massive sand beds attributed to deposition by dense water cascades in the bourcart canyon head gulf of lions northwestern mediterranean sea nowadays the gulf of lions continental shelf and slope are under the influence of dense water cascading wind induced bottom currents and the geostrophic northern current in order to characterize sedimentary activity at the shelf break several interface and piston cores were taken in the bourcart canyon head and a current meter equipped with temperature conductivity pressure and turbidity sensors was moored during the 2003 2004 winter season even if the canyon is not connected directly to continental sources since last glacial maximum detailed grain size x ray and sediment facies analysis of interface cores show that down to 350 m water depth the canyon head is blanketed by up to 1 5 m of structureless muddy medium grained sand 210pbexc activity measurements demonstrate present day sedimentary activity of the canyon head time series of currents with peak velocity reaching 0 37 m s suspended sediment concentration and temperature indicate that dense water cascading is the main process allowing the reworking transport and accumulation of sand within the canyon head even though winter 2003 2004 was characterized by low cascading events compared to other years these sand beds called cascadite constitute a new type of deposit that differs from other typical slope deposits turbidites hyperpycnites contourites in terms of flow duration and sedimentological characteristics they are similar to shallow water contourites they might be time equivalent to the recent turbidites described throughout the deep western gulf of lions basin

stable isotopic and biomarker evidence of terrigenous organic matter export to the deep sea during tropical storms abstract the global export of organic carbon oc is intimately linked to the total flux of terrestrial sediment to the ocean with the continental margins receiving 90 of the sediment generated by erosion on land recent studies suggest that a substantial amount of particulate oc poc might escape from the shelf and be exported to the continental slope deep sea sector although the mechanisms and magnitude of such deep sea poc transfer remain unknown here we investigate hyperpycnal flow associated total suspended matter tsm collected from water depths of 3000 m near the bottom of sea floor in the gaoping submarine canyon gsc off southwestern taiwan elemental c n isotopic 13 c 15 n and biomarker compositions of tsm were investigated to understand its biogeochemical characteristics a two end member 13 c mixing model indicates that deep sea tsm contains 90 terrigenous oc while a similar mixing model using 15 n reveals a lower proportion 58 organic biomarkers of tsm suggest contributions from a mixture of resuspended continental margin derived marine organic matter om mar and terrigenous sources revealing that terrestrial oc likely mixes with nitrogen rich marine material during rapid transport this study documents that rapid transfer of terrigenous organic matter om terr into the deeper regions of gsc occurred within a week of typhoon morakot likely through hyperpycnal injection of sediment laden warm freshwater from southern taiwan evidence from this typhoon morakot induced hyperpycnal plume event in taiwan demonstrates that extreme storm events provide an efficient way to export terrigenous oc without oxidation to hitherto unknown water depths of deep sea in the oceania region

downward particle fluxes in the guadiaro submarine canyon depositional system north western alboran sea a river flood dominated system abstract three moorings equipped with sediment traps were deployed in the north western alboran continental margin to study downward particle fluxes in the guadiaro submarine canyon depositional system this area is located close to the strait of gibraltar and is influenced by the upwelling induced by the atlantic jet and by episodic flood events from the guadiaro river sediment traps were installed in the guadiaro canyon in the guadiaro channel and in the adjacent continental slope the overall duration of the deployment was 12 months from november 1997 to october 1998 time series of downward particle fluxes major constituents organic carbon nitrogen biogenic opal calcium carbonate and lithogenics and 210pb were determined near the surface at mid depths and near the bottom total mass fluxes tmf in this area fluctuated more than two orders of magnitude and showed an important seasonal variability with higher fluxes in winter increases in tmf and lithogenics together with decreases in 210pb organic carbon and opal were recorded in all traps coinciding with river floods indicating a direct response of the system to these events and a rapid offshore transport of suspended matter affecting the entire water column the channel site received similar particle fluxes to the western open slope site indicating that this channel did not act as a preferential sediment conduit during the deployment period in the guadiaro canyon tmf were more than one order of magnitude higher 210pb concentration was lower one half and organic matter was more degraded than at the channel site during spring and summer as a consequence of receiving particles resuspended by internal waves and occasionally by trawling activities these particles were mainly retained in the canyon which works as a trap also during spring and summer the opal and organic carbon percentages increased in all traps both in magnitude and variability and peaks seem to be associated with biological blooms

particle dynamics and fluxes in canyons and open slopes of the southern cretan margin eastern mediterranean abstract the samaria and lithinon canyons at the southern cretan margin eastern mediterranean were studied with respect to hydrography deep currents particle dynamics and settling fluxes by utilizing a current meter and sediment trap records from may 2005 to may 2006 and b hydrographic and optical measurements along with particulate matter and particulate organic carbon concentrations pmc and poc respectively in two surveys may and october 2005 the deep currents were very weak with mean velocity 3 4 cm s 1 and their direction was controlled by the local bottom topography the entire area was characterized by very low pmc and poc depicted both by transmissometry profiles and discrete bottle data the fluxes of downward settling particles are comparable with the fluxes measured in the broader eastern mediterranean and hence point to an oligotrophic environment with low atmospheric and lateral inputs a series of relatively high total mass fluxes 1000 mg m 2 d 1 were recorded near the head of the samaria canyon at the trap closest to crete and was attributed to a high temporal lithogenic inputs mineral calcite transferred to the sea by a small intermittent stream flowing through the samaria gorge which was activated by short rainfall events and spring snowmelt and b inputs of numerous coccoliths of e huxleyi and calcite by shallow sediment resuspension generated by wind induced waves apart from this local scale event there was very little evidence of matter transfer through the canyons thus during the one year of observations the canyons were dormant because of this lack of down canyon transport during the study period open slopes and canyons exhibited roughly similar characteristics in terms both of particle dynamics and fluxes however the presence of coarse grained sediments along the canyon axes point to episodic canyon activity occurring at unknown time scales and periodicity

geomorphic characterization of four shelf sourced submarine canyons along the u s mid atlantic continental margin abstract shelf sourced submarine canyons are common features of continental margins and are fundamental to deep sea sedimentary systems despite their geomorphic and geologic significance relatively few passive margin shelf breaching canyons worldwide have been mapped using modern geophysical methods between 2007 and 2012 a series of geophysical surveys was conducted across four major canyons of the us mid atlantic margin wilmington baltimore washington and norfolk canyons more than 5700 km2 of high resolution multibeam bathymetry and 890 line km of sub bottom chirp profiles were collected along the outer shelf and uppermost slope depths of 80 1200 m the data allowed us to compare and contrast the fine scale morphology of each canyon system the canyons have marked differences in the morphology and orientation of canyon heads steepness and density of sidewall gullies and the character of the continental shelf surrounding canyon rims down canyon axial profiles for washington baltimore and wilmington canyons have linear shapes and each canyon thalweg exhibits morphological evidence for recent relatively small scale sediment transport for example washington canyon displays extremely steep wall gradients and contains 100 m wide 5 10 m deep v shaped incisions down the canyon axis suggesting modern or recent sediment transport in contrast the convex axial thalweg profile the absence of thalweg incision and evidence for sediment infilling at the canyon head suggest that depositional processes strongly influence norfolk canyon during the current sea level high stand the north walls of wilmington washington and norfolk canyons are steeper than the south walls due to differential erosion though the underlying cause for this asymmetry is not clear furthermore we speculate that most of the geomorphic features observed within the canyons e g terraces tributary canyons gullies and hanging valleys were formed during the pleistocene and show only subtle modification by holocene processes active during the present sea level high stand

impact of relative sea level and rapid climate changes on the architecture and lithofacies of the holocene rhone subaqueous delta western mediterranean sea abstract the modern rhone delta in the gulf of lions nw mediterranean is a typical wave dominated delta that developed after the stabilization of relative sea level following the last deglacial sea level rise similar to most other deltas worldwide it displays several stacked parasequences and lobes that reflect the complex interaction between accommodation sediment supply and autogenic processes on the architecture of a wave dominated delta the interpretation of a large set of newly acquired very high resolution seismic and sedimentological data well constrained by 14c dates provides a refined three dimensional image of the detailed architecture seismic bounding surfaces sedimentary facies of the rhone subaqueous delta and allows us to propose a scenario for delta evolution during the last deglaciation and holocene the subaqueous delta consists of parasequence like depositional wedges a few metres to 20 30 m in thickness these wedges first back stepped inland toward the nw in response to combined global sea level rise and overall westward oceanic circulation at a time when sediment supply could not keep pace with rapid absolute eustatic sea level rise at the younger dryas preboreal transition more rapid sea level rise led to the formation of a major flooding surface equivalent to a wave ravinement surface after stabilization of global sea level in the mid holocene accommodation became the leading factor in controlling delta architecture an eastward shift of depocentres occurred probably favoured by higher subsidence rate within the thick messinian rhone valley fill the transition between transgressive backstepping geometry and regressive prograding geometry para sequences resulted in creation of a maximum flooding surface mfs that differs from a classical mfs described in the literature it consists of a coarse grained interval incorporating reworked shoreface material within a silty clay matrix this distinct lithofacies results from condensation erosion which appears as an important process even within supply dominated deltaic systems due to avulsion of distributaries the age of the mfs varies along strike between ca 7 8 and 5 6 kyr cal bp in relation to the position of depocentres and climatically controlled sediment supply the last rapid climate change of the holocene the little ice age 1250 1850 ad had a distinct stratigraphic influence on the architecture and lithofacies of the rhone subaqueous delta through the progradation of two deltaic lobes in response to changes in sediment supply linked to rapid climate changes and to anthropic factors the rhone delta evolved from wave dominated to fluvial dominated and then wave dominated again

the dangeard and explorer canyons south western approaches uk geology sedimentology and newly discovered cold water coral mini mounds the celtic margin is a complex area in terms of sedimentary dynamics and evolution with a number of submarine canyons dissecting the continental slope and outer continental shelf the complex terrain and diverse range of sea bed sediments play a part in submarine canyons being described as areas of high habitat heterogeneity this study has concentrated on the heads of two canyons dangeard also known as dangaard and explorer first named here located in uk territorial waters in water depths between 138 and 1165 m multibeam echosounder 2d reflection seismic and photographic ground truthing data have been combined to map the sea bed geomorphology sedimentary features and canyon megafauna of these canyons in addition two previously unknown provinces of cold water coral cwc mini mounds were discovered on the interfluves of the dangeard and explorer canyons the study area comprises a dendritic network of gullies feeding into the canyon thalwegs amphitheatre rims where slope angles are commonly in excess of 20 occur along the margins and heads of both canyons and are interpreted as drainage basins indicative of retrogressive mass wasting in a shelfward direction the cwc mini mounds occur in water depths between 250 m and 410 m with more than 400 mounds identified they are up to 3 m in height and 50 150 m in diameter with no sub surface expression suggesting these mounds are in geological terms relatively young and possibly holocene in age biological analyses revealed that the mounds form a habitat for ophiuroids and munida associated with lophelia pertusa coral rubble suggesting these mini mounds are not present day living features

ploughing the deep sea floor bottom trawling is a fishing technique whereby heavy nets and gear scrape along the sea bed and is shown here to disturb sediment fluxes and modify the sea floor morphology over large spatial scales the direct impact of bottom trawling on local fish populations has received much attention but trawling also affects other aspects of the ocean environment this paper shows that bottom trawling a commercial practice in which heavy nets and gear are dragged along the ocean floor induces sediment reworking and erosion causing the gradient of the sea floor to become smoother over time this reduces the morphological complexity of deep sea environments the authors draw parallels between the effects of bottom trawling at sea and intensive agriculture on land with the important difference that on land ploughing takes place once or twice a year whereas at sea bottom trawling can be a frequent occurrence bottom trawling is a non selective commercial fishing technique whereby heavy nets and gear are pulled along the sea floor the direct impact of this technique on fish populations1 2 and benthic communities3 4 has received much attention but trawling can also modify the physical properties of seafloor sediments water sediment chemical exchanges and sediment fluxes5 6 most of the studies addressing the physical disturbances of trawl gear on the seabed have been undertaken in coastal and shelf environments7 8 however where the capacity of trawling to modify the seafloor morphology coexists with high energy natural processes driving sediment erosion transport and deposition9 here we show that on upper continental slopes the reworking of the deep sea floor by trawling gradually modifies the shape of the submarine landscape over large spatial scales we found that trawling induced sediment displacement and removal from fishing grounds causes the morphology of the deep sea floor to become smoother over time reducing its original complexity as shown by high resolution seafloor relief maps our results suggest that in recent decades following the industrialization of fishing fleets bottom trawling has become an important driver of deep seascape evolution given the global dimension of this type of fishery we anticipate that the morphology of the upper continental slope in many parts of the world s oceans could be altered by intensive bottom trawling producing comparable effects on the deep sea floor to those generated by agricultural ploughing on land

