submarine landforms and shallow acoustic stratigraphy of a 400 km long fjord shelf slope transect kangerlussuaq margin east greenland kangerlussuaq fjord is a relatively uniform steep walled basin whose floor has an almost smooth surface debris is supplied mainly from icebergs from the fast flowing kangerlussuaq glacier sedimentation after iceberg release from multi year sea ice is mainly by rain out of fine grained englacial debris streamlined glacial lineations and drumlins were produced at the sedimentary bed of an ice sheet that expanded into kangerlussuaq trough at the last glacial maximum lgm bedrock channels and crescentic overdeepenings indicate warm based ice and free water beneath parts of the former ice sheet cross cutting iceberg scour marks which characterise outer kangerlussuaq shelf were produced not only during deglaciation but also occasionally through the holocene by deep keeled icebergs from further north in east greenland the outward convex contours of the shelf edge and slope beyond kangerlussuaq trough and debris flows on the slope suggest a glacier influenced high latitude fan the distribution of streamlined subglacial landforms demonstrates that the greenland ice sheet extended throughout kangerlussuaq fjord and reached at least 200 km across the shelf in kangerlussuaq trough at the lgm streamlined landform orientation indicates ice flow from the interior of greenland down the axis of kangerlussuaq trough there is little evidence for discrete sedimentary depocentres in the trough implying that ice probably retreated rapidly from the outer and mid shelf during deglaciation

11 000 yrs of environmental change in the northwest passage a multiproxy core record from central parry channel canadian high arctic article i nfo piston core 97022 004pc 74 48 0 n 97 05 9 w 267 m water depth represents a rare paleoenvironmental archive from the understudied west central canadian arctic archipelago lithological biogeochemical and microfossil dinoflagellate cysts non pollen palynomorphs benthic and planktonic foraminifera character istics in combination with a chronostratigraphy based on seventeen radiocarbon dates show seven promi nent paleoenvironmental episodes since the end of the last regional glaciation the basal diamict zone i records decoupling of previously grounded glacial ice followed by ice proximal conditions zone iia commencing at 10 8 cal ka bp age depth model extrapolation after an interval of pervasive sea ice zone iib ice distal conditions are established zone iic although sparse microfossils are present in glaciomarine sediments zone ii noticeable biological activity with heightened abundances and diversities across all groups begins in the postglacial zone iii 10 3 10 0 cal ka bp when planktonic foraminifera neogloboquadrina pachyderma appear as planktonics are excluded from the study area today due to shal low inter channel sills this likely signals the inflow of relatively warm and saline atlantic derived arctic intermediate water below 250 m presumably facilitated by glacio isostatically enhanced deglacial water depths the subsequent zone iv 10 0 7 0 cal ka bp characterized by heightened biological productivity in both plankton and benthos and reduced seasonal sea ice cover may correspond to a previously proposed holocene thermal maximum this apparent amelioration ends by the mid holocene zone v 7 0 5 7 cal ka bp when arctic intermediate water is excluded from the study area and water depths approach modern values high arctic conditions with seasonal sea ice cover a circulation dominated by arctic ocean surface water and microfossil assemblages similar to modern are found from 5 7 cal ka bp onwards zones vi vii as only minor environmental fluctuations are apparent during the late holocene shorter term climatic episodes e g little ice age are not recognized in this record

late holocene terrestrial glacial history of miki and i c jacobsen fjords east greenland we present a late holocene glacial and environmental history of three valleys within miki and i c jacobsen fjords east greenland 68 n the fjords have no direct connection with the main ice sheet and are presently glacierized by a series of local ice caps and glaciers little sediment has been deposited within the study area but bedrock is distinctly glacially striated which suggests that extensive valley glaciers reached the present coastline in the past moraines are the prominent morphological features including distinct end and lateral moraines most of the moraines are related to the existing glaciers in the area apparent moraines extend as far as 2 to 2 5 km in front of present day glaciers based on morphological and stratigraphical studies of the sediments in these valleys five glacier advances during the late holocene are implied stabilization of the oldest moraines is lichenometrically dated to c 1450 to 1650 years ago younger moraines in both miki and i c jacobsen fjords are lichenometrically dated to c 1050 1100 years ago c 750 950 years ago and c 600 700 years ago the youngest moraines containing measurable lichens stabilized c 300 400 years ago the timing of this moraine formation correlates to marine records from previous research on the inner part of miki fjord where apparent intensification in sediment stratification is related to a glacier advance into the fjord c 290 years ago this glacial advance may correlate to the little ice age cooling observed in many records from the north atlantic region our glacial record from miki and i c jacobsen fjords also shows good correlation with temperature proxies within the grip ice core in greenland and foraminifera records from nansen fjord east greenland less pronounced correlation is observed with the icelandic sea ice index and records of glacier fluctuation in iceland during the last 1000 years these results suggest that widespread climatic cooling was the direct cause of many of the late holocene glacier variations documented in this study although the glacial advance at c 1050 1100 years ago coincides with the so called medieval warm period and could reflect the response of glaciers to increased precipitation within the area

sedimentation associated with antarctic peninsula ice shelves implications for palaeoenvironmental reconstructions of glacimarine sediments abstract recent disintegration of a number of antarctic peninsula ice shelves has given us a unique opportunity to investigate sub ice shelf sediments we characterize three sediment facies associations of two antarctic peninsula ice shelves larsen a and larsen inlet subglacial facies consist mainly of basal till diamicton with high shear strengths deposited under a grounded ice sheet progressive upward decrease in shear strength reflects a gradual decrease in the confining vertical effective pressure of grounded ice during till deposition proximal ice shelf glacimarine facies diamicton gravel rich and sand rich facies gravelly mud dropstone mud and sandy muds were deposited by sub ice shelf rain out bottom current activity and sediment gravity flows following decoupling of grounded ice from the sea floor distal ice shelf glacimarine and or open marine facies comprise terrigenous and diatom bearing bioturbated muds and gravelly muds that contain limited ice rafted debris these accumulated after recession of the grounding line to the coast with coarse grained surface sediments possibly documenting most recent ice shelf break up antarctic peninsula ice shelf sediments are more heterogeneous than ice shelf facies deposited elsewhere in antarctica cold polar antarctic ice shelves can be differentiated from temperate and sub polar marine terminated glacial sedimentary systems by the dominance of coarse grained proximal ice shelf glacimarine facies and an absence of subaqueous outwash meltwater sediment facies

a depositional record of deglaciation in a paleofjord late carboniferous pennsylvanian of san juan province argentina the role of catastrophic sedimentation the combination of high sediment supply rates and ample accommodation within fjords provides high resolution records of deglaciation ancient fjord fills provide the potential for three dimensional views of the evolution of depositional environments in response to changing sediment supply and base level through the deglacial process we describe the fill jejenes formation of a well exposed late carboniferous pennsylvanian glacial valley and its tributaries these deposits record the progressive marine flooding and infilling of topography by glacially derived sediments the geometry of the valley and its tributaries is controlled by the underlying lower paleozoic lithologies a deep valley with steep sides exists where the bedrock is massive limestones and a broader shallower valley exists where the bedrock is generally a fine grained olistostrome the valleys are locally floored with diamictites including both in situ tillites and remobilized diamictites in the trunk valley these are locally overlain by a small shallow water delta the major part of the valley fill consists of a 150 m thick mudstone dominated succession probably generated by plumes of glacial outwash containing numerous dropstones that decrease in abundance down the fjord the mudstones contain numerous thin sandstone and conglomerate turbidites that were supplied laterally via subaqueous gravel fans feeding in from the tributary valleys each of which has a distinctive clast suite related to the local subcrop the entire succession is overlain by 300 m of sandy turbidites of which the upper part includes large mass transport complexes intercalated within the succession in the trunk valley are structureless graded silty mudstones lacking dropstones but with abundant large wood fragments close to the steep western margin of the trunk valley each of these massive mudstones is underlain by a slump or debris flow locally containing meter scale blocks of ordovician limestone from the valley side we interpret these as a consequence of rockfalls from the steeper valley sides triggering debris flows on the subaqueous fjord slopes we suggest that large solitary waves were generated as the rockfalls entered the water traveling along the fjord and stripping vegetation from the shoreline large amounts of mud and silt were thrown into suspension during these events and subsequently settled from suspension to form the structureless graded beds these deposits and other mass flow deposits within the succession emphasize the potential importance of catastrophic sedimentation within deglacial successions

