late quaternary marine sediment accumulation in fiord shelf deep sea transects baffin island to baffin bay abstract piston cores from fiords shelf troughs and the deep sea off eastern baffin island n w t canada have been sampled for texture and detrital carbonate in the 2 ka over the last ca 10 ka three sets of two cores each lie on a fiord shelf transect and thus define variations in sediment accumulation gradients these continental margin data are compared with cruder estimates of holocene sediment accumulation at three sites farther offshore in baffin bay davis strait and the northern labrador sea minimum accumulation in a 2 ka interval was 200 kg m 2 with a maximum estimate of 8 800 kg m 2 detrital carbonate accumulation varies between 0 and 1 300 kg m 2 median accumulation for a typical fiord shelf deep sea transect over the last 10 ka have been 10 340 3493 and 820 kg m 2 at dsdp leg site 645 in central baffin bay the sedimentation rate ranged between 40 and 130 m ma ca 400 and 1200 kg m 2 2ka that is comparable with the late quaternary input into baffin bay

temporal offsets between surface temperature ice rafting and bottom flow speed proxies in the glacial mis 3 northern north atlantic rapid climatic switches during marine isotope stage 3 29 59 ka bp are often attributed to ocean circulation changes caused by freshwater input into the north atlantic through the melting of large amounts of icebergs and sea ice however recent studies have questioned this direct coupling between factors influencing the ocean climate system by combining multiple proxies from two mid depth northern north atlantic sediment cores we assess temporal offsets and links between freshwater input and response of the near bottom flow as well as between near bottom flow and sea surface temperatures changes grain size mineralogical and magnetic proxies for ice rafting and near bottom flow speed interpreted as indicators of freshwater input and deep circulation strength consistently indicate a delay in the recovery of the deep circulation after freshwater perturbations sea surface temperature variability is inferred from foraminiferal assemblages and mg ca and 18o of neogloboquadrina pachyderma s the records show rapid switches towards higher temperatures following the ice rafting events interestingly near sea surface temperatures increased and decreased again during periods of accelerating bottom flow speed likely reflecting the sudden release of heat from deeper in the water column rather than circulation changes our data thus confirm the impact of freshwater forcing on the atlantic deep circulation but suggest that temperature variability at the surface was not directly linked to these circulation changes

geomorphological evidence of holocene climatic change from northwest ellesmere island canadian high arctic proxy data from the northern coast of ellesmere island are used to reconstruct holocene palaeoclimate and appear to corroborate the ice core record from the canadian and greenland high arctic despite some regional variation geomorphological evidence indicates that deglaciation was associated with a marked climatic amelioration in the late pleistocene early holocene 10 ka bp this contrasts with glaciers on the south side of grant land mountains which started to retreat at 7 5 ka bp perhaps due to significant differences in glacioclimatic regime and the influence of the arctic ocean indicators of sea ice conditions on northern ellesmere island suggest that the early holocene was a period of considerable open water radiocarbon dates on driftwood collected from behind the north coast ice shelves suggest that the ice shelves formed during a mid holocene climatic deterioration geomorphic evidence shows that the ice shelves are presently breaking up and melting in response to recent warming glaciers hav

the limitations of three dimensional kinematic vorticity analysis abstract the kinematic vorticity number wk can be calculated for three dimensional as well as two dimensional geologic deformations for steady state deformations wk can be correlated to and analyzed in terms of finite strains the analysis shows that assumptions commonly made for two dimensional deformations are not applicable to three dimensional deformations a single wk describes an infinite number of three dimensional deformations further even knowledge of flow apophyses orientation instantaneous stretching axes orientation and or wk are not sufficient to describe deformation three dimensional deformations also require knowledge of the deformation type or boundary conditions of deformation e g transpression hence in addition to being difficult to estimate the value of knowing wk for three dimensional deformations is greatly reduced compared with plane strain the most useful methods of determining wk from naturally deformed rocks are presented

holocene glacimarine sedimentation and macrofossil palaeoecology in the canadian high arctic environmental controls abstract raised glacimarine sediments adjacent to strand bay axel heiberg island and on fosheim peninsula ellesmere island record sedimentation in environments proximal to tidewater glaciers and glacimarine deltas the different styles of sedimentation during early holocene deglaciation ca 8 10 ka bp of these regions are of particular interest in strand fiord axel heiberg island coarse grained sediments deposited from high density turbidity currents generated along the margin of tidewater glaciers are overlain by laminated fine grained sediments deposited by suspension settling in a shallow ice proximal environment the fining upward sequence records the reduction in sediment supply as tidewater glaciers retreated onto land in contrast on fosheim peninsula ellesmere island laminated to massive fine grained sediments were deposited from low density turbidity currents and by suspension settling in a deep prodeltaic environment several kilometres from upland ice caps sediment texture coarsens upward reflecting increasing proximity to sediment sources as deltas prograded during early holocene marine regression two macrofossil faunas a portlandia arctica assemblage and a hiatella arctica mya truncata assemblage occur in association with early holocene sediments mid holocene sedimentation ca 4 8 ka bp in both regions was characterized by the accumulation of laminated or massive fine grained sediments deposited from low density turbidity currents and by suspension settling in prodeltaic environments several macrofossil faunas are recorded in these sediments a portlandia arctica assemblage and an astarte borealis mya truncata assemblage associated with laminated muds deposited in shallow water and a deep water portlandia arctica assemblage associated with massive muds variations in sedimentation rates can be correlated with the summer melt layer record of the agassiz ice cap on ellesmere island early holocene deglaciation coincided with a period of increased summer ablation ca 8 5 11 5 ka bp that contributed to the massive influx of sediment into marine environments the mid holocene ice core record indicates a sharp decline in summer ablation ca 6 0 9 5 ka bp resulting in the reduction of sediment flux to marine environments

