catastrophic debris avalanche deposit of socompa volcano northern chile between 10 000 and 500 yr ago the socompa volcano in northern chile experienced a catastrophic collapse of a 70 deg sector of the original cone causing a debris avalanche that descended nearly 3000 m vertically and traveled more than 35 km from the volcano the deposits cover some 490 sq km and have a minimum volume of 15 cu km parts of the original cone slumped in a nearly coherent form and are now preserved as large blocks more than 400 m high the primary avalanche traveled northwestward over sloping ground before coming to rest transiently forming a prominent marginal ridge and then slid away northeastward to form a secondary flow overriding much of the primary avalanche deposit abundant prismatic jointed dacite blocks within the debris avalanche deposit and a thin fine grained pumiceous deposit beneath it suggest that the collapse was triggered by magmatic activity and may have been accompanied by a violent lateral blast collapse was followed by eruption of pumiceous pyroclastic flows and extrusion of voluminous dacite domes

late cenozoic glacial history and evolution of the storegga slide area and adjacent slide flank regions norwegian continental margin abstract acoustic data and sediment cores collected from the storegga slide and its adjacent slide flanks i e the voring plateau to the north and the north sea fan to the south have been used to study the late cenozoic glacial history and geological development of this region age constrains obtained from the investigated cores show that the fennoscandian ice sheet reached the shelf edge during marine isotope stages mis 12 10 8 6 and 2 ice sheet fluctuations within each glaciation might have occurred as is evidenced for the last glacial maximum mis 2 the first extensive ice advance is identified in the early pleistocene at c 1 1 ma however between 2 6 and 0 5 ma the ice sheets were largely restricted to the fjords and inner shelf during each glacial maximum glacigenic debris flows gdfs transported basal till deposited at the shelf edge into the deep sea along the entire studied margin the most voluminous gdf sequences are found on the southern storegga slide flank north sea fan where the individual flows are found as far as 500 km from the shelf edge on the voring plateau glacimarine hemipelagic sedimentation has dominated the last c 250 000 yr during mis 2 such sediments were rapidly deposited covering the upper slope limited gdf units in this region between c 15 700 and 15 000 14c yr bp i e during the last deglaciation of the norwegian margin a presumed meltwater plume released from the disintegrating norwegian channel ice stream transported and rapidly deposited up to 20 m of fine grained sediments in the region north of the north sea fan the rapid deposition of large volumes of gdfs glacimarine and meltwater related sediments might have influenced the stability of the slope sediments in the studied region promoting conditions favorable for failure furthermore these high sedimentation rates also partly account for the high subsidence rates observed on the norwegian continental margin in the late cenozoic

the norwegian greenland sea continental margins morphology and late quaternary sedimentary processes and environment the continental margins surrounding the norwegian greenland sea are to a large degree shaped by processes during the late quaternary the paper gives an overview of the morphology and the processes responsible for the formation of three main groups of morphological features slides trough mouth fans and channels several large late quaternary slides have been identified on the eastern norwegian greenland sea continental margin the origin of the slides may be due to high sedimentation rates leading to a build up of excess pore water pressure perhaps with additional pressure caused by gas bubbles triggering might have been prompted by earthquakes or by decomposition of gas hydrates trough mouth fans tmf are fans at the mouths of transverse troughs on presently or formerly glaciated continental shelves in the norwegian greenland sea seven tmfs have been identified varying in area from 2700 km2 to 215 000 km2 the trough mouth fans are depocentres of sediments which have accumulated in front of ice streams draining the large northwest european ice sheets the sediments deposited at the shelf break upper slope by the ice stream were remobilized and transported downslope mostly as debris flows the trough mouth fans hold the potential for giving information about the various ice streams feeding them with regard to velocity and ice discharge two large deep sea channel systems have been observed along the norwegian continental margin the lofoten basin channel and the inbis channel along the east greenland margin several channel systems have been identified the deep sea channels may have been formed by dense water originating from cooling sea ice formation and brine rejection close to the glacier margin or they may originate from small slides on the upper slope transforming into debris flows and turbidity currents

