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

lidar and 2d electrical resistivity tomography as a supplement of geomorphological investigations in urban areas a case study from the city of wroclaw sw poland in urbanized areas particularly in lowland terrains and floors of large river valleys the natural land configuration is often hard to recognize due to a long history of human activity accordingly archaeological works in cities which supply knowledge on settlement conditions are usually accompanied by geological and geomophological research lately data from light detection and ranging lidar have become a valuable source of information on urban land configuration geophysical methods are also becoming increasingly popular in background studies the paper presents a method of using and linking these sources of spatial information about landforms in such areas the main aim is to identify to what extent these complementary sources of data and the proposed method can be used in such a specific environment to reconstruct natural buried terrain morphology the city of wroclaw in central europe serves as an example to this end geomorphometric studies were conducted with the use of digital elevation models dems based on lidar scanning and derivated land surface parameters saga wetness index channel network base level and altitude above channel network the study also involved determining morphological edges and measurements of the meanders of the odra as well as expanding information on the spatial distribution of alluvia and the structure of slope breaks to this end geophysical measurements were conducted using the two dimensional electrical resistivity tomography method additionally five typical sequences of man made ground present within the perimeter of the city were distinguished as a result a map of the main landforms of wroclaw is presented finally we argue that although high resolution dem and derivate land surface parameters are very useful in terrain analysis places with thick man made ground or strongly levelled areas must be recognized by geoarchaeological excavations or geological bore holes the geophysical survey is useful to identify buried morphological edges and older relief elements in open areas

historical evolution and extreme climate events during the last 400years on the rhone prodelta nw mediterranean abstract the rhone river is the most important source of freshwater and sediment to the western mediterranean sea deltaic lobes and littoral prisms compose the sedimentary units that make up the whole rhone subaqueous delta which reaches up to 50 m in thickness individual lobes that accompanied the retreat of the rhone during sea level rise and the subsequent westward then eastward shift of the main outlet display averaged sedimentation rates in excess of 1 cm yr 1 containing both continental and marine material during the industrial period most of the river flow was delivered through the pegoulier and roustan distributary channels which evolved under human influence within the prodeltas associated to these distributaries very expanded sedimentation rates 10 cm yr 1 allow the documentation of historical extreme climate events a 7 71 m long piston core rhs ks57 was retrieved from the distal prodelta 79 m water depth a multi proxy study was carried out using microfossil assemblages ostracods benthic foraminifera and coccoliths in combination with sedimentological and geochemical proxies our results show that 1 four different intervals i iv spanning a time range comprised between 1600 ad and present day have been differentiated from this multi proxy analysis they correspond to a different position of distributary channels each interval correlates with the different phases of channel avulsion induced by climate events or by human activity 2 the signature of extreme floods that can be identified by the punctuated occurrence of freshwater continental ostracods e g candona spp ilyocypris sp correlating with increases in grain size and or organic carbon content they correspond to decadal scale increased runoffs reported in historical archives our study demonstrates the relevance of benthic microfossil studies for reconstructing paleoenvironmental changes in transitional marine continental settings

the importance of the number of points transect location and interpolation techniques in the analysis of bathymetric measurements abstract determining the bathymetric properties of a river lake or reservoir is important for many reasons because it identifies location of sections with sedimentation or erosion which indicate the key processes and biophysical habitat status this study used observational data of a 5 km section of the danube river transformed into a reservoir after 1972 to determine the best gis interpolation method and the optimal number of sampling points to get an accurate description of the riverbed nine interpolation methods were used to generate bathymetric maps of the danube course between km 955 and km 950 in the area of iron gates reservoir using a variable number of points n 1943 n 4328 n 17139 obtained by single beam echo sounder six methods of deterministic interpolation have been used inverse distance weighting idw criteria automatically determined cad and manually determined md local polynomial interpolation lpi criteria automatically determined cad and manually determined md radial basis function rbf fully regularized spline crs radial basis function rbf spline with tension swt and three geo statistics methods ordinary kriging ok simple kriging sk universal kriging uk cross validation and bathymetric digital elevation models dem s analysis were used to evaluate the accuracy of the estimated data and maps the two interpolation methods inverse distance weighting idw md and simple kriging sk provide satisfactory results even in the case of a small number of points n 1943 if the number of measured points grows and a section grid perpendicular longitudinal is developed the dem s bathymetric accuracy improves significantly especially in the case of complex morphology even if the positive and negative forms of the bed lead to sudden changes in the measured values the obtained results revealed differences between the interpolation methods used particularly in the case of a small number of points measured per perpendicular trajectories but by the addition of points on longitudinal paths a significant improvement of the bathymetric maps is obtained

holocene alluvial sediment storage in a small river catchment in the loess area of central belgium abstract soil erosion and sediment deposition widely affect landscape development particularly in erosion prone areas with loess derived soils nevertheless until now few attempts were made to quantify soil losses and sediment storage over long centennial or millennial timescales in this study the holocene alluvial sediment storage in a small river catchment 52 km2 of the belgian loess belt is estimated and a preliminary sediment budget for the catchment is presented in the valley of the nethen river c 13 km long a detailed survey of the alluvial sediment archive was conducted hand augerings and percussion drillings were made along cross valley transects at 12 locations in the catchment ams 14c dating of peat samples provided a temporal framework for the interpretation of the cores results show that the thickness of holocene sediment deposits in the nethen valley is 4 to 6 m which corresponds to a total clastic sediment mass of 14 106 t stored in the valley bottom three alluvial units could be distinguished and associated with deposition phases from 9600 to 2900 b c 2900 b c to a d 1000 and a d 1000 to present in contrast to the older sediments units 1 and 2 deposits from the last 1000 year unit 3 contain little organic matter they are seldom intercalated with peat layers and devoid of tufa unit 3 reaches a thickness of c 2 m thereby representing 50 of the holocene sediment mass stored in the alluvial plain the mean sedimentation rate in the alluvial plain for this last phase is 26 t ha 1 a 1 which is about tenfold larger than the sedimentation rates calculated for the older holocene sediment units sediment supply towards the alluvial plain has therefore increased tremendously since medieval times these results are in contrast to dating results obtained for colluvial sediments in a nearby dry valley within the catchment of the nethen where soil erosion and sediment deposition started in the early iron age and was already substantial during the roman age this means that there is a time lag of about one millennium between the onset of high sedimentation rates in the upstream area and high deposition rates in the alluvial plain this is probably caused by a change in coupling sediment connectivity between the plateau slopes and rivers as soil erosion proceeds first the dry zero order valleys in the catchment act as sediment traps and only after these are filled sediment reaches the floodplains the preliminary sediment budget for the nethen catchment illustrates that 50 of the sediment that was eroded during the holocene was stored in colluvial deposits which are mainly located on footslopes and in dry valley bottoms another 29 of the sediment mass is stored in the alluvial plain

rapid flooding of the sunda shelf a late glacial sea level record the increase in sea level from the last glacial maximum has been derived from a siliciclastic system on the tectonically stable sunda shelf in southeast asia the time from 21 to 14 thousand calendar years before the present has been poorly covered in other records the record generally confirms sea level reconstructions from coral reefs the rise of sea level during meltwater pulse 1a was as much as 16 meters within 300 years 14 6 to 14 3 thousand years ago

remote measurement of river morphology via fusion of lidar topography and spectrally based bathymetry this study developed and evaluated a hybrid approach to remote measurement of river morphology that combines lidar topography with spectrally based bathymetry comparison of filtered lidar point clouds with surveyed cross sections indicated that subtle features on low relief floodplains were accurately resolved by lidar but that submerged areas could not be detected due to strong absorption of near infrared laser pulses by water the reduced number of returns made the active channel evident in a lidar point density map a second dataset suggested that pulse intensity also could be used to discriminate land from water via a threshold based masking procedure fusion of lidar and optical data required accurate co registration of images to the lidar and we developed an object oriented procedure for achieving this alignment information on flow depths was derived by correlating pixel values with field measurements of depth highly turbid conditions dictated a positive relation between green band radiance and flow depth and contributed to under prediction of pool depths water surface elevations extracted from the lidar along the water s edge were used to produce a continuous water surface that preserved along channel variations in slope subtracting local flow depths from this surface yielded estimates of the bed elevation that were then combined with lidar topography for exposed areas to create a composite representation of the riverine terrain the accuracy of this terrain model was assessed via comparison with detailed field surveys a map of elevation residuals showed that the greatest errors were associated with underestimation of pool depths and failure to capture cross stream differences in water surface elevation nevertheless fusion of lidar and passive optical image data provided an efficient means of characterizing river morphology that would not have been possible if either dataset had been used in isolation copyright 2011 john wiley sons ltd

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 timing of mediterranean sapropel deposition relative to insolation sea level and african monsoon changes the mediterranean basin is sensitive to global sea level changes and african monsoon variability on orbital timescales both of these processes are thought to be important to the deposition of organic rich sediment layers or sapropels throughout the eastern mediterranean yet their relative influences remain ambiguous a related issue is that an assumed 3 kyr lag between boreal insolation maxima and sapropel mid points remains to be tested here we present new geochemical and ice volume corrected planktonic foraminiferal stable isotope records for sapropels s1 holocene s3 s4 and s5 marine isotope stage 5 in core lc21 from the southern aegean sea the records have a radiometrically constrained chronology that has already been synchronised with the red sea relative sea level record and this allows detailed examination of the timing of sapropel deposition relative to insolation sea level and african monsoon changes we find that sapropel onset was near synchronous with monsoon run off into the eastern mediterranean but that insolation sapropel monsoon phasings were not systematic through the last glacial cycle these latter phasings instead appear to relate to sea level changes we propose that persistent meltwater discharges into the north atlantic e g at glacial terminations modified the timing of sapropel deposition by delaying the timing of peak african monsoon run off these observations may reconcile apparent model data offsets with respect to the orbital pacing of the african monsoon our observations also imply that the previous assumption of a systematic 3 kyr lag between insolation maxima and sapropel midpoints may lead to overestimated insolation sapropel phasings finally we surmise that both sea level rise and monsoon run off contributed to surface water buoyancy changes at times of sapropel deposition and their relative influences differed per sapropel case depending on their magnitudes sea level rise was clearly important for sapropel s1 whereas monsoon forcing was more important for sapropels s3 s4 and s5

