overdeepened quaternary valleys in the eastern danish north sea morphology and origin abstract a system of 100 350 m deep overdeepened and buried valleys has been mapped in the eastern danish north sea individual valleys can be traced for several tens of kilometres and valleys generally begin and terminate abruptly a correlation to buried valleys onshore southwest denmark is possible the valleys post date glaciotectonic structures and are interpreted to be elsterian and possibly saalian in age the origin of valleys in the eastern danish north sea is explained by repeated cycles of sub glacial down cutting of meltwater channels and channel closure due to ice creep eventually producing deeply incised valleys glacial erosion may have been significant in cases where valleys are broad and shallow the origin of overdeepened quaternary valleys in general can be attributed to a combination of three end member processes i steady state drainage of meltwater ii catastrophic outbursts of meltwater and iii glacial erosion the main requirement for sub glacial valley formation is the presence of a melting ice sheet overlying a poorly consolidated substrate permeability variations of the substrate may produce subregional variations in the pattern of valley incision while pre glacial rivers faults or salt structures are of local importance only

the sequence and timing of large late pleistocene floods from glacial lake missoula abstract glacial lake missoula formed when the purcell trench lobe of the cordilleran ice sheet dammed clark fork river in montana during the fraser glaciation marine oxygen isotope stage 2 over a period of several thousand years the lake repeatedly filled and drained through its ice dam and floodwaters coursed across the landscape in eastern washington in this paper we describe the stratigraphy and sedimentology of a significant new section of fine grained glacial lake missoula sediment and compare this section to a similar previously described sequence of sediments at ninemile creek 26 km to the northwest the new exposure which we informally term the rail line section is located near missoula montana and exposes 29 units each of which consists of many silt and clay couplets that we interpret to be varves the deposits are similar to other fine grained sediments attributed to glacial lake missoula similar varved sediments overlie gravelly flood deposits elsewhere in the glacial lake missoula basin each of the 29 units represents a period when the lake was deepening and all units show evidence for substantial draining of glacial lake missoula that repeatedly exposed the lake floor the evidence includes erosion and deformation of glaciolacustrine sediment that we interpret happened during draining of the lake desiccation cracks that formed during exposure of the lake bottom and fluvial sand deposited as the lake began to refill the floods date to between approximately 21 4 and 13 4 cal ka ago based on regional chronological data the total number of varves at the rail line and ninemile sites are respectively 732 and 583 depending on lake refilling times each exposure probably records 1350 1500 years of time we present three new optical ages from the rail line and ninemile sites that further limit the age of the floods these ages in calendar years are 15 1 0 6 ka at the base of the ninemile exposure and 14 8 0 7 and 12 6 0 6 ka midway through the rail line exposure the sediment at the two sections was deposited during later stages of glacial lake missoula after the largest outburst events

seven glacial cycles in the middle late pleistocene of northwest europe geomorphic evidence from buried tunnel valleys the deep ocean marine isotope record and the antarctic and greenland ice caps record numerous glacial and interglacial cycles since the middle pleistocene and yet evidence for similar numbers of ice sheet advances over the continent and shallow shelves of northwest europe is absent here we document seven generations of regionally correlatable subglacial tunnel valleys that record the geomorphic imprint of ice sheets traversing the north sea basin between ca 500 and 40 ka consistent with that predicted by proxy records of glacial and interglacial climate change over 180 subglacial tunnel valleys that incise into pleistocene sediments in the north sea basin were mapped over 60 000 km 2 of three dimensional seismic reflection data using a subset of these data we identified seven separate episodes of subglacial erosion that can be correlated regionally in the uk sector of the central north sea the characteristics of the valley morphologies orientations and infill stratigraphy indicate that each set of tunnel valleys formed during a separate ice sheet advance and retreat cycle stratigraphic data suggest that the tunnel valleys formed significantly later than the brunhes matuyama reversal event at 780 ka and before the last glacial maximum marine isotope stage mis 2 21 ka these results imply a more complicated glacial history for northwest europe and more glaciations than the three glaciation model traditionally interpreted from the terrestrial record for the past 500 k y our data provide the most complete documentary evidence for repeated advance and retreat of the northwest european ice sheets since the middle pleistocene and for the first time indicate that terrestrial ice sheet advances in the north sea can be matched in number with the cold events recorded in oceanic and or ice core proxies of climate change over the past 500 k y

early cretaceous rifts of western and central africa an overview abstract the structure and evolution of early cretaceous rift basins in western and central africa are described two stages of rift development and fracturing have been identified 1 from neocomian to early aptian roughly e w and nw trending troughs upper benue n cameroon s chad sudan etc opened in response to a submeridian extensional regime in central africa while in western africa the n s trending transsaharian fault zone acted as a sinistral wrench 2 from middle aptian to late albian large northwest trending troughs e niger sudan sirte etc opened in response to a northeast extensional regime while the central african fault zone from benue to sudan exhibited strike slip movements generating pull apart basins these rift and fracture systems delimit three large blocks within the african plate a western block an arabian nubian block and an austral block the arabian nubian block tends to separate from the two other blocks migrating towards the north during the first stage of basin development and then towards the ne during the second stage the opening of the atlantic ocean was the dominant driving force for the western and austral blocks while the arabian nubian block probably moved in response to the opening of the indian ocean and to the evolution of the tethyan margin

late pliocene pleistocene environments and glacial history of the northern north sea abstract based on new geochronological amino acids and sr isotopes and lithological data combined with analyses of 3d seismic data the pliocene pleistocene development of the central northern north sea has been investigated at the start of the plio pleistocene transition the study area was dominated by a deltaic shallow marine or tidal depositional environment with sediments mainly sourced from the west these sand rich sediments include green glauconitic grains that belong to the utsira sand with a local provenance directly above the base quaternary r2 a 60 m thick layer of mud rich sediments of glacimarine origin were deposited at a rate of 12 cm ka between 2 1 5 ma and up to 80 cm ka between 1 5 and 1 2 ma possibly reflecting glacial ice advancing to the norwegian coastline the high rate of deposition in the early pleistocene occurred immediately before the initiation of the norwegian channel ice stream at 1 1 ma following this a large part of the sediment input from fennoscandia seems to have been directed away from the study area to the shelf break at the start of the mid pleistocene transition mpt subaerial conditions allowed the formation of a 50 km long fluvial channel across the study area draining water from the east to the south west the earliest evidence of grounded ice in the investigated area comes from mega scale glacial lineations formed during the mpt at or just after 1 2 ma following this a regional unconformity r4 was formed by one or more grounded ice advances across the study area possibly during or directly after the mpt and likely marks the boundary between the early and mid pleistocene glacimarine sediments the mid to late pleistocene stratigraphy is dominated by glacimarine sediments and tills and is associated with multiple generations of tunnel valleys observed within the seismic data a high shear strength till containing chalk clasts transported from the west and or south of the study area was likely deposited during mis6 and may have been more conducive to tunnel valley formation in comparison to lower shear strength tills deposited by later ice advances a thick till unit overlain by a sand layer in the study area was deposited by grounded ice during the last glacial maximum and subsequent drainage of an ice dammed lake in the southern north sea during the last deglaciation mis2 of the study area this study shows that much of the quaternary age sediments within the northern north sea were deposited relatively rapidly during short periods of time probably leaving significant hiatuses within the stratigraphic record this finding has implications for previous studies that use a chronological framework assuming a relatively continuous sedimentation rate and record for the early pleistocene within the north sea

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

geologic structure and neotectonics of the north african continental margin south of sicily abstract marine geological and geophysical data together with drilling information indicate that the north african passive continental margin has been subjected to extension and wrenching after it collided with the northern part of sicily the area of the tripolitania basin jarrafa trough melita and medina bank and the ragusa malta plateau has formed part of a sinking passive margin since the dispersal of gondwanaland at about 180 my ago as observed from geohistory diagrams a record of rifting in a nw se direction accompanied by dextral shear along the southern troughs is observed in seismic reflection data the rifting started during the neocomian and lasted until the eocene when activity became minor a pre middle miocene period of northward subduction of oceanic crust is inferred from the geology in ne sicily uplift of the northern part of the african margin after collision in the middle miocene is seen in wells in southern sicily after the messinian a rift and dextral shear zone established itself across the african margin from the strait of sicily to the medina ridge in the lonian basin the zone is marked by up to 1 7 km deep grabens narrow active wrench faulted channels volcanic fissures and local uplifted keilhorsts such as malta this zone which varies in width from 100 to 35 km forms the southern boundary of a microplate which includes sicily we speculate that the present motion of this microplate is partly due to the eastward movement of the calabrian arc with the sicilian block over the last remaining oceanic lithosphere in the eastern mediterranean

proglacial lakes character behaviour and geological importance proglacial lakes are ubiquitous within the quaternary record and can provide exceptional breadth and depth of palaeoenvironmental information present deglaciation is increasing the number and size of proglacial lakes around the world this study provides a synthesis of knowledge on proglacial lake character and behaviour and critically evaluates the importance of proglacial lakes from a geological perspective we show how ice marginal or ice contact lakes and other distal proglacial lakes can be distinguished from each other by geomorphological sedimentological chemical and biological characteristics the key controls on proglacial lake geomorphology and sedimentology are outlined and discussed proglacial lakes can exacerbate mountain glacier and ice sheet margin ablation via mechanical and thermal stresses but very large lakes can moderate summer air temperatures and relatively retard summer ice ablation proglacial lakes interrupt meltwater flux and are very efficient sediment traps hydrological routing and consequent geomorphological activity can be radically modified by sudden drainage of proglacial lakes and resultant glacial lake outburst floods exceptionally large proglacial lake drainages affected global ocean circulation and global climate during the quaternary overall analyses of proglacial lakes can provide a valuable insight into i patterns character and behaviour of mountain glaciers ice sheets and glaciations and ii the impacts of past present and future deglaciation

