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

variations in the provenance of sediment from ice sheets surrounding baffin bay during mis 2 and 3 and export to the labrador shelf sea site hu2008029 0008 davis strait based on quantitative x ray diffraction mineralogical analysis of cores hu2008029 0006 0008 857 m water depth located south of the davis strait sill we seek answers to two questions i the temporal correlation of nw labrador shelf sea heinrich h and baffin bay detrital carbonate bbdc events and ii the provenance of the sediments a sediment unmixing model sedunmix is used to determine provenance variations although 12 radiocarbon dates were obtained there were many age reversals and we favour a depth age model for hu2008029 0008pc based on correlations to well dated neighbouring cores north and south of davis strait we find no correlation between h and bbdc events except for h 0 which appears to be a broadly synchronous event along the ne canadian margin and is correlative with an episode of major moraine building along this flank of the laurentide ice sheet unmixing of the sediment composition based on six potential glacial source regions indicates that the bulk of the sediment in 0008pc is derived from glacial erosion of west greenland but is punctuated by intervals when dolomite rich sediments derived from outcrops north of baffin bay dominate the composition estimated dates on these bbdc events are 13 25 and 30 38 cal ka bp copyright 2013 john wiley sons ltd

the northwest atlantic mid ocean channel of the labrador sea v sedimentology of a giant deep sea channel the northwest atlantic mid ocean channel namoc is one of the largest deep sea channels of the world s oceans during the late cenozoic glacial period the channel played a major role in the depositional history of the labrador sea and northwest atlantic in controlling sedimentation of a broad approx 500 m thick and 200 km wide lens of turbidites this sediment sequence interfingers laterally with the acoustically transparent pelagic and contourite facies found in the labrador basin the meandering channel is a depositional erosional feature formed by submarine mass flows predominantly turbidity currents the channel contains a meandering talweg that appears to be associated with a sequence of submarine point bars containing thick bedded coarse grained turbidites and gravel layers channel fill facies old channel positions on seismic profiles indicate that the channel has migrated laterally up to 30 km both to the west and to the east natural levees flank the channel for its entire length extendin

holocene and pleistocene dissolution cycles in deep sea cores of baffin bay and davis strait palaeoceano graphic implications abstract calcium carbonate dissolution has been studied in several grab samples and piston cores from baffin bay and davis strait ranging in water depth from 200 to 2300 m the intensity of dissolution was determined from examining 1 the ratio of arenaceous to calcareous benthonic foraminifera 2 the ratio of benthonic to planktonic foraminifera 3 the relationships between the dissolution susceptible and dissolution resistant foraminifera 4 the degree of foraminiferal test fragmentation and 5 the relationships between plankton tows and the fauna in the surface sediments all core tops and grab samples from baffin bay surface sediments below 600 900 m water depth demonstrated intense dissolution of calcium carbonate sediments below 900 m were biogenic carbonate free indicating 100 foraminiferal loss due to dissolution possible causes of substantial undersaturation in calcium carbonate of baffin bay bottom water are very low temperatures and higher concentrations of carbon dioxide all cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1 3 5 7 and 9 similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom water masses during these periods the preservation state of biogenic carbonate debris in glacial isotope stages 2 4 6 8 and 10 is similar to the assemblage found in the water at present

a glacio isostatic facies model and amino acid stratigraphy for late quaternary events in spitsbergen and the arctic strong early holocene crustal uplift over the spitsbergen archipelago reflects disappearance of an ice mass centred just north east of the archipelago and which decayed rapidly just after 10 000 bp after a maximum extension between 12 600 and 10 000 bp from the lithofacies distributions associated with these events a glacio isostatic facies model can be defined which combined with analyses of amino acid racemization provides a valuable stratigraphic method for correlating pre holocene glacio isostatic events these are correlated with events in greenland and both are contrasted with weichselian glacial events at the southern margins of the two great northern hemisphere ice sheets and with contemporary water mass changes in the north atlantic and norwegian sea the geographical variation in glacier response through time is explained by three principal climatic circulation patterns

