the tritium krypton 85 age of denmark strait overflow water and gibbs fracture zone water just south of denmark strait the opposite time trends of the input of tritium and 85kr to the surface ocean produce a tritium 85kr ratio for surface water that is a strong function of time and this ratio was used to determine the age of denmark strait overflow water dsow and gibbs fracture zone water gfzw just south of denmark strait dsow and gfzw were identified by their temperature salinity oxygen and silica characteristics in a section of stations 460 km south of denmark strait taken during the transient tracers in the ocean north atlantic study expedition in 1981 dsow was the densest water observed in the section and there were two types a low salinity type and a slightly higher salinity more dense type both types originated from arctic intermediate water aiw behind the greenland iceland ridge the tritium and 85kr data reveal that the low salinity type resided behind the greenland iceland ridge for about 1 year before flowing into the irminger sea compared to about 15 years for the higher salinity type the volume transport of the low salinity type of dsow was estimated to have a lower limit of 0 8 sv gfzw forms in the northeastern atlantic from a mixture of water flowing out of the norwegian sea at about 900 m depth and the northeastern atlantic water into which it flows about 70 of the tritium and 85kr burden of gfzw comes from northeastern atlantic water and 30 from norwegian sea water the age of gfzw just south of denmark strait relative to its formation in the northeastern atlantic is 7 5 4 6 5 years which corresponds to a mean current speed of 1 6 10 1 0 6 cm s

abrupt changes in deep atlantic circulation during the transition to full glacial conditions 1 six ocean drilling program odp sites in the northwest atlantic have been used to investigate kinematic and chemical changes in the western boundary undercurrent wbuc during the development of full glacial conditions across the marine isotope stage 5a 4 boundary 70 000 years ago sortable silt mean grain size ss measurements are employed to examine changes in near bottom flow speeds together with carbon isotopes measured in benthic foraminifera and planktic foraminiferal fragmentation as proxies for changes in water mass chemistry a depth transect of cores spanning 1 8 4 6 km depth allows changes in both the strength and depth of the wbuc to be constrained across millennial scale events ss measurements reveal that the flow speed structure of the wbuc during warm intervals interstadials was comparable to modern holocene conditions however significant differences are observed during cold intervals with higher relative flow speeds inferred for the shallow component of the wbuc 2 km depth during all cold stadial intervals including heinrich stadial 6 and a substantial weakening of the deep component 3 4 km during full glacial conditions our results therefore reveal that the onset of full glacial conditions was associated with a regime shift to a shallower mode of circulation involving glacial north atlantic intermediate water that was quantitatively distinct from preceding cold stadial events furthermore our chemical proxy data show that the physical response of the wbuc during the last glacial inception was probably coupled to basin wide changes in the water mass composition of the deep northwest atlantic

on the average absolute transport of the deep western boundary currents east of abaco island the bahamas abstract data obtained from a line of absolute current profiler pegasus and ctd stations at 26 5 n east of abaco island in the northern bahamas are used to estimate the average transport and overall level of variability of the deep below 800 m southward flow associated with the so called deep western boundary current dwbc at this latitude from april 1985 to september 1987 a total of 11 sections were made along a line extending from near the island boundary to 85 km offshore as part of the subtropical atlantic climate studies stacs program in all but two cases when pegasus data were obtained over the total depth absolute velocities were determined from 0 to about 3000 db while ctd derived relative velocities were determined over the total depth using the combined datasets it is possible to reference the relative geostrophic velocity with pegasus data thereby obtaining an estimate of the absolute southward transport of the deep flow the average value of transport determined in this man

artificial radionuclide tracer supply to the denmark strait overflow between 1972 and 1981 measurements of the concentrations of the artificial radionuclides 3h 137cs and 90sr in the northern irminger sea in 1972 and 1981 are reported in both years tracer measurements from this area included data from samples of the dense overflow water from the north through denmark strait all three tracers were strongly correlated inversely with salinity in the dense outflows the tracer maxima being related directly to the salinity minimum when the tracer characteristics in the outflows in 1972 and 1981 were compared concentrations of all in 1981 were observed to be about double the 1972 values the individual tracer concentrations on a decay corrected density normalized basis were higher in increasing order 90sr 93 3h 115 137cs 150 the relatively greater increases for 3h and 137cs were attributed to contributions of new sources of these tracers in northern surface waters the 3h source is argued to derive from atmospheric hydrological recycling whereas the 137cs source is identified as the input to the greenland and iceland seas of advected european nuclear fuel reprocessing wastes both the tracer and hydrographic data are used to identify northern locations of intermediate water formation capable of supplying the observed dense overflow water characteristics it is argued from the time taken for the overflow water to reflect the new surface 137cs source that transport from the source to the overflow can be quite rapid about 2 years

tracing the thermohaline circulation in the western north atlantic using chlorofluorocarbons abstract measurement of chlorofluorocarbons cfcs f 11 and f 12 were obtained from vertical sections extending across the deep western boundary current dwbc along the western margin of the north atlantic ocean between 32 45 n in 1983 and 1986 these sections revealed an upper and a deep cfc maximun with highest concentrations along the continental slope the upper maximum had a potential temperature ranging from 4 2 4 6 c a core density of 1 5 34 56 and occurred at a depth of about 800m adjacent to the continental slope water with classical labrador sea water s characteristics occurs just above the cfc minimum between the upper and lower maxima and indicates that a significant volume of classical labrador sea water has not entered the region south of the grand banks for the last 3 decades the deep cfc maximum is from dense water overflowing the greenland iceland scotland ridge it occurred at about 3500m depth and had a potential temperature range of 2 02 2 18 c and a core density of 4 45 87 a source function of f 11 and f 12 for the deep maximum was estimated using temperature salinity and tracer data from previous studies the core of the dwbc defined by the deep cfc maximum was estimated to consist of roughly 2 3 gibbs fracture water and 1 3 denmark strait overflow water however 80 or more of the f 11 and f 12 signal was derived from denmark strait overflow water ages for the upper and lower cfc maxima in the dwbc were estimated from the cfc data these ages ranged from 11 12 years at the northernmost section to 18 years at the southernmost section for both features this corresponds to apparent mean current speeds of about 0 8cm s 1 for the upper maximum and 1 4cm s 1 for the deep maximum an age of 8 9 years with a corresponding apparent mean current speed of 2 2 2 5cm s 1 was also estimated for the deep cfc maximum from the observed increase in the f 11 concentration at 41 n between 1983 and 1986 the apparent mean current speeds are significantly less than current speeds measured with long term current meter moorings two reasons for this are 1 mixing between the dwbc core and adjacent water causes ages estimated from cfc data to be overestimated and hence the associated current speed to be underestimated pickart hogg and smethie 1989 and 2 water propagating along the western boundary spends some time in recirculation gyres the northern recirculation gyre south of the eastern north american continental margin is clearly apparent in the lateral distributions of f 11 and f 12 the apparent mean current speed in the northern recirculation gyre was estimated to be 1 3cm s 1 from the cfc data seaward of the dwbc north of the new england seamount chain high cfc low silica parcels of water were observed interspersed with low cfc high silica parcels of water along the bottom the high cfc low silica water is overflow water with a slightly greater component of denmark strait overflow water than contained in the dwbc deep cfc maximum the low cfc high silica water is of southern origin and has a component of antarctic bottom water

