weichselian and holocene growth of the northern high latitude lofoten contourite drift on the continental slope of norway abstract the weichselian and holocene sediments in the lofoten drift comprise six lithofacies brown sandy mud olive grey mud olive grey laminated mud dark brown mud massive sand and dark grey sandy mud during the weichselian the sediment input to the lofoten drift was from two main sources i e glacimarine sedimentation and ocean current winnowing during the holocene the sediment input was only from winnowing the sediment source area was the voring margin and the continental margin further south the sedimentation rate was 190 cm ka during the late weichelian and 9 cm ka during the holocene the weichselian rates are high compared with the deep sea contourite drifts comprising highly bioturbated sediments and probably explain why bioturbation is less pronounced in these slope drift sediments drifts on glaciated margins as exemplified by the lofoten contourite drift represent areas of high sedimentation rate during glacial maxima sediment input was not restricted to glacial maximum periods for sediments also accumulated during other stadial and interstadial periods

oxygen isotopes of phosphate and soil phosphorus cycling across a 6500 year chronosequence under lowland temperate rainforest abstract phosphorus p availability declines during ecosystem development due in part to chemical transformations of p in the soil here we report changes in soil p pools and the oxygen isotopic signature of inorganic phosphate 18op in these pools over a 6500 year soil coastal dune chronosequence in a temperate humid environment total p declined from 384 to 129 mg p kg 1 during the first few hundred years of pedogenesis due mainly to the depletion of primary mineral p in the hcl extractable pool the 18op of hcl extractable inorganic p initially reflected the signature of the parent material but shifted over time towards but not reaching isotopic equilibrium in contrast 18op signatures of inorganic p extracted in water and nahco3 approximately 9 and 39 mg p kg 1 respectively were variable but consistent with isotopic equilibrium with soil water in the naoh extractable p pool which doubled from 63 to 128 mg p kg 1 in the early stages of pedogenesis and then gradually declined the 18op of the extracted inorganic p changed from equilibrium values early in the chronosequence to more depleted signatures in older soils indicating greater rates of hydrolysis of labile organic p compounds such as dna and increase involvement in p cycling as overall p availability declines through the sequence in summary this application of 18op to a long term soil chronosequence provides novel insight into p dynamics indicating the importance of efficient recycling through tight uptake and mineralization in maintaining a stable bioavailable p pool during long term ecosystem development

rapid climatic shifts during isotope stages 2 4 in the polar north atlantic sediment cores from the polar north atlantic provide evidence of six periods of sea ice breakup during isotope stages 4 3 and 2 probably caused by inflow of north atlantic surface water into the polar north atlantic these periods are characterized by having a high number of foraminifera g they last from 2000 to 10000 yr and constitute 50 of the total time span these periods of sea ice breakup correlate temporarily to the heinrich events and the early temperature maximum in the bond cycles of the north atlantic and greenland ice record our hypothesis is that massive iceberg discharges that flooded the north atlantic during each heinrich event probably triggered an oceanographic regime that gave a much more vigorous surface circulation pattern in the polar north atlantic which contributed to the breakup of the sea ice cover open water conditions in the polar north atlantic are inversely related to terrestrial interstadials of coastal norway suggesting ice sheet starvation during the cold periods and ice sheet growth when an open water surface circulation existed in the polar north atlantic our data document synchronous variations on a october 1900 yr time scale between arctic oceanic climate northern hemisphere ice sheet dynamics and ocean atmosphere temperature changes

landform classification and soil distribution in hummocky terrain saskatchewan canada this study presents a classification of distinct three dimensional landform elements and examines the relationship between these landform elements and selected soil morphological properties of udic boroll soils in southern saskatchewan canada the classification is based on defined ranges of three criteria derived from topographic data gradient profile downslope curvature and plan across slope curvature seven landform elements are recognized convergent shoulders divergent shoulders convergent backslopes divergent backslopes convergent footslopes divergent footslopes and level elements all of the elements are easily identified in the field the thicknesses of a horizons and depths to calcium carbonate of the soils were consistently greater in convergent versus divergent elements in the same profile group e g shoulders and showed an overall increase in the sequence shoulders backslopes level footslope elements distinct groups of elements emerge from a statistical analysis of the differences between individual and bivariate means of soil morphological properties associated with each landform element the differences in soil properties among the elements can be largely explained by differences in water movement and distribution in hillslope systems the results of the study highlight the need to consider land surface morphology during the development of research designs for soil related studies

catastrophic fluid escape venting tunnels and related features associated with large submarine slides on the continental rise off vesteralen troms north norway abstract video inspection of the seabed on the continental rise ca 2200 m water depth off vesteralen troms north norway has revealed several remarkable features including large tunnels small tunnels chimney tunnels carbonate crusts and bacterial mats the structures occur in landslide areas with slide blocks up to 2 km long 1 km wide and 100 m high we hypothesize that the large seabed tunnels in and between slide blocks and with opening diameters up to 1 m and apparent inner diameters of 10 20 cm are formed by dewatering of fine grained sediments buried by the slide masses and possibly venting of underground gas reservoirs related to sliding and loading this process probably occurred instantaneously after sliding numerous small tunnels with diameters up to a few centimetres in slide blocks of compacted sediments may have formed by dewatering following sudden pressure release or by decomposition of gas hydrates following off loading of sediments due to sliding bacterial mats and carbonate crusts indicate active leakage of subsurface fluids and methane through the seabed and the gas hydrate stability zone either from thermogenic sources or from shallow reservoirs cemented chimney tunnels up to 15 cm tall and with inner diameters up to a few centimetres occur both on slide blocks and on flat and even seabed the presence of apparently both inactive and active chimney tunnels indicates that gas and fluid release is a process that has been periodically active possibly from before sliding up to the present

moisture supply for northern ice sheet growth during the last glacial maximum during the last ice age the barents sea ice sheet began to grow 22 kyr ago1 only 8 kyr before it began to disintegrate2 this implies that the ice must have grown very rapidly from the coast to the edge of the continental shelf such rapid growth of a large ice sheet requires significant amounts of moisture3 but the origin of this moisture has been unclear particularly as the climap climate reconstruction suggests4 5 that the greenland iceland norwegian gin seas were perennially ice covered during this period here we present data from deep sea sediment cores from the fram strait which suggest that relatively warm water from the north atlantic ocean was advected into the gin seas in two short term events 27 22 5 and 19 5 14 5 kyr ago we suggest that the resulting seasonally ice free waters were an important regional moisture source for the barents sea ice sheet and that the gin seas played a much more active role in climate during the last glaciation than has previously been supposed

origin and consequences of cyclic ice rafting in the northeast atlantic ocean during the past 130 000 years deep sea sediment cores recovered from the northeast atlantic ocean were examined in order to elucidate the influence of the earth s orbital parameters on major ice rafting analyses of coarse grained ice rafted debris and planktonic foraminifers revealed a strong reaction to the precession signal since 130 000 yr b p dropstone layers have been deposited each half period of a precessional cycle 11 000 1000 yr ice rafting occurs during times of winter minimum summer maximum insolation and summer minimum winter maximum insolation in the first case high summer insolation forces meltwater discharge from the ice sheets into the polar seas which subsequently enhances formation of sea ice during the winter in the second case growth of continental ice enhances iceberg production which also leads to a salinity reduction of surface seawater both situations result in a southward penetration of polar water thus the marine record of dropstones documents ice rafting not only during weichselian stades but also during cold events within interstades the regularity of ice rafting yields a useful framework to calibrate and elucidate climatic changes not only in the region of the north atlantic ocean but also in remote areas such as the pacific ocean and the antarctic

initiation of fennoscandian ice sheet retreat during the last deglaciation although the retreat history of the southern margin of the laurentide ice sheet during the last deglaciation has been well known for several decades1 3 and recently supported by evidence from accelerator mass spectrometer ams radiocarbon dating of meltwater in the gulf of mexico4 and the north atlantic subtropical gyre5 the retreat history of the fennoscandian ice sheet before 13kyr ago is still poorly documented from ams 14c dating and isotopic analysis of a rapidly deposited series of supra till sediments in the norwegian channel north sea we find that the southern margin of the fennoscandian ice sheet was in retreat by 15 kyr bp before present approximately 2 000 yr earlier than previously supposed oxygen isotope analyses in the channel sediments confirm earlier evidence from deep norwegian sea sediment cores for low salinity due to ice sheet discharge beginning 15 14 5 kyr bp ref 6 recent recalibration of the 14c timescale indicates that the onset of deglaciation within the norwegian sea occurred during an interval of rapidly increasing summer insolation beginning 18 000 calendar yr bp ref 7 suggesting that ice sheet retreat may have been caused by increasing insolation acting on a particularly climate sensitive ice sheet configuration fresh water and icebergs discharged into the norwegian sea at this time reached the north atlantic and may have contributed to a brief interval of extreme oceanic cooling8 and reduced production of north atlantic deep water9 10 these factors may also have helped to briefly reverse the deglaciation trend erie interstade already underway in north america

