assemblages of submarine landforms produced by tidewater glaciers in svalbard 1 high resolution swath bathymetry from the marine margins of several svalbard tidewater glaciers shows an assemblage of submarine landforms that is probably linked to glacier surging these landforms are essentially unmodified since their initial deposition over the past hundred years or so because they have not been subjected to subaerial erosion or periglacial activity swath images comprise an assemblage of superimposed landforms allowing reconstruction of relative age of deposition 1 large transverse ridges interpreted as recessional moraines overridden by a subsequent ice advance 2 a series of curvilinear streamlined bedforms orientated parallel to former ice flow interpreted as lineations formed subglacially during rapid advance 3 large terminal ridges marking the farthest extent of ice at the last advance with flow lobes immediately beyond interpreted as submarine debris flows 4 a series of interconnected rhombohedral ridges interpreted as a product of soft sediment squeezing into crevasses formed at the glacier bed probably formed during immediate post surge stagnation and 5 a series of fairly evenly spaced small transverse ridges interpreted as push moraines produced annually at tidewater glacier termini during retreat a simple descriptive landsystem model for tidewater glaciers of probable surge type is derived from these observations we also show that megascale glacial lineations can form not only beneath large ice streams but are also produced beneath surging tidewater glaciers lying on deforming sedimentary beds

submarine landforms in the fjords of southern chile implications for glacimarine processes and sedimentation in a mild glacier influenced environment abstract chilean fjords are the lowest latitude at which glaciers reach the sea today high accumulation and mass throughput sustain tidewater glacier margins in this relatively mild climatic and oceanographic setting 27 000 km 2 of swath bathymetry allow mapping of sea floor landforms and inferences on glacimarine sediments and sedimentation tidewater glaciers are present in several fjords beyond retreating tempano glacier a terminal moraine marks the limit of probable little ice age advance with smaller transverse ridges closer to the glacier beyond advancing pio xi glacier there are few signs of organised submarine landforms older moraine ridges along several fjords formed at still stands during deglaciation elsewhere meltwater fed braided rivers connect the glacial and marine sedimentary systems swath imagery shows glacifluvial and fluvial deltas with small channels and chutes that develop into long and sinuous turbidity current channels few iceberg ploughmarks and submarine slope failures were observed but several fields of pockmarks were present the fjords of chile are dominated by sediment delivery from turbid meltwater which distributes fine grained debris widely producing sorted and laminated fine grained ice proximal wedges and draping ice distal seismic architecture to give a predominantly smooth sea floor turbidity currents also transfer sediments to some ice distal environments the chilean fjordlands represent the mildest climatic and oceanographic end member of a continuum of glacier influenced marine settings similar to south east alaska in the northern hemisphere components of a landform assemblage model for climatically mild meltwater dominated fjords include ice contact moraine ridges glacifluvial and fluvial deltas and turbidity current channels full glacial and deglacial streamlined subglacial landforms are likely to have been buried in many areas by subsequent glacimarine sedimentation

seafloor geomorphology and glacimarine sedimentation associated with fast flowing ice sheet outlet glaciers in disko bay west greenland fast flowing outlet glaciers currently drain the greenland ice sheet gis delivering ice meltwater and debris to the fjords around greenland although such glaciers strongly affect the ice sheet s mass balance their glacimarine processes and associated products are still poorly understood this study provides a detailed analysis of lithological and geophysical data from disko bay and the vaigat strait in central west greenland disko bay is strongly influenced by jakobshavn isbrae greenland s fastest flowing glacier which currently drains 7 of the ice sheet streamlined glacial landforms record the former flow of an expanded jakobshavn isbrae and adjacent gis outlets through disko bay and the vaigat strait towards the continental shelf thirteen vibrocores contain a complex set of lithofacies including diamict stratified mud interbedded mud and sand and bioturbated mud deposited by 1 suspension settling from meltwater plumes and the water column 2 sediment gravity flows and 3 iceberg rafting and ploughing the importance of meltwater related processes to glacimarine sedimentation in west greenland fjords and bays is emphasised by the abundance of mud preserved in the cores radiocarbon dates constrain the position of the ice margin during deglaciation and suggest that jakobshavn isbrae had retreated into central disko bay before 10 6 cal ka bp and to beyond isfjeldsbanken by 7 6 7 1 cal ka bp sediment accumulation rates were up to 1 7 cm a 1 for ice proximal glacimarine mud and 0 007 0 05 cm a 1 for overlying distal sediments in addition to elucidating the deglacial retreat history of jakobshavn isbrae our findings show that the glacimarine sedimentary processes in west greenland are similar to those in east greenland and that variability in such processes is more a function of time and glacier proximity than of geographic location and associated climatic regime

glacial and tectonic control on fjord morphology and sediment deposition in the magellan region 53 s chile in the patagonian andes erosion by temperate pleistocene glaciers has produced a deeply incised fjord system in which glacial and non glacial sedimentswere deposited since the late glacial glacier retreat so far fjord bathymetry and structures in the sediment infill were widely unexplored here we report the results of an investigation of morphology and sediment characteristics of a 250 km long fjord transect across the southernmost andes 53 s using multibeam and parametric echosounder data and sediment cores subaquatic morphology reveals continuity of on land tectonic lineaments mapped using field and remote sensing data our results indicate that glacial erosion and fjord orientation are strongly controlled by three major strike slip fault zones furthermore erosion is partly controlled by older and or reactivated fracture zones as well as by differential resistance of the basement units to denudation basement morphology is regionally superimposed by late glacial and holocene subaquatic moraines which are associated to known glacier advances the moraines preferentially occur on basement highs which constrained the glacier flows this suggests that the extent of glacier advances was also controlled by basement morphology subaquatic mass flows fluid vent sites as well as distinct late glacial and holocene sediment infills have furthermore modified fjord bathymetry in the western fjord system close to the strait of magellan subaquatic terraces occur in 20 to 30 m water depth providing an important tag for proglacial lake level during the late glacial

