an intense cold core eddy in the north east atlantic we describe here a large intense mesoscale feature in the north atlantic 48 n 22 w observed in april 1985 from the thermal structure of this feature at a depth of 475 m fig 1a and from the pattern of larger scale flow dominated by a nearly rectilinear thermal front ne sw fig 1b we conclude that the feature is the eastern basin counterpart of the gulf stream cold core eddies often observed in the western basin1 2 to our knowledge this is the most intense coherent cold core eddy so far surveyed in this region and the only such eddy for which data bearing on the mechanism of formation are available

a coccolithophore based view on paleoenvironmental changes in the open ocean mid latitude north atlantic between 130 and 48 ka bp with special emphasis on mis 5e abstract as oceanographic changes in the north atlantic are known to modulate global climate they are key to the understanding of past and future climate changes especially the mid latitudes of the open ocean north atlantic may be of interest regarding the large area covered we therefore reconstructed past changes in productivity and hydrography from a new sediment core md08 3179cq taken in the open ocean mid latitude north atlantic in the vicinity of the azores current system concomitant to the reorganizations of environmental conditions in the north atlantic between 130 and 48 ka bp changes in coccolithophore assemblages and changes in the abundance of siliceous plankton diatoms indicate a southward shift of the azores front azf and hence a southward retreat of the north atlantic subtropical gyre as well as an increased productivity during glacial marine isotope stage mis 4 termination ii and during cold substages of mis 5 furthermore we hypothesize that the ecological changes led to distinct evolutionary patterns of coccolithophores resulting e g in a dominance of gephyrocapsa ornata between 76 and 105 ka bp additionally high resolution analysis of mis 5e indicate a short reversal towards cool conditions during mis 5e corresponding to a basin wide cooling event full interglacial conditions are reached only late in the azores region during mis 5e an increased advection of subantarctic mode water samw and or the possibility to occupy new habitats after glacial conditions result in a distinct coccolithophore productivity peak as global temperature during mis 5e are assumed to be similar to the expected future global climate change mis 5e serves as a possible scenario for future changes taking mis 5e as a possible analogue for expected future climate change our results indicate that an expected decrease in marine primary productivity due to the expansion of the oligotrophic gyres may be attenuated by increased coccolithophore productivity

impacts of storms on recent planktic foraminiferal test production and caco3 flux in the north atlantic at 47 n 20 w jgofs planktic foraminiferal assemblages are well known to vary in accordance with seasonal fluctuations in ocean properties periodic reproduction cycles and variations between water masses here we report that storms also can significantly influence foraminiferal assemblages during the rv meteor cruise 21 to the northeast atlantic ocean biotrans area from march to may 1992 planktic foraminifera were sampled using a multiple opening closing net while sampling two storms with wind forces up to 12 beaufort caused intensified surface layer mixing with shifts in the depth of the upper ocean mixed layer from 20 40 m to 170 240 m subsequently planktic foraminiferal growth rates increased resulting in an elevated quantity of small 100 150 m tests phase 1 when the wind strength increased a second time the mixed layer deepened to a depth below the former position of the pycnocline and again the abundance of small tests increased phase 2 during phase 2 the weight of calcite in specimens of the productive zone reached its maximum in the export zone an associated increase in empty tests occurred with a lag time depending on the test sinking velocity in the upper export zone down to 700 m water depth caco3 flux increased from 9 3 to 49 8 mg caco3 m 2 d 1 after the first storm and from 8 9 to 19 9 mg caco3 m 2d 1 after the second storm in the 700 to 2500 m depth interval the flux increased from 5 1 mg caco3 m 2 d 1 to about 9 2 mg caco m 2 d 1 thus the standing stock of living foraminifera and export of empty tests from the productive zone increased after the storms leading to pulses of caco3 exported from the surface to deep water

the influence of the hawaiian archipelago upon the wind driven subtropical gyre in the western north pacific in the middle of the subtropical gyre in the western north pacific is the subtropical counter current comprised of at least three narrow bands of eastward geostrophic mean flow near 20 n 24 n and 26 n each extending from the sea surface through the main pycrocline the origin of these narrow bands of eastward mean flow has not previously been explained in this study these bands are shown in the mean to extend zonally from the philippine sea i e 140 e to the vicinity of the hawaiian archipelago i e 160 w east of there they cannot be found therefore a hypothesis is presented wherein the hawaiian archipelago extending from 19 n to 26 n near 165 w is seen to act as an effective barrier modifying the response of the western subtropical north pacific to wind driven effects in the eastern subtropical north pacific and in so doing giving rise to these bands of eastward mean flow in the middle of the western subtropical gyre a test of this hypothesis utilizes a sverdrup 1947 model driven by the annual long term mean wind stress curl constructed on a 2 latitude longitude grid from synoptic 6 hourly surface wind observations for the 13 year period 1968 1980 two model simulations are conducted one in the absence of the hawaiian archipelago and one in the presence of it in the absence of the archipelago none of the bands of eastward mean flow are simulated in the presence of the archipelago the narrow bands of eastward mean flow at 20 n 26 n and 24 n are simulated although the latter band is very weak these narrow bands of eastward flow are shown to occur in response to the deflection northward of the wind driven geostrophic streamlines in the central subtropical north pacific by the hawaiian archipelago

