the stratigraphic and sedimentological significance of late devensian ice sheet surging in holderness yorkshire u k amino acid analyses of marine mollusc valves show that the basement till of holderness yorkshire is of late devensian age ca 20 000 bp and not pre ipswichian 125 000 bp as is traditionally supposed together with the overlying skipsea and withernsea tills the basement till is argued to be a deformation till resulting from the repeated onshore surging of late devensian ice over a muddy sea floor and the subglacial transport attenuation and mixing of marine sediment silts on the surface of the basement till yielding 14c dates of 18 500 and 18 240 bp have been regarded as minimum ages for late devensian glaciation in eastern england e g the dimlington stadial of rose 1985 1989 the amino acid data presented here indicates that the maximum of the late devensian glaciation in eastern england occurred earlier sedimentological interpretation of the late devensian tills of holderness as glacially reworked marine sediments supports previous glaciological models of the british ice sheet involving surging of ice lobes along the coast of eastern england the basement skipsea and withernsea tills are separated by shallow marine sediments and may be representative of deformable bed till facies deposited below pleistocene ice sheets moving over soft fine grained sediments

the late devensian 22 000 bp irish sea basin the sedimentary record of a collapsed ice sheet margin the late devensian 20 ka bp glacial geology of the irish sea basin 4000 km2 is an event stratigraphy recording the entry of marine waters into a glacio isostatically depressed basin and the rapid retreat of the irish sea glacier as a tidewater ice margin marine limits occur up to 140 m o d across much of the central basin the ice margin was uncoupled from its bed exposing a subglacially scoured topography to glaciomarine processes the irish sea glacier was a major drainage conduit of the last british ice sheet calving of the marine ice margin resulted in fast flow surging of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones e g cheshire shropshire lowlands and initiated the collapse of the ice sheet thick wedges of ice contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the irish sea coast where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins the development of fast flowing ice streams drumlinization and the pumping of subglacial sediment to tidewater raised delta complexes are locally associated with marine limits along the high relief coastal margins of wales east central ireland and the lake district associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat co eval offshore deposits are represented by well stratified glaciomarine complexes that infill a subglacially scoured topography that shows networks of tunnel valleys glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin e g north devon scilly islands southern ireland the age of these distal sediments previously mapped as pre devensian tills is constrained by amino acid ratios basin rebound following deglaciation was rapid with over 100 m recovery in 3 ka and was followed by a low marine still stand peat accumulating in offshore areas now as much as 55 m below sea level has been drowned by the postglacial eustatic rise in sea level the glacio sedimentary model identified in this paper involving rapid ice retreat and related sedimentation triggered by rising relative sea level suggests that isotatic downwarping is an important mechanism for deglaciating continental shelves

causes consequences and chronology of large magnitude palaeoflows in middle and late pleistocene river systems of northwest europe this study examines the record of high palaeoflow phases in river systems in northwest europe investigating their causes whether due to unique events such as the formation of the dover strait or as characteristic consequences of climate change examining their consequences with regard to landscape evolution and possible effects on climate and determining the chronology of key events large magnitude palaeoflows more than an order of magnitude larger than present day flood peaks are shown to be characteristic of rivers in this region at particular times within the pleistocene these events the most recent of which were during heinrich events 2 and 1 at 25 and 17 ka were evidently caused by the combined effects of glacial outwash rainfall snowmelt and melting of permafrost in some proportion they released such large volumes of water that the thermohaline circulation of the atlantic ocean and thus the climate may well have been affected these large magnitude palaeoflows are thus a significant aspect of the pleistocene earth system that has hitherto gone unquantified

millennial scale fluctuations of the european ice sheet at the end of the last glacial and their potential impact on global climate abstract reconstructing northern hemisphere ice sheet oscillations and meltwater routing to the ocean is important to better understand the mechanisms behind abrupt climate changes to date research efforts have mainly focused on the north american laurentide ice sheets lis leaving the potential role of the european ice sheet eis and of the scandinavian ice sheet sis in particular largely unexplored using neodymium isotopes in detrital sediments deposited off the channel river we provide a continuous and well dated record for the evolution of the eis southern margin through the end of the last glacial period and during the deglaciation our results reveal that the evolution of eis margins was accompanied with substantial ice recession especially of the sis and simultaneous release of meltwater to the north atlantic these events occurred both in the course of the eis to its lgm position i e during heinrich stadial hs 3 and hs2 31 29 ka and 26 23 ka respectively and during the deglaciation i e at 22 ka 20 19 ka and from 18 2 0 2 to 16 7 0 2 ka that corresponds to the first part of hs1 the deglaciation was discontinuous in character and similar in timing to that of the southern lis margin with moderate ice sheet retreat from 22 5 0 2 ka in the baltic lowlands as soon as the northern summer insolation increase from 23 ka and an acceleration of the margin retreat thereafter from 20 ka importantly our results show that eis retreat events and release of meltwater to the north atlantic during the deglaciation coincide with amoc destabilisation and interhemispheric climate changes they thus suggest that the eis together with the lis could have played a critical role in the climatic reorganization that accompanied the last deglaciation finally our data suggest that meltwater discharges to the north atlantic produced by large scale recession of continental parts of northern hemisphere ice sheets during hs could have been a possible source for the oceanic perturbations i e amoc shutdown responsible for the marine based ice stream purge cycle or so called he s that punctuate the last glacial period

ice rafting from the british irish ice sheet since the earliest pleistocene 2 6 million years ago implications for long term mid latitudinal ice sheet growth in the north atlantic region abstract the plio pleistocene intensification of northern hemisphere continental ice sheet development is known to have profoundly affected the global climate system evidence for early continental glaciation is preserved in sediments throughout the north atlantic ocean where ice rafted detritus ird layers attest to the calving of sediment loaded icebergs from circum atlantic ice sheets so far early pleistocene ird deposition has been attributed to the presence of high latitudinal ice sheets whereas the existence and extent of ice accumulation in more temperate mid latitudinal regions remains enigmatic here we present results from the multiproxy provenance analysis of a unique pleistocene holocene ird sequence from the irish ne atlantic continental margin there the challenger coral carbonate mound iodp expedition 307 site u1317 preserved an early pleistocene record of 16 distinctive ird events deposited between ca 2 6 and 1 7 ma strong and complex ird signals are also identified during the mid pleistocene climate transition ca 1 2 to 0 65 ma and throughout the middle late pleistocene interval radiogenic isotope source fingerprinting in combination with coarse lithic component analysis indicates a dominant sediment source in the nearby british irish isles even for the oldest early pleistocene ird deposits hence our findings demonstrate for the first time repeated and substantial i e marine terminating ice accumulation on the british irish isles since the beginning of the pleistocene contemporaneous expansion of both high and mid latitudinal ice sheets in the north atlantic region is therefore implied at the onset of the pleistocene moreover it suggests the recurrent establishment of climatically favourable conditions for ice sheet inception growth and instability in mid latitudinal regions even in the earliest stages of northern hemisphere glacial expansion and in an obliquity driven climate system

origins of the ice contact stratified ridges eskers of ireland abstract an extensive system of ridged landforms composed of ice contact stratified sediment was deposited in the central lowland of ireland during the most recent deglaciation 18 000 bp the ridges have been interpreted by others as deposits of an ice sheet drainage system i e eskers and as such have been used with other data to reconstruct the deglacial history the traditional deglaciation model shows systematic retreat of ice from south to north our study which involves an analysis of the ridged landforms using lithofacies sedimentary structures and paleocurrent data in conjunction with the geomorphology indicates that the pattern and nature of the ridges are not compatible with this model and support a new model of deglaciation warren 1991 in which the esker system fo med in an interlobate area during the simultaneous shrinking of two main glacial outflow centers an extensive lake system developed in the lowland between the two outflow centers ridges formed both perpendicular and parallel to ice margins involved both active and stagnating ice are both continuous and segmented beaded and were deposited in subaqueous and subaerial environments almost all of the ridges are associated with lacustrine sediments ice contact ridges are polygenetic and a genetic classification is proposed those that formed perpendicular to the ice margin are termed eskers those that formed parallel are termed moraines distinction between esker types continuous or beaded subglacial tunnel fills fluvial ice channel fills and subaqueous fans and moraine types s baqueous or subaerial is crucial to a reconstruction of the mode and pattern of deglaciation in the central irish lowlands

geometry and rate of faulting in the north baikal rift siberia we present a detailed morphotectonic analysis of late quaternary faulting in the north baikal rift nbr a region characterized by ranges and basins distributed over more than 800 km along strike in eastern siberia remote sensing techniques spot meteor scenes and aerial photographs are used to map the active fault network which displays a general en echelon distribution from the northern lake baikal to the easternmost basin with 30 km spaced overstepping segments of 10 80 km in length most faults have a dominant dip slip component over their cenozoic history the inherited crustal fabric strongly influences the overall geometry of the rifted basins we use 54 14c ages of postglacial terraces near the foot scarps of the muya basin to date offsets measured inside alluvial fans the last main postglacial event in this area appears to be the early holocene optimum dated at 10 2 ka following the onset of deglaciation at 13 ka using these time constraints a detailed leveling across two terraces offset by the taksimo fault west muya basin shows consistent minimum vertical slip rates of 1 6 0 6 mm yr 1 using 30 other active scarps analyzed in the field we find a lower bound for horizontal velocity of 3 2 0 5 mm yr 1 across the nbr a rate close to the one found in the southern rift from global positioning system measurements we then compare directions of slip vectors from holocene field data and slip directions from earthquake fault plane solutions although local discrepancies appear the mean directions of lesser horizontal stress 3 inverted from theses values are n130 e and n155 e respectively which are comparable within uncertainties and favor a rifting obliquity of 30 40 extrapolating our holocene rates we estimate basin ages younger than those generally believed less than 7 ma and propose a spatial and temporal evolution of rifted basins consistent with experimental models of oblique rifting total amounts of extension and vertical throw 7 and 12 km respectively across major faults appear rather constant from the central to the northern rift these results favor a progressive development of asymmetric grabens in a rift zone that widens with times and they indicate a strong rheological control on deformation which seems enhanced by other contributions than the far field effects of the indo eurasian collision

new evidence for a grounded irish sea glaciation of the isles of scilly uk abstract new geomorphological and sedimentological data support previously published reconstructions of an irish sea glacier advance as far south as the northern shores of the isles of scilly in the celtic sea 49 58 n offshore boulder covered bars with cores of diamicton are interpreted as moraines which together with onshore moraine ridges and trimlines mark the maximal extent of the irish sea glacier at bread and cheese cove st martin s a heterogeneous sediment unit wedged between periglacial gelifluctates is interpreted as a mixture of glacitectonized and cannibalized glacilacustrine and marine deposits as well as primary subglacial tills macrofabric signatures reflect a subglacial origin but the whole unit has been subject to down slope mass movement micromorphological analysis indicates highly variable response to deformation and glacitectonism with most features relating to ductile behaviour and wet deformation the characteristics suggest deposition during a short lived advance of the irish sea glacier over pre existing marine and contemporaneous proglacial lacustrine sediments once blocks of stratified sediment and diamicton had been driven onshore they were subject to paraglacial remobilization resulting at most locations in complete disaggregation the distribution of re worked glacigenic sediments coincides with the glacial limits inferred from the geomorphological evidence

cenozoic uplift of southwest england the uplift history of southwest england is inferred using a composite dataset including marine and fluvial terraces and karstic data the estimated post mid pliocene uplift increases eastward from 130 m in west cornwall and 135 m in south devon to 150 m in the hampshire basin the post early pleistocene uplift likewise increases eastward from 55 m in west cornwall to 60 m in south devon and 80 m in hampshire landscape and thermochronological evidence also indicates eocene uplift caused by the british tertiary igneous province magmatism this component tapers eastward from 300 m in west cornwall to 50 m in south devon with subsidence in east devon this uplift accompanied magmatic underplating the mafic layer added to the basal crust thins eastward from 6 km in west cornwall to 2 km in south devon evidently tapering to zero farther east the laterally variable crustal properties caused by this variation in underplating have affected the post mid pliocene uplift the study region is thus intermediate in terms of crustal strength and landscape evolution between central southern england with no underplating and ireland where 10 km thick underplating has resulted in extreme late cenozoic landscape stability the eocene mantle plume related uplift is distinct from the post mid pliocene phase which the modelling indicates has been driven by surface processes and thus by climate change copyright 2010 john wiley sons ltd

reconstructing the last irish ice sheet 2 a geomorphologically driven model of ice sheet growth retreat and dynamics the ice sheet that once covered ireland has a long history of investigation much prior work focussed on localised evidence based reconstructions and ice marginal dynamics and chronologies with le

