atlantic paleogene biserial heterohelicid foraminifera and oxygen minima through most of the paleogene the planktonic foraminifera called biserial heterohelicids record the most depleted carbon isotope ratios among planktonic foraminiferal species they are interpreted to occupy an oxygen minimum habitat stronger interplanktonic carbon isotope contrasts and more enriched near surface carbon isotope values correspond to higher abundances of biserial heterohelicids this group appears to have preferred latitudes and times when the oxygen minimum was well developed biserial heterohelicid generic and specific diversity are directly related to the interplanktonic carbon isotope contrast minimal specific diversity characterizes the oligocene when interplanktonic and surface to bottom carbon isotope contrasts were consistently low diversity and abundance decreases were coeval with increased oceanic ventilation

size distribution of holocene planktic foraminifer assemblages biogeography ecology and adaptation the size of any organism is influenced by the surrounding ecological conditions in this study we investigate the effects of such factors on the size spectra of planktic foraminiferal assemblages from holocene surface sediments we analyzed assemblages from 69 holocene samples which cover the major physical and chemical gradients of the oceans on a global scale the range of sizes in assemblages triples from the poles to the tropics this general temperature related size increase is interrupted by smaller sizes at temperatures characteristic of the polar and subtropical fronts at 2 c and 17 c respectively as well as in upwelling areas on a regional scale surface water stratification seasonality and primary productivity are highly correlated with the size patterns such environmentally controlled size changes are not only characteristic for entire assemblage but also for the dominant single species

global distribution of late paleogene hiatuses six global late paleogene hiatuses pha to phe have been identified from deep sea sequences these hiatuses occurred at the middle late eocene boundary late eocene eocene oligocene boundary late early oligocene late oligocene and oligocene miocene boundary horizons paleodepth distribution of hiatuses shows hiatus maxima characterized by major mechanical erosion below 4800 m at mid depth between 2000 and 3000 m and in shallower water above 1600 m paleodepth the geographic distribution and paleodepth of these hiatus maxima suggest that flow paths of major water masses and currents are the principal cause widespread short hiatuses due to carbonate dissolution or nondeposition occurred primarily during global cooling trends or climatic instability and appear to correlate to sea level transgressions or onlap sequences these hiatuses may have been caused by basin shelf fractionation of carbonates

antarctic marine temperatures late campanian through early paleocene an oxygen isotope paleotemperature study of benthic foraminifera from the upper campanian through lower paleocene section at seymour island near the coast of antarctica was done in conjunction with careful scanning electron microscope observations to monitor the state of foraminiferal preservation the isotopic compositions of those samples which were deemed to be well preserved were the basis of the conclusion that campanian through paleocene high latitude shelf waters near antarctica had temperatures between approximately 4 5 and 10 5 c temperatures during early and middle maastrichtian time were slightly higher than those of either the late campanian or late maastrichtian the inference of temperate climatic conditions in antarctica is in agreement with paleoclimatic conclusions drawn on the species composition of the planktonic foraminiferal assemblages and the character of the planktonic foraminifera as well as with published conclusions based upon paleobotanical evidence the maastrichtian and campanian water temperatures at seymour island are similar to those inferred from published isotope ratios of pacific late cretaceous benthic foraminifera from low latitudes indicating that campanian through early paleocene deep ocean waters at least in the pacific and perhaps elsewhere as well could have formed by sinking of surface waters in polar regions

size patterns of the coccolith watznaueria barnesiae in the lower cretaceous biotic versus abiotic forcing abstract body size is a major trait allowing the assessment of the respective control of evolution vs palaeo environment on unicellular micro organisms size patterns can be retraced for fossilisable micro organisms especially for coccolithophores over geological time spans here we present coccolith size patterns of watznaueria barnesiae which was a dominant and ubiquitous taxon in the mesozoic measurements were conducted at two sites spanning the upper berriasian to lower hauterivian namely the vergol la charce section in the epicontinental vocontian basin and the odp leg 185 hole 1149b located in the nadezhda basin in the pacific ocean the obtained results were treated using multivariate analysis in order to detect significant trends of the measured parameters size values of coccoliths from both sites are remarkably similar and display comparable patterns namely a statistically significant increase in the lower valanginian until maximum sizes recorded in the aftermath of the weissert event upper valanginian although w barnesiae coccolith size fluctuations in the short term might be related to environmental changes the observed long term size patterns are interpreted as the result of directional selection in which a single phenotype is favored through time comparison with data available in the literature shows a return to a smaller size after the turonian

trans dimensional joint inversion of seabed scattering and reflection data this paper examines joint inversion of acoustic scattering and reflection data to resolve seabed interface roughness parameters spectral strength exponent and cutoff and geoacoustic profiles trans dimensional trans d bayesian sampling is applied with both the number of sediment layers and the order zeroth or first of auto regressive parameters in the error model treated as unknowns a prior distribution that allows fluid sediment layers over an elastic basement in a trans d inversion is derived and implemented three cases are considered scattering only inversion joint scattering and reflection inversion and joint inversion with the trans d auto regressive error model including reflection data improves the resolution of scattering and geoacoustic parameters the trans d auto regressive model further improves scattering resolution and correctly differentiates between strongly and weakly correlated residual errors

ecological and evolutionary response of tethyan planktonic foraminifera to the middle eocene climatic optimum meco from the alano section ne italy abstract the enigmatic middle eocene climatic optimum meco is a transient 500 kyr warming event that significantly interrupted at 40 ma the long term cooling through the middle and late eocene eventually resulting in establishment of permanent antarctic ice sheet this event is still poorly known and data on the biotic response are so far scarce here we present a detailed planktonic foraminiferal analysis of the meco interval from a marginal basin of the central western tethys alano section northeastern italy the expanded and continuous alano section provides an excellent record of this event and offers an appealing opportunity to better understand the role of climate upon calcareous plankton evolution a sapropel like interval characterized by excursions in both the carbon and oxygen bulk carbonate isotope records represents the lithological expression of the post meco event in the study area and follows the 18 o negative shift interpreted as representing the meco warming high resolution quantitative analysis performed on both 38 m and 63 m fractions reveals pronounced and complex changes in planktonic foraminiferal assemblages indicating a strong environmental perturbation that parallels the variations of the stable isotope curves corresponding to the meco and post meco intervals these changes consist primarily in a marked increase in abundance of the relatively eutrophic subbotinids and of the small low oxygen tolerant streptochilus chiloguembelina and pseudohastigerina at the same time the arrival of the abundant opportunist eutrophic jenkinsina and pseudoglobigerinella bolivariana typical species of very high productivity areas also occurs the pronounced shift from oligotrophic to more eutrophic opportunist low oxygen tolerant planktonic foraminiferal assemblages suggests increased nutrient input and surface ocean productivity in response to the environmental perturbation associated with the meco particularly critical environmental conditions have been reached during the deposition of the sapropel like beds as testified by the presence of common giant and or odd morphotypes this is interpreted as evidence of transient alteration in the ocean chemistry the enhanced surface water productivity inferred by planktonic foraminiferal assemblages at the onset of the event should have resulted in heavier 13 c values the recorded lightening of the carbon stable isotope preceding the maximum warmth therefore represents a robust indication that it derives principally by a conspicuous increase of p co 2 the increased productivity of surface waters also supported by geochemical data may have acted as mechanism for p co 2 reduction and returned the climate system to the general eocene cooling trend the oxygen depleted deep waters and the organic carbon burial following the peak of the meco event represent the local response to the meco warming and suggest that high sequestration of organic matter if representing a widespread response to this event might have contributed to the decrease of p co 2 as well though the true mechanisms are still obscure several lines of evidence indicate a potential pressure on planktonic foraminiferal evolution during the meco event including permanent changes besides transient and ecologically controlled variations

estimating seabed scattering mechanisms via bayesian model selection a quantitative inversion procedure is developed and applied to determine the dominant scattering mechanism surface roughness and or volume scattering from seabed scattering strength data the classification system is based on trans dimensional bayesian inversion with the deviance information criterion used to select the dominant scattering mechanism scattering is modeled using first order perturbation theory as due to one of three mechanisms interface scattering from a rough seafloor volume scattering from a heterogeneous sediment layer or mixed scattering combining both interface and volume scattering the classification system is applied to six simulated test cases where it correctly identifies the true dominant scattering mechanism as having greater support from the data in five cases the remaining case is indecisive the approach is also applied to measured backscatter strength data where volume scattering is determined as the dominant scattering mechanism comparison of inversion results with core data indicates the method yields both a reasonable volume heterogeneity size distribution and a good estimate of the sub bottom depths at which scatterers occur