objective landslide detection and surface morphology mapping using high resolution airborne laser altimetry a map of extant slope failures is the most basic element of any landslide assessment without an accurate inventory of slope instability it is not possible to analyze the controls on the spatial and temporal patterns of mass movement or the environmental human or geomorphic consequences of slides landslide inventory maps are tedious to compile difficult to make in vegetated terrain using conventional techniques and tend to be subjective in addition most landslide inventories simply outline landslide boundaries and do not offer information about landslide mechanics as manifested by internal deformation features in an alternative approach we constructed accurate high resolution dems from airborne laser altimetry lidar data to characterize a large landslide complex and surrounding terrain near christchurch new zealand one dimensional circular 2 d and spherical 3 d statistics are used to map the local topographic roughness in the dems over a spatial scale of 1 5 to 10 m the bedrock landslide is rougher than adjacent unfailed terrain and any of the statistics can be employed to automatically detect and map the overall slide complex furthermore statistics that include a measure of the local variability of aspect successfully delineate four kinematic units within the gently sloping lower half of the slide features with a minimum size of surface folds that have a wavelength of about 11 to 12 m and amplitude of about 1 m are readily mapped two adjacent earthflows within the landslide complex are distinguished by a contrast in median roughness and texture and continuity of roughness elements the less active of the earthflows has a surface morphology that presumably has been smoothed by surface processes the laplacian operator also accurately maps the kinematic units and the folds and longitudinal levees within and at the margins of the units finally two dimensional power spectra analyses are used to quantify how roughness varies with length scale these results indicate that no dominant length scale of roughness exists for smooth unfailed terrain in contrast zones with different styles of landslide deformation exhibit distinctive spectral peaks that correspond to the scale of deformation features such as the compression folds the topographic based analyses described here may be used to objectively delineate landslide features generate mechanical inferences about landslide behavior and evaluate relatively the recent activity of slides published by elsevier science b v

paleo sea levels reconsidered from direct observation of paleoshoreline position during glacial maxima for the last 500 000 yr the drastic climatic changes which characterise the cooling trend of the last few million years of earth history led to variations in eustatic sea level that had tremendous impact on the geology and ecology of continental margins reconstructing a sea level curve back in time is not an easy task observations of shoreline positions are always a local measurement of relative sea level that needs to be corrected from the effect of tectonic and thermal subsidence sediment loading compaction and glacio hydro isostasy extensive studies have been done for the last deglaciation and for the last 100 000 yr cycle but very few studies deal with position of sea level during earlier cycles simply because conditions are very rarely favourable for the preservation of such witnesses the shelf of the golfe du lion western mediterranean reveals a unique record of shoreline paleopositions during glacial maxima of at least the last five circa 100 kyr glacial interglacial cycles in fact it is the entire glacial deltaic lobe of up to 50 m thick from delta front or shoreface to prodelta that has been preserved in place and which provides direct and independent constraints for relative sea level minima we measure a relative sea level of 112m 128 134 246 and 262 m for mis 2 6 8 10 and 12 respectively after corrections taking into account postdepositional movement of strata subsidence we find that sea level dropped to a depth of 102 6 m during the last three glaciations mis2 mis6 mis8 but reached exceptionally low values of more than 150 10 m during the preceding glaciations mis10 and mis 12 at about 340 and 434 kyr bp this general time framework and sedimentological interpretation has been confirmed by preliminary results from two deep drillings during the promess cruise july 2004 which validate our methodology however no detailed and absolute datings of such witnesses are available so far so that we cannot prove that these levels are the lowest ever reached during each glacials but they correspond undoubtedly to the last preserved shoreface before rapid sea level rise we also suggest that the abrupt change in sea level maxima might be the overprint of 400 kyr orbital periodicity cycles last but not least these results prove that the golfe du lion is indeed a unique laboratory to study paleoclimates and sea level variations on a larger time scale further work is needed for a complete glacio hydro sedimento isostatic modelling of each sequence and each glacial to further constraint local sea level versus global sea level and quantify in particular the relative effect of glacio hydro isostatic effect which differ according to ice sheet extend but also of erosion sedimentation isostatic effect erosion on land and deposition on the outer shelf and slope

sea level and climatic controls on turbidite occurrence for the past 26 kyr on the flank of the gaoping canyon off sw taiwan submarine canyons are major conduits for delivery of sediments originating from the continental margin into the deep sea here we analyze the effects of changing sea levels and climate e g sediment supply on the frequency of turbidites over the last 26 kyr our study is based on high resolution age controls for turbidites in core md178 10 3291 from a water depth of 2070 m on the flank of the gaoping canyon offshore in sw taiwan unlike most other submarine canyons worldwide the head of the gaoping canyon has remained connected to the river mouth during the recent flooding of the continental shelf our results reveal that turbidity currents are less frequent during periods of sea level lowstand in contrast turbidity currents have been more frequent since 12 kyr bp during the final stage of rising sea level and sea level highstands this may be the result of increased terrestrial sediment delivery due to enhanced rainfall intensity moreover comparing to other source to sink systems the turbidite occurrence in the flank of gaoping canyon through the last glacial cycle might have been more strongly influenced by climatic changes due to short sediment storage response time

evolution of channel morphology and hydrologic response in an urbanizing drainage basin the dead run catchment in baltimore county maryland has undergone intense urbanization since the late 1950s reconstruction of the channel planform from topographic maps dating back to the 1890s and aerial photographs dating back to the 1930s indicates that the channel has remained stable in planform since at least the 1930s the relative stability of dead run contrasts with the alterations in channel morphology reported for other urbanizing streams in the piedmont physiographic province of the eastern united states trend analyses of discharge records in dead run show that urban development and stormwater control measures have had significant impacts on the hydrologic response of the catchment the flood hydraulics of the dead run catchment are examined for the event that occurred on 22 june 1972 in association with hurricane agnes a two dimensional hydraulic model telemac 2d was used with a finite element mesh constructed from a combination of high resolution lidar topographic data and detailed field survey data to analyse the distribution of boundary shear stress and unit stream power along the channel and floodplain during flooding from hurricane agnes the spatial and temporal distributions of these parameters relative to channel gradient and channel valley bottom geometry provide valuable insights on the stability of the dean run channel the stability of dead run s channel planform in spite of extreme flooding and decades of urban development is most likely linked to geological controls of channel and floodplain morphology copyright 2006 john wiley sons ltd

from source to sink a new perspective on the past dynamics of the murray canyon group from benthic foraminiferal communities abstract we present fossil benthic foraminiferal assemblage data from marine sediment core ss02 06 gc2 located in the abyssal plain of the murray canyon group offshore south australia the sedimentological characteristics indicate the presence of turbidite deposits showing classical bouma like sequences dated between 40 and 12 cal ka bp these results confirm the previous interpretation of the observed large deep water holes in the abyssal area where the core was sampled as being gouged by surges of high energy turbidity currents the presence of good indicator taxa and unique assemblages occupying specific bathymetric depths allows the determination of the source origin of the sediments making the turbidites three distinct faunal groups are found 1 mostly shelf species 2 mostly bathyal species and 3 mostly abyssal species in the sediment core these groups present a quasi systematic succession with nearly all bouma like sequences starting with the dominance of bathyal species in the coarse grained base followed by the dominance of shallow species in the silty part and finally with abyssal species in the clays to explain such phenomena turbidites triggered by mixed hyperpycnal hypopycnal flow processes and turbidity currents during periods of river floods are considered for the first time within the murray canyon group they are mostly related to periods of increased fluvial discharges during wet phases in the murray darling basin

plio quaternary prograding clinoform wedges of the western gulf of lion continental margin nw mediterranean after the messinian salinity crisis in contrast to the much studied onshore and deep offshore post messinian sedimentary history of the gulf of lion the continental shelf had been poorly explored until recently new seismic data acquired by elf oil company on the languedoc roussillon shelf western mediterranean sea from cap creus in the sw to cap d agde in the ne together with data from previously drilled exploratory wells allow us to propose a scenario for margin reconstruction following the messinian salinity crisis the seismic data display a complex pattern of prograding clinoforms and buried submarine canyons following the crisis that eroded the previous margin clinoforms developed as the new pliocene margin prograded three major periods characterize the evolution of the post messinian margin during the first period after the filling of the early pliocene rias which are now above sea level the prograding sedimentary prisms rapidly migrated seaward and filled the underlying messinian topographic lows the second period consists of a transitional interval which began with a pronounced fall in sea level that probably corresponded with the end of the lower pliocene deposits were disturbed by large slumped structures the third period is characterized by the appearance and development of submarine canyons near the subsequent shelf edges maybe as a result of the increased glaciations and related sea level changes from that time onward most of the late pliocene and quaternary sediments were directly transferred down to the deep basin

rapid rise of sea level 19 000 years ago and its global implications evidence from the irish sea basin supports the existence of an abrupt rise in sea level meltwater pulse at 19 000 years before the present b p climate records indicate a large reduction in the strength of north atlantic deep water formation and attendant cooling of the north atlantic at this time indicating a source of the meltwater pulse from one or more northern hemisphere ice sheets warming of the tropical atlantic and pacific oceans and the southern hemisphere also began at 19 000 years b p these responses identify mechanisms responsible for the propagation of deglacial climate signals to the southern hemisphere and tropics while maintaining a cold climate in the northern hemisphere

hyperpycnal plume formation from riverine outflows with small sediment concentrations a series of laboratory experiments has been conducted in order to elucidate the sediment induced mixing processes accompanying riverine outflows specifically the discharge of a warm fresh particle laden fluid over a relatively dense cool brine in a parameter regime analogous to recently acquired field measurements hypopycnal surface plumes were subject to a convective instability driven by some combination of heat diffusing out of the warm fresh sediment laden plume and particle settling within it convection was robust in the presence or absence of intense turbulence at sediment concentrations as low as 1 kg m 3 and took the form of millimetre scale sediment laden fingers descending from the base of the surface plume a consequence of the convective instability of the original hypopycnal plume is the generation of a hyperpycnal bottom riding flow the experiments presented here indicate that natural river outflows may thus generate hyperpycnal plumes when sediment concentrations are 40 times less than those required to render the outflow heavy relative to the oceanic ambient the resulting hyperpycnal plumes may play an important role in transporting substantial quantities of sediment to the continental slope and beyond