moored observations of western boundary current variability and thermohaline circulation at 26 5 n in the subtropical north atlantic abstract a 5 8 year time series of moored current meter observations is used with hydrographic section data cme model results and gridded wind fields over the north atlantic to describe the mean structure and variability of circulation and volume transports east of abaco bahamas at 26 5 n a mean antilles current with 5 sv of northward transport is confined against the bahamas boundary in the upper 800 m and combines with approximately 19 sv of florida current transport to balance the sverdrup interior circulation and does not contribute to interhemispheric exchange the mean transport of the deep western boundary current dwbc off the bahamas is approximately 40 sv of which 13 sv compensates the upper branch of the thermohaline circulation requiring a 27 sv deep recirculation robust annual and semiannual cycles of meridional are found in both moored observations and model results with remarkable agreement in amplitude 13 sv and phase maximum northward transports occur in winter and summer

hemispheric asymmetry of deep water transport modes in the western atlantic subtropical studies of the atlantic meridional cold water flow show a hemispheric contrast in the dominant southward transport mode below 2000 m in the north atlantic lower deep water ldw 1 8 2 4 c dominates with small transport of middle deep water mdw 2 4 3 2 c while in the south atlantic the opposite is observed we use numerous observations in the western basins of the tropics to show that the transition occurs rapidly near the equator in the western atlantic a meridional section in the central brazil basin suggests zonal flows are responsible for the transition ldw transport from the guiana basin north of the equator flows eastward in the northern brazil basin and is inferred to continue on through the romanche fracture zone into the eastern atlantic an opposing flow of mdw from the eastern tropical atlantic flows toward the western boundary where it bifurcates to supply mdw to the deep western boundary current dwbc of the brazil basin as well as to feed the northward flow of mdw in the guiana basin offshore of the dwbc the magnitude of each of these oppositely directed flows is roughly 7 sv we furthermore speculate that they are connected predominantly by upwelling from ldw to mdw within the low latitude eastern basin the overall deep water transport system below 2000 m in the western basins of the mid and low latitude atlantic is thus found to comprise the following three distinct components 1 a strong dwbc transport of ldw with associated recirculation dominates the guiana basin north of the equator 2 in the northern brazil basin just south of the equator a narrow eastward flow absorbs the ldw and carries it eastward while a somewhat broader westward flow imports mdw into the western basin 3 this mdw flow then bifurcates with the southward branch causing the mdw dominance in the brazil basin where the mdw dominated dwbc and associated recirculations are the third component of the deepwater transport system

mineralogical composition and potential sources of dust fallout deposits in kuwait northern arabian gulf abstract detailed mineralogical investigations of dust fallout deposits collected at eleven locations in kuwait during april 1979 march 1980 were carried out the mineralogy of five size fractions medium sand fine sand very fine sand coarse silt and clay was determined occurrence frequency and potential sources of the mineral grains that form the various size fractions are discussed and the gross mineralogical composition of the dust fallout calculated it was found that dust fallout deposited in kuwait is quartzitic calcareous sandy silt and is mostly derived from the dry mesopotamian flood plain in the middle and south of iraq the occurrence of sand size particles is attributed to pick up from local recent surface deposits

the karoo sediments late palaeozoic to early jurassic of the ogaden basin ethiopia abstract the ogaden basin is a major sedimentary basin in east africa located in the south and southeast of ethiopia covering an area of about 350 000 km 2 it contains over 5 000 m of phanerozoic sediments as evidenced by recent drilling and seismic surveying a sedimentological investigation has been carried out on cored sections of the karoo these are the oldest sediments in the basin and occur only in the subsurface karoo sediments permian to lower jurassic in the ogaden basin have an average thickness of about 800 to 1 200 m the sequence is divided into four formations from oldest to youngest the calub sandstone the bokh shale the gumburo sandstone and the adigrat sandstone continental karoo sedimentation was ended by a progressive mesozoic marine transgression which initiated the deposition of the overlying hamanlei limestone the basal calub sandstone consists of arkosic and lithic conglomerate and sandstone of alluvial fan origin it is overlain by lacustrine shale siltstone and minor sandstone of the bokh shale the remaining two formations have a transitional boundary the gumburo and adigrat sandstones are fluviatile quartzitic sandstone deposited by braided and meandering rivers respectively initially karoo sedimentation took place within an extensional rift before becoming progressively more widespread during the deposition of the gumburo and adigrat sandstone

deep flow along the western boundary south of the blake bahama outer ridge abstract in june july 1990 hydrographic chlorofluorocarbon cfc and velocity observations were taken along the western boundary of the north atlantic south of the blake bahama outer ridge from 30 to 24 n between the northern bahamas and 71 w the deep flow in the region associated with the deep western boundary current forms a pattern of strong narrow currents and cyclonic gyres close to the continental slope with broad slower southward flow offshore the cfcs reveal that the most recently ventilated water i e having the highest cfc concentrations due to more recent contact with the atmosphere in the northern north atlantic is found along the western boundary in two distinct cores between potential temperatures 4 6 c and 1 9 2 4 c geostrophic transport streamlines were constructed for the deep flow referenced using direct velocity observations at 26 5 n and assuming mass conservation between closed areas bounded by the hydrographic sections the tracers and transports are used together

deepwater circulation on blake outer ridge western north atlantic during the holocene younger dryas and last glacial maximum three depth transects containing a total of 33 sediment cores were investigated along the blake outer ridge in the western subtropical north atlantic sortable silt mean grain size and stable isotope records were used to assess the position and relative intensity of the western boundary undercurrent wbuc during the holocene the last glacial maximum lgm and the younger dryas yd intervals the holocene reconstruction is consistent with modern physical and chemical hydrographic measurements in the area suggesting a deep position for the fast flowing core of the wbuc 3000 4000 m deepening to 4500 m water depth on the ridge flanks and a water column dominated by north atlantic deep water nadw the lgm and yd reconstructions show that a comparable hydrographic regime was present during both these intervals suggesting a similar mode of circulation that was appreciably different from the holocene reconstruction the wbuc s zone of maximum flow speed during these intervals is suggested to have shifted above 2500 m water depth consistent with nutrient depleted glacial north atlantic intermediate water formation with an increasing influence of southern source water ssw beneath below 4000 m water depth results hint at increased ssw flow vigor during both the lgm and yd with higher flow speeds than during the holocene this study provides a framework for aiding the interpretation of time series records of paleocurrent flow speed changes in the region of the wbuc

