regional neogene exhumation of britain and the western north sea tertiary exhumation of britain and the western north sea is interpreted to have taken place in two episodes each with amplitudes of about 1 km a palaeogene phase that principally affected the present onshore britain west of the present extent of the late cretaceous danian chalk group and a neogene phase that affected both onshore areas and the western north sea consequently maximum burial of mesozoic and older rocks in the present onshore areas generally occurred in the palaeocene c 60 ma in the western north sea the preservation of the chalk group today suggests relatively stable conditions prevailed immediately after its deposition rather than substantial palaeocene exhumation in this area maximum burial is interpreted to have occurred in the neogene the proposal is consistent with published exhumation estimates based on studies of sediment compaction offshore and of fission tracks onshore it also does away with unlikely high burial rates which are implied in the latest cretaceous earliest tertiary if removal of overburden from the chalk is assumed to have occurred in the palaeocene

the formation of longitudinal fronts in a coastal plain estuary longitudinal estuarine fronts aligned parallel to the axis of the estuary are characteristic of the york river their time scale for genesis and decay is of the order of hours they are usually located at the inner edge of the shoals or over the main channel field measurements have shown marked intratidal differences in density and current speeds across this estuary these can be correlated with changes in depth and the strength of the advective processes differential advection between the channel and shoal regions when acting upon a constant longitudinal density gradient is shown to be of sufficient magnitude to generate strong lateral density gradients and thus fronts at particular times within the tidal cycle

neogene stratigraphy and the sedimentary and oceanographic development of the nw european atlantic margin a regional correlation of neogene stratigraphy has been attempted along and across the nw european atlantic continental margin between mid norway and sw ireland two unconformity bounded successions are recognised these are referred to as the lower and upper neogene successions and have been dated as miocene early pliocene and early pliocene holocene respectively in age their development is interpreted to reflect plate wide tectonically driven changes in the sedimentary oceanographic and latterly climatic evolution of the ne atlantic region the lower neogene succession mainly preserves a record of deep water sedimentation that indicates an expansion of contourite sediment drifts above submarine unconformities within this succession on both sides of the eastern greenland scotland ridge from the mid miocene this is interpreted to record enhanced deep water exchange through the faroe conduit deepest part of the southern gateway and can be linked to compressive inversion of the wyville thomson ridge complex thus a pervasive interconnected arctic north atlantic deep water circulation system is a neogene phenomenon the upper neogene succession records a regional change at about 4 ma in the patterns of contourite sedimentation submarine erosion new depocentres coeval with the onset of rapid seaward progradation of the continental margin by up to 100 km this build out of the shelf and slope is inferred to record a marked increase in sediment supply in response to uplift and tilting of the continental margin associated changes in deep water circulation may be part of an atlantic wide reorganisation of ocean bottom currents glacial sediments form a major component of the prograding shelf margin shelf slope sediment wedges but stratigraphic data indicate that the onset of progradation pre dates significant high latitude glaciation by at least 1 ma and expansive northern hemisphere glaciation by at least 3 ma

a comparison of the nw european glaciated margin with other glaciated margins the present paper provides an overview of glacial related seabed features and sedimentary sequences found along the formerly glaciated nw european margin and compare it with those found on contemporary glaciated margins from both the southern and northern hemispheres a brief review of the seabed physiography and strata architecture of the margins under consideration is followed by comparison of the most relevant similarities and differences comparison of the present day bathymetric setting of both former and contemporary glaciated margins reveals no clear link to the effect of neither ice sheet or sediment load three different types of glacially eroded shelf transverse troughs have been identified while marginal troughs seem connected to similar geological settings everywhere beyond the shelf edge interaction between downslope and alongslope processes has occurred resulting amongst others in the formation of large sedimentary mounds on the rise more frequent large scale mass wasting occurs on the former glaciated nw european margin than the greenland and antarctic margins in the latest neogene to recent times a two stage evolution of the shelf prograding wedges is observed on all margins under consideration which may reflect a general development of an ice cover from an initial phase of non to restricted glaciation evolving to a mature stage of expansive glaciation

separation of palaeogene and neogene uplift on nuussuaq west greenland the geological record exposed on nuussuaq central west greenland shows that uplift in the palaeocene probably caused by impact of the iceland plume head was followed by kilometre scale subsidence analysis of apatite fission track and vitrinite reflectance data from borehole samples down to 3 km depth reveals that the samples cooled from maximum palaeotemperatures between 40 and 30 ma followed by two further cooling episodes beginning in the intervals 11 10 and 7 2 ma when the first cooling episode began the samples from the neighbouring gro 3 and gane 1 boreholes were buried 1500 2000 m deeper than at the present day and the palaeogeothermal gradient was 40 48 c km 1 it is not clear whether this cooling involved exhumation or if it was due solely to reduction in heat flow and a drop in surface temperature the two later episodes definitely involved exhumation because by then the palaeogeothermal gradient had declined to a value close to the assumed present value of 30 c km 1 which agrees with estimates from offshore wells the most recent cooling episode corresponds to the incision of the present day relief c 1100 m below the summits around the two boreholes we conclude that the present day high mountains of west greenland were not uplifted during the palaeogene but are erosional remnants of a landmass uplifted during the neogene