sources and exchanges of mercury in the waters of the northwestern mediterranean margin abstract ocean margins are focal regions in terms of mercury hg exchanges between the continent and the open sea the aim of this paper is to describe the distribution and partition of hg between the gaseous dissolved and particulate phases in the waters of the northwestern mediterranean nwm margin in order to assess the hg sources and exchanges within the continuum between the continental shelf gulf of lions and the open sea northern gyre mean standard deviation of total hg species hgt concentrations in unfiltered water samples were 1 52 1 00 pmol l 1 n 36 in the inner shelf 1 09 0 15 pmol l 1 n 30 along the slope and 1 10 0 13 pmol l 1 n 99 in the northern gyre the dissolved phase the hg from the open sea water is the largest hg input to the gulf of lions 5 7 kmol yr 1 whereas inputs from the riverine source account for 3 4 kmol yr 1 and atmospheric deposition for less than 0 5 kmol yr 1 the hg accumulated in the sediments of the shelf is 4 5 kmol yr 1 including 0 6 1 7 kmol yr 1 in the rhone prodelta sediments the evasion to the atmosphere represents a hg flux of 2 6 kmol yr 1

thick bottom nepheloid layers in the western mediterranean generated by deep dense shelf water cascading the analysis of a compilation of deep ctd casts conducted in the western mediterranean from 1998 to 2011 has documented the role that dense water formation and particularly deep dense shelf water cascading off the gulf of lions plays in transporting suspended particulate matter from the coastal regions down to the basin deep ctd casts reveal that after the 1999 and 2005 2006 deep cascading events the western mediterranean deep water wmdw was characterized by the presence of a thick bottom nepheloid layer bnl that corresponded in thickness with a thermohaline anomaly generated by the mixture of dense waters formed by deep convection in the open sea and by deep cascading this bnl can be hundreds of meters thick and in the central part of the basin usually exhibits suspended sediment concentrations of 1 mg l after winter 1999 the bnl spread from the gulf of lions and the catalan margin over the northwestern mediterranean basin reaching west of the balearic islands and the ligurian sea while after winters 2005 2006 the bnl covered the entire western mediterranean basin thickness and concentration of the bnl tend to diminish with time but this trend is highly dependent on the volume of dense water generated both by convection and cascading after winter 1999 the bnl signal vanished in one year but after winters 2005 2006 it lasted for longer and the turbidity signal can still be distinguished at present 2011 particle size distribution in the bnl reveals the presence of large aggregates up to 1 mm in size formed by a mixture of single particles with the same bimodal grain size distribution as the surface sediments found in the northwestern mediterranean slope and basin results presented in this paper highlight the fact that the wmdw can be periodically affected by the arrival of new dense waters loaded with suspended particles mainly introduced by resuspension processes during major cascading events being a key process that could ultimately affect deep sea biogeochemical cycles in the western mediterranean

theoretical analysis of particle number density in steady aeolian saltation abstract particle number density or particle concentration in aeolian saltation is one important input parameter to calculate the sand flux kinetic energy and mid air collision probability in the aeolian saltation and particle concentration is also related to the wind erosion capacity hence in the present paper the vertical distribution of particle number density in steady aeolian saltation is analyzed based on two different types of probability density functions of vertical lift off velocity of saltating particles one is the pdf probability density function of vertical velocity of lift off particles in the three dimensional space defined as a type a pdf which considers the number of particles in various velocity bins per unit volume and the other is the pdf of vertical velocity of lift off particles ejected from the sand bed surface in a period of time as a type b pdf which considers the number flux of particles in various velocity bins per unit surface area these two types of pdfs are from two different perspectives i e volume and surface based perspectives respectively and can be deduced from each other the half normal and exponential distributions are recommended for the type a pdf and the corresponding type b pdf is expressed by rayleigh and gamma 2 distributions the pdf distribution pattern of vertical velocity of lift off particles has an important influence on the vertical profile of particle number density if the type a pdf of vertical velocity of ejected particles is a half normal distribution the particle number density decays exponentially with height if the type a pdf is an exponential distribution the particle number density also decreases with height if the type a pdf is gamma 3 and rayleigh distributions the particle number density first increases then decreases with height the type a and type b height parameters which are calculated according to the mean vertical lift off velocity from the type a and type b pdfs respectively are not simply considered as the actual mean saltation height although if the type a pdf of vertical lift off velocity is half normal pdf the mean dispersion height of particle concentration equals the mean saltation height the vertical distribution of particle number density can determine the dislodgement rate on bed surface which further affects the surface bedforms

a walk down the cap de creus canyon northwestern mediterranean sea recent processes inferred from morphology and sediment bedforms the cap de creus canyon northwestern mediterranean sea belongs to a complex network of submarine canyons cutting the western gulf of lion continental shelf and opening into the larger sete canyon swath bathymetry data mak 1m deep towed side scan sonar imagery and 5 khz high resolution seismic reflection profiles show striking morphologies in the cap de creus canyon floor and walls as a consequence of the canyon head and the upper reach severe incision the continental shelf dramatically narrows in front of the creus cape promontory the upper canyon has a flat bottomed thalweg incised in a mega scale sediment furrow field displaying hyperbolic seismic facies the tens of kilometres long linear furrows extend also over the middle canyon down to 1400 m of water depth the furrows on either side of the canyon are not parallel but oblique and display varying degrees of excavation mid channel sediment bars are locally present in the thalweg which is made of sandy lag deposits as revealed by its acoustic response and verified by sediment samples the middle canyon is linear and steep with an up to 700 m high southern wall contrasting with the sinuous smooth lower canyon which is controlled by flowage of the underlying messinian evaporites large sections of the canyon are affected by sediment instability processes the lower cap de creus canyon hangs up to 260 m over its distalmost reach and the sete canyon through a narrow less than 1 km wide gorge numerous scours up to 10 m deep suggesting bed load transport occupy the lower sete canyon immediately downstream of the cap de creus canyon mouth the data set provides the first complete very high resolution imaging of a submarine canyon from its upper part down to its distalmost reach the observations evidence a wide set of erosion transport and deposition processes along the cap de creus canyon including sediment entrapment at the canyon head furrow generating dense water cascading through the southern wall along channel currents strong enough to excavate specific sections of the channel floor and bed load sediment transport as demonstrated by the presence of mega ripples crescent scours and grooves in the lower canyon

particle fluxes dynamics in blanes submarine canyon northwestern mediterranean abstract within the framework of the multidisciplinary recs project and with the aim of describing the particle flux transfer from the continental shelf to the deep basin an array of five mooring lines equipped with a total of five pairs of pps3 3 sequential sampling sediment traps and rcm 7 8 current meters were deployed 30 m above the bottom from march 2003 to march 2004 inside and outside the blanes canyon one mooring line was located in the upper canyon at 600 m depth one in the canyon axis at 1700 m depth and other two close to the canyon walls at 900 m depth a fifth mooring line was deployed in the continental open slope at 1500 m water depth the highest near bottom downward particle flux 14 50 g m 2 d 1 was recorded at the trap located in the upper canyon m1 where continental inputs associated with the presence of the tordera river are most relevant on the other hand the downward fluxes 4 35 g m 2 d 1 in the canyon axis m2 were of the same order as those found in the western flank m3 of the canyon both values were clearly higher than the value 1 95 g m 2 d 1 recorded at the eastern canyon wall m4 the open slope m5 mass flux 5 42 mg m 2 d 1 recorded by the sediment trap located outside the canyon system was three orders of magnitude lower than the other values registered by the inner canyon stations the relevance of our data is that it explains how the transport pathway in the canyon occurs through its western flank where a more active and persistent current toward the open ocean was recorded over the entire year of the experiment off shelf sediment transport along the canyon axis showed clear differences during the period of the study with some important events leading to strong intensifications of the current coupled with large transport of particle fluxes to the deepest parts of the canyon such events are primarily related to increases in river discharge and the occurrence of strong storms and cascading events during the winter in summary in this study it is shown that the dynamics of the water masses and the currents in the study area convert the sharp western flank of the blanes canyon in a more active region that favors erosion processes than the eastern flank which has a smoother topography and where the absence of erosional conditions yields to steadier sedimentary processes

strataform overview of its design and synthesis of its results abstract the strata formed on continental margins record the history of both marine and terrestrial events occurring on earth the strataform program was created to develop a better understanding of relationships between these events and margin stratigraphy in order to obtain the maximum information from strata they are being examined simultaneously on various temporal and spatial scales and their formation is being studied where events and accumulation are known to be active the general objectives of strataform are to add geological perspective to studies of sedimentary processes to constrain stratigraphic interpretations better and to develop numerical models relating processes and stratigraphy this research is being undertaken on margins off northern california and new jersey which provide unique opportunities for investigation of short term and long term stratigraphy respectively this volume and paper focus upon studies undertaken off northern california north of cape mendocino this area is tectonically active with a coastal mountain range narrow shelf and input of sediment primarily from the eel river recent estimates indicate that 1 to 3 10 7 t yr of mud silt and clay are supplied to the continental shelf sand accumulates on the inner shelf 70 reaches the continental slope or deeper during the previous lowstand of sea level sediment discharge was 25 greater and probably led to hyperpycnal debris and other flows transporting sediment down the slope on the eel shelf flood and storm events combine to create normally stratified fine grained layers with basal sand and much terrestrial organic debris these layers are modified through time but some can be buried and preserved subsurface flood layers seem to impact observations of acoustic backscatter on the middle shelf and subsurface fluids gas freshwater affect electromagnetic measurements on the inner shelf budgets of eel river mud accumulation for the past century indicate 20 trapped on the adjacent shelf and 20 on the upper slope 150 600 m the remaining 60 is dispersed to more distal locations over holocene time scales eel river sediment has built a small sandy subaqueous delta and a subtle bulge of muddy sediment on the middle shelf north of the river gullies have been eroded on the open slope during lowstands of sea level and have accreted upward during highstands a massive failure has formed the humboldt slide due to earthquake activity and unstable substrates possibly from excess pore pressures and gas the tectonic setting has impacted margin stratigraphy from small scales fluid expulsion pockmarks to large scales spatial variation of late cenozoic sedimentation the broad dispersal of eel sediment demonstrates the three dimensional character of the resulting stratigraphy including the large scale clinoform structure developed on the shelf upper slope the rollover point topset foreset boundary for this feature is the shelf break i e below sea level which is important information for stratigraphic interpretations of sea level change

