the last british ice sheet a review of the evidence utilised in the compilation of the glacial map of britain this paper reviews the evidence presently available as at december 2003 for the compilation of the glacial map of britain see clark c d evans d j a khatwa a bradwell t jordan c j marsh s h mitchell w a bateman m d 2004 map and gis database of glacial landforms and features related to the last british ice sheet boreas 33 359 375 and http www shef ac uk geography staff clark chris britice html in an effort to stimulate further research on the last british ice sheet and promote a reconstruction of ice sheet behaviour based on glacial geology and geomorphology the wide range of evidence that has been scrutinized for inclusion on the glacial map is assessed with respect to the variability of its quality and quantity and the existing controversies in ice sheet reconstructions landforms interpreted as being of unequivocal ice marginal origin moraines ice contact glacifluvial landforms and lateral meltwater channels and till sheet margins are used in conjunction with available chronological control to locate former glacier and ice sheet margins throughout the last glacial cycle subglacial landforms drumlins flutings and eskers have been used to demarcate former flow patterns within the ice sheet the compilation of evidence in a regional map is crucial to any future reconstructions of palaeo ice sheet dynamics and will provide a clearer understanding of ice sheet configuration ice divide migration and ice thickness and coverage for the british ice sheet as it evolved through the last glacial cycle

relative sea level changes from ne ireland during the last glacial termination deglacial sea level records from ne ireland between 21 and 11 cal ka bp record marine transgressions and sensitive lithospheric responses to ice loading the sawtooth sea level curve contains four intervals characterized by 1 strong net uplift subaerial channelling and a global meltwater pulse 21 19 cal ka bp 2 ice loading isostatic depression and high relative sea level 19 17 5 cal ka bp 3 ice loading renewed isostatic depression and high relative sea level for 1000 years 17 14 5 cal ka bp 4 catastrophic ice wastage rapid uplift and lowstand 14 5 13 cal ka bp geophysical models do not capture these fluctuations

deglacial chronology from county donegal ireland implications for deglaciation of the british irish ice sheet in the north of ireland ice advanced northwards onto the continental shelf from inland centres of dispersion at the last glacial maximum we constrain the timing of three subsequent events by accelerator mass spectrometry 14 c dating of marine microfaunas from muds at corvish county donegal early and rapid deglaciation of the continental shelf off northwestern ireland occurred before 17 1 k 14 c years bp when marine muds formed in trawbreaga bay ice subsequently readvanced into the bay some time between 15 0 and 14 0 k 14 c years bp and compressed contemporary sea stacks and beach cobbles into a ridge at ballycrampsey early deglacial muds were deformed during this ice readvance and redeposited with stratigraphically inverted 14 c ages between 16 0 and 15 2 k 14 c years bp the deformed mud is overlain by undeformed laminae deposited during the final deglaciation of the area after 14 1 k 14 c years bp the early deglaciation in the north at c 17 k 14 c years bp is correlative with deglaciation recorded in the irish sea basin western ireland and northeastern scotland indicating a response of the entire british irish ice sheet to early warming of the north atlantic ocean that resulted in a loss of up to two thirds of its mass subsequent ice sheet readvance between 15 0 and 14 1 k 14 c years bp in the north is part of a widespread response of the british irish ice sheet to heinrich event 1 during the killard point stadial high relative sea levels that accompanied deglaciation at 17 k 14 c years bp and again at 14 1 k 14 c years bp indicate substantial loading and attendant isostatic depression by the british irish ice sheet

surface lowering of limestone pavement as determined by cosmogenic 36cl analysis determination of the rate and total amount of limestone pavement surface lowering is a critical issue in developing models of regional landscape change in limestone terrain erratic capped pedestals have frequently been used for this purpose but problems concerning definition and measurement of pedestal height and the absence of a secure timeframe for erratic emplacement have resulted in conflicting interpretations we have used cosmogenic 36cl to establish the emplacement age of erratic boulders and the total amount of pavement surface lowering at sites in northwest england since erratic emplacement at 17 9 ka the limestone pavement has been lowered by 22 45 cm average 33 10 cm assuming lowering was continuous although indicating some spatial heterogeneity the results contrast with earlier reported values based on the measurement of pedestal heights and inferred age for deglaciation we consider that changes in climate and the character and duration of regolith covers to have been important influences in promoting surface lowering it is argued that nivation chemical and mechanical snow related processes associated with several cool cold periods is likely to have played an important role in surface lowering complicating factors associated with surface lowering thickness and longevity of snow and regolith covers are identified but as yet cannot be quantified copyright 2012 john wiley sons ltd

response to new data for the last glacial maximum in great britain and ireland a scottish perspective on the paper by bowen et al 2002 by a m hall j d peacock e r connell

vertical dimensions and age of the wicklow mountains ice dome eastern ireland and implications for the extent of the last irish ice sheet abstract patterns of erratic distribution show that the wicklow mountains formerly supported an independent ice cap or ice dome geomorphological mapping of the upper limits of evidence for glaciation ice scoured and moulded bedrock perched boulders and the distribution of features indicative of prolonged periglacial conditions tors frost shattered rock blockfields indicates that along the main axis of high ground erosive warm based ice buried all but the highest 725 m summits and over ran adjacent lower peaks and cols the presence of gibbsite in soil samples from above the inferred upper limit of glacial erosion and its absence in all samples from below this limit is consistent with the geomorphological evidence and implies removal of gibbsitic soils below 725 m by glacial erosion during the last glacial stage cosmogenic 10 be exposure ages for rock outcrops above the inferred upper limit of glacial erosion yield pre last glacial maximum lgm ages of 46 9 3 0 ka to 95 9 6 1 ka whereas rock outcrops on summits over ridden by warm based ice give post lgm ages of 18 2 1 2 to 19 1 1 2 ka all geomorphological and dating evidence thus indicates an lgm age for the ice dome the thickness of the ice dome and limited lateral dispersal of erratics indicate that at the lgm the wicklow ice was encircled by and confluent with thick powerful ice streams moving se from the irish midlands and southwards down the irish sea basin this conclusion is irreconcilable with the traditional view that the last irish ice sheet terminated at the south ireland end moraine but consistent with recent proposals that the last ice sheet was much more extensive than previously believed and over ran the south coast of ireland