full displacement pressuremeter testing in sand an alternative approach to pressuremeter testing in sand where the pressuremeter is pushed closed ended is discussed observations from cone penetration testing in sands are used to provide a theoretical background to the expected stress conditions around a full displacement pressuremeter probe pushed into sand the anticipated stress paths followed during the pressure expansion phase of the test are discussed data from both self boring and full displacement pressuremeter tests in sand are presented to support some of the suggested theoretical background key words pressuremeter testing in situ testing sand

planktic foraminifers and hydrography of the eastern and northern caribbean sea the distribution of living planktic foraminifers and their relation to the hydrography of the caribbean sea was investigated in plankton net tows and surface sediment samples taken along the antilles island arc during april may 1996 the planktic foraminiferal community was strongly influenced by spatial variations in salinity that were largely due to the influx of orinoco river water into the southeastern caribbean sea and inflowing sargasso sea water in the north along the antilles island arc globigerinoides ruber was the dominant species in the surface waters throughout in the southeastern caribbean sea where orinoco river outflow influences the planktic community standing stocks of planktic foraminifers 100 m between 4 and 50 specimens m 3 were medium to low the southeastern faunas between tobago and guadeloupe were characterized by increased proportions of neogloboquadrina dutertrei highest standing stocks of 159 specimens m 3 in the upper 20 m of the water column were recorded in the northeastern caribbean sea and the assemblages were characterized by high proportions of globigerinita glutinata associated with cyclonic eddies in the anegada passage where sargasso sea water flows into the caribbean sea low standing stocks of 18 specimens m 3 indicate oligotrophic conditions together with the oligotrophic surface waters the subtropical underwater enters the caribbean sea through the anegada passage in water depths between 100 and 300 m these waters are characterized by higher concentrations of globorotalia truncatulinoides relative to the adjacent water masses comparison of the living planktic foraminiferal fauna with empty test assemblages from the water column and from surface sediments shows that differences in the faunal composition mostly correspond to the distribution of water masses and to the differential dissolution of species in the vicinity of islands globigerinoides ruber reaches higher relative frequencies than in the open ocean pointing towards a higher tolerance of this species towards neritic conditions than in other species

integrated outcrop reservoir characterization modeling and simulation of the jackfork group at the baumgartner quarry area western arkansas implications to gulf of mexico deep water exploration and production the lower pennsylvanian jackfork group in arkansas has been the subject of studies field trips and publications for many years because of excellent outcrop exposures of different deep water architectural elements this latest study is focused on the baumgartner quarry located near kirby arkansas which exposes a series of vertical walls in three dimensions this quarry has not been as well documented as other popular exposures although three dimensional 3 d quarry faces exist and the quarry strata comprise part of a complete 600 m 1970 ft thick near continuous jackfork stratigraphic sequence not unlike younger deep water stratigraphic exploration targets in the gulf of mexico and elsewhere subsurface problems including reservoir uncertainties and reservoir performance of lobe versus channel fill deposits are addressed based on our work in the quarry a 3 d sequence stratigraphic model was developed using a correlation of seven measured stratigraphic sections in the quarry the 180 m 590 ft thick quarry strata consist of a lower lowstand systems tract lst lower sandstones dominated by channel fill sandstones overlain by a shaly transgressive systems tract condensed section and then by an upper lst upper sandstones dominated by sheet or lobe sandstones this model was translated into an updip against salt field which is analogous to some deep water gulf of mexico reservoirs performance simulation was conducted on the model using a one injector water well and two vertical producing wells one of which was connected to the injector via a channel sandstone and the other of which was offset from the channel sandstone results yielded 60 more production from the connected injector producer pair than from the nonconnected pair comparison between the lower channel prone sandstones and the upper sheet prone sandstones revealed that the sheet prone sandstone is more sustainable whereas the channel prone sandstone exhibits a larger drop in production rate during a 10 yr production period these results illustrate the value of 3 d outcrop models for reservoir performance simulation for development planning of deep water fields with limited data control such as in the deep water gulf of mexico