transfer of lipid molecules and polycyclic aromatic hydrocarbons to open marine waters by dense water cascading events abstract settling particles were collected by a set of moored sediment traps deployed during one year in the western gulf of lion along cap de creus and lacaze duthiers submarine canyons and on the adjacent southern open slope these traps collected particles during periods of pelagic settling and also during events of deep water flushing by dense shelf water cascading dswc analyses of lipid biomarkers n alkanes n alkan 1 ols sterols and c37 c38 alkenones and polycyclic aromatic hydrocarbons pahs showed much higher transfer of terrestrial lipids and pahs to open deep waters during dswc than in the absence of cascading the area of highest lateral fluxes was mostly located at 1000 m depth but also at 1500 m depth and extended along the canyons and to the adjacent slope higher fluxes were observed near the bottom 30 m above bottom mab than at intermediate waters 500 mab which is consistent with the formation and sinking of dense water over the continental shelf and its transport through the canyons towards the continental slope and deep basin dswc involved the highest settling fluxes of terrestrial lipids and pahs ever described in marine continental slopes and the pelagic domain as illustrated by peak values of c23 c33 odd carbon numbered alkanes 405 ng m 2 d 1 c22 c32 even carbon numbered alkan 1 ols 850 ng m 2 d 1 sitosterol sitostanol 4800 ng m 2 d 1 and pahs 55 g m 2 d 1 the algal lipids also showed higher transfer to deep waters during dswc but to a lower extent than the terrigenous compounds however the c37 c38 alkenones constituted an exception and their settling fluxes were not influenced by dswc the lack of influence of the dswc on the c37 c38 alkenone settling is consistent with absence of haptophyte algal inputs from the continental shelf and reinforces the reliability of these molecules for palaeothermometry and palaeoproductivity measurements in pelagic systems

particle fluxes induced by benthic storms during the 2012 dense shelf water cascading and open sea convection period in the northwestern mediterranean basin abstract the effects of deep dense shelf water cascading and open sea convection on the sediment dynamics of the northwestern mediterranean basin were studied by near bottom moored instruments recording trapped particle fluxes suspended particle fluxes water properties and hydrodynamics from november 2011 to july 2012 during this period near bottom currents induced by winter dense water formation generated benthic storms that caused resuspension at 2450 m water depth increasing by more than one order of magnitude the ambient suspended sediment concentrations the trapped particle fluxes and the suspended sediment fluxes during the preconditioning phase of the open sea convection from december 2011 to mid february 2012 currents 1 10 cm s 1 suspended sediment concentrations

composition and provenance of terrigenous organic matter transported along submarine canyons in the gulf of lion nw mediterranean sea abstract previous projects in the gulf of lion have investigated the path of terrigenous material in the rhone deltaic system the continental shelf and the nearby canyon heads this study focuses on the slope region of the gulf of lion to further describe particulate exchanges with ocean s interior through submarine canyons and atmospheric inputs nine sediment traps were deployed from the heads to the mouths of lacaze duthiers and cap de creus submarine canyons and on the southern open slope from october 2005 to october 2006 sediment trap samples were analyzed by cuo oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of terrigenous biomarkers such as lignin derived phenols and cutin acids sediment trap data show that the dense shelf water cascading event that took place in the months of winter 2006 january february and march had a profound impact on particle fluxes in both canyons this event was responsible for the majority of lignin phenol 55 4 and cutin acid 42 8 inputs to submarine canyons with lignin compositions similar to those measured along the mid and outer continental shelf which is consistent with the resuspension and lateral transfer of unconsolidated shelf sediment to the canyons the highest lithogenic normalized lignin derived phenols contents in sediment trap samples were found during late spring and summer at all stations i e 193 46 g vp g 1 lithogenic at deep slope station when river flow wave energy and total particle fluxes were relatively low during this period lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios 3 at almost all stations high p coumaric to ferulic acid ratios 3 and high yields of cutin acids relative to vanillyl phenols 1 all trends that are consistent with high pollen inputs our results suggest marked differences in the sources and transport processes responsible for terrigenous material export along submarine canyons mainly consisting of fluvial and shelf sediments during winter and atmospheric dust inputs during spring and summer

modeling the effects of martian surface frost on ice table depth abstract ground ice has been observed in small fresh craters in the vicinity of the viking 2 lander site 48 n 134 e to explain these observations current models for ground ice invoke levels of atmospheric water of 20 precipitable micrometers higher than observations however surface frost has been observed at the viking 2 site and surface water frost and snow have been shown to have a stabilizing effect on antarctic subsurface ice a snow or frost cover provides a source of humidity that should reduce the water vapor gradient and hence retard the sublimation loss from subsurface ice we have modeled this effect for the viking 2 landing site with combined ground ice and surface frost models our model is driven by atmospheric output fields from the nasa ames mars general circulation model mgcm our modeling results show that the inclusion of a thin seasonal frost layer present for a duration similar to that observed by the viking lander 2 produces ice table depths that are significantly shallower than a model that omits surface frost when a maximum frost albedo of 0 35 was permitted seasonal frost is present in our model from ls 182 to ls 16 resulting in an ice table depth of 64 cm which is 24 cm shallower than the frost free scenario the computed ice table depth is only slightly sensitive to the assumed maximum frost albedo or thickness in the model

morphology of turbidite systems within an active continental margin the palomares margin western mediterranean abstract the palomares margin an nne ssw segment of the south iberian margin located between the alboran and the algerian balearic basins is dissected by two major submarine canyon systems the gata in the south and the alias almanzora in the north new swath bathymetry side scan sonar images accompanied by 5 khz and topas subbottom profiles allow us to recognize these canyons as mediterranean examples of medium sized turbidite systems developed in a tectonically active margin the gata turbidite system is confined between residual basement seamounts and exhibits incised braided channels that feed a discrete deep sea fan which points to a dominantly coarse grained turbiditic system the alias almanzora turbidite system larger and less confined is a good example of nested turbiditic system within the canyon concentric sediment waves characterize the alias almanzora deep sea fan and the size and acoustic character of these bedforms suggest a fine grained turbidite system both canyons are deeply entrenched on a narrow continental shelf and terminate at the base of the continental slope as channels that feed deep sea fans while the alias almanzora turbidite system is the offshore continuation of seasonal rivers the gata turbidite system is exclusively formed by headward erosion along the continental slope in both cases left lateral transpressive deformation influences their location longitudinal profiles incision at the upper sections and canyon bending associated with specific fault segments

shelf to canyon connections transport related morphology and mass balance at the shallow headed rapidly aggrading swatch of no ground bay of bengal abstract the swatch of no ground song canyon in the bay of bengal is a shelf incising submarine canyon that is actively aggrading in its upper reaches despite regular gravity driven transport and mass wasting although the canyon lies 150 km downdrift of its main sediment source the ganges brahmaputra meghna gbm river mouth high sedimentation rates 5 50 cm year 1 are sustained by both progradation of the subaqueous delta into the canyon head and the conveyance of shelf generated hyperpycnal flows to the canyon floor this rapid accretion appears to be largely balanced by mass failures triggered by regularly occurring storms and less frequently by major earthquakes here we use high resolution sub bottom sonar data to elucidate dominant sediment dispersal pathways and their transport related morphology at the canyon head these include 1 a laterally prograding clinoform that intersects the canyon head at water depths of 20 120 m 2 several shelf incising bypass gullies that originate in 50 m the clinoform deposits reflect westward progradation of the gbm subaqueous delta into the upper canyon where its axis normal orientation leaves it dissected by cross cutting gullies and mass failures the morphology and acoustic stratigraphy of the gullies coupled with strong bed shear and high suspended sediment concentrations on the inner shelf suggest that these features are sustained by the regular conveyance of gravity driven fluid muds that are formed in shallow water

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

typhoon and earthquake enhanced concentration and inventory of dissolved and particulate trace metals along two submarine canyons off southwestern taiwan abstract the influence of typhoon and earthquake events on the distributions of dissolved and particulate trace metals al fe mn cd cu pb zn is evaluated along the gaoping canyon and fangliao canyon in a tectonically active margin off southwestern taiwan the fangliao canyon was mightily struck by a large pingtung earthquake ml 7 0 in winter when terrestrial inputs were insignificant this large earthquake clearly enhanced the concentration and inventory of total suspended matter tsm dissolved and particulate metals by 2 5 fold in fangliao canyon and nearby gaoping canyon as compared to those in normal winter conditions the gaoping canyon is typically inundated with massive amounts of terrestrial materials during summer typhoons from the mountainous gaoping river strong contrast of particle and metal distributions can be found between summer and winter and between typhoon and regular summer periods in the gaoping canyon which was apparently caused by various strengths of river inputs followed by sediment resuspension and lateral advection at intermediate and near bottom depths along the canyon the water column and canyon wide inventories of tsm dissolved and particulate metals increased up to 2 fold higher during the post typhoon period than during the rainy period in summer in the gaoping canyon after extreme events most metals tend to increase their release into the dissolved phase through the increase of tsm concentration in addition to huge river inputs during typhoon both typhoon and earthquake induce energetic sea conditions that cause sediment resuspension and enhance the concentration and inventory of particles and metals in submarine canyons

post glacial persistence of turbiditic activity within the rhone deep sea turbidite system gulf of lions western mediterranean linking the outer shelf and the basin sedimentary records emplacement of post glacial turbidites is commonly controlled by rapid changes in sea level or by seismicity on the continental rise of the gulf of lions western mediterranean an aseismic area we identified turbiditic beds deposited during the rising stage and highstand of sea level swath bathymetry sediment cores in situ cone penetrating tests cptu heavy mineral associations and radiocarbon dating determined the source composition distribution and age of the turbiditic beds turbidites are composed of homogeneous to positively graded silts to medium sand with quartz up to 90 shell debris and shelfal benthic faunas their distribution on the sea floor is very patchy and controlled by abundant inherited erosional bedforms their source is found in relict regressive sands at the outershelf their deposition occurred just after the onset of the post glacial sea level rise and the concomitant sediment starvation of the rhone deep sea turbiditic system until recently whilst canyons are fed with sand by strong seasonal hydro sedimentary dynamics on the outershelf the emplacement of post glacial turbidites is not controlled by sea level changes but probably by the periodic flushing of the canyons our study revealed that this low energy aseismic margin undergoes significant transport of sand down to the base of slope during the sea level rise and the holocene highstand

reexposure and advection of 14c depleted organic carbon from old deposits at the upper continental slope represents an additional source of 14 c depleted organic carbon supplied to the ocean in parallel with the weathering of fossil organic carbon delivered by rivers from land to understand the dynamics and implications of this reexposure at the shelf edge a biogeochemical study was carried out in the gulf of lions mediterranean sea where erosive processes driven by shelf dense water cascading are currently shaping the seafloor at the canyon heads mooring lines equipped with sediment traps and current meters were deployed during the cascading season in the southwestern canyon heads whereas sediment cores were collected along the sediment dispersal system from the prodelta regions down to the canyon heads evidence from grain size x radiographs and 210 pb activity indicate the presence in the upper slope of a shelly coarse surface stratum overlying a consolidated deposit this erosive discontinuity was interpreted as being a result of dense water cascading that is able to generate sufficient shear stress at the canyon heads to mobilize the coarse surface layer eroding the basal strata as a result a pool of aged organic carbon d 14 c 944 5 24 7 mean age 23 650 3 321 ybp outcrops at the modern seafloor and is reexposed to the contemporary carbon cycle this basal deposit was found to have relatively high terrigenous organic carbon lignin 1 48 0 14 mg 100 mg oc suggesting that this material was deposited during the last low sea level stand a few sediment trap samples showed anomalously depleted radiocarbon concentrations d 14 c 704 4 62 5 relative to inner shelf d 14 c 293 4 134 0 mid shelf d 14 c 366 6 51 1 and outer shelf d 14 c 384 47 8 surface sediments therefore although the major source of particulate material during the cascading season is resuspended shelf deposits there is evidence that this aged pool of organic carbon can be eroded and laterally advected downslope