temporal and spatial correlations between changes in plate motions and the evolution of rifted basins in africa we present the results of a backstripping study incorporating over 200 wells in 14 different basins or groups of basins located on the african interior or continental margins these results presented as mean tectonic subsidence rates averaged over appropriate periods are compared with the opening histories and changes in plate motions of the atlantic and indian oceans and the tethys mediterranean area for seven time steps from the late jurassic until present the results indicate a temporal and spatial correlation between phases of rapid subsidence in african basins and changes in plate motions and therefore are promising in terms of applicability of large scale plate motions in the studies of paleo stresses in sedimentary basins especially at times of initial rifting and formation of subduction zones reactivation of the basins appears to be primarily controlled by the orientation of the basin and underlying basement structures with respect to the stress direction the basins are preferably formed within weaker zones mostly pan african shear zones and the distance from the active plate boundary to the weak zone plays a minor role in whether or not it will be reactivated the presence of three important hot spots which were active during the early stages of break up of gondwana may have been important in preweakening the lithosphere at their sites this may have played an additional role in the localization of the basin deformation

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

the last glacial maximum british irish ice sheet a reconstruction using digital terrain mapping the use of digital terrain mapping in determining the anatomy of the late devensian british irish ice sheet at a resolution of 500 m cell size is illustrated for boulton et al s 1985 and 1991 models and lambeck s 1995 model of the ice sheet at its maximum extent as an independent ice mass area and volume of the ice sheet are given for each model and the spatial pattern of ice thickness shown in maps the analyses show that if no account is taken of topography beneath the ice surface models will seriously overestimate ice volume it is suggested that as reconstructions of the ice sheet improve detailed models of ice thickness at the resolution given in this paper may be of value in determining the contribution of the ice sheet to sea surface changes as well as in determining the effects of ice loading on glacio isostasy neotectonics and possibly on paraglacial processes in areas of high relief copyright 2007 john wiley sons ltd

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

the deglaciation of eastern scotland cosmogenic 10be evidence for a lateglacial stillstand cosmogenic nuclide analysis using 10be has been used to date a lateglacial stillstand in the eastern highlands of scotland at 16 6 13 6 kyr bp the dates constrain the extent of the local cairngorm ice cap and the larger scottish ice sheet at a particular stage during deglaciation the geomorphological and sedimentological evidence suggests that the glacial stillstand persisted for around 1 kyr independent 14c dating from loch etteridge within strathspey shows that deglaciation proceeded rapidly after ca 15 kyr bp critically this study demonstrates that glaciers last occupied the valleys of the cairngorms immediately prior to the lateglacial interstadial bolling allerod contrary to previous assumptions that the last large scale glaciation of the massif took place in the loch lomond stadial younger dryas this later event in the cairngorms was therefore confined to the high corries

pattern of deglaciation of the last late devensian scottish ice sheet evidence from ice marginal deposits in the dee valley northeast scotland the mode of deglaciation of the last scottish ice sheet is assessed from evidence provided by geomorphological mapping and sedimentology ice marginal deposits in the dee valley have a distinctive morphological expression and a characteristically varied sedimentology that strongly resembles those from subpolar glaciers the deposits tend to occur in certain topographic situations which can be accounted for by compression of ice near the margin and formation of an ice cored supraglacial land system a series of recessional stages of the ice front can be mapped demonstrating that active retreat occurred however additional evidence shows there was probably a thin marginal zone of stagnant ice recessional stages are inferred to be stillstands that are considered to be topographically controlled rather than related to climate development of the supraglacial land system during deglaciation suggests that the ice sheet had a polythermal basal regime with a cold based margin this implies that deglaciation took place in northeast scotland while the climate remained cold probably due to a precipitation deficit which agrees well with chronostratigraphic data

radiocarbon constraints on readvances of the british irish ice sheet in the northern irish sea basin during the last deglaciation moraines deposited by the dundalk bay ice lobe record two readvances of the irish ice sheet into the northern irish sea basin during the last deglaciation these readvances overrode and incorporated fossiliferous marine muds from the floor of dundalk bay ams 14c dates from monospecific microfaunas obtained from these muds indicate that the earlier clogher head readvance occurred sometime between 15 0 and 14 2 14c ka bp thus identifying a previously unrecognized ice margin fluctuation in the irish sea basin that is correlative with a readvance in northwest ireland the younger readvance occurred after 14 2 14c ka bp and is equivalent to the killard point readvance identified elsewhere in the irish sea basin these readvances occurred during the oldest dryas cold interval and bracket heinrich event 1 raised marine muds that were deposited between ice readvances require that a substantial ice sheet remained on ireland throughout much of the last deglaciation with attendant isostatic depression of at least 110 m

deglacial history of glacial lake windermere uk implications for the central british and irish ice sheet in the uk a combination of outcrop mapping satellite digital elevation models high resolution marine geophysical data and a range of dating techniques have constrained the maximum limit and overall retreat behaviour of the british and irish ice sheet biis the changing styles of deglaciation have been most extensively studied in the west and north western sectors of the biis primarily using offshore geophysical surveys the surviving record in the southern terrestrial sector is fragmentary permitting only large scale tens of kilometres and longer timescale c 1 ka reconstructions of ice margin movement with limited information on deglacial processes here we present a high resolution study of the retreat behaviour for a section of the southern ice margin from windermere in the the lake district using high resolution 2d multi channel seismic mcs data processed using prestack depth migration by combining the seismic stratigraphy with landform morphologies extant cores and seismic velocity measurements we are able to distinguish between over consolidated till recessional moraines de geer moraines flowed till ice front fan supra en glacial melt out till and subsequent glaciolacustrine lacustrine sedimentation the results reveal a complex and active valley glacier withdrawal from windermere that changed character between basins and produced two small localised areas of ice stagnation and downwasting this study indicates that similar active ice margin retreats probably took place in other valleys of the lake district during the late devensian deglaciation rather than the previously held view of rapid ice stagnation and downwasting when combined with the regional terrestrial record this supports a model of early ice loss in terrestrial england compared to other parts of the united kingdom