sedimentary environment and glacial history during the last 40 ka of the voring continental margin mid norway abstract this study is based on detailed investigation of sediment cores and high resolution seismics we identified and describe five lithofacies on the voring plateau and eight on the mid norwegian continental slope the various lithofacies are mainly related to the fluctuations of the fennoscandian ice sheet and the varying intensity of bottom currents and inflow of atlantic water masses ocean circulation was highly variable between 40 and 22 14 c ka bp being vigorous during interstadials and sluggish during stadials between ca 22 and 15 14 c ka bp the sedimentary environment was significantly influenced by fluctuations of the fennoscandian ice sheet repeatedly reaching the outermost shelf these fluctuations are reflected in the sedimentary record as ice rafted debris ird accumulation peaks deposition of stratified diamicton and glacigenic debris flows on the continental slope during this period the sediment accumulation rate increased bottom currents influenced the sedimentary pattern and surface waters were seasonally ice free indicating inflow of atlantic waters subsequent to ca 15 14 c ka bp the glacier influence decreased as the margin of the fennoscandian ice sheet retreated to reach the coast before 12 5 14 c ka bp the modern sedimentary environment is characterised by relatively strong bottom current action causing winnowing or non deposition down to approximately 1000 m water depth

mid late pleistocene glacimarine sedimentary processes of a high latitude deep sea sediment drift antarctic peninsula pacific margin the effects of glaciation on sediment drifts is recognised from marked sedimentary facies variation in deep sea cores taken from the continental rise of the antarctic peninsula pacific margin nineteen sediment cores were visually described logged for magnetic susceptibility and x radiographed about 1000 analyses were performed for grain size clay minerals and biostratigraphy foraminifera nannofossils and diatoms four sediment types associated with distinct sedimentary processes are recognised based on textural compositional analysis 1 hemipelagic mud forms the bulk of the interglacial sediment and accumulated from the pelagic settling of bioclasts and ice rafted wind transported detritus 2 terrigenous mud forms the bulk of the glacial sediment and accumulated from a combination of sedimentary processes including turbidity currents turbid plumes and bottom current reworking of nepheloid layers 3 silty deposits occurring as laminated layers and lenses represent the lateral spillout of low density turbidity currents 4 lastly glacial interglacial gravelly mud layers derive from settling of ice rafted detritus five depositional settings are interpreted within sediment drift 7 each characterised by the dominance interaction of one or several depositional processes the repetitive succession of typical sedimentary facies is inferred to reflect a sequence of four climatic stages glaciation glacial deglaciation and interglacial each one characterised by a distinctive clay mineral assemblage and bioclastic content variations in clay mineral assemblage within interglacial stage 5 core sed 06 suggest minor colder climatic fluctuations possibly correlatable with substages 5a to 5e

the norwegian greenland sea continental margins morphology and late quaternary sedimentary processes and environment the continental margins surrounding the norwegian greenland sea are to a large degree shaped by processes during the late quaternary the paper gives an overview of the morphology and the processes responsible for the formation of three main groups of morphological features slides trough mouth fans and channels several large late quaternary slides have been identified on the eastern norwegian greenland sea continental margin the origin of the slides may be due to high sedimentation rates leading to a build up of excess pore water pressure perhaps with additional pressure caused by gas bubbles triggering might have been prompted by earthquakes or by decomposition of gas hydrates trough mouth fans tmf are fans at the mouths of transverse troughs on presently or formerly glaciated continental shelves in the norwegian greenland sea seven tmfs have been identified varying in area from 2700 km2 to 215 000 km2 the trough mouth fans are depocentres of sediments which have accumulated in front of ice streams draining the large northwest european ice sheets the sediments deposited at the shelf break upper slope by the ice stream were remobilized and transported downslope mostly as debris flows the trough mouth fans hold the potential for giving information about the various ice streams feeding them with regard to velocity and ice discharge two large deep sea channel systems have been observed along the norwegian continental margin the lofoten basin channel and the inbis channel along the east greenland margin several channel systems have been identified the deep sea channels may have been formed by dense water originating from cooling sea ice formation and brine rejection close to the glacier margin or they may originate from small slides on the upper slope transforming into debris flows and turbidity currents

contourites from eirik ridge south of greenland abstract the eirik ridge is an 800 km long submarine sediment drift south of greenland in waterdepths of 2000 3500 m it has been constructed largely by bottom currents formed from cold norwegian sea water that overflows across the denmark strait ice rafting and normal hemipelagic settling may also contribute some sediment to the drift three cores recovered from the drift contain fine grained clayey and silty contourites these show a high degree of bioturbation in 99 of the core material primary lamination has been partially or totally disturbed where preserved contourite laminae consist of simple silt and clay alteration without systematic thickness variation and are largely composed of biogenic debris with some terrigenous material by contrast fine grained parallel laminated spill over turbidites on the levees of the nearby northwest atlantic mid ocean channel namoc in the center of the labrador sea are little affected by bioturbation and show systematic upward thickness variations between successive silt and clay laminae

the microbial cycling of phosphorus on long term fertilized soil insights from phosphate oxygen isotope ratios abstract microorganisms mobilize phosphorus p from soil and make it available for plants however the role of microbial activity in soil p dynamics especially among different p pools is poorly understood largely due to methodological limitations in this study we analyzed the oxygen isotope ratios in phosphate 18op of sequentially extracted inorganic p pi pools h2o pi nahco3 pi naoh pi and hcl pi in a long term agricultural research field in henan china with different fertilization histories and coupled with soil enzyme activity and p cycling bacteria gene abundance studies results showed the dominant enzymes were alkaline phosphatase apase and phosphodiesterase pde and the functional genes for p cycling were bpp cphy phox and pqqc after long term p fertilization the 18op values of h2o pi nahco3 pi and naoh pi pools approached to or achieved equilibrium suggesting that the externally applied p was actively mobilized and cycled by soil microorganisms and speciated into different p pools based on the extent of isotope excursion among different pi pools the equilibrium fractionation oriented the source signature in the nahco3 pi and naoh pi pools and hcl pi pool could be derived from p fertilizer but through multistep reactions and mixed with the hcl pi from rock weathering product which constituted hcl pi pool in the non p treatments overall the long term p fertilization especially the balanced fertilization with nitrogen n p and potassium k was found to be beneficial for extensive utilization of soil p with abundant biological uptake and cell internal pi cycling variation partitioning analysis vpa indicated that the expression of functional genes may be stimulated to mobilize soil p under specific p pools distribution in this alkaline environment overall our findings provide new insights to understand the roles of microbial activities in soil p biogeochemistry that are useful for agricultural p sustainability

shallow plio pleistocene contourites on the hebrides slope northwest u k continental margin abstract british geological survey borehole 88 7 was drilled on the continental margin of the northeast rockall trough in a water depth of 560 m with the intention of coring an unbroken plio pleistocene succession the borehole penetrated 102 m of pleistocene and tertiary sediments with 60 recovery the majority of the plio pleistocene succession is composed of bioturbated muds and sandy muds with rare dropstones in most of the core bioturbation has obscured any primary sedimentary structures although in places the muds are laminated and graded on a centimetric scale subtly different trace fossil assemblages in the homogeneous and laminated core indicate that the preservation of laminae is not simply the result of a decrease in burrowing activity x radiographs of the apparently homogeneous sections of core indicate that both coarsening and fining upward sequences between 5 and 50 cm in thickness are present particle size analysis has identified larger variations in grain size over several metres sands in the plio pleistocene are not common and comprise under 8 of the total succession most of which directly overlie older tertiary sediments the mineralogy of the plio pleistocene sands implies reworking of the lower beds and their base is marked by a conglomeratic lag deposit the change between homogeneous and laminated muds appears to be the result of variations in the style of sediment deposition at times deposition rate was relatively rapid and formed a laminated sediment with a trace fossil assemblage containing bedding parallel forms this more rapid sedimentation rate may be the result of greater down slope transport of material to the north or south of 88 7 giving rise to the lateral redistribution of fine sediment which was laid down in laminated beds similar in form to distal turbidites when this lateral source was not present the background sedimentation of ice rafted and ice margin derived material gave rise to a poorly sorted deposit which was reworked into both coarsening and fining upward units which have similarities with muddy contourites all the plio pleistocene muds have been influenced by along slope currents during deposition