the 100 ka and rapid sea level changes recorded by prograding shelf sand bodies in the gulf of lions western mediterranean sea thick forced regressive units on the wide continental shelf of the gulf of lions western mediterranean recorded the composite effect of sea level changes during the quaternary they are mostly composed of coastal siliciclastic and bioclastic wedges showing clinoform geometry these deposits have been intensively explored through high resolution seismic investigations but only recently it was possible to ground truth seismic interpretations based on a long 100 m borehole that crossed the succession and recovered a large part of the mainly sandy deposits similar to 84 recovery a multiproxy analysis of the sedimentary succession shows that 1 the stratal architecture of the shelf margin is defined by major bounding surfaces that are polygenic erosion surfaces associated with coarse grained material incorporating abundant and diverse shells including cold water fauna presently absent from the mediterranean sea between each surface coarsening upward units with steep up to 5 degrees foresets are made of massive more than 20 m thick sands with possible swaley and hummocky cross stratification passing seaward to sands with muddy intervals and further offshore alternating highly boiturbated sands and silts each prograding wedge corresponds to a forced regressive shoreface or delta front prodelta deposited during the overall sea level falls occurring at relatively slow interglacial glacial transition and therefore represents the record of 100 ka cyclicity higher frequency milankovitch cyclicities are also probably represented by distinct shoreface delta front wedges 2 detailed examination of the architecture and chronostratigraphy of the most recent sequence shows that minor bounding surfaces corresponding to abrupt shallowing of sedimentary facies separate downward stepping parasequences within the last 100 ka sequence

glacial erosion dynamics in a small mountainous watershed southern french alps a source to sink approach in this study we used major element composition neodymium isotopes ratios endend and concentration of ree to track and quantify the sediment routing in the var sedimentary system from source southern french alps to sink ligurian sea over the last 50 ka our data reveal that changes in sediment sources over that period associated with concomitant changes in the hyperpycnal i e flood generated turbidity currents activity in the var submarine canyon were mainly driven by paleoenvironmental conditions in the upper basin and in particular by the presence of glaciers during the last glacial period based on this evidence we determined when and how glacier derived sediments were produced then excavated and transferred to the ocean allowing us to ultimately tune offshore sedimentary records to onshore denudation rates in contrast to large glaciated systems we found that sediment export from the var river to the mediterranean sea directly responded to climate induced perturbations within the basin finally we estimated that sediment fluxes in the var routing system were 2 5 times higher during the last glacial maximum than today thus confirming that glacier denudation rates exceed fluvial rates and that such a pattern also governs the interglacial glacial sediment flux cycle in other small mountainous basins

airborne lidar in support of geomorphological and hydraulic modelling this paper considers the application of airborne laser altimetry lidar to the provision of elevation data at accuracies and spatial densities commensurate with the current generation of high resolution hydraulic models three sets of issues are addressed with reference to a telemac 2d model of a morphologically complex estuary in eastern england first the quality of airborne lidar data is assessed via multiscale calibration against surveyed sections and supplementary control points second image processing techniques are used for i identification of multiple regions of interest within large lidar mosaics ii subregional infilling of voids left by data drop outs iii filtering and subsampling to match topographic information content with model resolution and the density of the computational mesh third the implications of improved terrain data are considered with reference to the estimation of elevations and potential tidal volumes for a number of discrete flood compartments and the modelling of hypothetical inundation scenarios after minor offset correction to ensure registration with local benchmarks the quality of lidar elevation data within a 12 km x 4 kin coverage is found to be consistent with the published specification 0 10 to 0 15 m image processing tools provide an efficient means of managing information content and interfacing this with the gis based functionality of the preprocessing software used in conjunction with the hydraulic model the accuracy and spatial resolution of the lidar data allow the identification of subtle but important topographic variations between adjacent flood compartments in many cases differences in model results obtained using these data relative to previously estimated average flood compartment elevations are small importantly however lidar provides topographic information at an accuracy and resolution close to the present limits of model representation reliable representation of form allows the modeller to concentrate on the physical aspects of model parameterization whilst minimizing the conflation of parameter effects with those of poorly constrained geometric representation copyright c 2003 john wiley sons ltd

climate and sea level induced turbidite activity in a canyon system offshore the hyperarid western sahara mauritania the timiris canyon a major outcome from studying the sedimentary archives of the timiris canyon off mauritania is that climate shifts in the saharan hinterland not only influenced offshore pelagic sedimentation processes but also controlled turbidite activity in the canyon system sediment supply to the slope predominantly by eolian dust and remobilised eolian sands was greatest during hyperarid glacial and deglacial periods and due to overall increased trade wind strengths upwelling induced pelagic productivity attained highest magnitudes turbidite activity in the timiris canyon responded rapidly to these shifts in the surrounding sedimentary regime on the continental slope during high glacial and early deglacial times the tributary gullies on the uppermost slope were rapidly and repetitively filled subsequently turbidity currents were released and large turbulent flows passed through the lower timiris canyon leading to overspill sequences on its levees in addition to this scenario partial flooding of the exposed outer shelf during successive sea level rises in mis 3 may have caused re mobilization of huge aeolian dune fields that had expanded close to the shelf edge during glacial exposure during the holocene no turbidite activity is recorded in the lower timiris canyon whereas a core from a widened area in the upper timiris canyon reveals an interesting climate controlled 900 year cyclicity of carbonate and mud turbidite events throughout the holocene

sea level change along the french mediterranean coast for the past 30 000 years abstract observational evidence for sea level change along the french mediterranean coast has been examined and compared with glacio hydro isostatic models to predict the spatial and temporal patterns of change for about the past 30 000 14c years these predictions are pertinent to discussions of changing ocean volumes during this interval the tectonic stability or otherwise of the coastal areas mantle rheology and the timing of possible human occupation of the now submerged coastal plain and caves such as cosquer cave near marseille the principal results from the analysis are i sea levels along this section of the coast have risen continually since the time of the last glacial maximum lgm and at no time during the holocene has the mean sea level been higher than that of today ii the coast has been tectonically stable between marseille and nice as well as further to the west in roussillon western corsica may have experienced a slow tectonic uplift of between 0 15 0 3 mm year for the past 3000 years but northernmost corsica appears to have been stable during this same interval iii during the lgm sea levels along the coast and immediate off shore areas stood at between 105 115 m below present level the range reflecting the importance of the isostatic contributions during oxygen isotope stage 3 sea levels do not appear to have risen locally above about 60 m iv the rebound parameters describing the mantle rheology and ice sheets required to match the limited observational evidence are consistent with the results of similar analyses carried out for other parts of europe because of its distance from the former northern ice sheets the isostatic factors are particularly sensitive to the value of the lower mantle viscosity v the model predictions for sea level change at the cosquer cave site and for its immediate environments indicate that the cave was last readily accessible before about 10 700 500 14c years about 12 500 500 cal years bp and that the cave entrance was completely flooded by 9000 200 radiocarbon years bp between about 9800 and 10 300 calibrated years bp the cave was above sea level throughout the oxygen isotope stage 3

the first estimation of fleuve manche palaeoriver discharge during the last deglaciation evidence for fennoscandian ice sheet meltwater flow in the english channel ca 20 18 ka ago the fleuve manche english channel palaeoriver represents the largest river system that drained the european continent during pleistocene lowstands particularly during the elsterian marine isotope stage 12 and saalian drenthe mis 6 glaciations when extensive ice advances into the north sea area forced the central european rivers to flow southwards to the bay of biscay ne atlantic numerous long piston cores and high resolution acoustic data from the northern bay of biscay have been correlated using a well constrained chronostratigraphical framework and for the first time allow the estimation of the discharge of the fleuve manche palaeoriver at the end of the last glacial period i e weichselian our results discussed in the light of relationships between river loads and drainage area characteristics strongly suggest that the bay of biscay collected sediment laden meltwater from the northern european lowlands and the southern part of the fennoscandian ice sheet at the end of the last glacial period and particularly during the paroxysmal phase of the european deglaciation ca 20 18 ka ago this demonstrates that the fleuve manche drainage area at that time was equivalent to those dating from the major elsterian and saalian drenthe glaciations based on our data we propose a revision of the palaeogeographical and palaeoglaciological evolution of the north sea area while showing that the british and fennoscandian ice sheets entered the north sea basin until ca 18 ka initiating isostatic adjustment of the basin this allowed the north sea fluvial system to flow southwards through the dover strait finally we discuss the fleuve manche freshwater discharge during the maximum european ice sheet retreat ca 18 ka the estimated discharge at this time appears important and sufficiently sustained to possibly contribute to the profound destabilisation of the thermohaline circulation recognised in the north atlantic from ca 18 to 16 ka

the digital elevation model of italy for geomorphology and structural geology abstract the geomorphological setting and main geo structural features of the central southern italian peninsula have been investigated by creating and analyzing a digital elevation model dem and derived slope aspect and shaded relief images the dem has been assembled from the mean heights archive provided by the italian geological survey for the whole country the elevation data exhibit a grid mesh spacing of 7 5 latitude and 10 longitude firstly three different methods for calculating from a dem slope and aspect are discussed the four contiguous right triangles the maximum downward gradient and the bicubic spline first derivative the resulting maps have been compared with each other at regional scale and for a small area with a slope map obtained by using classical techniques the main goal of the comparison has been the choice of the best technique for the computation of the digital slope map of italy the four contiguous right triangles method yields better results both at local and at regional scale and is being used to create from the dem a slope map and a shaded relief of the whole country which will be published by the italian geological survey secondly the integrated analysis of dem derived slope digital map and shaded relief has permitted verification for the italian peninsula of the trends of already mapped fractures and faults and detection of previously unmapped structures showing morphological evidence the analysis of 1520 regional structural features has showed that the morphological setting of the studied area is strictly related to the tectonics about 90 of the mapped faults and folds are detectable on the shaded relief which proved to be the most useful byproduct of the dem for morphological analysis

time scales of tectonic landscapes and their sediment routing systems abstract in regions undergoing active tectonics the coupling between the tectonic displacement field the overlying landscape and the redistribution of mass at the earth9s surface in the form of sediment routing systems is particularly marked and variable coupling between deformation and surface processes takes place at a range of scales from the whole orogen to individual extensional fault blocks or contractional anticlines at the large scale the attainment of a steady state between the overlying topography and the prevailing tectonic conditions in active contractional orogens requires an efficient erosional system with a time scale dependent on the vigour of the erosional system generally in the range 10 6 10 7 years the catchment fan systems associated with extensional fault blocks and basins of the western usa are valuable natural examples to study the coupling between tectonic deformation landscape and sediment routing systems even relatively simple coupled systems such as an extensional fault block and its associated basin margin fans have a range of time scales in response to a tectonic perturbation these response times originate from the development of uniform steady state relief during the accumulation of displacement on a normal fault c 10 6 years the upstream propagation of a bedrock knickpoint in transverse catchments following a change in tectonic uplift rate c 10 6 years or the relaxation times of the integrated catchment fan system in response to changes in climatic and tectonic boundary conditions 10 5 10 6 years the presence of extensive bedrock or alluvial piedmonts increases response times significantly the sediment efflux of a mountain catchment is a boundary condition for far field fluvial transport but the fluvial system is much more than a simple transmitter of the sediment supply signal to a neighbouring depocentre fluvial systems appear to act as buffers to incoming sediment supply signals with a diffusive time scale c 10 5 10 6 years dependent on the length of the system and the extent of its floodplains stream channels and proximal gravel fans the vocabulary for explaining landscapes would benefit from a greater recognition of the importance of the repeat time and magnitude of perturbations in relation to the response and relaxation times of the landscape and its sediment routing systems landscapes are best differentiated as buffered or reactive depending on the ratio of the response time to the repeat time of the perturbation furthermore landscapes may be regarded as steady or transient depending on the ratio of the response time to the time elapsed since the most recent change in boundary conditions the response of tectonically and climatically perturbed landscapes has profound implications for the interpretation of stratigraphic architecture