interlaminated ice proximal glacimarine sediments in muir inlet alaska muir inlet in glacier bay alaska is a glacial fjord receiving a tremendous volume of sediment annually the rate of sediment accumulation is greatest proximal to muir glacier about 9 m yr 1 and decreases away from the glacier the primary sediment sources are meltwater streams discharging at subglacial and ice marginal positions to form overflows interflows and underflows continuous turbidity currents overflows and interflows interact with diurnal tidal currents and their volume and sediment concentration varies diurnally and annually with meltwater discharge these effects produce cyclic deposits of a thin fine grained sand or silt lamina that grades normally to a thicker poorly to very poorly sorted mud lamina this lamina couplet is termed a cyclopel underflows are suggested to occur in this glacimarine environment because of conditions unique to subglacial fluvial systems underflow deposits occur only in proximal positions 0 5 km from glacier face and are coarse grained reverse to normal graded and exhibit an increase in sorting and sand content up layer ice rafted debris identified as particles 177 m is ubiquitous though low 5 by weight and occurs as isolated particles frozen pellets or as lenses that in cores may have a lamina appearance proximally ice rafted debris is difficult to identify because proximal sediment is often as coarse grained deposited sediment may be reworked by tidal currents and sediment gravity flows depositional processes operating in muir inlet produce interlaminated sand silt clay that characterizes sediment proximal to a glacier and fines seaward to mud sediment is classified into one of three sediment types 1 1 type i sediment is very fine grained mean 8 65 7 17 o low in sand 0 1 11 2 and very poorly to poorly sorted it is the dominant sediment type in muir inlet and is transported by plumes and deposited by suspension settling 2 2 type ii sediment is fine to coarse grained mean 6 70 3 12 o low to high in sand 5 1 86 6 and very poorly to moderately sorted it represents reworked sediment proximal plume deposits or coarse grained laminae of cyclopels 3 3 type iii sediment is coarse grained mean 3 89 2 38 o high in sand 58 0 100 0 and poorly to well sorted it is deposited by sediment gravity flows or underflows

arctic ice shelves and ice islands origin growth and disintegration physical characteristics structural stratigraphic variability and dynamics ice shelves are thick floating ice masses most often associated with antarctica where they are seaward extensions of the grounded antarctic ice sheet and sources of many icebergs however there are also ice shelves in the arctic primarily located along the north coast of ellesmere island in the canadian high arctic the only ice shelves in north america and the most extensive in the north polar region the ellesmere ice shelves originate from glaciers and from sea ice and are the source of ice islands the tabular icebergs of the arctic ocean the present state of knowledge and understanding of these ice features is summarized in this paper it includes historical background to the discovery and early study of ice shelves and ice islands including the use of ice islands as floating laboratories for polar geophysical research growth mechanisms and age the former extent and the twentieth century disintegration of the ellesmere ice shelves and the processes and mechanisms of ice island calving are summarized surface features thickness thermal regime and the size shape and numbers of ice islands are discussed the structural stratigraphic variability of ice islands and ice shelves and the complex nature of their growth and development are described large scale and small scale dynamics of ice islands are described and the results of modeling their drift and recurrence intervals are presented the conclusion identifies some unanswered questions and future research opportunities and needs

the occurrence and fission track ages of late neogene and quaternary volcanic sediments siwalik group northern pakistan abstract volcanic sediments now mostly bentonites and bentonitic mudstones occur throughout the late neogene and quaternary siwalik group of northern pakistan a number of these deposits have been dated by the fission track method utilizing zircon phenocrysts from these deposits and provide the chronometric constraints upon which a paleomagnetic stratigraphy is developed for the siwalik group notable in the occurrence of these altered tuff horizons is an apparent mode in their stratigraphic development from approximately 3 0 to 1 5 m y b p which coincides with the period of activity of the dacht e nawar volcanic complex of east central afghanistan fission track ages of certain tuffs for critical areas of northern pakistan are reported herein

