postglacial emergence and distribution of late weichselian ice sheet loads in the northern barents and kara seas russia reconstructions of late weichselian glacier coverage on the continental shelves of the russian arctic range from a large ice sheet terminating in northern siberia to isolated ice caps restricted to arctic archipelagos this disparity in glacier reconstructions reflects the lack of chronological control on glacial and deglacial landforms we present new holocene relative sea level data from franz josef land and northern novaya zemlya russia that place the thickest glacier loads in the northern barents sea and not over novaya zemlya radiocarbon ages from shelf and terrestrial areas at the former ice sheet margin support deglaciation of the northern barents sea between 13 0 and 10 3 ka considerably later than inferred from isotopic records for the arctic ocean this analysis indicates that the barents sea ice sheet was a dominant sea level reservoir in northern eurasia and that glacier loading of novaya zemlya was comparatively limited during the last glaciation

deglaciation of a marine based ice sheet late weichselian palaeo ice dynamics and retreat in the southern barents sea reconstructed from onshore and offshore glacial geomorphology abstract marine and terrestrial datasets swath bathymetry 2d and 3d seismic and remote sensing data are used to map the megascale glacial geomorphology of the southern barents sea seafloor northern fennoscandia and the kola peninsula giving new insights into the dynamics and behaviour of the barents sea ice sheet during retreat the glacial geomorphology indicates clear spatial and temporal variations in ice dynamics with evidence for both active ice streaming and frozen bed conditions at the maximum and during deglaciation a five stage reconstruction of the late weichselian deglaciation is proposed at the late weichselian maximum ice covered the whole of the barents sea shelf and the configuration and dynamics of the ice sheet were controlled by the bjornoyrenna bear island trough ice stream this was fed by source areas in the central and north eastern barents sea and in the fennoscandian mainland deglaciation was initiated along the western continental margin available dating results show that this occurred after 19 cal ka bp the bjornoyrenna ice stream retreated rapidly ice margin retreat rates of 275 m a 1 but was periodically grounded as evidenced by a well developed series of grounding zone wedges this was followed by an advance of two short lived ice streams from the eastern sector of the ice sheet into the south western barents sea these ice streams advanced and retreated very rapidly with no evidence for ice margin standstills correlation to dated cores suggests an age of around 16 000 cal ka bp for this readvance the period of operation of these two ice streams was coincident with maximum ice extent along the eastern margin in russia the western barents sea ice margin then retreated onshore with deglaciation continuing at a reduced rate the initiation of deglaciation coincided with rising global eustatic sea level acceleration of calving due to grounding line floatation rapidly opened up a major calving bay in bjornoyrenna encouraging rapid loss of the marine based ice the retreat rate stabilised only once the ice sheet retreated onshore and calving ceased we note that the observed pattern of rapid retreat with high variability in ice streaming for the marine based barents sea ice sheet is similar to that of the marine based sectors of the late weichselian british laurentide and west antarctic ice sheets

insolation values for the climate of the last 10 million years new values for the astronomical parameters of the earth s orbit and rotation eccentricity obliquity and precession are proposed for paleoclimatic research related to the late miocene the pliocene and the quaternary they have been obtained from a numerical solution of the lagrangian system of the planetary point masses and from an analytical solution of the poisson equations of the earth moon system the analytical expansion allows the direct determination of the main frequencies with their phase and amplitude numerical and analytical comparisons with the former astronomical solution ber78 are performed so that the accuracy and the interval of time over which the new solution is valid can be estimated the corresponding insolation values have also been computed this analysis leads to the conclusion that the new values are expected to be reliable over the last 5 ma in the time domain and at least over the last 10 ma in the frequency domain

glacial geomorphic features in the northern barents sea direct evidence for grounded ice and implications for the pattern of deglaciation and late glacial sedimentation

did the black mat impact airburst reach the antarctic evidence from new mountain near the taylor glacier in the dry valley mountains abstractdetailed microscopic investigations of horizons in a surface paleosol part of a pedostratigraphic stack of tills at new mountain antarctica dated to the middle miocene climatic optimum e

moisture supply for northern ice sheet growth during the last glacial maximum during the last ice age the barents sea ice sheet began to grow 22 kyr ago1 only 8 kyr before it began to disintegrate2 this implies that the ice must have grown very rapidly from the coast to the edge of the continental shelf such rapid growth of a large ice sheet requires significant amounts of moisture3 but the origin of this moisture has been unclear particularly as the climap climate reconstruction suggests4 5 that the greenland iceland norwegian gin seas were perennially ice covered during this period here we present data from deep sea sediment cores from the fram strait which suggest that relatively warm water from the north atlantic ocean was advected into the gin seas in two short term events 27 22 5 and 19 5 14 5 kyr ago we suggest that the resulting seasonally ice free waters were an important regional moisture source for the barents sea ice sheet and that the gin seas played a much more active role in climate during the last glaciation than has previously been supposed

the marine based nw fennoscandian ice sheet glacial and deglacial dynamics as reconstructed from submarine landforms abstract the configuration of the marine based nw fennoscandian ice sheet during the last glacial maximum lgm and deglaciation is reconstructed using detailed swath bathymetry and high resolution seismic data the investigated area covers about 10 000 km 2 of the continental shelf off troms northern norway large scale morphology is characterized by cross shelf troughs coast parallel troughs and banks based on mega scale glacial lineations msgl lateral and shear zone moraines and grounding zone systems the extent and dynamics of the ice sheet during the lgm are deduced msgl indicate fast flowing ice streams in the cross shelf troughs while the glacial morphology on the banks indicates more sluggish ice here the marine based part of the fennoscandian ice sheet was sourced from ice domes in the east via fjord and valley systems inshore using a balance flux approach we estimate palaeo ice stream velocities during the lgm to be approximately 350 m year three deglaciation events have been reconstructed i during the torsken 1 event the ice sheet halted or readvanced to form groundings zone wedges gzw and the torsken moraine ii several still stands or readvances characterized the ice behaviour on the shallower banks during the torsken 2 event iii during the flesen event prominent end moraines in the inner parts of the troughs and banks were deposited the locations of the end moraines and gzw in the troughs indicate that the retreat of marine based ice streams in areas of reverse bed slope was episodic probably mainly due to the variation in widths of the cross shelf troughs