isotope stratigraphy sedimentation rates deep circulation and carbonate events in the labrador sea during the last 200 ka high resolution stable isotope and accelerator mass spectrometry 14c measurements in 25 box and piston cores from the labrador sea allow the reconstruction of major paleoceanographical changes during the last 200 ka in this basin and also document the links between the interior of the laurentide ice sheet and the north atlantic ocean during this interval two deep circulation regimes are indicated by contrasting sedimentation rates on the slopes i the modern situation is characterized by a gyre of the north atlantic deep water nadw components into the basin which is responsible for the high energy western boundary undercurrent this regime also prevailed during the former true interglacials and possibly during shorter warm intervals e g bolling allerod ii a more frequent nadw free situation during glacial and interstadial intervals is marked by the presence of a vertically homogeneous water mass in the basin sedimentological records also indicate that carbonate events i e pulses of

catastrophic ice shelf breakup as the source of heinrich event icebergs 1 heinrich layers of the glacial north atlantic record abrupt widespread iceberg rafting of detrital carbonate and other lithic material at the extreme cold culminations of bond climate cycles both internal glaciologic and external climate forcings have been proposed here we suggest an explanation for the iceberg release that encompasses external climate forcing on the basis of a new glaciological process recently witnessed along the antarctic peninsula rapid disintegrations of fringing ice shelves induced by climate controlled meltwater infilling of surface crevasses we postulate that peripheral ice shelves formed along the eastern canadian seaboard during extreme cold conditions would be vulnerable to sudden climate driven disintegration during any climate amelioration ice shelf disintegration then would be the source of heinrich event icebergs

anatomy of labrador sea heinrich layers abstract heinrich layers h layers are distinct decimetre to centimetre thick layers of ice rafted debris ird that were deposited in the north atlantic during the late and middle pleistocene h layers h layers are characterized by high detrital carbonate and low foraminifera contents in the labrador sea h layers reach metre thickness in some proximal core sites near the iceberg source of the hudson strait ice stream and show five distinct depositional facies involving sediment lofting and low density turbidity currents as sediment delivery processes besides ice rafting thick massive ice rafted layers type i h layers occur in the most proximal parts of h layer 3 and older h layers within 300 km distance from the assumed hudson strait ice stream terminus h layers somewhat more distal than type i h layers consist predominantly of stacked thin layers of graded muds containing ird type ii h layers the graded muds that are spiked with ird resulted from the deposition of fine grained lofted sediment that collected dropstones and grains under the iceberg route at greater distance from the hudson strait outlet on the slope and rise south of the strait h layers on the levees of tributary canyons to the northwest atlantic mid ocean channel namoc consist of alternations of thin mud turbidites with intercalated laminae of ird type iii h layers on the levees of namoc type iv h layers consist of layers of ird alternating with fewer fine grained spill over turbidites because the spill over frequency from the deep channel was less than that from the less deep canyons on the slope type v is made up of bioturbated hemipelagic muds with coarser ird and occurs in regions between canyons not reached by spill over turbidity currents and in distal regions of the open ocean or on seamounts transport of significant portions of the sediment in h layers by suspended sediment columns lofted from sand carrying fresh water turbidity currents type ii and by low density turbidity currents types iii and iv explains the high percentage of detrital carbonate in the fine 80 of the total detrital carbonate of the bulk sediment which cannot be derived from icebergs alone it also explains the low magnetic susceptibility and low grey levels on the colour scale compared to h layers in the north atlantic east of greenland the anomalously great thickness of individual h layers on the slope and rise off the hudson strait as documented in isopach maps reflects the combined effect of the various processes involved in their deposition four hypotheses for the origin of h events are discussed i the binge purge model ii the subglacial outburst flow model iii the external forcing model and iv the catastrophic ice shelf break up model

pleistocene and holocene distribution of the radiolarian amphimelissa setosa cleve in the north pacific and north atlantic evidence for water mass movement abstract the radiolarian amphimelissa setosa is one of the prominent species of the pleistocene radiolarian assemblages in the sea of okhotsk below the marine isotope stage mis boundary 5 4 and it represents one of the most abundant radiolarian species in holocene and modern environments of the nordic seas we studied the a setosa distribution in six cores from the sea of okhotsk and established morphometric measurements on a setosa specimens from two cores of the sea of okhotsk and one core from the labrador sea we further compared our data with other available studies from the subarctic pacific the labrador sea the north atlantic the norwegian sea and the iceland greenland seas in order to discuss the possible settling of the species from the north pacific via the arctic ocean into the iceland greenland seas a setosa exhibits a stable abundant population in the sea of okhotsk during most of the last ca 0 7 m y and might repeatedly extend its population into the north atlantic through the arctic ocean during the pleistocene interglacial optima the species declines from the sea of okhotsk and from the subarctic pacific at the end of mis 5 its final documented settling into the north atlantic is during mis 5 when a setosa appears in low numbers in sediments of the labrador sea however reaching significant percentages at the boundary of mis 5 4 based on the available information we propose that a setosa could migrate from the north pacific into the arctic ocean during the interglacial optimum mis 5e and then through the channels of the canadian arctic archipelago into the baffin bay and labrador sea a further migration step of a setosa occurs at the boundary of mis 5 4 when a setosa migrated from the labrador sea into the north atlantic probably related to a southward expansion of cold waters at the end of the mis 5 during the warming at termination i a setosa moved from the north atlantic into the nordic seas the abundant occurrence of a setosa in sediments south of iceland the norwegian and north seas within the younger dryas period points to a marked cooling and a southward movement of polar water masses restricted to this time interval