the late quaternary history of hall land northwest greenland reply the last ice limit on hall land northwest greenland is marked by the newman and petermann moraines which were deposited 40 60 km beyond the present ice margins in newman bay and petermann fiord respectively these moraines flank the eastern and western coasts of hall land but do not extend into its intervening central plain as a result of glacioisostatic depression at this time a full glacial sea transgressed the entire central plain via a narrow estuary located between the newman moraine and the northern plateau of hall land the limit of this full glacial sea is isostatically tilted from 116 m asl on the adjacent coast of ellesmere island to 150 m asl on the southwest extremity of the central plain where it reaches its apex pervasive marine silts cover the central plain and laterally thicken towards the newman and petermann moraines because of the height of the full glacial sea these moraines were deposited in a submarine environment and mark the grounded margins of ice shelves floating in hal

sedimentary processes of canadian arctic fjords abstract conceptual models of circulation and sedimentation in arctic fjords are presented to illustrate the current understanding of these environments circulation is a vigorous process in these fjords and is enhanced by the loss of the freshwater cap during the long winter period of near zero inflow the process of brine rejection during the formation of sea ice and the role of glaciers and icebergs injecting freshwater at depth on the other hand the presence of sea ice blocks reduces the mixing action of wind which may otherwise represent the largest input of energy to fjord circulation it also provides a freshwater layer on melting and may in some circumstances damp the amplitude of tides during summer large loads of glacial sediment entering arctic fjords are separated into streams of overflowing suspended load and bed load in the presence of salt water as the concentrations of suspended load in the freshwater are normally much less than required to overcome the density of the salt water deposition occurs throughout the fjord by rapid settling of flocculated particles from the overflowing brackish water and from grain flows in the proximal environment created as the fluvial traction carpet moves over the delta foreset slope after sediment has been deposited it may be remobilized by slides which in turn may develop into fully turbulent flows as they move down the fjord floor a range of deposits from slump debris to minor turbidites are postulated to occur with the flocculated muds although not all have yet been examined in the arctic fjord stratigraphic record sea ice is an important sedimentological agent in arctic fjords it passively carries fluvial aeolian and colluvial material which is subsequently released from the ice during the stage of puddle draining at break up sea ice also actively incorporates fine and coarse sediments up to large boulders during freezing along the shores in winter and by wave and tidal current washing controlled by the presence of the ice during break up

sediments of the lomonosov ridge and makarov basin a pleistocene stratigraphy for the north pole sediments of 16 short cores taken as part of the lomonosov ridge experiment lorex can be organized into the first pleistocene stratigraphy for the north polar region this stratigraphy can be correlated with stratigraphic units described from the alpha chukchi areas 300 km distant the lorex cores include at least 12 sedimentary subunits differentiated by texture color and carbonate content the units are silty and arenaceous lutites and are principally glacial marine benthic and planktonic foraminifera degree of bioturbation and fe mn micro nodule abundance generally are positively correlated foraminifera in core b 8 from 3 956 m in the makarov basin may have been affected by ccd fluctuations that did not affect fossils in core b 24 from 1 600 m on the crest of the lomonosov ridge the 12 stratigraphic units were deposited during the late pleistocene and represent the same major sedimentary events as those of stratigraphic units k l and m of the amerasian basin this correlation is excellent evidence for the remarkable and widespread uniform depositional style of glacial marine sediment times of major glacial ice transport reflect deglaciation events in the central arctic ocean surface currents during deglaciation transport glacial ice in a more or less uniform pattern over at least 50 of the arctic ocean even thin sedimentary units deposited during relatively long time intervals are correlated over 500 000 km 2

rainstorm induced event sedimentation at the tidewater front of a temperate glacier runoff from a late summer storm drained rapidly to a subglacial stream of mcbride glacier southeast alaska the stream transported large volumes of sediment that discharged from the glacier s tidewater front directly into fjord water at 40 m depth measurements of salinity temperature and suspended sediment concentration indicate that the sediment was transported by interflows within brackish fjord water sedimentation rates were exceptionally high up to five times normal laminated fine sand accumulated in proximal sediment traps and silty mud accumulated in distal traps the low frequency of large storms late in the melt season indicates that the sedimentary products would be rare but significant marker horizons in temperate glaciomarine sequences

the glacimarine sedimentary environment of expedition fiord canadian high arctic abstract expedition fiord is a small shallow inlet on the west coast of axel heiberg island near 80 n latitude it receives runoff and sediment at its head from a 1079 km 2 drainage basin 72 of which is glacier covered subbottom acoustic survey and cores from the fiord floor were used to assess the sedimentary environment most of the sediment is deposited within 3 km of the inflow from suspension in the overflowing cap and by gravity flows on the foreset beds of the delta occasionally weak turbidity currents reach the mid fiord where they deposit fine grained sediments icebergs from a large calving glacier in an adjacent fiord raft additional sediment especially to the outer part of the fiord they also scour the seafloor although the persistent ice cover and slow currents in the fiord restrict this process except near the inflow the total sediment accumulation since deglaciation is less than 20 m and the rates of 0 5 1 mm yr have not varied significantly to the present a thicker deposit in the outer fiord is probably related to an early holocene glacier margin near that location