new data on speleothem deposition and palaeoclimate in britain over the last forty thousand years 230th 234u dates are presented for 26 speleothems from three areas in britain assynt n w scotland n w yorkshire mendip hills somerset these dates suggest that speleothem growth was widespread but rare in the period from 40 to 26 ka absent from 26 to 15 ka and abundant from 15 ka to the present the absence of speleothems between 26 and 15 ka is attributed to glaciation in yorkshire and assynt and tentatively to continuous permafrost development in the mendip hills the occurrence of speleothems before 26 ka places restrictions on the extent of any ice sheet which may have been present in scotland and indicates that n w scotland was not subjected to continuous permafrost at that time

tectonic setting of the bela ophiolites southern pakistan abstract the bela ophiolites consist of a 3 5 km thick sequence of basaltic pillow lava inter flow sedimentary rocks chert argillite limestone and diabase gabbro sills debris of serpentinite up to kilometer sized blocks serpentinite carbonate breccia and less commonly of basalt gabbro peridotite pelagic limestone and their metamorphic equivalents occur throughout the ophiolite sequence and may form extensive horizons the age of the ophiolites as indicated by pelagic microfauna is aptian early maestrichtian the lava flows belong to a spilite keratophyre basaltic andesite suite of tholeiites enriched in fe tio 2 and other trace elements the lava flows although similar to the e type morb differ in details such as la ta ratio ranges 9 62 18 04 for the bela lavas versus 10 15 for the morb the diabase gabbro sills are similar to the associated lava flows however due to their relative enrichment in certain elements e g fe ti hf th and ta etc they may represent more fractionated late melts a comparison of the stratigraphic and structural features of the bela ophiolites with modern oceanic environments reveals that these ophiolites probably originated in a large oceanic fracture zone leaky transform this is based on lithotectonic features such as the common occurrence of debris of foliated serpentinite and serpentinite carbonate breccia bearing rocks in the ophiolite sequence and on geodynamic considerations the fracture zone ancestral to the bela ophiolites probably acted as a boundary between the indian and the neo tethys plates during the cretaceous analogous to the present day owen fracture zone which separates the indian and the arabian plates this ancestral fracture zone was destroyed when transform movement gave way to oblique convergence culminating in the ophiolite obduction in paleocene early eocene time the ophiolite obduction on the west indian continental margin was preceded by alkaline wpb type volcanism which is represented by the porali basalts the bibai lavas and the deccan basalts

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

an mis 3 age organic deposit from balglass burn central scotland palaeoenvironmental significance and implications for the timing of the onset of the lgm ice sheet in the vicinity of the british isles this paper reports the analysis of a glaciotectonised organic deposit located between a lower weathered till and an upper unweathered till at balglass burn north of the campsie fells in central scotland uk close to the centre of ice accumulation in scotland sedimentology pollen macroscopic plant remains and coleoptera indicate accumulation in a small pond as part of an open tundra landscape with low floral diversity mcr palaeotemperature reconstructions for the coleoptera give a mean temperature for the warmest and the coldest months of 8 to 10 c and 26 to 10 c respectively indicating the presence of at least discontinuous permafrost six ams dates on carex fruit and coleoptera fragments give ages between 34 480 and 28 050 14c yr bp ca 39 8 to ca 32 8 cal yr bp fairbanks et al 2005 the upper till and the glaciotectonism are attributed to glaciation during the lgm glaciotectonic deformation means that the ages do not indicate sequential development and it is not possible to relate this palaeo evidence to the fine resolution palaeoclimatic signature for mis 3 however the fact that this part of central scotland was ice free at this time means that some recent proposals suggesting that the british ice sheet began to accumulate around the middle of mis 3 are unlikely to be correct copyright 2006 john wiley sons ltd

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

the donegal ice dome northwest ireland dimensions and chronology geomorphological evidence indicates that donegal was formerly occupied by an ice dome that extended offshore to the west northwest and north and was confluent with adjacent ice masses to the east and south erosive warm based ice over rode almost all the highest mountains implying an ice divide altitude greater than 700 m only six peripheral summits escaped glacial modification implying either that they remained above the ice surface as nunataks or supported a thin cover of protective cold based ice gibbsite a pre last glacial weathering product is preferentially represented on summits that escaped glacial modification cosmogenic 10be exposure ages of 18 6 1 4 to 15 9 1 0 k yr for coastal sites confirm that donegal ice extended offshore at the last glacial maximum reconstruction of the form of the donegal ice dome suggests a former minimum ice thickness of 500 m close to the present coastline in the west and northwest and 400 m near the coast of the inishowen peninsula in the north with the ice extending at least 20 km across the adjacent shelf to the west and northwest copyright 2007 john wiley sons ltd

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

a revised model for the last deglaciation of eastern scotland accelerator mass spectrometry 14 c ages on monospecific marine microfauna from raised mud record initial deglaciation of the eastern coast of scotland before 21 0 cal ka bp two subsequent ice margin readvances occurred prior to the loch lomond advance and are identified from ice contact deposits overlying marine mud the lunan bay readvance dates to 20 2 cal ka bp and possibly 18 2 cal ka bp the younger perth readvance occurred between c 17 5 cal ka bp and 14 5 10 be ka within dating uncertainties these readvances are similar in age to ice margin fluctuations documented from the irish sea basin and northwestern ireland and record three near synchronous fluctuations of much of the british irish ice sheet margin during the last deglaciation suggesting a common response to regional climate forcing