the western boundary undercurrent off the bahamas abstract two tritium sections through the deep western boundary current east of the bahamas taken in late 1980 and early 1981 are presented tritium from the bomb tests in the late 1950s and early 1960s is used to identify recently formed deep waters in the sections high concentrations are found in the north atlantic deep water low tritium values occur in the labrador sea water found above the core of this deep water this is consistent with the suggestion by talley and mccartney that this water mass has not been ventilated at the temperatures observed in these sections since the mid 1950s tritium in the sections is correlated with maxima in potential vorticity this is inconsistent with deep convection as a direct source for the water mass the potential vorticity maxima may be associated with plume dynamics near the overflow regions or with the dynamics of the deep western boundary current the sections are south of the section discussed by jenkins and rhines where high tritium concentrations were fo

direct observations of the current structure east of the bahamas quasisynoptic absolute velocity sections were obtained in the western north atlantic to the east of the bahamas on five cruises from 1992 to 1994 showing complex spatial and temporal variability of the currents throughout the water column lowered acoustic doppler current profilers were used on all cruises for comparison an acoustically tracked free fall profiler was used on the august 1992 and june 1993 cruises where simultaneous profiles from both methods are available depth averaged differences are less than 0 01 m s 1 in the ensemble mean and standard deviation though small the mean difference appears to be statistically non zero for one of the two doppler profilers used no cause has been found the individual velocity sections show a banded structure of currents in the offshore direction with strong baroclinic and depth averaged components extending over the full sampling domain two sections show a picture of the southward flowing deep western boundary current dwbc differing from previous observations during august 1992 and june 1993 the mean dwbc core was located more than 100 km offshore in observations prior to 1990 it was usually near 50 km offshore net southward transport below 800 m integrated from the coast to 400 km offshore varied from 15 to 50 sv with a mean of about 40 sv 1 sv 1 106 m s 1 our mean is consistent with previous estimates our sections add new evidence that the transport is highly variable to at least 400 km offshore

temperature and salinity variability in the deep western boundary current abstract a ten year time series 1984 1993 of repeat hydrographic sections from offshore abaco island the bahamas 26 5 n is used to define the mean and time dependent characteristics of the deep western boundary current dwbc the dwbc flow is divided into four vertical layers based on chlorofluorocarbon cfc concentration and formation regions upper layer cfc core 3 9 5 0 c second layer classical labrador sea water 3 2 3 9 c third layer cfc minimum 2 4 3 2 c deepest layer cfc core 1 85 2 4 c time series analysis of mean layer properties and their anomalies showed that the temperature and salinity of each layer did not increase or decrease monotonically with time variations in temperature and salinity were characterized by 2 3 yr period oscillations variability between years is illustrated by subtracting repeat sections of temperature and salinity along levels of both constant pressure and constant potential density to determine an original water mass modificati

variability of shallow and deep western boundary currents off the bahamas during 2004 05 results from the 26 n rapid moc array data from an array of six moorings deployed east of abaco bahamas along 26 5 n during march 2004 may 2005 are analyzed these moorings formed the western boundary array of a transbasin observing system designed to continuously monitor the meridional overturning circulation and meridional heat flux in the subtropical north atlantic under the framework of the joint u k u s rapid climate change rapid meridional overturning circulation moc program important features of the western boundary circulation include the southward flowing deep western boundary current dwbc below 1000 m and the northward flowing antilles current in the upper 1000 m transports in the western boundary layer are estimated from direct current meter observations and from dynamic height moorings that measure the spatially integrated geostrophic flow between moorings the results of these methods are combined to estimate the time varying transports in the upper and deep ocean over the width of the western boundary layer to a distance of 500 km offshore of the bahamas escarpment the net southward transport of the dwbc across this region inclusive of northward deep recirculation is 26 5 sv sv 10 6 m 3 s 1 which is divided nearly equally between upper 13 9 sv and lower 12 6 sv north atlantic deep water nadw in the top 1000 m 6 0 sv flows northward in a thermocline intensified jet near the western boundary these transports are found to agree well with historical current meter data in the region collected between 1986 and 1997 variability in both shallow and deep components of the circulation is large with transports above 1000 m varying between 15 and 25 sv and deep transports varying between 60 and 3 sv much of this transport variability associated with barotropic fluctuations occurs on relatively short time scales of several days to a few weeks upon removal of the barotropic fluctuations slower baroclinic transport variations are revealed including a temporary stoppage of the lower nadw transport in the dwbc during november 2004

a modified swanson method to determine permeability from mercury intrusion data in marine muds abstract the permeability of shallow marine sediments is an extremely important parameter to constrain as it affects fluid and nutrient transport near the sediment water interface mediates mass exchange between igneous basement and oceans and plays a role in seismicity along convergent margins determining the permeability of these sediments in the laboratory is difficult because existing methods typically require fully saturated intact samples of large volume tens of cm3 which are usually not collected with high spatial resolution in scientific ocean drilling operations we demonstrate how mercury injection capillary pressure micp data may be used to predict the permeability of marine muds using a modification of the widely used swanson method our results show that micp measurements performed on small irregular and most importantly unpreserved samples can yield important permeability information this will improve the spatial resolution of permeability data in the shallow marine subsurface and allow analyses to be performed on the significant quantities of existing legacy core

distribution and circulation of labrador sea water abstract labrador sea water is the final product of the cyclonic circulation of subpolar mode water in the open northern north atlantic mccartney and talley 1982 the temperature and salinity of the convectively formed subpolar mode water decrease from 14 7 c 36 08 to 3 4 c 34 88 on account of the cumulative effects of excess precipitation and cooling the coldest mode water is labrador sea water which spreads at mid depths and is found throughout the north atlantic ocean north of 40 n and along its western boundary to 18 n a vertical minimum in potential vorticity is used as the primary tracer for labrador sea water labrador sea water is advected in three main directions out of the labrador sea 1 northeastward into the irminger sea 2 southeastward across the atlantic beneath the north atlantic current and 3 southward past newfoundland with the labrador current and thence westward into the slope water region crossing under the gulf stream off cape hatteras the labrador sea water core is