seismic architecture and sedimentation in northwest spitsbergen fjords abstract acoustic records from several spitsbergern fjords yield a characteristic sedimentary architecture subaqueous fans 1 3 surface slope fed by tidewater glacier derived sediments are particularly well developed an upper fan has been built on an underlying fan in response to a shift in the position of the tidewater glacier sediment source the sequence of tidewater glacier fluctuations and sedimentation since the late weichselian interpreted from seismic records comprises the following 1 deposition of an acoustically transparent unit interpreted as either basal till deposited during late weichselian glaciation or a glacimarine unit formed during early rapid ice retreat 2 ice retreat up fjords by about 9000 10 000 yrs b p 3 deposition of a lower fan complex over several thousand years and slow infilling of bedrock controlled basins in more ice distal locations 4 ice readvance to 2 3 km beyond modern ice margins linked to little ice age climatic deterioration from the 13 14th century overriding of part of the lower fan complex inducing deformation 5 deposition of little ice age submarine terminal moraines and basal till by readvancing glaciers deposition of the upper fan during 500 yr little ice age ice advance 6 retreat of tidewater glacier termini to their present positions since little ice age termination at the end of the 19th century deposition of a thin veneer of sediment inside the little ice age submarine moraines as glacier retreat takes place

lithofacies and seismic reflection interpretation of temperate glacimarine sedimentation in tarr inlet glacier bay alaska abstract high resolution seismic reflection profiles of sediment fill within tarr inlet of glacier bay alaska show seismic facies changes with increasing distance from the glacial termini five types of seismic facies are recognized from analysis of huntec and minisparker records and seven lithofacies are determined from detailed sedimentologic study of gravity vibro and box cores and bottom grab samples lithofacies and seismic facies associations and fjordfloor morphology allow us to divide the fjord into three sedimentary environments ice proximal iceberg zone and ice distal the ice proximal environment characterized by a morainal bank depositional system can be subdivided into bank back bank core and bank front subenvironments each of which is characterized by a different depositional subsystem a bank back subsystem shows chaotic seismic facies with a mounded surface which we infer consists mainly of unsorted diamicton and poorly sorted coarse grained sediments a bank core depositional subsystem is a mixture of diamicton rubble gravel sand and mud seismic reflection records of this subsystem are characterized by chaotic seismic facies with abundant hyperbolic diffractions and a hummocky surface a bank front depositional subsystem consists of mainly stratified and massive sand and is characterized by internal hummocky facies on seismic reflection records with significant surface relief and sediment gravity flow channels the depositional system formed in the iceberg zone environment consists of rhythmically laminated mud interbedded with thin beds of weakly stratified diamicton and stratified or massive sand and silt on seismic reflection profiles this depositional system is characterized by discontinuously stratified facies with multiple channels on the surface in the proximal zone and a single channel on the largely flat sediment surface in the distal zone the depositional system formed in the ice distal environment consists of interbedded homogeneous or laminated mud and massive or stratified sand and coarse silt this depositional system shows continuously stratified seismic facies with smooth and flat surfaces on minisparker records and continuously stratified seismic facies which are interlayered with thin weakly stratified facies on huntec records

obliquity forcing of organic matter accumulation during oceanic anoxic event 2 1 an analysis of orbitally influenced climate sensitive sedimentation is conducted across a meridional transect of the proto north atlantic to reconstruct the behavior of the carbon cycle and climate during oceanic anoxic event 2 oae 2 94 ma midlatitude to near equatorial sites spanning deep ocean to shelf environments are evaluated using a new inverse method for the identification and calibration of orbital influence in ancient strata the results yield consistent independent astrochronologies at each location compatible with the recently published radioisotopic astrochronologic time scale at the cenomanian turonian gssp and thus provide a unified high resolution temporal context for evaluation of the event the proto north atlantic astrochronologies document an amplification of obliquity power during oae 2 indicating that obliquity was the dominant pacemaker of organic matter accumulation by the latter portion of the event the strong obliquity signal suggests an influence of high latitude climate processes across midlatitude deep ocean to tropical shelf environments changes in oceanic circulation during oae 2 represent a likely mechanism for the propagation of a high latitude signal and proxy data from demerara rise reveal the development of a new intermediate water mass source synchronous with the record of obliquity amplification we hypothesize that a dense high latitude water mass displaced a pre existing nutrient rich anoxic deep water layer in the proto north atlantic augmented by enhanced volcanism driving an episode of high productivity that lasted 700 800 ka the development and intensification of the new intermediate deep water source was potentially driven by eustatic sea level rise which created expansive seaways in mid to high latitudes

the sedimentary record of glacial retreat marinelli fjord patagonia regional correlations and climate ties abstract the inland passage of chile comprises the most continuous latitudinal transect of ice fields ice caps and alpine glaciers in the southern hemisphere providing an excellent natural laboratory for the study of glacial response to climate change during the holocene here we report results from a marine geological investigation of marinelli fjord tierra del fuego 54 25 s 69 35 w and ainsworth fjord which merges with marinelli fjord data acquired during july 2005 onboard the rv ib nathaniel b palmer include high resolution seismic data multibeam swath bathymetry data and sediment cores post cruise analyses include detailed seismic facies and lithofacies analysis and radiocarbon dating the results indicate that a major transition in the glacimarine record from ice proximal facies to ice distal facies occurred in the outer basins of the fjord at 15 5 kyr to 12 5 kyr the ice proximal facies consists of pebbly mud with abundant laminations and is characterized by high average sedimentation rates 28 mm yr in contrast an ice distal facies is dominantly bioturbated mud with low average sedimentation rates 0 56 mm yr this transition marks the retreat of marinelli glacier from the outer basins with no evidence for glacial re advance subsequently during the mid to late holocene ainsworth glacier retreated and exposed ainsworth fjord our results are consistent with the climatic trends for southern south america where the final deglaciation of the region ended at 12 5 ka during the holocene stable ice conditions persisted until the mid 1960s when marinelli glacier began rapidly retreating to its modern day position

push moraines and glacier contact fans in marine and terrestrial environments the local climatic regime and the mass balance state are important determinants of the dynamics of terrestrial and marine glacier fronts which in turn determine the sediments and landforms produced at the glacier front many modern glaciers undergoing overall retreat in areas of maritime climate produce winter push moraines during a late winter readvance followed by a summer retreat whilst in more continental regions no significant winter readvance occurs and annual push moraines are absent the frontal dynamics which lead to these changes are analysed and the form structure sequence and field relations of both terrestrial and marine push moraines are described from iceland spitsbergen and baffin island long term changes in mass balance leading to major glacier advances or readvances also generate large push moraines in terrestrial environments push moraine formation is accompanied by uplift rejuvenation and down cutting of outwash systems whose sediments become closely associated with glaciotectonic structures which permit pre syn and post tectonic sequences to be identified the development of ice marginal fan moraine complexes is modelled as a function of the relative magnitude of two parameters the velocity of ice movement and the calving rate a high ice velocity just exceeded by the calving rate gives closely spaced push moraines and confluent ice marginal fans a high velocity far exceeded by the calving rate produces closely spaced moraines but separate ice marginal fans a low ice velocity in combination with a high calving rate results in well separated and feebly developed push moraines while a low ice velocity and a low calving rate produces feeble push moraines and coalescent fans