glaciodynamics of the central sector of the last british irish ice sheet in northern england the central sector of the last british irish ice sheet biis was characterised by considerable complexity both in terms of its glacial stratigraphy and geomorphological signature this complexity is reflected by the large number and long history of papers that have attempted to decipher the glaciodynamic history of the region despite significant advances in our understanding reconstructions remain hotly debated and relatively local thereby hindering attempts to piece together biis dynamics this paper seeks to address these issues by reviewing geomorphological mapping evidence of palimpsest flow signatures and providing an up to date stratigraphy of the region reconciling geomorphological and sedimentological evidence with relative and absolute dating constraints has allowed us to develop a new six stage glacial model of ice flow history and behaviour in the central sector of the last biis with three major phases of glacial advance this includes i eastwards ice flow through prominent topographic corridors of the north pennines ii cessation of the stainmore ice flow pathway and northwards migration of the north irish sea basin ice divide iii stagnation and retreat of the tyne gap ice stream iv blackhall wood gosforth oscillation v deglaciation of the solway lowlands and vi scottish re advance and subsequent final retreat of ice out of the central sector of the last biis the ice sheet was characterised by considerable dynamism with flow switches initiation and termination of ice streams draw down of ice into marine ice streams repeated ice marginal fluctuations and the production of large volumes of meltwater locally impounded to form ice dammed glacial lakes significantly we tie this reconstruction to work carried out and models developed for the entire ice sheet this therefore situates research in the central sector within contemporary understanding of how the last biis evolved over time

pattern style and timing of british irish ice sheet retreat shetland and northern north sea sector the offshore sector around shetland remains one of the least well studied parts of the former british irish ice sheet with several long standing scientific issues unresolved these key issues include i the dominance of a locally sourced shetland ice cap vs an invasive fennoscandian ice sheet ii the flow configuration and style of glaciation at the last glacial maximum i e terrestrial vs marine glaciation iii the nature of confluence between the british irish and fennoscandian ice sheets iv the cause style and rate of ice sheet separation and v the wider implications of ice sheet uncoupling on the tempo of subsequent deglaciation as part of the britice chrono project we present new geological seabed cores geomorphological marine geophysical and geochronological data from the northernmost sector of the last british irish ice sheet north of 59 5 n to address these questions the study area covers ca 95 000 km2 an area approximately the size of ireland and includes the islands of shetland and the surrounding continental shelf some of the continental slope and the western margin of the norwegian channel we collect and analyse data from onshore in shetland and along key transects offshore to establish the most coherent picture so far of former ice sheet deglaciation in this important sector alongside new seabed mapping and quaternary sediment analysis we use a multi proxy suite of new isotopic age assessments including 32 cosmogenic nuclide exposure ages from glacially transported boulders and 35 radiocarbon dates from deglacial marine sediments to develop a synoptic sector wide reconstruction combining strong onshore and offshore geological evidence with bayesian chronosequence modelling the results show widespread and significant spatial fluctuations in size shape and flow configuration of an ice sheet ice cap centred on or to the east of the orkney shetland platform between 30 and 15 ka bp at its maximum extent ca 26 25 ka bp this ice sheet was coalescent with the fennoscandian ice sheet to the east between 25 and 23 ka bp the ice sheet in this sector underwent a significant size reduction from ca 85 000 to 50 000 km2 accompanied by several ice margin oscillations soon after connection was lost with the fennoscandian ice sheet and a marine corridor opened to the east of shetland this triggered initial and unstable re growth of a glaciologically independent shetland ice cap ca 21 20 ka bp with a strong east west asymmetry with respect to topography ice mass growth was followed by rapid collapse from an area of ca 45 000 km2 to ca 15 000 km2 between 19 and 18 ka bp stabilizing at ca 2000 km2 by 17 ka bp final deglaciation of shetland occurred ca 17 15 ka bp and may have involved one or more subsidiary ice centres on now submerged parts of the continental shelf we suggest that the unusually dynamic behaviour of the northernmost sector of the british irish ice sheet between 21 and 18 ka bp characterized by numerous extensive ice sheet ice mass readvances rapid loss and flow redistributions was driven by significant changes in ice mass geometry ice divide location and calving flux as the glaciologically independent ice cap adjusted to new boundary conditions we propose that this dynamism was forced to a large degree by internal glaciological factors specific to the strongly marine influenced shetland ice cap

response of the irish ice sheet to abrupt climate change during the last deglaciation we summarize 121 14c and in situ cosmogenic 10be and 36cl ages that constrain fluctuations of the irish ice sheet iis since the last glacial maximum lgm that can be linked to abrupt climate changes in the north atlantic region these data provide a robust means to date ice sheet fluctuations because similar age events can be identified from widely spaced sites they are constrained by stratigraphy and they can be related to large changes in the configuration of a dynamic ice sheet the following events are recognized 1 ams 14c ages and 10be and 36cl ages as well as offshore data suggest that the last maximum advance of the iis occurred between 27 and 23 cal ka 2 deglaciation began on the western continental shelf and in the irish sea basin at 23 cal ka dated sites from around ireland constrain subsequent widespread retreat of ice sheet margins from the shelf onto irish coastlines during the cooley point interstadial 20 cal ka ams 14c ages suggest that the cooley point interstadial continued until 18 2 cal ka b p during this interstadial retreat of the ice sheet margin into the northern irish sea basin indicates that the iis may have lost up to two thirds of its mass 3 dated sites from northwestern and eastern ireland indicate that the cooley point interstadial was terminated by ice readvance during the clogher head stadial at 18 2 cal ka 4 the linns interstadial was a brief interval 17 0 16 5 cal ka of ice recession following the clogher head stadial that is identified from raised marine sediments in eastern and northern ireland and cosmogenic ages elsewhere in ireland 5 the iis subsequently readvanced during the killard point stadial reaching its maximum extent 16 5 cal ka indicating that the readvance began sometime earlier 6 widespread retreat of the iis began by 15 5 cal ka during the rough island interstadial 6 readvance of cirque glaciers in western ireland occurred during the younger dryas equivalent nahanagan stadial

the last glacial maximum in the north sea basin micromorphological evidence of extensive glaciation despite a long history of investigation critical issues regarding the last glacial cycle in northwest europe remain unresolved one of these refers to the extent timing and dynamics of late devensian weichselian glaciation of the north sea basin and whether the british and scandinavian ice sheets were confluent at any time during this period this has been the result of the lack of the detailed sedimentological data required to reconstruct processes and environment of sediments recovered through coring this study presents the results of seismic sedimentological and micromorphological evidence used to reconstruct the depositional processes of regionally extensive seismic units across the north sea basin thin section micromorphology is used here to provide an effective means of discriminating between subglacial and glacimarine sediments from cored samples and deriving process based interpretations from sediment cores on the basis of micromorphology critical formations from the basin have been reinterpreted with consequent stratigraphic implications within the current stratigraphic understanding of the north sea basin a complex reconstruction is suggested with a minimum of three major glacial episodes inferred on at least two occasions during the weichselian devensian the british and scandinavian ice sheets were confluent in the central north sea whilst micromorphology can provide much greater confidence in the interpretation of late quaternary offshore stratigraphic sequences it is noted that a much better geochronology is required to resolve key stratigraphic issues between the onshore and offshore stratigraphic records copyright 2006 john wiley sons ltd

depositional model in subglacial cavities killiney bay ireland interactions between sedimentation deformation and glacial dynamics subglacial meltwater drainage and sedimentary processes play a major role in ice sheet dynamic but there is a lack of study of subglacial environment because modern ice sheet beds remain inaccessible previous authors already intended to provide diagnostic criterion and recent investigations suggest that fluid pressure variations are a key factor in subglacial environment this paper investigated the late devensian sedimentary record in order to describe subglacial sedimentological facies associations and deformation features related to fluid overpressures we used an integrated approach based on stratigraphy sedimentology and deformations styles to demonstrate a subglacial depositional model the studied interval is composed of stratified gravel and sand interbedded with diamicton and boulder pavement deposited in depressions formed by irregularity of the upper surface of diamicton deformation structures include convolutes dykes and normal micro faulting dykes show different dip directions from vertical oblique to subhorizontal from which both directions of shortening and extension can be determined vertical dykes are formed under pure shear strain related to ice weight only oblique dykes imply both ice bed coupling and simple shear strain between ice and substrate induced by flowing ice related to progressively increasing meltwater drainage intensity horizontal dykes are formed when minimum strain is vertical and therefore the overpressure exceeds the weight of overburden they are associated with high meltwater drainage intensity and ice bed uncoupling and refer to hydrofracturing overall depositional and deformation sequence also illustrates the increasing intensity of meltwater drainage in small cavity as high energy channelised deposits and in large cavities where subaqueous fan are deposited under hydraulic jump conditions moreover large cavities represent lee side cavities formed by fast flowing ice over an obstacle hydrofracturing is likely to occur when a dense fluid potentially associated with catastrophic drainage of an upstream cavity enters the low pressure confined environment of a downstream cavity and is injected under pressure in the soft substrate the studied glacial sequence represents a regional pattern probably related to an allocyclic control on sedimentation linked to long term glacial dynamics rather than local depositional conditions based on these results we provided a synthetic model linking depositional and deformation processes during ice sheet growth and decay but also valid at different timescales from annual to seasonal scale

palaeoglaciology of the last irish ice sheet reconstructed from striae evidence abstract a database comprising some 5200 individual striation measurements on bedrock surfaces across the island of ireland was used to produce maps of flowsets corresponding to individual ice flow events during the last late devensian glacial cycle these flowsets were identified on the basis of regional scale correspondence between striae orientations which when linked together spatially are able to identify consistent ice flow vectors four main chronological stages are identified on the basis of this evidence i incursion of scottish ice into ireland ii glacial maximum conditions iii ice retreat and dissolution and iv development of localised ice domes striae based reconstructions of the glaciology of the last irish ice sheet are qualitatively different from those based on bedform mainly drumlin and ribbed moraine evidence significant differences are apparent in upland areas which have fewer preserved bedforms and a higher concentration of striae combining bedform and striae datasets will enable a better understanding of the temporal evolution of the ice sheet it is likely that both datasets record a snapshot of ice flow direction and subglacial conditions and environments immediately prior to preservation of this directional evidence

dynamic cycles ice streams and their impact on the extent chronology and deglaciation of the british irish ice sheet we present results from a suite of forward transient numerical modelling experiments of the british and irish ice sheet biis consisting of scottish welsh and irish accumulation centres spanning the last glacial period from 38 to 10 ka bp the 3d thermomechanical model employed uses higher order physics to solve longitudinal membrane stresses and to reproduce grounding line dynamics surface mass balance is derived using a distributed degree day calculation based on a reference climatology from mean 1961 1990 precipitation and temperature patterns the model is perturbed from this reference state by a scaled ngrip oxygen isotope curve and the specmap sea level reconstruction isostatic response to ice loading is computed using an elastic lithosphere relaxed asthenosphere scheme a suite of 350 simulations were designed to explore the parameter space of model uncertainties and sensitivities to yield a subset of experiments that showed close correspondence to offshore and onshore ice directional indicators broad biis chronology and the relative sea level record three of these simulations are described in further detail and indicate that the separate ice centres of the modelled biis complex are dynamically interdependent during the build up to maximum conditions but remain largely independent throughout much of the simulation the modelled biis is extremely dynamic drained mainly by a number of transient but recurrent ice streams which dynamically switch and fluctuate in extent and intensity on a centennial time scale a series of binge purge advance retreat cycles are identified which correspond to alternating periods of relatively cold based ice associated with a high aspect ratio and net growth and wet based ice with a lower aspect ratio characterised by streaming the timing and dynamics of these events are determined through a combination of basal thermomechanical switching spatially propagated and amplified through longitudinal coupling but are modulated and phase lagged to the oscillations within the ngrip record of climate forcing phases of predominant streaming activity coincide with periods of maximum ice extent and are triggered by abrupt transitions from a cold to relatively warm climate resulting in major iceberg melt discharge events into the north sea and atlantic ocean the broad chronology of the modelled biis indicates a maximum extent at 20 ka with fast flowing ice across its western and northern sectors that extended to the continental shelf edge fast flowing streams also dominate the irish sea and north sea basin sectors and impinge onto sw england and east anglia from 19 ka bp deglaciation is achieved in less than 2000 years discharging the freshwater equivalent of 2 m global sea level rise a much reduced ice sheet centred on scotland undergoes subsequent retrenchment and a series of advance retreat cycles into the north sea basin from 17 ka onwards culminating in a sustained younger dryas event from 13 to 11 5 ka bp modelled ice cover is persistent across the western and central highlands until the last remnant glaciers disappear around 10 5 ka bp

