carbon cycling and burial in the glacially influenced polar north atlantic 1 we have collated published records of carbon storage wt calcium carbonate and organic carbon in polar north atlantic sediments in order to assess the role that the glacial history of greenland and fennoscandia may have had on carbon cycling in this oceanographically important region the proportion of carbonate in sediment varies between 0 and 50 while that of organic carbon varies between 0 and 2 0 the spatial variation of the concentration and accumulation of both constituents is markedly different bulk accumulation shows a strong relationship with depth distance offshore and the location of major glacial outlets on neighboring landmasses therefore ice sheet dynamics and erosion influence carbon especially organic carbon storage strongly during the late weichselian 27 12 14c ka via their impact on sedimentation rates and constituents in contrast water mass characteristics are important in determining the pattern of carbon storage during the holocene carbonate fluxes to the polar north atlantic sediment column fall by 50 during glacials to 1 1 1013 kg kyr 1 but organic carbon storage is maintained at or greater than interglacial levels 4 6 1011 kg kyr 1 this represents a 100 change in the ratio of preserved inorganic to organic carbon when combined with reduced deep water ventilation respiration of this relatively greater organic carbon flux in both the water and sediment columns provides a good explanation for the observed periodic enhanced dissolution of carbonate in polar north atlantic late weichselian sections perhaps enhancing co2 storage in deep waters

integration of modern and past pollen accumulation rate par records across the arctic tree line a method for more precise vegetation reconstructions abstract in order to assess the potential role of the boreal forest in the early to mid holocene global dynamics it is critical that the tree line reconstructions are based on precise palaeorecords pollen accumulation rate par calculations provide a technique for estimating past plant population densities independently for each species when considering tree lines an important concept is the threshold par value for the absence presence and dominance of the most common tree species such threshold values are often based on modern lake sediment core top par values in northern fennoscandia records obtained through pollen monitoring now add an important element to these studies as they allow more precise definitions of the temporal and spatial limits of par values here we compare modern par values based on pollen monitoring data with sediment core top data to evaluate the robustness of the threshold values for the major tree species of finnish lapland we apply these threshold values to two fossil par records from this tree line region and as an example of the potential of the approach map the vegetation patterns in the area at 7000 cal yr bp the results indicate that the extent of the mid holocene tree line advance in northern fennoscandia was substantially less than climate vegetation model simulations have predicted despite their value and potential in vegetation reconstructions the use of par values requires careful validation of the data we stress the importance of basin size of precise and reliable sediment dating age depth modelling and assessment of the sedimentary processes in each study basin as prerequisites for par based studies

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

canyons and late quaternary sedimentation on the north norwegian margin the presence of erosive canyons on high latitude passive margins is unusual such margins are more normally dominated by subsidence and glacially influenced deposition however ten canyons are identified at the edge of the narrow shelf on the north norwegian margin off the lofoten islands between the traenadjupet and andoya slides on the basis of gloria long range side scan sonar and contemporaneous 3 5 khz profiler data combined with a detailed bathymetry the canyons are located down stream of sediments transported through the lofoten drift and the margin is characterized by an absence of cross shelf troughs canyons are up to 420 m deep u shaped display steep gradients in their upper parts and sediments derived from them have short runout distances onto the continental rise the canyons are estimated to be 20 30 ma old being incised into only thinly covered lithified pre miocene sediments as a response to cenozoic uplift late quaternary sedimentation processes associated with the canyons are inferred to occur during both glacials and interglacials glacial sedimentation is probably in the form of direct subglacial debris input in addition to turbid subglacial meltwater plumes interglacial sedimentation processes are probably dominated by the along shelf transport of sediments by strong ocean currents canyon heads capture sediment from the shelf the remobilization of this coarse material and erosion of the canyons occurs through debris flows and turbidity currents canyon preservation and continued development can be attributed directly to the comparatively low sedimentation rates during full glacial conditions as ice streams located to the north and south produce regional depocentres away from this area of relatively slow flowing ice

late quaternary architecture of trough mouth fans debris flows and suspended sediments on the norwegian margin abstract trough mouth fans are the main marine depocentres for glacier derived sediments in the polar north atlantic but their growth through the late quaternary is complex glacigenic debris flows gdfs are sourced from a common and homogeneous part of the upper fan and only develop as coherent individual flows after downslope transport their genesis and mode of deposition mean that gdfs are confined to particular areas of trough mouth fans accumulation of these subglacial sediments is controlled by a combination of margin glaciology and fan morphology although most of the fan sediment is deposited as gdfs during glacials considerable areas of trough mouth fans are dominated by sedimentation of suspension deposits associated with extensive meltwater release from a warm based ice sheet and probable contour current activity the depositional sequence of these two sediment types may be important in generating the long run out distances of gdfs which are initiated and sustained over low gradients furthermore emplacement of gdfs is interpreted to be a relatively low frequency event and temporally at least fans are not dominated by this mode of sediment emplacement whilst ice sheets are at the shelf break large scale trough mouth fan development is therefore asynchronous and non uniform a result of the interaction between glaciology morphology and oceanography