towards an understanding of the neogene tectonostratigraphic framework of the ne atlantic margin between ireland and the faroe islands abstract the neogene succession preserved on the continental margin between ireland and the faroe islands can be divided into two megasequences of miocene and pliocene holocene age the base of each megasequence is marked by a regional unconformity these are of latest oligocene early miocene and early pliocene age respectively and reflect major phases of neogene margin evolution the megasequences and their bounding unconformities reflect a gross two stage depositional history predominantly a response to intra plate tectonism that modified sedimentation patterns and palaeoceanographic circulation the latest oligocene early miocene event marks a major change in the oceanographic regime and can be linked to the establishment of deep water exchange between the arctic and north atlantic oceans the submergence of the greenland scotland ridge which includes the iceland faroe rise and the wyville thomson ridge in the area of study resulted in locally vigorous deep water erosion as northern source deep water flowed through the faroe conduit which is part of the southern gateway for deep water exchange coeval deposition of sediment drifts occurred in the faroe shetland channel and rockall trough as the deep water currents stabilised the early pliocene event marked the widespread instigation of shelf margin progradation to the north west of britain and ireland and to the east of the faroe islands this event is linked to the uplift and erosion of britain ireland and the faroe islands and is part of a larger north atlantic scale uplift significant deep water erosion in the rockall trough suggests that the water circulation pattern was also modified by this event the formation of the key megasequence boundaries occurred during times of significant plate rearrangement and suggests that these events may be correlatable across the whole nw european margin

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

foraminiferal assemblages and caco3 dissolution since the last deglaciation in the maxwell bay king george island antarctica abstract three sediment cores a10 01 02 and 08 from the maxwell bay king george island antarctica were quantitatively analyzed for foraminiferal fauna planktonic foraminifera of three cores are rare due to the special antarctica environment benthic foraminifera is mainly composed of globocassidulina biora globocassidulina crassa rossensis cassidulinoides parkerianus and miliammina arenacea g biora and g crassa rossensis show high percentages in the shallower core a10 08 while m arenacea displays obviously high percentage in deeper core a10 02 the lower parts of the cores have a lower abundance of foraminifera while the upper parts have a relatively higher abundance the down core variations of benthic foraminifera reflect the contrast of surface water environment between the last deglaciation and post glacial during the last deglaciation lower parts of the cores the lower abundant foraminifera was consistent with the lower toc which reflected that the extensive sea ice prevented the production of primary organisms and therefore lower flux of organic particles was delivered to the sea floor abundant foraminifera together with higher toc in the upper parts of the cores suggested a higher primary productivity after the glaciation the shallowest water depth core a10 08 45 m displayed a better carbonate preservation than the other two cores a10 01 and 02 from the depths of 85 and 105 m respectively the disparity in carbonate dissolution reflected the remarkable shallow lysocline and carbonate compensation depth ccd in the antarctic area and also reflected significant variations in water properties even within such a difference only about 60 m in water depth down core variations of benthic foraminifera dissolution index bdi and caco 3 content indicated the existence of stronger carbonate dissolution in the upper parts than those in the lower parts of the cores the down core variations of carbonate dissolution suggested changes of water properties linked to the shallow ccd in this area it was supposed that the less influence of the saline shelf water during the last deglaciation enhanced the carbonate preservation with the sea level increasing and retreat of the coastal ice after the glacial erosive water masses and the higher co 2 accumulated by the increased flux of organic material led to severe dissolution of caco 3 and foraminiferal shells in the sediment

provenance of the lower tertiary murree redbeds hazara kashmir syntaxis pakistan and initial rising of the himalayas abstract the murree supergroup of northern pakistan is represented by an over 6 km thick succession of deltaic redbeds and intercalated impure foraminiferal limestones of latest palcocene to middle eocene ilerdian to lutetian age cropping out in the northern part of the hazara syntaxis and by redbeds of younger age early middle eocene to early miocene cropping out in the southern part of the syntaxis rawalpindi area the quartzolithic composition of the murree redbeds testifies to a collision orogen provenance detritus was derived from a suture belt including thrust sheets of metasedimentary and subordinately sedimentary rocks volcanic or volcaniclastic rocks and ophiolites phyllite rock fragments are most common in the ilerdian sandstones whereas volcanic and carbonate rock fragments are more abundant in the lutetian sandstones minor quantities of chert and serpentineschist indicating contribution from uplifted subduction complex sources as well as siltstone shale and limestone grains are invariably present detrital modes of sandstones and southwestward progradation of tertiary clastic wedges both testify to provenance from the proto himalayan chain located to the north and uplifted since the very first stages of the india asia continental collision at the end of the paleocene the coeval chulung la redbeds of the tethys himalaya instead consisting of volcanic and subordinate ophiolitic detritus testify to exclusive provenance from the obducting trans himalayan are trench system this major petrographic difference may be accounted for by the different structural setting of the chulung la piggy back and murree foreland basins these two distinct collisional basins have been separated probably since the onset of collision by a fold thrust belt beginning to rise in the position occupied today by the high and lesser himalayan structural domains throughout the murree supergroup main petrographic parameters do not vary greatly and volcanic sedimentary low grade metasedimentary and ophiolitic detritus persisted until the early miocene indicating slow progressive growth of the chain only during the middle miocene when the highly metamorphosed rocks of the high himalaya were carried southward along the main central thrust mct the mountain range began to rise to dramatic heights and huge amounts of detritus started to feed the siwalik foreland basin sandstones and the remnant ocean turbidites of the indus and bengal fans