paleohydraulic reconstruction of the largest glacial lake missoula draining s glacial lake missoula glm was the source of earth s largest known peak flood discharges onto the channeled scabland northwestern united states the original studies of glm were based on geomorphological mapping of lake sediments and shorelines more recently studies have emphasized the computational fluid dynamics of downstream megaflood routing and characteristics in the channeled scabland and adjacent areas however actual details of the lake draining processes glm have received little scientific attention in this paper we employ two dimensional hydraulic modelling to understand the paleoflow conditions for different scenarios of draining glm at its highest stands values are calculated for three glm drainage hydrographs 2 6 13 17 10 6 m 3 s 1 that previous studies had estimated for outlet flows consistent with regional mapping and with the original interpretation of fluvial geomorphology by other studies the modelling shows that lake silt sequences in the gorges of glm must postdate the most highly energetic outburst events from the lake this is because the flows generated in the lake by megaflood outflows are sufficiently energetic to erode any accumulated silt deposits in contrast the gravels underlying the silts in these zones include boulder sized clasts largescale cross stratification and 70e100 m high bars forms all of which indicate very high energy flood flow conditions the modelling also shows that the paleohydraulic conditions which developed in the lake basin during the largest megaflood outflows would be capable of accounting for the observed bedrock scour at rainbow lake pass various high eddy deposits eddy bars of flood gravel in gorges and the giant ripple marks subaqueous gravel dunes that were classically described in the 1940s previous studies interpreted the glacial lake silt rhythmites and related deposits such as the ninemile section as evidence for numerous fillings and drainings of glm our modelling suggests that these inferred events must have been relatively low in energy and magnitude relative to the earlier outburst s that emplaced the flood gravels subaqueous gravel dunes and scabland like erosion surfaces

the northern sector of the last british ice sheet maximum extent and demise abstract strongly divided opinion has led to competing apparently contradictory views on the timing extent flow configuration and decay mechanism of the last british ice sheet we review the existing literature and reconcile some of these differences using remarkable new sea bed imagery this bathymetric data provides unprecedented empirical evidence of confluence and subsequent separation of the last british and fennoscandian ice sheets critically it also allows a viable pattern of ice sheet disintegration to be proposed for the first time covering the continental shelf around the northern united kingdom extensive echosounder data reveals striking geomorphic evidence in the form of tunnel valleys and moraines relating to the former british and fennoscandian ice sheets the pattern of tunnel valleys in the northern north sea basin and the presence of large moraines on the west shetland shelf coupled with stratigraphic evidence from the witch ground basin all suggest that at its maximum extent a grounded ice sheet flowed from se to nw across the northern north sea basin terminating at the continental shelf edge the zone of confluence between the british and much larger fennoscandian ice sheets was probably across the northern orkney islands with fast flowing ice in the fair isle channel focusing sediment delivery to the rona and foula wedges this period of maximum confluent glaciation c 30 25 ka bp was followed by a remarkable period of large scale ice sheet re organisation we present evidence suggesting that as sea level rose a large marine embayment opened in the northern north sea basin as far south as the witch ground basin forcing the two ice sheets to decouple rapidly along a north south axis east of shetland as a result both ice sheets rapidly adjusted to new quasi stable margin positions forming a second distinct set of moraines c 24 18 ka bp the lobate overprinted morphology of these moraines on the mid shelf west of orkney and shetland indicates that the re organisation of the british ice sheet was extremely dynamic probably dominated by a series of internally forced readvances critically much of the ice in the low lying north sea basin may have disintegrated catastrophically as decoupling progressed in response to rising sea levels final stage deglaciation was marked by near shore ice streaming and increasing topographic control on ice flow direction punctuated retreat of the british ice sheet continued until c 16 ka bp when following the north atlantic iceberg discharge event heinrich 1 ice was situated at the present day coastline in nw scotland

doggerland the cultural dynamics of a shifting coastline the landmass now covered by the north sea here referred to as doggerland has had an important but neglected influence on the course of prehistory in northwestern europe the physical character of doggerland in the late glacial and earlier holocene is assessed together with its re colonization by humans after the last glacial maximum the development of a maritime based society along the northern coast of doggerland is postulated and it is argued that the coastal inhabitants with their specialized adaptation to this zone will have moved with the coast as relative sea levels changed the interactions of coastal and inland populations are considered including the probable influence of the coastal groups in delaying the spread of farming into the region in northwestern europe from ireland to south ern scandinavia there is an absence of archae ological evidence dated to the last glacial devensian weichselian maximum conditions approximating those of an arctic desert per tained in front of the british and scandinavian ice sheets and it is generally accepted that the lack of evidence for human occupation is due quite simply to the absence of humans for 10000 years from about 23000be to about 13 500bp radiocarbon years the region was uninhabited housley et al 1997 as conditions ameliorated people began to explore the land beyond their glacial refugia the changing character of the archaeological evidence indi cates that within a few centuries of pioneering visits permanent human occupation was estab lished for southern britain and southern jut land the presence of settled groups of people can be dated to about 12 400 bp i e to the earlier part of the windermere or bolling interstadial at this time land was continuous between the two regions and it too will have been inhabited the land between subsequently submerged by the north sea is here referred to as doggerland named after the dogger bank which has long been recognized as a former area of dryland and fresh waters reid 1913 although there has as yet been no specifically archaeological survey of the region something of its character can be gleaned from the results of geological exploration and by extrapolating from the data available for adjacent regions the evidence for the physical condition of doggerland in successive periods is discussed in coles 1998 including that for coast line position and for the major river courses sea level change in northwestern europe has recently been modelled in a series of papers by lambeck and colleagues e g lambeck 1993 lambeck et al 1998 which should in due course enable greater precision and confidence in coastline reconstruction the more that is known of the former landmass the more its relevance to late glacial and postglacial pre history becomes clear coles 1998 1999 in the present context the focus will be predominantly on doggerland s coastal zone following a brief consideration first of inland conditions at the time of the windermere bolling allerod inter stadial and then of the initial character of human occupation of the land

stratigraphic evidence for multiple drainings of glacial lake missoula along the clark fork river montana usa abstract glacial lake missoula a source of channeled scabland flood waters inundated valleys of northwest montana to altitudes of 1265 m and to depths of 600 m as evidenced by shorelines and silty lacustrine deposits this study describes previously unrecognized catastrophic lake drainage deposits that lie stratigraphically beneath the glacial lake silts the unconsolidated gravelly flood alluvium contains imbricated boulder sized clasts cross stratified gravel with slip face heights of 2 35 m and 70 to 100 m high gravel bars which all indicate a high energy high volume alluvial environment gravel bars and high scablands were formed by catastrophic draining of one or possibly more early high lake stands 1200 1265 m most glacial lake silt such as the ninemile section was deposited stratigraphically above the earlier deposits represents a lower lake stand s 1050 1150 m and was not deposited in lake s responsible for the highest discharge events the glaciolacustrine silt covered benches are incised by relict networks of valleys formed during the drainage of the last glacial lake significant erosion associated with the last lake draining was confined to the inner clark fork river canyon

late cretaceous ca 84 ma compressive deformation of the stable platform of northeast africa egypt far field stress effects of the santonian event and origin of the syrian arc deformation belt large scale northeast trending asymmetric folds and associated contractional faults seismically induced slump structures and strike slip and extensional faults of santonian age occur within the eastern desert of egypt 150 km south of the syrian arc mobile belt the region also displays a locally developed angular unconformity at the base of the flat lying campanian limestone these features demonstrate that the deformation event responsible for the syrian arc also led to northwest southeast shortening in central egypt ca 84 ma the late santonian shortening corresponds precisely with a brief period of compression that swept across the entire african plate coeval with a significant change in the poles of opening of the north atlantic this santonian event is a prominent example of the role that far field compressional stresses can play in stable intraplate settings

late quaternary seismic stratigraphy and geological development of the south voring margin norwegian sea abstract high resolution seismic data and sediment cores show that an up to 280 m thick sedimentary sequence has been deposited on the south voring margin off mid norway the last ca 250 ka the sedimentary succession has been divided into six seismic units dominated by hemipelagic sediments five wedge shaped massive sequences of marine isotope stages 8 6 and 2 interfinger the hemipelagic deposits on the upper slope the wedge shaped sequences represent glacigenic debris flows that have been fed by till transported to the shelf edge by grounded ice sheets during maximum glaciations the hemipelagic units show well defined depocentres of various thicknesses on the upper continental slope seismic facies interpretation indicates that the sediment distribution locally has been controlled by currents commonly the hemipelagic units are characterised by parallel and continuous reflectors however the second youngest unit identified deposited between 15 7 and 15 0 14 c ka bp is acoustic transparent we suggest that this unit has been sourced by along slope transported meltwater plume deposits released during the initial stage of the last deglaciation of the norwegian channel the hemipelagic sedimentation rates have varied considerably throughout the studied time period until ca 21 14 c ka bp the rates did not exceed 1 4 m kyr whereas during the last glacial maximum the rates increased and reached values of about 36 m kyr before decreasing again at ca 15 14 c ka bp observation of iceberg scourings of mis 8 age about 800 m below the present day sea level suggest that the south voring margin has subsided by a rate of 1 2 m kyr in the late quaternary

seismic reflection structure of intracratonic palmyride fold thrust belt and surrounding arabian platform syria copyright 1990 aapg reprinted by permission of the aapg whose permission is required for further use see also http aapgbull geoscienceworld org http atlas geo cornell edu syria mcbride aapg 1990 html