late quaternary deltaic lowstand wedges on the rhone continental shelf france abstract shallow seismic profiles on the rhone continental shelf have shown the existence of stacked progradational lowstand wedges on the outer shelf accumulated during late quaternary glacioeustatic lowstands the wedges are bounded by sharp to erosional sequence boundaries and onlap onto the middle shelf the thickness of individual wedges attains 50 meters at the shelf edge where they are sheared by slumping the wedges exhibit well developed progradational clinoforms episodically interrupted by internal unconformities on which there is a downward shift of the succeeding clinoforms these represent small scale in the order of a few meters falls in sea level during the quaternary eustatic cycles the durations of the stable highstand conditions appear to have been too brief to permit the regressive highstand tract to prograde to the outer shelf therefore the shelf edge builds up entirely with lowstand wedges

sedimentary responses to the east asian monsoon and sea level variations recorded in the northern south china sea over the past 36 kyr abstract sediment grain size is an important proxy to detect sedimentary process and record paleoenvironmental variations in continental slopes grain size measurements were performed for 298 samples of the 5 96 m long core pc338 spanning the past 36 kyr recovered from the northern south china sea scs results show that sea level and climatic influences on grain size distributions are crucial a turbidite formed during the last glacial maximum lgm is ascribed to the favorable topography close to the red river estuary induced by the low sea level four end member em components for the normal sediment layers were unmixed using a lognormal parametric end member modeling emm with the sea level decreasing more em4 15 100 m and less em1 0 2 m supplied the scs slope because em2 2 10 m consisted of fluvial suspension is dominated by the east asian summer monsoon easm precipitation it has the potential to substitute for the easm intensity em2 varied in phase with many south china paleoclimate records and the 30 n july insolation over the past 36 kyr and cooling climate events including the lgm heinrich events h1 and h3 younger dryas 8 2 ka and 10 3 ka lowered the em2 content our results further confirm the synchronous easm evolution in the south china continent mainly forced by the northern hemisphere summer insolation

spatial characterization resolution and volumetric change of coastal dunes using airborne lidar cape hatteras north carolina the technological advancement in topographic mapping known as airborne light detection and ranging lidar allows researchers to gather highly accurate and densely sampled coastal elevation data at a rapid rate the problem is to determine the optimal resolutions at which to represent coastal dunes for volumetric change analysis this study uses digital elevation models dem generated from lidar data and spatial statistics to better understand dune characterization at a series of spatial resolutions the lidar data were collected jointly by the national aeronautics and space administration nasa the national oceanic and atmospheric administration noaa and the u s geological survey usgs dems of two study sites 100 200 m located in cape hatteras national seashore north carolina were generated using a raster based geographic information system gis changes in the dune volume were calculated for a 1 year period of time fall 1996 1997 at grid cell resolutions ranging from 1 1 to 20 20 m directional statistics algorithms were used to calculate local variance and characterize topographic complexity data processing was described in detail in order to provide an introduction to working with lidar data in a gis results from these study sites indicated that a 1 2 m resolution provided the most reliable representation of coastal dunes on cape hatteras and most accurate volumetric change measurements results may vary at other sites and at different spatial extents but the methods developed here can be applied to other locations to determine the optimum resolutions at which to represent and characterize topography using common gis and database software

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

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

geomorphological change detection of an urban meander loop caused by an extreme flood using remote sensing and bathymetry measurements a case study of karoon river iran abstract flooding and flood inundation are key hydrological characteristics of meander loop rivers however the effects of extreme floods on river morphology and spatial patterns of erosion and deposition are poorly understood a detailed geomorphologic change detection and sediment erosion process caused by an extreme flood more than 100 year recurrence interval discharge on 14 apr 2016 was surveyed for a single urban meander loop of the karoon river iran the studied meander loop is located next to the city of the ahavz and has a centerline length of about 14 km the bathymetry in 8892 stable points was measured also the detailed bathymetry layers for before 8 apr 2016 and after 24 apr 2016 the extreme flood event were compared geomorphological change detection gcd results show that in the studied reach about 106 ha of bank erosion was detected with a total volume of approximately 450 600 m3 furthermore total volume of surface lowering and the total volume of surface rising volumes that were obtained were 95421 6 m3 and 98619 0 m3 respectively the talweg length of the studied meander loop decreased about 126 m and the average depth decreased from 3 71 m to 3 14 m after the flood event channel widening as a consequence of the extreme flood was found to be about 21 m 17 the findings of this study indicate that extreme floods play an important role in the sediment budget and morphological evolution of meandering rivers

external controls on turbidite sedimentation on the glacially influenced armorican margin bay of biscay western european margin abstract sequence stratigraphic models predict increased sediment delivery to deep water areas during sea level lowstand the armorican margin bay of biscay western european margin is an interesting area to test this hypothesis because the margin has a wide continental shelf still partly flooded during sea level lowstand and the armorican turbidite system has experienced fluctuating sediment fluxes since the last glacial period the stratigraphic response of the armorican turbidite system to sea level oscillations and climate changes was assessed for the last 35 000 years through the study of the guilcher crozon and audierne levees millennial timescale resolution chronostratigraphy allowed us to reconstruct the sediment accumulation and turbidite frequency thickness and grain size over this period of time we found that the armorican turbidite system was sediment starved during highstand conditions ca 8 0 ka and that glacial conditions favoured sediment delivery to the deep bay of biscay however contrary to what would be expected from sequence stratigraphic models the turbidite flux did not reach a maximum during the lgm lowstand ca 26 20 ka but at the onset of termination i between ca 20 and 17 ka this makes the armorican turbidite system a transgression dominated one this sediment pulse can be interpreted as a huge increase in the meltwater discharge of the fleuve manche palaeoriver in response to the decay of the british and fennoscandian ice sheets at that time despite the rising sea level a large deltaic system had to have developed on the outer shelf leading to the delivery of the fleuve manche sediment load into the canyon heads on the other hand our dataset suggest that the delivery of sediment into canyons was mainly forced by the winnowing and reworking of the sediment stored on the wide drowned shelf during the last glacial period between ca 35 and 20 ka and between 17 and 8 ka these findings illustrate the competing influences of accommodation and sediment supply on the armorican margin over the last 35 000 years with a shelf acting as a buffer for the sediment supply signal for most of the period except during the last deglaciation at that time the western european sediment routing system was reactive the climatic signal rapidly propagated from the southern limb of the european ice sheet to the armorican turbidite system finally our study demonstrates that precise reconstruction of turbidite flux in deep water areas added to knowledge about the morphology of the margin and the palaeoenvironmental changes fluvial system shoreline position etc are crucial for determining the response of turbidite systems to external forcing

meltwater channel scars and the extent of mid pleistocene glaciation in central pennsylvania abstract high resolution digital topographic data permit morphological analyses of glacial processes in detail that was previously infeasible high level glaciofluvial erosional scars in central pennsylvania identified and delimited using lidar data define the approximate ice depth during a pre wisconsin advance 770 000 bp on a landscape unaffected by wisconsin glaciation distinctive scars on the prows of anticlinal ridges at 175 350 m above the valley floor locate the levels of subice meltwater channels a two component planar gis model of the ice surface is derived using these features and intersected with a digital model of contemporary topography to create a glacial limit map the map is compared to published maps demonstrating the limits of conventional sediment based mapping additional distinctive meltwater features that were cut during deglaciation are modeled in a similar fashion

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

sediment instability on the portuguese continental margin under abrupt glacial climate changes last 60 kyr abstract it is well established that orbital scale sea level changes generated larger transport of sediments into the deep sea during the last glacial maximum than the holocene however the response of sedimentary processes to abrupt millennial scale climate variability is rather unknown frequency of distal turbidites and amounts of advected detrital carbonate are estimated off the lisbon setubal canyons core md03 2698 at 4602 mwd within a chronostratigraphy based on radiometric ages oxygen isotopes and paleomagnetic key global anomalies we found that 1 higher frequency of turbidites concurred with northern hemisphere coldest temperatures greenland stadials gs including heinrich h events but more than that an escalating frequency of turbidites starts with the onset of global sea level rising and warming in antarctica and culminates during h events at the time when rising is still in its early mid stage and the atlantic meridional overturning circulation amoc is re starting this short time span coincides with maximum gradients of ocean surface and bottom temperatures between gs and antarctic warmings antarctic isotope maximum aim 17 14 12 8 4 2 and rapid sea level rises 2 trigger of turbidity currents is not the only sedimentary process responding to millennial variability land detrital carbonate with a very negative bulk 18o signature enters the deep sea by density driven slope lateral advection accordingly during gs 3 possible mechanisms to create slope instability on the portuguese continental margin are sea level variations as small as 20 m and slope friction by rapid deep and intermediate re accommodation of water masses circulation 4 common forcing mechanisms appear to drive slope instability at both millennial and orbital scales

lateglacial changes in river morphologies of northwestern europe an example of a smooth response to climate forcing cher river france climatic oscillations occurring during the pleniglacial and lateglacial periods are generally associated with several changes in fluvial morphology and processes this study investigated two reaches of the cher river basin noyers sur cher and thenioux regarding morphological adjustments during the lateglacial period and the early holocene transitions from the pleniglacial to the lateglacial and from the lateglacial to the early holocene ca 14 700 11 500 cal bp are considered as interesting study cases because it consists of rapid and abrupt climate oscillations generally clearly recorded in current floodplains the sites studied are located in the cher river floodplain which is one of the main tributaries of the loire river several investigations have been conducted in the main valley but few of them specifically focused on geomorphological evolutions of medium sized catchments such as tributaries of the loire river therefore we examined this specific period through investigations recently conducted in the middle valley of the cher river this study aimed to 1 provide a geomorphological approach to fluvial adjustments during the lateglacial from cases located in lowland areas of a medium sized basin and 2 analyse the spatio temporal variability of fluvial responses assessment of geomorphological trajectories of the two reaches studied highlights that fluvial metamorphosis occurring during the lateglacial and early holocene seems to be characterised by lateral readjustments and a low signal of morphological instability shallow incision and aggradation processes slow and progressive change in channel morphology this observation is enhanced by the comparison with known geomorphological evolution patterns of adjacent basins the intrinsic components of the cher basin such as slope and valley width were considered as explanatory factors for the lack of morphogenetic processes in addition the geographical location of the reaches studied may also have led to a moderated expression of climate forcing indeed the elevation as well as the north south and east west gradients may contribute to the low level of geomorphological adjustments in response to these climatic oscillations this gradient could also have support this the fluvial response because of the weakly developed loess cover which may have limited the fine sediment supply and the aggradation of the valley bottom

