factors influencing recent benthic foraminifera distribution on the guadiana shelf southwestern iberia abstract benthic foraminiferal assemblages in 24 sediment surface samples collected at water depths ranging from 9 to 103 m on the continental shelf off guadiana river were analysed leading to the identification of a total of 270 species cluster analyses performed on species with a relative abundance higher than 5 led to the identification of four assemblages the shallowest assemblage down to 12 m water depth is represented by ammonia beccarii asterigerinata mamila eggerelloides scaber mississipina concentrica planorbulina mediterranensis elphidium crispum and quinqueloculina laevigata a second assemblage between 12 and 40 m water depth is characterised by bulimina elongata cribrononion gerthi and nonion fabum the assemblage between 40 and 95 m water depth is characterised by bolivina dilatata epistominella vitrea bulimina aculeata bolivina ordinaria spiroloxostoma croarae and nonionella iridea finally below a depth of 95 m on the upper outer shelf an assemblage exists characterised by brizalina spathulata bulimina marginata cassidulina minuta brizalina subaenariensis cassidulina laevigata and uvigerina peregrina the spatial distribution of assemblages is closely associated with sea bottom sedimentary environments and bathymetry the number of benthic foraminiferal tests and the distribution of several nearshore species within the two shallowest assemblages are clearly influenced by the outflow of the guadiana estuary and by local hydrodynamic conditions the deeper water assemblages on the other hand were found to be more related to low levels of tidal energy low oxygen environments associated to fine grained sediments and cold water filaments related to seasonal upwelling

integrated 3d density modelling and segmentation of the dead sea transform a 3d interpretation of the newly compiled bouguer anomaly in the area of the dead sea rift is presented a high resolution 3d model constrained with the seismic results reveals the crustal thickness and density distribution beneath the arava araba valley av the region between the dead sea and the gulf of aqaba elat the bouguer anomalies along the axial portion of the av as deduced from the modelling results are mainly caused by deep seated sedimentary basins d 10 km an inferred zone of intrusion coincides with the maximum gravity anomaly on the eastern flank of the av the intrusion is displaced at different sectors along the nnw sse direction the zone of maximum crustal thinning depth 30 km is attained in the western sector at the mediterranean the southeastern plateau on the other hand shows by far the largest crustal thickness of the region 38 42 km linked to the left lateral movement of approx 105 km at the boundary between the african and arabian plate and constrained with recent seismic data a small asymmetric topography of the moho beneath the dead sea transform dst was modelled the thickness and density of the crust suggest that the av is underlain by continental crust the deep basins the relatively large intrusion and the asymmetric topography of the moho lead to the conclusion that a small scale asthenospheric upwelling could be responsible for the thinning of the crust and subsequent creation of the dead sea basin during the left lateral movement a clear segmentation along the strike of the dst was obtained by curvature analysis the northern part in the neighbourhood of the dead sea is characterised by high curvature of the residual gravity field flexural rigidity calculations result in very low values of effective elastic lithospheric thickness te 5 km this points to decoupling of crust in the dead sea area in the central av the curvature is less pronounced and te increases to approximately 10 km curvature is high again in the southernmost part near the aqaba region solutions of euler deconvolution were visualised together with modelled density bodies and fit very well into the density model structures

inverse modelling of elastic thickness by convolution method the eastern alps as a case example an unconventional scheme is used to estimate the flexural rigidity or equivalently the elastic thickness of the lithosphere given the topography and gravity data the flexural rigidity is the parameter that governs the flexural response of the lithosphere in the frame of the thin plate flexure model the scheme is an alternative to the widely used calculation of admittance of topography sea floor or continental topography and gravity bearing some advantages which are explained in the paper the scheme involves the inversion of the gravity data in order to formulate a model of the crust mantle interface cmi undulations in a second step the flexure parameter is then evaluated from the relation between topography and cmi variations instead of calculating the admittance function using a spectral analysis a set of point load response functions are used in order to retrieve the optimal flexure parameter this has two main advantages instabilities of the numerical admittance evaluation at wavenumbers with low spectral energy in the topography are overcome and the analysis can be made over an area which is not necessarily rectangular as required for the spectral analysis the proposed method allows a higher space resolution of elastic thickness than any spectral method for validation the numerical strategy is applied to the situation of a realistic synthetic model where all inputs and outputs are known a priori finally the spatial variations of the elastic thickness are studied in an area across the eastern alps 4 2002 elsevier science b v all rights reserved

spatial distribution of live benthic foraminifera in the rhone prodelta faunal response to a continental marine organic matter gradient abstract benthic foraminifera were collected in the rhone prodelta gulf of lions mediterranean sea an enriched zone with high organic matter content in june 2005 sediment cores were sampled at depths ranging from 20 to 100 m four distinct foraminiferal assemblages were determined in the study area reflecting the geographical distribution of the impact of river supply the living foraminiferal faunas present a typical picture with strongly impoverished faunas composed exclusively of stress tolerant taxa fursenkoina fusiformis bulimina aculeata leptohyalis scottii and adelosina longirostra in the immediate vicinity of the river mouth this assemblage is well adapted to a high input of continental organic matter and a minimum oxygen penetration depth into the sediment to the southwest under the main corridor followed by the river plume high organic input with a dominantly terrestrial signature more refractory may be stressful for many taxa which need organic matter of a more labile quality in this area nonion scaphum nonionella turgida and rectuvigerina phlegeri are present in low densities on the edge of this area these taxa show much higher densities a greater proportion of marine organic carbon could explain their increasing abundances in this area towards the east and towards the deepest stations in the outer part of the enriched zone biodiversity increases faunas at these stations have intermediate densities and contain a number of taxa cassidulina carinata epistominella vitrea valvulineria bradyana nonionella iridea bradyi at the deepest stations bolivina dilatata spathulata and textularia porrecta at the eastern stations that seem to benefit from more marine organic matter the comparison of geochemical measurements and foraminiferal data strongly suggests that the spatial distribution of foraminifera in the rhone prodelta is mainly governed by the quality and the quantity of organic matter reaching the sediment water interface since bottom waters are well oxygenated 215 260 mol l and oxygen penetration into the sediment is less than 1 cm at all stations benthic ecosystem oxygenation appears to have only a minor impact on regional differences in faunal distribution

