holocene evolution of seasonal stratification in the celtic sea refined age model mixing depths and foraminiferal stratigraphy published stable isotopic oxygen carbon and preliminary foraminiferal data from a holocene vibrocore from the celtic sea northwest european continental shelf have been interpreted in terms of the progressive replacement of tidally mixed by seasonally stratified water the first study of the long term dynamics of seasonal stratification this study was hampered by poor age control and the foraminiferal data were based on processing with a 125 m sieve which has been shown not to recover critical small taxa we present here a new age model for this vibrocore bgs 51 07 199 based on 12 accelerator mass spectrometry 14c dates on foraminifera and molluscs radionuclide 137cs 40k profiles from the vibrocore and juxtaposed multicores and a complete foraminiferal stratigraphy based on sieving at 63 m together the three datasets enable a mixing model to be proposed which clarifies the resolution of the record which is confirmed as extending from the late glacial to the late holocene correction for autocompaction reveals an increase in sedimentation rate and mixing depth from the early to the late holocene a temporary increase in sedimentation rate at 6650 yr cal bp is attributed to migration of the productive frontal zone across the core site some time after 3000 yr cal bp sedimentation either slowed abruptly or ceased completely giving the modern mixed layer an apparent age of 3000 yr cal bp the mixed layer depth indicates strongly that the apparent transition to stratification during the early holocene is primarily a threshold change attenuated by bioturbation secondary attentuation is related to reworking the mixed layer model adopted suggests that this isotopic transition occured between 8990 and 8440 yr cal bp 8720 2 the foraminiferal analyses in the light of modern foraminiferal distributional data support the inference that the succession can be interpreted as a response to the progressive seasonal stratification of the celtic sea during the holocene the data highlight the value of key taxa as indicators of shelf palaeostratification in the geological record notably of textularia bocki and stainforthia fusiformis as mixed frontal and frontal stratified indicators respectively the critical change to this frontal assemblage occurs at the same depth as the isotopic threshold based on the mixing model these data affirm the earlier interpretation of the isotopic record as registering bottom water temperature and water column productivity changes driven by the evolution of seasonal stratification the clear association between grain size and sedimentation as well as these isotopic and faunal data indicates that the shelf record of highstand sedimentation is preferentially biased towards the preservation of sequences deposited under seasonally stratified rather than mixed water masses

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

foraminifera from the irish sea glacigenic deposits at aberdaron western lleyn north wales palaeoenvironmental implications in a sequence of glacigenic sediments at aberdaron foraminifera were obtained from samples located specifically in order to differentiate between opposing models of depositional environment all the diamict samples yielded remarkably uniform assemblages with similar numbers of benthic specimens and benthic species per unit weight of sediment similar planktic benthic ratios and similar ratios of clearly allochthonous to possibly autochthonous elements this is precisely as predicted by the terrestrial model of sedimentation where all of the sediments are interpreted as being derived from the melting of glacier ice rich in marine debris entrained during passage along the irish sea basin the results lend no support to a glacial marine model since no faunal responses to increasingly distal sedimentary environments are observed however the fauna is dominated by the foraminifera elphidium excavatum terquem forma clavata cushman which is commonly assumed to indicate glacial marine conditions the modern distribution of similar assemblages suggests that it is just as likely to represent the cold reduced salinity conditions that would have prevailed in the northern irish sea basin for much of the quaternary

palaeoclimatology and palaeohydrography of the glacial stages on celtic and armorican margins over the last 360000 yrs core md03 2692 was retrieved in a water depth of 4064 m on the celtic margin bay of biscay during the sedicar cruise onboard the rv marion dufresne ii it covers the last 360 ka in a total length of 39 m multidisciplinary analyses have been applied to this sequence with the aim of studying the palaeoclimatic and palaeoenvironmental signals of the last few climatic cycles the analyses undertaken include 1 non destructive logging with physical properties magnetic susceptibility sediment colour x ray radiography and measurement of the major elements by x ray fluorescence 2 analyses of planktonic and benthic foraminifera lithic grains and stable isotopic measurements oxygen and carbon we have focused on the longterm evolution of glacial stages with special attention to terminations and heinrich events the results obtained confirm the close correlation between deep sea sedimentation recorded on the celtic margin and changes in the terrestrial environment of the adjacent continent heinrich layers have been identified in mis 2 3 6 and 8 we note the occurrence of laminated facies within deglacial sequences deposited during termination i and mis 6 these facies are closely linked to disintegration phases of the british irish ice sheet bis the laminations contain lower ice rafted detritus ird concentrations than the equivalent heinrich layers and are linked to abrupt changes in sea surface palaeotemperatures we suggest that the laminations are formed by an annual cycle of meltwater and iceberg release from the disintegrating bis generating cascading plumes of dense turbid meltwater coeval with ird release d 2005 elsevier b v all rights reserved

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

european contribution of ice rafted sand to heinrich layers h3 and h4 abstract this paper reports the sr nd isotopic composition of the carbonate free sand 63 m 1 mm fraction of heinrich layers 3 and 4 from about 17 cores from the northern atlantic ocean 38 n to 68 n the results indicate that the transporting icebergs were calved from many ice sheets from around the north atlantic at least the fennoscandian icelandic and laurentide our isotopic data show a more distinctly european origin for ice rafted debris ird deposited during the atypical heinrich event h3 than for background ird in contrast heinrich layer h4 a representative of typical heinrich events h1 h2 h4 and h5 presents a clear dominant laurentide signal this result confirms that these typical heinrich events are associated with a massive discharge of icebergs from the laurentide ice sheet however the theory that the laurentide ice sheet set the events into motion alley r b macayeal d r 1993 ice rafted debris associated with binge purge oscillations of the laurentide ice sheet paleoceanography 9 4 503 511 cannot explain the fact that a european signal of an early h4 sample has been observed prior to the laurentide signature of a late h4 sample in the same core along the european margin this observation indicates that the european ice sheets may have surged before the north american ones and suggests that the laurentide ice sheet was not the sole motor behind the heinrich events moreover in the norwegian sea ird has a scandinavian origin in both h3 and h4

clastic dykes in over consolidated tills evidence for subglacial hydrofracturing at killiney bay eastern ireland abstract a swarm of vertical gravel filled dykes up to 6 m high and several decimetres wide cut through an over consolidated till at killiney bay the dykes are rooted in a gravel layer and many display plumes of clastic debris ejected into the overlying sediments burst out structures such features have not previously been described these clastic dykes are interpreted as the infillings of hydrofractures which formed when water pressures in the basal gravel layer exceeded the overburden pressure and tensile shear strength of the capping till the burst out structures extend up to 7 m from the tops of the dykes and provide strong evidence for forceful upward flow evidence suggests that the hydrofractures formed subglacially probably during a minor re advance their presence in late devensian 26 13 ka bp tills with an irish sea provenance irish sea till may have important implications for the subglacial hydrology of the last irish sea ice sheet these hydrofractures cannot form in unconsolidated glacimarine sediment and their presence precludes a glacimarine origin for these deposits they greatly affect the geotechnical properties of irish sea tills in particular providing very permeable routes through otherwise impermeable layers with important consequences in situations elsewhere in the irish sea basin where they have been used as aquicludes in landfill and low level nuclear waste disposal sites