sedimentary evidence for deforming bed conditions associated with a grounded irish sea glacier southern ireland along the south coast of ireland a shelly diamict facies the irish sea till has been variously ascribed to subglacial deposition by a grounded irish sea glacier or to glacimarine sedimentation by suspension settling and iceberg rafting observations are presented here from five sites along the south coast to directly address this question at these sites sedimentary evidence is preserved for the onshore advance of a grounded irish sea glacier which glacitectonically disturbed and eroded pre existing sediments and redeposited them as deformation till recession of this irish sea glacier resulted in the damming of ice marginal lakes in embayments along the south coast into which glacilacustrine sedimentation then took place these lake sediments were subsequently glacitectonised and reworked by overriding glacier ice of inland origin which deposited deformation till on top of the succession there is no evidence for deposition of the irish sea diamicts by glacimarine sedimentation at these sites the widespread development of subglacial deforming bed conditions reflected the abundance of fine grained marine and lacustrine sediments available for subglacial erosion and reworking stratigraphical and chronological data suggest that the advance of a grounded irish sea glacier along the south coast occurred during the last glaciation and this is regionally consistent with marine geological data from the celtic sea these observations demonstrate extension of glacier ice far beyond its traditional limits in the celtic sea and on land in southern ireland during the last glaciation and remove the stratigraphical basis for chronological differentiation of surficial glacial drifts and thus the munsterian glaciation in southern ireland copyright 2001 john wiley sons ltd

marine geophysical evidence for late pleistocene ice sheet extent and recession off northwest ireland abstract multibeam swath bathymetry data collected through the irish national seabed survey provides direct evidence for extensive glaciation of the continental shelf off northwest ireland streamlined subglacial bedforms on the inner shelf record former offshore directed ice flow the major glacial features however consist of well developed nested arcuate moraines which mark the position of former ice sheet margins on the shelf distal to these moraines on the outermost shelf prominent zones of iceberg ploughmarks give way into a well developed system of gullies and canyons which incise the continental slope the large scale nested arcuate moraines record the episodic retreat probably punctuated by minor readvances or oscillations of a lobate grounded ice sheet across this sector of the continental shelf during deglaciation initial retreat from the outer shelf was associated with an episode of ice sheet break up and calving as recorded by extensive zones of iceberg ploughmarks distal to the outermost moraine it is conceivable that this initial phase of retreat could have been driven by rising sea level the data indicate a major reorganisation of the irish ice sheet on the northwest shelf during deglaciation an initial elongate ice sheet configuration extending along the shelf edge changed to a pronounced lobate form during retreat consideration of dated marine stratigraphic records from the wider northwest margin suggests that ice sheet advance to the shelf edge likely occurred at about 29 27 cal ka bp but that retreat from this shelf edge position did not take place until after 24 cal ka bp large scale contrasts in continental margin morphology west of ireland from trough mouth fans in the north to gully canyon systems further to south reflects a combination of factors including spatial variations in sediment flux related to palaeo glaciology

bayesian modelling the retreat of the irish sea ice stream we present an 8000 year history spanning 650km of ice margin retreat for the largest marine terminating ice stream draining the former british irish ice sheet bayesian modelling of the geochronological data shows the isis expanded 34 0 25 3ka accelerating into the celtic sea to reach maximum limits 25 3 24 5ka before a collapse with rapid marginal retreat to the northern irish sea basin isb this retreat was rapid and driven by climatic warming sea level rise mega tidal amplitudes and reactivation of meridional circulation in the north atlantic the retreat though rapid is uneven with the stepped retreat pattern possibly a function of the passage of the ice stream between normal and adverse ice bed gradients and changing ice stream geometry initially wide calving margins and adverse slopes encouraged rapid retreat 550m a 1 that slowed 100m a 1 at the topographic constriction and bathymetric high between southern ireland and wales before rates increased 200m a 1 across adverse bed slopes and wider and deeper basin configuration in the northern isb these data point to the importance of the ice bed slope and lateral extent in predicting the longer term 1000 a patterns and rates of ice marginal retreat during phases of rapid collapse which has implications for the modelling of projected rapid retreat of present day ice streams copyright 2013 john wiley sons ltd

timing of massive fleuve manche discharges over the last 350 kyr insights into the european ice sheet oscillations and the european drainage network from mis 10 to 2 continuous high resolution mass accumulation rates mar and x ray fluorescence xrf measurements from marine sediment records in the bay of biscay ne atlantic have allowed the determination of the timing and the amplitude of the fleuve manche channel river discharges during glacial stages mis 10 mis 8 mis 6 and mis 4 2 these results have yielded detailed insight into the middle and late pleistocene glaciations in europe and the drainage network of the western and central european rivers over the last 350 kyr this study provides clear evidence that the fleuve manche connected the southern north sea basin with the bay of biscay during each glacial period and reveals that fleuve manche activity during the glaciations mis 10 and mis 8 was significantly less than during mis 6 and mis 2 we correlate the significant fleuve manche activity detected during mis 6 and mis 2 with the extensive saalian drenthe substage and the weichselian glaciations respectively confirming that the major elsterian glaciation precedes the glacial mis 10 in detail massive fleuve manche discharges occurred at ca 155 ka mid mis 6 and during termination i while no significant discharges are found during termination ii it is assumed that a substantial retreat of the european ice sheet at ca 155 kyr followed by the formation of ice free conditions between the british isles and scandinavia until termination ii allowed meltwater to flow northwards through the north sea basin during the second part of the mis 6 we assume that this glacial pattern corresponds to the warthe substage glacial maximum therefore indicating that the data presented here equates to the drenthe and the warthe glacial advances at ca 175 160 ka and ca 150 140 ka respectively finally the correlation of our records with odp site 980 reveals that massive fleuve manche discharges related to partial or complete melting of the european ice masses were synchronous with strong decreases in both the rate of deep water formation and the strength of the atlantic thermohaline circulation fleuve manche discharges over the last 350 kyr probably participated with other meltwater sources in the collapse of the thermohaline circulation by freshening the northern atlantic surface water

sensitivity of palaeotidal models of the northwest european shelf seas to glacial isostatic adjustment since the last glacial maximum abstract the spatial and temporal distribution of relative sea level change over the northwest european shelf seas has varied considerably since the last glacial maximum due to eustatic sea level rise and a complex isostatic response to deglaciation of both near and far field ice sheets because of the complex pattern of relative sea level changes the region is an ideal focus for modelling the impact of significant sea level change on shelf sea tidal dynamics changes in tidal dynamics influence tidal range the location of tidal mixing fronts dissipation of tidal energy shelf sea biogeochemistry and sediment transport pathways significant advancements in glacial isostatic adjustment gia modelling of the region have been made in recent years and earlier palaeotidal models of the northwest european shelf seas were developed using output from less well constrained gia models as input to generate palaeobathymetric grids we use the most up to date and well constrained gia model for the region as palaeotopographic input for a new high resolution three dimensional tidal model roms of the northwest european shelf seas with focus on model output for 1 ka time slices from the last glacial maximum taken as being 21 ka bp to present day we demonstrate that spatial and temporal changes in simulated tidal dynamics are very sensitive to relative sea level distribution the new high resolution palaeotidal model is considered a significant improvement on previous depth averaged palaeotidal models in particular where the outputs are to be used in sediment transport studies where consideration of the near bed stress is critical and for constraining sea level index points

ice sheet variability around the north atlantic ocean during the last deglaciation millennial scale variability in the flux of ice rafted detritus to north atlantic sediments during the last glacial period has been interpreted to reflect a climate forced increase in the discharge of icebergs from ice sheet margins surrounding the northern north atlantic ocean 1 but the relationship between ice sheet variability and climate change is not clear as both the sources of ice rafted detritus and the ice marginal processes are varied and complex 2 4 terrestrial records are helpful in unravelling this complexity because they can demonstrate the scale of ice sheet oscillations and whether the ice sheet or sector was advancing or retreating with respect to climate change here we constrain the age and anatomy of a prominent readvance of the british ice sheet in the northern irish sea region at similar to 14 14 c kyr bp similar to 16 4 calendar kyr bp the analysis indicates that the british ice sheet participated in an iceberg discharge episode known as heinrich event 1 comparison with other terrestrial and marine ice sheet records suggests that the dynamic collapse of the laurentide ice sheet beginning at 14 6 15 0 c 14 kyr bp1 4 similar to 17 2 17 6 calendar kyr bp 5 initiated varied responses from other ice sheet margins around the northern north atlantic region these observations support the argument that the release of icebergs and meltwater during heinrich event 1 disrupted the north atlantic thermohaline circulation 6 8 leading to a delay or reversal of deglaciation of the northern hemisphere and at least as far south as 40 degrees s for two to three thousand years 5 9 10 suggesting a climate forcing and response similar to that of the ensuing younger dryas cold snap 11 12

quaternary glaciations of northern europe this paper presents the outcome of a workshop held in berlin in february 2009 concerned with current research on the glacial history of northern europe including the british isles the methodologies presently used to resolve this topic are outlined particular attention is given to new analytical methods deriving from high resolution remote imaging of glacial terrain both on land and on the sea bed key new stratigraphic sections higher resolution results from conventional geochronological methods like radiocarbon and more recently developed technologies such as luminescence and cosmogenic radionuclide dating the relationships between the results derived from these two methods are discussed in further detail along with possible explanations for these differences an outline of a most likely glacial history of the scandinavian and british and irish ice sheets is presented along with possible links to global climate change as represented by the marine isotope mis record tentative evidence for glaciation is identified in mis 22 16 12 10 8 6 4 and 2 and correlations of phases within the last glaciation are also explored for both the scandinavian and british and irish ice sheets the results show that the character and extent of glaciation in different parts of the region are not synchronous and much more geochronological work is required before regional correlations can be established with confidence

morphological and sedimentary responses to ice mass interaction during the last deglaciation during decline of the last british irish ice sheet biis down wasting of ice meant that local sources played a larger role in regulating ice flow dynamics and driving the sediment and landform record at the last glacial maximum glaciers in north western england interacted with an irish sea ice stream isis occupying the eastern irish sea basin isb and advanced as a unified ice mass during a retreat constrained to 21 17 3 ka the sediment landform assemblages lain down reflect the progressive unzipping of the ice masses oscillations of the ice margin during retreat and then rapid wastage and disintegration evacuation of ice from the ribble valley and lancashire occurred first while the isis occupied the isb to the west creating ice dammed lakes deglaciation complete after 18 6 17 3 ka was rapid 50 25 m a 1 but slower than rates identified for the western isis 550 100 m a 1 the slower pace is interpreted as reflecting the lack of a calving margin and the decline of a terrestrial grounded glacier ice marginal oscillations during retreat were probably forced by ice sheet dynamics rather than climatic variation these data demonstrate that large grounded glaciers can display complex uncoupling and realignment during deglaciation with asynchronous behaviour between adjacent ice lobes generating complex landform records

