turbulence structure over two dimensional bed forms implications for sediment transport turbulence measurements from the flow over two dimensional fixed dune shapes are presented along with analysis and discussion of the ramifications of the observations for transport of sediment as bed load over bed forms the spatial structure of the local transport rate determines the shape and stability of bed forms such as ripples and dunes and the transport of sediment is a highly nonlinear process that is profoundly affected by the statistics of the temporal fluctuations in the near bed flow field the measurements presented herein show strong spatial evolution of the joint probability distribution of the streamwise and bednormal fluctuating velocity components unlike measurements in uniform boundary layers these distributions and the higher moments of the velocity do not scale with the local shear velocity indicating that it is probably inappropriate to use the shear stress to characterize the sediment flux this conclusion is supported by observations of sediment flux over a dune

effect of organic carbon flux and dissolved oxygen on the benthic foraminiferal oxygen index bfoi variations in oceanic primary productivity flux of organic carbon to the sediments and dissolved oxygen levels in the water column are thought to be important in the control of benthic foraminiferal test size wall thickness morphology and species composition of assemblages by many foraminiferal paleontologists aspects of these processes should be reflected by the benthic foraminiferal oxygen index bfoi based on these foraminiferal characteristics however analyses indicate that the bfoi correlates most strongly with dissolved oxygen levels in overlying water r2 0 81 weakly with oceanic primary productivity r2 0 55 and weakly with organic carbon flux to the sediments r2 0 51 although both dissolved oxygen and organic carbon flux are main controlling factors for benthic foraminiferal assemblages the bfoi is a useful indicator extracted from benthic foraminiferal assemblages for estimating the condition of dissolved oxygen in cretaceous and cenozoic oceans

late pliocene caribbean surface water dynamics and climatic changes based on calcareous nannofossil records abstract quantitative analyses of nannofossil assemblages from two odp sites were performed to determine changes in the surface water structure in the caribbean sea and implications for climatic changes during the late pliocene analysis was made by calculation of accumulation rates and division of nannofossils into ecological groups based on their depth distributions and trophic regime oligotrophic vs eutrophic between 3 5 and 2 7 ma separate surface water masses existed in the northern and southern caribbean the northern surface water was strongly oligotrophic with a deep thermocline nutricline prior to 3 1 ma the southern caribbean was characterized by a shallower thermocline nutricline with minor upwelling induced by the presence of the past itcz intertropical convergence zone after 3 1 ma the thermocline nutricline deepened in the southern caribbean and the upper water became oligotrophic as a result of the completion of the closure of the isthmus after an episodic invasion of cooler surface waters associated with high latitude cooling at approximately 2 7 ma coccolith productivity in the caribbean was at its lowest a deep thermocline existed between 2 7 and 2 4 ma and nutrient depleted waters spread on the suw subtropical under water in the caribbean after 2 4 ma the increase of terrigenous materials from the south american continent caused an abundance of eutrophic taxa this suggests that recent climate systems were established due to the intensification of the northern hemisphere glaciation

bryozoan faunas in the middle miocene of hungary biodiversity and biogeography a study of the badenian middle miocene marine deposits of hungary yielded a rich bryozoan fauna of 238 species comprising 59 cyclostomes 176 cheilostomes and 3 ctenostomes six palaeobiogeographic groups have been identified among this fauna on the basis of the present day and fossil distribution of the species similarities within the central paratethys and between the central paratethys the mediterranean and the atlantic have then been calculated using jaccard s index the results indicate strong affinities between the central paratethyan basins of hungary austria poland and romania the higher number of species and the lower level of endemism observed in hungary is explained by the vicinity of this basin to the entrance of the water seaway connecting the mediterranean to the paratethys a decrease in taxonomic diversity between the early and the late badenian is also observed accompanied by the absence of most tropical taxa from the late badenian this points towards a less optimal climate and a more pronounced isolation of the badenian sea from the oceanic waters the major result of the comparative study between central paratethyan and mediterranean bryozoan faunas is the presence of numerous common species the number of endemic paratethyan species is however relatively high indicating that the bryozoan faunas of both seas evolved in a relative isolation the exchange of faunas between the mediterranean and the paratethys was probably regulated by an anti estuarine circulation permitting an easier incursion of mediterranean species into the paratethys but hindering the paratethyan endemics from entering the mediterranean the stronger affinity between hungarian and mediterranean faunas also shows that this basin was closer to the entrance of the water seaway connecting the two areas and thus the mediterranean species entered more easily the similarity index between central paratethys and atlantic faunas is much lower than with the mediterranean this indicates that the palaeobiogeographic domain formed by the mediterranean and the paratethys was relatively homogeneous during the middle miocene and that the relationships with the atlantic were weaker exchange of benthic organisms between the central paratethys and the indo pacific during the middle miocene is considered here as extremely improbable

how do bedform patterns arise new views on the role of bedform interactions within a set of boundary conditions one explanation for bedform patterns is self organization in which the pattern emerges because of interactions among the bedforms themselves models remote images field studies and lab experiments have identified bedform interactions that involve whole bedforms only bedform defects or that are remote interactions between bedforms it is proposed that bedform interactions form a spectrum from constructive to regenerative in pattern development constructive interactions including merging lateral linking cannibalization and remote transfer of sediment push the system toward fewer larger more widely spaced bedforms regenerative interactions including bedform splitting defect creation and calving push the system back toward a more initial state other interactions including off center collision defect migration and bedform and defect repulsion cause pattern change but may not be strongly constructive or regenerative although bedform interactions are ubiquitous to any field of bedforms their dynamics flow field modification and impact upon measurable pattern parameters are yet poorly understood most bedform interactions span bedform types and fluids supporting the hypothesis that pattern emerges from dynamics at the bedform level in a hierarchy that includes lower levels of bedform flow and grain fluid interactions bedform interactions alone however cannot account for the rich diversity of bedform patterns in nature it is proposed that field diversity arises because of boundary conditions which are the environmental variables within which a field evolves conceptually boundary conditions modify the shape of the attractor toward which a field evolves possibly by altering the type and frequency of bedform interactions boundary conditions are broadly similar within system types but are unique for each bedform field so that no two are ever exactly alike although aeolian and fluvial systems share some types of boundary conditions flow depth is a unique boundary condition in shallow fluvial systems copyright 2009 john wiley sons ltd

hyporheic transport and biogeochemical reactions in pool riffle systems under varying ambient groundwater flow conditions at the interface between stream water groundwater and the hyporheic zone hz important biogeochemical processes that play a crucial role in fluvial ecology occur solutes that infiltrate into the hz can react with each other and possibly also with upwelling solutes from the groundwater in this study we systematically evaluate how variations of gaining and losing conditions stream discharge and pool riffle morphology affect aerobic respiration ar and denitrification dn in the hz for this purpose a computational fluid dynamics model of stream water flow is coupled to a reactive transport model scenarios of variations of the solute concentration in the upwelling groundwater were conducted our results show that solute influx residence time and the size of reactive zones strongly depend on presence magnitude and direction of ambient groundwater flow high magnitudes of ambient groundwater flow lower ar efficiency by up to 4 times and dn by up to 3 orders of magnitude compared to neutral conditions the influence of stream discharge and morphology on the efficiency of ar and dn are minor in comparison to that of ambient groundwater flow different scenarios of o2 and no3 concentrations in the upwelling groundwater reveal that dn efficiency of the hz is highest under low upwelling magnitudes accompanied with low concentrations of o2 and no3 our results demonstrate how ambient groundwater flow influences solute transport ar and dn in the hz neglecting groundwater flow in stream groundwater interactions would lead to a significant overestimation of the efficiency of biogeochemical reactions in fluvial systems

the sedimentary structure of linear sand dunes linear sand dunes dunes that extend parallel to each other rather than in star like or crescentic forms are the most abundant type of desert sand dune1 but because their development and their internal structure are poorly understood they are rarely recognized in the rock record2 models of linear dune development2 3 4 5 6 have not been able to take into account the sub surface structure of existing dunes but have relied instead either on the extrapolation of short term measurements of winds and sediment transport or on observations of near surface internal sedimentary structures from such studies it has not been clear if linear dunes can migrate laterally2 7 8 here we present images produced by ground penetrating radar showing the three dimensional sedimentary structure of a linear dune in the namib sand sea where some of the world s largest linear dunes are situated these profiles show clear evidence for lateral migration in a linear dune moreover the migration of a sinuous crest line along the dune produces divergent sets of cross stratification which can become stacked as the dune height increases and large linear dunes can support superimposed dunes that produce stacked sets of trough cross stratification these clear structural signatures of linear dunes should facilitate their recognition in geological records

the influence of ambient groundwater discharge on exchange zones induced by current bedform interactions summary we use numerical modeling to investigate the interactions between laminar flow in a water column current bedform induced flow in underlying permeable sediments and discharge of deep groundwater to the water column groundwater discharge reduces the spatial extent of current induced exchange zones within the sediments and may completely prevent the development of current bedform induced flow at high groundwater discharge although exchange zone size is reduced by groundwater discharge the reduction in exchange flux is not significant suggesting reduced residence times of materials cycled through these smaller zones fluid exchange zones tend to be centered around the reattachment points of eddies that also mark the location of flow divides within the sediments while deep groundwater is discharged preferentially along troughs exchange zone depth and the water column reynolds number are functionally related through a morgan mercer flodin model the relationship between the current induced flux through the sediments and the reynolds number is described by low order monotonic polynomial functions