u series and amino acid dates from jersey understanding of the raised beach and other interglacial sequences in the southern part of the british isles has been improved through use of the amino acid racemization technique this method has permitted correlation of these isolated and fragmentary marine deposits1 2 which except for the portland site are located around the shores of the bristol channel1 by applying this technique with the u series method we have obtained a geochronometric date from the 8 m raised beach of the belle hougue cave jersey channel islands our results suggest that the 8 m raised beach of the channel should be correlated with isotope stage 5 and that raised beaches above this altitude in the area may pre date this stage and thus also the ipswichian interglacial which forms part of it

the last ice sheet in snowdonia in snowdonia there is a marked contrast between weathered summits often with well developed blockfields or tors and lower ice moulded terrain the boundary is interpreted as a trimline marking the upper surface of the last ice sheet this interpretation is supported by the presence of gibbsite an end product of prolonged weathering at the base of soils above but not below the trimline the reconstructed ice surface reaches about 850 m above present sea level along an ice divide running ne sw through the massif there is no evidence to support the popular view that ice centred further south extended over snowdonia and breaching to form the major glacial troughs can be explained by the action of local ice the field evidence presented here demonstrates that most models of the southern british and irish sea ice sheets are significantly flawed the earliest being far too thick and the most recent far too thin copyright 2000 john wiley sons ltd

the offshore quaternary sediment bodies of the english channel and its western approaches after a short review of present day surficial sediments on the sea floor of the english channel and its western approaches this paper summarises recent results on the present quaternary sandy accumulations tidal bank systems based on sea floor imaging very high resolution seismic surveys and a few piston cores the english channel a typical funnel shaped tidal shelf is presently starved of terrigenous sediments most of mobile sediments at the sea floor are autochthonous either skeletal carbonates or siliciclastic sands reworked from old littoral deposits or incised valley fills three zones are considered 1 the central and western central channel which is a bedload parting zone characterised by a pebbly lag making up the sole of the quaternary sediments throughout the shelf area 2 the eastern channel a flood dominated area characterised by medium to fine siliciclastic sands mainly of aeolian periglacial origin 3 the western approaches an ebb dominated area with a polygenic sediment cover characterised by coarse carbonate rich gravelly to muddy sands of marine to glaciomarine origin with a diachronous faunal content these sediments are sourced by reworking of a former littoral barrier or incised valley fills the seismic stratigraphy of quaternary sediment accumulations 10 50 m points to the predominant control of tidal dynamics together with the general interplay between the channel morphology and the sea level story the thickest deposits in the eastern channel and western approaches are built up into bank systems whereas the interpretation of the active eastern channel banks finds a general agreement the moribund banks in the western approaches i e the southern celtic banks remains under debate owing to the lack of long cores in our hypothesis both systems were built up during the last post glacial sea level rise the celtic banks would represent the tidal transgressive systems tract whereas the eastern channel banks correspond to the highstand systems tract the architecture of both bank systems is studied from two examples the bassure de baas bank in the eastern channel and the kaiser bank in the western approaches both examples show transgressive features the bassure de baas exhibits from base to top an estuarine mouth barrier a wave erosion surface a shoreface bank and finally a classic tidal bank by contrast the kaiser bank consists of the offshore reworking of fully marine deposits its base would correspond to the amalgamation of the last glacial sea level fall with a strong tidal ravinement surface from base to top the bank underwent tidal bar accretion very large dune field aggradation perched channels incision storm erosion and deposition

glacial interglacial variation in organic carbon burial on the slope of the n w european continental margin 48 50 n the sources and fate of organic carbon corg were examined at two sites on the goban spur and a single site within the porcupine sea bight on the n w european slope between 48 n and 50 n here we present data on the sedimentary corg concentration its 13c 12c composition 13corg and corg n of 224 total and 119 fine fraction 63 m samples as a time series running from the instantaneous marker horizon heinrich layer 2 25 5 ka bp through the last glacial isotope stage 2 and interglacial isotope stage 1 to the present the significance of the n w european slope as a depositional sink for corg has declined in the past twenty thousand years with flux values decreasing two to three fold from the late glacial 60 70 mg c cm 2 ka 1 to low late holocene values significant shifts are seen in the 13corg signature of both the total and fine fractions between the present interglacial and last glacial the open slope of the goban spur is characterised by relatively low values over the last glacial with minimum values for the total sediment of around 24 5 occurring at ca 18 ka bp and generally increasing values during the holocene with the most recent samples having values of ca 19 2 to 20 2 in the porcupine sea bight a different relationship is evident with samples from the last glacial maximum being generally higher while values from the holocene are lower with a minimum of 23 3 occurring just below the mixed layer similar trends are observed in the fine fraction albeit with a different dynamic range paired analysis of 13corg and corg n are consistent with the organic matter being a climatically forced mixture from c3 photosynthetic terrigenous and marine organic matter sources an increased influence of terrestrial corg is suggested on the glacial goban spur and holocene porcupine sea bight and vice versa we suggest that this may be explained by modern wind driven flushing of terrigenous carbon across the armorican and celtic shelves to the n w and thence into porcupine sea bight during the last glacial increased strength of westerly winds created a residual current regime driving material to the s w where it was transported in vigorous tidal off shelf flushing to the upper slope followed by slope current transfer to the goban spur much of this material was presumably delivered by the great channel river to the outer shelf thus leading to enhanced flux of terrestrial corg on the goban spur the influence of a freshwater plume from meltwater discharge of the european ice sheet in this region is supported by foramininiferal 18o data from which a palaeo salinity reconstruction shows a greatest negative anomaly of 2 55 that is s 35 at the time of maximum terrestrial corg content in the sedimentary material in addition to showing that surface waters over goban spur were relatively fresh throughout the glacial our results also reveal variability in surface salinity on shorter timescales

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

relative sea level changes glacial isostatic modelling and ice sheet reconstructions from the british isles since the last glacial maximum while contributing 1 m equivalent eustatic sea level rise the british isles ice sheet produced glacio isostatic rebound in northern britain of similar magnitude to eustatic sea level change or global meltwater influx over the last 18 000 years the resulting spatially variable relative sea level changes combine with observations from far field locations to produce a rigorous test for quantitative models of glacial isostatic adjustment local ice sheet history and global meltwater influx after a review of the attributes of relative sea level observations significant for constraining large scale models of the isostatic adjustment process we summarise long records of relative sea level change from the british isles and far field locations we give an overview of different global theoretical models of the isostatic adjustment process before presenting intercomparisons of observed and predicted relative sea levels at sites in the british isles and far field for a range of earth and ice model parameters in order to demonstrate model sensitivity and the resolving power available from using evidence from the british isles for the first time we show a good degree of fit between relative sea level observations and predictions that are based upon global earth and ice model parameters independently derived from analysis of far field data with a terrain corrected model of the british isles ice sheet that includes extensive glaciation of the north sea and western continental shelf that does not assume isostatic equilibrium at the last glacial maximum and keeps to trimline constraints of ice surface elevation we do not attempt to identify a unique solution for the model lithosphere thickness parameter or the local scale detail of the ice model in order to provide a fit for all sites but argue that the next stage should be to incorporate an ice sheet model that is based on quantitative glaciological model simulations we hope that this paper will stimulate this debate and help to integrate research in glacial geomorphology glaciology sea level change earth rheology and quantitative modelling copyright 2006 john wiley sons ltd