seismic facies and regional architecture of the oak ridges moraine area southern ontario analysis of over 50 line kilometres of land based shallow seismic reflection profiles has provided a means of investigating the subsurface architecture and stratigraphic relationships of the glac

morphodynamic evolution of kongsfjorden krossfjorden svalbard during the late weichselian and holocene we present a combination of fjord bathymetry and shallow seismic data from kongsfjorden and krossfjorden svalbard to characterize and analyse change in the fjord coastal environment physiography and the glaciosedimentary processes since the last glacial maximum swath bathymetry reveals a series of several styles of landform frequently superimposed upon each other permitting the reconstruction of the relative timings of deposition of each landform with the oldest successively overlain and cross cut by younger landforms and erosional processes large transverse ridges interpreted as recessional moraines are overlain by streamlined lineations formed subglacially during a subsequent ice advance a complex of recessional morainal ridges occurring within the central fjord are incised by glacial lineations and meltwater channels from younger glacial events

a critical evaluation of carbon isotope stratigraphy and biostratigraphic implications for late cretaceous global correlation abstract climate variability is driven by a complex interplay of global scale processes and our understanding of them depends on sufficient temporal resolution of the geologic records and their precise inter regional correlation which in most cases cannot be obtained with biostratigraphic methods alone chemostratigraphic correlation based on bulk sediment carbon isotopes is increasingly used to facilitate high resolution correlation over large distances but complications arise from a multitude of possible influences from local differences in biological diagenetic and physico chemical factors on individual 13c records that can mask the global signal to better assess the global versus local contribution in a 13c record it is necessary to compare numerous isotopic records on a global scale as a contribution to this objective this paper reviews bulk sediment 13ccarb records from the late cretaceous in order to identify differences and similarities in secular 13c trends that help establish a global reference 13c record for this period the study presents a global scale comparison of twenty 13c records from sections representing various palaeo latitudes in both hemispheres and different oceanic settings from the boreal tethys western interior indian ocean and pacific ocean and with various diagenetic overprinting the isotopic patterns are correlated based on independent dating with biostratigraphic and paleomagnetic data and reveal good agreement of the major isotope events despite offsets in absolute 13c values and variation in amplitude between the sites these differences reflect the varying local influences e g from depositional settings bottom water age and diagenetic history whereas the concordant patterns in 13c shifts might represent 13c fluctuations in the global seawater dissolved inorganic carbon the latter is modulated by variations in organic matter burial relative to re mineralization in the global scale formation of authigenic carbonate and in partitioning of carbon between organic carbon and carbonate sinks these variations are mainly controlled by changes in climate and eustasy additionally some globally synchronous shifts in the bulk 13ccarb records could result from parallel variation in the contribution of authigenic carbonate to the sediment formation of these cements through biologically mediated early diagenetic processes is related to availability of oxygen and organic material and thus can be globally synchronized by fluctuations in eustasy atmospheric and oceanic oxygen levels or in large scale oceanic circulation because the influence of early diagenetic cements on the bulk 13ccarb signal can but need not be synchronized chemostratigraphy should not be used as a stand alone method for trans continental correlation and especially minor isotopic shifts have to be interpreted with utmost care nevertheless the observed consistency of the 13c correlations confirms global scale applicability of bulk sediment 13c chemostratigraphy for the late cretaceous including sediments that underwent lithification and burial diagenesis such as the sediments from the himalayan and alpine sections limitations arise from increased uncertainties 1 in sediments with very low carbonate content 2 from larger 13c variability in sediments from very shallow marine environments 3 from unrecognized hiatuses or strong changes in sedimentation rates and 4 in sections with short stratigraphic coverage or with few biostratigraphic marker horizons the combination of chemostratigraphy with biostratigraphy and magnetostratigraphy substantially increases the precision and temporal resolution of inter regional correlations and helps overcome problems that arise from differences in biostratigraphic schemes facies or provincialism of key fossils by using an iterative approach to stepwise increase precision of the correlations isochroneity of first and last occurrences of marker species versus chemostratigraphy is tested which helps to improve biostratigraphic zonations to assess zonal boundary ages and to identify useful criteria for defining late cretaceous stage boundaries many of which are still not formally defined the presented correlations indicate a consistent position for most planktic foraminifer zonal boundaries relative to corresponding isotope shifts during the mid cretaceous sea level high whereas diachroneity appears to be more pronounced during the late campanian and maastrichtian global sea level fall a similar pattern is observed for trans continental consistency in the 13c shifts graphic correlation of isotopic shifts magnetostratigraphic and biostratigraphic events among the compared sections is used to detect hiatuses or relative changes sediment accumulation rates and visualizes consistency or offsets of individual biostratigraphic markers relative to chemo and magnetostratigraphy finally an attempt of a global average 13c stack is presented for the turonian through maastrichtian

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

the seismic architecture and geometry of grounding zone wedges formed at the marine margins of past ice sheets grounding zone wedges form where halts of decades to centuries during ice sheet retreat across polar shelves allow sediment buildup at the grounding zone through delivery of deforming basal debris from fast flowing ice streams thirty grounding zone wedges were identified on two dimensional seismic reflection profiles across the continental shelves of ne and nw greenland grounding zone wedges close to the seafloor are probably of late weichselian age others are on paleoshelves buried beneath thick prograding glacial sediments several greenland shelf grounding zone wedges occur on topographic highs that provide stabilizing pinning points in relatively shallow water grounding zone wedges are asymmetric in the ice flow direction with steeper ice distal sides typical grounding zone wedges are approximately 5 20 km long and 50 100 m thick with a lateral width of several tens of kilometers forty grounding zone wedges from the greenland norwegian and antarctica margins show considerable variability about these values grounding zone wedge dimensions are controlled by sediment flux the duration of halts in ice retreat subice cavity shape and ice stream width low angle ice shelf cavity roofs immediately beyond the grounding zone probably restrict vertical accommodation space preventing formation of high amplitude ridges grounding zone wedges are mainly transparent or chaotic on seismic profiles probably resulting from delivery of diamictic debris offlapping reflectors represent progradation into an ice roofed cavity reflector truncations of grounding zone wedge bases indicate erosion during initiation channels are present within some grounding zone wedges meltwater flow is under high pressure and v shaped incisions suggest high energy flow channels are not ubiquitous within greenland grounding zone wedges and may represent nonsteady meltwater release perhaps through lake drainage where ice sheet mass loss is dominated by meltwater runoff grounding zone wedges probably contain more sorted sediment than those from greenland simple models of grounding zone wedge architecture are presented grounding zone wedges indicate episodic rather than catastrophic ice sheet retreat and are a mechanism for ice shelf stabilization because wedge growth counteracts collapse induced by ice sheet thinning and sea level rise