paleoenvironmental reconstruction of the early to middle miocene central paratethys using stable isotopes from bryozoan skeletons stable carbon and oxygen isotope values from single bryozoan colonies were used to reconstruct the paleoenvironments of the early to middle miocene ottnangian to badenian sediments of the central paratethys this approach utilizes a locally abundant allochem while avoiding matrix and multiple allochem contamination from bulk rock samples bryozoan colonies and a few foraminifera and rock matrix samples from 14 localities yielded 399 carbon and oxygen isotope values data from six of the localities 15 of the total number of samples were interpreted as having been diagenetically altered and were rejected the remaining data indicate a primarily localized upwelling signal with lesser variation caused by global climatic and regional tectonic forcing of sea level salinity and temperature paleotemperatures were calculated to range from 12 to 21 c despite potential taxonomic and diagenetic problems bryozoan colonies are a powerful underutilized source of paleoenvironmental carbon and oxygen isotope data

comparison of methods to determine q in shallow marine sediments from vertical reflection seismograms four methods for the determination of q in marine sediments are compared two traditional methods i e the risetime and the spectral ratio method and two newly established ones the spectrum modeling and the wavelet modeling method in the latter one q and the reflection time t are determined simultaneously which gives a much better accuracy for t than reading it from the seismogram the risetime and the spectral ratio methods are used for obtaining q directly from the data the principle of the modeling methods is to calculate the effect of absorption and dispersion on a reference wavelet or its spectrum for various values of q and the best fit between the observed and the calculated data leads to the optimum result numerical tests on synthetic data show that a precision of more than 25 for data containing noise or superposed arrivals can hardly be achieved in any case wavelet modeling is the superior method application to data from a vertical reflection profile in the baltic sea yields q in the range of 15 100 for different layers which is to be expected in the sedimentary environment of this area

elongation and migration of sand dunes two distinct processes are known to act on dynamic dunes the process of migration by erosion on the windward side and deposition on the lee side typical for transverse dunes and the process of elongation typical for linear dunes these two processes are determined by wind direction relative to the dune alignment this article reviews the assertion that linear dunes experience lateral displacement in addition to elongation fieldwork on vegetated linear dunes vlds and gis work on seif dunes indicates no lateral migration for these dunes linear dunes can shift laterally only when a slip face formed on the lee side reaches the plinth of the dune the winds from both sides of the seif dune are never symmetric usually winds from one direction are more dominant and effective the outcome is the formation of peaks and saddles along the dune the strongest winds create a slip face on the lee side of the peak segments of the dune oblique to the dune alignment which reaches the base of the dune and displaces the peak downwind along the dune alignment the internal structure of the seif dune is formed mostly by this dominant wind direction and gives the impression that the dune has shifted laterally on the other hand there are cases in which the wind directions relative to dune alignment fall between those of transverse and seif dunes in such cases both processes act on the dune which subsequently experiences migration as well as elongation

bryozoa foraminifera and calcareous nannoplankton as environmental proxies of the bryozoan event in the middle miocene of the central paratethys czech republic abstract in order to improve the reliability of using bryozoans as an indicator of the palaeoenvironment a detailed study of the ancient environmental parameters of the middle miocene bryozoan event was carried out using foraminifera calcareous nannoplankton and oxygen and carbon stable isotope data abundant occurrence of bryozoa in the middle miocene of the central paratethys was an isochronous event which can be correlated with m6 zone between fo of orbulina suturalis and lo of praeorbulina circularis 14 8 14 58 ma the ecosystems of the central paratethys marine basins during this time were generally influenced by the middle miocene climatic optimum and the large transgression which covered the central paratethys basins with tropical subtropical waters these events triggered the expansion of bryozoa which settled in the narrow shallow water zone of the basin and were accompanied by epiphytic foraminifera such as asterigerinata lobatula and elphidium and large foraminifera such as amphistegina rarely cibicidoids although foraminiferal assemblages show only small palaeoenvironmental variations bryozoan species compositions remarkably vary according to palaeoenvironments in this study four clusters with differing bryozoan assemblages can be distinguished in shallow water environment as follows 1 reteporella hornera verrucosa assemblage indicative of a high energy environment 2 buffonellodes rhynchozoon assemblage occurred on carbonate substratum with seagrass meadows influenced by the middle miocene warm water incursion 3 smittina metrarabdotos assemblage indicative of toleration of suboxic zone in sediment 4 schizomavella tenella schizoporella tetragona assemblage recorded almost in all shallow water environments this cluster probably represents species with high adaptation potential exceptionally deeper water conditions were inferred at one section and represented by a tervia irregularis dominated assemblage this assemblage was only present for a short period of time

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

barchan shaped ripple marks in a wave flume barchans isolated crescent shaped bedforms are believed to be formed under almost unidirectional wind or water ows and limited sand supply the formation of barchan morphologies under the action of purely oscillatory wave motion has not yet been fully investigated the present study attempted to form barchan topography in a wave ume and to compare this with barchans in the eld barchan morphologies of ripple size called the barchan ripples were generated from a at bed by the action of waves the horn width the distance between horn tips of the barchan ripples increased linearly with an increase in the total length the overall length projected on the centre line of the barchan with a coef cient common to barchan dunes in deserts the ratio of horn length to horn width of the barchan ripples was smaller than that of barchan dunes but similar to that of subaqueous barchans in the eld the longer the wave period was the larger the ratio of the body length to horn width became most subaqueous barchans formed under waves in the laboratory and unidirectional ows in the eld had blunter horns than subaerial barchans the shape of the barchan ripples changed with wave period the outer rim became rounder with increasing wave period the relationship between the base area and the height of barchan morphologies seems to be linear with a constant coef cient for the scale from ripples to dunes the barchan ripples showed a linear relationship between the height and the horn width similar to that for barchan dunes the migration speed of the barchan ripples was proportional to the cube of the ow velocity and was inversely proportional to height the same relation with a different value of the coef cient was obtained for barchan dunes copyright 2004 john wiley sons ltd

attenuation of explosion generated pulse in rock masses recordings were made of seismic pulses by explosive sources in rock underground at mount isa mine queensland australia analysis of the experimental results in light of the theory of kjartansson 1979 indicates that the simple rise time law tau tau sub 0 ct q is inadequate for describing the attenuation of seismic pulses generated by a realistic source the rise time law makes no allowance for the spectral characteristics of the source except by assigning a value of tau sub 0 to each source and is an oversimplification of the process of source propagation through rocks consequently the constant c is source dependent an alternative method of estimating pulse attenuation is presented which overcomes the difficulties inherent in the rise time law

measurement of rise times of seismic pulses in rock rise times for seismic pulses in rock are discussed for both nearly constant q ncq and constant q cq theories of pulse attenuation the frequency content of the ncq pulse is examined in detail frequencies close to the megahertz region are shown to have a significant contribution to the rise time of pulses a meter or so from an impulsive source hence the measurement of such rise times is significantly influenced by the frequency response of the measurement system itself in giving a numerical assessment of the system influence i propose a model for a general system transfer function the effect of such a system on the measurement of rise times of seismic pulses is then obtained by convolving the system impulse response with the given seismic pulse for even the most broad band seismic measurement systems presently available rise time measurements made especially within 10 m or so of an impulsive source show a large contribution dependent upon the rise time of the measurement system itself

fault plane solutions for microearthquakes induced at the fenton hill hot dry rock geothermal site implications for the state of stress near a quaternary volcanic center fault plane solutions of earthquakes induced during attempts to stimulate two hot dry rock reservoirs at fenton hill have significantly different patterns of first motions the fault plane solution for the lower reservoir indicates strike slip either left lateral strike slip on a n s vertical plane or right lateral slip on an e w vertical plane in contrast the solution for the upper zone includes largely vertical slip on a n s nearly vertical plane or oblique slip on a nearly horizontal plane because the n s nodal plane is common in both solutions we infer that this represents the true fracture plane faulting thus seems to occur on a series of parallel faults or joints that intersect both reservoirs but a change in the slip vector indicates a major change in the state of stress between the upper and lower reservoirs this latter conclusion is surprising because the two reservoirs are separated by less than 1 km we suggest that this rapid change in the stress field may be related to the structure and subsidence of the nearby valles caldera

the miocene climatic optimum evidence from ectothermic vertebrates of central europe abstract data sets of central european temporal distributions of thermophilic ectothermic vertebrates channidae varanidae chamaeleonidae cordylidae tomistomidae alligatoridae giant turtles and of north alpine foreland basin nafb distributions of ectothermic vertebrates adapted to dryer habitats albanerpeton inexpectatum salamandra sansaniensis bufo cf viridis chamaeleo caroliquarti gekkonidae varanus hofmanni bransateryx sp are analysed two main migration events of thermophilic ectotherms at 20 ma and 18 ma in the lower miocene are discerned they indicate the beginning of the miocene climatic optimum in central europe 42 45 n palaeolatitude with a lower limit of the mean annual temperature mat of 17 4 c derived from the minimal mat of their extant relatives furthermore additional palaeobotanical data and records of bauxite point to a mat of 22 c this warm and humid optimum peaked at 18 16 5 ma ottnangian karpatian and is confirmed by the coexistence of all investigated thermophilic taxa the following period early badenian is characterised by probably unchanged temperatures but a seasonality in precipitation with dry periods up to six months two major seasonal phases between 16 3 and 15 7 ma earliest early badenian and between 14 7 and 14 5 ma early middle badenian transition are indicated by an immigration of dry adapted taxa from the surrounding karst plateau to the nafb it is presumed that the tectonical reorganisation of the central paratethys realm had considerable influence on this regional humidity pattern the warm period ended abruptly between 14 0 and 13 5 ma middle late badenian transition with major regional extinction events of most of the thermophilic groups in central europe and a drop of the mat of probably more than 7 c to temperatures around 14 8 15 7 c this drop can be attributed predominantly to a decrease of more than 11 c of the minimum cold months temperature this temperature decrease marked the beginning of a climatic zonation of the european continent and is also evidenced by a progressively southward disappearance of the crocodile diplocynodon from 38 45 n palaeolatitude to 30 37 n during the middle and earliest late miocene the results correlate well with palaeobotanical data from the mid latitudes of europe and north america and the deep sea temperature curve generated from oxygen isotope ratios