cold water coral ecosystems in cassidaigne canyon an assessment of their environmental living conditions abstract the cassidaigne canyon is one of the two canyons together with lacaze duthiers of the french mediterranean coast in which cold water corals have settled and formed large colonies providing a structural habitat for other species nevertheless the communities settled in the cassidaigne canyon are physically impacted by discharges of bauxite residues new information on the distribution of the species madrepora oculata and the associated species diversity in cassidaigne canyon was provided by videos and photos acquired in 2013 an area investigated at 515 m depth harbored a high density of small colonies of m oculata the water column structure of the area was described by using a ctd transect deployed along the axis of the canyon high resolution 10 m and 2 m bathymetric data were collected in the cassidaigne canyon in 2010 and 2014 seafloor characteristics were derived from the 10 m resolution bathymetric data data on local hydrodynamic conditions in the first 10 m above the seafloor were produced by applying the mars3d hydrodynamic model in the cassidaigne canyon at a horizontal resolution of 80 m cascans model configuration these environmental datasets combined with the geographic coordinates of the known occurrences of dense m oculata colonies in the canyon allowed establishing a model using the maxent software package to predict the habitat distribution in terms of probability of occurrence according to the water mass analysis m oculata habitats are mainly located in the layer of the intermediate waters originating from the eastern mediterranean basin a high concentration of suspended sediment due to the bauxite residues expelled into the canyon was observed in the axis of the canyon where we measured 1 ntu 2 5 mg l at 100 m above the bottom while concentrations were even higher 2 ntu 5 mg l closer to the bottom the habitat suitability model indicates that the living conditions of m oculata can be found in areas of the cassidaigne canyon where the substratum shows irregularities slopes and topographic highs concerning environmental variables resulting from the hydrodynamic model temperature and high current velocities were identified as explanatory factors of the distribution of m oculata suitable areas for m oculata habitat settlement were mapped at the scale of the canyon this study gathers multiple disciplines combined to consider a submarine canyon as a global functioning system and is an approach intended to promote the management of sensitive ecosystems in complex topographic features such as canyons

impact of climate and sea level changes on the ventilation of intermediate water and benthic foraminifer assemblages in the gulf of lions off south france during mis 6 and 7 abstract benthic and planktic foraminifer assemblages together with oxygen stable isotope were studied in the prgl1 borehole promess1 drilled on the upper slope of the gulf of lions with a view to reconstruct the impact of climate changes on surface and bottom waters between mis7 and mis6 foraminifer species were grouped by r mode principal components analysis we obtained 3 factors in benthic assemblages that were related to eutrophic mesotrophic and oxygenated environments in the planktic foraminifer assemblages four factors were considered that explained the changes of sea surface temperature productivity and turbulence in the water column variations in the terrestrial organic carbon supply associated with eustatic sea level changes mainly controlled oxygen consumption and the benthic communities during mis7 the benthic communities were mainly mesotrophic owing to the low supply of terrestrial organic carbon because the coastline was distant from the slope however during mis6 the sea level drop caused a rapid progradation of the river rhone prodelta and dramatically increased the supply of terrestrial organic carbon resulting in a pronounced increase in eutrophic foraminifers apart from the effect of the river discharge which contributed to the reduced oxygen content we recognized periods of intense bottom ventilation during mis 6 and to a lesser extent in the substadial stages of mis 7 the ventilation events are well matched by higher turbulence and convection in the water column during cold episodes associated with an intensification of the northwesterlies in contrast during the short millennial scale warming events of mis6 the stratification of the water column rapidly reduced bottom ventilation these results are consistent with those reported in previous studies that point to enhanced dense water formation in the gulf of lions during cold stages

origin and transport of trace metals deposited in the canyons off lisboa and adjacent slopes portuguese margin in the last century abstract submarine canyons play an important role in the transfer of contaminated sediments from shelf areas to the deeper ocean to evaluate the importance of submarine canyons adjacent to the tagus and sado estuaries portuguese margin as sediment pathway major and trace elements 210 pb radionuclides organic carbon calcium carbonate and grain size were analyzed in fifteen short sediment cores from the cascais and lisboa setubal submarine canyons and neighbor slopes at the estremadura spur and off sines mass accumulation rates mar vary between 0 02 and 0 40 g cm 2 y 1 with the highest values in the upper cascais and lisboa canyons mercury and pb enrichment factors exceed 2 and show a continuously increasing trend since 1950 ad in the upper sections of the cascais canyon and in the lisboa setubal canyon system implying an anthropogenic source mercury and pb anthropogenic inventories also present highest values in the canyon heads which is consistent with its proximity to the tagus and sado river mouths to a lesser extent the estremadura and sines slopes and the deeper sections of the canyons also have slightly increasing hg and pb enrichment factor trends towards the present day for these areas with a major influence of pelagic sedimentation we infer atmospheric transport as a complementary source of contaminants therefore our data suggest that although canyons are preferential conduits to transport sediments to the deep sea when compared to the slopes hg and pb derived from human activities have reached both domains with different intensities down to a depth of 2000 mwd

changes in planktic and benthic foraminifer assemblages in the gulf of lions off south france response to climate and sea level change from mis 6 to mis 11 1 a multidisciplinary study involving micropaleontological and geochemical tools was carried out in borehole prgl1 promess 1 with the aim of reconstructing the impact of climate change and sea level variation between 133 ka and 406 ka in the upper slope of the gulf of lions we used factor analysis to obtain three main benthic assemblages related to eutrophic mesotrophic and oxygenated environments planktic foraminifers were grouped as warm water and cold turbulent species these results were compared with records of caco3 and major and trace elements al ca k sr as well as the c n ratio of organic matter power and cross spectral analysis showed a straightforward relationship between precession minima and thermal stratification of the water column as well as the occurrence of eutrophic bottom conditions during lowstand periods and mesotrophic environments at times of highstand these eutrophic mesotrophic oscillations usually driven by global eustatic change also involved regional variations in caco3 source to this environment during periods of precession maxima enhancement of northwesterly winds increased primary productivity by mixing enhancing the percentage of cold turbulent species in the water column and the proportion of oxygenated benthic species on the bottom during interglacial stages these events were recorded by lower biogenic carbonate at the expense of higher silicate related components most likely due to a higher supply from pyrenees rivers the record of oxygenated benthic species can be a good proxy to monitor past changes in winter intermediate water dynamics driven by northwesterly winds

20th century sediment budget trends on the western gulf of lions shoreface france an application of an integrated method for the study of sediment coastal reservoirs abstract this paper presents a shoreface sediment budget established for the 20th century 1895 1984 2009 along the microtidal wave dominated coast of the western gulf of lions languedoc roussillon mediterranean sea se france the implementation of a diachronic bathymetric approach coupled with the definition of sand reservoirs upper sand unit usu by very high resolution seismic surveys and the results of lidar investigations offers a new means of defining precisely the magnitude and change trends of the sediment budget the aim of this study is to link the large scale coastal behaviour lscb of the littoral prism expressed in terms of shoreface sediment budget shoreface sediment volume and spatial distribution pattern of cells to climatic change river sediment input to the coast longshore sediment transport distribution impact of hard coastal defence structures and artificial beach nourishment the results show a significant reduction of the volume of the western gulf of lions littoral prism over 114 years 26 1 4 6 10 6 m 3 from 1895 to 1984 the overall budget is slightly positive with a volume estimated at 4 1 3 5 10 6 m 3 for 1984 2009 however the estimated sediment budgets clearly indicate that erosion is dominant over the last 25 years with a volume loss of 30 2 4 2 10 6 m 3 in relation to the long term sediment budget and longshore drift pattern the long term trend of the usu volume distribution displays strong spatio temporal contrasts linked to longshore sediment drift spatial distribution of fluvial sediment inputs and hard engineering structures locally the sedimentary reservoir is significantly eroded within a century 80 of usu since the initial amount present was low and not sustainable the emphasis is on the importance of considering the volume changes of available sediment reservoirs rather than their losses and gains erosion of the languedoc roussillon shoreface is likely to continue in the future due to the natural decrease of river sediment input and the sand removal for human purposes consequently the littoral sand prism results in sedimentary reservoirs that are gradually being used up

spatial and temporal variability of meiobenthic density in the blanes submarine canyon nw mediterranean abstract meiofaunal density distribution was studied from 400 m to 1500 m depth inside blanes submarine canyon nw mediterranean and on the eastern open slope in autumn 2003 and spring 2004 our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the blanes canyon that characterize it as highly heterogeneous environment inside the canyon area particle fluxes were higher than on the slope area increased from autumn to spring and mostly consisted of lithogenic material moreover the canyon s locations experienced more intense bottoms currents and sediment disturbance being reflected in a greater variability of meiobenthic densities both between stations and sampling times than on the open slope no clear trends e g declining densities associated with increasing depths were observed contrary in the open slope current velocities were relatively lower compared with the canyon area and showed lower temporal variability at the same time the nutritional quality of the particle fluxes at deeper grounds were higher probably allowing the meiofaunal densities not to change over time in conclusion the meiobenthos in our system apparently showed a higher temporal variability inside the canyon area strongly affected by particle fluxes or erosive and sediment mixing processes linked to current modifications induced by the canyon topography

late quaternary bottom current activity in the south aegean sea reflecting climate driven dense water production abstract the eastern mediterranean transient emt represents a recent early 1990s to today water circulation phenomenon during which more arid climatic conditions in the mediterranean lead to the production of very dense surface water masses in the north aegean sea the produced north aegean dense water nadw sinks to seafloor flows to the south aegean sea and then spills into the eastern mediterranean sea through the cretan straits contributing to the rejuvenation of the bottom water a large dataset of vintage high resolution seismic reflection profiles indicates that the floors of the basins in the southwest aegean sea are characterised by late quaternary erosional gullies abraded surfaces and channel related sediment drifts such structures provide evidence for the presence of strong bottom currents which originate from the southward propagation of nadw masses the basins have depths of 300 m to 1000 m and are connected to each other by narrow a few km straits and sills the dominance of abraded surfaces and erosional gullies on the northern flank of the basins and in the narrow straits sills between them provides evidence that the southward propagation of the nadw occurs by the filling and flooding of each basin by dense water which then spills and cascades into the next basin southward seismic stratigraphy suggests that the formation of the drifts started at marine isotope stage mis 11 420 ka bp the coincidence of at least three erosional surfaces within the sediment drifts with interglacial mis 11 5 and 1 respectively suggests that bottom currents were mostly active during high sea level stands and sluggish during glacial low sea level stands a 90 100 m drop of the sea level below the current level would have resulted in the emergence of the eastern cyclades plateau and thus in the disconnection of the southwest aegean sea from the north aegean sea several 0 05 0 5 m thick beds of gravelly sand with algal and mollusc debris laminated to mottled sand and mottled mud are observed in the sediment cores analysed in this paper these beds can be confidently correlated from core to core and are interpreted as bottom current deposits the separation of these beds by hemipelagic sediments indicates that bottom current activity in the southwest aegean is not permanently established but episodic six episodes of intense bottom current activity are recorded in the mis 2 4 10 80 ka sediments and they appear to correlate well with the cold and dry younger dryas and heinrich 3 4 5 6 and 7 events in contrast at least three episodes of intense bottom current activity are recorded in the cores during the holocene the higher frequency of strong bottom current episodes in the southwest aegean sea during the holocene is attributed to the higher sea level stand that makes the circulation of water masses in the aegean sea more sensitive to climatic changes

near bottom particulate matter dynamics in the nazare submarine canyon under calm and stormy conditions two mooring lines equipped with near bottom sediment traps were deployed in the axis of the nazare submarine canyon at similar to 1600 and similar to 3300 m depth respectively we studied time series of particle flux composition biogenic silica carbonates organic matter and lithogenic fractions granulometry mineralogy and pb 210 concentration of particulate matter over five sediment trap deployments between october 2002 and december 2004 current meters equipped with turbidimeters were also deployed at trap depths to monitor the water flow temperature salinity and suspended particle concentration the composition of the collected particles was fairly constant year round dominated by the lithogenic fraction and with oc n ratios in the range 11 21 suggesting an important terrigenous influence inside the canyon the results show contrasting dynamic environments in the upper 1600 m depth and middle 3300 m depth canyon high current speeds spring tides up to 80 cm s 1 and high apparent mass fluxes of particulate matter mean 65 g m 2 d 1 maximum 265 g m 2 d 1 are permanent at the shallowest station at the deepest site fluxes were below 10 g m 2 d 1 most of the time and the annual flux was governed by events of sharp flux increase storms affecting the continental shelf during autumn and winter are a major driver of down canyon dispersal of sediments to the middle canyon and beyond important nepheloid activity developed inside the canyon in response to storms with significant wave heights between 4 and 6 m as testified by turbidimeters deployed in midwater and near the seabed at 1600 m water depth on three occasions during the study period significant wave heights of incident storms surpassed 7 m leading to notable episodes of down canyon transport that were clearly observed in the middle canyon during one of these stormy periods january 2003 a sediment gravity flow transporting unusual quantities of sand and coastal plant debris was observed at 3200 m however a storm with significant wave heights as low as 5 m was apparently able to trigger a sediment gravity flow reaching beyond the middle canyon the role of storms in the offshore dispersal of sediments is clearly relevant but seems to be modulated by synergic factors such as river flooding