late weichselian submarine debris flow deposits on the bear island trough mouth fan sedimentary processes on the bear island trough mouth fan during the last glacial were studied using high resolution reflection seismics and gravity cores the fan succession is dominated by large debris flow deposits of up to 24 km in width and 50 m thick debris lobes can be followed over 100 km downslope and the largest cover an area of 1880 km2 the large debris flows were generated when the barents sea ice sheet reached the shelf break glacigenic sediments transported to the grounding line were temporarily stored on the upper slope due to the high sedimentation rate the sediments were unstable and earthquakes oversteepening and or build up of excess pore pressure triggered sediment release generating large debris flows sediments were also eroded and incorporated during the downslope flow debris flows were the most important sediment distributing process due to the relatively high shear strength low flow mobility of the glacigenic diamicton and the low fan gradient the weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the early and mid weichselian the barents sea ice sheet might have reached the shelf break twice during the late weichselian on average one large debris flow comprising 18 km3 of sediments was released between every 35 to 75 years during the last glacial maximum

the glacier influenced scoresby sund fan east greenland continental margin evidence from gloria and 3 5 khz records a major submarine fan gradient about 2 offshore of the scoresby sund fjord system is indicated by the crescentic shape of the shelf break gloria long range side scan sonar imagery was obtained over about 20 000 km2 of the fan along with 1000 km of 3 5 khz records three acoustic facies were defined from gloria backscatter signatures and sea floor morphology and sediment acoustic character on 3 5 khz records facies 1 includes a series of acoustically transparent features 0 5 2 km in width elongate downslope with irregular surface topography which are interpreted as debris flows this makes up the bulk of relatively recent sedimentation on the upper fan diamictic sediments in a core support a debris flow origin facies 2 is featureless on gloria images 3 5 khz profiles reveal irregular former sea floor morphology above which is a draping unit 15 m thick this northern region of the fan is a less active area where hemipelagic sediments and limited ice rafted debris overlie older material formed by past debris flow activity the more distal area of the adjacent ocean basin has a flat floor with parallel sub bottom reflectors of facies 3 this facies is probably an area of low energy hemipelagic sedimentation punctuated by occasional ice rafting and turbidity current activity the debris flows interpreted from gloria and 3 5 khz data are basic building blocks in the long term development of the scoresby sund fan glacier influenced fan volume is about 15 000 5000 km3 based on seismic reflection studies during full glacials in east greenland the inland ice sheet advances to fill the scoresby sund fjord system and extends across the shelf to reach the shelf break in some glacial cycles debris flows form in areas of most rapid sediment flux the scoresby sund fan is relatively similar to the storfjorden fan on the eastern polar north atlantic margin but differs from the larger bear island fan in having a steeper fan gradient much smaller debris flows and no large scale slides

a new dead sea pollen record reveals the last glacial paleoenvironment of the southern levant abstract the southern levant is a key region for studying vegetation developments in relation to climate dynamics and hominin migration processes in the past due to the sensitivity of the vegetation to climate variations and the long history of different anthropogenic occupation phases however paleoenvironmental conditions in the southern levant during the late pleistocene were still insufficiently understood therefore we investigated the vegetation and fire history of the dead sea region during the last glacial period we present a new palynological study conducted on sediments of lake lisan the last glacial precursor of the dead sea the sediments were recovered from the center of the modern dead sea within an icdp campaign the palynological results suggest that irano turanian steppe and saharo arabian desert vegetation prevailed in the dead sea region during the investigated period ca 88 000 14 000 years bp nevertheless mediterranean woodland elements significantly contributed to the vegetation composition suggesting moderate amounts of available water for plants the early last glacial was characterized by dynamic climate conditions with pronounced dry phases and high but unstable fire activity anatomically modern humans entered the southern levant during a climatically stable phase late mis 4 mis 3 with diverse habitats constant moisture availability and low fire activity mis 2 was the coldest phase of the investigated timeframe causing changes in woodland composition and a widespread occurrence of steppe we used a biome modeling approach to assess regional vegetation patterns under changing climate conditions and to evaluate different climate scenarios for the last glacial levant the study provides new insights into the environmental responses of the dead sea region to climate variations through time it contributes towards our understanding of the paleoenvironmental conditions in the southern levant which functioned as an important corridor for human migration processes

