quaternary sediments and environments on the continental shelf off northern norway abstract based on lithologic palaeontologic and chronostratigraphic investigations of close to 200 gravity cores from troughs deep banks and shallow banks the following late quaternary environment can be outlined in the weichselian deposition of basal tills was followed by deposition of laminated clay in a sea ice environment later a pebbly pelite was deposited in the troughs at the same time as the banks were iceberg ploughed then 13 000 yrs b p a period with incipient winnowing occurred on the deep banks and deposition of sandy pelite took place in the troughs the holocene commenced with a marked environmental change due to intrusion of atlantic water the fauna changed from arctic to boreal high energy winnowing forming a lag deposit took place on the banks and high accumulation rates in the troughs occurred due to the winnowing and sediment influx from the downwasting continental icesheet during the later part of the holocene the winnowing diminished on the deeper banks on the shallow banks and on the shelf break it still prevails and in the troughs calcareous sandy mud is being deposited the surface sediments comprise three main facies bouldery and pebbly sand sand and sandy mud whose distribution mainly depends on the prevailing bottom current regime the composition of the older quaternary sediments is demonstrated by some selected seismic profiles

a re evaluation of the pleistocene behavior of the scoresby sund sector of the greenland ice sheet limited data on the past dynamics of the greenland ice sheet exceeding the ice core records have led to partly contradictory reconstructions whereas the scoresby sund sector of the greenland ice sheet has been suggested to be stable and not much larger than at present during the peak pleistocene glaciations the southeastern sector of the ice sheet has been inferred to be much more dynamic here we present seismic data showing that glacigenic debris flow deposits dominate the younger than ca 2 58 ma succession of the scoresby sund trough mouth fan on the east greenland continental margin suggesting much more frequent expansions of the greenland ice sheet to the shelf break than found previously from our new observations of the pleistocene stratigraphy we revise previous findings and conclude that the scoresby sund sector of the greenland ice sheet during the pleistocene 1 developed in line with other parts of the east greenland ice sheet and 2 was more dynamic and sensitive to past climatic changes than hitherto realized this rapid response of the glacier to climate forcing indicates how dynamic is the glacier ice front and what one might expect of the glacier as the influences of climate warming become more pronounced

the quaternary geology of the labrador shelf the regional distribution of glacial and postglacial sediments on the labrador shelf was mapped by medium and high resolution seismics and shows a succession of tills that extend to the continental shelf edge at approximately 600 m the uppermost of these tills is less laterally extensive and does not occur on the labrador shelf bank tops in water depths less than 160 m we infer that the last glacial episode was less extensive than the preceding ones glaciomarine stratified silts and postglacial muds are found overlying the upper till in the deep basins that separate the banks the upper till glaciomarine silts and postglacial muds are interpreted to constitute one complete deglacial cycle radiocarbon age determination suggests this deglacial sequence began at approximately 20 000 years bp on the northernmost labrador shelf and hudson strait seismic evidence indicates a late glacial readvance locally deposited a till that overlies the glaciomarine sediments associated with the last glacial advance

seismic stratigraphy of the central bransfield basin nw antarctic peninsula interpretation of deposits and sedimentary processes in a glacio marine environment abstract the central bransfield basin is a deep narrow trough between the northern tip of the antarctic peninsula and the south shetland islands analyses of single channel high resolution seismic reflection data are used to characterise the seismic stratigraphy of the central bransfield basin the tectonised acoustic basement is overlain by a 1 s thick sedimentary cover composed of two main sedimentary sequences the lower sequence which shows synsedimentary deformation has only been identified on the antarctic peninsula margin the upper sequence is a complex sedimentary package composed of eight seismic units whose distribution geometry and seismic facies allow two types of seismic units to be distinguished slope and basinal units the slope units constituted by progradational stratified seismic facies form a sedimentary wedge extending from the shelf edge the basinal units fill the basin floor showing chaotic and undulated seismic facies that change basinward into stratified seismic facies both types of seismic units display an interfingering pattern at the base of the slope suggesting an alternating shift of the sedimentary depocentre from the slope to the basinfloor and vice versa this alternate pattern indicates that the sedimentary processes responsible for the infilling of the central bransfield basin followed a cyclic pattern which has likely been associated with the advance and retreat of the ice sheets over the margins during glacial and interglacial episodes during glacial periods the ice sheets advanced eroded the shallower sea floor areas and deposited diamicton and debris flow deposits along the moving grounding line resulting in a progradational sedimentary wedge on the slope at the end of glacial periods coinciding with the retreat of the ice sheets extensive sediment failures affected the continental margin during interglacial periods the ice sheets remained restricted to coastal locations and glacial troughs where processes of meltwater formation might have been significant sediment laden underflows are generated within these troughs from where they flow and spread over the shelf and down the slope to the basinfloor as sediment gravity flow deposits the combined effect of these processes is a progradational build up of the shelf and an aggradational infilling of the basin floor together with the development of the interfingering pattern at the base of the slope

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

geophysical evidence of a late pleistocene glaciation and paleo ice stream on the atlantic continental shelf offshore massachusetts usa abstract interpretations of seismic reflection data collected offshore massachusetts usa reveal the first conclusive geophysical evidence of a pre wisconsinan glaciation that extended beyond the limits of the last glacial maximum lgm in the region the data image numerous glacial geomorphic features that define the extent of a paleo ice stream including 1 a regionally distributed erosion surface that forms a 50 km wide trough with steeply eroded sidewalls 4 18 and nearly 100 m in relief at the margins 2 a network of sub ice sheet meltwater channels and 3 a transparent glacigenic seismic unit the orientation of the paleo ice stream trough indicates that the ice stream flowed to the south southwest toward the shelf break this suggests that the ice stream formed further to the north where it appears that georges bank southeast of the gulf of maine usa redirected ice flow limited well data constrain the glacial erosion event up to 300 m below sea level to occur within the pleistocene the glacial event represents a time of larger ice volume on the northern atlantic continental shelf as compared to the lgm thus we suggest that the event corresponds to marine oxygen isotope stage 12 late pleistocene when the first major pleistocene shelf crossing glaciation began offshore southeastern canada these geophysical constraints on a late pleistocene glaciation offshore massachusetts have important implications for 1 models of the laurentide ice sheet as the geomorphic evidence of pre lgm ice streams are difficult to characterize yet account for most of the ice sheet s mass flux and 2 the pore water salinity pattern offshore new england as sedimentary basins near an ice sheet margin often contain large volumes of glacially emplaced freshwater

late quaternary iceberg rafted detritus events on the denmark strait southeast greenland continental slope 65 n related to north atlantic heinrich events hu93030 007 lcf 65o01 39 0 n and 30o14 81 0 w is a 4 5 m long giant 11 cm diameter piston core from 1800 m water depth on the continental slope south of the denmark strait sill the core sampled acoustically stratified sediments at a site below the kangerlussuaq trough nine ams 14 c dates on planktic foraminifera indicate that the core spans 14 to 28 14 c ka the sediments consists of two principal lithofacies lithofacies i li comprises tan ochre intervals with abundant ice rafted sandstone siltstone clasts larger than 2 mm and with an average thickness of 47 cm it is also associated with peaks in carbonate content and toc lithofacies ii lii consists of fine grained dark gray hemipelagic sediment there are three distinct intervals of li dated between 14 3 and 15 5 lic 20 1 and 21 9 lib 24 7 and 25 8 lia ka the ages suggest that deposition of li is approximately coeval with heinrich events 1 and 2 in the north atlantic whereas lia appears younger than h 3 lithofacies i is derived from far travelled ice bergs from an unknown source but not from the northeastern laurentide ice sheet stable isotope studies on neogloboquadrina pachydermasinistral show little evidence for significant meltwater events associated with li but surprisingly light oxygen isotopic events are present in the benthic foraminiferal analyses cibicidoides wuellerstorfiand melonis zaandamae the ages of the hu93030 007 iceberg rafted detritus ird events are similar to ird peaks in cores north of denmark strait on the east greenland slope hu87033 009 lcf se baffin slope 62o30 99 0 n and 59o26 82 0 w 1437 m wd is situated in a similar position to hu93030 007 but with respect to the laurentide ice sheet its d 18 o record on planktic foraminifera is virtually identical to that of hu93030 007 the timing of ird events is similar in both these cores between 14 and 30 ka h 3 may be present in hu87033 009 as an ird event but in contrast to h 1 and h 2 it is not evident as a discernible detrital carbonate event 1998 elsevier science b v all rights reserved