glaciomarine sedimentation in disraeli fiord high arctic canada abstract disraeli fiord represents a glaciomarine environment unique to the north coast of ellesmere island featuring floating glacier tongues multi year landfast sea ice and a strongly stratified water body which results from enclosure of the fiord by ward hunt ice shelf it is a very low energy depositional environment even at sites proximal to glaciers sediment enters the fiord by interflow and is deposited through suspension settling ice rafting is precluded by the year round sea ice cover sedimentation rates in the inner fiord since about 7000 yrs b p are estimated to be 5 10 cm ka a reflection of the limited sediment influx from the cold based glaciers which contact the fiord changes in sediment structure through the holocene reflect changes in the rate and process of sediment input as well as changes in fiord circulation all of which relate to regional climate during deglaciation early holocene sedimentation rates were orders of magnitude greater than at present subglacial meltwater was the dominant source of inflow with sediment transported in turbid plumes as over or interflow and deposited through suspension settling this is supportive of other studies indicating that a pronounced climatic amelioration led to warm based glaciers at this time

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

marine sedimentation at a calving glacier margin a 2 month study at a subpolar tidewater glacier was conducted at anvers island antarctic peninsula lat 64 s to improve understanding of sedimentary processes and associated deposits in glacial marine settings data collected in the ice proximal environment were 1 brash ice size distribution and melt rates to assess sediment source and transport mechanisms 2 conductivity temperature turbidity depth cttd profiles water samples and sediment trap catches to study processes and patterns of sediment dispersal 3 bottom cores and grabs to document recent glacial marine sedimentation and 4 remotely operated vehicle video surveys of the ice terminus and sea bottom to obtain images of physical and biological processes the water column is stratified and a halocline occurs at 20 30 m water temperature ranged from 1 to 1 6 c salinity was 32 34 and suspended solids were 3 5 mg l well above the bottom ephemeral turbid horizons contain 8 15 mg l suspended solids rare surface plumes and a quasipermanent turbid layer produced by resuspension during calving events reach 25 35 mg l meltwater drains from the glacier surface but no subglacial meltwater was detected directly entering the sea the most important sources of sediment appear to be the direct melting of the submerged ice front and melting of calved glacial ice most fragments of floating ice melt within 1 km of the ice front some sediment may be contributed as low density 1 1 g cm 3 algae bound sediment pellets by meltwater streams draining the ablating ice surface sediment enters the stratified water column and is moved by tidal and wind driven circulation marine sedimentation rates are low 3 mm yr relative to depth of bioturbation resulting in unstratified sandy mud with dispersed clasts

geomorphic and sedimentary signatures of early holocene deglaciation in high arctic fiords ellesmere island canada implications for deglacial ice dynamics and thermal regime integrated studies of glacial geomorphology sedimentology marine limit elevations and radiocarbon dating in two adjacent fiords on southwestern ellesmere island indicate that early holocene regional deglaciation was characterized by a two step retreat pattern where initial rapid breakup of marine based ice preceded slower terrestrial retreat these data also indicate interfiord variations in early holocene deglacial thermal regime and illustrate the role of fiord topography as a control on glacier retreat in starfish bay deglacial landform sediment associations are preferentially located at fiord side topographic irregularities and record ice proximal glaciomarine sedimentation during stillstands at pinning points abundant fine grained subaquatic outwash indicates that the retreating trunk glacier was characterized by a warm based thermal regime the discrete location of these deposits and associated radiocarbon dates suggest rapid early holocene deglaciation of the outer and middle fiord inter

climatic control of sedimentation in bays and fjords of the northern antarctic peninsula abstract the northern antarctic peninsula is dominated by strong climatic gradients which are locally enhanced by subsidiary orographic and topographic effects these gradients are reflected in the sediments of the bays and fjords of the region the climate of the south shetland islands is relatively warm with high levels of precipitation this leads to a temperate glacial setting in which many glaciers terminate on land and bay waters which are turbid with terrigenous debris sediments which consist of terrigenous muds and sands with a low ice rafted debris ird content are relatively thick 70 m and have now filled in and almost completely mask the underlying basement topography the palmer archipelago is colder than the south shetland islands and is the wettest area of the antarctic it is heavily glaciated and all major glaciers are grounded below sea level only rarely have sediment plumes been seen the sediments which are primarily terrigenous muds and sands with a variable ird component are thin maximum 40 m but are ponding in every available bathymetric depression the pristine nature of the ice visible above sea level indicates that terrigenous debris is entering the bays from below sea level sediment gravity flows are important in redistributing sediment the danco coast lies within the precipitation shadow of the graham land plateau its climate is slightly colder and is the driest in the study area with less than half of the precipitation of the palmer archipelago nevertheless it is also heavily glaciated with few exceptions sediments here are diatomaceous muds and oozes they are very thin and drape across the rugged basement topography rather than ponding in lows sediment gravity flow deposits are rare these observations indicate a lower rate of production of terrigenous sediment here a consequence of the drier climatic setting