geoacoustic inversion of broadband data by matched beam processing this paper describes results of geoacoustic inversion using broadband signals from an experiment carried out at a site near the south florida ocean measurement centre in the florida straits m sequence coded pulse trains at different center carrier frequencies from 100to3200hz were recorded at a vertical line array at a distance around 10km geoacoustic inversion was carried out to determine the feasibility of inverting the environmental parameters from this long range propagation experiment the received signal at lower frequencies below 400hz consisted of a dominant water column signal and a secondary arrival delayed by 0 4s the secondary signal was spatially filtered by beamforming the array data and the beam data were inverted by matched beam processing in the time domain combined with an adaptive simplex simulated annealing algorithm the estimated values of compressional wave speed and density were in good agreement with ground truth values from sediment cores the inverted shear wave speed appea

similarities between planktonic and larger foraminiferal evolutionary trends through paleogene paleoceanographic changes abstract the paleogene evolutionary records of planktonic foraminifera and larger benthic foraminifera show parallel patterns in development that may in part reflect changes in nutrient flux to surface waters following the terminal cretaceous extinctions faunas were dominated by a few cosmopolitan opportunistic species more specialized k strategists in both groups diversified during the paleocene dominating into the early eocene consistent with he globally mild climatic regime and probable limited rates of nutrient flux to surface waters high latitude cooling intensified in the middle eocene promoting diversification of less specialized taxa characteristic of cooler and deeper waters higher latitudes meridional upwelling zones and boundary currents geographic ranges of warm water taxa diminished and fragmented yet many species survived thus global diversities during the middle eocene were the highest in the cenozoic as cooling and increased rates of nutrient flux further intensified in the late eocene extinction rates of warm water planktonic and larger benthic species exceeded origination rates of cooler water and less specialized forms so diversity dropped to intermediate levels where it remained through the late eocene and oligocene previous observations that planktonic foraminiferal faunas dominated by warm water taxa are often replaced by cool water faunas even though oxygen isotopes only recorded relatively minor cooling can be reconciled by the explanation that the biotic communities responded to changes in trophic resources and euphotic habitats that accompany the temperature reduction as well as to temperature change itself

cenozoic palaeotemperature changes and planktonic foraminiferal speciation the interaction of plate movements and progressive climatic deterioration produced a constantly changing oceanic environment during the cenozoic the destruction of the tethyan seaway and the severing of low latitude oceanographic connections during the past 65 myr ref 1 coupled with the initiation of unrestricted circum antarctic circulation in the middle to late oligocene2 provided the necessary boundary conditions for the development of a global ocean marked by steep latitudinal temperature gradients this is in contrast to the rather mild climate of the mesozoic which was characterized by an ocean with a homogeneous thermal structure and weak latitudinal temperature gradients1 throughout the cenozoic marine plankton were constantly adapting to major changes in the oceanic environment this can be seen for example in the continual development of latitudinal provincialization as a response to polar coolings1 3 here i attempt to evaluate the relationship between palaeotemperature change and planktonic foraminiferal speciation during the past 65 myr

bayesian inference for ultralow velocity zones in the earth s lowermost mantle complex ulvz beneath the east of the philippines national collaborative research infrastructure strategy ncris and the education investment fund eif3

oxygen isotope ranking of late eocene and oligocene planktonic foraminifers implications for oligocene sea surface temperatures and global ice volume abstract oxygen isotope analyses of late eocene and oligocene planktonic foraminifers from low and middle latitude sites in the atlantic basin show that different species from the same samples can yield significantly different isotopic values the range of isotopic values observed between species is greatest at low latitudes and declines poleward many planktonic foraminifers exhibit a systematic isotopic ranking with respect to each other and can therefore be grouped on the basis of their isotopic ranking the isotopic ranking of some taxa however appears to vary geographically and or through time isotopic and paleontologic data from dsdp site 522 indicate that commonly used isotopic temperature scales underestimate oligocene sea surface temperatures we suggest these temperature scales require revision to reflect the presence of oligocene glaciation comparison of isotopic and paleontologic data from sites 522 511 and 277 suggests cold low salinity surface waters were present in high southern latitudes during the early oligocene lowsalinity high latitude surface waters could be caused by eocene oligocene paleogeography or by the production of warm saline bottom water

taxonomic evolution of neogene planktonic foraminifera and paleoceanographic relations the taxonomic evolution of neogene 24 ma to present day planktonic foraminiferal species are described using four indices rate of speciation rate of extinction rate of diversification and rate of turnover the evolution of neogene planktonic foraminifera is marked by three principal stages 1 a diversification stage 24 to 16 ma early miocene 2 an equilibrium stage 16 to 5 ma middle and late miocene and 3 a declining stage 5 ma to recent pliocene and quaternary the early miocene diversification was in response to an increase in polar to equatorial thermal gradients and related subdivision of surface water masses during the middle and late miocene the assemblages remained close to their equilibria with relatively low diversification rates the decline in diversity during the pliocene and quaternary probably resulted from adverse effects imposed by both large scale paleoceanographic fluctuations that began about 6 ma and high frequency climatic oscillations related to northern hemisphere glaciations and deglaciations that began at about 2 5 ma bursts of evolutionary activity marked by higher rates of turnover coincided with major paleoceanographic changes average evolutionary rates appear to be similar for tropical transitional and temperate assemblages although the actual numbers of extinctions and speciations are higher in tropical assemblages because of higher standing diversity contemporaneity of turnover peaks in the three climatic regimes indicates global control of paleoceanographic perturbations upon planktonic foraminiferal evolution the observed evolutionary pattern supports the stationary model of stenseth and maynard smith 1984

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

evolutionary consequences of the latest paleocene thermal maximum for tropical planktonic foraminifera study of planktonic foraminiferal assemblages preserved in the central equatorial pacific odp site 865 reveal that genera which inhabited the near surface mixed layer diversified during the latest paleocene thermal maximum lptm this transient diversification gave rise to a suite of short lived 50 to several 100 ka distinctive morphotypes morozovella allisonensis sp nov m africana and acarinina sibaiyaensis that are restricted to the lptm interval parallel morphometric and stable isotopic data have been recorded from individual shells of members of the m velascoensis m allisonensis and a soldadoensis a sibaiyaensis lineages the single specimen isotope data confirm that m allisonensis and a sibaiyaensis are indeed stratigraphically restricted to the lptm carbon isotope excursion all specimens recorded anomalously low 13c values a stratigraphic succession of single specimen isotope data from within the 13c excursion interval was used to reconstruct the complex population dynamics which mediated the rapid 10 ka evolution of the lptm taxa these data reveal that local populations of ancestral m velascoensis temporarily collapsed with the descendant m allisonensis suddenly originating from a peripherally isolated population this pattern is most consistent with peripatric speciation overall the evolutionary transition from acarinina soldadoensis to a sibaiyaensis is most consistent with sympatric speciation although certain elements of this transition are suggestive of a parapatric mechanism we postulate that the rapid evolution of the lptm taxa a sibaiyaensis and m allisonensis was fostered by a deepening of the nutrient depleted mixed layer alternatively the lptm morphotypes m allisonensis and a sibaiyaensis may have been extreme ecophenotypic variants arrayed along an intensified ecological gradient support for this latter interpretation is derived from the morphometric data which clearly show the morphological intergradation of the lptm taxa with their respective ancestors thus the morphologic diversification seen during the lptm may represent failed speciations both scenarios invoke a temporary steepening of clinal gradients in response to intensified oligotrophy the strong size dependencies displayed by the 18o and 13c signatures of m allisonensis and a sibaiyaensis suggest that photosymbiosis facilitated the evolutionary success of the morozovellids and acarininids during the lptm

high resolution geoacoustic inversion in shallow water a joint time and frequency domain technique high resolution geoacoustic data are required for accurate predictions of acoustic propagation and scattering in shallow water since direct measurement of geoacoustic data is difficult time consuming and expensive inversion of acoustic data is a promising alternative however the main problem encountered in geoacoustic inversion is the problem of uniqueness i e many diverse geoacoustic models can be made to fit the same data set a key and perhaps unique aspect of this approach is the combination of data analysis in both the space time and the space frequency domains this combination attempts to ameliorate the uniqueness problem by exploiting as much independent data as possible in order to meet the stringent requirements of high spatial resolution and uniqueness an entire method has been developed including a new measurement technique processing analysis technique and inversion strategy these techniques are described and then illustrated with a shallow water data set sound speed gradients in the upper few meters of the sub bottom appear to be much higher one order of magnitude than generally assumed and although often ignored a large density gradient was observed in the top layer that played an acoustically significant role