turbiditic levee deposition in response to climate changes the var sedimentary ridge ligurian sea abstract article history received 31 may 2010received in revised form 25 october 2010accepted 25 october 2010available online 31 october 2010communicated by d j w piperkeywords last deglaciationoverbank depositsturbidity currentsvar sedimentary ridgeligurian sea the var turbiditic system located in the ligurian sea se france is an intermediate mud sand rich system theparticularityofthevardeep seafanisitssinglechannelwithabruptbendsanditsasymmetricandhyper developed levee on the right hand side the var sedimentary ridge long term sediment accumulation on thevar sedimentary ridge makes this an ideal target for studying the link between onshore climate change anddeep sea turbidite stratigraphy this paper focuses on the establishment of the rst detailed stratigraphy ofthe levee which is used to analyze the timing of overbank deposition throughout the last deglaciation mainresults indicate that high variability in turbidite frequencies and deposition rates along the var sedimentaryridgearedeterminedbytwomainparameters 1 theprogressivedecreaseoftheleveeheightcontrollingtheabilityofturbiditycurrentstospilloutfromthechannelontothelevee and2 climaticvariationsaffectingthedrainage basin in particular changes in glacial condition since late last glacial maximum to early holocene compared to other deep water areas this study con rms the ability of turbiditic systems to record pastclimatic events on millennial timescales and underlines the in uence of european deglaciation on theobserved decrease in turbidite activity in the var canyon the presence of a very narrow continental shelf andasingle largechannel leveesystemmakesthevarsedimentaryridgeauniqueexampleofclimate controlledturbiditic accumulations 2010 elsevier b v all rights reserved

carbon and silica megasink in deep sea sediments of the congo terminal lobes carbon and silicon cycles at the earth surface are linked to long term variations of atmospheric co2 and oceanic primary production in these cycles the river sea interface is considered a biogeochemical hotspot and deltas presently receive and preserve a major fraction of riverine particles in shallow water sediments in contrast periods of glacial maximum lowstand were characterized by massive exports of sediments to the deep sea via submarine canyons and accumulation in deep sea fans here we calculate present day mass balances for organic carbon oc and amorphous silica asi in the terminal lobe complex of the congo river deep sea fan as an analogue for glacial periods we show that this lobe complex constitutes a megasink with the current accumulation of 18 and 35 of the oc and asi river input respectively this increases the estimates of organic carbon burial by 19 in the south atlantic ocean in a zone representing less than 0 01 of the basin these megasinks might have played a role in carbon trapping in oceanic sediments during glacial times

millennial scale response of a western mediterranean river to late quaternary climate changes a view from the deep sea abstractalthough it is widely accepted that erosion and sediment transfer respond to millennial scale climatic variability these changes remain difficult to detect in marine sedimentary archives in the var sediment routing system northwestern mediterranean sea the absence of a continental shelf results in a direct connection between the var river mouth and the deep basin during both highstand and lowstand conditions this makes the var sediment routing system an ideal target to test whether rivers can transmit climate driven high frequency changes in sediment flux to the ocean on the basis of an unprecedented centennial to millennial scale resolution in turbidite sequences we reconstructed the activity of turbidity current overflows along the deep sea var sedimentary ridge over the past 75 kyr the overflow activity is highest one event every 10 30 yr during maximum glacial conditions 30 kyr 16 kyr ago ka and rapidly decreases down to one event every 100 500 yr during the last glacial inte

evaluating short term morphological changes in a gravel bed braided river using terrestrial laser scanner abstract braided rivers are dynamic and complex environments shaped by the balance of the flow and sediment regimes and by the influence of the riparian vegetation and disturbances such as floods in particular the balance between sediment supply and transport capacity can determine the morphological evolution of a river for instance aggrading and widening trends are distinctive of reaches where sediment supply is higher than transport capacity in contrast incising and narrowing tendencies are dominant the aim of the present study is to analyze the short term morphological dynamics and the processes of erosion and sediment deposition along a small reach of a relatively unimpacted gravel bed braided river tagliamento river northeast italy using a terrestrial laser scanner tls the study area is around 23 ha and has been surveyed before after two periods with relevant flood events two of which were higher than the bankfull level and occurred between september 2010 and september 2011 the very high point clouds density allowed us to derive three high resolution digital elevation models dems with 0 125 0 125 m pixel size scan data cloud merging was achieved with an overall high degree of accuracy and resolution subcentimeter topographic data were more accurate for exposed surfaces than those collected in wet areas a detailed net of dgps control points allowed us to verify the high quality of the dems derived from the surveys rmse of about 5 cm two dems of difference dod were computed revealing different and consistent episodes of erosion and deposition within the analyzed area and changes in morphology of channel and bars could also be detected such as bar edge accretion and bank erosion demonstrating a strong dynamicity of the tagliamento river moreover a very detailed estimation of the surface roughness in the study area has been carried out permitting a large scale analysis of the roughness values distribution the results of the analysis on the tls collected data show that along a river with a high natural character i e tagliamento river the dynamic processes are also common during low magnitude events

high resolution interpretative geomorphological mapping of river valley environments using airborne lidar data the availability of airborne lidar data provides a new opportunity to overcome some of the problems associated with traditional field based geomorphological mapping such as restrictions on access and constraints of time or cost the combination of airborne lidar data and gis technology facilitates the rapid production of geomorphological maps of floodplain environments however unfiltered lidar data which include vegetation and buildings are currently more suitable for geomorphological mapping than data that have been filtered to remove these features classification of lidar data according to elevation in a gis enables the user to identify and delineate geomorphological features in a manner similar to field mapping but it is necessary to use a range of classification intervals in order to map the various types of feature that occur within a single reach comparison of a lidar derived geomorphological map with an independently produced field geomorphological map showed a high degree of similarity between the results of the two methods although ground truthing is essential in cases where a high degree of accuracy is required ground truthing of a lidar derived geomorphological map showed that around 80 of features mapped using both methods were identified from the lidar data suggesting that the method is suitable for applications such as production of base maps for use in field mapping and selection of sites for detailed investigation copyright 2007 john wiley sons ltd

impact of hydroelectric power releases on the morphology and sedimentology of the bed of the warche river belgium the butgenbach dam on the warche river was built in 1932 in order to maintain a suf cient supply of water to the robertville reservoir situated 7 km downstream for the production of hydroelectricity during winter months releases are made almost every day from the butgenbach dam from a hydrological point of view this has resulted in signi cantly reducing the number of discharges that are higher than bankfull despite the reduction in peak discharge there is a signi cant increase in the number of ef cient discharges 0 6 bankfull the impacts of these hydrological modi cations on the bed morphology and sedimentology below the butgenbach dam have been studied and the following geomorphological modi cations have been identi ed a doubling of the width of the channel in 45 years a reduction in the number of rif es and pools an increase in the number of gravel bars and islets and an increase in bedrock outcrops in the channel moreover the nest bed particles are mobilized by the almost daily releases inducing a signi cant increase in bed material size sorting the reduction of sinuosity and the disappearance of bed differentiation and rif e pool sequences have produced a diminution of bed roughness and an increase of the competence of the river thus relatively small oods can remove the armoured layer copyright 2003 john wiley sons ltd

late glacial to preboreal sea level rise recorded by the rhone deltaic system nw mediterranean abstract a unique late glacial preboreal record of changes in sea level and sediment fluxes originating from the alps is recorded in the rhone subaqueous delta in the western mediterranean sea the compilation of detailed bathymetric charts together with high resolution seismic profiles and long cores reveals the detailed architecture of several sediment lobes related to periods of decreased sea level rise and or increased sediment flux they are situated along the retreat path of the rhone distributaries from the shelf edge and canyon heads up to the modern coastline they form transgressive backstepping parasequences across the shelf the late holocene highstand deltas being confined to the inner shelf the most prominent feature is an elongated paleo shoreface deltaic system with an uppermost sandy fraction remolded into subaqueous dunes a long piston core into the bottomsets of this prograding unit allows precise dating of this ancient deltaic system in seismic data it displays aggradation starting at 15 cal kyr bp followed by progradation initiated during the first phase of the younger dryas a period of reduced sea level rise or stillstand the delta kept pace with resumed sea level rise during the preboreal which is estimated at about 1 cm yr as a result of increased sediment supply from the alps melting of glaciers and more humid climate flushing the sediment down to the sea abandonment of the delta occurred around 10 500 cal yr bp that is to say about 1000 yr after the end of the younger dryas probably because of decreased sediment flux

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

historical analysis indicates seepage control on initiation of meandering in analytical and numerical models of river meandering initiation of meandering typically occurs uniformly along the streamwise coordinate in the channel based on a historical analysis of the nierskanaal here we show how and under which circumstances meandering has initiated in isolated sections of a channel the nierskanaal was constructed by the end of the 18th century as a straight channel between the river niers and the river meuse the purpose of this measure was to reduce flood risk in the downstream reaches of the river niers the banks on the dutch part of the channel were left unprotected and developed into a morphodynamically active channel featuring a meandering planform and valley incision the planform development and incision process is analysed using topographic maps and airborne lidar data meandering initiated in three sections of the channel where the channel sinuosity developed asynchronously sedimentary successions in the study area show layers of iron oxide indicating groundwater seepage from aeolian river dunes and river deposits located nearby only at the spots where meandering has initiated iron oxide is found close to the surface level this provides a clue that seepage triggered bank erosion by increasing moisture content of the banks the isolated meandering sections expanded in the longitudinal direction valley incision has developed in the first decades after the construction of the channel and diminished after a gravel layer was reached gravel was deposited in the downstream half of the channel bed acting as an armouring layer the spatial variation in meandering behaviour as observed in the nierskanaal justifies efforts to implement the influence of floodplain heterogeneity and the effect of seepage on bank erosion in meander models