paleobathymetry in the backstripping procedure correction for oxygenation effects on depth estimates abstract this paper aims to provide a straightforward and easily applicable method for estimating the depositional depth evolution of marine basins vertical movements of the basin floor can be reconstructed from the sedimentary record and more accurately constrained when information from the sedimentary history is combined with palaeodepth estimates derived from fauna to this end we propose to extend an existing method based on the percentage of planktonic foraminifera with respect to the total planktonic and benthic foraminiferal association which is expressed as the percentage planktonics p the ratio between planktonic and benthic foraminifera is related to water depth and the p generally increases with increasing distance to shore however next to water depth the oxygen level of bottom waters has a profound effect on the abundance of benthic foraminifera and as such influences the p depending on basin configuration the oxygen level at the sea floor can vary on milankovitch time scales and is reflected by the fraction of benthic foraminiferal species that indicate an effect of oxygen stress on the biotic system these species can be used as stress markers and their percentage with respect to the total benthic population is here expressed as s to assess whether the effect of sea floor oxygenation impairs depth reconstructions we studied the percentage of planktonic foraminifera p in five well dated sedimentary successions from the lower pliocene of crete corfu and milos in greece additionally we assessed whether different foraminiferal size fractions and counting methods affect the determination of the percentage of planktonic foraminifera the palaeobathymetric evolution calculated for each basin was confirmed for all successions by an independent check on depth related occurrences of benthic foraminifera after correction for bathymetry changes of the basin due to sedimentation compaction and eustatic sea level variations the vertical movement history of the basin floor was inferred we propose a standard methodology for reconstructions of palaeobathymetry of marine sedimentary successions from foraminiferal associations

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

morphology and flow fields of three dimensional dunes rio parana argentina results from simultaneous multibeam echo sounding and acoustic doppler current profiling 1 most past studies of river dune dynamics have concentrated on two dimensional 2 d bed forms with constant heights and straight crest lines transverse to the flow and their associated turbulent flow structure this morphological simplification imposes inherent limitations on the interpretation and understanding of dune form and flow dynamics in natural channels where dune form is predominantly three dimensional for example studies over 2 d forms neglect the significant influence that lateral flows and secondary circulation may have on the flow structure and thus dune morphology this paper details a field study of a swath of 3 d dunes in the rio parana argentina a large 0 35 km wide 1 2 km long area of dunes was surveyed using a multibeam echo sounder mbes that provided high resolution 3 d detail of the river bed simultaneous with the mbes survey 3 d flow information was obtained with an acoustic doppler current profiler adcp revealing a complicated pattern of dune morphology and associated flow structure within the swath dune three dimensionality appears intimately connected to the morphology of the upstream dune with changes in crest line curvature and crest line bifurcations junctions significantly influencing the downstream dune form dunes with lobe or saddle shaped crest lines were found to have larger more structured regions of vertical velocity with smaller separation zones than more 2 d straight crested dunes these results represent the first integrated study of 3 d dune form and mean flow structure from the field and show several similarities to recent laboratory models of flow over 3 d dunes

measured anisotropy in pierre shale the five elastic coefficients which characterize a transversely isotropic medium have been measured for the pierre shale the first arrival times deduced from two closely spaced vertical seismic profiles provide values of magnitude and direction of the phase velocity at a given depth for different locations of the sources from these velocities we can estimate the five elastic coefficients by assuming that the p and sv wave velocities have only a small dependence on the angle of propagation on the other hand it is shown that the accuracy in the difference between the directions of propagation and particle motion is not sufficient to determine the anisotropy this work was industrially sponsored through the integrated geophysics project

mosaic of environments recorded by bryozoan faunas from the middle miocene of hungary the marine sediments of the badenian middle miocene of hungary pannonian basin central paratethys are composed of abundant bryozoan skeletal grains seventy one bulk samples collected at 18 localities outcrops and boreholes yielded a total number of 238 bryozoan species in order to reconstruct the badenian palaeoenvironments the present study investigates the composition of this very diverse fauna using a combination of statistical and palaeoecological methods the statistical analyses make use of cluster analysis and non metric multi dimensional scaling the palaeoecological approaches are based on the known ecological requirements of the bryozoan colonial growth forms and of the numerous extant species five facies have first been differentiated on the basis of sedimentological and palaeontological features coral buildups coralline algal limestones biocalcarenites sands and marls each of them is characterized by the abundance the diversity and the types of growth forms of the bryozoans the palaeoecological statistical and facies analyses further permitted to identify four depositional settings carbonate platform distal and proximal terrigenous platform slope and basin these environments developed at depths between 0 to about 300 m in a mixed carbonate siliciclastic depositional system skeletal production and spatial distribution of carbonate factories were predominantly controlled by terrigenous input this resulted in a complex mosaic of facies habitats where rich bryozoan faunas could thrive many warm water organisms among them foraminifers zooxanthellate corals molluscs bryozoans and echinoids were recorded from the study sites the coexistence of coralgal and bryomol carbonate skeletal assemblages in this subtropical setting is explained mostly by variations in the productivity of surface waters periods of nutrient enrichment and increased benthic eutrophication affected coral diversity and abundance in favour of bryozoans

hyporheic exchange in gravel bed rivers with pool riffle morphology laboratory experiments and three dimensional modeling received 7 june 2005 revised 30 june 2006 accepted 25 august 2006 published 31 january 2007 1 we report the first laboratory simulations of hyporheic exchange in gravel pool riffle channels which are characterized by coarse sediment steep slopes and three dimensional bed forms that strongly influence surface flow these channels are particularly important habitat for salmonids many of which are currently at risk worldwide and which incubate their offspring within the hyporheic zone here we perform a set of laboratory experiments examining the effects of discharge and bed form amplitude on hyporheic exchange with surface subsurface mixing measured directly from the concentration decay of a conservative tracer fluorescein injected into the surface flow near bed pressure measurements were also used to predict hyporheic exchange from a three dimensional pumping transport model comparison of the predicted and observed hyporheic exchange shows good agreement indicating that the major mechanism for exchange is bed form induced advection however the effect of bed forms is modulated by discharge and the degree of topographic submergence we also tested the performance of the hydrostatic pressure as a proxy for the observed near bed pressure in driving hyporheic exchange which would facilitate field measurement and analysis of hyporheic flow in natural rivers we found agreement with measured hyporheic exchange only for low bed form amplitudes and high flows

response of nannoplankton to major changes in sea surface temperature and movements of hydrological fronts over site dsdp 594 south chatham rise southeastern new zealand during the last 130 kyr abstract a high resolution history of paleoceanographic changes in the subpolar waters of the southern margin of the subtropical convergence zone during the last 130 kyr is present in foraminiferal assemblages of dsdp site 594 the foraminifera indicate that sea surface temperatures during the last interglacial climax were warmer than today and that between substage 5d through to the end of isotope stage 2 temperatures were mostly cooler than holocene temperatures the paleotemperatures suggest that 1 the subtropical convergence was located over the site during substage 5e later moving further north then moving southwards to near the site during the holocene and 2 the polar front was positioned over the site during glacial stages 6 4 2 and possibly parts of stage 3 several major events are indicated by the nannofloral assemblages during these large changes in sea surface temperature and associated reorganization of ocean circulation first the time progressive trends between e huxleyi and medium to large gephyrocapsa are unique to this site with e huxleyi dominating over medium gephyrocapsa during stages 5c a middle part of stage 4 and after the middle point of stage 3 this unusual trend may at least partly be caused by the shift of the polar front across the site second upwelling flora e huxleyi and small placoliths increase in abundance during stages 1 3 and 5 suggesting that upwelling or disturbance of water stratification took place during the interglacials thirdly there are no significant differences between the distribution patterns of the various morphotypes of medium to large gephyrocapsa and the combined value of all medium gephyrocapsa increases in abundance during glacials stages 2 and 4 and the end of stage 6 similar to the abundance trends in benthic foraminifera finally subordinate nannofossil taxa also show distinctive climatic trends during the last glacial cycle 1 syracosphaera spp are present in increased abundance during warmer extremes in climate substages 5e 5a and stage 1 2 coccolithus pelagicus and calcidiscus leptoporus dominate the subordinate nannofossil taxa and their relative proportions seem to provide a useful paleoceanographic index with c pelagicus dominating when the polar front zone is over the site stages 6 4 and 2 whilst c leptoporus is relatively more abundant when the stc is positioned over the site stages 1 and 5e increased abundance of c pelagicus also can indicate intensified coastal upwelling

pattern analysis of dune field parameters as a basic form of pattern analysis the parameters of dune spacing defect density crest orientation and crest length are measured from remote images and treated statistically for dunes at white sands in new mexico the algodones in california the agneitir in mauritania and the namib in namibia statistical populations are identified from frequency plots of dune spacing and crest length field scale calculations of defect density and rose diagrams of crest orientation single populations characterize simple dune fields white sands whereas multiple populations characterize compound complex dunes algodones namib and complex dune fields agneitir as time increases dune fields show an increase in dune spacing and crest length a decrease in defect density more tightly clustered crest orientation and a reduction in the variance associated with measurements of these parameters the results are consistent with models of dune fields as self organizing complex systems in which a characteristic pattern emerges as a function of constructional time because pattern evolution is a function of time it may be possible to use pattern analysis to augment current methods of age determination statistically defined populations can be used in geomorphic backstripping to unstack generations of simple patterns that give rise to complex patterns and to reconstruct each generation in terms of construction time and palaeo wind regime copyright 2006 john wiley sons ltd