an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics abstract the jackfork group in arkansas u s a is a major training ground for academics students and petroleum industry geoscientists interested in deep water exploration and development several superb outcrop sections are exposed and over the years numerous papers have been published on these rocks the kirby sections in western arkansas provide a unique opportunity to build a complete and continuous sequence stratigraphic framework for early pennsylvanian time in the ancient ouachita basin there are 25 outcrops including 12 roadcuts on highway 27 and 13 measured sections in the baumgartner quarry all the measurements and interpretations on the outcrops were integrated with previous work using modern concepts of deepwater turbidite geology including 1 regional tectonic and sequence stratigraphic framework of the stanley group jackfork group and johns valley shale in the ouachita basin 2 deepwater outcrop characterization and correlation from the degray lake section dierks section and big rock quarry which are on the trend of the depositional fairway 3 chemostrata data from key shale layers which are considered as potential correlative condensed sections twenty five key shale samples from kirby degray and dierks sections have been tested using inductively coupled plasma and mass spectrometry icp ms tests an additional 525 samples were later collected for handheld x ray fluorescence xrf tests for both major and trace elements results of sequence and chemostrata analysis indicate that the entire kirby sections consist of at least three 3rd order sequences from the bottom of the jackfork group to the middle of the johns valley group and over ten 4th order sequences caused by a combined effect of tectonic uplift eustatic sea level change mixed sediment provenance and shifting of depositional fairways when the ouachita basin was transitioning from a passive margin to a remnant marine basin rare earth and trace element results are compared with known tectonic data to further pinpoint the tectonic environment of the ouachita basin during early pennsylvanian time which is dominantly a continental arc setting

geographical variability of the first baroclinic rossby radius of deformation global 1 83 18 climatologies of the first baroclinic gravity wave phase speed c1 and the rossby radius of deformation l1 are computed from climatological average temperature and salinity profiles these new atlases are compared with previously published 5 83 58 coarse resolution maps of l1 for the northern hemisphere and the south atlantic and with a 1 83 18 fine resolution map of c1 for the tropical pacific it is concluded that the methods used in these earlier estimates yield values that are biased systematically low by 5 15 owing to seemingly minor computational errors geographical variations in the new high resolution maps of c1 and l1 are discussed in terms of a wkb approximation that elucidates the effects of earth rotation stratification and water depth on these quantities it is shown that the effects of temporal variations of the stratification can be neglected in the estimation of c1 and l1 at any particular location in the world ocean this is rationalized from consideration of the wkb approximation

mean temperature salinity salinity depth and temperature depth curves for the north atlantic and the north pacific abstract all available hydrographic data are used to compute average temperature salinity salinity depth and temperature depth curves for 5 squares in the north atlantic and north pacific 10 s to 60 n both objective and subjective methods are used to filter out obviously erroneous data summary maps of all 5 square mean curves and their corresponding standard deviations are used to select regions of spatial homogeneity over which the curves are averaged scatter diagrams of each parameter pair are used to identify 5 squares containing a variety of water masses the area average curves and their standard deviations are presented individually along with tables of the parameter values these curves in conjunction with the 5 square summary maps provide a comprehensive picture of the distributions of these properties in the upper and mid depth portions of these oceans this well resolved picture of the water mass structure both confirms and adds new insights into the traditional concepts of these property distributions the application of the mean temperature salinity and salinity depth curves to the inference of salinity from observed temperature profiles is examined shallow 0 500 db dynamic heights calculated from observations of temperature and salinity true dynamic height are compared with dynamic heights computed from observed temperature profiles and salinities inferred from the mean property curves maps of the rms differences between true and inferred dynamic heights by 5 square reveal those areas where salinities inferred from either temperature salinity or salinity depth curves yield reliable dynamic heights

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion the pennsylvanian jackfork group in the ouachita mountains of arkansas and oklahoma has conventionally been interpreted by many workers including us as a classic flysch sequence dominated by turbidites in a submarine fan setting however normal size grading and bouma sequences indicative of turbidite deposition are essentially absent in these sandstone beds they appear massive i e structureless in outcrop but when slabbed reveal diagnostic internal features these beds exhibit sharp and irregular upper bedding contacts inverse size grading floating mudstone clasts a planar clast fabric lateral pinch out geometries moderate to high detrital matrix up to 25 sigmoidal deformation duplex structures and contorted layers all these features indicate sand mplacement by debris flows mass flows and slumps mud matrix in these sandstones was sufficient to provide cohesive strength to the flow discrete units of current ripples and horizontal laminae have been interpreted to represent traction processes associated with bottom current reworking the dominance of sandy debris flow and slump deposits nearly 70 at degray spillway section and bottom current reworked deposits 40 at kiamichi mountain section and the lack of turbidites in the jackfork group have led us to propose a slope setting our rejection of a submarine fan setting has important implications for predicting sand body geometry and continuity because deposits of fluidal turbidity currents in fans are laterally more continuous than those of plastic debris flows and slumps on slopes a turbidite dominated fan model would predict an outer fan environment with laterally continuous sheetlike sandstones for the jackfork group in southern oklahoma and western arkansas whereas a debris flow slump model would predict predominantly a slope environment with disconne ted sandstone bodies for the same area