atmospheric circulation patterns during glacial inception a possible candidate abstract models of atmospheric circulation in the north atlantic sector during glacial inception can be expanded to a hemispheric scale with the aid of diagnostic studies of the present climate the present greenland above ga atmospheric circulation type may be a candidate for the atmospheric circulation type required during glacial inception the pattern is an amplification with only minor phase shifts of the present average winter circulation pattern in the extratropical northern hemisphere southerly flow in the northwest atlantic is associated with warm ocean temperatures low sea ice in the davis strait and increased precipitation over northeast canada evidence from modeling of the present climate indicates that the ga pattern could be maintained by increased snow cover over eastern north america enhanced snow cover due to decreased northern hemisphere summer insolation could cause a similar response on an ice age time scale

an ice shelf mechanism for heinrich layer production the effect of an ice shelf in the labrador sea on ice rafted sediment delivery to the glacial north atlantic is investigated using a finite element numerical model of ice shelf flow discharge into the shelf from hudson strait creates a thick central core extending downstream into the shelf that is flanked by relatively thin ice melting at the base of the deep keel would produce cool fresh water which would rise to refreeze along the keel s flanks debris deposited by melting deep central ice could create the heinrich layers observed in the labrador sea while the debris rich ice protected by basal freezing on the flanks of the thick ice plume could transport sediment over large distances heinrich layers would be produced solely by external climate forcing without changes in ice sheet flow the mechanism is plausible if the lifetime of the ice shelf is about 1000 years

milankovitch theory of ice ages hypothesis of ice sheet linkage between regional insolation and global climate abstract j d hays j imbrie and n j shackleton 1976 science 194 1121 1132 showed that the astronomical theory explained many features of late quaternary ice age climates but they did not specify the physical mechanisms involved here it is proposed that interlocked variations of ice sheet heat sinks in both polar hemispheres amplified and transmitted milankovitch summer half year insolation changes a version of the astronomical theory between 45 and 75 n into the globally synchronous climate changes recorded in geologic records it is suggested that late quaternary ice sheets had terrestrial components grounded above sea level melting margins fluctuations controlled by climate and marine components grounded below sea level drained largely by ice streams limited melting margins fluctuations controlled primarily by sea level and secondarily by climate interior surface elevations coupled to downdraw through ice streams northern hemisphere ice sheets were largely marine with minor melting margins in the arctic and terrestrial with major melting margins in the midlatitudes west antarctic and peripheral east antarctic ice was marine based and lacked melting margins because of their geographic array these terrestrial and marine components formed an ice sheet system whose variations were coupled on a global scale milankovitch summer isolation changes near midlatitude northern hemisphere melting margins controlled most variations of this system because advance or retreat of melting margins initiated concurrent eustatic sea level change such sea level change afforded the critical interlocking mechanism between terrestrial and marine components because it forced simultaneous expansion or contraction of marine margins in both polar hemispheres this initiated an amplifying feedback loop among all marine components and influenced interior downdraw through ice streams arctic summer insolation change was less important because northern melting margins were relatively minor its greatest influence was on surface ablation of ice streams that controlled interior downdraw this affected eustatic sea level and activated global linkage of marine sectors by analogy with present day antarctica late quaternary ice sheets were enormous planetary heat sinks due to their reflective and radiative surface characteristics it is suggested that the effectiveness of these ice sheet heat sinks varied with their areal extent and interior surface elevation thus it is postulated that concurrent growth or decay of these interlocked ice sheet heat sinks in both polar hemispheres served as the global amplifier of regional milankovitch summer insolation