chronology of the last glacial cycle in the european alps chronological data for glacier advances in the european alps between the last interglacial eemian and the holocene are summarised 115 to 11 ka during this time glaciers were most extensive extending tens of kilometres out onto the forelands between 30 and 18 ka that is synchronous with the global ice volume maximum of marine isotope stage mis 2 evidence for ice expanding to just past the mountain front for an earlier major glacier advance comes from swiss sites where advances have been luminescence dated to mis 5d 100 ka and mis 4 70 ka up to now no such evidence has been found in the eastern alps by 18 ka more than 80 of the late wurmian ice volume had gone subsequently glaciers readvanced reaching into the upper reaches of the main valleys during the lateglacial gschnitz stadial which likely occurred around 17 ka with final moraine stabilisation no later than 15 4 ka the link of the egesen stadial with the younger dryas climate deterioration is supported by exposure ages from four sites as well as minimum limiting radiocarbon dates from bogs within former glacier tongue areas key questions on the spatial and temporal variability of ice extents throughout the last glacial cycle have yet to be answered copyright 2008 john wiley sons ltd

a new greenland ice core chronology for the last glacial termination 1 we present a new common stratigraphic timescale for the north greenland ice core project ngrip and grip ice cores the timescale covers the period 7 9 14 8 kyr before present and includes the bolling allerod younger dryas and early holocene periods we use a combination of new and previously published data the most prominent being new high resolution continuous flow analysis cfa impurity records from the ngrip ice core several investigators have identified and counted annual layers using a multiparameter approach and the maximum counting error is estimated to be up to 2 in the holocene part and about 3 for the older parts these counting error estimates reflect the number of annual layers that were hard to interpret but not a possible bias in the set of rules used for annual layer identification as the grip and ngrip ice cores are not optimal for annual layer counting in the middle and late holocene the timescale is tied to a prominent volcanic event inside the 8 2 kyr cold event recently dated in the dye 3 ice core to 8236 years before a d 2000 b2k with a maximum counting error of 47 years the new timescale dates the younger dryas preboreal transition to 11 703 b2k which is 100 150 years older than according to the present grip and ngrip timescales the age of the transition matches the gisp2 timescale within a few years but viewed over the entire 7 9 14 8 kyr section there are significant differences between the new timescale and the gisp2 timescale the transition from the glacial into the bolling interstadial is dated to 14 692 b2k the presented timescale is a part of a new greenland ice core chronology common to the dye 3 grip and ngrip ice cores named the greenland ice core chronology 2005 gicc05 the annual layer thicknesses are observed to be log normally distributed with good approximation and compared to the early holocene the mean accumulation rates in the younger dryas and bolling periods are found to be 47 2 and 88 2 respectively

multi scale assessment of overflow driven lateral connectivity in floodplain and backwater channels using lidar imagery overflow driven lateral connectivity significantly influences the spatial distribution and diversity of floodplain habitats and biota proper understanding of lateral connectivity in floodplain and backwater channels is therefore critical for assessment of river quality and for targeting management or restoration actions in this study we present a methodological framework for spatial and temporal assessments of overflow driven lateral connectivity at two spatial scales bypass reach and backwater channel firstly we compute the relative elevations as well as overflow discharge duration and frequency using a simple raster based method that uses a lidar digital elevation model dem rating curves and streamflow time series subsequently we analyse the accuracy of this approach with respect to the accuracy of a dem and evaluate its further applications altogether four 10 km long bypass reaches and 11 backwater channels are analysed located along the rhone river corridor in france the results proved the precision of the method to be affected by the lidar dem accuracy which was on average more precise in a typically homogeneous floodplain setting rather than for backwater channel plugs with pronounced topographic complexity and usually riparian forest canopy amongst the four studied reaches bregnier cordon proved to have the greatest flooding dynamics followed by belley and chautagne the hydrological connectivity pattern of pierre benite differed significantly three longitudinal patterns of hydrological connectivity of backwater channels displayed stepwise advancement of the water the presented results can be used to assess ecological potential of floodplain habitats and their historic and prospective evolution through time copyright 2014 john wiley sons ltd

late quaternary climatic events and sea level changes recorded by turbidite activity dakar canyon nw africa the relationship of sea level changes and short term climatic changes with turbidite deposition is poorly documented although the mechanisms of gravity driven sediment transport in submarine canyons during sea level changes have been reported from many regions this study focuses on the activity of the dakar canyon off southern senegal in response to major glacial interglacial sea level shifts and variability in the nw african continental climate the sedimentary record from the canyon allows us to determine the timing of turbidite events and on the basis of xrf scanning element data we have identified the climate signal at a sub millennial time scale from the surrounding hemipelagic sediments over the late quaternary the highest frequency in turbidite activity in the dakar canyon is confined to major climatic terminations when remobilisation of sediments from the shelf was triggered by the eustatic sea level rise however episodic turbidite events coincide with the timing of heinrich events in the north atlantic during these times continental climate has changed rapidly with evidence for higher dust supply over nw africa which has fed turbidity currents increased aridity and enhanced wind strength in the southern saharan sahelian zone may have provided a source for this dust

postglacial after 18 ka deep sea sedimentation along the hikurangi subduction margin new zealand characterisation timing and origin of turbidites recent sedimentation along the hikurangi subduction margin off northeastern new zealand is investigated using a series of piston cores collected between 2003 and 2008 the active hikurangi margin lies along the pacific australia subduction plate boundary and contains a diverse range of geomorphologic settings slope basin stratigraphy is thick and complex resulting from sustained high rates of sedimentation from adjacent muddy rivers throughout the quaternary turbidites deposited since c 18 ka in the poverty ruatoria and matakaoa re entrants are central to this study in that they provide a detailed record of the past climatic conditions and tectonic activity here alternating hemipelagite turbidite debrite and tephra layers reflect distinctive depositional modes of marine sedimentation turbidity current debris flow and volcanic eruption respectively turbidites dominate the record ranging in lithofacies from muddy to sandy turbidites and include some basal reverse graded turbidites inferred to be derived from hyperpycnal flows stacked turbidites are common and indicate multiple gravity flows over short time periods the chronology of turbidites is determined by collating an extremely dense set of radiocarbon ages and dated tephra which facilitate sedimentation rate calculation and identification of the origin of turbidites sedimentation rates range from 285 cm ka during late glacial time 18 5 17 ka to 15 to 109 cm ka during postglacial time 17 0 ka turbidite deposition is controlled by 1 the emplacement of slope avalanches reorganising sediment pathways 2 the postglacial marine transgression leading to a five fold reduction in sediment supply to the slope due to disconnection of river mouths from the shelf edge and 3 the holocene pleistocene boundary climate warming resulting in a drastic decrease in the average turbidite grain size flood induced turbidites are scarce nine hyperpycnites are recognised since 18 ka and the youngest is correlated to the largest enso related storm event recorded onland lake tutira other turbidites contain a benthic foraminiferal assemblage which is strictly reworked from the upper slope and which relates to large earthquakes over the last c 7 ka they yield a shorter return time 270 430 years than the published coastal records for large earthquakes c 670 years but the offshore record is likely to be more complete the deep sea sedimentation along the new zealand active margin illustrates the complex interaction of tectonic and climate in turbidite generation climate warming and glacio eustatic fluctuations are well recorded at a millennial timescale 18 ka while tectonic deformation and earthquakes appear predominant in fostering turbidite production at a centennial timescale 270 430 years

avo in transversely isotropic media an overview the amplitude variation with offset avo responses of elastic transversely isotropic media are sensitive to contrasts in both of thomsen s anisotropic parameters and e the equation describing p p reflections indicates that the smaller the contrasts in isotropic properties compressional velocity shear velocity and density and the larger the contrasts in and e across an interface of reflection the greater the effects of anisotropy on the avo signature contrasts in are most important under small to medium angles of incidence as previously described by banik 1987 while contrasts in e can have a strong influence on amplitudes for the larger angles of incidence commonly encountered in exploration 20 degrees and beyond consequently using rutherford and williams avo classification of isotropic gas sands type i gas sands overlain by a transversely isotropic ti shale exhibit a larger decrease in avo than if the shale had been isotropic and type iii gas sands overlain by a transversely isot

making riverscapes real abstract the structure and function of rivers have long been characterized either by 1 qualitative models such as the river continuum concept or serial discontinuity concept which paint broad descriptive portraits of how river habitats and communities vary or 2 quantitative models such as downstream hydraulic geometry which rely on a limited number of measurements spread widely throughout a river basin in contrast authors such as fausch et al 2002 and wiens 2002 proposed applying existing quantitative spatially comprehensive ecology and landscape ecology methods to rivers this new framework for river sciences which preserves variability and spatial relationships is called a riverine landscape or a riverscape application of this riverscape concept requires information on the spatial distribution of organism scale habitats throughout entire river systems this article examines the ways in which recent technical and methodological developments can allow us to quantitatively implement and realize the riverscape concept using 3 cm true color aerial photos and 5 m resolution elevation data from the river tromie scotland we apply the newly developed fluvial information system which integrates a suite of cutting edge high resolution remote sensing methods in a spatially explicit framework this new integrated approach allows for the extraction of primary fluvial variables such as width depth particle size and elevation from these first order variables we derive second order geomorphic and hydraulic variables including velocity stream power froude number and shear stress channel slope can be approximated from available topographic data based on these first and second order variables we produce riverscape metrics that begin to explore how geomorphic structures may influence river habitats including connectivity patchiness of habitat and habitat distributions the results show a complex interplay of geomorphic variable and habitat patchiness that is not predicted by existing fluvial theory riverscapes thus challenge the existing understanding of how rivers structure themselves and will force development of new paradigms

correction timing of the last glacial maximum from observed sea level minima nature 406 713 716 2000 in this letter a statement on page 715 that the eustatic sea level eus t differs from the ice volume equivalent sea level e t is erroneous we thank w r peltier for drawing this error in interpretation to our attention the two definitions were initially introduced to distinguish changes in sea level that were the result of ice mass being added to the oceans from other changes caused by thermal expansion for example

how plausible are high frequency sediment supply driven cycles in the stratigraphic record abstract this paper is an attempt to quantify the plausible time scales of clastic sediment supply variations at the entrance of sedimentary basins our approach is based on the sedimentary system concept which simplifies natural systems by dividing them into three zones of dominant processes the erosion the transfer and the sedimentation subsystems we examine recent results from geomorphology which show that frequent climate changes can induce high frequency sediment flux variations at the outlet of the source area we put forward the crucial role of the transfer subsystem which conveys sediment from the erosion zone to the basin by applying a diffusive model to a number of worldwide rivers we extend from large 1000 km to intermediate 300 km rivers the previous finding that the transfer subsystem acts as a buffer for short periods sediment pulses tens to hundreds of kiloyears this implies that high frequency stratigraphic cycles in clastic accumulations fed by large drainage systems are unlikely to reflect sediment supply cycles of tens to hundreds of thousands of years of periodicities