210pb derived sediment accumulation and mixing rates for the washington continental slope abstract total sediment accumulation rates g yr in four canyons indenting the washington continental shelf are about twice those on the nearby open slope even though canyons comprise less than 40 of the depositional area of the entire slope this is because 210 pb derived sediment accumulation rates g cm 2 yr for astoria and quinault canyons are 3 4 times greater than those for willapa and grays canyons and intermediate open slope areas supporting the hypothesis that columbia river derived solids are preferentially transported to these two canyons quinault canyon currently appears to be accumulating solids at rates much greater than its low long term accumulation rate which is attributed to turbidity currents transporting solids down this canyon roughly every 500 years the following four different approaches all show that mixing may cause 210 pb derived sediment accumulation rates for slope and canyon sediments to be 2 3 times higher than true accumulation rates 1 comparison between accumulation rates calculated from 210 pb profiles with and without surface zones in which mixing has obviously affected 210 pb distributions 2 comparison between 210 pb derived and independently determined long term accumulation rates 3 comparison between 210 pb derived accumulation and modern columbia river discharge rates 4 comparison between two and three layer steady state one dimensional diffusion advection decay models mixing coefficients for surface sediments calculated using a one dimensional two layer vertical eddy diffusion model show large differences within the region with most in the 3 30 cm 2 yr range mixing rates are several times larger in canyon sediments from 0 2 1 1 km water depth probably due to physical reworking processes erroneously neglected mixing at depth of no more than 5 of that calculated for the surface mixed layer can cause the 2 3 fold calculated overestimation of true sediment accumulation rates and 2 4 fold calculated underestimation of true mixing coefficients

dispersal and deposition of suspended sediment on the shelf off the tagus and sado estuaries s w portugal abstract the portuguese margin in front of the tagus and sado rivers is characterized by a narrow shelf incised by numerous canyons and by a large mud deposit the two estuaries that feed this continental margin have distinct impact the suspended particulate matter concentration values in the mouth of the tagus are four times higher than in the sado during the summer the surface nepheloid layer is always larger than during the winter when it is restricted near the mouth of the estuary this nepheloid layer may reach 30 km in length extending westward the bottom nepheloid layer usually shows higher nephelometer values and has a typical distribution it is usually diverted southward in the direction of the lisbon submarine canyon we estimate the amount of suspended matter being discharged annually from the tagus estuary to be between 0 4 and 1 10 6 t the area covered by fine deposits is about 560 km 2 hence the thickness of sediments deposited annually should be between 0 07 and 0 18 cm the sedimentation rates calculated from the 210 pb excess vary between 0 16 and 2 13 cm y 1 which correspond to the maximum rate for a layer of 1 cm thick 81 000 t of particulate organic carbon poc should be trapped that would represent with a minimum sedimentation rate between 0 07 and 0 18 cm y 1 an entrapment of 6000 15 000 t poc y 1 the trace metals content of box core samples clearly shows the anthropogenic impact in the uppermost level 5 cm thick in the tagus estuary and in all the sedimentary deposits 15 cm thick on the shelf muddy area despite the narrowness of the shelf a significant part of continental fluxes fails to reach the deep ocean

modeling of seismic guided waves at the dead sea transform 1 on several recordings of linear seismometer arrays crossing the arava fault af in the middle east we see prominent wave trains emerging from in fault explosions which we interpret as waves being guided by a fault zone related low velocity layer the af is located in the arava valley and is considered the principal active fault of the mainly n s striking dead sea transform system in this section observations of these wave trains are confined to certain segments of the receiver lines and occur only for particular shot locations they exhibit large amplitudes and are almost monochromatic we model them by a two dimensional 2 d analytical solution for the scalar wave field in models with a vertical waveguide embedded in two quarter spaces a hybrid search scheme combining genetic algorithm and a local random search is employed to explore the multimodal parameter space resolution is investigated by synthetic tests the observations are adequately fit by models with a narrow only 3 12 m wide waveguide with s wave velocity reduced by 10 60 of the surrounding rock we relate this vertical low velocity layer with the damage zone of the af since the location of receivers observing and of shots generating the guided waves respectively match with the surface trace of the fault the thickness of the damage zone of the af at least at shallow depths seems to be much smaller than in other major fault zones this could be due to less total slip on this fault

permian early mesozoic tectonism and continental margin formation in israel and its implications for the history of the eastern mediterranean summary the early mesozoic tectonic reorganization of the tethys region also affected the levant area here two processes were superimposed a the pattern of long wavelength vertical motions of the arabo nubian platform changed in the late permian when israel and nearby areas began to subside b rifting occurred in this subsiding area probably in several phases late anisian and ladinian carnian norian and liassic differential movements reached 2 3 km and magmatism occurred in the liassic and perhaps also in the triassic the tectonism was strongly felt up to 50 km landward of the present coast the crust was thinned and modified under the present continental margin and in the main rifts passive margin conditions were established in late liassic times over the previously faulted area later in the jurassic a carbonate shelf was constructed along this subsiding margin its basinward edge was 1 1 5 km high which shows that the adjacent se mediterranean was already a deep sea hence this basin and its passive margin are considered to have been shaped by the early mesozoic rifting which is recognized in israel the rifting process probably signifies oblique separation of the tauride block from the levant part of gondwana

turbidity of waters over the northwest iberian continental margin in omex ii ii 9 cruises gathered optical data principally by transmissometer the distribution of optical turbidity caused by concentration of particulate matter pmc in the water column over the northern iberianmargin shows several features related to hydrography it is concluded that a signal of pmc seen in mediterranean water mw found north of 42 n is not carried from its source at the gibraltar sill and gulf of cadiz because it is shown using intermediate stations that this turbid plume decays mainly by fall out but also partly by mixing to very low levels around southern portugal pmc maxima sometimes seen in mw on the northern iberianmargin are thus most likely to result from intermittent local resuspension by mw interacting with slope sediments the highest turbidity is found over the upper slope and is the result of i shelf edge resuspension and off shelf flow of turbid plumes mainly between 100 and 300 m depth and ii resuspension under the slope current aided by internal waves in the depth range 500 800 m where the density gradient between enacw and mw is maximal below the mw flows are generally slow and turbidity is low the bottom nepheloid layer in deep water is also weak with pmc values 100 mg m 3 the focus of resuspension activity on the upper slope means that the region is an efficient exporter to the ocean of sediment that either escapes from the shelf or sinks to the bed from surface production this accounts for upper slope sediments recorded in other studies as sandy or in places as rocky bottom

