coarse clastic barrier environments evolution and implications for quaternary sea level interpretation abstract this paper reviews recent work particularly from eastern canada on the dynamics and evolution of coarse clastic barriers it is argued that an understanding of quaternary coastal changes on paraglacial glacially influenced coasts can only be achieved with a knowledge of gravel barrier morphodynamics and sedimentation gravel barriers are distinctive coastal forms in which morphological inheritance and sediment sorting provide major behavioral controls spatially adjacent gravel barriers may display different depositional tendencies prograde seawards migrate landward or aggrade vertically such inconsistent spatial behaviour must be considered in terms of an erosional front advancing landward under stationary or rising sea level redistribution of sediment across or along the erosional front supplies sediment for the development of gravel barriers which in turn provides environments for fine grained deposition which is favourable for further barrier migration an example of an erosional front is given from chezzetcook inlet nova scotia three stages are recognized in the development of gravel barriers starting with the initiation of small drift aligned forms at the leading edge of the erosional front as sea level rises this is followed by a period of consolidation and stabilization when drift aligned forms may become swash aligned conditions for this transition are discussed under rising sea levels it is difficult to explain the conditions leading to the formation of multiple parallel swash aligned ridges although three hypotheses are advanced all of which may operate in different locations the third stage is associated with the breakdown of barriers as sediment supply fails and or sea level rises drift aligned forms are inherently unstable and show signs of pre breakdown stress in the form of reworking and remobilization of proximal sediments into cells swash aligned barriers may be breached revert to drift alignment become segmented or be overstepped some gravel is re incoporated in barriers farther landward while other material is passed seaward of the erosional front and becomes abandoned on the shoreface gravel barriers may exert a major influence on estuary and back barrier environments especially where they control the depositional record the implications for the reconstruction and interpretation of quaternary environments are summarized

the relationship between the rate of mesoscale sea level rise and the rate of retreat of swash aligned gravel dominated barriers abstract in theory a rise in sea level should force swash aligned gravel barriers to retreat landwards evidence from three single crested swash aligned gravel barriers from eastern canada and northwest europe indicates that barrier retreat rate correlates with the rate of sea level rise measured over the lower end of the mesoscale time spectrum subdecadal 10 0 yr 10 1 yr there is also a relationship between a barrier s rate of change in retreat rate and the decadal mesoscale mean rate of sea level rise specified by the duration of the tide gauge record 10 1 yr 10 2 yr specifically the higher the decadal mesoscale sea level rise rate the faster the rate of retreat of the swash aligned gravel barrier however this latter relationship may also be a function of the barrier s inertia as defined by the barrier s cross sectional volume in that barrier retreat rate correlates negatively with barrier inertia

volume and area changes of the milne ice shelf ellesmere island nunavut canada since 1950 1 ground penetrating radar gpr surveys of the 205 km2milne ice shelf conducted in 2008 and 2009 are compared with radio echo sounding res data from 1981 to provide the first direct measurements of thinning for any northern ellesmere island ice shelf our results show an average thinning for the ice shelf as a whole of 8 1 2 8 m with a maximum of 30 m over this 28 year period direct line comparisons along a 7 5 km transect near the front of ice shelf indicate a mean thinning of 2 63 2 47 m over the same period reductions in areal extent 29 82 8 4 km2 1950 2009 and volume 13 1 5 0 73 km3 water equivalent w e 1981 2008 2009 indicate that the milne ice shelf has been in a state of negative mass balance for at least the last 59 years a comparison of mean annual specific mass balance measurements with the nearby ward hunt ice shelf whis suggests that basal melt is a key contributor to milne ice shelf thinning glacier inflow to the ice shelf has also reduced markedly over the past 28 years the transition of ice shelf ice to lake ice was the most important source of mass loss a 28 5 km2 epishelf lake now exists on the landward side of the ice shelf given these recent changes disintegration of the milne ice shelf will almost certainly continue in the future