8000 year marine record of climate variability and fjord dynamics from southern greenland abstract holocene sediment records of glacio marine environmental and climatic changes from ikersuaq fjord and narsaq sound in southern greenland have been studied the ikersuaq fjord record representing the last c 500 years is dominated by turbidite sedimentation and very high sedimentations rates of up to 1 cm yr the adjacent narsaq sound site on the other hand represents a continuous and more slowly accumulating sedimentation record of the last c 8000 years the narsaq record reveals changes in position and melting rates of glacier termini of the nearby greenland ice sheet from the holocene thermal optimum period terminating at about 5 0 ka to the neoglaciation period during the late holocene from 8 0 ka to 4 8 ka ice rafted debris ird influx progressively became reduced supporting a landward retraction of glacier termini neoglaciation of the region appears to have been initiated at about 4 8 ka with a culmination of ird rain at about 4 6 ka 3 6 ka 2 2 ka 1 0 ka 0 7 ka and 0 5 ka and onward some of these ird events appear to be associated with enhanced melting and glacier instability during warming episodes however at the transition to the little ice age at about 1450 years ad a marked increase in ird influx took place the bottom water of narsaq sound appears to have been dominated by modified irminger water atlantic during most of the holocene bottom current flow was quite sluggish before 3 2 ka whereas the late holocene period appears to have been characterised by three pronounced episodes of increased bottom current velocity and increased calcareous benthic foraminifera productivity the long term climate pattern in the narsaq sound record follows climate changes consistent with patterns of east greenland current variability which is partly related to dominant north atlantic oscillation forcing of wind and ice drift patterns

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

sedimentation in isolated glaciomarine embayments during glacio isostatically induced relative sea level fall northern champlain sea basin the nature of glaciomarine sediments deposited during ice margin retreat can vary according to physiographic setting and relative sea level fluctuations to understand the effects of these two parameters on sedimentation we analyzed the sediment records of four lakes located within former isolated glaciomarine embayments of the northern champlain sea basin these lakes were initially inundated by marine water of the champlain sea following deglaciation and have subsequently experienced basin isolation owing to glacio isostatic rebound three of these lakes reveal a common litho and acoustic stratigraphic succession characterized by an ird free glaciomarine to marine facies consisting of homogeneous to faintly laminated clayey silts grading into well laminated silts with rapidly deposited layers these two units recorded the transitional environment from glaciomarine sedimentation below multiyear shorefast ice to increased terrestrial runoff and rapid glacio isostatic rebound once the ice margin retre

spatial and temporal patterns of iceberg rafting ird along the east greenland margin ca 68 n over the last 14 cal ka twelve 1 2 m 10 cm diameter gravity cores collected in 1988 and 1991 from the continental shelf and fjords of east greenland near kangerlussuaq fjord trough ca 68 n 32 w have distinct changes in lithofacies and in the quantity of iceberg rafted ird sediments these changes are readily observed in x radiographs of the split cores we quantify the ird contribution through grain size analyses and counting the number of clasts 2 mm from the x radiographs chronological control is provided by acclerated mass spectroscopy 14c dates on foraminifera during deglaciation after 14 cal ka there was one interval of ird accumulation ca 12 13 cal ka followed by a brief return to ird conditions centred at 9 cal ka thereafter a prominent feature of most cores on the shelf is an increase in ird accumulation that started ca 5 6 cal ka and which has increased toward the present indicators of iceberg rafting such as the net sand flux and numbers of clasts 2 mm ka 1 follow a power law distribution when graphed against distance from the present east greenland coast a measure of the position of the glacier margins the form of the relationship indicates that there is a dramatic decrease in the supply of sediment from the fjords to the shelf these relationships are used to estimate changes in the location of the ice margin during the late quaternary based on a site on the east greenland slope denmark strait and to discuss factors that can negate such a simple transfer function 1997 by john wiley sons ltd

late quaternary sedimentation in kejser franz joseph fjord and the continental margin of east greenland the marine sedimentary record in kejser franz joseph fjord and on the east greenland continental margin contains a history of late quaternary glaciation and sedimentation evidence suggests that a middle shelf moraine represents the maximum shelfward extent of the greenland ice sheet during the last glacial maximum on the upper slope coarse grained sediments are derived from the release of significant quantities of iceberg rafted debris ird and subsequent remobilization by subaqueous mass flows the middle lower slope is characterized by hemipelagic sedimentation with lower quantities of ird dropstone mud and sandy mud punctuated episodically by deposition of diamicton and graded sand gravel facies by subaqueous debris flows and turbidity currents derived from the mass failure of upper slope sediments the downslope decrease of ird reflects either the action of the east greenland current egc confining icebergs to the upper slope or to the more ice proximal setting of the upper slope relative to the lgm ice margin sediment gravity flows on the slope are likely to have fed into the east greenland channel system contributing to its formation in conjunction with the cascade of dense brines down the slope following sea ice formation across the shelf deglaciation commenced after 15 300 14c years as indicated by meltwater derived light oxygen isotope ratios an abrupt decrease in both ird deposition and delivery of coarse grained debris to the slope at this time supports ice recession with icebergs confined to the shelf by the egc glacier ice had abandoned the middle shelf before 13 000 14c years with ice loss through iceberg calving and deposition of diamicton continued retreat of glacier ice from the inner shelf and through the fjord is marked by a transition from subglacial till bedrock in acoustic records to ice proximal meltwater derived laminated mud to ice distal bioturbated mud ice abandoned the inner shelf before 9100 14c years and probably stabilized in fosters bugt at 10 000 14c years distinct oxygen isotope minima on the inner shelf indicate meltwater production during ice retreat the outer fjord was free of ice before 7440 14c years glacier retreat through the mid outer fjord was punctuated by topographically controlled stillstands where ice proximal sediment was fed into fjord basins the dominance of fine grained commonly laminated facies during deglaciation supports ablation controlled ice mass loss glacimarine sedimentation within the holocene middle outer fjord system is dominated by sediment gravity flow and suspension settling from meltwater plumes suspension sediments comprise mainly mud facies indicating significant meltwater deposition that overwhelms debris release from icebergs in this east greenland fjord system the relatively widespread occurrence of fine grained lithofacies in east greenland fjords suggests that meltwater sedimentation can be significant in polar glacimarine environments the ice distal continental margin is characterized by meltwater sedimentation in the inner shelf deep iceberg scouring over shallow shelf regions winnowing and erosion by the east greenland current on the middle outer shelf and hemipelagic sedimentation on the continental slope