calcareous nannofossils planktonic foraminifera and oxygen isotopes in the late quaternary sapropels of the ionian sea core m 25 4 12 a long piston core 12 20 m recovered in the ionian sea during cruise m25 4 of the r v meteor summer 1993 at a water depth of 2467 m shows an almost complete sequence of sapropels s 1 s 3 to s 10 over the last 330 ka this paper presents the results of an integrated study based on quantitative biostratigraphic analyses performed on both calcareous nannofossils and planktonic foraminifera coupled with the 18o record a decrease in syracosphaera sp 1 and an increase in the abundance of the genus rhabdosphaera and of helicosphaera carteri florisphaera profunda and of the reworked specimens has been found in the calcareous nannofossil assemblage within the sapropels the planktonic foraminiferal assemblage of the sapropels is characterized by a peak in the frequency of globigerinoides ruber var alba and rosea and neogloboquadrina dutertrei the 18o record of globigerinoides ruber and globigerina bulloides allows recognition of isotope stages 1 to 9 and shows a negative fluctuation that corresponds to the sapropel layers these features support the idea of increased productivity coupled to the presence of reduced salinity surface waters that caused the deposition of the sapropels however the need for a good understanding of the ecological requirements of modern assemblages is stressed this is necessary to correctly interpret fossil assemblages this in turn will allow a better understanding of the palaeoceanographic conditions leading to sapropel deposition

induced seismicity monitoring of an underground salt cavern prone to collapse within the framework of a large research project launched to assess the feasibility of microseismic monitoring of growing underground caverns this specific work focuses on the analysis of the induced seismicity recorded in a salt mine environment a local seismic network has been installed over an underground salt cavern located in the lorraine basin northeast of france the microseismic network includes four 3 components and three single component geophones deployed at depths between 30 and 125 m in cemented boreholes drilled in the vicinity of the study area the underground cavern under monitoring is located within a salt layer at 180 m depth and it presents a rather irregular shape that can be approximated by a cylindrical volume of 50 m height and 180 m diameter presently the cavern is full of saturated brine inducing a significant pressure on its walls 2 0 mpa to keep the overburden mechanically stable nevertheless some small microseismic events were recorded by the network and analyzed approximately 2 000 events in 2 years of recording in october 2005 and april 2007 two controlled pressure transient experiments were carried out in the cavern in order to analyze the mechanical response of the overburden by tracking the induced microseismicity the recorded events were mainly grouped in clusters of 3 30 s of signal duration with emergent first arrivals and rather low frequency content between 20 and 120 hz some of these events have been spatially located by travel time picking close to the actual cavern and its immediate roof preliminary spectral analysis of isolated microearthquakes suggests sources with non negligible tensile components possibly related to fluid filled cracks rock debris falling into the cavern from delamination of clay marls in the immediate roof is probably another source of seismic excitation this was later confirmed when the most important seismic swarms occurred at the site during may 2007 accompanied by the detachment of more than 8 104 m3 of marly material on top of the cavern roof in any case no clear evidence of classical brittle ruptures in the most competent layers of the overburden has been observed during the analyzed period current work is focused on the discrimination of all these possible mechanisms to better understand the damage processes in the cavern overburden and to assess its final collapse hazard

the last 100 000 years in the western mediterranean sea surface water and frontal dynamics as revealed by coccolithophores a quantitative analysis was carried out on coccolith assemblages from two pleistocene cores k1 and k10 from the western mediterranean the distribution of selected coccolithophore species provides new paleoclimatic and paleoceano graphic data a continuous sequence from the top of isotope stage 5 to the holocene was recorded the reversal in dominance between gephyrocapsa muellerae and emiliania huxleyi was dated in both cores at ca 73 ka at about 47 ka e huxleyi shows a regular increase whereas g muellerae progressively decreases in abundance during interglacial periods high concentrations of coccoliths are observed whereas in glacial times coccoliths are more diluted and the percentage of reworked forms increases as a consequence of the higher terrigenous input after taking careful account of the dilution factor we conclude that the production of coccolithophores was higher during warm periods maxima in coccolith concentrations coincide with highstand episodes probably as a result of the intensification of the atlantic flux into the mediterranean across the gibraltar strait this intensification could have produced an increase in nutrient content in the surface mediterranean waters during cold periods the western mediterranean front underwent a reduction in activity probably due to an increase in the saline and or thermal gradients between the superficial waters and intermediate waters in the liguro provencal basin

climate changes in the early to middle miocene of the central paratethys and the origin of its echinoderm fauna abstract this study uses echinoderm diversity to assess climatic changes in the early to middle miocene of the central paratethys it is based mainly on a taxonomically standardised dataset of central paratethys echinoids supplemented by data on asteroid ophiuroid crinoid and holothuroid distributions potential constraints of the raw diversity data are explored and possible biases are identified these include a heterogeneous rock record in terms of outcrop area and facies of the preserved sedimentary rocks stage duration and sampling bias the latter was overcome by utilising rarefaction analysis to investigate species richness these analyses show that the patterns observed in the raw data are robust and not severely biased by sampling intensity the potential influence of a heterogeneous rock record was assessed by comparing surface outcrop areas of the various stages to standing diversity a second bias involving a heterogeneous rock record the non preservation of distinct habitats was overcome by carrying out within habitat comparison of standing diversity and faunal composition the observed patterns were therefore established as true signals rather than artefacts produced by various biases consequently echinoderm diversity is used to evaluate climate changes during the neogene of the central paratethys as well as to interpret minimum winter and summer sea surface temperatures in the badenian middle miocene climatic conditions during the deposition of the badenian leitha limestone were addressed along with the presence of n s gradients within the central paratethys the presently available data suggest warm temperate conditions for the late eggenburgian early burdigalian followed by a brief temperature drop in the ottnangian early late burdigalian temperatures increased again in the karpatian and a climatic optimum was reached in the early badenian a slight cooling during the middle badenian was reflected by the southwards shift of predominantly temperate genera from the northern fringes of the central paratethys in the early badenian to the central parts in the late badenian the faunal gradients observed in the early badenian of the central paratethys suggest that the boundary between the warm temperate and tropical zone lay somewhere within the paratethys at that time considering the more southerly position of the study area about 34 palaeolatitude in the early middle miocene this implies that the tropical climate zone was much wider during the early middle miocene than today biogeographic investigations of the central paratethyan echinoid faunas show that the overwhelming part of the central paratethys echinoid species are immigrants from the mediterranean area immigration occurred in three distinct waves during the late eggenburgian the karpatian and early badenian while no common echinoid species were identified between the boreal region and the central paratethys two species of asteroids from the northern most fringes of the central paratethys also occur in the north sea basin endemism is low in most of the stages except for the ottnangian when geodynamic processes and global cooling resulted in a large scale re organisation of central paratethyan faunas

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

analysis of the microseismicity induced by a fluid injection in a granitic rock mass the microseismicity induced by a fluid injection at a depth of 443 m in a granitic rock mass has been monitored with a 16 station network the location of the five events observed on the near totality of the network suggests that flow away from the well occurred along a preexisting fracture nearly parallel to the maximum horizontal principal stress direction and not along the fractures observed at the wellbore focal mechanisms of these events are coherent with shear motions along fissures which intersect the main flow path a difficulty has been encountered in the determination of source parameters from spectral analysis of signals because of attenuation effects indeed for uncorrected spectra the corner frequency was found to decrease as the source to station distance increased this demonstrates the effect of attenuation on the signals and therefore the necessity of correcting spectra for attenuation effects before estimating source parameters

transfer of nonsorbing solutes to a streambed with bed forms theory a theoretical analysis of the exchange of nonsorbing solutes between a permeable streambed and the overlying water of a stream or river is presented in this paper in a companion paper elliott and brooks this issue the results of experimental studies of such exchange are presented the analysis focuses on water movements into within and out of the bed which result from the presence of bed forms ripples and dunes and highlights the mechanisms of pumping and turnover pumping is the movement of fluid through the bed induced by steady dynamic pressure variations over bed forms turnover occurs as moving bed forms trap and release interstitial fluid the detailed analysis was used to generate the distribution of the residence time of solute within the bed which can be used to calculate the net mass exchange due to pumping and turnover

paleotemperatures and ice volume of the past 27 myr revisited with paired mg ca and 18o 16o measurements on benthic foraminifera 1 we explore the applicability of paired mg ca and 18o 16o measurements on benthic foraminifera from southern ocean site 747 to paleoceanographic reconstructions on pre pleistocene timescales we focus on the late oligocene through pleistocene 27 0 ma history of paleotemperatures and the evolution of the 18o values of seawater 18osw at a temporal resolution of 100 200 kyr absolute paleotemperature estimates depend on assumptions of how mg ca ratios of seawater have changed over the past 27 myr but relative changes that occur on geologically brief timescales are robust results indicate that at the oligocene to miocene boundary 23 8 ma temperatures lag the increase in global ice volume deduced from benthic foraminiferal 18o values but the smaller scale miocene glaciations are accompanied by ocean cooling of 1 c during the mid miocene phase of antarctic ice sheet growth 15 13 ma water temperatures cool by 3 c unlike the benthic foraminiferal 18o values which remain relatively constant thereafter temperatures vary by 3 c and reach maxima at 12 and 8 5 ma the onset of significant northern hemisphere glaciation during the late pliocene is synchronous with an 4 c cooling at site 747 a comparison of our 18osw curve to the haq et al 1987 sea level curve yields excellent agreement between sequence boundaries and times of increasing seawater 18o 16o ratios at 12 11 ma in particular when benthic foraminiferal 18o values do not support a further increase in ice volume the 18osw curve comes to a maximum that corresponds to a major mid miocene sea level regression the agreement between the character of our mg ca based 18osw curve and sequence stratigraphy demonstrates that benthic foramaniferal mg ca ratios can be used to trace the 18osw on pre pleistocene timescales despite a number of uncertainties related to poorly constrained temperature calibrations and paleoseawater mg ca ratios the mg ca record also highlights that deep ocean temperatures can vary independently and unexpectedly from ice volume changes which can lead to misinterpretations of the 18o record