the upper cainozoic of the norwegian continental shelf correlated with the deep sea record of the norwegian sea and the north atlantic a stratigraphic framework has been developed for the cainozoic succession of the norwegian continental shelf and margin this framework is consistent for the entire margin from the central north sea to the barents sea and also facilitates a correlation with the deep sea record of the norwegian sea and north atlantic a local system mainly utilising planktonic and benthic foraminiferal assemblages and bolboforma species is developed it can be potentially used for regional stratigraphic syntheses using this framework a more precise and detailed identification and age assignments of cainozoic and in particular neogene strata can be performed several revisions of previous age assignments and a more detailed dating of the various sediment packages are presented the most complete neogene succession is recorded in the central north sea further north the succession is interrupted by an increasing number of hiati of increasing duration after a period of erosion in the late middle to early late miocene there is a marked increase in the influx of terrigenous sediment in the late miocene a period of transgression in the early pliocene resulted in strongly reduced rates of deposition and sediments of this age are preserved mainly in the central north sea a period of regression in earliest late pliocene probably resulted in erosion of most of the norwegian continental shelf with the exception of the deeper areas of the central and viking grabens this period was immediately followed in the later part of late pliocene by rapid deposition of glacially derived sediment prograding along the entire shelf in general pleistocene development is a continuation of the late pliocene evolution but is marked by more extensive erosion of the inner shelf this is inferred from the flat truncation of underlying prograding strata and the extensive build up of debris flow sediments within glacial fan depocentres the entire neogene development is closely related to the climatic evolution of high latitude regions surrounding the north atlantic and the norwegian greenland sea

a record of late cenozoic stratigraphy sedimentation and climate change from the hebrides slope ne atlantic ocean a punctuated 103 3 m thick succession of upper palaeogene to quaternary sediments has been recovered in a borehole from the upper hebrides slope west of britain the borehole proved 11 2m of upper oligocene carbonate rich muds at the base unconformably overlain by 2 85 m of middle to upper miocene glauconitic sands this is in turn unconformably overlain by 89 25 m of predominantly plio pleistocene sands and muds with a holocene sea bed veneer the post miocene succession is subdivided into two units the sand dominated pliocene to lower middle pleistocene lower macleod sequence between 89 25 and 67 82 m and the mud dominated middle pleistocene to holocene upper macleod sequence above 67 82 m regional mapping indicates that these sequences are commonly associated with large scale shelf margin progradation and slope front fan construction the borehole core provides an excellent record of the transition from pre glacial to glacial conditions in the mid latitude ne atlantic ocean climatic conditions warmer than present prevailed in the late oligocene mid to late miocene and pliocene although the influx of ice rafted detritus in the late pliocene marks the onset of climatic deterioration this deterioration continued in a fluctuating manner until the early mid pleistocene 0 44 ma when fully glacial conditions were established on the hebridean margin

cenozoic uplift and subsidence in the north atlantic region geological evidence revisited abstract the topographic evolution of the passive margins of the north atlantic during the last 65 myr is the subject of extensive debate due to inherent limitations of the geological geomorphological and geophysical methods used for studies of uplift and subsidence we have compiled a database of sign time and amplitude where possible of topographic changes in the north atlantic region during the cenozoic 65 0 ma our compilation is based on published results from reflection seismic studies aft apatite fission track studies vr vitrinite reflectance trends maximum burial sediment supply studies mass balance calculations and extrapolation of seismic profiles to onshore geomorphological features the integration of about 200 published results reveal a clear pattern of topographic changes in the north atlantic region during the cenozoic 1 the first major phase of cenozoic regional uplift occurred in the late palaeocene early eocene ca 60 50 ma probably related to the break up of the north atlantic between europe and greenland as indicated by the northward propagation of uplift it was preceded by middle palaeocene uplift and over deepening of some basins of the north sea and the surrounding areas 2 a regional increase in subsidence in the offshore marginal areas of norway the northern north sea the northern british isles and west greenland took place in the eocene ca 57 35 ma 3 the oligocene and miocene 35 5 ma were characterized by regional tectonic quiescence with only localised uplift probably related to changes in plate dynamics 4 the second major phase of regional uplift that affected all marginal areas of the north atlantic occurred in the plio pleistocene 5 0 ma its amplitude was enhanced by erosion driven glacio isostatic compensation despite inconclusive evidence this phase is likely to be ongoing at present

palaeothermal and compaction studies in the mochras borehole nw wales reveal early cretaceous and neogene exhumation and argue against regional palaeogene uplift in the southern irish sea the north atlantic continental margins have been subject to widespread exhumation although the timing magnitude and causes of this uplift and erosion are debated exhumation is thought to be most severe across the irish sea basin system western uk and recent years have seen an increasing emphasis on the role of palaeogene underplating as the primary mechanism of uplift we present a study of palaeothermal and compaction data from the mochras borehole nw wales located near the presumed locus of exhumation mochras penetrated thick successions of lower jurassic and oligo miocene sediments our results indicate that both these successions experienced considerably deeper burial prior to early cretaceous and neogene exhumation respectively apatite fission track analysis afta and vitrinite reflectance data from the borehole reveal evidence for exhumation related cooling episodes beginning during the cretaceous 150 80 ma and cenozoic 50 0 ma regional afta results and stratigraphic constraints refine the timing estimates to the early cretaceous 120 115 ma and neogene 20 0 ma estimates of exhumation magnitudes during these episodes based on palaeothermal and compaction data are c 2 5 km and c 1 5 km respectively palaeothermal data provide no evidence for elevated palaeogene palaeotemperatures indicative of deeper burial and thus question the basis of palaeogene exhumation