sand bodies at the shelf edge in the gulf of lions western mediterranean deglacial history and modern processes abstract the outer continental shelf of the gulf of lions is covered by thick mainly regressive sand deposits a combination of seismic sedimentological and geochronological methods allows us to demonstrate that a veneer of transgressive sand bodies few m to less than 1 m thick reworks these deposits they take the form of sand ridges and transverse dunes that formed at different periods in fact the low gradient outer shelf of the gulf of lions displays a complete record of deglacial history including not only transgressive deposits that formed during sea level rise but also bedforms that still evolve under episodic high energy events that occur under more highstand conditions core lithology 14 c dates and regional sea level curve suggest that the formation of the sand ridges was favoured during a period of deceleration of sea level rise such as during the younger dryas event the dunes are part of a mobile carpet here u160 the deposition of this marine sand veneer is possibly related to the interplay between different factors that trigger the turning on off for bottom currents sand deposition transport on the outer shelf in fact the sands appear to have been reworked intermittently due to high energy conditions in shallow water depth currents wave regime and wind driven circulation as well as they form current ridges superimposed to the transgressive deposits in the westernmost part of the studied area at the bourcart canyon s head

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

the first deep sea mooring station in the eastern levantine basin deeplev outline and insights into regional sedimentological processes abstract the eastern levantine basin elb is an ultra oligotrophic warm and saline marine system significantly affected by climate change during the past several decades the deployment of the first moored station at the elb deeplev at 1500 m water depth 50 km offshore haifa israel aimed at enhancing synchronized measurements of physical and biogeochemical dynamics the station carries an array of sediment traps and sensors that measure physical chemical and biological attributes along the water column here we describe the station and present sediment flux data from the first 1 5 years of operation since november 2016 we show that despite deeplev s offshore location and the open sea characteristics of the water column lateral transport from the continental margin contributes the greatest fraction of particulate flux to the seafloor at this site this mostly occurs via intermediate nepheloid layer plumes entering the study area between depths of 180 and 800 m bottom currents are weak average sd 3 5 2 cm s 1 and are unlikely to cause significant resuspension based on sedimentation rates obtained from nearby sediment cores and sediment particle fluxes sampled in the traps calculated accumulation rates of total particulate matter and of particulate organic carbon at the seafloor were 95 108 g m 2 y 1 and 0 5 0 6 g m 2 y 1 respectively offshore changes in sedimentation rates and in surface sediment elemental ratios indicate that sediment originating from the continental margins is transported at least 100 km offshore

oceanographic processes and morphosedimentary products along the iberian margins a new multidisciplinary approach abstract our understanding of bottom currents and associated oceanographic processes e g overflows barotropic tidal currents including intermittent processes e g vertical eddies deep sea storms horizontal vortices internal waves and tsunamis is rapidly evolving many deep water processes remain poorly understood due to limited direct observations but can generate significant depositional and erosional features on both short and long term time scales this paper represents a review work which describes for the first time these oceanographic processes and examines their potential role in the sedimentary features along the iberian continental margins this review explores the implications of the studied processes given their secondary role relative to other factors such as mass transport and turbiditic processes and highlights three major results a contourite depositional and erosional features are ubiquitous along the margins indicating that bottom currents and associated oceanographic processes control the physiography and sedimentation b the position of interfaces between major water masses and their vertical and spatial variation in time specifically appears to exert primary control in determining major morphologic changes along the slope gradient including the contourite terraces development and c contourites deposits exhibit greater variation than the established facies model suggests therefore a consistent facies model however faces substantial challenges in terms of the wide range of oceanographic processes that can influence in their development an integrated interpretation of these oceanographic processes requires an understanding of contourites seafloor features their spatial and temporal evolution and the near bottom flows that form them this approach will synthesize oceanographic data seafloor morphology sediments and seismic images to improve our knowledge of permanent and intermittent processes around iberia and evaluate their conceptual and regional role in the margin s sedimentary evolution given their complexes three dimensional and temporally variable nature integration of these processes into sedimentary oceanographic and climatological frameworks will require a multidisciplinary approach that includes geology physical oceanography paleoceanography and benthic biology

tectonic evolution geomorphology and influence of bottom currents along a large submarine canyon system the sao vicente canyon sw iberian margin abstract a multi scale dataset consisting of multi beam echo sounder 2d multi channel seismic and sidescan sonar tobi data allows us to identify a large variety of morphologies originating from sedimentary and tectonic processes along the sao vicente canyon svc which is the largest submarine canyon developed in the external part of the gulf of cadiz the svc is located in one of the most seismogenic areas of western europe the convergence between the eurasian and african plates has controlled the formation and evolution of the canyon the svc is tectonically controlled by three main thrust faults the marques de pombal fault the sao vicente fault and the horseshoe fault no major rivers feed sediment to the canyon head but the main sediment source is related to the dismantling of canyon flanks and the mow mediterranean overflow water this current contributes sediments by two different processes a conturites deposition at the head and flanks of the svc that periodically fail into the canyon and b the coarser grained and denser sediment of the mow might be trapped at the head of the canyon and could develops into hyperpycnal flows the svc is characterized by retrogressive erosion being submarine landslide deposits and scars the main seafloor morphologies the tectonic and stratigraphic interpretation of seismic profiles indicate that the svc is a clear example of a diachronous and segmented canyon developed since the late miocene in an area of present day active plate tectonics this study investigates the interaction between active tectonics the dynamics of submarine canyons and the resulting geomorphologies

anthropogenic trace metals in the sedimentary record of the llobregat continental shelf and adjacent foix submarine canyon northwestern mediterranean abstract anthropogenic trace metal concentrations and inventories were studied on the llobregat continental margin from the llobregat river mouth to the foix submarine canyon a prodelta sedimentary depocentre was identified along with a previously known canyon depocentre significant upward increases in trace metal contents were detected in sediment cores of the prodelta and upper part of the canyon down to 860 m depth metal enrichment factors ranged between 1 8 and 10 on the continental shelf and between 1 2 and 2 7 in the submarine canyon these metal enrichments occurred during the 20th century and can be correlated with the period of maximum increase of population and industrial activities in the barcelona area and the consequent anthropogenic metal inputs maximum trace metal enrichments are located in the prodelta depocentre and significant enrichments were also measured in the southern prodelta and in the foix upper canyon as a consequence of efficient shelf canyon sediment and metal transfer deeper in the canyon at 1370 m depth no metal enrichments were detected probably because of particle dispersion and dilution with uncontaminated sediment within the canyon this study shows that in some mediterranean sedimentation systems anthropogenic trace metal contamination is affecting not only the littoral and the continental shelf but also the adjacent continental slope sediments through submarine canyons

benthic foraminifera from capbreton canyon revisited faunal evolution after repetitive sediment disturbance abstract at a 650 m deep site in the axis of capbreton canyon an 18 cm thick turbidite was deposited in december 1999 during subsequent campaigns an almost monospecific fauna of the benthic foraminifer technitella melo considered as a pioneer species was found in may 2000 in 2001 this fauna had disappeared and was replaced by an exceptionally rich fauna strongly dominated by the opportunistic species bolivina subaenariensis we present sedimentological radionuclide and foraminiferal data of new cores sampled in 2005 and 2011 taken with the aim to study the further evolution of the benthic ecosystem cores sampled in 2005 show that in the canyon axis a new ca 5 cm thick turbidite has been deposited the live benthic foraminiferal faunas were much poorer than in 2001 but still had a high dominance and low diversity although less extreme than in 2001 we conclude that in the canyon axis benthic foraminiferal faunas remain in an early stage of ecosystem colonization it appears that the very thick 1999 turbidite marks an exceptional event the uncommonly rich faunas observed in 2001 could be a response to the concentration of organic rich material in the fine grained top of this deposit in 2011 cores were sampled at a slightly different site on the lower canyon flank the sedimentary sequence here is marked by the absence of coarse turbidite layers although some levels show slightly increased grain size and lower 210 pb xs activities indicative of an admixture with advected older sediments live foraminiferal faunas are much more equilibrated as shown by their higher diversity lower dominance and deeper penetration into the sediment all these characteristics are indicative of a much more stable ecosystem dead faunas are present throughout the core indicating that the levels with slightly elevated grain size are not typical turbidites resulting from hyperpycnal currents which are characterized by levels barren of foraminifera but denote other more long term sedimentary processes leading to the advection of older material such as bottom nepheloid layers or repetitive fine grained turbidite deposits due to small scale slumping the comparison of live and dead fauna shows that at both sites the foraminiferal turnover rates are fairly low at the lower canyon flank site sampled in 2011 the foraminiferal faunas are renewed every 1 5 2 years such a fairly long foraminiferal lifespan corresponds to earlier estimates but is surprisingly high for the opportunistic taxa that dominate the faunal assemblages in these unstable and food enriched submarine canyon settings

marine litter on the floor of deep submarine canyons of the northwestern mediterranean sea the role of hydrodynamic processes marine litter represents a widespread type of pollution in the world s oceans this study is based on direct observation of the seafloor by means of remotely operated vehicle rov dives and reports litter abundance type and distribution in three large submarine canyons of the nw mediterranean sea namely cap de creus la fonera and blanes canyons our ultimate objective is establishing the links between active hydrodynamic processes and litter distribution thus going beyond previous essentially descriptive studies litter was monitored using the liropus 2000 rov litter items were identified in 24 of the 26 dives carried out in the study area at depths ranging from 140 to 1731 m relative abundance of litter objects by type size and apparent weight and distribution of litter in relation to depth and canyon environments i e floor and flanks were analysed plastics are the dominant litter component 72 followed by lost fishing gear disregarding their composition 17 and metal objects 8 most of the observed litter seems to be land sourced it reaches the ocean through wind transport river discharge and after direct dumping along the coastline while coastal towns and industrial areas represent a permanent source of litter tourism and associated activities relevantly increase litter production during summer months ready to be transported to the deep sea by extreme events after being lost fishing gear such as nets and long lines has the potential of being harmful for marine life e g by ghost fishing at least for some time but also provides shelter and a substrate on which some species like cold water corals are capable to settle and grow la fonera and cap de creus canyons show the highest mean concentrations of litter ever seen on the deep sea floor with 15 057 and 8090 items km 2 respectively and for a single dive litter observed reached 167 540 items km 2 while most of the largest concentrations were found on the canyon floors at water depths exceeding 1000 m relatively little litter was identified on the canyon walls the finding of litter hotspots i e large accumulations of litter formed by mixtures of land and marine sourced litter items and natural debris such as sea urchin carcasses evidences an efficient transport to the floor of mid and lower canyon reaches at least high energy down canyon near bottom flows are known to occur in the investigated canyons these are associated to seasonal dense shelf water cascading and severe coastal storms which are the most energetic hydrodynamic processes in the study area thus becoming the best candidates as main carriers of debris to the deep the fact that the investigated canyons have their heads at short distance 4 km from the shoreline enhances their ability to trap littoral drift currents and also to convey the signal of the above mentioned high energy events to the deep including their litter load this study contributes to assess the origin and transport mechanisms of litter to the deep sea as well as its potential impact on deep sea ecosystems