late weichselian submarine debris flow deposits on the bear island trough mouth fan sedimentary processes on the bear island trough mouth fan during the last glacial were studied using high resolution reflection seismics and gravity cores the fan succession is dominated by large debris flow deposits of up to 24 km in width and 50 m thick debris lobes can be followed over 100 km downslope and the largest cover an area of 1880 km2 the large debris flows were generated when the barents sea ice sheet reached the shelf break glacigenic sediments transported to the grounding line were temporarily stored on the upper slope due to the high sedimentation rate the sediments were unstable and earthquakes oversteepening and or build up of excess pore pressure triggered sediment release generating large debris flows sediments were also eroded and incorporated during the downslope flow debris flows were the most important sediment distributing process due to the relatively high shear strength low flow mobility of the glacigenic diamicton and the low fan gradient the weichselian evolution of the fan was characterized by a relatively low sedimentation rate during the early and mid weichselian the barents sea ice sheet might have reached the shelf break twice during the late weichselian on average one large debris flow comprising 18 km3 of sediments was released between every 35 to 75 years during the last glacial maximum

glacial contourites on the antarctic peninsula margin insight for palaeoenvironmental and palaeoclimatic conditions deep sea finely laminated and barren glacial sediments occur in the sediment drift field offshore the pacific margin of the antarctic peninsula where a weak contour current flows at present to the sw atypical sedimentary facies were related to the coexistence and interaction of different sedimentary processes three end members of radiograph facies were defined to represent the sedimentary sequences controlled by a dominant process as follows 1 direct influence of turbidity currents on sedimentation is observed in the area surrounding the alexander channel system with silty layers interbedded with laminated mud free of ice rafted debris ird 2 distal meltwater turbid flows dominate the more proximal area of the top plateau with structureless and coarser grained sediments containing ird 3 along the crest of the drift persistent weak bottom currents control the deposition of fine grained sediments conveyed into the system through other processes these laminated sediments contain ird and are atypically not bioturbated because of unusual climatically related environmental conditions of suppressed primary productivity and oxygen reduced deep waters these glacial contourites were observed on most of the antarctic margin with the exception of the areas in which polynyas were maintained during the glacial stages glacial contourites can be used as a proxy to define temporal and spatial extension of the antarctic sea ice deep sea sediments of the sediment drifts offshore the pacific margin of the antarctic peninsula were investigated within the sedano sediment drifts of the antarctic offshore and mogam morphology and geology of antarctic margins antarctic peninsula and wilkes land projects of the italian programma nazionale di ricerche in antartide fig 1 the continental shelf of the pacific margin of the antarctic peninsula is dissected by a number of modern u shaped troughs that reflect the neogene path of large ice streams rebesco et al 1998 2002 sediments across the continental shelf were transported mainly by ice streams and delivered to the continental slope and rise during the periods of maximum glacial expansion the continental rise hosts a number of large sediment drifts separated by dendritic deep sea channel systems that originated on the lower continental slope in alignment with the reaches of each glacial trough amblas et al 2006 rebesco et al 2007 two main alternating lithologies related to climatic changes were initially distinguished pudsey camerlenghi 1998 pudsey 2000 interglacial brown bioturbated mud containing sparse icerafted debris ird and glacial grey laminated mud further detailed studies consisting of over 1000 sedimentological compositional and biostratigraphic analyses diatoms foraminifers and nannofossils allowed lucchi et al 2002a to distinguish four distinctive sets of sedimentary facies connected to a sequence of four climatic stages each characterized by the onset of typical sedimentary processes fig 2 as follows 1 strongly bioturbated mud with abundant ird and aeolian sediment input was produced during the interglacial phase fig 2a the increased bioactivity is matched by insignificant downand along slope processes negligible suspended load and sediment transport by the southwesterly flowing bottom currents is occurring at present on the continental rise giorgetti et al 2003 2 terrigenous structureless mud including a series of close spaced ird layers was produced during the deglaciation transition from glacial to interglacial conditions by the disintegration of the retreating grounded ice sheet fig 2b the absence of calcareous microfossils is related to strong carbonate dissolution and rise of the carbonate compensation depth ccd as a result of major meltwater discharge which in turn caused water stratification with less oxygenated and nutrient enriched conditions at the sea bottom 3 a large variety of from viana a r rebesco m eds economic and palaeoceanographic significance of contourite deposits geological society london special publications 276 111 127 0305 8719 07 15 00 the geological society of london 2007

interbedded late quaternary turbidites and contourites in flemish pass off southeast canada their recognition origin and temporal variation abstract the recognition of contourite and turbidite deposits in deep marine sequences can be challenging as deposits may show similar sedimentary characteristics in flemish pass a small 1100 m deep perched basin along the southeast canadian continental margin both types of deposits occur late quaternary sediments include thin sand layers interbedded with hemipelagic muds the distribution age sedimentary structures and petrology of these sands were used to distinguish between turbidite and contourite deposits which were then characterized by detailed grain size distribution for understanding the conditions leading to deposition of each type seven sediment facies each with a distinctive grain size distribution were recognized they are 1 transported contourites 2 winnowed beds 3 possible jokulhlaup deposits 4 sandy turbidites 5 muddy turbidites 6 hemipelagic sediment and 7 turbidites from well sorted materials sand packets comprised of several stacked turbidite sand beds some with erosive contacts were correlated from the margin to the basin floor showing clear distal fining and creating a small lobe the temporal distribution of the sand beds indicates that most turbidites and contourites were deposited at stadial to interstadial transitions this linkage may be related to variations in the oceanic circulation in flemish pass which winnowed turbidites and may have triggered turbidity currents by moving sands into canyon heads

cenozoic alongslope processes and sedimentation on the nw european atlantic margin based on studies of sediment accumulations deposited from and erode by alongslope flowing ocean currents on the european continental margin from porcupine ireland to lofoten norway the evolution of the cenozoic paleocirculation was reconstructed as part of the stratagem project there is evidence of ocean current controlled erosion and deposition in the rockall trough in the faeroe shetland channel and on the voring plateau since the late eocene although the circulation pattern remains ambiguous the late palaeogene flow in the rockall trough was almost probably driven by southerly derived tethyan outflow water the extent and strength of any northerly derived flow is uncertain from the early neogene early mid miocene there was a massive regional expansion of contourite drift development both in the north atlantic and in the norwegian greenland sea this was most probably related to the development of the faroe conduit the opening of the fram strait and the general subsidence of the greenland scotland ridge these may have combined to cause a considerable acceleration in the exchange and overflow of deep waters between the arctic and atlantic oceans an early late neogene late early pliocene regional erosional event has been ascribed to a vigorous pulse of bottom current activity most probably the result of a global reorganisation of ocean currents associated with the closure of the central american seaway during the late neogene contourites and sediment drifts developed in deep water basins between units of glacigenic sediments as well as infill of several paleo slide scars these sediments were derived from areas of bottom current erosion as well as from the development of plio pleistocene prograding sediment wedges incorporating the extensive sediment supply derived from shelf wide ice sheets presently a profound winnowing prevails along the shelf and upper slope due to the inflowing currents of atlantic water depocentres of sediments derived from the winnowing are located locally in lower slope embayments and in slide scars

water mass exchange between the north atlantic and the norwegian sea during the past 28 000 years the greenland iceland and norwegian gin seas are important regulators of heat transport in the northern hemisphere and of ocean atmosphere co2exchange1 5 rapid changes in the circulation of surface and deep waters in this region may induce nonlinear climatic effects and climate instabilities2 3 here we present carbon and oxygen isotope data that provide a record of circulation changes in the gin seas during and at the termination of the last glacial maximum lgm inflow of nutrient depleted waters from the gin seas to form intermediate waters of the north atlantic resulted in nutrient enrichment of north atlantic deep water and consequent enhanced drawdown of atmospheric co2 contributing to the lower atmospheric during the lgm the onset of deglaciation occurred at a time of low salinity in the gin seas and thus of reduced thermohaline circulation although strong thermohaline circulation was later reinitiated in the north atlantic as deglaciation proceeded it cannot therefore have caused the onset of warming similarly we find that rapid changes in thermohaline circulation cannot account for the transient return to a cooler climate during the younger dryas episode

quaternary sedimentation margin architecture and ocean circulation variability around the faroe islands north atlantic abstract the quaternary development offshore the faroe islands has been studied using high resolution seismic and core data from the r v dana 2000 cruise and previous cruises several glacial related features and deposits are observed all bearing witness to former extensive glaciations of the faroe area on the shelves overlaying a mid pleistocene glacial erosional surface glacial and glacimarine deposits form a sheet geometry interrupted by ridges of sediment that are likely to represent ice front deposits an iceberg turbate north of the faroe islands provides evidence of large scale drift of ultra deep draft 600 m icebergs in the nordic seas at pre weichselian glacial stage s marginal and transverse troughs found on the eastern and western shelf are suggested to have formed during the same glacial period s as the iceberg turbate iceberg plough marks and abundant ice rafted material of non faroese origin together with the relict moraine ridges encircling the faroe islands at around the 100 and 200 m water depth contours indicate that the outer shelf was probably ice free during the weichselian ice age on the slopes and basinal parts the formation of fine grained contourites was favoured during weichselian glacial stages when bottom currents were reduced sediment overloading during these glacial stages resulted in repeated slope instability causing mass failures of the contourite deposits