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

correlation of lg amplitude ratios from peaceful nuclear explosions to crustal structure in northern eurasia because the lg phase is strongly affected by the variations of crustal structure in some areas understanding these factors is important for nuclear test monitoring this study examines the effects of regional tectonic structure on lg propagation by using the peaceful nuclear explosion pne profiles in russia the logarithms of lg sn and lg pcoda pne amplitude ratios within the 0 5 to 3 hz frequency band are measured and correlated with the regional crustal structures both ratios are found to decrease within the areas with thick low velocity sedimentary cover and across tectonic boundaries with abrupt variations of crustal thickness for the offset derivatives of both the logarithmic ratios a linear relationship to the slopes of the moho and the vertical travel times within the sedimentary cover is determined a strong negative slope is observed along both crustal thinning and crustal thickening segments and a positive slope follows the negative slope across a crustal thickening segment therefore crustal thinning appears to affect the lg propagation stronger than crustal thickening which could be due to focusing lg energy within the crustal wave guide the log amplitude regression provided in this article could be useful for predicting lg behavior in areas where amplitude measurements are not available

p and s wave velocities of consolidated sediments from a seafloor seismic survey in the north celtic sea basin offshore ireland a geophysical survey was conducted over a hydrocarbon prospect in the north celtic sea basin using a small array of ocean bottom seismographs obss the purpose of this study was to determine the ratio of p compressional to s shear wave velocity of consolidated sedimentary rocks in order to constrain possible subsurface variations in pore fluid content the ratio of vp and vs is known to be particularly sensitive to lithology porosity and pore fluid content making it a useful parameter for evaluating hydrocarbon prospects obss offer a relatively cheap and time effective means of acquiring multi component data compared with ocean bottom cables in this contribution we demonstrate the ability of an obs survey comprising three pairs of two obss spaced at 1 6 km to recover lateral variations in the vp vs ratio a key requirement of this type of study is that s waves will be generated by mode conversions in the subsurface since they cannot be generated in nor travel through fluids in this survey the contrast in physical properties of the hard seabed of the north celtic sea basin provided a means of generating converted s waves two dimensional ray tracing and forward modeling was used to create both vp and vs models along a profile crossing the blackrock prospect in the north celtic sea basin these models comprise four layers and extend to a maximum depth of 1 1 km the observed northward decrease in the vp vs ratio at depths of 500 1000 m below the seafloor in the study area is interpreted to represent lateral variation in the amount of gas present in the pore space of upper cretaceous chalks and shales overlying the prospective reservoir

celtic sea linear tidal sand ridges the irish sea ice stream and the fleuve manche palaeotidal modelling of a transitional passive margin depositional system abstract the linear tidal sand ridges ltsr of the celtic sea constitute the largest examples of their bedform type on earth previous sedimentological and seismic stratigraphic interpretation suggests that the ltsr are moribund tidally remobilised sediments representing the transgressive systems tract this interpretation is supported by two dimensional finite difference model reconstructions of the m 2 tide forced using the output from a glacial isostatic adjustment model to derive palaeotopography and a global ocean model to derive the tides on the ocean boundary used here to reconstruct peak bed stress vectors for the celtic sea for timesteps covering the transgression since the last glacial maximum last 21 ka these data are coupled with interpretation of recent published observations on the outer shelf depocentres of the fleuve manche and the irish sea ice stream isis to confirm that the ltsr distribution is consistent with modelled sand transport paths during transgression the main phase of ltsr growth was between 20 cal ka and 12 cal ka ridge axis orientations reflect the final phase of ltsr construction around 12 cal ka with some later growth of the most southerly ltsr as late as 10 cal ka ltsr growth was from the sw across the shelf towards the ne strong tidal pumping of sediments into slope canyon heads on the outer shelf occurred between 20 cal ka and 12 cal ka contributing to turbidite activity and the growth of the celtic and armorican deep sea fans it is proposed that 1 the fleuve manche shelfal estuary delta and the irish sea ice stream isis shelf fan were the main sediment depocentres supplying the growing ltsr 2 the lack of sediments available in the western channel limited ltsr growth in this area and that the easterly termination of the ltsr in this sector results from sediment starvation and 3 the northeasterly termination in the celtic sea sector is a function of declining peak bed stresses rather than sediment starvation the celtic sea margin represents a passive margin depositional system transitional between true glacial ice stream trough mouth fan systems to the north and the fluvial canyon systems characteristic of the margin to the south this interpretation therefore complements studies of macroscale sedimentation linked to glaciation on the continental margins of the north atlantic

extent and timing of the last glacial maximum lgm in britain and ireland a review the last glacial maximum lgm of marine isotope stage mis 2 is defined here as the period either of maximum global ice volume or in which major ice sheets reached their maximum extent both definitions lack clarity as there is no reason to suppose that maximum volumes or limits were reached simultaneously at either all ice sheets or around the margins of individual ice sheets here we review the traditional terrestrial limits of the biis british irish ice sheet examine developments in understanding the offshore record and attempt a redefinition of the extent and timing of the mis 2 maximum as a working chronological model the build up of the biis is assigned to after 35 32 ka the maximum to the period 27 21 ka and a more limited readvance after 19 ka as marginal oscillations driven by ice sheet dynamics appear to have characterised much of the advance and especially the retreat of the biis caution should be exercised in assigning climatic significance to the many identified ice limits or still stands while much of the terrestrial limit in britain remains relatively unaltered significant revision is required offshore around britain and ireland to portray an extensive ice advance to the shelf edge and a period when the biis was conjoined with the adjacent fenno scandinavian ice sheet although there appears to be a broad synchrony between the biis and other major ice sheets local controls have produced some variation in the timing of advance to and retreat from maximum limits for particular ice streams or lobes but much of the offshore limit remains very poorly age constrained consequently a key objective in future research should be to improve and refine the chronological control for all portions of the maximum margin of the biis and its subsequent retreat stages copyright 2010 john wiley sons ltd

devising quality assurance procedures for assessment of legacy geochronological data relating to deglaciation of the last british irish ice sheet this contribution documents the process of assessing the quality of data within a compilation of legacy geochronological data relating to the last british irish ice sheet a task undertaken as part of a larger community based project britice chrono that aims to improve understanding of the ice sheet s deglacial evolution as accurate reconstructions depend on the quality of the available data some form of assessment is needed of the reliability and suitability of each given age s in our dataset we outline the background considerations that informed the quality assurance procedures devised given our specific research question we describe criteria that have been used to make an objective assessment of the likelihood that an age is influenced by the technique specific sources of geological uncertainty when these criteria were applied to an existing database of all geochronological data relating to the last british irish ice sheet they resulted in a significant reduction in data considered suitable for synthesis the assessed data set was used to test a bayesian approach to age modelling ice stream retreat and we outline our procedure that allows us to minimise the influence of potentially erroneous data and maximise the accuracy of the resultant age models

a marine isotope stage 4 age for pleistocene raised beach deposits near fethard southern ireland raised beach deposits around the irish coast have been interpreted as interglacial or last glacial in age on the south coast of ireland the courtmacsherry formation raised beach cfb near fethard county wexford was dated using optically stimulated luminescence osl this site was previously dated to marine isotope stage mis 6 5 but more recent dating of the cfb elsewhere along the south coast shows it is considerably younger mis 4 3 the osl analyses in this paper aimed to determine if new dating would support the greater age of the fethard raised beach or realign it with the cfb the new osl ages place the formation of the fethard raised beach between 57 6 and 45 6 ka with 53 5 ka the most likely age if a single depositional event is assumed this is consistent with osl dates of the cfb elsewhere an mis 4 3 age has important implications in understanding the palaeogeography and timing of glaciation in ireland and requires a reassessment of regional relative sea level history as the eustatic response to global ice volume resulted in lowered relative sea level during mis 4 2 a crustal response to glaciation is implied by the new dates

segmentation and along strike asymmetry of the passive margin in socotra eastern gulf of aden are they controlled by detachment faults on the island of socotra the southern passive margin of the gulf of aden displays along its strike two different types of asymmetric structures western socotra is made up of a series of southward tilted blocks bounded by consistently northward dipping normal faults eastern socotra consists of a broad asymmetric anticline with a steep northern limb and a gently dipping southern limb a zone of ne sw striking strike slip and normal faults separates the two areas the overall structure is interpreted as representing two rift segments separated by a transfer zone the along strike juxtaposition of crustal scale asymmetric structures on the southern margin of the gulf of aden is complemented by the asymmetry of the conjugate margins on either side of the gulf whereas the western socotra margin is narrow and characterized by oceanward dipping normal faults the conjugate oman margin is broader and dominated by horsts and graben considering that asymmetric structures in the upper crust are often associated with synthetic shear zones at deeper ductile levels we propose that the western and eastern socotra margin segments were controlled at depth by two detachment faults with opposite dips and senses of shear the normal faults of western socotra would sole out into a top to the north ductile shear zone whereas the asymmetric anticline of eastern socotra would be associated with a top to the south detachment fault

testing an approach to osl dating of late devensian glaciofluvial sediments of the british isles in the british and irish isles the understanding of expansion and retreat of the last ice sheet in marine isotope stage mis 2 has been hindered by a lack of chronological control for the timing of its maximum extent and subsequent retreat stages in this research a suite of lithofacies from a former distal ice marginal sandur at orrisdale isle of man were identified and selected for optically stimulated luminescence dating different size fractions of quartz grains were extracted from selected lithofacies types with the aim of identifying which depositional environments and grain size fractions are best suited for optical dating tests have been undertaken to identify the luminescence properties of this quartz including preheat dose recovery and constant wave optically stimulated luminescence osl decay curve fitting equivalent dose distributions for all samples were wide and positively skewed indicative of heterogeneous bleaching a comprehensive statistically based decision making protocol has been defined in order to find the appropriate statistical model for burial dose estimation ages in the range of 17 14 ka have been obtained which agree with the expected geologically constrained chronology the orrisdale formation is contemporaneous with heinrich event 1 and the killard point stadial identified in eastern ireland ca 16 4 ka the suggested approach for osl dating of glaciofluvial sediments has the potential for much wider application to high latitude or temperate areas where there is an abundance of such sediments and where improved chronological control is much needed copyright 2009 john wiley sons ltd

quaternary deposits and glacial stratigraphy in ireland quaternary stratigraphic studies in ireland have been based largely on lithostratigraphy the division of complex sedimentary sequences into the traditional framework of munsterian and midlandian events has created a series of stratigraphic scenarios which cannot be fully substantiated either by biostratigraphy or by facies basin analysis many of the current problems of glacial stratigraphy in ireland therefore arise directly from the field procedures used and the frameworks used to subdivide sedimentary sequences these problems are centred on the selection of type sites the subdivision of sedimentary sequences into unnatural divisions the concepts of direct and indirect stratigraphy classical models of climatically determined ice advance retreat cycles and the genetic inferences of the term till the conceptual basis of various stratigraphic schemes has changed little since the work of farrington 1934 1966 it is argued that a more realistic approach to description and assessment of glacigenic sediments should be based on basinal facies analysis and must include a documentation of the composition and geometry of three dimensional facies variations palaeoenvironmental interpretations of complex glacigenic sequences especially in coastal locations should take account of the influences of marine ice sheets on the sedimentary record in the past most sequences were interpreted in terms of glacioterrestrial models a large body of sedimentary evidence now indicates that shallow glaciomarine environments occurred along the margins of the last ice sheet during its maximum and subsequent retreat phases the locations and patterns of associated icemarginal systems indicate that the magnitude of and patterns of crustal deformation were greater and more complex than formerly realised thus the primary control on sea level variation at successive ice sheet margins was largely a function of glacioisostatic disequilibrium although complex glacial and glacially related sequences are known it is argued here that most of the multiple glacigenic sequences in ireland can be accommodated within the midlandian cold stage the basal units from certain sequences and erratic fans have been attributed to events earlier than the midlandian however it is difficult to compare these traces of earlier events from different sectors of the island due to poor dating correlation and the fact that direct and indirect stratigraphy is not adequately defined or separated the age of the gortian style interglacial sequences the implications of their floristic composition and their relationships to drift stratigraphy remains a major problem in stratigraphic constructions of the irish quaternary the stratigraphic significance of many till units must remain largely unknown until these matters are resolved at present it is not clear if the gortian sequences represent more than one interglacial a series of exposures in ulster provide evidence for major environmental changes during the midlandian cold stage these include an early stadial an early forest biozone 48 1 ka bp an early herb biozone 41 5 ka bp a middle interstadial phase of cold but non glacial aspect 30 5 ka bp a late stadial max 24 22 ka bp and a late glacial climatic oscillation the late midlandian stadial comprises a major glaciation that almost covered the island and a later more restricted phase when drumlins formed in the northern and western parts of the island max 17 ka bp

ice sheet extension to the celtic sea shelf edge at the last glacial maximum previous reconstructions of the british irish ice sheet biis envisage ice streaming from the irish sea to the celtic sea at the last glacial maximum to a limit on the mid shelf of the irish uk sectors we present evidence from sediment cores and geophysical profiles that the biis extended 150 km farther seaward to reach the continental shelf edge three cores recently acquired from the flank of outer cockburn bank a shelf crossing sediment ridge terminated in an eroded glacigenic layer including two facies overconsolidated stratified diamicts and finely bedded muddy sand containing micro and macrofossil species of cold water affinities we interpret these facies to result from subglacial deformation and glacimarine deposition from turbid meltwater plumes a date of 24 265 195 cal bp on a chipped but unabraded mollusc valve in the glacimarine sediments indicates withdrawal of a tidewater ice sheet margin from the shelf edge by this time consistent with evidence from deep sea cores for ice rafted debris peaks of celtic sea provenance between 25 5 and 23 4 ka bp together with terrestrial evidence this supports rapid ca 2 ka purging of the biis by an ice stream that advanced from the irish sea to the shelf edge and collapsed back during heinrich event 2

the evolution of the terrestrial terminating irish sea glacier during the last glaciation abstract here we reconstruct the last advance to maximum limits and retreat of the irish sea glacier isg the only land terminating ice lobe of the western british irish ice sheet a series of reverse bedrock slopes rendered proglacial lakes endemic forming time transgressive moraine and bedrock dammed basins that evolved with ice marginal retreat combining for the first time on glacial sediments optically stimulated luminescence osl bleaching profiles for cobbles with single grain and small aliquot osl measurements on sands has produced a coherent chronology from these heterogeneously bleached samples this chronology constrains what is globally an early build up of ice during late marine isotope stage 3 and greenland stadial gs 5 with ice margins reaching south lancashire by 30 1 2 ka followed by a 120 km advance at 28 3 1 4 ka reaching its 26 5 1 1 ka maximum extent during gs 3 early retreat during gs 3 reflects piracy of ice sources shared with the irish sea ice stream isis starving the isg with isg retreat an opportunistic readvance of welsh ice during gs 2 rode over the isg moraines occupying the space vacated with ice margins oscillating within a substantial glacial over deepening our geomorphological chronosequence shows a glacial system forced by climate but mediated by piracy of ice sources shared with the isis changing flow regimes and fronting environments