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

hummock fields in the norway basin and eastern iceland plateau rayleigh taylor instabilities side scan imagery and 3 5 khz profiles in the norway basin reveal 3 4 10 4 km 2 of sea floor covered by regularly spaced 500 2000 m low relief hummocks previously attributed to bottom currents extrapolating from nearby borehole data i attribute these mound fields to gravitational rayleigh taylor instabilities resulting from superposition of 50 100 m of thick pliocene pleistocene glacigenic glacier derived sandy clays density 1800 kg m 3 on a several hundred metre thickness of miocene biosiliceous oozes having a density of 1300 kg m 3 this hypothesis predicts or explains similar hummock fields in many oceanic regions where such density inversions exist

large scale sedimentation on the glacier influenced polar north atlantic margins long range side scan sonar evidence long range side scan sonar gloria imagery of over 600 000 km of the polar north atlantic provides a large scale view of sedimentation patterns on this glacier influenced continental margin high latitude margins are influenced strongly by glacial history and ice dynamics and linked to this the rate of sediment supply extensive glacial fans up to 350 000 km were built up from stacked series of large debris flows transferring sediment down the continental slope the fans were linked with high debris inputs from quaternary glaciers at the mouths of cross shelf troughs and deep fjords where ice was slower moving but still extended to the shelf break large scale slide deposits are observed where ice failed to cross the continental shelf during full glacials the continental slope was sediment starved and submarine channels and smaller slides developed a simple model for large scale sedimentation on the glaciated continental margins of the polar north atlantic is presented

large scale development of the mid norwegian shelf over the last three million years and potential for hydrocarbon reservoirs in glacial sediments about 3 million years ago major ice sheets developed over scandinavia and began to deliverlargevolumesofsedimenttothemid norwegianshelf theshelfwasbuilt outina prograd ing pattern towards the west and more than 1000 m of sedimentswas deposited over large areas on the middle outer shelf the dominating large scale depositional pattern is a series of prograding wedges and flat lying sheet like units mainly of glacial origin on top of these units are flat lying till units deposited during the last few glaciations commonly separated from the underlying units by one or several erosional unconformities the lithology of these layers is generally fine grained mainly clay and silt but with sporadic clasts up to boulder size based on regional and detailed bathymetry the ice flow pattern from the last glaciation has been reconstructed on the shelf this involved a very dynamic ice sheet with fast flowing ice streams in the transverse cross shelf troughs separated by more passive ice domes on the intermediate shallow banks theicestreamsappeartofollowthecross shelftroughsfromglaciationtoglaciation butoccasion ally they switched to new flow paths the thick quaternary sediments on the outer part of the mid norwegian shelf represent a challenge for hydrocarbon exploration several large slides have occurred from the shelf break and down the continental slope during the last few years there has been an increased focus on investigating the quaternary succession in order to search for hydrocarbon prospects the potential for finding reservoirs in these sediments is discussed and a few examples of gas discoveries are shown the peon gas field c 250 km 2 is located in the gla cially eroded norwegian channel above the upper regional unconformity uru separating flat lying glaciogenic sediments from dipping sedimentary units the reservoir is developed in glacio fluvial sands a few hundred thousand years old and sealed by flat lying glaciomarine sediments and till units

morphology and late quaternary sedimentation on the north faeroes slope and abyssal plain north atlantic whilst the interplay between tectonics glaciation and oceanography is reasonably well understood on some high latitude margins relatively little is known about the nature of quaternary processes affecting the continental margin north of the faeroe islands we therefore present side scan sonar gloria and tobi and 3 5 khz data in combination with a new regional bathymetry in order to characterise and analyse the margin s physiography and the sedimentary processes that have occurred in the area during the late quaternary seven acoustic facies are identified and interpreted in combination with published core records the margin is subject to differing sedimentation regimes over glacial interglacial cycles relating to the changing importance of contouritic hemipelagic glacimarine and mass movement processes mass movement is much more extensive than previously thought with a total sediment volume of 2000 km3 similar to that of the storegga slide 5500 km3 and may occur primarily at glacial terminations the downslope limit of instabilities is associated with a series of channels focusing the deposition of distal turbiditic sediments into the regional deep beyond together with glacigenic debris flows from the western margin of the north sea fan mass movement processes are identified to have affected 52 70 of the north faeroes margin area in contrast distal glacimarine sedimentation alternating with hemipelagic and contouritic development is found on the remaining 30 48 of the margin during glacials and hemipelagic and contouritic sedimentation are active across 90 of the margin in interglacial conditions despite a lack of any local direct glacial influence these observations on the relative importance of sedimentation processes are comparable with other glacially influenced passive margins