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

modelling rates of sedimentation from icebergs abstract icebergs transport debris from ice masses into the glacimarine environment but iceberg production debris content and sedimentation rate will vary with glacier dynamics and the nature of marine waters a model incorporating glaciological and oceanographic parameters calculates the flux of debris calved in icebergs iceberg melt rates and sedimentation rates with distance from calving tidewater ice fronts the flux of basal debris calved through a 1 m width of tidewater margin is h d c 100 v c where h d and c are basal debris rich ice thickness and sediment content and v c is iceberg calving rate iceberg basal melting for any horizontal interval d x away from the calving glacier is dy m b d x v b where m b is iceberg melt rate and v b is horizontal iceberg velocity sediment release for any x increment depends on iceberg debris concentration and previous berg melt history model parameters vary with the nature of climatic conditions on a continuum from cold polar environments e g high canadian arctic antarctic peninsula through sub polar environments e g baffin island svalbard to more temperate environments e g se alaska these parameters include glacier flow velocity glacier thermal regime basal debris rich ice thickness and marine water temperature model results suggest that iceberg sedimentation rates are lowest for high polar settings and most rapid in warm maritime and some sub polar areas however icebergs in cold waters transport debris to significantly greater distances from the parent glacier the model provides calculations of order of magnitude rates of iceberg sedimentation in varying glacimarine settings

temperate glacimarine varves an example from disenchantment bay southern alaska abstract the sediment record of disenchantment bay southern alaska a large marine calving embayment contains distinctive annual deposits each year a glacimarine couplet forms with a clast rich stratified to massive diamicton deposited in winter by intense iceberg rafting and a summer meltwater deposit of thinly laminated mud and turbidite sand beds although iceberg rafting occurs throughout the year coarse debris is deposited in high concentrations and forms diamicton only during the winter because of minimal fine sediment from meltwater discharges and a longer residence time of icebergs in the bay due to winter fjord circulation and meteorological factors when meltwater discharge commences in summer laminated mud with dropstones is deposited spring and fall conditions are recorded a transitional phases between winter and summer by clast poor diamictons average sediment accumulation rates calculated from varve thicknesses range from 48 cm yr 3 4 km from hubbard glacier at the head of the bay to 14 cm yr 15 km away sediment accumulation rates estimated from 210pb dating of core sediments are in the same range deposits from the 1986 russell fiord outburst flood are identified from anomalously high 210pb activities in sediments indicating an alternative sediment source to disenchantment bay glacimarine varves are a dating tool for the barren proximal sediments commonly deposited near calving glacier termini they yield paleoclimatic information because they are a product of both glacial ice in the sea and laminated sediments deposited from significant melt water discharge found in a temperate to subpolar climate

the sedimentary record of drifting ice early wisconsin sunnybrook deposit in an ancestral ice dammed lake ontario canada abstract outcrops of pebbly mud diamict at scarborough in southern ontario canada the so called sunnybrook till are associated with the earliest incursion of the laurentide ice sheet lis into mid continent north america some 45 000 years ago the sunnybrook is a blanket like deposit containing deepwater ostracodes and occurs conformably within a thick 100 m succession of deltaic and glaciolacustrine facies that record water depth changes in a large proglacial lake contextual evidence associated facies sedimentary structures deposit geometry and landforms indicates a low energy depositional setting in an ice dammed ancestral lake ontario in which scouring by floating ice masses was an important process u shaped iceberg cut scours with lateral berms up to 7 m deep occur on the upper surface of the sunnybrook and are underlain by sub scour structures that extend several meters below the scour base ice rafted concentrations of clasts clast layers grooved surfaces formed by floating ice glissading over a muddy lake floor soft sediment striations and melanges of sand and mud mixed by grounding ice keels ice keel turbates are present and are all well known from modern cold environments the wider significance of this depositional model is that the lis margin lay east of scarborough and did not overrun southern ontario this finding is in agreement with recent data from the erie basin of canada ohio and indiana where deposits formerly correlated with the sunnybrook and thus implying an extensive early wisconsin ice sheet are now regarded as illinoian a speculative hypothesis is proposed that relates deposition of the sunnybrook and two younger deposits of similar sedimentology to surge like instabilities of the southern lis margin

submarine processes of the middle atlantic continental rise based on gloria imagery approximately 6 100 km of 3 5 khz echo sounding profiles was correlated with a gloria side scan sonar image of the mid atlantic united states 34 n 70 w lower slope upper continental rise the image allows us to map the major erosional and depositional features and to identify major processes that have shaped the area the gloria imagery shows three approximately triangular shaped sediment gather areas that cover the upper rise and slope transition areas near wilmington baltimore and norfolk canyons the gather areas which are interspersed with hemipelagic drape areas are composed of dendritic networks of channels that extend from the base of the slope toward major channel systems on the middle rise such as wilmington valley seaward of cape hatteras a tongue shaped area of mottled high back scatter on the gloria imagery denotes the albemarle currituck mass movement complex a large 60 km wide by 190 km long area of the sea floor that is marked by the disruption of upper rise sedimentary strata and by mass flow deposits interpretation of gloria imagery and echo sounding profiles indicates that mass movement is the predominant process affecting sediment on the united states east coast mid atlantic slope and upper rise and that isobath parallel sediment movement by geostrophic currents is restricted mainly to the lower continental rise the mass movement processes evident on the rise probably were most active during the pleistocene when sea level was lower and sediment input more active

glacier and ocean variability in ata sund west greenland since 1400 ce to improve knowledge of marine terminating glaciers in western greenland marine sediment cores from the ata sund fjord system hosting two outlet glaciers eqip sermia and kangilerngata sermia were investigated the main objective was to reconstruct glacial activity and paleoceanographic conditions during the past 600 years ice rafted debris ird was quantified by wet sieving sediment samples and by using a computed tomography scan variability in relative bottom water temperatures in the fjord was reconstructed using foraminiferal analysis on the basis of this three periods of distinct glacial regimes were identified period 1 1380 1810 ce which covers the culmination of the little ice age lia and is interpreted as having advanced glaciers with high ird content period 2 1810 1920 ce the end of the lia which was characterised by a lowering of the glaciers calving flux in response to climate cooling during period 3 1920 2014 ce both glaciers retreated substantially to their present day extent the bottom water temperature started to decrease just before period 2 and remained relatively low until just before the end of period 3 this is interpreted as a local response to increased glacial meltwater input our study was compared with a study in disko bay nearby jakobshavn glacier and the result shows that both of these greenlandic marine terminating glaciers are responding to large scale climate change however the specific imprint on the glaciers and the different fjord waters in front of them result in contrasting glacial responses and sediment archives in their respective fjords

western north atlantic evidence for millennial scale changes in ocean circulation and climate two late quaternary series of high resolution percent carbonate data from western north atlantic sediment drifts bermuda rise and bahama outer ridge show millennial scale oscillations superimposed on the familiar longer period oscillations of orbital origin the dominant high frequency oscillation in these records has a quasi period of about 4000 years these percent caco3 changes most likely result from the influence of climate change on the flux of terrigenous material from eastern canada the resuspension of continental margin sediment by deep eddy kinetic energy and carbonate dissolution sediment is transported to the bermuda rise by deep recirculating gyres and to the bahama outer ridge by the deep western boundary current system stable isotope results on foraminifera across several of these oscillations from interstadial climate conditions and from a glacial inception display variability similar to that of percent caco3 oxygen isotope ratios of planktonic foraminifera suggest large variations in near surface temperature and or salinity and carbon isotope ratios of benthic foraminifera indicate that there were significant oscillations in the flux of north atlantic deep water nadw these data support models which couple surface ocean conditions in the north atlantic production of nadw north atlantic heat flux and evidence for temperature oscillations in ice cores