foraminiferal distribution on the continental margin off nova scotia abstract q mode factor analysis of total foraminiferal abundance data living plus dead from 250 grab samples taken from the continental margin off nova scotia allows the determination of eight factor assemblages on the northeastern shelf an exclusively agglutinated assemblage dominated byadercotryma glomerata occupies both banks and basins central shelf basins contain a predominantly calcareous assemblage dominated byglobobulimina auriculata andnonionellina labradorica transitional between these two factor assemblages is an agglutinated assemblage dominated bysaccammina atlantica consistently present along the shelf edge is atrifarina angulosa assemblage in northeastern bays and a few samples near sable island an agglutinatedeggerella advena assemblage is found a relict and transport affected assemblage dominated byelphidium excavatum occurs in the southwestern approaches to emerald basin sandy gravelly areas of the inner shelf and outer bank regions are characterized by acibicides lobatulus assemblage the statistical relationships of these defined assemblages to various aspects of the marine environment depth temperature salinity percent gravel sand and mud were investigated through multiple regression techniques results indicate that the present foraminiferal distribution patterns off nova scotia are influenced by the prevailing watermass characters and substrate theadercotryma glomerata assemblage is influenced by the presence of cold 0 4 c low salinity waters 32 33 of arctic labrador current origin the central basin assemblage g auriculata is related to warmer 8 12 c more saline waters 35 of slope origin the transition between these two bottom waters is marked by the opportunisticsaccammina atlantica assemblage preferred substrate character possibly determines the occurrence of thecibicides lobatulus islandiella islandica andeggerella advena assemblages trifarina angulosa shows a significant relationship to salinity and depth although the surficial sediments on the nova scotian shelf are largely the product of reworking of glacial deposits during late glacial and early holocene times all but thee excavatum factor assemblage appear to be in equilibrium with the modern oceanographic regime

dansgaard oeschger events is there a signal off the hudson strait ice stream abstract it is generally accepted that the dramatic heinrich h events were principally sourced from the major hudson strait drainage basin of the laurentide ice sheet but it is not known whether the higher frequency dansgaard oeschger d o events have an imprint on sediments deposited during the inter h intervals in ice proximal slope sediments this paper examines this question by an analysis of data from cores on the se baffin slope because the proxies for heinrich events are so massive in scale we removed the major h events h 1 h 2 and h 4 from the records so as to better examine the structure of data in the intervening hemipelagic sediments the period of interest extends between 15 and 40 cal ka interstadial events 2 8 resolution varies with the proxy to between 210 and 700 yrs per sample in hu87033 009 from the lower slope a total of twelve variables for example 18o mass magnetic susceptibility calcite dolomite ratio number of ird 2 mm show a variety of multi millennial oscillations although not all of the same amplitude nor frequency several parameters show little correlation with the gisp2 18o record however a comparison of cie sediment color l from hu87033 009 and hu97048 007 from the upper slope with the gisp2 oxygen isotope record suggests that a substantial correlation exists between the records such changes might be associated with either detrital carbonate content or foraminiferal concentrations analysis suggests however that the first possibility is correct hence suggestive of a glaciological response of the hudson strait ice stream with d o events in the nw labrador sea the sediment records from around h 3 time 30 cal ka show excursions which might be correlative within this event but its amplitude is not unusual compared to events both before and after this reaffirms the argument that h 3 represents a different glaciological response a significant issue discussed in this paper is the inherent ambiguity of correlating records whose errors in the time domain approach that of a dominating periodicity in this case ca 1 5 kyr

pollen distribution in recent marine sediments eastern canada analysis of 90 samples from coastal and continental shelf areas off eastern canada between 42 and 69 n shows that quaternary pollen and spores are present in recent marine muds throughout this region pollen and spore concentrations range from 50 000 to 100 grains per cm3 and they decrease both offshore as a function of distance from vegetation sources and northwards as a function of lower vegetation density north of the summer arctic frontal zone isopercentage contours show that maximum relative abundances of most palynomorphs occur in marine sediments adjacent to their regions of highest vegetation representation onshore however pinus and picea pollen tend to increase in percentage abundance with distance offshore presence of these tree pollen in marine sediments off baffin island implies that wind transport is an important pathway by which bisaccate pollen types enter the ocean in addition to fluvial transport q mode factor analysis shows that four major factors account for 89 of the variance amo