convective transport within stable river sediments local pressure variations of the order of 100 1000 n m2 can be observed between the upstream and downstream faces of the typically triangular shaped dunelike sediment structures that form at the sediment water interface of rivers laboratory experiments were conducted examining the influence of this localized pressure variation on contaminant transport processes within the sediment numerical modeling of the in bed flow via boundary element methods was also undertaken in order to predict convective transport under typical field conditions the laboratory experiments and numerical simulation of the in bed flow in several rivers verified that the pressure distribution observed on the sediment surface and the resulting interstitial fluid convection can control transport of chemically inert nonsorbed contaminants in stable sediments in bed peclet numbers were of the order of 100 1000 indicating the negligible influence of diffusion under the conditions examined

biostratigraphical and palaeoenvironmental implications of isotopic studies 18o 13c of middle miocene badenian foraminifers in the central paratethys the cause of the middle miocene badenian salinity crisis in the central paratethys is addressed by examining the palaeotemperature evolution of badenian waters before and after the deposition of evaporites selected foraminifer taxa globigerinoides spp globigerina bulloides and uvigerina characterizing respectively the near surface intermediate and bottom layers of the water column were studied in two boreholes of sw poland the 18o and 13c values for these taxa show distinct differences which can be explained by the temperature difference between surface and bottom waters during deposition these values also show temporal changes corresponding to the water temperature evolution in the badenian basin different and quickly changing environmental conditions have been inferred from changes in foraminifer assemblages they explain why biostratigraphic subdivisions based on well recognized assemblages are the most accurate approach for determining the biostratigraphy of middle miocene deposits in the central paratethys the results of isotopic studies indicate that evaporites occur in a part of the badenian section that was characterized by the lowest temperatures in the studied sections

effects of stream discharge alluvial depth and bar amplitude on hyporheic flow in pool riffle channels 1 hyporheic flow results from the interaction between streamflow and channel morphology and is an important component of stream ecosystems because it enhances water and solute exchange between the river and its bed hyporheic flow in pool riffle channels is particularly complex because of three dimensional topography that spans a range of partially to fully submerged conditions inducing both static and dynamic head variations hence these channels exhibit transitional conditions of streambed pressure and hyporheic flow compared to previous studies of fully submerged two dimensional bed forms here we conduct a series of three dimensional simulations to investigate the effects of bed topography depth of alluvium and stream discharge on hyporheic flow in pool riffle reaches with variable bed form submergence and we propose three empirical formulae to predict the mean depth of hyporheic exchange and characteristic values of the residence time distribution mean and standard deviation hyporheic exchange is predicted with a three dimensional pumping model and hyporheic flow is modeled as a darcy flow we find that the hyporheic residence time is well approximated by a lognormal distribution for both partially and entirely submerged pool riffle topography with the parameters of the distribution defined by the mean and variance of the log transformed residence time depth of alluvium has a substantial effect on hyporheic flow when alluvial depth is less than a third of the bed form wavelength for the conditions examined

badenian middle miocene basin development in sw hungary subsidence history based on quantitative paleobathymetry of foraminifera a quantitative paleobathymetric study of badenian foraminifera was carried out from tekeres 1 and tengelic 2 boreholes north of the mecsek mts sw hungary paleobathymetric data based on plankton benthos ratio provided input for the analysis of the subsidence history the biostratigraphic framework is mainly provided by calcareous nannoplankton zones nn5 nn7 changes in sedimentation rates are also considered partly calculated from number of benthos per unit sediment and partly estimated from the changes of lithofacies relative sea level changes are calculated from changes of paleowater depth and coeval sedimentary thickness the result is examined as the sum of accommodation space created by subsidence and eustasy in that period of time eustatic changes were about an order of magnitude smaller than changes created by movements of the basin floor according to our model in early badenian up to the half of nn5 nannozone a very rapid transtension related subsidence of about 500 m occurred this was interrupted by a short period of uplift of minor magnitude at about the first third of nn5 zone thereafter subsidence continued and the basin floor reached its deepest position still within the nn5 nannozone early badenian a significant uplift occurred terminating the life of the deep basin the late badenian nn6 is characterized by a relatively small rate of subsidence and presumably quiet tectonism during this period bathymetric changes are thought to be controlled primarily by eustatic changes the first uplift only interrupting subsidence is regarded as the result of the change of the local stress field because of convergence along the curvature of strike slip faults the second uplift which stopped the subsidence of the basin floor is thought to be of a regional character and is attributed to the compression generated between tisza and alcapa tectonic units

shifts in oxygen and carbon isotope signals in marine molluscs from the central paratethys europe around the lower middle miocene transition abstract stable isotope data of mollusc shells from two adjacent time slices karpatian badenian from the central paratethys were investigated to detect differences in environmental parameters and to depict shifts in the isotope signature of the paratethyan seawater around the early middle miocene transition altogether seventeen different gastropod species and one bivalve species from the karpatian korneuburg basin and the badenian northern alpine foreland basin were selected representatives of various ecological guilds yielded different isotope patterns especially in 13c reflecting different original habitats or nutrition although molluscs precipitate their shells in oxygen isotopic equilibrium we preferred to compare isotope data of shells of the same genus of the family turritellidae from the karpatian and badenian the badenian turritella shells from the northern alpine foreland basin yielded distinctly higher 18o and 13c values than the respective karpatian shells from the korneuburg basin as the main factors controlling 18o values in gastropod shells are temperature and 18o of the water during precipitation the differences between the oxygen isotope data of the two time slices can only be explained by these factors good independent palaeotemperature proxies exist for the early to middle miocene of central europe they do not indicate a significant temperature variation therefore different 18o values of the seawater in the different basins of the central paratethys must be responsible for the contrasting 18o values when calculated with commonly assumed 18o seawater values for the miocene badenian turritella shells indicate too cold temperatures these data clearly document the danger of palaeotemperature interpretations based solely on stable isotopes as smaller and marginal marine settings such as the paratethys sea can be seriously influenced by regional differences in the isotope composition of the seawater only a thorough consistent control by other climate proxies e g palaeoecology of molluscs as in this study allows a sensible interpretation

geodynamic impact on the stable isotope signatures in a shallow epicontinental sea analyses were made of a mollusc based meta dataset of 859 d 13 c and d 18 o data of miocene nearshore settings in the european paratethys sea and its descendant lake pannon the observed trends document a strong tie to geodynamics which are largely decoupled from miocene open ocean isotope curves semi to fully enclosed initially marine water bodies such as the paratethys sea are prone to switching seawater isotope signatures because they respond rapidly to changes in the evaporation precipitation ratio two phases of positive deviations of oxygen isotope values of water relative to the modern ocean value smow occurred during the middle miocene both were initiated by tectonic constrictions of the seaways and became amplified by global warming and regionally decreasing precipitation with the final disintegration of the paratethys the marine isotope signatures vanish instead the observed isotope trends suggest a comparably simple system of an alkaline lake with steadily declining salinity the oceanderived paratethys sea may thus act as a key for understanding isotope trends in epicontinental seas

the fluid dynamics of river dunes a review and some future research directions 1 dunes are present in nearly all fluvial channels and are vital in predicting flow resistance sediment transport and deposition within many rivers progress in understanding the fluid dynamics associated with alluvial dunes has been significant in the last 15 years and has witnessed huge advances in field laboratory and numerical investigations progress has been made in detailing the principal features of mean and turbulent flow over asymmetric dunes that possess flow separation in their leesides and how these forms affect both downstream boundary layer structure and stress partitioning over the dune additionally the links between sediment transport over dunes and instantaneous coherent flow structures are being increasingly understood with the feedback of dune three dimensionality upon flow and sediment dynamics over these bed forms beginning to be recognized as vital such research now provides an outstanding background for beginning to address areas of greater complexity that will enable a fuller understanding of these important natural features this review paper summarizes the principal features of mean and turbulent flow over alluvial sand dunes five areas are then highlighted and discussed as a possible focus for future research 1 the influence of dune leeside angle upon flow processes in the dune wake and downstream flow field 2 the influence of three dimensionality in dune shape upon the generation of turbulence and distribution of bed shear stress 3 flow field modification resulting from bed form superimposition and amalgamation 4 the scale and topology of dune related turbulence and its interactions with sediment transport and the flow surface and 5 the influence of suspended sediment on the dune flow field and dune morphology

bryozoan event from middle miocene early badenian lower neritic sediments from the locality kralice nad oslavou central paratethys moravian part of the carpathian foredeep fossil bryozoa occurs usually in shallow water environments one of the rare deep water associations of bryozoa has been studied in a profile at kralice nad oslavou according to studies of foraminifera the paleodepth was more than 150 m and less than 500 m the bryozoan assemblages are poor consisting of four species only dominated by tervia irregularis cyclostomatida and reteporella kralicensis sp n cheilostomatida a new species being described in detail