reliability of self boring pressuremeter in sand the cone penetration test cpt is viewed by a majority in the geotechnical engineering profession as a preferred in situ testing tool while the self boring pressuremeter test sbpmt is sometimes

currents fronts and eddy fluxes in the canary basin hydrographic data from two cruises in the canary basin meteor 57 july 1981 poseidon 86 april 1982 are analysed with respect to current distribution and lateral heat flux in the azores madeira region the first part of the data base consists of long transects of xbt and g e k measurements between cape finisterre north west spain and the northern canary basin where several year long current meter records exist further information is obtained by thermosalinograph surface data and by expendable current profilers xcp geostrophic currents are derived from xbt profiles using the tight temperature salinity relationship in the depth range of the warmwassersphare the results compare well with the g e k and xcp current observations the second part consists of ctd data from an eddy resolving box shaped ctd survey 500 500 km2 centered at the mooring location 33 n 22 w the observations are supplemented by satellite buoy trajectories horizontal parameter distribution is shown in terms of objectively contoured maps bands of spatially enhanced energetic structures seen in the long transects are further resolved by the box survey as a deep jet like current system cross the canary basin in a west east direction associated with this azores current is a frontal zone with near surface temperature and salinity steps of order 2 k and 0 3 practical salinity units the dynamic topography field can be decomposed into a linear background field a rossby wave and a mesoscale eddy field we find that major contributions to the meridional eddy heat flux are confined to the vicinity of the azores current frontal zone it is shown that the principal balance in the temperature equation is between heating by the mean horizontal advection terms and cooling by the eddy flux divergence

interpretation of moduli from self boring pressuremeter tests in sand the pressuremeter is a unique method for assessing directly the in situ shear stiffness of soils however the correct interpretation and application of the measured modulus must account for the relevant stress and strain level acting around the pressuremeter during the test a method to correct the measured unload reload shear modulus from self bored pressuremeter tests in sands is proposed the method has been evaluated using extensive data obtained from 47 tests performed in a large calibration chamber using pluvially deposited silica sand and from 25 tests performed in situ in a natural deposit of relatively clean silica sand at the river po italy a consistent relationship was obtained between the corrected unload reload shear modulus and the small strain shear modulus determined from resonant column tests and field cross hole tests suggestions are given to link the measured moduli with moduli values required for geotechnical design problems the importance of strain level stress strain model yie

barium stable isotopes in the global ocean tracer of ba inputs and utilization abstract barium has been used as a biogeochemical tracer for alkalinity productivity and riverine inputs in the ocean but its oceanic cycle remains poorly constrained barium stable isotope measurements may improve the use of ba as a tracer and better constrain the cycling of ba but data are only available in limited regions of the oceans in this study we present dissolved seawater ba isotopic compositions in a sample collection spanning the north atlantic south atlantic north pacific and southern oceans compiled global upper ocean ba data show a relatively constant ba 35 45 nm in the near surface waters throughout the global ocean with the exception of areas near river inputs or strong upwelling the relatively uniform distribution of ba in the upper ocean seawater indicates that ba removal is slow relative to supply and mixing and implies that near surface ba isotope values are controlled by basin scale balances rather than by regional or short term processes seawater ba isotopic compositions show a large variation of 138 134 ba values ranging from 0 24 to 0 65 and a tight relationship with ba this global relationship can be simply modelled assuming a primary deep southern ocean source for ba to yield a maximum isotope fractionation of 1 00058 0 00010 ba seawater 138 134 ba particle 138 134 this suggested isotope fractionation during ba removal from seawater is larger than implied by laboratory measurement during barite formation suggesting additional fractionating phases or a two stage fractionation process riverine input from the rio de la plata to the south atlantic has a signature of 138 134 ba 0 06 0 11 which is too light to explain the heavy values 0 58 observed in the surface open ocean globally the ba isotope composition of the upper ocean waters is correlated with the fraction of ba utilization at the basin scale which varies from 138 134 ba signals in the northern sourced 0 45 and the southern sourced water 0 25 trace mixing and allow identification of non conservative behaviour of ba reflecting additional inputs or sinks of ba during transport most likely addition from sediment or hydrothermal ba isotopes may be useful to trace such inputs in the present and past ocean

a quasi synoptic survey of the thermocline circulation and water mass distribution within the canary basin shipboard hydrographic measurements and moored current meters are used to infer both the large scale and mesoscale water mass distribution and features of the general circulation in the canary basin we found a convoluted current system dominated by the time dependent meandering of the eastward flowing azores current and the formation of mesoscale eddies at middepths several distinctly different water masses are identified subpolar mode and labrador sea water are centered in the northwest subantarctic intermediate water is centered in the southeast and the saltier warmer mediterranean tongue lies between them mesoscale structures of these water masses suggest the presence of middepth meanders and detached eddies which may be caused by fluctuations of the azores current