multiple deglaciations of the hudson bay lowlands canada since deposition of the missinaibi last integlacial formation abstract the stratigraphic record in the james and hudson bay lowlands indicates that the sequence of glacial events at the geographical center of the 12 6 10 6 km 2 laurentide ice sheet may have been more complex than hitherto imagined isoleucine epimerization ratios of in situ and transported shells recovered from till and associated marine and fluvial sediments cluster into at least 4 discrete groups two alternative explanations of the data are offered of which we strongly favor the first hypothesis 1 setting the age of the last interglacial marine incursion the bell sea at 130 000 yr b p results in a long term average diagenetic temperature for the lowlands of 0 6 c using this temperature enables us to predict the age of shells intermediate in age between the last interglaciation and the incursion of the tyrrell sea 8000 yr ago between these two interglacial marine inundations hudson bay is predicted to have been free of ice along its southern shore about 35 000 75 000 and 105 000 yr ago based on amino acid ratios from shells occurring as erratics in several superimposed tills and fluvial sediments these results suggest 1 that traditional concepts of ice sheet build up and decay must be reexamined 2 that high sea levels may have occurred during the wisconsin glaciation and 3 that a critical reappraisal is required of the open ocean 18 o record as a simple indicator of global ice volume an alternative hypothesis 2 is also examined it is based on the assumption that the 35 000 yr old deposits calculated on the basis of hypothesis 1 date from the last interglaciation this in effect indicates that the missinaibi formation commonly accepted as sediments of the last interglaciation are about 500 000 yr old and that the effective diagenetic temperature in the lowlands during approximately the last 130 000 yr has been close to 6 c we argue for rejection of this alternative hypothesis

oceanic mechanisms for amplification of the 23 000 year ice volume cycle situated adjacent to the largest northern hemispher ice sheets of the ice ages the mid latitude north atlantic ocean has an important role in the earth s climate history it provides a significant local source of moisture for the atmosphere and adjacent continents forms a corridor that guides moisture bearing storms northward from low latitudes and at times makes direct contact along its shorelines with continental ice masses evidence of major ice ocean air interactions involving the north atlantic during the last 250 000 years is summarized outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures summer heat storage winter sea ice extent and global sea level these oceanic responses in turn influence the winter moisture flux back to the ice sheets as well as ablation of land ice by calving spectral data indicate that the oceanic moisture and sea level feedbacks in part controlled by glacial melt products amplify milankovitch insolation forcing of the volumetrically dominant mid latitude ice sheets at the 23 000 year precessional cycle

late quaternary stratigraphy and paleoecology of northwest labrador sea abstract sedimentological study of 20 piston cores from the northwestern labrador sea shows that thin bedded distal turbidites are important constituents of the quaternary strata on the continental slope and rise sedimentation on the outer shelf ca 500 900 m is dominated by ice rafting and hemipelagic deposition detailed study of two outer shelf cores reveals a stratigraphic record extending to oxygen isotopic stage 9 studies of foraminifera and dinoflagellates show that subarctic surface waters penetrated into the northern labrador sea during the early middle glacial stages and pollen data indicate that northward advection of warm air masses occurred at the same time microfossil data indicate that late glacial stages were characterized by year around sea ice cover and arctic surface water and by the dominance of cold dry arctic air masses transitions from glacial to interglacial stages are marked by the presence of low salinity melt water these data support models which postulate that open water in the labrador sea played an important role in supplying moisture to laurentide and greenland ice sheets

shelf erosion and glacial ice proximity in the labrador sea during and after heinrich events h 3 or 4 to h 0 as shown by foraminifera

holocene history of bedford basin nova scotia foraminifera dinoflagellate and pollen records three piston cores from bedford basin a silled coastal inlet provide the basis for a micropaleontological study of postglacial to recent sediments five faunal units four foraminiferal one arcellacean are found in core 79 11 a surface assemblage followed by deep estuarine marginal marine transition and freshwater arcellacean assemblages the other cores contain only expanded marine sequences the top of the transition zone in core 79 11 has a c 14 age of 5830 230 years bp indicating a rise in sea level of at least 20 m the sill depth during the holocene four dinoflagellate assemblage zones are found in core 79 11 the first o centrocarpum b tepikiense is typical of a silled basin with marine water of near normal salinity the second p conicoides cyst c indicates a temperate marine environment with strong fluvial influence marginal marine the third p limbatum is dominated by freshwater cysts and the fourth dinocyst sp a is dominated by subarctic brackish water cysts fo