fjord stratigraphy and processes evidence from the ne atlantic fensfjorden system fjords commonly hold sediment basins with high temporal resolution that mirror land and marine based processes and depositional environments during a glacial interglacial cycle here we present topas seismic profiles with a vertical resolution of 30 cm bathymetric records and a gravity core from fensfjorden west norway which allow a detailed study of sedimentary processes and depositional environments in a ne atlantic fjord system fensfjorden hosts a sediment volume of 0 70 km3 and the sediment basins evolved reach a maximum thickness of 100 m the basins are characterized by a lower acoustically well laminated glacimarine unit of allerod and younger dryas age this unit is overlain by several acoustically transparent lenses interpreted to be slide debrites we suggest these slide debrites to be a result of recurrent mass failures that occurred between 11 500 and 2100 cal a bp a thin late holocene hemipelagic unit drapes the slide debrites during the late holocene the sedimentation rates in fensfjorden decreased from 0 110 to 0 040 cm a 1 and two turbidity currents occurred in the 2040 1190 cal a bp time period this ability to map fjord processes in more detail has furthermore made it possible to revise the established stratigraphical framework for ne atlantic fjords copyright 2013 john wiley sons ltd

morphology and morphogenesis of a high latitude canyon the andoya canyon norwegian sea abstract the morphology of the high latitude andoya canyon in the norwegian sea was studied using multi beam bathymetry data the canyon excavation processes include sliding and slumping axial incision and gullying sliding and slumping has most frequently occurred in muddy sediments of the western sidewall due to canyon axial incision and undercutting and failures during infilling of a high relief terrain by alongslope transported sediments axial incision is inferred to be due to turbidity current erosion the turbidity currents were mainly the result of piracy of shelf sediments the eastern sidewall is dominated by gullies speculated to be the initial forms generated on a steep slope constructed from stiff poorly sorted glacigenic sediments from the present canyon morphology including the overall convex upwards form of the topographic long profile with a steep 20 25 upper headwall we favour a bottom up canyon development i e mass wasting and subsequent piracy of alongslope transported slope and shelf sediments in contrast to most other canyons the development of the andoya canyon was not only a result of side and headwall instability and axial incision most active during periods of high sediment transfer but also due to infilling of the canyon by sediments transported by alongslope flowing ocean currents and from the fennoscandian ice sheet at the shelf break there are little or no slide deposits covering the thalweg this leads us to suggest that the most recent process dominating within the canyon is turbidity current flushing and erosion inferred to have occurred during the holocene

sedimentary growth pattern on the northern argentine slope the impact of north atlantic deep water on southern hemisphere slope architecture large sedimentary deposits consisting of several major contourite drifts were studied by means of high resolution multichannel seismic data at the middle slope along the northern argentina continental margin to determine their evolutionary stages as well as to identify and assess the possible impact of northern source deep water nsdw on the slope architecture the imaged contouritic sediments allow decoding on the regional paleo oceanographic setting of the last 32 ma earliest contouritic sedimentation can be observed close to the eocene oligocene boundary based on an aggradational stacking pattern with a complex and wavy seismic facies pointing toward a hydrodynamically turbulent flow pattern this facies is most likely related to the opening of the drake passage associated with global cooling and a strengthening of surface intermediate and deep ocean currents in the southern ocean during the middle miocene plastered drift sequences with an aggradational reflection pattern were deposited their depositional style indicates weak non turbulent current conditions which are interpreted to be related to a vertical shift of water mass interfaces caused by the first formation of nsdw during the mid miocene climatic optimum on top the formation of plastered drift sequences led to the modern extent of the ewing terrace which was probably controlled by the continuous strengthening and thickening of nsdw until the final closure of the central american seaway cas during the pliocene and quaternary after the complete closure of the cas and under the influence of the full force of the nsdw mounded plastered drift sequences are built upon the ewing terrace generating the modern slope morphology therefore we suggest that deep water production in the northern hemisphere plays a significant role by controlling the shape of the continental slopes in the southwestern south atlantic since the middle miocene highlights slope of northern argentine continental margin is current controlled since 32 ma variability of northern source deep water nsdw controls sedimentary processes sedimentary processes are susceptible to changes of the brazil malvinas confluence impact of nsdw on slope processes is underestimated in the southern hemisphere

patterns of ice rafted detritus in the glacial north atlantic 40 55 n the observation by heinrich 1988 that during the last glacial period much of the input of ice rafted detritus to the north atlantic sediments may have occurred as a succession of catastrophic events rekindled interest on the history of the northern ice sheets over the last glacial period in this paper we present a rapid method to study the distribution of these events both in space and time using whole core low field magnetic susceptibility we report on approximately 20 cores covering the last 150 to 250 kyr well defined patterns of ice rafted detritus appear during periods of large continental ice sheet extent although these are not always associated within their maxima most of the events may be traced across the north atlantic ocean for the six most recent heinrich layers hl two distinct patterns exist hl1 hl2 hl4 hl5 are distributed along the northern boundary of the glacial polar front over most of the north atlantic between 40 and 50 n hl3 is more restricted to the central and eastern part of the northern atlantic the nd sr isotopic composition of the material constituting different heinrich events indicates the different provenance of the two patterns hl3 has a typical scandinavia arctic icelandic young crust signature and the others have a large component of northern quebec and northern west greenland old crust material these isotopic results obtained on core su 9008 from the north american basin are in agreement with the study by jantschik and huon 1992 who used k ar dating of silt and clay size fractions of an eastern basin core me 68 89 these data confirm the large spatial scale of these events and the enormous amount of ice rafted detritus they represent

ice sheet dynamics on the lofoten vesteralen shelf north norway from late mis 3 to heinrich stadial 1 abstract we present an account of the glacial dynamics from late marine isotope stage mis 3 to the heinrich stadial hs 1 on the lofoten vesteralen margin northern norway this account is based on an analysis of the sedimentary stratigraphy on the upper slope close to the ice sheet grounding line at the continental shelf edge and an analysis of the glacial morphology on the shelf areas our results point to a dynamic ice sheet that waxed and waned on the lofoten vesteralen continental shelf from the late mis 3 through the last glacial maximum lgm and the hs 1 glacigenic debris flows and deposition of laminated diamicts suggest that the ice sheet reached the shelf edge on several occasions these are dated to 25 5 ka bp hs3 between 21 1 and 21 7 ka bp 19 5 ka bp 15 6 ka bp and 14 4 ka bp uncorrected 14c ages a contouritic sorted sand sediment unit that formed in a relatively warm interval during late mis 3 suggests that a strong norwegian atlantic slope current also developed during glacial interstadials implying that the oceanic circulation in the eastern norwegian sea was similar as today the general pattern is that the ice sheet advanced onto the shelf during cold period with little influx of atlantic water to the norwegian sea and that it retreated toward the coast during intervals with higher temperatures and higher influx of warm atlantic water the last ice advance to the edge of the continental shelf occurred during hs 1

relation between phosphorus fractions and development of soils from galicia nw spain abstract the relationship between soil development and the distribution of p among its fractions in the surface horizons of native soils in galicia nw spain was studied p forms were determined by sequential fractionations and the fractions were regrouped as slow turnover and rapid turnover organic and inorganic forms in soils developed on siliceous rock an accumulation of slow turnover organic p sonic naoh extractable organic p is accompanied by an increase in rapid turnover inorganic p resin extractable p bicarbonate extractable inorganic p and a decrease in slow turnover inorganic p naoh sonic naoh hcl extractable inorganic p that could be due to destruction of inorganic p adsorbing complex in soils developed on carbonate bearing rock slow turnover organic p declined and rapid turnover organic p bicarbonate naoh extractable organic p increased these trends are explained in terms of soil processes

glacial interglacial changes in global deepwater circulation variations in the areal extent of the cryosphere appear to exert an important control over glacial interglacial changes in the mode of formation and source areas for deepwater and bottom water masses during interglacials when ice extents are minimal these water masses form by mechanisms which are well documented for the present interglacial climatically related advances and retreats of sea ice in the northern hemisphere during glacials probably resulted in shifting loci of formation for each of the three types of north atlantic deep water nadw probable glacial advances of grounded ice sheets to the continental shelf margins in antarctica precluded formation of antarctic bottom water aabw at the presently active continental shelf sites because these shifts in source areas for aabw and nadw probably involved source waters with salinity temperature oxygen content and nutrient levels that differed from modern values deep and bottom waters are likely to have had different characteristics in glacials than they do during interglacials