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

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

palaeoclimate determination from cave calcite deposits calcite deposits formed in limestone caves have been found to be an excellent repository of palaeoclimatic data for terrestrial environments the very presence of a relict deposit indicates non glacial conditions at the time of formation and both 14c and uranium series methods can be used to date the deposit and hence the age of these climatic conditions variations in 13c and 18o content of the calcite in 2h and 18o content of fluid inclusions in trace element concentrations and more recently in pollen assemblages trapped in the calcite are all potentially available as synchronous palaeoclimatic indicators previous work has tended to concentrate mainly on abundance of deposits as a palaeoclimatic indicator for the last 300 000 years this literature is briefly reviewed here together with the theory and methods of analysis of the u series and stable isotopic techniques the combined use of u series ages and 13c and 18o variations in cave calcites illustrates the potential for palaeoclimate determination previously unpublished results of stable isotopic variations in dated calcites from caves in northern england indicate the level of detail of stable isotopic variations and time resolution that can be obtained and the complexity of interpretation that may arise tentative palaeoclimatic signals for the periods 90 125 ka and 170 300 ka are presented more comprehensive studies are needed in future work especially in view of the difficulty in obtaining suitable deposits and the ethics of cave deposits conservation

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

flora fauna and climate of scotland during the weichselian middle pleniglacial palynological macrofossil and coleopteran investigations thin lenses of organic rich material on the upper surface of a layer of glacio fluvial deposits have been studied in an open cast coal mine near sourlie western scotland radiocarbon dates on antler fragments plant debris and bulk organic matter from silt showed that the sediments accumulated between ca 33 500 and 29 000 14c yr bp during a period when this part of western scotland was free of glaciers the organic rich sediments yielded a very rich flora and fauna and in total about 160 plant taxa and 61 coleopteran taxa were recorded together with other invertebrates the sourlie flora is one of the richest late middle weichselian floras yet studied within the british isles leg bones of coelodonta antiquitatis woolly rhinoceros and rangifer tarandus reindeer were also found at the site during this period the landscape was treeless and the vegetation could be characterised as an intermediate between a low shrub tundra and sedge grass moss tundra both the flora and arthropod fauna suggest that during formation of the organic rich layers at sourlie mean july temperatures were 9 10 c the flora suggests also that at the beginning of formation of these layers minimum mean july temperatures increased from 7 to 9 10 c but later dropped again to 7 8 c a possible time correlation with one of the warmer periods of the dansgaard oeschger cycles in the stable oxygen isotope record of the greenland ice cores during this period is proposed the arthropod fauna suggests that mean january temperatures were somewhere between 34 and 11 c mean annual temperatures lay probably between 1 and 10 c which implies the possible presence of discontinuous or continuous permafrost in the area during winter a protective snow cover of varying thickness probably enabled perennial plants especially shrubs to survive

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

comment and reply on glaciomarine sediments of the isle of man as a key to late pleistocene stratigraphic investigations in the irish sea basin

dimensions and deglacial chronology of the outer hebrides ice cap northwest scotland implications of cosmic ray exposure dating cosmic ray exposure ages of frost weathered bedrock from mountain summits in the outer hebrides exceed the age of late devensian glaciation exposure ages of most glacially abraded bedrock surfaces at low and intermediate elevations are younger than the age of maximum late devensian glaciation these results confirm that previously mapped periglacial trimlines in the outer hebrides define the upper limit of bedrock erosion by late devensian ice they are consistent with the interpretation based on geomorphological evidence that the trimlines mark the approximate upper limit of a late devensian outer hebrides ice cap a postglacial exposure age from the summit of oreval 662 m suggests that this mountain was overrun during the last glaciation indicating thicker ice cover and a lower surface gradient west of the ice cap divide than previously inferred although bedrock surfaces below the trimlines are strongly ice moulded some show evidence of prior cosmic ray exposure which we attribute to limited erosion during late devensian glaciation if this interpretation is correct the youngest apparent ages from these surfaces give the most reliable dates for deglaciation at ca 14 5 14 ka this implies that ice persisted at favourable sites through the warm opening phase of the windermere interstade comparison with radiocarbon dated evidence from offshore cores suggests net ice margin retreat of 74 km eastwards across the adjacent shelf in 2 3 1 0 ka the dating evidence is consistent with relatively rapid retreat of calving margins to the coast then slower withdrawal of ice margins to high ground copyright 2005 john wiley sons ltd

the greenland ice core chronology 2005 15 42 ka part 2 comparison to other records a new greenland ice core chronology gicc05 based on multi parameter counting of annual layers has been obtained for the last 42 ka here we compare the glacial part of the new time scale which is based entirely on records from the northgrip ice core to existing time scales and reference horizons covering the same period these include the grip and northgrip modelled time scales the meese sowers gisp2 counted time scale the shackleton fairbanks grip time scale sfcp04 based on 14c calibration of a marine core the hulu cave record three volcanic reference horizons and the laschamp geomagnetic excursion event occurring around greenland interstadial 10 gicc05 is generally in good long term agreement with the existing greenland ice core chronologies and with the hulu cave record but on shorter time scales there are significant discrepancies around the last glacial maximum there is a more than 1 ka age difference between gicc05 and sfcp04 and a more than 0 5 ka discrepancy in the same direction between gicc05 and the age of a recently identified tephra layer in the northgrip ice core both sfcp04 and the tephra age are based on 14c dated marine cores and fixed marine reservoir ages for the laschamp event gicc05 agrees with a recent independent dating within the uncertainties