multivariate analysis and quantitative paleoecology of benthic foraminifera in surface and late quaternary shelf sediments northern canada abstract benthic foraminifera in surface sediments from northeastern canada and the beaufort shelf were studied to determine the quantitative relationship between recent assemblage distributions and modern water depth temperature and salinity factor analysis shows that 7 factor assemblages account for 92 of the variance between samples multiple linear regression shows that different factors are significantly related to water depth august bottom water temperature or salinity multiple correlation coefficients for depth temperature and salinity are 0 94 0 72 and 0 92 respectively labrador fjords contain arenaceous faunas dominated by eithersaccammina atlantica andreophax fusiformis or byeggerella advena regression analysis shows that thesaccammina reophax factor is most strongly related to salinity theeggerella factor is related to depth and temperature a fauna dominated bytrochammina nana andbuliminella elegantissima is correlated with warm deep water in davis strait calcareous assemblages dominated byelphidium excavatum orcassidulina reniforme are found in arctic bays and shelf areas these factor assemblages are strongly related to temperature and depth cassidulina is also related to salinity anislandiella helenae fauna on the inner labrador shelf is strongly correlated with depth and salinity anonionellina labradorica fauna in deep shelf basins is closely related to salinity the multiple regression model for the sea bed data estimates water depth august bottom water temperature and salinity within confidence limits of 67 m 1 3 c and 1 0 paleoecological transfer functions were used to quantify environmental changes recorded by the foraminifera in two piston cores on a transect across the labrador shelf paleo depth estimates obtained from the core data produce relative sea level curves which are similar in shape to theoretical curves for this region paleo salinity and temperature estimates for offshore core 12 show that the change from a postglacialnonionellina fauna to a late glaciale excavatum fauna is accompanied by a decrease of about 2 in salinity and 4 c in temperature paleoecological estimates for fjord core 111 show that the change from a modernsaccammina reophax fauna to a mid holocenei helenae fauna corresponds to a salinity increase of 3 5 and temperature increase of 1 2 c

modeling of streaming potential responses caused by oil well pumping the occurrence of streaming potentials is directly related to movement of fluids in the subsurface to investigate whether streaming potential measurements in boreholes and at the surface can be used to monitor subsurface flow and detect subsurface flow patterns in oil reservoirs we model streaming potential responses caused by oil well pumping in monitoring wells and at the earth s surface since the model parameters permeabilities cross coupling properties and electric conductivities depend on a few basic rock physics parameters such as brine conductivity amount of water saturation and porosity the model parameters are evaluated self consistently using rock physics models using a threedimensional 3 d finite difference algorithm the governing differential equations that are drawn from nonequilibrium thermodynamics are solved numerically in three self consistent steps solution of the hydraulic problem computation of the streaming current sources based on the principle of conservation of char

abrupt changes heinrich events in late quaternary north atlantic marine environments a history and review of data and concepts in the last several years evidence has mounted that a series of abrupt changes in sediment delivery and palaeoceanography effected the north atlantic they are recorded in a variety of proxy records but most dramatically in changes of grain size and mineralogy associated with postulated iceberg rafting events specifically heinrich h events this review paper examines the evidence for such evidence prior to the development of the heinrich event concept 1988 1992 and then examines the explosion of data and correlations that stemmed from the acceptance and use of this paradigm specific attention is focused on ideas pertaining to the cause s of glaciological mechanisms sediment delivery and sediment source and major gaps in our understanding of the underlying glaciological glacial geological and glacial marine processes are stressed abrupt changes across boundaries associated with h 2 in the labrador sea are illustrated from core hu87033 009lcf the case is made that correlations between records need to be more rigorous especially within the range of radiocarbon dating but it appears that abrupt changes in the delivery of iceberg rafted debris which characterize these intervals are multisourced it is unclear how global climate can simultaneously influence the abrupt behaviour of ice margins in different parts of the world for marine based margins changes in relative sea level are one possibility a qualitative model is presented for triggering h events which includes global changes in mass balance changes in relative sea level at ice margins due to glacial isostasy and changes in the basal thermal regime of tidewater ice streams 1998 john wiley sons ltd