raised beaches and sea levels in the english channel in the middle and late pleistocene problems of interpretation and implications for the isolation of the british isles

changes in northeast atlantic hydrology during termination 1 insights from celtic margin s benthic foraminifera abstract using benthic foraminiferal based proxies in sediments from the celtic margin we provide a well dated record across the last deglaciation of the channel river dynamics and its potential impact on the hydrology of intermediate water masses along the european margin our results describe three main periods 1 during the last glacial maximum and before 21 ka bp the predominance of meso oligotrophic species suggests well oxygenated water masses after 21 ka bp increasing proportions of eutrophic species related to enhanced riverine supply occurs concomitantly with early warming in greenland air temperatures 2 a thick laminated deposit occurring during a 1500 years long period of seasonal melting of the european ice sheet eis is associated with early heinrich stadial 1 period 18 2 16 7 ka bp the benthic proxies describe low salinity episodes cold temperatures severe dysoxia and eutrophic conditions on the sea floor perhaps evidence for cascading of turbid meltwaters 3 during late hs1 16 7 14 7 ka bp conditions on the celtic margin s seafloor changed drastically and faunas indicate oligotrophic conditions as a result of the ceasing of eis meltwater discharges while surface waters were cold due to laurentide ice sheet lis icebergs releases increasing benthic mg ca ratios reveal a progressive warming of intermediate water masses whereas oxygen proxies indicate overall well oxygenated conditions in addition to the well known effect of eis meltwaters on surface waters in the celtic margin our benthic record documents a pronounced impact on intermediate water depths during hs1 which coincided with major amoc disruptions

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

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

glaciomarine sediments of the isle of man as a key to late pleistocene stratigraphic investigations in the irish sea basin the northern part of the isle of man in the central irish sea basin is identified as a raised marine foreland containing the largest subaerial exposure of last glaciation marine and glaciomarine sediments yet recognized on the british continental shelf a large push ridge that crosses the foreland identifies a major ice limit the ridge divides the foreland stratigraphy into a coarsening upward marine sequence of pelagic muds with dropstones sand and gravel to the south from offlapping stratified and massive sandy diamict assemblages overlying glaciotectonized marine sediments to the north coarse grained diamicts are argued to form part of a push ridge subaqueous outwash depositional system deposited when processes of suspension deposition density underflow ice rafting highly variable traction current activity and sediment gravity flow were operative adjacent to a grounded marine ice margin the identification of large offshore submarine banks aligned parallel to the bride moraine suggests that construction of the push ridge subaqueous outwash depositional system may have been repeated during ice recession this and published descriptions of other irish sea tills indicate that analogous structures and sediments are present offshore and around the irish sea basin

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

amino acid geochronology of raised beaches in south west britain abstract based on 1 the epimerization of l isoleucine to d alloisoleucine d l ratios in patella vulgata littorina littorea l littoralis l saxatilis littorina species and nucella lapillus from raised beaches in south west britain 2 statistical analysis of the d l ratios and 3 lithostratigraphic and geomorphic evaluation three d l stages are proposed the d l ratios for all the species measured are converted to a patella vulgata standard the three d l stages are 1 1 the minchin hole d l stage d l ratios 0 175 0 014 defined at a stratotype in minchin hole cave gower wales 2 2 a provisionally defined but as yet unamed d l stage because of the current unavailability of a suitable stratotype with d l ratios of 0 135 0 014 3 3 the pennard d l stage d l ratios 0 105 0 016 defined at a stratotype in minchin hole cave gower wales two geochronological models of the three high sea level events representing the d l stages are constrained by uranium series age determinations on stalagmite interbedded with marine beds in minchin hole and bacon hole caves gower wales a potential fixed point in model evaluation is an age determination which is equivalent to oxygen isotope sub stage 5e 122 ka the two models are oxygen isotope stage and age ka bp d l stage d l ratio model 1a model 1b model 2 pennard 0 105 0 016 5a ca 80 5e 122 5e 122 5c ca 100 unnamed 0 135 0 014 5e 122 7 194 minchin hole 0 175 0 014 7 186 245 7 186 245 7 216 the ages of the raised beaches are used to constrain the timing and extent of glaciation in the area the extent of the late devensian glaciation is fixed by reference to localities where raised beaches of the pennard d l stage outcrop as well as by using unpublished data on molluscs incorporated into glacial deposits two pre devensian glaciations antedate the minchin hole d l stage the irish sea glaciation of the bristol channel irish sea older drift of south wales fremington till of north devon is ascribed to oxygen isotope 10 or earlier while the paviland welsh glaciation is ascribed to oxygen isotope stage 8 or earlier an earlier glaciation berwyn glaciation is inferred from erratics of known welsh provenance in essex

were the north atlantic heinrich events triggered by the behavior of the european ice sheets theories explaining the origin and distribution of heinrich layers abrupt massive discharges of ice rafted detritus generally attribute these layers to the laurentide ice sheet however doubt has been cast by the discovery that sediments also originated from european ice sheets here we present isotopic sr nd fingerprints of heinrich layers obtained in cores from the european margin they reveal that for most of the heinrich layers the icebergs were calved first from the european ice sheets predating the laurentide surges accelerator mass spectrometry 14c ages reveal that the oceanic heinrich events were synchronous with their dust equivalents in the greenland ice cores implying a direct ocean atmosphere link the typical laurentide surge seems to have occurred over a short time span after about 1 5 k y of iceberg release from the european ice sheets this suggests that the laurentide ice sheet responded to a stimulus created by events in the european sector

age of pleistocene faunas from bacon hole wales at present it is difficult to match british early upper pleistocene vertebrate faunas with the growing evidence for complex climatic change at this time derived from the oceanic oxygen isotope record and from long pollen cores however we report here new analyses of dated faunal assemblages from bacon hole wales which indicate that the ipswichian interglacial fauna dated at 125 kyr bp was followed by a devensian interstadial fauna dated at 81 kyr bp which still supported some supposedly typical inter glacial mammals combined with evidence of an intervening cold fauna from stump cross cave dated at more than 83 kyr bp these indications of complexity in faunal change at the ipswichian devensian transition are more consistent with the oxygen isotope and pollen core data than traditional views

periglacial trimlines and the extent of the kerry cork ice cap sw ireland abstract periglacial trimlines on the mountains of sw ireland demarcate a contrast between glacially scoured bedrock on lower ground and thick periglacial regolith covers on summits and plateaus and have previously been interpreted as marking the maximum altitude of the kerry cork ice cap kcic glacially eroded bedrock extends to the highest points on the beara peninsula but the highest summits on the iveragh peninsula support thick regolith covers trimline altitudes on the iveragh peninsula decline radially from a former ice divide near the head of kenmare river from 700 m altitude near the divide to 470 m near dingle bay contrasts in the clay mineral content of above and below trimline soils and cosmogenic isotope exposure ages indicate a lgm age for the trimlines assumption that the trimlines represent the maximum thickness of the kcic implies an ice divide altitude of 825 m however modelling of ice surface profiles demonstrates that an ice divide at 825 m is irreconcilable with stratigraphic evidence for extension of the kcic at least as far as garryvoe 115 km east of the divide we infer that the iveragh trimlines represent a former englacial transition between warm based sliding ice on low ground and cold based ice on high ground rather than delimiting nunataks as previously interpreted modelling of ice surface altitudes suggests that during the lgm the kcic probably overtopped all of the mountains in sw ireland the trimlines of sw ireland thus define the minimum rather than maximum altitude of the kcic at the lgm as well as the sites of former cold patches within the kcic