evidence for heinrich event 1 in the british isles in the north irish sea basin isb sedimentary successions constrained by ams 14c dates obtained from marine microfaunas record three major palaeoenvironmental shifts during the last deglacial cycle i marine muds cooley point interstadial dated to between 16 7 and 14 7 14c kyr bp record a major deglaciation of the isb following the late glacial maximum lgm ii terminal outwash and ice contact landforms killard point stadial were deposited during an extensive ice readvance which occurred after 14 7 14c kyr bp and reached a maximum extent at ca 14 14c kyr bp at this time the lowlands surrounding the north isb were drumlinised coeval flowlines reconstructed from these bedforms end at prominent moraines killard point bride st bees and indicate contemporaneity of drumlinisation from separate ice dispersal centres substrate erosion by fast ice flow and subglacial sediment transfer to ice sheet margins in north central ireland bed reorganisation associated with this fast ice flow phase involved overprinting and drumlinisation of earlier transverse ridges rogen type moraines by headward erosion along ice streams that exited through tidewater ice margins this is the first direct terrestrial evidence that the british ice sheet bis participated in heinrich event 1 h1 iii regional mud drapes directly overlying drumlins record high relative sea level rsl with stagnation zone retreat after 13 7 14c kyr bp rough island interstadial elsewhere in lowland areas of northern britain ice marginal sediments and morainic belts record millennial scale oscillations of the bis which post date the lgm advance on to the continental shelf and pre date the loch lomond stadial younger dryas advance in the highlands of western scotland ca 11 10 14c kyr bp in western northwestern and northern ireland killard point stadial h1 ice limits are reconstructed from ice flow lines that are coeval with those in the north isb and end at prominent moraines on the scottish continental shelf possible h1 age ice limits are reconstructed from dated marine muds and associated ice marginal moraines it is argued that the last major offshore ice expansion from the scottish mountains post dated ca 15 14c kyr bp and is therefore part of the h1 event in eastern england the stratigraphic significance of the dimlington silts is re evaluated because evidence shows that there was only one major ice oscillation post dating ca 18 14c kyr bp in these lowlands in a wider context the sequence of deglacial events in the isb widespread deglaciation of southern part of the bis major readvance during h1 ice sheet collapse is similar to records of ice sheet variability from the southern margins of the laurentide ice sheet lis well dated ice marginal records however show that during the killard point readvance the bis was at its maximum position when retreat of the lis was well underway this phasing relationship supports the idea that the bis readvance was a response to north atlantic cooling induced by collapse of the lis 1998 john wiley sons ltd

late devensian and flandrian palaeoenvironmental changes on the scottish continental shelf west of the outer hebrides examination of two radiocarbon dated vibrocores taken from south of st kilda at a water depth of about 155 m a short distance within the maximum position of the late devensian dimlington stadial ice sheet suggests that the st kilda basin became free of glacier ice after 15250 yr bp sedimentation in a shallow low energy high arctic muddy environment continued until after 13500 yr bp there followed a higher energy temperate episode during which water depths were roughly about 40 m this is correlated with the latter part of the windermere interstadial and with the warmer interval known in shallow scottish seas about or a little before 11 000 yr bp the loch lomond younger dryas stadial is marked in the vibrocores by the return of muddy sediments and a cold water fauna relatively shallow water conditions seem to have persisted into the earliest flandrian when the water depth was still roughly 60 m corresponding to a sea level in the area 90 100 m below present it is suggested that pack ice was widespread in the northeast atlantic before the windermere interstadial and also during the loch lomond stadial when it transported shards of icelandic volcanic ash into the st kilda basin estimates of sea surface temperature for the last part of the windermere interstadial are close to those derived from the deep sea record for the same period

people and large carnivores as biostratinomic agents in lateglacial cave assemblages biostratinomic analysis processes acting between death and burial of lateglacial mammal bone assemblages from three caves in northern england demonstrates the value of re examining archived assemblages with ams radiocarbon dating of key specimens these assemblages shed light on the ecology of a region at the northern limit of lateglacial human activity in britain during the lateglacial interstadial bears wolves and humans expanded into the region bears by around 12 500 14c yr bp and the earliest evidence for human presence is around 12 300 14c yr bp at victoria cave wolf activity included predation and scavenging of large ungulates and scavenging bear carcasses apparently resulting from hibernation deaths the scavenging of bear carcasses is possibly confined to the first part of the lateglacial interstadial whereas evidence for wolf scavenging large ungulates increases later in the interstadial after about 11 800 14c yr bp perhaps reflecting changes in the productivity of the lateglacial ecosystem and in human subsistence patterns the assemblage from sewell s cave is wolf den debris from the very end of the lateglacial interstadial around 10 800 14c yr bp whilst that from kinsey cave is dominated by large bodied carnivores and is argued to have a quite different taphonomic history copyright 2007 john wiley sons ltd

ice margin oscillations during deglaciation of the northern irish sea basin we present a new chronology to constrain ice margin retreat in the northern irish sea basin estimates on the timing of ice thinning derived from surface exposure ages for boulders from the summits of the isle of man and south west cumbria suggest that ice thinning was commensurate with the rapid retreat that followed the short lived advance of the irish sea ice stream isis to maximum limits in the celtic sea this ice retreat in the northern irish sea basin was fastest at 20 ka in response to a wider calving margin but slowed as ice stabilized and oscillated against the isle of man we provide the first age constraints for the scottish readvance 19 2 18 2 ka and demonstrate that it was a potentially regional event across the isle of man and cumbrian lowlands not linked with heinrich event 1 after the scottish readvance the ice front retreated northwards towards the southern uplands of scotland at the same time as climate north of 45 n warmed in response to summer insolation this sequence demonstrates the importance of internal dynamics in controlling ice retreat rates in the irish sea but also that deglaciation of the northern irish sea basin was a response to climate warming

