empirical relationships among seismic velocity effective pressure porosity and clay content in sandstone we use a multivariate analysis to investigate the influence of effective pressure pe porosity and clay content c on the compressional velocity vp and shear velocity vs of sandstones laboratory measurements on water saturated samples of 64 different sandstones provide a large data set that was analyzed statistically for each sample relationships between effective pressure and vp and vs have been determined all samples were well fit by relationships that have an exponential increase in velocity at low pe tapering to a linear increase with pe for pe greater than 0 2 kbar there are differences in the pressure dependences of velocity for different rocks particularly at very low pressures however the differences cannot be attributed to or c for the combined set of measurements from all samples the best fitting formulations are vp 5 77 6 94 1 73c 0 446 pe e 16 7pe and vs 3 70 4 94 1 57c 0 361 pe e 16 7pe while this is admittedly a very simplified parameterization it is remarkable how well

changes in mobility patterns as a factor for site density variation in the recent epigravettian of northern italy and southeastern france abstract this paper critically considers the use of radiocarbon dates as a demographic proxy for past population our goal is not to reject or valid this approach we even did not focus on the various bias of this approach or on the several correction methods used to reduce them we rather argue that when trying to interpret 14c dates in a demographic perspective it is essential to analyze socio economic parameters studying the case of the lateglacial upper palaeolithic of southeastern france and northern italy we demonstrate that the use of techno economic approaches allows discussing this way to interpret the radiocarbon data from this analysis we argue that a change in the density of dates cannot be simply interpreted in term of demography we demonstrate that these variations can be the result of changes in the way people organize themselves in a territory in other word we argue that mobility patterns are somehow responsible for the density of dates and sites

geothermal structure of the miura boso plate subduction margin central japan abstract we have constrained the geothermal structure of the miura boso plate subduction margin located in central japan using maximum paleo temperature data derived from vitrinite reflectance measurements we established that higher maximum paleo temperatures are restricted to the western part of the early miocene hota accretionary complex hota and hayama groups indicating a spatial difference in the amount of slip upon the out of sequence thrust potentially associated with the izu bonin island arc collision the weakly deformed sedimentary sequences overlying the highly deformed hota group strata have much lower vitrinite reflectance values than the latter this variation indicates that the sedimentary sequences of the trench slope experienced a markedly lower maximum burial depth than the relatively deep buried and uplifted hota accretionary complex conversely maximum paleo temperatures obtained for tectonic blocks hosted by the neighboring mineoka ophiolite complex are very high ca 140 c for the large early miocene haccho formation blocks and 65 90 c for the other blocks this result suggests that the individual tectonic blocks enclosed in the ophiolite complex were subjected exhumation from depths of 3 5 km

smectite swelling in the miura boso accretionary prism possible cause for incipient decollement zone formation abstract an analysis of the mineralogy of the miura boso accretionary prism which consists of off scraped upper miocene strata exposed on the southern parts of the miura and boso peninsulas in central japan revealed homogeneous mineral composition throughout all levels of silt layers hosting deformation structures associated with sediment accretion xrd analyses showed that the sediment consists of randomly ordered mixed layer illite smectite i s with low illite content 40 wt quartz 30 wt illite 10 20 wt plagioclase 10 wt kaolinite chlorite 5 wt and calcite 0 10 wt the observed mineralogical assemblage indicates that location of the decollement formation was not constrained by mechanical heterogeneities associated with mineralogical variations but was controlled by spatial variations in effective pressure within the over consolidated sediment located above the incipient decollement zone the occurrence of abundant smectite with a shape preferred orientation gave rise to smectite swelling producing pressures in the order of 3 0 mpa the combined effect of high swelling pressure and high pore pressure resulted in an overpressured zone at the base of the over consolidated zone facilitating the development of a decollement zone within the prism

elevated pore pressure and anomalously low stress in regions of low frequency earthquakes along the nankai trough subduction megathrust 1 recent seismic reflection and ocean bottom seismometer obs studies reveal broad regions of low seismic velocity along the nankai subduction plate boundary megathrust offshore sw japan these low velocity zones lvz s extend 55 km landward from the trench corresponding to depths of 10 km below sea floor here we estimate the in situ pore pressure and stress state within these lvz s by combining p wave velocities obtained from the geophysical surveys with new well constrained empirical relations between p wave velocity porosity and effective mean stress defined by laboratory deformation tests on drill core samples of the incoming oceanic sediment we document excess pore pressures of 17 87 mpa that extend 55 km into the subduction zone indicating that trapped pore fluids support 45 91 of the overburden stress along the base of the upper plate and surrounding major fault zones the resulting effective stresses in the lvz are limited to 1 3 of the values expected for non overpressured conditions these low effective stresses should lead to a mechanically weak and predominantly aseismic plate boundary the region of lowest effective stress coincides with precisely located very low frequency earthquakes providing the first quantitative evidence linking these anomalous slip events to low stress and high pore pressure

influence of thermal and mechanical cracks on permeability and elastic wave velocities in a basalt from mt etna volcano subjected to elevated pressure abstract we report simultaneous laboratory measurements of seismic velocities and fluid permeability on lava flow basalt from etna italy results were obtained for dry and saturated samples deformed under triaxial compression during each test the effective pressure was first increased up to 190 mpa to investigate the effect of pre existing crack closure on seismic properties then the effective pressure was unloaded down to 20 mpa a pressure which mirrors the stress field acting under a lava pile of approximately 1 5 2 km thick and deviatoric stress was increased until failure of the specimens using an effective medium model the measured elastic wave velocities were inverted in terms of two crack densities i the crack density of the pre existing thermal cracks and v the crack density of the stress induced cracks in addition a link was established between elastic properties elastic wave velocities vp and vs and permeability using a statistical permeability model our results show that the velocities increase with increasing hydrostatic pressure up to 190 mpa due to the closure of the pre existing thermal cracks this is interpreted by a decrease of the crack density i from 1 to 0 2 the effect of pre existing cracks closure is also highlighted by the permeability evolution which decreases of more than two orders of magnitude under deviatoric loading the velocities signature is interpreted in the first stage of the loading by the closure of the pre existing thermal cracks however with increasing deviatoric loading newly formed vertical cracks nucleate and propagate this is clearly seen from the velocity signature and its interpretation in term of crack density from the location of the acoustic emission sources and from microstructural observations this competition between pre existing cracks closure and propagation of vertical cracks is also seen from the permeability evolution and our study shows that mechanically induced cracks has lesser influence on permeability change than pre existing thermal cracks

compaction in the nankai and barbados accretionary prisms new insights from logging while drilling data 1 sediment deformation changes in physical properties and fluid migration can be studied under well defined conditions in accretionary prisms our investigations focused on the accretionary prisms of barbados caribbean and nankai japan to interpret the effects of compaction on different lithologies during accretion the interpretation is based on very good quality logging while drilling data statistical data analysis is used to determine sediment composition and its specific physical properties finally the sediments are decompacted to determine the initial compaction before accretion and thus to quantify both the lateral and the vertical compaction components this investigation shows that different lithologies undergo similar compaction and porosity reduction the porosity differences of selected sediment layers between adjacent sites are significantly lower in nankai than in barbados which implies higher fluid expulsion in nankai decompaction of these sediment layers proves that the lateral compaction component is higher than the vertical compaction component