live stained deep sea benthic foraminiferans in the western weddell sea trends in abundance diversity and taxonomic composition along a depth transect entire live foraminiferal assemblages i e including soft walled species were analysed using replicate subcores 3 45 cm2 surface area 0 1 cm layer 63 m fraction from multiple corer samples collected along a transect 1100 5000 m water depth of the continental slope and rise and adjacent abyssal plain to the east of the antarctic peninsula foraminiferans usually accounted for 61 83 of all meiofaunal organisms mean densities were highest 576 individuals indiv 10 cm 2 at 2100 m water depth and declined to 240 indiv 10 cm 2 at 5000 m although there was considerable variability between replicates at some stations e g 304 333 1090 indiv 10 cm 2 at 2100 m foraminiferan and metazoan meiofaunal densities were broadly coherent across the depth range sampled a total of 158 live foraminiferal species was recognized assemblages were most diverse on the lower slope with species numbers peaking at 3100 m and the fisher diversity index at 3100 4100 m monothalamous taxa increased in relative abundance from 8 at 1100 m to 33 at 4975 m and there was a corresponding decrease in the proportion of calcareous taxa from 65 to 16 on the continental slope 1100 3100 m the most abundant hard walled species were epistominella exigua adercotryma glomeratum alabaminella weddellensis and stetsonia hovarthi in the deeper samples 4100 5000 m a glomeratum became the dominant hard walled species important soft walled species included tinogullmia riemanni and bathyallogromia weddellensis in some samples from 1100 and 2100 m more than a third of the live assemblage was hidden within phytodetrital aggregates species such as e exigua a weddellensis and t riemanni were concentrated within these microhabitats many of the weddell sea species are typical bathyal and abyssal forms well known from the north atlantic and elsewhere the phytodetrital assemblages are strikingly similar to those reported from abyssal sites in the north atlantic our observations suggest that there are close faunal links between the deep water faunas of the weddell sea and those of other oceanic regions perhaps mediated by thermohaline circulation

benthic foraminifera in the nazare canyon portuguese continental margin sedimentary environments and disturbance abstract living rose bengal stained benthic foraminifera were investigated from thirteen stations ranging from 146 4976 m water depth in the nazare canyon located on the western iberian continental margin the total standing stocks tss species assemblages and in sediment distributions are compared between stations located on the highly disturbed axis of the upper 4000 m in addition the community changes were investigated in relation to water depth and bio available organic carbon overall low total standing stocks of foraminifera were found in the disturbed canyon axis which experiences frequent sediment resuspension and gravity flows at the upper canyon axis station at 1118 m a rather exceptional fauna was recovered dominated by a species of technitella that made up 75 of the tss the highest tsss were recorded in the upper canyon terrace stations where fine grained sediment and organic carbon are able to accumulate standing stocks on the terraces decreased with increasing water depths the quiescent terrace stations recorded high abundances of infaunal species including melonis barleeanum globobulimina spp and chilostomella oolina the occurrence of these species reflects the low pore water oxygen concentrations and high bio available carbon supply several tubular bathysiphon species were found in the upper canyon terrace stations instead the deepest stations of the lower canyon were dominated by another large agglutinated protozoan saccorhiza ramosa the change in the arborescent tubular foraminiferal community may reflect the increase in sediment oxygenation with increasing water depth in the canyon bathysiphon spp occurring in sediments with higher bio available carbon flux and s ramosa inhabiting more oligotrophic areas

winter dynamics on the northern portuguese shelf part 1 physical processes results of a program of observations carried out on the northern portuguese shelf and slope between july 1996 and june 1999 are used to characterise the main physical processes of the winter regime the data set includes time series of waves and currents at mid shelf 86 m depth and of winds atmospheric pressure and sea level at the coast as well as hydrographic and suspended particle matter spm observations carried during three multidisciplinary surveys the wave regime was found to be characterised by highly energetic conditions during the winter with storm events leading to waves of significant heights exceeding 5 m with mean periods of over 10 s prevailing southerly winds force a downwelling regime over the shelf with poleward flow at mid shelf 10 20 cm s and offshore transport in the bottom ekman layer episodic strong upwelling events can occur during this period leading to important changes in the near bottom stratification at mid shelf tidal currents at mid shelf are dominated by the contribution of the m2 tide 3 cm s and are polarised in the cross shelf direction reflecting the guiding effect of the porto canyon

sources and distribution of terrigenous organic matter delivered by the atchafalaya river to sediments in the northern gulf of mexico abstract suspended sediments ss from the atchafalaya river ar and the mississippi river and surficial sediment samples from seven shallow cross shelf transects west of the ar in the northern gulf of mexico were examined using elemental oc c n isotopic 13c 14c and terrigenous biomarker analyses the organic matter om delivered by the ar is isotopically enriched 24 5 and relatively degraded suggesting that soil derived om with a c4 signature is the predominant om source for these ss the shelf sediments display oc values that generally decrease seaward within each transect and westward parallel to the coastline a strong terrigenous c n 29 signal is observed in sediments deposited close to the mouth of the river but values along the remainder of the shelf fall within a narrow range 8 13 with no apparent offshore trends depleted stable carbon isotope 13c values typical of c3 plant debris 27 are found near the river mouth and become more enriched 22 to 21 offshore the spatial distribution of lignin in shelf sediments mirrors that of oc with high lignin yields found inshore relative to that found offshore water depth 10 m the isotopic and biomarker data indicate that at least two types of terrigenous om are deposited within the study area relatively undegraded c3 plant debris is deposited close to the mouth of the ar whereas more degraded isotopically enriched soil derived om appears to be deposited along the remainder of the shelf an important input from marine carbon is found at the stations offshore from the 10 m isobath quantification of the terrigenous component of sedimentary om is complicated by the heterogeneous composition of the terrigenous end member a three end member mixing model is therefore required to more accurately evaluate the sources of om deposited in the study area the results of the mixing calculation indicate that terrigenous om soil derived om and vascular plant debris accounts for 79 of the om deposited as inshore sediments and 66 of om deposited as offshore sediments importantly the abundance of terrigenous om is 40 higher in inshore sediments and nearly 85 higher in offshore sediments than indicated by a two end member mixing model such a result highlights the need to reevaluate the inputs and cycling of soil derived om in the coastal ocean

tectonic evolution of northern wadi araba jordan abstract in the area east of northern wadi araba several phases of tectonic fracturing can be distinguished the oldest is of precambrian age and is represented by a system of dikes a second pre cretaceous tectonic phase is represented by a distinct joint system which is restricted to the cambrian sediments and has not cut the cretaceous sediments the major tectonic movements which lead to the formation of the dead sea rift produced faults and joint systems which cut all rock sequences the major deformation of the area started in the early tertiary when the accumulation of the se nw directed compressive stresses produced fold structures which are older than the rift movements as a result of this stress a conjugate system of fractures was produced ese trending right lateral antithetic faults and sse trending left lateral synthetic faults a major group of tensional faults and fractures trending 130 was produced due to this compression the major displacement along the rift followed the formation of the above mentioned faults these fault systems dissected the area into different blocks as the compression continued the faults and the blocks between them were rotated relative to each other two phases of rotational movements were recorded contemporaneous with the two phases of the rift formation during its northward movement the arabian plate came into collision with the sinai palestine plate in the dahal area in northern wadi araba various indications prove that the wadi araba fault is still active and the northward displacement of the arabian plate along this fault continues in recent time