central water vortices of the eastern north atlantic abstract a set of 102 high resolution hydrographic lines mostly xbt lines in the eastern north atlantic is used to study baroclinic vortices dynamically intensified within the central water layer first for the sake of comparison with recent results from altimetry spatial statistics of the main thermocline dynamic height are computed the dynamic height wavenumber spectrum slope close to k 3 at wavelengths shorter than 300 km and the decrease with latitude of eddy scales deduced from its autocorrelation function are found to be consistent with previous local altimetric results then using a criterion of local temperature anomaly relative to the large scale trend along each line 162 central water mesoscale vortices are detected their distribution is heterogeneous vortices of different size sign and intensity being found in most places they have a mean apparent diameter chord along the line of 110 50 km it is estimated that a range of 100 145 central water vortices coexist at the same t

disturbance effects in pressuremeter tests in clay this paper analyzes the effect of borehole disturbance caused by installation of pressuremeter probes in clays on the derived stress strain curves both overpushing and overcutting induced distu

influence of test size water depth and ecology on mg ca sr ca δ18o and δ13c in nine modern species of planktic foraminifers abstract mg ca palaeothermometry in foraminiferal calcite is a widely applied tool in palaeoceanography however our understanding of the effects of planktic foraminiferal ecology and early diagenesis on test calcite mg ca is limited here we report results of a study designed to shed new light on ecological size related and very early water column diagenetic controls on mg ca in planktic foraminiferal calcite we analysed mg ca and stable isotopes of nine modern planktic foraminiferal species across fourteen mostly 50 m window sieve fractions in a core top sample from the north atlantic ocean we also analysed mg ca in four of these nine species from plankton tow samples collected from 0 to 2500 m water depth in the north atlantic ocean and arabian sea our core top study confirms that sensitivity of mg ca to change in test size is species specific but reveals an overall decrease in mg ca with increasing test size in all but one species orbulina universa for which mg ca increases with size these findings are broadly consistent with known ecological behaviour suggesting that the size related signal is largely environmentally rather than calcification rate controlled our results underscore the need to undertake mg ca palaeothermometry on narrow size fractions of planktic foraminifers particularly for shallow dwelling species such as g bulloides and g ruber where mg ca is most sensitive to test size across the size range of 200 350 m our plankton tow data from the arabian sea are in agreement with in situ temperatures in contrast our data from the north atlantic ocean reveal large variability and marked offsets to warmer values from in situ temperatures that are interpreted to reflect lateral advection from the south storm induced vertical mixing of the water column and or the influence of surface water salinity on the mg ca signal none of our plankton tow mg ca data shows any evidence of test dissolution in the water column our study provides important verification that the mg ca signal recorded during calcification does not undergo diagenetic degradation during test transport to the sea floor thereby satisfying an important precondition of its palaeo proxy utility

statistical analysis of turbidite bed thickness patterns from the alpine fold and thrust belt of western and southeastern greece abstract a statistical evaluation of turbidite bed thickness was performed for 11 turbidite successions which constitute part of foreland basins formed along the alpine fold and thrust belt of western and southeastern greece the purpose was to compare the results from this study with previously published investigations and discuss if and how statistical approaches could contribute to the environmental analysis of turbidite deposits in tectonically complex areas bed thickness datasets exhibit a clear non normal signal in their distribution behavior statistical analysis was focused on i fitting of widely used non normal theoretical distribution models using robust non parametric goodness of fit statistical tests and ii detecting the possible presence of asymmetric bed thickness cycles and or non random bed thickness clustering results indicate that the studied bed thickness datasets are well characterized by a bimodal lognormal distribution model probably reflecting deposition from both high and low density turbidity currents several datasets exhibit distributions characterized by power law tails exponential distribution types were not observed all datasets exhibit non random thinning upward bed thickness trends probably due to tectonically induced gravity flows proposed methods for identifying depositional sub environments using turbidite bed thickness statistics were found to have limited applicability observations of the present study may prove useful for the environmental analysis of turbidite deposits in fold and thrust belt areas characterized by limited outcrop exposures