fluctuations in the trophic resource continuum a factor in global diversity cycles the trophic resource continuum trc in euphotic zones of the world s oceans is the spectrum of conditions from the richest runoff and upwelling areas to the most nutrient deficient subtropical seas that spectral range has likely varied through geologic history as more efficient phytoplankton taxa evolved as oceanic circulation rates changed and in response to oceanic mixing events reduced rates of oceanic turnover should produce regionally intensified eutrophy and oligotrophy that is trc expansion because oceanic waters as a whole are relatively nutrient rich increased rates of oceanic turnover should prevent extremely eutrophic and extremely oligotrophic conditions from developing causing trc contraction global biotic diversities in the oceans are strongly influenced by communities in oligotrophic environments nutrient deficient waters are more stable and more transparent than richer waters permitting higher degrees of specialization sparse nutrient supplies necessitate smaller phytoplankton and longer more complex food chains preservation potential of oligotrophic biotas is also greater because calcareous taxa are more prevalent and because calcium carbonate is less apt to be bioeroded or dissolved fluctuations in the trc should profoundly affect diversity of habitats within the euphotic zone of the oceans the evolutionary response to a trc expansion diversification would occur in a geologic time frame of millions of years while evolutionary responses to a trc contraction including extinction could occur in a biological time frame of generations a simple model indicates that a reduction in the trophic resource continuum from expansion during a major marine transgression down to modern levels could result in loss of 40 of the euphotic habitats how fluctuations in the trc control diversity of euphotic habitats in the oceans provides an hypothesis by which to interpret global taxonomic diversity cycles as well as taxonomically selective extinctions changes in species dominance and some morphologic trends

shell size variation of the planktonic foraminifer neogloboquadrina pachyderma sin in the norwegian greenland sea during the last 1 3 myrs implications for paleoceanographic reconstructions we present measurements of the maximum diameter of the planktonic foraminifer neogloboquadrina pachyderma sin from six sediment cores ocean drilling program sites 643 644 907 909 985 and 987 from the norwegian greenland sea our data show a distinct net increase in mean shell size of n pachyderma sin at all sites during the last 1 3 ma with largest shell sizes reached after 0 4 ma external factors such as glacial interglacial variability and carbonate dissolution alone cannot account for the observed variation in mean shell size of n pachyderma sin we consider the observed shell size increase to mirror an evolutionary trend towards better adaptation of n pachyderma sin to the cold water environment after 1 1 1 0 ma probably the mid pleistocene climate shift and the associated change of amplitude and frequency of glacial interglacial fluctuations have triggered the evolution of this planktonic foraminifer oxygen and carbon stable isotope analyses of diverent shell size classes indicate that the observed shell size increase could not be explained by the functional concept that larger shells promote increasing sinking velocities during gametogenesis for paleoceanographic reconstructions the evolutionary adaptation of neogloboquadrina pachyderma sin to the cold water habitat has significant implications carbonate sedimentation in highest latitudes is highly dependent on the presence of this species in the norwegian greenland sea carbonate poor intervals before 1 1 ma are therefore not necessarily related to severe glacial conditions they are probably attributed to the absence of this not yet polar adapted species further transfer function and modern analog techniques used for the reconstruction of surface water conditions in high latitudes could therefore contain a large range of errors if they were applied to samples older than 1 1 1 0 myrs 2000 elsevier science b v all rights reserved

a record of the last 460 thousand years of upper ocean stratification from the central walvis ridge south atlantic the upper branch of the atlantic meridional overturning circulation predominantly enters the atlantic ocean through the southeast where the subtropical gyre is exposed to the influence of the agulhas leakage al to understand how the transfer of indian ocean waters via the al affected the upper water column of this region we have generated new proxy records of planktic foraminifera from a core on the central walvis ridge on the eastern flank of the south atlantic gyre sag we analyzed the isotopic composition of subsurface dweller globigerinoides ruber sensu lato and thermocline globorotalia truncatulinoides sinistral spanning the last five pleistocene glacial interglacial g ig cycles the former displays a response to obliquity suggesting connection with high latitude forcing and a warming tendency during each glacial termination in response to the interhemispheric seesaw the 18o difference between the two species interpreted as a proxy for upper ocean stratification reveals a remarkably regular sawtooth pattern bound to g ig cyclicity it rises from interglacials until glacial terminations with fast subsequent decrease appearing to promptly respond to deglacial peaks of al stratification however bears a different structure during the last cycle being minimal at last glacial maximum and peaking at termination i we suggest this to be the result of the intensified glacial wind field over the sag and or of the invasion of the south atlantic thermocline by glacial north atlantic intermediate waters the 13c time series of the two species have similar g ig pattern whereas their difference is higher during interglacials we propose that this may be the result of the alternation of intermediate water masses in different circulation modes and of a regionally more efficient biological pump at times of high pco2

bayesian inversion of marine csem data with a trans dimensional self parametrizing algorithm summary the posterior distribution of earth models that fit observed geophysical data convey information on the uncertainty with which they are resolved from another perspective the non uniqueness inherent in most geophysical inverse problems of interest can be quantified by examining the posterior model distribution converged upon by a bayesian inversion in this work we apply a reversible jump markov chain monte carlo method to sample the posterior model distribution for the anisotropic 1 d seafloor conductivity constrained by marine controlled source electromagnetic data unlike conventional gradient based inversion approaches our algorithm does not require any subjective choice of regularization parameter and it is self parametrizing and trans dimensional in that the number of interfaces with a resistivity contrast at depth is variable as are their positions a synthetic example demonstrates how the algorithm can be used to appraise the resolution capabilities of various electromagnetic field components for mapping a thin resistive reservoir buried beneath anisotropic conductive sediments a second example applies the method to survey data collected over the pluto gas field on the northwest australian shelf a benefit of our bayesian approach is that subsets of the posterior model probabilities can be selected to test various hypotheses about the model structure without requiring further inversions as examples the subset of model probabilities can be viewed for models only containing a certain number of layers or for models where resistive layers are present between a certain interval as suggested by other geological constraints such as seismic stratigraphy or nearby well logs

trans dimensional finite fault inversion summary this paper develops a probabilistic bayesian approach to the problem of inferring the spatiotemporal evolution of earthquake rupture on a fault surface from seismic data with rigorous uncertainty estimation to date uncertainties of rupture parameters are poorly understood and the effect of choices such as fault discretization on uncertainties has not been studied we show that model choice is fundamentally linked to uncertainty estimation and can have profound effects on results the approach developed here is based on a trans dimensional selfparametrizationofthefault avoidsregularizationconstraintsandprovidesrigorousuncertainty estimationthataccountsformodel selectionambiguityassociatedwiththefaultdiscretization in particular the fault is parametrized using self adapting irregular grids which intrinsically match the local resolving power of the data and provide parsimonious solutions requiring few parameters to capture complex rupture characteristics rupture causality is ensured by parametrizing rupture onset time by a rupture velocity field and obtaining first rupture times from the eikonal equation the bayesian sampling of the parameter space is implemented on a computer cluster with a highly efficient parallel tempering algorithm the inversion is applied to simulated and observed w phase waveforms from the 2010 maule chile earthquake simulation results show that our approach avoids both over and underparametrization to ensure unbiased inversion results with uncertainty estimates that are consistent with data information the simulation results also show the ability of w phase data to resolve the spatial variability of slip magnitude and rake angles in addition sensitivity to spatially dependent rupture velocities exists for kinematic slip models application to the observed data indicates that residual errors are highly correlated and likely dominated by theory error necessitating the iterative estimation of a non stationary data covariance matrix the moment magnitude for the maule earthquake is estimated to be 8 9 with slip concentrated in two zones updip of and north and south of the hypocentre respectively while this aspect of the slip distribution is similar to previous studies we show that the slip maximum in the southern zone is poorly resolved compared to the northern zone both slip maxima are higher than reported in previous studies which we speculate may be due to the lack of bias caused by the regularization used in other studies

pattern of first and last appearance in diatoms oceanic circulation and the position of polar fronts during the cenozoic 1 first and last occurrences of 389 diatom species from the first global cenozoic record are used to reconstruct the position of major oceanographic boundaries first appearances and extinctions group in three latitudinal bands middle to high northern latitudes equatorial region and high southern latitudes sparse paleogene occurrences were limited to southern high latitudes along the equivalent of the modern antarctic polar front its late middle eocene to middle miocene position varied within 10 and within a 20 band from middle miocene to present suggesting an association with global cooling first and last occurrence events appear in the two remaining latitudinal regions during the eocene and increase in a stepwise fashion mimicking significant cooling events at about 16 ma first and last appearances shift from the north atlantic to the north pacific low latitude data suggest low surface water productivity prior to 40 ma while increased abundance from the middle miocene correlates with expansion of the east antarctic ice sheet

