origin and accumulation of trace elements in sediments of the northwestern mediterranean margin continental margins receive natural and anthropogenic trace elements tes from direct atmospheric deposition of aerosols onto the sea surface and from advection of riverine suspended particles and or resuspended sediments from the continental shelf slope when the margin is incised by submarine canyons as for example in the northwestern mediterranean sea most of these particles are preferentially transferred via these topographic features towards their final repositories in the abyssal plain the gulf of lions gol shelf receives the largest particulate riverine input to the western mediterranean with its associated chemical contaminants originating from the industrialized and urbanized rhone valley sediments samples grabs cores and moored traps collected in the cap de creus cdc canyon and its adjacent areas at the southwestern exit of the gol were analyzed to explore the origin dispersion transfer and accumulation of a suite of tes ag cd co cr cu ni pb zn and v from the gol shelf to the adjacent continental rise distributions of cu cr ni pb zn and v in the surface sediments of the shelf confirm their terrigenous origin in association with clay minerals whereas ag and cd are more associated with organic matter om all these tes are anthropogenically enriched in the rhone prodelta sediments anthropogenic influence remains clearly discernible in the gol shelf surface sediments for ag pb and zn hydrodynamical resuspension and sorting of shelf sediments occur at the head of the cdc canyon during dense shelf water cascading events during these events the material collected in moored sediment traps contains a higher coarse carbonate fraction slightly impoverished in tes compared to the clays of the nepheloid layer and the organically rich particles deposited before and at the end of the cascading period upper and middle canyon sediments are characterized by high sedimentation rates 0 2 cm yr 1 of fine clay material conversely sediments from the lower continental slope and rise exhibit low sedimentation rates 0 06 cm yr 1 and receive carbonaceous planktonic detritus from the water column at the lower continental slope coarse material includes foraminifers and pteropods whereas at the continental rise finer planktonic derived material is more abundant both in the cdc canyon and in its adjacent lower continental slope rise sediments co cu cr ni and v are associated with clay whereas ag cu and pb are preferentially associated with om cadmium cr and zn are also associated with om in canyon sediments carbonaceous plankton appears to be especially efficient for scavenging ag

effects of ice coverage and ice rafted material on sedimentation in the fram strait as little is known about pelagic sedimentation processes in arctic environments1 the interpretation of biological and chemical processes as well as the reconstruction of ancient conditions including those in the glacial north atlantic is difficult here we provide sediment trap results which show that the position of the sea ice boundary significantly influences the particle flux the seasonal variability of the particle flux differed markedly in the various sediment trap sites in fram strait depending on the behaviour of the sea ice under complete ice cover sedimentation is very low whereas maximum sedimentation is found at the ice margin the highest particle flux observed showing a large lithogenic component was observed at the ice edge where the water was warmer 2 c we find that high biogenic opal fluxes are characteristic of the summer ice margin indicating that the sedimentary record of opal fluxes may allow the position of ice margins in the past to be reconstructed

the arctic ocean ice balance a kalman smoother estimate the methodology of kalman filtering and smoothing is used to integrate a 7 year time series of buoy derived ice motion fields and satellite passive microwave observations the result is a record of the concentrations of open water first year ice and multiyear ice that we believe is better than the estimates based on the microwave data alone the kalman procedure interprets the evolution of the ice cover in terms of advection melt growth ridging and aging of first year into multiyear ice generally the regions along the coasts of alaska and siberia and the area just north of fram strait are sources of first year ice with the rest of the arctic ocean acting as a sink for first year ice via ridging and aging all the arctic ocean except for the beaufort and chukchi seas is a source of multiyear ice with the chukchi being the only internal multiyear ice sink export through fram strait is a major ice sink but we find only about two thirds the export and greater interannual variation than found in previous studies there is no discernible trend in the area of multiyear ice in the arctic ocean during the 7 years

observation and modeling of the winter coastal oceanic circulation in the gulf of lion under wind conditions influenced by the continental orography fetch experiment fluxes surfaces waves remote sensing and ocean circulation in the north mediterranean sea results from the fetch experiment 1 hydrological and currentmeter observations were collected on the continental shelf and slope of the gulf of lion during the fetch experiment 13 march to 15 april 1998 results from the first part of the cruise characterized by strong northern winds are presented the hydrological structures evidence well mixed water masses on the eastern and western ends of the shelf in the central part the situation is more complex with the influence of the rhone river s freshwater plume in the first 40 m of the water column and closer from the bottom with the confrontation of downwelled coastal cold water and upwelled warmer and saltier slope water current measurements show the path of the cyclonic circulation along the slope which is part of the general circulation of the western mediterranean and suggest the presence of large and temporary eddies on the shelf this oceanic circulation is simulated with a free surface three dimensional model using realistic forcing the model outputs are in agreement with the main hydrological and circulation patterns the results further indicate that coastal eddies are generated by the mesoscale structure of the wind field

timeseries of polar water properties in fram strait 1 timeseries of temperature and salinity of polar water in the east greenland current egc and on the east greenland shelf at 79 n are presented the observations in the egc are made in the 45 74 dbar layer carrying liquid freshwater from the arctic ocean to subarctic seas the properties on the outer fringe of the egc are dominated by shifts of the position of the east greenland front egf in the inner part of the egc and on the shelf the seasonal cycle of the properties are dominated by the annual cycle of sea ice freezing and melting comparing the observations with the world ocean atlas woa and other climatologies demonstrates that the climatologies in the egc and on the shelf at 79 n are poor due to poor data coverage

rapid and widespread dispersal of flood sediment on the northern california margin the dispersal of flood sediment from small river systems is a poorly studied yet potentially important aspect of active continental margin sedimentation in january 1995 during a flood with a 30 yr return period the eel river northern california delivered an estimated 25 3 106 t metric tons of fine grained 62 m sediment to the ocean the flood formed a distinct layer on the sea bed that was centered on the 70 m isobath extended for 30 km along shelf and 8 km across shelf and was as thick as 8 5 cm but contained only 6 106 t of sediment thus 75 of the flood derived sediment did not form a recognizable deposit but was instead rapidly and widely dispersed over the continental margin stratigraphic models of and compilations of sediment flux to active continental margins need to take the dispersive nature of small river systems into account

