum diameter width or length calcareous hyaline taxa during widespread dysaerobic quasi anaerobic episodes highly oxygen depleted bottom conditions are marked by the absence of benthonic microfauna minor taxonomic differences between the two studied areas are mostly due to palaeobiogeographic provincialism

low productivity and slow deep water circulation in mid cretaceous oceans paleofertility estimates are derived from organic carbon accumulation rates determined in nonbioturbated mid cretaceous deep sea deposits using organic carbon preservation factors observed in laminated sediments from anoxic holocene environments the estimated mid cretaceous primary production rates are as much as an order of magnitude lower than those measured in today s oceans an evaluation of dissolved oxygen budgets using a simple oceanic circulation model indicates very low deep water renewal rates in mid cretaceous oceans 28 references 2 tables 4 figures

short term environmental changes in the cretaceous tethyan ocean micropalaeontological evidence from the early albian oceanic anoxic event 1b to better understand the linkage between climate and ocean circulation under greenhouse conditions we have studied calcareous nannofossils palynomorphs and benthic foraminifera from the early albian oceanic anoxic event 1b black shale oae 1b in the vocontian basin se france we propose that monsoonal activity resulting from precessional forcing and modulated by eccentricity driven temperature changes represents the driving factor of oae 1b formation in low latitudes with the onset of oae 1b increasingly warm and humid conditions stronger winds and enhanced terrestrial input led to higher surface water productivity therefore increased productivity is an important factor for oae 1b formation in the vocontian basin however monsoonally forced productivity changes are a regional climate signal only the supraregional occurrence of the oae 1b is probably due to a reduction of deep water formation in the low latitudes under extremely warm and humid conditions leading to enhanced preservation of organic matter

applications of engineering seismology in urban areas i present two case studies which describe applications of engineering seismology in urban areas high resolution shallow offshore 3d seismic survey for the bosphorus subsea road tunnel project and seismic geotechnical and earthquake engineering site characterization for a residential project in istanbul in case study 1 i conducted a 3d high resolution shallow seismic survey in 2011 to confirm the geometry of the future bosphorus subsea road tunnel traverse i processed the data to obtain 3d pstm and psdm volumes and interpreted these image volumes and correlated the interpretation results with the offshore borehole data with the recoverable signal band of 30 960 hz i attained a vertical resolution of less than 1 m

pore scale imaging of geological carbon dioxide storage under in situ conditions 1 while geological carbon dioxide co2 storage could contribute to reducing global emissions it must be designed such that the co2 cannot escape from the porous rock into which it is injected an important mechanism to immobilize the co2 preventing escape is capillary trapping where co2 is stranded as disconnected pore scale droplets ganglia in the rock surrounded by water we used x ray microtomography to image at a resolution of 6 4 m the pore scale arrangement and distribution of trapped co2 clusters in a limestone we applied high pressures and temperatures typical of a storage formation while maintaining chemical equilibrium between the co2 brine and rock substantial amounts of co2 were trapped with an average saturation of 0 18 the cluster sizes obeyed a power law distribution with an exponent of approximately 2 1 consistent with predictions from percolation theory this work confirms that residual trapping could aid storage security in carbonate aquifers

no extinctions during oceanic anoxic event 1b the aptian albian benthic foraminiferal record of odp leg 171

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

planktic foraminifera from the mid cretaceous barremian early albian of the north sea basin palaeoecological and palaeoceanographic implications abstract a marine cretaceous succession barremian albian of a cored borehole bgs 81 40 located in the central north sea basin has been examined with respect to its planktic and benthic foraminiferal content as well as for calcareous nannofossils the distribution patterns of foraminifera and calcareous nannofossils allow for a two fold division of the investigated interval 1 the barremian earliest aptian interval which reflects a marine temporary restricted setting this is indicated by sporadic occurrences of planktic foraminifera with very rare planispiral forms suggesting short term connections of the boreal and tethyan realms the benthic foraminiferal assemblages indicate aerobic sometimes dysaerobic bottom water conditions high abundances of nannoconids in the barremian suggest enhanced stratification and or warm oligotrophic surface water 2 the late aptian early albian interval which was characterised by an open oceanic environment with cool and aerobic surface water conditions planktic foraminifera are more abundant and diverse than in the lower interval trochospiral hedbergellids dominate the foraminiferal assemblages the episodic occurrences of planispiral clavate and trochospiral flattened planktic morphotypes indicate the existence of a seaway between the boreal and the tethyan realms aerobic to dysaerobic bottom water conditions are suggested by the composition of the benthic foraminiferal assemblages high abundances of cool water taxa within the calcareous nannofossil assemblages indicate a cooling trend across the latest aptian and earliest albian