initiation of fennoscandian ice sheet retreat during the last deglaciation although the retreat history of the southern margin of the laurentide ice sheet during the last deglaciation has been well known for several decades1 3 and recently supported by evidence from accelerator mass spectrometer ams radiocarbon dating of meltwater in the gulf of mexico4 and the north atlantic subtropical gyre5 the retreat history of the fennoscandian ice sheet before 13kyr ago is still poorly documented from ams 14c dating and isotopic analysis of a rapidly deposited series of supra till sediments in the norwegian channel north sea we find that the southern margin of the fennoscandian ice sheet was in retreat by 15 kyr bp before present approximately 2 000 yr earlier than previously supposed oxygen isotope analyses in the channel sediments confirm earlier evidence from deep norwegian sea sediment cores for low salinity due to ice sheet discharge beginning 15 14 5 kyr bp ref 6 recent recalibration of the 14c timescale indicates that the onset of deglaciation within the norwegian sea occurred during an interval of rapidly increasing summer insolation beginning 18 000 calendar yr bp ref 7 suggesting that ice sheet retreat may have been caused by increasing insolation acting on a particularly climate sensitive ice sheet configuration fresh water and icebergs discharged into the norwegian sea at this time reached the north atlantic and may have contributed to a brief interval of extreme oceanic cooling8 and reduced production of north atlantic deep water9 10 these factors may also have helped to briefly reverse the deglaciation trend erie interstade already underway in north america

sedimentary environment and glacial history during the last 40 ka of the voring continental margin mid norway abstract this study is based on detailed investigation of sediment cores and high resolution seismics we identified and describe five lithofacies on the voring plateau and eight on the mid norwegian continental slope the various lithofacies are mainly related to the fluctuations of the fennoscandian ice sheet and the varying intensity of bottom currents and inflow of atlantic water masses ocean circulation was highly variable between 40 and 22 14 c ka bp being vigorous during interstadials and sluggish during stadials between ca 22 and 15 14 c ka bp the sedimentary environment was significantly influenced by fluctuations of the fennoscandian ice sheet repeatedly reaching the outermost shelf these fluctuations are reflected in the sedimentary record as ice rafted debris ird accumulation peaks deposition of stratified diamicton and glacigenic debris flows on the continental slope during this period the sediment accumulation rate increased bottom currents influenced the sedimentary pattern and surface waters were seasonally ice free indicating inflow of atlantic waters subsequent to ca 15 14 c ka bp the glacier influence decreased as the margin of the fennoscandian ice sheet retreated to reach the coast before 12 5 14 c ka bp the modern sedimentary environment is characterised by relatively strong bottom current action causing winnowing or non deposition down to approximately 1000 m water depth

seafloor geomorphology of the sw barents sea and its glaci dynamic implications abstract three dimensional 3d reflection seismic imaging techniques provide a unique means of identifying large scale submarine geomorphic features produced by former ice sheets we have used such techniques to image the geomorphology of the sw barents sea but using a dense grid of 2d seismic covering a 240 000 2 km large study area supplemented with 3d seismic from selected areas the study area is located at the convergence of ice flow from the former fennoscandian barents sea and svalbard ice sheets the morphology of the major cross shelf troughs is characterized by elongated ridge groove features interpreted to be glacial bedforms produced by fast flowing grounded glaciers mega scale glacial lineations have been grouped into distinct flow sets related to three specific ice flow events these events document the last glacial maximum lgm and two readvances during deglaciation of specific interest is a detailed and well preserved set of seafloor imprints in the bjornoyrenna trough which acted as the main pathway for ice streams draining the surrounding ice sheets the geomorphic features indicate that bjornoyrenna hosted six separate ice stream lobes that diverged fan like at their margins but were not all active simultaneously an end moraine zone 68 km wide up to 85 m high and 300 km long filled the whole width of this major glacial trough as a result of high sediment flux within sub ice stream deformable beds the imprint of this ice stream system can be followed on our seabed images for 500 km however detailed geomorphologic elements demonstrate that these imprints reflect time transgressive behaviour and do not indicate the length or width of single ice streams the seismic derived seafloor geomorphology demonstrates that the barents sea ice behaved in a much more dynamic way during the last glaciation than previously assumed with major shifts between ice originating from the fennoscandian spitsbergen and barents sea ice sheets

iceberg discharges into the north atlantic on millennial time scales during the last glaciation high resolution studies of north atlantic deep sea cores demonstrate that prominent increases in iceberg calving recurred at intervals of 2000 to 3000 years much more frequently than the 7000 to 10 000 year pacing of massive ice discharges associated with heinrich events the calving cycles correlate with warm cold oscillations called dansgaard oeschger events in greenland ice cores each cycle records synchronous discharges of ice from different sources and the cycles are decoupled from sea surface temperatures these findings point to a mechanism operating within the atmosphere that caused rapid oscillations in air temperatures above greenland and in calving from more than one ice sheet

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

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

evolution of a high latitude sediment drift inside a glacially carved trough based on high resolution seismic stratigraphy kveithola nw barents sea abstract kveithola is a glacially carved e w trending trough located in the nw barents sea an epicontinental shelf sea of the arctic ocean located off northern norway and russia a set of confined sediment drifts the kveithola drift is located in the inner part of the trough in general drift deposits are commonly characterized by high lateral continuity restricted occurrence of hiatuses and relatively high accumulation rates and thus represent excellent repositories of paleo environmental information we provide for the first time a detailed morphological and seismostratigraphic insight into this sediment drift which is further supported by some preliminary lithological and sedimentological analyses the complex morphology of the drift imaged by combining all available multibeam data includes a main and a minor drift body two drift lenses in the outer part of the trough more or less connected drift patches in the innermost part and small perched sediment patches in a structurally controlled channel to the north the seismic parasound data show that the main and minor drift bodies are mainly well stratified characterized by sub parallel reflections of moderate to high amplitude and good lateral continuity the reflectors show an abrupt pinch out on the northern edge where a distinct moat is present and a gradual tapering to the south internally we identify the base of the drift and four internal horizons which we correlate throughout the drift two units display high amplitude reflectors marked lensoidal character and restricted lateral extent suggesting the occurrence of more energetic sedimentary conditions facies typical for contourite deposition are found in the sediment cores with strongly bioturbated sediments and abundant silty sandy mottles that contain shell fragments these characteristics along with the morphological and seismic information suggest a strong control by a bottom current flowing along the moat on the northern edge of the drift though both atlantic and arctic waters are known to enter the trough from the west and the north respectively brine enriched shelf water bsw produced during winter and flowing westward in the moat is suggested to be responsible for the genesis of the kveithola drift the formation of bsw is inferred to have started around 13 cal ka bp the onset of drift deposition suggesting that conditions leading to atmospheric cooling of the surface waters and or the presence of coastal polynyas and wind or floating ice shelves have persisted on the western barents shelf since that time the units inferred to have been deposited under more energetic sedimentary conditions tentatively dated to the younger dryas and to 8 9 8 2 cal ka bp are suggestive of stronger bsw formation in general we infer that variations in the bottom current regime were mainly related to bsw formation due to atmospheric changes they could also have been a response to successive episodes of grounded and sea ice retreat that allowed for a first limited later open shelf current which progressively established on the western barents sea shelf