late cretaceous early tertiary convergence between the indian and arabian plates recorded in ophiolites and related sediments abstract remnants of ocean floor forming the eastern ophiolite belt in oman and the western ophiolite belt in pakistan have a common plate tectonic history culminating in emplacement at the cretaceous tertiary boundary fragments of ocean floor in these two belts have ages between 150 and 65 ma and recorded tectonic events in the early indian ocean at 150 ma 130 120 ma 110 100 ma and 70 65 ma new radiometric and chronostratigraphic ages and paleomagnetic and sedimentary information are used to relocate these ophiolites in the frame of the evolving indian ocean which was characterised by the stepwise breakup of gondwana at 158 ma east and west gondwana 130 ma southern atlantic breakup of east gondwana 95 84 ma madagascar and india seychelles 65 ma india and seychelles and finally at 40 ma rifting between africa and arabia the 150 ma old oceanic rocks of masirah island in oman originally formed the extension of the basins now preserved along the eastern edge of the afro arabian plate masirah drifted together with india seychelles when a new ridge formed at approximately 130 ma separating microplates e g kabul block from the northern edge of greater india parts of this new ocean were later emplaced to form the western ophiolite belt in pakistan consumption of oceanic crust and emplacement of ophiolites during the closure of the neotethys occurred not only north of india seychelles but also along two or three subduction zones between the afro arabian plate and india seychelles documented by the formation of metamorphic soles beneath ophiolites relics of ocean floor formed approximately 65 70 ma ago now form the upper units in the western ophiolite belt of pakistan where they overlie an accretionary prism of pillow lavas of dominantly aptian albian age and sedimentary rocks the breakup of india and the seychelles at 65 ma was associated with the eruption of flood basalts deccan and seychelles and enhanced counter clockwise movement of india this breakup possibly caused the late jurassic early cretaceous fragments of ocean floor e g masirah to be thrust onto the eastern edge of oman the ophiolites which were emplaced onto the western edge of india drifted as part of this plate farther north where collision with eurasia and the accreted microplates occurred in the eocene 55 ma

rates of cave and landform development in the yorkshire dales from speleothem age data uranium series ages have been obtained for 87 speleothems collected from nine major cave systems in the craven district of northern england large systems such as ease gill caverns the west kingsdale caves and gaping gill ingleborough cave which contain relict high level tunnels are found to be older than 350 000 years the limit of the 230th 234u dating method there is little evidence to indicate a significant enlargement of these passages since this time estimates of the age of victoria cave from 234u 238u isotopic ratios suggest that the cave has been fully relict for more than 500 000 years ages of in situ speleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr these rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets using the present elevation of caves with respect to adjacent valley floor levels mean maximum valley entrenchment rates are found to range between 5 cm ky and 20cm ky which corresponds to 6 m to 24 m of lowering per glacial interglacial cycle these rates suggest that upper beds of the limestone were incised to form the yorkshire dales between 1 and 2 million years ago the results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the literature

temporal constraints for the late wisconsinan deglaciation of western canada using eolian dune luminescence chronologies from alberta abstract the laurentide ice sheet lis covered most of canada during the last glacial maximum sometime after 20 cal ka bp the lis began to recede from western canada and by 11 cal ka bp it had retreated from most of the province of alberta due to the scarcity of datable contemporaneous organic materials the precise timing of the retreat of the ice sheet from the region remains poorly constrained so that the chronology of the sequential positions of the ice sheet margin between 20 and 11 cal ka bp is largely tentative in this study we use luminescence dating of postglacial eolian deposits sourced primarily from glaciolacustrine and deltaic sediments in central and northern alberta to provide an updated chronology for the retreat of the lis from the region we examine 14 new and 13 previously published quartz optically stimulated luminescence osl ages as well as 19 previously published k feldspar infrared stimulated luminescence ages the chronologies are used to constrain successive regional ice sheet margin positions that are geomorphically recognizable across the region between 16 and 11 ka calendar years these data suggest that the lis may have retreated from central alberta earlier than portrayed in radiocarbon derived deglaciation models we propose that the osl chronology from postglacial dunes constrains the deglaciation of the region more accurately because luminescence dating does not rely on the development of vegetation to produce material for dating implications for the revised chronology include an improved timing of the emergence of an ice free corridor that may have been used for paleoindian migration into the americas as well as enhanced age constraints on when meltwater drainage routes to the arctic became open in relationship to the younger dryas the chronology could also provide improved constraints for geophysical models that reconstruct regional isostatic rebound which followed deglaciation

high resolution seismic imaging of a younger dryas and holocene mass movement complex in glacial lake windermere uk the stratigraphy and sedimentological processes operating over the last 15 000 years within glacial lake windermere uk at the mouth of cunsey beck were imaged by a decimetre resolution seismic reflection survey a complex of fifteen mass movement deposits was identified as contemporaneous with the younger dryas and two within the overlying holocene drape the high vertical resolution and dense grid of profiles allowed pseudo three dimensional mapping of individual events along with the determination of their relative temporal relationships the size of the mass wasting deposits has been estimated to range between 2100 and 100 000 m3 the geometry structure and relationship to the existing stratigraphy suggest a rapid emplacement of the younger dryas mass movement deposits facilitated by climatic changes making subaqueous slopes unstable with possible triggering by seismic activity morphometric parameters such as volume and planar surface area indicate a greater mobility of the younger dryas mass movement deposits compared to the holocene events the sediments of all imaged mass movement deposits are believed to originate from the slope deposits of the lake the age of two holocene mass movement deposits triggered by flooding or terrestrial debris flows is estimated to be 2400 and 4400 years bp

optically stimulated luminescence osl dating of loessic sediments and cemented scree in northwest england optically stimulated luminescence osl dates are reported for silts and very fine sands believed to be loessic sediments from northwest england at three sites loessic sediments were initially interpreted as primary aeolian deposits and at two other sites as loess incorporated into the matrix of cemented scree however the results of osl dating indicate a more complex pattern of accumulation than originally hypothesized and have prompted reconsideration of these materials whatever the process es and underlying cause s it is evident that significant amounts of soil erosion occurred on the limestone uplands earlier than previously thought all but one of the ages fall entirely within the holocene period and suggest that these deposits contain reworked rather than primary loess four of the five sites are characterized by non gaussian dose distributions and consequently equivalent doses have been estimated using a range of appropriate age models the implications of differences in the ages derived f