morphological changes and sedimentary processes induced by the december 2003 flood event at the present mouth of the grand rhone river southern france the study which is based on repetitive bathymetric surveys assesses changes and effects of one of the most important floods recorded in the rhone delta area bottom morphology and sediment distribution in the rhone outlet after the december 2003 flood are discussed by comparison between digital terrain maps dtms of november 2003 and january 2004 the post flood morphology shows that the whole of the system is active mainly in the east the channel of the rhone has been hollowed out on the left bank by more than 5 m the eastern coast of the mouth has retreated 400 m the mouth bar has prograded 200 m and the slope of the delta front has increased by 0 19 the overlay of pre and post flood dtms makes it possible to estimate the total volume deposited in the 0 to 20 m zone as 7 8 10 the acquisition of bathymetric measurements immediately before and after a major flood allows more than a simple morphological description in addition an analysis of the solid load transfer processes towards the prodelta is achievable three mechanisms are highlighted most of the material eroded in the channel and supplied to the delta front corresponds to fine sediment that drape homogeneously over the pre flood morphology of the delta front the transit of the coarsest sediment primarily sand is slowed down in the channel of the rhone this sediment builds up in relatively small areas leading to the formation of gullies on the prodelta slope the gullies have fixed positions and disappear gradually towards the west following the progressive migration of the active band towards the east these old features are not reactivated by floods occurring after their formation during the flood only a small volume of coarse sediment bypasses through the gullies and the fine deposits are remobilised rapidly or compacted flood input concerns essentially the delta front which traps 90 of the fluvial solid discharge between 0 and 20 m depth the coarse prodelta supply is then due mainly to mass movements of unconsolidated material deposited beforehand on the top of the delta front consequently the main nourishment of the prodelta does not occur directly during and or immediately after a flood event but is delayed by sediment being temporarily trapped on the delta front

pathways and modification of the upper and intermediate waters of the arctic ocean 1 the purpose of this study is to investigate the pathways and the ventilation of source water masses of the upper and intermediate waters of the arctic ocean for the arctic and subarctic domain a coupled ice ocean general circulation model is set up to be integrated for several decades it is driven by a climatological seasonal cycle of monthly mean atmospheric data from 1980 to 1989 and by restored sea surface salinities passive tracers are used to visualize and interpret the modeled flow and to compare it with observations the model is able to reproduce known features of the arctic ocean circulation like the inflow of two branches of atlantic origin via the fram strait and the barents sea and their subsequent passage at middepths in several cyclonic circulation cells the fate of these atlantic source water masses river water and bering strait inflow water in the model are studied the branch crossing the barents sea is subject to an intense heat loss and ice formation as a result water of this branch leaves the shelf toward the central part of the arctic ocean not only at the surface but also in denser varieties which finally feed the central arctic at halocline and middepths the lightest part turns northward and finally westward joining the transpolar drift the densest part 200 1000 m depth moves eastward along the continental slope a similar path is taken by the atlantic water branch from the fram strait the inflowing branch over the barents sea turns out to be the dominant source for the lower atlantic water layer in the arctic ocean in this investigation atlantic tracers starting in fram strait need 6 years to reach the northern laptev sea slope travel times to return to fram strait are 15 20 years along the lomonossov ridge and about 30 years along the continental slope of the canadian basin tracers that mark the pacific water or the mackenzie river water flow eastward and leave the arctic mainly via the canadian archipelago the siberian river water tracers at the surface penetrate far into the canadian basin before they join the transpolar drift the travel times of the river water from the river mouths are 2 3 years to the shelf edge and 12 14 years to fram strait

sediment dynamics during wet and dry storm events on the tet inner shelf sw gulf of lions abstract the importance of short term processes such as floods and storms on sediment delivery and reworking on the tet inner shelf was investigated the tet inner shelf is a small event dominated system located in the south western part of the gulf of lions the expected sedimentary scenario in this environment is that fluvial sediment should be deposited on the prodelta and later dispersed around the shelf and slope by wave and current reworking during storms this paper investigates differences in inner shelf sediment dynamics between storm events occurring during usual river discharges and those occurring during river floods waves current velocities near bottom water turbidity bottom sediment grain size and sea floor erosion accretion were concurrently measured at 28 m water depth on the tet inner shelf from november 2003 to march 2004 two major storms took place on 4 december 2003 and 21 february 2004 and two moderate storms occurred on 8 december 2003 and 14 march 2004 the two major storms displayed similar wave characteristics maximum significant wave height h s 7 m peak period t p 12 s and wave direction around 90 the main environmental differences during the two major storm events correspond to the amount of sediment discharged from the tet river about 2 10 4 t of sediment was delivered by the river during the 4 december flood wet storm and less than 5 10 2 t during the 21 february storm dry storm sediment dynamics were quite similar during the storm events resuspension caused by waves and sediment advection towards the southeast due to near bottom shelf currents were the dominant sedimentary processes the result was a bottom sediment erosion of several centimetres at the study site during both the wet and dry events the main differences between the wet and dry events arose after the storm immediately after the peak of the wet storm sediment supplied by the tet river and probably from other rivers was deposited around the river mouth a few days later during a moderate storm this unconsolidated sediment was resuspended transported offshore and deposited on the inner shelf in contrast a moderate storm which occurred some days after the dry february storm caused bottom erosion on the inner shelf because no fresh sediment was available on the shallower area the results from this study indicate that the tet inner shelf at 28 m water depth is mainly a bypass zone for sediment that is transported s se towards the middle outer shelf and slope although ephemeral sediment deposits may be favoured by the sediment supplied from flood events sediment transport across the shelf from the river to the slope follows a complex multi step pattern that needs to be addressed using a multi event approach

diagnostic study of the fram strait marginal ice zone during summer from 1983 and 1984 marginal ice zone experiment lagrangian observations from 1984 marginal ice zone experiment observations in fram strait three main results concerning large scale mesoscale and summer marginal ice zone miz features are presented and discussed in this paper regarding the large scale the main conclusion is that the east greenland current egc is a narrow stable current in contradiction with past results presenting the egc as a broad and unstable current in the mesoscale the west spitsbergen current wsc and the norwegian current are the main generators for eddies in fram strait these eddies propagate northwestward preferentially following topographic features like fracture zones which are quite abundant in this region in our opinion these wsc eddies represent an important part of the atlantic water recirculation in fram strait when approaching the east greenland continental slope they interact with the egc and they form well developed eddies these ice edge eddies associated with ice edge tongues are quite recognizable with remote sensing techniques the summer marginal ice zone in fram strait is clearly characterized by sea ice concentrations from 1 10 to 3 10 and floe sizes limited to 1 km or less there is a well defined limit which separates the pack ice from the miz where no big ice floes are ever recorded the breaking action of waves and swell propagating into the ice are likely to be the only mechanisms explaining such a drastic filtering effect according to their amplitudes and directions winds and eddies act in the miz in shrinking or stretching this zone