sea floor morphology outside a grounded surging glacier brasvellbreen svalbard abstract acoustical profiling and bottom photography reveal several different sea floor morphological features adjacent to the grounded brasvellbreen glacier on svalbard northwestern barents sea some of the features and their distribution may be closely related to a major glacial surge in 1936 1938 and as such are valuable in identifying former surges in other locations a continuous wide ridge with a characteristic asymmetrical cross section running subparallel to the glacier is the end moraine defining the maximum extent of the surge a large part of the material forming this ridge is most likely rapidly deposited from meltwater during the surge a rhombohedral pattern of smaller mounds inside the ridge is probably an expression of relief in the glacier sole during the surge discontinuous arcuate ridges define local minor oscillations during retreat of the ice at a later stage iceberg plough marks are most frequent seaward of the end moraine their orientation is controlled by the combination of a coastal current offshore katabatic winds and topography superimposed on plough marks are secondary features such as a washboard pattern and striae most likely caused by push up of overconsolidated material during gouging and multi keel icebergs respectively bottom sediments observed in photographs and cores are loose pebbly muds with high variability in clast content resting on overconsolidated material probably basal till mud deposition presently prevails close to the glacier

neogene fjordal sedimentation on the western margin of the lambert graben east antarctica neogene glacial sedimentation east antarctica

debris in icebergs and rates of glaci marine sedimentation observations from spitsbergen and a simple model debris distribution and content in spitsbergen icebergs varies but basal debris rich layers often 1 m thick are the most important sources of iceberg rafted material angular iceberg rafted clasts in the glaci marine record imply the presence of nunataks or valley walls rather than unbroken ice sheet surfaces indicating paleo ice mass configuration calculated iceberg melt rates imply that most iceberg rafted debris is released within spitsbergen fjords sedimentation from icebergs is calculated as 1 mm a 1 for inner mollerfjorden and 8 mm a 1 for inner kongsfjorden an order of magnitude lower than total sediment inputs turbid subglacial meltwater is a more important debris source a simple model is proposed to calculate the flux of basal debris in icebergs and iceberg sedimentation rates

elastic deformation modulus for estimating convergence when tunnelling through squeezing ground squeezing in tunnelling is commonly assessed using the linearly elastic perfectly plastic mohr coulomb mc model weak rocks and fault materials however exhibit confining stress dependent and strain hardening behaviour prior to failure in other words the higher the confining stress and the lower the shear strain the stiffer the rock behaviour as the mc model assumes a strain and stress independent young s modulus the selection of an appropriate operational value emc remains a major problem in tunnel studies using this model although emc has a significant effect on the deformation predictions they are inversely proportional to this value under small strain theory there is no widely accepted or well validated approach to its selection this paper shows using the results of triaxial compression tests on weak rocks and fault materials from the gotthard base tunnel and five other projects and performing a theoretical analysis of the ground response to tunnel excavation that emc can be taken

imaging evidence for hubbard glacier advances and retreats since the last glacial maximum in yakutat and disenchantment bays alaska high resolution 2 d multichannel seismic data collected during the 2012 utig usgs national earthquake hazards reduction program survey of disenchantment and yakutat bays in southeast alaska provide insight into their glacial history these data show evidence of two unconformities appearing in the form of channels and are interpreted to be advance pathways for hubbard glacier the youngest observable channel thought to have culminated near the main phase of the little ice age lia is imaged in disenchantment bay and ends at a terminal moraine near blizhni point an older channel thought to be from an advance that culminated in the early phase of the lia extends from disenchantment bay into the northeastern edge of yakutat bay turning southward at knight island and terminating on the southeastern edge of yakutat bay our interpretation is that hubbard glacier has repeatedly advanced around the east side of yakutat bay in knight island channel possibly due to the presence of malaspina glacier cutting off access to central yakutat bay during times of mutual advance we observe two distinct erosional surfaces and retreat sequences of hubbard glacier in yakutat bay supporting the hypothesis that minor glacial advances in fjords do not erode all prior sediment accumulations interpretation of chaotic seismic facies between these two unconformities suggests that hubbard glacier exhibits rapid retreats and that disenchantment bay is subject to numerous episodes of outburst flooding and morainal bank collapse these findings also suggest that tidewater glaciers preferentially reoccupy the same channels in bay and marine settings during advances

sediment accumulation rates in subpolar fjords impact of post little ice age glaciers retreat billefjorden svalbard abstract the little ice age 1600 1900 ad and 20th century sediment accumulation rates in billefjorden a subpolar fjord on svalbard were reconstructed by applying 210 pb 137 cs and ams 14 c datings the modern sediment accumulation rate decreases from more than 0 39 cm y 1 at the fjord head to 0 08 cm y 1 close to the fjord mouth however during the little ice age the sediments accumulated at a much lower rate of 0 02 cm y 1 in the central fjord basin this difference is most likely related to the rapid retreat of glaciers during the 20th century when most of them withdrew up to 2 km the post little ice age increases in temperature and a negative glacier mass balance resulted in a larger meltwater discharge transferring substantial amounts of sediments released from the glaciers as well as those eroded from previously stored unconsolidated glacial sediments a comparison of data from the subpolar fjords of svalbard suggests that the increase in the sediment accumulation rate is a common trend and further increases might be expected if climate warming continues the properties of the fjord sediments grain size ird coarse fraction composition clay mineralogy from the little ice age and the 20th century showed no distinct differences the change in the accumulation rate may be the most evident sedimentary record of this climatic change

environmental assessment from the sedimentary record of high latitude fiords the sedimentary record of fiords at high latitude where global change may be occurring earliest and will be greatest has the potential for assessment of environmental change at both low resolution the scale of millennia and high resolution decadal to less than daily unlike the lacustrine record which has been used very successfully in these studies the sedimentary processes and thus the sedimentary deposits of fiords differ 1 in the role of salt water in inhibiting mixing and promoting flocculation and through the role of sea ice 2 in the exchange of mass and energy with the much larger ocean beyond and 3 in the role of benthic biota in the sedimentary environment the work reviewed in this paper shows that fiord sediments are being used to assess sedimentary and oceanic processes as well as glacial periglacial and geomorphic history and that they are important proxies for long term climate and hydrology recommendations for advancing this work include long term monitoring of conditions in fiords and their drainage basins so that the transfer relations can be more solidly constructed from the proxy of fiord sediment integration of results from fiords in opposite polar latitudes and among proxies especially from lacustrine and ice core records will produce valuable insights assessment of the range of conditions in fiords from the most polar to temperate regions is important to building models of their processes and understanding of the paleoenvironmental signals that can be interpreted from each type