10be and 26al exposure age dating of bedrock surfaces on the aran ridge wales evidence for a thick welsh ice cap at the last glacial maximum this paper presents results of the analysis of paired cosmogenic isotopes 10be and 26al from eight quartz rich samples collected from ice moulded bedrock on the aran ridge the highest land in the british isles south of snowdon on the aran ridge comprising the summits of aran fawddwy 905 m a s l and aran benllyn 885 m a s l 26al and 10be ages indicate complete ice coverage and glacial erosion at the global last glacial maximum lgm six samples from the summit ridge above 750 800 m a s l yielded paired 10be and 26al ages ranging from 17 2 to 34 4 ka respectively four of these samples are very close in age 10be ages of 17 5 0 6 17 5 0 7 19 7 0 8 and 20 0 0 7 ka and are interpreted as representing the exposure age of the summit ridge two other summit samples are much older 10be ages of 27 5 1 0 and 33 9 1 2 ka and these results may indicate nuclide inheritance the 26al 10be ratios for all samples are indistinguishable within one sigma uncertainty from the production rate ratio line indicating that there is no evidence for a complex exposure history these results indicate that the last welsh ice cap was thick enough to completely cover the aran ridge and achieve glacial erosion at the lgm however between c 20 and 17 ka ridge summits were exposed as nunataks at a time when glacial erosion at lower elevations below 750 800 m a s l was achieved by large outlet glaciers in the valleys surrounding the mountains copyright 2011 john wiley sons ltd

depositional and tectonic framework of the rift basins of lake baikal from multichannel seismic data recent multichannel seismic reflection data from lake baikal located in a large active continental rift in central asia image three major stratigraphic units totaling 3 5 to 7 5 km thick in four subbasins a major change in rift deposition and faulting between the oldest and middle rift units probably corresponds to the change from slow to fast rifting in early pliocene time inferred from on land studies a minor modification of fault patterns characterizes the youngest unit a brief comparison of the basins of lake baikal with those of the east african rift system highlights differences in structural style that can be explained by differences in age and evolution of the surrounding basement rocks

growth dynamics and deglaciation of the last british irish ice sheet the deep sea ice rafted detritus record the evolution and dynamics of the last british irish ice sheet biis have hitherto largely been reconstructed from onshore and shallow marine glacial geological and geomorphological data this reconstruction has been problematic because these sequences and data are spatially and temporally incomplete and fragmentary in order to enhance biis reconstruction we present a compilation of new and previously published ice rafted detritus ird flux and concentration data from high resolution sediment cores recovered from the ne atlantic deep sea continental slope adjacent to the last biis these cores are situated adjacent to the full latitudinal extent of the last biis and cover marine isotope stages mis 2 and 3 age models are based on radiocarbon dating and graphical tuning of abundances of the polar planktonic foraminifera neogloboquadrina pachyderma sinistral nps to the greenland gisp2 ice core record multiple ird fingerprinting techniques indicate that at the selected locations most ird are sourced from adjacent biis ice streams except in the centre of heinrich h layers in which ird shows a prominent laurentide ice sheet provenance ird flux data are interpreted with reference to a conceptual model explaining the relations between flux north atlantic hydrography and ice dynamics both positive and rapid negative mass balance can cause increases and prominent peaks in ird flux first order interpretation of the ird record indicates the timing of the presence of the biis with an actively calving marine margin the records show a coherent latitudinal but partly phased signal during mis 3 and 2 published data indicate that the last biis initiated during the mis 5 4 cooling transition renewed growth just before h5 46 ka was succeeded by very strong millennial scale variability apparently corresponding with dansgaard oeschger do cycles closely coupled to millennial scale climate variability in the north atlantic region involving latitudinal migration of the north atlantic polar front this indicates that the previously defined precursor events are not uniquely associated with h events but are part of the millennial scale variability major growth of the ice sheet occurred after 29 ka with the barra ice stream attaining a shelf edge position and generating turbiditic flows on the barra donegal fan at 27 ka the ice sheet reached its maximum extent at h2 24 ka earlier than interpreted in previous studies rapid retreat initially characterised by peak ird flux during greenland interstadial 2 23 ka was followed by readvance between 22 and 16 ka readvance during h1 was only characterised by biis ice streams draining central dome s of the ice sheet and was followed by rapid deglaciation and ice exhaustion the evidence for a calving margin and ird supply from the biis during greenland stadial 1 younger dryas event is equivocal the timing of the initiation maximum extent deglacial and readvance phases of the biis interpreted from the ird flux record is strongly supported by recent independent data from both the irish sea and north sea sectors of the ice sheet

geophysical evidence of deep keeled icebergs on the rockall bank northeast atlantic ocean high resolution multibeam swath bathymetric data acquired from the rockall bank reveal an abundance of linear to slightly sinuous seabed incisions these features interpreted as relict iceberg scours provide for the first time evidence that the rockall bank was intensively scoured by iceberg keels while the shallower portion of the rockall bank lacks evidence of iceberg scouring on the western and southern flanks between 250 and 450 m water depth the seabed is almost completely covered by thousands of cross cutting scours more isolated scours up to 800 m wide and 25 km long are also observed down to nearly 600 m water depth based on a full glacial sea level low stand of 120 m these isolated scour marks must have been carved bygigantic icebergs with keels up to 500 m deep and able to create incisions up to 15 m deep in the seabed analysis of scour orientation length width and depth indicates that these mega icebergs were likely calved from large fast flowing ice sheet outlets draining circum north atlantic ice sheets prevailing scour orientations suggest a number of possible ice sheet sources including southeast and southern greenland and the donegal barra ice stream of the last british irish ice sheet the bimodal distribution of the scour depth observed across the rockall bank suggest either different icebergs provenances or physical and climatic controlson icebergs draft

advance and retreat of the marine terminating irish sea ice stream into the celtic sea during the last glacial timing and maximum extent abstract the dynamics of the british irish ice sheet biis during the last glacial were conditioned by marine based ice streams the largest of which by far was the irish sea ice stream isis which drained southwest across the celtic shelf the maximum extent and timing of the isis have been constrained by onshore evidence from the uk and ireland and by glacigenic sediments encountered in a small suite of vibrocores from the uk irish continental shelf from which a single radiocarbon date is available these data have long supported ice advance to at least the mid shelf while recent results suggest the isis may have extended 150 km farther seaward to the shelf edge the glacigenic sequences have not been placed within a secure seismic stratigraphic context and the relationship between glaciation and the linear sediment megaridges observed on the outer shelf of the celtic sea has remained uncertain here we report results of sedimentological geochemical geochronological and micropalaeontological analyses combined with a seismic stratigraphic investigation of the glacigenic sequences of the celtic sea with the aims of establishing maximum extent depositional context timing and retreat chronology of isis eight lithofacies packages are identified six of which correlate with seismic facies lithofacies lf1 and lf2 correlate to a seafloor seismic facies sf1 that we interpret to record the postglacial and holocene transgressive flooding of the shelf lithofacies lf10 till lf3 lf4 and lf8 glacimarine correlate to different seismic facies that we interpret to be of glacigenic origin based on sedimentological geotechnical and micropalaeontological evidence and their distribution supported by geochemical evidence from lithofacies lf8 and lf10 indicate extension of isis as far as the celtic sea shelf break new radiocarbon ages on calcareous micro and macrofauna constrain this advance to be between 24 and 27 cal ka bp consistent with pre existing geochronological constraints glacimarine lithofacies lf8 is in places glacitectonically contorted and deformed indicating ice readvance but the nature and timing of this readvance is unclear retreat out of the celtic sea was initially rapid and may have been triggered by high relative sea levels driven by significant glacio isostatic depression consistent with greater ice loads over britain and ireland than previously considered

a major ice drainage pathway of the last british irish ice sheet the tyne gap northern england the tyne gap is a wide pass situated between the scottish southern uplands and the english pennines that connects western and eastern england it was a major ice flow drainage pathway of the last british irish ice sheet this study presents new glacial geomorphological and sedimentological data from the tyne gap region that has allowed detailed reconstructions of palaeo ice flow dynamics during the late devensian marine isotope stage 2 mapped lineations reveal a complex palimpsest pattern which shows that ice flow was subject to multiple switches in direction these are summarised into three major ice flow phases stage i was characterised by convergent lake district and scottish ice that flowed east through the tyne gap as a topographically controlled ice stream this ice stream was identified from glacial geomorphological evidence in the form of convergent bedforms streamlined subglacial bedforms and evidence for deformable bed conditions stage ii involved northerly migration of the solway firth ice divide back into the southern uplands causing the easterly flow of ice to be weakened and resulting in southeasterly flow of ice down the north tyne valley and stage iii was characterised by strong drawdown of ice into the irish sea ice basin thus starving the tyne gap of ice and causing progressive ice sheet retreat westwards back across the watershed prior to ice stagnation copyright 2009 john wiley sons ltd

a stratigraphic investigation of the celtic sea megaridges based on seismic and core data from the irish uk sectors the celtic sea contains the world s largest continental shelf sediment ridges these megaridges were initially interpreted as tidal features formed during post glacial marine transgression but glacigenic sediments have been recovered from their flanks we examine the stratigraphy of the megaridges using new decimetric resolution geophysical data correlated to sediment cores to test hypothetical tidal vs glacial modes of formation the megaridges comprise three main units 1 a superficial fining upward drape that extends across the shelf above an unconformity underlying this drape is 2 the melville formation mfm which comprises the upper bulk of the megaridges sometimes displaying dipping internal acoustic reflections and consisting of medium to coarse sand and shell fragments characteristics consistent with either a tidal or glacifluvial origin the mfm unconformably overlies 3 the upper little sole formation ulsfm previously interpreted to be of late pliocene to early pleistocene age but here shown to correlate to late pleistocene glacigenic sediments forming a precursor topography the superficial drape is interpreted as a product of prolonged wave energy as tidal currents diminished during the final stages of post glacial marine transgression we argue that the stratigraphy constrains the age of the mfm to between 24 3 and 14 ka bp based on published dates coeval with deglaciation and a modelled period of megatidal conditions during post glacial marine transgression stratigraphically and sedimentologically the megaridges could represent preserved glacifluvial features but we suggest that they comprise post glacial tidal deposits mfm mantling a partially eroded glacial topography ulsfm the observed stratigraphy suggests that ice extended to the continental shelf edge

radiocarbon constraints on the age of the maximum advance of the british irish ice sheet in the celtic sea reconstructions of the british irish ice sheet biis during the last glacial maximum lgm in the celtic sea and southern ireland have been hampered by a paucity of well dated stratigraphic records as a result the timing of the last advance of the largest outlet of the biis the irish sea ice stream to its maximum limit in the celtic sea has been variously proposed as being pre last glaciation early devensian and lgm the irish sea till was deposited by the irish sea ice stream during its last advance into the celtic sea we present 26 stratigraphically well constrained new ams radiocarbon dates on glacially transported marine shells from the irish sea till in southern ireland which constrain the maximum age of this advance the youngest of these dates indicate that the biis advanced to its overall maximum limit in the celtic sea after 26 000 20 000 14c yr bp thus during the last glaciation the most extensive phase of biis growth therefore appears to have occurred during the lgm at least along the celtic sea and irish margins these data further demonstrate that the uppermost inland glacial tills from the area of supposed older drift in southern ireland a region previously regarded as having been unglaciated during the lgm also date from the last glaciation thus most of southern ireland was ice covered at the lgm advance of the biis to its maximum southern limit in the celtic sea may have been a short lived glaciodynamic response facilitated by subglacial bed conditions rather than a steady state response to climate forcing alone