sedimentation beneath ice shelves the view from ice stream b abstract ice shelf development is favored by rapid flow of cold ice from outlet glaciers or ice streams into protected embayments with localized high spots basal melting of ice shelves is rapid near the ice front and may occur near the grounding line ice from outlet glaciers may contain significant englacial debris that is deposited as a dropstone diamicton in regions of basal melting englacial debris is sparse or absent in ice streams evidence from ice stream b draining into the ross ice shelf of west antarctica suggests that the rapid ice velocity arises from deformation of a several meter thick water saturated basal till layer that is eroding an unconformity on sediments beneath and that has deposited a till delta tens of meters thick and tens of kilometers long at the grounding line sea level fall would cause conveyor belt recycling of this till delta and grounding line advance across the ross sea to the edge of the continental shelf forming an ice sheet with a low ice stream profile resting on a several meter thick deforming till layer eroding an unconformity the modern ross sea is characterized by a regional unconformity overlain by a diamicton of probable latest pliocene pleistocene age measuring several meters to tens of meters thick we hypothesize that this diamicton is a deformed glacial till and that the ross sea sediments record one or more expansions of the till lubricated west antarctic ice sheet to the edge of the continental shelf

two step deglaciation of the southeastern barents sea marine geologic evidence from the western barents sea shelf leaves little doubt that theareawascoveredbygroundediceduringthelastglaciation butthepatternandtiming of the subsequent deglaciation were not well determined here we reconstruct the timing and mechanism of ice sheet retreat as constrained by seismic stratigraphy and lithostratigraphy and accelerator mass spectrometer 14 c dating of foraminifera and mollusc shellsinsedimentboringsfromthesoutheasternbarentssea 1000kmfromthewestern shelf edge and former ice sheet margin the deposition of ice proximal glaciomarine sediments upon till began at or shortly before 12 7 ka indicating that the ice sheet retreat whichmostlikelycommencedalongthewesternmarginofthebarentsseashelfat15 14 5 ka reached the southeastern part of the shelf in 2 ka the subsequent accumulation of glaciomarinesedimentstookplaceintwodistinctpulses 12 7 12 1kaand 10 5 9 4ka separatedbyanintervalofnondepositionlasting 1 5ka thetwopulsesofsedimentation were coeval with periods of increasing surface water and air temperatures in the northern atlanticregionandacceleratedeustaticsea levelrise suggestingthattheremainingretreat of the barents shelf ice sheet was paced by these factors

cenozoic erosion and sedimentation in the western barents sea abstract seismic reflection data and well logs are used to interpret cenozoic sedimentary environments in the south western barents sea using volumetric calculations and compaction trend analysis the cenozoic erosion and sedimentation rates have been quantified marine environments ranging from neritic to bathyal water depths dominated the southern barents sea during the late palaeocene at the palaeocene eocene boundary a southwards progradation commenced along the uplifted and eroded loppa and stappen highs during the early eocene to mid miocene sedimentation continued in the intracratonic basins as well as along the newly established continent ocean boundary in the embryonic northern norwegian greenland sea substantial erosion occurred on the westernmost margin particularly on the stappen high during this time interval in the mid miocene during a period of relative lowstand of sea level a system of lowstand fans was deposited west of the stappen high later a pronounced progradation of the shelf edge commenced during the mid miocene to late pliocene the shelf edge prograded between 20 and 40 km during the mid pliocene to early pleistocene the barents sea and adjacent land areas were uplifted a fluvial glaciofluvial drainage system developed on the continental shelf resulting in pronounced erosion there and very high sedimentation rates on the continental margin during the last 0 8 ma several large glaciations on the barents sea shelf proper have resulted in overdeepened troughs and high sedimentation rates at the continental shelfbreak and on the continental slope the overall cenozoic erosion varies spatially as well as temporally in the svalbard area close to 3 km of rocks have been eroded since the oligocene the same amount or more was eroded from the stappen high during the palaeocene and early neogene in the south western areas during the eocene mid miocene erosion occurred along the margin in addition the loppa high and adjacent areas served as sediment source areas during the late pliocene and pleistoncene the average erosion in the south western barents sea amounted to about 600 m erosion was greater in the south east than to the west and north and was more extensive where the former glacial ice streams had flowed

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

postglacial uplift and relative sea level changes in finnmark northern norway abstract the outer coast of finnmark in northern norway is where the former fennoscandian and barents sea ice sheets coalesced this key area for isostatic modelling and deglaciation history of the ice sheets has abundant raised shorelines but only a few existing radiocarbon dates constrain their chronology here we present three holocene sea level curves based on radiocarbon dated deposits from isolation basins at the outermost coast of finnmark located at the islands soroya and rolvsoya and at the nordkinn peninsula we analysed animal and plant remains in the basin deposits to identify the transitions between marine and lacustrine sediments terrestrial plant fragments from these transitions were then radiocarbon dated radiocarbon dated mollusk shells and marine macroalgae from the lowermost deposits in several basins suggest that the first land at the outer coast became ice free around 14 600 cal yr bp we find that the gradients of the shorelines are much lower than elsewhere along the norwegian coast because of substantial uplift of the barents sea also the anomalously high elevation of the marine limit in the region can be attributed to uplift of the adjacent seafloor after the younger dryas the coast emerged 1 6 1 0 cm per year until about 9500 9000 cal yr bp between 9000 and 7000 cal yr bp relative sea level rose 2 4 m and several of the studied lakes became submerged at the outermost locality rolvsoya relative sea level was stable at the transgression highstand for more than 3000 years between ca 8000 and 5000 cal yr bp deposits in five of the studied lakes were disturbed by the storegga tsunami ca 8200 8100 cal yr bp