reconstruction of atmospheric co2 from ice core data and the deep sea record of ontong java plateau the milankovitch chron we provide a reconstruction of atmospheric co2 from deep sea sediments for the past 625000 years milankovitch chron our database consists of a milankovitch template of sea level variation in combination with a unique data set for the deep sea record for ontong java plateau in the western equatorial pacific we redate the vostok ice core data of barnola et al 1987 to make the reconstructions we employ multiple regression between deep sea data on one hand and ice core co2 data in antarctica on the other the patterns of correlation suggest that the main factors controlling atmospheric co2 can be described as a combination of sea level state and sea level change for best results squared values of state and change are used the square of sea level rule agrees with the concept that shelf processes are important modulators of atmospheric co2 e g budgets of shelf organic carbon and shelf carbonate nitrate reduction the square of change rule implies that on short timescales any major disturbance of the system results in a temporary rise in atmospheric co2

intraspecific morphological variation with biometry of distephanus speculum silicoflagellata article i nfo living specimens of distephanus speculum silicoflagellata were collected in waters of b150 m depth in the pacific sector of the southern ocean 57 31 6 s 150 02 9 e south of tasman island and a biometric study has been conducted the skeleton of d speculum has a simple morphology which can be readily expressed quantitatively using a new methodology repeated measurements were obtained and converted to numer ical indices the circumference of the basal rings was the most useful character for subdivision into groups and using this parameter we recognized two populations in the 620 studied specimens 1 500 individuals were placed in group a with a basal ring circumference of 53 to 67 m and a difference in length of spine axes from 2 to 6 m and 2 120 individuals were placed in group b basal ring circumference 80 to 105 m difference in length of spine axes 3 to 6 m the circumference of the basal ring in group b is approximately 10 m smaller than in distephanus speculum giganteus bukry d 1979 comments on opal phytoliths and stratigraphyofneogenesilicoflagellatesandcoccolithsatdeepseadrillingprojectsite397offnorthwestafrica initial report of the dsdp washington 49 977 1009 and distephanus boliviensis bukry d 1976a silico flagellate and coccolith stratigraphy norwegian greenland sea initial report of dsdp leg 38 initial report of the dsdp washington 38 843 855 bukry d 1976b silicoflagellate and coccolith stratigraphy southeastern

numerical models of diagenesis sediment properties and pore fluid chemistry on a paleoceanographic transect blake nose ocean drilling program leg 171b a critical issue in many paleoceanographic studies is the potential of diagenetic processes to compromise the fidelity of geochemical proxies e g 18o in deep sea carbonate sediments and microfossils a recently established strategy for dealing with this issue is to drill depth transects in anomalously shallowly buried and therefore presumably well preserved target sediments here we report the results of an experiment designed to test the validity of this approach we apply a simple one dimensional numerical model to complex pore water chemical profiles for ca mg sr 87sr 86sr and 18o observed in a shallowly buried paleoceanographic transect of paleogene and cretaceous age drilled on blake nose during ocean drilling program leg 171b we show that it is possible to reproduce these complex pore water profiles simply by invoking 1 a deep seated zone of chemical reaction well below the recovered sections and 2 minimal chemical alteration within the overlying recovered sediments but significant restriction of advective flow by embedded low porosity layers these results suggest that the sediments recovered during ocean drilling program leg 171b can be considered to be virtually chemically inert at their present burial depth their carbonate recrystallization histories having been largely limited to events during early 10 ma timescale burial these findings support the strategy of selecting unusually shallowly buried sections for paleoceanographic transect drilling ironically however the very attraction of targeting such sections the lack of overlying sediments dictates that it is not possible to use pore water chemistry to constrain the early diagenetic histories of such sections because of the diffusion of the pore water signal through the sediment water interface diffusional loss may also account for the absence of pore water chemical anomalies associated with the ooze chalk transition at blake nose however our work suggests that traditional interpretations of this boundary as the inferred locus of maximum rates of carbonate recrystallization require reevaluation

dwarfism of irregular echinoids echinocorys from poland during the campanian maastrichtian boundary event abstract the echinoid genus echinocorys is one of the dominant irregular echinoid in the cretaceous of poland our analysis of the body size trends of these echinoids shows that they underwent dwarfism in the early maastrichtian the reduction in body size in these echinoids was likely an ecological response to the major climate perturbations connected with the campanian maastrichtian boundary event cmbe that was characterized by a long lasting negative carbon isotope excursion and cooling this is consistent with the fact that food limitations and cold temperatures are among the major factors decreasing growth rates in modern echinoids so far in the case of echinoids the so called lilliput effect has been only recognized in the early danian early paleogene heart urchins atelostomata thus our study shows that the reduction in the body size in echinoids was a more common biotic response to environmental stress than previously thought

the evolutionary history of size variation of planktic foraminiferal assemblages in the cenozoic abstract the iterative evolutionary radiation of planktic foraminifers is a well documented macroevolutionary process here we document the accompanying size changes in entire planktic foraminiferal assemblages for the past 70 my and their relationship to paleoenvironmental changes after the size decrease at the cretaceous paleogene k p boundary high latitude assemblages remained consistently small size evolution in low latitudes can be divided into three major phases the first is characterized by dwarfs 65 42 ma the second shows moderate size fluctuations 42 14 ma and in the third phase planktic foraminifers have grown to the unprecedented sizes observed today our analyses of size variability with paleoproxy records indicate that periods of size increase coincided with phases of global cooling eocene and neogene these periods were characterized by enhanced latitudinal and vertical temperature gradients in the oceans and high diversity polytaxy in the paleocene and during the oligocene the observed minor size changes of the largely low diversity oligotaxic assemblages seem to correlate with productivity changes however polytaxy per se was not responsible for larger test sizes

analyses of high frequency bottom and subbottom backscattering for two distinct shallow water environments high frequency 40 khz bottom backscattering data obtained by the benthic acoustic measurement system from two different shallow water locations were analyzed one of the sites has a hard sandy bottom and the other a soft silty bottom since the data were recorded on two slightly separated arrays the differential phase technique was used to locate the scatterers it is found that scattering at the sandy site originated from the seafloor interface while the scattering at the silty bottom was caused by a scattering layer about 1 m beneath the seafloor believed to be methane gas voids the backscattering strengths at the silty bottom were about 3 db higher than those at the sandy bottom a simple sub bottom scattering model for the silty bottom is assumed and compared with the data when the sound refraction and attenuation are taken into account the model data fit yields reasonable results

atlantic eocene planktonic foraminiferal paleohydrographic indicators and stable isotope paleoceanography reconstruction of atlantic ocean vertical and meridional water characteristics is based on combined synoptic fossil census data stable isotope records and measurements of individual planktonic foraminiferal species correlations between planktonic foraminiferal indices and specific water types and or chemical conditions are used to trace seven stages in the history of atlantic circulation during eocene climatic changes 1 warm equable probably saline productive ocean of the early eocene characterized by lowest meridional and vertical thermal gradients and the maximal extent of tropical surface water 2 early middle eocene expansion of subtropical waters and faunas accompanying the first climatic cooling and eutrophication of equatorial surface waters 3 maximal partitioning of water types faunas and bioprovinces in middle eocene zone p11 accompanying maximum planktonic foraminiferal diversity accelerated near surface and deepwater cooling and intensified upwelling 4 latest middle eocene zone p14 maximal planktonic foraminiferal evolutionary overturn during accelerated cooling deep and surface water ventilation and transformation of tropical surface water habitat with the expansion of temperate water types and faunas this accompanied the reduction of meridional heat transport in boundary currents 5 late eocene bottom water and middle latitude cooling broadening of meridional temperature gradients and expanded oxygen minimum but faunal homogenization following the decreased import of mediterranean water ourflow 6 weakening and or shoaling of the nutricline an oxygen minimum and the thermocline preceding a diminution of primary productivity at the eocene oligocene boundary and 7 earliest oligocene low productivty ocean marked by diminished vertical thermal contrasts and homogeneous foraminiferal faunas dominated by small sized individuals the increased areal extent of upwelling with the outcropping of cooler waters over large geographic regions provides an important climatic forcing mechanism in the latest middle and late eocene