the first estimation of fleuve manche palaeoriver discharge during the last deglaciation evidence for fennoscandian ice sheet meltwater flow in the english channel ca 20 18 ka ago the fleuve manche english channel palaeoriver represents the largest river system that drained the european continent during pleistocene lowstands particularly during the elsterian marine isotope stage 12 and saalian drenthe mis 6 glaciations when extensive ice advances into the north sea area forced the central european rivers to flow southwards to the bay of biscay ne atlantic numerous long piston cores and high resolution acoustic data from the northern bay of biscay have been correlated using a well constrained chronostratigraphical framework and for the first time allow the estimation of the discharge of the fleuve manche palaeoriver at the end of the last glacial period i e weichselian our results discussed in the light of relationships between river loads and drainage area characteristics strongly suggest that the bay of biscay collected sediment laden meltwater from the northern european lowlands and the southern part of the fennoscandian ice sheet at the end of the last glacial period and particularly during the paroxysmal phase of the european deglaciation ca 20 18 ka ago this demonstrates that the fleuve manche drainage area at that time was equivalent to those dating from the major elsterian and saalian drenthe glaciations based on our data we propose a revision of the palaeogeographical and palaeoglaciological evolution of the north sea area while showing that the british and fennoscandian ice sheets entered the north sea basin until ca 18 ka initiating isostatic adjustment of the basin this allowed the north sea fluvial system to flow southwards through the dover strait finally we discuss the fleuve manche freshwater discharge during the maximum european ice sheet retreat ca 18 ka the estimated discharge at this time appears important and sufficiently sustained to possibly contribute to the profound destabilisation of the thermohaline circulation recognised in the north atlantic from ca 18 to 16 ka

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

freshwater megaflood sedimentation what can we learn about generic processes abstract there is growing recognition that sedimentary deposits related to high energy large scale freshwater floods are widespread across the continents and in the main can be related to quaternary outbreak flows from ice dammed lakes such deposits may also occur in the neogene and earlier recognition of these megaflood deposits is hindered by the lack of well conditioned stratigraphic models of depositional successions however descriptions of successions from many locations often exhibit commonalities when compared carefully thus the primary purpose of this paper is to examine and condense the published stratigraphic and sedimentological evidence so as to identify the key signatures of megaflood successions the deposits often are the only record of a flood and so the secondary purpose is to interpret the sedimentary sequences in order to recreate the behaviour of floods through single and multiple events finally some pointers are provided as to those areas of sedimentological research that might be profitably explored in more depth to improve understanding of megaflood dynamics a key characteristic of megaflood deposits is the apparent massive appearance of single units which on closer inspection usually are amalgamated layers of similar grain size distribution individual beds and sets of beds are commonly near horizontal planar and laterally extensive successions evidently are not channelized and extensivity is indicative of simultaneous and coherent deposition over large areas localised large scale clinoforms or smaller scale cross beds are common associated with bar front or dune progradation respectively but otherwise extensivity implies that cross cutting erosional contacts notably steeply inclined examples and small scale scours are not common except immediately around large isolated clasts such as dropstones and ice blocks a common vertical stack of sequences in any one succession consists of 1 basal thick coarse parallel bedded units 2 large scale clinoforms 3 horizontally bedded thin laminated units 4 ripple and dune cross beds 5 silt beds and 6 succession capping debris flow deposits in some cases such a succession usually is indicative of a single cycle of waxing and waning flood flow generally dominated by high concentration suspension deposition onto plane beds the high power allows the transport of fine gravel and coarse sand in suspension leading upon deposition to relatively coarse beds from suspension fall out clay and silt is generally sparse or absent being transported further down the system at the scale of the hydrograph the successions indicate that flows initially accelerate and then decelerate with significant shorter period flow pulses also evident in the sedimentary signatures in parallel bedded sequences primarily during waxing flows bedload transport often was ineffective in sorting sediment due to the high rates of deposition from the highly sediment charged waters resulting in diffuse accretion surfaces at each location similar sequence stacks are common leading to the impression of rhythmic deposition from pulsing flow including from repetitive series of floods although often composed of coarse grains many sequence stacks excluding any debris flows are not dissimilar to turbidity flow sequences the bouma sequence in particular although there is limited experimental evidence for turbidity currents associated with high energy freshwater flows theory does not preclude the deposition of similar sedimentary motifs from high concentration flows such that an analogy between some megaflood sedimentary beds and turbidites is not unreasonable despite considerable variation in megaflood sedimentary successions commonalities occur which are indicative of similar processes of deposition from high energy floods at geographically different locations the changes in style of deposition throughout a succession provide clues as to the nature of the flood flows and this information could be used to improve estimates of flood hydrograph behaviour however hypotheses linking deposit characteristics to flow dynamics are currently ill conditioned and often poorly tested the majority of published studies describe the coarser scale stratigraphy with only passing reference to the fine scale structure of individual beds closer attention to lamination styles particle orientation and syn depositional deformation structures for example should provide information on the flow mechanics at the time of bed deposition thus better consideration of the sedimentology of megaflood deposit beds will lead to better understanding of the controlling hydraulics and should result in better models of flood deposition

pre weichselian quaternary glaciations of the british isles the netherlands norway and adjacent marine areas south of 68 n implications for long term ice sheet development in northern europe within this paper we review the pre weichselian glacial history of northern europe focussing on evidence from the british isles netherlands norway and adjacent marine areas that record the activity of the british bis and scandinavian sis ice sheets the objective of the paper is to examine the long term evolution of the two ice sheets in order to determine their level of synchronicity and their relationship to the plio pleistocene record of northern hemisphere glaciation geological evidence demonstrates striking long term similarities between the behaviour of the bis and sis with a step wise intensification in the glacial signal 1 first ice rafted debris ird input onto the continental margin at ca 2 7 2 6 ma and restricted glaciation prior to ca 1 1 ma 2 initiation of more lowland style glaciation from 1 1 ma 3 repeated shelf edge glaciations from 0 45 ma these steps coincide with a major intensification of the northern hemisphere climate signal at the beginning of the quaternary and the mid pleistocene transition temporal and spatial variabilities in the behaviour of different sectors of the bis and sis appear to reflect regional scale geographic latitude elevation climatic moisture temperature and glaciological deformable beds controls that modulate the build up of ice volume in the main ice accumulation areas relative to global climate forcing and its subsequent lateral expansion 2010 nerc

middle pleistocene saalian lake outburst floods in the munsterland embayment nw germany impacts and magnitudes abstract during the late saalian drenthe glaciation ice damming of the upper weser valley led to the formation of glacial lake weser the lake drained catastrophically into the munsterland embayment as the western ice dam failed releasing up to 110 km3 of water with a calculated peak discharge of 2 5 105 m3 s to 1 3 106 m3 s geographic information systems gis and high resolution digital elevation models dem were used to map streamlined landforms and channel systems in front of lake overspills geological maps 2450 boreholes and the dem were integrated into the 3d modeling program gocad to reconstruct the distribution of flood related deposits palaeotopographic surfaces and the internal facies architecture of streamlined hills the drainage pathways are characterized by the occurrence of deep plunge pools channels streamlined hills and 4 km long and 12 m deep v shaped megaflutes plunge pools are deeply incised into mesozoic basement rocks and occur in front of three major overspill channels the plunge pools are up to 780 m long 400 m wide and 35 m deep approximately 1 10 5 km downslope of the overspill channels fan shaped arrays of streamlined hills are developed each covering an area of 60 130 km2 indicating rapid flow expansion the hills commonly have quadrilateral to elongated shapes and formed under submerged to partly submerged flow conditions when the outburst flood entered a shallow lake in the munsterland embayment hills are up to 4300 m long 1200 m wide 11 m high and have characteristic average aspect ratios of 1 3 3 they are separated by shallow anabranching channels in the outer zones and up to 30 m deep channels in the central zones hills partly display v shaped chevron like bedforms that have apices facing upslope are 1 6 2 5 km long 3 10 m high 0 8 1 2 m from limb to limb with limb separation angels of 20 35 these bedforms are interpreted as mixed erosional depositional features it is hypothesized that the post saalian landscape evolution of the munsterland embayment has considerably been influenced by catastrophic floods of glacial lake weser creating large and deep valleys which subsequently became the new site of river systems the outburst floods probably followed the east west trending saalian rhine meuse river system eventually flowing into the north sea the strait of dover and the bay of biscay it is speculated that the hondsrug ice stream may have been enhanced or even triggered by the formation and outburst of glacial lakes in the study area

the calabrian arc and the ionian sea in the dynamic evolution of the central mediterranean in the central mediterranean area it is possible to recognize three main realms the tyrrhenian sea the pelagian block and the ionian block these domains are limited by important fracture zones that are easily recognizable on land and offshore these fracture zones can be grouped into four main trends 1 the nw se trend which is characterized by dextral horizontal movements 2 the ne sw trend which is generally characterized by sinistral lateral horizontal movements 3 the e w trend which also shows dextral shear movements and 4 the n s trend which is characterized by normal faults only the tyrrhenian sea realm is characterized by a thinned crust of oceanic type and is connected to the apenninic chain by means of listric faults from a geophysical point of view the area shows a high heat flow which follows the main structural trends and positive gravimetric anomalies which are compatible with seismic refraction data and can be explained by the proposed model the pelagian block shows a continental crust about 20 km thick which progressively increases beneath the sicilian chain here an abrupt interruption with the tyrrhenian block takes place in the pelagian realm rifting processes developed according to the nw se and n s trend the n s trend characterizes the westernmost zone of the realm where volcanic processes and a relatively high heat flow can also be observed the ionian block is characterized by the following a thinned crust 17 20 km which increases 40 km towards the southern calabrian chain a thick sedimentary sequence high positive bouguer anomalies 300 mgal and very low heat flow 50 mw m 2 geophysical and structural analyses allowed us to evaluate the post tortonian evolution of the whole area under consideration this evolution resulted in continental crust formation according to a rigid plastic deformation model according to our model the ionian block can be considered as a domain characterized by a thinned continental crust and affected by intrusive material derived from the upper mantle furthermore this domain of probably jurassic age can be considered as a pelagic basin bordered by the pelagian block to the west and by the apulian block to the east northeast this basin according to its position with respect to the apenninic and sicilian chains has not been affected by tectogenesis and still represents a site of continuous sedimentation from a kinematic point of view the ionian realm can be linked with the pelagian block shifting towards the east northeast whereas it is limited towards the north by an e w fracture zone which regulates the opening of the tyrrhenian sea and the counterclockwise rotation of the apenninic chain according to the proposed model the opening of the tyrrhenian sea can be considered as a megaextension fracture which developed parallel to the maximum principal stress direction and evolved as a triangular shaped structural feature in preparing the model the authors have taken into account a large set of data collected both on land and offshore