latest pleistocene holocene paleoceanographic trends on the continental margin of eastern canada foraminiferal dinoflagellate and pollen evidence micropaleontological studies were made of cores from four shelf basins on the eastern canadian margin emerald and canso basins on the scotian shelf 44 46 n notre dame channel newfoundland shelf 50 n and cartwright saddle labrador shelf 55 events were correlated using a combination of14c dates and pollen stratigraphies surface and bottom water changes were compared on the basis of dinoflagellates and benthic foraminifera respectively the results indicate significant paleoceanographic shifts along a north south gradient both prior to and during the holocene distinct late pleistocene holocene paleoceanographic events were distinguished in the emerald canso and notre dame basins these events are less obvious in cartwright saddle which is in deeper water and further off shore pleistocene glaciomarine sediments in all basins contain a fauna dominated byelphidium excavatum f clavata dinoflagellates and pollen are rare or absent the widespreadelphidium fauna probably reflects turbid glacial meltwater and or a permanent ice shelf cover from 20 000 10 000 yrs bp the notre dame core also penetrates older sediment with an outer labrador current fauna which may represent a late wisconsinian interstade at about 23 000 yrs bp from 7 000 10 000 yrs bp a cold water fauna occurred which is similar to modern outer labrador current faunas from about 5000 7000 yrs bp a warm interval is indicated by a relatively warm water calcareous benthonic foraminiferal fauna and increased representation of typical gulf stream dinoflagellates the most recent change occurred in the last 2000 years with an abrupt cooling associated with stronger flow of the arctic inner labrador current this cooling event is marked by an increase in arctic dinoflagellates and by an exclusively agglutinated benthonic foraminiferal fauna at two sites canso and notre dame these holocene paleoceanographic changes are not clearly seen in the benthic fauna of the deep northern basin cartwright saddle although dinoflagellate data at this site indicate that surface water changes have occurred that are similar to those found in shallower basins shifts in the zonal position of the gulf stream and changes in the relative mass transports of the west greenland and labrador currents are mechanisms which may account for the paleoceanographic events the glacial interstadial glacial sequence recorded in the notre dame channel in conjunction with other theories on glacial triggering mechanisms provides biostratigraphic evidence which suggests the onset of a glacial stage in the near future

thermoluminescence dating of sediments abstract the potential for using the thermoluminescence behaviour of sediments for dating them was first recognized by soviet scientists g v morozov and v n shelkoplyas and for over a decade their tl dates obtained from a variety of sediments have appeared in the soviet literature since 1977 tl sediment dates have been published by six additional groups using a variety of methods in this review we describe the principles of tl dating the various methods used and contrast tl dating of sediments with the now well accepted tl dating of pottery we conclude that while tl dating has the potential to solve many sedimentary problems more fundamental research needs to be carried out before such dates should be accepted a set of criteria for acceptable dates is proposed

upper cenozoic history of the labrador sea baffin bay and the arctic ocean a paleoclimatic and paleoceanographic summary foraminifera palynomorphs and stable isotopes in planktonic foraminifera have been studied in piston cores from the northern labrador sea southern baffin bay and the alpha ridge region of the central arctic ocean foraminifera in cores from the labrador sea and southern baffin bay show glacial interglacial 18o values similar to those reported from the norwegian and greenland seas in contrast to the eastern north atlantic ocean however peaks of subarctic foraminifera and dinoflagellates in the western north atlantic cores show that relatively warm atlantic surface water continued to flow into the northern labrador sea during the early glaciation growth phases of isotopic stages 2 4 6 and 8 boreal and subarctic pollen suggest that warm atlantic air flowed into the northern labrador sea and baffin bay during the ice sheet growth phases the advection of warm air masses and the presence of open waters during the summer probably provided moisture for the growth of the laurentide innuitian and greenland ice sheets isotopic and microfossil records in arctic cores can also be tentatively correlated with major high latitude north atlantic glacial interglacial events magnetostratigraphic palynological and amino acid dating however shows that sedimentation on the alpha ridge has been very slow during the past 0 73 m y therefore events of less than 20 000 years duration cannot be clearly discerned interpretation of pre pleistocene paleoenvironments is further limited by the sparseness of calcareous and siliceous microfossils