systematic variation of shear induced physical properties and fabrics in the miura boso accretionary prism the earliest processes during off scraping abstract the interrelations between deformation and variations in the physical properties and fabrics of a shallow level accretionary prism have been clarified using measurements of porosity pore size distribution and the anisotropy of magnetic susceptibility ams within the miura boso accretionary prism central japan based on the mode of deformation this onland example of an off scraped body can be divided into three parts from bottom to top imbricate thrusts corresponding to a decollement zone a thrust unit in the lower part of the off scraped body and an upper coherent unit in the top part of the off scraped body physical properties and fabrics are quite variable in each of the three parts even within a particular lithology these observations reflect each structural unit s individual strain history during shallow off scraping and accretion prior to the accretion the sediments underwent vertical compaction when horizontal compressional stresses subsequently began to deform the sediments precursory shear disturbed the previous compaction fabric accompanied by a pervasive porosity decrease over a zone several tens to hundreds of meters in thickness the porosity decrease occurred by large pore collapse which led to the development of an impermeable over consolidated horizon and inevitable high pore fluid pressures below that controlled the position of the subsequent decollement zone displacement along imbricate thrusts within the decollement zone took place just below the over consolidated horizon where high fluid pressure had been generated here a flattening fabric parallel to the imbricate thrust and associated further porosity and pore size reductions occurred in association with the fault movement these findings imply unrecoverable pre fractured strain information of sediments before being included in the decollement zone and suggest that the precursory formation of an over consolidated zone via grain rearrangement and pore size reduction is an essential control on subsequent large deformation i e within a decollement zone in the shallow part of an accretionary prism especially within lithologically homogeneous material

structural characteristics of shallowly buried accretionary prism rapidly uplifted neogene accreted sediments on the miura boso peninsula central japan 1 the upper miocene misaki and nishizaki formations on the miura and boso peninsulas in central japan preserve the deformation features of an off scraped accretionary prism the spatial distribution geometry and style of accretion related deformation with paleotemperature and burial depth estimation are elucidated in this study the deformation structures and textures are similar to those of modern accretionary prisms the low maximum paleotemperature 50 c and high preserved porosity of the sediments 30 50 imply a maximum burial depth of less than 1000 m on the basis of the mode of deformation this off scraped body is divided into an imbricate thrust a thrust unit and an upper coherent unit in ascending order the imbricate thrust corresponds to a branch from the basal decollement zone and is subdivided into a brecciated zone a main gouge zone and a shear band zone the thrust unit hosts a concentration of thrust systems that form various orders of duplex structures while the upper coherent unit is characterized by gravitational instability and earthquake induced deformation without thrust faulting the duplex distribution shear strain and fluid migration associated with the off scraping processes are clearly localized within the imbricate thrust and thrust unit this accretion related deformation occurred before lithification of the sediment and under high fluid pressure induced by shear deformation thickening of the sedimentary sequence and earthquake induced liquefaction these processes are inferred to control the effect on the mode of deformation and the location of thrusting during early deformation of the accretionary prism

evidence for a weak and overpressured decollement beneath sediment dominated accretionary prisms we present structural data from several underthrust sequences in southwest alaska that suggest that the deformation regime beneath accretionary prisms is characterized by a subvertical 1 and regionally extensive layer parallel shearing these results contrast markedly with the results obtained from the more shallow parts of accretionary prisms and fold and thrust belts where 1 plunges gently seaward or toward the deformation front on the basis of mohr circle diagrams we propose that these different stress directions are consistent only with a model in which the two regimes are separated by a very weak decollement and calculate coefficient of friction values that range from 0 25 to 0 08 these values are significantly lower than coefficient of friction values calculated for the basal decollement in the taiwan fold and thrust belt e g 0 2 barr and dahlen 1989a and they are also lower than laboratory friction measurements for most rocks e g 0 6 0 8 byerlee 1978 consequently these low values suggest the presence of rocks with unusual material properties e g montmorillonite logan and rauenzahn 1987 or anomalous fluid pressures along the decollement on the basis of the occurrence of shale diapirs the distribution of early veins and the absence of montmorillonite in the underthrust sequences we propose that there was an anomalously high fluid pressure along the decollement fault instead of there being such a low coefficient of friction these results emphasize the importance of dewatering and fluid flow in controlling the position of the decollement which in turn determines how the accretionary prism grows in essence it is the development of a weak overpressured decollement within a thick sediment pile that allows plate convergence to be partitioned into offscraping and underthrusting regimes

an imprint of the mediterranean middle miocene circulation pattern in a satellite sea during the langhian a case study from the carpathian foredeep central paratethys abstract the langhian central paratethys sea represents a unique marine environment with a complicated circulation pattern influenced by the mediterranean sea here we present a review study based on previously published stable isotopic foraminiferal and calcareous nannoplankton data from various locations in the central paratethys supplemented by new datasets from the interval of 14 6 13 9 ma we compared the paratethyan data with data reported from the mediterranean area together with the results of computer models and with the latest paleogeographical studies as a tool for comparison of particular water masses we chose 18o data from various benthic and planktonic foraminiferal species globigerinoides trilobus globigerina bulloides cibicidoides spp to obtain information for both surficial and bottom waters hydrography moreover we chose 13c data as an indicator of the relationship between the surficial and bottom waters at particular localities the composition of foraminiferal and calcareous nannoplankton assemblages was used to verify the paleoecological situation at the studied localities it was discovered that an anti estuarine circulation regime was the basic circulation pattern during the studied interval this is supported by a similarity in hydrography of surficial waters surface mixed layer between the paratethys and the mediterranean sea which is shown by the isotopic data nevertheless the isotopic data comparison revealed differences regarding the bottom waters pointing to an existence of the paratethyan bottom waters and a subsequent change in the bottom waters isotopic composition between 14 4 13 9 ma this change could be linked with the shallowing of the basin that is indicated by various paleobiological data furthermore we tried to summarize possible regional consequences of the suggested paleocirculation patterns

water flow in the barbados accretionary complex we present a simple analytic kinematic model of the barbados accretionary complex assuming a porosity depth law and deformation by pure vertical shear the model is applied to two sections a northern one with a 900 m thick basin sedimentary column near 16 n and a southern one with a 4 5 km thick one to the south this simple model is compatible with growth of the barbados accretionary complex since 50 ma assuming a constant subduction rate and a constant basin sedimentary column equal to the present one this conclusion is not affected by reasonable changes in the porosity depth law it suggests that the totality of the entering sedimentary column is either accreted or subcreted to the wedge the accretion velocity decreases dramatically with age and its variation should be taken into account in any quantitative model the average strain rates show remarkably different distributions between the two sections the thinner wedge having a much higher rate in a narrow area at the toe we then use the model to compute the sediment grains flow the fluid flow and their thermal effects these effects are small and do not exceed 5 of the heat flow in the absence of other internal flows in contrast the thermal effect of the burial of the slab can result in a lowering of the surface heat flow by as much as 40 the temperature at the base of the wedge on its arc side is close to 300 c on the southern section and half that amount on the northern one this high temperature could account for the absence of large earthquakes to the south and their presence to the north the amount of water discharged if collected by faults over the whole toe area is unable to account for some of the manifestations observed over the toe or seaward of the toe in the barbados area we suggest two possible other sources one for the southern section is the orinoco fan area the other for the northern section might be seismic pumping at the limit of the seismogenic zone along the backthrusts between the accretionary wedge and the forearc basin