dynamics of tidewater surge type glaciers in northwest svalbard the evolution of ice dynamics through surges of four tidewater terminating glaciers in northwest svalbard is investigated by remote sensing a 20 year time series of glacier surface flow speeds and frontal positions is presented covering the recent surges of monacobreen comfortlessbreen blomstrandbreen and fjortende julibreen surface flow speeds were derived using feature tracking between pairs of ers sar and alos palsar images while frontal positions were taken from the same imagery as well as more frequent but lower spatial resolution envisat wide swath mode images during all four surges increased ice flow caused the tidewater margin to advance while the calving flux was initially reduced to near zero due to compressive stresses limiting crevasse propagation as ice speed decreased the terminus continued to advance until the glacier s speed had returned to its pre surge flow rate only at this time did the terminus start to retreat and peak iceberg calving flux was established we conclude that terminus advance closely tracks glacier speed up that there is little mass loss through calving during the most active phase of the surge and that seasonal cycles of terminus positions diminish during the active surge phase

the timing of initiation of fast flowing ice streams during a glacial cycle inferred from glacimarine sedimentation fast flowing ice streams drain huge basins within modern ice sheets and are a mechanism for rapid iceberg production and mass loss some ice streams are known to be unstable and to switch between fast flow and stagnation numerical ice sheet models and geophysical observations of large scale streamlined glacial landforms and large glacier derived sedimentary fans along high latitude continental margins indicate the presence of ice streams in quaternary ice sheets high resolution ams dated sedimentary records from an inter fan area on the svalbard continental margin yield evidence on the timing of initiation of fast glacier flow during a glacial cycle of ice sheet growth and decay sedimentation rates and iceberg rafted debris influx show that debris delivery to the svalbard margin was relatively high during the period of late weichselian ice sheet growth from about 30 000 18 000 yr bp both parameters fell dramatically in inter fan areas when full glacial conditions with ice at the continental shelf edge were established at about 18 000 yr bp this shift is interpreted to mark the initiation of a fast flowing ice stream the convergence of flow from the surrounding ice sheet into this ice stream and the consequent slowing of ice flow and sediment delivery to the inter fan area beyond the ice stream margins this provides a constraint on the timing of icestream initiation during the cycle of ice sheet growth and decay 4 2002 elsevier science b v all rights reserved

seasonal patterns of shell flux δ18o and δ13c of small and large n pachyderma s and g bulloides in the subpolar north atlantic past water column stratification can be assessed through comparison of the delta o 18 of different planktonic foraminiferal species the underlying assumption is that different species form their shells simultaneously but at different depths in the water column we evaluate this assumption using a sediment trap time series of neogloboquadrina pachyderma s and globigerina bulloides from the nw north atlantic we determined fluxes delta o 18 and delta c 13 of shells from two size fractions to assess size related effects on shell chemistry and to better constrain the underlying causes of isotopic differences between foraminifera in deep sea sediments our data indicate that in the subpolar north atlantic differences in the seasonality of the shell flux and not in depth habitat or test size determine the interspecies delta delta o 18 n pachyderma s preferentially forms from early spring to late summer whereas the flux of g bulloides peaks later in the season and is sustained until autumn likewise seasonality influences large and small specimens differently with large shells settling earlier in the season the similarity of the seasonal delta o 18 patterns between the two species indicates that they calcify in an overlapping depth zone close to the surface however their delta c 13 patterns are markedly different 1 parts per thousand both species have a seasonally variable offset from delta c 13 dic that appears to be governed primarily by temperature with larger offsets associated with higher temperatures the variable offset from delta c 13 dic implies that seasonality of the flux affects the fossil delta c 13 signal which has implications for reconstruction of the past oceanic carbon cycle citation jonkers l s van heuven r zahn and f j c peeters 2013 seasonal patterns of shell flux delta o 18 and delta c 13 of small and large n pachyderma s and g bulloides in the subpolar north atlantic paleoceanography 28 164 174 doi 10 1002 palo 20018

autonomous underwater vehicle auv observations of recent tidewater glacier retreat western svalbard abstract recent studies have highlighted the need to improve our understanding of the relationship between glacial front bathymetry and oceanography in order to better predict the behaviour of tidewater glaciers the glaciomarine fjords of western svalbard are strongly influenced by temperate atlantic water advected from the west spitsbergen current marine terminating tidewater glaciers locally influence many svalbard fjords through fluxes of sediments nutrients and freshwater however their response to ocean warming and the imprint left by their recent retreat on the seabed remains unresolved here we present glacial front data collected by an autonomous underwater vehicle auv from four tidewater glaciers fjortende julibreen krossfjorden conwaybreen kongsbreen and kronebreen kongsfjorden the seabed adjacent to the glacial terminus has been mapped providing high resolution bathymetry 0 5 m 1 0 m grid cell size side scan and photographs with additional simultaneous oceanographic observations the aim being to survey the glacial front submarine landforms to identify the water mass structure and to observe any melt water plume activity the bathymetry data displays a diverse assemblage of glacial landforms including numerous retreat moraines glacial lineations crevasse squeeze ridges and sediment debris flows reflecting the dynamic depositional environment of the glacial front the age of the features and the annual rate of retreat have been estimated using satellite remote sensing imagery to digitise the glacial front positions over time the glacial landforms have been produced by the last few years of retreat as these glaciers gradually become land terminating the auv also observed in situ subglacial meltwater plumes at the two most active glaciers kongsbreen and kronebreen and an associated signature of warm atlantic water occurring at the glacier face the presence of relatively warm oceanic waters enhances subsurface melting accelerating the ablation rate while fresh melt water injection at depth influences local water mass structure and the wider fjord circulation at the glacial fronts of kongsbreen and kronebreen sedimentation from subglacial meltwater plumes dominate the ice proximal zone and settling from suspension is more prevalent away from the glacier this study shows how sensitive dynamic glaciomarine systems are to change in the local marine environment and how the use of autonomous vehicles can greatly aid in the monitoring of glacial change by collecting simultaneous high resolution in situ datasets where vessel based observations are lacking