radiocarbon dating of irish sea sediments abstract radiocarbon dating has been carried out on three cores from areas of muddy sediments in the n irish sea to estimate rates of sediment accumulation 14c age profiles of the two eastern basin cores revealed a near constant age from the sediment surface to the base of the core 12 500 1000 years bp the 14c age profile of the western basin core revealed a zone of apparent mixing to a depth of 55 cm underlain by a zone of constant sedimentation rate 0 018 cm y 1 to 160 cm these data are discussed in relation both to previously reported sedimentological studies of the area and to the authorised discharges of low level radioactive waste from the sellafield nuclear fuel reprocessing plant

dimensions and chronology of the last ice sheet in western ireland abstract on the mountains of western ireland the upper limit of glacial evidence descends from 730 m in the connemara mountains to 400 m on achill island this limit is interpreted as a trimline marking the upper limit of erosive warm based ice implying that higher summits remained above a former ice sheet as nunataks or supported a cover of cold based ice significantly greater representation of gibbsite in soils above the trimline indicates that it relates to the last glacial stage 10 be exposure ages for bedrock samples above the trimline fall within the range 36 0 2 3 ka to 61 6 4 0 ka whereas ice scoured bedrock below the trimline yielded 10 be exposure ages 24 0 1 6 ka and in all but two cases 17 2 1 1 ka consistent with deglaciation after the lgm reconstruction of the minimum altitude of the lgm ice surface implies that inland ice was diverted northwestwards by an ice dome on the connemara mountains and extended at least 25 km offshore this evidence conflicts with previous accounts that place the lgm ice limit onshore and implies that recent models underestimate lgm ice thickness in western ireland

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

ams c 14 dating of deglacial events in the irish sea basin and other sectors of the british irish ice sheet sedimentary sequences deposited by the decaying marine margin of the british irish ice sheet biis record isostatic depression and successive ice sheet retreat towards centres of ice dispersion radiocarbon dating by accelerator mass spectrometry ams of in situ marine microfaunas that are commonly associated with these sequences constrain the timing of glacial and sea level fluctuations during the last deglaciation enabling us to evaluate the dynamics of the bus and its response to north atlantic climate change here we use our radiocarbon dated stratigraphy to define six major glacial and sea level events since the last glacial maximum 1 initial deglaciation may have occurred 18 3 kyr c 14 bp along the northwestern irish coast in agreement with a deglacial age of similar to 22 cl 36 kyr bp for southwestern ireland ice retreated to inland centres and areas of transverse moraine began to form across the north irish lowlands 2 channels cut into glaciomarine deglacial sediments along the western irish sea coast are graded to below present sea level identifying a fall of relative sea level rsl in response to isostatic emergence of the coast 3 marine mud that rapidly infilled these channels records an abrupt rise in global sea level of 10 15 m similar to 16 7 c 14 kyr bp that flooded the irish sea coast and may have triggered deglaciation of a marine based margin in donegal bay 4 intertidal boulder pavements in dundalk bay indicate that rsl similar to 15 0 c 14 kyr bp was similar to present 5 a major readvance of all sectors of the biis occurred between 14 and 15 kyr 14 c bp which overprinted subglacial transverse moraines and delivered a substantial sediment flux to tidewater ice sheet margins this event the killard point stadial indicates that the bus participated in heinrich event 1 6 subsequent deposition of marine muds on drumlins 12 7 c 14 kyr bp indicates isostatic depression and attendant high rsl resulting from the killard point readvance these events identify a dynamic biis during the last deglaciation as well as significant changes in rsl that reflect a combination of isostatic loading and eustatic changes in global sea level c 2005 elsevier ltd all rights reserved

mass spectrometric dating of flowstones from stump cross caverns and lancaster hole yorkshire palaeoclimate implications a terrestrial flowstone sequence 97 cm thick from stump cross caverns yorkshire has been dated by both mass spectrometric and alpha spectrometric 238u 234u 230th dating and is demonstrated to have been deposited predominantly during interstadial periods over the last 170 ka with no growth in periods of glaciation or within the oxygen isotope stage 5 interglacial growth also occurs within oxygen isotope stages 4 and 6 the former possibly correlating with interstadials recognised in high resolution ice and ocean core records comparison with the timing of growth of a mass spectrometrically dated lancaster hole flowstone also from the same region demonstrates only limited agreement these differences are due to two factors limiting deposition at stump cross flooding of the cave passage in warm periods and the development of continuous permafrost or glacier cover in periods of severe climatic deterioration deposition at lancaster hole was controlled by limitations in ground water supply rather than flooding of the cave passage the results presented here demonstrate that in addition to regional palaeoclimate factors local site conditions may limit speleothem growth we conclude that in future palaeoclimate studies the growth record from several coeval speleothem samples must be considered before a regional palaeoclimate interpretation can be made

tectonics and structural zonation of southern tibet china the yarlung zangbo suture zone is composed of several thrust sheets with distinct stratigraphies states of deformation and metamorphic grades successive deformations have been produced by persistent north south shortening since obduction of the ophiolites by late cretaceous palaeocene times a possible decoupling of the crust may be associated with the intracontinental thrust system which has formed in the subducted indian plate this article emphasizes the role of shear deformations in the building of a collision belt

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

tectonic geomorphology of the southern sierra nevada mountains california evidence for uplift and basin formation hypotheses regarding uplift of the sierra nevada mountains sierra california usa vary from a single slowly tilting block to rapid pliocene and or quaternary uplift in the south exclusively to test these hypotheses we examined geomorphic indices of the western sierra we interpret longitudinal profiles of the larger westerly flowing rivers mountain front sinuosity valley floor to width to height ratio and relief ratio to show that relative tectonic activity is greater in the southern sierra near the kern river gorge fault the sierra range crest profile indicates that the increased tectonism is related to more recent uplift in the southern sierra only westward migration of basin and range extension is consistent with the locus of uplift in the southern sierra we hypothesize that the sierra topography is the result of pliocene delamination related uplift in the central sierra and post pliocene interaction of the san andreas garlock and sierra nevada frontal fault zones