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

early oligocene initiation of north atlantic deep water formation dating the onset of deep water flow between the arctic and north atlantic oceans is critical for modelling climate change in the northern hemisphere1 2 and for explaining changes in global ocean circulation throughout the cenozoic era3 from about 65 million years ago to the present in the early cenozoic era exchange between these two ocean basins was inhibited by the greenland scotland ridge3 4 but a gateway through the faeroe shetland basin has been hypothesized3 5 previous estimates of the date marking the onset of deep water circulation through this basin on the basis of circumstantial evidence from neighbouring basins have been contradictory5 6 7 8 9 ranging from about 35 to 15 million years ago here we describe the newly discovered southeast faeroes drift which extends for 120 km parallel to the basin axis the onset of deposition in this drift has been dated to the early oligocene epoch 35 million years ago from a petroleum exploration borehole we show that the drift was deposited under a southerly flow regime and conclude that the initiation of deep water circulation from the norwegian sea into the north atlantic ocean took place much earlier than is currently assumed in most numerical models of ancient ocean circulation

late cenozoic sediment drift complex northeast rockall trough north atlantic seismic reflection profiles and two shallow cores have revealed a sediment drift complex in the northeastern rockall trough the drift complex consists of an elongate drift with associated sediment waves a broad sheeted drift with a larger field of sediment waves and smaller moat related isolated drifts the internal reflection configuration of these features indicates consistent upslope migration throughout the late cenozoic the larger field of sediment waves has been described previously with a southerly migration a reevalution of these waves suggests a migration direction to the east conforming with the other drift complex features the most vigorous current activity probably occurred during the miocene with a more reduced current flow prevailing during the pliocene to holocene interval core evidence from the elongate drift and the moat has revealed upper pleistocene and lower holocene glaciomarine sediments reworked to produce muddy silty and sandy contourites sedimentation rates for the early holocene pre 7 5 ka are up to 4 times greater on the drift compared to the moat it is suggested that the sediment drift complex has formed through the interaction of a northward flowing slope current of north atlantic deep water origin with an area of complex bathymetry at the northeastern end of the rockall trough where the wyville thomson ridge intersects the hebridean margin

stratigraphy and facies distribution of the utsira formation and the pliocene sequences in the northern north sea abstract the upper cenozoic deposits of the northern north sea have been analysed in order to establish a regional and detailed stratigraphy the utsira formation is subdivided into four log units and mapped and two main depocentres are outlined the lower part of the utsira formation consists of thick marine mounded sand bodies interpreted as overall stacked lowstand fan deposits while the upper part of the formation consists of more clayey silty intervals indicating increased relative sea level the succeeding progradational pliocene deposits are subdivided into 13 high frequency depositional sequences and are mapped the sequences are grouped into four composite sequences each of the four pliocene composite sequences is composed of one or two rather locally distributed prograding sequences lowstand sequence set succeeded by one or two more widely distributed aggrading prograding sequences transgressive highstand sequence set boundaries between the composite sequences are recorded as marked changes in distribution of depocentres and sequence architecture the regional uplift of scandinavia is believed to be the main control on sediment input feeding the succeeding general prograding pliocene sequences oscillations of the eustatic sea level punctuated the tectonically controlled progradation and affected variations in the accommodation space and thus created the high frequency sequences

late cenozoic seismic stratigraphy and glacial geological development of the east greenland and svalbard barents sea continental margins abstract the european program on the late cenozoic evolution of the polar north atlantic margins ponam running from 1990 to 1994 resulted in a wealth of seismic data and sediment cores particularly from the svalbard and barents sea continental margin but also from areas of the east greenland margin deep sediment coring was undertaken on both margins during odp legs 152 and 162 this paper uses the ponam generated information as well as previous and subsequent seismic and core data to review our present understanding of the glacial geological development of these regions four main depositional facies have been identified these are represented by hemipelagic glaciomarine sediments sandy silty debris flows diamictic debris flows and tills deposited directly beneath grounded ice the temporal and spatial distribution of these four facies determines the architecture and seismic character of the two continental margins the two regions show significant differences with regard to both the timing of initial glaciation and the response of the ice sheets to climatic variability glacial deposition has taken place on the east greenland margin at least since 7 ma but apparently only since 2 5 ma on the svalbard barents sea margin significant glacial expansion across the continental shelf probably occurred in the early and late pliocene in east greenland whereas the glaciers on svalbard and the barents sea did not reach the shelf edge until the early pleistocene despite a shorter glacial period average glacial sedimentation rates are 2 3 times higher on the svalbard barents sea margin than on the studied parts of the east greenland margin the svalbard barents sea ice sheet has advanced and retreated much more frequently during the plio pleistocene than the greenland ice sheet glacial regime polar on greenland and polythermal to temperate in svalbard and the barents sea and the more easily erodible preglacial bedrock of svalbard and the barents sea are thought to be main factors responsible for the differences in ice sheet behavior and consequently glacial sediment production