clay mineralogy of late cenozoic sediments in the cesar cores alpha ridge central arctic ocean the clay sized 2 m fraction of the silty and arenaceous lutites constituting cesar cores 14 and 103 alpha ridge central arctic ocean is composed predominantly of mica 40 60 with subequal percentages 10 20 of kaolinite and chlorite and lesser amounts 5 of smectite quartz plagioclase and potassium feldspar calcite and dolomite also occur but only intermittently in the upper 1 2 m dissolution is probably responsible for their absence in other units the silty lutites have a constant mineralogy throughout the 4 5 m long 4 25 ma section whereas some of the arenaceous intervals in the upper 2 1 m have markedly higher amounts of kaolinite calcite dolomite and to a lesser extent smectite the silty lutites were most likely derived from the beaufort sea shelf during nonglacial periods whereas the distinctive components in the sandy layers suggest that they were transported from the canadian arctic islands and greenland by glacial ice the absence of kaolinite peaks in the lower

contrasting glacimarine sedimentary environments of two arctic fiords on disko west greenland abstract two fiords kangerluk and akulliit on the island of disko central west greenland have very different sedimentary regimes caused by differences in the characteristics of their drainage basins and in the exposure of their waters to the open sea of baffin bay their insular location also results in much lower input of water and sediment than in nearby fiords on the mainland of greenland that are affected by glaciers from the greenland ice cap akulliit has a small drainage basin and low input of water and sediment it is directly exposed to the higher energy wave environment of baffin bay as a consequence the mean thickness of holocene glacimarine sediment assessed in acoustic records is less than 6 m in the inner and middle reaches of the fiord mean holocene accumulation 0 4 mm a and about 11 m 1 mm a near the mouth dated core sediment indicates that rates are less than 0 5 mm a in the outer fiord in the last 2 ka the larger more glacier covered drainage basin of kangerluk contributes much larger loads of sediment to a fiord environment protected from the open sea as a result holocene glacimarine sediment is more than 80 m thick in the inner fiord mean holocene accumulation up to 5 mm a decreasing to 10 40 m about 1 mm a in the middle reaches accumulation rates in kangerluk are within the range of arctic fiords including those of baffin island but those in akulliit are near the lower limit the decrease in thickness distally in kangerluk is typical of arctic fiords but the opposite trend in akulliit is probably due to erosion and re distribution of sediment in the higher energy environment there

canadian geomorphology 2000 geomorphology has a distinguished history in canada as old as the country itself initially the science of geomorphology of canada drew on rich british and french scientific traditions but later it developed its own character strongly influenced by the richness and diversity of the canadian landscape the strong imprint of glaciation and the importance of periglacial processes permafrost and sea ice canada is the second largest country in the world its coastline is longer and more varied than that of any other country nearly one third of canada is underlain by permafrost some up to 700 m thick the country s physiography ranges from nearly flat coastal and interior plains to the glacierised mountains of baffin and ellesmere islands british columbia and the yukon its climate and vegetation are equally diverse ranging from the cold semiarid tundra of the high arctic to the temperate rainforest of the pacific coast given this diversity it is not surprising that canada is active in many areas of geomorphic research an incredible spectrum of landforms and geomorphic processes has fostered world class research in canada both by canadians and by scientists from other countries much of this research is field based and empirical rooted in field observation in recent decades however there have been important advances in inductive laboratory and

late quaternary glacial and sea level events clements markham inlet northern ellesmere island arctic canada clements markham inlet cuts into the grant land mountains of the northernmost coast of ellesmere island the head of the inlet is bounded on three sides by mountain ice caps that surround lowlands mantled by extensive raised marine deposits fieldwork and mapping of late quaternary sediments were used to determine the limits of past glaciations and the nature of ice retreat from the inlet head forty five radiocarbon dates on driftwood and marine shells provide a deglacial chronology and document related sea level adjustments high level ice marginal meltwater channels and mountain summit erratics indicate that ice once inundated all of clements markham inlet during at least one of these undated glaciations ice flowed unconstrained by the local topography in contrast the most recent glaciation involved confluent trunk glaciers which terminated near the head of the inlet beyond this terminus smaller glaciers entering the sides of the inlet debouched into a glacioisostatically depressed sea full glac

holocene sedimentation in glacial tasikutaaq lake baffin island tasikutaaq lake on cumberland peninsula baffin island receives inflow and fine sediment from a 448 km2 drainage basin 21 of which is glacier covered during the summer of 1983 the lake remained essentially isothermal between about 4 and 6 c the suspended sediment concentration of inflow never exceeded 100 mg l 1 with overflow and homopycnal flow dominant surface sediments are clearly laminated although varves are not apparent the sediments are very fine with less than 3 sand in all but the most proximal sites average sedimentation rates between 1976 and 1983 ranged from about 4 mm a 1 to 0 25 mm a 1 down lake from the point of inflow the absence of varves is a function of the low rates of sediment accumulation and the long residence time of the fine sediments in the water column three sediment cores up to 135 cm in length reveal marked changes in sediment characteristics and diatom assemblages through the holocene during the late foxe glaciation it is likely that glacier ice contacted the la