variability of the deep western boundary current at 26 5 n during 2004 2009 five years of data from a line of dynamic height moorings dhm bottom pressure recorders bpr and pressure equipped inverted echo sounders pies near the atlantic ocean western boundary at 26 51n are used to evaluate the structure and variability of the deep western boundary current dwbc during 2004 2009 comparisons made between transports estimated from the dhm bpr and those made by the pies demonstrate that the two systems are collecting equivalent volume transport information correlation coefficient r 0 96 root mean square difference 6 sv 1 sv 10 6 m 3 s 1 integrated to 450 km off from the continental shelf and between 800 and 4800 dbar the dwbc has a mean transport of approximately 32 sv and a standard deviation during these five years of 16 sv both the barotropic full depth vertical mean and baroclinic flows have significant variability changes exceeding 10 sv on time scales ranging from a few days to months with the barotropic variations being larger and more energetic at all time scales the annual cycle of the deep transport is highly dependent on the horizontal integration distance integrating 100 km offshore yields an annual cycle of roughly similar magnitude but shifted in phase relative to that found from current meter arrays in the 1980 1990s while the annual cycle becomes quite weak when integrating 450 km offshore variations in the dwbc transport far exceed those of the total basin wide meridional overturning circulation standard deviations of 16 sv vs 5 sv transport integrated in the deep layer out to the west side of the mid atlantic ridge still demonstrates a surprisingly high variance indicating that some compensation of the western basin deep variability must occur in the eastern basin published by elsevier ltd

topographic influences on recirculation in the deep western boundary current results from rafos float trajectories between the blake bahama outer ridge and the san salvador gate abstract over a period of several years rafos floats were launched into three levels of the deep western boundary current dwbc east of the northern bahamas in order to identify and study any local recirculations that might be present in addition to the thermohaline driven component of the current these float trajectories reveal the presence of recirculations that are clearly caused by features of the lateral and bottom topography in particular the san salvador spur exerts a major influence on the paths of these floats although the floats exhibit a complicated set of motions some order is imposed by relating periods when floats move directly along the boundary versus periods when they leave the launch site anomalously i e to the cast or northeast due to motions of the dwbc core comparison to current meter records along 26 30 n near the launch site shows that floats in the latter group were deployed when the dwbc core was located offshore the eruption of floats into the interior recirculat

how does the deep western boundary current cross the gulf stream abstract the manner in which the deep western boundary current dwbc crosses the gulf stream is investigated using data from a hydrographic survey conducted in 1990 absolute geostrophic velocity vectors are computed using in situ float data to obtain the reference level three density layers are considered in detail two mid depth layers which together make up the shallowest water mass component of the dwbc 500 1200 m and a deep layer consisting of the norwegian greenland overflow water 2500 3500 m the shallowest layer does not make it through the crossover and is completely entrained by the gulf stream however the resulting drop in equatorward transport is almost completely replenished by offshore entrainment just south of the crossover in the intermediate layer which is denser than the gulf stream coming off the shelf part of the dwbc recirculates to the northeast while the onshoremost portion continues equatorward in the deep layer only a small amount of recirculation occurs the lateral

calcrete and near surface geology of kuwait city and suburbs kuwait arabian gulf abstract near surface accumulation of pedogenic carbonate calcrete is a common and characteristic feature of the landscape of kuwait city and its suburbs the principal host material for these calcretes is a thick sequence of unconsolidated quartzose sand a typical fully developed soil profile can be divided into five zones in descending order these are 1 a top calcareous aeolian soil 2 a zone of friable sand with powdery or tightly cemented calcrete lumps nodules 3 a massive calcrete zone 4 a mottled calcrete zone and 5 unaltered parent material episodic formation of calcrete is indicated by the occurrence of multiple profiles in which zones are repeated calcrete ooids and pseudo ooids of accretionary origin are characteristic of the upper calcrete zone the carbonate fraction in the upper calcrete zone consists dominantly of low mg calcite with minor amounts of dolomite replacement was a major process in formation of the massive calcrete and the dominant cementing material is largely low mg calcite and or microcrystalline dolomite aeolian dust is considered to be the major source of ions for calcrete formation in kuwait city and suburbs an earlier introduced model is applied to explain the mechanisms of formation and precipitation of low mg calcite and dolomite the calcrete thickness in the study area is explained by episodic deposition of fluviatile sand and calcrete formation during the oligocene through lower miocene period

geotechnical properties of calcrete soil gatch in kuwait abstract this paper presents the results of a comprehensive laboratory testing program carried out to study the geotechnical properties of gatch calcrete soil samples a total of 17 samples collected from 17 different sites in kuwait city and its suburbs were used for the study the testing program included determination of physical index and engineering properties of gatch samples the sensitivity of various geotechnical properties of compacted gatch was examined by testing specimens at various moisture contents and also at different soaking periods

observations of the boundary current system at 26 5 n in the subtropical north atlantic ocean abstract five current meter moorings and four horizontal electric field records spanning june 1990 february 1992 are used to describe the mean structure and variability of the vertically averaged velocity field and volume transport extending 425 km east of abaco the bahamas at 26 5 n examination of zonal and meridional velocity sections shows that while meandering may explain part of the variability there is substantial evidence for pulsation of the core dwbc velocity in the record intermittently strong northward flow is observed 225 km east of abaco that is significantly coherent and out of phase with the currents closer to the boundary at periods of 50 100 d and longer suggesting recirculation this is never observed 315 km offshore at 380 km offshore and extending east at least 60 km a strong dominantly southward flow is observed that is coherent with both that near abaco in phase and in the intervening recirculation zone out of phase at long periods the net mean transport over 17 month

extending nmr data for permeability estimation in fine grained sediments abstract we combine nuclear magnetic resonance nmr transverse relaxation time data and gamma ray data to estimate lithology dependent permeability in silt and clay rich sediments this approach extends the utility of the schlumberger doll research sdr permeability equation from reservoirs to aquicludes and seals and thus improves the value and robustness of nmr data data from keathley canyon northern gulf of mexico show that nmr data can be used to define permeability from 10 18 to 10 14 m 2 0 001 10 millidarcies as calibrated and tested by direct measurements on core samples we performed uniaxial constant rate of strain consolidation experiments on sediments from keathley canyon to determine core scale permeability permeabilities from these experiments were compared to permeabilities calculated from logging while drilling data a better fit between log derived permeability and laboratory measured permeability was obtained using the sdr equation with a variable coefficient a rather than a constant a as is typically used we show how a is a function of lithology and can be modeled from gamma ray data the relationship between a and gamma ray values suggests that variations in a are caused by platy clay minerals and the effect they have on the pore system our results provide improved means for permeability estimation for application in basin flow modeling hydrocarbon migration modeling and well completion design

deep western boundary current variability in the subtropical northwest atlantic ocean during marine isotope stages 12 10 high resolution 125 500 year temporal resolution sortable silt mean grain size data of subtropical northwest atlantic ocean drilling program odp leg 172 site 1061 monitor fluctuations of the deep western boundary current dwbc throughout marine oxygen isotope stages mis 12 10 330 460 kyr in great detail comparison with foraminiferal stable isotope data from the same site and odp site 1063 bermuda rise data of poli et al 2000 shows that the dwbc shoals during glacial times in relation to a reduced north atlantic deep water production and increased advection of southern ocean waters superimposed fluctuations in the flow speed position of the dwbc at a semiprecession scale are persistent throughout mis 10 12 and independent of the glacial state additional millennial scale variations in dwbc flow speed parallel surface water cooling events and ice rafted debris episodes especially at the transition of mis 11 10 indicating the sensitivity of deep current flow variations to changes in the surface water conditions these millennial scale variations are amplified when benthic foraminiferal 18o values exceed 3 8 and may be related to the transition of an ice volume threshold where climate variability is possibly amplified by feedback mechanisms associated with ice sheet growth