benthic oxygen consumption rates during hypoxic conditions on the oregon continental shelf evaluation of the eddy correlation method 1 three stations at 80 m water depth on the oregon shelf between 44 7 n and 43 9 n were studied under hypoxic conditions in late spring and summer of 2009 to determine benthic oxygen consumption rates oxygen fluxes were derived from eddy correlation ec measurements made from an autonomous lander deployed for 11 15 h at a time average oxygen consumption rates ranged from 3 2 to 9 8 mmol m 2 d 1 and were highest at the southernmost station methods for separating eddy components and rotating coordinates were examined for effects on ec fluxes it was found that oscillations at frequencies associated with surface and internal waves made significant contributions but horizontal component biasing could be minimized by wave based rotation methods additional measurements included benthic boundary layer properties and sediment permeability and profiles of sediment organic c chlorophyll a excess 210pb and fines comparative flux estimates were determined from benthic chamber measurements and microelectrode profiles at two of the stations the chamber o2 consumption rates exceeded the ec fluxes by factors of 1 2 1 8 which may reflect enclosure effects the different spatial and temporal scales of the measurements and or inhomogeneous benthic respiration rates the magnitudes of the fluxes by either method however are low for shelf depths thus for benthic o2 consumption to contribute to oregon shelf hypoxia bottom waters must be slowly renewed and minimally ventilated by along or across shelf advection and turbulent mixing circulation studies indicate these conditions are favored by increased near bottom stratification during persistent summer upwelling relaxation cycles

a simple general expression for longshore transport of sand gravel and shingle abstract longshore transport of sand gravel and shingle has been studied using field and laboratory data over a wide range of conditions a detailed model crosmor for cross shore and longshore sediment transport has been used to determine the effects of wave period grain size beach surf zone slope and type of waves wind waves or swell waves the longshore transport was found to be proportional to wave height to the power 3 1 h3 1 to grain size to the power 0 6 d50 0 6 and to beach slope to the power 0 4 tan 0 4 regular swell waves yield much larger factor 1 5 longshore transport rates than irregular wind waves of the same height it is proposed to take this effect into account by a swell correction factor based on all results a new simple and general dimensionally correct expression for longshore transport of sand gravel and shingle beaches with grain sizes between 0 1 and 100 mm has been derived short term and long term field data of sand gravel and shingle have been used for verification in most cases the predicted longshore transport rates are within a factor of 2 of the measured values the cerc and kamphuis formulas have also been tested

examination of mesoscale forcing of a swash aligned gravel barrier from nova scotia abstract the possibility by which the retreat of a swash aligned gravel barrier on nova scotia s atlantic coast may be influenced by varying mesoscale time domains of differential process conditions is examined tide gauge data are used to generate definition of mesoscale process domains regarded as influential in barrier behaviour semi diurnal high water tidal residuals from halifax nova scotia tide gauge 1920 1990 are characterised for both surge magnitude and frequency on an annual basis these two variables are combined to define three event types of annual surge histories first order n th step markov analyses show that significant memory exists in 6 year and 22 year transitions between surge event types the longer transition sequence mirrors a major decadal mesoscale domain change in surge generation which is suggested to be associated with phases of barrier crest reworking that enhance barrier retreat when the domain change occurs the shorter transition sequence may reflect cyclonic activity cycles on the scotian shelf superimposed on the longer term transition

human impact around settlement sites a phytolith and mineralogical study for assessing site boundaries phytolith preservation and implications for spatial reconstructions using plant remains abstract defining the extent of human activity around settlement sites is of particular significance in archaeology as it may define peripheral activity areas and thus the site s boundary in near eastern archaeology site boundaries are usually defined by the presence of architectural and other macroscopic archaeological remains here we use the phytolith concentrations and morphotype assemblages as well as changes in the mineralogical composition of the sediments in and around the small iron age site of izbet sartah in central israel to determine the site boundaries the site has a shallow stratigraphy and highly bioturbated sediments coincidental changes in the clay quartz ratio and phytolith concentrations define the boundary between high and low impact anthropogenic activities this boundary is generally some 20 m away from the architectural remains in addition we note that the phytoliths in the site s core show clear evidence of having been affected by chemical dissolution i e diagenesis while those in the vicinity of the site s boundary have undergone severe diagenesis these observations indicate that phytolith diagenesis will affect site boundaries determination as well as phytolith based reconstructions of activity areas we propose that phytolith preservation depends on the initial amount of available silica the depth of burial with respect to the active root area of modern vegetation and the presence of fresh phytoliths in the soil