strontium isotope composition of middle miocene primary gypsum badenian of the polish carpathian foredeep basin evidence for continual non marine inflow of radiogenic strontium into evaporite basin strontium isotope compositions of ancient sulphate deposits not only provide chemostratigraphic information but also offer insight into the system in which the evaporites precipitated primary gypsum from two middle miocene badenian sections in southern poland shows steadily higher 87sr 86sr ratios than those expected from a marine derived formation the ratios are interpreted as the result of increasing inflow into the basin at the time of gypsum precipitation palaeogeographic reconstructions suggest that riverine runoff sources were situated in the west and east european platforms to the north and east respectively and the carpathians to the south which are mostly composed of mesozoic sedimentary rocks their dissolution cannot be responsible for the higher 87sr 86sr ratios recorded we conclude that archaean and palaeoproterozoic igneous and supracrustal rocks of the ukrainian shield were the source of the higher 87sr 86sr ratios recorded in the badenian primary gypsum a distinctive decreasing trend of 87sr 86sr ratios from western ukraine to southern poland is explained by a consistent direction of brine inflow during gypsum crystallization typical cyclonic circulation controlled by the coriolis effect

living stained benthic foraminifera within surficial sediments of the skagerrak abstract an analysis of living stained benthic foraminifera within four box cores raised from water depths of 74 to 621 m in the skagerrak shows that faunal patterns at different water depths are strikingly different within this relatively shallow organicrich marginal sea environment although some genera show vertical stratification within the sediments a number of taxa are found over wide intervals or have different patterns between cores the vertical distributional data are compared with deep sea data from the eastern margin of north america benthic foraminifera from a deep core at 530 m in the skagerrak have similar faunal patterns within the surficial sediments as found in the deep sea but shallow cores at 74 and 212 m have more complex patterns this difference between shallow and deep cores within the skagerrak and the north atlantic is attributed to higher biological activity in the shallow environments which creates a greater amount of heterogeneity within the shallow water sediments than is found in deeper environments the faunal data suggest that the use of benthic foraminifera for paleoenvironmental reconstructions in shallow organicrich regions will be complicated in future studies the ecology of individual species is difficult to assess because of the complex faunal patterns observed within the surficial sediments geochemical studies for estimating bottom water oxygen or organic carbon flux will also be difficult since these studies assume that taxa occupy particular microhabitats within the surficial sediments

in situ formed and redeposited gypsum breccias in the middle miocene badenian of southern poland abstract gypsum arenites gypsum rudites and laminated gypsum occur in the upper part of the middle miocene badenian gypsum in southern poland we interpret these as resedimented deposits the large size of the clasts and precipitated rain from low density turbid layers these resedimented deep water depositss overlie a shelf evaporite complex of mostly shallow water gypsum the sequence is therefore generally deepening upward similar sequences with important redeposition episodes are characteristic of the final stage of development of many other evaporite basins the important environmental change that occurred at the top of the lower part of the gypsum sequence was induced by changes in basin dynamics and resulted climate change which we relate to an increased tectonic activity the resulting differentiation of the intrabasinal relief combined with possible brine level fluctuations and earthquakes led to a widespread redeposition of gypsum deposits the presence of in situ brecciation as well as levels of breccias recorded in the borkow quarry indicate that within the part of the discussed sequence the source of gypsum was not at the periphery of the basin

porosity of sediments in accretionary prisms and some implications for dewatering processes rapid dewatering largely through loss of porosity is one of the most striking changes affecting deformed sediments in accretionary prisms analysis of porosity from sample and seismic data confirms that porosity in accretionary prisms is significantly less than that in basinal strata of similar lithology more specifically the porosity depth gradient increases arcward across the prism until porosities less than 10 occur within a few kilometers of the surface in deeper parts of the prism dewatering and volume reduction occur not only during loss of porosity but also during dehydration and metamorphic reactions calculations involving volume change lead us to define a function which reflects total volume reduction the distribution of the relative intensity of dewatering within the prism can be calculated from the porosity contours and trajectories of sediment elements an initial attempt indicates that in the toe region the rate of dewatering is accelerated at depth relative to the basinal section and may be greatest near the base of the prism toward the rear of the prism the maximum rate of dewatering occurs at progressively shallower depths several lines of evidence suggest that in addition to gradual diffuse dewatering localized zones of strong dewatering are associated with zones of intense shear this model of shear dewatering based on critical state soil mechanics suggests that sediments adjacent to the basal decollement should be strongly dewatered

age of the badenian salinity crisis impact of miocene climate variability on the circum mediterranean region massive evaporites were deposited in the central european paratethys sea during the badenian salinity crisis bsc the scarcity of absolute age data has hampered a thorough understanding of these salt deposits here we present a robust chronology for this catastrophic event by 40 ar 39 ar dating of volcanic tuffs below and within the badenian salts in southern poland the onset of bsc evaporite deposition is dated at 13 81 0 08 ma and the entire event is estimated to have lasted 200 600 k y correlation to oxygen isotope records shows that the bsc evaporites were just preceded by glacial event mi 3b suggesting a causal relationship the corresponding sea level fall most likely restricted the open marine connection to the mediterranean thereby trapping the salt in the deep paratethys basins

fluid accumulation and channeling along the northern barbados ridge decollement thrust a volume of three dimensional seismic reflection data acquired in 1992 imaged the decollement beneath the northern barbados ridge accretionary prism revealing reflection amplitude and waveform variations attributed to fluid accumulations along the plate boundary fault we model the seismic reflection by inversion for seismic impedance the product of velocity and density throughout the 5 x 25 km survey area and thus map physical property variations in 1997 ocean drilling program leg 171a penetrated the protodecollement and decollement at five sites with a logging while drilling lwd tool to log density and other physical properties of the decollement we construct a regional map of density and inferred porosity within the decollement from seismic models calibrated with lwd density data in the sediments out in front of the trench the protodecollement forms in a radiolarian rich miocene mudstone with an anomalously high porosity 70 75 that appears as a pervasive inherent characteristic of this interval seaward of the deformation front in the decollement beneath the wedge a consolidation trend of decreasing porosity runs perpendicular to the deformation front with porosity decreasing from 70 at the wedge toe to 50 4 km from the wedge toe a second distinct trend also forms along a 10 km long 1 to 2 km wide ne sw zone in which porosity is 70 as high as it is in the protodecollement this zone can be explained as an area of the decollement where fluid accumulations develop by maintaining high fluid content we postulate that high fluid content is maintained by continuous recharge flowing into and along this channel this porosity distribution within the decollement also strongly influences fluid migration into the overlying accretionary wedge and is directly associated with fluid charging of ramps and out of sequence thrusts above the decollement