cenozoic post rift sedimentation off northwest britain recording the detritus of episodic uplift on a passive continental margin the cenozoic sedimentary basins on the atlantic margin of nw britain contain a remarkable record of tectonically influenced post breakup sedimentation we have mapped the distribution and quantified the solid grain volume of four unconformity bound successions in the region the eocene 6 8 104 km3 oligocene 2 104 km3 miocene lower pliocene 4 5 104 km3 and lower pliocene holocene 4 5 104 km3 complementing previous work on the paleocene succession approximately 80 of the total cenozoic sediment volume on the atlantic margin of nw britain was deposited in eocene and later times the relative volumes of the cenozoic succession do not support previous claims that the paleocene was the main period of cenozoic uplift and erosion of sediment source areas rather the cenozoic sedimentary basins on the atlantic margin of nw britain record the detritus of four major episodes of cenozoic uplift of the british isles paleocene eocene oligocene miocene and pliocene pleistocene

neogene and quaternary depositional environments on the norwegian continental margin 62 n 68 n abstract 2d multichannel seismic and mini sleeve gun profiles reveal that an up to 1 5 s twt thick sedimentary succession has been deposited on the norwegian continental margin 62 n 68 n during neogene and quaternary well defined miocene depocentres have evolved both in the north sea fan region and along the flanks of structural highs in the voring basin miocene sediments are on the other hand mainly absent within the storegga slide scar seismic facies analyses show that these deposits locally are characterised by a mounded and or migration aggradation pattern which we relate to a current influenced depositional environment hence the early neogene sediments on the norwegian continental margin are classified as contourites the contourites have most likely been deposited in connection with the establishment of a deep water exchange in the norwegian greenland sea due to the opening of the fram strait and subsidence of the greenland scotland ridge at about 2 5 ma a significant change in this depositional environment took place down slope sedimentary processes became now more important and throughout the late plio pleistocene sediments were mainly sourced from the norwegian mainland and the adjacent continental shelf causing depocentres to evolve along the shelf edge

control of north atlantic deep water circulation by the greenland scotland ridge coherent bathymetric features along the reykjanes ridge indicate that there were significant changes in the flux of buoyant material within the icelandic hot spot during the neogene the radial extent of the topographic swell associated with this hot spot is of the order of 1000 to 2000 km and therefore these changes affected the greenland scotland ridge gsr at present sill depths along the gsr are generally less than 500 m with the deepest passage being less than 1000 m making the overflow water sensitive to even small changes in the ridge depths reconstructions of neogene mantle plume activity correlate with the deepwater circulation patterns in the north atlantic times of high mantle plume activity caused northern component water ncw production to cease ncw fluxes resumed once this phase of high mantle plume activity slowed the long term climate change during the neogene must be controlled by factors other than ncw production however climatic optima during the late early miocene and early pliocene appear to have been augmented by high ncw fluxes while subsequent middle miocene and middle pliocene coolings correlate with uplifts on the gsr and reduced ncw flux we suggest that reductions in ncw may have contributed to both of these cooling events

sediment drifts and contourites on the continental margin off northwest britain abstract seismic reflection profiles and short cores from the continental margin off northwest britain have revealed a variety of sediment drift styles and contourite deposits preserved in the northeast rockall trough and faeroe shetland channel the sediment drifts include 1 distinctly mounded elongate drifts both single and multi crested 2 broad sheeted drift forms varying from gently domed to flat lying and 3 isolated patch drifts including moat related drifts fields of sediment waves are locally developed in association with the elongate and gently domed broad sheeted drifts the contrasting styles of the sediment drifts most probably reflect the interaction between a variable bottom current regime and the complex bathymetry of the continental margin the bulk of the mounded gently domed drifts occur in the northeast rockall trough whereas the flat lying sheet form deposits occur in the faeroe shetland channel a much narrower basin which appears to have been an area more of sediment export than drift accumulation patch drifts are present in both basins in the northeast rockall trough the along strike variation from single to multi crested elongate drifts may be a response to bottom current changes influenced by developing drift topography muddy silty muddy and sandy contourites have been recovered in sediment cores from the uppermost parts of the drift sequences on the basis of their glaciomarine origin these mid to high latitude contourites can be referred to collectively as glacigenic contourites both partial and complete contourite sequences are preserved the former consist largely of sandy mid only and top only contourites sandy contourites by their coarse grained nature and their formation under strongest bottom current flows are the most likely to be preserved in the rock record however the very large scale of sediment drifts should be borne in mind with regard to the recognition of fossil contourites in ancient successions