spatial heterogeneity of benthic biogeochemistry in two contrasted marine environments arcachon bay and bay of biscay sw france we have studied the heterogeneity of vertical profiles of biogeochemical components obtained from sediment core slicing sediment cores were collected in the intertidal zone of the arcachon bay and on the continental slope of the bay of biscay at 550 and 1000 m depth at each station of the arcachon bay five 1 m side zones were delimited at low tide in each square 3 cores were collected spatial heterogeneity on the continental slope was obtained from the study of 3 cores of multi corer while 2 or 3 multi corer deployments were used during the same oceanographic cruise similarity between profiles was determined to estimate the spatial heterogeneity at different scales in the arcachon bay results showed a spatial heterogeneity at a decimetre scale on apparently homogeneous areas despite the spatial variability all the replicated profiles in arcachon bay sediments had similar trends suggesting homogeneous benthic properties however a sampling with replicate cores handling is required for seasonal monitoring or study of biogeochemical mechanisms in coastal environments we observe that the spatial variability on the continental margin of the bay of biscay is lower than in coastal environment of the arcachon bay heterogeneity is equivalent at a decimetre scale and at a hundred meters scale which is the precision of the sampling positioning due to the drift of the boat and the tilt of the corer cable in addition our 10 year long database for the bay of biscay showed that differences in the shape of profiles obtained in sediment cores collected at the same stations throughout this long period may not be interpreted in terms of evolution with time because the observed variability is as high as the spatial heterogeneity

methane and sulfide fluxes in permanent anoxia in situ studies at the dvurechenskii mud volcano sorokin trough black sea the dvurechenskii mud volcano dmv is located in permanently anoxic waters at 2060 m depth sorokin trough black sea the dmv was studied during the rv meteor expedition m72 2 as an example of an active mud volcano system to investigate the significance of submarine mud volcanism for the methane and sulfide budget of the anoxic black sea hydrosphere our studies included benthic fluxes of methane and sulfide as well as the factors controlling transport consumption and production of both compounds within the sediment the pie shaped mud volcano showed temperature anomalies as well as solute and gas fluxes indicating high fluid flow at its summit north of the geographical center the anaerobic oxidation of methane aom coupled to sulfate reduction sr was repressed in this zone due to the upward flow of sulfate depleted fluids through recently deposited subsurface muds apparently limiting microbial methanotrophic activity consequently the emission of dissolved methane into the water column was high with an estimated rate of 0 46 mol m 2 d 1 on the wide plateau and edge of the mud volcano surrounding the summit fluid flow and total methane flux were lower allowing higher sr and aom rates correlated with an increase in sulfate penetration into the sediment here between 50 and 70 of the methane flux 0 07 0 1 mol m 2 d 1 was consumed within the upper 10 cm of the sediment the overall amount of dissolved methane released from the entire mud volcano structure into the water column was significant with a discharge of 1 3 107 mol yr 1 the dmv maintains also high areal rates of methane fueled sulfide production and emission of on average 0 05 mol m 2 d 1 this is a difference to mud volcanoes in oxic waters which emit similar amounts of methane but not sulfide however based on a comparison of this and other mud volcanoes of the black sea we conclude that sulfide and methane emission into the hydrosphere from deep water mud volcanoes does not significantly contribute to the sulfide and methane inventory of the black sea