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

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

a reconstruction of sea surface warming in the northern north atlantic during mis 3 ice rafting events marine isotope stage 3 29 59 kyr bp is characterised by rapid shifts from cold stadial to warm interstadial periods which may be linked to changes in the vigour of the atlantic meridional overturning circulation due to variable freshwater input by melting ice here we present two northern north atlantic multi proxy records of sea surface conditions that indicate warm near sea surface conditions during such ice rafting events we infer near surface temperature from planktonic foraminiferal counts mg ca and oxygen isotopes of left coiling neogloboquadrina pachyderma and from calcite content temperatures increased during ice rafting and rose rapidly to interstadial values after ice rafting ceased this pattern is clearest during heinrich event 4 but also present throughout the other millennial scale ice rafting events it indicates that stadials in the greenland ice cores are concurrent with a near surface warming in the north atlantic which was probably restricted to the summer as winter temperatures must have remained low for sediment laden ice to reach the site as similar warming during ice rafting events is seen regionally in the northern north atlantic it cannot be explained by a rerouting of the north atlantic current rather we attribute it to a shoaling of a warm subsurface water mass that was formed as a result of decreased ventilation of the upper waters and a continued northward subsurface flow of warm water planktonic carbon isotopes support this suggestion showing coincident decreased ventilation during deposition of ice rafted detritus ird the absence of a clear meltwater spike in the 18o records during ird input suggests that besides glacial freshwater sea ice may have been responsible for the ventilation decrease and associated near surface heat built up the proposed scenario is in agreement with modelling studies that require the release of heat trapped below the surface to restart the overturning circulation

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

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

continental slope sedimentation adjacent to an ice margin iii the upper labrador slope abstract the upper labrador slope is the key area for sediment transfer from the northeastern margin of the pleistocene laurentide ice sheets lis to the deep basin it is subdivided from north to south into 8 sectors based on relief differences and echo character on 750 line km of continuous sleeve gun and 3 5 khz seismic profiles high to moderate relief sectors 2 and 4 and in part 6 and 8 are seismically transparent and well stratified with continuous individual high amplitude reflections and deep penetration low relief sectors 1 3 5 and 7 show strong bottom reflections and with the exception of sector 1 low seismic penetration poor stratification and low amplitude if any subbottom reflections the lateral distribution of these alternating high to moderate and low relief sectors reflects fundamental differences in the sediment transfer mechanisms through outlets from the lis onto the slope low relief slope sectors represent debrite and turbidite slopes and are located in front of ice outlets on the slope and adjacent regions to the north they originate from mass wasting on the upper slope of glacial detritus with a significant coarse component originally delivered as englacial or subglacial material and deposited in end moraines or as bedload by subglacial or supraglacial rivers high to moderate relief sectors originate from fall out of suspended sediment from turbid surface plumes tsp and preferentially occur off the southern half of outlets and south of major outlets as exemplified by sector 2 south of the hudson strait outlet this asymmetry is caused by the south flowing labrador current which entrains the buoyantly rising turbid meltwater plumes at the glacier front the present high relief topography which shows a dendritic pattern of upslope canyon branching is the result of retrograde headward canyon erosion by mass wasting processes of an originally much smoother mud blanket surface the sediment is remobilized by slumping and entrained in debris flows and turbidity currents the occurrence of tsp deposits on the high to moderate relief upper slope sectors requires a summer sea surface not frozen over during major parts of the pleistocene including glacial maxima tps deposition on the upper slope ice rafting and a plethora of ice margin depositional phenomena many of which give rise to mass wasting and mass flow phenomena are the main features that make high latitude continental slopes adjacent to continental ice sheets different from their lower latitude counterparts

a model for sedimentation by tidewater glaciers sampling of sediment from the fjord floor in front of tidewater glaciers in glacier bay alaska has provided information about processes in this restricted glacimarine dreimanis 1979 setting sediment sampling in conjunction with oceanographic and glacial dynamics data has also enabled the discrimination of sediment types and their facies associations deposits are strongly controlled by sea water characteristics position and sediment discharge of melt water streams iceberg calving and rate of glacierfront retreat five distinct facies associations have been found to reflect glacier fjord regimes the facies associations and ice fjord conditions responsible for them form the basis for constructing a preliminary model for glacimarine sedimentation by tidewater glaciers the model can be used to predict i rapid retreat of an actively calving ice front ii slow retreat or stabilization of a calving ice front at a channel constriction iii stabilization of a melting very rarely calving ice front when the glacier base is near tidewater elevation and iv large outwash delta progradation into a fjord when the ice front retreats onto land this model can be used to interpret facies associations found in a stratigraphic record