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

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

glaciology of the british isles ice sheet during the last glacial cycle form flow streams and lobes abstract the last ice sheet over the british isles together with other mid latitude pleistocene ice sheets and in contrast to the modern ice sheets of greenland and antarctica had a relatively low profile low summit elevation and extensive elongated lobes at its margin a thermo mechanically coupled numerical ice sheet model driven by a proxy climate has been used to explore the properties that would have permitted these characteristics to develop the approach the key to quantitative palaeoglaciology is to determine the boundary conditions that permit the simulated ice sheet to mimic the evolution of the real ice sheet through the last glacial cycle simulations show how a british ice sheet may have been confluent with a scandinavian ice sheet during some parts of its history and how unforced periodic and asynchronous oscillations could occur in different parts of its margins marginal lobes are a reflection of streaming within the ice sheet such streams can be ephemeral dynamic streams located because of ice sheet properties or fixed streams whose location is determined by bed properties the simulations that best satisfy constraints of extent elevation and relative sea levels are those with major fixed streams that strongly draw down the ice sheet surface in these the core upland areas of the ice sheet were cold based at the last glacial maximum basal streaming velocities were between 500 and 1000 ma 1 compared with surface velocities of 10 50 ma 1 in inter stream zones shear stresses were as low as 15 25 kpa in streams compared with 70 110 kpa in upland areas and 60 84 of the ice flux was delivered to the margin via streams

ground penetrating radar examination of thin tsunami beds a case study from phra thong island thailand coastal overwash deposits from tsunamis and storms have been identified and characterised from many coastal environments to date these investigations have utilised ad hoc time energy and cost intensive invasive techniques such as pits and trenches or taking core samples here we present the application of high frequency ground penetrating radar gpr to identify and characterise the 2004 indian ocean tsunami iot and palaeotsunami deposits from phra thong island thailand this site is one of the most intensively studied palaeotsunami sites globally and preserves a series of late holocene stacked sandy tsunami deposits within an organic muddy low energy backbeach environment using 100 500 and 1000 mhz gpr antennas 29 reflection profiles were collected from two swales x and y inland of the modern beach and two common mid point cmp profiles using the 200 mhz antennas were collected from swale y detailed examination of the cmps allowed accurate velocity estimates to be applied to each profile the reflection profiles included across swale profiles and a high resolution grid in swale x and were collected to investigate the feasibility of gpr to image the palaeotsunami deposits and two profiles from swale y where the tsunami deposits are poorly known the 500 mhz antennas provided the best stratigraphic resolution which was independently validated from the stratigraphy and sedimentology recovered from 17 auger cores collected along the profiles it is clear from the augers and gpr data that the different dielectric properties of the individual layers allow the identification of the iot and earlier tsunami deposits on phra thong island although applied in a coastal setting here this technique can be applied to other environments where thin sand beds are preserved in order to prioritise sites for detailed examination

trace fossils of talitrid sandhoppers in interglacial littoral calcareous sandstones cornwall u k small 6cm isolated cylindrical shafts observed in carbonate cemented current bedded interglacial littoral sands sandrock in cornwall have previously been interpreted as intrasedimentary stalactites an alternative explanation as trace fossils of the ichnogenus skolithos is proposed probable attribution to talitrid amphipoda sandhoppers in particular talitrus saltator montagu is supported by the similarity of the features to the modern burrows of this organism the facies dependence of the features and by independent evidence on the backshore frontal dune environment of deposition the ecological requirements of t saltator support the interpretation of the raised beaches as interglacial in status based on thermoluminescence tl dating and aminostratigraphy and conflict with a recent suggestion that they may be of cold stage origin

till and moraine emplacement in a deforming bed surge an example from a marine environment the glacier sefstrombreen in spitsbergen surged across an arm of the sea between qsr 1882 and 1886 and rode up onto the island coraholmen marine and terrestrial geological observations and archive records show that the glacier advanced on a deforming carpet of marine mud which was eroded from its original location transported and smeared over the sea bed and coraholmen as a deformation till the glacier emplaced about 210sm 0 2 km 3 of drift in the terminal 2 km of its advance in a maximum of 14 years leaving a thickness of up to 20 m on coraholmen which was doubled in size as a result during the surge subglacial muds were characterised by high water pressures low effective pressures and low frictional resistance to glacier movement original sedimentary inhomogenities permit fold structures to be identified but repeated refolding and progressive remoulding produce mixing and homogenisation of deformation tills the surge was probably shortlived and as the heavily crevassed glacier stagnated underlying water saturated muds were intruded into crevasses and then extruded on the glacier surface reticulate crevasse intrusion ridges on coraholmen and the sea floor reflect the orientation of surge generated crevasses water and sediment was also extruded beyond the glacier at its maximum extent to form extensive flows producing till tongues both on coraholmen and the sea floor extending over 1 3 km from the glacier it is argued that subglacial deformation of pre existing sediment will almost invariably be associated with glaciation of marine areas and that this process will not only produce deformation tills through remoulding of pre existing sediments but will also play a fundamental role in glacier dynamics criteria which perrait glacial tills produced by such events from marine and glaciomarine muds are discussed copyright 1996 elsevier science ltd

glaciation and sea level change for ireland and the irish sea since late devensian midlandian time the sea level change around the coast of ireland and the irish sea for the past 20 000 years is primarily the combined result of the glacio isostatic adjustment of the crust to the removal of ice over the british isles and the total eustatic change from the global ice sheets however the isostatic effects due to the removal of ice from northern europe and north america and the addition of meltwater into the oceans also make a significant contribution predictions of sea level change based on glacio hydro isostatic models are compared with observations to constrain the ice volume over ireland at the time of the last glacial maximum and the maximum ice height appears to have been of the order of 600 m the models predict well the spatial variability in sea level change observed across the region for holocene and lateglacial time with levels above present being predicted only for northeastern ireland and north of about morecambe bay the models do not support suggestions that lateglacial levels along the east coast of ireland or the coast of wales were 50 150 m above their present levels consistent models that would produce such large lateglacial highstands are incompatible with all other sea level and glacial evidence for the british isles palaeobathymetry and palaeoshoreline reconstructions for the irish sea indicates that a tenuous landbridge between britain and ireland developed only across the celtic sea between about 18000 and 14000 years bp

coda wave interferometry for estimating nonlinear behavior in seismic velocity in coda wave interferometry one records multiply scattered waves at a limited number of receivers to infer changes in the medium over time with this technique we have determined the nonlinear dependence of the seismic velocity in granite on temperature and the associated acoustic emissions this technique can be used in warning mode to detect the presence of temporal changes in the medium or in diagnostic mode where the temporal change in the medium is quantified