seismic stratigraphy of the west shetland drift implications for late neogene paleocirculation in the faeroe shetland gateway 1 the morphology and anatomy of a late neogene contourite drift on the british margin of the faeroe shetland channel is investigated in unprecedented detail using industrial two dimensional and three dimensional seismic data the west shetland drift is constructed by a succession of mounded asymmetric strata that in the basin and on the midslope has accumulated on a regional unconformity of early pliocene age the midslope component of the drift system forms a 400 m thick convex elongate sedimentary body that can be traced from the outlet of the norwegian channel and 250 km southwest along the shetland margin contourite drifts occupying the basin are evident as a succession of sheeted mounded and wavy migrating units intercalated by three mega debrite sequences the seismic architecture of the west shetland drift and tentative age estimates of its bounding surfaces suggests that it formed rapidly 5 10 cm kyr 1 by alongslope transport of hemipelagic sediments derived from the nw european shelf the change from erosion nondeposition to enhanced contourite drift accumulation during the early pliocene suggests that a moderate thermohaline current regime prevailed in the faeroe shetland channel prior to the main phase of northern hemisphere glaciation at 3 0 2 5 ma a reduction in meridional heat transport associated with a decrease in the flux of north atlantic deep waters may have been an important factor for the growth of northern hemisphere ice sheets

deep marine seabed erosion and gravel lags in the northwestern rockall trough north atlantic ocean a zone of active seabed erosion has been identified in the northwestern rockall trough using seismic reflection profiles and cores the region from george bligh bank to rockall bank has been subject to vigorous bottom current activity for at least the last 35 ma bottom currents originate from southward flowing north atlantic deep water in water depths of 500 2000 m acoustic character mapping reveals a zone of erosion extending over 8500 km 2 along the northwestern margins of the trough the erosion surface is characterized by an acoustically reflective seabed with occasional parallel to transparent reflectors these are the result of strong bottom currents exposing the underlying volcanic basement drift sequences and fan sediments the erosion surface is covered by a

passive margin uplift around the north atlantic region and its role in northern hemisphere late cenozoic glaciation tectonic climatic models of late cenozoic global cooling emphasize the importance of middle latitude uplifts e g tibetan plateau and the american west but ignore widespread tectonic events on the margins of the north atlantic ocean pleistocene glaciations after 2 5 ma are characterized by circum north atlantic continental ice sheets that formed by the coalescence of perennial snow fields on extensive plateau surfaces in eastern canada northwest britain and scandinavia plateaus record cenozoic uplift of peneplains in response to semisynchronous magmatic underplating and thermal buoyancy of rifted continental margins high standing plateaus are very sensitive to small reductions in summer temperature as late cenozoic climate cooling proceeded driven by uplift in regions external to the north atlantic region elevated plateaus became sites for extensive snow fields and ultimately ice sheets circum atlantic uplift took place in the key latitudinal belt that is most sensitive to orbitally forced changes in solar irradiation this together with albedo effects from large snow fields could have amplified the relatively weak milankovitch signal

the geology of the uk hatton rockall margin abstract seismic potential field sea bed sample and shallow drilling data have been used to investigate the geology of the uk part of the rockall plateau most of the rockall plateau is underlain by early proterozoic rockall bank islay terrane metamorphic basement although george bligh bank and the north eastern end of hatton bank may be underlain at depth by lewisian rocks the basement crops out on rockall bank but occurs at a much deeper level beneath hatton bank and hatton basin the widespread palaeogene lavas of rockall plateau have been sourced from large central igneous complexes rockall swithin sandastre mammal lyonesse and sandarro local volcanoes and fissures some of the lavas may also have been derived from the incipient rift axis west of hatton bank at the time of continental break up differences in seismic facies allow the extent of the lavas from the large centres to be mapped where the lavas are absent beneath parts of hatton bank either due to non emplacement or subsequent erosion during the cenozoic seismic data image the underlying mesozoic and older rocks here bgs boreholes 99 1 and 99 2a have proved mid cretaceous albian shales and sandstones respectively beneath a thin cenozoic cover the mesozoic and older rocks appear to be quite extensive and are folded and faulted mesozoic strata are not observed on rockall bank in uk waters the post lava cenozoic succession of rockall plateau can be sub divided into three megasequences separated by two unconformities which by analogy with rockall basin have been designated c30 intra late eocene and c10 intra early pliocene the ages can be corroborated by dsdp odp boreholes in the hatton basin the cenozoic succession contains eocene prograding fan sequences contourite deposits on the flanks of the banks and shallow faulting some of which affects the present day sea bed structurally rockall high appears mainly as a large basement block whereas hatton high is more complex exhibiting half grabens inversion structures and reverse fault geometries due to cenozoic tectonism the northern end of hatton high is a large anticline with its axis aligned ene wsw the structural differences between the highs may be due to their locations with rockall high exhibiting fewer tectonic effects due to its more landward intraplate setting further away from plate margin deformation