benthic foraminiferal thanatocoenoses from the cap ferret canyon area ne atlantic a complex interplay between hydro sedimentary and biological processes abstract benthic foraminiferal thanatocoenoses from the cap ferret canyon area were studied in the 150 m fraction of 4 5 cm deep sediment levels at 13 stations the shallowest station 151 m depth is located at the shelf break close to the canyon head all other stations are located along two bathymetric transects seven stations along the canyon axis between 300 and 3000 m depth and five stations from 300 m to 2000 m depth along the southern flank of the canyon the comparison between the live rose bengal stained and dead assemblages shows that biological i e population dynamic and taphonomic processes i e test destruction transport generate important discrepancies between live and dead assemblages an important question is to what degree post mortem transport and redeposition of foraminiferal tests contribute to the difference between living and dead assemblages the composition of the thanatocoenoses 150 m from the inner continental shelf to the cap ferret canyon axis however transport of tests from outer shelf or upper canyon axis towards deeper sites occurs as indicated by an increase of diversity indices of the dead fauna along the canyon axis moreover some species e g cassidulina carinata are observed in the living fauna restricted to the shallow sites but occur in important amounts in the dead fauna at deeper stations suggesting that these taxa have been transported from upper canyon stations toward deeper sites since cap ferret canyon is inactive in terms of massive sediment transport i e gravity events downslope transport of foraminiferal tests probably takes place in nepheloid layers downslope transports of foraminiferal tests may create important biases for the utilisation of paleoceanographic proxies using the assemblage characteristics and or the geochemical composition of selected species however the study of dead assemblages along a canyon axis can give important clues about the sedimentary dynamics especially an idea of the quantity of reworked foraminifera transported through the canyon axis along the adjacent flank such evidence of downslope transport was not observed despite taphonomic test destruction and biological processes population dynamics the live fauna closely resembles the distribution and the composition of the dead assemblage therefore ecological information obtained from the fossil flank samples can be more reliably used to reconstruct paleoenvironmental conditions

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

abrupt climate change sea surface salinity and paleoproductivity in the western mediterranean sea gulf of lion during the last 28 kyr abstract the planktonic foraminiferal record of core md99 2346 gulf of lion shows a decrease of sea surface temperature sst at the time of heinrich event h2 24 23 5 cal kyr bp younger dryas and during the early to middle holocene these events were associated with a decrease of surface water salinity the salinity lowering events were similar and synchronous to those recorded in the north atlantic ocean during h1 h2 and the younger dryas they can be explained by a decrease in the salinity of the atlantic surface water entering the mediterranean through the strait of gibraltar this result indicates that the mediterranean sea remained a concentration basin and that its freshwater budget was not significantly different from the modern conditions at the time of these low salinity events higher abundances of the benthic foraminifer cibicidoides pachydermus at the time of heinrich events h2 and h1 may result from a seasonal and more pulsed supply of labile organic matter a high abundance of intermediate and deep infaunal taxa globobulimina spp during the warm bolling allerod period is interpreted as a result of an increased lateral advection of organic matter to the deeper environments of the gulf of lion surface water productivity as reflected by the organic flux to the benthic ecosystem reaches a maximum during the cold younger dryas period it is possible that cold conditions at the time of the younger dryas have allowed an enhanced vertical mixing and deep water cascading in the gulf of lion this may have resulted in an increase of primary and export production this putative intensification of deep water cascading would have occurred after the sustained rise of the global sea level from 16 to 12 5 cal kyr bp the deglacial sea level rise may also have played an important role in favouring the downslope movement of dense shelf water enriched in organic matter originating from the early rhone delta complex the conditions during the holocene were characterized by a low surface productivity and oligotrophic environment similar to the modern situation

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

late quaternary terrestrial climatic variability recorded in deep sea turbidites along the toyama deep sea channel central japan sea abstract stratigraphic variations of coarse fraction and frequency and thickness of turbidites in three cores collected along the toyama deep sea channel tdsc in the central japan sea show consistent temporal trends with changes in terrestrial climatic records these temporal changes in turbidite deposition may reflect climatic forcing in the sediment source areas for the last 70 ka comparison of temporal changes in turbidite deposition with paleoclimatic and paleoceanographic records in the central japanese mainland and the japan sea revealed the following modes of climatic linkages 1 during the stadials and interstadials of the last glacial period 70 22 ka when the tsushima warm current twc periodically flowed into the japan sea the japanese mainland climate was cold and periodically wet resulting in occasional glacial advances in adjacent mountains turbidite flux increased in the tdsc system during the major glacial advances because of the increased production of coarse debris by glacial processes and high transport potential due to high precipitation 2 during the last glacial maximum 22 18 ka when the japan sea was capped by cold low salinity surface water the terrestrial climate was cold and dry due to low evaporation from the japan sea as a result of low precipitation less coarse debris was transported into deep basins and so during this period the turbidite flux along the tdsc was reduced 3 during the last deglaciation 18 8 ka precipitation in central japan increased due to intensified summer monsoons this resulted in destabilization of mountain slopes and increased transport of detritus to the lowlands and also to the tdsc system 4 after the twc flowed into the japan sea the land climate became warm wet and stable enhanced vegetation and re stabilized mountain slopes have reduced sediment input to the tdsc system since 8 ka

impact of iceberg melting on mediterranean thermohaline circulation during heinrich events down core samples of planktonic and benthic foraminifera were analyzed for oxygen and carbon isotopes in international marine past global changes study images core md99 2343 in order to study the interactions between climate change in the northern hemisphere and the western mediterranean thermohaline circulation at times of heinrich events he our results confirm the antiphase correlation between enhanced north atlantic deep water formation and low ventilation in the mediterranean however this study reveals that this antiphase relationship in deepwater formation between the north atlantic and mediterranean was interrupted during times of he when the injection of large volumes of water from melting icebergs reached the entrance to the mediterranean these events which lasted less than 1000 years are represented by pronounced decreases in both planktonic d18o and benthic d13c signals lower salinities of mediterranean surface water resulted in a slowdown of western mediterranean deepwater overturn even though cold sea surface temperatures and drier climate should have resulted in enhanced deepwater formation

timing of the last glacial maximum from observed sea level minima during the last glacial maximum ice sheets covered large areas in northern latitudes and global temperatures were significantly lower than today but few direct estimates exist of the volume of the ice sheets or the timing and rates of change during their advance and retreat here we analyze four distinct sediment facies in the shallow tectonically stable bonaparte gulf australia each of which is characteristic of a distinct range in sea level to estimate the maximum volume of land based ice during the last glaciation and the timing of the initial melting phase we use faunal assemblages and preservation status of the sediments to distinguish open marine shallow marine marginal marine and brackish conditions and estimate the timing and the mass of the ice sheets using radiocarbon dating and glacio hydroisostatic modelling our results indicate that from at least 22 000 to 19 000 calendar years before present land based ice volume was at its maximum exceeding today s grounded ice sheets by 52 5 x 10 exp 6 cu km a rapid decrease in ice volume by about 10 percent within a few hundred years terminated the last glacial maximum at 19 000 250 years

fluvial responses to environmental perturbations in the northern mediterranean since the last glacial maximum abstract the numerical model hydrotrend that produces daily time series of water discharge and sediment load to the ocean is applied to three mediterranean drainage basins to i simulate the water and sediment flux changes to sedimentary basins through time and ii determine the impact of potential forcing factors on sediment and water fluxes to sedimentary basins and how this impact varied through time climate precipitation temperature and glacier equilibrium line and drainage basin basin elevation drainage area and reservoir reconstructions of the po rhone and tet river basins over the last 21 000 cal years b p are used as input to the model simulated sediment fluxes at the river mouth for the po rhone and tet river systems during the late pleistocene were considerably higher compared to holocene pristine sediment flux with a factor 3 5 2 4 and 2 4 respectively for the po river system and the rhone river deglaciation in the late pleistocene is the main factor responsible for these higher sediment fluxes drainage basin area change due to sea level rise is the main cause of decrease in sediment flux for the tet river system and to a certain extent for the po river system man made reservoirs reduced sediment flux to the ocean for the po rhone and tet rivers over the last 3 6 decades with a factor of 1 3 3 8 and 2 4 respectively fluvial responses to climate and basin variations are reflected in the peak flood discharge and sediment concentration curves where present day water peak flood curves for all three rivers are the highest in the last 21 000 cal years b p however their associated sediment concentration curves show opposite results because of diminishing glacial area and the impact of reservoirs the tet river system has the ability to generate hyperpycnal plumes although the occurrence frequency changes over time prior to 15 500 cal years b p the river system area was extended due to the low sea level causing a less favorable regime to generate hyperpycnal events presently sediment trapping due to man made reservoirs alters the river ability to generate hyperpycnal events

the late quaternary climatic signal recorded in a deep sea turbiditic levee rhone neofan gulf of lions nw mediterranean palynological constraints abstract siliciclastic turbidites represent huge volumes of sediments which are of particular significance for 1 petroleum researchers interested in their potential as oil reservoirs and 2 sedimentologists who aim at understanding sediment transport processes from continent to deep basins an important challenge when studying marine turbidites has been to establish a reliable chronology for the deposits indeed conventional marine proxies applied to hemipelagic sediments are often unreliable in detrital clays in siliciclastic turbidites those proxies can be used only in hemipelagic intervals providing a poor constraint on their chronology in this study we have used sediments from the rhone neofan nw mediterranean sea to demonstrate that pollen grains can provide a high resolution chronostratigraphical framework for detrital clays in turbidites vegetation changes occurring from the end of marine isotopic stage 3 to the end of marine isotopic stage 2 from 30 to 18 ka cal bp are clearly recorded where other proxies have failed previously mainly because the scarcity of foraminifers in these sediments prevented any continuous sea surface temperature sst record and radiocarbon dating to be obtained we show also that the use of palynology in turbidite deposits is able to contribute to oceanographical and sedimentological purposes 1 pinus pollen grains can document the timing of sea level rise 2 the ratio between pollen grains transported from the continent via rivers and dinoflagellate cysts elutriating allows us to distinguish clearly detrital sediments from pelagic clays finally taken together all these tools show evidence that the rhone river disconnected from the canyon during the sea level rise and thus evidence the subsequent rapid starvation of the neofan at 18 5 ka cal bp younger sediments are hemipelagic the frequency of foraminifers allowed to date sediments with radiocarbon first results of sea surface temperature obtained on foraminifers are in good agreement with the dinoflagellate cysts climatic signal both provide information on the end of the deglaciation and the holocene