sedimentary labile organic carbon and pore water redox control on species distribution of benthic foraminifera a case study from lisbon setubal canyon southern portugal abstract rose bengal stained benthic foraminifera were studied from 11 cores collected along two depth transects off southern portugal one in the lisbon setubal canyon and the other along the canyon edge the total standing stocks and distribution of foraminifera were investigated in relation to sediment and pore water geochemistry nitrate was used as a redox indicator sedimentary chlorophyll a and cpe chloroplastic pigment equivalents contents as a measure of labile organic matter and total organic carbon as a measure of bulk organic matter availability the canyon sediments were enriched in organic carbon and phytopigments at all water depths in comparison with the canyon edge water depth seemed to control sedimentary phytopigment content but not total organic carbon no significant correlation was seen between pigment and total organic carbon content the abundance of calcareous foraminifera correlated with the phytodetritus content whereas a weaker correlation was observed for the agglutinated taxa therefore calcareous foraminifera appear to require a fresher food input than agglutinated taxa the foraminiferal species composition also varied with pigment content and nitrate penetration depth in the sediment in line with the trox concept phytopigment rich surficial cpe content 20 g cm3 sediments with a shallow nitrate penetration depth 1 cm depth were inhabited by generally infaunal species such as chilostomella oolina melonis barleeanus and globobulimina spp as the nitrate penetration increased to 2 cm depth in sediment and the pigment content remained relatively high 15 g cm3 uvigerina mediterranea and uvigerina elongatastriata became dominant species with declining cpe content and increasing nitrate penetration depth the foraminiferal assemblages changed from the mesotrophic cibicides kullenbergi uvigerina peregrina assemblage to the oligotrophic abyssal assemblage mainly consisting of agglutinated taxa

the ecology of living stained deep sea benthic foraminifera from the sulu sea the distribution of living rose bengal stained deep sea benthic foraminifera was determined in the upper 20 cm of sediments of eight soutar box cores taken from two depth transects 510 4515 m in the thermospheric 10 c sulu sea despite the uniformity of bottom water temperatures salinities and dissolved oxygen levels below 1000 m significant faunal differences exist at different depths in the low oxygen 1 25 ml l below 1000 m basin the shallowest site 510 m is dominated 10 of the calcareous fauna by cibicidoides uvigerina 150 m and bolivina 63 m while siphonina is codominant with cibicidoides and uvigerina in the 1005 m core the 2000 m cores are dominated by cibicidoides gyroidinoides and oridorsalis while cibicidoides bradyi and oridorsalis umbonatus dominate the 3000 and 4000 m cores infaunal assemblages of valvulineria mexicana are found in the sediments of the 4515 m core relatively low bottom water oxygen values do not necessarily yield typical low oxygen taxa such as bolivina uvigerina chilostomella bulimina and globobulimina changes in the abundances of these taxa in fossil assemblages have been used as indicators of changes in ancient bottom water oxygen levels but may instead reflect organic carbon contents of the sediments an examination of the vertical distributions of foraminiferal assemblages from the 63 m and 150 m fractions reveals that taxa have microhabitat preferences similar to those observed in other regions taxa found in the upper 0 to 1 cm interval epifaunal include cibicidoides wuellerstorfi and hoeglundina elegans while taxa such as chilostomella and globobulimina reach maximum abundances in subsurface sediments and have infaunal microhabitat preferences cibicidoides bradyi and o umbonatus live in sediment depths from 0 to 4 cm and have transitional preferences with both epifaunal and infaunal occurrences intrageneric differences in test morphologies including pore distribution rounded peripheries and variable spire height are observed in cibicidoides and gyroidinoides and are suggested to be related to microhabitat preferences vertical distributions of a number of taxa found in both the 63 to 150 m and 150 m fractions are similar suggesting that juveniles and adults live under similar microhabitat conditions ontogenetic changes in microhabitat preferences of most species are not observed in this study and therefore would not be expected to account for isotopic vital effects reported for some taxa in previous studies

boundary layer mantle flow under the dead sea transform fault inferred from seismic anisotropy lithospheric scale transform faults play an important role in the dynamics of global plate motion near surface deformation fields for such faults are relatively well documented by satellite geodesy strain measurements and earthquake source studies and deeper crustal structure has been imaged by seismic profiling relatively little is known however about deformation taking place in the subcrustal lithosphere that is the width and depth of the region associated with the deformation the transition between deformed and undeformed lithosphere and the interaction between lithospheric and asthenospheric mantle flow at the plate boundary here we present evidence for a narrow approximately 20 km wide subcrustal anisotropic zone of fault parallel mineral alignment beneath the dead sea transform obtained from an inversion of shear wave splitting observations along a dense receiver profile the geometry of this zone and the contrast between distinct anisotropic domains suggest subhorizontal mantle flow within a vertical boundary layer that extends through the entire lithosphere and accommodates the transform motion between the african and arabian plates within this relatively narrow zone

tidal and river discharge forcing upon water and sediment circulation at a rock bound estuary guadiana estuary portugal the relative impacts of tidal neap spring and river discharge including a flood event forcing upon water and sediment circulation have been examined at the rock bound guadiana estuary near bed and vertical profiles of current salinity turbidity plus surface suspended sediment concentrations ssc at some stations only were collected at the lower and central upper estuary during tidal and fortnightly cycles in addition vertical salinity and turbidity profiles were collected around high and low water along the estuary tidal asymmetry produced faster currents on the ebb than on the flood especially at the mouth this pattern of seaward current dominance was enhanced with increasing river flow due to horizontal advection that was confined within the narrow estuarine channel the freshwater inputs and at a degree less the tidal range controlled the vertical mixing and stratification importance well mixed spring and partially stratified neap conditions alternated during periods of low river flows with significant intratidal variations induced by tidal straining especially at the partially stratified estuary highly stratified conditions developed with increasing river discharge intratidal variability in the pycnocline depth and thickness resulted from current shear during the ebb a salt wedge with tidal motion was observed at the lower estuary during the flood event depending on the intensity of turbulent mixing the residual water circulation was dominantly controlled either by tidal asymmetry or gravitational circulation the ssc was governed by cyclical local processes resuspension deposition mixing advection driven by the neap spring fluctuations in tidal current velocities more intratidal variability in stratification indicated the significance of tidal pumping at the partially and highly stratified estuary the estuary turbidity maximum etm was enhanced with increasing current velocities and displaced downstream during periods of high river discharge during the flood event the etm was expelled out of the estuary and the ssc along the estuary was controlled by the sediment load from the drainage basin under these highly variable river flow conditions our observations suggest that sand is exported to the nearshore over the long term years