relationship among submarine instabilities sea level variations and the presence of an ice sheet on the continental shelf an example from the verrill canyon area scotian shelf sea level low stands are associated with the growth of glacial ice sheets during maximum stages of glaciation ice sheets may extend to the outer continental shelf these glacial maxima normally correspond to sea level low stands consequently ice sheets may be supported directly by the seafloor inducing increased pore pressures in the sediment and increasing the overall bearing stresses on the margin these stresses trigger undrained failure in upper slope sediment and bearing capacity failure in the middle to lower slope after complete ice melting and dissipation of excess pore pressure the inter glacial sediments become overconsolidated shear resistance is higher and no gravity or earthquake induced failure occurs the gravity events can only occur in underconsolidated and normally consolidated glacial and postglacial deposits this explains the variation in volume and activity of mass wasting events during low and high sea level periods in areas where a glacial ice exists analyses of maximum ice loading events are presented for the scotian slope in contrast with traditional thought these analyses suggest that ice loading rather than high sedimentation rates is the dominant mechanism for slope instability on glaciated margins

glacigenic debris flows on the north sea trough mouth fan during ice stream maxima abstract numerous short sediment cores which penetrate through the glacimarine section and into glacigenic debris flow debrites gdfs on the north sea fan are investigated the sampled gdfs represent the uppermost of several sequences of these stacked bodies many hundreds of metres thick the gdfs occurred over slopes from 0 3 to 0 7 and examples are found from the shelf break at the mouth of the norwegian channel to the norway basin floor 300 km distant the gdf diamicts are structureless and homogeneous in terms of grain size magnetic susceptibility nrm bulk density water carbonate foraminiferal and rock fragment content this applies both from gdf to gdf across the fan and in a proximal distal sense comparison of the investigated lithologic parameters with weichselian till from a borehole in the norwegian channel 200 km up ice shows striking similarity to the gdf debrites ams 14c dates at the gdf glacimarine contact and stratigraphic relationships indicate voluminous deposition before 18 ka continuing possibly uninterrupted until ca 16 ka and a final phase halting just before 15 ka when the norwegian channel became ice free this chronology the comparable lithologic character between till and gdf debrites and a seismic continuity confirms inferences that the gdfs are directly associated with glacial ice at the shelf break the glacial efflux has not been subject to subsequent sorting and the homogeneity of the gdf is thought to reflect thorough mixing in a deforming till layer beneath a fast flowing ice stream the glacimarine section subsequent to gdfs shows no indications of turbidity flow observations are compatible with a slow non disintegrating cohesive plug flow transport mechanism with little sediment water interaction on the upper surface minor distal differentiation might reflect a change in flow process deposition on the fan margins from water borne glacimarine processes simultaneous with gdf deposition is limited

submarine slope stability on high latitude glaciated svalbard barents sea margin abstract slope stability is evaluated at two locations on high latitude deep sea fans along the svalbard barents sea margin based on available samples and using an infinite slope analysis the stability evaluation uses the mohr coulomb failure criterion and a semi analytical approach based on gibson s formulation for determining the excess pore pressure build up due to sedimentation the main results are presented in the form of contour plots of slope safety factors in a diagram with axes of time and thickness of deposit the results show that during rapid sedimentation which mostly takes place during periods of maximum glaciation with the ice front located along the shelf edge slope failure will occur with a frequency varying between 95 and 170 years only part of the upper sedimented layer will be mobilised 10 30 m while the remaining thickness 40 70 m will remain at the initial sedimentation site these results may explain why the continental slope is characterised by relatively uniform sediment thickness from upper to lower slope

morphology of a submarine slide kitimat arm british columbia a digitally acquired scale corrected side scan sonar survey yielded high resolution imagery of a submarine landslide in british columbia the landslide in a fjord head setting at kitimat was last active in 1975 and created a wide area of deformed sea floor the sediment failure involved shallow rotational movements on the slopes of a fjord head delta marginal tearing translational sliding compressional folding and block gliding of fjord bottom marine clays the slide is shallow and elongate and appears to have been produced by failure in mobile low strength sediments