predicting cold water coral distribution in the cap de creus canyon nw mediterranean implications for marine conservation planning abstract predictive habitat mapping has shown great promise to improve the understanding of the spatial distribution and complexity of benthic habitats and is a valuable means to highlight species environment relationships where field data are limited although spatial distribution models may represent an important step forward in science based ecosystem management reliable predictions are hard to obtain in deep sea environments mainly owing to the usual paucity of high resolution maps in these settings the aim of this study is to apply and test different spatial models to statistically predict the distribution of two cold water coral cwc species madrepora oculata dendrophyllia cornigera in the cap de creus canyon nw mediterranean based on high resolution swath bathymetry 5 m resolution and video observations through the manned submersible jago ifm geomar several submarine canyons host cwc communities as the environmental conditions tend to be particularly suitable for their settlement and development along the cap de creus canyon presence absence of cwc was estimated in each 5 m resolution pixel based on video imagery maximum entropy maxent general additive model gam and random forest were applied to represent non linear species environment relationships using terrain variables derived from multibeam bathymetry slope rugosity aspect backscatter according to the models cwc were most likely to be found on the steep walls of the southern flank which face the head and the thalweg of the canyon aligning with the known cwc ecology acquired from previous studies outputs from the three models showed similar average performances in predicting cwc distribution from the available environmental variables slope and aspect for madrepora oculata and rugosity for dendrophyllia cornigera drive their distribution although in some cases the three models identified different variables controlling each species to reduce differences and associated uncertainties between model outputs 5 m resolution ensembles were produced for the two species as a final step an up scaled 50 m resolution predictive map based on the fine scale ensembles is proposed as a valuable contribution for stakeholders which need to manage large natural areas using objective and repeatable science based approaches

general patterns of circulation sediment fluxes and ecology of the palamos la fonera submarine canyon northwestern mediterranean abstract currents particle fluxes and ecology were studied in the palamos submarine canyon also known as the fonera canyon located in the northwestern mediterranean seven mooring arrays equipped with current meters and sediment traps were deployed along the main canyon axis on the canyon walls and on the adjacent slope additionally local and regional hydrographic cruises were carried out current data showed that mean near surface and mid depth currents were oriented along the mean flow direction ne sw although at 400 and 1200 m depth within the canyon current reversals were significant indicating a more closed circulation inside the canyon mean near bottom currents were constrained by the local bathymetry especially at the canyon head the most significant frequency at all levels was the inertial frequency a second frequency of about three days attributed to a topographic wave was observed at all depths suggesting that this wave was probably not trapped near the bottom the current field observed during the most complete survey revealed a meandering pattern with cyclonic vorticity just upstream from and within the canyon the associated vertical velocity ranged between 10 and 20 m day and was constrained to the upper 300 m this latter feature together with other computations suggests that during this survey the meander was not induced by the canyon but by some kind of instability of the mean flow in the canyon suspended sediment concentration downward particle fluxes chlorophyll and particulate c and n were significantly higher up canyon from about 1200 m depth than offshore defining along with the different hydrodynamics two canyon domains one from the canyon head to about 1200 m depth more affected by the canyon confinement and the other deeper than 1200 m depth more controlled by the mean flow and the shelf slope front the higher near bottom downward total mass fluxes were recorded in the canyon axis at 1200 m depth along with sharp turbidity increases and are related to sediment gravity flows during the deployment period the increase in downward particle fluxes occurred by mid november when a severe storm took place on the canyon walls at 1200 m depth suspended sediment concentrations downward particle fluxes chlorophyll and particulate c and n were higher on the southern wall than on the northern wall inversely to the current s energy this could be caused by an upward water supply on the southern canyon wall and or the mean flow interacting with the canyon bathymetry in the swimmers collected by the sediment traps the dominant species was an elasipod holothurian which has not been recorded in other canyons or elsewhere in the mediterranean indicating particular speciation

unraveling signatures of biogeochemical processes and the depositional setting in the molecular composition of pore water dom across different marine environments abstract dissolved organic matter dom in marine sediment pore waters derives largely from decomposition of particulate organic matter and its composition is influenced by various biogeochemical and oceanographic processes in yet undetermined ways here we determine the molecular inventory of pore water dom in marine sediments of contrasting depositional regimes with ultrahigh resolution mass spectrometry and complementary bulk chemical analyses in order to elucidate the factors that shape dom composition our sample sets from the mediterranean marmara and black seas covered different sediment depths ages and a range of marine environments with different i organic matter sources ii balances of organic matter production and preservation and iii geochemical conditions in sediment and water column including anoxic sulfidic and hypersaline conditions pore water dom had a higher molecular formula richness than overlying water with up to 11 295 vs 2114 different molecular formulas in the mass range of 299 600 da and covered a broader range of element ratios h c 0 35 2 19 o c 0 03 1 19 vs h c 0 56 2 13 o c 0 15 1 14 formula richness was independent of concentrations of doc and toc near surface pore water dom was more similar to water column dom than to deep pore water dom from the same core with respect to formula richness and the molecular composition suggesting exchange at the sediment water interface the dom composition in the deeper sediments was controlled by organic matter source selective decomposition of specific dom fractions and early diagenetic molecule transformations compounds in pelagic sediment pore waters were predominantly highly unsaturated and n bearing formulas whereas oxygen rich cho formulas and aromatic compounds were more abundant in pore water dom from terrigenous sediments the increase of s bearing molecular formulas in the water column and pore waters of the black sea and the mediterranean discovery basin was consistent with elevated hs concentrations reflecting the incorporation of sulfur into biomolecules during early diagenesis sulfurization resulted in an increased average molecular mass of dom and higher formula richness up to 5899 formulas per sample in sediments from the methanogenic zone in the black sea the dom pool was distinctly more reduced than overlying sediments from the sulfate reducing zone bottom and pore water dom from the discovery basin contained the highest abundances of aliphatic compounds in the entire dataset a large fraction of abundant n bearing formulas possibly represented peptide and nucleotide formulas suggesting preservation of these molecules in the life inhibiting environment of the discovery basin our unique data set provides the basis for a comprehensive understanding of the molecular signatures in pore water dom and the turnover of sedimentary organic matter in marine sediments

the effect of a submarine canyon on the river sediment dispersal and inner shelf sediment movements in southern taiwan abstract this study examines the influence of a submarine canyon on the dispersal of sediments discharged by a nearby river and on the sediment movement on the inner shelf the study area includes the head region of the kao ping submarine canyon whose landward terminus is located approximately 1 km seaward from the mouth of the kao ping river in southern taiwan within the study area 143 surficial sediment samples were taken from the seafloor six hydrographic surveys along the axis of the submarine canyon were also conducted over the span of 1 yr three different approaches were used in the analysis of grain size distribution pattern they include 1 a combination of filtering and the empirical orthogonal eigen function eof analysis technique 2 the mclaren model and 3 the transport vector technique the results of the three methods not only agree with one another they also complement one another this study reveals that the kao ping submarine canyon is relatively a stratified and statically stable environment the hydrographic characteristics of the canyon display seasonal variability controlled primarily by the temperature field and the effluent of the kao ping river the hydrographic condition and the bottom topography in the canyon suggest the propagation of internal tides during the flood season summer of the kao ping river the submarine canyon acts as a trap and conduit for mud exchange between the kao ping river and offshore near the head of the canyon there is a region of sediment transport convergence this region is also characterized by high mud abundance on the seafloor that coincides with the presence of high suspended sediment concentration ssc spots in the bottom nepheloid layer outside the submarine canyon on the shelf where the evidence of wave reworking is strong the northwestward alongshore transport dominates over the southeastward transport which is a common theme on the west coast in southern taiwan

development of submarine canyons after the mid pleistocene transition on the ebro margin nw mediterranean the role of fluvial connections after the messinian salinity crisis msc the ebro margin like other mediterranean deltaic margins rebuilt through progradation and increasingly significant aggradation the plio quaternary transition from a ramp like system to a new margin with large clinoforms is an opportunity to understand the processes that govern canyon initiation and evolution we used a 3d seismic data set located at the outer shelf upper slope of the ebro margin we tied major bounding surfaces to chrono stratigraphic constraints from borehole data or for the most recent interval from averaged accumulation rates derived from borehole stratigraphy the major shelfal erosion surfaces are interpreted as sequence boundaries tied to major glacial maxima along these surfaces seismic attributes characterize the fluvial canyon connection viewed as one of the key factors in canyon development the first appearance of proto canyons dense networks of channels and gullies 50 100 m deep and 1 2 km wide occurs in the late zanclean their size increased progressively throughout the pliocene and early quaternary in relation to the increase in clinoform heights true canyons with distinct interfluves more than 200 m deep and 3 4 km wide appeared during the mid pleistocene transition mpt 1250 700 ka bp the first evidence of direct connection between canyon heads and fluvial systems is observed during marine isotope stage 22 one of the most pronounced glacial stages of the quaternary similar connections also existed at least during mis 16 and mis 12 which are also stages of pronounced low sea level the topography of fluvial channels in the outer shelf is not imaged in detail in the picked horizons at the resolution of our seismic data but sinuous fluvial systems are very well imaged through amplitude and coherency attributes direct connection of fluvial systems during and after mis 22 also favored headward erosion and the formation of shelf indenting canyons probably during early phases of sea level rise

impact of dense shelf water cascading on the transfer of organic matter to the deep western mediterranean basin 1 during winter 2005 2006 particle fluxes and near bottom currents were measured in and around the lacaze duthiers and cap de creus submarine canyons western gulf of lion current anomalies show the occurrence of a major dense shelf water cascading event down to the slope the latest recorded up to date in the area concomitant increased total mass fluxes highlight the ability of cascading waters to transport large amounts of coarse sediment and organic matter which is predominantly of terrestrial origin in addition results reveal that the current regime and associated grain size sorting is the responsible for a geochemical gradient of settling organic particles along the slope

turbidity events observed in situ along the congo submarine channel abstract as part of the multidisciplinary programme biozaire devoted to studying deep sea benthic ecosystems in the gulf of guinea particulate input and its relationship with near bottom hydrodynamics were monitored using long term moorings from 2000 to early 2005 particular attention was given to material input through the congo ex zaire submarine channel that extends 760 km from the congo river mouth to the abyssal plain 5100 m near 6 s due to its direct connection to the congo river the congo canyon and channel system are characterised by particularly active recent sediment transport during this first in situ long term monitoring along the channel an energetic turbidity event was observed in january 2004 at three locations along the channel from 3420 to 4790 m in depth this event tilted and displaced the moorings installed at 3420 m site zr and 4070 m site zd and resulted in high sediment deposition at all three mooring sites the event moved at an average velocity of 3 5 m s 1 along the numerous channel meanders between 3420 and 4070 m then at 0 7 m s 1 between 4070 m and the end of the channel at 4790 m the particle cloud rose above the top of the valley at 4070 m site zd but not at 3420 m site zr where the channel was too deep lastly the mooring line broke at site zd in october 2004 probably due to a strong event like that of 2001 previously described by khripounoff et al khripounoff a vangriesheim a babonneau n crassous p denniellou b savoye b 2003 direct observation of intense turbidity activity in the zaire submarine valley at 4000 m water depth marine geology 194 151 158 between these strong events several peaks of high turbidity and particle flux occurred but without noticeable current increases these events were probably due to local sliding of sediment accumulated on the walls or terraces on the side of the channel the area near 4000 m depth and the lobe appear to be the main depocentres of particulate input rich in organic matter derived from the congo river

large sediment waves over the gulf of roses upper continental slope nw mediterranean recently acquired swath bathymetry and seismic datasets on the gulf of roses continental slope revealed the presence of large sediment waves that have developed between 200 and 400 m water depth geometric parameters were computed from the multibeam dataset and the obtained results showed mean sediment wave lengths of 2000 m and maximum heights of 60 m the analysis of seismic profiles showed the general architecture of the late quaternary deposits over the gulf of roses outer shelf and slope the outer continental shelf is characterized by morphological erosional features affecting the upper part of the most recent seismic unit over the continental slope five main unconformity bounded seismic units are differentiated with sediment waves developed in all of them the sediment waves observed over the continental slope are presumably generated by bottom currents intensified during major dense shelf water cascading events flowing downslope at an oblique angle with respect to the main bathymetry