the relationship between microseismicity and high pore pressures during hydraulic stimulation experiments in low permeability granitic rocks several hundred microearthquakes with local magnitudes ranging between 4 and 2 were recorded during hydraulic stimulation experiments at the hot dry rock demonstration site fenton hill new mexico these events are probably caused by shear failure induced by high pore fluid pressures since the event locations seem to cluster in a narrow band near the hydraulic fracture we were able to use micro seismic techniques to locate the hydraulic fracture and monitor its growth we calculate the minimum pore pressure increase necessary to induce rock failure using a simple model of slippage on preexisting fractures by comparing a pore pressure distribution calculated using a one dimensional diffusion model with the distribution of event foci we demonstrate that high pore pressures are a probable cause for these microearthquakes stress drops for these microearthquakes calculated from spectral parameters increased by a factor of 3 during the course of the experiment the stress drop increase correlates with a migration of seismic activity away from the injection well bore which suggests relatively low in situ shear stresses near the well bore caused by strain release in this region during previous pressurizations

a unifying model for planform straightness of ripples and dunes in air and water abstract geologists physicists and mathematicians have studied ripples and dunes for more than a century but despite considerable effort no general model has been proposed to explain perhaps the most fundamental property of their morphology why are some bedforms straight continuous parallel and uniform in planform geometry i e two dimensional whereas others are irregular three dimensional here we argue that physical coupling along the crest of a bedform is required to produce straight crests and that along crest flow and sand transport provide effective physical mechanisms for that coupling ripples and dunes with the straightest and most continuous crests include longitudinal and oblique dunes in unidirectional flows wave ripples dunes in reversing flows wind ripples and ripples migrating along a slope at first glance these bedforms appear quite different ripples and dunes air and water transverse oblique and longitudinal orientations relative to the net sand transport direction but they all have one property in common a process that increases the amount of along crest sand transport that lengthens and straightens their crests relative to the across crest transport that makes them migrate and take the more typical and more three dimensional planform geometry in unidirectional flows that produce straight bedforms along crest transport of sand is caused by along crest flow non transverse bedform orientation gravitational transport along an inclined crest or ballistic splash in air bedforms in reversing flows tend to be straighter than their unidirectional counterparts because reverse transport across the bedform crest reduces the net across crest transport that causes the more typical irregular geometry relative to the along crest transport that smoothes and straightens planform geometry

paleoceanography and climate of the badenian middle miocene 16 4 13 0 ma in the central paratethys based on foraminifera and stable isotope δ 18 o and δ 13 c evidence benthic foraminifera and stable isotopes analyses revealed changes emerging in the paleoceanographic scenery in the paratethys the percentage of inbenthic oxyphylic taxa and diversity in the benthic foraminiferal assemblage showed increasing food supply organic matter decreasing oxygen level and growing stress on the sea floor oxygen isotopes measured in planktonic and benthic foraminifera pointed to strengthening stratification during the badenian period the carbon isotopes indicated intensified accumulation of light marine organic matter this increasing stratification trend is especially pronounced by late badenian 13 5 13 ma when surface water oxygen isotope values are rather negative a simple two layer circulation model was worked out for the badenian paratethys explaining these characteristic environmental changes an antiestuarine lagoonal circulation is assumed for the central paratethys during the early 16 4 15 ma and mid badenian 15 13 5 ma the mid badenian period of time comprises the short episode of evaporite formation in the carpathian foredeep and the transylvanian basin evidence presented here supported a reversal of circulation to estuarine type after the deposition of salts by late badenian 13 5 13 ma the early badenian antiestuarine circulation is suggested to associate with the high temperatures of the mid miocene climatic optimum and the late badenian estuarine circulation with the cooler period following it

estimation of environmental paleogradient values based on presence absence data a case study using benthic foraminifera for paleodepth estimation abstract a two step procedure for estimating paleogradient values based on the presence absence of variates e g species chemical elements and traits is presented the first step requires information about the general basic distributions of variates along the gradient using species as variates fundamental ecological niches corresponding to the gradient represent these general distributions the second step involves a transfer equation which is the arithmetic mean of location parameters of variates weighted by their dispersion parameters this procedure strengthens variates with narrow dispersions yielding more information about the location at the gradient than variates with wide dispersion the method proposed here does not require information about frequencies solely the presence of variates is sufficient objective criteria are used to eliminate non overlapping variates along the gradient e g species whose distributions do not overlap in living individuals but are mixed in samples of empty tests this is important in estimating paleogradients because mixing of non overlapping variates is a common effect due to post mortem transport bioturbation or sediment reworking the new method is calibrated for depth estimation using living symbiont bearing benthic foraminifera and empty tests from the nw pacific and living smaller benthic foraminifera from the shelf and continental slope of senegal this approach is then successfully applied for paleodepth estimation of a lower to middle miocene transect in the styrian basin austria where plankton benthos ratios of foraminifera yield poor depth estimations

a hydrogeomorphic river network model predicts where and why hyporheic exchange is important in large basins hyporheic exchange has been hypothesized to have basin scale consequences however predictions throughout river networks are limited by available geomorphic and hydrogeologic data and by models that can analyze and aggregate hyporheic exchange flows across large spatial scales we developed a parsimonious but physically based model of hyporheic flow for application in large river basins networks with exchange and subsurface storage nexss we applied nexss across a broad range of geomorphic diversity in river reaches and synthetic river networks nexss demonstrates that vertical exchange beneath submerged bed forms rather than lateral exchange through meanders dominates hyporheic fluxes and turnover rates along river corridors per kilometer low order streams have a biogeochemical potential at least 2 orders of magnitude larger than higher order streams however when biogeochemical potential is examined per average length of each stream order low and high order streams were often found to be comparable as a result the hyporheic zone s intrinsic potential for biogeochemical transformations is comparable across different stream orders but the greater river miles and larger total streambed area of lower order streams result in the highest cumulative impact from low order streams lateral exchange through meander banks may be important in some cases but generally only in large rivers

injection induced microseismicity in colorado shales imperial oil resources limited uses cyclic steam stimulation to recover oil from their cold lake oil field in alberta this operation in particular situations can be associated with the failure of well casings in the colorado shales above the oil bearing formation a number of fluid injection operations was undertaken at this site and the associated microseismicity was detected using two three component geophones and fifteen hydrophones the purpose of this experiment was to simulate the occurrence of a casing failure determine the feasibility of monitoring in a shallow environment and characterize the microseismic activity a calibration survey provided values of 1786 108 m s for p wave velocity 643 56 mks for s wave velocity and 0 428 0 017 for poisson s ratio in the shale formation estimates of the quality factor q p were 15 for the horizontal direction and 38 for the vertical direction corroborating the evidence of velocity anisotropy calibration shots were located to within 10 m of the actual shot points using triangulation and polarization techniques several hundred microseismic events were recorded and 135 events were located the results showed that microseismic activity was confined to depths within 10 meters of the injection depth the experiment clearly established the feasibility of detecting microseismicity induced by fluid injection rates typical of casing failures in shales at distances over 100 m

effects of current bed form induced fluid flow on the thermal regime of sediments 1 heat transport associated with current bed form fluid exchange affects biogeochemical and ecological process in a variety of aquatic settings we simulate turbulent flow over dunes induced darcy flow in sediments and sediment heat transport forced by a diel variation of water column temperature heat conduction dominates when the water column current cannot induce rapid fluid exchange heat advection becomes important with increasing sediment permeability and or current velocity resulting in a complicated space time temperature pattern weak temperature variations are found beneath dune crests where water upwells out of the sediments strong variations are located below dune stoss faces where water downwells the relative dominance of heat conduction versus advection is captured by a global peclet number that depends on dune geometry and hydrodynamic and thermal properties including the period of thermal forcing thermally induced fluid viscosity variations cause periodic but nonsymmetric changes in fluid flux through the sediments but do not significantly influence temperature patterns

cyclostratigraphic dating in the lower badenian middle miocene of the vienna basin austria the baden sooss core the scientific borehole baden sooss penetrates a succession of badenian langhian middle miocene sediments at the type locality of the badenian the old brickyard baden sooss in the vienna basin the sedimentary succession of the 102 m cored interval consists of more than 95 bioturbated medium to dark gray marly shales with carbonate contents between 11 and 25 and organic carbon contents between 0 35 and 0 65 biostratigraphic investigations on foraminifera mainly lower part of upper lagenid zone and calcareous nannoplankton standard zone nn5 indicate an early badenian langhian age cycles in carbonate content organic carbon content and magnetic susceptibility have been identified by power spectra analysis correlations between the three variables are extremely significant using cross correlation periods around 40 m correlate significantly with the 100 kyr 1 eccentricity cycle the 20 m periods with the obliquity cycle and the 15 to 11 m periods with both precession cycles wavelet transformation and decomposition of composite periodic functions were used to obtain the position of the cycle peaks in the profile cross correlation with orbital cycles la2004 dates the baden sooss core between 14 379 1 and 14 142 my 9 kyr

q and the rise and fall of a seismic pulse summary gladwin stacey and others have shown that if q the specific quality factor is independent of frequency or nearly so then the rise time of a seismic pulse is proportional to the anelastic attenuation it has experienced during propagation in this paper the use of rise times to estimate the attenuation of seismic body wavesis examined numerically and the method is extended to include the fall time of a pulse although the proportionality of both rise and fall time with attenuation is shown here to be valid only for an impulse source function it is possible to estimate the maximum attenuation experienced by a seismic pulse from the source to the receiver with no a priori assumptions about the shape of the radiated pulse the method developed for a constant q model can still be applied if q has an acceptable power law dependency on frequency application to teleseismic body waves from earthquakes and an underground nuclear explosion indicates that transmission paths exist over which the attenuation is much lower than is often assumed in seismogram modelling