contour current driven continental slope situated sandwaves with effects from secondary current processes on the barents sea margin offshore norway abstract seabed data acquired from the southern barents sea continental margin offshore norway reveal detailed morphology of large sandwave fields multibeam echosounder bathymetry and backscatter shallow seismic sediment samples and seabed video data collected by the mareano program have been used to describe and interpret the morphology distribution and transport of the sandwaves the bedforms lie on a slope dominated by relict glacial forms and muddy sandy gravelly sediments sandwave migration across small gravity mass failures of the glacial mud constrains the field initiation as early post glacial or later the contour parallel nature of the fields and crestlines normal to the bathymetry contours and the geostrophic norwegian atlantic current nwac demonstrate that the nnw flowing oceanographic circulation is the primary driving current the fields coincide with the depth range at which a transition between warm saline and underlying cooler less saline waters fluctuate across the seabed statistically rigorous measurements of height width and various parameters of slope and symmetry confirm a tendency to downstream nnw sandwave migration but with significant exceptions anomalous bedform symmetry domains within the fields are tuned to meso scale topography along relict glacial debris flow chutes indicating current focusing upstream and upper slope derived winnowed sand transport eroded from the glacial sediments is the supposed source sandwave flank slope values are comparable to the regional slope such that the gravitational vector would have a cumulative downslope migration affect unless balanced by upslope drivers perpendicular cross cutting of stoss face 3 d ripples by linear 2 d ripples in the sandwave troughs and lee faces is evidence for non synchronous episodic current variations though deep ekman transport and internal wave action are unproven here these could explain chute related tuning of bedform symmetry through funneling in the debris flow chutes and favor sand recycling thus contributing to long term maintenance of the sandwave field

geometry and genesis of glacigenic debris flows on the north sea fan tobi imagery and deep tow boomer evidence abstract acoustic data have been used to study the upper sequence of glacigenic debris flows gdfs deposited during the last glacial maximum on the north sea fan the presumed gdf release area at the shelf break 450 m water depth exhibits a sequence up to 90 m thick thinning to less than 45 m basinward at approx 750 800 m depth on a low slope 0 6 0 8 a seismically featureless sequence at the shelf break changes distinctly the first kilometers basinward showing a significant occurrence of features interpreted as infilled transport chutes the straight or sinuous chutes feed into well defined relief building gdf lobes 10 40 km from the shelf break a lack of failure scarps at the shelf break suggests that the gdfs have been sourced by a relatively continuous release of material flow lines concentrated along the chutes and center of the gdfs suggest a laminar movement pattern in the gdf core supported by passive flanks based on the flow morphology high pore pressure and low sediment strength within a central core of the flow is assumed to have contributed to the mobility of the gdfs dissipation of pore pressure along the margins of the flow may have caused the margins freeze while the sediment in the core remained mobile

late quaternary sediments and stratigraphy on the continental shelf off more trondelag w norway abstract a study of more than 400 bottom sediment samples collected from the continental shelf between the stad peninsula and the halten bank shows that with regard to sediment distribution the area can be divided into two parts 1 a southern area off more with depths mostly less than 200 m and to a great extent covered by winnowed glacial deposits consisting of sand gravel and coarser material and in the depressions covered with sand and pelitic sand and 2 a northern area off trondelag where depths mainly are between 200 m and 500 m and where the sediments show great variation in textural character to a certain degree dependant on depth but also with great differences within areas of the same depths moderately well to poorly sorted sand is present in a broad belt along the outer margin of the shelf and on the slope leading up to the more shelf inside this sand belt the sediments become finer and more poorly sorted with pelitic sand silty sand changing into sandy pelite clayey sand and sand silt clay pelitic gravelly sand occupies large parts of the shelf especially on the western flank of the halten bank and the eastern slope of the haltendjup depression coarse lag deposits are present in the most shallow parts of the halten bank the origin of the surface sediments on the trondelag shelf is thought to represent retransported glacial deposits the material consists of particles winnowed out from the shallow part of the halten bank and from the shallow more shelf to the south the glacial origin of the material is shown by the form and roundness of gravel and stones which agrees with typical glacial deposits and by the form and microtextures of the sand grains the winnowing and retransport of the glacial deposits is shown from the study of cores to have taken place mainly during the last 10 000 years i e during the holocene after the warm atlantic water entered the area of the norwegian continental shelf the sediment transport is a result of the hydraulic regime and in general sediments have been transported from areas of coarse skewed deposits to areas of finer and fine skewed deposits from recent current measurements on the trondelag shelf it seems probable that erosion and transport of sand as well as of unconsolidated silt and clay takes place today at least down to depths of 300 400 m on the continental slope this zone reaches down to 600 700 m the present sediment distribution is therefore thought to represent at least to a certain degree the effect of the present hydraulic regime the lithologic paleontologic and chronostratigraphic investigation of 18 cores from the trondelag shelf and a comparison with cores sampled off stad indicates the following environmental evolution following the retreat of the ice on the continental shelf during the middle weichselian the sea conditions were high mid arctic with a great deal of seaice and icebergs causing ice rafting and the formation of glacial diamictons this environment was succeeded by a somewhat less arctic environment which lasted till about 13 000 yr b p when the sea became distinctly less arctic probably low arctic with a warmer element in the fauna and with less ice rafting this was probably due to a certain influence of atlantic water the change from low arctic to boreal conditions took place about 10 000 yr b p at the same time the hydraulic regime must have changed drastically with currents and waves beginning to have a strong winnowing effect on the bottom sediments this is thought to indicate the real introduction of the atlantic current in the area