contourites and their relevance for mass wasting along the mid norwegian margin between about 12 and 4 3 ma slope parallel bottom currents dominated the neogene sedimentation on the slope of the mid norwegian margin and large scale sediment bodies accumulated to thicknesses up to 1000 m these bedforms are morphologically classified as sheeted and elongated mounded contourite drifts an increase in sediment supply from about 4 to 3 ma due to onshore uplift and glaciation resulted in a massive influx of downslope derived material onto the continental margin only on the voring plateau was contourite sedimentation little affected by this change in sedimentary style during the last 0 5 my contouritic deposits occurred also in the storegga area as 100 150 m thick infill drifts inside the scars of two palaeo slides r and s holocene post slide deposits in the scar of the storegga slide 8 2 ka have the typical morphological features and distribution of contourite drifts with the upslope limit at the lower base of the warm northward flowing north atlantic current at 500 700 m depth and the downslope limit at depths of approximately 1200 m detailed chronostratigraphy of the post slide sediments show relatively constant high sedimentation rates in the order of 1 2 m ky during the last 8000 years this is equivalent to the estimated rates for the older infill drifts the infill drifts consist mainly of clays with silty and sandy lamina and represents marine and glaciomarine conditions the main influence of contourite drifts on slope stability relates to their physical properties forming a more sensitive and brittle deposit than the glacial deposits and their exposure to downslope sedimentation in addition the potential for build up of excess pore pressure due to rapid loading from subsequent glacial depositions their seabed smoothing effect and great lateral extent make the contourite drift deposits particularly important for slope instability in this region

episodic cenozoic tectonism and the development of the nw european passive continental margin the north atlantic margins are archetypally passive yet they have experienced post rift vertical movements of up to kilometre scale the cenozoic history of such movements along the nw european margin from ireland to mid norway is examined by integrating published analyses of uplift and subsidence with higher resolution tectono stratigraphic indicators of relative movements including results from the stratagem project three episodes of epeirogenic movement are identified in the early mid and late cenozoic distinct from at least one phase of compressive tectonism two forms of epeirogenic movement are recognised referred to as tilting coeval subsidence and uplift rotations 1 over distances of 100s of kilometres and sagging strongly differential subsidence rotations up to 4 over distances 100 km each epeirogenic episode involved relatively rapid 10 ma km scale tectonic movements that drove major changes in patterns of sedimentation to find expression in regional unconformity bounded stratigraphic units early cenozoic tilting late paleocene to early eocene c 60 50 ma caused the basinward progradation of shelf slope wedges from elongate uplifts along the inner continental margin and from offshore highs mid cenozoic sagging late eocene to early oligocene c 35 25 ma ended wedge progradation and caused the onset of contourite deposition in deep water basins late cenozoic tilting early pliocene to present 4 0 5 ma again caused the basinward progradation of shelf slope wedges from uplifts along the inner margin including broad dome like features and from offshore highs the early mid and late cenozoic epeirogenic episodes coincided with atlantic plate reorganisations but the observed km scale tectonic movements are too large to be accounted for as flexural deflections due to intra plate stress variations mantle lithosphere interactions are implied but the succession of epeirogenic episodes of differing form are difficult to reconcile with the various syn to post rift mechanisms of permanent and or transient movements proposed in the hypothetical context of a plume beneath iceland the epeirogenic movements can be explained as dynamic topographic responses to changing forms of small scale convective flow in the upper mantle tilting as coeval upwelling and downwelling above an edge driven convection cell sagging as a loss of dynamic support above a former upwelling the inferred cenozoic succession of epeirogenic tilting sagging and tilting is proposed to record the episodic evolution of upper mantle convection during ocean opening a process that may also be the underlying cause of plate reorganisations the postulated episodes of flow reorganisation in the ne atlantic region have testable implications for epeirogenic movements along the adjacent oceanic spreading ridge and conjugate continental margin as well as on other atlantic type passive margins

episodic rapid uplift in the himalaya revealed by 40ar 39ar analysis of detrital k feldspar and muscovite bengal fan detrital k feldspar and muscovite samples from ocean drilling program leg 116 cores have been dated by the sup 40 ar sup 39 ar technique and have depositional ages from 0 to 18 ma from 4 to 13 individual k feldspars and 1 to 12 individual muscovites have been dated from 7 stratigraphic levels in every level at least one k feldspar and one muscovite yielded a minimum age identical within uncertainty to the age of deposition these results indicate that a significant portion of the material in the bengal fan is first cycle detritus derived from the himalaya therefore the substantial amount of sediment deposited in the distal fan in early to middle miocene time can be ascribed to a significant pulse of uplift and erosion in the collision zone at this time moreover these data indicate that throughout the neogene some part of the himalayan orogen was undergoing rapid erosion 1 to 10 mm yr this erosion must have been less than or equal to uplift relative to sea level the lack of granulite facies rocks in the eastern himalaya and tibetan plateau suggests to us that very rapid uplift must have been distributed in brief pulses over different parts of the mountain belt these datamore are incompatible with tectonic models in which the himalaya and tibetan plateau are uplifted either uniformly over the past 40 m y or mostly within the past 2 to 5 m y less