sediment thicknesses and holocene glacial marine sedimentation rates in three east greenland fjords ca 68 n we compared measured and estimated sediment budgets in heavily glaciated fjords in east greenland mass balance calculations and regional glacio climatic conditions suggest that the sediment flux to the seafloor in kangerdlugssuaq and nansen fjords should be dominated by iceberg rafting and not by the rain out of suspended particulates in meltwater as the glacier calving flux is estimated at 15 and 2 km 3 yr compared to meltwater volumes of 4 4 and 1 7 km 3 yr respectively gravity cores in the three fjords indicate that the uppermost 1 2 5 m of sediment consists of diamictons or fine grained laminated muds ams radiocarbon dates on calcareous foramininfera or shells 16 total indicate sedimentation rates of 110 to 340 cm ka within the fjords over the last 1 ka and 10 20 cm ka during the holecene on the inner and middle shelf annual sediment discharge is around 0 67 times 10 6 tonnes yr within the kangerdlugssuaq fjord and trough system which translates into an average basin wide rate

holocene glacimarine sedimentary environments in fiords of disko bugt west greenland abstract acoustic and sedimentary properties of three fiord systems were examined in the region of disko bugt west greenland to understand variability in the processes rates and sources of sediment delivery during the late glacial and holocene kangerluk and kangersooq of western disko are dominated by meltwater inputs of sediment from local ice fields of the island interior modern sediments are delivered primarily via overflow currents rainout occasional bottom currents and small amounts of iceberg rafting where exposure to baffin bay allows penetration of the west greenland current 14 c and acoustic derived accumulation rates for the last 1 2 ka vary from about 1 mm a 1 in distal fiord settings to more than 5 mm a 1 in proximal sites adjacent to actively building deltas these rates are generally larger than has been observed in other greenland and baffin bay fiords the tidewater terminus of inland ice at ikerasak is also meltwater dominated but produces lower than expected sediment accumulation due to low gradients of the outlet ice and resistant substrates these high latitude west greenland fiords are subarctic in character and contrast significantly with colder polar type fiords at similar latitudes in east greenland sediment deposition which was focused in the outer disko fiords during the late glacial and early holocene is due to one of two possible mechanisms standstill of local ice or enhanced rafting of sediment from disko bugt icebergs this study contributes to the debate on the extent of glaciation and holocene spatial variability in fiord processes of west greenland

morphology of abyssal mudwaves at project mudwaves sites in the argentine basin abstract extensive fields of mudwaves are present in the argentine basin mudwaves and water parameters at three sites were studied to provide detailed information on bathymetry mudwave structure sediment parameters and bottom water flow characteristics two sites 5 and 6 are discussed in this paper crests of mudwaves at site 5 on the north flank of the zapiola drift are oriented 45 anti clockwise from the measured westward flow direction and migrate to the left of the flow direction mudwaves at site 6 on the south flank of the zapiola drift are oriented 20 anti clockwise from the inferred southeast bottom flow direction and also migrate to the left of direction evidence from current meters and surface sediments suggests that the mudwaves at site 5 are active today while those at site 6 have been active in the holocene but perhaps not within the last 100 years mudwave orientation anti clockwise to mean flow preferential sediment accumulation on the left wave flank and apparent sediment accumulation on the wave crest agree with a model for mudwave growth presented by blumsack and weatherly 1989 deep sea research 36 1327 1339 cross wave asymmetry in sediment accumulation pattern is sufficient to cause a 10 change in surface sediment bulk density over the wave profile the record of mudwave migration obtained from sites 5 and 6 in the southern argentine basin and from site 7 in the northern argentine basin suggests that bottom water flow has changed over a number of time scales during the last 200 000 years thus the analysis of abyssal bed forms can provide independent evidence about past changes in bottom flow

centennial to millennial scale ice ocean interactions in the subpolar northeast atlantic 18 41 kyr ago in order to monitor the evolution of the british irish ice sheet biis and its influence in surface ocean structure during marine isotopic stages mis 2 and 3 we have analyzed the sediments recovered in core md04 2829cq rosemary bank north rockall trough northeast atlantic dated between 41 and 18 ka b p ice rafted debris flux and composition 40ar 39ar ages of individual hornblende grains multispecies planktonic stable isotope records planktonic foraminifera assemblage data and faunal based sea surface temperatures ssts demonstrate a close interaction between biis dynamics and surface ocean structure and water properties in this region the core location lies beneath the north atlantic current nac and is ideal for monitoring the shifts in the position of its associated oceanic fronts as recorded by faunal changes these data reveal a succession of biis sourced iceberg calving events related to low sst usually synchronous with dramatic changes in the composition of the planktonic foraminifera assemblage and with variations in the stable isotope records of the taxa neogloboquadrina pachyderma sinistral coiling and globigerina bulloides the pacing of the calving events from typically dansgaard oeschger millennial timescales during late mis 3 to multicentennial cyclicity from 28 ka b p represents the build up of the biis and its growing instability toward heinrich event he 2 and the last glacial maximum our data confirm the strong coupling between biis instabilities and the temperature and salinity of surface waters in the adjacent northeast atlantic and demonstrate the biis s ability to modify the nac on its flow toward the nordic seas in contrast subsurface water masses were less affected except during the greenland stadials that contain hes when most intense water column reorganizations occurred simultaneously with the deposition of cream colored carbonate sourced from the laurentide ice sheet

stratigraphic signature of the late palaeozoic ice age in the parmeener supergroup of tasmania se australia and inter regional comparisons abstract recent research in eastern australia has established that rather than being a single long lived epoch the late palaeozoic ice age comprised a series of glacial intervals each 1 8 million years in duration separated by non glacial intervals of comparable duration in order to test whether the glacial events recognized in new south wales and queensland have broader extent we conducted a reappraisal of the parmeener supergroup of tasmania southeast australia a facies analysis of the pennsylvanian to permian section was carried out allowing rationalization of the succession into four recurrent facies associations a glacigenic facies association restricted to the basal pennsylvanian earliest permian wynyard formation and correlatives b glacially cold climate influenced to open marine shelf facies association which accounts for large parts of the permian succession c deltaic facies association which specifically describes the lower permian lower freshwater sequence interval and d fluvial to estuarine facies association which specifically addresses the upper permian cygnet coal measures and correlatives indicators of sediment accumulation under glacial influence and cold climate are restricted to four discrete stratigraphic intervals all of which indicate that glaciation was temperate in nature the lowermost of these incorporating the basal wynyard formation and its correlatives and overlying woody island formation shows evidence of proximal glacial influence subglacial grounding line fan and fjordal facies and is likely a composite of one or more pennsylvanian glacial event s and an earliest permian asselian glacial the second of late sakmarian to early artinskian age comprises an initial more proximal ice influenced section and an overlying more distal ice influenced interval the third kungurian to roadian and fourth capitanian intervals are both distal glacimarine records the four intervals are of comparable age to glacials p1 p4 respectively recognized in new south wales and queensland notwithstanding apparent discrepancies of