determination of sediment volumes accumulation rates and turbidite emplacement frequencies on the madeira abyssal plain ne atlantic a correlation between seismic and borehole data the sedimentary infill history of the madeira abyssal plain map is established from correlation of odp leg 157 drillsites sites 950 952 with an almost regular grid of 7000 km of intermediate resolution seismic reflection profiles covering the central part of the abyssal plain the most conspicuous seismic reflectors bounding the seismostratigraphic units have been identified and mapped correlation between seismic and borehole data using synthetic seismograms allows the lithological attribution and dating of the reflectors and seismostratigraphic units lateral mapping and correlation of seismic units also allows both the volumes and rates of accumulation of sediments within each seismostratigraphic unit and equivalent time periods of deposition to be determined these calculations have been corrected for the effect of compaction calculated at around 40 at the base of the drillholes three main turbidite types have been identified at the drillsites and their emplacement frequency has been calculated for each site and time period our results show that cretaceous oceanic crust was draped with red pelagic clays and the fracture zone valleys were completely infilled and levelled in a geologically rather short time probably during the latest oligocene and early miocene by organic rich turbidites derived from the nw african continental margin at 16 ma the topography was levelled enough to allow large turbidity current flows to cover the entire plain during the middle and late miocene 16 5 9 ma organic rich turbidites were emplaced on the abyssal plain at a low rate of accumulation 12 m my in the uppermost miocene early pliocene 5 9 3 6 ma turbidite emplacement increased markedly in both frequency and accumulation rate e g 26 m my for organic rich turbidites during this time period emplacement of volcanic rich turbidites also increased in volume and frequency a trend that continued into the pliocene increased volcanic rich turbidite emplacement correlates well with increased volcanic activity on the canary islands and increased organic rich turbidite emplacement may correlate with periods of erosion on the nw african continental margin these erosional periods may be related to global cooling and falling sea level intensification of bottom water currents and enhanced upwelling on the margin

the andoya slide and the andoya canyon north eastern norwegian greenland sea based on gloria side scan sonar imagery echo sounder records 3 5 khz profiles multichannel seismics and gravity cores the andoya slide and andoya canyon north eastern norwegian greenland sea were mapped and interpreted the andoya slide covers an area of about 9700 km2 of which the slide scar area comprise ca 3600 km2 the slide has a total run out distance of about 190 km slope failure is inferred to have occurred during the holocene because the slide scar has prominent relief on the present sea floor the area of sediment removal is characterised by an irregular relief were relatively consolidated sediments are exposed at the sea floor little or no unconsolidated sediments overlies the slide deposits earthquake activity is inferred to have triggered the slide a holocene age of the andoya slide implies that three giant slides the storegga traenadjupet and andoya slides have occurred along the continental slope of norway during the last 10 000 years a large canyon the andoya canyon is located immediately south of the andoya slide on the upper slope the canyon has been incised about 1000 m in the bedrock and the maximum width at the bottom and between the canyon shoulders is 2 and 12 km respectively the andoya canyon represents the upper part of the lofoten basin channel based on analogy with other deep sea canyon channel systems the andoya canyon lofoten basin channel is possibly of pre quaternary age holocene sediments recovered from within the canyon and draping the flanking channel deposits indicate that the andoya canyon is not presently active and has probably not been active during the holocene during the holocene the canyon acted as a trap for sediments settling from the winnowing norwegian current

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

ice sheet numerical modeling and marine geophysical measurements of glacier derived sedimentation on the eurasian arctic continental margins long range side scan sonar images of the barents sea continental margin have been analyzed in conjunction with results from previous geophysical investigations to determine a qualitative model for sedimentation over the bear island and storfjorden trough mouth fans these data indicate that gravity driven debris flows are major processes in the downslope transport of glacial material delivered to the shelf break when ice sheets advanced across the continental shelf during late weichselian time 4000 km 3 of sediments were deposited over the bear island fan 280 000 km 2 while 700 km 3 of sediments were deposited over the storfjorden fan 40 000 km 2 a numerical ice sheet model including sediment deformation and transport beneath ice streams reconstructs the glacial conditions required to transport large volumes of sediment to the late weichselian eurasian continental margin model results indicate that glaciation of the eurasian high arctic occurred after 28 ka and that ice streams within bathymetric troughs were active by ca 25 ka the maximum ice sheet thickness over the barents sea was about 1400 m there was a secondary dome 1 0 13 cm yr 1 averaged over the fan the rate was 6 cm yr 1 equivalent to 0 6 cm yr 1 over the fan over the storfjorden trough mouth the modeled sediment volume at the continental margin of the bear island and storfjorden troughs agrees well with the volumes of late weichselian sediment inferred from seismic records from these large prograding submarine fans sensitivity experiments show that adjustments to model environmental inputs do not significantly affect the results