facies of slurry flow deposits britannia formation lower cretaceous north sea implications for flow evolution and deposit geometry mud rich sandstone beds in the lower cretaceous britannia formation uk north sea were deposited by sediment flows transitional between debris flows and turbidity currents termed slurry flows much of the mud in these flows was transported as sand and silt sized grains that were approximately hydraulically equivalent to suspended quartz and feldspar in the eastern britannia field individual slurry beds are continuous over long distances and abundant core makes it possible to document facies changes across the field most beds display regular areal grain size changes in this study fining trends especially in the size of the largest grains are used to estimate palaeoflow and palaeoslope directions in the middle part of the britannia formation stratigraphic zones 40 and 45 slurry flows moved from south west and south towards the north east and north most zone 45 beds lens out before reaching the northern edge of the field apparently by wedging out against the northern basin slope zone 40 and 45 beds show downflow facies transitions from low mud content dish structured and wispy laminated sandstone to high mud content banded units in zone 50 at the top of the formation flows moved from north to south or north west to south east and their deposits show transitions from proximal mud rich banded and mixed slurried beds to more distal lower mud content banded and wispy laminated units the contrasting facies trends in zones 40 and 45 and zone 50 may reflect differing grain size relationships between quartz and feldspar grains and mud particles in the depositing flows in zones 40 and 45 quartz grains average 0 30 0 32 mm in diameter 0 10 mm coarser than in zone 50 the medium grained quartz in zones 40 and 45 flows may have been slightly coarser than the associated mud grains resulting in the preferential deposition of quartz in proximal areas and downslope enrichment of the flows in mud in zone 50 flows mud was probably slightly coarser than the associated fine grained quartz resulting in early mud sedimentation and enrichment of the distal flows in fine grained quartz and feldspar mud particles in all flows may have had an effective grain size of 0 25 mm both mud content and suspended load fallout rate played key roles in the sedimentation of britannia slurry flows and structuring of the resulting deposits during deposition of zones 40 and 45 the area of the eastern britannia field in block 16 26 may have been a locally enclosed subbasin within which the depositing slurry flows were locally ponded slurry beds in the eastern britannia field are lumpy sheet like bodies that show facies changes but little additional complexity there is no thin bedded facies that might represent waning flows analogous to low density turbidity currents the dominance of laminar cohesion dominated shear layers during sedimentation prevented most bed erosion and the deposystem lacked channel levee and overbank facies that commonly make up turbidity current dominated systems britannia slurry flows although turbulent and capable of size fractionating even fine grained sediments left sand bodies with geometries and facies more like those deposited by poorly differentiated laminar debris flows

allogenic vs autogenic controls on megaflute formation abstract megaflutes are large concave up erosional scours within turbidite successions and have been described from modern and ancient settings they are interpreted to represent the passage of erosive largely bypassing turbidity currents here two categories of megaflute are distinguished 1 allogenic corresponding to the case above where erosion is associated with sediment bypass leading to deposition farther into the basin e g the classical megaflutes of the ross formation 2 autogenic where the erosion occurs during aggradation of the host bed both types are illustrated with examples from the carboniferous succession of northern england the distinction is important because the formative processes are different leading to distinct facies associations for each group for example allogenic flutes are interpreted to form in systems with large variations in flow magnitude and imply significant down dip sediment accumulation whereas autogenic megaflutes are thought to be formed by unsteady flows and imply less significant bypass autogenic megaflutes occur above inversely graded poorly sorted sandstones which improve in sorting and decrease in mud content upwards to the megaflute surface which is overlain by a well sorted mantle of the coarsest sediment found within the bed detailed grain size profiles suggest that autogenic megaflutes develop in response to waxing of flows from a depositional to an erosional state cannibalizing the already deposited sand bed as the flow wanes reverting to a depositional state the coarsest grained fraction of its remaining load is deposited first forming the basal part of a variably well developed normally graded and overall finer grained interval thus it is interpreted that flow unsteadiness promotes the formation of these features which has implications for the reconstruction of paleoenvironmental conditions specifically the generation mechanisms return periods flow routing into the basin and the resultant flow characteristics of turbidity currents

a real time dynamical forecast of ocean synoptic mesoscale eddies energetic eddy currents are the oceanic analogue of atmospheric weather and have time scales of days to weeks and space scales of tens to hundreds of kilometres1 we have predicted their evolution in time by internal dynamical processes for the forecasts we transferred initialization data from ship to shore based computers during two 2 week periods in june and july of 1983 from an approximately 150 km 2 region in the deep north east pacific off california this is to the best of our knowledge the first such real time forecast at sea the results were substantially successful the dynamics predicted a prominent zonal jet absent in the initial flow also the model forecast revealed a strong eddy merger event otherwise obscured in the data prospects are encouraging for future forecasting which should have important implications for research and practical operations at sea2

reinterpretation of depositional processes in a classic flysch sequence pennsylvanian jackfork group ouachita mountains arkansas and oklahoma discussion authors reply