hyporheic zone hydrologic science a historical account of its emergence and a prospectus the hyporheic zone defined by shallow subsurface pathways through river beds and banks beginning and ending at the river is an integral and unique component of fluvial systems it hosts myriad hydrologically controlled processes that are potentially coupled in complex ways understanding these processes and the connections between them is critical since these processes are not only important locally but integrate to impact increasingly larger scale biogeochemical functioning of the river corridor up to the river network scale thus the hyporheic zone continues to be a growing research focus for many hydrologists for more than half the history of water resources research this manuscript partly summarizes the historical development of hyporheic zone hydrologic science as gleaned from papers published in water resources research from the birth of the concept of the hyporheic zone as a hydrologic black box sometimes referred to as transient storage zone to its adolescent years of being torn between occasionally competing research perspectives of interrogating the hyporheic zone from a surface or subsurface view to its mature emergence as an interdisciplinary research field that employs the wide array of state of the art tools available to the modern hydrologist the field is vibrant and moving in the right direction of addressing critical fundamental and applied questions with no clear end in sight in its growth there are exciting opportunities for scientists that are able to tightly link the allied fields of geology geomorphology hydrology geochemistry and ecology to tackle the many open problems in hyporheic zone science

coral microbialite environment in a middle miocene reef of hungary abstract the presence of microbial crusts microbialites is reported here for the first time from a middle miocene badenian coral reef in hungary the succession of initiation and development of the microbial crusts is described in relation to the reef architecture the main features of the palaeoenvironment are discussed with focus on the associated invertebrate faunas mostly corals molluscs bryozoans and crabs we conclude that the microbial crusts developed under normal marine conditions and were a significant contributor to reef framework development including its strengthening through calcification of the microbial organisms microbialites are anticipated in other early and middle miocene coral reef occurrences of the mediterranean paratethys realm and to date may have simply escaped positive recognition

bedform alignment in directionally varying flows many kinds of sediment bedforms are presumed to trend either normal or parallel to the direction of sediment transport for this reason the trend of bedforms observed by remote sensing or by field observations is commonly used as an indicator of the direction of sediment transport such presumptions regarding bedform trend were tested experimentally in bidirectional flows by rotating a sand covered board in steady winds transverse oblique and longitudinal bedforms were created by changing only two parameters the angle between the two winds and the proportions of sand transported in the two directions regardless of whether the experimental bedforms were transverse oblique or longitudinal as defined by the bedform trend relative to the resultant transport direction they all had trends that yielded the maximum gross transport across the bedforms the fact that many of the experimental bedforms were neither transverse nor parallel to the resultant transport direction suggests that transport directions cannot be accurately determined by presuming such alignment

a multiscale model for integrating hyporheic exchange from ripples to meanders 1 it is necessary to improve our understanding of the exchange of dissolved constituents between surface and subsurface waters in river systems in order to better evaluate the fate of water borne contaminants and nutrients and their effects on water quality and aquatic ecosystems here we present a model that can predict hyporheic exchange at the bed form to reach scale using readily measurable system characteristics the objective of this effort was to compare subsurface flow induced at scales ranging from very small scale bed forms up to much larger planform geomorphic features such as meanders in order to compare exchange consistently over this range of scales we employed a spectral scaling approach as the basis for a generalized analysis of topography induced stream subsurface exchange the spectral model involves a first order approximation for local flow boundary interactions but is fully three dimensional and includes the lateral hyporheic zone in addition to the flow directly beneath the streambed the primary model input parameters are stream velocity and slope sediment permeability and porosity and detailed measurements of the stream channel topography the primary outputs are the distribution of water flux across the stream channel boundary the resulting pore water flow paths and the subsurface residence time distribution we tested the bed form exchange component of the model using a highly detailed two dimensional data set for exchange with ripples and dunes and then applied the model to a three dimensional meandering stream in a laboratory flume having spatially explicit information allowed us to evaluate the contributions of both gravitational and current driven hyporheic flow through various classes of stream channel features including ripples dunes bars and meanders the model simulations indicate that all scales of topography between ripples and meanders have a significant effect on pore water flow fields and residence time distributions furthermore complex interactions across the spectrum of topographic features play an important role in controlling the net interfacial flux and spatial distribution of hyporheic exchange for example shallow exchange induced by current driven interactions with small bed forms dominates the interfacial flux but local pore water flows are modified significantly by larger scale surface groundwater interactions as a result simplified representations of the stream topography do not adequately characterize patterns and rates of hyporheic exchange

width height and slope relationships and aerodynamic maintenance of barchans the allometric relationship between the height of barchan dunes and horn to horn widths is re examined the addition of new data from barchans in the namib desert and elsewhere confirms the relationship that the height of a barchan is approximately one tenth of the width of the dune height and width of the dune are closely linked to the three dimensional morphology of the dune in particular the relatively constant mean angles of around 11 at which the side slopes of the dune are maintained we suggest that the 3 d barchan form is directly controlled by aerodynamic processes constant feedback between three dimensional stoss face windward shape of the dune slipface height and horn to horn width and shear stress produces an equilibrium dune form

palaeoenvironmental reconstructions by stable isotopes of middle miocene gastropods of the central paratethys abstract the stable isotopes of carbon and oxygen were used to provide information of mixing of marine and freshwater and subsequently used to determine palaeosalinities in the middle to late miocene st margarethen zollhaus section upper sarmatian mactra zone pannonian a succession of three gastropod assemblages indicates changing environmental conditions from a limnic fluviatile to littoral mudflat and a sublittoral marine environment several shells of the main representatives of the three assemblages potamides hartbergensis hilber granulolabium bicinctum brocchi potamides disjunctus sowerby and additionally shells of lymnaea sp a typical freshwater gastropod and pomatias conicus a terrestrial gastropod were taken for stable isotope analyses oxygen and carbon isotope data of the freshwater endmember are distinctively lower 18 o 4 5 13 c 9 than of the marine endmembers 18 o 2 2 13 c 2 3 in contrast to the expected intermediate isotopic composition between the freshwater and marine environment the shells of supposed brackish environments have higher 18 o values than the shells of the marine environment these higher 18 o values are explained by evaporation which affected the protected areas of riverine to lacustrine environments and small pools on mudflats formerly considered to be the habitats of the brackish assemblages thus the oxygen and carbon isotope data extend the already existing palaeoenvironmental information

three dimensional versus two dimensional bed form induced hyporheic exchange the hyporheic zone is often a critical component of river systems hyporheic exchange is generally forced by variation in riverbed topography such as due to bed forms most previous research on bed form driven hyporheic flow has focused on two dimensional 2 d dunes and ripples while little has been done on their three dimensional 3 d counterparts here we compared hyporheic exchange and associated metrics for a previously studied pair of corresponding 2 d and 3 d bed forms to accomplish this a series of multiphysics computational fluid dynamics models were conducted both in 2 d and 3 d with similar open channel reynolds numbers re results show that the pressure gradient along the sediment water interface is highly sensitive to the spatial structure of bed forms which consequently determines hyporheic flow dynamics hyporheic flux is a function of re for both 2 d and 3 d dunes via a power law however the equivalent 3 d dunes have a higher flux since the 3 d form induces more drag the hyporheic zone depths and volumes are only slightly different with the 3 d case having a larger volume the mean fluid residence times for both cases are related to re by an inverse power law relationship with the 3 d dune having smaller residence times at moderate to high re the effects of increasing flux on residence time in 3 d dunes are partly modulated by a slightly increasing hyporheic volume our results suggest that a 2 d idealization is a reasonable approximation for the more complex 3 d situation if local details are unimportant but that development of predictive models for mean fluxes and residence times which are critical for biogeochemical processes based on 2 d models may be insufficient

interactions between hyporheic flow produced by stream meanders bars and dunes 1 stream channel morphology from grain scale roughness to large meanders drives hyporheic exchange flow in practice it is difficult to model hyporheic flow over the wide spectrum of topographic features typically found in rivers as a result many studies only characterize isolated exchange processes at a single spatial scale in this work we simulated hyporheic flows induced by a range of geomorphic features including meanders bars and dunes in sand bed streams twenty cases were examined with 5 degrees of river meandering each meandering river model was run initially without any small topographic features models were run again after superimposing only bars and then only dunes and then run a final time after including all scales of topographic features this allowed us to investigate the relative importance and interactions between flows induced by different scales of topography we found that dunes typically contributed more to hyporheic exchange than bars and meanders furthermore our simulations show that the volume of water exchanged and the distributions of hyporheic residence times resulting from various scales of topographic features are close to but not linearly additive these findings can potentially be used to develop scaling laws for hyporheic flow that can be widely applied in streams and rivers

bed forms created by simulated waves and currents in a large flume 1 the morphology and evolution of bed forms created by combinations of waves and currents were investigated using an oscillating plate in a 4 m wide flume current speed ranged from 0 to 30 cm s maximum oscillatory velocity ranged from 20 to 48 cm s oscillation period was 8 s except for one run with 12 s period and the median grain size was 0 27 mm the angle between oscillations and current was 90 60 or 45 at the end of each run the sand bed was photographed and ripple dimensions were measured ripple wavelength was also determined from sonar images collected throughout the runs increasing the ratio of current to wave i e oscillatory velocity decreased ripple height and wavelength in part because of the increased fluid excursion during the wave period increasing the ratio of current to waves or decreasing the angle between current and waves increased the three dimensionality of bed forms during the runs ripple wavelength increased by a factor of about 2 the average number of wave periods for evolution of ripple wavelength to 90 of its final value was 184 for two dimensional ripples starting from a flat bed bed form orientations at the end of each run were compared to four potential controlling factors the directions of waves current maximum instantaneous bed shear stress and maximum gross bed form normal transport mgbnt the directions of waves and of mgbnt were equally good predictors of bed form orientations and were significantly better than the other two factors