an overview of the surface and near surface geology geomorphology and natural resources of kuwait abstract the surface and near surface geology geomorphology and natural resources of kuwait have been reviewed based on the published work the stratigraphy and structure of the near surface sediments of kuwait have been mainly controlled by the tertiary tectonic activity of the arabian shield the shield started separating from the african mainland by the close of the eocene and drifted northeastward towards the asian plate giving rise to the folding and thrusting of the zagros mountains of iran the tectonic activity superimposed a northwest southeast trend over an earlier north south structural trend and gave rise to parallel ridges and valleys trending northwest southeast through differential erosion it has been possible to identify 15 geomorphic zones and 11 morphostructures from analysis of the surface features of kuwait seven of these morphostructures can be attributed to tectonic processes and two to fluvial processes it has not been possible however to explain satisfactorily the origin of the jal az zor escarpment or the ad dalmaniyah cliff the whole of kuwait can be divided into seven drainage zones of these the internal drainage systems of the ar raudhatain umm al aish drainage system and the ad dibdibba drainage system are hydrogeologically most important the clastic deposits of kuwait group sediments often affected by low temperature carbonate calcite and dolomite and sulfate gypsum precipitation form the surface rock of kuwait these are covered by recent aeolian and residual deposits playa deposits in the enclosed basins and near the coast oolitic sediments beach sands and sabkha deposits the surface and near surface deposits of kuwait contain important reserves of construction sand and gravel as well as the only naturally occurring freshwater reserves of the country an understanding of the nature of these surface deposits is required for the management of environmental issues like sand encroachment land use planning and soil and groundwater pollution

genesis of calcrete in quaternary soil profiles hutt and leeman lagoons western australia abstract soil profiles exposed along the margins of hutt and leeman lagoons contain a succession of calcrete horizons that exhibit oolitic pisolitic grainstone lithoclast breccia and pelloidal wackestone mudstone stone lithologies the typical coastal profile consists of an upper laminar calcrete horizon which is usually overlain by a transitional pisolitic loose soil horizon underlying the laminar calcrete is breccia and or massive calcrete downward gradation into the host is through a mottled calcrete horizon structure textures and fabrics are utilized to classify the following different calcrete types pisolitic loose soil is composed of sandy soils calcrete ooids and pisolites eolianite clasts and shell fragments laminar calcrete is composed of parallel laminated sheets of micritic carbonate that develop by segregation processes massive calcrete is dense relatively structureless calcrete with a secondary mudstone fabric resulting from diagenetic alteration of primary constituents calcrete mottles form in response to localized diagenesis in the host sediment breccia calcrete develops as a result of prolonged weathering involving repeated episodes of calcretization dissolution and brecciation diminution of permeability of the host sediment by development of massive calcrete is a major process in genesis of the profile and occurs in the lowermost part of the zone of alternate wetting and drying where the effect of water input overcomes the cumulative effects of evapotranspiration profile development is thereafter topographically controlled and restricted to horizons overlying the massive calcrete redevelopment of zones of alternate wetting and drying in older deposits may produce multiple soil profiles

compaction driven evolution of porosity and permeability in natural mudstones an experimental study this paper describes a series of experiments designed to investigate the influence of lithology on the compactional loss of porosity and permeability in mudstones two intact samples of london clay with clay fractions of 40 and 67 were compacted to 33 mpa effective stress clay fraction permeability porosity pore size distribution and specific surface area were measured and their evolution was monitored throughout the compaction process electron microscopy was combined with mercury porosimetry to trace the collapse of the pore structure with increasing effective stress in both cases porosity loss occurred primarily by the collapse of large pores this process is more obvious in the coarser grained sample because throughout the compaction process it has a much broader range of pore radii and a much greater mean pore radius consistent with the pore size distributions the permeability of the coarser sample ranges from 10 10 m s 1 to 10 12 m s 1 while that of the finer grained sample ranges from 4 10 12 m s 1 to 5 10 14 m s 1 during progressive compaction from 2 to 33 mpa the compressibility of the finer grained sample is greater than that of the coarser grained sample 0 15 as opposed to 0 07 however in both cases the compressibility is much lower than that inferred for lithologically similar samples compacted over geological timescales the demonstration that both porosity and lithology clay fraction influence the permeability of mudstones should allow the development of more realistic porosity permeability relationships which take into account lithological variations exhibited by mudstones

lagrangian observations of the deep western boundary current in the north atlantic ocean part i large scale pathways and spreading rates twenty six rafos floats were deployed in the deep western boundary current dwbc of the north atlantic ocean between the grand banks and cape hatteras in 1994 95 and tracked acoustically for up to two years half of the floats were launched in the upper chlorofluorocarbon cfc maximum associated with upper labrador sea water 800 m and the other half near the deep cfc maximum that identifies the overflow water from the nordic seas 3000 m the float observations reveal the large scale pathways of these recently ventilated water masses in the subtropics the shallow float tracks show directly that upper labrador sea water is diverted away from the western boundary and into the interior at the location where the dwbc encounters the gulf stream near 368n the crossover region consistent with previous hydrographic studies east of the crossover region only one upper labrador sea water float out of seven 15 permanently crossed to the south side of the stream in two years caught in a cold core ring formation event the other shallow floats recirculated north of the gulf stream apparently confined by the mean potential vorticity gradient aligned with the stream the deep floats closely followed the topography to the crossover region then revealed a bifurcation in fluid parcel pathways one branch continues equatorward along the western boundary and the other turns first eastward along the gulf stream path then southward the deep float pathways including the bifurcation in the crossover region can be explained in terms of the deep potential vorticity distribution comparison of the float results with results from recent modeling studies suggests that the deep flow is strongly influenced by both the depth of the main pycnocline and bottom depth the effective spreading rates of upper labrador sea water and overflow water estimated directly from the float data southward at 0 6 6 0 2 cm s21 and 1 4 6 0 4 cm s21 respectively agree well with tracer derived spreading rates mean velocities in the dwbc equatorward at 2 4 cm s21 upper labrador sea water and 4 5 cm s21 overflow water are consistent with other in situ measurements one deep float drifted almost 4000 km along the western boundary in two years revealing a fast track for the spreading of overflow water in the dwbc these observations emphasize the importance of the crossover region in the spreading and mixing of recently ventilated water masses addressed in part ii of this study