quaternary glaciations in southern fennoscandia evidence from southwestern norway and the northern north sea region abstract based on records from the northern north sea and southern norway quaternary fennoscandian glaciations are described and discussed maximum glaciation defined as the presence of shelf edge glaciation an ice stream flowing out of the norwegian channel and most likely an ice divide over the central part of fennoscandia sweden gulf of bothnia occurred for the first time in the late cenozoic at ca 1 1 myr the fedje glaciation this glaciation was followed by a ca 600 kyr period with at least two glaciations with ice extension somewhat larger than the younger dryas event in the region the first maximum glaciation of the bruhnes chron was during isotope stage 12 and was followed by repeated maximum glaciations within each of the light isotopic stages until stage 2 during the weichselian the southwestern part of the fennoscandian ice sheet reached maximum position three times sometime between 22 and 28 37 and 50 and 60 and 80 ka limited glaciations probably occurred during stadials between the early and middle weichselian interstadials between 500 ka and 1 1 myr and most likely also prior to 1 1 myr deep norwegian sea ice rafted detritus ird records reflecting contributions from several different ice sheets fennoscandian barents sea iceland and greenland each with large variations in history of ice extent to their respective margins yet to some degree they reflect the glaciation of the northern north sea region with an increasing ird input around 1 1 myr and a relatively low input of north sea components during some cycles around the b m boundary maximum glaciations occurred during insolation minima in the earlier part of the middle pleistocene however not all such minima are reflected by maximum glaciation in southern parts of fennoscandia the relatively poor chronological control and non continuous character of the data on weichselian interstadials stadials precludes a clear relationship to atmospheric changes recorded in greenland ice cores as well as to precession and or obliquity cycles in insolation

chronology of tertiary fan deposits off the western barents sea implications for the uplift and erosion history of the barents shelf abstract a combined biostratigraphic and seismic study was performed on three holes drilled in the western barents sea two holes penetrate the thick sedimentary wedge which forms a large fan located off a trough on the barents sea shelf the bjornoyrenna fan the study shows that the fan was built over a short time span in the late pliocene pleistocene mainly due to glacial erosion of the barents shelf region this contrasts earlier age assignments which concluded that fan deposition started in the oligocene the results have a major impact on the understanding of trough mouth fan formation and has important bearing on the history of the sedimentary basins of the barents shelf

till beneath ice stream b 3 till deformation evidence and implications most of the velocity of ice stream b near the upstream b camp upb west antarctica appears to arise from deformation of a seismically detected subglacial till layer that averages 6 m thick available evidence indicates that the entire thickness of this till layer is deforming and is eroding subjacent bedrock into flutes parallel to ice flow and hundreds of meters across the resulting till flux beneath upb is equivalent to an average erosion rate of about 0 4 mm yr 1 in the catchment area and suggests that till deltas tens of kilometers long have been deposited at the grounding line during the holocene such deltas should be characterized by partial ice till decoupling across a water film and by a small ice air surface slope they may have been discovered by recent geophysical work

macrofaunal palaeoecology and stratigraphy in late quaternary shelf sediments off northern norway abstract in a late pleistocene holocene glaciomarine marine sequence a minimum of 115 taxa macrofossils and trace fossils are recognized on the basis of 690 samples from gravity cores from andfjorden nine and malangsdjupet one the biostratigraphy is proposed on the basis of reconstructions of autochthonous macrofaunal assemblages a total of seven zones are defined five in the pleistocene and two in the holocene the ages of which are estimated by radiocarbon datings in ascending order the zones are mixed assemblage zone barren interzone arctinula greenlandica assemblage zone before 14 000 yr b p yoldiella intermedia assemblage zone 14 000 13 000 yr b p bathyarca glacialis assemblage zozne 13 000 yr b p bathyarca glacialis kelliella miliaris interval zone 10 000 ca 7800 yr b p and kelliella miliaris assemblage zone ca 7800 present the bathyarca glacialis zone is divided into three faunules i 13 000 12 000 yr b p ii 12 200 11 100 yr b p and iii 11 100 10 000 yr b p the palaeoecology of the faunal succession is elucidated by means of the sample frequency method two major environmental events have influenced the faunal history the first was the onset of the deglaciation of the thoughs the second the intrusion of the norwegian current bringing warm saline atlantic water into the troughs at 10 000 yr b p the pleistocene fossils demonstrate an arctic macrofaunal succession from a low order stage to a high order equilibrium stage that is in principle identical to that of a modern faunal development in fjords following a disturbance causing anoxia an estimated polychaete mollusc ratio together with changes in sediment influx depositional rates and grain size of substrate indicate the presence of different energy regimes where the inner and outer reaches of andfjorden are compared about 10 000 yr b p a major faunal change took place the previous arctic fauna was replaced by a boreal fauna which developed into the modern fauna the most important factor causing the replacement and renewed faunal succession were probably the rise in temperature and salinity as well as an increase in nutrient supply brought about by the intrusion of the norwegian current a comparison with shallower shelf areas indicates a somewhat different faunal composition in the pleistocene brought about by different depositional environments however a similar major faunal change took place at 10 000 yr b p and there are fewer discrepancies among the holocene faunas regional comparison indicates that some of the phases in the development of the fauna probably are rather local while other have a more regional nature

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

glacial north atlantic sea surface conditions reconstructed by glamap 2000 the response of the tropical ocean to global climate change and the extent of sea ice in the glacial nordic seas belong to the great controversies in paleoclimatology our new reconstruction of peak glacial sea surface temperatures ssts in the atlantic is based on census counts of planktic foraminifera using the maximum similarity technique version 28 simmax 28 modern analog technique with 947 modern analog samples and 119 well dated sediment cores our study compares two slightly different scenarios of the last glacial maximum lgm the environmental processes of the ice age land oceans glaciers epilog and glacial atlantic ocean mapping glamap 2000 time slices the comparison shows that the maximum lgm cooling in the southern hemisphere slightly preceeded that in the north in both time slices sea ice was restricted to the north western margin of the nordic seas during glacial northern summer while the central and eastern parts were ice free during northern glacial winter sea ice advanced to the south of iceland and faeroe in the central northern north atlantic an anticyclonic gyre formed between 45degrees and 60degreesn with a cool water mass centered west of ireland where glacial cooling reached a maximum of 12degreesc in the subtropical ocean gyres the new reconstruction supports the glacial to interglacial stability of sst as shown by climap project members climap 1981 the zonal belt of minimum sst seasonality between 2degrees and 6degreesn suggests that the lgm caloric equator occupied the same latitude as today in contrast to the climap reconstruction the glacial cooling of the tropical east atlantic upwelling belt reached up to 6degrees 8degreesc during northern hemisphere summer differences between these simmax based and published u37 k and mg ca based equatorial sst records are ascribed to strong sst seasonalities and sst signals that were produced by different planktic species groups during different seasons