correlating environmental changes during early albian oceanic anoxic event 1b using benthic foraminiferal paleoecology abstract the nature and consequences of mid cretaceous oceanic anoxic events oaes are the subject of ongoing debate and recent studies have shown that different scenarios are needed to explain each of these events nevertheless similarities between the different oaes can be observed here we have reconstructed paleoenvironmental changes during the early albian oae 1b using benthic foraminiferal distributions and lithologies in three sections from different basins and paleowater depths eutrophic conditions as indicated by the presence of infaunal as well as opportunistic genera such as gyroidinoides pseudobolivina pleurostomella and bolivinitids prevailed before and during the oae and led to dysoxic to anoxic conditions dysoxia was most intense in the bathyal sections but also occurred in the outer shelf where more heterogeneous patterns of foraminiferal distributions are believed to reflect fluctuations of the upper boundary of an oxygen minimum zone a change from eutrophic to mesotrophic conditions caused the termination of oae 1b and opportunistic benthic foraminifera e g pseudobolivina pleurostomella were the first to subsequently repopulate the bathyal sea floor repopulation occurred rapidly in the shallow settings and gradually in the deeper sites where a normal diverse pre event fauna was established a few tens of thousands of years after oae 1b

episodes of intensified biological productivity in the subtropical atlantic ocean during the termination of the middle eocene climatic optimum meco the middle eocene climatic optimum meco is an 500 kyr interval of pronounced global warming from which the climate system recovered in 50 kyr the deep sea sedimentary record can provide valuable insight on the marine ecosystem response to this protracted global warming event and consequently on the ecological changes during this time here we present new benthic foraminiferal assemblage data from ocean drilling program site 1051 in the subtropical north atlantic spanning the meco and post meco interval 41 1 to 39 5 ma we find little change in the species composition of benthic foraminiferal assemblages during the studied interval suggesting that the rate of environmental change was gradual enough that these organisms were able to adapt however we identify two transient intervals associated with peak warming higher productivity interval hpi 1 40 07 39 96 ma and shortly after the meco hpi 2 39 68 39 55 ma where benthic foraminiferal accumulation rates increase by an order of magnitude these hpis at site 1051 appear to coincide with intervals of strengthened productivity in the tethys southern ocean and south atlantic and we suggest that an intensified hydrological cycle during the climatic warmth of the meco was responsible for eutrophication of marine shelf and slope environments

black shales and carbon isotopes in pelagic sediments from the tethyan lower jurassic detailed sampling and analysis of jurassic pelagic limestones and marls from italy hungary and switzerland have enabled construction of an isotope stratigraphy across the pliensbachian toarcian boundary with resolution to the zonal level the oxygen isotope record is unremarkable the carbon isotopes however show two positive excursions one relatively minor during the pliensbachian margaritatus zone subnodosus subzone the other more major during the toarcian early falciferum zone where a maximum 13c value of 4 52 pdb is attained these intervals are known to be favoured periods of organic rich sedimentation in diverse parts of the globe and the isotopic excursions are interpreted as a response to abnormally high rates of storage of organic carbon in the sedimentary record a comparable phenomenon has been documented from the cenomanian turonian boundary in the cretaceous where it has been referred to the influence of an oceanic anoxic event some italian sections spanning this lower jurassic interval contain organic rich shales in the falciferum zone the isotopic signatures from their included locally manganiferous carbonate betray a considerable diagenetic overprint and they cannot therefore be incorporated in a composite isotopic curve carbon isotopes from the organic carbon itself are extremely negative falling to 33 pdb and in one section examined in detail correlate with the calcium carbonate content of the shales they may reflect a partial change to a non calcified planktonic biota during deposition of this lime poor interval possibly responding to upwelling and increased fertility of near surface waters the onset of upwelling may have been as early as spinatum tenuicostatum zone time that is at the pliensbachian toarcian boundary