transport and depositional process of soil organic matter during wet and dry storms on the tet inner shelf nw mediterranean article i nfo river floods and storm waves are major processes for the dispersal and deposition of terrestrial organic matter om in river dominated coastal areas a wet storm is connected to a flood with a high river discharge while a dry storm is not associated with a flood to better understand the sedimentation dynamics of terrestrial om especially soil om at the land ocean interface during wet and dry storms we studied sediment trap and core material collected on the tet inner shelf nw mediterranean using multiple organic proxies in combination with hydrodynamic parameters the proportion of soil om to the total om in the trap material calculated based on the bit branched and isoprenoid tetraether index was higher during both wet 40 and dry 30 storms than during non storm periods 10 however only surface sediments 1 cm thick layers recovered after december wet and moderate storms in 2003 showed enhanced soil om percentages compared to the deeper sediments deposited during the last century given that the wet storm eroded 4 cm of seabed at the study site flood induced fresh soil om was not deposited on the tet inner shelf during the wet storm however the following moderate storm caused resuspension of flood associated soil om which was previously trapped nearshore accordingly soil om was transported to the tet inner shelf and stored there until the dry storm occurred

recent changes in arctic ocean sea ice motion associated with the north atlantic oscillation examination of a new ice motion dataset of the arctic ocean over a recent eighteen year period 1978 1996 reveals patterns of variability that can be linked directly to the north atlantic oscillation the intensity of the icelandic low one of its centers of action modulates the sea level pressure distribution over a broad region of the arctic ocean and the greenland iceland norwegian and barents seas over the winters of 1988 through 1995 the oscillation has remained in its positive phase contributing to coherent large scale changes in the intensity and character of ice transport in the arctic ocean the significant changes include the weakening of the beaufort gyre the increase in ice export through the fram strait the increase in ice import from the barents kara seas the enhanced eastward transport of sea ice from the laptev sea the weakening of the transpolar drift stream and the reduction in ice extent in the nordic seas all of these changes affect the regional and total sea ice mass balance of the arctic ocean

modern accumulation rates and a sediment budget for the eel shelf a flood dominated depositional environment the northern california continental margin is periodically impacted by geologically significant storms which have a marked influence on terrigenous sediment supply flood deposition and long term accumulation of fine grained sediment on the eel shelf accumulation of eel river muds on the adjacent shelf was investigated using 210pb and 137cs geochronologies in order to understand the fate of sediment discharged by the eel river and to relate patterns of net sediment accumulation 100 yr time scale to sediment dynamics 210pb data demonstrate that modern accumulation of river mud occurs from the 50 m isobath seaward across shelf accumulation rates decrease from maximum mid shelf values of 0 6 1 7 g cm 2 yr 1 to values of 0 2 0 4 g cm 2 yr 1 at the shelf break with a spatially weighted mean of 0 5 g cm 2 yr 1 0 4 cm yr for the entire shelf 210pbxs sediment depth profiles from the region of highest accumulation rate are characterized by subsurface intervals of low and uniform activity which are produced by flood deposition in some cores particular 210pbxs activity intervals may be associated with major eel river floods of 1955 1964 and 1974 it is postulated that because of the coincidence of high river flow events and southerly winds during cyclonic winter storms net northward transport allows for preferential deposition of fine grained sediment north of the river mouth over the past 100 years fluvial sediment input combined with marine dispersal processes have produced a mid shelf depocenter evident by both the spatial distribution of 210pb accumulation rates and by clay rich flood layers partially preserved in shelf deposits a fine grained sediment budget for the dispersal system based on hydrological data and 210pb geochronologies demonstrates that a maximum of 20 3 109 kg yr of the mean annual supply of fluvial mud 14 109 kg yr is trapped on the shelf the results of this study demonstrate that 1 short term sedimentation processes associated with floods can influence sediment accumulation on longer time scales and 2 a major fraction of fine grained sediment supplied to tectonically active margins by flood prone mountainous rivers bypasses narrow continental shelves

small rivers contribution to the quaternary evolution of a mediterranean littoral system the western gulf of lion france abstract along the mediterranean coasts and the atlantic french coast former and actual research programs focused on major river systems estuaries and deltas characterized by a last glacial relative sea level lowstand and incision and a well developed sedimentary incised valley infilling deposited during the following sea level rise and highstand this paper presents the preliminary results of a program focused on a particular area of the gulf of lion coast with a thin sedimentary cover over the substratum and only minor rivers with non apparent and important sedimentary contribution during the late quaternary the results show that in this area the best pliocene to actual sedimentary record is preserved the paper rests on the analysis of an extensive database of recent high resolution and very high resolution seismic reflection lines and previously published core data seismic data show that a major complex of paleovalleys connected with the orb aude and agly rivers is preserved on the inner shelf and adjacent coastal plain on the inner shelf the separated incised valleys merged in a unique broad and shoreparallel incision dipping southward at the southward extremity the incision turns eastward and seaward the basal surface of this incision extends seawards under six to seven late quaternary depositional sequences preserved on the mid and outer shelf the infilling of the complex of paleovalleys is characterized by aggrading deposits attributed to periods of relative sea level rise transgressive systems tracts organized into several subunits bounded by internal discontinuities locally deeply incising the discontinuities are amalgamated surfaces including successive sequence boundaries indicative of phases of relative sea level falls merged with transgressive surfaces indistinct tidal and wave ravinement surfaces the subunits are the part of late quaternary depositional sequences preserved in estuarine environments they are the lateral equivalents of landward fluvial terraces and seaward coastal and prodeltaic deposits on the shelf using borehole dataset the underlying and eroded deposits below the basal unconformity are correlated with pliocene deposits outcropping landward in the hinterland the top of the incised valleys complex is capped by the last glacial lowstand surface of erosion 18 ky b p reworked by the postglacial transgressive surface ts dissociated near the shoreline into a tidal and a wave ravinement surfaces above the ts the very high resolution vhr seismic data in the lagoons the tidal channels and cores reveal in details the stratigraphic architecture of the deposits at the base a small wedge constitutes the postglacial transgressive systems tract tst locally thinning in the areas distant of the sediment point sources the tst is capped by a flat surface of wave reworking maximum flooding surface or mfs prolongating under the leucate lagoon and merging offshore at the seafloor boreholes and vhr seismic lines trough the coastal barrier and in the lagoon show that the shoreline probably migrated far landward at the end of the transgression when the rate of sea level rise decreased strongly the shoreline migrated seaward and prograding and aggrading sandy material with landward muddy lateral equivalent facies deposited early highstand systems tract hst above the mfs offshore fine material deposited as a sigmoidal blanket of mud originating in part from the north east and rhone river under oceanic circulation equivalent to a subaqueous prodelta subsequently the modern beach barrier built up by wave reworking of the early hst this new study of the western part of the gulf of lion inner shelf and littoral illustrates an incised valley complex and thus presents the best preserved example of the sedimentary record of the effects of the relative sea level changes during the pliocene to actual period for the first time the land to sea transition is preserved and the late quaternary depositional sequences are in a great part observed the last post glacial deposits present a simplified but very different organisation compared to a record front of the adjacent rhone river consequently a synthesis is now possible