impact of biomineralization processes on the mg content of foraminiferal shells a biological perspective the mg ca ratio in foraminiferal shells is widely used as a proxy for paleotemperatures nevertheless it seems that the basic mg content of foraminifera is determined by biological factors as can be concluded from the large inter species and intrashell variability and the frequent deviations from inorganic behavior this paper discusses three possible ways by which foraminifera can control or modify the mg content in their shell 1 involvement of organic matrix in the precipitation process that may alter the partition coefficient of mg in biogenic calcite 2 controlled conversion of transient amorphous phases to calcite and 3 modification of the mg concentration in the parent solution from which the crystals precipitate the first two mechanisms are probably responsible for the precipitation of high mg calcite phases whole shell or sublayers while the third mechanism leads to the formation of low mg calcite phases we propose a model adapted from epithelial cells that allows massive mg2 removal from the biomineralization site this model is especially relevant to the planktonic and deep benthic low mg foraminifera that are frequently used for paleotemperature reconstructions we discuss the possible biological roles of mg in the shell in terms of the calcite polymorph conservation the in vivo chemical stability of the shell the functions of mg as a stabilizer of transient phases and as a controlling agent of the precipitation process several temperature sensitive biological processes that may influence the mg ca ratio of the shell are suggested and a model that combines biogenic and inorganic considerations is presented the model uses mg heterogeneity in the shell together with temperature response biologic and inorganic of biomineralization processes to account for the deviation of planktonic foraminifera from inorganic calcite at equilibrium with seawater

morainal bank progradation and sediment accumulation in disenchantment bay alaska response to advancing hubbard glacier 1 morainal banks are primary features at the margins of advancing and stable to quasi stable temperate tidewater glaciers yet their roles in glacier dynamics and terminus stability are poorly defined by submarine observations analysis of new and archival multibeam data and landsat images of the advancing hubbard glacier southeast alaska reveal that between 1978 and 2010 the ice face and morainal bank advanced together at an average rate of 34 m yr varying spatially and temporally between 14 and 80 m yr morphological features including gullies and a boulder lag suggest cyclical deposition and gravitational erosion on the proximal slope of the morainal bank 15 18 and possible ice pushing in an area without recent sedimentation in contrast the morainal bank of the nearby quasi stable surging turner glacier advanced steadily since 1978 by proximal sedimentation on the steep fjord wall below its hanging valley sedimentation in the deep 220 m basin of disenchantment bay increased from 0 88 m yr spanning 1978 to 1999 to 1 22 m yr thereafter this change appears to be a combined response to glacier advance and sediment dispersal farther down fjord and to an increase in sediment yield from other glacial and non glacial sources analysis of hubbard glacier illustrates the direct correlation between movement of the terminus and morainal bank in advancing the grounding line of a marine terminating glacier and that morainal banks provide a fundamental stabilizing role for advance into a deep water fjord compensating for changes in water depth at the grounding line

ice sheet grounding zone wedges gzws on high latitude continental margins abstract grounding zone wedges gzws are asymmetric sedimentary depocentres which form through the rapid accumulation of glacigenic debris along a line source at the grounding zone of marine terminating ice sheets during still stands in ice sheet retreat gzws form largely through the delivery of deforming subglacial sediments the presence of gzws in the geological record indicates an episodic style of ice retreat punctuated by still stands in grounding zone position moraine ridges and ice proximal fans may also build up at the grounding zone during still stands of the ice margin but these require either considerable vertical accommodation space or sediment derived from point sourced subglacial meltwater streams by contrast gzws form mainly where floating ice shelves constrain vertical accommodation space immediately beyond the grounding zone an inventory of gzws is compiled from available studies of bathymetric and acoustic data from high latitude continental margins the locations and dimensions of gzws from the arctic and antarctic alongside a synthesis of their key architectural and geomorphic characteristics are presented gzws are only observed within cross shelf troughs and major fjord systems which are the former locations of ice streams and fast flowing outlet glaciers typical high latitude gzws are less than 15 km in along flow direction and 15 to 100 m thick gzws possess a transparent to chaotic acoustic character which reflects the delivery of diamictic subglacial debris many gzws contain seaward dipping reflections which indicate sediment progradation and wedge growth through continued delivery of basal sediments gzw formation is inferred to require high rates of sediment delivery to a fast flowing ice margin that is relatively stable for probably decades to centuries although the long term stability of the grounding zone is controlled by ice sheet mass balance the precise location of any still stands is influenced strongly by the geometry of the continental shelf the majority of high latitude gzws occur at vertical or lateral pinning points which encourage grounding zone stabilisation through increasing basal and lateral drag and reducing mass flow across the grounding zone

submarine landforms and glacimarine sedimentary processes in lomfjorden east spitsbergen understanding the role of fjords in modulating the long term interaction between ice sheets and glaciers with the surrounding ocean requires the investigation of glacigenic landform and sediment archives in svalbard there is a wealth of data from fjords in west spitsbergen that constrains the glacial history of this sector of the svalbard barents sea ice sheet sbis since the last glacial maximum lgm and the nature and timing of subsequent ice retreat in contrast however very little is known about the glacial history of fjords in east spitsbergen this paper combines multibeam swath bathymetry sub bottom profiles lithological data and radiocarbon dates from lomfjorden svalbard to provide the first insights into the dynamics of tidewater glaciers and associated glacimarine sedimentary processes in a northeast spitsbergen fjord at the lgm a fast flowing ice stream drained the sbis through lomfjorden serving as a tributary to a south north flowing ice stream in hinlopenstretet ice advance is recorded by streamlined bedrock glacial lineations and drumlins a radiocarbon date of 9 7 ka bp from the outer fjord provides a minimum date for retreat of this ice stream and suggests that lomfjorden was ice free earlier than fjords in west spitsbergen ice retreat occurred in a slow and step wise manner indicated by the presence of recessional moraines and de geer moraines by 4 5 ka bp the local tidewater glaciers had probably retreated inland of their present positions the limited extent of glacigenic landform assemblages in front of these glaciers implies that any holocene re advances were probably restricted the principal sedimentary processes during deglaciation were suspension settling from meltwater causing deposition of weakly stratified bioturbated mud in ice distal settings at rates of 0 02 0 08 cm a 1 and gravitational mass flows forming sandy turbidites in ice proximal areas iceberg ploughmarks and ice rafted debris provide evidence for the presence of large icebergs during deglaciation our data suggest an early and extensive deglaciation in east spitsbergen fjords and show that previous reconstructions of the extent of the sbis need to be revised as new data emerges from east spitsbergen the data confirm that tidewater glaciers from different regions of spitsbergen behaved differently since the lgm and that variations in landform sediment assemblages occur even within geographically adjacent fjords