morphology and microstructure of chromite crystals in chromitites from the merensky reef bushveld complex south africa the merensky reef of the bushveld complex consists of two chromitite layers separated by coarse grained melanorite microstructural analysis of the chromitite layers using electron backscatter diffraction analysis ebsd high resolution x ray microtomography and crystal size distribution analyses distinguished two populations of chromite crystals fine grained idiomorphic and large silicate inclusion bearing crystals the lower chromitite layer contains both populations whereas the upper contains only fine idiomorphic grains most of the inclusion bearing chromites have characteristic amoeboidal shapes that have been previously explained as products of sintering of pre existing smaller idiomorphic crystals two possible mechanisms have been proposed for sintering of chromite crystals 1 amalgamation of a cluster of grains with the same original crystallographic orientation and 2 sintering of randomly orientated crystals followed by annealing into a single grain the ebsd data show no evidence for clusters of similarly oriented grains among the idiomorphic population nor for earlier presence of idiomorphic subgrains spatially related to inclusions and therefore are evidence against both of the proposed sintering mechanisms electron backscatter diffraction analysis maps show deformation related misorientations and curved subgrain boundaries within the large amoeboidal crystals and absence of such features in the fine grained population microstructures observed in the lower chromitite layer are interpreted as the result of deformation during compaction of the orthocumulate layers and constitute evidence for the formation of the amoeboid morphologies at an early stage of consolidation an alternative model is proposed whereby silicate inclusions are incorporated during maturation and recrystallisation of initially dendritic chromite crystals formed as a result of supercooling during emplacement of the lower chromite layer against cooler anorthosite during the magma influx that formed the merensky reef the upper chromite layer formed from a subsequent magma influx and hence lacked a mechanism to form dendritic chromite this accounts for the difference between the two layers

the last glacial maximum on spitsbergen svalbard most scientists have concluded previously that the west coast of spitsbergen svalbard remained ice free during the late weichselian between 25 000 and 10 000 yr b p we conclude that the glaciation was more extensive terraces that were postulated to have been ice free are covered by a thin late weichselian till sudden drop in the marine limit and basal radiocarbon dates of raised glaciomarine sediments demonstrates that the glaciers in the main fjords isfjorden and van mijenfjorden terminated west outside of the fjord mouths basal radiocarbon dates from glaciomarine clay above till in cores from the continental shelf west of spitsbergen yielded ages of about 12 500 yr b p from which we conclude that the ice extended to the shelf edge based on the extent of amino acid diagenesis in radiocarbon dated molluscs the duration of the maximum extension of the late weichselian glaciation was short certainly less than 10 000 years during the ice free period preceding that glaciation at least back to 40 000 yr b p the glaciers on svalbard were not significantly larger than at present as shown by marine deposits close to the glacier snouts many radiocarbon dates place deglaciation of the outer coast at about 12 500 yr b p at about 10 000 yr b p the rest of the archipelago rapidly became ice free

the decay of the barents ice sheet as documented in nordic seas ice rafted debris abstract a large marine based ice sheet that covered the barents sea and svalbard during the height of the weichselian glaciation began to disintegrate at 15 ka the decay produced enormous quantities of icebergs that drifted parallel to the norwegian continental margin southward and northwestward into the fram strait this drifttrack is reflected by a trace of ice rafted clastic sedimentary rocks from the bottom of the barents sea in deep sea sediments of the norwegian sea and the fram strait the petrographic composition of ice rafted lithic particles dropstones 0 5 mm in late quaternary 20 ka recent deep sea sediments of the norwegian greenland sea was analyzed in order to determine the source areas of the dropstones the dropstone provenance was deciphered from the regional distribution of some precisely defined lithotypes during the maximum glaciation between 20 and 15 ka the norwegian sea received crystalline rocks primarily from western norway but also from svalbard and the northwestern british isles the greenland sea was supplied with clay silt and sandstones from central and northern east greenland and rocks from circum arctic areas at 15 ka a dramatic shift in provenance from crystalline rocks to clastic sedimentary rocks is recorded in the dropstone composition of the northern and eastern norwegian sea this impulse was the ultimate result of the deterioration of the barents ice sheet the dispersal area of clastic rock fragments reaches from the barents shelf between 72 and 76 n and 15 and 20 e to the voring plateau eastern norwegian sea at 67 n and 5 e the main direction of iceberg drift was to the south and southeast after an initial period of only 500 years duration and extremely high dropstone deposition rates the influx from the barents shelf ceased and gradually changed into the modern surface current system

seismic architecture and sedimentology of a major grounding zone system deposited by the bjornoyrenna ice stream during late weichselian deglaciation abstract a 280 km wide sediment wedge in outer bjornoyrenna bear island trough south western barents sea has been investigated using 2d and 3d seismic data sediment gravity cores as well as regional swath and large scale bathymetry data the bathymetry data indicate a division into an up to 35 m high frontal wedge with large depressions and an upstream part characterized by mega scale glacial lineations msgl from seismic sections increasing erosion is demonstrated for the upstream part coinciding with the location of msgl whether the latter are depositional features postdating an extensive erosional event or formed by erosion remains inconclusive based on the distinct morphology and internal structures we infer that the system was deposited during a rapid readvance whereby the ice front pushed and bulldozed predominantly soft diluted proglacial sediments analyses in the eastern part of the sediment system reveal the existence of imbricated thrust sheets in the frontal part of the wedge this is suggested to imply upstream erosion of sedimentary rock and incorporation of thrusted blocks into the moraine forming a composite ridge locally we argue that observed large scale depressions are dead ice features in the marine environment it is envisioned that intense englacial thrusting may have developed into a decollement as the cold glacier snout got overrun by ice masses from the interior thereby enabling the inclusion of slabs of ice in the push moraine mass radiocarbon dates indicate that the sediment wedge was deposited around 17 090 cal yrs bp 14 530 14 c yrs bp and that the ice front probably remained stable until 16 580 cal yrs bp 13 835 14 c yrs bp