description and numerical model of pleistocene iceberg scours and ice keel turbated facies at toronto canada near toronto in southern ontario canada glaciolacustrine muds and shoreface sands of late pleistocene age early wisconsin glaciation 45 ka were deformed by icebergs ploughing the floor of an ancestral ice dammed lake ontario outcrop mapping and a ground penetrating radar survey identify ice scour structures up to 4 m deep up to 10 m wide and at least several hundred metres long with high standing lateral margins berms ploughing of lake floor sediment is also recorded by ice keel turbated facies in which storm deposited shoreface sands have been mechanically mixed with underlying muds palaeoenvironmental information for one prominent scour such as water depths estimates of the mass and draft of the ice mass and scouring forces can be determined using a simple finite element numerical model a mass of 0 04 million tonnes a keel draft of between 10 and 30 m and a scouring force of 5 103 kn is consistent with scouring by a small iceberg bergy bit or pressure ridged lake ice the former is preferred because of the considerable depth of the scour and the overall glacial depositional setting estimates of ice mass dimensions agree with independent reconstructions of palaeobathymetry no greater than 20 m derived from storm deposited hummocky and swaley cross stratified facies that fill the scour data presented here aid the identification of ice scour structures and turbated sediment in the ancient record despite being a common process on modern high latitude shelves descriptions of ancient structures and facies are few

biogenic facies in the antarctic glacimarine environment basis for a polar glacimarine summary abstract the association of glacial deposits diamicts or tillites with biogenic and or chemically derived sedimentary rocks in the ancient record is one which continues to challenge interpretation an analogous association can be found on portions of the east antarctic continental shelf where relict glacial and glacimarine diamictons are overlain by a varied and complex suite of modern biogenic deposits carbonate bioclastic material can be found in two distinct zones and its deposition may have been contemporaneous with partial glacial expansion onto the shelf a nearshore carbonate facies consists of in situ and partially reworked barnacles bryozoans ostracods pelycepods gastropods planktonic and benthonic foraminifera a siliceous biogenic component is intermixed within the shallow water 500 m siliceous facies of pelagic hemipelagic and sediment gravity flow origin is found within inner shelf depressions and consists predominantly of diatom frustules and radiolaria these accumulations of siliceous ooze and mud clearly post date glacial recession from the shelf and contain laminated cross laminated and massive interbeds which are accumulating at rates of 0 3 cm yr the extreme polar climate inhibits meltwater production and terrigenous influx into marine basins this allows for the accumulation of biogenic rich material which is also favored by the high seasonal productivity inherent in the south polar oceans ancient analogs to these modern deposits exist and their association with glacimarine strata could be used to infer polar climatic settings and glacial retreat that is related to eustatic sea level rather than regional warming

abyssal bedforms as indicators of changing bottom current flow examples from the u s east coast continental rise direct indications of circulation patterns in the deep sea especially along continental rises and sediment drifts can be obtained through the analysis of abyssal bedforms such as furrows and mud waves such direct evidence of current flow will supplement indirect indicators of circulation provide by paleochemical indicators preserved in ocean sediments water that sinks in the northern north atlantic forms part of the western boundary undercurrent along the continental rise of eastern north america and the understanding of temporal changes in the speed and depth of flow along this continental rise can provide important information on how the speed at which the global conveyor system is operating changes with time studies of furrows and mud waves along the blake bahama outer ridges show that they are active sedimentary features today and that bottom flow speeds near the time of the younger dryas were increased over later intervals a more detailed analysis of bedform structure and sediments is needed to more clearly show the timing and reason for this change in sedimentation pattern

the origin of massive diamicton facies by iceberg rafting and scouring scoresby sund east greenland almost 90 of 39 m of core material recovered from scoresby sund and the adjacent east greenland shelf is massive diamicton interpreted to be formed predominantly by the release of iceberg rafted debris and reworking by iceberg scouring there is also likely to be a contribution from suspension settling of fines derived from glaciofluvial sources model calculations suggest that the 14c derived holocene sedimentation rate of 0 1 0 3 m 1000 yr 1 in scoresby sund can be accounted for mainly by iceberg rafting of debris a further 4 of core material is of gravel or coarse sand lenses interpreted to reflect iceberg dumping of debris intensive iceberg scouring which reworks sea floor sediments is observed on acoustic records from over 30 000 km2 of the scoresby sund fiord system and the adjacent east greenland shelf 69 72 n and 75 n the rate of iceberg production from greenland ice sheet outlet glaciers and iceberg drift tracks on the shelf suggests that iceberg rafting and scouring may be important over a significant proportion of the 500 000 km2 area above the shelf break the relatively extensive modern occurrence of massive diamicton formed by iceberg rafting and scouring together with suspension settling of fines suggests that it may also be a significant facies in the glacier influenced geological record the recognition in the geological record of the massive diamicton facies described above may also indicate the former presence of fast flowing ice sheet outlet glaciers

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

sediment characteristics in iceberg dominated fjords kangerlussuaq region east greenland abstract sediment cores from three east greenland fjords contain sediment lithofacies and depositional processes in an iceberg dominated glacial marine setting three major lithofacies diamicton fine grained mud and sand are deposited by two processes sediment rain out and sediment gravity flows the sediments in kangerlussuaq fjord are predominately fine grained muds deposited by rain out from icebergs and glacier meltwater with sediment gravity flows acting as secondary agents of deposition miki fjord records rain out of fine grained muds from a river plume emanating from a proglacial delta at the fjord head alternating units of diamicton and fine grained mud in nansen fjord are deposited by sediment rain out from icebergs particle size is governed by the oceanographic conditions in the fjord at the time of deposition despite their proximity to each other each fjord is distinguished by a distinct sedimentological signature kangerlussuaq fjord has low total organic carbon contact miki fjord has high mass magnetic susceptibility and nansen fjord has high amounts of ice rafted debris comparison of the east greenland iceberg dominated and alaska glacial meltwater dominated environments indicates few major differences between sediments deposited in these two settings this similarity raises doubt as to how well glacial marine sedimentary sequences can be used to interpret and reconstruct differences between glacial marine environments in the past without knowledge of sediment accumulation rates environmental conditions at the time of sediment deposition and comparable sedimentological data between studies

significant differences in late quaternary bedrock erosion and transport east versus west greenland 70 n evidence from the mineralogy of offshore glacial marine sediments

correcting for the influence of ice rafted detritus on grain size based paleocurrent speed estimates the grain size of deep sea sediments provides an apparently simple proxy for current speed however grain size based proxies may be ambiguous when the size distribution reflects a combination of processes with current sorting only one of them in particular such sediment mixing hinders reconstruction of deep circulation changes associated with ice rafting events in the glacial north atlantic because variable ice rafted detritus ird input may falsely suggest current speed changes inverse modelling has been suggested as a way to overcome this problem however this approach requires high precision size measurements that register small changes in the size distribution here we show that such data can be obtained using electro sensing and laser diffraction techniques despite issues previously raised on the low precision of electro sensing methods and potential grain shape effects on laser diffraction down core size patterns obtained from a sediment core from the north atlantic are similar for both techniques reinforcing the conclusion that both techniques yield comparable results however ird input leads to a coarsening that spuriously suggests faster current speed we show that this ird influence can be accounted for using inverse modelling as long as wide size spectra are taken into account this yields current speed variations that are in agreement with other proxies our experiments thus show that for current speed reconstruction the choice of instrument is subordinate to a proper recognition of the various processes that determine the size distribution and that by using inverse modelling meaningful current speed reconstructions can be obtained from mixed sediments