submarine landform assemblages and sedimentary processes in front of spitsbergen tidewater glaciers new swath bathymetric data from the inner parts of the three svalbard fjords ymerbukta trygghamna and magdalenefjorden reveal the landform assemblages deposited in front of tidewater glaciers in west and northwest spitsbergen overridden moraines in ymerbukta a tributary of isfjorden in central west spitsbergen record several re advances of the esmarkbreen glacier at the head of the fjord after deglaciation and glacial lineations formed in seafloor sediments are indicative of fast ice advance during one of these events a terminal moraine and associated debris lobe mark the maximum ice extent during the holocene which implied by the presence of crevasse squeeze ridges is likely related to a surge of esmarkbreen several de geer moraines provide evidence for subsequent slow and step wise retreat in the adjacent trygghamna and in magdalenefjorden in northwest spitsbergen the landforms are similar but the absence of overridden moraines and glacial lineations shows that the glaciers probably only re advanced once during the holocene and that ice flow was relatively slow terminal moraines and associated debris lobes mark the maximum extent of these advances and formed during the little ice age lia in magdalenefjorden the relatively small size of the debris lobe suggests that the ice margin was at its maximum position for only a short period of time or that sediment availability was restricted during the lia advance similar to esmarkbreen the retreat phase of the glaciers in trygghamna and magdalenefjorden was also characterised by periods of still stand or small re advances although the comparatively small number of de geer moraines in all three fjords shows that these landforms probably formed much less frequently than previously thought sub bottom profiler data four sediment cores and six radiocarbon dates from magdalenefjorden further provide information about the holocene sedimentary environments in a northwest spitsbergen fjord the main source of sediment is glacial meltwater entering the fjord from the surrounding coastline which has led to the accumulation of thick sequences of fine grained mud stratified and laminated muds record glacier proximal conditions probably related to a lia re advance of waggonwaybreen around 300 cal a bp where the interplay of a range of glacimarine processes led to the formation of partially rhythmic couplets of one coarser and one finer layer accumulated at a rate of around 3 cm a 1 multiple sandy layers intercalated with the glacimarine mud provide evidence for the occurrence of gravitational mass flow events like turbidity currents in ice distal settings massive to weakly stratified occasionally bioturbated mud accumulated at a lower rate of 0 04 0 49 cm a 1 occasional clasts and diamictic layers show that the depositional environment in magdalenefjorden is also influenced by sedimentation from icebergs and sea ice but the ubiquitous glacimarine mud underscores the predominance of meltwater related sedimentation in the fjord

glacimarine sedimentary processes and depositional environments in an embayment fed by west greenland ice streams abstract the extent and behaviour of the central west greenland sector of the greenland ice sheet gis during the last glacial maximum lgm and the following deglaciation remains poorly constrained to investigate deglacial marine environments and sedimentary processes in an area fed by several lgm ice streams we now report findings from a 3 5 khz sub bottom profiler survey acquired in and around disko bay in 2009 sediment thicknesses and volumes in three glaciated areas disko bay southern vaigat and egedesminde dyb are fully constrained for the first time acoustic facies types and distributions were also mapped the largest sediment thicknesses 256 m and widest variation in acoustic character was observed in disko bay adjacent to the mouth of jakobshavns isfjord significant sediment thicknesses were also observed in isolated basins in the egedesminde dyb trough and in a trough in southern vaigat strait up to 110 m given low modern sedimentation rates these thick sediment packages are inferred to record the retreat of glaciers from the middle shelf through disko bay and into both the jakobshavns and torssukatak fjord systems in central west greenland our results highlight similarities in deglacial sedimentary processes across the study area when the margins of retreating glaciers supplied large volumes of sediment to the marine environment from sediment laden meltwater plumes and melting icebergs we estimate the sediment flux for the palaeo jakobshavn ice stream while the ice margin was stable at a fjord entrance sill to be 1 6 3 6 10 7 m 3 a 1 assuming a flux at the upper end of our range for the torssukatak fjord system requires the grounded ice margin to be stable for about 450 years during retreat the sediment fluxes we estimate are within the range of previously calculated fluxes for other arctic and antarctic ice streams and suggest that large volumes of meltwater and sediment were available at the base of the outlet glaciers during deglaciation even during periods of quasi stability retreat of the ice margins into the fjord systems is characterised by a rapid transition to ice distal sedimentation by rainout of iceberg rafted detritus ird and hemipelagic material accumulation rates drop to 2 mm a 1 this study demonstrates the variability in glacimarine processes and environments on high latitude continental margins and highlights the importance of local factors such as bedrock morphology as well as glacio dynamic factors on sedimentation

submarine landforms and the reconstruction of fast flowing ice streams within a large quaternary ice sheet the 2500 km long norwegian svalbard margin 57 80 n morphological interpretation of regional and detailed bathymetric data sets on the 2500 km long norwegian shelf from the north sea 57 n to svalbard 80 n has revealed a dynamic ice flow pattern along the western marginof the scandinavian and barents svalbard ice sheets about 20 cross shelf troughs with megascale glacial lineations msgl elongate ridges and grooves oriented parallel to trough long axes are interpreted as former pathways for fast flowing ice streams studies of large scale margin morphology and seismic profiles have identified large submarine fans at the mouths of several major cross shelf troughs less dynamic ice probably existed on shallower banks the two largest paleo ice streams were the norwegian channel ice stream and bear island trough ice stream each 150 200 km wide at the mouth the lengths of individual msgl vary from hundreds of meters to several tens of kilometers and the distance between ridges varies from 0 1 to 3 km msgl amplitudes reach 15 m but are commonly 10 m the onset of msgl and hence fast ice flow is generally close to the outer coast at the border zone between crystalline rocks and softer sedimentary rocks transverse submarine ridges on various scales commonly parallel to the shelf edge reflect either the maximum ice sheet position or the recessional pattern of the ice sheet lateral ice stream moraines several tens of kilometers long have also been mapped along the sides of several cross shelf troughs identifying the border zone between fast ice flow and stagnant or slow flowing ice on intervening banks