late middle pleistocene deposits at norton farm on the west sussex coastal plain southern england the coastal plain of west sussex southern england is internationally important because of the sequence of discrete high sea level events preserved at various elevations across it new evidence is presented from a site at norton farm near chichester on the lower coastal plain where pleistocene marine sands fining upwards into silts occur between 5 3 m and 9 1 m od the sequence reflects a regressive tendency at the transition from an interglacial to a cold stage the marine sands have yielded foraminifera ostracods and molluscs that indicate a declining marine influence through the sequence culminating in a tidal mudflat strongly weathered in places cool climate foraminifera including elphidium clavatum cassidulina reniformis and elphidium albiumbilicatum and ostracods have been recovered from the marine sands some species with an apparent preference for warmer water conditions however are also present freshwater taxa washed into the terminal marine sediments include some cold climate indicators such as pisidium stewarti and p obtusale lapponicum additional evidence for cool climatic conditions during the deposition of the upper part of the marine sequence is provided by the lack of tree taxa in the pollen record and by features of the micromorphology the marine sediments probably began accumulating during ois 7 a conclusion based on their elevation on amino acid ratios from shells but especially on vertebrate evidence particularly the presence of a small form of horse together with a large distinctive form of northern vole microtus oeconomus the occurrence of cool climate indicators in these marine sediments may demonstrate a lag between the climatic deterioration and the expected glacio eustatic fall in relative sea level this evidence appears to support the conclusions drawn from the study of coral terraces in barbados such a scenario would provide the conditions necessary for the emplacement of the large erratic boulders reported from the lower coastal plain of west sussex copyright c 2000 john wiley sons ltd

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

upper pleistocene facies sequences and relative sea level trends along the south coast of ireland upper pleistocene sequences deposited around 20 ka provide a record of sedimentation during the last glacial deglacial cycle along the south coast of ireland a stratigraphy based on eight lithofacies associations is recognized typically the facies sequences overlie a glaciated shore platform furrowed by subglacial meltwaters elements within the stratigraphy comprise 1 ice advance southwards onto the continental shelf 2 stagnation zone retreat triggered by rising sea level related to isostatic depression coupled with subglacial meltwater events that furrowed the platform 3 progressive rise in relative sea level recorded by a submergent facies sequence on an isostatically depressed slope beach gravels 2 subaqueous jet afflux sediments 2 wave influenced sands 2 glaciomarine mud drape ice marginal oscillation is recorded by glaciotectonically deformed gravels sands and foliated diamict 4 terrestrial emergence is marked by angular breccias derived from local slopes by periglacial weathering there is a clear facies transition between the breccias and underlying wave influenced sands facies sequences suggest that the local deglacial cycle was out of phase with the global eustatic cycle along the south coast of ireland stagnation zone retreat was largely dependent on magnitudes of isostatic depression high relative sea level and meltwater events and not on climatic forcing

late pleistocene tidewater glaciers and glaciomarine sequences from north county mayo republic of ireland late pleistocene deposits in north county mayo were deposited in three main glacigenic environments 1 drumlins and basal tills were formed when ice moved from the irish lowlands and local mountain catchments into donegal bay 2 gilbert type deltas accumulated up to 80m i o d on the lowlands and subaqueous moraines formed across minor valleys when marine based ice grounded inland 3 a thick drape of fossiliferous glaciomarine mud along the coastal fringe was deposited from meltwater plumes and by ice rafting immediately outside of these ice limits the muds contain an elphidium clavatum dominated low diversity microfauna which is characteristic of cold water conditions adjacent to glacier termini valves of macoma calcarea from the mud have been 14c dated at 16940 120 and 17300 100 bp the high level delta complex was deposited from tidewater glaciers in a peripheral depression adjacent to the drumlin ice limits of north county mayo although the field evidence cannot be used to determine former sea level history with any accuracy it poses general problems for sea level history and isostatic effects of the last major ice sheet in the west of ireland raised glaciomarine sequences commonly occur in close association with drumlin ice limits elsewhere in ireland and represent marine transgressions prior to glacial unloading it is suggested that the magnitudes and patterns of crustal depression are greater and geometrically more complex at the margins of ice sheets in ireland than hitherto realised

the bytham river reconsidered abstract the english midlands is one of the most important regions for british pleistocene geology the middle pleistocene glacial sediments of the region termed the wolston formation overlie deposits of a pre existing river system the baginton formation the latter are characteristically composed of quartz rich sediment derived from underlying triassic bedrock this sw ne aligned proto soar system was overridden by the wolstonian ice its lack of terraces or discrete sedimentary units implies that the river can only have existed for a limited period the deposits accumulated during a period of climate change from boreal interstadial to subarctic conditions a reinterpretation of these sediments as the headwaters of a pre anglian bytham river aligned towards east anglia across the fenland where they were linked to the ingham formation deposits found favour for two decades this was especially so when the wolston formation sediments were reassigned to the earlier anglian stage however recent work has shown that the bytham river could not have existed in the form suggested by some authors since pre anglian age fluvial sediments are absent from the eastern fenland margin except possibly certain deposits at high lodge suffolk therefore a re examination of the evidence is required it is concluded that the wolstonian glaciation late saalian marine isotope stage mis 6 indeed post dates that during the anglian stage elsterian mis 12 in addition it appears that the baginton proto soar stream as originally conceived almost certainly did not exist before the early wolstonian early saalian stage following a significant period of fluvial incision rather than being aligned towards east anglia the substantial proto soar flowed into south lincolnshire and thence potentially to the north sea via the wash and the silver pit depression by contrast the pre anglian ingham formation deposits of central east anglia were almost certainly deposited by a separate proto trent river that drained the east midlands over an extended period as a left bank thames tributary together these conclusions reinforce the view that the main drainage alignment in southern england during the pre anglian period was nw to se parallel to the regional tilt of the landmass

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

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

thermoluminescence dating of late devensian loesses in southern england scattered across southern england are many isolated deposits of loess like material1 a few such as that at pegwell bay in kent are highly calcareous and unweathered but most have been reworked by fluvial or colluvial processes there is good stratigraphical evidence for a few pre devensian loesses also in kent but dating of more recent loess has so far been based on indirect evidence much work has been done on the pegwell bay loess as it is the most extensive truly aeolian loessic deposit in britain kerney2 compared the late devensian deposits in the isle of thanet and at pegwell bay with similar deposits in holland and belgium where radiocarbon dates have been obtained for interstadial deposits correlation of the east kent deposits with these in northern europe indicates that the loesses in kent were formed between 30 000 and 14 000 yr ago i report here dates for six of the more recent deposits in southern britain from the scilly isles to kent the dates have been obtained on the loess itself using a recently developed thermoluminescence tl dating technique3 4 and confirm the ages as being late devensian

late devensian and holocene shorelines of the british isles and north sea from models of glacio hydro isostatic rebound sea level change around the british isles since the time of the last glacial maximum is largely due to of the crustal rebound from the glacial unloading of northern britain and the concomitant melt water loading of the adjacent seas and atlantic ocean minor but not insignificant contributions also result from the rebound caused by the unloading of the distant ice sheets including fennoscandia and north america observations of sea level change for this period constrain the glacio hydro isostatic rebound model parameters describing the effective lithospheric thickness or rigidity and the effective mantle viscosity as well as certain ice sheet characteristics such as the ice thickness at the time of the last glacial maximum the models permit palaeobathymetry and palaeoshorelines to be predicted for the british isles region including the north sea the resulting evolution of the coastlines exhibits a complex behaviour through time one that is quite different from the usual models in which sea level change is assumed to be a function of time only in part this is because of the delayed response of the mantle to the spatially variable and time dependent ice and water loads and in part because the unloading history of the british ice sheet is different from those of the major global ice sheets thus maximum emergence of the north sea occurred after deglaciation had started and lasted for an extended period from about 15 000 to 12 000 radiocarbon years bp during this relative sea level still stand shoreline features could have formed for example along the western edge of the norwegian trough when access to the firths of eastern scotland would have been via a long and shallow marine inlet shoreline retreat across the north sea became relatively rapid after about 10000 years the model predictions for the irish and celtic seas also suggest a complex behaviour with the formation of a wide land bridge between about 20000 and 13 000 years ago the model also suggests that as long as the scottish ice extended across the northern irish sea until about 14 000 years ago there would have been a large freshwater periglacial lake located further south both the predicted sea level height age relations and the shoreline positions are consistent with a large body of observational evidence but some discrepancies occur particularly in northern scotland and ireland where the ice heights may have been somewhat greater than assumed in the model