geophysical investigations of a high latitude submarine channel system and associated channel mouth lobe in the lofoten basin polar north atlantic the lofoten basin channel forms one of two major submarine channels on the norwegian margin of the polar north atlantic the channel system connects upslope with the andoya canyon which is the only canyon to cut back across the continental shelf in this region high resolution geophysical records including multibeam swath bathymetric and tobi side scan sonar data show that the distal part of the channel system is braided and connects to a low gradient 0 01 channel mouth lobe on the abyssal plain of the lofoten basin geophysical data indicate that the channel floor is composed of sandy material deposited by turbidity currents these turbidity currents spilled out over the channel sides to deposit acoustically stratified sediment in the channel levees side scan sonar data supplemented by sediment cores indicate that the channel mouth lobe is sandy in composition the lofoten channel and its associated channel mouth lobe is therefore related to turbidity current activity and formation of the system appears to pre date the holocene morphological variation between the upper reaches of the andoya canyon lofoten channel system and the submarine channels of the greenland basin is proposed to relate to differences in the nature of the flows feeding both systems the andoya canyon lofoten channel system bears strong similarities to some mid and low latitude submarine fans with respect to its morphology and architecture

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

pliocene pleistocene glaciomarine sedimentation in eastern prydz bay and development of the prydz trough mouth fan odp sites 1166 and 1167 east antarctica abstract lithostratigraphy grain sizes and down hole logs of site 1166 on the continental shelf and site 1167 on the upper slope are analyzed to reconstruct glacial processes in eastern prydz bay and the development of the prydz trough mouth fan in eastern prydz bay upper pliocene lower pleistocene glaciomarine sediments occur interbedded with open marine muds and grade upward into waterlaid tills and subglacial tills lower pleistocene sediments of the trough mouth fan consist of coarse grained debrites interbedded with bottom current deposits and hemipelagic muds indicating repeated advances and retreats of the lambert glacier amery ice shelf system with respect to the shelf break systematic fluctuations in lithofacies and down hole logs characterize the upper pliocene lower pleistocene transition at sites 1166 and 1167 and indicate that an ice stream advanced and retreated within the prydz channel until the mid pleistocene the record from site 1167 shows that the grounding line of the lambert glacier did not extend to the shelf break after 0 78 ma published ice rafted debris records in the southern ocean show peak abundances in the pliocene and the early pleistocene suggesting a link between the nature of the glacial drainage system as recorded by the trough mouth fans and increased delivery of ice rafted debris to the southern ocean

reactivation of precambrian faults on the southwestern continental margin of india evidence from gravity anomalies abstract gravimetric and bathymetric studies on the southwestern continental margin of india confirm the extension of onshore nw se nnw sse n s ne sw ene wsw and e w trending lineaments of precambrian age over a considerable distance into the offshore region the bight in the bathymetry off coondapoor the offsets of bessas de pedro bank and the cora divh island of the laccadive group the prathap ridge and the inferred mid shelf basement ridge suggest block movements on the southwestern continental margin the physiographic expression on the prathap ridge around 14 20 n and 72 50 e is unaffected by some of the ene wsw lineaments which probably indicates that these lineaments predate the evolution of the topographic expression as seafloor spreading advanced with respect to the carlsberg ridge some of the ene wsw and ne sw lineaments on the western continental margin appear to have been reactivated and block movements took place the presence of a basement ridge in the mid shelf and the shelf margin basement high prathap ridge west of the slope resembles the structural style of a passive continental margin

alkenones and coccoliths in ice rafted debris during the last glacial maximum in the north atlantic implications for the use of uk37 as a sea surface temperature proxy the uk37 index has proven to be a robust proxy to estimate past sea surface temperatures ssts over a range of time scales but like any other proxy it has uncertainties for instance in reconstructions of the last glacial maximum lgm in the northern north atlantic uk37 indicates higher temperatures than those derived from foraminiferal proxies here we evaluate whether such warm glacial estimates are caused by the advection of reworked alkenones in ice rafted debris ird to deep sea sediments we have quantified both coccolith assemblages and alkenones in sediments from glaciogenic debris flows in the continental margins of the northern north atlantic and from a deep sea core from the reykjanes ridge certain debris flow deposits in the north atlantic were generated by the presence of massive ice sheets in the past and their associated ice streams such deposits are composed of the same materials that were present in the ird at the time they were generated we conclude that ice rafting from some locations was a transport pathway to the deep sea floor of reworked alkenones and pre quaternary coccolith species during glacial stages but that not all of the ird contained alkenones even when reworked coccoliths were present we speculate that the ratio of reworked coccoliths to alkenone concentration might be useful to infer whether significant reworked alkenone inputs from ird did occur at a particular site in the glacial north atlantic we also observe that alkenones in some of the debris flows contain a colder signal than estimated for lgm sediments in the northern north atlantic this is also clear in the deep sea core studied where the warmest intervals do not correspond to the intervals with large inputs of reworked coccoliths or ird we conclude that any possible bias to uk37 estimates associated with reworked alkenones is not necessarily towards higher values and that the high sst anomalies for the lgm are unlikely to be the result of a bias caused by ird inputs

late cenozoic evolution of high gradient trough mouth fans and canyons on the glaciated continental margin offshore troms northern norway paleoclimatic implications and sediment yield trough mouth fans contain information about the evolution of high latitude continental margins including rates of glacial sedimentation and hinterland erosion here the late cenozoic evolution of high gradient trough mouth fans and canyons on the troms margin northern norway is reconstructed paleocanyons were active prior to the quaternary glaciations glaciomarine and glaciofluvial conditions prevailed between ca 2 7 ma and ca 1 5 ma and ice sheets possibly reached the paleo shelf break at least once the minimum average sedimentation rate of this period was 0 22 m k y from ca 1 5 ma to ca 0 7 ma the glaciations intensified and fast flowing ice streams reaching the shelf break were established in the cross shelf troughs subglacial deformation till was deposited at the outer shelf and later reworked by debris flows and turbidity currents the fennoscandian ice sheet started to route much of its ice mass to the north and south of the study area and so the troms margin possibly was a low ice flow sector from this time with a minimum average sedimentation rate of 0 15 m k y during the last ca 0 7 m y ice streams continued to traverse the troughs while sluggish flowing ice prevailed on the banks a minimum average sedimentation rate of 0 14 m k y is estimated for this period the minimum total erosion and erosion rate for the quaternary are 50 140 m and 0 02 0 05 m k y respectively compared with previous studies from other areas this implies up to one order of magnitude variation in average glacial erosion rates along the western sector of the fennoscandian barents sea ice sheets this is interpreted to be due to the size and bedrock composition of the catchment areas and the timing of ice growth and ice sheet dynamics in addition the steep preglacial continental slope promoted high sediment flow velocity for the glacigenic sediments causing much of the debris flows to transform into turbidity currents which efficiently transported sediments across the slope and thereby maintained its steep gradient

pleistocene glacial history of the nw european continental margin abstract in this paper new and previously published data on the pleistocene glacial impact on the nw european margin from ireland to svalbard between c 48 n 80 n are compiled the morphology of the glaciated part of the european margin strongly reflects repeated occurrence of fast moving ice streams creating numerous glacial troughs channels that are separated by shallow bank areas end moraines have been identified at several locations on the shelf suggesting shelf edge glaciation along the major part of the margin during the last glacial maximum deposition of stacked units of glacigenic debris flows on the continental slope form fans at a number of locations from 55 n and northwards whereas the margin to the south of this is characterised by the presence of submarine canyons glaciation curves based primarily on information from the glacial fed fan systems that depict the pleistocene trends in extent of glaciations along the margin have been compiled these curves suggest that extensive shelf glaciations started around svalbard at 1 6 1 3 ma while repeated periods of shelf edge glaciations on the uk margin started with mis 12 c 0 45 ma the available evidence for mis 2 suggest that shelf edge glaciation for the whole margin was reached between c 28 and 22 14 c ka bp and maximum positions after this were more limited in some regions north sea and lofoten the last glacial advance on the margin has been dated to 15 13 5 14 c ka bp and by c 13 14 c ka bp the shelf areas were completely deglaciated the younger dryas loch lomond advance reached the coastal areas in only a few regions