lateral shear moraines and lateral marginal moraines of palaeo ice streams abstract an understanding of the nature of sedimentation at ice stream lateral margins is important in reconstructing the dynamics of former ice sheets and modelling the mechanisms by which sediment is transported beneath contemporary ice streams theories of the formation of ice stream lateral moraines islms have hitherto been based on a relatively limited number of terrestrial and marine examples here an inventory of islms is compiled from available studies together with independent analysis of seismic reflection and bathymetric datasets the locations and dimensions of 70 islms alongside a synthesis of their key architectural and geomorphic characteristics are presented two different types of islms are identified type 1 islms are up to 3 5 km wide and 60 m thick they maintain a constant width thickness and cross sectional shape along their length type 1 islms are interpreted and referred to as ice stream lateral shear moraines that form subglacially in the shear zone between ice streams and slower flowing regions of an ice sheet in contrast type 2 islms are up to 50 km wide and 300 m thick they are only identified close to the shelf break in the marine environment type 2 islms exhibit an increase in width and thickness along their length and their distal slopes become steeper in a seaward direction they contain internal dipping reflections that indicate sediment progradation away from the former ice stream type 2 islms are interpreted and referred to as ice stream lateral marginal moraines that were formed at the lateral boundary between ice streams and seafloor terrain that was free of grounded ice we suggest that using bathymetric images and acoustic profiles it is possible to differentiate between ice stream lateral shear moraines and lateral marginal moraines in the geological record this distinction is important for understanding the mechanisms of sediment transfer beneath ice streams and for making inferences about the conditions that existed beyond the lateral ice stream margin at the time of lateral moraine formation slow moving ice beyond lateral shear moraines and ocean water rather than ice beyond lateral marginal moraines

subglacial meltwater discharge in the open marine tidewater glacier environment observations from nordaustlandet svalbard archipelago the ice proximal environment of the nordaustlandet tidewater ice cap svalbard archipelago is one of the best analogues for understanding glacial geologic processes of northern continental shelves during initial pleistocene deglaciation investigations of the proglacial region in 1980 1983 showed that the sedimentary environment is dominated by numerous meltwater outflows which discharge sediment laden water from subglacial meltwater streams during the summer two large stable meltwater outflows were observed in embayments along the southern part of the ice front landsat images show that both outflows have been in approximately the same position since at least 1976 they are located at the intersection of glacial drainage basins and centered over depressions in the underlying bedrock an outflow valley extending away from the ice front was observed in front of the western meltwater outflow sidescan sonar profiling along the glacier front showed a 200 m wide gap in acoustic reflection at the base of the western meltwater outflow probably caused by meltwater effluence enhanced sediment accumulations in this region observed as a 3 ms sediment drape in front of the outflow and large arcuate ridges in the outflow valley testify to the transport efficiency of the subglacial meltwater stream several mounds up to about 25 m high and 200 m wide are observed on sidescan and 3 5 khz profiles directly in front of the outflow although samples from these structures are absent they are most likely composed of sediment and are similar to beaded eskers observed in pleistocene glacimarine sequences indicating locally very high sedimentation rates fine grained components of the subglacial discharge incorporated in the buoyant meltwater plume are usually entrained in a westerly coastal current elevated suspended particulate material concentrations are observed within the coastal waters in a region extending about 15 km perpendicular to the glacier front and at least 60 km along the ice front extending into the northwestern barents sea

submarine landforms reveal varying rates and styles of deglaciation in north west greenland fjords during this work c l batchelor was in receipt of a junior research fellowship at newnham college cambridge the bathymetric data that was collected during jr175 of the rrs james clark ross to west greenland in 2009 was funded by natural environment research council nerc grant ne d001951 1 to c o cofaigh

an inter ice stream glaciated margin submarine landforms and a geomorphic model based on marine geophysical data from svalbard well preserved submarine landforms from the continental shelf and fjords of northwest ernmost svalbard provide an example of ice sheet deposition in an inter ice stream setting em1002 swath bathymetric imagery covering 1280 km 2 was examined at the shelf edge a distinctive and continuous belt of hum mocky topography represents the grounding zone of a slow moving late weichselian ice sheet active ice on the outer shelf is inferred from subtle lineations orientated parallel to fl ow low amplitude transverse moraines crosscut the lineations suggesting ice retreat across the outer shelf with brief stillstands on the middle and inner shelf large moraine ridges indicate multiple stillstands during de glaciation there are arcuate moraine ridges at fjord mouths streamlined crag and tail landforms are preserved from when ac tive full glacial ice fl owed out of the fjords clusters of smaller transverse ridges indi cate slow retreat of grounded ice through the fjords holocene sedimentation is by rainout from sediment rich meltwater producing smooth basin fi ll small slides from the fjord walls are common little ice age glacier readvance produced another set of terminal moraines and smaller retreat moraines in the innermost fjords a schematic model of this inter ice stream glacial landform assem blage summarizes the geomorphic record it is compared with a model derived from sev eral svalbard cross shelf troughs occupied by fast fl owing late weichselian ice streams in general the seafl oor morphology of continen tal margins affected by ice streams is domi nated by streamlined subglacially produced landforms oriented in the former ice fl ow direction interrupted by major grounding zone wedges formed during temporary halts in ice retreat by contrast between ice streams shelf and fjord morphology records submarine landforms of various dimensions oriented mainly transverse to ice fl ow pro duced at slowly retreating grounded ice sheet margins there is little evidence for channeled subglacial water fl ow in the form of eskers and ice contact fans on the sval bard margin implying that basal water is drained or advected mainly within soft sub glacial sediments

laminated sediments in glacimarine environments diagnostic criteria for their interpretation abstract fine grained laminated deposits are often reported from contemporary and ancient glacimarine sedimentary sequences laminated glacimarine sediments form by a variety of processes including suspension settling from turbid overflow plumes turbidity current deposition and contour current activity subglacial deformation of pre existing sediments may also produce laminated deposits in the form of glacitectonite and deformation till the development of diagnostic criteria for genetic discrimination of laminated glacimarine sediments is important both for their correct interpretation in sedimentary sequences and also for the accurate reconstruction of former glacier extent and geometry as laminated sediments may form in subglacial ice proximal and ice distal environments this paper reviews the processes by which laminated glacimarine sediments form and their resulting sedimentology the aim is to provide a synthesis of diagnostic sedimentological criteria for laminated glacimarine deposits that will assist in the interpretation of such sediments in the geological record laminated sediments are genetically differentiated on the basis of sedimentary structures bedding contacts stratigraphic relationships and macrofaunal content bioturbation these attributes also facilitate discrimination between glacimarine and glacilacustrine rhythmites the paper concludes by discussing the glaciological significance of laminated glacimarine sediments in terms of glacier hydrology reconstructions of former ice dynamics and basal thermal regime