storm flood impacts along the shores of micro tidal inland seas a morphological and sedimentological study of the vesterlyng beach the belt sea denmark abstract the morphological and sedimentological impacts of an extreme storm event bodil in december 2013 were investigated at a mixed sand and gravel beach vesterlyng in a micro tidal environment along the belt sea denmark the storm response was characteristic for mixed sand and gravel beaches gravelly storm berms with sandy to gravelly washover fans were formed at the upper beach where swash processes dominated during extreme water levels in combination with overtopping and overwash in addition storm scarps and gravel flats were formed the elevation of the storm berm crest was identical to a summation of the still water level 1 60 m in the belt sea during the storm flood and the wave run up 0 75 m at the shore the crest of 2 35 m is therefore a precise measure of the storm flood level this storm flood was classified as a large scale extreme event in a holocene perspective it is suggested that storm berm beach ridge heights above contemporaneous sea level can be used as a proxy of past flood events along micro tidal shores

bedload dynamics and associated snowmelt influence in mountainous and semiarid alluvial rivers abstract the influence of snowmelt in semiarid alluvial rivers is determined by the river bed configuration and erosion processes moreover the large amount of available sediment in the floodplains of these rivers limits traditional bedload sampling methodologies and suggests the use of large control volumes and long term studies to understand erosive dynamics in this study bedload monitoring in a large control volume 0 2 hm3 from 2004 to 2010 was used to study erosive processes of the guadalfeo river a semiarid alluvial river in southeastern spain with high mountain influences and a hydrological regime conditioned by snow dynamics the methodological approach to testing the performance of different transport models included characterization of the forcing agents precipitation and snowmelt events hydraulic configuration of the river determination of the river bed material surface and substrate and one off measurements for particular events the results indicate a sediment volume effective runoff relationship that is consistent with the existence of steep channels with a flashy runoff regime although the existence of an armored layer derived from snowmelt events greatly controls the transport dynamics with equivalent fractions of cobble gravel and sand in the measured bedload this apparent predominance of near equal mobility was confirmed by the calibrated hiding function exponent x 0 94 0 97 the thresholds for entrainment and transport efficiency are similar to those observed for mountain rivers that exhibit torrential flow although notable differences can be observed in the dynamics of the processes the strong performance of the original meyer peter and muller model with c 8 is shown to estimate the total transported volume associated with intense events when the variability of d50 is included in the analysis however this model does not sufficiently capture transport because of moderate events rain or snowmelt and thus underestimates bedload on medium and long timescales the calibrated model of parker klingeman adequately represents erosive dynamics with r50 values between 0 03 and 0 041 for moderate and intense events respectively and a flow threshold of 14 2 m3 s 1 that separates these two situations nevertheless these models based on hiding functions present greater dispersion if the variability of diameters related to cobbles and pebbles is considered for such cases the wilcock and crowe model performed better for both intense and moderate events the latter is important in the study area where snowmelt pulses occasionally exceed the critical flow and break the surface layer with significant sediment contributions these processes differentiate the transport dynamics from other studies and are distinctive characteristics that are more closely related to mountainous influences in semiarid environments where pulses of intense snowmelt are common despite its limitations the proposed methodology based on a large check dam has proven to be adequate and representative for assessment of erosion processes

two dimensional ph distributions and dynamics in bioturbated marine sediments the seafloor is the site of intense biogeochemical and mineral dissolution precipitation reactions which generate strong gradients in ph near the sediment overlying water interface these gradients are usually measured in one dimension vertically with depth two dimensional ph distributions in marine sediments were examined at high resolution 65 65 m pixel and analytical precision over areas of 150 to 225 cm2 using a newly developed ph planar fluorosensor dramatic three dimensional gradients complex heterogeneity and dynamic changes of ph occur in the surficial zone of deposits inhabited by macrofauna ph can vary by 2 units horizontally as well as vertically over millimeter scales ph minima zones often form in association with redoxclines within a few millimeters of inner burrow walls and become more pronounced with time if burrows remain stable and irrigated for extended periods microenvironmental ph minima also form locally around decaying biomass and relict burrow tracks and dissipate with time 5 d h concentrations and fluxes in sandy mud show complex acid base reaction distributions with net h fluxes around burrows up to 12 nmol cm 2 d 1 and maximum net reaction rates varying between 90 consumption to 120 production m d 1 90 nmol cm 1 d 1 burrow length acid producing zones that surround irrigated burrows are largely balanced by acid titration zones along inner burrow walls and outer radial boundaries the geometry and scaling of ph microenvironments are functions of diagenetic reaction rates and three dimensional transport patterns determined by sediment properties such as diffusive tortuosity and by benthic community characteristics such as the abundance mobility and size of infauna previously undocumented biogeochemical phenomena such as low ph regions associated with in filled relict biogenic structures and burrowing tracks are readily demonstrated by two dimensional and time dependent images of ph and sedimentary structure