near surface circulation in the southern gulf of cadiz abstract we have used several data sets expandable bathythermograph sections buoy trajectories current meter moorings and surface wind stress to investigate the temporal variation of the upper thermocline north atlantic central waters circulation patterns in the southern gulf of cadiz the main data set consists of eight expandable bathythermograph sections two per season running between the strait of gibraltar and cape beddouza just offshore the continental slope and approximately parallel to the morocco coastline a salinity temperature polynomial obtained from historical conductivity temperature depth data is used to infer dynamic properties salinity density dynamic height geostrophic velocity and transport dynamic heights are calculated referred to the 1027 25 kg m 3 neutral density surface which we justify is a good reference level for this section these observations are then combined with a process oriented one layer quasigeostrophic model for the northeastern corner of the north atlantic subtropical gyre with modified eastern boundary conditions the results indicate the existence of about 1 sv onshore transport all year long into a 300 km long coastal transition zone off morocco which must follow south as a narrow current during winter the flow is zonal towards the slope and recirculates south as a very narrow jet of less than 100 km width during summer the flow probably becomes more intense but is deflected southeastward before reaching the slope such that the onshore geostrophic transport into the coastal transition zone decreases and the recirculating band widens

effect of disturbance on parameters derived from self boring pressuremeter tests in sand a series of field tests has been performed to investigate the effects of drilling disturbance on the values of the parameters derived from self boring pressuremeter tests in sand the approach adopted consisted of using different drilling shoe and cutter geometries thereby deliberately causing varying amounts of drilling disturbance the results show that the values of friction angle and dilation angle are sensitive to drilling disturbance a procedure for correcting for the effects of drilling disturbance is proposed however it is demonstrated that the best results are obtained when drilling disturbance is kept to a minimum une serie d essais in situ a ete executee pour examiner les effets du remaniement par le forage sur les valeurs des parametres derives des essais d autoforage pressiometrique dans le sable la methode adoptee comporte l emploi de differentes geometries du sabot de forage et de l outil de coupe afin de provoquer expres des valeurs variees de remaniement par le forage les res

interpretation of in situ horizontal stress from self boring pressuremeter tests in sands via cavity pressure less than limit pressure a numerical study the paper presents a numerical finite difference model of self boring pressuremeter test sbpm using flac software different cavity expansion theories in sand have been compared to the results of numerical analyses carried out in this study limit pressure is believed to be used as a key parameter for the estimation of soil parameters from pressuremeter tests in practice sbpm tests are conducted up to 10 15 cavity strains and the strain level associated with the limit pressure state is not reached therefore determination of limit pressure usually needs extrapolation in this paper the authors suggest to use cavity pressure at 10 strain p10 for the interpretation of in situ horizontal stress from sbpm test rather than limit pressure for this purpose more than 5000 numerical analyses of sbpm are carried out and cavity pressures associated with 10 strain are deduced based on these extensive numbers of numerical analyses a new relationship is established with the aid of genetic algorithm which correlates p10 to soil parameters the estimated values of p10 from the proposed relationship are compared to a large database of measured ones obtained from laboratory and field results available in the literature it was shown that the proposed relationship gives satisfactory predictions of p10 a chart was established for deduction of the in situ horizontal stress using the proposed relationship this method can be used as a complement to liftoff method which is not reliable for estimation of the in situ horizontal stress when soil disturbance occurs at cavity wall

coccolithophore paleoproductivity and ecology response to deglacial and holocene changes in the azores current system 1 in order to test the sensitivity of marine primary productivity in the midlatitude open ocean north atlantic to changes in the atlantic meridional overturning circulation amoc we investigated two spliced sediment cores from a site south of the azores islands at the northern rim of the north atlantic subtropical gyre for this purpose we analyzed coccolithophore assemblages diatom abundances alkenones and conducted x ray fluorescence xrf core scanning during times of reduced amoc especially during heinrich event 1 h1 and the younger dryas we observe a strong increase in productivity as evidenced by high coccolith accumulation rates high alkenone concentrations accumulation rates high ba ti ratios high abundances of diatoms and low abundances off profunda the increased productivity is partly caused by a more southern position of the azores front azf and hence by a less northward extension of the subtropical gyre as deduced from high abundances of the temperate coccolithophore species g muellerae and low abundances of subtropical species oolithotus spp umbellosphaera spp umbilicosphaeraspp however to explain the full range of the observed productivity increase other factors like increased westerly winds and advection of nutrient rich surface waters have also to be considered because this pattern can also be observed in other sediment cores from the midlatitude north atlantic we propose that during times of reduced amoc there has been a band of strongly increased productivity across the north atlantic at the northern rim of the contracted subtropical gyre which partly counteracts the decreased organic carbon pump in the high northern latitudes