the distribution of living benthic foraminifera on the continental slope and rise off southwest norway abstract surface sediment samples taken by corer from 45 stations on the norwegian continental margin and in the norway basin have been investigated for their benthic foraminiferal content unlike previous studies the living benthic foraminiferal fauna was differentiated from empty tests comprising the foraminiferal death assemblage factor analysis of both the living and dead faunal data reveals six living species assemblages and five corresponding dead assemblages the additional living assemblage is characterized by the arenaceous speciescribrostomoides subglobosum that dominates between 1400 and 2000 m water depth but is rare in the dead faunal data trifarina angulosa and to a lesser extent cibicides lobatulus characterize the shallowest foraminiferal assemblage from 200 to 600 m water depth where it is associated with strong bottom currents and warm saline atlantic water of the north atlantic drift on the slope between 600 and 1200 m water depth themelonis zaandami species assemblage dominates particularly in areas characterized today by rapid sedimentation of terrigeneous material between 1000 and 1400 m depth where the slope is covered by fine grained organic rich terrigeneous mud the living foraminiferal assemblage is characterized bycassidulina teretis andpullenia bulloides below 1400 m three foraminiferal assemblages are found c subglobosum is found from 1400 to 2000 m cibicidoides wuellerstorfi andepistominella exigua predominantly live from 2000 to 3000 m water depth and below 3000 m oridorsalis umbonatus andtriloculina frigida dominate the fauna all of theelphidium excavatum tests found in this study and thecassidulina reniforme tests found above 500 m water depth were found to be reworked analysis of the sediment grain size distribution and the organic carbon content in surface samples from the deepest stations suggest that the abundance ofc wuellerstorfi ande exigua is positively correlated to relatively coarse caused by planktic foraminifera and organic rich sediments whereas high frequencies ofo umbonatus andt frigida coincide with low organic carbon content we suggest thatc wuellerstorfi is adapted to deep sea environments with relatively high food supply tolerating relatively low interstitial water oxygen content whereaso umbonatus may tolerate lower food supply prefering well oxygenated interstitial waters

variations in benthic foraminiferal assemblages in the tagus mud belt during the last 5700 years implications for tagus river discharge the netherlands organization for scientific research nwo hamoc anr project national research foundation of korea nrf

crustal shear velocity structure across the dead sea transform from two dimensional modelling of desert project explosion seismic data an analysis of the shear s waves recorded during the wide angle reflection refraction wrr experiment as part of the desert project crossing the dead sea transform dst reveals average crustal s wave velocities of 3 3 3 5 km s 1 beneath the wrr profile together with average crustal p wave velocities of 5 8 6 1 km s 1 from an already published study this provides average crustal poisson s ratios of 0 26 0 27 v p v s 1 76 1 78 below the profile the top two layers consisting predominantly of sedimentary rocks have s wave velocities of 1 8 2 7kms 1 and poisson s ratios of 0 25 0 31 v p v s 1 73 1 91 beneath these two layers the seismic basement has average s wave velocities of around 3 6 km s 1 east of the dst and about 3 7 km s 1 west of the dst and poisson s ratios of 0 24 0 25 v p v s 1 71 1 73 the lower crust has an average s wave velocity of about 3 75 km s 1 and an average poisson s ratio of around 0 27 v p v s 1 78 no sn phase refracted through the uppermost mantle was observed the results provide for the first time information from controlled source data on the crustal s wave velocity structure for the region west of the dst in israel and palestine and agree with earlier results for the region east of the dst in the jordanian highlands a shear wave splitting study using sks waves has found evidence for crustal anisotropy beneath the wrr profile while a receiver function study has found evidence for a lower crustal high s wave velocity layer east of the dst below the profile although no evidence was found in the s wave data for either feature the s wave data are not incompatible with crustal anisotropy being present as the wrr profile only lies 30 degrees off the proposed symmetry axis of the anisotropy where the difference in the two s wave velocities is still very small in the case of the lower crustal high s wave velocity layer if the velocity change at the top of this layer comprises a small first order discontinuity underlain by a 2 km thick transition zone instead of just a large first order discontinuity then both the receiver function data and the wrr data presented here can be satisfied finally the s wave velocities and poisson s ratios which have been derived in this study are typical of continental crust and do not require extensional processes to explain them

the dead sea transform evidence for a strong fault abstract geological and geochemical studies have been conducted on the arava fault segment which forms the major branch of the dead sea transform between the dead sea and the gulf of aqaba mesoscale to microscale faulting and veining related to this fault are described from limestone sequences of two locations areas a and b that represent different depth sections in area a pressure ridges expose the exhumed fault deformation mechanisms indicate that faulting took place at temperatures between 150 c and 300 c which suggests faulting depths between 2 and 5 km with respect to published geothermal gradients in area b brittle fault damage forms a zone up to 150 m wide the fault core is not exposed faulting took place at temperatures below 200 c up to a 3 km depth in both areas we found indications for a strong fault our kinematic analysis exhibits that the angle between 1 and the strike of the dead sea transform immediately adjacent to the fault is 45 the twin density technique yields di

a new look at modern agglutinated benthic foraminiferal morphogroups their value in palaeoecological interpretation morphogroups offer a way of overcoming taxonomic differences and thereby making comparisons between assemblages of different geological ages relating morphogroups to environments has proved useful in palaeoecological interpretations the model proposed by jones and charnock in 1985 has subsequently been adapted and still serves as the main reference for such palaeoecological interpretations new data from 400 samples from marsh to deep sea off nw europe are used here to refine the model by providing the range of abundance of each morphogroup in each environment it is shown that this range of variation is great so that there is considerable overlap between environments nevertheless the mean values show patterns of distribution tubular forms morphogroup a are characteristic of slope environments especially those under the influence of geostrophic currents morphogroup b is not common in marginal marine environments but is an indicator of shallow fjord to deep sea the elongate forms of morphogroup c are widely distributed but c1 is especially common in marginal marine and shelf to upper slope settings the quinqueloculine coiled c2 subgroup is characteristic of marsh and marginal marine environments in the temperate zone but around antarctica this form is common down to 2000 m the plano convex low trochospiral trochamminids of morphogroup d are typical of marshes therefore these trends have application to palaeoecology of similar well oxygenated temperate environments