response of planktic foraminiferal size to late quaternary climate change 1 geographical size distribution within entire holocene foraminiferal assemblages is related to global environmental gradients such as temperature primary productivity and environmental variability this study demonstrates that these correlations are also recognizable in late quaternary assemblages from three locations in the south atlantic on temporal and latitudinal scales the size response to temporal paleoenvironmental changes during glacial interglacial cycles mimics the geographic holocene size variability the amplitude of size variability is directly related to the amplitude of the climatic fluctuations as shown by the stable size temperature relationship over time the documented changes in the assemblage size are caused by species replacement and intraspecific size variability the relative importance of these processes depends on the environmental setting species have been shown to reach their maximum size and abundance under certain optimum conditions and decrease in size if environmental conditions differ from these optima we confirm that late quaternary species sizes were largest at paleotemperatures identical to holocene ones

reconstruction of a pleistocene paleocatena using micromorphology and geochemistry of lake margin paleo vertisols olduvai gorge tanzania abstract olduvai gorge tanzania contains a rich record of pleistocene paleoclimate and paleoenvironment as well as an abundance of paleontological and archaeological data the 2 2 ma of volcaniclastic infill can be divided into time slices using dated tuffs sediments were deposited in a semi arid closed rift basin containing a shallow saline alkaline lake until 1 75 ma four trenches in uppermost bed i sample a 20 ka time slice between ng eju tuff base 1 818 0 006 ma and tuff if top 1 803 0 002 ma they form a 1 km transect of the lake margin flat that contains both stacked and cumulative paleosols that are interpreted as a heterogeneous paleocatena closer to the lake paleosols are thinner vertically stacked and separated by thin tuffs or tufa further from the lake margin there is additional volcaniclastic input and paleosols are thicker and cumulative macroscale and micromorphological features identify these clay rich paleosols as paleo vertisols abundant pedogenic slickensides and a variety of ped shapes were observed in the field as well as micro ped structures and stress cutans in thin section although weakly developed these paleo vertisols also have distinct horizons defined by soil color changes differing ped shapes and bulk geochemistry and are indicative of monsoonal precipitation seasonality paleosols and parent materials were analyzed for bulk geochemistry of major rare and trace elements geochemical proxies reveal changing hydrology not definitively identifiable in the field or micromorphology molecular weathering ratios show increased weathering and mass balance calculations indicate greater translocations positive and negative through time lower soil moisture due to a drier climate likely created better drained conditions allowing for increased pedogenesis the records of femn oxides and zeolites precipitated in rhizoliths are further evidence for changing redox conditions and water chemistry redox sensitive elements such as fe and mn were mobilized during saturated soil conditions and precipitated during drier conditions as the hydrology changed due to increased aridity zeolites precipitated as rhizoliths due to capillary rise and evaporative pumping of saline alkaline water the fluctuating hydrology identified in the paleo vertisols deposited between 1 79 and 1 81 ma is indicative of a precession cycle and consistent with records from olduvai gorge and throughout east africa this 20 ka time slice of the 2 ma drying trend identified in africa coincides with the first hominin migrations out of africa at 1 8 ma and suggests that hominins were living in a water stressed environment with annual precipitation seasonality and large variations in precipitation due to precession

barium and the late paleocene δ13c maximum evidence of increased marine surface productivity deep sea sediment ba ba al2o3 sample 15 ba aluminosilicate records show increasing values synchronous with the evolution of the late paleocene global 13c maximum reflecting an increase in marine surface primary production and biogenic barite formation at this time at two oligotrophic locations deep sea drilling project dsdp sites 384 and 527 in the north and south atlantic respectively ba increases from 160 360 ppm in the early paleocene to 1100 3000 ppm during the 13c maximum at equatorial dsdp site 577 positioned within or near the high productivity zone ba increases from 15 500 ppm in the early paleocene to 25 400 ppm in conjunction with late paleocene maximum 13c values linear fitted correlation plots of sediment ba content versus surface water 13c in all three regions support barite originating in the euphotic zone the early to late paleocene relative increase in ba illustrates how burial rates of corg relative to al2o3 accelerated by a factor of 1 8 and 6 0 in the eutrophic and oligotrophic areas respectively a tentative estimate weighing our result for the entire ocean suggests that accumulation rates of organic carbon increased by a factor of 2 during the late paleocene 13c maximum

geochemical evidence for suppression of pelagic marine productivity at the cretaceous tertiary boundary the normal biologically productive ocean is characterized by a gradient of the 13c 12c ratio from surface to deep waters here we present stable isotope data from planktonic and benthic micro fossils across the cretaceous tertiary boundary in the north pacific which reveal a rapid and complete breakdown in this biologically mediated gradient the fluxes of barium a proxy for organic carbon and caco3 also decrease significantly at the time of the major marine plankton extinctions the implied substantial reduction in oceanic primary productivity persisted for 0 5 myr before the carbon isotope gradient was gradually re established in addition the stable isotope and preservational data indicate that environmental change including cooling began at least 200 kyr before the cretaceous tertiary boundary and a peak warming of 3 c occurred 600 kyr after the boundary event

distribution of paleogene planktonic foraminifera analogies with the recent abstract distribution patterns and morphologies of modern and paleogene planktonic foraminifera in the atlantic ocean were compared although many paleogene and modern planktonic foraminifera are homeomorphs they are not ecomorphs morozovellid homeomorphs of the modern higher spired globorotaliids inhabited warmest layers of the mixed layer the planorotalitids homeomorphic with modern low trochospiral globorotaliids have different geographic ranges they predominated at temperature and higher latitudes where they grew to largest sizes the cool water low spired subbotinids little resemble the non spinose modern neogloboquadrinids which dominate polar faunas today spinosity of paleogene polar forms indicates that they could have been carnivorous or omnivorous rather than herbivorous like the modern neogloboquadrinids early paleogene polar seas may have been relatively oligotrophic for at least part of the year some paleogene genera may have been ecomorphic with their modern analogues the dentoglobigerinids and globoquadrinids occupied equatorial and offshore upwellings much as neogloboquadrina dutertrei does today because the globorotaloids and catapsydracids deposited calcitic crusts and register most enriched oxygen isotope values they may have lived within and below the thermocline like some modern globorotaliids globorotaloids and catapsydracids may have been strictly herbivorous as are most modern non spinose species their predominance in later paleogene lower latitude upwellings but their near exclusion from polar regions indicates that subeuphotic equatorial waters may have been more eutrophic paleogene type warming in zones p1d p3a p5 p6 7 late p12 late p16 late p19 and early p22 involves proliferation evolutionary diversification and poleward migration of thermophilic forms but decreased species abundance at low latitudes and diminished numbers of fertility indices the guembelitrids biserial heterohelicids globigerinathekids globoquadrinids or dentoglobigerinids neogene type warmings in zones p4 and probably p alpha and p21a involved diversification of cooler water taxa retreat of thermophilic forms from higher latitudes and their concentration in lower latitudes and proliferation of fertility indices under these conditions oxygen isotope records include lower latitude warming but cooling of temperature and higher latitudes and tropospheric waters planktonic foraminiferal diversity and population structure reflect changes in oceanic fertility and the depth of the thermocline cooling and eutrophication resulting in a contraction of the trc trophic resource continuum in atlantic surface waters from late middle eocene through mid oligocene time explain the low diversities extinctions of morphologically complex thermophilic species increased dominance of opportunistic subeuphotic and temperature species proliferation of euphotic and subeuphotic fertility indices and geographic expansion of siliceous primary producers

joint time frequency domain inversion of reflection data for seabed geoacoustic profiles and uncertainties this paper develops a joint time frequency domain inversion for high resolution single bounce reflection data with the potential to resolve fine scale profiles of sediment velocity density and attenuation over small seafloor footprints approximately 100 m the approach utilizes sequential bayesian inversion of time and frequency domain reflection data employing ray tracing inversion for reflection travel times and a layer packet stripping method for spherical wave reflection coefficient inversion posterior credibility intervals from the travel time inversion are passed on as prior information to the reflection coefficient inversion within the reflection coefficient inversion parameter information is passed from one layer packet inversion to the next in terms of marginal probability distributions rotated into principal components providing an efficient approach to partially account for multi dimensional parameter correlations with one dimensional numerical distributions quantitative geoacoustic parameter uncertainties are provided by a nonlinear gibbs sampling approach employing full data error covariance estimation including nonstationary effects and accounting for possible biases in travel time picks posterior examination of data residuals shows the importance of including data covariance estimates in the inversion the joint inversion is applied to data collected on the malta plateau during the scarab98 experiment