evidence of sea level change from coastal caves with raised beach deposits terrestrial faunas and dated stalagmites abstract investigation of interfingering marine and terrestrial quaternary deposits preserved in minchin hole and bacon hole on the coast of south wales uk provides evidence of two phases of high sea level equal to or greater than that of today the younger of these is assigned to the 125 000y by high sea level event of oxygen isotope sub stage 5e overlying the deposits which represent this event a series of terrestrial vertebrate faunas indicate a further significant cool warm oscillation before the onset of major frost shattering attributed to the devensian cold stage

dating and rhythmicity from the last deglacial cycle in the british isles in northern britain glaciotectonically thickened sediment piles represent the sediment flux transferred to ice margins by phases of fast ice flow and drumlin streamlining during the last deglacial cycle radiocarbon dating of marine faunas within deglacial muds age constrain phases of drumlinisation shaping to between 19 and 14 5 ka bp individual phases of drumlinization can be correlated with millennial time scale discharge events documented from the circum north atlantic which are probably climate driven the overall deglacial cycle records at least five major millennial time scale ice margin oscillations and phases of sediment sequence rhythmicity

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

structural and depositional evidence for repeated ice marginal oscillation along the eastern margin of the late devensian irish sea ice stream abstract late devensian glacigenic sediments and landforms along the north west coast of wales document the advance and subsequent retreat of the eastern margin of an irish sea ice stream that met coalesced and ultimately uncoupled from ice radiating outwards from the adjacent welsh ice cap centred over snowdonia across the boundary between the two former ice masses is a set of sediment landform assemblages that reflect rapidly changing erosional and depositional conditions during ice interaction from the inner part of the ice stream the assemblages range outwards from a subglacial depositional assemblage characterised by drumlin swarms through a subglacial erosional assemblage marked by prominent bedrock scours and large subglacial rock channels through an ice marginal assemblage identified by closely spaced glaciotectonised push moraines and intervening marginal sandur troughs into a freely expanding proglacial sandur and lacustrine delta assemblage the ice marginal assemblage provides evidence for numerous oscillatory episodes during retreat and at least 20 ice marginal limits can be identified at least 11 of these display multiple criteria for identifying readvance and in the ideal case is characterised by a moraine form built by localised tectonic stacking of diamict to the rear fronted by a clastic wedge of ice front alluvial fan gravel and intercalated flow till the distribution of sediment landform assemblages suggests a highly dynamic convergent ice stream flow pattern with high ice velocity a sharply delineated lateral shear margin pervasive ice marginal glaciotectonic deformation and a tightly focused ice marginal sediment delivery system all signature characteristics of contemporary ice streams

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 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

thermoluminescence dating and geochemistry of loessic deposits in southeast england the results of a thermoluminescence tl dating and geochemical survey of loessic deposits in southeast england involving sampling at 26 localities demonstrate that the loessic deposits appear to be the product of at least three depositional phases of aeolian silt during the late pleistocene namely 10 25 ka bp 50 125 ka bp and 170 ka bp the majority of localities sampled date to the late devensian but isolated pockets of older material were found throughout the area the majority of the samples analysed were of decalcified material the results of geochemical analyses of major oxide and trace element concentrations indicate the uniformity of material and suggest a common provenance

deglaciation of the irish sea basin a critique of the glaciomarine hypothesis the glaciomarine model for deglaciation of the irish sea basin suggests that the weight of ice at the last glacial maximum was sufficient to raise relative sea levels far above their present height destabilising the ice margin and causing rapid deglaciation glacigenic deposits throughout the basin have been interpreted as glaciomarine the six main lines of evidence on which the hypothesis rests sedimentology deformation structures delta deposits marine fauna amino acid ratios and radiocarbon dates are reviewed critically the sedimentological interpretation of many sections has been challenged and it is argued that subglacial sediments are common rather than rare and that there is widespread evidence of glaciotectonism density driven deformation associated with waterlain sediments is rare and occurs where water was ponded locally sand and gravel deposits interpreted as gilbert type deltas are similarly the result of local ponding or occur where glaciers from different source areas uncoupled they do not record past sea levels and the ad hoc theory of piano key tectonics is not required to explain the irregular pattern of altitudes the cold water foraminifers interpreted as in situ are regarded as reworked from irish sea sediments that accumulated during much of the late quaternary when the basin was cold and shallow with reduced salinities amino acid age estimates used in support of the glaciomarine model are regarded as unreliable radiocarbon dates from distinctive foraminiferal assemblages in northeast ireland show that glaciomarine sediments do occur above present sea level but they are restricted to low altitudes in the north of the basin and record a rise rather than a fall in sea level it is suggested here that the oldest dates around 17 000 yr bp record the first late devensian weichselian marine inundation above present sea level this accords with the pattern but not the detail of recent models of sea level change copyright 2001 john wiley sons ltd

the glaciation of dartmoor the southernmost independent pleistocene ice cap in the british isles the granite uplands of dartmoor have traditionally been considered to be relict permafrost and periglacial landscapes that lay beyond the limits of quaternary glaciations but a variety of landform evidence indicates that a plateau icefield existed on the northern part of the moor constituting the southernmost independent ice cap in the british isles overdeepened or weakly u shaped valley segments fringing north dartmoor document an early extensive phase of glaciation but the most convincing landform evidence relates to more recent valley based glacier occupancy a moraine ridge on the slipper stones represents the most unequivocal palaeo glacier on north dartmoor with a palaeo ela of c 460 m above sea level asl although this relates to the youngest and most restricted phase of glaciation a longer term ela is likely to be represented by the corn ridge proto cirque at 370 410 m asl more extensive valley glaciers are recorded in each of the major drainage basins of north dartmoor by arcuate and linear bouldery ridges and hummocky valley floor drift which are interpreted as latero frontal moraines deposited by outlet lobes of a plateau icefield recession of these lobes is marked by inset sequences of such ridges and occasional meltwater channels plateau ice was predominantly thin and protective and snowblow and preferential accumulation in valley heads facilitated the modest glacial erosion and debris transport recorded in the landforms and sediments it is proposed that the highest plateaux have been occupied by ice for the longest cumulative period of time throughout the quaternary average glacial conditions explaining the distribution of different tor types on northern dartmoor this also explains the lack of tors on the most expansive of the highest plateau terrain ice dispersal centres as the product of a average glacial conditions preferentially removing tors or dampening their production rates b the survival of high relief type 1 tors during glaciation if they occupy summits too narrow to develop significant plateau icefields and or ridges that are bypassed by faster moving ice in adjacent deep valleys and c the survival of subdued type 2 tors in areas glaciated less regularly during the quaternary simple ice flow modelling indicates that a plateau icefield type glaciation is required for significant ice flow to occur and confirms thin ice cover in particular on narrow summits thereby supporting the explanation of tor class distribution the modelling allows us to spatially correlate the geomorphological evidence of margin positions into two major stages and further indicates a strong altitude mass balance feedback leading to an ice cap that is not in balance with its climate and with an extent that is limited by the length of the cold phases rather than their severity