in situ microscale variation in distribution and consumption of 2 a case study from a deep ocean margin sediment sagami bay japan a transecting microprofiler documented a pronounced small scale variation in the benthic o2 concentration at 1450 m water depth sagami bay japan data obtained during a single deployment revealed that within a sediment area of 190 cm2 the o2 penetration depth varied from 2 6 mm to 17 8 mm average 6 6 2 5 mm and the diffusive o2 uptake calculated from the vertical concentration gradient within the diffusive boundary layer ranged from 0 6 mmol m 2 d 1 to 3 9 mmol m 2 d 1 average 1 8 0 7 mmol m 2 d 1 n 129 however correction for microtopography and horizontal diffusion increased the average diffusive o2 uptake by a factor of 1 26 0 06 detailed 2d calculations on the volume specific o2 consumption exhibited high variability the oxic zone was characterized by a mosaic of sediment parcels with markedly different activity levels millimeter to centimeter sized hot spots with o2 consumption rates up to 10 pmol cm 3 s 1 were separated by parcels of low or insignificant o2 consumption the variation in aerobic activity must reflect an inhomogeneous distribution of electron donors and suggests that the turnover of material within the oxic zone to a large extent was confined to hot spots the in situ benthic o2 uptakes measured during four cruises reflected a seasonal signal overlying the observed small scale variability the annual benthic mineralization balanced 50 of the estimated pelagic production however the central bay is characterized by a significant downslope sediment transport and mass balance estimates indicate 90 retention of the total organic material reaching the bottom of the central bay

transport processes deduced from geochemistry and the void ratio of surface core samples deep sea sagami bay central japan abstract sagami bay is a deep water foreland basin with an average sedimentary rate of approximately 0 1 g cm 2 year it is an appropriate area to study for better understanding of sedimentary processes in a setting with a high sedimentation rate seven multiple core samples 30 50 cm thick were obtained from sagami bay four of the core samples were taken from the tokyo submarine fan system tokyo canyon floor tokyo fan valley and its levee the distal fan margin two samples were obtained from the sakawa fan delta and the adjacent topographic high the remaining one was from an escarpment of the sagami submarine fault variations in chemical composition can be recognized at every coring site they show two different sediment sources the sediments of the tokyo submarine fan system and those from sakawa fan delta further there are differences in chemical composition between canyon floor and levees even within the tokyo submarine fan system the results suggest that the sedimentary process is strongly controlled not by vertical particle settling but by a hyperpycnal flow process the proxies obtained from the core samples do not reflect conditions in the water column immediately overlying the sea floor rather they are controlled by conditions on the adjacent continental shelf or and shallow basins which are the areas of primary accumulation

large scale experiments on gravel and mixed beaches experimental procedure data documentation and initial results abstract this paper provides information on the experimental set up data collection methods and results to date for the project large scale modelling of coarse grained beaches undertaken at the large wave channel gwk of fzk in hannover by an international group of researchers in spring 2002 the main objective of the experiments was to provide full scale measurements of cross shore processes on gravel and mixed beaches for the verification and further development of cross shore numerical models of gravel and mixed sediment beaches identical random and regular wave tests were undertaken for a gravel beach and a mixed sand gravel beach set up in the flume measurements included profile development water surface elevation along the flume internal pressures in the swash zone piezometric head levels within the beach run up flow velocities in the surf zone and sediment size distributions the purpose of the paper is to present to the scientific community the experimental procedure a summary of the data collected some initial results as well as a brief outline of the on going research being carried out with the data by different research groups the experimental data is available to all the scientific community following submission of a statement of objectives specification of data requirements and an agreement to abide with the gwk and eu protocols