hydrothermal hexahydrite spherules erupted during the 2008 2010 summit eruption of kīlauea volcano hawai i small 1 3 mm hollow spherules of hexahydrite have been collected falling out of the magmatic gas plume downwind of k lauea s summit vent the spherules were observed on eight separate occasions during 2009 2010 when a lake of actively spattering lava was present 150 200 m below the rim of the vent the shells of the spherules have a fine bubbly foam structure less than 0 1 mm thick composed almost entirely of hexahydrite mgso4 6h2o small microspherules of lava 5 m across along with mineral and rock fragments from the magmatic plume adhered to the outside of the hexahydrite spherules phase relationships and the particulate matter in the magmatic plume indicate that the spherules originated as a bubbly solution injected into and mixed with the magmatic plume the most likely mechanism for production of hexahydrite spherules is boiling of mgso4 saturated meteoric water in the walls of the conduit above the surface of the lava lake solfataric sulfates may thus be recycled and reinjected into the plume creating particulates of sulfate minerals that can be distributed far from their original source

late cenozoic environments in the barents sea we examine the paleoceanography and paleogeography of the barents sea during the late cenozoic glacial regime by seismostratigraphy and core analysis during the smaller glaciations which probably dominated the first period of the glaciogenic regime approximately 2 5 0 8 ma glaciomarine processes with sediment influx from the adjacent mainland prevailed the barents sea has been covered by grounded ice sheets several five to 10 times during the late cenozoic we speculate that these glaciations occurred during the last 0 8 ma during these larger glaciations the margin of the ice sheet expanded to the shelf edge and the continental shelf break and slope acted as a depocenter and prograded rapidly frequent sediment gravity flows accumulated on the lower continental slope during interglacials the barents sea was converted to a starved continental margin most of the barents sea was glaciated during the maximum of the last glaciation 19 16 ka a two stepped deglaciation 16 to 13 ka and 13 to 10 ka occurred incipient atlantic water reached the western areas about 13 ka and totally replaced the arctic water by 10 ka these paleoceanographic events were delayed in the eastern barents sea

glacigenic sediments on a passive continental margin as exemplified by the barents sea abstract reflection seismics data borehole data and gravity cores have been used to map the sedimentary facies of the epicontinental southwestern barents sea its continental margin and adjacent coastal areas an upper unconformity with a glacially eroded morphology extends over most of the continental shelf up to 300 m of stratiform glacigenic sediments overlie this unconformity these sediments can be grouped into seismic units which are separated by smooth or irregular erosional surfaces each sequence may be up to 150 m thick normally with a lateral extent of 100 300 km three dominant seismic signatures may be discerned semi transparent stratified and chaotic reflection patterns these sediments are partly glacifluvial in origin but on the whole they represent more or less tectonized glacimarine deposits the deeper troughs on the continental shelf contain an undeformed postglacial glacimarine marine trough fill the greatest thickness up to 1000 m of glacigenic sediments occurs at the shelf break and below the upper slope the depocentres are situated at trough mouth fans the sediments comprise several prograding sequences with a complex sigmoid oblique character indicating alternating upbuilding and depositional bypass erosion in the topset segment small and large scale slide scars are observed on the upper slope and debris lobes on the lower slope a marked progradation seems to have occurred during the plio pleistocene glacial periods this progradation also resulted in an unstable slope with various types of sediment gravity flows currents flowing along the slope were established during interglacials and gullying by cold dense shelf water and downslope transport occurred maximum net sedimentation rates are 0 2 m ka continental slope 0 4 m ka shelf break 0 1 m ka shelf stratiform diamictons 1 m ka shelf trough fills and 60 m ka fjord trough fills