the last glaciation of marvin peninsula northern ellesmere island high arctic canada the limit of the last glaciation on marvin peninsula northernmost ellesmere island is recorded by extensive ice marginal landforms and early holocene glaciomarine sediments while glaciers occupied most valleys on the peninsula other areas remained ice free as did most of the adjacent fiords beyond the ice limit sparse erratics and degraded meltwater channels within weathered bedrock are evidence of older more extensive glaciation s shorelines and marine shells 50 m above the limit of the holocene sea along the north coast relate to these older glacial events thirty four new radiocarbon dates provide a chronology of ice buildup and retreat glaciers reached their limit after 23 ka and locally as late as 11 ka this was achieved by both expansion of existing glaciers and accumulation on plateau and lowland sites which are presently ice free late wisconsinan climate was characterized by cold and extreme aridity five dates ranging from 11 to 31 ka bp on subfossil bryophytes suggest that ice free

weichselian sediments at foss eikeland jaeren southwest norway sea level changes and glaciation history the jaeren area in southwestern norway has experienced great changes in sea levels and sedimentary environments during the weichselian and some of these changes are recorded at foss eikeland four diamictons interbedded with glaciomarine and glaciofluvial sediments are exposed in a large gravel pit situated above the post glacial marine limit the interpretation of these sediments has implications for the history of both the inland ice and the norwegian channel ice stream during a middle weichselian interstadial a large glaciofluvial delta prograded into a shallow marine environment along the coast of jaeren a minor glacial advance deposited a gravelly diamicton and a glaciomarine diamicton was deposited during a following marine transgression this subsequently was reworked by grounded ice forming a well defined boulder pavement the boulder pavement is followed by glaciomarine clay with a lower laminated part and an upper part of sandy clay the laminated clay probably was deposited under sea ice whereas more open glaciomarine conditions prevailed during deposition of the upper part the clay is intersected by clastic dykes protruding from the overlying late weichselian till preconsolidation values from the marine clay suggest an ice thickness of at least 500 m during the last glacial phase the large variations in sea level probably are a combined effect of eustasy and glacio isostatic changes caused by an inland ice sheet and an ice stream in the norwegian channel copyright 2002 john wiley sons ltd

glacial geology and quaternary marine stratigraphy of the robeson channel area northeastern ellesmere island northwest territories glacial and marine deposits associated with two phases of glaciation are exposed along a 60 km corridor on ellesmere island that borders robeson channel the oldest sediments tentatively dated at 70 000 bp were deposited during a major advance of the northwest greenland ice sheet across robeson channel during subsequent retreat of this ice mass glaciomarine sediments containing a high arctic macro and microfauna were deposited in the isostatic downwarp on ellesmere island this marine unit was radiocarbon dated at 31 300 900 and 32 000 bp mean aile ile ratios are 0 218 0 03 for the free fraction and 0 063 0 011 for the total acid hydrolysate the last ice advance late wisconsin early holocene did not extend into the field area from either interior ellesmere island or northwest greenland the ice marginal sea transgressed to the marine limit 116 m and overlapped the deposits of the previous maximum greenland advance local plateau ice caps did however spill over into one major valle

provenance of sediment in the labrador current a record of hinterland glaciation over the past 125 ka the labrador current flows southward along the continental margin off eastern canada and is the principal source of sediment to the outer continental margin areas where ice sheets did not cross the continental shelf we present multi proxy mineralogical and geochemical records based principally on x ray diffraction and x ray fluorescence for core 2011031 059 from northern flemish cap to determine changes in supply and hence to reconstruct provenance evolution during the last glacial cycle the calcite to dolomite ratios in heinrich layers ranged from 2 to 4 suggesting carbonate layers derived from hudson strait as early as marine isotope stage mis 5a d mineral abundance shows three time dependent predominant sediment sources other than in heinrich layers i baffin bay shelves and adjacent land in mis 5 and 1 with high ca sr kaolinite and feldspars and low clay minerals and calcite dolomite ratios ii labrador in mis 3 with low clays and grey color and iii north east newfoundland shelf in mis 2 and 4 with higher concentrations of clay minerals red sandstones and transition elements these results allow a reconstruction of principal ice streams supplying the north west atlantic over the last full glacial cycle