mediterranean quaternary sapropels an immediate response of the african monsoon to variation of insolation abstract in the subsurface of the east mediterranean sea eleven discrete basin wide organic rich black sapropels were deposited during the last 465 000 years they are dated by oxygen isotopic chronostratigraphy the most recent sapropel has been shown to be the consequence of heavy nile river summer floods due to increased monsoonal summer precipitation over ethiopia and not of scandinavian ice sheet meltwater influx into the east mediterranean sea as was previously believed while most sapropels were deposited during interglacials two thick sapropels formed during glacial periods as shown by their position in the oxygen isotopic stratigraphy and by their pollen record in core rc9 181 the new evidence presented here is that the sapropel sequence in this core including the two glacial sapropels correlates on a one to one basis with the highest values of an index of insolation on top of the atmosphere the concept of this index derives from an analysis of the african monsoon process the index variation is computed for the last 465 000 years from the caloric northern summer insolation in the tropical latitudes controlled by variations of the earth s orbital parameters it is conjectured that this index might be linked through the climate system to the monsoonal precipitation which in africa produces the nile river summer flood

relative sea level change and carbon isotopes data from the upper jurassic oxfordian of central and southern europe studies on cretaceous pelagic limestones have shown a close correspondence between putative sea level curves and the carbon isotope profile suggesting a possible relationship between the two phenomena such a relationship could relate to shelf sea area governing the global burial rate of organic carbon which in turn controls the 13c 12c ratio of dissolved inorganic carbon in the oceanic reservoir in order to see whether or not this relationship might be of more general applicability the major mid oxfordian jurassic transgression is documented to zonal level and appropriate carbon isotope data are presented although the applicability of ammonite zonation to the mid oxfordian is problematic on a regional scale a clear 13c excursion is present in the trunsversariurn zone which is coincident with regional overstep and or evidence of shoreline retreat and or evidence of bathymetric deepening in europe and elsewhere the use of the carbon isotope curve as a proxy for shelf sea area or relative sea level is worthy of further exploration

end cenomanian benthic foraminiferal extinctions and oceanic dysoxic events in the northwestern pacific ocean abstract the second largest cretaceous extinction event coincided with an oceanic anoxic event at the cenomanian turonian c t boundary this high resolution analysis of upper bathyal benthic foraminifera in central hokkaido japan indicates that the extinction event occurred in the latest cenomanian over a period of 0 2 m y 93 6 93 4 ma analysis of the dissolved oxygen index based on calcareous benthic foraminiferal wall thickness size and morphology shows that low oxygen 0 1 1 5 ml l conditions developed during a period of 0 15 m y before the c t boundary and 1 5 m y after the minimum oxygen condition 0 1 1 ml l prevailed twice during this interval similarly benthic foraminiferal extinctions occurred twice in concert with initiation of the two minimum oxygen levels coincidence of the two extinction horizons with developemt of low oxygen conditions suggests that the main cause of the extinctions was formation of dysoxic intermediate water this report suggests that the global c t boundary extinction event occurred in a stepwise fashion during the latest cenomanian 0 2 0 5 m y due to development of widespread oceanic anoxic dysoxic conditions within intermediate water masses

geochemical events documented in inorganic carbon isotopes abstract screening of sampling and analytical data is crucial for the detection of real global shifts in marine 13c against the noise of diagenesis the real global shifts of 13c are of two types 1 long term secular shifts caused by changes in the fractional burial of organic carbon and 2 transient shifts caused by abrupt changes of biological productivity in the surface photic zone both are applicable to stratigraphic correlation but differ in their application to modelling of changes in oceanographic or atmospheric composition a recent compilation found 34 carbon isotope events in the phanerozoic and neoproterozoic equally distributed among positive and negative shifts this in itself attests to a variety of proximate causes of the shifts