coupling cross shore and longshore sediment transport to model storm response along a mixed sand gravel coast under varying wave directions abstract this paper investigates the profile response of a mixed sand gravel deltaic beach playa granada southern spain forced by storm waves from varying directions beach morphology was monitored over a 36 day period with variable wave conditions and profile response was compared to model predictions using the xbeach g model and a longshore sediment transport lst formulation xbeach g was applied over 2 day periods of low energy south westerly sw storm and south easterly se storm conditions and was coupled to lst using a parametric approach which distributes the lst across the swash surf and nearshore zones a calibrated wave propagation model delft3d was used to obtain the inshore conditions required to drive the xbeach g model and the lst formulation the storm response is clearly influenced by the free board difference between the height of the berm and the total run up and is also strongly dependent on storm wave direction with the sw storm eroding the surveyed area while the se storm induced beach accretion model results indicate that xbeach g on its own is capable of adequately reproducing the response of the beach under sw storm conditions b s s 0 95 but not under se storms due to the higher lst gradients at the study location the combination of xbeach g and lst fits the measured profiles reasonably well under both sw b s s 0 96 and se b s s 0 88 storms inspiring confidence in the coupled model to predict the storm response under varying wave conditions the combined xbeach g lst model was applied to the entire 6 8 km deltaic coastline to investigate the impact of extreme sw and se storm events and the model results reiterate the importance of cross shore and longshore sediment transport in driving coastal storm response at this location the approach proposed in this work can be extended to other worldwide coasts highly influenced by both cross shore and longshore sediment transport such as beaches with different coastline orientations and or forced by varying wave directions

high rates of microbial carbon turnover in sediments in the deepest oceanic trench on earth microbes regulate the decomposition of organic matter in marine sediments measurements at the deepest oceanic site on earth reveal high rates of microbial activity potentially fuelled by the deposition of organic matter microbes control the decomposition of organic matter inmarine sediments decomposition in turn contributes to oceanic nutrient regeneration and influences the preservation of organic carbon1 generally rates of benthic decomposition decline with increasing water depth although given the vast extent of the abyss deep sea sediments are quantitatively important for the global carbon cycle2 3 however the deepest regions of the ocean have remained virtually unexplored4 here we present observations of microbial activity in sediments at challenger deep in the mariana trench in the central west pacific which at almost 11 000 m depth represents the deepest oceanic site on earth we used an autonomous micro profiling system to assess benthic oxygen consumption rates we show that although the presence of macrofauna is restricted at challenger deep rates of biological consumption of oxygen are high exceeding rates at a nearby 6 000 m deep site by a factor of two consistently analyses of sediments collected from the two sites reveal higher concentrations of microbial cells at challenger deep furthermore analyses of sediment 210pb profiles reveal relatively high sediment deposition in the trench we conclude that the elevated deposition of organic matter at challenger deep maintains intensified microbial activity at the extreme pressures that characterize this environment