palaeoclimate of baffin bay from 300 000 year record of foraminifera dinoflagellates and pollen several different models1 5 have attempted to relate quaternary marine and terrestrial records of ice sheet growth in the north atlantic region the models are derived from either discontinuous terrestrial records including marine fossils in raised shorelines1 2 or from deep sea calcareous microfossils3 4 this study correlates arctic marine and terrestrial data directly by comparing 18o foraminiferal dinoflagellate and pollen records from a core taken in baffin bay the core contains an almost continuous sequence of sediments deposited during isotope stages 1 10 subarctic foraminifera and atlantic dinoflagellates in early isotope stages 2 4 6 and 8 show that subarctic water entered southern baffin bay before the glacial maxima boreal subarctic pollen suggest that atlantic air flowed into baffin bay during the ice sheet growth phases these data support models which postulate that open water in the labrador sea had an important role in supplying moisture to laurentide and greenland ice sheets

land ocean correlations during the last interglacial glacial transition baffin bay northwestern north atlantic a review abstract evidence from terrestrial sections ice cores and marine cores are reviewed and used to develop a scenario for environmental change in the area of the extreme northwest north atlantic during marine isotope stages 5 and 4 the critical physical link between the landbased glacial chronology and marine events in baffin bay is the presence of carbonate rich drift along the baffin bay coast of bylot island and a detrital carbonate facies facies b in baffin bay sediments cores from baffin bay labrador sea can be dated by means of oxygen isotope variations and by peaks in the abundance of volcanic glass shards one occurrence of facies b is dated between late stage 5 and stage 4 and we correlate this event with the eclipse glaciation of bylot island and the ayr lake stade of the foxe glaciation of baffin island kogalu aminozone in contrast on west greenland amino acid racemization evidence suggests that the greenland ice sheet developed throughout stage 4 and reached a maximum in stage 3 svartenhuk advance 40 ka the oxygen isotope record in the devon island ice cap northwest baffin bay indicates that baffin bay was largely open during marine isotope stage 5 analyses of shallow water molluscan and foraminiferal assemblages deep water foraminifera pollen from iand sections and deep sea cores and dinoflagellates from marine cores indicate that interglacial conditions prevailed during much of the stage 5 4 glaciation

the origin and glaciodynamic significance of sandstone ridge networks from the hirnantian glaciation of the djado basin niger the djado basin niger was located beneath the inner part of the late ordovician ice sheet the felar felar formation consists mainly of glaciomarine deposits associated with the major ice sheet recession within the glaciation and is bounded by two glacial unconformities structures corresponding to sandstone ridges are found within the felar felar formation sandstone ridges are several metres high about 10 m wide and hundreds of metres long these structures are organized in extensive anastomosed to subpolygonal networks the association of sandstone ridge networks with the later glacial unconformity and with other glacial evidence suggests sub glacial conditions for their origin sandstone ridge sedimentological characteristics indicate that sandstone ridges result from the scouring of the felar felar formation by sub glacial turbulent and pressurized meltwater then subglacial cavities were infilled with sand derived from glacial abrasion sandstone ridge networks are comparable with tunnel channels and document unusual drainage structures of the inner part of the palaeo ice sheet

a high resolution opal and radiolarian record from the subpolar north atlantic during the mid pleistocene transition 1069 779ka palaeoceanographic implications abstract a high resolution record of radiolarian assemblages from site u1314 was studied to reconstruct hydrographic and climatic changes in the north atlantic ocean during the mid pleistocene transition period 1069 779 ka besides the faunal record absolute accumulation of radiolarians and total biogenic opal are used to determine changes in surface water productivity results show that the north atlantic arctic front shifted back and forth repeatedly at a glacial interglacial timescale bringing the site under the influence of both cold arctic glacial and much warmer atlantic interglacial waters during glacial intervals and ice rafted debris ird events the deep dwelling taxon cycladophora davisiana was the greatest contributor of the radiolarian assemblage suggesting cold surface conditions melt water discharge and changes in deep and intermediate circulation interglacial intervals were characterized by abundant shallow dwelling taxa like pseudodyctiophimus gracilipes and lithomelissa setosa increased opal accumulation and higher radiolarian diversities indicating a northward flow of warm atlantic surface waters to the site u1314 area a marked change in the structure of the radiolarian assemblage occurred after mis 22 860 ka with large taxa differences between warm and cold periods probably in response to changing ocean conditions due to the higher amplitude of glacial interglacial changes as the dominant periodicity of high latitude climate oscillations shifted from 41 kyr to 100 kyr thus we conclude that the radiolarian assemblage from the north atlantic have changed drastically along with variations in ocean circulation in response to orbital and millennial scale climatic variations that occurred in the early and mid pleistocene