the atlantic deep western boundary current water masses and transports near the equator the distributions and transports of deepwater masses at the western boundary in the tropical atlantic off brazil have been studied on three surveys along 35 degrees w and 5 degrees s and one at 10 degrees s transports are obtained from direct measurements of the velocity fields pegasus profiling system and lowered acoustic doppler current profiler and from geostrophic computations using chlorofluoromethane cfm and hydrographic distributions four water masses could be identified forming the north atlantic deep water nadw system two of these have a high cfm content the shallow upper nadw sunadw and the overflow lower nadw olnadw these exhibit the highest velocity signals at 35 degrees w where distinct flow cores seem to exist most of the southeastward flow of the sunadw centered around 1600 m occurs 320 km offshore between 3 degrees 09 s and 1 degrees 50 s 9 7 3 3 sv farther north in that section a highly variable reversing flow is found in a second velocity maximum the transport of olnadw centered around 3800 m of 4 6 2 6 sv is guided by the parnaiba ridge at 1 degrees 45 s 35 degrees w the water masses located between the two cfm maxima the labrador sea water lsw and the lnadw old water mass lnadw old did not show any persistent flow features however a rather constant transport of 11 1 2 6 sv was observed for these two layers the total southeastward flow of the nadw at 35 degrees w showed a transport of 26 8 7 0 sv if one neglects the reversing sunadw north of 1 degrees 50 s at 5 degrees s the flow of all deepwater masses shows vertically aligned cores the main southward transport occurred near the coast 19 5 5 3 sv the boundary current is limited offshore by a flow reversal present in all three surveys but located at different longitudes at 10 degrees s a southward transport of 4 7 sv was observed in november 1992 however the section extended only to 32 degrees 30 w so that probably a significant part of the flow has been missed an important result is the large transport variability between single cruises as well as variability of the spatial distribution of the flow at 35 degrees w which could lead to large uncertainties in the interpretation of single cruise observations despite these uncertainties we suggest a circulation pattern of the various deepwater masses near the equator by combining our mean transport estimates with other observations

carboniferous calcretes in the canadian arctic calcrete palaeosols have been found in the upper carboniferous canyon fiord formation of southwestern ellesmere island canadian arctic these calcretes were developed in fluvial and shallow marine sediments that accumulated within two adjacent subbasins in which the tectono sedimentary environment led to the deposition of five different sedimentary facies i floodbasin sandstones ii alluvial fan sandstones iii alluvial fan conglomerates iv braided fluvial sandstones and v shallow marine limestones nodular massive palaeosol profiles consisting of cryptic nodular massive and laminar horizons occur within the floodbasin sandstone and alluvial fan sandstone facies plugged palaeosol profiles consisting of cryptic plugged and laminar horizons are restricted to the alluvial fan conglomerate facies massive brecciated palaeosol profiles consisting of cryptic massive brecciated and laminar horizons occur essentially within the shallow marine limestone facies the relationships between calcrete profiles and sedimentary facies suggest that profile types were controlled mainly by the texture and composition of the parent material nodular massive profiles are restricted to silicate rich sandstone hosts plugged profiles are restricted to carbonate rich conglomerate hosts and massive brecciated profiles are restricted to limestone hosts important relationships also exist between the maturity levels of nodular massive profiles and sedimentary facies profiles are generally mature in the floodbasin sandstones invariably immature in the alluvial fan sandstones and absent from the braided fluvial sandstones these different maturity levels were probably controlled mainly by exposure time vegetation and substrate composition

intermediate water links to deep western boundary current variability in the subtropical nw atlantic during marine isotope stages 5 and 4 records from ocean drilling program sites 1057 and 1059 2584 m and 2985 m water depth respectively have been used to reconstruct the behavior of the deep western boundary current dwbc on the blake outer ridge bor from 130 to 60 kyr b p marine isotope stage mis 5 and the 5 4 transition site 1057 lies within labrador sea water lsw but close to the present day boundary with lower north atlantic deep water lnadw while site 1059 lies within lnadw high resolution sortable silt mean inline equation grain size and benthic 13c records were obtained and changes in the dwbc intensity and spatial variability were inferred comparisons are made with similar proxy records generated for the holocene from equivalent depth cores on the bor during mis 5e inline equation evidence at site 1057 suggests slower relative flow speeds consistent with a weakening and a possible shoaling of the lsw sourced shallower limb of the dwbc that occupies these depths today in contrast the paleocurrent record from the deeper site suggests that the fast flowing deep core of the dwbc was located close to its modern depth below 3500 m during this interval the benthic 13c suggests little chemical stratification of the water column and the presence of a near uniform lnadw dominated water mass after 111 kyr b p the inline equation record at site 1057 increases to reach values similar to site 1059 for the rest of mis 5 the strengthening of flow speeds at the shallow site may correspond to the initiation of glacial north atlantic intermediate water formation also suggested by a divergence in the benthic 13c records with site 1057 values increasing to 1 2 coupled suborbital oscillations in dwbc flow variability and paleohydrography persisted throughout mis 5 comparison of these data with planktonic 18o records from the sites and alkenone derived sea surface temperature sst estimates from the nearby bermuda rise suggest a hitherto unrecognized degree of linkage between oscillations in subtropical north atlantic sst and dwbc flow

insights into pore scale controls on mudstone permeability through resedimentation experiments at a given porosity mudstone permeability increases by an order of magnitude for clay contents ranging from 57 to 36 2 m this increase in vertical permeability results from a dual porosity system that develops through three mechanisms 1 silt bridging preserves large pore throats 2 stress bridges inhibit clay particle alignment and 3 local clay particle compression within stress bridges alters pore throat size distribution uniaxial consolidation experiments on resedimented clay silt mixtures illuminate how permeability varies as a function of clay fraction during burial backscattered electron microscope images show that silty mixtures have larger pore throats and fewer aligned clay particles than do more clay rich mixtures we describe the permeability of clay silt mixtures with a geometric mean model our method provides a promising framework for modeling of mudstone permeability as a function of clay fraction and porosity how permeability and consolidation evolve during burial affects the ability of mudstones to seal co2 and hydrocarbons in the subsurface how mudstones behave as gas reservoirs and under what conditions mudstones will be overpressured dual porosity systems have fundamentally different transient flow and solute transport behaviors

updip limit of the seismogenic zone beneath the accretionary prism of southwest japan an effect of diagenetic to low grade metamorphic processes and increasing effective stress off southwest japan the seaward limit of coseismic displacement or updip limit of the seismogenic zone of the 1946 mw 8 3 thrust earthquake reaches to 4 km depth and 40 km landward of the trench this limit coincides with the estimated location of the 150 c isotherm and has been linked to changes in physical properties associated with the smectite to illite clay mineral transition here we show that this limit correlates with a suite of diagenetic to low grade metamorphic processes characterized by 1 declining fluid production and decreasing fluid pressure ratio and 2 active clay carbonate and zeolite cementation and the transition to pressure solution and quartz cementation these diagenetic to low grade metamorphic changes cause the onset of velocity weakening during thrust faulting an increase in effective stress and strengthening of the hanging wall which together combine to produce recordable earthquakes