routing of meltwater from the laurentide ice sheet during the younger dryas cold episode rooth1 proposed that the younger dryas cold episode which chilled the north atlantic region from 11 000 to 10 000 yr bp was initiated by a diversion of meltwater from the mississippi drainage to the st lawrence drainage system the link between these events is postulated to be a turnoff during the younger dryas cold episode of the north atlantic s conveyor belt circulation system which currently supplies an enormous amount of heat to the atmosphere over the north atlantic region2 this turnoff is attributed to a reduction in surface water salinity and hence also in density of the waters in the region where north atlantic deep water nadw now forms here we present oxygen isotope and accelerator radiocarbon measurements on planktonic foraminifera from orca basin core en32 pc4 which reveal a significant reduction in meltwater flow through the mississippi river to the gulf of mexico from about 11 200 to 10 000 radiocarbon years ago this finding is consistent with the record for lake agassiz which indicates that the meltwater from the southwestern margin of the laurentide ice sheet was diverted to the northern atlantic ocean through the st lawrence valley during the interval from 11 000 to 10 000 years before present yr bp

evidence of an ice dammed lake outburst in the north sea during the last deglaciation abstract recent reconstructions suggest that the british irish and fennoscandian ice sheets coalesced and covered the central and northern north sea from ca 26 cal ka bp and until ca 19 cal ka bp at ca 19 cal ka bp the norwegian channel ice stream started to retreat and the ice sheets broke apart at ca 18 7 cal ka bp this led to a drainage of an ice dammed lake in the southern north sea northwards via the norwegian channel into the se nordic seas in this paper we combine information from high resolution topas profiles bathymetric records and shallow borings to study the ice dammed lake outburst a common deglaciation process but which rarely has been evidenced in such a detail from the marine realm a 12 m deep and 3 km wide incision at the northeastern part of the dogger bank is suggested to represent the point where the ice dammed lake breached the glacial lake outburst flood which had an estimated peak discharge of 9 8 104 2 9 105 m3 s and lasted for about 5 15 months flowed between the withdrawing british irish and fennoscandian ice sheets following the crest of the ling bank northwards along this path about 300 km downstream of the break through point an up to 10 m thick sediment package with a prograding aggrading sedimentation pattern typical for ice dammed lake outburst deposits has been deposited this sediment package was deposited in a high energy environment immediately following extensive erosion of the underlying till unit of last glacial maximum age an oxygen isotope anomaly and an associated ultra rapidly deposited meltwater plume on the norwegian continental margin dated to ca 18 7 cal ka bp also witness this lake outburst the ice dammed lake outburst flood occurred when evidence suggest a sea level at least 110 m lower than at present in the region as the sea level rose following the melting of the last glacial maximum ice sheet the ling bank delta developed on top the outburst deposits the delta indicating a sea level close to 80 m below present has an extent of 80 km and up to 12 m deep fluvial channels are associated with the topset beds this fluvial environment may have lasted until the end of the younger dryas time period when the ling bank was submerged and attained its present water depth

quaternary stratigraphy of the fladen area central north sea a multidisciplinary study based on detailed stratigraphic investigations on a 200 6m long core bgs borehole no 81 26 from the fladen ground area british sector core material from the sleipner field norwegian sector and shallow seismic profiles between the core sites the following conclusions are drawn 1 the north sea was glaciated sometime during th elaterpart of matuyama reversed period a complete glacial interglacial glacial cycle is recorded in these sediments 2 in a period of marine sedimentation in the middle pleistocene a transgression regression cycle under boreal arctic regime is recorded 3 the fladen area has subsided between 0 9 and 0 6 m ka through the later parts of the quaternary 4 a major glacial event dated at between 130 and 200 ka is recorded as a thick till unit in 81 26 this till which was deposited by ice moving from the southwest scotland probably represents a period when the scandinavian and british ice sheets coalesced in the north sea 5 based on the seismic data and the stratigraphy of the sleipner core an ice free open embayment dry land is favoured for the central north sea during the late weichselian 6 from the amino acid data it is shown that there has been an episodic style of sedimentation through the quaternary 7 of the investigated sediments which span the last 1 mill year ca 98 have been deposited under arctic to boreal arctic conditions

the 8k event cause and consequences of a major holocene abrupt climate change abstract a prominent abrupt climate event about 8200 years ago brought generally cold and dry conditions to broad northern hemisphere regions especially in wintertime in response to a very large outburst flood that freshened the north atlantic changes were much larger than typical climate variability before and after the event with anomalies up to many degrees contributing to major displacement of vegetative patterns this 8k event provides a clear case of cause and effect in the paleoclimatic realm and so offers an excellent opportunity for model testing the response to north atlantic freshening has the same general anomaly pattern as observed for older events associated with abrupt climate changes following north atlantic freshening and so greatly strengthens the case that those older events also reflect north atlantic changes the north atlantic involvement in the 8k event helps in estimating limits on climate anomalies that might result in the future if warming caused ice melt and hydrologic cycle intensification at high latitudes lead to major changes in north atlantic circulation few model experiments have directly addressed the 8k event and most studies of proxy records across this event lack the time resolution to fully characterize the anomalies so much work remains to be done

freshwater outbursts to the oceans from glacial lake agassiz and their role in climate change during the last deglaciation abstract lake agassiz was the largest lake in north america during the last deglaciation as the laurentide ice sheet lis retreated large volumes of water stored in this proglacial lake were episodically released into the oceans these waters were variably routed to the gulf of mexico arctic ocean north atlantic ocean and hudson bay during this period the three largest cooling events in the northern hemisphere closely followed 4 of the 5 largest outbursts from lake agassiz 1 the younger dryas which was preceded by a release of 9500 km 3 2 the preboreal oscillation preceded by releases of 9300 km 3 and 5900 km 3 and 3 the 8 2 ka cold event preceded by a 163 000 km 3 outburst these are respectively fluxes of 0 30 sv 0 29 sv 0 19 sv and 5 2 sv if released in 1 year because the influx of freshwater reaching the north atlantic ocean can inhibit thermohaline circulation partly depending on whether the ocean was in a glacial interglacial or transitional mode of circulation we believe that at least these large outbursts from lake agassiz may have provided the triggers for changes in ocean circulation and in turn for widespread climate change

space geodesy constrains ice age terminal deglaciation the global ice 6g_c vm5a model a new model of the last deglaciation event of the late quaternary ice age is here described and denoted as ice 6g c vm5a it differs from previously published models in this sequence in that it has been explicitly refined by applying all of the available global positioning system gps measurements of vertical motion of the crust that may be brought to bear to constrain the thickness of local ice cover as well as the timing of its removal additional space geodetic constraints have also been applied to specify the reference frame within which the gps data are described the focus of the paper is upon the three main regions of last glacial maximum ice cover namely north america northwestern europe eurasia and antarctica although greenland and the british isles will also be included if peripherally in the discussion in each of the three major regions the model predictions of the time rate of change of the gravitational field are also compared to that being measured by the gravity recovery and climate experiment satellites as an independent means of verifying the improvement of the model achieved by applying the gps constraints several aspects of the global characteristics of this new model are also discussed including the nature of relative sea level history predictions at far field locations in particular the caribbean island of barbados from which especially high quality records of postglacial sea level change are available but which records were not employed in the development of the model although ice 6g c vm5a is a significant improvement insofar as the most recently available gps observations are concerned comparison of model predictions with such far field relative sea level histories enables us to identify a series of additional improvements that should follow from a further stage of model iteration

glacigenic debris flows on the north sea trough mouth fan during ice stream maxima abstract numerous short sediment cores which penetrate through the glacimarine section and into glacigenic debris flow debrites gdfs on the north sea fan are investigated the sampled gdfs represent the uppermost of several sequences of these stacked bodies many hundreds of metres thick the gdfs occurred over slopes from 0 3 to 0 7 and examples are found from the shelf break at the mouth of the norwegian channel to the norway basin floor 300 km distant the gdf diamicts are structureless and homogeneous in terms of grain size magnetic susceptibility nrm bulk density water carbonate foraminiferal and rock fragment content this applies both from gdf to gdf across the fan and in a proximal distal sense comparison of the investigated lithologic parameters with weichselian till from a borehole in the norwegian channel 200 km up ice shows striking similarity to the gdf debrites ams 14c dates at the gdf glacimarine contact and stratigraphic relationships indicate voluminous deposition before 18 ka continuing possibly uninterrupted until ca 16 ka and a final phase halting just before 15 ka when the norwegian channel became ice free this chronology the comparable lithologic character between till and gdf debrites and a seismic continuity confirms inferences that the gdfs are directly associated with glacial ice at the shelf break the glacial efflux has not been subject to subsequent sorting and the homogeneity of the gdf is thought to reflect thorough mixing in a deforming till layer beneath a fast flowing ice stream the glacimarine section subsequent to gdfs shows no indications of turbidity flow observations are compatible with a slow non disintegrating cohesive plug flow transport mechanism with little sediment water interaction on the upper surface minor distal differentiation might reflect a change in flow process deposition on the fan margins from water borne glacimarine processes simultaneous with gdf deposition is limited