observation of the whole process of interaction between barchans by flume experiments 1 through laboratory experiments generating unidirectional water flows we examine the process of interaction between two moving barchans sandy bed configurations in a crescentic plan shape which may take dozens of years for barchan dunes in the nature three types of the interaction were observed the first type was absorption of two barchans into one the second was that the upstream fast barchan rode on the downstream slow barchan and simultaneously a newly born barchan was ejected from the lee side of the slow barchan the third was that the downstream slow barchan was split into two before the upstream fast barchan touched the downstream the type of the interaction was determined by both relative and absolute size of two barchans

on the transition between 2d and 3d dunes sediment transport in sand bedded alluvial channels is strongly conditioned by bedforms the planimetric morphology of which can be either two or threedimensional experiments were undertaken to examine the processes that transform the bed configuration from two dimensional 2d dunes to threedimensional 3d dunes a narrowly graded 500 lm size sand was subjected to a 0ae15 m deep non varying mean flow ranging from 0ae30 to 0ae55 m sec 1 in a 1 m wide flume changes in the planimetric configuration of the bed were monitored using a high resolution video camera that produced a series of 10 sec time lapsed digital images image analysis was used to define a critical value of the non dimensional span sinuosity of the bedform crestlines that divides 2d forms from 3d forms significant variation in the non dimensional span is observed that cannot be linked to properties of the flow or bedforms and thus appears random images also reveal that once 2d bedforms are established minor transient excesses or deficiencies of sand are passed from one bedform to another the bedform field appears capable of absorbing a small number of such defects but as the number grows with time the resulting morphological perturbations produce a transition in bed state to 3d forms that continue to evolve but are pattern stable the 3d pattern is maintained by the constant rearrangement of crestlines through lobe extension and starving downstream bedforms of sediment which leads to bifurcation the experiments demonstrate that 2d bedforms are not stable in this calibre sand and call into question the reliability of bedform phase diagrams that use crestline shape as a discriminator

turbulent flow over three dimensional dunes 2 fluid and bed stresses 1 dunes formed in response to fluid flow exert a total boundary stress on the fluid that is made up of form drag and skin friction the latter of which is generally considered important for predicting sediment transport and dune evolution previous research has used various methods to estimate the total stress and its subcomponents with recent work suggesting the application of a spatial average to the equations of motion a complete three dimensional 3 d form of this analysis is derived and applied to recent measurements of turbulent open channel flow over 3 d dunes spatial averages of reynolds shear stresses over 3 d dunes cannot be used to predict total boundary shear stress however estimations of total boundary shear stress from the spatially averaged equations of motion agree with not only the sum of form drag and skin friction but also the direct measurements of average free surface slope form induced stresses from secondary circulations augment the relatively low reynolds shear stresses over the 3 d dunes these low turbulence levels have ramifications for sediment transport predictions in that use of the total boundary shear stress in prediction of sediment transport over 3 d dunes must account for these low turbulence levels so as not to overpredict transport rates

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

coupled 3 d stream flow and hyporheic flow model under varying stream and ambient groundwater flow conditions in a pool riffle system 1 exchange of water and solutes across the stream sediment interface is an important control for biogeochemical transformations in the hyporheic zone hz in this paper we investigate the interplay between turbulent stream flow and hz flow in pool riffle streams under various ambient groundwater flow conditions streambed pressures derived from a computational fluid dynamics cfd model are assigned at the top of the groundwater model and fluxes at the bottom of the groundwater model domain represent losing and gaining conditions simulations for different reynolds numbers re and pool riffle morphologies are performed results show increasing hyporheic exchange flows m3 d for larger re and a concurrent decrease in residence time rt losing and gaining conditions were found to significantly affect the hyporheic flow field and diminish its spatial extent as well as rates of hyporheic exchange flow the fraction of stream water circulating through the hyporheic zone is in the range of 1 10 5 to 1 10 6 per meter stream length decreasing with increasing discharge complex distributions of pressure across the streambed cause significant lateral hyporheic flow components with a mean lateral travel distance of 20 of the longitudinal flow paths length we found that the relationship between pool riffle height and hyporheic exchange flow is characterized by a threshold in pool riffle amplitude beyond which hyporheic exchange flow becomes independent of riffle height hyporheic residence time distributions rtd are log normally distributed with medians ranging between 0 7 and 19 h

identification of p s wave successions for application in microseismicity interpretation ofp s wave successions is used in induced or passive microseismicity it makes the location of microseismic events possible when the triangulation technique cannot be used to improve the reliability of the method we propose a technique that identifies thep s wave successions among recorded wave successions a polarization software is used to verify the orthogonality between thep ands polarization axes the polarization parameters are computed all along the 3 component acoustic signal then the algorithm detects time windows within which the signal polarization axis is perpendicular to the polarization axis of the wave in the reference time window representative of thep wave the technique is demonstrated for a synthetic event and three application cases are presented the first one corresponds to a calibration shot within which the arrivals of perpendicularly polarized waves are correctly detected in spite of their moderate amplitude the second example presents a microseismic event recorded during gas withdrawal from an underground gas storage reservoir the last example is chosen as a counter example concerning a microseismic event recorded during a hydraulic fracturing job the detection algorithm reveals that in this case the wave succession does not correspond to ap s one this implies that such an event must not be located by the method based on the interpretation of ap s wave succession as no such a succession is confirmed

plankton in the norwegian greenland sea from living communities to sediment assemblages an actualistic approach a synoptic study is carried out to reconstruct the development of the plankton community in the late quaternary in the norwegian greenland sea it comprises quantitative analyses of coccolithophores dinoflagellate cysts diatoms and radiolarians an actualistic approach is applied to evaluate the different fossil records of these plankton groups the preliminary results of the current investigation are reported here

benthic foraminifera as proxies of organic matter flux and bottom water oxygenation a case history from the northern arabian sea abstract benthic foraminifera have been quantified in two sediment cores from a topographic high murray ridge in the northern arabian sea one core is from a station within the present day oxygen minimum zone omz the other from a station below the omz changes in the intensity of the omz linked to monsoonal climate variability had a strong impact on benthic foraminiferal composition and accumulation rates at the shallower omz station 920 m an intensification of the omz resulted in lower diversities and high dominances of low oxygen tolerant species the deeper station 1470 m was far less affected though at least once during the last 225 000 years the benthic faunal composition and accumulation rates show evidence for a deepening of the base of the omz to a level close to or even below 1470 m we suggest that percentages of miliolids can be used for rapid reconstruction of periods of increased ventilation in the northern arabian sea and are a promising proxy for tracing changes in bottom and pore water oxygenation in general omz conditions are characterised by high abundances of deep infaunal species and increased burial efficiency of organic matter the proportion of deep infaunal species appears to be a measure for the anoxic burial efficiency of organic matter and not a direct measure for the arriving flux at the seabed results furthermore show that benthic foraminiferal accumulation rates cannot be used as a proxy for surface water productivity under the prevalence of severe dysoxia

field evidence for surface wave induced instability of sand dunes barchans are crescent shaped dunes that move faster over desert surfaces than most other dune types a three year field study shows how they do it collisions and changes in wind direction destabilize the dunes generating surface waves that form new smaller barchans this prevents the formation of a single giant dune so plays a fundamental role in the development of dune patterns field studies of barchans crescent shaped dunes that propagate over solid ground under conditions of unidirectional wind1 have long focused on the investigation of an equilibrium between sand transport by wind and the control of air flow by dune topography2 3 4 which are thought to control dune morphology and kinematics5 6 7 because of the long timescale involved however the underlying dynamic processes responsible for the evolution of dune fields remain poorly understood8 here we combine data from a three year field study in the moroccan sahara with a model study to show that barchans are fundamentally unstable and do not necessarily behave like stable solitary waves as suggested previously9 10 11 12 we find that dune collisions and changes in wind direction destabilize the dunes and generate surface waves on the barchans because the resulting surface waves propagate at a higher speed than the dunes themselves they can produce a series of new barchans of elementary size by breaking the horns of large dunes the creation of these new dunes provides a mechanism for sand loss that prevents dune fields from merging into a single giant dune and therefore plays a fundamental role in the control of size selection and the development of dune patterns

locating microearthquakes induced by hydraulic fracturing in crystalline rock microearthquakes induced by hydraulic fracturing in crystalline rock at a depth of 3 5 km were located with a precision of better than 30 m to obtain information about the geometry and dimensions of the fracture system produced the induced microseismicity was monitored by a network of five vorehole seismic stations a total of about 800 induced events were reliably located from arrival times event locations show a tabular distribution that strikes 350 sup 0 and dips 65 sup 0 east subparallel to the injection well the injection was intended to produce a fracture system that would hydraulically connect two subparallel wells a lack of fluid communication between them is consistent with a lack of induced microearthquakes near the target wellbore the 150 m thickness of the zone of seismicity far exceeds the relative locational uncertainties the injected fluid appears to have stimulated a zone of rock rather than simply a single fracture the distribution of microseismic events presumably envelopes the zone of fluid paths created by the fracture experiment