environmental change in eastern greenland during the last 1300 years evidence from foraminifera and lithofacies in nansen fjord 68 n lithofacies and benthic foraminiferal analyses of two sediment cores bs1191 k13b and k14 from nansen fjord eastern greenland show evidence of changing oceanographic and sea ice conditions from

lithofacies types and vertical profile models an alternative approach to the description and environmental interpretation of glacial diamict and diamictite sequences abstract increased knowledge of modern glacial depositional environments has resulted in rapidly evolving classifications of glacial tills these are based to a large degree on theoretical considerations of likely depositional processes the classifications are sophisticated and more advanced than the establishment of simple field criteria whereby individual till facies can be identified in quaternary and pre quaternary successions this situation is compounded in many quaternary terrains by the continued description of tills in terms of laboratory derived analytical data only reflecting a traditional interest in stratigraphic correlation rather than reconstruction of depositional environment detailed sedimentological logging of lithofacies is rarely undertaken there is thus considerable confusion as to what is being described or sampled when analytical data are presented for many pleistocene tills the same remarks apply to pre pleistocene tillites a lithofacies code is presented here for the rapid description and visual appraisal of field sequences or drill cores containing unconsolidated diamicts or lithified diamictites the term till is not used as it has a strict genetic definition referring to direct aggregation and deposition by glacier ice use of a four part code in conjunction with codes already published for fluvial sediments allows fundamental field properties to be depicted independent of genetic terminology and provides a firm basis for subsequent environmental interpretation and analytical work the value of this approach is illustrated by comparing a representative suite of vertical profiles of diamict assemblages deposited by modern grounded glaciers with a classic late pleistocene glacigenic sequence at scarborough bluffs ontario

glacimarine sedimentary processes and facies on the polar north atlantic margins abstract major contrasts in the glaciological oceanic and atmospheric parameters affecting the polar north atlantic both over space between its eastern and western margins and through time from full glacial to interglacial conditions have lead to the deposition of a wide variety of sedimentary facies in these ice influenced seas the dynamics of the glaciers and ice sheets on the hinterlands surrounding the polar north atlantic have exterted a major influence on the processes rates and patterns of sedimentation on the continental margins of the norwegian and greenland seas over the late cenozoic the western margin is influenced by the cold east greenland current and the svalbard margin by the northernmost extent of the warm north atlantic drift and the passage of relatively warm cyclonic air masses in the fjords of spitsbergen and the northwestern barents sea glacial meltwater is dominant in delivering sediments in the fjords of east greenland the large numbers of icebergs produced from fast flowing outlets of the greenland ice sheet play a more significant role in sedimentation during full glacials sediments are delivered to the shelf break from fast flowing ice streams which drain huge basins within the parent ice sheet large prograding fans located on the continental slope offshore of these ice streams are made up of stacked debris flows large scale mass failures turbidity currents and gas escape structures also rework debris in continental slope and shelf settings even during interglacials both the margins and the deep ocean basins beyond them retain a glacimarine overprint derived from debris in far travelled icebergs and sea ice under full glacial conditions the glacier influence is correspondingly stronger and this is reflected in the glacial and glacimarine facies deposited at these times

iceberg scouring in scoresby sund and on the east greenland continental shelf modern and relict scours produced by iceberg keels have been reported from a number of high latitude continental shelves in the northern hemisphere and antarctica but observations are largely absent from the east greenland shelf about 18 km3 yr 1 of icebergs are calved into the scoresby sund fjord system east greenland these icebergs have submarine keels with drafts up to 550 m modern iceberg contacts with the sea floor are inferred from calculated keel depths and stationary icebergs identified on sequential landsat imagery acoustic profiles parasound 3 5 khz of the sea floor show that scouring is a significant process in water depths 550 m iceberg scouring intensity varies inversely with water depth the most intense scouring occurs at depths of 300 400 m iceberg scours were observed on over 25 000 km2 of the east greenland shelf at 69 72 n and 75 n scours are being actively produced on the modern shelf but relict scours probably dating back to the late weichselian are also present the rate of iceberg production from greenland ice sheet outlet glaciers and iceberg drift tracks on the shelf suggests that iceberg scouring is important over a significant proportion of the 500 000 km2 area above the shelf break around greenland

along slope variations in sediment lithofacies and depositional processes since the last glacial maximum on the northeast baffin margin canada abstract twelve piston cores were used to characterize late quaternary lithofacies depositional processes and deglacial history along the baffin bay slope between lancaster sound and home bay core investigations show four distinct laterally correlatable lithofacies along the slope basal and upper diamicton laminated red brown mud tan carbonate gravelly sandy mud and bioturbated brown mud basal diamicton largely represents glacigenic debris flow deposits during a glacial advance from baffin island at 25 cal ka the distribution and character of laminated red brown mud suggests a lateral supply to baffin bay slope from ice proximal meltwater plumes and turbidity currents sourced in glacial ice from both baffin bay shelf and home bay between 41 5 cal ka to 14 2 cal ka an upper diamicton records a lesser localized glacial advance that ended at about 14 2 cal ka tan carbonate mud events represent ice rafted enhanced detrital carbonate delivery to the slope between 25 cal ka and 11 cal ka a gradual thinning of these events from northern to southern baffin bay corroborates a northern baffin bay lancaster sound or nares strait iceberg source proglacial facies seaward of home bay contain beds with slightly elevated detrital carbonate that may represent the distal edge of carbonate ice rafted from lancaster sound baffin bay is a type example of a polar glacial basin in which direct glacial supply predominates over the effects of glacial meltwater as a result axial supply from the large ice streams north of baffin bay particularly lancaster sound is dominant in the baffin bay basin and lateral supply from smaller ice streams on baffin island predominates on the ne baffin slope

on deep current and hydrographic observations from a mudwave region and elsewhere in the argentine basin near bottom current measurements from both sides of a mudwave in an extensive mudwave region of the mid argentine basin are examined for evidence of lee waves such waves appear to exist when the across crest flow exceeds a critical value predicted by flood 1988 deep sea research 35 973 983 of about 9 cm s 1 the observations agree with the predictions of blumsack and weatherly 1989 deep sea research 36 155 172 in three of four cases however if it is assumed that the flow perturbations induced by lee waves are shifted slightly downcurrent from that predicted by the blumsack and weatherly model then there is agreement in all four cases the mudwave region is characterized as having a strong 10 cm s 1 steady eddy kinetic energy mean kinetic energy current the westward flow is consistent with the anticyclonic abyssal gyre centered about the zapiola drift inferred by flood and shor 1987 deep sea research 35 973 983 near bottom flow measurements made further to the west in the region of confluence of the brazil and malvinas current extensions reveal relatively energetic fluctuations and equatorward flowing deep western boundary currents along the continental slope along the continental rise a poleward flow is observed consistent with that inferred by reid 1989 progress in oceanography 23 149 244 too cold bottom layers were found to be common only on the lower continental slope 4000 m depth and at the mid basin mudwave site