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

a 2000 yr record of sacramento san joaquin river inflow to san francisco bay estuary california oxygen and carbon isotopic measurements of fossil bivalves macoma naarfa contained in estuarine sediment are used to reconstruct a late llolocene record of sitlinity and stream flow in san francisco bay discharge into the bay is a particularly good indicator of paleoclin ate in california because the bay s influent streams drain 40 of the state the isotopic record suggests that hetween al oul 1670 ant1 1900 calcnd r yc trs yr cal 1i i inflow to the bay was sul stantially greirler tlian the cstinli tecl precliversion inllow ol 1100 m3 s an unconforn ity representing a 900 yr hiatus is present in the core between 1670 ancl 750 yr cirl ii 13 possil ly r lusc cl by i n tjor 11ydrologic rl event over the p ist 750 yr strcitn ilow to s iii i ril cisco ikty ii is vitrirtl wit11 i pcriotl ol 200 yr i1lter11itte wet iltttl tlry i tlrougl t intc r rls typiritlly 11 rvc i lstecl 40 to 100 yr

shoreface migrations at the shelf edge and sea level changes around the last glacial maximum gulf of lions nw mediterranean the bourcart herault canyon interfluve in the gulf of lions nw mediterranean was the site of very high sedimentation up to 2 5 m kyr around the last glacial maximum due to the vicinity of major fluvial systems that fed the shelf edge shoreface deposits and offshore muds deposited during each glacial interglacial 100 kyr cycle created a repeated motif with high angle and low angle clinoforms on seismic profiles new detailed morphological sedimentological and paleo environmental data constrained by 14c dating allow us to propose a scenario for the evolution of this critical area between 46 and 15 cal kyr bp the major seismic sequence s5 formed as a forced regression during the overall sea level fall between mis 3 and mis 2 can be sub divided into several prograding units which indicate that relative sea level changes were punctuated by intervals of increased fall or slow down or even stillstand similarly the onset of sea level rise was marked by steps during which wave cut terraces formed and can be tracked all around the gulf of lions three stillstands or slow downs of sea level change are identified and dated by deposits found at 90 m relative sea level 21 cal kyr bp 110 115 m rsl 18 17 cal kyr bp and 98 105 m rsl before 15 9 cal kyr bp cementation of beach rocks that now form eroded pinnacles culminating at 90 m occurred during the 21 kyr stillstand the position of relative sea level during the maximum lowstand is not known but should be deeper than 115 m periods of increased northwesterly winds favoured transport of coarser sediment at the shelf edge in relation with deep water cascading this created a distinct sandy interval during the period of heinrich event 2 around 24 cal kyr bp at the origin of amplitude anomaly on very high resolution seismic data the increased sea level rise around 15 cal kyr bp resulted in an abrupt decrease of sedimentation

sediment budget of the rhone delta shoreface since the middle of the 19th century this study analyses long term 1841 1872 1895 1974 changes in the grand rhone prodeltaic lobe to 1 quantify the accumulation 2 determine the evolution of relict prodeltaic lobes and 3 establish long term relationships between river sediment discharge the shoreface and the continental shelf our results show a reduction of the sedimentation of the prodeltaic lobe at the main river mouth since 150 yr by a factor of 3 7 12 63 to 3 41 10 6 m 3 yr 1 at the minor mouth of the river erosion dominates and speeds up during the same period 0 53 to 1 34 10 6 m 3 yr 1 these changes are found to directly result from the river sediment input decrease related to the natural decreasing of the frequency of major floods end of the little ice age the reforestation in the catchment area the dam construction and the dredging activities since the 1950s our results indicate that while there is large sediment accumulation in the area around a growing prodeltaic lobe there is also a reduced contribution of the river sediments to the non adjacent beaches of the mouth following a shift in the river channel and mouth the relict prodeltaic lobes petit rhone st ferreol bras de fer and pegoulier are reworked by waves and their sediments contribute partially to the growth of the spits espiguette beauduc and gracieuse this suggests that there is a time shift between the input of river sediment to the sea and the build up of a beach the chronic erosion of the coastline is likely to continue in the future since 1 a river shift is not possible because the river channels are controlled by dykes and human intervention 2 the decrease of river sediment input and 3 the relict prodeltaic lobes constitute sedimentary reservoirs that are gradually being used up 2006 published by elsevier b v

formation of the aude orb and herault prodeltas and their characterisation using physicochemical and sedimentological parameters abstract the formation of mediterranean prodeltas depends on microtidal estuarine dynamics the study of the aude estuary and others shows the usual presence of a salt wedge which induces the formation of two turbidity maxima created by two different processes pauc h 1997 fluvio marine interface in a microtidal mediterranean estuarine environment the nepheloid layer supply problem journ rech oceanogr 22 3 83 90 the first process is a loss of charge due to the annulment of the current momentum driving sedimentation of the silt size material the second process is flocculation which results in deposition of fine sediment the end results of the combination of these two processes is a sedimentary sequence with two distinct sediment units silt below and clay minerals above granulometrical and mineralogical analysis of the sediment body enables the zone of sedimentation of each type of material to be determined and hence the style of sedimentation to be inferred illite quartz and dolomite are of detrital origin and accumulate close to the river mouths while smectite is deposited by both dynamical and flocculation processes and accumulating over the surface of the prodelta and also seaward by some 30 40 m depth calcite is of biogenic origin and is found further offshore associated with muddy sediments only