sedimentology of badenian middle miocene gypsum in eastern galicia podolia and bukovina west ukraine primary gypsum is the main evaporite mineral in the middle miocene badenian of the west ukraine the lower part of the gypsum sequence is built of autochthonous gypsum while the upper part is composed of allochthonous gypsum that formed following a major tectonically induced change in basin morphology this change resulted in the destruction of the gypsum deposited on the margins of the basin and formation of redeposition features autochthonous gypsum facies were deposited in two main environments 1 giant gypsum intergrowths precipitated from highly concentrated brines 2 very shallow subaqueous gypsum deposited in a vast brine pan the brine pan was characterized by a facies mosaic that reflects an interplay of concentrated brines from the central part of the evaporite basin and diluted brines due to the influx of continental meteoric waters the facies continuum microbial gypsum bedded selenite massive selenite sabre gypsum indicates increasing salinity of the brine with time this type of facies pattern has been established in recent salinas that are analogous to badenian gypsum in their lateral facies changes however the pattern of facies distribution with respect to the open sea in the badenian basin is opposite to that found in recent salinas the pattern of the badenian gypsum facies in the ukraine indicates that facies repetition may have been related to climatically controlled salinity changes and not to depth changes as is commonly used to explain the repetition of sulphate facies in a vertical succession

foraminiferal record of environmental changes messinian of the los yesos area sorbas basin se spain the late messinian of the sorbas basin betic cordillera se spain has been sampled to estimate 1 the paleoenvironmental changes recorded by the benthic foraminifers in pre evaporitic and evaporitic units and 2 the impact of the messinian salinity crisis on the foraminiferal biodiversity in the pre evaporitic unit foraminifers indicate a circalittoral to bathyal environments and show significant changes in bottom water oxygenation simultaneously the occurrences of epiphytic damaged foraminifers and the blocks of porites point out the presence of plant substrates and coral reefs on the infralittoral zone the overlying evaporitic unit is characterized by four subaqeous selenitic gypsum layers and three marine fossiliferous intercalations each episode of gypsum deposition ends with a desiccation event each fossiliferous intercalations traduce a rapid reflooding of the basin by marine waters corresponding to infralittoral to upper bathyal environments with normal marine conditions during the evaporitic period the ecological conditions in the water column were intermittently favorable to the development of marine organisms and moreover the marginal basins of the betic cordillera were not continuously desiccated during the messinian the low percentage of extinct species 5 at the messinian pliocene boundary and the occurrences of benthic foraminifers in the evaporitic unit indicate that the infralittoral to upper bathyal environments have not been completely modified and or barren during the messinian salinity crisis i e the messinian salinity crisis is not associated with a biological crisis

salinity changes during late oligocene to early miocene asmari formation deposition zagros mountains iran abstract the distributions of sediment grain types and microfacies in two outcrop sections in the central part of the zagros fold and thrust belt iran are used to interpret changes in salinity during late oligocene chattian to early miocene burdigalian deposition of the asmari formation conditions of hypersalinity are interpreted from analogy with the modern salinity gradient in shark bay western australia and the time scale is derived from foraminiferal biozonation and sr isotope stratigraphy the study demonstrates that frequent changes in sedimentary facies and salinity conditions took place in the central zagros basin during the late chattian aquitanian and burdigalian five main findings of the study are as follows 1 a significant shallowing from the outer neritic zone 100 m to 200 m deep to the innermost neritic zone 50 psu occurred during aquitanian deposition of the asmari formation at both localities 5 deposition of the upper asmari formation and lowest gachsaran formation burdigalian was mainly under slightly hypersaline conditions 40 psu to 50 psu with some normal marine intervals at tang e sapou and some normal marine intervals as well as severe hypersaline episodes 50 psu at tang e ban to the west the patterns of salinity change seem to have been widespread in the central zagros foreland basin and transitions from normal marine to hypersaline conditions may represent falls in relative sea level or be due to build up of sand banks forming sills that restricted water circulation changes from hypersaline to normal marine conditions may represent relative sea level rise however there is insufficient chronological resolution at present to allow confident correlation of the major salinity changes to sequence boundaries and surfaces previously recognized in the basin

benchmark data of a changing sea palaeogeography palaeobiogeography and events in the central paratethys during the miocene abstract the reconstruction and interpretation of terrestrial ecosystems and vegetational patterns in the central european miocene have to take into account the influence of a vast landlocked water body namely the paratethys sea as a northern appendage of the early mediterranean sea it spanned a north south gradient of at least 4 latitude and has been suggested to represent some kind of palaeothermometer which reflected slight expansions or restrictions of climatic belts due to its vulnerable marine connections it was also highly susceptible to major global sea level fluctuations which are reflected in phases of endemism hence a fairly continuous record of marine nearshore assemblages throughout the miocene reflects an extraordinary interplay of sea level fluctuations changes in climate immigrations and blooms in autochthonous elements whilst biostratigraphic implications of these patterns were recognised early in palaeontology a biogeographic model is still lacking the intermingling of palaeogeographic terms with those restricted to biogeography is still commonly used a situation which can be overcome by integrating data from different biota into a new palaeobiogeographic scheme herein a data set of 1809 species level taxa gastropoda and foraminifera serves as the base for interpretations gastropods in particular turned out to be of greatest value for the differentiation of palaeobiogeographic units due to sensitive reactions to all environmental parameters and occupying a wide range of ecological niches based on the excellent gastropod record the proto danubian province early danubian p danubian p balatonian p and a proto caspian subprovince are defined the biogeographic reorganisations are associated with five major biotic events within the gastropod faunas these big five comprise four extinctions the late ottnangian extinction event loee the mid badenian extinction event mbee the badenian sarmatian extinction event bsee the sarmatian pannonian extinction event spee and one exceptional immigration origination event termed the early badenian build up event ebbe foraminifera are less valuable for palaeobiogeographic purposes in the area and time slice studied endemisms are generally lower and turn over rates less dramatic they are however very useful for stratigraphic correlations with the mediterranean and atlantic areas this fairly well calibrated marine biostratigraphy of the central paratethys serves as stratigraphic backbone and control for continental stratigraphy

the hydrological setting occurrence and significance of gypsum in late quaternary salt lakes in south australia well exposed often laminated gypsum sequences occur in many quarternary salt lakes in southern south australia the gypsum in the salt lakes is classified by increasing grain size into gypsite gypsarenite and selenite the salt lakes are classified by age and hydrological setting into coastal salinas which are holocene sea water fed groundwater lakes and continental playas which are late pleistocene endorheic basins a study of the relationships between coastal salina hydrology and the associated gypsum deposition has shown the different types of gypsum form under distinct hydrological regimes as the hydrology above a coastal salina depositional surface changes through time so does the type of gypsum deposited application of a gypsum depositional model derived from a study of the coastal salina gypsum to those portions of a continental playa gypsum unit where deposition is no longer occurring confirms the applicability of the model to non salina gypsum deposits