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

late quaternary palaeoenvironment and chronology in the traenadjupet slide area offshore norway the northern mid norwegian continental slope was studied based on high resolution side scan sonar data multibeam bathymetry high resolution and multichannel seismics together with gravity cores sedimentary provinces identified include a partly buried slide on the eastern inner voring plateau an area dominated by glacigenic debris flows south west of the traenadjupet slide the traenadjupet slide and an area of glacimarine sedimentation and a slide scar north east of the traenadjupet slide the traenadjupet slide affected an area of about 14100 km2 and mobilised about 900 km3 of sediments little is known about the areal extent and volume of the older events the glacigenic debris flows and glacimarine sediments were deposited while the fennoscandian ice sheet was at the shelf break during the late weichselian glacial maximum prior to 13 2 14c kyr bp hemipelagic and or contouritic sedimentation prevailed during the holocene period two large slide scars were probably formed sometime prior to or during the late weichselian glacial maximum inner voring plateau and north east of the traenadjupet slide and another during the mid holocene interglacial period immediately prior to 4000 14c kyr bp the traenadjupet slide the two older scars may represent one event or two separate events deposition of poorly permeable glacigenic sediments over high water content fine grained hemipelagic and or contourites may have prevented water escape and increased failure potential thus continental slope areas of episodically high sediment input of glacigenic sediments are prone to failure as illustrated by this study which has identified at least two large slope failures failures have occurred both during glacial maxima periods of climate deterioration and low global eustatic sea level and during interglacials as today with improved climatic conditions and a high global eustatic sea level

mud aprons in front of svalbard surge moraines evidence of subglacial deforming layers or proglacial glaciotectonics abstract large debris flow units commonly occur on the distal sides of subaqueous end moraines deposited by surges of svalbard tidewater glaciers but have rarely been described in terrestrial settings some researchers have argued that these kinds of debris flows reflect processes unique to the subaqueous environment such as the extrusion of subglacial deforming layers or extensive failure of oversteepened moraine fronts in this paper we describe terrestrial and subaqueous parts of a single late holocene moraine system deposited by a major surge of the tidewater glacier paulabreen in west spitsbergen the ice marginal landforms on land closely resemble the corresponding landforms on the seabed as evidenced by geomorphic mapping and geophysical profiles from both environments both onland and offshore extensive areas of hummocky moraine occur on the proximal side of the maximum glacier position and large mud aprons interpreted as debris flows occur on the distal side we show that the debris flow sediments were pushed in front of the advancing glacier as a continuously failing mobile push moraine we propose that the mud aprons are end members of a proglacial landforms continuum that has thrust block moraines as the opposite end member two clusters of dates 8000 ybp and 700 ybp have previously been interpreted to indicate two separate surges responsible for the moraine formation new dates suggest that the early cluster indicates a local extinction of the abounded species chlamys islandica other changes corresponding to the widespread 8 2 ka event within the fjord may suggest that the extinction of the c islandica corresponds to that time

seismic stratigraphy of the central basin in northwestern ross sea slope and rise antarctica clues to the late cenozoic ice sheet dynamics and bottom current activity abstract sedimentation processes influenced by late cenozoic ice sheet dynamics and bottom current activity can be extracted from the seismic stratigraphic record of the ross sea continental slope and rise where more continuous sedimentary successions are preserved compared to the continental shelf in this study we present a seismic stratigraphic analysis of the central basin that lies in the northwestern ross sea using newly acquired and existing legacy seismic reflection data that are correlated to adjacent scientific drill sites the chronostratigraphy of ross sea seismic sequences lying above the mid miocene sequence boundary rsu4 ca 16 5 15 5 ma is based on the former antarctic offshore stratigraphy antostrat project depth contour and isopach maps of sedimentary sequences bounded by two major unconformities of rsu4 and rsu2 the late pliocene boundary ca 4 0 2 8 ma and the present day seafloor were produced to illustrate the evolution of paleo seafloor morphology distribution of sediments and depocenter migration in the western ross sea outer margin the results of seismic stratigraphic analysis indicate that gravity sedimentation processes dominated the central basin infill up to the mid miocene and then downslope sediment supply gradually diminished through the late miocene and quaternary likely reflecting a shift toward a cooler less erosive glacial regime change since the late pliocene a topset truncated glacial prograding wedge developed in the upper continental slope at the mouth of the joides basin and the sediment depocenter was shifted from the basin floor to the upper slope suggesting the more persistent occurrence of grounded ice sheets on the outer continental shelf meanwhile persistent along slope bottom current processes formed contourites on the slope and over the crests of banks surrounding the central basin since the mid miocene in the late pliocene the contourites that formed off the joides basin mouth were overlain by glaciogenic debris flows while the growth of contourites continued over and along the flanks of banks farther to the north this suggests that along slope bottom current processes near the joides basin mouth were diminished or dominated by the glacial discharge to the continental shelf edge the sediment stacking patterns differ between the joides central basins and the drygalski adare basins located on the westernmost ross sea margin suggesting that distinctive glacial interglacial behavior of the former grounded ice streams and sediment supplies in the troughs feeding these basins were largely controlled by the paleo seafloor morphology of the western ross sea continental shelf

magnetic studies of basement off the coast of bombay west of india abstract bathymetric and total magnetic intensity data along 45 closely spaced profiles in 20 100 m of water totalling 2400 line km were collected on the continental shelf off bombay west of india magnetic intensity anomaly maps were prepared the anomalies show prominent trends in e w nnw sse and ene wsw directions correlations of the anomaly signatures with the geology known from the drill well logs and seismic results infer 1 1 the mostly basaltic nature of the basement overlain by the tertiary sediments except in the murud depression and isolated patches of the bombay high and inner shelf where granites are interpreted 2 2 the lateral extent of the two nnw sse trending regional faults between longitudes 70 50 e and 71 40 e 3 3 the outlines of the magnetic signatures associated with the structural highs and depressions two dimensional model and spectral studies of the anomalies under numerical constraints have revealed the structure of the basement overlain by 1 5 5 0 km thick sediments a crustal section along a transect across the inner shelf the bassein high structure and the offshore basin in the middle shelf the bombay high structure in the middle outer shelf and further west is interpreted the section depicts the structure of the tertiary sediments the late cretaceous early tertiary basalts and the archaean precambrian granites thick basalt constructs occur in the paleoslopes of the archaean precambrian basement down faulting of parts of the western indian peninsula into the arabian sea along the regional faults is suggested due to the lithologically similar sequences of the tertiary sediments the basalts deccan traps and granitic gneisses of the study and onshore areas therefore the area is considered to be divided into three structural blocks consisting of the inner shelf the offshore basin and the bombay high separated by nnw sse trending deep seated faults which result from rifting of the crust the basement faults mostly extending to the overlying young sediments and the tectogenes indicate a continued stress regime the continued subsidence both mechanical and thermal of the crust in the study area under increased sediments the drift of the indian continent from the south to the present latitudes and the dynamic interaction of the oceanic continental lithospheres appear to deform the crust by thinning and shearing

precise three dimensional stereo localization of corner reflectors and persistent scatterers with terrasar x this paper reports on the absolute 3 d localization of radar corner reflectors and persistent scatterers pss by stereo synthetic aperture radar sar carried out with terrasar x and tandem x the novel combination of rigorously linearized range doppler equations with thorough sensor modeling consideration of atmospheric delays geodynamic signals satellite dynamics and geometrical calibration allows a direct target localization at the centimeter level therefore there is no need for the application of geocoding since our approach delivers 3 d positions directly in the international terrestrial reference frame itrf 2008 four radar corner reflectors located at the wettzell geodetic observatory metsahovi geodetic observatory and german antarctic receiving station o higgins were localized in 3 d with a precision better than 4 cm by introducing an updated geometrical calibration of terrasar x and tandem x the absolute accuracy of the same level becomes possible which was demonstrated by externally validating the reflector positions at metsahovi and wettzell against results of terrestrial geodetic surveying furthermore pss located in berlin were retrieved with a precision of 10 cm making the method a suitable tool for radar positioning in urban environments potential fields of application for our approach are the joint analysis with phase based methods geometrical calibration of radar satellites and direct integration of sar observations into global navigation satellite system networks