late weichselian depositional processes fluxes and sediment volumes on the margins of the norwegian sea 62 75 n abstract quaternary continental margin sedimentation in the norwegian greenland sea has been a response to a combination of tectonic oceanographic and glacial activity using geophysical survey data 6 5 khz side scan sonar and 3 5 khz penetration echo sounding in association with bathymetric datasets the magnitude and frequency of the main forms of margin sedimentation into the lofoten and norwegian basins of the norwegian sea during the late weichselian and holocene are estimated by comparing these geophysically determined estimates of sediment fluxes with numerically modelled ice sheet sediment delivery the role of ice sheets in shaping the processes acting on this margin is assessed sediment flux at the shelf edge during the late quaternary is dominated by ice sheet delivery of sediments focused at the mouths of fast flowing ice streams formed in bathymetric troughs interglacials are by contrast characterised by comparatively little sediment accumulation submarine fans at the margins of cross shelf troughs are major depocentres on this glacier influenced margin however occasional large scale failures of the continental slope account for approximately 75 of the basin sediment accumulation during the past 30 000 yr by eroding substantial quantities of pre quaternary deposits trough mouth fan and a combination of hemipelagic and glacimarine processes are responsible for the accumulation of the remaining 15 and 7 of basin sediments respectively

the lofoten contourite drift off norway abstract based on high resolution and multichannel seismic data a contourite drift the lofoten drift has been identified below ca 1000 m water depth on the continental slope off norway the lofoten drift has a maximum thickness of about 360 m correlation to published seismic stratigraphy implies a neogene age the onset of the lofoten drift may have been a result of increased circulation within the norwegian greenland sea probably controlled by the subsidence of the greenland scotland ridge the drift has probably originated from deposition of suspended sediments derived from winnowing of the continental shelf and upper slope the geometry of the youngest seismic drift unit characterised by a maximum thickness at the crest of the mound indicates that the lofoten drift is active at present the maximum holocene sedimentation rate is ca 1 m ka the downslope sediment input to the study area was probably relatively low during glacial periods because the lofoten islands may have acted as a sediment barrier causing large fluvial and or glacial drainage systems from central fennoscandia to be routed south and north of the study area as a result alongslope sediment transport has been the main sediment input to this part of the continental slope

recent sedimentary processes in the prestige site area galicia bank nw iberian margin evidenced by high resolution marine geophysical methods an echo character analysis of the oil tanker prestige wreck area was undertaken using high resolution marine geophysical methods topas and airgun seismic reflection profiles multibeam echosounder and tobi sidescan sonar integration and comparison of the results using all these methods is presented given some practical applications for indirect near surface and seafloor interpretations ten different echo types were identified and grouped into four main classes i distinct ii indistinct iii irregular and iv hyperbolic echo character distribution enabled us to determine recent sedimentary processes in the area two major depositional systems can be found through the identification of these sedimentary processes a a slope depositional system sds located in the eastern and central area where mass movement processes are dominant and b a turbiditic main channel depositional system tds located in the western area where channel related processes are dominant both of these interact over the half graben structure of the southwestern sector of the galicia bank where the prestige wreck is located within the sds erosive and depositional mass movement processes characterised a complex depositional system erosive processes occur on the fault scarp channels head inter lobe channels and distal part of the sedimentary lobes moreover depositional processes take place on the top of the fault scarp sedimentary wedges sedimentary lobes and on the west flank of the main channel both depositional systems interact but the sds should be more active during fault scarp reactivation periods through relief rejuvenation and new exposed deposits microearthquake activity would favour the available materials being weathered eroded and transported by mass movements in such a situation the tds acts as the main collector of eroded sediment derived from the fault scarp throughout the sds being responsible for its evacuation into the iberian abyssal plain however outside of fault reactivation periods the sds is less active such as during the present situation

quaternary evolution of the northern north sea margin through glacigenic debris flow and contourite deposition the norwegian channel ice stream of the scandinavian ice sheet extended across the northern north sea margin during the mid to late quaternary eroding older sediment from the continental shelf consequently little is known about early quaternary sedimentation on this margin we use two and threedimensional seismic reflection data to investigate changing sediment volumes and sources in the northern north sea through the quaternary the northern north sea basin was infilled during the early quaternary by intercalated glacigenic debris flows and contourites which provide a record of the delivery of glacigenic sediment to the slope and the intensity of north atlantic thermohaline circulation during early quaternary glacial interglacial cycles the infilling of the basin reduced accommodation and led to the deflection of mid to late quaternary sediments into the norwegian sea forming the north sea fan close to the onset of the mid quaternary the south western scandinavian ice sheet margin was drained by an ice stream located beneath maluy plateau 60 km east of the last glacial maximum norwegian channel ice stream the southward flowing norwegian sea bottom water current was directed into the partially filled northern north sea basin during the early quaternary and deflected progressively northwards as the basin became infilled