seabed roughness parameters from joint backscatter and reflection inversion at the malta plateau this paper presents estimates of seabed roughness and geoacoustic parameters and uncertainties on the malta plateau mediterranean sea by joint bayesian inversion of mono static backscatter and spherical wave reflection coefficient data the data are modeled using homogeneous fluid sediment layers overlying an elastic basement the scattering model assumes a randomly rough water sediment interface with a von karman roughness power spectrum scattering and reflection data are inverted simultaneously using a population of interacting markov chains to sample roughness and geoacoustic parameters as well as residual error parameters trans dimensional sampling is applied to treat the number of sediment layers and the order zeroth or first of an autoregressive error model to represent potential residual correlation as unknowns results are considered in terms of marginal posterior probability profiles and distributions which quantify the effective data information content to resolve scattering geoacoustic structure results indicate well defined scattering roughness parameters in good agreement with existing measurements and a multi layer sediment profile over a high speed elastic basement consistent with independent knowledge of sand layers over limestone

abiotic forcing of plankton evolution in the cenozoic we characterize the evolutionary radiation of planktic foraminifera by the test size distributions of entire assemblages in more than 500 cenozoic marine sediment samples including more than 1 million tests calibration of holocene size patterns with environmental parameters and comparisons with cenozoic paleoproxy data show a consistently positive correlation between test size and surface water stratification intensity we infer that the observed macroevolutionary increase in test size of planktic foraminifera through the cenozoic was an adaptive response to intensifying surface water stratification in low latitudes which was driven by polar cooling

resolving meso scale seabed variability using reflection measurements from an autonomous underwater vehicle seabed geoacoustic variability is driven by geological processes that occur over a wide spectrum of space time scales while the acoustics community has some understanding of horizontal fine scale geoacoustic variability less than o 100 m and large scale variability greater than o 103 m there is a paucity of data resolving the geoacoustic meso scale o 100 103 m measurements of the meso scale along an ostensibly benign portion of the outer shelf reveal three classes of variability the first class was expected and is due to horizontal variability of layer thicknesses this was the only class that could be directly tied to seismic reflection data the second class is due to rapid changes in layer properties and or boundaries occurring over scales of meters to hundreds of meters the third class was observed as rapid variations of the angle frequency dependent reflection coefficient within a single observation and is suggestive of variability at scales of meter or less though generally assumed to be negligible in acoustic modeling the second and third classes are indicative of strong horizontal geoacoustic variability within a given layer the observations give early insight into possible effects of horizontal geoacoustic variability on long range acoustic propagation and reverberation

measurement technique for bottom scattering in shallow water sonar performance predictions of reverberation in shallow water rely upon good estimates of the bottom scattering strength however little is understood about bottom scattering in shallow water in the frequency range 400 4000 hz particularly its dependency upon frequency and its relationship to the physical properties of the seafloor in order to address these issues a new measurement technique has been developed to probe the frequency and angular dependency of bottom scattering strength the experimental technique is described which employs either coherent or incoherent sources lightbulbs in addition measurement and modeling results for two diverse shallow water sites are presented at one site the scattering appears to arise at or near the water sediment interface at the other site scattering from a 23 m sub bottom horizon is clearly apparent in the data at and below 1800 hz the fact that our measurement technique can directly reveal the presence of sub bottom scattering is a significant advance in the development of methods to explore the physical mechanisms that control bottom scattering

evolution of cenozoic seaways in the circum antarctic region abstract a complete circum antarctic seaway did not open until both the south tasman rise cleared the oates land coast of east antarctica and drake passage opened between the southern tip of south america and the northern end of the antarctic peninsula major plate motions based on dated seafloor spreading anomalies and distinct fracture zone lineations constrain the age of the opening of a seaway between the south tasman rise and antarctica as very close to the eocene oligocene boundary with an unrestricted opening deeper than 2000 m dating from 32 ma timing of the opening of drake passage is more circumstantial because the exact motions of certain micro continental fragments are not known the motion of africa with respect to south america as well as the motion of east antarctica with respect to africa are well constrained for the cenozoic these major plate motions are used with the reasonable assumption of no cenozoic motion of the antarctic peninsula with respect to east antarctica to constrain the location of the antarctic peninsula with respect to the southern tip of south america for the critical period of late eocene to late oligocene uncertainty of motion of the south georgia and south orkney microcontinents and other possible continental fragments make an exact time for opening of drake passage difficult to ascertain even so the early oligocene position of the antarctic peninsula with respect to south america requires a through going deep water seaway to have been open at drake passage prior to 28 ma even given the unconstrained motion of various high standing crustal fragments in the scotia sea with reasonable assumptions concerning motion of the crustal fragments in the western and central scotia sea it is likely that drake passage or passage through powell basin was open to deep water circulation by 31 2 ma

bayesian geoacoustic inversion of ship noise on a horizontal array this paper applies geoacoustic inversion to low frequency narrow band acoustic data from a quiet surface ship recorded on a bottom moored horizontal line array in shallow water a bayesian matched field inversion method is employed which quantifies geoacoustic uncertainties and allows for meaningful comparison of inversion results from different data sets geoacoustic inversion results for ship noise data are compared with inversion results for multitone data from a towed controlled source collected in the same experiment and with independent geophysical measurements to increase the information content of low level ship noise data the effect of including multiple independent data segments in the inversion is investigated and shown to significantly reduce geoacoustic parameter uncertainties geoacoustic uncertainties are also shown to depend on ship range and orientation with increased uncertainties for long ranges and for the ship stern oriented away from the array

a trans dimensional polynomial spline parameterization for gradient based geoacoustic inversion this paper presents a polynomial spline based parameterization for trans dimensional geoacoustic inversion the parameterization is demonstrated for both simulated and measured data and shown to be an effective method of representing sediment geoacoustic profiles dominated by gradients as typically occur for example in muddy seabeds specifically the spline parameterization is compared using the deviance information criterion dic to the standard stack of homogeneous layers parameterization for the inversion of bottom loss data measured at a muddy seabed experiment site on the malta plateau the dic is an information criterion that is well suited to trans d bayesian inversion and is introduced to geoacoustics in this paper inversion results for both parameterizations are in good agreement with measurements on a sediment core extracted at the site however the spline parameterization more accurately resolves the power law like structure of the core density profile and provides smaller overall uncertainties in geoacoustic parameters in addition the spline parameterization is found to be more parsimonious and hence preferred according to the dic the trans dimensional polynomial spline approach is general and applicable to any inverse problem for gradient based profiles work supported by onr

oligocene planktonic foraminiferal biostratigraphy and paleoclimatic interpretation from hole 538a dsdp leg 77 gulf of mexico abstract a relatively extended oligocene pelagic sequence with good to medium recovery drilled during dsdp leg 77 in the gulf of mexico yielded rich and well diversified planktonic foraminiferal faunas planktonic foraminifera recorded in hole 538a span the interval from zone p19 through p22 evolutionary lineages were observed among the globoquadrinids the globigernitids and the globigerina ciperoensis and globigerinoides primordius groups quantitative analysis of planktonic foraminiferal assemblages shows that faunas fluctuate in abundance and species diversity throughout the sequence a few of these fluctuations that could be related to selective dissolution are mainly confined to the early mid oligocene a climatic curve was constructed using a warmer indicators turborotalia pseudoampliapertura globoquadrina tripartita dentoglobigerina globularis dentoglobigerina baroemoenensis globigerina ciperoensis and globigerinoides groups and cassigerinella chipolensis and as cooler indicators catapsydrax spp globorotaloides spp subbotina angiporoides group globigerina s str and the tenuitellids three major intervals are identifiable in the climatic curve interval 1 lower up to zone p20 predominantly cooler interval 2 intermediate up to the upper part of zone p21a with warm and cool fluctuations and interval 3 upper warmer with large positive peak due to abundant g angulisuturalis at the beginning of zone p21b with recooling midway in zone p22 in intervals 1 and 2 planktonic foraminiferal faunas are dominated by temperate forms interpretation of planktonic foraminiferal data suggests that cooler water conditions characterize the early mid oligocene during the mid oligocene most of zone p21a water masses exhibit peculiar characteristics transitional to the warmer waters prevailing during the late oligocene warmer conditions were not definitely settled in zone p22 however as indicated by the cooler episode following the warmest peak these climatic trends are inconsistent with those inferred from oxygen isotopes except at small scale in fact oxygen isotope values for oligocene atlantic ocean are too heavy thus too cool in comparison with the high abundance and diversity of warm taxa especially in zone p22 when values are lighter warmer as in zone p19 abundance and diversity of warm indices are too low to explain such a cool isotope values in presence of highly diversified and abundant warm planktonic foraminifera we suggest 1 that the oxygen isotope ratio used for estimating oligocene paleotemperatures might be 1 heavier than eocene values and further increased for the late oligocene this hypothesis implies the presence of a relatively extended ice cap in antarctica in the early and mid oligocene and probably an increase in ice volume during the late oligocene 2 heavier isotope values might be related to an increase in salinity or 3 by a combination of both ice cap and increase in salinity