bed level changes on intertidal wetland in response to waves and tides a case study from the yangtze river delta short term bed level variability in tidal wetlands has important implication both for ecology and engineering in this study we combined in situ measurements with model simulations to quantify short term bed level changes on a meso macrotidal wetland in the yangtze river delta on the middle flat we observed erosion during neap to mean tides under onshore moderate to strong winds and bed recovery during subsequent spring tides when winds were both offshore and weaker suggesting that winds can overturn the neap spring cyclicity of bed level changes even on meso macrotidal mudflats the magnitude of bed level changes was smaller on both sides of the middle flat while the smallest changes occurred on the salt marsh observed bed level changes were reconstructed using a single point bed level change model which incorporates in situ measured parameters of hydrodynamics waves and currents suspended sediment concentrations and bed sediment properties we conclude that the relative importance of waves and tides in intertidal wetland erosion and accretion can vary temporally due to changes in balance between wave and tidal energies and spatially because of changes in elevation and vegetation in the cross shore profile our study also reflects the advantage of combination of in situ measurement with simulation in detecting short term variability of tidal flats

suspended sediment fluxes and transport processes in the gulf of lions submarine canyons the role of storms and dense water cascading contemporary suspended sediment transport was studied in seven submarine canyons of the gulf of lions gol current meters equipped with turbidity sensors were moored 4 m above bottom at 300 m depth in the canyon axis from november 2003 to may 2004 sediment transport events were monitored and studied in relation to forcing conditions there was a large flood in early december during which discharges from all of the coastal rivers increased by more than one order of magnitude a smaller flood of the rhone river occurred later in mid january followed by a persistent high river discharge that lasted until mid february there were also several e se storm events during the measurement period two of them causing large swell one in early december max hs 8 4 m coinciding with the major river flood andoneinlatefebruary maxhs 7m duringaperiodoflowerriverdischarge mostofthevariabilityindown canyoncurrentspeeds waslinkedtostrongdownwellinginducedbye sestormsandtocascadingofdenseshelfwaterinducedbynandnwwinds theintensity and timing of these processes strongly varied spatially eastern storms generated higher waves and induced stronger downwelling in the western than in the eastern sector of the gol shelf dense water cascading events were enhanced during eastern storms and they were also more intense in the western sector of the gol these events occurred frequently from january to may along the western canyons and from february to april along the eastern canyons from february to april they occurred simultaneously in all the canyons sediment transport was mainly down canyon and mostly concentrated during storm induced downwelling and dense water cascading events during the high river discharge season most of the newly supplied and resuspended sediment remained stored on theshelf however duringthelatefebruarystormandcascadingevent thestoredsedimentwasquicklyresuspendedandtransported mainly through the westernmost submarine canyon cap de creus following a flushing pattern later although minor storms and shelfdensewatercascadinghardlyincreasedsuspendedsedimentconcentrationswithinthecanyons theyinducedstrongnear bottom current velocities increasing down canyon sediment fluxes and generating small but significant sediment transport events most of the shelf canyon transfer took place during the late february storm and cascading event through the cap de creus canyon where the net suspended sediment flux was between one and two orders of magnitude higher than in the other canyons

lateral advection of organic matter in cascading dominated submarine canyons in the gulf of lions gol dense water overflowing off the shelf occurs seasonally and represents the main mechanism affecting the shelf slope exchange of particulate organic matter om most of the dense water export takes place in the south western gol and in particular through cap de creus cdc submarine canyon here benthic instruments were deployed to collect down canyon particulate fluxes whereas surface sediments were taken after the cascading event along the sediment dispersal system on the shelf in cdc canyon and in the nearby lacaze duthiers ld canyon the chemical composition of the suspended material and surface sediments were investigated using several proxies including organic and inorganic carbon total nitrogen biogenic silica 13c 14c and alkaline cuo oxidation products thermohaline anomalies and high current speed events were measured in cdc canyon since december 2004 until mid april 2005 indicating a marked off shelf export of dense water trough the canyon during the cascading mud and relatively coarse shelf and upper canyon sediments were the major component of the mass flux conversely advection of fine material via nepheloid layers dominated down slope fluxes during pre and post cascading the resulting change in grain size affected the flux of mineral bound terrigenous oc indicating that the down canyon transport of land derived om did not occur as bulk but rather its composition is driven by sediment sorting associated with different transport mechanisms both surface sediments and sediment trap samples indicated that cdc canyon is well connected to the gol terrigenous dispersal system conversely our results suggest an overall limited influence of land derived om in ld canyon in spite of the reduced fluvial nutrient supply a significant pulsed input of modern marine om was observed in april 2005 at the end of the cascading period both intense mixing and lack of strong water column stratification likely played a key role allowing for both diffusion of nutrients rich waters into the euphotic zone and efficient vertical sink of marine oc on its way toward the seafloor this fresh pool of oc interacted with the dense plume overflowing off the shelf becoming part of the material laterally advected to the slope

deposition rates mixing intensity and organic content in two contrasting submarine canyons the hydrographically different conditions characterising the western iberian margin ne atlantic and the gulf of lions mediterranean may play an important role in determining the biogeochemical characteristics of the sediments to investigate this we compared the nazare and cap de creus canyons and their respective adjacent open slopes in terms of the organic carbon corg contents chlorophyll a chl a concentrations c n and chl a phaeopigment ratios and also in terms of modelled mixing intensities chl a and 210pb deposition and background concentrations in sediments chlorophyll a and 210pb profiles were fitted simultaneously with a reactive transport model to estimate mixing intensity deposition and background concentrations further to account for the possibility that the decay of chl a may be lower in the deep sea than in shallow areas we estimated the model parameters with two models in one approach model 1 the temperature dependent decay rate of chl a as given by sun et al sun m y lee c aller r c 1993 laboratory studies of oxic and anoxic degradation of chlorophyll a in long island sound sediments geochimica et cosmochimica acta 57 147 157 for estuaries was used in the other approach model 2 an extra parameter was estimated to derive the chlorophyll a degradation rate an f test taking into account the different number of parameters in the models was used to single out the model that significantly fitted the data best in most cases the model parameters were best explained with model 1 indicating the empirical relationship by sun et al 1993 is a valid means to estimate the chlorophyll a degradation rate in deep sea sediments to assess the robustness with which the model parameters were estimated we provide a first application of bayesian analysis in the modelling of tracers in sediments bayesian analysis allows calculating the mean and standard deviation for each model parameter and correlations among parameters the model parameters for stations for which 210pb and chlorophyll a profiles were available were robustly fitted as evidenced by an average coefficient of variation of 0 22 corg contents chl a concentrations chl a phaeo ratios mixing intensities depositions and background concentrations of chl a and 210pb indicated that the cap de creus canyon and adjacent slope were less active in terms of organic matter accumulation and burial than the nazare canyon and respective open slope

suspended particle movement in and around quinault submarine canyon abstract time and space dependent light transmission temperature salinity and velocity data obtained during two winter experiments in the vicinity of quinault submarine canyon are used to examine processes controlling subtidal cpd fluctuations in suspended particulate concentration in the region in particular local resuspension of particles by waves and currents horizontal advection and vertical advection data include time series from four to eight mooring locations as many as 16 current meters and 10 transmissometers on the shelf over the open slope and in the canyon during each experiment spatial distributions from five ctd transmission surveys and gravity wave information particle concentration in the bottom boundary layer at the shelf edge was dominated by resuspension events the mechanism for resuspension had a large inter annual variation in the first year wave induced resuspension dominated whereas in the second year current induced resuspension dominated the cut off depth for storm related resuspension was generally m subtidal advection across isobaths upwelling downwelling accounted for 20 of the variance in concentration fluctuations at the shelf edge in the bottom boundary layer horizontal advection of material suspended in the bottom nepheloid layer on the shelf resulted in the formation of shelf break depth intermediate nepheloid layers over the canyon in regions where the flow crosses isobaths the existence strength onshore offshore extent and vertical structure of such nepheloid layers at a given time in this asymmetrical canyon appear to be a function of the direction of flow over the outer shelf and over the upper slope in the canyon whether active resuspension is occurring over the shelf and the maximum resuspension depth and magnitude of the active resuspension event the frequency timing and magnitude of previous resuspension events spatial and temporal continuity magnitude and direction of flow over the open slope north and south of the canyon vertical settling and upwelling or downwelling related to the along isobath flow over the upper slope fluctuations in particle concentration below the shelf break depth over the canyon slope were controlled by vertical rather than horizontal advection vertical excursions by the water mass of 100 m occurred both as a result of isopycnal adjustment to the quasi geostrophic along isobath flow and as a result of semidiurnal tidal oscillations when an overhead nepheloid layer was present such water mass excursions produced concentration fluctuations at depths below the maximum depth of storm related local resuspension in open slope regions where strong inls intermediate depth nepheloid layers were absent the portion of concentration variance that could be explained by advective models with constant spatial gradients was almost negligible only one resuspension event was documented in the bottom boundary layer within the deep canyon bottom depth 1000 m suggesting that advection must account for the observed variance in particle concentration however the large scale gradients at these depths are sufficiently weak cf the smaller scale gradients or noise that advective control could only be demonstrated during the second winter experiment when velocities along the canyon axis were relatively large finally the data demonstrate that subtidal concentration fluctuations within 50 m of the canyon floor are correlated to those at the shelf edge this correlation reflects a correlation in the velocity field rather than a transfer of particles as might occur with a turbidity current

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

megafauna of vulnerable marine ecosystems in french mediterranean submarine canyons spatial distribution and anthropogenic impacts abstract vulnerable marine ecosystems vme in the deep mediterranean sea have been identified by the general fisheries commission for the mediterranean as consisting of communities of scleractinia lophelia pertusa and madrepora oculata pennatulacea funiculina quadrangularis and alcyonacea isidella elongata this paper deals with video data recorded in the heads of french mediterranean canyons quantitative observations were extracted from 101 video films recorded during the medseacan cruise in 2009 aamp comex qualitative information was extracted from four other cruises two marum comex cruises in 2009 and 2011 and two ifremer cruises in 1995 and 2010 to support the previous observations in the cassidaigne and lacaze duthiers canyons all the species fishing impacts and litter recognized in the video films recorded from 180 to 700 m depth were mapped using gis the abundances and distributions of benthic fishing resources marketable fishes aristeidae octopodidae vulnerable marine species trawling scars and litter of 17 canyons were calculated and compared as was the open slope between the stoechades and toulon canyons funiculina quadrangularis was rarely observed being confined for the most part to the marti canyon and i elongata was abundant in three canyons bourcart marti petit rhone these two cnidarians were encountered in relatively low abundances and it may be that they have been swept away by repeated trawling the lacaze duthiers and cassidaigne canyons comprised the highest densities and largest colony sizes of scleractinian cold water corals whose distribution was mapped in detail these colonies were often seen to be entangled in fishing lines the alcyonacean callogorgia verticillata was observed to be highly abundant in the bourcart canyon and less abundant in several other canyons this alcyonacean was also severely affected by bottom fishing gears and is proposed as a vulnerable marine species our studies on anthropogenic impacts show that seafloor disturbance by benthic fishing is mainly attributable to trawling in the gulf of lion and to long lines where rocky substrates are present the bauxite residue red mud expelled in the cassidaigne canyon was seen to prevent fauna from settling at the bottom of the canyon and it covered much of the flanks litter was present in all of the canyons and especially in considerable quantities in the ligurian sea where the heads of the canyons are closer to the coast three marine protected areas and one fishing area with restricted access have recently been established and should permit the preservation of these deep ecosystems

nepheloid layer distribution in the whittard canyon ne atlantic margin article i nfo article history the dynamics and distribution of nepheloid layers in multiple branches of the whittard canyon were observed during three hydrographic surveys carried out between 2011 and 2013 the sources of permanent and temporal variation of the layers were investigated seasonal variations in primary production at the surface were reflected in the nepheloid layers extending down in the water column particularly in the upper reaches of the canyon benthic nepheloid layers were observed along the canyon axes to depths greater than 2500 m a distance of 30 km intermediate nepheloid layers were detected as lateral extensions of the benthic nepheloid layer centredat 550m 850m 1150 mand1600m and stretching 20 25kmoff slope criticalandsupercriticalcon ditions for semidiurnal tide reflection were identified coinciding with the occurrence of intermediate nepheloid layers with other hotspots found at the boundaries of the permanent thermocline and mediterranean outflow water weak seasonal stratification during the survey in 2012 appeared to permit storm induced mixing at deeper water depths than expected altering the distribution of material in the nepheloid layers the dynamic conditions of the canyon encourage nepheloid layer formation with implications ensued for deposition rates and food supply to the unique communities that are found in the whittard canyon and likely other similar can yon systems

high frequency of sediment gravity flow events in the var submarine canyon mediterranean sea this study aimed to analyze the role river floods play in triggering gravity flows and to investigate the role of submarine canyon systems as a conduit for terrigenous material to the deep sea two years of measurements in the var canyon at depths ranging from 1200 m to 2350 m indicate that six floods of the var river triggered hyperpycnal flows an important mechanism for transporting particulate matter to the deep sea floor these sediment gravity flows were characterized by a sudden increase of current velocity that lasted 8 to 22 h and by downward particle fluxes that reached up to 600 g m 2 d 1