reefal coralline algal build ups within the arctic circle morphology and sedimentary dynamics under extreme environmental seasonality abstract carbonate frameworks secreted by phototrophic organisms within the arctic circle are not well documented underwater surveys of the inner shelf off troms northern norway 70 n reveal extended fixed algal build ups which are fringed by rhodolith belts affected by storms reefd growth by coralline algae under temperature and light regimes of extreme seasonality is made possible because of a decoupling of carbon fixation during summer and utilization of stored carbon during the period of winter darkness although the annual growth of the framework constructing algae is comparatively low the annual carbonate production rate is similar to subtropical tropical counterparts because of a remarkably high standing stock early diagenetic alteration is restricted to intraparticle cementation processes which start in vivo bioerosional destruction is the dominant control on the preservation of high latitude build ups preservation of holocene autochthonous coralline algal biostromes is enhanced by rapid burial during storm events redeposition during storms is the most important process in forming a distinct sedimentary facies zonation

ichnofabrics of a pleistocene slope succession new jersey margin relations to climate and sea level dynamics abstract trace fossil and sedimentologic data were collected at 10 cm intervals throughout a virtually continuous 520 m thick upper pleistocene siliciclastic succession recovered at odp site 1073 new jersey margin these data were examined in the context of isotopic seismic and palynologic proxies to document depositional and ichnologic responses to quaternary climate and sea level dynamics in an upper slope setting two broad texturally defined sedimentary facies assemblages are recognized the clay rich assemblage reflects relatively rapid deposition in part from turbidity currents and suspended plumes and appears to be linked to cooler sea level fall and lowstand phases the sand rich assemblage reflects overall slower sedimentation by offshelf spillover and periodic winnowing and erosion under the influence of contour and other bottom currents during warmer transgressive highstand phases facies of the sand rich assemblage muds sandy muds muddy sands and sands are completely bioturbated and are characterized by high densities of biogenic structures including distinct burrow forms in contrast the clay rich assemblage includes facies that exhibit limited biogenic disruption laminated clay silty clay and graded silt or fine sand to clay couplets and on the whole is characterized by lower densities of biogenic structures most of which are diffuse burrow mottles these ichnofabric trends reflect changes in ecological and taphonomic parameters e g substrate stability and consistency residence time of sediments in the benthic boundary layer and degree of inter and intrabed textural variability many of which were governed by variations in sedimentation rate as mediated by glacio eustacy recurring identifiable ichnofossils are most common in facies of the sand rich assemblage in the upper half of the pleistocene succession finer grained components of this assemblage e g muds and sandy muds representing quieter phases of highstand deposition are characterized by a low diversity distal cruziana ichnofacies assemblage dominated by schaubcylindrichnus and phycosiphon anconichnus both of which represent the work of deposit feeding worms narrow facies transitions that correspond to phases of rapid transgression are marked by occurrences of thalassinoides these crustacean burrow systems were excavated in coarser grained higher energy facies sands and muddy sands and in closely associated firmground substrates produced by exhumation of consolidated muds by bottom currents and or mass wasting processes the association of firmground ichnofabrics with marine flooding events in an upper slope setting demonstrates that the sequence stratigraphic utility of the glossifungites ichnofacies extends beyond shelf depositional sequences to deeper water deposits the distribution of texturally defined facies and general ichnofabric parameters e g degree of bioturbation appears to respond to glacio eustatic cycles through the entire pleistocene record however the schaubcylindrichnus phycosiphon assemblage and thalassinoides are rare or absent altogether in the lower half of the succession indicating that biological responses to and the ichnologic record of climate and sea level dynamics may be strongly dependent on margin physiographic and bathymetric evolution

a model of basement structure from magnetic anomalies of the bombay high oil field west of india abstract bathymetric and magnetic data along 25 profiles covering the bombay high and adjacent area on the mid shelf and inner shelf off the bombay coast are studied except for the nw se and ene wsw trending anomaly closures in the east of the high the magnetic anomalies mostly trend e w correlation of the anomalies with well logs reveals that the positive magnetic anomalies arise from the basalts deccan traps underlain by granites two dimensional model studies of the anomalies under numerical constraints reveal 1 the structure of the magnetic basement and 2 sediments of 2 0 to 3 5 km thickness resting on the basalts the latter reaching 0 8 km in thickness maps of the surface model of the basalts and granites the basalt isopachs and the nature of the basement are prepared the basement structure models with steep slopes in the south and discontinuous zones in the east which are interpreted in terms of pre to post basement faults the faults which are of regional extent divide the crustal blocks underlying the mid shelf from those of the inner shelf the significance of the present study is discussed in the context of hotspot and plate tectonic concepts relating to mascarene plateau and western india

extension of structural and tectonic trends from the indian subcontinent into the eastern arabian sea abstract trends of basement highs faults and structural patterns on the india pakistan indus continental shelf and slope and in the deep waters extending to the lakshmi laxmi chagos laccadive ridge complex in the eastern arabian sea are parallel to the ancient precambrian structural and tectonic grain of the indian subcontinent these trends the occurrence of horst graben style features of the basement of the lakshmi ridge and of the region north and east of it both in deep waters and shelf areas and the oceanic nature of the basement west of the ridge suggest that the rifted transitional crust extends as far as the lakshmi chagos laccadive ridge complex the extension of rifted crust with horst graben style tectonic features into deep offshore areas of the arabian sea has implications for future hydrocarbon exploration in the region

very high resolution spaceborne sar tomography in urban environment synthetic aperture radar tomography tomosar extends the synthetic aperture principle into the elevation direction for 3 d imaging it uses stacks of several acquisitions from slightly different viewing angles the elevation aperture to reconstruct the reflectivity function along the elevation direction by means of spectral analysis for every azimuth range pixel the new class of meter resolution spaceborne sar systems terrasar x and cosmo skymed offers a tremendous improvement in tomographic reconstruction of urban areas and man made infrastructure the high resolution fits well to the inherent scale of buildings floor height distance of windows etc this paper demonstrates the tomographic potential of these sars and the achievable quality on the basis of terrasar x spotlight data of urban environment a new wiener type regularization to the singular value decomposition method equivalent to a maximum a posteriori estimator for tomosar is introduced and is extended to the differential case 4 d i e space time different model selection schemes for the estimation of the number of scatterers in a resolution cell are compared and proven to be applicable in practice two parametric estimation algorithms of the scatterers elevation and their velocities are evaluated first 3 d and 4 d reconstructions of an entire building complex including its radar reflectivity with very high level of detail from spaceborne sar data by pixelwise tomosar are presented

study of the atmospheric pressure loading signal in very long baseline interferometry observations 1 redistribution of air masses due to atmospheric circulation causes loading deformation of the earth s crust which can be as large as 20 mm for the vertical component and 3 mm for horizontal components rigorous computation of site displacements caused by pressure loading requires knowledge of the surface pressure field over the entire earth surface a procedure for computing three dimensional displacements of geodetic sites of interest using a 6 hourly pressure field from the national centers for environmental prediction numerical weather models and the ponte and ray 2002 model of atmospheric tides is presented we investigated possible error sources and found that the errors of our pressure loading time series are below the 15 level we validated our model by estimating the admittance factors of the pressure loading time series using a data set of 3 5 million very long baseline interferometry observations from 1980 to 2002 the admittance factors averaged over all sites are 0 95 0 02 for the vertical displacement and 1 00 0 07 for the horizontal displacements for the first time horizontal displacements caused by atmospheric pressure loading have been detected the closeness of these admittance factors to unity allows us to conclude that on average our model quantitatively agrees with the observations within the error budget of the model at the same time we found that the model is not accurate for several stations that are near a coast or in mountain regions we conclude that our model is suitable for routine data reduction of space geodesy observations