modeling subsurface flow in sedimentary basins groundwater flows that arise in sedimentary basins from the effects of topographic relief buoyant convection sediment compaction erosional unloading and combinations of these driving forces can be described using quantitative modeling techniques models can be constructed to consider the effects of heat and solute transport petroleum migration and the chemical interaction of water and rocks the accuracy of model predictions however is limited by the difficulty of predicting hydrologic properties of sediments on regional dimensions estimating past conditions such as topographic relief and knowledge of how physical and chemical processes interact over gelogic time scales progress in basin modeling will accelerate as hydrologic research efforts are better integrated with those of other specialities such as sedimentology rock mechanics and geochemistry

kuwaiti dolocrete petrology geochemistry and groundwater origin abstract near surface sediments in southern kuwait show extensive development of duricrusts the host materials are siliciclastic sandstones of the post eocene kuwait group inland the duricrusts are dominantly pedogenic calcrete with some silcrete and gypcrete whereas within 10 20 km of the coast dolomite is the dominant duricrust mineral both these dolocretes and the inland calcretes display a similar maturation sequence in which carbonate rich nodules develop and coalesce carbonate progressively replacing and displacing detrital grains the dolomite of the dolocretes forms mosaics of crystals typically 10 70 m in size varying from simple rhombs to spherulites an intermediate morphology named artichoke dolomite from its appearance in sem is particularly abundant authigenic palygorskite is associated with the dolomite dissolution of cores or zones within dolomite crystals has occurred calcite is present as sparry crystals always post dating dolomite and is the expected precipitate from present day soil and groundwaters chemical analyses of dolomite show highly negative values of 13 c to 10 7 pdb and 18 o varying from 0 6 to 3 3 pdb the oxygen isotope values are interpreted as reflecting evaporation of a marine based fluid manganese values of around 1000 ppm show that this fluid was reducing strontium data show variability reflecting mineral fluid reactions the general absence of metastable carbonates and presence of zoning in dolomite crystals suggests that meteoric dilution of seawater also occurred given that the duricrusts lack biogenic features the light carbon isotope values are taken to indicate oxidation of seeping hydrocarbons the dolocretes are interpreted as groundwater precipitates near the water table of a brackish water body formed at a time of higher relative sea level than today

geomorphological analysis of paleo drainage systems and their environmental implications in the desert of kuwait a well developed drainage network is carved in the hard calcretized and gypcretized gravelly sand of the pleistocene dibdibba formation in northern kuwait the present day aridity suggests that these drainages were developed during pluvial episodes that took place in the post pleistocene time and therefore are considered as paleo drainage detailed morphometrical analysis of the endoeric drainage systems was performed and the degree of correlation among their different morphometric parameters was investigated based on these parameters the studied drainage basins are statistically grouped into three groups such grouping was confirmed by discriminant analysis the categorical data analysis demonstrated the dependence of these groupings on the surface geology regional topography and local geomorphological settings infiltration measurements revealed that the drainage bedrocks have a low infiltration rate 20 cm h 1 whereas the drainage fill deposits have a relatively high infiltration rate 67 30 cm h 1 the impact of the drainage system pattern and morphometry on the hydrological conditions is discussed and potential near surface low salinity to freshwater aquifers is delineated the role of the studied drainage systems in the occurrence of mobile sand and sand dunes rainwater harvesting and land capability are discussed

recirculating components to the deep boundary current of the northern north atlantic abstract the meridional overturning system of the north atlantic is conventionally thought of as transporting warm water 4 c to high latitudes and covd water to low latitudes the northern cold water sources for this system are dense overflow from the nordic seas and less dense water from the labrador sea lsw the overflow components are carried westward by a deep northern boundary current dnbc that is shown here actually to begin southeast of the overflow regions the dnbc lies along the southern side of a system of islands and submarine ridges that divides the nordic seas from the subpolar basins the overflows act to increase the transport of the dnbc and this transport is further increased through the entrainment of warm waters once inside the labrador sea the dnbc is joined by lsw before continuing south to low latitudes as a cold deep western boundary current dwbc however published transport estimates are larger than can be explained by warm water entrainment alone thus indicating entrainment also of recirculating cold components the subject of this paper their sources are shown to be the lsw and cold abyssal waters originating from the southern hemisphere the lsw is entrained downward into the denser part of the dnbc and laterally into the upper part of the dwbc whereas the cold abyssal waters are supplied by an eastern intensified northward flow in the eastern atlantic that serves as the initial source of the dnbc and by a similar northward flow in the western atlantic the meridional overturning system described includes recirculations and poleward transport of cold water in addition tothe components described by the conventional system the cold abyssal waters in both the eastern and western basins have relatively low levels of oxygen and high concentrations of silicate reflecting their southern origin but their influence in the northwestern atlantic is somewhat obscurred by strong recirculating cyclonic gyres in the newfoundland and labrador basins this influence is detected by a deep silicate maximum extending poleward from the mid latitude western atlantic through the two gyres with eastern concentration and recirculating back diluted toward the south in the dwbc within the respective basins such a maximum also extends northward through the irminger basin into the dnbc but there is an ambiguity as to whether this is a direct extension of the signal from the south in the western basin or if it comes from the mid latitude eastern basin by way of westward flow through the charlie gibbs fracture zone it is perhaps consequence of both estimates of the volume transports of the various recirculating cold components indicate that they supply about as much water to the deep boundary currents as do the combined cold water sources in the north

sedimentological characteristics of the surficial deposits of the jal az zor area kuwait abstract the purpose of this article is to discuss the nature and characteristics of the surface geology of the jal az zor escarpment and the adjacent area to better understand the sedimentology of desert landforms and the main factors controlling depositional and diagenetic processes active in this environment the oldest outcrops along the face of the escarpment are the sand and sandstone sequences of the mutla and jal az zor formations of the kuwait group neogene gravelly deposits of the upper member of the kuwait group dibdibba formation pleistocene are restricted to a few hillocks and ridges in the summit area of the escarpment the neogene deposits in most of the study area are overlain by a veneer of unconsolidated holocene sediments these were classified according to their morphological setting and field occurrence into coastal deposits intertidal mud sabkha deposits and sand dunes and inland deposits sand drifts slope deposits wadi fills residual deposits and playa deposits wind born quartzitic sand is the most common holocene sediment in the study area indicating the dominance of the aeolian processes gypsum and carbonate present as cementing materials or in the form of gypcrete and calcrete respectively are characteristic sedimentological features of the pre holocene deposits gypcrete and gypsum cement are abundant in the upper section of the escarpment and decreases downward whereas the carbonate calcrete shows a reverse pattern i e it becomes more dominant in the lower section of the escarpment the source of sulphate ions in the groundwater that is responsible for the development of gypcrete is believed to be the evaporites in the lower section of the neogene sequence the source of ions for the formation of calcrete and calcite cement is less understood due to the lack of significant primary carbonates in the near surface deposits it is believed that the nature and distribution of the chemically precipitated material gypsum and carbonates are controlled by the chemistry and hydrodynamics of the groundwater which in turn are controlled mostly by the climatic conditions during their development and the lithology of the host sediments arid and semi arid climatic and paleoclimatic conditions are considered the most critical factors affecting the depositional and diagenetic processes impacting surficial deposits of the jal az zor area