crustal structure of the levant basin eastern mediterranean abstract a seismic refraction wide angle reflection experiment was undertaken in the levant basin eastern mediterranean two roughly east west profiles extend from the continental shelf of israel toward the levant basin the northern profile crosses the eratosthenes seamount and the southern profile crosses several distinct magnetic anomalies the marine operation used 16 ocean bottom seismometers deployed along the profiles with an air gun array and explosive charges as energy sources the results of this study strongly suggest the existence of oceanic crust under portions of the levant basin and continental crust under the eratosthenes seamount the seismic refraction data also indicate a large sedimentary sequence 10 14 km thick in the levant basin and below the levant continental margin assuming the crust is of cretaceous age this gives a fairly high sedimentation rate the sequence can be divided into several units a prominent unit is the 4 2 km s layer which is probably composed of the messinian evaporites overlying the evaporitic layer are layers composed of plio pleistocene sediments whose velocity is 2 0 km s the refraction profiles and gravity and magnetic models indicate that a transition from a two layer continental to a single layer oceanic crust takes place along the levant margin the transition in the structure along the southern profile is located beyond the continental margin and it is quite gradual the northern profile north of the carmel structure presents a different structure the continental crust is much thinner there and the transition in the crustal structure is more rapid the crustal thinning begins under western galilee and terminates at the continental slope the results of the present study indicate that the levant basin is composed of distinct crustal units and that the levant continental margin is divided into at least two provinces of different crustal structure

live and dead benthic foraminiferal faunas from whittard canyon ne atlantic focus on taphonomic processes and paleo environmental applications abstract dead benthic foraminiferal assemblages were studied in the 150 m fraction of 4 5 cm deep sediment levels at 18 stations in the whittard canyon area in june 2007 this sediment layer is composed of fairly recent sediment in both canyon branches the population dynamics such as seasonal response to phytodetritus deposition certainly contribute to differences between live and dead faunas for instance bulimina marginata which is usually considered as an opportunistic species is over represented in the dead assemblage the fragility of the tests of some species can explain their total absence in the thanatocoenoses this concerns many organic cemented arenaceous tests miliolid tests sensitive to dissolution and perforate taxa with thin tests furthermore transport e g sediment gravity flows active in both canyon branches leads to an increasing relative contribution of allochthonous individuals originating from outer shelf and upper canyon sites towards the deeper canyon stations consequently the dead faunas do no reflect local environmental conditions the high abundance of transported dead foraminifera in both canyon branches leads to important biases in the foraminiferal assemblage composition but may also significantly bias the interpretation of 13 c 18 o trace elements and 14 c concentration in foraminiferal shells it may therefore strongly complicate the reconstruction of environmental parameters such as bottom water temperature or exported paleoproductivity and radiocarbon dating of the foraminiferal assemblages therefore in both canyon axes the use of dead foraminiferal faunas to reconstruct paleoenvironmental in situ conditions is precluded however the study of dead assemblages in the canyon branches in particular the quantity of allochthonous foraminifera can give important clues about the downslope sedimentary dynamics on both open slopes despite taphonomic test destruction and biological processes population dynamics the distribution and the composition of the live fauna resemble those of the dead assemblage in these areas dead foraminiferal faunas include much less material derived from downslope transport consequently on the open slope dead assemblages appear to better reflect local conditions therefore the ecological information obtained from fossil open slope samples can be more reliably used to reconstruct paleoenvironmental conditions

comparison between the dead and living benthic foraminiferal assemblages in aveiro lagoon portugal abstract this work provides a comparison between living las and dead das benthic foraminiferal assemblages in 53 sampled sites located in intertidal and subtidal areas of ria de aveiro portugal the results of multivariate statistical analysis provide evidence for the main factors that control the distribution of das and las which seems to correspond to different gradients of marine continental influence conditioned by differences in the hydrodynamics of tidal currents in addition to these factors the las are clearly influenced by the total organic carbon biopolymers and pollutants the main factor that however drives the high level of agreement or the degree of disorder between the das and the las seems to be the hydrodynamics the highest level of agreement between the das and the las is found in sheltered inner lagoon areas out of the tidal currents strongest influence this study shows an interesting application of advanced statistical analysis to study the similarity between las and das aiming to identify the zones or conditions of a coastal system in which the das can potentially be a better record of las through similar studies conducted in coastal systems it is possible to select the most suitable sites to collect cores in view of the development of paleoenvironmental studies

lateral and vertical distributions of living benthic foraminifera off the douro river western iberian margin impact of the organic matter quality abstract in this study we assess the impact of the quantity and quality of the organic matter on the distribution of live benthic foraminifera on a cross margin transect off the douro river western iberian margin surface sediments from five stations ranging from 50 to 2000 m water depth were collected in march 2011 at the end of the period of maximal river runoff in order to better evaluate the importance of terrestrial input living stained benthic foraminiferal assemblages 150 m and environmental parameters grain size total organic carbon toc total nitrogen tn c n ratio 13 c toc pigments and amino acids were investigated organic matter amounts follow the sediment grain size pattern with higher concentration in fine sediments and seem to control faunal density except at the shallowest station where toc is low and faunal density high at this coastal site a massive sandy deposit is identified and associated with very low faunal diversity labile organic matter is richest at the shelf stations where benthic foraminifera standing stocks are high this is particularly evident on the douro mud patch where both density and diversity are high foraminiferal faunas living at the shelf stations are dominated by species e g nonion scaphum ammonia beccari i bulimina aculeata and eggerella scabra characteristic of the rich trophic conditions with organic matter of mixed estuarine and marine origin very low total standing stocks on the upper slope are associated with coarse sediments probably resulting from intense bottom currents at this depth resulting in poor trophic conditions deeper environments are characterized by species e g hoeglundina elegans uvigerina mediterranea and reophax scorpiurus indicative of fairly abundant but low quality organic matter finally the faunal differences between the shelf stations may reflect different successional stages an early stage at 50 m water depth where unstable conditions are observed with faunas dominated by opportunistic species and a more mature fauna in the mud patch where more stable conditions prevail

isostasy equivalent elastic thickness and inelastic rheology of continents and oceans the equivalent elastic thickness eet is used to estimate lithospheric strength expressed in response to loading by topography and subsurface loads the data on eet allow comparisons between different plates and detection of thermal events in oceans the eet corresponds to the mechanical core of the lithosphere i e a geotherm 400 600 c in continents the eet has no relation to any depth this has led to doubts in applicability of a unique approach to the continents and oceans and in the utility of estimates of eet for continents rheological data suggest that most rocks are inelastic in the long term 0 1 m y this requires interpretation of the eet in terms of real rheology we propose an analytical model that gives rheological interpretation of both the oceanic and continental eet it also allows estimates of the mechanical thickness of the lithosphere the eet depends upon three parameters geotherm age crustal thickness and flexural plate curvature any one of these values can be estimated if the others are known comparisons of model predictions with the observed eet suggest that most continental plates have a weak lower crust allowing mechanical decoupling between the upper crust and the mantle lithosphere such decoupling leads to strong reduction in the eet and thus can be easily detected flow of rocks in the weak lower crust may have a significant influence on the temporal evolution of relief mountain building erosion differences in the mechanical behavior of oceans and continents can be explained by domination of different parameters geotherm age has a major control in the oceans whereas in the continents crustal thickness is equally important additional local variations of the eet result from weakening by flexural stresses