quaternary erosion and depositional processes western norwegian fjords norwegian channel and north sea fan abstract the southern norwegian fjords the northern north sea and north sea margin represent major pathways of sediment flux from the southern part of fennoscandia to the deep sea basin volumes genesis and chronology of the temporary and semi permanent quaternary sediment repositories are reviewed the fjord infill is dominated by sediments from the last deglaciation 150 km 3 the norwegian channel is occupied by tills and glaciomarine marine sediments 5000 km 3 the north sea fan comprises glacially fed debris flow fingers lobes constituting 80 of deposits in the mid to late pleistocene together with hemipelagic and mass transport slide sediments totalling 15 000 km 3 the norwegian channel represents a dynamic transport conduit whereby during peak glaciation a fast flowing ice stream has drained large parts of the southern fennoscandian ice sheet several times the sediment flux to the deep sea is temporarily interrupted between glacials when stored in the channel but under glacial maxima the channel is probably largely bypassed with material transported as subglacial load and deposited as debris flows on the north sea fan sediments on the fan have a much longer storage time numerous glaciation cycles but are further transported to the deep sea in large slide events the volume of quaternary sediments found along this sediment pathway plus that which slid to the deep sea total at least 25 000 km 3 corresponding to an averaged 120 m of erosion across southern norway

trough mouth fans palaeoclimate and ice sheet monitors abstract trough mouth fans are fans at the mouth of transverse troughs channels on glaciated continental shelves on the northwest european glaciated continental margin eight trough mouth fans varying in size between 2700 and 215 000 km 2 have been identified the trough mouth fans are depocentres dominated by debris flows accumulated in front of ice streams draining the former large northwest european ice sheets the debris flow units are separated by hemmipelagic interglacial interstadial sediments it is inferred that the number of debris flow units record the number of shelfbreak positions of the ice sheet margins the number found varies between three in the south and eight in the north typical trough mouth fans and related debris flow units seem to have been formed later than the early mid pleistocene thus the north european ice sheets did not form ice streams extending to the shelfbreak in any appreciable length before the mid pleistocene besides being loci for sediment deposition the trough mouth fans were also the main sites of fresh water supply to the ocean in the form of icebergs during the mid late pleistocene ice ages

late cenozoic prograding wedges on the nw european continental margin their formation and relationship to tectonics and climate abstract during late pliocene to pleistocene times prominent prograding wedges were deposited along the continental margin of nw europe resulting in seaward shelf break migration of up to 150 km much of the sediment accumulation occurred marginal to the former mid to high latitude ice sheets the geographical distribution and stratigraphical and chronological data may suggest that the instigation of the wedges was variously related to tectonic uplift as well as a response to the late pliocene to pleistocene climate deterioration and onset of major northern hemisphere glaciations the onset of wedge growth on the nw uk and irish margins was initiated at about 4 ma in response to tectonic tilting of the margin in that region however glacially derived sediments here comprise a significant proportion of the wedges especially since 0 44 ma for the faroe margin no detailed chronology is available however it may be inferred that onset of glacigenic wedge growth here did not post date that observed on the nw uk and irish margins offshore norway wedge growth has largely occurred since ca 2 7 ma in response to northern hemisphere glaciations also recording a major change in sediments transport routes at 0 8 1 1 ma reflecting larger fennoscandian ice sheets presently it is uncertain whether the glacigenic wedge growth was preceded by a fluvial phase in response to uplift in this area in the western barents sea an early phase of wedge growth was glacio fluvial in character off western spitsbergen the development was similar to that of the barents sea although the glacigenic wedge growth phase may have started somewhat earlier the wedges commonly display gently inclined seaward prograding clinoforms and transparent to chaotic internal acoustic facies sampling of their sediments reveals that they are mainly composed of glacigenic diamicton interbedded with marine and glaciomarine sediments that to various extents have been affected by bottom current action the clinoforms of these wedges vary in geometry from oblique to sigmoidal and they also show varying degrees of aggradation throughout their development the resulting stratal stacking pattern can be attributed to a combination of variations in sediment supply sedimentary processes and accommodation space the latter being a function of tectonic movements and or loading induced subsidence as well as eustatic sea level fluctuations

bottom current sediment waves sediment drifts and contourites in the northern rockall trough four types of large scale sediment bedform occur in the northeast rockall trough broad sheeted drifts elongate drifts sediment waves and thin contourite sheets a large sheeted drift occupies the northern basin its crest can be traced for 40 km perpendicular to the bottom current flow direction elongate drifts occur adjacent to steep areas of continental slope separated from the break of slope by a moat drift crests are oriented alongslope parallel to bottom current flow elongate drifts are asymmetric with the steeper flank facing upslope sedimentation rates are higher on the downslope flank sediment waves with a wavelength of 1 2 km and wave height up to 20 m occur locally on the flanks of sheeted and elongate drifts larger waves wavelength of 3 4 km and wave height of 50 100 m occur on the flank of the wyville thomson ridge wave crests are oblique to bathymetric contours to drift crests and to bottom current flow the association of sediment waves and drifts their orientation oblique to regional slopes and the presence of contourite sediments in cores indicate that these are bottom current rather than turbidity current waves a contourite sheet typically 10 25 cm in thickness and composed of well sorted sand covers the present day seafloor along the lower slope bedform evolution through time has involved a complex interaction between bottom currents of variable intensity sea level change and sediment input the present sea level highstand is characterised by minimal sediment input and redistribution of sediments by strong bottom currents giving active bedform growth and contourite development variability of sediment input is the main factor affecting sedimentation during sea level lowstands where input was high as when ice sheets reached the shelf edge downslope sediment transport dominated overwhelming any bottom currents that were active when input was low such as during the last lowstand some evidence for active currents can be observed although these were less energetic than those during highstands