stratigraphic architecture and sedimentology of a late pleistocene subaqueous moraine complex southwest ireland glacigenic sediments exposed in coastal cliffs cut through undulatory terrain fronting the last glacial maximum laterofrontal moraine at waterville on the iveragh peninsula southwest ireland comprise three lithofacies lithofacies 1 and 2 consist of interdigitated offlapping and superimposed ice proximal subaqueous outwash and stacked sequences of cohesionless and cohesive subaqueous debris flows winnowed lag gravels and coarse grained suspension deposits these are indicative of sedimentation in and around small grounding line fans that prograded from an oscillating glacier margin into a proglacial interlobate lake lithofacies 3 comprises braided river deposits that have undergone significant syn sedimentary soft sediment deformation deposition was likely related to proglacial outwash activity and records the reduction of accommodation space for subaqueous sedimentation either through the lowering of proglacial water levels or due to basin infilling the stratigraphic architecture and sedimentology of the moraine at waterville highlight the role of ice marginal depositional processes in the construction of morphostratigraphically significant end moraine complexes in great britain and ireland traditional tills in these moraines are often crudely stratified diamictons and gravelly clinoforms deposited in ice proximal subaqueous and subaerial fans copyright 2011 john wiley sons ltd

maximum extent and dynamic behaviour of the last british irish ice sheet west of ireland a complete reconstruction of the last british irish ice sheet biis is hindered by uncertainty surrounding its offshore extent and dynamic behaviour this study addresses this problem by reconstructing the depositional history of four sediment cores taken from a series of sinuous glacigenic sediment ridges on the continental shelf west of ireland we present new geomorphic sedimentary and micropaleontological data that record a maximum westward biis extent that was at least 80 km farther offshore from any previous estimates the data suggests that a large ice shelf formed over parts of the shelf prior to retreat this new data increases the areal extent of grounded biis ice by 6700 km2 from previous estimates which represents a 3 increase in the irish sector of the ice sheet three new ams radiocarbon dates demonstrate for the first time that the biis advanced to the shelf edge during last glaciation late midlandian late devensian with ice advance onto the porcupine bank occurring after 24 720 260 yr cal bp deglaciation was complete by 19 182 155 yr cal bp thus constraining biis occupation over the porcupine bank to less than 5500 years estimated retreat rates of marine terminating ice across the shelf range from 70 to 180 myr 1

construction of an evolutionary deglaciation model for the irish midlands based on the integration of morphostratigraphic and geophysical data analyses alternative established models for the deglaciation of the midlands of ireland are tested against an interpretation of a suite of deglacial sediments covering an area of 600 km2 in the east central midland area interpretation of the sediments is based on geomorphological mapping lithostratigraphic characterization of exposures and geotechnical data supported by electrical resistivity tomography ert and ground penetrating radar gpr gpr depicted small scale sedimentological and deformational structures within low conductivity soft sediments such as cross bedding planar bedding channel like features and faulting planes and revealed the internal architecture of eskers glaciodeltas subaqueous fans and raised bogs ert data permitted the detection of depth to bedrock and the lithological characterization of unconsolidated sediments the ten sites presented were surveyed by traditional mapping methods and or geophysical techniques this allowed the construction of a local model of the deglaciation of the area which recognized five main stages an ice sheet covering most of ireland withdrew as a single body as far as the midlands at this stage two main directions of ice retreat are identified from the spatial distribution of meltwater overflow channels esker and morainic ridges and ice marginal glaciolacustrine deposits a pattern of deglacial sedimentation into an expanding ice marginal glacial lake is depicted the glacial lake was dammed to the west by two ice dome fronts one decaying to the north west and another to the south west and by the shannon basin watershed to the east glacial lake outlets identified along the watershed and the altitude of the topset foreset interface zone depicted in glaciodeltaic deposits allowed the identification of three lake water levels the highest level is at 87 89 m ordnance datum od the second lake level at 84 m od and the third at 78 m od copyright 2012 john wiley sons ltd

new constraints on the age of the last ice sheet glaciation in nw england using optically stimulated luminescence dating optically stimulated luminescence osl has been used to date silts interpreted as either primary or colluviated loess deposited in karstic depressions at three sites on the carboniferous limestone of nw england two of the ages presented here constrain the onset of the last late devensian ice in this region to later than ca 27 2 ka and the other two date initial deglaciation prior to ca 19 2 ka in the morecambe bay area and ca 17 2 ka in the karst of the yorkshire dales while these ages are broadly consistent with existing estimates from lacustrine and speleothem evidence they offer the tightest constraints yet published on the presence of the last ice sheet from northern england copyright 2009 john wiley sons ltd

quaternary depositional systems in northern lake baikal siberia abstract new high resolution seismic reflection data from northern lake baikal and detailed land based morphological and sedimentological data reveal a variety of coarse grained deposits in the northern baikal rift each depositional facies is assigned to a specific structural domain alluvial fans onshore and small fan deltas offshore dominate the western border fault flank glacial deposits onshore and large glacio lacustrine fans offshore characterize the eastern flexural margin in the north the axial rift termination comprises a large fluvial delta this distinct pattern of depositional environments reflects the pronounced asymmetry of the rift and emphasizes the role of rift structure in controlling drainage and the location and type of rift basin fill climate however exerts a profound influence on the generation and availability of coarse grained material this is best documented along the eastern rift margin where pleistocene valley glaciers advanced at 50 40 35 and 26 13 ka from th

a critical review of the glaciomarine model for irish sea deglaciation evidence from southern britain the celtic shelf and adjacent continental slope in support of their glaciomarine model for the deglaciation of the irish sea basin eyles and mccabe cited the occurrence of distal glaciomarine mud drapes onshore in the isles of scilly and north devon and of arctic beach face gravels and sands around the shores of the celtic sea glacial and sea level data from the southern part of the irish sea in the terminal zone of the ice stream and the adjacent continental slope are reviewed here to test this aspect of the model the suggestion that the glacial sequences of both the isles of scilly and fremington in north devon are glaciomarine mud drapes is rejected an actively calving tidewater margin only occurred early in the deglacial sequence close to the terminal zone in the south central celtic sea relative sea levels were lower and therefore glacio isostatic depression less than envisaged in the glaciomarine model geochronological sedimentological and biostratigraphical data indicate that the raised beach sequences around the shores of the celtic sea and english channel were deposited at or during regression soon after interglacial eustatic highstands evidence for ice rafting at a time of high relative sea levels is restricted to a phase s earlier than the late devensian these data indicate that the raised beach sequences have no bearing on the style of irish sea deglaciation copyright 2001 john wiley sons ltd

ice marginal depositional responses to readvance episodes in the late devensian deglaciation of the isle of man abstract remapping of the quaternary geology of the isle of man and consequent revision of the stratigraphic succession identifies three glacigenic formations each separated by a major unconformity the oldest formation the shellag represents an extensive ice advance beyond the island limits to the last glacial maximum lgm the overlying formation the orrisdale represents a major readvance episode during retreat from the lgm and is associated with the construction of the bride moraine and the deposition of extensive proglacial subaqeous sediment examination of the sedimentology and micropalaeontology of these sediments indicates that the water body was most likely lacustrine and not marine application of sequence stratigraphy to the overlying jurby formation identifies evidence for three further phases of readvance each off lapping one another into the margin of the lake basin via a complex system of ice contact subaqueous fans and outwash fan deltas the jurby formation is dated by organic sediments overlying it as older than 18 5 14 4 kyr bp and provides an ice marginal correlative for heinrich event 1 readvance limits identified 50 km to the west in eastern ireland

reconstructing the last irish ice sheet 1 changing flow geometries and ice flow dynamics deciphered from the glacial landform record the glacial geomorphological record provides an effective means to reconstruct former ice sheets at ice sheet scale in this paper we document our approach and methods for synthesising and interpre

exposure age constraints on the extent timing and rate of retreat of the last irish sea ice stream abstract we report 23 cosmogenic isotope exposure ages 10be and 36cl relating to the maximum extent and deglaciation chronology of the irish sea ice stream isis which drained the sw sector of the last british irish ice sheet these show that the isis failed to reach the preseli hills of north pembrokeshire yet extended southwards to impinge on northern isles of scilly 50 n during the last glacial maximum four samples from western anglesey demonstrate deglaciation of the southern irish sea basin by c 20 18 ka and two from the ll n peninsula in northwest wales if valid suggest deglaciation by c 23 22 ka followed by gradual oscillatory northwards retreat of the ice margin for over 3000 years an alternative interpretation of our data suggests that ice reached scilly as late as 22 21 ka then retreated 450 km northwards within the following three millennia possibly in response to sea level rise and or intrinsic reorganisation within the last british irish ice sheet samples from upland source areas of the isis in nw england and sw scotland produced exposure ages 14 3 ka suggesting possible persistence of ice in such areas into the lateglacial interstade of 14 7 12 9 ka

flow pattern evolution of the last british ice sheet we present a 10 stage reconstruction of the evolution in ice flow patterns of the last british ice sheet from build up to demise derived from geomorphological evidence 100 flowsets identified in the subglacial bedform record drumlins mega scale glacial lineations and ribbed moraine are combined with ancillary evidence erratic transport paths absolute dates and a semi independently reconstructed retreat pattern to define flow patterns ice divides and ice sheet margins during build up maximum glaciation and retreat overprinting and cross cutting of landform assemblages are used to define the relative chronology of flow patterns and a tentative absolute chronology is presented based on a collation of available dates for ice advance and retreat the ice flow configuration of the last british ice sheet was not static some ice divides were remarkably stable persisting through multiple stages of the ice sheet evolution whereas others were transient features existing for a short time and or shifting in position 10s km the 10 reconstructed stages of ice sheet geometry capture two main modes of operation first as an integrated ice sheet with a broadly n s orientated ice divide and second as a multi domed ice sheet orientated parallel with the shelf edge a thick integrated ice sheet developed as ice expanded out of source areas in scotland to envelop southerly ice caps in northern england and wales and connect with the irish ice sheet to the west and the scandinavian ice sheet across the north sea following break up of ice over the north sea ice streaming probably drove mass loss and ice sheet thinning to create a more complex divide structure where ice flow patterns were largely controlled by the form of the underlying topography ice surface lowering occurred before separation of and retreat to multiple ice centres centred over high ground we consider this 10 stage reconstruction of the evolution in ice sheet configuration to be the simplest palaeo glaciological interpretation of the flowsets identified from the geomorphological record and their relative timing this empirically based reconstruction of flow pattern geometry provides a framework for more detailed local and regional studies and numerical modelling to provide robust explanations of the observed changes in ice sheet structure in terms of climate and glacial dynamics as a minimum numerical model outputs should be able to reproduce the identified flowset patterns in space and satisfy their chronological order

trough geometry was a greater influence than climate ocean forcing in regulating retreat of the marine based irish sea ice stream marine terminating ice streams are a major component of contemporary ice sheets and are likely to have a fundamental influence on their future evolution and concomitant contribution to sea level rise to accurately predict this evolution requires that modern day observations can be placed into a longer term context and that numerical ice sheet models used for making predictions are validated against known evolution of former ice masses new geochronological data document a stepped retreat of the paleo irish sea ice stream from its last glacial maximum limits constraining changes in the time averaged retreat rates between well defined ice marginal positions the timing and pace of this retreat is compatible with the sediment landform record and suggests that ice marginal retreat was primarily conditioned by trough geometry and that its pacing was independent of ocean climate forcing we present and integrate new luminescence and cosmogenic exposure ages in a spatial bayesian sequence model for a north south 173km transect of the largest marine terminating ice stream draining the last british irish ice sheet from the south and east coasts of ireland initial rates of ice margin retreat were as high as 300 600 m a 1 but retreat slowed to 26 m a 1 as the ice stream became topographically constricted within st george s channel a sea channel between ireland to the west and great britain to the east and then stabilized retreating at only 3 m a 1 at the narrowest point of the trough during the climatic warming of greenland interstadial 2 gi 2 23 3 22 9 ka later retreat across a normal bed slope during the cooler conditions of greenland stadial 2 was unexpectedly rapid 152 m a 1 we demonstrate that trough geometry had a profound influence on ice margin retreat and suggest that the final rapid retreat was conditioned by ice sheet drawdown dynamic thinning during stabilization at the trough constriction which was exacerbated by increased calving due to warmer ocean waters during gi 2

new age constraints for the limit of the british irish ice sheet on the isles of scilly the southernmost terrestrial extent of the irish sea ice stream isis which drained a large proportion of the last british irish ice sheet impinged on to the isles of scilly during marine isotope stage 2 however the age of this ice limit has been contested and the interpretation that this occurred during the last glacial maximum lgm remains controversial this study reports new ages using optically stimulated luminescence osl dating of outwash sediments at battery tresco 25 5 1 5 ka and terrestrial cosmogenic nuclide exposure dating of boulders overlying till on scilly rock 25 9 1 6 ka which confirm that the isis reached the isles of scilly during the lgm the ages demonstrate this ice advance on to the northern isles of scilly occurred at 26 ka around the time of increased ice rafted debris in the adjacent marine record from the continental margin which coincided with heinrich event 2 at 24 ka osl dating 19 6 1 5 ka of the post glacial hell bay gravel at battery suggests there was then an 5 ka delay between primary deposition and aeolian reworking of the glacigenic sediment during a time when the isis ice front was oscillating on and around the ll n peninsula 390 km to the north