late cenozoic erosion of the high latitude southwestern barents sea shelf revisited the southwestern barents sea has experienced profound erosion during the last 2 7 m y that has resulted in the development of a characteristic glacial morphology of the continental shelf and deposition of a several kilometer thick sediment fan along the western margin prograding into the deep sea in the period from ca 2 7 to 1 5 ma proglacial processes including fluvial and glaciofluvial erosion dominated for this period the total average erosion of the shelf was 170 230 m the average erosion rate was 0 15 0 2 mm yr and the average sedimentation rates on the fan were 16 22 cm k y subglacial erosion affected an area of 575 000 km 2 during the period from ca 1 5 to 0 7 ma total average erosion is estimated at 330 420 m for this interval and the average erosion rate was 0 4 0 5 mm yr average sedimentation rates were 50 64 cm k y during the last 0 7 m y glacial erosion mainly has occurred beneath fast flowing paleo ice streams topographically confined to troughs 200 000 km 2 the total average erosion is estimated at 440 530 m average erosion rate is 0 6 0 8 mm yr and average sedimentation rate on the continental slope is 18 22 cm k y the amount of erosion was mainly determined by the duration of the glaciations and the location velocity and basal properties of the ice streams in total glacial erosion of the troughs has been relatively high throughout the last 2 7 m y at 1000 1100 m for the banks erosion is inferred to have increased from ca 2 7 ma to a peak between 1 5 and 0 7 ma subsequently little erosion occurred in these areas which implies a total of 500 650 m of erosion compared with other high latitude areas our rates are among the highest so far reported this comparison also demonstrates that there have been large variations in the rate of sediment delivery to the glaciated continental margins

hydrocarbon plumbing systems above the snohvit gas field structural control and implications for thermogenic methane leakage in the hammerfest basin sw barents sea abstract based on the analysis of the high resolution 3d seismic data from the sw barents sea we study the hydrocarbon plumbing system above the snohvit and albatross gas field to investigate the geo morphological manifestation and the dynamics of leakage from the reservoir fluid and gas escape to the seafloor is manifested in this area as mega pockmarks 1 2 km wide large pockmarks

ice stream flow switching during deglaciation of the southwestern barents sea ice streams dominate the discharge of continental ice sheets recent observations and reconstructions have revealed that large scale reorganizations in their flow trajectory flow switching can occur over relatively short time scales however the underlying causes of such behavior and the extent to which they are predictable are poorly known this paper documents a major episode of ice stream flow switching during the late weichselian deglaciation of the southwestern barents sea and explores various hypotheses for its causation regional bathymetric data show that two ice streams that had similar adjoining topographically constrained source areas had very different trajectories and dynamics on the outer shelf at the late weichselian maximum the hakjerringdjupet ice stream flowed westward along the cross shelf trough of hakjerringdjupet while the soroya trough ice stream flowed northward into ingoydjupet forming a tributary of the bjornoyrenna ice stream initial retreat of the hakjerringdjupet ice stream was rapid but with episodic periods of grounding as it retreated onto the higher rougher topography of the inner shelf we infer a reduction in ice velocity and a dramatic decrease in the pace of retreat as recorded by nested sequences of recessional moraines following and probably in response to this we suggest that there was a short lived surge readvance of an adjacent lobe onto fugloybanken in contrast the adjacent soroya trough ice stream remained active throughout deglaciation before retreating rapidly with no stillstands or readvances we argue that the different retreat histories of the ice streams were determined by variations in bed topography bathymetry which modulated the grounding line response to sea level variation such a mechanism is likely to be an important control on the long term behavior of marine based ice streams and outlet glaciers in antarctica and greenland and suggests that gathering data on their subglacial topography should be a priority

late weichselian and holocene sediment fluxes of the northern north sea margin abstract an event chronology has been determined for temporal and lateral magnitudes of material fluxes across the northern north sea margin including the norwegian channel and the north sea fan this has allowed the governing factors for the sediment processes on the margin to be estimated the chronological model of selected cores is based on 14 c ams dates regional tephra layers and planktonic foraminiferal stratigraphy based on this chronological framework the core sediments across the north sea margin have been divided into four main climatostratigraphic intervals a oldest dryas 15 13 ka b bolling allerod 13 11 ka c younger dryas 11 10 ka and d holocene 10 0 ka further the holocene period has also been divided into two subperiods the preboreal 10 9 ka and the holocene interglacial 9 0 ka creating five well defined lithological units deposition phases in all of which the deglaciation units 15 9 ka usually constitute 90 of the sediment budget the recognition of an almost identical lithological succession both in the records on the fan and in the high resolution record of the channel suggests that sedimentation on the north sea margin must be governed dominantly by regional sedimentary processes for each time interval the sedimentation rate in the norwegian channel is on average an order of magnitude higher than on the north sea fan diminishing distally from the shelf edge sedimentation under the holocene interglacial period 9 0 ka contrasts totally from the deglaciation pattern controlled dominantly by pelagic productivity in the area close to 50 of the hemipelagic sediments on the north sea margin are of bolling allerod age 15 13 ka this extreme sedimentation resulted from a combination of a rapid sea level rise constantly exposing new areas for marine erosion winnowing and aggressive surface ocean current activity surface ocean currents and the associated bottom currents provide the dominant control on the pattern of deglacial sedimentation on the north sea margin 15 9 ka this is especially apparent during the oldest dryas and the bolling allerod periods where the distribution pattern across the margin is essentially hydrodynamically controlled only during the younger dryas period are the surface ocean processes overprinted by sedimentary processes from melting icebergs the high resolution records reveal that the shifts in the lithological style of sedimentation are directly linked to the rapid reorganisation of the surface ocean system frequently taking place during the deglacial and holocene time period suggesting a fairly regional type of sedimentation pattern as the shift between the different lithological styles of sediments is both abrupt and regional they should be detectable on the seismic high frequency records

the barents sea ice sheet a model of its growth and decay during the last ice maximum on the basis of geomorphological and sedimentological data we believe that the entire barents sea was covered by grounded ice during the last glacial maximum 14c dates on shells embedded in tills suggest marine conditions in the barents sea as late as 22 ka bp and models of the deglaciation history based on uplift data from the northern norwegian coast suggest that significant parts of the barents sea ice sheet calved off as early as 15 ka bp the growth of the ice sheet is related to glacioeustatic fall and the exposure of shallow banks in the central barents sea where ice caps may develop and expand to finally coalesce with the expanding ice masses from svalbard and fennoscandia the outlined model for growth and decay of the barents sea ice sheet suggests a system which developed and existed under periods of maximum climatic deterioration and where its growth and decay were strongly related to the fall and rise of sea level