strain accumulation across the eastern california shear zone at latitude 36 30 n the motion of a linear array of monuments extending across the eastern california shear zone ecsz has been measured from 1994 to 1999 with the global positioning system the linear array is oriented n54 e perpendicular to the tangent to the local small circle drawn about the pacific north america pole of rotation and the observed motion across the ecsz is approximated by differential rotation about that pole the observations suggest uniform deformation within the ecsz strike n23 w 26 nstrain yr 1 extension normal to the zone and 39 nstrain yr 1 simple right lateral shear across it with no significant deformation in the two blocks the sierra nevada mountains and southern nevada on either side the deformation may be imposed by right lateral slip at depth on the individual major fault systems within the zone if the slip rates are death valley furnace creek fault 3 2 0 9 mm yr 1 hunter mountain panamint valley fault 3 3 1 6 mm yr 1 and owens valley fault 6 9 1 6 mm yr 1 however this estimate of the slip rate on the owens valley fault is 3 times greater than the geologic estimate

evidence for long term instability in the storegga slide region off western norway abstract shallow seismic surveys around the storegga slide off western norway have allowed greater understanding of the development of this part of the european margin the northern flank of the scarp is formed of seismically well layered hemipelagic and distal glaciomarine deposits in which a variety of luid escape structures probably due to gas are locally abundant there is evidence of slides that substantially pre date the earliest slide previously recognized surveying on the north sea fan to the southwest of the storegga slide shows the markedly different nature of the autochthonous sediments on the southern flank of the storegga slide there is a predominance of glacigenic debris flows in the upper part of the sequence lesser maximum slopes and an apparent absence of interstitial gas and or hydrates this contrast has had considerable effect on slope stability and has influenced the position of the southwestern storegga slide boundary the north sea fan succession includes at least three major buried slides termed the vigra more and tampen slides all of which substantially pre date the storegga event and probably pre date predominantly glacigenic margin sedimentation post late weichselian slope failure is locally significant the region has a long but as yet chronologically poorly defined history of instability in which seismic triggering is considered to have been important

sediment reworking on high latitude continental margins and its implications for palaeoceanographic studies insights from the norwegian greenland sea geological evidence indicates that sediment reworking is common around the continental margins and abyssal depths of the norwegian greenland sea a high latitude setting with glacier influenced margins detailed analysis of 22 cores up to 5 in long placed in context by accompanying geophysical data including high resolution sub bottom profiles swath bathymetry and backscatter maps indicates that reworking is variable and ranges from debris flows and turbidity currents to bottom current activity as well as iceberg scouring reworking by debris flows appears to be restricted mainly to the main trough mouth fans and sediment slides elsewhere turbidity current activity frequently dominates although iceberg ploughing down to 600 in depth and current winnowing assume increasing significance on continental shelves reworking in the norwegian greenland sea reflects variations in ice sheet dynamics that in turn influence the rate of sediment delivery and location of depocentres spatial variations in the style of reworking may also reflect the influence of continental slope gradient and bedrock geology on continental shelves the widespread nature of sediment reworking has important implications for palaeoceanographic investigations in the region as reworking can result in erosion and disturbance of the sediment column it is estimated that less than 7 of material delivered to the norwegian greenland sea since the late weichselian is derived from hemipelagic and pelagic sedimentation this problem is significant where continuous high resolution records of hemipelagic and pelagic sedimentation are required and attempts are made to correlate with other high resolution proxy records such as ice cores at sub millennial scales bioturbation results in the smoothing of high resolution records and imposes a maximum resolution for sediment core time slices of generally 400 years or more in the norwegian greenland sea areas of high sedimentation such as trough mouth fans or contourite drifts are commonly associated with extensive reworking identification of reworking is particularly important where attempts are made to link records of iceberg rafted debris to past ice sheet dynamics as bottom current winnowing and mass flow processes can increase the concentration of coarse grained iceberg rafted debris such localized accentuation of the iceberg rafted debris signal may lead to erroneous palaeo environmental interpretations it is therefore critical that palaeoceanographic interpretations are firmly underpinned by an explicit sedimentological assessment of reworking