the influence of topography on the functional exchange surface of marine soft sediments assessed from sediment topography measured in situ we investigated the influence of small scale topography on the exchange surface between sediment and water in two coastal marine sediments one site was a sandy silt at giglio island italy the sediment was rich in organic material had a very active fauna and a rich surface topography the second site was an estuarine mud in aarhus bay denmark which had a less active fauna and less surface topography the topography at both sites was measured in situ with a horizontal resolution of 0 1 mm the topographic data were used to calculate the area of the three dimensional exchange surface which was 12 larger than the projected base area on giglio and 7 larger in aarhus bay in addition to enlarging the surface area topography also caused horizontal gradients that were not included in the vertical o2 flux calculated from the concentration gradient in the diffusive boundary layer to account for both effects fluxes calculated from the vertical o 2 gradient in the diffusive boundary layer were corrected by a factor of 1 14 in the estuarine mud and 1 25 in the nearshore sand by considering the constraints on exchange surface enlargement and by comparing with previous studies we argue that it is unlikely to find topographic influences much larger than this range topography had an even smaller effect on the area of the oxic anoxic interface than on the exchange surface between sediment and water in the nearshore sand the oxic anoxic interface was a factor of 1 06 larger than the projected horizontal area and in the estuarine mud the enlargement was by a factor of 1 03 oxygen consumption can be considered as an integration of both anaerobic and aerobic carbon turnover which makes the oxygen flux between sediment and water one of the most important parameters in biogeochemistry to separate different pathways and processes in the redox cycles of cohesive sediments it is useful to divide the oxygen flux into two parts the diffusive o2 uptake through the visible sediment surface and the fauna mediated oxygen consumption fou in which oxygen enters the sediment through the burrows of benthic animals in fine grained sediments diffusive o2 uptake takes place through the diffusive boundary layer dbl boudreau and jorgensen 2001 the oxygen gradient in the dbl can be measured with microelectrodes and the vertical diffusive flux jz is then calculated from fick s first law of diffusion jz 52 d dc dz where d is the molecular diffusion coefficient and dc dz the vertical concentration gradient the fou comprises all o2 consumption associated with ventilated macrofauna burrows this includes the respiratory oxygen consumption of the animals themselves the oxygen uptake of burrow walls with the associated microbial community and the oxygen consumed by

internal architecture of a raised beach ridge system anholt denmark resolved by ground penetrating radar investigations abstract the internal architecture of raised beach ridge and associated swale deposits on anholt records an ancient sea level the holocene beach ridges form part of a progradational beach ridge plain which has been interpreted to have formed during an isostatic uplift and a relative fall in the sea level over the past 7700 years the ridges are covered by pebbles and cobbles and commonly show evidence of deflation material presumably removed from the beach ridges and adjacent swales form the present dune forms on anholt ground penetrating radar gpr reflection lines have been collected with 250 mhz shielded antennae across the fossil ridge and swale structures the signals penetrate the subsurface to a maximum depth of 10 m below the fossil features the gpr data resolve the internal architecture of the beach ridges and swales with a vertical resolution of about 0 1 m gpr mapping indicates that the holocene beach ridges are composed of seaward dipping beachface deposits as well as minor amounts of inland dipping deposits of wash over origin the beachface deposits downlap on underlying shoreface deposits and we use these surfaces as markers of a relative palaeo sea level the new data indicate that the highest relative sea level at about 8 5 m was reached 6500 years ago 700 years later the relative sea level had dropped 0 7 m indicating a change in the relative sea level around 1 mm year this fall in the relative sea level most likely records the influence of an isostatic rebound causing younger beach ridge deposits to indicate lower sea levels

nitrogen cycling in a deep ocean margin sediment sagami bay japan on the basis of in situ no microprofiles and chamber incubations complemented by laboratory based assessments of anammox and denitrification we evaluate the nitrogen turnover of an ocean margin sediment at 1450 m water depth in situ no profiles horizontally separated by 12 mm reflected highly variable no penetration depths no consumption rates and nitrification on average the turnover time of the pore water no pool was 0 2 d net release of nh z during mineralization 0 95 mmol m 22 d21 sustained a net efflux of ammonia 53 nitrification 24 and anammox activity 23 the sediment had a relatively high in situ net influx of no 1 44 mmol m22 d21 that balanced the n2 production as assessed by onboard tracer experiments n2 production was attributed to prokaryotic denitrification 59 anammox 37 and foraminifera based denitrification 4 anammox thereby represented an important nutrient sink but the n2 production was dominated by denitrification despite the fact that no stored inside foraminifera represented 80 of the total benthic no pool the slow intracellular no turnover that on average sustained foraminifera metabolism for 12 52 d contributed only to a minor extent to the overall n2 production the microbial activity in the surface sediment is a net nutrient sink of 1 1 mmol n m 22 d 21 which aligns with many studies performed in coastal and shelf environments continental margin areas can act as significant n sinks and play an important role in regional n budgets