kinematic consistency between the dead sea fault zone and the neogene and quaternary left lateral faulting in se turkey a revised quantitative kinematic model has been determined for the dead sea fault zone dsfz and the left lateral fault zones in se turkey the relative motions of the african and arabian plates across the dsfz are represented by relative rotation about 31 1 n 26 7 e at 0 40 0 02 ma 1 the northern dsfz in syria and southern turkey is interpreted for the first time as a series of transpressional stepovers along which the left lateral slip rate is substantially less than the rate of relative plate motion because this slip is oblique to the plate motion the slip rate on the east anatolian fault zone eafz is estimated as 8 mm a 1 restoring its observed slip thus requires its age to be 4 ma the previous phase of deformation which involved slip on the malatya ovacik fault zone mofz before the eafz came into being is thus dated to 7 4 ma suggesting initiation of the north anatolian fault zone nafz at 7 ma not 5 ma as previously thought the total left lateral slip on the northern dsfz in southernmost turkey is estimated as at least 65 km partitioned with 45 km on the amanos fault 10 km on the east hatay fault and a further 10 km on the kirkpinar fault farther east much of this slip is inferred to have occurred during the miocene before the modern geometry of this plate boundary zone developed when it first formed the af ar plate boundary was relatively complex it initially reactivated preexisting structures in the palmyra foldbelt in syria and in the gaziantep region of southern turkey which were significantly misaligned relative to the plate motion requiring major components of shortening as well as left lateral slip the transition from this initial rather diffuse geometry to the present localised geometry of the dsfz across western syria occurred within the miocene the predicted rate of relative motion between the stable interiors of the turkish and african plates in the vicinity of their common boundary onshore of iskenderun gulf in southern turkey is estimated as westward at 9 mm a 1 however this promontory of the african plate is itself moving westward relative to the stable interior of this plate at 7 8 mm a 1 the rate of localised left lateral slip on the onshore part of this boundary the ne trending yakapinar goksun fault is thus estimated as only 2 mm a 1 this locality can also be regarded as within the distributed boundary zone between the turkish and arabian plates the estimated relative motion between these plates is at 8 7 mm a 1 towards the ssw partitioned between localised left lateral slip at 2 mm a 1 on the yakapinar goksun fault and at least 1 mm a 1 on the amanos fault and 2 5 mm a 1 on east hatay fault with at most distributed left lateral simple shear at 3 2 mm a 1 across the amanos mountains in between however the combined slip on left lateral faults east of the amanos mountains may be as high as 6 mm a 1 with slip at 1 7 mm a 1 on the amanos fault and at 4 3 mm a 1 on the east hatay fault and any active faults farther east this requires no more than 0 7 mm a 1 of distributed simple shear across the amanos mountains raising the possibility that this component of deformation may in fact be zero this small nonzero estimate possibly indicating a closure error arising from minor errors in predicted values of other relative motion vectors it is proposed that this boundary between the turkish and african plates first developed at the same time as the mofz and nafz but its original geometry involving left lateral slip on the karatas osmaniye fault has since become locked by the presence of relatively strong ophiolitic crust within this fault zone this quantitative kinematic model demonstrates for the first time how it is possible for the left lateral faulting accommodating the nnw sse relative motion between the arabian and african plates in nw syria to dovetail into the left lateral faulting accommodating the wsw ene relative motion between the turkish and arabian plates in se turkey

late miocene deformation kinematics along the nw zagros fold thrust belt kurdistan region of iraq constraints from apatite u th he thermochronometry and balanced cross sections

the jaeren area a border zone of the norwegian channel ice stream abstract the coastal lowlands of jaeren southwestern norway have an extensive cover of quaternary sediments lithological biostratigraphical and geochronological investigations of a series of boreholes across jaeren have allowed us to combine earlier and new information on these deposits into a temporal model of quaternary sedimentation the cores show evidence of at least four ice free episodes with marine deposition during mainly arctic conditions the oldest of these is considered to be ca 200 ka old and the youngest one is the sandnes interstadial which is 14 c ams dated to 32 ka bp interbedded between these units are 10 40 m thick units of till with components of marine material these findings together with a re evaluation of distinct morphological features on jaeren as well as earlier provenance studies strongly suggest that jaeren has been a boundary zone between an ice stream following the norwegian channel draining a substantial part of the southern region of the fennoscandian ice sheet and local ice from south western norway through multiple periods of glaciation starting ca 1 1 myr million years ago the norwegian channel ice stream has been the main conduit of erosion products from southern scandinavia to the deep norwegian sea comparison with ice stream profiles from antarctica suggests that the deposition of relatively young marine sediments as high as ca 200 m a s l on jaeren is a result of glacial isostasy rather than regional tectonic movements

senonian basin inversion and rejuvenation of rifting in africa and arabia synthesis and implications to plate scale tectonics abstract the late paleozoic to tertiary stratigraphic record of much of the african plate reflects the effects of continental rifting and passive margin development several short lived but widespread and tectonically important compressional or wrench dominated events occurred however during the permian to recent evolution of africa we focus here on the best documented of these events which occurred during the late santonian at that time older sedimentary basins mostly ene wsw trending were folded and inverted including some basins along the tethyan margin from morocco to the syrian arc and the intraplate benue southern chad basins and the lugh mandera basin in oman ophiolites were obducted following the santonian tectonism an extensive phase of rifting occurred in central and north africa and northern arabia spanning from campanian to maastrichtian or paleocene times rejuvenation or acceleration of subsidence occurred in several basins located along the tethyan margin along the atlantic and indian ocean margins as well as within the intraplate domain rifting was sometimes accompanied by magmatic activity especially in offshore northern libya and along the indian ocean margin compressional deformations rejuvenated or developed by latest maastrichtian times along the tethyan margin and locally within the intraplate domain one of the most remarkable attributes of the santonian tectonic event which we consider representative of the major trans african stress field changes is the rapidity with which the change was reflected stratigraphically across north and central africa and its short duration the cause of the santonian compressional event is directly linked to the change in poles of rotation for the opening of the atlantic at 83 85 ma the end of the cretaceous normal magnetic quiet zone this was also synchronous with the obduction of ophiolites along the northeast margin of arabia oman the onset of separation between india and madagascar with formation of the mascarene oceanic basin and the development of the european alpine chain we interpret these phenomena as causally related aspects of a global tectonic event the santonian compressional event as well as the campanian maastrichtian rifting event and the end cretaceous compressional event illustrate the critical connection between intraplate tectonic histories and processes occurring at sometimes very distant plate boundaries

mega deposits and erosive features related to the glacial lake nedre glomsjo outburst flood southeastern norway abstract in this paper we present a suite of erosional remnants mega deposits and subtle bar morphology that we relate to the outburst flood from the glacial lake nedre glomsjo at the end of the last ice age by using large datasets of airborne lidar data implemented in a geographic information system gis we have mapped flood related features along the glomma and vrangselva rivers in southeastern norway the unprecedented overview of the valley reaches obtained by the vegetation free lidar derived digital elevation models dem has revealed a set of hitherto undocumented landforms persisting erosive lines indicators of the uppermost flooded level are carved into surficial deposits in the hillsides and are found as high as 80 90 m above the modern valley floor by using the indicators as an upper flood boundary we have computed cross sectional profiles showing that the flood in some reaches inundated more than 120 000 m2 of the valley large streamlined bed forms which we interpret as flood bars drape sections of the valley floor some several kilometers long the most morphologically striking pendant bars are developed behind flood flow projections such as bedrock knolls or in lee of a valley bend flood bars occur in the entire study area but are more widespread in the north and generally decrease in size moving in a downstream direction kettle holes and ice block obstacle marks from icebergs arrested during the flood are common these features support the theory of a catastrophic drainage event but also indicate a pattern of differential erosion and deposition that allowed us to interpret palaeoflow on individual bars vast aeolian dune fields in the region are interpreted as a secondary product of the flood as deposits related to the event were mobilised by northerly winds momentarily after the flood waned the dune fields cover an excess of 50 km2 and reveal that the region was a highly active periglacial desert after the flood our mapping highlights the outburst flood s role as a landscape defining event morphological evidence determine the southern fringe of the scandinavian ice sheet to c 15 km north of elverum at the time of the outburst flood from calibrating existing 14c dates we postulate an age of c 10 10 4 cal ka bp for the nedre glomsjo drainage event and the contemporaneous margin of the ice sheet

the glacial north sea fan southern norwegian margin architecture and evolution from the upper continental slope to the deep sea basin abstract high resolution seismic data have been used to study the ice stream fed north sea fan deposited from approximately marine isotope stage mis 12 and onwards located at the outlet of the norwegian channel on the se nordic seas continental slope the 110 000 km2 fan is dominated by glacigenic debris flows and slide debrites the fan is divided in two provinces by the volcanic more marginal high the proximal province has been characterised by alternation between deposition and erosion while the distal province has been dominated by deposition from mis 12 until the present the fan has received 32 000 km3 of sediments age constraints on fan stratigraphy provided by core investigations indicate that the fennoscandian ice sheet advanced to the shelf edge during mis 2 6 8 10 and probably 12 the fan experienced megaslides in late mis 6 9 and during mis 11 12