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

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

periodic resuspension in baltimore canyon by focusing of internal waves high concentrations of particulate matter are frequently reported in submarine canyons this study demonstrates that in baltimore submarine canyon elevated concentrations result from periodic resuspension events the sloping bottom and v shaped topography of submarine canyons could accelerate tidal flows in the canyon axis sufficiently to cause resuspension which occurs predominantly at tidal frequencies however current meter and transmissometer data show that resuspension events are often associated with a borelike intrusion of cold water moving upslope near the canyon head an event that is consistent with the focusing of internal wave energy toward the canyon head at tidal frequencies hydrographic conditions for the focusing of energy are most favorable in late winter and early spring when stratification in the canyon is diminished direct observations reveal that the most pronounced resuspension events occur during those seasons bottom stresses generated in the canyon are sufficient to resuspend sediment along the axis at least between 200 and 800 m with little resuspension occurring deeper along the axis on the canyon walls adjacent slope or shelf during a resuspension event the sediment laden water is forced upcanyon then sloshes back down the canyon until it reaches a layer of higher density water detaches from the canyon floor and moves seaward along a density surface this is a means of transferring sediment and associated pollutants intercepted at the canyon head to deeper water across the shelf slope front over geologic time frequent resuspension and seaward transport may aid in the headward erosion of submarine canyons or at least inhibit their infilling during interglacial times

present deep submarine canyons activity in the bay of biscay ne atlantic present sedimentation in three canyons of the bay of biscay audierne blackmud and capbreton is studied by the combined analysis of cores and current meter data collected over a 7 month period at the current meter mooring locations interface cores were collected to characterize the recent sedimentation processes in the two canyons located in the northern part of the bay of biscay audierne and blackmud there is no evidence of recent sedimentary deposits canyons are by passing or erosive areas in the southern part of the bay of biscay capbreton recent turbidite are deposited in the three canyons current meters recorded energetic currents with velocities showing alternating upslope and downslope motions and a period corresponding to the semi diurnal component m2 these currents are supposed to be related to deep internal tides the high speed of the current 1 m s in audierne and blackmud is consistent with the lack of preservation of recent sediments on the canyon floors in capbreton canyon the magnitude of currents is less and recent turbidites are preserved in addition to periodical current motion small magnitude gravity event corresponding to a low concentration turbulent surge or a high concentration nepheloid layer initiated during a storm was recorded during the mooring period these results suggest that deep sea canyons in the bay of biscay have behaviour at present varying between by passing or erosion areas and sediment trapping these examples suggest that sediments are moved up and down by low energy tide initiated hydrodynamic events during most of the time during higher magnitude short duration gravity events the sediments are transferred down canyon towards the deep sea

impact of storm induced remobilization on grain size distribution and organic carbon content in sediments from the blanes canyon area nw mediterranean sea abstract interactions between organic carbon and mineral particles are known to play a key role for the preservation of organic carbon in marine sediments in this study we combine meteorological hydrological and oceanographic information with grain size and geochemical analyses organic carbon oc its stable isotope 13 c and the nitrogen to oc ratio in different grain size fractions of surface sediments to determine the impact of a major storm on organic matter redistribution in a deep continental margin of the nw mediterranean sea sediment cores were obtained from the continental shelf along the axis of the blanes submarine canyon bc and in the adjacent southern open slope before november 2008 and after february and may 2009 the occurrence of one of the most severe coastal storms recorded in the last century in the study area the storm occurred the 26 of december 2008 and dramatically impacted the north catalan coast and its offshore area the high shear stress produced by this event on the shelf floor led to sediment erosion and subsequently to its transport and deposition into bc while sand and gravel sized particles up to 2500 m in diameter were deposited at 300 m of water depth in the canyon head the finer particles the results obtained show that the hydrodynamic processes that controlled the sorting and differential deposition of particles according to their grain size also controlled the redistribution of particles with different loads of oc thus whereas coarse particles transported to the canyon head were poorly loaded with oc fine particles reaching greater depths were relatively rich in oc a significant proportion of which was of marine origin i e derived from marine primary production this adds to evidence that the physical action of waves and currents during storms plays a key role in determining the amount of oc stored in surface sediments not only in the shelf but also in the deep margin and possibly deeper

dynamics of particles along the western margin of the southern adriatic processes involved in transferring particulate matter to the deep basin abstract the southern adriatic is an area of dense shelf water dsw cascading and open ocean convection the impact of dsw cascading events in transferring organic matter to the deep benthic community and in producing a wide range of bedforms along the continental margin has been highlighted in recent years in order to improve our knowledge on the interannual variability of the dsw cascading with the ultimate goal to understand timing of dsw formation and transport as well as the cascading process its variability in intensity and duration and the ultimate impact of the dense water on the deep sea in march 2009 we deployed an instrumented mooring in a field of sediment waves 860 m depth located down current to the bari canyon in march 2010 a second mooring was installed in the northern channel of the canyon winters 2009 2010 and 2011 were mild and particularly wet and the po river discharge remained relatively high throughout the whole winter hence we expected weak dense shelf water formation associated with a shallow shelf water overflowing off the adriatic shelf by contrast in winter 2012 the north adriatic experienced a severe cold wave with ne bora winds and reduced fresh water input these weather conditions allowed the formation of extremely dense shelf water three additional moorings were quickly deployed during this cold event in the southern adriatic sea to investigate the spatial variability of particle and organic matter fluxes exiting from the adriatic continental shelf under the influence of a strong dsw cascading event slow near bottom currents never exceeding 40 cm s 1 were recorded between march 2009 and february 2012 water temperatures depicted minor negative shifts total mass fluxes tmfs were low annual avg 1 7 2 8 g m 2 d 1 and 0 3 0 6 g m 2 d 1 in the canyon and in the sediment wave field respectively and peak values 6 8 g m 2 d 1 but showed significant seasonal and interannual variability fluxes in the canyon were higher than those measured in the sediment wave field at deeper water depth mass flux peaks during the 2112 dsw cascading were up to 5 times higher than the peaks of previous years up to 18 70 g m 2 d 1 with a spatial variability mainly driven by the localized pathways of dsw cascading in the canyon near bottom currents exceeded 70 cm s 1 and temperature dropped to 12 2 c while current speeds were high also at 1200 m depth 60 cm s 1 in the moat surrounding the dauno seamount surprisingly mass flux peaks occurred from the 16th february to the 1st of march 3 4 weeks ahead of the usual dsw occurrence suggesting an early arrival of the dsw the deep dsw cascading was the main process driving the particle transfer across the southern adriatic margin during late winter spring 2012 mooring data showed a nw se gradient of temperature and kinetic energy from upslope to basin floor indicating slope transverse flow modulated by local obstruction caused by the rugged seafloor topography bari canyon is one of the sites of dsw flow and in this area we have the possibility to extend observations back in time using continuous mooring data since 2009 and previous published materials this approach allowed evaluation of additional mechanisms of particle transport e g open ocean convection storm driven downward transport shallow dense water cascading that are particularly relevant in years when the dsw formation is less vigorous and cascading processes are sluggish the small amplitude of total mass flux peaks the weak currents and the relatively high and constant temperatures recorded during 2009 2010 and 2011 springs are consistent with an enhanced vertical particle rain from a mid water nepheloid layer triggered in turn by a shallow cascading of not particularly dense shelf water detaching from the seafloor when reaches its neutral buoyancy thus the intensity of dsw cascading shallow vs deep plays a first order control on the particulate fluxes through the western margin of the southern adriatic while storm induced sediment transport can occasionally be relevant too

sea level control on turbidite activity in the rhone canyon and the upper fan during the last glacial maximum and early deglacial abstract the timing routing and processes of sediment transfer from the continents to the oceans at millennial time scale are still largely unknown the potential of turbidite systems dominantly deposited during sea level lowstands to record global or regional environmental fluctuations is usually under exploited because of the difficulty to obtain robust chronostratigraphic constraints in turbiditic deposits and therefore to tie changes in sedimentary processes to environmental fluctuations we were able to obtain a millennial scale chronostratigraphy based on oxygen isotopes of the scarce foraminifera preserved in turbiditic deposits of the rhone turbidite system within the western mediterranean our results show that 1 objective criteria can be defined for the selection of foraminifera preserved within the pelagic intervals between the turbiditic sequences in order to obtain a reliable isotope stratigraphy 2 turbidites triggered by hyperpycnal currents are described for the first time within the rhone turbidite system they are related to the periods of direct fluvial connection with the canyon head during the sea level lowstand and early rise and to a period of high sediment flux in relation to the massive recession of the rhone glaciers in the alps 3 the lithofacies change passing from hyperpycnal to bouma type is dated at ca 19 cal ka bp which might correspond to an acceleration of sea level rise 19 ka meltwater pulse

sediment transport processes at the head of halibut canyon eastern canada margin an interplay between internal tides and dense shelf water cascading abstract to investigate the processes by which sediment is transported through a submarine canyon incised in a glaciated margin the bottom boundary layer quadrapod ralph was deployed at 276 m depth in the west halibut canyon off newfoundland during winter 2008 2009 two main sediment transport processes were identified throughout the deployment firstly periodic increases of near bottom suspended sediment concentrations ssc were recorded associated with the up canyon propagation of the semidiurnal internal tidal bore along the canyon axis carrying fine sediment particles resuspended from deeper canyon regions the recorded ssc peaks lasting less than 1 h were observed sporadically and were linked to bottom intensified up canyon flows 40 cm s 1 concomitant with sharp drops in temperature secondly sediment transport was also observed during events of intensified down canyon current velocities that occurred during periods of sustained heat loss from surface waters but were not associated with large storm waves high resolution velocity profiles throughout the water column during these events revealed that the highest current speeds 1 m s 1 were centered several meters above the sea floor and corresponded to the region of maximum velocities of a gravity flow such flows had associated low ssc and cold water temperatures and are interpreted as dense shelf water cascading events channelized along the canyon axis sediment transport during these events was largely restricted to bedload and saltation producing winnowing of sands and fine sediments around larger gravel particles analysis of historical hydrographic data suggests that such gravity flows are not related to the formation of coastal dense waters advected towards the outer shelf that reached the canyon head rather the dense shelf waters appear to be generated around the outer shelf where convection during winter is able to reach the sea floor and generate a pool of near bottom dense water that cascades into the canyon during one or two tidal cycles a similar transport mechanism is likely to occur in other submarine canyons along the eastern canadian margin as well in other canyoned margins where winter convection can reach the shelf edge