morphology sedimentary infill and depositional environments of the early quaternary north sea basin 56 62 n abstract the north sea basin has been subsiding during the quaternary and contains hundreds of metres of fill seismic surveys 170 000 km2 provide new evidence on early quaternary sedimentation from about 2 75 ma to around the brunhes matuyama boundary 0 78 ma we present an informal seismic stratigraphy for the early quaternary of the north sea and calculate sediment volumes for major units early quaternary sediment thickness is 1000 m in the northern basin and 700 m in the central basin total about 40 000 km3 northern north sea basin fill comprises several clinoform units prograding westward over 60 000 km2 architecture of the central basin also comprises clinoforms building from the southeast to the west an acoustically layered and mounded unit unit z was deposited remaining accommodation space was filled with fine grained sediments of two central basin units above these units an upper regional unconformity equivalent uru records a conformable surface with flat lying units that indicate stronger direct glacial influence than on the sediments below on the north sea plateau north of 59 n the upper regional unconformity uru is defined by a shift from westward to eastward dipping seismic reflectors recording a major change in sedimentation with the shetland platform becoming a significant source a model of early quaternary sediment delivery to the north sea shows sources from the scandinavian ice sheet and major european rivers clinoforms prograding west in the northern north sea basin representing glacigenic debris flows indicate an ice sheet on the western scandinavian margin in the central basin sediments are generally fine grained suggesting a distal fluvial or glacifluvial origin from european rivers ploughmarks also demonstrate that icebergs derived from an ice sheet to the north drifted into the central north sea basin by contrast sediments and glacial landforms above the uru provide evidence for the later presence of a grounded ice sheet

the role of the cryosphere in source to sink systems abstract glacial erosion and sediment production are of interest to diverse scientific communities concerned with the interaction of climatic tectonic and surface processes that influence the evolution of orogens and with the climatic signals archived in glacigenic strata we review the current state of knowledge on the generation transfer and accumulation of glacigenic sediment from land to sea we draw from geomorphology marine geology geochronology numerical modeling of surface processes and landscape evolution and experimental and field observations of glacier erosion and deposition and the interaction of ice with its bed and the ocean boundary our primary goal is to examine glacial systems using a holistic source to sink approach with a focus on describing a how glacial motion produces sediment b how the sediments sink record the dynamic nature of glacial systems under different climatic thermal regimes c the challenges in using the sedimentary record to interpret these dynamics in space and time and d the approaches still needed to further our understanding of how ice and associated sediment fluxes respond to climatic and other perturbations the dynamic state of ice i e the ice flux and ice extent is defined differently between the source and sink communities reflecting the challenges of establishing a stratigraphic signal that volumetrically constrains glacigenic sediment production as a function of the ice response to climate advances in marine geophysics have greatly assisted our understanding of mass transfer pathways and of former ice extents as a measure of ice dynamics and have identified the primary depocenters and key lithofacies of glacial sinks sediment fluxes associated with the dynamic state of the ice are best constrained where sediment volumes derived from key lithofacies and seismic reflection isopachs can be temporally partitioned of which there are few examples rather than from discrete point measures of sediment flux that are subject to sediment transfer biases forward numerical modeling of sediment fluxes as a function of ice dynamics agree with observational data at the continental margin scale but finer time space scale ice dynamic models do not yet recreate observed ice extent or flowpaths future source to sink work in glaciated systems should focus on refining empirical relationships between ice velocity and sediment production and expand the application of existing methods to develop sediment volumes and fluxes in known depocenters of former and modern ice streams

sedimentation history of the northern north sea margin during the last 150 ka the norwegian channel ice stream ncis is one the defining features of the fennoscandian icesheet still little is known of the detailed dynamics of this ice stream in relation to regional changes in ice cover paleoceanographic and climatic changes sedimentological data from core md99 2283 in combination with seismic data allow a detailed chronological reconstruction of the outbuilding of the margin and the ice extent in southern scandinavia through the last 150 ka an integrated stratigraphy of the margin is presented and compared to the glacial history changes in the regional ice cover are reflected in the accumulation rates the clay mineralogy the coarse chalk fraction and the number of ird 2 mm in core md99 2283 while the sedimentation on the north sea fan as derived from seismic data provides direct evidence for the glacial activity at the shelf edge tentative evidence was found for two early weichselian glacial advances in southern scandinavia and possibly scotland at around 110 and 80 ka bp from 42 cal ka bp the ice cover expanded in southern fennoscandia and led to increased deposition on the margin and the occurrence of local melt water outbursts significantly increased accumulation rates coarse chalk local meltwater output and smectite occur during the ice expansion in the north sea from around 34 cal ka bp the main outbuilding phase of the nsf during the last glacial cycle occurred after 30 cal ka bp from around 24 cal ka bp the ncis became highly active and advanced at least three times prior to the final retreat from the shelf edge around 19 0 cal ka bp