planktonic foraminiferal paleoclimatic implications across the oligocene miocene transition in the oceanic record atlantic indian and south pacific abstract a detailed paleoclimatic investigation was performed on planktonic foraminiferal assemblages spanning the interval from zone p21a late oligocene to zone n5 early miocene in pelagic sequences recovered in dsdp and odp holes in the atlantic south pacific and indian oceans the often rich and well preserved assemblages show that faunas fluctuate in abundance and species richness throughout the sequences from the percent abundances of single taxa at different latitudes biogeographic indices were identified planktonic foraminiferal distribution trends are roughly consistent with the recent species richness is however higher in upper oligocene and lower miocene sequence than it is today northern and southern atlantic bioprovinces were delimited the latter is characterized by cooler climate and by species previously described as endemic to new zealand on the basis of single species or grouped species abundance at low middle and high latitudes and on isotope data reported in the literature paleoclimatic indices are identified 1 warmer indices include guembelitria columbiana and gallitellia and the globigerinoides cassigerinella dentoglobigerina altispira globigerina ciperoensis globorotalia s s groups 2 cooler indices include the globorotaloides catapsydrax and the globigerina s s groups and tenuitellids 3 warm temperate indices include the paragloborotalia siakensis paragloborotalia mayeri tenuitellinata angustiumbilicata and globoquadrina tripartita dentoglobigerina baroemoenensis sphaeroidinellopsis disjuncta praeglobigerinoides and globigerina ottnangiensis groups and 4 cool temperate indices include paragloborotalia nana paragloborotalia pseudocontinuosa globigerina aff praebulloides and the zeaglobigerina woodi group climatic curves were constructed for each hole the identified positive and negative peaks in the climatic curves are sometimes correlative from hole to hole general paleoclimatic trends can be summarized as follow cooling in subzone p21a late oligocene warming in subzone p21b to upper zone p22 late oligocene followed by a cooling and strong climatic instability from the uppermost zone p22 through zone n4 probably responsible for the discrepancies in distributions of some taxa reported in the literature across the oligocene miocene boundary and renewed warming from the upper part of zone n4b into zone n5 early miocene based on their abundance in the upwelling zones paragloborotalia kugleri globorotaloides hexagonus globorotaloides stainforthi and protentellids were identified as upwelling indices high abundances of these species associated with radiolarians diatoms and sponge spicules allowed identification of a major upwelling pulse in the lower part of zone n4

formation of holocene sedimentary laminae in the black sea and the role of the benthic flocculent layer holocene black sea sediments recovered in 1988 and 1993 from box cores and gravity cores were analyzed geochemically microscopically and with backscattered electron imagery bsei in order to determine the temporal geochemical and sedimentological relationships between the benthic flocculent layer often referred to as the fluff layer and the formation of underlying laminated unit i sediments existence of a permanent benthic fluff layer in the black sea basin is suggested acting as a geochemical transition layer within which all sedimentary particles are hydraulically sorted and particles subject to dissolution or organic remineralization are altered prior to accumulation we propose that particle residence time within the benthic fluff layer is a key factor in determining sedimentary microfabric and geochemical composition of laminated unit i sediments we present a schematic model depicting the above relationships and use it to propose a paleoflux scenario for laminae formation in the unit ii sapropel

latest cretaceous early neogene oxygen and carbon isotopic record at dsdp sites in the indian ocean abstract stable isotopic data of calcareous nannofossil monogeneric and monospecific planktic and benthic foraminifera from five indian ocean dsdp sites 212 217 220 237 and 253 leads to the following paleoclimatic and paleoceanographic conclusions the latest cretaceous oxygen isotopic record implies a cooling 3 4 c during the maastrichtian at the cretaceous tertiary boundary only a minor warming about 2 c has been recorded the parallel 13 c decrease of more than 1 indicates a significant decrease in productivity during the latest paleocene a positive 13 c excursion was detected in sites 217 and 237 this transient enrichment in 13 c may be due to productivity changes on continents and or a change in the storage rate of organic matter in marginal basins or shelf areas the most striking feature in the oxygen isotopic record is noted at the early middle eocene transition the shift towards more positive values which were probably enhanced to a certain extent by a preceding diagenetic alteration delineates a dramatic climatic deterioration at high and mid latitudes during the earlier tertiary near the eocene oligocene boundary a cooling is evident within the latest eocene interval during the earliest oligocene time a hiatus at sites 217 and 253 partially obscures the climatic record several climatic fluctuations have been noted during the oligocene a cooling at the base of zone np 23 a warming at the top of zone np 23 through np 24 and a cooling during zone np 25 the miocene oxygen isotopic record is dominated by changes in surface and bottom water environments during zone nn5 the decreasing and then increasing 18 o values together with the subsequent steepening of the vertical 18 o gradient point towards major climatic instabilities these events coincide with the mid miocene build up of antarctic ice sheets during the latest miocene to the earliest pliocene the 18 o record of planktic foraminifera indicates a significant warming of the indian ocean at mid latitudes the 13 c record during the oligocene and miocene reveals several cycles 13 c enrichments np 24 nn2 nn5 nn9 and base nn 11 which are most likely related to changes in storage rates of organic matter and biological productivity due to climatic changes and transgression regression cycles in addition changes in the circulation patterns may also have influenced the carbon isotopic record

miocene equatorial and southwest pacific paleoceanography from stable isotope evidence abstract stable isotope results from seven miocene deep sea drilling projects in the equatorial and southwest pacific ocean previously correlated using carbon isotope stratigraphy have been examined discussed and interpreted in terms of the development of the miocene pacific ocean the most obvious features of the benthonic foraminiferal stable isotopic records are a major increase in 18o 1 0 during the middle miocene a series of long term oscillations 2 3 my of amplitude 0 5 0 75 and a decrease in 13c values 0 5 1 0 during the latest miocene planktonic foraminiferal 18o records show different trends for high and low latitude regions in the equatorial pacific planktonic 18o values actually decrease during the miocene whereas in the higher southern latitudes planktonic 18o values become more positive in response to cooling surface waters planktonic 13c records show opposite trends to 18o with the high latitude values becoming more negative relative to the tropical regions the development of the miocene pacific ocean in terms of its vertical and horizontal thermal structure and isotopic composition is well illustrated by examining changes in the isotopic difference between planktonic and benthonic foraminifera 18ob p benthonic planktonic is a measure of the thermal structure of the water column 18oph pl high latitude low latitude planktonic values is a measure of the latitudinal temperature gradient 13cb p is an indirect measure of nutrient concentrations in the water column and 13cph pl measures differences in surface water nutrient concentrations between high and low latitude 18ob p increases during the miocene with the greatest increase occurring in the middel miocene at about 14 ma by the latest miocene the isotopic gradient at site 289 in the equatorial pacific approaches the present day isotopic gradient about 4 5 an increase in 18oph pl during the miocene suggests that the latitudinal temperature gradient increased by about 6 c to a value of 12 c in the latest miocene between sites 289 equator and 281 subantarctic 13cb p and 13cph pl values are relatively constant through the early miocene but begin to increase during the middle miocene bottom water 13c values respond similarly at all sites but surface water 13c values exhibit different trends because higher latitude values begin to decrease this decrease perhaps suggests that phosphate concentrations may have increased due to increased upwelling as the circum antarctic circulation system evolved its present day characteristics the isotopic data compiled in this paper suggest that the southwest pacific was responding uniformly to some global or at least pacific wide control during the early miocene in the middle miocene the response became more complex as the low and high latitudes began to show independent trends the changes in the thermal vertical and latitudinal structure probably occurred in respons to the build up of the east antarctic ice sheet intensification of bottom water circulation and an increase in zonal circulation in surface waters in the southern hemisphere the changes in 13c vertical and latitudinal gradients are due to some complex interaction of sea level continental hypsometry climate and biological processes coupled with oceanic circulation changes a strong correlation between estimated sea level changes and 13c values suggests that transgressions and regressions play a critical role in controlling the flux of oxidized organic carbon enriched in12c from the continental shelves and epicontinental seas to the open ocean