cenozoic exhumation on the southwestern barents shelf estimates and uncertainties constrained from compaction and thermal maturity analyses abstract the barents sea is believed to have been influenced in most parts by cenozoic uplift and erosion episodes the rocks in the area are not currently at their maximum burial depth the exhumation of the sedimentary rocks has had large effects on rock physical properties and hydrocarbon maturation and migration the current study seeks to estimate exhumation from shale compaction and thermal maturity techniques and discuss its implications for hydrocarbon exploration in the uplifted barents sea area this study uses well logs and thermal maturity data together with widely distributed shot gather data along long offset seismic reflection lines the use of shale compaction techniques to estimate exhumation was focused particularly on the regionally preserved aptian albian kolmule formation and paleogene torsk formation shales normal compaction reference curves were established for these units in areas currently at their maximum burial depth e g sorvestsnaget basin and vestbakken volcanic province the results suggest widespread cenozoic exhumation throughout the southwestern barents sea the exhumation magnitudes increase towards east and northeast the average exhumation estimates from the three data sources range from 800 to 1400 m within the hammerfest basin 1150 1950 m on the loppa high 1200 1400 m on the finmark platform and 1250 2400 m on the bjarmeland platform the marked differences in glacial erosion from mass balance and average erosion estimates from the current study suggest a significant pre glacial uplift and erosion in the southwestern barents sea area the observed stratigraphy and presence of significant volumes of late oligocene middle miocene sediments in basins at the outer margin and increased erosion rates at the same time in source areas suggest that maximum burial in the southwestern barents sea may have occurred sometime during the oligocene or even earlier in the eocene the results from this study are useful input for modelling of source rock maturation generation migration and trapping of hydrocarbons in the area these results are also an important input for the prediction of more precise reservoir and seal rock properties in frontier areas away from the exploration wells and provide valuable knowledge for the use of interval velocities in the uplifted areas

organo and lithofacies of glacial interglacial deposits in the norwegian greenland sea responses to paleoceanographic and paleoclimatic changes abstract based on a multiparameter approach a combined litho and organofacies concept was developed for glacial and interglacial sediment sections along an e w transect through the central part of the norwegian greenland sea ngs modern and past surface water regimes are clearly displayed by specific litho and organofacies patterns interglacial conditions reveal specific atlantic water associated lithofacies a and b3 in the eastern and central sector of the norwegian greenland sea ngs corresponding interglacial organofacies in general are not well correlated to lithofacies due to strong diagenetic degradation of labile e g autochthonous organic matter om while in near surface sediments a marine dominated organofacies i 1 is preserved under atlantic water masses this correlation is not evident for lower holocene and isotope stage 5 deposits however during isotopic event 5 5 1 increased proportions of marine om are recorded in a high accumulating core on the voring plateau glaciomarine background lithofacies b and c indicate minor input of ice rafted debris ird and seasonal variable sea ice cover corresponding organofacies ii 1 non oxidized and ii 2 oxidized are dominated by allochthonous om most spectacular are glacial diamictons lithofacies e and f evidencing short term sediment pulses due to a sudden disintegration of far advanced tide water ice margins on the outer shelves these diamictons bear specific organofacies iii 1 and iii 2 with a clear predominance of terrigenous and reworked om some of the diamictons seem to occur contemporaneous with the so called heinrich layers h1 and h2 suggesting a common trigger mechanism for the almost simultaneous disintegration of huge continental ice masses along the shelves of north america and the eastern margin of the ngs application of a combined organo and lithofacies concept provides essential information on spatial and temporal variations of water mass characteristics the oceanic effects of ice sheet dynamics and circulation models

seismic facies changes along a nearly continuous 24 latitudinal transect the fjords of chile and the northern antarctic peninsula abstract high resolution seismic reflection profiles and piston cores from bays fjords and straits of the inland passage of chile and the northern antarctic peninsula region were used to examine changes in seismic facies along a nearly continuous 24 latitudinal transect that encompasses temperate subpolar and polar climatic regimes these climatic regimes are characterized by differences in seismic facies eight seismic facies are recognized on the basis of reflection character intensity of acoustic contrast at bounding surfaces and external shape of the unit the northern and central chilean fjord region is a temperate maritime setting characterized by thick ice proximal and ice distal glacial marine strata and a variety of morainal features the southern inland passage and the south shetland islands of antarctica represent transitional sub polar glacial marine settings these areas are characterized by relict ice proximal glacialmarine facies and relatively thin ice distal glacial marine facies morainal ridges occur in bays and fjords of chile the northern antarctic peninsula is a polar climatic setting the straits bays and fjords of the region have been virtually scraped clean of sediments a thin draping glacial marine unit occurs locally in these areas

antarctic palaeo ice streams we review the geomorphological sedimentological and chronological evidence for palaeo ice streams on the continental shelf of antarctica and use this information to investigate basal conditions and processes and to identify factors controlling grounding line retreat a comprehensive circum antarctic inventory of known palaeo ice streams their basal characteristics and minimum ages for their retreat following the last glacial maximum lgm is also provided antarctic palaeo ice streams are identified by a set of diagnostic landforms that nonetheless display considerable spatial variability due to the influence of substrate flow velocity and subglacial processes during the lgm palaeo ice streams extended via bathymetric troughs to the shelf edge of the antarctic peninsula and west antarctica and typically to the mid outer shelf of east antarctica the retreat history of the antarctic ice sheet since the lgm is characterised by considerable asynchroneity with individual ice streams exhibiting different retreat histories this variability allows antarctic palaeo ice streams to be classified into discrete retreat styles and the controls on grounding line retreat to be investigated such analysis highlights the important impact of internal factors on ice stream dynamics such as bed characteristics and slope and drainage basin size whilst grounding line retreat may be triggered and to some extent paced by external atmospheric and oceanic forcing the individual characteristics of each ice stream will modulate the precise timing and rate of retreat through time

isostatic response to glacial erosion deposition and ice loading impact on hydrocarbon traps of the southwestern barents sea abstract previous work indicates that a part of hydrocarbon loss from traps in the barents sea is attributed to the pleistocene glacially related spillage due to isostatically driven depth changes and tilting it is however unknown how severe the pleistocene spillage was and how much hydrocarbons were depleted due to other mechanisms including leakage and pre glacial spillage in addition it remains uncertain how much the orientation of the hydrocarbon traps and thus trap capacities and spill directions was affected by glacial sediment redistribution and ice loading the effect of the pleistocene burial history on trap capacity and spillage is addressed by using a combination of the flexural isostasy and secondary migration modelling the impact is modelled in three trap structures in the bjornoyrenna fault complex the results show that the pleistocene burial history led to either increase or decrease the trap capacities in the range of 5 14 the geometrical changes also affected the spill directions of some of the traps apart from the tilt magnitude the most important factor controlling the trap capacity change and spill directions in the analyzed traps was the initial geometric setting of the traps the traps in the western barents sea with present spill points to the west and south experienced trap capacity increase and were not susceptible to spillage during the pleistocene location of the pre glacial spill points determines whether the traps with the present spill points to the east and north experienced capacity increase or reduction structural changes of the traps caused only by the tilting could not have resulted in major loss of oil and gas the tilting together with gas volume expansion might however have been responsible for some part of the hydrocarbon loss during the cenozoic

crustal structure from deep seismic soundings along the koyna ii kelsi loni profile in the deccan trap area india abstract the crustal depth section obtained from deep seismic soundings along the koyna ii kelsi loni profile which lies near latitude 18 n roughly in the east west direction in that part of the deccan trap maharashtra state india shows a number of reflection segments below the deccan traps down to the moho discontinuity a deep fault below the deccan traps 13 km east of mahad divides the entire cross section including the moho boundary into two crustal blocks the reflection segments show updip towards the west coast in the western block the moho discontinuity which is at a depth of 39 km near the deep fault starts rising towards the coast reaching a depth of 31 5 km at the west coast the eastern block is thrown up by 1 5 km with respect to the western block along the deep fault a structural contour map of the moho discontinuity for the koyna reservoir area has been prepared from the present results and the crustal information obtained along the koyna i profile kaila et al 1979a shows that the deep fault in the koyna area is aligned in the nnw sse direction refraction seismic data analysis by the wave front method reveals that the thickness of the deccan trap increases towards the west coast the deccan trap is 600 700 m thick in the eastern region between nira sp 130 and loni sp 200 and attains a thickness of 1500 m at 10 km east of the west coast the longitudinal wave velocity in the deccan traps along the profile varies from 4 8 to 5 0 km sec and in the crystalline basement from 6 0 to 6 15 km sec a tentative isopach contour map of the deccan traps and a tentative structural contour map of the pre deccan trap contact have been prepared for the koyna reservoir area from the results along the koyna ii and koyna i profiles a flexure aligned in a nnw sse direction in the pre deccan trap contact which is an expression of the deep fault into the basement has been clearly brought out the flexure coincides in general with the orientation of the deccan volcanic scarp in this area