evidence for general instability of past climate from a 250 kyr ice core record recent results1 2 from two ice cores drilled in central greenland have revealed large abrupt climate changes of at least regional extent during the late stages of the last glaciation suggesting that climate in the north atlantic region is able to reorganize itself rapidly perhaps even within a few decades here we present a detailed stable isotope record for the full length of the greenland ice core project summit ice core extending over the past 250 kyr according to a calculated timescale we find that climate instability was not confined to the last glaciation but appears also to have been marked during the last interglacial as explored more fully in a companion paper3 and during the previous saale holstein glacial cycle this is in contrast with the extreme stability of the holocene suggesting that recent climate stability may be the exception rather than the rule the last interglacial seems to have lasted longer than is implied by the deep sea specmap record4 in agreement with other land based observations5 6 we suggest that climate instability in the early part of the last interglacial may have delayed the melting of the saalean ice sheets in america and eurasia perhaps accounting for this discrepancy

onset and growth of trough mouth fans on the north western barents sea margin implications for the evolution of the barents sea svalbard ice sheet abstract the aim of this study is to discuss the onset and growth of the bellsund hornsund and storfjorden trough mouth fans tmfs on the north western barents sea margin this is done on the basis of a seismo stratigraphic analysis of new 2d seismic reflection profiles and a new correlation between odp site 986 west of spitsbergen and the seismo stratigraphic network in the central part of the western barents sea margin we infer that reflector r4a marks the onset of both the development of the tmfs and the contourite deposition which dominate this part of the margin from this time onward we conclude that these deposits were frequently affected by episodes of small scale mass wasting focused at the mouth of the glacially eroded cross shelf troughs with a new interpolation between the few available constraints we propose an age of about 1 3 ma for the onset of both the development of the tmfs and the contourite deposition thus we hypothesize from our results and from previous studies that the barents sea svalbard ice sheet expanded first beyond the coast north of svalbard later reaching the shelf edge at the mouth of bjornoyrenna and then to storfjorden southern spitsbergen

holocene sedimentary processes in the andoya canyon system north norway abstract the andoya canyon system is the most pronounced of the ten canyon systems identified on the norwegian continental margin none of these canyon systems is linked to any present active drainage area and are interpreted to have been basically non active since the last glacial maximum and the deglaciation period our knowledge on these canyon systems is however still limited as no high resolution stratigraphical or acoustic data sets are available from these areas the main target for analysing the long term history of the andoya canyon has been to study the distal accumulation part of this system in the lofoten basin the lofoten basin area is characterized by repeated stacks of extensive turbidite units where the details of the stratigraphical succession can be studied in undisturbed settings about 3000 km 2 of high resolution multibeam data em300 along with three gravity cores have been collected from the lofoten basin area the analyses carried out on the cores revealed that the predominant process results in single turbidite units interbedded with thin units of hemipelagic sedimentation the radiocarbon dating revealed that turbidites have been transported through this channel system at least twice during the holocene the two uppermost dated turbidite sequences give a maximum age of 7 9 ka 14 c bp for the lower sequence and an age of ca 4 0 ka 14 c bp for the upper sequence the upper sequence is of a similar age as the traenadjupet slide failure whereas the lower sequence indicates an age close to the storegga slide failure event taking into consideration the erosive lower boundary of that sequence the location of the investigated cores which are far away from both the traenadjupet slide and the storegga slide indicate that the instability in these canyon systems during the holocene period has most probably been influenced by these large scale failure events what triggered the release of these turbidites is still not understood but earthquakes or tsunami waves associated with the mega scale traenadjupet slide and the storegga slide events are considered to be the most likely mechanism at least during the holocene interglacial period

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

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

transport of terrestrial organic matter to the deep north atlantic ocean by ice rafting abstract total organic carbon toc 13c values of toc 13corg and glycerol dialkyl glycerol tetraethers gdgts were analysed for a sediment core from the north atlantic covering the last 30 kyr to investigate organic matter deposition due to ice rafting toc content was low in sediments representing glacial times 0 2 0 4 and even lower in holocene sediments

norwegian margin outer shelf cracking a consequence of climate induced gas hydrate dissociation a series of en echelon cracks run nearly parallel to the outer shelf edge of the mid norwegian margin the features can be followed in a 60 km long and 5 km wide zone in which up to 10 m deep cracks developed in the seabed at 400 550 m water depth the time of the seabed cracking has been dated to 7350 14c years bp 8180 cal years bp which corresponds with the main storegga slide event 8100 250 cal years bp reflection seismic data suggest that the cracks do not appear to result from deep seated faults but it cannot be ruled out completely that tension crevices were created in relation to past movements on the headwall of the storegga slide the cracking zone corresponds well to the zone where the base of the hydrate stability zone bhsz outcrops evidence of fluid release in the bhsz outcrop zone comes from an extensive pockmark field we suggest that post glacial ocean warming triggered the dissociation of gas hydrates while the interplay between dissociation overpressure and sediment fracturing on the outer shelf remains to be understood