depositional processes in large scale debris flow experiments this study examines the depositional process and characteristics of deposits of large scale experimental debris flows to 15 m3 composed of mixtures of gravel to 32 mm sand and mud the experiments were performed using a 95 m long 2 m wide debris flow flume that slopes 31 following release experimental debris flows invariably developed numerous shallow 10 cm deep surges sediment transported by surges accumulated abruptly on a 3 runout slope at the mouth of the flume deposits developed in a complex manner through a combination of shoving forward and shouldering aside previously deposited debris and through progressive vertical accretion progressive accretion by the experimental flows is contrary to commonly assumed en masse sedimentation by debris flows despite progressive sediment emplacement deposits were composed of unstratified accumulations of generally unsorted debris hence massively textured poorly sorted debris flow deposits are not emplaced uniquely en masse the depositional

pleistocene development of the se nordic seas margin abstract throughout the pleistocene the sedimentary environment on the se nordic seas continental slope outer shelf off western norway has been strongly controlled by variability in the norwegian atlantic current nwac glaciations of the shelf areas and sea level changes acoustic and core data from the southern voring plateau show a pleistocene sequence characterised by hemipelagic sediments interfingered by diamictons on the upper slope the area of the 7 25 14 c ka bp storegga slide shows evidence of a long history of pleistocene mega slides during the last interglacial and most likely also during previous interglacials the slide region has been the locus of rapid deposition between water depths of 800 and 1200 m as a result of nwac winnowing along the upper slope the north sea fan region is strongly influenced by glacigenic debris flows gdfs deposited during glacial advances reaching the shelf edge when the norwegian channel was occupied by the norwegian channel ice stream it appears that gdf activity was initiated at ca marine isotope stage 12 interbedded between the debris flow sequences mega slide events such as the more and tampen slides have been identified during glaciations when the entire se nordic seas continental shelf was covered by extensive grounded ice sheets basal till were transported to the shelf edge from where subsequent mass movement occurred during late glaciation early deglaciation meltwater plumes were released at the time of disintegration of ice streams in the norwegian channel as is evidenced from the last deglaciation of the margin at ca 15 14 c ka bp the plume material was transported northwards by currents before rapidly deposited as a thick package within the storegga slide area and on the south voring plateau based on identification and dating of iceberg scourings glacial erosion surfaces and delta deposits on the shelf subsidence rates between 0 7 and 1 2 m ky have been calculated for the last ca 250 ka

glaciogenic debris flow deposits of orphan basin offshore eastern canada sedimentological and rheological properties origin and relationship to meltwater discharge abstract glaciogenic debris flow deposits gdfs have been recognized in the last decade seaward of many shelf crossing ice streams the rheology of gdfs remains poorly understood ultra high resolution sparker seismic profiles and 25 long piston cores were used to define the architecture age and sediment properties of the gdf deposits in trinity trough mouth fan tmf offshore northeast newfoundland and hence understand their origin and emplacement the gdf deposits comprise poorly sorted gravelly mud individual gdf lenses are 5 30 m thick 2 10 km wide and up to 250 km long shear strength measurements and grain size analysis indicate that gdfs have a different more fluid rheology at their margins and tops exhibiting a surging flow behavior on the upper slope the transition from hard over consolidated till to thin proximal gdf deposits is exposed in a mid holocene landslide scar the transition between the two lithotypes appears gradual and no pre holocene failure scarps were detected a process involving the continuous release of subglacial flowing material with high pore pressure and low shear strength is invoked for the production of gdfs five stacked gdf units a e were deposited during the last glacial maximum 20 5 28 cal ka and can be correlated into a regional lithostratigraphy based on the presence of heinrich beds and 8 local meltwater events r1 8 represented by red plumite deposits south of the trinity tmf this correlation indicates that the timing of major gdf pulses corresponds to the early part of five meltwater discharge events 20 5 21 23 23 5 23 8 24 5 25 27 and 27 5 28 5 cal ka so that gdf deposits represent only a small period of time during a major glacial advance three meltwater events 19 2 20 23 23 5 and 25 27 cal ka produced hyperpycnal flows that resulted in the formation of channel systems and distal sand turbidites the presence of such erosional features in tmfs on the continental margins of the norwegian greenland sea suggests that this novel relationship between gdfs and hyperpycnal turbidites may be widespread and thus important for understanding the glaciological processes involved