on the oxidation and burial of organic carbon in sediments of the iberian margin and nazare canyon ne atlantic abstract as a contribution to the ec omex ii program sediment carbon and nitrogen budgets are presented for the iberian margin northeastern atlantic the budgets for degradable organic carbon and associated nitrogen were calculated from sediment and pore water properties using a steady state version of a numerical coupled diagenetic model omexdia data were collected throughout the major upwelling period along five transects four of which were located on the open margin and one positioned in a major submarine canyon the nazare canyon a comparison of in situ oxygen profiles measured with monocathodic microelectrodes and with clark type microelectrodes showed that monocathodic electrodes overestimate the oxygen concentration gradient near the sediment water interface this artifact probably results from the loss in sensitivity of the monocathodic microelectrode during profiling shipboard time course measurements with clark type electrodes demonstrated transient conditions upon sediment retrieval on deck and indicated enhanced rates of oxygen consumption in the surface sediment presumably as a result of lysis or exudation of oxidisable substrates by infauna as a result oxygen fluxes calculated from shipboard oxygen profiles overestimated in situ fluxes by up to a factor of 5 for water depths 1000 m the sediments from the canyon and from a depositional area on the shelf were enriched in organic carbon 3 4 5 wt relative to the open margin stations 0 5 2 wt and showed c n ratios exceeding redfield stoichiometry for marine organic matter indicating there was deposition of organic carbon of terrestrial origin in these areas the oxidation of organic carbon on the open margin declined from 11 gcm 2 y 1 on the shelf to 2 gcm 2 y 1 at 5000 m water depth and was dominated by aerobic oxidation the reactivity of the degradable organic carbon at the time of deposition was 1 on the shelf and declined to 1 offshore the burial of refractory organic carbon at the stations along the open margin transects also declined with increasing water depth from 5 gcm 2 y 1 on the shelf to 2 y 1 at 2000 m depth whereas the burial of particulate inorganic carbon declined from 20 gcm 2 y 1 to 2 y 1 a comparison of the estimated total organic carbon deposition and predicted delivery for the shelf suggest that 58 to 165 gcm 2 y 1 is oxidized in the water column laterally advected or focused into one of the canyons anaerobic oxidation denitrification and therefore total oxidation of organic carbon was enhanced within the canyon relative to the open margin total organic carbon oxidation decreased with water depth from 22 gcm 2 y 1 at the head of the canyon to 3 gcm 2 y 1 over its fan the reactivity of the organic carbon deposited in the canyon was lower than those of the shelf stations suggesting that the canyon is being enriched in older laterally advected organic matter the burial of refractory organic carbon in sediments from the nazare canyon was considerably higher than in the sediments from the open margin it also decreased with depth from 20 gcm 2 y 1 at 343 m to 2 5 gcm 2 y 1 at 4298 m water depth the burial of particulate inorganic carbon was slightly lower than that of refractory organic carbon the burial of refractory organic carbon and the deposition of degradable organic carbon were both positively correlated with the sedimentation rates for the iberian margin and indicated burial efficiencies were 0 6 to 48 a single trend for burial efficiency versus sedimentation rate for both the canyon and the open margin indicates that the sedimentation rate was the master variable for the geographical distribution of organic carbon oxidation and carbon preservation on the nw iberian margin

comparison of living and dead benthic foraminifera on the portuguese margin understanding the taphonomical processes abstract dead benthic foraminifera 150 m were studied in 23 sediment cores from the portuguese margin at water depths between 20 and 2000 m and located on 4 transects off the douro mondego tagus and sado river mouths and 1 transect in the estremadura for 10 stations the dead faunal vertical distribution 0 8 cm was first investigated in 4 different sediment horizons per core to evaluate the sampling effort necessary to have a representation of the dead fauna deposited under different environmental areas as a result it appears that the faunal vertical distribution is constant except for the deepest environments where fragile taxa were identified in the top layers only dead foraminiferal assemblages in the 4 5 cm layer for all stations were then compared to previously published living foraminiferal assemblages of march 2011 from the same cores to evaluate the taphonomical processes affecting major species this improves the knowledge of the faunal distribution for a better benthic foraminiferal proxy for paleostudies there was a considerable loss of some species in the dead fauna firstly this concerns the fragile organic cemented agglutinated taxa such as reophax spp glomospira charoides or bathysiphon spp secondly some calcitic species such as nonion scaphum cancris auriculus ammonia beccarii or bulimina aculeata that were particularly abundant in the living fauna on the inner shelf under the late winter high river discharge conditions were also far less dominant in the dead fauna lastly other species like cassidulina carinata valvulineria bradyana and bulimina marginata systematically showed higher abundance in the dead fauna at the mid shelf these species related to eutrophic conditions occurring in summer during the upwelling activity were therefore not well represented in the living fauna collected in march transport of allochthonous specimens may also account for higher contribution in the dead community of some species like cibicides lobatulus asterigerinata mamilla or haynesina depressula especially in coastal environments where hydrodynamic processes river flood winter storm coastal drift are more vigorous several species u mediterranea u bifurcata t agglutinans h balthica or b costata however show little or no difference in both abundance and spatial occurrence between the living and dead faunas and provide a stable signal for paleoclimatic investigations

the effect of sediment mixing on pb 210 accumulation rates for the washington continental shelf abstract nine cores from the washington continental shelf were examined by radiochemical techniques in order to evaluate the effect of mixing on the calculation of sediment accumulation rates from pb 210 profiles th 234 profiles indicate mixing coefficients of 140 cm 2 yr 1 for the seabed offshore from the columbia river and 47 cm 2 yr 1 for the seabed of the mid shelf silt deposit 75 km north of the columbia river these large mixing coefficients demonstrate that particles can penetrate to the base of the intensely mixed surface layer 10 cm within one year after emplacement at the seabed surface observed depths of cs 137 penetration within the seabed are compared with depths predicted from the surface mixed layer thickness and the pb 210 accumulation rate the observed and predicted depths agree well at all but one station at this station a combination of th 234 co 60 pb 210 and cs 137 profiles suggests that active mixing occurs below the intensely mixed surface layer the agreement of pb 210 and cs 137 data at the other stations however indicates a general absence of deep mixing on the washington shelf thus the apparent accumulation rates calculated from pb 210 profiles below the intensely mixed surface layer on the washington shelf generally reflect the true rates of sediment accumulation