architecture and sedimentary processes on the mid norwegian continental slope a 2 7 myr record from extensive seismic evidence abstract quaternary architectural evolution and sedimentary processes on the mid norwegian continental slope are investigated using margin wide three and two dimensional seismic datasets of 100 000 km3 sediments delivered to the mid norwegian shelf and slope over the quaternary 75 000 km3 comprise the slope succession the structural high of the voring plateau characterised by initially low 1 2 slope gradients and reduced accommodation space exerted a strong control over the long term architectural evolution of the margin slope sediment fluxes were higher on the voring plateau area increasing up to 32 km3 ka 1 during the middle pleistocene when fast flowing ice streams advanced to the palaeo shelf edge resulted in a more rapid slope progradation on the voring plateau these rates of sediment delivery are high compared to the maximum of 7 km3 ka 1 in the adjacent sectors of the slope characterised by steeper slope 3 5 more available accommodation space and smaller or no palaeo ice streams on the adjacent shelves in addition to the broad scale architectural evolution identification of more than 300 buried slope landforms provides an unprecedented level of detailed process based palaeoenvironmental reconstruction channels dominate the early pleistocene record 2 7 0 8 ma during which glacimarine sedimentation on the slope was influenced by dense bottom water flow and turbidity currents morphologic signature of glacigenic debris flows appear within the middle late pleistocene 0 8 0 ma succession their abundance increases towards late pleistocene marking a decreasing role for channelized turbidity currents and dense water flows this broad scale palaeo environmental shift coincides with the intensification of northern hemispheric glaciations highlighting first order climate control on the sedimentary processes in high latitude continental slopes

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

morphology and pattern of quaternary sedimentation in the north sea basin 52 62 n abstract the quaternary north sea basin which extends from northwest mainland europe in the south 52 n to the norwegian sea in the north 62 n contains a thick up to 1 km sedimentary succession that records the changing nature of sediment supply from surrounding land areas during the last c 2 6 ma we use an extensive 2d and 3d seismic database to correlate major quaternary seismo stratigraphic surfaces and units across the north sea and reconstruct the broad scale infill pattern of the entire quaternary north sea basin the total volume of quaternary sediments in the north sea 350 000 km2 is c 140 000 km3 while the area inside the 500 m contour of the base quaternary surface has a volume of 109 000 km3 two largely independent depocentres developed in the north sea basin during the early quaternary the southern and central sub basin was infilled by shelf fluvio deltaic and prodeltaic sediments delivered from the east and south east whilst the northern sub basin was infilled mainly by prograding glacigenic debris flows deposited from an ice mass centred on the norwegian mainland contour currents were an important mechanism of sediment deposition and reworking with water circulation in the basin probably occurring in an anti clockwise direction whilst most of the southern north sea basin was infilled by around 1 6 1 7 ma a depression persisted in the central north sea until around 1 ma the analysis of landforms on 3d seismic data suggests that the fennoscandian ice sheet fis extended intermittently to the palaeo shelf break in the northern north sea during the earliest quaternary and expanded into the central north sea prior to the excavation of the norwegian channel

large scale development of the mid norwegian margin during the last 3 million years abstract during the last c 2 7 my large quantities of glacially derived material were transported westwards from the norwegian mainland areas and inner shelf and deposited mainly as prograding sediment wedges into a basin of intermediate depth offshore mid norway the deposits are more than 1000 m thick in extensive areas and are defined as the naust formation in the haltenbanken traenabanken region the shelf edge migrated 100 150 km westwards the narrow more shelf was built out only in the order of 30 50 km mainly due to a steeper pre existing slope dipping towards a much deeper basin in this area the holocene storegga slide as well as older slides displaced slope sediments towards the deeper part of the basin in early naust time the most extensive progradation occurred in the northern area possibly due to the combined effect of land uplift and glaciations the importance of glaciations for the progradation of the more shelf and areas farther south increased through the pleistocene period the norwegian channel ice stream became very important during the last three glaciations and a thick succession of glacigenic debris flows was deposited on the north sea fan more than 400 m of sediments accumulated during the weichselian all the last three glaciations supplied glacial debris beyond the shelf edge the most extensive progradation in the north was in the skjoldryggen region particularly during the elsterian glaciation during ice free periods hemipelagic and contouritic sediments were deposited on the slope such sediments are most common in the storegga slide area where they hosted glide planes beneath the major slides