only four major 100 ka glaciations during the brunhes chron early attempts at land sea correlations between continental glaciations and the marine 18o record were premature without a high resolution continental stratigraphy existing schemes of continental subdivision and correlation based facies floras and facies faunas do not provide the necessary resolution this paper reports on a new high resolution subdivision and correlation of the pleistocene of the british isles subdivision and correlation is accomplished primarily by aminostratigraphy based on aminozones which is calibrated by other geochronological means u series tl osl esr 14c palaeomagnetic and 36cl rock exposure dating for correlation with oxygen isotope stratigraphy these data are then used to test the hypotheses of shackleton 1987 and raymo 1997 that only four major glaciations occurred in the brunhes chron during oxygen isotope stages 16 12 6 and 2 their hypotheses are confirmed except for stage 2 when at least part of the british ice sheet was at its maximum somewhat earlier during stages 4 and 3

palynology aminostratigraphy and u series dating of marine gortian interglacial sediments in cork harbour southern ireland abstract palynological analysis amino acid epimerization analysis and uranium thorium disequilibrium age determination of three irish interglacial cores support the suggestion that there may have been more than one holsteinian style temperate interval in europe the cores were taken from estuarine deposits beneath glacial diamicton in cork harbour southwest ireland the pollen records an incomplete temperate stage the biotic signature is similar to those from several interglacial sites in ireland and is considered part of the gortian group the pollen signature is holsteinian hoxnian in character amino acid epimerization analysis suggests the deposits to be oxygen isotope stage 7 in age whereas uranium thorium disequilibrium suggests a minimum stage 5 age possible correlatives of the gortian group in europe are suggested

amino acid evidence for devensian ice west gower south wales complete inundation of south wales by ice during the penultimate wolstonian glaciation has been widely suggested1 3 although it is generally agreed that the last glaciation was less extensive than the preceding one4 6 there has been controversy concerning its limits stemming mainly from the lack of clear geomorphological evidence and the dearth of datable material7 9 14c dates from the shelly till in pembrokeshire were first thought to indicate an extension of last glaciation ice into the area10 but serious doubts were subsequently raised about the reliability of finite dates on shells of this age range11 12 we present here results of amino acid analysis of shells from recently exposed till and from underlying raised beach remnants at broughton bay west gower total d allo l iso ratios from the raised beach are consistent with analyses on shells from comparative beach remnants elsewhere in south west britain7 13 15 shells of 21 identifiable littoral species extracted from the till suggest inshore marine conditions similar to those at present amino acid ratios from littorina spp provide firm evidence for the encroachment of devensian ice on to gower approximately to the limit suggested by bowen7 fig 1a

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

geological constraints on geophysical models of relative sea level change during deglaciation of the western irish sea basin numerical model predictions of low late devensian sea levels around britain are inconsistent with dated sea level indicators contained in the geological record stratigraphies from the western irish sea basin record high sea levels throughout the last deglacial cycle 21 13 ka bp and onshore ice marginal glaciomarine and marine sedimentation sedimentary evidence emphasizes the role played by delayed isostatic uplift coupled with rapid tidewater evacuation of ice from the basin drumlinization and marine downdraw in the northern irish sea basin records subglacial sediment transfer towards tidewater ice margins and headward extension of ice streams deep into the ice sheet around 14 ka bp

holocene sea levels last glacial maximum glaciomarine environments and geophysical models in the northern irish sea basin uk newly acquired geological records from the isle of man reveal intercalated intertidal and terrestrial sediments that record a relative sea level rise from ca 3 86 m in the early holocene up to a mid holocene maximum between ca 6 6 and 4 5 cal kyr bp at ca 2 25 m when compared with similar marine records from elsewhere in the northern irish sea basin the sea level data confirm a strong north south trend in glacioisostatic loading but little east to west difference in loading this pattern results from the central northern sectors of the british ice sheet over scotland strongly influencing the glacioisostatic downwarping throughout the northern irish sea basin differential ice thicknesses over the irish sea the lake district and ireland did not cause perturbations of local glacioisostatic signatures the holocene marine data in the central irish sea record a slow termination of global eustatic sea level rise during the early holocene geophysical predictions of relative sea level partially constrained by the holocene rsl observations but extrapolated to the last glacial maximum show the potential for shallow marine conditions in the central irish sea basin and in northeast ireland between ca 21 0 16 0 cal kyr bp however glaciomarine deposits in northeast ireland suggest the model relative sea level predictions are too low and require increased ice loading or a thinner lithosphere to generate extra glacioisostatic depression at the time of deglaciation furthermore predicted deglacial relative sea level for northeast ireland does not match the geological record highlighting complex ice margin ocean interaction during deglaciation on the isle of man where glacioisostatic loading is of a similar magnitude to that across northeast ireland the presence of grounded ice inhibited marine incursion during early deglaciation but the occurrence of glaciolacustrine conditions along the ice margin as it moved northwards supports model predictions that relative sea level fell below present during the late glacial early holocene due to rapid glacioisostatic rebound

a dated cave sediment record of pleistocene transgressions on berry head southwest england berry head a limestone headland in torbay southwest england exhibits a series of subaerial marine erosion platforms and raised beaches spanning an altitude range of 97 m solution caves on the headland show preferred horizontal development at elevations that are correlated with the marine erosion platforms and developed in a marine freshwater mixing zone whose position was controlled by high sea level still stands corbridge cave in berry head quarry lies below the raised beaches in torbay and contains evidence of three marine transgressions in the form of fine grained marine ponding deposits with a marine microfauna uranium series dating of intercalated speleothems indicates that a transgression during oxygen isotope stage 5e reached an elevation of 5 8 m od while an earlier transgression probably during stage 7 reached at least 7 2 m od these findings are used to constrain possible interpretations of the aminostratigraphy of raised beaches in southwest britain and a correlation of the unnamed stage of bowen sykes reeves miller andrews brew and hare with oxygen isotope stage 5e is proposed

the fleuve manche the submarine sedimentary features from the outer shelf to the deep sea fans bathymetric seismic and coring surveys have been carried out since the beginning of the 1990s on the outer shelf the slope and the continental rise of the western approaches margin most of the sedimentary features studied belong to a sedimentary system built up since the oligocene and fed by a palaeoriver the fleuve manche that flowed in the english channel during eustatic lowstands a geomorphological map details the spatial distributions of the palaeovalleys on the outer shelf the drainage basin like organised canyons on the slope and the channel levee and lobe complexes on the rise the obvious channel canyon connections and the assessed palaeovalley canyon links demonstrate that the fleuve manche was the single source for terrigeneous fluxes of the armorican deep sea fan when it was one of two sources of the celtic deep sea fan amongst parameters controlling the sedimentation two factors play a major role i subsidence controlled the possibly messinian riverine incision the turbidite activities during lowstands as well as marine infilling of the seawards part of the fleuve manche ii quaternary sedimentary supplies were influenced by the melting ice sheets and the connections with the onshore catchment basins copyright 2003 john wiley sons ltd