paleohydraulics of the last outburst flood from glacial lake agassiz and the 8200 bp cold event abstract during the last deglaciation of north america huge proglacial lakes formed along the southern margin of the laurentide ice sheet the largest of these was glacial lake agassiz which formed about 11 7 14 c kyr and drained into hudson bay about 7 7 14 c kyr 8 45 cal kyr overflow from these lakes was variably directed to the mississippi st lawrence and mackenzie drainage systems and it is thought that switches in routing were accompanied by a response in ocean circulation that produced abrupt climate events when the ice dam across hudson bay finally was breached a massive flood drained lake agassiz which was routed through hudson strait to the labrador sea in terms of stored water volume the largest reservoir was associated with the kinojevis level of lake agassiz for this maximum filling the impounded water volume available to produce floods is estimated as 40 000 151 000 km 3 depending on the location of the ice margin and route used the timing of this rapid release of stored freshwater just precedes the early holocene cooling event at 8 2 cal kyr bp we use the spring hutter theory to simulate flood hydrographs for floods that originate in subglacial drainage conduits and find that flood magnitude and duration are 5 sv and 0 5 yr multiple fillings and floods are possible as are single floods having a complex multipulse structure modelling results suggest that the outburst flood from lake agassiz may have terminated before the lake surface elevation dropped to sea level and that the flood ended when a stable drainage channel was established connecting lake agassiz to the tyrrell sea

a review of the tectonics of the northern middle east region the structure of the northern part of the arabian platform is reviewed in the light of hitherto unpublished exploration data and the presently accepted kinematic model of plate motion in the region the palmyra and sinjar zones share a common history of development involving two stages of rifting one in the triassic jurassic and the other during late cretaceous to early tertiary times deformation of the palmyra zone during the mio pliocene is attributed to north south compression on the eastern block of the dead sea transcurrent system which occurred after continental collision in the north in southeast turkey the asymmetry of the palmyra zone is believed to result from northward underthrusting along the southern boundary facilitated by the presence of shallow triassic evaporites an important nw se cross plate shear zone has been identified which can be traced for 600 km and which controls the course of the river euphrates over long distances in syria and iraq transcurrent motion along this zone resulted in the formation of narrow grabens during the late cretaceous which were compressed during the mio pliocene to a large extent present day structures in the region result from compressional reactivation of old lineaments within the arabian plate by the transcurrent motion of the dead sea fault zone and subsequent continental collision

rapid ice sheet retreat triggered by ice stream debuttressing evidence from the north sea using high resolution bathymetric and shallow seismic data from the north sea we have mapped hitherto unknown glacial landforms that connect and resolve longstanding gaps in the quaternary geological history of the basin we use these data combined with published information and dates from sediment cores to reconstruct the extent of the fennoscandian and british ice sheets fis and bis in the north sea during the last phases of the last glacial stage it is concluded that the bis occupied a much larger part of the north sea than previously suggested and that north sea ice underwent a dramatic disintegration 18 500 yr ago this was triggered by grounding line retreat of the norwegian channel ice stream which debuttressed adjacent ice masses and led to an unzipping of the bis and fis accompanied by drainage of a large ice dammed lake our reconstruction of events provides an opportunity to improve understanding and modeling of the disintegration of marine based ice sheets and the complex interplay between ocean circulation and the cryosphere

pleistocene rhine thames landscapes geological background for hominin occupation of the southern north sea region this paper links research questions in quaternary geology with those in palaeolithic archaeology a detailed geological reconstruction of the netherlands south west offshore area provides a stratigraphical context for archaeological and palaeontological finds progressive environmental developments have left a strong imprint on the area s palaeolithic record we highlight aspects of landscape evolution and related taphonomical changes visualized in maps for critical periods of the pleistocene in the wider southern north sea region the middle pleistocene record is divided into two palaeogeographical stages the pre anglian elsterian stage during which a wide land bridge existed between england and belgium even during marine highstands and the anglian elsterian to saalian interglacial with a narrower land bridge lowered by proglacial erosion but not yet fully eroded the late pleistocene landscape was very different with the land bridge fully dissected by an axial rhine thames valley eroded deep enough to fully connect the english channel and the north sea during periods of highstand this tripartite staging implies great differences in i possible migration routes of herds of herbivores as well as hominins preying upon them ii the erosion base of axial and tributary rivers causing an increase in the availability of flint raw materials and iii conditions for loess accumulation in northern france and belgium and the resulting preservation of middle palaeolithic sites 2011 john wiley sons ltd

glacial lake agassiz a 5000 yr history of change and its relationship to the δ18o record of greenland lake agassiz was the largest lake in north america during the last period of deglaciation the lake extended over a total of 1 5 10 6 km 2 before it drained at ca 7 7 14 c ka 8 4 cal calendar ka new computer reconstructions controlled by beaches isostatic rebound data the margin of the laurentide ice sheet outlet elevations and a digital elevation model dem of modern topographic data show how variable the size and depth of this lake were during its 4000 14 c yr 5000 cal yr history abrupt reductions in lake level ranging from 8 to 110 m occurred on at least 18 occasions when new outlets were opened reducing the extent of the lake and sending large outbursts of water to the oceans three of the largest outbursts correlate closely in time with the start of large 18 o excursions in the isotopic records of the greenland ice cap suggesting that those freshwaters may have had an impact on thermohaline circulation and in turn on climate

gps constraints on africa nubia and arabia plate motions summary we use continuously recording gps cgps and survey mode gps sgps observations to determine euler vectors for relative motion of the african nubian arabian and eurasian plates we present a well constrained eurasia nubia euler vector derived from 23 igs sites in europe and four cgps and three sgps sites on the nubian plate 0 95 4 8 n 21 8 4 3 e 0 06 0 005 myr 1 we see no significant 1m m yr 1 internal deformation of the nubian plate the gps nubian eurasian euler vector differs significantly from nuvel 1a 21 0 4 2 n 20 6 0 6 e 0 12 0 015 myr 1 implying more westward motion of africa relative to eurasia and slower convergence in the eastern mediterranean the arabia eurasia and arabia nubia gps euler vectors are less well determined based on only one cgps and three sgps sites on the arabian plate the preliminary arabia eurasia and arabia nubia euler vectors are 27 4 1 0 n 18 4 2 5 e 0 40 0 04 myr 1 and 30 5 1 0 n 25 7 2 3 e 0 37 0 04 myr 1 respectively the gps arabia nubia euler vector differs significantly from nuvel 1a 24 1 1 7 n 24 0 3 5 e 0 40 0 05 myr 1 but is statistically consistent at the 95 per cent confidence level with the revised euler vector reported by chu gordon based on a re evaluation of magnetic anomalies in the red sea 31 5 1 2 n 23 0 2 7 e 0 40 0 05 myr 1 the motion implied in the gulf of aqaba and on the dead sea fault dsf by the new gps nubia arabia euler vector i e ignoring possible sinai block motion and possible internal plate deformation grades from pure left lateral strike slip in the gulf and on the southern dsf with increasing compression on the central and northern dsf with relative motion increasing from 5 6 to 7 5 mm yr 1 1m m yr 1 from south to north along the northern dsf i e north of the lebanon restraining bend motion is partitioned between 6 1m m yr 1 left lateral motion parallel to the fault trace and 4 1m m yr 1 faultnormal compression relative motions on other plate boundaries including the anatolian and aegean microplates derived from the gps euler vectors agree qualitatively with the sense of motion indicated by focal mechanisms for large crustal earthquakes m 6 where data are available on fault slip rates on plate bounding faults north anatolian fault east anatolian fault dead sea fault red sea rift they are generally lower than but not significantly different from the full plate motion estimates suggesting that the majority of relative plate motion is accommodated on these structures

extreme sediment and ice discharge from marine based ice streams new evidence from the north sea a major problem for understanding the dynamics of ice streams has been a lack of precise data on ice streaming longevity and sediment transport efficacy here we present the first well constrained data on sediment flux from a paleoice stream this has been achieved by computing the volume of sediment deposited as debris flows on the fan located at the outlet of the norwegian channel ice stream and converting to a flux measurement by accounting for the duration of streaming in this episode between 20 and 19 ka during the last glacial stage in this period the ice stream delivered an average 1 1 gt of sediment per year equivalent to 8000 m 3 yr 1 per meter width of ice stream front the calculated flux is an order of magnitude higher than most previous estimates for other paleoice streams and is comparable to the present sediment flux from the world9s largest rivers the short period of debris flow deposition suggests that the norwegian channel ice stream underwent rapid on off switching with punctuated iceberg delivery to the north atlantic as a consequence

ice marginal dynamics of the last british irish ice sheet in the southern north sea ice limits timing and the influence of the dogger bank the southern north sea is a particularly important area for understanding the behaviour of the british irish ice sheet biis during the last glacial cycle it preserves a record of the maximum extent of the eastern sector of the biis as well as evidence for multiple different ice flow phases and the dynamic re organisation of the biis however to date the known ice sheet history and geochronology of this region is predominantly derived from onshore geological evidence and the offshore imprint and dynamic history of the last ice sheet remain largely unknown using new data collected by the britice chrono project this paper explores the origin and age of the dogger bank re assesses the extent and age of the glaciogenic deposits across the shallow areas of the north sea between the dogger bank and the north norfolk coast and re examines the dynamic behaviour of the biis in the southern north sea between 31 6 and 21 5 ka this paper shows the core of the dogger bank to be composed glaciolacustrine sediment deposited between 31 6 and 25 8 ka following its formation the western end of the dogger lake was overridden with ice reaching 54 n where the ice margin is co incident with the southerly extent of subglacial tills previously mapped as bolders bank fm this initial ice override and retreat northwards back across the dogger lake was complete by 23 1 ka but resulted in widespread compressive glaciotectonism of the lake sediments and the formation of thrust moraine complexes along the northern edge of the bank moraines are on lapped by later phase glaciolacustrine and marine sediments but do not show evidence of subsequent ice override the shallow seafloor to the west and southwest of the dogger bank records several later phases of ice advance and retreat as the north sea lobe flowed between the dogger bank and the yorkshire lincolnshire coasts and reached north norfolk new optically stimulated luminescence osl ages from garrett hill on outwash limit the arrival of the biis on the norfolk coast to 22 8 21 5 ka multiple till sheets and chains of moraines on the seafloor north of norfolk mark dynamic oscillation of the north sea lobe margin as it retreated northwards this pattern of behaviour is broadly synchronous with the terrestrial record of deposition of subglacial glaciofluvial and glaciolacustrine sediments along the yorkshire coast which relate to post dimlington stadial ice marginal oscillations after 21 5 ka with respect to forcing mechanisms it is likely that during the early phases of the last glacial maximum 30 23ka the interaction between the southern margin of the biis and the dogger lake was critical in influencing flow instability and rapid ice advance and retreat however during the latter part of the last glacial maximum 22 21 ka late phase ice advance in the southern north sea became restricted to the western side of the dogger bank which was a substantial topographic feature by this time this topographic confinement in addition to decoupling of the biis and the fennoscandian ice sheet fis further north enabled ice to reach the north norfolk coast overprinting the seabed with late phase tills of the bolders bank fm