macrofaunal palaeoecology and stratigraphy in late quaternary shelf sediments off northern norway abstract in a late pleistocene holocene glaciomarine marine sequence a minimum of 115 taxa macrofossils and trace fossils are recognized on the basis of 690 samples from gravity cores from andfjorden nine and malangsdjupet one the biostratigraphy is proposed on the basis of reconstructions of autochthonous macrofaunal assemblages a total of seven zones are defined five in the pleistocene and two in the holocene the ages of which are estimated by radiocarbon datings in ascending order the zones are mixed assemblage zone barren interzone arctinula greenlandica assemblage zone before 14 000 yr b p yoldiella intermedia assemblage zone 14 000 13 000 yr b p bathyarca glacialis assemblage zozne 13 000 yr b p bathyarca glacialis kelliella miliaris interval zone 10 000 ca 7800 yr b p and kelliella miliaris assemblage zone ca 7800 present the bathyarca glacialis zone is divided into three faunules i 13 000 12 000 yr b p ii 12 200 11 100 yr b p and iii 11 100 10 000 yr b p the palaeoecology of the faunal succession is elucidated by means of the sample frequency method two major environmental events have influenced the faunal history the first was the onset of the deglaciation of the thoughs the second the intrusion of the norwegian current bringing warm saline atlantic water into the troughs at 10 000 yr b p the pleistocene fossils demonstrate an arctic macrofaunal succession from a low order stage to a high order equilibrium stage that is in principle identical to that of a modern faunal development in fjords following a disturbance causing anoxia an estimated polychaete mollusc ratio together with changes in sediment influx depositional rates and grain size of substrate indicate the presence of different energy regimes where the inner and outer reaches of andfjorden are compared about 10 000 yr b p a major faunal change took place the previous arctic fauna was replaced by a boreal fauna which developed into the modern fauna the most important factor causing the replacement and renewed faunal succession were probably the rise in temperature and salinity as well as an increase in nutrient supply brought about by the intrusion of the norwegian current a comparison with shallower shelf areas indicates a somewhat different faunal composition in the pleistocene brought about by different depositional environments however a similar major faunal change took place at 10 000 yr b p and there are fewer discrepancies among the holocene faunas regional comparison indicates that some of the phases in the development of the fauna probably are rather local while other have a more regional nature

paleoceanography of the last interglacial glacial cycle in the polar north atlantic abstract using to its position close to the sites of waxing and waning of the major northern hemisphere ice sheets during the late quaternary climatic cycles the polar north atlantic plays a key role in driving global change therefore analyzing the present day sedimentation processes and reconstructing the late quaternary paleoceanography in this region has been a focus of major scientific interest through the last fifteen years this paper aims to combine the vast amount of new results about modern sediment fluxes surface sediment distribution and the paleoceanographic record and to present a comprehensive overview of the paleoceanography in the polar north atlantic through the last 200 000 years which is based on the basinwide analysis of carbonate and ice rafted detritus records during the last fifteen years the climap paleoceanographic view of the glacial polar north atlantic as an almost permanently isolated sea covered by heavy sea ice throughout the year has been shifted to a much more dynamic view of the environmental conditions a meridional current system similar to the present day conditions secured the exchange of water ice and heat between the polar north atlantic and the alantic and arctic oceans although affected by variations in strength and intensity this meridional current pattern resulted in an almost permanent presence of at least some seasonally ice free areas with all the consequences for e g marine life and deep water formation in addition the development of the continental ice sheets namely the fennoscandian and the barents sea ice sheets is closely related to this dynamic circulation pattern during the so called nordway events the pronounced inflow of temperate waters from the south provided moisture for the growth of the ice sheets the most prominent of these events stage 6 stage 4 and substage 3 1 2 ended in major glaciations reflected in the terrestrial sequences and in the deep sea ird records

late wisconsinan and holocene history of southwestern saskatchewan the late wisconsinan laurentide ice sheet reached the limit of glaciation along the north facing slope of the unglaciated part of the cypress hills nunatak but elsewhere around the cypress hills and wood mountain uplands of southwestern saskatchewan it did not reach the limit of glaciation an interval of deglaciation was followed by a readvance of the ice sheet about 15 ka to a position near the late wisconsinan limit and was marked by strong flow of keewatin ice from the north and weaker flow of hudson ice from the northeast final deglaciation resulted in the formation of glacial lakes around the cypress hills nunatak a network of ice marginal and subglacial trenches presently occupied by the frenchman valley and its tributaries was formed when these lakes drained along over and under ice towards the western part of the wood mountain upland to the east the main trench joined an ancestral part of frenchman valley along the ice free southern slopes of wood mountain upland meltwater from the ic

the use of magnetic susceptibility to measure long term soil redistribution abstract several studies have documented the severity of recent soil erosion on the canadian prairies where cultivation started about a century ago little quantitative information is available on erosion before 1960 this study attempts to quantify post and pre 1960 soil erosion in a small cultivated basin near saskatoon saskatchewan canada by measuring 137cs and magnetic susceptibility distribution with depth soil cores were collected along six transects three across closed depressions and three across the drainage channel in the cultivated field and one transect across an uncultivated depression the cores were sliced into 3 cm layers and the soil analyzed for 137cs and organic and inorganic c high variability in with depth in eroding areas as indicated by 137cs made it impossible to use to quantify past soil losses in these locations however these eroding upper and middle slope positions have a much higher than lower slope areas where soil deposition occurs and where the variability in with depth could be used to estimate soil deposition estimating soil deposition from the vs depth profiles was more successful in the closed depressions than in the drainage channel where the profiles may reflect the variable source areas of the materials rather than the pedological conditions the data indicated that soil deposition since 1960 has been about 30 to 50 of that prior to 1960 this suggests that soil deposition rates and by implication soil erosion rates have been relatively steady since cultivation of these soils started although there are clear indications that the spatial pattern of deposition has varied

a contour based topographic model for hydrological and ecological applications a digital model for discretizing three dimensional terrain into small irregularly shaped polygons or elements based on contour lines and their orthogonals is described from this subdivision the model estimates a number of topographic attributes for each element including the total upslope contributing area element area slope and aspect this form of discretization of a catchment produces natural units for problems involving water flow as either a surface or subsurface flow phenomenon the model therefore has wide potential application for representing the three dimensionality of natural terrain and water flow processes in the fields of hydrology sedimentology and geomorphology three example applications are presented and discussed they are the prediction of zones of surface saturation the prediction of the distribution of potential daily solar radiation and the prediction of zones of erosion and deposition in a catchment

late quaternary calcareous nannofossil biostratigraphy and sedimentation patterns fram strait arctica sediment cores from the fram strait are dated by means of calcareous nannofossil biostratigraphy and are shown to represent at the most the last 300 kyr oxygen isotope stages 1 8 differences in sedimentation rates are mainly controlled by the bottom topography and the intensity of ice rafted deposition sedimentation rates are normally in the order of a few centimeters per kiloyear in the central fram strait but increase to over 10 cm kyr in cores located on the continental slope the highest sediment accumulation rates occurred on the shelf several tens of centimeters per kiloyear

cenozoic sediment accumulation on drifts in the northern north atlantic the northern north atlantic sediment drifts have a much greater areal extent than has previously been indicated the northern north atlantic extends from the east greenland to european continental shelves and from the charlie gibbs fracture zone to the greenland scotland ridge within this region are seven major sediment drifts containing some of the best clues for pre quaternary bottom water circulation in the north atlantic feni drift is the oldest in the region originating near the eocene oligocene boundary it was followed by accumulation of bjorn gardar hatton and snorri drifts from the late early to middle miocene eirik drift may have started to accumulate in the late miocene and gloria drift in the early pliocene through analysis of the cenozoic sediment mass age distribution and the change in area of seafloor for the study area through time it can be concluded that there is a deficit of oligocene to miocene sediment in the region this could be explained by sediment cycling the erosion of older sediment to produce young sediment the mass of pliocene to quaternary sediment is much larger than that of the older sediment and may have been derived primarily through the erosion of eocene and oligocene sediment by deepwater currents the sediment drift portion of the total regional sediment mass increased significantly three times during the cenozoic each of these drift growth phases lasted between 3 and 4 m y the first two growth phases from the late eocene to early oligocene and from the early to middle miocene were accompanied by northward shifts of depocenters to the newly forming sediment drifts the third and largest growth phase occurred between 7 and 3 ma and may have been preceded by the initiation of accumulation on eirik drift 8 7 ma this most recent growth phase was accompanied by high apparent accumulation rates over southern gardar drift as it expanded to the east erosion rates over reykjanes ridge may have been higher during the mid pliocene than in the quaternary there are two main sites where dense water could have formed and flowed south through the rockall trough to start the accumulation of feni drift if the atmosphere were cool enough dense water could have formed in the norwegian sea or on the faeroe shelf dense water may also have formed on the rockall plateau due to salinity increase through evaporation in an arid climate as an alternative to the hypothesis of arctic ocean water overflowing the iceland faeroe ridge in the early middle miocene it is suggested that dense water formed along shallow segments of the iceland faeroe ridge and then flowed into the south iceland basin to begin accumulation of bjorn gardar and snorri drifts the initiation of sediment drift formation in the south iceland basin may have been caused by a decreased rate of deep water production combined with a higher rate of detrital input due to a middle miocene uplift event along the iceland faeroe ridge a second uplift event along the greenland scotland ridge and a decreased production of northern component water in the early pliocene may be responsible for increased sediment accumulation in bjorn gardar and eirik drifts