mean atlantic meridional overturning circulation across 26 5 n from eddy resolving simulations compared to observations 1 observations along 26 5 n are used to examine the time mean structure of the atlantic meridional overturning circulation amoc in eddy resolving simulations with the hybrid coordinate ocean model hycom the model results yield a 5 year mean amoc transport of 18 2 sv compared to 18 4 sv based on data the modeled northward limb of the amoc has a vertical structure similar to observations the southward limb is shallower than observed but deeper than other ocean general circulation models and includes a secondary transport maximum near 4000 m corresponding to nordic seas overflow water the modeled flow through the florida strait and the deep western boundary current dwbc east of abaco bahamas are also approximately consistent with observations the model results are used to clarify the sources of the northward amoc transport and to explore the circulation pattern of the southward transport in the western subtropical north atlantic in the range 18 33 n about 14 1 sv of the modeled northward amoc transport is through the florida strait and the remainder through the mid ocean primarily in the ekman layer but also below 600 m the modeled amoc transport is about 2 3 surface water and 1 3 antarctic intermediate water with no contribution from the thermocline water in between in the western subtropical north atlantic the model results depict a complicated deep circulation pattern associated with the complex bathymetry the dwbc flows southward then eastward in both the upper and lower north atlantic deep water nadw layers but with different offshore recirculation pathways and there exists a second more northern branch of eastward flow in the lower nadw layer

western boundary current structure and variability east of abaco bahamas at 26 5 n abstract during april 1987 to june 1988 a four mooring transport resolving current meter array was deployed in a section extending 70 km eastward from abaco bahamas at 26 5 n mean currents in the upper layer 800 m showed a clockwise rotation that appears to be associated with a small scale quasi permanent anticyclonic gyre centered just northeast or the bahamas deep mean currents were persistenly southward and indicated a strong deep jet the deep western boundary current dwbc reaching core speeds of 20 cm s 1at 2500 m depth about 25 km seaward of the western boundary vertically integrated meridional volume transport over the section showed a surprisingly large variability ranging from approximately 20 sv northward to 70 sv southward 1 sv 106m3s 1 the mean meridional volume transport was 30 sv to the south with about 3 sv flowing northward above 800 m which could be produced by a weak antilles current and 33 sv flowing southward below 800 m the deep southward transport of 33 sv i

an overview of the tertiary geology and hydrogeology of the northern part of the arabian gulf region with special reference to kuwait abstract tertiary sediments constitute the main source of usable groundwater in kuwait tectonics depositional environment lithology and the hydrogeology of these sediments have been reviewed on a regional scale with special reference to kuwait the review showed that kuwait was situated at the boundary of the stable shelf towards southwest and the unstable shelf towards northeast throughout the tertiary period the tertiary sedimentation started in this area with a marine transgression in the palaeocene shallow marine to sabkha conditions prevailed in the area until the end of the eocene a carbonate evaporite sequence umm er radhuma rus and dammam formation was deposited during this period the sea regressed at the end of eocene and a widespread unconformity causing the absence of oligocene deposits over most of the area marked the event the karstification of the dammam limestone formation that provides localized easier pathways for ground water took place during this period the deposition of the clastic sediments of the kuwait group and its equivalents on the stable shelf under mostly continental conditions started in the early miocene the tertiary aquifers of the area are recharged by occasional rainstorms in the outcrops of saudi arabia and iraq the water flows towards the north and east in the direction of the regional dip and discharges along the present day coast of the gulf the water quality deteriorates in the same direction being more mineralized as it flows through the aquifers the aquifers are presently being exploited at a comparatively high rate since the aquifers extend beyond the political boundaries cooperation among the countries of the region is recommended to ensure the optimum utilization of the scarce water resources of this desert environment

an improved technique for computing permeability from nmr measurements in mudstones 1 we develop a technique for extending nuclear magnetic resonance nmr permeability estimation to clay rich sediments our technique builds on the schlumberger doll research sdr equation by using porosity grain size specific surface and magnetic susceptibility data to yield more accurate permeability estimation in mudstones with large pore surface areas and complex mineralogies based on measurements of natural sediments as well as resedimented laboratory mixtures of silica bentonite and kaolinite powders we find that our method predicts permeability values that match measured values over four orders of magnitude and among lithologies that vary widely in grain size mineralogy and surface area our results show that the relationship between nmr data and permeability is a function of mineralogy and grain geometry and that permeability predictions in clay rich sediments can be improved with insights regarding the nature of the pore system made by the kozeny theory this technique extends the utility of nmr measurements beyond typical reservoir quality rocks to a wide range of lithologies

tracing lower north atlantic deep water across the equator water whose ultimate source is the overflow at the denmark strait can be traced using maps of salinity dissolved oxygen and silica concentration on deep density surfaces south along the american continent to at least 5 s several property extrema whose resolution is at the limit of accuracy of the measurements occur on these density surfaces which nevertheless may indicate areas of stronger mixing along the crest of the mid atlantic ridge transport estimates for that part of the southward flow within 600 km of the western boundary near 10 n suggest that 10 3 106 m3 s 1 of lower north atlantic deep water moves south there the total southward deep water transport near 10 n is estimated to be closed to 25 106 m3 s 1

a laboratory model of exchange and mixing between western boundary layers and subbasin recirculation gyres chaotic advection is suggested as a possible mechanism for fluid exchange and mixing among a western boundary current and subbasin recirculation gyres applications include the north atlantic deep western boundary current and its adjacent mesoscale recirculation gyres visualization and quantification of certain aspects of chaotic advection in a laboratory analog are described depending on the strength of the forcing recirculating fluid offshore of the western boundary layer may be contained in a single gyre not favorable for chaotic advection or twin gyre with a figure eight geometry favorable for chaotic advection when time dependence is imposed on these steady flows by varying the forcing periodically the resulting fluid exchange stirring and mixing is most dramatic in the case of the twin gyre a template for these processes can be formed by highlighting certain material contours invariant manifolds using dye and other techniques these objects can be used to identify blobs of fluid turnstile lobes that are carried into and out of the gyres the associated transports and flushing times can be estimated the preferential stirring and mixing in the twin gyre case is quantified by calculating the effective diffusivity of the flow field based on snapshots of the dye fields at longer times the experiment suggests how tracers in a western boundary current might be transported into and out of neighboring recirculations and where regions of strong zonal or meridional transport might occur