evidence for late jurassic release of methane from gas hydrate four late jurassic carbonate successions deposited in the tethys atlantic ocean record a negative carbon isotope excursion of at least 2 the excursion is present in both organic and carbonate carbon records and is comparable in magnitude and duration to isotopic changes during the late paleocene thermal maximum our results indicate that during the late jurassic long considered a warm greenhouse time additional greenhouse gas was input to the atmosphere by a sudden release of methane from buried gas hydrate a potential triggering mechanism may have been the opening of an oceanic gateway through the early atlantic between the ancient tethys and pacific oceans

stable oxygen and carbon isotope systematics of exquisitely preserved turonian foraminifera from tanzania understanding isotopic signatures in fossils the interpretation of 18o and 13c analyses of extinct foraminifera is hampered by insufficient knowledge on the contribution of environmental versus biological factors on the measured values we present single species stable isotope data for 18 benthic and 11 planktic foraminiferal species and one calcareous dinoflagellate cyst species from a turonian equatorial record measured on samples collected in se tanzania all microfossils analyzed were excellently preserved and results are compared to isotopic measurements from bulk sediment of the same material remarkably low intra specific variability standard deviations 0 2 across the studied interval and consistently large benthic planktic offsets in 18o 2 8 and 13c 1 5 indicate absence of major long term environmental fluctuations and presence of a well stratified water column stratigraphic isotopic trends show small shifts that are parallel in all studied benthic species with the exception of the 13c record of lenticulina species but within sample inter specific offsets reflect a combination of habitat differences and species specific isotopic disequilibrium fractionation among planktic taxa closely related taxa tend to have similar isotopic values biserial taxa have the lowest 18o values 4 7 but also have relatively low 13c values 1 6 indicating that for the assumption of a surface water habitat additional metabolic effects need to be involved which supports the concept of their opportunistic lifestyle among trochospiral planktics the keeled taxa with compressed chambers have slightly higher 18o 4 2 and lower 13c 2 3 values than taxa with globular chambers 4 4 and 2 4 respectively suggesting differences in habitat or in peak seasonal abundance benthic taxa are subdivided into three isotopically distinct groups with differences reflecting mineralogy life strategy and habitat group i aragonitic taxa epistomina colomia africana group ii calcitic trochospiral taxa with isotopic values seemingly close to equilibrium berthelina berthelini oridorsalis umbonatus lingulogavelinella globosa lingulogavelinella convexa and group iii calcitic taxa with low 18o values and large scatter in 13c values lenticulina four other benthic species show values between groups ii and iii the wealth and consistency of data especially for benthic taxa permit refined conclusions the five studied species of epistomina have a similar isotopic signature and are inferred to form their aragonitic shells with close to equilibrium values small isotopic offsets are seen among species that differ in orientation of the septal foramen but no offsets are seen that seem to co vary with test shape or ornamentation the conical species c africana has 18o values 0 2 lower and 13c values 0 7 lower than species of epistomina the latter offset probably reflects an infaunal habitat for c africana epistomina and group ii species are recommended for paleoenviromental studies mono specific lenticulina 18o values may be used if increased by correction factors of 0 4 to 0 9 but this taxon s low and variable 13c values are interpreted to reflect incorporation of respiratory co2 possibly combined with fast growth rates related to opportunism rather than equilibrium with benthic dissolved inorganic carbon the observed stability of inter specific isotopic offsets suggests disequilibrium isotopic effects are relatively consistent for many taxa in this section and correction factors are proposed that may help to generate more robust upper cretaceous foraminiferal isotopic records however 18o 13c covariance in some benthic inter specific comparisons suggests offsets might vary with changes in temperature food supply or other factors so the appropriateness of the correction factors should be confirmed before being applied at different sites similarities between the observed single species isotopic patterns from this and other studies are used to present a summarizing scheme of influences on the stable isotopic composition in foraminiferal tests by applying the new insights from our study to data from other cretaceous studies we demonstrate that the selection of species for isotopic analysis and understanding these signals are critical to the outcome of paleoceanographic interpretations