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

the greenland ice core chronology 2005 15 42 ka part 1 constructing the time scale the greenland ice core chronology 2005 gicc05 is extended back to 42 ka b2k before 2000 ad i e to the end of greenland stadial 11 the chronology is based on independent multi parameter counting of annual layers using comprehensive high resolution measurements available from the north greenland ice core project ngrip these are measurements of visual stratigraphy conductivity of the solid ice electrolytical melt water conductivity and the concentration of na c a 2 s o 4 n o 3 n h 4 a n uncertainty estimate of the time scale is obtained from identification of uncertain annual layers which are counted as 0 570 5 years the sum of the uncertain annual layers the so called maximum counting error of the presented chronology ranges from 4 in the warm interstadial periods to 7 in the cold stadials the annual accumulation rates of the stadials and interstadials are on average one third and half of the present day values respectively and the onset of the greenland interstadials 2 3 and 8 based on 20 year averaged d 18 o

wolverine in northern england at about 83 000 yr b p faunal evidence for climatic change during isotope stage 5 abstract cave sediments from stump cross cave in northern england contain pleistocene mammal remains uranium series dating of calcium carbonate deposits closely associated with the fossiliferous horizons has established an absolute age of 83 000 6000 yr b p for a faunal assemblage largely comprised of wolverines gulo gulo this date lies firmly within the younger portion of oxygen isotope stage 5 the occurrence of wolverines in the vicinity of stump cross cave at ca 83 000 yr b p indicates a significant climatic deterioration from ca 120 000 yr b p when an ipswichian interglacial fauna with hippopotamus was present in this part of northern england

surface exposure dating 36cl and 10be of post last glacial maximum valley moraines lake district northwest england some issues and implications surface exposure ages 36cl and 10be have been obtained from 16 boulders at the margins of and within the limits of former valley glaciers at four sites in the lake district northwest england the established view is that the lake district functioned as an independent centre of ice dispersal during the last glacial maximum lgm 26 21 ka of the dimlington stade greenland stades 2 3 and that the glacial depositional landforms at the sampled sites are products of stillstands or readvances of the ice margins following the lgm however several of the apparent 36cl surface exposure ages pre date rather than post date the lgm it is inferred that these boulders retain levels of 36cl inherited from a previous period of exposure rather than indicating moraine formation prior to the lgm and their subsequent survival beneath lgm ice an implication is that lake district glaciers achieved limited erosion of bedrock during the build up to and at the maximum of the lgm and that glacial erosion rates increased at a late stage in that period single 36cl and 10be exposure ages from two sites suggest a stillstand or readvance of valley glaciers prior to the loch lomond younger dryas stade lls greenland stade 1 and windermere lateglacial interstade greenland interstade 1 but additional ages are required in order to confirm or refute these individual ages an lls age for glacial depositional landforms at both these sites had previously been proposed 36cl surface exposure ages for boulders on moraines within the lls limit do not fully support emplacement at that time there is a possibility that these moraines are associated with a pre lls stillstand or readvance of the valley glacier copyright 2013 john wiley sons ltd

reply to the comments of faulkner on wilson et al 2012 surface lowering of limestone pavement as determined by cosmogenic 36cl analysis earth surface processes and landforms 37 1518 1526

equivalent dose determinations for polymineralic fine grains using the sar protocol application to a holocene sequence of the chinese loess plateau abstract a single aliquot regenerative dose sar protocol involving stimulation of the same disc with an infra red laser diode followed by blue leds was applied to polymineralic fine grains infra red stimulated luminescence irsl and post ir optically stimulated luminescence osl ages are presented for a series of 19 fine grain 4 11 m samples taken from a loess section duowa in the western chinese loess plateau there are significant differences between the equivalent doses and thus the ages for the irsl and post ir osl measurements three potential explanations are investigated incomplete bleaching prior to deposition thermal transfer of charge and initial sensitivity change the question regarding which sequence of ages ir or post ir osl is correct if either is not resolved although the 19 post ir osl ages yield more consistent results it is proposed that the double sar protocol employed may not be correctly monitoring the sensitivity changes relating to either or both natural signals

a late pleistocene intertidal boulder pavement from an isostatically emergent coast dundalk bay eastern ireland late pleistocene sequences around dundalk bay eastern ireland record glaciomarine sedimentation near the margin of a grounded ice lobe around 15 ka sp a coastal exposure at cooley point consists of four major facies deposited outside this ice limit 1 a basal mud facies deposited from sediment plumes accumulated following the initial ice marginal retreat inland it contains a well preserved arctic microfauna dominated by the foram elphidium clavatum and the ostracod roundstonia globulifera 2 a flat to undulating boulder facies pavement mostly one clast thick is found pressed into the mud and is characterized by bevelled and striated upper clast surfaces pavement attributes are a result of intertidal activity in a cold climate the boulder source is due to rafting by ice flees from glacigenic debris deposited during an ice advance 3 laminated sand facies drape the pavement and are a result of variable current activity 4 the overlying gravel facies is separated from the sand facies by a marine erosion surface the gravel facies is subaqueous channelized and is overlain by late glacial raised beach ridges locally the gravels have been deformed by ice pressure from partially floating ice flees facies changes record terrestrial submergence and provide evidence for changes in relative sea level during part of the last deglacial cycle the boulder pavement and deformed gravel facies suggest that ice flees and sea ice effects may be more common within stratigraphies along emergent coasts than previously thought though they have a low preservation potential extreme conditions during the deglacial favoured opportunistic microfaunas during mud deposition this event may be related to a major meltwater event within the irish sea basin