upwelling history of the mediterranean sea revealed by stunted growth in the planktic foraminifera orbulina universa early messinian crete greece microfossil and stable isotope data 13c 18o from deep water sediments of late miocene age in the mediterranean region have revealed a stepwise restriction of the mediterranean prior to the messinian salinity crisis which was modulated by a cyclicity responding to orbital precession very little is known with regard to the effects of these changes on shallow water environments of carbonate platforms and ramps this work is based on a geological section on crete greece exposing sediments of early messinian age which documents the coeval response of pelagic and neritic systems to oceanographic changes we discuss a dataset of planktic and benthic foraminifera assemblages in conjunction with size measurements n 6 777 and isotope analyses 18o 13c of the planktic foraminifera orbulina universa with regard to reef growth patterns the planktic foraminifera fauna displays pronounced cyclical abundance changes of warm oligotrophic o universa and cold meso to eu trophic taxa globigerinids neogloboquadrinids this cyclicity corresponds to lithological changes from laminated to homogeneous marls on the precessional frequency band in beds rich in mesotrophic foraminifera o universa is rare and the test is 50 smaller than average growth and size of o universa is affected by various environmental factors including temperature trophic resources illumination and o2 content of ambient water explaining size variability by water temperature implies a change of 11 c over one precessional cycle this estimate is in disagreement with growth patterns and stable isotope data of displaced reef corals porites tarbellastraea documenting almost constant sea surface temperatures but substantial evaporation therefore moderate temperature changes in a context of intense evaporation high salinity and water column destabilization associated with upward mixing of colder water masses with higher nutrient concentrations and low o2 content better fits size variation of o universa from the presence of halimeda bioherms intercalated with the sapropel cycles we infer cyclic photic zone anoxia and at least some sections with sapropel couplets to have formed in the neritic zone we also suggest further testing of stunted growth of o universa as a proxy for enhanced nutrient availability in future palaeoceanographic studies

eocene to miocene terrigenous inputs and export production geochemical evidence from odp leg 177 site 1090 abstract changes in ocean circulation and climate during the cenozoic led to the development of the antarctic circum polar current acc and permanent antarctic ice sheets however the timing of the opening of the drake passage and the establishment of the acc is poorly constrained we present geochemical proxies of terrigenous inputs and export production at a single site in the southeastern atlantic ocean that suggest the drake passage had opened to intermediate and deep water by 32 8 ma two separate styles of sedimentation and geochemical composition of terrigenous material are observed with the change in sediment geochemical characteristics occurring at 32 8 ma middle to late eocene records are highly variable while latest eocene to early miocene records exhibit cyclic variations in elemental records and terrigenous material based on al ti ratios metal sources change from continental crust to oceanic crust sources at the eocene oligocene transition which we suggest reflects a change in deep water circulation phosphorus metal ratios indicate that there are two distinct intervals of enhanced export production one in the middle eocene and one throughout the eocene oligocene transition elevated al ti ratios greater than any lithic source in the middle eocene provide evidence of particulate scavenging and thus increased export production barium ratios further support changes in productivity in the middle eocene and at the eocene oligocene transition permanent changes in the ba concentration record in the early oligocene further support a change in deep water circulation due to the opening and deepening of the drake passage at 32 8 ma

hantkeninid depth adaptation an evolving life strategy in a changing ocean the interplay between evolution paleoecology and environmental change is examined in a geochemical study of a group of eocene planktonic foraminifera the hantkeninids which are well known biostratigraphic inde fossils underwent spectacular long term evolution in the middle and upper eocene 49 0 33 7 ma a time when major global climate and oceanic changes were occurring we use oxygen and carbon isotope analysis of their shell calcite to investigate how their habitat changed as they evolved the hantkeninids originated in a deep water oxygen minimum environment but migrated into fully oxygenated near surface waters as global temperatures decreased and water column stratification declined this change in depth ecology coincided with pronounced morphological evolution involving changes in chamber shape and degree of inflation and modification of the primary aperture these developments are considered to be adaptations to a near surface habitat

palaeoenvironmental vs evolutionary control on size variation of coccoliths across the lower middle jurassic size is an easily quantifiable trait probing the respective influence of evolution and palaeoenvironment on organisms through time after the stressed period that spanned across western tethys epicontinental seas during the early toarcian the following rebuilding of a restored water column ecosystem is coeval with the size increase of the lotharingius genus coccoliths one of the main pelagic producers at that time in order to quantitatively assess the coccolith size evolution during a time span of 10 myr measurements of seven morphospecies of lotharingius across the toarcian and early aalenian were performed this study was carried out on a total of 5500 specimens from samples retrieved from two distinctive palaeoenvironmental settings in the western mediterranean tethys three sections from the lusitanian basin in portugal and one section from the causses basin in southern france for each specimen coccolith length width and central area length and width were measured using specific measurement software statistical and data analysis tools were used in order to evaluate significant resemblances and or differences between different size groups and samples two main clusters are acknowledged from this study small sized lotharingius is 4 m in addition to common evolutionary processes changes in palaeoenvironmental conditions were taken into account to explain such a size distribution although background evolution pushed the lotharingius genus toward larger sizes palaeoenvironmental conditions seemed to play an important role in the toarcian early aalenian morphological evolution of this taxon the production of larger coccoliths profited from stable environmental conditions whereas smaller morphotypes dominated during periods marked by stress the transition from small to large lotharingius was synchronous in the two investigated western tethys basins at the bifrons gradata or variabilis ammonite zone boundary middle toarcian thus representing an important event for the lower jurassic calcareous nannofossil biostratigraphy

cenozoic deep sea temperatures and global ice volumes from mg ca in benthic foraminiferal calcite a deep sea temperature record for the past 50 million years has been produced from the magnesium calcium ratio mg ca in benthic foraminiferal calcite the record is strikingly similar in form to the corresponding benthic oxygen isotope 18o record and defines an overall cooling of about 12 c in the deep oceans with four main cooling periods used in conjunction with the benthic 18o record the magnesium temperature record indicates that the first major accumulation of antarctic ice occurred rapidly in the earliest oligocene 34 million years ago and was not accompanied by a decrease in deep sea temperatures

orbitally induced climate and geochemical variability across the oligocene miocene boundary to assess the influence of orbital scale variations on late oligocene to early miocene climate and ocean chemistry high resolution 5 kyr benthic foraminiferal carbon and oxygen isotope and percent coarse fraction time series were constructed for ocean drilling program site 929 on ceara rise in the western equatorial atlantic these time series exhibit pervasive low to high frequency variability across a 5 myr interval 20 5 25 4 ma the records also reveal several large scale secular variations including two positive 1 6 oxygen isotope excursions at 22 95 and 21 1 ma suggestive of large but brief glacial maxima mi 1 and mi 1a events of miller et al 1991 and a long term cyclical increase in the carbon isotopic composition of seawater shift of 1 52 that reaches a maximum coincident with peak 18o values at 22 95 ma lower resolution 25 kyr records constructed from benthic and planktonic foraminifera as well as bulk carbonate at a shallower site on ceara rise site 926 for the period 21 7 24 9 ma covary with site 929 18o values reflecting changes in antarctic ice volume likewise covariance among carbon isotopic records of bulk sediment benthic and planktonic foraminifera suggest that the low frequency cycles 400 kyr and long term increase in 13c values represent changes in the mean carbon composition of seawater co2 the time series presented here constitute the longest most continuous and highest resolution records of pre pliocene climate and oceanography to date the site 929 carbon and oxygen isotope power spectra show significant concentrations of variance at 400 100 and 41 kyr demonstrating that orbitally induced oscillations have been a normal characteristic of the global climate system since at least the oligocene including periods of equable climate and times with no apparent northern component water production

evidence for a common scale o 0 1 m that controls seabed scattering and reverberation in shallow water analysis of the spectral content of long range reverberation yields two observations first there is a remarkably similar scale o 0 1 m between three diverse continental shelf regions this is surprising given the complexity and diversity of geologic processes second there is strong evidence that the scale is associated with heterogeneities within the sediment thus sediment volume scattering not interface scattering controls long range reverberation from a few hundred hertz to several kilohertz this is also unexpected given that at long ranges the vertical grazing angles are less than the critical angle and hence the penetration of the acoustic field into the sub bottom is expected to be modest the consistency of the scale o 0 1 m suggests an underlying feature or mechanism that is consistent across many ostensibly diverse geological settings neither the feature nor mechanism is known at this time