near surface circulation of the nordic seas as measured by lagrangian drifters in the period june 1991 to august 1993 107 argos tracked drifters drogued to 15 m depth were released in the nordic seas or greenland iceland and norwegian seas the drifter movements revealed the strong and spatially confined current systems along the surface salinity fronts of the iceland faroe frontal zone and of the norwegian coast and along the continental margins and their extensions to the barents sea and spitsbergen the norwegian atlantic current is composed of three distinct streams two continental margin and one coastal branches which join into one single swift mean current west of the lofoten and vesteralen islands where the strongest measured currents are in excess of 110 cm s 1 in addition to the general cyclonic gyre circulation in the nordic seas the drifters indicate smaller cyclonic circulation patterns in all the major subbasins i e the iceland plateau the norwegian the lofoten and the greenland basins no surface signature of the east icelandic current is disclosed by the drifters interpolated and low pass filtered position data were used to construct maps of 15 m depth ensemble mean velocity velocity variability and residence time vigorous eddy fields are dominant in the strong currents and in the lofoten basin eulerian correlations indicate that they tend to propagate to the west in contrast the iceland plateau appears quiescent both in the mean and eddy velocities single particle diffusivities are computed and are found to be in the range 1 7 107 cm2 s 1 the corresponding lagrangian timescale and space scale are 1 3 days and 10 40 km respectively these lagrangian drifter measurements compose the first basin scale accurate near surface velocity data set of the nordic seas

reflection of scandinavian ice sheet fluctuations in norwegian sea sediments during the past 150 000 years the record of glacier fluctuations in western scandinavia as reconstructed from continental data has been correlated with records of ice rafted detritus ird from well dated sediment cores from the norwegian sea covering the past 150 000 yr b p the input of ird into the ocean is used as a proxy for ice sheet advances onto the shelf and thus for the calibration of a glaciation curve the marine results generally support land based reconstructions of glacier fluctuations and improve the time control on glacial advances the saalian ice sheet decayed very rapidly approximately 125 000 yr b p in the early weichselian a minor but significant ird maximum indicates the presence of icebergs in isotope substage 5b especially between 95 000 and 83 000 yr b p reduced amounts of calcareous nannofossils indicate that surface waters were influenced by meltwater discharges during isotope substages 5d and 5b an extensive build up of inland ice began again during isotope stage 4 but maximum glaciation was reached only in early stage 3 58 000 53 000 yr b p marine sediments have minimum carbonate content indicating strong dilution by lithogenic ice rafted material generally the ird accumulation rate was considerably higher in stages 4 2 than in stage 5 a marked peak in ird accumulation rates from 47 000 to 43 000 yr b p correlates well with a second middle weichselian ice sheet advance dated by the laschamp olby paleomagnetic event minimum ice extent during the alesund interstade 38 500 32 500 yr b p and several glacial oscillations during the late weichselian are also seen in the ird record of several late weichselian glacial oscillations on the shelf at least four correspond to the north atlantic heinrich events ice sheet behavior was either coupled or linked by external forcing during these events whereas internal ice sheet mechanisms may account for the noncoherent fluctuations

impact of coral spawning on the biogeochemistry of a hawaiian reef abstract we examined the impact of montipora capitata coral spawning on local biogeochemistry in kane ohe bay hawai i this event supplied labile spawn derived organic matter sdom to the water column triggering a cascading series of related effects on the biogeochemistry of the reef specifically we measured the isotopic composition and nutrient ratios of spawning material and coral tissues and utilized these signatures to track pathways of sdom incorporation into this coral dominated ecosystem we observed 1 shifts in the isotopic signatures of coral tissues after the spawning event 2 rapid turnover of sdom within the water column and enhanced deposition of pom to the sediment surface 3 enhanced sediment efflux of nh 4 after the spawning event that triggered a phytoplankton bloom in the overlying water and 4 drawdown of dissolved nutrients in the water column after spawning that coincided with the occurrence of a water column phytoplankton bloom our results show that single species spawning events can serve as a source of substantial nutrient input to the water column contributing in similar ways to storm driven river nutrient input and with measurable impact on the biogeochemistry of the reef

a holocene soil geomorphic record from the ham site near frontier southwestern saskatchewan the soil geomorphic evolution of a hillslope in hummocky moraine terrain in one of the most arid parts of the palliser triangle is reconstructed from ca 12 600 bp to the present a transect from a moraine plateau into an internally drained basin provided evidence for seven postglacial landscape cycles each cycle includes a phase of land surface instability marked by erosional and depositional imprints and a phase of stability marked by pedologic imprints five cycles of slope wash dominated erosion left behind four superposed downslope thickening and downslope fining sediment mantles and were followed by two eolian cycles each of which left behind a loess mantle that accumulated from a local loess dispersal system accumulation of long range calcareous dust coincided with each of these loess cycles the five complete buried soil catenas and the surficial catena have systematic textural differentiation reflecting the preceding geomorphic regimen and color differentiation reflecting the soil draina

sedimentary processes and variations in slope current activity during the last glacial interglacial episode on the hebrides slope northern rockall trough north atlantic ocean abstract shallow cores and high resolution seismic reflection data collected from two areas along the hebrides slope indicate that a variety of depositional processes have been active since the last glacial interval seismic reflection profiles from the most northerly slope area immediately south of the wyville thomson ridge reveal a slope apron and an embayed area with a relict mid upper slope channel five cores from this locality consist of distal muddy turbidites in the area of the channel with muddy contourites interbedded with glaciomarine ice rafted sediments and thin debris flow deposits most of the cores are topped by sandy contourites the preserved sequence suggests that lowered sea levels during the last glaciation 10 ka resulted in a predominance of downslope and glaciomarine sedimentation with bottom current activity greatly suppressed at the onset of deglaciation alongslope activity increased as bottom currents gained in strength with climatic fluctuation and the retreat of ice sheets from the shelf producing muddy and sandy contourites present day current activity is still much in evidence with two current meter stations on the mid and lower slope recording a northward flowing current following the bathymetric contours recorded peak velocities at 468 m and 403 m were 26 48 cm s some elements of reverse flow at the deeper site may be tidal oscillation compounded by short duration high intensity benthic storms cores from the more southerly area in the vicinity of the geikie escarpment penetrated hemipelagites erosively overlain by sandy contourites dinoflagellate and nannofossil dating of these deposits indicate that the lower hemipelagites are of late glacial age 13 ka the sandy contourites are probably of early holocene age the lack of the allerod bolling interstadial and younger dryas stadial may be indicative of a hiatus in sedimentation a possible cause of this may be the increasing slope angles up to 28 on the escarpment concentrating the effects of a thermohaline slope current current flow was also strengthened during deglaciation producing erosion or non deposition of the lower units leaving the coarser top only sandy contourites

the lofoten contourite drift off norway abstract based on high resolution and multichannel seismic data a contourite drift the lofoten drift has been identified below ca 1000 m water depth on the continental slope off norway the lofoten drift has a maximum thickness of about 360 m correlation to published seismic stratigraphy implies a neogene age the onset of the lofoten drift may have been a result of increased circulation within the norwegian greenland sea probably controlled by the subsidence of the greenland scotland ridge the drift has probably originated from deposition of suspended sediments derived from winnowing of the continental shelf and upper slope the geometry of the youngest seismic drift unit characterised by a maximum thickness at the crest of the mound indicates that the lofoten drift is active at present the maximum holocene sedimentation rate is ca 1 m ka the downslope sediment input to the study area was probably relatively low during glacial periods because the lofoten islands may have acted as a sediment barrier causing large fluvial and or glacial drainage systems from central fennoscandia to be routed south and north of the study area as a result alongslope sediment transport has been the main sediment input to this part of the continental slope