the origin of heinrich layers evidence from h2 for european precursor events recent well dated isotopic sr nd fingerprinting of heinrich layer ice rafted detritus ird on the european margin indicates supply from european ice sheets as precursors to laurentide ice sheet lis supply f e grousset et al geology 28 2000 123 126 h snoeckx et al mar geol 158 1999 197 208 these precursorevents lead lis input by up to 1 5 ka f e grousset et al geology 28 2000 123 126 and have been interpreted to indicate lis collapse during heinrichevents stimulated by events originating on the european side of the atlantic f e grousset et al geology 28 2000 123 126 such phasing of ird supply from different sources within heinrich layers therefore has implications for the origin and mechanics of heinrichevents we present evidence here that the ird comprising heinrich layer 2 h2 20 21 14c ka bp on the european continental margin contains detrital campanian upper chalk deriving from bedrock sources eroded on the celtic shelf by the british ice sheet bis in addition to lithic material sourced from the lis high resolution radiocarbon chronology indicates chalk grain deposition as discrete pulses both before and coincident with supply of lis sourced detritus the specificity of the chalk fingerprint to the bis enables a 700 1000 yr lag between the bis and lis events to be identified this phasing indicates a more rapid response of the outlet lobes draining the smaller bis than those draining the lis and implicates external climatic forcing of heinrichevents it is unlikely that this precursorevent represents ird event 18 the recently identified 1 2 ka ird cycle event which immediately precedes h2 because the lag between precursor and main event is here less than 1 5 ka and because such pervasive periodicity is not apparent in european continental margin ird records the later synchroneity between the bis and lis input in h2 identifies glacio eustatic sea level rise associated with lis discharges as a possible feedback mechanism causing destabilisation of ice streams elsewhere during heinrichevents

the late devensian glaciation of the eastern lleyn peninsula north wales evidence for terrestrial depositional environments the glacial deposits of the eastern lleyn peninsula record the advance coalescence and subsequent retreat and uncoupling of welsh and irish sea ice sheets during the late devensian cold stage during advance a thick sheet of basal diamict was deposited over much of the area and during retreat and uncoupling which occurred after 14 5 ka the eastern part of the area was dominated by the formation of a large sandur system draining from the retreating margin of the irish sea ice sheet subsequent stages of retreat are marked by a series of arcuate cross valley moraines formed either by ice contact deposition during stillstand or by structural deformation during minor snout oscillation in the western part of the area sedimentation was controlled by a series of dead ice ridges running parallel to the retreating ice margin and this led to the development of a complex assemblage of localised depositional environments including ice front alluvial fans marginal sandur troughs and pro glacial lake basins all formed under supraglacial ice marginal conditions no evidence of glaciomarine deposition is recorded 1998 john wiley sons ltd

the chronology palaeogeography and archaeological significance of the marine quaternary record of the west sussex coastal plain southern england u k abstract the quaternary sediments of the west sussex coastal plain have produced a wide range of floral faunal and archaeological remains these sediments consist of marine sands and gravels exhibiting transgressive and regressive trends which occur from present day sea level to c 43 0 m o d and are overlain by terrestrial silts and cold climate periglacial sediments at the present day coastline channel fill deposits occur below modern beach levels new field observations coupled with a re investigation of old sites and literature suggest that five discrete high stands of sea level may be preserved in the area of the west sussex coastal plain age estimates for these deposits suggest that they span large parts of the middle and upper pleistocene oxygen isotope stages 13 to 5 conformable relationships between many of the marine and terrestrial sediments suggest that the potential exists within the area to correlate the marine and terrestrial quaternary stratigraphic records in addition sediments associated with two of these high sea level stands are associated with extensive buried landsurfaces covering large areas of the coastal plain at some locations these intact landsurfaces are associated with evidence for human activity and represent stratigraphic and cultural resources of international importance

sea level change in the irish sea since the last glacial maximum constraints from isostatic modelling models of glacio hydroisostatic sea level change have been published for the british isles that are broadly consistent with the observational evidence as well as with glaciological constraints it has been argued however that the models fail to represent sea level change along the irish sea margins and in southern ireland for the post deglaciation period the argument rests on the interpretation of the depositional environment of the elevated irish sea drift on both sides of the irish sea whether this is terrestrial or glaciomarine the isostatic models for the british isles are consistent with the former interpretation in that sea levels on either side of the irish sea south of about the isle of man are not predicted to have risen above present sea level at any time since the deglaciation of the irish sea this implies that ice over both the irish sea and ireland was relatively thin ca 600 700 m over ireland if the glaciomarine interpretation of the elevated irish sea drift is correct then the maximum ice thickness over central and southern ireland would have to reach 2000 m exceeding that over scotland furthermore for the resulting sea level change to be consistent with the holocene evidence this thick ice sheet could not have extended to the eastern side of the irish sea nor could it have been very thick at its northern and western limits if such an ice model is extreme and incompatible with glaciological observations then the alternative is to accept the interpretation of the irish sea drift as terrestrial in origin copyright 2001 john wiley sons ltd

the quaternary history of the central and southwestern celtic sea abstract the british sector of the celtic sea south of the isles of scilly has recently been investigated by the institute of geological sciences igs using several types of bottom sampler and several types of acoustic device by this means the bathymetry has been improved a surface sediment chart constructed and the stratigraphy established by comparison of boreholes with seismic sections a great deal of new information has emerged regarding the late pliocene quaternary history of the area the celtic sea shelf is very wide with a low general gradient and a relatively deep shelf edge the inner shelf is topographically almost featureless whereas the middle and outer shelf are diversified by a series of large tidal sand ridges tsr running approximately normal to the shelf edge the late pliocene quaternary sediments in the area consist of two main formations the late pliocene early pleistocene upper part of the little sole formation and the late devensian early flandrian melville formation both formations appear to be composed predominantly of sand with subordinate gravel and a minor proportion of mud the upper little sole probably consists mainly of fluvial deposits accompanied by subordinate shallow marine deposits in its upper part whereas the melville consists essentially of tidal deposits which have been fashioned probably by the huthnance mechanism into the tidal sand ridges later erosion has developed a gravelly lag pavement layer b across the top of the melville formation and across exposures of upper little sole or older formations between the ridges above this comes a layer of mobile sandy sediment layer a never more than a few metres thick but fashioned in most places into bedforms appropriate to the local current regime these include ripples megaripples sand waves and sand ribbons ice rafting has evidently been responsible for depositing 1 occasional small mounds of material revealed by side scan sonar which are found on the sea bed between the tsr 2 scattered boulders which occur in the normally pebbly lag pavement and 3 scattered outcrops of till revealed by sampling some of which may represent mounds massive marine planation has occurred in the celtic sea shelf area prior to the upper little sole following the deposition of that formation and probably many times during the pleistocene depths of deposition of samples from the upper little sole together with similar data from the almost coeval st erth beds on the cornish mainland indicate that the area has been tilted oceanwards subsidence of the outer shelf area is confirmed by the relatively deep shell edge the most likely mechanism for these displacements appears to be the resolution of large scale gravity anomalies in the asthenosphere