monitoring ice thickness in fram strait time series of ice thickness in fram strait are evaluated together with ice drift for estimation of the ice flux from the arctic ocean ice draft was measured from moored sonars every 4 min suggesting a nominal sampling interval of 30 m on the basis of these data the annual cycle of many statistics can be resolved the modal ice thickness shows a maximum of 3 15 m in may and a minimum in september of 2 43 m indicating an annual variation range of 0 72 m this compares with model results comprehensive drillings and most of the submarine observations during the last 2 3 decades indicating no significant long term ice thickness change this is also concurrent with the lack of significant temperature changes in the arctic ocean during the same period the mean ice thickness in the central core of the ice stream shows an annual amplitude of 1 m with a minimum in september of 2 25 m and a maximum in april may of 3 25 m the mean thickness of ice only open water excluded is 3 27 m and compares with 3 29 m which is the mean thickness of ice only from 17 submarine tracks in the arctic ocean 1960 1982 the mean annual ice export which is equal to the mean annual net production of ice in the arctic ocean is 2850 km 3 yr 1 for the period 1990 1996 this efflux shows significant variations from year to year with a minimum in 1990 1991 of 2050 km 3 yr 1 and a maximum in 1994 1995 of 4700 km 3 yr 1 this significant variation of nearly 130 is mainly caused by an increased atmospheric forcing and to a lesser degree by an increase in the annual mean ice thickness of 20 over the same period

evolution of the rhone delta plain in the holocene abstract the delta plain of the rhone shows many sandy beach ridges cropping out at the surface we propose here a radiocarbon chronology for the accumulation of the sedimentary bodies and an interpretation of the morphology of the mouth lobes that they form morphologies of the lobes depend on four principal factors 1 the variation of the relative sea level which constitutes the morphogenic base level 2 the fluvial input volume of water discharge and sedimentary input number and position of the mouths 3 marine dynamics volume and direction of the longshore drift dominant wave direction 4 the accommodation space created by the rise of relative sea level along with the paleobathymetry onto which the lobe will prograde immediately in front of the delta and at sea our conclusions are the main holocene paleo delta lobes of ulmet and saint ferreol were contemporaneous being deposited from 4000 to 2000 yr bp however the fluvial style of their downstream channel meandering for ulmet channel and linear for saint ferreol and the lobe morphologies of both channels are contrasted rounded in the case of ulmet and elongated for saint ferreol the role of the accommodation space is confirmed by two recent drillholes traversing the entire holocene succession which reveal a prior stage of sedimentary filling in the case of the saint ferreol lobe thus limiting the accommodation space and favouring a rapid and pointed progradation of this lobe the decoupling between hydrological activity and progradation of lobe indicates the complexity of mechanisms in the large catchment basin of rhone however the high rate of progradation of saint ferreol lobe after 2900 bp is probably a consequence of the increase of human activity after this date the variation of relative sea level remains an important factor controlling the evolution of the rhone delta after 6000 bp the local stabilization of the relative sea level between 4585 bp and 3520 bp played an important role in the triggering of coastal progradation saint ferreol lobe eastern margin rhone delta

interannual variability in the hydrography of atlantic water northwest of svalbard using data from 1910 to 1997 we study the mean structure as well as the interannual variability in the autumn hydrography of the part of the west spitsbergen current wsc confined over the upper continental slope and of its continuation the svalbard branch this is known to provide a major pathway for warm and saline atlantic water to the arctic ocean we focus our study on the area northwest of svalbard around 80 n the time series of subsurface hydrography 100 300 m layer show interannual variations which are in the 1980s and 1990s quite coherent with hydrographic time series obtained upstream in the wsc around 76 n as well as with variations in the large scale atmospheric patterns as indicated by the north atlantic oscillation nao index however in the 1970s the coherence is poorer our results suggest that it may be important to focus on the narrow domain of the part of the wsc confined over the upper continental slope in order to get consistent estimates of the arctic ocean inflow signal in the fram strait the warming in this inflow signal in 1970 1996 does not seem to have been as strong as previously suggested

variability of fram strait ice flux and north atlantic oscillation we estimate the winter sea ice export through the fram strait using ice motion from satellite passive microwave data sea ice motion october may is obtained by tracking the displacement of common features in sequential 85 and 37 ghz brightness temperature fields the average winter area flux over the 18 year record 1978 1996 is 670 000 km2 7 of the area of the arctic ocean the winter area flux ranges from a minimum of 450 000 km2 in 1984 to a maximum of 906 000 km2 in 1995 the daily monthly and interannual variabilities of the ice area flux are high there is an upward trend in the ice area flux over the 18 year record the average winter volume flux over the winters of october 1990 through may 1995 is 1745 km3 ranging from a low of 1375 km3 in the 1990 flux to a high of 2791 km3 in 1994 the sea level pressure gradient across the fram strait explains more than 80 of the variance in the ice flux over the 18 year record we use the coefficients from the regression of the time series of area flux versus pressure gradient across the fram strait and ice thickness data to estimate the summer area and volume flux the average 12 month area flux and volume flux are 919 000 km2 and 2366 km3 we find a significant correlation r 0 86 between the area flux and positive phases of the north atlantic oscillation nao index over the months of december march correlation between our 5 years of volume flux estimates and the nao index gives r 0 56 during the high nao years a more intense icelandic low increases the gradient in the sea level pressure by almost 1 mbar across the fram strait thus increasing the atmospheric forcing on ice transport correlation is reduced during the negative nao years because of decreased dominance of this large scale atmospheric pattern on the sea level pressure gradient across the fram strait