kelvin waves and internal bores in the marine boundary layer inversion and their relationship to coastally trapped wind reversals abstract detailed observations of a coastally trapped disturbance or wind reversal on 10 11 june 1994 along the california coast provide comprehensive documentation of its structure based on aircraft wind profiler radio acoustic sounding system and buoy measurements unlike the expectations from earlier studies based on limited data which concluded that the deepening of the marine boundary layer mbl was a key factor the 1994 data show that the perturbation was better characterized as an upward thickening of the inversion capping the mbl as the event propagated over a site the reversal in the alongshore wind direction occurred first within the inversion and then 3 4 h later at the surface a node in the vertical structure defined here as the altitude of zero vertical displacement is found just above the inversion base with up to 200 m upward displacements of isentropic surfaces above the node and 70 m downward displacements below although this is a single event it is shown that the vertic

new insights into the quaternary evolution of the bristol channel uk a synthesis of new publically available borehole and bathymetric data combined with a wealth of other existing disparate data sources reveals new insights into the quaternary history of the bristol channel area sediment boreholes throughout the bristol channel confirm the area was glaciated in the pleistocene till is present below marine deposits and in some areas is visible morphologically as submerged moraines in the central and eastern bristol channel the submerged valley course of the palaeo severn is very clear in new high resolution bathymetric surveys this former river course and associated tributaries cross cut through glacial sediments in the bristol channel at least three phases of glaciation are recorded in the bristol channel one related to the southern limits of a late devensian substage marine isotope stage mis 2 welsh ice cap which reached into swansea bay an earlier devensian mis 4 3 glaciation associated with irish sea ice and another older glaciation that is associated with ice that filled the entire outer and central bristol channel the age of the older bristol channel glaciation is still open although it pre dates the devensian late pleistocene and must date to the middle pleistocene it is therefore evident that pleistocene glacial and fluvial activity combined with subsequent post glacial sea transgression directly account for current morphometries of the bristol channel and severn estuary and the current geography of the sw british isles

sedimentology and micropalaeontology of glacimarine sediments from the central and southwestern celtic sea thin discontinuous glacigenic sediments occur at or close to the sea bed as far south as 49 n in the celtic sea the northern samples facies a are clast rich overconsolidated lodgement tills or proximal glacimarine sediments containing sparse reworked microfaunas the southern samples facies b are distal glacimarine plastic silty clays containing abundant cold water microfaunas both these facies are correlated with the late devensian scilly till enabling a quantitative reconstruction of ice thicknesses grounding line sea level and shoreline elevations in the celtic sea at 19 000 years bp the ice advance terminated in marine waters towards the shelf edge break and is likely to have constituted a thin lobate surge over deformable marine sediments 1990 the geological society

extent and deglacial chronology of the last british irish ice sheet implications of exposure dating using cosmogenic isotopes over 160 10be and 36cl exposure ages pertaining to the extent and chronology of the last british irish ice sheet biis are critically reviewed despite uncertainties inherent in the use of exposure ages this approach has demonstrated that at the last glacial maximum lgm ca 26 21 ka the biis extended over all low ground in scotland and all or almost all of ireland consistent with recent models depicting extension of the last biis to the atlantic shelf edge all exposure ages obtained for high level sites above trimlines on the mountains of northwestern scotland and ireland pre date the lgm this finding confirms that high plateaux in these areas escaped significant glacial erosion probably under a protective cover of cold based glacier ice that remained frozen to the underlying substrate in terms of deglaciation chronology the southern irish sea basin was probably deglaciated by 19 18 ka with extensive deglaciation of low ground in ireland and northeastern scotland prior to ca 14 5 ka ice cover on low ground in northwestern scotland apparently persisted after 14 0 ka suggesting survival of ice in favourable locations during the lateglacial interstade ca 14 5 12 9 ka attempts to date readvances have had mixed success the wester ross readvance in northwestern scotland was initially dated to ca 16 3 ka but more recent research implies a much younger age ca 14 0 13 5 ka exposure ages indicating a prolonged stillstand during ice sheet retreat in the cairngorms at ca 14 5 14 0 ka conflict with ages obtained on postglacial rockslides and basal radiocarbon dates which indicate deglaciation before ca 15 5 15 0 ka exposure dating has been successfully employed to confirm a loch lomond stadial ca 12 9 11 5 ka age for moraines in several mountain areas and to constrain the minimum altitude of the ice cap that extended over the western grampians at that time copyright 2009 john wiley sons ltd

new data for the last glacial maximum in great britain and ireland abstract understanding the history of the british and irish ice sheet biis at the last glacial maximum lgm has been advanced by new approaches in particular by cosmogenic nuclide surface exposure dating aminostratigraphy of shelly glacial deposits ams radiocarbon dating and the evidence from continental margin marine cores all of which supersede the previously weak geochronologic control it was formerly believed that great britain and ireland was largely ice free between the last interglacial oxygen isotope sub stage 5e and the late devensian when the lgm occurred as such the biis was effectively out of phase with laurentide and scandinavian ice sheets as well as inferences of ice volume from oxygen isotope stratigraphy the biis during the late devensian maximum was also perceived as having been relatively stationary new evidence shows that the lgm was an important event during the evolution of an earlier biis when the extent of ice was greater repeated iceberg rafting events over the past 50 ka are shown by marine cores while the derivative inference of numerous corresponding glacial advances is supported by several clusters of 36 cl ages on glaciated surfaces and glacial boulders that are indicative of deglacial events between 40 and 12 ka these appear to be associated with heinrich events the earliest being inferred as heinrich 4 at about 40 ka during this advance the biis and scandinavian ice sheet sis were in contact and all of ireland was glaciated the ice sheet appears to have fluctuated several times between 40 and 25 ka although evidence for this is poorly preserved but the 36 cl and 14 c evidence is clear that the biis reached its lgm maximum size about 22 ka soon after heinrich event 2 when the biis and sis were not in contact one cluster of 36 cl and 14 c ages at 21 4 1 3 ka records an initial pulse of deglaciation that was followed by extensive deglaciation about 17 4 0 4 ka just before heinrich event 1 when the ice sheet readvanced contrary to previous views the biis probably existed throughout much of devensian time as a mobile and sensitive ice sheet during which the lgm advance was but one important event in places glacial deposits of the earlier devensian glaciation have previously been incorrectly identified as products of the later lgm glaciation

3d seismic evidence of buried iceberg ploughmarks from the mid norwegian continental margin reveals largely persistent north atlantic current through the quaternary over 7500 buried linear and curvilinear depressions interpreted as iceberg ploughmarks were identified within the quaternary naust formation from an extensive three dimensional seismic dataset that covers 40 000 km2 of the mid norwegian continental margin the morphology and net orientation of ploughmarks were mapped and analysed these features are up to 28 km long 700 m wide and are incised up to 31 m deep on average ploughmarks are incised 5 m deep with median width of 185 m and median lengths ranging from 1 2 to 2 7 km for individual palaeo surfaces width to depth ratio ranges from 8 1 to 400 1 and is on average 36 1 the presence of ploughmarks buried deeply within some palaeo slope surfaces implies the occasional presence of very large icebergs since the middle quaternary suggesting that thick ice sheet margins with fast flowing ice streams were present in order to calve icebergs of such dimensions into the norwegian sea the wide geographical distribution of ploughmarks suggests unrestricted iceberg drift and an open norwegian sea during the periods of iceberg calving since the early quaternary ploughmark trajectory analysis demonstrates that the ocean current circulation now dominated by the northeasterly flowing norwegian atlantic current nwac has largely persisted throughout the quaternary despite the overall strikingly consistent pattern of iceberg drift ploughmark mapping also shows evidence for short lived nwac reductions possibly related to major phases of iceberg discharge and or meltwater pulses from the fennoscandian ice sheet during the middle and late quaternary

sedimentation at the margins of a late pleistocene ice lobe terminating in shallow marine environments dundalk bay eastern ireland late pleistocene morainic sequences around dundalk bay eastern ireland were deposited in a variety of shallow glaciomarine environments at the margins of a grounded ice lobe the deposits are essentially ice proximal delta fan and apron sequences and are divided into two lithofacies associations lithofacies association 1 occurs as a series of morainal banks formed at the southern margin of the ice lobe in a body of water open to influences from the irish sea the morainal banks consist mainly of diamictic muds deposited from turbid plumes and by ice rafting with minor occurrences of turbidites cross bedded gravels subaqueous outwash and massive boulder gravels high density debris flows lithofacies association 2 was deposited in a narrow arm of the sea at the north eastern margin of the ice lobe the deposits consist mainly of a series of coalescing ice proximal gilbert type fan deltas which are interbedded distally with tabular and lens shaped subaqueous deposits the latter are mainly ice rafted diamictons debris flow deposits and subaqueous sands and gravels both lithofacies associations are draped by diamictons formed by a combination of rain out debris flow and traction current activity at a few localities the upper parts of the sequence have been sheared by minor oscillations of the ice sheet margin these sequences form part of an extensive belt of glaciomarine deposits which border the drumlin swarms of east central ireland lithostratigraphic variability is partially related to the arrival of large volumes of debris at the ice lobe margin when the main lowland ice sheet surged during drumlin formation complex depositional continua of this type lack any major erosional breaks and should not be used either as climatic proxies or for stratigraphic correlations

deforming bed conditions associated with a major ice stream of the last british ice sheet the irish sea ice stream was the largest ice stream to drain the last british ice sheet and around the margins of the celtic sea it deposited a shelly diamict facies that has been variously interpreted as subglacial till or distal glacial marine mud we present new observations on the sedimentology of the shelly diamict and overlying sediments from the south coast of ireland and demonstrate that the shelly diamict facies is a subglacial deformation till deposited during onshore movement of a grounded irish sea ice stream stratigraphic and chronological data indicate that this occurred during the last glaciation and this is regionally consistent with marine geological evidence from the celtic sea we propose that the deforming bed tills along the south coast of ireland are the onshore record of a rapid advance of an unstable irish sea ice stream into the celtic sea this advance was facilitated at least in part by a saturated substrate of readily deformable fine grained marine sediment this implies an unstable and dynamic irish sea ice stream during oxygen isotope stage 2 and therefore extension of the last british ice sheet into the celtic sea far south of its traditionally interpreted limits

sedimentology and chronology of the advance and retreat of the last british irish ice sheet on the continental shelf west of ireland the last british irish ice sheet biis had extensive marine terminating margins and was drained by multiple large ice streams and is thus a useful analogue for marine based areas of modern ice sheets however despite recent advances from investigating the offshore record of the biis the dynamic history of its marine margins which would have been sensitive to external forcing s remain inadequately understood this study is the first reconstruction of the retreat dynamics and chronology of the western marine terminating margin of the last late midlandian biis analyses of shelf geomorphology and core sedimentology and chronology enable a reconstruction of the late midlandian history of the biis west of ireland from initial advance to final retreat onshore five ams radiocarbon dates from marine cores constrain the timing of retreat and associated readvances during deglaciation the biis advanced without streaming or surging depositing a bed of highly consolidated subglacial traction till and reached to within 20 km of the shelf break by 24 000 cal bp ice margin retreat was likely preceded by thinning grounding zone retreat and ice shelf formation on the outer shelf by 22 000 cal bp this ice shelf persisted for 2500 years while retreating at a minimum rate of 24 m yr and buttressing a 150 km long 20 km wide bathymetrically controlled grounding zone a large 150 km long arcuate flat topped grounding zone wedge termed here the galway lobe grounding zone wedge glgzw was deposited below this ice shelf and records a significant stillstand in biis retreat geomorphic relationships indicate that the biis experienced continued thinning during its retreat across the shelf which led to increased topographic influence on its flow dynamics following ice shelf break up and grounding zone retreat past the glgzw at this stage of retreat the western biis was comprised of several discrete asynchronous lobes that underwent several readvances sedimentary evidence of dilatant till deposition suggests that the readvances may have been rapid and possibly associated with ice streaming or surging the largest lobe extended offshore from galway bay and deposited the galway lobe readvance moraine by 18 500 cal bp further to the north an ice lobe readvanced at least 50 km offshore from killary harbour possibly by 15 100 cal bp the existing chronology currently does not allow us to determine conclusively whether these readvances were a glaciodynamic internally driven response of the ice sheet during deglaciation or were climatically driven following the 18 500 cal bp readvance the galway lobe experienced accelerated eastward retreat at an estimated rate of 113 m yr