contour current driven continental slope situated sandwaves with effects from secondary current processes on the barents sea margin offshore norway abstract seabed data acquired from the southern barents sea continental margin offshore norway reveal detailed morphology of large sandwave fields multibeam echosounder bathymetry and backscatter shallow seismic sediment samples and seabed video data collected by the mareano program have been used to describe and interpret the morphology distribution and transport of the sandwaves the bedforms lie on a slope dominated by relict glacial forms and muddy sandy gravelly sediments sandwave migration across small gravity mass failures of the glacial mud constrains the field initiation as early post glacial or later the contour parallel nature of the fields and crestlines normal to the bathymetry contours and the geostrophic norwegian atlantic current nwac demonstrate that the nnw flowing oceanographic circulation is the primary driving current the fields coincide with the depth range at which a transition between warm saline and underlying cooler less saline waters fluctuate across the seabed statistically rigorous measurements of height width and various parameters of slope and symmetry confirm a tendency to downstream nnw sandwave migration but with significant exceptions anomalous bedform symmetry domains within the fields are tuned to meso scale topography along relict glacial debris flow chutes indicating current focusing upstream and upper slope derived winnowed sand transport eroded from the glacial sediments is the supposed source sandwave flank slope values are comparable to the regional slope such that the gravitational vector would have a cumulative downslope migration affect unless balanced by upslope drivers perpendicular cross cutting of stoss face 3 d ripples by linear 2 d ripples in the sandwave troughs and lee faces is evidence for non synchronous episodic current variations though deep ekman transport and internal wave action are unproven here these could explain chute related tuning of bedform symmetry through funneling in the debris flow chutes and favor sand recycling thus contributing to long term maintenance of the sandwave field

origin of shallow submarine mass movements and their glide planes sedimentological and geotechnical analyses from the continental slope off northern norway submarine landslides are often characterized by a basal surface of rupture parallel to the stratigraphy in which downslope movement is initiated however little is known about the sedimentology and physical properties of the sediments within these surfaces in this study we present a multiproxy analysis of the sediments collected from a giant piston core penetrating a shallow submarine mass transport deposit in combination with high resolution seismoacoustic data to identify and characterize the basal glide plane and the weaker sediments in which movement was initiated the initial phase of instability consists of a single fracture that formed due to the downslope movement of a mostly intact slab of sediments the 16 m long core comprising mostly undisturbed massive and laminated ice rafted debris rich clay penetrated this slab the base of the slab is characterized by a high amplitude semicontinuous reflection visible on the subbottom profiler data at about 12 5 m depth interpreted to originate from the glide plane on top of a plumite deposit this plumite has dilative behavior with pore pressure decrease with increasing shear strain and high undrained shear strength movement probably started within contouritic sediments immediately above the glide plane characterized by higher sensitivities and higher water contents the occurrence of the mass movements documented in this study are likely affected by the presence of a submarine landslide complex directly downslope the slide scar of this landslide complex promoted retrogressive movement farther upslope and progressive spreading of strain softening along the slide base and in the slide mass numerical models infinite slope bing and retrogressive slope models illustrate that the present day continental slope is essentially stable and allow reconstruction of the failure processes when initiated by an external trigger

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

formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern norway laberg jan sverre baeten nicole jeanne lagstad petter arthur forwick matthias vorren tore ola formation of a large submarine crack during the final stage of retrogressive mass wasting on the continental slope offshore northern norway marine geology 2013 volum 346 s 73 78

late quaternary glacial development of the mid norwegian margin 65 to 68 n abstract we have studied the younger part of the large plio pleistocene prograding wedge on the northern part of the mid norwegian margin using high resolution seismic data the wedge is mainly composed of thick glacigenic debris flow packages interbedded with hemipelagic and contouritic sediments age constraints of the seismic stratigraphy obtained through correlation to odp 644a show that the fennoscandian ice sheet advanced to the shelf break during marine isotope stages mis 2 ca 15 22 ka bp 6 128 186 ka bp 10 339 362 ka bp 12 423 478 ka bp and 14 524 565 ka bp and to the inner shelf during mis 8 245 303 ka bp the stratal geometry and sedimentary pattern locally indicate rapid subsidence up to ca 1 2 m ka of the outer shelf and slope area since 350 ka bp the subsidence is most likely a response to the rapid deposition of glacigenic sediments during the plio pleistocene it is inferred that sediment loading was an important factor behind the diapirism in the vema dome area

bioturbation on the pelagian platform ichnofacies variations as paleoclimatic indicator abstract x radiographs of apparently structureless split cores collected on the outer pelagian platform tunisia display highly bioturbated sequences the study of these sequences enabled us to determine ichnofacies variations that might be related to hydrologic and climatic changes occurring in this area during the late quarternary epoch this interpretation is supported by mineralogic and paleontologic analyses and by the radiocarbon dating

intermediate water ventilation in the nordic seas during mis 2 1 a high resolution marine record from the northern norwegian continental margin off lofoten is used to reconstruct changes in the oceanography of the nordic seas during marine isotope stage mis 2 including the last glacial maximum and early deglaciation circa 25 to 16 ka the period was characterized by generally warm subsurface water temperatures 2 c and inflow of atlantic surface water several events were characterized by decrease in ventilation of the intermediate water and low subsurface temperature and salinity they correlate with colder atmospheric temperatures as seen in ice cores the events terminated with gradual strengthening of the intermediate water ventilation and increase in subsurface temperature the generation of intermediate water was unstable and experienced climate and ventilation changes on millennial and centennial timescales the changes appear consistent with modeling experiments that predict short lasting circulation stops during mis 2 due to release of meltwater in the nordic seas

interaction of alongslope and downslope processes in the alentejo margin sw iberia implications on slope stability abstract an integrated analysis of multibeam bathymetry and single and multichannel seismic records were used to image the morpho stratigraphy of the alentejo margin southwest portuguese continental margin the complex interaction of several alongslope and downslope processes in the area leads to the formation of various bottom current driven depositional and erosive features moat as well as gravity driven features gullies and landslides in the alentejo margin these processes feed each other contributing for the active sedimentary pattern on the area sines contourite drift scd is a 2311 km2 sedimentary feature with a perimeter of 303 9 km 98 km length and 35 km width landslides occur either on steep and on gentle slopes between 200 and 3200 mwd meters water depth in the study area which has a total extent of 85 km 82 km scar concentration is higher in the middle and lower slope whereas the thickest debris deposits are found in the slope basin area lebre basin lb translational landslides with planar failure planes parallel to the slope surface are the main landslide typology verified in the study area several triggering and pre conditioning factors resulting from the interaction of alongslope and downslope processes contribute for varied landslides scar concentration steep slope and high sedimentation rates favour sediments under consolidation promoting excess pore water pressure and weak layers formation in this paper we show that the interaction of bottom currents with pre existing tectonic structures promotes the complex interaction of both alongslope and downslope processes thus promoting an active and diversified geomorphological evolution and generalised slope instability

some highly weathered soils of puerto rico 3 chemical properties some chemical properties of 11 soils developed in highly weathered regoliths in puerto rico have been recorded particular attention has been given to properties which reflect the extent to which weathering has progressed and to properties which may be most useful for developing valid soil management practices if the pina soil were excluded the saturation extracts of oxisols generally contained less si than the ultisols the saturation extract of pina soil which was 89 quartz sand contained 10 ppm si a value out of keeping with highly weathered soils phosphate solubility was greatest in the pina soil also phosphate adsorption by the puerto rico soils when corrected for dilution by sand was approximately that of highly weathered soils of hawaii north carolina or colombia most of the soils contained more than 4000 kg s ha in the 120 cm profiles the most striking difference between the oxisol and ultisol groups was in extractable aluminum in general these oxisols have been weathered beyond the point where aluminum is readily extracted with a neutral salt the ph at which net charge of the soils was zero was lower than the soil ph usually encountered in the field the soils were poorly buffered at low ph as a group the oxisols contained less exchangeable k than the ultisols in 6 of the 11 soils both calcium and magnesium were 1 meq 100 g in some horizon in most soil samples the balance among exchangeable cations was appropriate for reasonable potassium nutrition even so the quantity of exchangeable nutrient cations was low in most cases mineralization of organic nitrogen tended to stop with nh4 in the acid soils

pedogenesis soil mass balance phosphorus dynamics and vegetation communities across a holocene soil chronosequence in a super humid climate south westland new zealand abstract this study quantifies progressive pedogenesis under a super humid climate on the west coast of south island new zealand it focuses on soil morphology pedogenic oxides soil mass balance phosphorus transformation and linking pedogenesis trajectories to vegetation communities the study comprises a set of dune ridges of a coastal sand dune complex covered by unmodified conifer podocarp angiosperm forest the surface ages of the chronosequence range from 370 y to 6500 y rapid podzolisation is characteristic for the study area within 1000 y soils reach the spodosol stage with typical eluvial illuvial horizons and mobilisation of fe and al this period is also characterised by the most rapid losses of total phosphorus at a rate of 110 g m 2 ky 1 a relative loss of 41 beyond 3000 y changes in soil chemistry and losses for all nutrients markedly slow soil mass balance shows that the 6500 y soil has lost 75 total p 62 k 52 ca and 54 na soil p fractions substantially change across the gradient high leaching losses of apatite and non occluded p in the first hundreds of years coincide with accumulation of organic and occluded inorganic forms in the topsoil and subsoil which mitigate total p loss beyond 1000 y of pedogenesis all p fractions decline at similar rates to low more persistent levels with apatite non occluded p being the dominant p form after 6500 y of pedogenesis this incipient steady state is assumed to be sustained by the advection of parent material derived p through surface lowering and reduced biological cycling vegetation communities change from more diverse communities on young and less impoverished soils in the first 1000 y to less diverse and less variable communities beyond 1000 y of ecosystem development the soil evolution correlated vegetation changes documented in this study are consistent with general schemes of vegetation succession for the west coast of south island