the formation of sedimentary strata in an allochthonous shelf environment the washington continental shelf nittrouer c a and sternberg r w 1981 the formation of sedimentary strata in an allochthonous shelf environment the washington continental shelf mar geol 42 201 232 models of fine scale 120 m shelf regions the inner shelf sand and mid shelf sandy silt are the predominant accretionary deposits on the shelf important sedimento logical observations obtained by boxcoring the upper 1 2 m of these deposits are a progressive decrease in grain size with distance from the columbia b downward coarsening within the seabed c loss of distinct sedimentary structure homogenization of sediment with distance from the columbia non dimensional parameters based on sediment transport and benthic biological studies can be used to relate rates of sediment mixing re working to rates of accumulation these parameters have the potential for quantitative prediction of strata formation from measurements of active processes physical and biological mixing can be assumed to remain relatively constant in an alongshelf direction on the washington shelf and accumulation rate is known from pb 210 geochronology to decrease away from the columbia together these factors tend to increase the ratio of mixing to accumulation with distance from the columbia and predict the sedimentological observations listed above

fate of metals in coastal sediments of a mediterranean flood dominated system an approach based on total and labile fractions the dynamics of sediment bound metals cs cu ni pb ti and zn were studied off the tet river western gulf of lion a typical mediterranean coastal river punctuated by short and violent flash floods spatial and temporal sampling strategies were combined to elucidate the fate of these elements in response to both the riverine sediment input and the offshore transport of these sediments through hydrodynamics our results show the temporal entrapment of riverborne particles and associated metals consecutively to a major flood event in the nearshore sedimentary unit called prodelta here deposition and resuspension mechanisms define a sedimentological cycle that could be followed completely in this study in terms of speciation between reactive labile and residual fractions along the fluvio deltaic continuum our results show that cu pb and zn are the most labile potentially mobile metals in the river in accordance with their contributions from anthropogenic sources but in the marine surficial sediments two main behaviours can be discriminated when compared to the riverine suspended particulate matter while pb and zn depict rather a constant labile fraction cu is characterized by decreasing levels up to 50 difference in terms of environmental impact these contrasting trends have direct repercussions for the contaminant dispersal in the coastal area whereas pb and zn conserve their enhanced levels because of their stronger affinity with fine sediments cu is marked by the entire loss of its anthropogenic component that is progressively transferred to the dissolved phase likely mediated by organic ligands we ascribe these behaviours to different post depositional partition mechanisms with respect to oxidation of the particulate organic phase at the bottom sediment water interface also analysis of one sediment core from the prodelta indicates that these early diagenetic processes govern the chemical forms of land derived contaminants sequestrated in the nearshore sedimentary archives c 2011 elsevier ltd all rights reserved

3 d process modelling of ancient storm dominated deposits by an event based approach application to pleistocene to modern gulf of lions deposits abstract a new numerical model was developed for 3 d characterization of deposits generated by storms along clastic coasts away from major rivers it is based on the assumption that the preserved sedimentary heterogeneities result mainly from a succession of deposits generated during both fair weather periods and major events storms in our case hydro sedimentary processes are first modelled during these major storms i transport parallel and transverse to the coast of suspended sediment by the strongest unidirectional currents littoral drift and downwelling currents ii sea bed erosion due to shear stress generated by unidirectional and wave induced oscillatory currents iii deposition of sediment fair weather deposits are modelled by an average deposition process the results of the numerical model i e the description of the sedimentary deposits are multi lithologic in three dimensions and with a flexible vertical resolution the latter is one of the main strengths of the model because the vertical description of the deposits can be adapted to the duration and extent of the simulation in order to save computation time very precise results definition of less than 1 mm can be obtained at a small time scale for storms lasting several hours to several days and reservoir scale results at a longer time scale the numerical model was applied to the gulf of lions which is located off the southern french coast in the north western mediterranean first present day storm deposits are simulated in order to validate the storm process modelling then sedimentary deposits formed over several thousands of years during the pleistocene are simulated in order to validate the sediment deposit modelling the model results fit well with observations and validate the approach of simulating the shelf deposits and their associated sedimentary heterogeneities at reservoir scale with an event and process based method this innovative approach seems promising for providing future geological models with realistic petrophysical properties

cretaceous paleogeography in china abstract the paleogeography of china is represented by four maps the neocomian aptian albian cenomanian santonian and the campanian maastrichtian the continental interior of china was characterized by large lake systems in tectonic depressions and intermontane basins with little or no marine influence shallow epicontinental cretaceous seas were limited by the eastern margins and to the tectonic troughs of the southern and western tibetan plateau in contrast to the detailed knowledge of the interior cretaceous deposits of china the record of the marine invasions is known only in a general way

early muddy deposits along the gulf of lions shoreline a key for a better understanding of land to sea transfer of sediments and associated pollutant fluxes large quantities of sediment introduced by rivers especially during flood events lead to the formation of prodeltaic structures characterized by fine grained deposits in the proximal area of the shelf according to their mean grain size it is largely admitted in the literature that these deposits mainly stand below the storm wave base in the gulf of lions nw mediterranean however our data show that these muddy sediments also exist above the storm wave limit in the uppermost unit of the holocene prism the purpose of this work is therefore to draw a detailed sedimentological and geochemical portrait of these units and to discuss the processes involved in the sedimentation and remobilization of these sediments our results show that the fine particles accumulate earlier in the inner shelf in front of the nearby rivers in association with the chemical elements which are commonly associated with this grain size fraction e g organic carbon radionuclides and heavy metals this accumulation probably mainly occurs during storm and flood events the early deposits are then exposed to resuspension events and can actively participate to the distribution of fine grained sediment in the entire margin by advective transfers via the benthic nepheloid layer these fine grained nearshore prodeltas are a common feature of the mediterranean deltaic systems and mark the frontal processes that occur at the continent sea interface of non tidal seas our results especially point out the potential use of heavy metals as markers of the tracking of riverine sediments which is naturally an important condition when evaluating the ultimate fate of land derived pollutants in the marine realm but also more fundamental studies on the understanding of sedimentological processes and reconstruction of margin stratigraphies should consider these deposits as functional units for the distribution of platform sediments