glacial geology of outer bjornoyrenna southwestern barents sea the upper cenozoic glacigenic succession in outer bjornoyrenna bear island trough southwestern barents sea is investigated utilizing data from six shallow boreholes 143 m below sea bed and seismic profiling overdeepened troughs in the lowermost part of a large plio pleistocene wedge at the shelf margin are interpreted as glacial erosion forms this suggests that the overlying succession which basinward attains a thickness of several km was deposited during a period with glaciations large scale possible sand ridges in the stratigraphic lower part of this succession are confined to two north south trending zones parallel to the present shelf break they probably formed in a continental shelf coastal environment with exceptionally high sediment supply and fluctuating relative sea level related to glaciations a core from a channel fill in the lower part of the succession consists of possibly glaciofluvial gravelly sand intercalated with till most of the other cores are dominated by middle and upper pleistocene muddy massive partly fissile diamictons interpreted to be mainly tills undrained shear strength of these cores ranges from about 20 kn m 2 to more than 300 kn m 2 and both underconsolidated intervals compared to the present burial depth are found an underconsolidated interval comprising eemian interglacial biourbated marine sediments overlain by laminated weichselian glaciomarine sediments on the outher shelf is covered by 50 100 m of muddy diamicton this diamicton is suggested to be mainly till deposited by a late weichselian ice sheet which was grounded to more than 500 m below present sea level earlier weichselian ice expansions did not reach the outer shelf based on the stratigraphy in the shallow cores and seismic interpretation we suggest that there have been five major expansions of grounded ice to the shelf break since ca 440 ka the present study suggests that glacial erosion was a major process in the late cenozoic denudation of the barents sea and in large areas perhaps as much as 200 250 m of preexisting strata could have been eroded by glaciers since about 440 ka

deglacial to holocene history of ice sheet retreat and bottom current strength on the western barents sea shelf abstract high resolution sediment echosounder data combined with radiocarbon dated sediment cores allowed us to reconstruct the late quaternary stratigraphic architecture of the kveithola trough and surrounding spitsbergenbanken the deposits display the successive deglacial retreat of the svalbard barents sea ice sheet basal subglacial till indicates that the grounded ice sheet covered both bank and trough during the late weichselian a glaciomarine blanket inside the trough coinciding with laminated plumites on the bank formed during the initial ice melting phase from at least 16 1 to 13 5 cal ka bp in close proximity to the ice margin after the establishment of open marine conditions at around 13 5 cal ka bp a sediment drift developed in the confined setting of the kveithola trough contemporary with crudely laminated mud an overlying lag deposit and modern bioclastic rich sand on spitsbergenbanken the kveithola drift shows a remarkable grain size coarsening from the moat towards the southern flank of the trough this trend contradicts the concept of a separated drift which would imply coarser grain sizes in proximity of the moat and indicates that the southern bank is the main sediment source for the coarse material building up the kveithola drift this depocenter represents therefore a yet undescribed combination of off bank wedge and confined drift although the deposits inside kveithola trough and on spitsbergenbanken display different depocenter geometries time equivalent grain size changes imply a region wide sediment dynamic connection we thus relate a phase of coarsest sediment supply 8 8 6 3 cal ka bp to an increase in bottom current strength which might be related to a stronger atlantic water inflow from the southeast across the bank leading to winnowing and off bank export of sandy sediments

response of the high latitude northern hemisphere to orbital climate forcing evidence from the nordic seas sediment cores from the nordic greenland iceland and norwegian seas provide evidence that this area acts as an initial responder to the forcing effect of orbitally driven changes in insolation on the climate system as postulated by j imbrie et al the 18 o record of the cores documents a widespread initial deglacial signal in the area between 15 and 13 ka 1000 yr before other deglacial signals from other parts of the northern hemisphere an even earlier meltwater event has been dated to 16 090 185 yr b p north of iceland at the initial rise of northern hemisphere insolation after the last glacial maximum during the period with lowered surface salinities the nordic seas were still cold reconstructions of the surface water conditions of the area show that as the summer insolation values of the northern hemisphere reached half of maximum values a sea ice free corridor opened along norway at 13 4 ka nearly contemporaneous fluctuations of the polar front and the sea surface temperatures with the insolation changes indicate that the nordic seas are very sensitive to insolation forcing especially in regions close to the sea ice margin a decrease in sea surface temperature and an increase in the areal extent of sea ice cover since 7 ka indicate that the area is currently on the way to glacial conditions supporting the predictions made earlier by j imbrie et al

constraints on the late weichselian ice sheet over the barents sea from observations of raised shorelines abstract direct evidence for late weichselian grounded glacier ice over extensive areas of the barents sea is based largely on indirect observations including elevations of old shorelines on svalbard and arguments of isostatic rebound such isostatic models are discussed here for two cases representing maximum and minimum ice sheet reconstructions in the former model the ice extends over the kara sea whereas in the latter the ice is limited to the barents sea and island archipelagos comparisons of predictions with observations from a number of areas including spitsbergen nordaustlandet edgeoya kong karls land franz josef land novaya zemlya and finnmark support arguments for the existence of a large ice sheet over the region at the time of the last glacial maximum this ice sheet is likely to have had the following characteristics conclusions that are independent of assumptions made about the earth s rheological parameters i the maximum thickness of this ice was about 1500 2000 m with the centre of the load occurring to the south and east of kong karls land ii the ice sheet extended out to the western edge of the continental shelf and its maximum thickness over western spitsbergen was about 800 m iii to the north of svalberg and frans josef land the ice sheet extended out to the northern shelf edge iv retreat of the grounded ice across the southern barents sea occurred relatively early such that this region was largely ice free by about 15 000 bp v by 12 000 bp the grounded ice had retreated to the northern archipelagos and was largely gone by 10 000 bp vi the ice sheet may have extended to the kara sea but ice thicknesses were only a fraction of those proposed in those reconstructions where the maximum ice thickness is centered on novaya zemlya models for the palaeobathymetry for the barents sea at the time of the last glacial maximum indicate that large parts of the barents sea were either very shallow or above sea level providing the opportunity for ice growth on the emerged plateaux as well as on the islands but only towards the end of the period of fennoscandian ice sheet build up