mid carboniferous deglaciation of the protoprecordillera argentina recorded in the agua de jaguel palaeovalley abstract the agua de jaguel formation near uspallata mendoza province argentina was deposited within a palaeovalley along the southeastern margin of the calingasta uspallata basin adjacent to the protoprecordillera the basal glacigenic sequence of the formation was deposited in the serpukhovian early bashkirian near the beginning of the late palaeozoic ice age the sequence is composed of diamictite conglomerate sandstone and mudrock and records four depositional stages within a palaeofjord 1 morainal bank deposition by a wet based tidewater glacier 2 glacial retreat succession where ice retreated up the fjord out of the immediate area allowing iceberg deposition of dropstones and dump deposits 3 continued glacial retreat with ice receding onto land allowing a shoreface to develop within the palaeovalley and 4 transgression across the shoreface and resumption of iceberg deposition the thickness and facies of this succession are similar to deposits within modern alaskan fjords housing temperate tidewater glaciers comparison of the agua de jaguel formation with alaskan fjords indicates that sequence stratigraphy used for low latitude deposits must be applied with caution as glacimarine ice retreat within a fjord produces strata surfaces that are easily misidentified as flooding surfaces resulting from changes in water depth likewise the transgression during stage 4 is significant as it indicates a rise in sea level that occurred during glaciation of the protoprecordillera thus suggesting that the transgression between stages 3 and 4 was not driven by input of glacial meltwater additionally the sediment geochemistry suggests that the bottom waters of the palaeovalley were anoxic which may help explain the absence of bioturbation in the sequence as well as in other ancient glacimarine palaeovalleys the deglaciation succession and transgression are also recorded in the nearby hoyada verde and tramojo formations so it is proposed that all three formations record one glacial event in the protoprecordillera overlying fluvial and shallow marine strata in the agua de jaguel hoyada verde and tramojo formations show no indication of continued glaciation in the protoprecordillera following stage 4 and equivalent strata the deglaciation succession of the agua de jaguel formation affirms the emerging concept that the late palaeozoic ice age was characterized by alpine glaciers ice caps and small ice sheets that were not massive enough to have driven eustatic fluctuations of 100 m as previously understood and that ice never covered westernmost gondwana during later lpia events

late quaternary sedimentation along a fjord to shelf trough transect east greenland c 68 n the east greenland continental margin between c 66 and 68 n consists of a major fjord trough system that extends from kangerdlugssuaq fjord along kangerdlugssuaq trough to denmark strait measurements of the temperature and salinity of the water column along this transect indicates that warm water 0 2 c underlies the surface polar water of the east greenland current a series of short 1 3 m gravity cores along the fjord trough transect have sufficient numbers of foraminifera that a suite of ams 14c dates has been obtained including both basal and core top age estimates rates of sediment accumulation vary through space and time over the last 1 ka estimates vary from c 3 to 0 1 m these dates and measurements of sediment density together with measurements of the percentages by weight of total organic carbon and biogenic silica are used to show graphs of fluxes of the organic and inorganic sediment components over the last 1 14 ka an analysis of the net flux of foraminifera indicates a reduction in numbers during the younger dryas chronozone and a general similarity with data from the renland east greenland ice core data

mapping tide water glacier dynamics in east greenland using landsat data landsat multispectral scanner and thematic mapper images were co registered for the kangerdlugssuaq fjord region in east greenland and were used to map glacier drainage basin areas changes in the positions of tide water glacier termini and to estimate surface velocities of the larger tide water glaciers statistics were compiled to document distance and area changes to glacier termini the methodologies developed in this study are broadly applicable to the investigation of tide water glaciers in other areas the number of images available for consecutive years and the accuracy with which images are co registered are key factors that influence the degree to which regional glacier dynamics can be characterized using remotely sensed data three domains of glacier state were interpreted net increase in terminus area in the southern part of the study area net loss of terminus area for glaciers in upper kangerdlugssuaq fjord and a slight loss of glacier terminus area northward from ryberg fjord local increases in the concentrations of drifting icebergs in the fjords coincide with the observed extension of glacier termini positions ice surface velocity estimates were derived for several glaciers using automated image cross correlation techniques the velocity determined for kangerdlugssuaq gletscher is approximately 5 0 km a 1 and that for kong christian iv gletscher is 0 9 km a 1 the continuous presence of icebergs and brash ice in front of these glaciers indicates sustained rates of ice front calving

holocene glacimarine sedimentation inner scoresby sund east greenland the influence of fast flowing ice sheet outlet glaciers abstract holocene glacimarine sedimentation associated with fast flowing outlet glaciers draining the greenland ice sheet is investigated using sedimentary and acoustic data from inner scoresby sund east greenland sedimentation in inner scoresby sund is dominated by three processes which are influenced by differences in proximity to fast flowing outlet glaciers extent of glacier ice cover and fjord bathymetry 1 sediment gravity flow principally in the form of turbidity currents and debris flows 2 suspension sedimentation from turbid meltwater plumes and 3 iceberg rafting these processes result in texturally and sedimentologically heterogeneous lithofacies proportionally fine grained muds laminated stratified and massive facies dominate cores recovered from inner scoresby sund accounting for 80 of the total whereas diamict facies account for only 15 abundant fine grained muds demonstrate that meltwater flux and sedimentation is significant in this high arctic glacimarine environment in settings proximal to fast flowing outlet glaciers with increasing distance from these glacier termini muds are replaced progressively by iceberg rafted coarse grained sediment the dominance of this iceberg rafted sediment in outer scoresby sund reflects both its more distal location from fast flowing glacier termini and the high calving flux associated with these ice masses laminated muds deposited by turbidity currents and suspension settling from overflow plumes in inner scoresby sund are similar to lithofacies produced in temperate and subpolar glacimarine systems this implies a similarity in sedimentation processes and resulting facies across a wide spectrum of climatically glaciologically fast flowing and non fast flowing ice masses and oceanographically variable glacimarine settings recognition of laminated fine grained facies in the geological record therefore does not necessarily indicate a temperate palaeo glacial setting however the predominance of iceberg rafted diamict facies in ice distal sedimentary records suggests the former presence of relatively cold environmental conditions in which iceberg sedimentation played a dominant role

deglaciation of a major palaeo ice stream in disko trough west greenland recent work has confirmed that grounded ice reached the shelf break in central west greenland during the last glacial maximum lgm here we use a combination of marine sediment core data including glacimarine lithofacies and ird proxy records and geomorphological and acoustic facies evidence to examine the nature of and controls on the retreat of a major outlet of the western sector of the greenland ice sheet gris across the shelf retreat of this outlet which contained the ancestral jakobshavns isbrae ice stream from the outer shelf in disko trough was rapid and progressed predominantly through iceberg calving however minor pauses in retreat tens of years occurred on the middle shelf at a trough narrowing forming subtle grounding zone wedges by 12 1 cal kyr bp ice had retreated to a basalt escarpment and shallow banks on the inner continental shelf where it was pinned and stabilised for at least 100 years during this time the ice margin appears to have formed a calving bay over the trough and melting became an important mechanism of ice mass loss fine grained sediments muds were deposited alternately with ird rich sediments diamictons forming a characteristic deglacial lithofacies that may be related to seasonal climatic cycles high influxes of subglacial meltwater emanating from the nearby ice margins deposited muddy sediments during the warmer summer months whereas winters were dominated by iceberg calving leading to the deposition of the diamictons this is the first example of this glacimarine lithofacies from a continental shelf setting and we suggest that the calving bay configuration of the ice margin plus the switching between calving and melting as ablation mechanisms facilitated its deposition by channelling meltwater and icebergs through the inner trough the occurrence of a major stillstand on the inner shelf in disko trough demonstrates that the ice dynamical response to local topography was a crucial control on the behaviour of a major outlet in this sector of the gris during retreat

modeling iceberg rafted sedimentation in high latitude fjord environments 1 an iceberg model sedberg has been developed to simulate sedimentation in high latitude glaciated fjords sediments deposited in fjords provide an important record of glaciological response to changing climatic conditions the model simulates the formation drift and melt of a population of icebergs utilizing monte carlo based techniques with a number of underlying parametric probability distributions to describe the stochastic behavior of iceberg formation and dynamics the model captures iceberg dynamics and melt in fjord environments and has been applied to kangerdlugssuaq fjord in east greenland as an example of an iceberg dominated sedimentary environment sedimentation has been simulated over the past 1500 years encompassing the climatic intervals of the medieval warm period mwp and the little ice age lia model results have been compared with the observed sedimentary record the model demonstrates that the glaciological regime e g basal debris thickness mean annual calving rate mean iceberg size plays a more important role than the direct influence of climate ocean and air temperatures on iceberg sedimentation rate although often changes in climate result in changes to the glaciological regime