nature and classification of waterlain glaciogenic sediments exemplified by pleistocene late paleozoic and late precambrian deposits this study of waterlain glaciogenic sediments is designed to present both a review and new information on glaciogenic subaquatic deposits of differing age in a number of localities in north and south america and south africa the late paleozoic glaciogenic deposits of the parana basin in brazil and the karoo basin of south africa are singled out for special attention as they show a reasonably complete lateral sequence of terrestrial to off shore glaciogenic sedimentation although the environment of subaquatic glaciogenic sedimentation varies from one area to the next certain common elements are found which can be used to develop a generalized model for both glaciomarine and glaciolacustrine sedimentation for descriptive purposes the model is divided into two broad categories a shelf facies and a basinal facies the shelf facies is marked by massive diamicton ite which may be 200 m or more in thickness and which is frequently overlain by a complex of clastic sediments consisting primarily of gravity and fluid flows the basinal facies is marked by products of subaquatic slumps and more distal turbidites and glaciomarine sediments new terminology is introduced the massive diamicton ite which is diagnostic of the shelf facies probably represents deposition from the base of active ice in a subaquatic environment and is termed undermelt diamicton ite the gravity and fluid flows which are usually found overlying undermelt diamicton ite and in the basinal facies are subdivided into six categories glaciogenic subaquatic outwash glaciogenic suspension flow glaciogenic chaotic debris flow glaciogenic subaquatic debris flow glaciogenic slurry flow and glaciogenic turbidity flow the relative abundance of undermelt diamicton ite and the various types of gravity and fluid flows can be used to define inner shelf outer shelf inner basin and outer basin facies of glaciomarine sedimentation

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

models of glaciomarine sedimentation and their application to the interpretation of ancient glacial sequences abstract this paper argues that glaciomarine environments can be regarded as special glacially influenced types of continental margin environments e g continental shelf slope rise and basin plain knowledge of the stratigraphic architecture and typical sedimentary sequences of non glacial margins is becoming well known but remains limited for those that have been glacially modified the principal influences on sedimentation in these environments relate to the glacial sediment input controlled by relief of basin margin glacier thermal regime and ice flow dynamics and depositional environments influence of traction currents substrate relief and proximity to nearby ice margins typical ranges of sedimentation rates can be established for glacially influenced continental margin environments and these may provide a framework for ancient sequences starvation of sediment supply to glacially influenced continental margins is common the nature of sub ice shelf sedimentation a model that has been applied to many ancient glacial sequences is critically reviewed the significance of such sedimentation in the rock record has probably been exaggerated because of oversimplistic interpretations of diamictite sequences existing process models of glaciomarine sedimentation derived from study of modern environments are sometimes difficult to employ in investigation of ancient sedimentary sequences because simple lithofacies criteria and typical vertical profiles are not available to aid in interpretation in addition compositional data emphasized by many workers for distinguishing glaciomarine from continental glacial diamict ite s frequently fingerprint sediment source and not mode of deposition the importance of facies analysis methods for isolating depositional environments is illustrated by three examples of ancient glaciomarine sequences these are the early proterozoic gowganda formation 2 3 ga of northern ontario canada the late proterozoic port askaig formation 670 ma of scotland and ireland and the late cenozoic yakataga formation 20 ma to recent of the gulf of alaska these examples illustrate the significance of detailed genetic studies of ancient glacial rocks in the interpretation of palaeogeographic and tectonic settings diamictite units in ancient glaciomarine sequences cannot be easily interpreted in terms of climatic or ice advance retreat cycles because of the varied controls on diamict accumulation and diamictite preservation in marine basins

glacimarine processes and inductive lithofacies modelling of ice shelf and tidewater glacier sediments based on quaternary examples abstract three variables control the type of glacial debris source and where and when debris is introduced to an ocean 1 type of glacial ice source ice sheet or valley glacier 2 condition of a grounded glacier melting freezing or frozen base and cold or warm internal ice and 3 type of glacier front ice shelf or tidewater using these variables in different combinations eight glacimarine regimes are postulated to exist by integrating information from holocene sediment and pleistocene glacimarine sequences with the eight inductive regimes lithofacies relationships are predicted and modelled the models show a complexity of glacimarine lithofacies the importance of recognizing this complexity lies in realistic interpretations of ancient sequences ice shelf sediment may be limited in the geologic record because of tectonic and climatic constraints required for ice shelf formation alternatively in some tidewater glacier regimes larger volumes of glacimarine sediment are produced than in ice shelf regimes ice proximal sediment is distinctive especially near subglacial meltwater stream effluxes ice shelves and tidewater glaciers may produce similar ice proximal lithofacies e g morainal bank associations and laminites in certain regimes however details of lithofacies may aid in distinguishing ice shelf from tidewater regimes ice shelf and tidewater iceberg zone sediment can be distinguished from each other if basal and high level englacial debris can be distinguished ice shelf zone sediment out from the grounding line has a basal debris source high level englacial debris is deposited in more distal ice shelf zones resulting in sediment by pass in corresponding positions of a tidewater glacier regime iceberg rafted debris comprises mixed basal and high level englacial debris deeper water zones receive large volumes of sediment when a melting freezing base grounding line is at the edge of a continental shelf when the grounding line retreats sediment supply may be drastically reduced because of a back sloping continental shelf and trapping by morainal banks cool water bioclastic carbonates may accumulate once a grounding line has retreated although ice shelf iceberg zones are more extensive than those in tidewater regimes ice shelf icebergs have low debris content and resulting ice rafted debris may be scarce the smallest volume of sediment is produced by a frozen base ice sheet ending as a tidewater front and the largest volume by a melting freezing base valley tidewater glacier glacimarine sediment has a relatively high preservation potential near continental interiors or margins however at continental margins mass flow olistostrome and tectonic melange deposits may be preserved with glacimarine diamictites these deposits may be difficult to distinguish from each other especially if metamorphosed such as at a convergent margin the models presented do not fully represent the glacimarine environment because many other variables are omitted however the principal concepts of generating glacimarine lithofacies associations are considered continued research will verify if each regime exists and will provide data on those regimes that exist today to compare and modify these models

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

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

late 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

problems in applying preservation facies and sequence models to sinian neoproterozoic glacial sequences in australia and asia abstract the sinian 800 530 ma is an extraordinary period of earth history characterized by the transition from simple to complex multicellular organisms and by extreme variations in climate eustasy and possibly tectonics understanding sinian stratigraphy may help interpret the co evolution of life and environment during the period though sinian successions are poorly dated and difficult to correlate preservation facies and sequence models based on mesozoic recent successions may be used to interpret them preservation models based on basin subsidence permit estimates of how thick and complete successions can be in different tectonic settings and how long it took for them to be deposited facies models for rift craton shelf slope and basin environments help in identification of these different tectonic settings sequence models facilitate interpretation of the interplay of tectonic subsidence eustasy rates of sedimentation and climate such models applied to the sinian successions of australia and asia indicate the following great shallowing upwards megacycles occur in sinian successions and each ends with regional glaciations deep rift basins formed around 850 800 ma preserve the oldest megacycles but these basins soon were filled with rapidly deposited glaciogenic sediments relatively complete sequences are found only in deep basins subject to repeated rifting cratons and shallow shelves preserve only the youngest megacycles older deposits have been removed by younger glacial advances deep shelves and slopes preserve one to three megacycles depending on the timing of the start of passive margin subsidence megasequences can be correlated based on limited radiometric dating and inferred regional distribution of unique rock types but these sequences are not developed to the same extent in all blocks problems in correlating the four great megacycles recognized elsewhere with those of asia will persist until the requisite facies analysis and u pb dating of interbedded volcanics are done