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

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

arctic ocean glacial history while there are numerous hypotheses concerning glacial interglacial environmental and climatic regime shifts in the arctic ocean a holistic view on the northern hemisphere s late quaternary ice sh

characterization of microbial activity in pockmark fields of the sw barents sea abstract multibeam bathymetry revealed the occurrence of numerous craterlike depressions so called pockmarks on the sea floor of the hammerfest basin and the loppa high south western barents sea to investigate whether these pockmarks are related to ongoing gas seepage microbial processes associated with methane metabolism were analyzed using geochemical biogeochemical and microbiological techniques gravity cores were collected along transects crossing individual pockmarks allowing a direct comparison between different locations inside assumed activity center on the rim and outside of a pockmark reference sites concentrations of hydrocarbons in the sediment particularly methane were measured as headspace free gas and in the occluded and adsorbed gas fraction down to a depth of 2 6 m below sea floor mbsf sulfate reduction rates were quantified by radiotracer incubations concentrations of dissolved sulfate in the porewater were determined as well neither the sulfate profiles nor the gas measurements show any evidence of microbial activity or active fluid venting methane concentrations and sulfate reduction rates were extremely low or even below the detection limit the results show that the observed sediment structures are most likely paleo pockmarks their formation probably occurred during the last deglaciation

cenozoic microfossils in northern finland local reworking or distant wind transport abstract allochthonous cenozoic microfossils have been reported from late pleistocene lake and mire host sediments across an area of 30 000 km2 in northern finland two main groups of microfossils are recognised palaeogene marine diatoms silicoflagellates and ebridians that include taxa from around the time of the palaeocene eocene thermal maximum and pliocene to early pleistocene freshwater diatoms the presence of these microfossils has been regarded as evidence that eocene marine and late neogene freshwater sediments formerly existed on the shield surface both groups have been referred to frequently in reconstructions of the sea level tectonic and erosion history of the northern fennoscandian shield the questions raised by the presence of allochthonous cenozoic microfossils in northern finland are however strongly resonant of the debate over the biota origin and age of the pliocene sirius group in antarctica where competing hypotheses have been put forward of local deposition and reworking versus distant wind transport of marine diatoms from the continental shelf this review explores alternative origins for the allochthonous cenozoic microfossils in northern finland local reworking of palaeogene marine sediments during pleistocene glaciation is unlikely as no source rocks of palaeogene age are known from the shield surface or from surrounding sedimentary basins in the baltic and white sea moreover at all sites except akanvaara the marine diatom taxa cover wide age ranges and occur only as minor components in diatom assemblages that are dominated by quaternary freshwater taxa local reworking of pliocene pleistocene freshwater diatoms is however compatible with the widespread survival of pre pleistocene deep weathering although no in situ or unmixed ice rafted pliocene pleistocene lacustrine sediment has yet been found an alternative origin for the marine palaeogene microfossils by distant wind transport is proposed in this hypothesis palaeogene diatomites on the barents sea shelf were exposed to deep glacial and fluvioglacial erosion during the pliocene and early pleistocene and in low sea level stages of the middle and late pleistocene intense wind action acting on comminuted mudstones on outwash plains carried dust including microfossils into northern fennoscandia to be deposited by rain out in lakes and wetlands this material may have been later further recycled by glacial and meltwater transport and more localised wind action processes that also may help to account for the distribution of eemian marine diatoms well beyond eemian shorelines the distant wind transport hypothesis implies that the presence of marine palaeogene diatoms on the shield surface in northern finland cannot be regarded as vestiges of former marine sediments and so do not constrain the tectonic and geomorphic history of the northern fennoscandian shield in the cenozoic

late glacial holocene clay minerals elucidating glacial history in the sw barents sea abstract detailed investigations of the distribution of clay minerals of late glacial holocene sediments from the sw barents sea provide important new information about the provenance and transport paths of the sediments this information leads to better understanding of the onset of the last deglaciation and subsequent advances retreats of the barents sea and fennoscandian ice sheets the results show interaction and changes in the fennoscandian ice sheet and bjornoyrenna ice stream during the last deglaciation high illite content and maximum kaolinite content 18 700 cal yr b p indicate glacial erosion from both the fennoscandian ice sheet and bjornoyrenna ice stream lgm ii the occurrence of a c reniforme dominated benthic foraminiferal assemblage 18 700 cal yr b p indicates that the northern most cores site in ingoydjupet had already been deglaciated and was probably situated in a glacier distal environment in addition smectite content reaching its highest level concurrent with the presence of neogloboquadrina pachyderma sin dominated planktic foraminifera can be related to the strengthening of the atlantic current the inflow of the atlantic water may have triggered deglaciation of the fennoscandian ice sheet bolling interstadial a rapid increase in illite content reflecting strong melting of the fennoscandian ice sheet 15 000 cal yr b p indicates the onset of deglaciation in a core closer to the continent decrease of illite and ird content together with the deposition of laminated sediments during the older dryas stadial 15 000 14 000 cal yr b p indicates colder conditions and formation of at least seasonal sea ice in addition increased kaolinite content indicates increased glacial erosion of the bjornoyrenna ice stream the highest values of illite content and increased ird content 14 000 13 000 cal yr b p can be related to strong melting of the fennoscandian ice sheet a slight indication of the younger dryas cold period is given by the decrease in illite and ird contents all clay contents are more stable during holocene compared to lgm and the last deglaciation

evidence from fram strait 78 n for early deglaciation recent syntheses of the history of the last northern hemisphere glaciation and deglaciation illustrate that understanding of the mechanisms and timing of deglaciation before approximately 12 000 years bp1 5 is limited after 12 000 yr bp however there is sufficient evidence from radiocarbon dated moraines raised beaches varved lake sediments and pollen records to provide a reasonable temporal and geographic picture of the decay of the ice sheets here we report on the first oxygen isotope record from the norwegian greenland sea that is radiocarbon dated directly by accelerator mass spectrometry a significant light oxygen isotope event is recorded at approximately 15 000 years bp which suggests that the marine based barents shelf ice sheet disintegrated rapidly at this time recent studies6 7 have estimated that the decay of this ice sheet could have contributed as much as 15 metres to eustatic sea level rise the decay of the barents shelf ice sheet is the earliest major deglacial event yet dated and may have triggered subsequent deglacial events through eustatic sea level effects

the last interglacial glacial period on spitsbergen svalbard the glaciation history of svalbard 78 n and the nw barents sea is reconstructed for the last 130 ka based on studies of sediments exposed in coastal cliffs at the head of isfjorden four different till beds separated by marine sediments are recognized the lowest marine formation containing mytilus edulis reflects warmer conditions than at present and is correlated with the last interglacial the eemian of europe and oxygen isotope substage 5e in the deep sea the post eemian tills are inferred to represent major glaciations around 110 ka bp 75 50 ka bp and 25 10 ka bp during the intervening intervals the glaciers on svalbard were not significantly larger than at present and the nw barents sea was probably ice free the ice free periods named phantomodden and kapp ekholm interstadials lasted from about 110 to 75 and from 50 to 25 ka bp respectively the marine fauna from both these interstadials indicate seasonally ice free conditions the ages of the recorded glaciations coincide with or are slightly younger than periods with insolation minima which at this latitude is determined by a low tilt of the earth s axis thus we postulate that the quaternary glaciations of svalbard were driven by orbital variations with the 41 ka tilt period in contrast to the lower latitude glaciations of scandinavia that were partly driven by the precession cycle with a periodicity of around 23 ka