planktonic response to main oceanographic changes in the alboran sea western mediterranean as documented in sediment traps and surface sediments abstract in order to determine the influence of seasonal oceanographic changes to the export of particulates and the flux of organisms as well as its corresponding integrated signal left in the bottom sediments of the alboran sea western mediterranean two mooring lines alb 1f and alb 1d were deployed from july 1997 to may 1998 on the continental slope south of malaga at 36 01 n 04 16 w and 36 14 n 04 28 w and a water depth of 1004 and 958 m respectively the mooring locations are under the influence of the incoming atlantic surface water asw at the northern and productive edge of the western alboran gyre wag and of the wind induced upwelling offshore the spanish coast additionally a total of five core tops located in the same area were studied the results are compared to information based on seawifs images of chlorophyll a concentration sst meteorological data on wind direction and intensity and fluvial discharges from the main rivers of the alboran basin the temporal oceanographic evolution of the alboran sea during the studied period was divided into five episodes e1 july 1997 e2 august october 1997 e3 november to mid december 1997 e4 december march 1998 and e5 april may 1998 the episodes represent different oceanographic conditions in the alboran sea during the studied period detailed analyses of the recorded pattern of bulk components calcareous nannoplankton planktonic foraminifera diatoms and phytoliths reflect seasonal changes in the main hydrographic regimes in the western alboran sea all biogenic bulk components as well as the annual evolution of the floral and faunal assemblages follow a tri modal pattern with maximum fluxes recorded during e1 e3 and e5 representing periods of higher productivity and wind induced upwelling during these periods species such as the small gephyrocapsa group gephyrocapsa muellerae and calcidiscus leptoporus the foraminifer globigerina bulloides and the diatom chaetoceros resting spores rs were dominant gephirocapsa oceanica and globorotalia inflata were coupled to the evolution of the atlantic surface water asw or related to surface water stability e2 and e4 the diatom leptocylindrus danicus responded to upwelling relaxation and water stratification e1 e2 and e4 and benthic diatoms were related to eddy intensity at bottom phytolith fluxes were directly related to wind intensities and the prevailing westerly winds e3 and e5 the distribution of microfossils in surface sediments differs from the biogenic assemblages recorded in the sediment traps in this sense during 1997 1998 the strongest el nino event in the last century took place which could have forced an unusual seasonality in the alboran sea reflecting an exceptional micropaleontological signal not observed in the surface sediments

between atlantic and mediterranean changes in technology during the late glacial in western europe and the climate hypothesis abstract during the second half of the upper paleolithic europe seems to have been divided in two vast techno cultural entities with their particular chronological sequence the western europe classical sequence and the epigravettian sequence in the south essentially because of an imbalance of data and differences in methodologies between these two regions their upper paleolithic sequences have rarely been compared thanks to the development of lithic technology in europe and a recent active research about the late glacial it is today possible to attempt such a challenging exercise of comparing these two long sequences in this paper we solely focus on the late glacial if the rare existing attempts of comparison focused on typology of lithic assemblages our paper aims for a more global approach of lithic industries based on recent technological studies this approach allows highlighting key elements in term of human behaviors our data suggest a similar process of change between western europe and the epigravettian during gi 1 bolling allerod all the criteria of the so called azilianization process are actually present in the epigravettian evolution sequence this similar trend within both evolution sequences stopped abruptly during the gs 1 younger dryas during this period and the very beginning of the holocene preboreal a massive return of blades and bladelets with high qualitative standards occurred in western europe while the simplification process is still in course in the epigravettian region in this paper we attempt to compare the various responses of vegetation to the major climatic instability of the late glacial across europe using a critical survey of the available environmental data considering the boundary that could have represented the alps between epigravettian and the western europe sequence two high resolution environmental sequences from north and south of the alps are especially examined are the differences in terms of environmental changes between these two areas significant did they play a role in human behaviors and motivate technological changes the comparison of palaeoenvironmental data with archaeological results tends to comfort some hypothesis of environmental determinism proposed by scholars but also provide new elements moderating regional models that cannot really be applied at a continental scale climatic correlations with socioeconomic changes highlighted in this paper are no more than one possible way of investigation that will need to be tested and discussed in further research

post evaporitic restricted deposition in the middle miocene chokrakian karaganian of east crimea ukraine abstract in the middle miocene of east crimea gypsum evaporites formed in a shallow basin from mixed seawater nonmarine waters are overlain by marl siltstone and claystone which contain a few horizons of stromatolitic limestone the thickness and abundance of the stromatolitic horizons increase up the section in the siliciclastic portion of the section a very poor and taxonomically impoverished assemblage of benthic foraminifers jadammina nonion haynesina astrononion and eponides is recorded it is typical for a shallow water marsh or lagoon environment with a lowered salinity accordingly the brackish conditions prevailing during gypsum precipitation in east crimea continued afterwards although at the end of evaporite deposition the basin became desiccated and then it was rapidly reflooded by brackish water the impoverished biota and the occurrence of microbialites in the ptashkino section indicate extremely unfavourable conditions for most living organisms during the deposition of both the terrigenous and carbonate beds the water salinity thus was probably not only lowered but also anomalous in composition if compared to normal marine water the occurrence of carbonate stromatolitic horizons is probably related to the periodic shallowing of the basin caused by a drop of the lake water table driven by climatic factors the resulted changes allowed for a growth of the bizarre microbial serpulid communities that gave birth to most of the stromatolites in karaganian time the eastern paratethys was a huge lake isolated from the tethys this lake responded to any climatic fluctuation that in turn might lead to water level oscillations in humid climate periods the lake could be open with a surface outflow and when it was drier it could be a closed system without surface outflow gypsum evaporites and stromatolitic carbonates are clear evidence of strong evaporation in a dry climate that probably induced water level fall in the whole basin however all the time the environmental conditions were predominantly brackish even during gypsum precipitation as suggested by the chemical composition of fluid inclusions in gypsum similar conditions may be expected in other evaporite hosted predominantly brackish basins such as some messinian basins of the eastern mediterranean where some evaporites were deposited in the oligohaline to mesohaline conditions typical of the lago mare deposits

effects of porosity and clay content on wave velocities in sandstones the ultrasonic compressional vp and shear vs velocities and first arrival peak amplitude ap were measured as functions of differential pressure to 50 mpa and to a state of saturation on 75 different sandstone samples with porosities ranging from 2 to 30 percent and volume clay content c ranging from 0 to 50 percent respectively both vp and vs were found to correlate linearly with porosity and clay content in shaly sandstones at confining pressure of 40 mpa and pore pressure of 1 0 mpa the best least squares fits to the velocity data are vp km s 5 59 6 93 2 18c and vs km s 3 52 4 91 1 89c deviations from these equations are less than 3 percent and 5 percent for vp and vs respectively the velocities of clean sandstones are significantly higher than those predicted by the above linear fits about 7 percent for vp and 11 percent for vs which indicates that a very small amount of clay 1 or a few percent of volume fraction significantly reduces the elastic moduli of sandstones for shaly

mechanical properties and processes of deformation in shallow sedimentary rocks from subduction zones an experimental study to better constrain the mechanical behavior of sediments accreted to accretionary prism we conducted triaxial mechanical tests on natural samples from the miura boso paleo accretionary prism japan in drained conditions with confining pressures up to 200 mpa as well as postexperiments p wave velocity vp measurements during experiments deformation is principally noncoaxial and accommodated by two successive modes of deformation both associated with strain hardening and velocity strengthening behavior 1 compaction assisted shearing distributed in a several mm wide shear zone and 2 faulting localized within a few tens of m wide dilatant fault zone deformation is also associated with 1 a decrease in young s modulus all over the tests 2 anomalously low vp in the deformed samples compared to their porosity and 3 an increase in sensitivity of vp to effective pressure we interpret this evolution of the poroelastic properties of the material as reflecting the progressive breakage of intergrain cement and the formation of microcracks along with macroscopic deformation when applied to natural conditions these results suggest that the deformation style localized versus distributed of shallow z a few km sediments is mainly controlled by the variations in stress strain rate during the seismic cycle and is therefore independent of the porosity of sediments finally we show that the effect of strain through cement breakage and microcracks formation may lower vp for effective pressure up to 40 mpa as a consequence the low vp anomalies observed in nankai accretionary prisms by seismic imaging between 2 and 4 km depth could reflect sediment deformation rather than porosity anomalies