the late weichselian glaciation of the franz victoria trough northern barents sea ice sheet extent and timing high resolution seismic profiles parasound 4 khz and three sediment cores from the franz victoria trough and the adjacent continental slope were studied in order to constrain the timing and extent of the northern svalbard barents sea ice sheet during the late weichselian glaciation stacked debris flow lobes and layers of glacimarine diamicton on the lower continental slope indicate that large quantities of glacially derived sediments were deposited by the northern svalbard barents sea ice sheet directly onto the upper continental slope at approximately 23 14 c ka a grounding line advance to the shelf break is supported by the identification of diamicton interpreted as till in the seismic profile near the shelf break after several ice sheet instabilities marked by significant input of ice rafted detritus to the continental margin the disintegration of the northern svalbard barents sea ice sheet termination ia is indicated by a distinct pulse of ice rafted detritus at 15 4 14 c ka and the transition to an isotopically defined meltwater signal the drastic change in sedimentary pattern on the upper continental slope dated to about 13 4 14 c ka is interpreted as grounding line retreat from the shelf edge a further stepwise retreat of the northern svalbard barents sea ice sheet is indicated by pulses of ice rafted detritus which appear to be contemporaneous with the onset of distinct ice rafting events in adjacent areas and pulses of glacimarine sedimentation in the southwestern barents sea q 2000 elsevier science b v all rights reserved

sedimentary facies and depositional architecture of ice contact glaciomarine systems abstract the characteristics of ice contact glaciomarine systems are reviewed based on a range of weichselian and holocene examples from the fjordal basins in norway and svalbard these depositional systems occur as large morphological ridges end moraines including push moraines which are coarse grained and show large scale foreset bedding the paper addresses some of the major problems with regard to the recognition classification and stratigraphic analysis of these systems the ice proximal glaciomarine systems are classified here into three categories 1 ice contact submarine fans 2 ice contact deltas and 3 glaciofluvial deltas this classification integrates morphological and sedimentological criteria and renders these glaciomarine systems not only easier to recognize in the stratigraphic record but also possible to compare with common non glacial deltaic systems the emphasis is on the criteria for the recognition of the ice contact glaciomarine systems i e ice contact fans and ice contact deltas and their discrimination from common gilbert type deltas and fan deltas the review further focuses on ice contact glaciomarine systems as highly sensitive recorders of glacier dynamics and climatic fluctuations it is shown that both the periods of ice front stability and changes in the ice front position as well as the magnitude and rate of those changes are all recorded in the ice contact depositional system the sedimentary record further reflects glacio isostatic sea level changes and local palaeogeography a new conceptual model is suggested which places these ice contact glaciomarine systems in a dynamic stratigraphic context the model integrates sedimentary facies and their depositional architecture in an allostratigraphic framework and is meant to be a guide for the analysis of the sedimentary record of ice contact systems

marine magnetic anomalies off ratnagiri western continental shelf of india abstract total magnetic intensity and bathymetric surveys were carried out in the offshore area of ratnagiri on the western continental shelf of india and an isomagnetic anomalies map at a contour interval of 50 nt was prepared which reveals n s trends of magnetic anomalies two dimensional model and spectral studies of these anomalies were carried out and subsurface models of the geology in the area have been derived from anomalies at a number of places the results suggest that the anomalies occur over a magnetic crystalline basement at a depth of 1 1 2 km which is similar in magnetization to onshore basalts of northwest india these anomalies are believed to be an expression of a considerable thickness around 1 7 km of basalt underlain by sediments identification of these basalts in offshore areas along the northwestern continental shelf of india would support 1 the idea that the onshore deccan basalts of western india and the rhyolitic tuffs at the laccadive ridge system dsdp site 210 are related to the same volcanic events and 2 subsequent downfaulting of onshore deccan basalts into the arabian sea and submergence below the tertiary sediments

the glacier fed fan at the mouth of storfjorden trough western barents sea a comparative study the middle and late pleistocene succession on the glacier fed fan at the mouth of storfjorden trough was studied using high resolution seismic data seven glacial advances to the shelf break during middle and late pleistocene resulted in episodic high sediment input to the fan with real sedimentation rates of up to 172 cm 1000 years separated by sediment starved interstadials and interglacials on the upper fan the high sediment input resulted in frequent slides and slumps generating debris flows which dominate the mid fan strata compared with the larger neighbouring bear island trough mouth fan the storfjorden trough mouth fan has a steeper fan gradient narrower thinner and shorter debris flow deposits and lower frequency of large scale sliding glacier fed submarine fans receive their main sediment input from a glacier margin at the shelf break as opposed to river fed fans where sediment input occurs through a channel levee complex as a result the depocentre of a river fed fan is found on the mid fan and the upper slope is mainly an area of sediment bypass whereas the glacier fed fan has an elongated depocentre across the uppermost fan the river fed fans are dominated by deposition from turbidity currents whereas glacier fed fans are dominated by debris flow deposits

three dimensional deformation monitoring of urban infrastructure by tomographic sar using multitrack terrasar x data stacks differential synthetic aperture radar tomography d tomosar similar to its conventional counterparts such as differential interferometric sar and persistent scatterer interferometry is only capable of capturing 1 d deformation along the satellite s line of sight in this paper we propose a method based on l1 norm minimization within local spatial cubes to reconstruct 3 d displacement vectors from tomosar point clouds available from at least three different viewing geometries the methodology is applied on two pairs of cross heading combination of ascending and descending terrasar x ts x spotlight image stacks over the city of berlin the linear deformation rate and the amplitude of seasonal deformation are decomposed and the results from two test sites with remarkable deformation pattern are discussed in detail the results to our knowledge demonstrate the first attempt for motion decomposition using tomosar data from multiple viewing geometries

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

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

modern nearshore cold temperate calcareous sediments in the troms district northern norway abstract during the past 6400 years rocky coastal platforms and outer fjord troughs in the troms district northern norway 70 n became sites of considerable production and deposition of skeletal carbonate in a cold temperate environment under arctic solar radiation conditions because of poleward heat transfer by the norwegian current along the eastern margin of the north atlantic ocean the cold temperate marine climate persists beyond the arctic circle in the shallow subtidal zone carbonate generation is confined to benthic macroalgal ecosystems along the wave exposed margins of the coastal platforms kelp forests provide habitats for numerous carbonate secreting organisms such as barnacles echinoids and bivalves kelp with attached calcareous organisms is involved in many redistributional processes such as rafting and phylloid drift reef growth of coralline algae together with maerl deposits and rhodolith pavements dominate in wave sheltered platform areas this windward leeward zonation of carbonate production along the rocky coasts reflects specific properties of coralline algae versus kelp to withstand physical disturbances of episodic storms carbonate sediment in gullies or outer fjord troughs consists of molluscs bryozoans benthic foraminifers and verrucid barnacles terrigenous sediment loads delivered as spring meltwater discharge is trapped in the inner fjord troughs hydrodynamic concentration of calcareous skeletons is fostered by a complex topography that offers numerous sediment trapping areas along the rocky coastline and outer fjord troughs physiological adaptation of coralline algae to cope with extreme seasonality in solar radiation is a prerequisite for the formation of coralline algal reefs beyond the arctic circle which have carbonate production rates near those of subtropical coralline algal grounds

geolocation and stereo height estimation using terrasar x spotlight image data we have studied the geographic position of several high resolution spotlight tsx images by investigating the location of deployed radar corner reflectors results show that the geolocation accuracy is better than the resolution cell in both azimuth and range directions the same corner reflectors as well as distinct points on buildings are used to estimate the absolute height from stereo viewing spotlight tsx images to within a few decimeters accuracy

subsurface precambrian ridge on the continental shelf of western india between coondapoor and kasaragod abstract bathymetric and magnetic data along seven ene wsw and seventeen nnw sse and n s profiles collected on the southwestern continental shelf of india between coondapoor and kasaragod within water depths of 20 2000 m are studied model studies of magnetic data suggest that the depth to the top of the basement in the study area varies from 1 0 to 4 0 km and provide evidence for the occurrence of a graben below the inner shelf and basement ridge below the mid shelf it is also suggested that the inferred basement ridge below the mid shelf is of continental type and precambrian in age