quaternary seismic stratigraphy of the north sea fan glacially fed gravity flow aprons hemipelagic sediments and large submarine slides abstract approximately 1000 km of high resolution sleeve gun array transects on the north sea fan located at the mouth of the norwegian channel reveal three dominant styles of sedimentation within a thick 900 m quaternary sediment wedge comprising numerous sequences these are interpreted as terrigenous hemipelagic sedimentation large scale translational slides and aprons of glaciogenic debris flow deposits contributing to considerable fan construction four large buried translational slides involved sediment volumes upwards of 3000 km 3 each and preceded the similarly dimensioned first storegga slide on the ne fan flank several thick 100 m terrigenous hemipelagic deposits apparently represent long lived 150 200 kyr periods of sedimentation whose distribution indicates fan input via the norwegian channel the upper sequences are each made upper sequences are each made up of one or several thick 100 m aprons comprising stacked lensoid and or lobate forms which range from 2 to 40 km in width and 15 to 60 m in thickness they characterize debris flows attributed to periodic input from several phases of a norwegian channel ice stream reaching the shelf edge subsidence in the outer norwegian channel allowed preservation of several glaciation cycles represented by sheet erosion bounded tills and progradational units much of the shelf slope transition has been preserved allowing a preliminary chronology of the fan sequences through correlation with borehole sediments in the norwegian channel debris flows which signal the initial shelf edge glaciation are not recognized from the initial glaciation in the channel 1 1 myr but are associated with a middle pleistocene and all following glacial erosion surfaces ges in the outer norwegian channel this was followed by six further sequences probably totalling over 13 000 km 3 of sediment at least four of these were shelf edge ice maximum events the last of which was late weichselian age 14 c ams considering earlier glaciation related hemipelagic sedimentation material since removed by the large slides and extensive unmapped areas total quaternary fan sedimentation was in the vicinity of 20 000 km 3

quaternary erosion and depositional processes western norwegian fjords norwegian channel and north sea fan abstract the southern norwegian fjords the northern north sea and north sea margin represent major pathways of sediment flux from the southern part of fennoscandia to the deep sea basin volumes genesis and chronology of the temporary and semi permanent quaternary sediment repositories are reviewed the fjord infill is dominated by sediments from the last deglaciation 150 km 3 the norwegian channel is occupied by tills and glaciomarine marine sediments 5000 km 3 the north sea fan comprises glacially fed debris flow fingers lobes constituting 80 of deposits in the mid to late pleistocene together with hemipelagic and mass transport slide sediments totalling 15 000 km 3 the norwegian channel represents a dynamic transport conduit whereby during peak glaciation a fast flowing ice stream has drained large parts of the southern fennoscandian ice sheet several times the sediment flux to the deep sea is temporarily interrupted between glacials when stored in the channel but under glacial maxima the channel is probably largely bypassed with material transported as subglacial load and deposited as debris flows on the north sea fan sediments on the fan have a much longer storage time numerous glaciation cycles but are further transported to the deep sea in large slide events the volume of quaternary sediments found along this sediment pathway plus that which slid to the deep sea total at least 25 000 km 3 corresponding to an averaged 120 m of erosion across southern norway

shingled quaternary debris flow lenses on the north east newfoundland slope debris flow deposits are the principal component of quaternary continental slope sediments between the north east newfoundland shelf and central orphan basin in seismic profiles these deposits occur as shingled elongate acoustically transparent lenses with their long axes orientated downslope deposits of individual flows form positive mounds on the sea floor subsequent flows were diverted by the pre existing topography into bathymetric lows between older debris flow deposits these deposits show a large variation in the area of sea floor covered by individual flows about 60 1000 km2 average thickness of deposits 9 37 m and volume of sediment displaced 1 27 km3 the ratio of average thickness to a measure of deposit diameter termed the aspect ratio has a threefold variation from 0 0006 to 0 0021 very low depositional slopes and low aspect ratios suggest relatively low viscosities probably due to inmixing of water during downslope transport stratified sediments form three distinct horizons and are locally interbedded with the debris flow deposits these are mainly hemipelagic deposits the slope and rise to the west of the orphan basin are constructional in character the apparent absence of upper slope erosional features and the abundance of debris flow deposits on the slope suggest that the supply of sediment to the continental slope occurred predominantly during times of maximum extent of quaternary glacial ice the ice sheet grounding line during several glacial maxima must have been situated at or near the present shelf break supplying vast amounts of sediment directly to the upper slope oversteepening and subsequent slope failures fed material into deeper water