marine to non marine sedimentation in the upper miocene evaporites of the eastern betics se spain sedimentological and geochemical evidence abstract several neogene basins in the eastern betics contain a record of thick upper miocene evaporites the inner basins those located distal to the mediterranean coast include evaporite units ranging from the late tortonian to the early messinian whereas the marginal basins those located in the vicinity of the mediterranean coast include evaporite units corresponding to the late messinian that are linked to the salinity crisis the sedimentological and geochemical comparison of the evaporites in the inner and marginal basins enable us to show their differences in the modes of deposition under local structural controls and differentiated palaeogeography in the inner basins of the murcia alicante region a number of evaporite units have been differentiated whose gypsum lithofacies have 1 variable strontium contents with mean values primary gypsum between 1121 and 2380 ppm 2 isotopic compositions of sulphur 34 s ranging from those characteristic of the tertiary marine water 20 3 to 25 5 to those characteristic of the triassic sulphates 8 0 to 16 0 the latter suggesting recycling of the sulphate anion in meteoric waters intermediate values 17 4 to 19 6 are attributed to mixed mother brines and 3 strontium ratios 87 sr 86 sr comprised between 0 70804 and 0 70888 these values range from those of the tertiary marine water to those exceeding the triassic sulphates suggesting additional continental contributions from country rocks and hydrothermal solutions the comparison between the sulphur and strontium isotopic compositions of the sulphates together with the study of the biota present in the marls associated with the gypsum allows us to distinguish between marine continental and mixed units in the marginal basins of the eastern betics where single evaporite units characterized by selenitic gypsum prevail 1 the strontium contents are more homogeneous with mean values primary gypsum between 493 and 625 ppm 2 the isotopic compositions of oxygen 18 o and sulphur 34 s are comprised between 12 2 and 14 8 and between 22 0 and 23 5 respectively and 3 the strontium ratios 87 sr 86 sr vary from 0 70890 to 0 70895 all these isotopic values reveal a marine origin and the lack of contribution of significant continental water during the late messinian evaporite deposition in the betic strait these characteristics are similar to those of the lower evaporite

marginal marine environments of the skagerrak and kattegat a baseline study of living stained benthic foraminiferal ecology this is the first detailed investigation of the distribution and ecology of living stained shallow water 0 6 m foraminifera along the skagerrak kattegat coast eastern north sea a total of 25 species 13 agglutinated 12 calcareous are common in the 169 sediment surface samples which were collected from 27 geographic areas the sediment grain size and total organic carbon toc content are strongly variable and the salinity and temperature ranges were 10 31 and 9 30 c respectively at the time of sampling july to october but temperatures down to freezing occur during the winter the species are divided into six environmental categories of which the first five comprise euryhaline and the sixth essentially stenohaline taxa 1 species associated only with marsh plants 2 species basically but not entirely associated with marsh plants 3 species basically but not entirely restricted to non marsh areas 4 species solely recorded in non marsh intertidal to subtidal environments 5 species restricted to subtidal areas 6 species basically living in the most open marine areas in this region marshes have a patchy distribution and they are small and compressed due to low tidal ranges 80 mud ammoscalaria runiana is common only in coarse grained sediments 20 mud with low toc 0 7 there are no marked biogeographic boundaries within the skagerrak kattegat area but 10 of the 25 commonly occurring species have not been reported from the adjacent baltic sea probably partly due to the brackish character of the water there the southern limits of distribution of the northern species elphidium albiumbilicatum ammotium cassis and ophthalmina kilianensis are in the kattegat baltic sea

splay fault branching along the nankai subduction zone seismic reflection profiles reveal steeply landward dipping splay faults in the rupture area of the magnitude m 8 1 tonankai earthquake in the nankai subduction zone these splay faults branch upward from the plate boundary interface that is the subduction zone at a depth of approximately 10 kilometers approximately 50 to 55 kilometers landward of the trough axis breaking through the upper crustal plate slip on the active splay fault may be an important mechanism that accommodates the elastic strain caused by relative plate motion

locking of the chile subduction zone controlled by fluid pressure before the 2010 earthquake large subduction zone earthquakes are thought to occur where the down going and overriding tectonic plates are strongly locked analysis of geodetic and seismic data collected in the decade before the 2010 chile earthquake shows that variations in pore fluid pressure correlate with the degree of plate interface locking and may therefore control earthquake rupture

acoustic and mechanical properties of nankai accretionary prism core samples we studied undeformed sediment and accreted strata recently recovered by ocean drilling program integrated ocean drilling program odp iodp drilling in nankai trough convergent margin to unravel the changes in physical properties from initial deposition to incipient deformation we have derived acoustic vp and mechanical uniaxial poroelastic compliance compaction amplitude properties of samples from various drill sites along the muroto odp 1173 and kii transects iodp c0001 c0002 c0006 and c0007 from isotropic loading tests where confining and pore pressure were independently applied we quantified the dependence of vp on both effective peff and confining pc pressure which can be used to correct atmospheric pressure measurements of vp experimental vp obtained on core samples extrapolated to in situ conditions are slightly higher than logging derived velocities which can be attributed either to velocity dispersion or to the effect of large scale faults and weak zones on waves with longer wavelength in the high porosity 30 60 tested sediments velocities are controlled at first order by porosity and not by lithology which is in agreement with our static measurements of drained framework incompressibility much smaller than fluid incompressibility rather than framework incompressibility shear modulus is probably the second order control on vp accounting for most of the difference between actual vp and the prediction by wood s 1941 suspension model we also quantified the mechanical state of nankai samples in terms of anisotropy diagenesis and consolidation both acoustic and mechanical parameters reveal similar values in vertical and horizontal directions attesting to the very low anisotropy of the tested material when considering the porous samples of the upper shikoku basin sediments site 1173 as examples of diagenetically cemented material several mechanical and acoustic attributes appeared as reliable experimental indicators of the presence of intergrain cementation we also detected incipient cementation in samples from iodp site c0001 accretionary prism unit in terms of consolidation we distinguished two classes of material response shallow deformable samples and deep hardly deformable ones based on the amount of compaction upon application of a peff large with respect to the inferred in situ value with a transition that might be related to a critical porosity

velocity porosity relationships for water saturated siliciclastic sediments seeking a global empirical relationship between compressional wave velocity and porosity for siliciclastic sediments we have brought together an extensive suite of both new and published log and core based data we undertook a detailed statistical analysis of ocean drilling program data from amazon fan to examine variables affecting compressional velocity in shallow unconsolidated sediments we identify three dominant variables porosity shale fraction and consolidation history and present two empirically determined boundary curves one for normally consolidated sediments and a second for highly consolidated environments e g accretionary prisms these two empirical relationships predict the compressional velocity of siliciclastic sedimentary rocks with water filled pores as a function of porosity and clay content for the full range of observed porosities velocities of siliciclastic sedimentary rocks decrease rapidly with both increasing porosity and increasing clay content at fractional porosities higher than about 0 4 fluid dominates the elastic properties and velocity exhibits a subtle dependence on porosity remarkably the amazon fan data show that clay content has no direct influence on velocity at high porosities both clay content and sorting do indirectly affect velocity through their control of porosity burial affects velocity not only by compaction related porosity decrease but also by pressure induced increase of intergrain coupling because of the sensitivity of velocity to consolidation history particularly at intermediate fractional porosities of about 0 30 0 40 no single velocity porosity relationship can apply to all high porosity sediments the two proposed relationships fit the majority of published and new data they are applicable however only for normally pressured in situ conditions and water filled pores