mean circulation and eddy kinetic energy in the eastern north atlantic sixty two satellite tracked buoys have been released in the northern part of the western and central north atlantic during 1981 and 1982 by the institut fur meereskunde universitat kiel federal republic of germany additionally six buoys deployed in spring 1980 by the bedford institute have been taken over mean values and variances about the mean have been calculated for 3 by 3 areas the mean velocities confirm the large scale gyre circulation as deduced from hydrographie data and numerical models the center of the gyre is located at about 33 n eddy kinetic energy decreases east and southward and is concentrated along the north atlantic current it appears that the north atlantic current polar front is the main source of eddy kinetic energy for the northern north atlantic whereas the mid atlantic ridge is no source of eddy energy eddy kinetic energy along the north atlantic current decreases from about 1000 cm2 s 2 near newfoundland to 300 cm2 s 2 west of scotland a homogeneous pool of low eddy kinetic energy less than 100 cm2 s 2 appears in the central north atlantic east of the mid atlantic ridge the level increases towards the european and african shelf where the mean southward flow also becomes stronger the results concern the upper ocean

anisotropic borehole response from pressuremeter testing in deep clay shale formations this paper presents the result of five pressuremeter tests conducted in deep three clay shale formations at a thermal operation site pressuremeter loading was imposed parallel to the bedding plane

determination of silica sand stiffness site investigation and evaluation of properties of soil or rock are important aspects of geotechnical design determination of the ground stiffness is one of the important parameters in geotechnical engineering since the measurement of shear modulus is very sensitive to soil disturbance especially for sand determination of the stiffness of soil in the field is more reliable than in laboratory tests on sampled specimens measurement of shear modulus is one of the most common applications of self boring pressuremeter testing as an in situ device the pressuremeter provides a unique method for assessing directly the in situ shear modulus of a soil this paper describes a laboratory study of silica sand stiffness which varies with stress level and strain amplitude the results show that the elastic shear modulus value is mainly dependent on the value of the mean effective stress and relative density

a long lived eddy in the iceland basin 1998 a survey was made of a large 100 km eddy in the iceland basin in june 1998 in situ observations from a shallow undulating conductivity temperature depth profiler and vessel mounted acoustic doppler current profiler were used to generate sea surface height along two topex poseidon tracks comparisons were made with the altimetric measurements to arrive at an estimate of the sea surface height for 6 years of topex poseidon altimeter data the 3 month track of a drifting buoy was used to estimate the location of the center of the eddy comparison with the altimetric sea surface height showed that the position of the eddy correlated well with an elevated sea surface signal of 25 30 cm having identified this signal as a characteristic signature of eddies inspection of the 6 year record revealed other similar features whose presence and longevity varied considerably the presence or absence of eddies appeared to link with the large scale variability of the subpolar gyre when the gyre expanded e g 1993 1994 the north atlantic current tended to follow a southerly route and eddies in the iceland basin were few and weak especially compared to periods when the gyre contracted e g 1992 1993 and 1996 1998 and the north atlantic current turned through the iceland basin then saltier water from the eastern north atlantic extended westward into the iceland basin and into large long lived eddies

three dimensional modeling of a shoreface shelf parasequence reservoir analog part 2 geologic controls on fluid flow and hydrocarbon recovery wave dominated shoreface shelf parasequences are commonly modeled as simple layer cake reservoirs yet analysis of modern and ancient analogs demonstrates that these intervals contain a more complex physical stratigraphy we investigate the impact of depositional and diagenetic heterogeneity associated with gently dipping clinoform surfaces on fluid flow and recovery during water flooding using a three dimensional model reconstructed from a well exposed outcrop analog we demonstrate that the volume of oil in place is affected by variations in facies thickness associated with interfingering along clinoforms whereas waterflood sweep efficiency is affected by barriers to flow along clinoform surfaces such as calcite cemented layers mudstones and siltstones sweep efficiency is low when water flooding is down depositional dip because oil is bypassed at the toe of each clinothem as water flows preferentially through high quality sandstone facies in the upper part of the parasequence sweep efficiency is higher when water flooding is up depositional dip because the gravity driven downward flow of water sweeps poorer quality sandstone facies in the lower part of the parasequence in both cases injectors may offer limited pressure support to producers water flooding along depositional strike yields good pressure support but poor sweep because the gravity driven flow of water into the lower part of the parasequence is significantly reduced this yields highly variable fluid saturations but a uniform pressure gradient which is consistent with pressure and fluid saturation data from the mature rannoch formation reservoir brent field united kingdom north sea simple layer cake models fail to capture the range of flow behaviors described above and overpredict recovery by up to 20 as a result

penetration of nonlinear rossby eddies into south china sea evidenced by cruise data national basic research program of china 2009cb421208 2007cb411803 natural science foundation of china 40976013 41121091 united states of america national oceanic atmospheric administration national environmental satellite data and information service ocean remote sensing 3000 11 03241

comment on a paper by zou et al 2017 entitled an integrated chemo and sequence stratigraphic framework of the early pennsylvanian deepwater outcrops near kirby arkansas usa and its implications on remnant basin tectonics