glaciation and the evolution of the canadian high arctic landscape the canadian arctic islands represent a tertiary fluvial landscape developed on a contiguous landmass subsequently fractured by block faulting nonetheless some theoretical models invoke pervasive high latitude ice sheets and continue to misattribute the faulted landscape to glacially scoured river valleys quaternary fieldwork on northern ellesmere island suggests that these models are inappropriate for high latitude ice sheets and should be abandoned if there was ever a regional ice sheet over arctic canada it likely occurred on a prefaulted contiguous landmass that had a more temperate climate than at present possibly during the late tertiary after block faulting the marine channels permanently prevented the ice from inundating the landscape it once crossed tectonics and not climate have led to a fundamental change in glacial style this block faulting also may have played a role in terminating the late tertiary boreal forest to 80 n by establishing cold marine channels that diminished the continentality of the once contiguous landmass for a thorough understanding of the canadian arctic landscape future research should determine the continuity between the tertiary and quaternary paleoenvironments the unknown ages of the fiords and interisland channels are of primary importance

isostatic adjustments in a full glacial sea during the last glaciation an ice free corridor existed between the northeast ellesmere island and northwest greenland ice sheets this corridor constituted a peripheral depression in which the marine limit marks the uppermost extent of a full glacial sea the full glacial sea is characterized by 1 14c dates on in situ marine shells that predate initial emergence unloading followed by 2 synchronous emergence from the marine limit throughout the peripheral depression relative sea level curves from the full glacial sea confirm previous morphostratigraphic and glacioisostatic evidence for limited ice extent during the last glaciation these curves also document the history of glacial unloading and the form of the relative sea level curve that one would theoretically expect in the peripheral depression the form of the curves presented here is unlike any other published emergence curves from arctic canada or from fennoscandia the relative sea level curves for northeast ellesmere island show three segme

marine controls on modern sedimentation on the antarctic continental shelf abstract the extreme depth and rugged topography of the antarctic continental shelf its seasonal to perennial sea ice cover and its large slowly calving ice shelves exert major influences on the adjacent ocean and sediments regionally variable exchanges of heat and momentum between the atmosphere and ocean result in net off shelf transport of sea ice and net downward salt flux this buoyancy partitioning drives a vertical convection that is followed by westward and northward flows of ventilated dense water across the continental shelves shelf waters meet mix with and modify circumpolar deep water at a dynamic slope front near the continental shelf break locally or periodically forming antarctic bottom water nutrient rich deep water upwells along this front regionally intruding onto the continental shelf in long thermally attenuated filaments these intrusions are frequently linked to mass balance processes at the base of ice tongues and ice shelves melting freezing and tidal currents beneath glacial ice are related to the larger scale circulation and to the fate of basal debris in the ice sheet the ocean circulation near ice fronts and decadal variability in ice front positions may account for several features of the sediment record time series 1 yr current measurements in the ross and weddell seas have revealed moderate to strong currents that are seasonally variable vertically coherent and dominated by the diurnal tide and longer term events few long term current measurements exist in the shelf and slope bottom boundary layers that are most important to sediment deposition and erosion icebergs may frequent certain routes e g in association with currents and fronts near the edge of the continental shelf and are capable of scouring and resuspending sediments down to shelf break depths sea ice plays a role in shelf sedimentation by rafting eolian and bottom debris away from the nearshore regions in addition generally offshore winds produce numerous leads and polynyas along the coastline and within the sea ice fields higher biological productivity in these polynyas may be linked to higher local sedimentation rates biogenic marine sediments apparently comprise a major percentage of the regionally variable modern shelf deposits despite the impressive glacial setting and polar environment

an origin for laminated glacimarine sediments through sea ice build up and suppressed iceberg rafting laminated glacimarine sediments are observed in visual core logs and x radiographs from scoresby sund and nansen fjord east greenland they are mostly underlain and overlain by massive or stratified glacimarine diamicton dmm or dms which is a product of iceberg delivery of heterogeneous debris and in scoresby sund reworking by deep drafted iceberg keels the laminated sediments are ams radiocarbon dated to two cold periods since the last late weichselian deglaciation the younger dryas stadial milne land stadial in east greenland and the little ice age during cold climatic events multiyear shorefast sea ice sikussak formed in these fjords and trapped the icebergs fine grained laminated muds fl were deposited in scoresby sund when the flux of icebergs was suppressed but turbid meltwater continued to provide some sediment flux to the fjord systems varying through time to produce laminations in nansen fjord thinner and often massive mud layers fm resulted from shorter intervals of sea ice cover with no ice rafting stratified diamicton layers dms which alternate with mud deposition to produce a laminated unit probably represent intervening times of more open conditions with iceberg rafting in scoresby sund foraminifera are either absent from the laminated unit or begin to appear towards the end of its deposition the absence of both benthic and planktonic foraminifera also suggests that multiyear sea ice was covering the core sites there is no evidence of macrofaunal activity and bioturbation is absent from the laminated sediments satellite data show that multiyear shorefast sea ice is present in several areas of the high arctic today and this traps icebergs calved from interior ice cap drainage basins thus the process of laminated glacimarine sediment formation is likely to be applicable to a number of areas of the modern and quaternary arctic