improved astronomical age constraints for the middle miocene climate transition based on high resolution stable isotope records from the central mediterranean maltese islands 1 marine outcrops of the globigerina limestone and blue clay formations on the maltese islands in the central mediterranean document the middle miocene climate transition between 15 and 13 5 million years ago here high resolution benthic and planktic oxygen isotope records have been constructed for this enigmatic interval in cenozoic climate evolution detailed biostratigraphic correlations to the astronomically tuned la vedova section in northern italy allow revision of the tuning of the blue clay formation constraining the age of the sediments directly above the formation boundary and hence the mi 3b oxygen isotope event and serravallian global stratotype section and point gssp biostratigraphic age control and cyclic patterns in the benthic carbon isotope record further lead to an astronomically tuned age model for the upper member of the globigerina limestone formation start of sedimentation of the upper globigerina limestone is dated at 14 95 ma and the oldest blue clay sediments have a revised astronomical age of 13 76 0 02 ma our data indicates that a hiatus between 13 95 and 13 76 ma cannot be excluded and could have implications for the serravallian gssp currently defined in this section the global middle miocene cooling is reflected in the benthic oxygen isotope record showing a 0 6 increase mi 3b between 13 95 and 13 76 ma a divergence between the planktic and benthic oxygen and carbon isotope records after 13 76 ma could point to a decrease in ventilation possibly related to increased fresh water influx after the climate transition

the beginning development and termination of the middle miocene badenian salinity crisis in central paratethys abstract middle miocene badenian evaporites of the carpathian region are underlain and overlain by deep water deposits the onset of evaporite deposition was sudden but not synchronous in all facies zones and the deposition of evaporites was controlled by the evolution of carpathian orogen in the carpathian foredeep and most probably in other basins the badenian evaporites represent the lower part of the nn6 zone halite and associated deposits in the central part of the badenian evaporite basin show the same facies successions and marker beds can be traced across and between individual basins characteristic marker beds made it possible to correlate various facies zones of the marginal ca sulfate platform these marker beds seem to reflect events that may be related to sudden and widespread changes in water chemistry which in turn imply major changes in basin hydrology the onset of the evaporitic deposition in the carpathian foredeep was clearly diachronous and the evaporites deposited in the basin centre preceded the beginning of evaporite sedimentation in the marginal basin however depositional history in the marginal basin and the basin centre was the same a general transgressive sequence of evaporites found in the carpathian foredeep resulted from the migration of facies zones induced by the nappe movement isotopic studies of badenian foraminifers occurring below evaporites suggest that the interrupted communication of the paratethys with the ocean was a consequence of eustatic sea level fall possibly related to climatic cooling and it was coupled with a tectonic closure of connection with the tethys thus both tectonics and eustacy have contributed to the origin of salinity crisis sedimentological and geochemical data indicate recycling of evaporites throughout most of the evaporite deposition the recycling at the end of gypsum deposition in the marginal sulfate platform was accompanied by a change in the hydrology of the central paratethys that was tectonically driven and possibly related to the block tectonic phase manifested in the marginal part of the carpathian foredeep basin the change in hydrology implied the dilution of brines by inflowing marine water and this terminated the middle miocene badenian salinity crisis the onset of the badenian salinity crisis shows great similarities to the onset of the messinian salinity crisis and the terminations of both crises were different

mechanical and hydraulic properties of nankai accretionary prism sediments effect of stress path 1 we have conducted triaxial deformation experiments along different loading paths on prism sediments from the nankai trough different load paths of isotropic loading uniaxial strain loading triaxial compression at constant confining pressure pc undrained pc reduction drained pc reduction and triaxial unloading at constant pc were used to understand the evolution of mechanical and hydraulic properties under complicated stress states and loading histories in accretionary subduction zones five deformation experiments were conducted on three sediment core samples for the nankai prism specifically from older accreted sediments at the forearc basin underthrust slope sediments beneath the megasplay fault and overthrust upper shikoku basin sediments along the frontal thrust yield envelopes for each sample were constructed based on the stress paths of pc reduction using the modified cam clay model and in situ stress states of the prism were constrained using the results from the other load paths and accounting for horizontal stress results suggest that the sediments in the vicinity of the megasplay fault and frontal thrust are highly overconsolidated and thus likely to deform brittle rather than ductile the porosity of sediments decreases as the yield envelope expands while the reduction in permeability mainly depends on the effective mean stress before yield and the differential stress after yield an improved understanding of sediment yield strength and hydromechanical properties along different load paths is necessary to treat accurately the coupling of deformation and fluid flow in accretionary subduction zones

response of benthic foraminiferal communities to changes in productivity and watermass conditions in the epicontinental paratethys during the middle miocene abstract the langhian epicontinental sea the central paratethys represented a dynamic environment experiencing many changes making it an ideal system for testing various geochemical proxies here we present a result of a study based on a combination of organic geochemistry 13corg n alkane based indices toc tic with benthic foraminiferal stable isotopic 13c 18o and paleoecological data from the time interval of 14 4 to 14 36 ma moreover we evaluated foraminiferal paleoecological data selected species melonis pompilioides gyroidinoides spp cibicidoides spp together with the 13c and 18o to interpret the paleoecological consequences at the seafloor doing so we assessed the problematics regarding the origin of the organic matter together with changes in productivity and subsequent reaction of benthic foraminiferal assemblages at the seafloor we used the 13corg toc tic and the n alkane based indices to estimate the primary production rate and to determine the origin of the organic matter at the studied locality the reconstructed paleoenvironment represented an open marine realm without significant freshwater influence where the primary productivity was generated by marine algae a gradual decrease of productivity could be observed linked with shallowing of the basin towards a more carbonate dominated environment changes in nutrient flux and vertical migration of the less oxygenated zone turned out to be the main phenomena responsible for physicochemical and paleoecological changes in the foraminiferal communities within the sediment in addition we tried to characterize the population dynamics of the studied benthic foraminiferal species under a variety of existing conditions at the seafloor

distribution of diatoms coccolithophores and planktic foraminifers along a trophic gradient during sw monsoon in the arabian sea the distribution of diatoms coccolithophores and planktic foraminifers mirrored the hydrographic and trophic conditions of the surface ocean 0 100 m across the upwelling area off the oman coast to the central arabian sea during may june 1997 and july august 1995 the number of diatoms was increased in waters with local temperature minimum and enhanced nutrient concentration nitrate phosphate silicate caused by upwelling vegetative cells of chaetoceros dominated the diatom assemblage in the coastal upwelling area towards the more nutrient depleted and stratified surface waters to the southeast the number of diatoms decreased coccolithophore and planktic foraminiferal numbers increased and floral and faunal composition changed in particular the transition between the eutrophic upwelling region off oman and the oligotrophic central arabian sea was marked by moderate nutrient concentration and high coccolithophore and foraminifer numbers florisphaera profunda previously often referred as a lower photic zone species was frequent in water depths as shallow as 20 m and at high nutrient concentration up to 14 mol no3 l 1 and 1 2 mol po4 l 1 to the oligotrophic southeast of the divergence cell densities of coccolithophores declined and umbellosphaera irregularis prevailed throughout the water column down to 100 m depth in general total coccolithophore numbers were limited by nutrient threshold concentration with low numbers 70 103 cells l 1 at low no3 and po4 the components of the complex microplankton succession diatoms coccoliths and planktic foraminifers and possibly others should ideally be used as a combined paleoceanographic proxy consequently models on plankton ecology should be resolved at least for the seasonality to account for the bias of paleoceanographic transfer calculations