river sediment discharge to the oceans present day controls and global budgets empirical relationships between river sediment yields and a large number of hydroclimatic biological and geomorphological parameters are investigated at the global scale for a set of 60 major world river basins the environmental characteristics were extracted from various global computer data sets and natural river sediment fluxes were taken from the literature it is found that sediment yields can be best correlated by forming the products of hydroclimatic and geomorphological factors that is runoff intensity basin slope an index characterizing rock hardness and an index characterizing rainfall variability over the year the best parameter combination varies to some extent when the rivers are grouped according to their average climatic situation but it is always a combination of the above mentioned parameters that yields the most significant models in arid climates however regression coefficients are greater than in humid climates indicating that erodibility is much greater than in arid climates when extrapolated to the total continental area on the basis of the corresponding data sets the empirical models result in a total sediment flux of about 16 gigatons discharged to the oceans every year which is in good agreement with previous estimates derived from compilations of world wide river data consequently two global maps are proposed showing the spatial distributions of river sediment yields on the continents as well as the inputs of these sediments to the oceans in a grid point scale by far most of the sediments originate from the young orogenic belts of the continents mainly due to a combination of steep morphologies and high runoff intensities

last millennia sedimentary record on a micro tidal low accumulation prodelta tet nw mediterranean statistical sequential analysis was performed on a series of sediment cores collected from the tet prodelta in the gulf of lions northwestern mediterranean sea between october 2003 and october 2004 seabed changes during that period were correlated to hydrodynamic conditions waves and currents and river discharge low sediment supply prevents full preservation of new sediment strata on this low accumulation prodelta located on a microtidal storm dominated inner shelf severe meteorological events caused a rapid succession of erosion and deposition phases for example the december 2003 flood and storm produced a flood layer deposit that persisted for 2 months with only slight transformations due to early diagenesis and or bioturbation until a new storm event eroded this layer a typical sedimentary sequence was observed for the secular deposits composed of a 10 cm thick sandy layer overlaying siltyclayey layers these characteristic features were used to analyse the last millennia sedimentary record of the tet prodelta the low preservation of freshly deposited sediments and variable sedimentation rates during the last millennia period yield a sedimentary sequence formed by the outcropping of muddy prodeltaic units intersected by heterogeneous siltysandy units similar to those formed under present day hydrodynamic conditions no flood layer was found related to catastrophic flooding of the last century in the sedimentary record the little ice age 1550 1850 ad probably favoured the formation of a well developed muddy prodelta in the mouth of the tet river later on the decrease of sediment supply by rivers due to climate change and or human activities damming irrigation and the increase of the number of high energy storms reaching the coast induced a coarsening of the top sediment layer on this prodelta this modern change of the substrate is also observed in the composition of benthic biota found in the substrate

sediment entrainment on a wave graded shelf roussillon france abstract the sands of the inner shelf off the roussillon coast of the microtidal golfe du lion display a seaward fining texture and merge in water deeper than 20 30 m with midshelf muds there is a qualitative correspondence between the textural gradient and the seaward attenuating annual surface gravity wave power expended by tangential stress on the shelf surface various equations used to quantify the relation of sediment texture to fluid energy predict the trend of the observed textural gradient but overestimate its value an empirical threshold equation komar and miller 1975a b and a theoretical null point equation johnson and eagleson 1966 give comparable results implying that both may be describing the same state there is a disparity between the predictions of an incipient motion equation johnson and eagleson 1966 and the threshold equation probably because static instability of grains occurs prior to dynamic instability of grains in an increasing fluid velocity field theory forecasts that in water shallower than 30 m the sands are frequently entrained by shoaling waves particularly during the winter months the threshold of movement of sands in 5 m of water is exceeded for more than 40 of the year hence the grain size of the shallow water sands does not reflect the maximum energy level of the environment

near bottom suspended sediment variability caused by storms and near inertial internal waves on the ebro mid continental shelf nw mediterranean abstract near bottom currents and suspended sediment concentrations ssc recorded on the ebro continental shelf at 60 m depth during the transition between fair and stormy weather have revealed some of the major processes controlling the sediment re suspension and transport at mid shelf depths in this nw mediterranean area storm waves were the main contributor to the transport of sediment although they only resuspended surface sediments during extreme wave conditions h s 4 5 m and t s 11 s during the recording period the net suspended sediment flux along the shelf was one order of magnitude higher than the net suspended sediment flux across the shelf and the resultant transport was towards the sw and seaward fluctuations of the near bottom ssc during fair weather showed a periodicity around 17 h and were related to the occurrence of near inertial internal waves caused by wind pulses during storm events the energy propagation of these internal waves reached critical angles at the mid and outer shelf which could favor the development and maintenance of the bottom nepheloid layer on the ebro continental shelf as well as on other mediterranean continental shelves

physical and biological characteristics of the pelagic system across fram strait to kongsfjorden abstract the fram strait is very important with regard to heat and mass exchange in the arctic ocean and the large quantities of heat carried north by the west spitsbergen current wsc influence the climate in the arctic region as a whole a large volume of water and ice is transported through fram strait with net water transport of 1 7 3 2 sv southward in the east greenland current and a volume ice flux in the range of 0 06 0 11 sv the mean annual ice flux is about 866 000 km2 yr 1 the kongsfjorden krossfjorden fjord system on the coast of spitsbergen or at the eastern extreme of fram strait is mainly affected by the northbound transport of water in the wsc mixing processes on the shelf result in transformed atlantic water in the fjords and the advection of atlantic water also carries boreal fauna into the fjords the phytoplankton production is about 80 g c m 2 yr 1 in fram strait and has been estimated both below and above this for kongsfjorden the zooplankton fauna is diverse but dominated in terms of biomass by calanoid copepods particularly calanus glacialis and c finmarchicus other important copepods include c hyperboreus metridia longa and the smaller more numerous pseudocalanus p minutus and p acuspes microcalanus m pusillus and m pygmaeus and oithona similis the most important species of other taxa appear to be the amphipods themisto libellula and t abyssorum the euphausiids thysanoessa inermis and t longicaudata and the chaetognaths sagitta elegans and eukrohnia hamata a comparison between the open ocean of fram strait and the restricted fjord system of kongsfjorden krossfjorden can be made within limitations the same species tend to dominate but the fram strait zooplankton fauna differs by the presence of meso and bathypelagic copepods the seasonal and inter annual variation in zooplankton is described for kongsfjorden based on the record during july 1996 2002 the ice macrofauna is much less diverse consisting of a handful of amphipod species and the polar cod the ice associated biomass transport of ice amphipods was calculated based on the ice area transport at about 3 55 106 ton wet weight per year or about 4 2 105 t c yr 1 this represents a large energy input to the greenland sea but also a drain on the core population residing in the multi year pack ice myi in the arctic ocean a continuous habitat loss of myi due to climate warming will likely reduce dramatically the sympagic food source the pelagic and sympagic food web structures were revealed by stable isotopes the carbon sources of particulate organic matter pom being ice pom and pelagic pom revealed different isotopic signals in the organisms of the food web and also provided information about the sympagic pelagic and pelagic benthic couplings the marine food web and energy pathways were further determined by fatty acid trophic markers which to a large extent supported the stable isotope picture of the marine food web although some discrepancies were noted particularly with regard to predator prey relationships of ctenophores and pteropods