a crustal structure study of jordan derived from seismic refraction data abstract the interpretation of a deep seismic refraction study in jordan performed in may 1984 shows that much of the country is underlain by continental crust 32 35 km thick and normal mantle with a velocity of 8 0 8 2 km s in the aqaba region southwest and central jordan east of wadi araba the crustal thickness is of the order of 32 35 km while in the amman region it is not less than 35 km in southeast jordan the crust thickens to at least 37 km in what is probably the transition to the arabian shield type of crust the boundaries between the upper and lower crust at about 20 km depth and the lower crust and uppermost mantle are probably transition zones the upper crystalline crust has velocities of 5 8 6 5 km s while the lower crust has velocities greater than or around 6 65 km s while the crystalline basement is exposed in southwest jordan and is at a depth of 2 2 5 km north of amman it is at a depth of not less than 5 km in central jordan a comparison of the crustal type and structure of jordan and the adjacent dead sea rift with that of the black forest and the rhine valley yields a striking resemblance the situation of the jordan dead sea rift is explained in terms of the continental crust of arabia rifting in preference to the thin oceanic crust of the mediterranean sea

recent sediment transport and deposition in the lisbon setubal and cascais submarine canyons portuguese continental margin abstract recent sediment transport and deposition in the lisbon setubal and cascais submarine canyons portuguese continental margin were investigated on the basis of water column profiles of suspended particulate matter records of near bottom currents and settling fluxes of particulate matter obtained with benthic landers and analysis of surface sediments the results show that fine grained predominantly lithogenic sediment derived from adjacent shelf areas accumulates in the upper reaches of the canyons sediment deposited further down in the middle and lower reaches of the canyons is essentially similar to the hemipelagic sediment found on the adjacent continental slope indicating that down canyon transport of sediment from the upper to the lower canyon is limited tidal currents measured at various depths in the lisbon setubal canyon appear sufficiently strong to resuspend and transport sediment but net up canyon flow of the bottom water may retain shelf derived lithogenic sediment in the upper canyon sediment gravity flows which in the nearby nazare canyon are an effective mechanism for down canyon sediment transport appear rare in the lisbon setubal canyon and probably also in the cascais canyon turbidity current events recorded in the sedimentary record of the canyons may correspond to seismic events of 1969 and 1755 ad

provenance of organic matter and nutrient conditions on a river and upwelling influenced shelf a case study from the portuguese margin organic matter contained in surface sediments from four regions on the western portuguese shelf which are influenced by coastal upwelling and fluvial input was analysed with respect to elemental organic carbon c org and nitrogen n total content and isotopic carbon and nitrogen ratios delta c 13 org delta n 15 c org n total weight ratios and delta c 13 org values are interpreted in terms of terrigenous or marine organic matter sources supported by caco3 content organic matter in the shelf sediments is mainly of marine origin with increasing terrigenous components only close to rivers and estuaries in the northern shelf region the data indicates significant terrigenous supply by the douro river north of the nazare canyon organic matter composition implies a mainly marine origin with a higher terrestrial influence close to the canyon head organic matter composition in the central shelf region which is dominated by the tagus estuary and the tagus prodelta reveals a change from a continental type signature within the estuary to a more marine type signature further to the west and south of the estuary mouth in the southern region near cape sines the geochemical properties clearly reflect the marine origin of sedimentary organic matter sedimentary delta n 15 values are interpreted to reflect various degrees of assimilation of seasonally upwelled nitrate in relation to the upwelling centres in the estuarine environment inputs of agriculturally influenced dissolved inorganic nitrogen are reflected in the sediments no evidence for n 2 fixation or denitrification is found on the central shelf north of the nazare canyon sedimentary delta n 15 values are close to marine delta no3 n 15 and thus indicate a complete no3 assimilation and n limitation of marine production light delta n 15 values in distal sediments off the douro river mouth and in samples south of c sines reflect high no3 supply and a close proximity to the seasonal upwelling centres particularly in sediments form the sines region light delta n 15 values in southern samples reflect stronger upwelling further south c 2007 elsevier b v all rights reserved

distribution of live benthic foraminifera in the ria de vigo nw spain abstract the spatial and vertical distributions of live benthic foraminifera from the muddy central axis of the ria de vigo were examined under downwelling and upwelling conditions the spatial distribution of the main benthic foraminiferal species is controlled by salinity variations san simon assemblage food availability outer ria assemblage and oxygen concentrations and or reducing microenvironmental conditions in the sediment inner ria assemblage the microhabitat distribution of benthic foraminifera is mainly dependant on the oxygenation redox conditions in the sediment and the vertical segregation of food in the inner areas of the ria low oxygen and or reducing microenvironmental conditions prevent the vertical segregation of microhabitats in outer areas oxygen penetration is deep but microhabitat partitioning only occurs in the presence of additional food resources mainly fresh organic carbon from phytoplankton blooms which triggers the colonisation of the surface layer by new species and the migration upwards and reproduction of opportunistic species

present day sedimentary processes on the northern iberian shelf abstract the galicia minho shelf features two large mud patches the douro and the galicia mud patches these are recent sediment bodies that have accumulated under a combination of conditions including 1 abundant supplies of sediment 2 morphological barriers that act as sediment traps and 3 hydrographic conditions that favour the accumulation of fine sediment in these sinks this paper describes the mechanisms controlling the deposition of the fine grained sediment depositions and the processes that result in resuspension processes on the galicia minho shelf fine grained sediments are provided from discharges from the river basins on the southern sector of the shelf mainly the douro and minho rivers sediments are exported from river estuaries onto the shelf during episodic flood events in contrast most of the sediments originating from the galician hinterland fail to contribute significantly to sedimentation on the shelf because they are retained in the galician rias which function as sediment traps sediments deposited on the shelf are frequently remobilized particularly during southwesterly storms that coincide with downwelling conditions once in suspension the fine grained sediments are transported northwards by the poleward flowing bottom currents and are eventually deposited on the douro and galicia mud patches after a series of resuspension events the locations of the two mud patches are strongly influenced by the shelf morphology fines already deposited on the mud patches are occasionally reintroduced into the system by large storm events some material from the douro mud patch and adjacent areas is re deposited in the galicia mud patch it is probable that sediments re suspended from the galicia mud patch are carried off the shelf when storm events coincide with downwelling conditions