how cracks modify permeability and introduce velocity dispersion examples of glass and basalt the porosity of igneous rocks is usually very small although for some basalts it can be nonnegligible due to gas exsolution in the case of glass it is vanishingly small why is it of any interest to look at this kind of material from the point of view of rock physics two series of reasons indeed motivate such investigations

broad weak regions of the nankai megathrust and implications for shallow coseismic slip abstract deep within the nankai trough subduction zone the plate boundary thrust slips along a well imaged megasplay fault system during the megathrust earthquakes that regularly strike southwest japan the routing of the active plate boundary thrust along an upward branching splay fault causes deep underthrusting of an unusually thick section of material attached to the subducting ocean crust here we present three dimensional seismic reflection data that shows this unusually thick section is fluid rich sediment that results in broad weakly coupled regions of the megathrust down into the updip end of the seismogenic zone the weakly coupled regions lie above an underthrust low seismic impedance presumed to be low velocity and low density sediment section that is between one and two kilometers thick and covers 3300 km2 at least one eighth of the total rupture area of the 1944 mw 8 1 tonankai earthquake this underthrust sediment section is broader and much deeper than inferred at other margins sediment underthrusting into the normally well coupled seismogenic zone likely releases fluids and elevates fluid pressure which reduces inter plate coupling along portions of the megasplay fault and allows coseismic rupture to propagate to unusually shallow depths and generate large tsunami as inferred for the 1944 tonankai event splay faults may be a common yet transient mechanism for developing weak subduction zone thrusts

palaeoclimatic interpretation based on middle miocene planktonic foraminifera the silesia basin paratethys and monferrato tethys records a comparative study of the distribution and palaeoclimatic interpretation of temperature related taxa of middle miocene planktonic foraminifera from the paratethys silesia basin southern poland and tethys monferrato area northwestern italy is presented the time span considered badenian langhian serravallian is the last period of significant connection between the paratethys and mediterranean tethys even though the depositional conditions water circulation and connection with the oceanic realm were not always favourable to the life and preservation of significant planktonic foraminiferal taxa the silesia basin located in the western segment of the karpathian foredeep is filled by an autochthonous non folded cover of miocene deposits four stratigraphic sections were studied in this area characterised by carpathian sandy deposits of the klodnica formation lower badenian unbedded marly clays marls and strongly bedded lithothamnium marls skawina formation middle badenian anhydrite and laminated clay shales krzy anowice formation upper badenian unbedded marly clays followed by fine grained sands sandy limestone layers and bioclastic levels rich in molluscs and calcareous algae gliwice formation the monferrato area corresponds to the northwestern termination of the apennines thrust belt and consists of an eocene miocene mainly terrigenous succession resting unconformably on upper cretaceous and eocene ligurian flysch three stratigraphic sections are studied in the eastern area characterised by late oligocene to early burdigalian deepwater terrigenous sediments marne di antognola formation followed unconformably by early to middle miocene carbonate sediments originating in a foramol platform depositional environment pietra da cantoni group and by grey whitish glauconitic marls of the marne di mincengo formation late langhian serravallian twenty three species of tethys and paratethys planktonic foraminifera were grouped in cold globigerina bulloides globigerina quinqueloba globigerina praebulloides gr globorotaloides spp catapsydrax spp cold temperate zeaglobigerina woodi z brazieri globorotalia scitula gr globorotalia bykovae warm globigerinoides spp orbuliniforms including praeorbulina spp and orbulina spp globigerina ciperoensis dentoglobigerina altispira gr velapertina indigena globorotalia praemenardii and warm temperate indices paragloborotalia siakensis gr dentoglobigerina baroemoenensis gr globoquadrina praedehiscens and g dehiscens tenuitellinata angustiumbilicata globigerinella obesa globigerina venezuelana their relative abundance was used to reconstruct palaeoclimatic curves comparison of the palaeoclimatic curves makes it possible to recognise a climatic change from warmer conditions in the langhian towards relatively colder conditions in the serravallian the fall in warm related taxa was much more pronounced in the silesia basin than in the monferrato area this palaeoclimatic evidence may be interpreted as the beginning of a series of oscillations pointing to a period of cooling corresponding to one of the major global changes in the palaeoclimatic palaeoceanographic history of the cenozoic i e the mid miocene event mi3 miller et al 1991 paleoceanography 6 33 52

sea surface temperature variability in the subpolar atlantic over the last two millennia 1 a decadal resolution time series of sea surface temperature sst spanning the last two millennia is reconstructed by combining a proxy record from a new sediment sequence with previously published data from core md99 2275 north of iceland the alkenone based sst reconstruction is validated with historic observational data and compared to a new similar temporal resolution reconstruction obtained from sediment core rapid21 3k in the subpolar north atlantic the two sst paleorecords show consistent multidecadal scale coolings throughout the interval and similar expressions during the contrasted climatic periods colloquially known as the medieval climatic anomaly mca and little ice age lia in order to further understand the temporal and spatial sst variations and investigate the influence of natural forcings on the observed sst changes during the last millennium we compare our time series to simulations using the institut pierre simon laplace ipslcm4 v2 climate model this comparison highlights the potential importance of volcanism as a natural forcing driving coherent abrupt cooling events captured in the subpolar north atlantic records

foraminiferal record of marine transgression during deposition of the middle miocene badenian evaporites in central paratethys borkow section polish carpathian foredeep benthic and planktonic foraminifera from a marly clay intercalation sandwiched between mid badenian middle miocene gypsum deposited in an environment of an evaporitic shoal 1 m deep at borkow southern poland indicate a major marine flooding event in the previously isolated carpathian foredeep basin central paratethys after this very short term environmental change benthic foraminifers started to colonize a new niche which was previously defaunated and the pattern of benthic foraminiferal colonization is similar to that related to the reflooding which terminated the badenian evaporite deposition the benthic foraminifer assemblages are composed of pioneer opportunistic r selected species dominated by elphidiids the connection of the carpathian foredeep basin with the marine reservoir was short lived the marly clay intercalations in evaporite sequences originating in bared basins can thus register major environmental changes

marmota marmota the most common prey species at grotta del clusantin insights from an unusual case study in the italian alps archaeozoological investigations carried out at grotta del clusantin in the italian north eastern alps suggest that this late upper palaeolithic site hosted small groups of marmot hunters taxonomic data describe an alpine grassland environment with arboreal and shrubby vegetation in proximity the bone assemblage is extremely fragmented as a result of anthropic activities and post depositional agents the presence of percussion cones butchering cutmarks burnt bones and the almost total absence of carnivore traces and animal lairs suggests that humans are responsible for faunal accumulation experimental approaches on marmot specimens supported archaeological evidence demonstrating elements of systematics and or explaining anatomical absences from field evidence lithic and functional data it has been inferred that this site was a specialized camp used for exploiting and consuming several rodent carcasses in the context of the first human occupations of the highlands at the onset of the lateglacial interstadial