structure and tectonics of the eastern cyprean arc abstract the geometry and nature of the eastern segment of the cyprean arc are little understood several hypotheses have been put forward to explain the tectonic situation there recent marine geophysical data for this region mapped several deep and shallow structural elements the most prominent element is a ridge the latakia ridge which extends from the syrian coast near latakia south westward to meet with an east west trending bathymetric escarpment east of the hecateus ridge the new seismic profiles suggest that these two elements mark the present plate boundary along the eastern cyprean arc the latakia ridge is a young and still active feature it was formed by southward migration of the plate boundary the ridge probably originated as a large thrust sheet which later when the convergence direction was changed became a zone of wrench faulting the ridge is still forming today and serves as a dam to the sediments north of it the wrench faulting activity is more pronounced in the eastern segment of the ridge

middle and late pleistocene glacial lakes of lowland britain and the southern north sea basin focusing on lowland britain and the southern north sea basin this article reviews the sedimentary and geomorphic evidence for the main glacial lakes inferred during the middle and late pleistocene and evaluates their impacts on drainage basin development glacial lakes are best known from glaciations during marine isotope stages mis 12 6 and 2 although glacial lakes have also been inferred during mis 10 and 4 some lakes for example bosworth low level humber and the lakes of the eastern fenland margin are reconstructed from unequivocal sedimentary evidence including rhythmites and subaqueous outwash whereas others lakes for example lapworth and fenland are inferred mostly from erosional features and remain to be substantiated the largest known glacial lake developed in the southern north sea basin between an ice sheet to the north and a chalk bedrock ridge in the strait of dover area first during the anglian elsterian glaciation of mis 12 and again during the late wolstonian late saalian drenthe glaciation of mis 6 the palaeohydological impacts of lake drainage are thought to include cutting of the strait of dover as a result of catastrophic drainage from the north sea lake during mis 12 incision of a number of gorges and river valleys in england and diversion or even reversal of major rivers such as the thames and the proto soar avon system recently varve chronologies have been correlated with the greenland ice core record although caution is needed to discriminate between varves and non annual rhythmites future work on pleistocene glacial lakes needs to test chronologies of lake development by luminescence dating of glaciolacustrine sediments deposited in non ice proximal locations 1 fine grained rainout deposits and 2 wave rippled sands deposited in shallow water and to model the impacts of glacial isostasy in order to reconstruct lake extents all of this work should be based on the rigorous application of sedimentology to interpret sedimentary facies and depositional environments

eurasian ice sheet collapse was a major source of meltwater pulse 1a 14 600 years ago rapid sea level rise caused by the collapse of large ice sheets is a threat to human societies in the last deglacial period the rate of global sea level rise peaked at more than 4 cm yr 1 during meltwater pulse 1a which coincided with the bolling warming event some 14 650 years ago however the sources of the meltwater have proven elusive and the contribution from eurasian ice sheets has been considered negligible here we present a regional carbon 14 calibration curve for the norwegian sea and recalibrate marine 14c dates linked to the eurasian ice sheet retreat we find that marine based sectors of the eurasian ice sheet collapsed at the bolling transition and lost an ice volume of 4 5 7 9 m sea level equivalents sle over 500 years during peak melting 3 3 6 7 m sle of ice was lost potentially explaining up to half of meltwater pulse 1a a mean meltwater flux of 0 2 sv over 300 years was injected into the norwegian sea and the arctic ocean at a time when proxy evidence suggests vigorous atlantic meridional overturning circulation our reconstruction shows that massive marine based ice sheets can collapse in as little as 300 500 years marine based sections of the eurasian ice sheet collapsed rapidly during a warming event 14 600 years ago and contributed to the meltwater pulse 1a event according to a recalibrated age model for sediments from the norwegian sea

lateral and vertical facies relationships of bedforms deposited by aggrading supercritical flows from cyclic steps to humpback dunes abstract the preservation of bedforms related to supercritical flows and hydraulic jumps is commonly considered to be rare in the geologic record although these bedforms are known from a variety of depositional environments this field based study presents a detailed analysis of the sedimentary facies and stacking pattern of deposits of cyclic steps chutes and pools antidunes and humpback dunes from three dimensional outcrops the well exposed middle pleistocene successions from northern germany comprise glacilacustrine ice contact subaqueous fan and glacial lake outburst flood deposits the studied successions give new insights into the depositional architecture of bedforms related to supercritical flows and may serve as an analogue for other high energy depositional environments such as fluvial settings coarse grained deltas or turbidite systems deposits of cyclic steps occur within the glacial lake outburst flood succession and are characterised by lenticular scours infilled by gently to steeply dipping backsets cyclic steps formed due to acceleration and flow thinning when the glacial lake outburst flood spilled over a push moraine ridge these bedforms are commonly laterally and vertically truncated and alternate with deposits of chutes and pools and antidunes the subaqueous fan successions are dominated by laterally extensive sinusoidal waveforms which are interpreted as deposits of aggrading stationary antidunes which require quasi steady flows at the lower limit of the supercritical flow stage and high rates of sedimentation humpback dunes are characterised by downflow divergent cross stratification displaying differentiation into topsets foresets and bottomsets and are interpreted as deposited at the transition from subcritical to supercritical flow conditions or vice versa gradual lateral and vertical transitions between humpback dunes and antidune deposits are very common the absence of planar parallel stratification in all studied successions suggests that the formation of these bedforms is suppressed in flows characterised by hydraulic jumps under highly aggradational conditions the large scale lateral and vertical successions of bedforms are interpreted as representing the temporal and spatial evolution of the initial supercritical flows which was strongly affected by the occurrence of hydraulic jumps small scale facies changes and the formation of individual bedforms are interpreted as controlled by fluctuating discharge bed topography and pulsating unstable flows

continental margin evolution of the northern arabian platform in syria copyright aapg 1993 reprinted by permission of the aapg whose permission is required for further use see also http atlas geo cornell edu syria best 1993 html

a review of the history of the baltic sea 13 0 8 0 ka bp abstract the dynamic history of the baltic sea during the millennia following the last deglaciation has been one of the main topics for many generations of quaternary geologists around the baltic sea based on the present state of knowledge and certain hypotheses a model for the development during the baltic ice lake yoldia sea and ancylus lake stages are presented the oresund strait was the threshold of the initial stage of the baltic ice lake and was eroded down to bedrock as a result of the isostatic uplift the emerging threshold forced the baltic ice lake to rise above sea level at ca 12 0 ka bp this gradual up damming ended at ca 11 2 ka bp when the large glacial lake was lowered 5 10m by possible subglacial drainage at mt billingen a glacial readvance during the younger dryas ended a ca 400 year long land bridge between sweden and the continent by blocking the former drainage route once again the baltic ice lake had to rise above sea level to be drained over the oresund strait at ca 10 5 ka bp a gradual ice recession began and 200 years later when the receding ice sheet could not withhold the up dammed water masses the final drainage of the baltic ice lake occurred which rapidly lowered the water level within the baltic basin with ca 25 m and ended the baltic ice lake stage the next stage the yoldia sea was characterized by a complex pattern of relative sea level changes with large differences within the baltic basin a very restricted baltic sea in the south and thus an extensive landbridge at ca 9 9 ka bp a short 100 200 years saline ingression is seen in the baltic sediment records from stockholm in the north to the southernmost parts of the yoldia sea the gradually shallower strait in south central sweden the narke strait ended the saline influence 300 400 years later the two remaining outlets west of lake vanern gota alv and otteid steinselva had become too shallow to swallow the outflowing yoldia sea waters at this stage the baltic lake vanern level could thus not fall in pace with the relative sea level fall outside the outlet areas this was the isolation of lake vanern and the baltic from the sea and the beginning of the ancylus lake since the water depth of the larger gota alv outlet had to be more or less maintained the ancylus lake level had to rise in pace with the uplift of the outlet region this caused a significant and rapid transgression 10 30 m in ca 300 years in the southern baltic which flooded large areas with recently immigrated pine forests since the oresund strait during the yoldia sea stage had been uplifted more than southerly areas the ancylus transgression ended with a new drainage pathway at ca 9 2 ka bp through the darss sill area in the southern baltic and northwards through the store belt strait this so called dana river had cut off the former large land bridge the quaternary deposits of this new threshold were eroded and a fairly rapid regression set in at ca 9 0 ka bp the dana river had eroded down to the sea level which isolated lake vanern from the ancylus lake and created a land bridge between southern sweden and northwards ca 800 years later when the sea level rose above the oresund threshold marine water could enter the baltic and at ca 8 0 ka bp brackish water characterized the southern baltic this marks the end of the ancylus lake