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

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

holocene variations in mineral and grain size composition along the east greenland glaciated margin ca 67 70 n local versus long distance sediment transport quantitative x ray diffraction qxrd analysis of the 2 mm sediment fraction from surface sea floor samples and marine sediment cores that span the last 10 12 cal ka bp are used to describe spatial and temporal variations in non clay mineral compositions for an area between kangerlussuaq trough and scoresby sund 67 70 n east greenland bedrock consists primarily of an early tertiary alkaline complex with high weight of pyroxene and plagioclase farther inland and to the north the bedrock is dominantly felsic with a high fraction of quartz and potassium feldspars principal component pc analysis of the non clay sediment compositions indicates the importance of quartz and pyroxene as compositional end members with an abrupt shift from quartz and k feldspar dominated sediments north of scoresby sund to sediments rich in pyroxene and plagioclase feldspars offshore from the early tertiary basaltic outcrop coarse 2 mm or 1 mm ice rafted sediments are largely absent from the trough sediments between 8 and 5 cal ka bp but then increase in the last 4 cal ka bp compositional unmixing of the sediments in grivel basin and kangerlussuaq trough indicate the dominance of local over long distance sediment sources with pulses of sediment from tidewater glaciers in kangerlussuaq and nansen fjords reaching the inner shelf during the neoglaciation the change in ird is more dramatic in the sediment grain size proxies than in the quartz wt forty to seventy percent of the variance in the quartz records from either side of denmark strait is explained by low frequency trends but the data from the grivel basin east greenland are distinctly different with an approximate 2500 yr periodicity

meltwater and ice rafting in the southern norwegian sea between 20 and 40 calendar kyr b p implications for fennoscandian heinrich events 1 the timing of meltwater release in the southern norwegian sea in relation to millennial scale climate variability is studied from core md99 2283 based on down core analysis of stable oxygen and carbon isotopes calcium carbonate and ice rafted debris ird between 20 and 40 calendar cal kyr b p strong dansgaard oeschger cyclicity is expressed in increased carbonate content and reduced total organic carbon during warm interstadials and ird marking the end of cold stadials the planktonic 18o record of core md99 2283 compared to available isotopic records in the region confirms the existence of multisourced synchronized meltwater anomalies during heinrich h events 2 to 4 it was found that the sudden release of meltwater occurs near major ice streams and that no significant increase in ird was associated with the peaks of the meltwater events in the southern norwegian sea suggesting meltwater discharges from ice dammed lakes significant meltwater events not related to the h events were also observed between 33 and 35 cal kyr b p indicating that the release of meltwater is not necessarily connected with major cooling and enhanced ird delivery the simultaneous release of fresh water during h events in the nordic seas through icebergs and ice dammed lakes is thought to be the result of sea level increase the meltwater input to the nordic seas provides a significant additional contribution to global sea level rise associated with h3 and h4

palaeoenvironmental interpretation of an ice contact glacial lake succession an example from the late devensian of southwest wales uk abstract during the late devensian late weichselian glaciation a number of large proglacial lakes developed in dammed river valleys along the southwest coast of wales u k this paper presents sedimentological data together with a digital terrain model to establish the sedimentation history dynamics and evolution of the largest lake glacial llyn lake teifi buried valley fill sequences within the margins of the former lake basin reveal a thick succession of glaciolacustrine muds which coarsen upward into or are locally abruptly overlain by proximal deltaic subglacial and glaciofluvial deposits sediment delivery pathways represented in the lacustrine succession include gravity flows suspension settling deltaic aggradation and iceberg rafting the latter indicating ice contact conditions the lacustrine muds are variably deformed with a range of syn and post depositional structures some of which indicate subglacial deformation associated with overriding of the lacustrine succession syn depositional structures indicate high sedimentation rates which may explain an absence of bioturbation structures the overall coarsening upward succession and cap of subglacial and or glaciofluvial deposits support recent theories suggesting that glacial llyn teifi formed during glacial advance there is no evidence to support glaciomarine conditions of sedimentation in this area of the irish sea basin

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

meltwater and tidal currents controls on circulation in a small glacial fjord mcbride inlet is a small glacial fjord that receives freshwater from a submarine tunnel at the base of a tidewater glacier at its head the upwelling buoyant plume mixes with basin water lowering the salinity throughout the ice proximal basin freshwater also upwells from the melting ice face but the effects are only important in winter when discharge is low deep water renewal occurs in summer because the water mass crossing the sill inward is denser than the deep basin water the thick low velocity surface layer is affected by tides and wind producing a slow moving gyre near the glacier meltwater discharge from a submarine position and the resultant circulation in mcbride inlet result in extremely high ice proximal sedimentation rates

holocene sediment properties of the east greenland and iceland continental shelves bordering denmark strait 64 68 n north atlantic the oceanographic polar front separates the east greenland and iceland margins surface water temperatures across denmark strait vary by 8 12 c and represent one of the steepest oceanographic gradients on earth the eastgreenland margin is a polar environment with extensive sea ice cover and calving glacier margins in contrast the iceland shelf is much more temperate and freshwater run off is a key component in land ocean sediment transfers average sediment properties from these two contrasting climate and oceanographic continental shelf environments are compared in the spatial domain at 13 sites the data represent the last 10 000 radiocarbon years of normal marine sedimentation for the two regions the two regions have similar average rates of sediment accumulation around 43 5 cm kyr 1 so that this key variable is factored out in explaining any differences in sediment properties dry sediment density moisture content hygroscopic moisture total organic carbon and carbonate contents mass magnetic susceptibility and the percentages of sand and silt are compared focusing on 1 median values for sediment properties and 2 downcore variability measured by the coefficient of variation cv there are significant differences in all but one hygroscopic moisture of the sediment properties between iceland and east greenland in four cases the sense of the differences was not as predicted in terms of downcore variation cv no difference was found between the two regions nor between the 13 sites whereas there are some significant differences between the variables carbonate and mass magnetic susceptibility have the largest spreads and moisture content and dry sediment density are the least variable protocols are developed to identify the type core in a regional series of sites the results indicate a need to develop a regional perspective on sediment properties both as inputs to models of sedimentary processes in different polar arctic environments and as an indication of which sediment properties might be best suited for palaeoenvironmental downcore time series

holocene ice rafting and sediment transport from the glaciated margin of east greenland 67 70 n to the n iceland shelves detecting and modelling changing sediment sources abstract we examine variations in the ice rafted sources for sediments in the iceland east greenland offshore marine archives by utilizing a sediment unmixing model and link the results to a coupled iceberg ocean model surface samples from around iceland and along the e ne greenland shelf are used to define potential sediment sources and these are examined within the context of the down core variations in mineralogy in the

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