late quaternary ice flow and sediment delivery through hinlopen trough northern svalbard margin submarine landforms and depositional fan abstract the morphology and distribution of submarine landforms in hinlopen trough northern svalbard margin and the upper continental slope beyond are investigated using swath bathymetric data together with side scan sonar acoustic profiler records and sediment cores sun illuminated images reveal a number of landform assemblages on the sea floor of hinlopen trough and confirm that this depression was occupied by an ice stream during the late weichselian glaciation around 20 ka before present the geomorphology of the inner shelf is characterised by bedrock drumlins and ice sculpted bedrock there is a middle shelf transition from a rock bed to an unconsolidated sedimentary bed that contains highly attenuated drumlins and megaflutes formed within a dark grey matrix supported diamict interpreted as subglacial till outer shelf landforms are mainly iceberg ploughmarks the geomorphological imprint identified from hinlopen trough is similar to that of many former ice streams the trough is dominated by elongate landforms orientated parallel to the inferred flow direction and is lacking in transverse features indicative of inter ice stream locations a characteristic down flow progression in landform elongation is also observed suggesting an increase in ice velocity across the continental shelf the lack of grounding zone features imaged from swath bathymetric data implies that deglaciation was probably rapid within the trough a large depositional fan exists on the upper continental slope beyond the trough characterised by debris flow deposits relating to the down slope transport of glacigenic sediment order of magnitude calculations of the volume of glacigenic sediment on the continental slope indicate that the ice stream provided high rates of debris delivery of around 5 7 5 m ka this suggests that hinlopen trough ice stream represented a major route for the transfer of ice and debris to the hinlopen fan on the northern continental margin of svalbard during the late weichselian glaciation

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

geodetic sar tomography in this paper we propose a framework referred to as geodetic synthetic aperture radar sar tomography that fuses the sar imaging geodesy and tomographic sar inversion tomosar approaches to obtain absolute 3 d positions of a large amount of natural scatterers the methodology is applied on four very high resolution terrasar x spotlight image stacks acquired over the city of berlin since all the tomosar estimates are relative to the same reference point object whose absolute 3 d positions are retrieved by means of stereo sar the point clouds reconstructed using data acquired from different viewing angles can be geodetically fused to assess the accuracy of the position estimates the resulting absolute shadow free 3 d tomosar point clouds are compared with a digital surface model obtained by airborne lidar it is demonstrated that an absolute positioning accuracy of around 20 cm and a meter order relative positioning accuracy can be achieved by the proposed framework using terrasar x data

the late mesozoic and cenozoic evolution of the sorvestsnaget basin a tectonostratigraphic mirror for regional events along the southwestern barents sea margin abstract seismic interpretation and mapping of the sorvestsnaget basin at the southwestern barents sea margin has revealed a complex basin history related to large scale plate tectonic movements in the norwegian greenland sea area the pre cenozoic evolution of the sorvestsnaget basin is poorly understood due to lack of well data and poor seismic data quality regional pre cenozoic geologic models that includes the sorvestsnaget basin should await more and better data prior to break up and sea floor spreading in the norwegian greenland sea late cretaceous and palaeocene shear movements along the senja fracture zone led to structuring and possibly elevation of the southern part of the basin as sea floor spreading took place and propagated northwards along the senja fracture zone the western areas of the basin were uplifted and eroded two large and two smaller intrabasinal features in the southern sorvestsnaget basin are characterised by a low values on the gravimetric anomaly maps b surrounding synforms and c little response on magnetic anomaly maps the features have been interpreted as salt structures the tertiary evolution of intrabasinal salt structures seems to have been governed by extensional faulting and subsidence of the margin during the late palaeocene and eocene periods the oligocene and miocene periods were characterised by local and regional uplift of the sorvestsnaget basin respectively during these periods the area in particular the western part of the basin was subjected to transpressional compressional forces which can be tentatively correlated to contemporaneous large scale plate reorganisations and variations of sea floor spreading rates in the norwegian greenland sea the oligocene and miocene transpressional compressional events influenced the salt structures and is here suggested to be partially responsible for the complex expression of the largest salt structures the late neogene and pleistocene periods are represented by a thick westward prograding wedge indicating subsiden3e with coinciding high sediment input to and minor adjustment of the salt structures in the sorvestsnaget basin

depositional processes on the distal scoresby trough mouth fan odp site 987 implications for the pleistocene evolution of the scoresby sund sector of the greenland ice sheet accepted manuscript version licensed cc by nc nd 4 0 published version available at https doi org 10 1016 j margeo 2017 11 018

the barra fan a bottom current reworked glacially fed submarine fan system abstract on the basis of sedimentary structures textures and ichofauna seven depositional facies have been recognised in cores from the barra fan region of the hebrides slope sedimentary facies are combined into three genetic groups a c that represent their primary mode of deposition a sandy to muddy contourite facies a a1 and a2 which represent an overall coarsening upward sequence caused by an increase in bottom current velocity over time b disorganised glaciomarine deposits including the glaciomarine dumpstone of facies b and facies b1 deposited as a result of ice rafting and glaciomarine sedimentation and c hemipelagite facies c and c1 which are the result of normal marine hemipelagic settling it is most likely that all contourite facies a a2 identified in this study are holocene in terms of its diverse morphological elements and varied facies this high latitude submarine fan is truly composite in nature however a broad three stage glacial to post glacial evolutionary system is recognised during which different processes and process combinations were dominant during the last glacial period low stand system tract downslope processes including debris flows and minor turbidity currents sculpted an irregular slope topography little in the way of bottom current activity was evident staged deglaciation was accompanied by rising sea level and high sedimentation rates across the region this created an unstable margin prone to extensive sliding and slumping that masked any effects of an incipient alongslope current the present high stand system tract is dominated by a strong slope current that became fully active during the early part of the holocene low sedimentation rates diminished sediment supply and strong bottom current activity led to development of the sandy contourite sheeted drift system across the mid slope region little downslope movement is evident during this period so that the slope topography is being slowly smoothed and remoulded by active bottom currents

imaging geodesy toward centimeter level ranging accuracy with terrasar x in this paper we report on experiments to measure large scale earth surface displacements such as those caused by solid earth tides with centimeter level accuracy using terrasar x radar images with two totally different approaches corner reflectors and image correlation techniques we show the clear interrelation between the radar range measurements and the projection of the solid earth tide motion vector onto the radar line of sight pixel location accuracies of up to 2 6 cm standard deviation can be achieved after a single calibration we further demonstrate that solid earth tides and tropospheric water vapor variations are the largest sources of ranging error if not compensated for alternatively tropospheric water vapor can be estimated with centimeter accuracy using our proposed technique of synthetic aperture radar sar image correlation and solid earth motion compensation by the existing models we also consider ionospheric delays which improve the results marginally in the x band our results show the best ranging accuracies so far reported for spaceborne radar amplitude images and make terrasar x together with our simple compensation methodology suitable for the imaging of centimeter level earth displacements absolute measurements of volcanoes or glaciers are possible without the use of ground equipment and without the use of sar interferometry thus avoiding the associated problems of phase ambiguity phase unwrapping and reference points

till and moraine emplacement in a deforming bed surge an example from a marine environment the glacier sefstrombreen in spitsbergen surged across an arm of the sea between qsr 1882 and 1886 and rode up onto the island coraholmen marine and terrestrial geological observations and archive records show that the glacier advanced on a deforming carpet of marine mud which was eroded from its original location transported and smeared over the sea bed and coraholmen as a deformation till the glacier emplaced about 210sm 0 2 km 3 of drift in the terminal 2 km of its advance in a maximum of 14 years leaving a thickness of up to 20 m on coraholmen which was doubled in size as a result during the surge subglacial muds were characterised by high water pressures low effective pressures and low frictional resistance to glacier movement original sedimentary inhomogenities permit fold structures to be identified but repeated refolding and progressive remoulding produce mixing and homogenisation of deformation tills the surge was probably shortlived and as the heavily crevassed glacier stagnated underlying water saturated muds were intruded into crevasses and then extruded on the glacier surface reticulate crevasse intrusion ridges on coraholmen and the sea floor reflect the orientation of surge generated crevasses water and sediment was also extruded beyond the glacier at its maximum extent to form extensive flows producing till tongues both on coraholmen and the sea floor extending over 1 3 km from the glacier it is argued that subglacial deformation of pre existing sediment will almost invariably be associated with glaciation of marine areas and that this process will not only produce deformation tills through remoulding of pre existing sediments but will also play a fundamental role in glacier dynamics criteria which perrait glacial tills produced by such events from marine and glaciomarine muds are discussed copyright 1996 elsevier science ltd