the seismicity seismotectonics and earthquake hazards of libya with detailed analysis of the 1935 april 19 m 7 1 earthquake sequence summary we have investigated the seismicity of libya in order to understand better the earthquake hazards the tectonics of the region and the present day evolution of the sirt basin we first relocated all events occurring between 1931 and 1988 using a bootstrap location technique we then determined focal mechanisms from firstmotion data finally we used waveform modelling techniques to determine source parameters for the 1935 main shock and its two largest aftershocks relocation of the 1930s events are in some cases significantly different from those given by the international seismological summary iss the first motion results suggest a combination of strike slip and normal faulting for the 1935 and 1939 sequences the waveform modelling results of the 1935 mainshock suggest a strike slip mechanism with one fault plane similar to the strike of the eastern edge of the hun graben about 5 hr after the mainshock an aftershock mb 6 0 occurred about 40 km to the south which was followed about 9 hr later by another aftershock mb 6 4 in the same area waveform modelling results for this earthquake sequence suggest focal depths ranged from 15 21km with rupture lengths of 14 16 km an average displacement of 1 8 m is estimated for the mainshock but no surface rupture has been noted for the event in the vicinity of the hun graben area the number of large earthquakes that have been reported through history is an indication that the area is seismically active most of the activity appears to be concentrated along the eastern margin of the nw se trending hun graben the focal mechanisms suggest that the maximum compressive stress in northwestern libya is oriented wnw in the north eastern part of the country the stress direction changes to a more ne sw orientation as evidenced by the 1963 february 21 al marj and the 1967 al jabal al akhdar mainshocks

cyrenaican shock absorber and associated inversion strain shadow in the collision zone of northeast africa far field compressional stresses resulting from arc collisions with the northeast coast of africa arabia propagated across the african plate in the santonian ca 84 ma and later similar pulses occurred through much of the cenozoic waves of inversion related features including folds thrusts and igneous activity developed during the compressional events structures generated were uneven in intensity and distribution and were commonly concentrated in existing rifts because of the irregular shapes of the north african continental margin and associated inboard basins cyrenaica underwent the most severe shortening although deformation extended eastward from libya to the levant areas south and southeast of cyrenaica the sirt basin and the far western desert of egypt underwent very little shortening because they occupied a regional strain shadow the eastern region of the western desert and sinai which were not sheltered by the stress absorbing cyrenaica inversion recorded strong compressional deformation synchronous with that in cyrenaica as closure of the mediterranean continues cyrenaica will become an indenter comparable to those of other orogenic belts the detailed tectonic evolution of individual northeast african basins has depended on their positions in relation to the cyrenaican strain shadow no single subsidence and paleostress history reflects the complete regional development of the converging mediterranean north african margin

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

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

ocean ice sheet interaction along the se nordic seas margin from 35 to 15 ka bp abstract sediment cores from the south eastern nordic seas simultaneously archive the variability of the fennoscandian ice sheet fis the british irish ice sheet biis and the regional oceanic conditions this study aims to contribute to our understanding of the marine based section of the fis and the biis between 35 000 and 15 000 years bp by using cores md99 2283 md99 2284 and md99 2289 retrieved along the upper continental slope between the faroe shetland channel and the voring plateau for this we present a revised radiocarbon based bayesian modelled chronological framework and a compilation of new and published sedimentological geochemical and micro paleontological datasets our results show a possibly first weichselian fis biis confluence at ca 25 500 years bp in the central north sea which buttressed the biis to the east potentially leading to a northwards biis deflection via the shetlands the norwegian channel ice stream ncis most likely only reached the shelf edge after 23 300 500 years bp possibly for the first time during the weichselian the ncis onset directly preceded a pronounced influx of warm atlantic water to the northern north sea margin possibly implying forcing through ocean melt we find a highly variable ncis with three 1400 yearlong episodes of increased ice rafted debris flux interrupted by 600 yearlong minima when compared to other sides of the european ice sheet these episodes appear to correlate well suggesting a common forcing mechanism in conclusion our data supports recent suggestions that the last glacial stage of the biis was more extensive in the central north sea and the confluence later than previously thought

quaternary seismic stratigraphy of the north sea fan glacially fed gravity flow aprons hemipelagic sediments and large submarine slides abstract approximately 1000 km of high resolution sleeve gun array transects on the north sea fan located at the mouth of the norwegian channel reveal three dominant styles of sedimentation within a thick 900 m quaternary sediment wedge comprising numerous sequences these are interpreted as terrigenous hemipelagic sedimentation large scale translational slides and aprons of glaciogenic debris flow deposits contributing to considerable fan construction four large buried translational slides involved sediment volumes upwards of 3000 km 3 each and preceded the similarly dimensioned first storegga slide on the ne fan flank several thick 100 m terrigenous hemipelagic deposits apparently represent long lived 150 200 kyr periods of sedimentation whose distribution indicates fan input via the norwegian channel the upper sequences are each made upper sequences are each made up of one or several thick 100 m aprons comprising stacked lensoid and or lobate forms which range from 2 to 40 km in width and 15 to 60 m in thickness they characterize debris flows attributed to periodic input from several phases of a norwegian channel ice stream reaching the shelf edge subsidence in the outer norwegian channel allowed preservation of several glaciation cycles represented by sheet erosion bounded tills and progradational units much of the shelf slope transition has been preserved allowing a preliminary chronology of the fan sequences through correlation with borehole sediments in the norwegian channel debris flows which signal the initial shelf edge glaciation are not recognized from the initial glaciation in the channel 1 1 myr but are associated with a middle pleistocene and all following glacial erosion surfaces ges in the outer norwegian channel this was followed by six further sequences probably totalling over 13 000 km 3 of sediment at least four of these were shelf edge ice maximum events the last of which was late weichselian age 14 c ams considering earlier glaciation related hemipelagic sedimentation material since removed by the large slides and extensive unmapped areas total quaternary fan sedimentation was in the vicinity of 20 000 km 3

late cenozoic environmental changes along the norwegian margin abstract our ability to understand the rates and consequences of contemporary climate change is limited by the insufficient duration of instrumental records thus we are not able to fully understand the processes that provide a fundamental control in driving climate changes across different timescales palaeo climate archives like those preserved offshore norway provide our only real window through which to observe long term rates and styles of climate change this paper reviews the extensive geological and geophysical data available from the late cenozoic atlantic margin of norway along the margin periods of erosion and deposition have been controlled by agents including fluvial glacial and oceanographic processes current controlled sedimentation along the margin provides insight into the connection of the arctic and atlantic oceans from the miocene onward plio pleistocene shelf edge progradation of up to 150 km can be linked to the grounding of ice sheets on the continental shelf through observations of buried grounding zone wedges and mega scale glacial lineations the margin is also important for understanding the ability of glaciation to cause topographic relief changes and generate offshore geohazards such as the storegga slide which mobilised some 3000 km 3 of sediments during the holocene whilst the processes operating along the norwegian margin are well understood through the late cenozoic there is little geochronological control with which to constrain the environmental changes that have been observed concomitant with the wealth of knowledge and the extensive data that are currently available we propose that the norwegian margin is an ideal location to be considered for future ocean drilling the observations of multiple processes acting independently and together means ocean drilling could yield information of global significance due to the bridging location of norway s atlantic margin between the arctic and lower latitudes

record of glacial lake missoula floods in glacial lake columbia washington abstract during the last glaciation marine oxygen isotope stage 2 outburst floods from glacial lake missoula deposited diagnostic sediments within glacial lake columbia two dominant outburst flood lithofacies are present within glacial lake columbia deposits a flood expansion bar facies and a finer grained hyperpycnite facies we conclude that the flood sediments have a glacial lake missoula source because 1 current indicators indicate westward flow through the lake and upvalley flow followed by downvalley flow in tributary valleys 2 no flood sediments are found north of a certain point 3 there is a dominance of belt purcell supergroup clasts in a flood expansion bar and 4 some of the finer grained beds have a pink colour reflective of glacial lake missoula lake bottom sediments a new radiocarbon age of 13 400 100 14c bp on plant detritus found below 37 flood beds helps constrain the timing of outburst flooding from glacial lake missoula

laminated sediments preceding heinrich event 1 in the northern north sea and southern norwegian sea origin processes and regional linkage abstract rapidly deposited laminated sediments dated between 18 and 21 cal ka bp have been observed at several core locations in the northern north sea and the southern norwegian sea sedimentation rates range from 20 cm ka up to 2000 cm ka compared to a normal background sedimentation rate in the area of 5 10 cm ka dropstones in situ paired bivalves and grain size distribution indicate a hemipelagic origin for the laminae in core md99 2291 from the upper continental slope of southern norway ams radiocarbon dating and cyclic changes in the number of planktonic foraminifera and lithological parameters suggest that the laminations in the core are annual varves the laminated sediments are interpreted to be suspension plume deposits and two phases of plume deposition have been dated to 21 5 and 18 6 cal ka bp large fluxes of meltwater were generated during this period as reflected in oxygen and carbon isotopes records from cores in the area the meltwater and the laminated plume deposits are interpreted to be associated with the presence and disintegration of the norwegian channel ice stream observations from other regions demonstrate that laminated high rate deposition is very widespread on glaciated continental margins around 18 6 cal ka bp increases in sediment fluxes also occurred on the barra fan the north sea fan the lofoten contourite drift and the svalbard margin preceding increased sediment and meltwater fluxes on the greenland margin and the labrador sea associated with heinrich event 1 warm water inflow to the norwegian sea together with rising sea level probably triggered the destabilisation of the ice streams of the fennoscandian ice sheet while a similar response of the laurentide ice sheet was delayed by 500 1000 yr