use of lidar derived images for mapping old landslides under forest large deep seated landslides are common features in the flemish ardennes belgium as most of these old 100 years landslides are located under forest in this hilly region aerial photograph interpretation is not an appropriate landslide mapping method this study tested the potential of lidar light detection and ranging images for mapping old landslides under forest landslide inventory maps were created for a 125 km2 area by applying the expert knowledge of seven geomorphologists to lidar derived hillshade slope and contour line maps in a gis environment each of the seven lidar based landslide inventories was compared i with the other six ii with a detailed field survey based inventory and iii with a comparable study in which topographic data were extracted from a topographical map the combination of the percentage of field landslides indicated by an expert and the percentage of positional discrepancies expressed in terms of positional mismatch were used to evaluate the quality of the lidar based inventory maps high quality lidar derived landslide inventory maps contain more than 70 per cent of the landslides mapped during the field survey and have positional discrepancies smaller than 70 per cent when compared with the field survey based inventory map four experts and the combination map of all experts satisfied these criteria together the seven experts indicated all landslides mapped in the field importantly lidar enabled the experts to find ten new landslides and to correct the boundaries of eleven of the 77 landslides mapped during the field survey hence this study showed that large scale lidar derived maps analysed by experienced geomorphologists can significantly improve field survey based inventories of landslides with a subdued morphology in hilly regions copyright 2006 john wiley sons ltd

an automated method to extract fluvial terraces from lidar based high resolution digital elevation models the oiartzun valley a case study in the cantabrian margin abstract combined climatic and tectonic conditions controlled the quaternary incision of rivers and the fluvial terraces are the most significant landforms to untangle their evolutionary history increasing availability of high resolution topography data over large areas offers an opportunity to increment greatly the quantity and the quality of information feasible for the development of semi automated techniques for identification and characterization of these features in this study we apply a methodology based on demoulin et al 2007 for the detection of fluvial terraces in digital elevation models dem with the novelty of using dems derived from high resolution lidar data that are processed using geographical information system gis routines the method is based on the recognition of slope variations and change of sign of profile curvature across the hillslopes considering scatter plots over valley segments of given length every minimum of slope value as a function of either distance to or elevation above the base of the valley is considered a possible terrace remnant the compilation of these slope minima retained within the successive segments covering the whole length of the valley will finally provide a two dimensional plot of terrace remnants in respect to the present day long profile of the river we successfully tested this method in the oiartzun valley in the eastern area of the cantabrian margin western pyrenees where terrace maps were previously developed via aerial photo interpretation and field mapping campaigns despite the highly erosive nature of the cantabrian fluvial systems the poor preservation of fluvial landforms and the abundant vegetation cover our method obtained good results due to its objectivity exhaustiveness and rapidity allowing fast and coherent analysis of fluvial valleys and their comparison

qualitative and quantitative applications of lidar imagery in fluvial geomorphology the potential for geomorphological mapping and quantitative calculations of light detection and ranging lidar data within fluvial geomorphology was studied for two river catchments within belgium dijle and ambleve which differ in physical settings and floodplain morphology two commercial of the shelf lidar datasets with different specifications horizontal resolution and vertical accuracy were available for parts of the floodplains of both catchments real time kinematic rtk global positioning system gps data were used as ground truth for error calculations qualitative analysis of lidar data allowed the identification of former channel patterns levees colluvial hillslope and fan deposits these results were confirmed by field data topographic surveys and historical maps the pixel resolution proved to be an important factor in the identification of small landforms only features with a width equal to or larger than lidar resolution can be detected this poses limits on the usability of regionally available lidar data which often have a horizontal resolution of several metres the lidar data were also used in a quantitative analysis of channel dynamics in the study area the width of the dijle river channel increased 3 m on average between 1969 and 2003 a sediment budget of channel processes for the period 1969 2003 indicated a total river bank erosion of 16 1 103 m3 and a total within channel deposition of 7 1 103 m3 resulting in a net river erosion of 9 0 103 m3 or c 0 4 mg year 1 per metre river length sequential lidar data can in theory be used to calculate vertical sedimentation rates as long as there is control on the error of the reference levels used copyright 2008 john wiley and sons ltd

implications of salt sediment interactions on the architecture of the gulf of lions deep water sedimentary systems western mediterranean sea we integrated structural analysis of multichannel seismic data and isopach maps of the quaternary sedimentary cover to evaluate how salt tectonics has influenced the stratigraphic evolution offshore the gulf of lions the interplay between salt tectonics and sedimentation occurs at two scales at local scale listric normal faults create bathymetric relief able to deviate sediment transport axes with implications on depocenters configuration at depocenter scale overburden vertical movements due to salt evacuation or salt diapiric rise create sub basins providing accommodation space for clastic deposition these mechanisms have significant implications on the architecture and the internal organization of turbidite systems offshore the gulf of lions

phase relationship between sea level and abrupt climate change direct traces of past sea levels are based on the elevation of old coral reefs at times of sea level high stands however these measurements are discontinuous and cannot be easily correlated with climate records from ice cores in this study we show a new approach to recognizing the imprint of sea level changes in continuous sediment records taken from the continental slope at locations that were continuously submerged even during periods of sea level lowstand by using a sediment core precisely synchronized with greenland ice cores we were able to recognize major floods of the mediterranean continental shelf over the past 270 kyr during the last glacial period five flooding events were observed at the onset of the warmest greenland interstadials consistent correspondence between warm climate episodes and eustatic sea level rises shows that these global flooding events were generated by pronounced melting of the northern hemisphere ice sheets due to rapid intensification of atlantic meridional overturning circulation the method described in this study opens a new perspective for inter hemi spheric synchronization of marine climate records if applied in other continental margins from the southern hemisphere or the equatorial regions c 2009 elsevier ltd all rights reserved

residual relief separation digital elevation model enhancement for geomorphological mapping geomorphologically mapped data form a primary set of observations that can be used to infer former environmental conditions thus objective and consistent mapping of landforms from remotely sensed data e g satellite imagery digital elevation models dems is paramount for reconstructing palaeoenvironments this paper proposes a technique residual relief separation to enhance landforms in dems prior to visualization and digital mapping this is applied to a 600 km2 region surrounding lough gara ireland where drumlins 200 m wide overlie a regional relief of hills 10 km wide here residual relief separation uses this difference in width scale regional relief is approximated by a 1 km wide median filter then subtracted to leave the drumlins in a residual topography in a second step the residual relief is normalized to allow for amplitude variations in the drumlins across the area 5 40 m high finally visualization uses a simple black to white colour scale for height although not numerically outperforming other visualization techniques this method performs equally well and as the data are not illuminated there is no azimuthal bias additional benefits include the relatively simple calculation intuitive visual comprehension no emphasis of noise and the possibility of using any desired visualization technique after the landscape has been topographically manipulated

activity of the turbidite levees of the celtic armorican margin bay of biscay during the last 30 000 years imprints of the last european deglaciation and heinrich events abstract high resolution sedimentological and micropaleontological studies of several deep sea cores retrieved from the levees of the celtic and armorican turbidite systems bay of biscay north atlantic ocean allow the detection of the major oscillations of the british irish ice sheet biis and fleuve manche palaeoriver discharges over the last 30 000 years which were mainly triggered by climate changes between 30 and 20 cal ka the turbiditic activity on the celtic armorican margin was weak contrasting with previous stratigraphic models which predicted a substantial increase of sediment supply during low sea level stands this low turbidite deposit frequency was most likely the result of a weak activity of the fleuve manche palaeoriver and or of a reduced seaward transfer of sediments from the shelf to the margin however two episodes of turbiditic activity increase were detected in the celtic armorican margin during heinrich events he 3 and 2 this strengthening of the turbiditic activity was triggered by the meltwater releases from european ice sheets and glaciers favouring the seaward transfer of subglacial material at least via fleuve manche palaeoriver at around 20 cal ka a significant increase of turbidite deposit frequency occurred as a response to the onset of the last deglaciation the retreat of the european ice sheets and glaciers induced a substantial increase of the fleuve manche palaeoriver discharges and seaward transfer of continentally derived material into the armorican turbidite system the intensification of the turbiditic activity on the celtic system was directly sustained by the widespread transport of subglacial sediments from the british irish ice sheet biis to the celtic sea via the irish sea basin a sudden reduction of turbiditic activity in the armorican system between ca 19 and 18 3 cal ka could have been triggered by the first well known abrupt sea level rise meltwater pulse at around 19 cal ka favouring the trapping of sediment in the fleuve manche palaeoriver valleys and the decrease of the seaward transfer of continentally derived material the maximum of turbiditic activity strengthening in the celtic armorican margin between ca 18 3 and 17 cal ka was induced by the decay of european ice sheets and glaciers producing the most extreme episode of the fleuve manche palaeoriver runoff and a great seaward transfer of subglacial material into the bay of biscay between ca 17 5 and 16 cal ka the turbiditic activity significantly decreased in both celtic and armorican turbidite systems in response to a global re advance of glaciers and ice sheets in europe the last episode of ice sheet retreat between ca 16 and 14 cal ka is well expressed in the celtic system by a new increase of the turbiditic activity the major episode of sea level rise at around 14 cal ka meltwater pulse 1a precluding the seaward transfer of sediments induced the end of turbiditic activity in both the celtic and the armorican system although two main phases of global sea level rise seem to have had an effect on the celtic armorican margin this work proposes the biis retreat and associated riverine discharges as the main trigger mechanisms of the turbiditic activity in this region during the last 30 000 years

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

geomorphological mapping of glacial landforms from remotely sensed data an evaluation of the principal data sources and an assessment of their quality abstract this paper presents the results of an experiment to compare glacial geomorphology mapped from remotely sensed imagery with 1 10 000 scale field mapping the field mapping was validated against high resolution lidar imagery of an area glacierized during the younger dryas and found to provide an essentially reliable if not complete representation of the glacial geomorphology the experiment consists of comparing the field mapping with digital elevation models shuttle radar topography mission c band landmap os panorama os profile nextmap and satellite imagery landsat thematic mapper of a 100 km2 region of central scotland north of glasgow that was last glaciated during the last glacial maximum and during the younger dryas respectively c 14 5 and 11 5 cal ka bp for the purposes of this exercise we concentrated on glacial lineaments flutes drumlins and crag and tail but attention was also given to moraine ridges and eskers qualitative and quantitative comparisons are performed and the results show that of the remotely sensed data sets only nextmap great britain provided results that showed any approximation to the field mapping os panorama and os profile provided very poor approximations and the other methods fail to provide any information of value attention is given to the issues of scale and the differences between a small scale detailed study such as this experiment in which a high resolution glacial geomorphological reconstruction is required and the small scale studies where the remote sensing techniques used here provide important evidence of regional significance when glaciers formed the largest elements of the landscape the paper concludes with a consideration of protocols for future geomorphological mapping exercises and outlines some of the requirements that must be adopted as these protocols are developed