pattern and timing of retreat of the last british irish ice sheet during the last glacial the ice sheet that subsumed most of britain ireland and the north sea attained its maximum extent by 27 ka bp and with an ice volume sufficient to raise global sea level by ca 2 5 m when it melted we reconstruct the demise of this british irish ice sheet biis and present palaeo glaciological maps of retreat stages between 27 and 15 ka bp the whole land area was investigated using remote sensing data and we present maps of moraines meltwater channels eskers and drumlins and a methodology of how to interpret and bring them together for the continental shelf numerous large moraines were discovered recording an extensive pattern of retreat stretching from sw ireland to the shetland isles from an integration of this new mapping of glacial geomorphology 26 000 landforms with previously published evidence compiled in the britice database we derive a pattern of retreat for the whole biis we review and compile relevant dates 881 examples that constrain the timing of retreat all data are held within a geographic information system gis and are deciphered to produce a best estimate of the combined pattern and timing of retreat pattern information reveals an ice sheet mainly comprised of a shelf parallel configuration from sw ireland to ne scotland but it spread far enough to the south to incorporate outlying ice domes over wales the lake district and kerry final disintegration was into a number of separate ice caps rather than reduction as a single mass and paradoxically retreat was not always back to high ground by 23 ka bp ice withdrew along its northern boundaries at the same time as the southern margins were expanding including transient ice streaming down the irish sea and advances of lobes in the cheshire basin vale of york and east coast of england ice divides migrated south by 19 ka the ice sheet was in crisis with widespread marine based ice losses particularly in the northern north sea and the irish sea considerable dynamic thinning occurred during this phase final collapse of all marine sectors occurred by 17 ka bp and with most margins beginning to back step onshore disintegration of the north sea ice bridge between britain and norway remains loosely constrained in time but the possibility of catastrophic collapse of this sector is highlighted the north channel and irish sea ice streams had finally cleaved the ice sheet into separate irish and scottish ice sheets by 16 ka bp rates of ice loss were found to vary widely over space and time e g 65 260 km3 per year the role of ice streams and calving losses of marine based sectors are examined retreat rates of up to ca 150 ma 1 were found for some ice stream margins that large parts 2 3 of the biis were marine based drained by ice streams and possibly with fringing ice shelves in places makes it a useful analogue for the west antarctic ice sheet wais this is especially so because the biis deglaciated in response to rising temperatures and a rising sea level driven by melting of other ice masses which are the current forcings that might cause collapse of the wais our reconstruction when viewed from the opposite perspective documents when fresh land became exposed for exploitation by plants animals and man and records for how long such land has been available for soil and geochemical development and ecological succession

paired 26al and 10be exposure ages from lundy new evidence for the extent and timing of devensian glaciation in the southern british isles lundy lies in a strategic geographical position for understanding the glacial history of the british isles the island bears evidence of glaciation largely in the form of ice moulded bedrock and glaciallytransported boulders e an unusual occurrence this far south in the british isles irish sea ice penetrated the western bristol channel overriding lundy from the northwest during the last phase of glaciation in this area the results of paired terrestrial cosmogenic nuclide analyses 26al 10be constrain the timing of this extensive glaciation and provide for the first time an age for the exposure of lundy granite following deglaciation the results from nine paired samples yield 26al 10be exposure ages of 31 4e48 8 ka 10be and 31 7e60 0 ka 26al this challenges the view that any glaciation this far south must belong to middle pleistocene glaciations such as the anglian stage c 480e420 ka and a devensian age for the last glaciation is consistent with findings from the isles of scilly further south however the findings suggest early mid devensian marine isotope stage mis 4e3 glaciation of lundy it also implies that the island was exposed or covered for a short time by non erosive cold based ice at the global last glacial maximum lgm during mis 2 26e21 ka the potential exposure of the island throughout mis 2 contrasts with the evidence from the isles of scilly and the celtic sea which were glaciated at the lgm

age limits on middle pleistocene glacial sediments from osl dating north norfolk uk the lowland region of north norfolk contains some of the best preserved evidence for glacial deposition during the middle pleistocene in northwest europe despite the importance of these deposits there is limited chronological control and it is debated whether they belong to a single glaciation equated to the anglian glaciation marine isotope stage 12 or represent deposition over a number of middle pleistocene cold stages in order to develop an improved chronology for glaciation in this region we obtained 18 samples for optical stimulated luminescence osl dating from glacial outwash facies samples of coarse grained quartz sand were measured using the sar single aliquot regenerative dose protocol the low radioactive isotope concentrations in sediments of this region enable the traditionally accepted age limit of luminescence dating to be extended the form of the dose response curves pre heat plateaux tests and dose recovery experiments also indicate that laboratory doses can be reliably measured in these samples age overestimation due to partial bleaching is thought to be insignificant the osl ages suggest that the glacial sediments studied were deposited during mis 12 rather than in different post mis 12 stages

the importance of the terrigenous fraction within a cold water coral mound a case study in the nineties cold water coral mounds were discovered in the porcupine seabight ne atlantic west of ireland a decade later this discovery led to the drilling of the entire challenger cold water coral mound eastern slope porcupine seabight during iodp expedition 307 as more than 50 of the sediment within challenger mound consists of terrigenous material the terrigenous component is equally important for the build up of the mound as the framework building corals moreover the terrigenous fraction contains important information on the dynamics and the conditions of the depositional environment during mound development in this study the first in depth investigation of the terrigenous sediment fraction of a cold water coral mound is performed combining clay mineralogy sedimentology petrography and sr nd isotopic analysis on a gravity core md01 2451g collected at the top of challenger mound sr and nd isotopic fingerprinting identifies ireland as the main contributor of terrigenous material in challenger mound besides this a variable input of volcanic material from the northern volcanic provinces iceland and or the nw british isles is recognized in most of the samples this volcanic material was most likely transported to challenger mound during cold climatic stages in three samples the isotopic ratios indicate a minor contribution of sediment deriving from the old cratons on greenland scandinavia or canada the grain size distributions of glacial sediments demonstrate that ice rafted debris was deposited with little or no sorting indicating a slow bottom current regime in contrast interglacial intervals contain strongly current sorted sediments including reworked glacio marine grains the micro textures of the quartz sand grains confirm the presence of grains transported by icebergs in interglacial intervals these observations highlight the role of ice rafting as an important transport mechanism of terrigenous material towards the mound during the late quaternary furthermore elevated smectite content in the siliciclastic glaciomarine sediment intervals is linked to the deglaciation history of the british irish ice sheet biis the increase of smectite is attributed to the initial stage of chemical weathering processes which became activated following glacial retreat and the onset of warmer climatic conditions during these deglaciations a significant change in the signature of the detrital fraction and a lack of coral growth is observed therefore we postulate that the deglaciation of the biis has an important effect on mound growth it can seriously alter the hydrography nutrient supply and sedimentation processes thereby affecting both sediment input and coral growth and hence coral mound development

activity of the turbidite levees of the celtic armorican margin bay of biscay during the last 30 000 years imprints of the last european deglaciation and heinrich events abstract high resolution sedimentological and micropaleontological studies of several deep sea cores retrieved from the levees of the celtic and armorican turbidite systems bay of biscay north atlantic ocean allow the detection of the major oscillations of the british irish ice sheet biis and fleuve manche palaeoriver discharges over the last 30 000 years which were mainly triggered by climate changes between 30 and 20 cal ka the turbiditic activity on the celtic armorican margin was weak contrasting with previous stratigraphic models which predicted a substantial increase of sediment supply during low sea level stands this low turbidite deposit frequency was most likely the result of a weak activity of the fleuve manche palaeoriver and or of a reduced seaward transfer of sediments from the shelf to the margin however two episodes of turbiditic activity increase were detected in the celtic armorican margin during heinrich events he 3 and 2 this strengthening of the turbiditic activity was triggered by the meltwater releases from european ice sheets and glaciers favouring the seaward transfer of subglacial material at least via fleuve manche palaeoriver at around 20 cal ka a significant increase of turbidite deposit frequency occurred as a response to the onset of the last deglaciation the retreat of the european ice sheets and glaciers induced a substantial increase of the fleuve manche palaeoriver discharges and seaward transfer of continentally derived material into the armorican turbidite system the intensification of the turbiditic activity on the celtic system was directly sustained by the widespread transport of subglacial sediments from the british irish ice sheet biis to the celtic sea via the irish sea basin a sudden reduction of turbiditic activity in the armorican system between ca 19 and 18 3 cal ka could have been triggered by the first well known abrupt sea level rise meltwater pulse at around 19 cal ka favouring the trapping of sediment in the fleuve manche palaeoriver valleys and the decrease of the seaward transfer of continentally derived material the maximum of turbiditic activity strengthening in the celtic armorican margin between ca 18 3 and 17 cal ka was induced by the decay of european ice sheets and glaciers producing the most extreme episode of the fleuve manche palaeoriver runoff and a great seaward transfer of subglacial material into the bay of biscay between ca 17 5 and 16 cal ka the turbiditic activity significantly decreased in both celtic and armorican turbidite systems in response to a global re advance of glaciers and ice sheets in europe the last episode of ice sheet retreat between ca 16 and 14 cal ka is well expressed in the celtic system by a new increase of the turbiditic activity the major episode of sea level rise at around 14 cal ka meltwater pulse 1a precluding the seaward transfer of sediments induced the end of turbiditic activity in both the celtic and the armorican system although two main phases of global sea level rise seem to have had an effect on the celtic armorican margin this work proposes the biis retreat and associated riverine discharges as the main trigger mechanisms of the turbiditic activity in this region during the last 30 000 years

late pleistocene chronostratigraphy and ice sheet limits southern ireland abstract the morpho stratigraphic subdivision of the surficial glacial drifts of ireland into older drift and younger drift is a long standing convention in irish quaternary studies across southern ireland a broad swath of terrain has traditionally been interpreted as munsterian penultimate glaciation in age and large end moraine complexes bordering this zone of older drift such as the south ireland end moraine have long been regarded as marking the limit of the late midlandian last glaciation ice sheet sedimentary sequences exposed along the south coast of ireland provide a window into the stratigraphy of the older drift and have been studied for over a century the present paper supports a fundamental revision of the traditional interpretation of ice sheet limits in southern ireland and argues for an extensive last irish ice sheet which covered much of the area of the older drift at the last glacial maximum the basis for this revision is threefold firstly nineteen new optically stimulated luminescence osl dates on the courtmacsherry raised beach and overlying shallow marine sands demonstrate that on the south coast the beach and shallow marine sands formed during marine isotope stages 4 3 secondly ams radiocarbon dates on reworked shells from the irish sea till demonstrate that this till and overlying inland tills from central and sw ireland were formed after 24 cal ka bp thirdly new osl dates of 24 21 ka bp from deglacial outwash overlying the irish sea till collectively these data are consistent with a last glaciation age for the glacigenic sequence along the south coast of ireland thus supporting a fundamental revision of the age of the older munsterian drifts of southern ireland most of southern ireland was glaciated during the lgm and the moraine belts which have traditionally been interpreted as marking the last glacial limit such as the south ireland end moraine are reinterpreted here as recessional features formed during ice sheet retreat

the palaeoglaciology of the central sector of the british and irish ice sheet reconciling glacial geomorphology and preliminary ice sheet modelling digital elevation models of the area around the solway lowlands reveal complex subglacial bedform imprints relating the central sector of the lgm british and irish ice sheet drumlin and lineation mapping in four case studies show that glacier flow directions switched significantly through time these are summarised in four major flow phases in the region phase i flow was from a dominant scottish dispersal centre which transported criffel granite erratics to the eden valley and forced lake district ice eastwards over the pennines at stainmore phase ii involved easterly flow of lake district and scottish ice through the tyne gap and stainmore gap with an ice divide located over the solway firth phase iii was a dominant westerly flow from upland dispersal centres into the solway lowlands and along the solway firth due to draw down of ice into the irish sea basin phase iv was characterised by unconstrained advance of scottish ice across the solway firth forcing of a numerical model of ice sheet inception and decay by the greenland ice core record facilitates an assessment of the potential for rapid ice flow directional switching during one glacial cycle the model indicates that after fluctuations of smaller radially flowing ice caps prior to 30 ka bp the ice sheet grows to produce an elongate triangular shaped dome over nw england and sw scotland at the lgm at 19 5 ka bp recession after 18 5 ka bp displays a complex pattern of significant ice flow directional switches over relatively short timescales complementing the geomorphologically based assessments of palaeo ice dynamics the palaeoglaciological implications of this combined geomorphic and modelling approach are that a the central sector of the biis was as a major dispersal centre for only ca 2 5 ka after the lgm b the ice sheet had no real steady state and comprised constantly migrating dispersal centres and ice divides c subglacial streamlining of flow sets was completed over short phases of fast flow activity with some flow reversals taking place in less than 300 years