a high resolution study of holocene paleoclimatic and paleoceanographic changes in the nordic seas 1 high resolution records from images core md95 2011 in the eastern norwegian sea provide evidence for relatively large and small scale high latitude climate variability throughout the holocene during the early and mid holocene a situation possibly driven by consistent stronger westerlies increased the eastward influence of arctic intermediate and near surface waters for the late holocene a relaxation of the atmospheric forcing resulted in increased influence of atlantic water the main changes in holocene climate show no obvious connection to changing solar irradiance and spectral analysis reveals no consistent signature for any periodic behavior of holocene climate at millennial or centennial timescales there are however indications of consistent multidecadal variability

observation and modeling of the winter coastal oceanic circulation in the gulf of lion under wind conditions influenced by the continental orography fetch experiment 1 hydrological and currentmeter observations were collected on the continental shelf and slope of the gulf of lion during the fetch experiment 13 march to 15 april 1998 results from the first part of the cruise characterized by strong northern winds are presented the hydrological structures evidence well mixed water masses on the eastern and western ends of the shelf in the central part the situation is more complex with the influence of the rhone river s freshwater plume in the first 40 m of the water column and closer from the bottom with the confrontation of downwelled coastal cold water and upwelled warmer and saltier slope water current measurements show the path of the cyclonic circulation along the slope which is part of the general circulation of the western mediterranean and suggest the presence of large and temporary eddies on the shelf this oceanic circulation is simulated with a free surface three dimensional model using realistic forcing the model outputs are in agreement with the main hydrological and circulation patterns the results further indicate that coastal eddies are generated by the mesoscale structure of the wind field

assimilating satellite concentration data into an arctic sea ice mass balance model 1979 1985 using satellite ice concentration data observed buoy velocities and a thermodynamic ice growth model we compute the time histories of the thickness distributions of four ice types level and ridged first year ice and level and ridged multiyear ice these histories are computed for seven regions covering the arctic ocean with a 10 day time step for 1979 through 1985 a blend of observed buoy motions and wind driven free drift velocities drives the advective and ridging parts of the model while climatological growth and melt rates determine the ice thickness the model adjusts the thickness distributions so that the modeled concentrations of open water first year ice and multiyear ice match the concentrations derived by kalman filtering of satellite passive microwave observations the major adjustment is to reduce modeled ice concentrations in summer and particularly in the peripheral seas to account for unmodeled melt the model includes an ice salinity parameterization which along with changes in ice volume gives the salt or freshwater flux from the ice our results show that the arctic ice cover consists primarily of multiyear ice 60 by area and 82 by volume and that most of this ice is ridged the average ice thickness is 2 7 m with a seasonal variation of 30 and an interannual variation of 10 the study also shows that for each cell and the arctic as a whole the changes in ice volume caused by growth minus melt approximately balance the changes caused by import minus export the annual ice export through fram strait varies from 1100 to 3000 km3 primarily because of variations in ice velocity all regions except the chukchi sea have a net ice growth a net export and a net salt input to the ocean surface the annual mean salt flux to the ocean surface from net ice production is 7 3 kg m 2 downward fluxes along the transpolar drift stream are larger than elsewhere the largest downward flux of 33 kg m 2 yr 1 in the nansen basin can be attributed to the strong divergence near fram strait a companion paper steele et al this issue uses these fluxes and ice velocities to derive the arctic ocean freshwater balance

post depositional alteration and preservation of sedimentary event layers on continental margins i the role of episodic sedimentation the degree of post depositional alteration and hence the preservation potential of sedimentary event beds and transient signals is determined by the outcome of a race between biological and to a lesser extent physical processes that conspire to destroy a signal and sediment accumulation which advects the layer or signal out of the surface mixing zone preservation potential specifically depends on the relative magnitudes of the 1 biological mixing intensity sometimes parameterized as a biodiffusivity db 2 mixing layer thickness 3 layer or signal thickness and 4 sediment accumulation rate these terms control the dissipation time i e time required to destroy a signal and the transit time i e time necessary to advect a signal through the surface mixing layer on fine grained upper continental margins in general and the eel river shelf northern california in particular biological mixing intensity is high i e db ranges from 10 to 100 cm2 yr mixing layer thickness is large 10 cm and sediment accumulation rates are rapid 0 1 1 cm yr despite the high sediment accumulation rates transit times through the surface mixing layer range from decades to a century signal dissipation times are considerably shorter 1 3 yr for beds up to 6 cm thick imaged in x radiographs and 2 15 yr for the grain size signature of beds up to 8 cm thick therefore event layers and their corresponding grain size signature have a low probability of preservation however short lived episodic sedimentation events e g oceanic floods can instantaneously advect material through the surface mixing layer thereby preserving event beds and transient signals on the eel river shelf the sequential timing of episodic sedimentation events has exerted a first order control on the resultant stratigraphic record presence absence of layers and grain size fluctuations episodic sedimentation a hallmark of continental shelf settings is key to understanding strata formation and preservation on margins

evidence of recent sedimentation in the eastern irish sea the recent sedimentation history of the eastern irish sea has been investigated by radiocarbon dating age versus depth profiles of the shells of the gastropod turritella communis risso indicate that sedimentation has been taking place at two sites at a relatively slow but constant rate 0 02 0 08 cm a 1 for the past 3000 4000 years at a third site sedimentation appears to have been more variable and more rapid 0 3 cm a 1 dating t communis shells provides a more reliable indicator of the sediment accumulation rate than dating the bulk sediment carbonate fraction the latter is predominantly of marine origin but has been reworked and unlike the shells is subject to the intense mixing by bioturbation which characterizes the muddy sediments of this area bulk sediment carbonate ages are much greater than those of t communis at equivalent depths 10 300 15 300 yrs and 130 3800 yrs respectively and the profiles are more variable leading to difficulties in interpretation