behavior of the northwestern part of the fennoscandian ice sheet during the last glacial maximum a response to external forcing abstract a sediment core from the lofoten contourite drift on the continental slope off northern norway proximal to the former vestfjorden traenadjupet ice stream details the development variability and decline of marine margins of the northwestern fennoscandian ice sheet during the time interval 25 3 14 cal ka bp including the last glacial maximum and onset of the deglaciation based on high resolution ird records from the core interval between 25 3 and 17 7 cal ka bp we report data points with a mean time step of 10 years between 17 7 cal ka bp and the holocene time steps are typically 50 years the core is divided into 7 informal ice rafted debris ird zones based on the variations in ird including 7 major ird maxima a g inferred to represent periods of high iceberg production petrological identification reveals dominance of crystalline ird monocrystalline plutonic and metamorphic rock fragments accounting for 75 80 of total ird assemblages while sedimentary fragments generally account for 15 20 the crystalline fragments including eclogite and mangerite from a nearby terrestrial source increase across the ird peaks while the sedimentary fragments remain constant this points to the importance of erosional products from icebergs originating from fast flowing paleo ice streams including the vestfjorden traenadjupet ice stream draining from the fennoscandian mainland during the ird maxima periods increased temperature of the adjacent surface water masses was probably an important external forcing factor on the fennoscandian ice sheet behavior because some ird maxima and plumite deposition from meltwater plumes post date periods of increased sea surface temperatures the peak ird depositions occur in centennial and millennial time cycles 200 1030 and 3900 year indicating some external forcing by solar variation both mechanisms could explain the observed synchronous instability of the northwestern fennoscandian ice sheet to other european ice sheets

sedimentary characteristics of late pleistocene bottom current deposits barents sea slope off northern norway abstract the barents sea slope off northern norway received large amounts of terrigenous sediments from an extensively glaciated norwegian continental margin during the late pleistocene a sedimentological study of seven gravity cores from the barents sea slope suggests that some terrigenous sediments were transported by both downslope currents and contour following bottom currents the bottom current deposits comprise four sedimentary facies 1 indistinctly laminated mud 2 layered mud 3 indistinctly layered mud and 4 bioturbated mud the indistinctly laminated mud on the mid to lower slope is characterized by a relatively low degree of bioturbation and consists of monotonous diffuse and discontinuous silt rich and silt depleted laminae 1 mm scale and or discontinuous trains of coarse grains these characteristics are suggestive of sedimentation from contour currents driven by water exchange with the north atlantic ocean these bottom current deposits can be distinguished from fine grained turbidites silt clay couplets and intensively bioturbated hemipelagites on the barents sea slope

water and solute transfer between a prairie wetland and adjacent uplands 2 chloride cycle the quality of water in lakes and wetlands depends on the exchange of solutes with adjacent uplands in many prairie wetlands the input of water is dominated by snowmelt runoff and the outputis dominated by groundwater flow we use chloride as a tracer to quantify the mass transfer processes associated with surface runoff and groundwater flow between a wetland in saskatchewan canada and the surrounding upland snowmelt runoff transports 4 5 kg yr 1 of chloride from the upland to the wetland most of this chloride infiltrates under the wetland and moves laterally to the upland with shallow groundwater under the upland chloride moves upward in the vadose zone with soil water and accumulates near the surface as water is consumed by evapotranspiration part of this chloride mixes with snowmelt runoff and moves back to the wetland therefore chloride is cycled between the wetland and the upland at an approximate rate of 5 kg yr 1 the chloride cycle occurs within 5 6 m of the ground surface a small amount of chloride escapes from the cycle with the downward flow of groundwater into the deep aquifer the estimated flux of chloride leaving the cycle is 0 1 0 6 kg yr 1 which is of the same order of magnitude as the rate at which the catchment receives atmospheric deposition of chloride because the atmospheric input is reasonably well known over the prairie region the concentration of chloride in groundwater under recharge wetlands can be used to estimate the recharge rate of deep aquifers

terrain controls on depressional soil distribution in a hummocky morainal landscape in hummocky morainal landscapes soil distribution in well drained landscape positions tends to follow a consistent pattern soils in depressions however are more difficult to predict reliably this study had two objectives 1 to determine the parent material and landscape properties controlling the formation of the different depressional soils and 2 to use these controls to identify quantitative terrain based predictors of soil type in depressions only two terrain attributes specific dispersal area sda and elevation relative to open water bodies were required to distinguish three main soil groups gley recharge non gley recharge and discharge soils specific dispersal area is the downslope area draining flow from a given grid cell gley recharge soils occur primarily at points with sda of less than 2 m2 m 1 regardless of elevation within a given site because most of the runoff flowing to a point with very low sda values will pond or infiltrate vertically rather than flow downslope non gley recharge soils and discharge soils both occur at points with sda of greater than 2 m2 m 1 the majority of the non gley recharge soils occur above 5 m elevation relative to an open water body and the majority of the discharge soils occur below 5 m elevation relative to an open water body reflecting the importance of solute cycling in the development of discharge conditions buried and depositional soils could not be predicted from current terrain attributes because their profile characteristics were derived from the paleosurface

glacigenic sediments on a passive continental margin as exemplified by the barents sea abstract reflection seismics data borehole data and gravity cores have been used to map the sedimentary facies of the epicontinental southwestern barents sea its continental margin and adjacent coastal areas an upper unconformity with a glacially eroded morphology extends over most of the continental shelf up to 300 m of stratiform glacigenic sediments overlie this unconformity these sediments can be grouped into seismic units which are separated by smooth or irregular erosional surfaces each sequence may be up to 150 m thick normally with a lateral extent of 100 300 km three dominant seismic signatures may be discerned semi transparent stratified and chaotic reflection patterns these sediments are partly glacifluvial in origin but on the whole they represent more or less tectonized glacimarine deposits the deeper troughs on the continental shelf contain an undeformed postglacial glacimarine marine trough fill the greatest thickness up to 1000 m of glacigenic sediments occurs at the shelf break and below the upper slope the depocentres are situated at trough mouth fans the sediments comprise several prograding sequences with a complex sigmoid oblique character indicating alternating upbuilding and depositional bypass erosion in the topset segment small and large scale slide scars are observed on the upper slope and debris lobes on the lower slope a marked progradation seems to have occurred during the plio pleistocene glacial periods this progradation also resulted in an unstable slope with various types of sediment gravity flows currents flowing along the slope were established during interglacials and gullying by cold dense shelf water and downslope transport occurred maximum net sedimentation rates are 0 2 m ka continental slope 0 4 m ka shelf break 0 1 m ka shelf stratiform diamictons 1 m ka shelf trough fills and 60 m ka fjord trough fills

paleoclimatic significance of subpolar foraminifera in high latitude marine sediments census data of subpolar planktonic foraminifera in high latitude sediment cores obtained using a 149 m mesh can be directly related to past surface water conditions in contrast analyses performed using material sieved with a 62 m mesh produce results that must be interpreted with regard to past dissolution conditions of the local deep or bottom waters this conclusion bears directly on the validity of several recent papers purporting to relate baffin bay and labrador sea paleo oceanography with wisconsinan glacial events in northeastern canada

evidence for massive discharges of icebergs into the north atlantic ocean during the last glacial period sediments in the north atlantic ocean contain a series of layers that are rich in ice rafted debris and unusually poor in foraminifera1 here we present evidence that the most recent six of these heinrich layers deposited between 14 000 and 70 000 years ago record marked decreases in sea surface temperature and salinity decreases in the flux of planktonic foraminifera to the sediments and short lived massive discharges of icebergs originating in eastern canada the path of the icebergs clearly marked by the presence of ice rafted detrital carbonate can be traced for more than 3 000 km a remarkable distance attesting to extreme cooling of surface waters and enormous amounts of drifting ice the cause of these extreme events is puzzling they may reflect repeated rapid advances of the laurentide ice sheet perhaps associated with reductions in air temperatures yet temperature records from greenland ice cores appear to exhibit only a weak corresponding signal moreover the 5 10 000 yr intervals between the events are inconsistent with milankovitch orbital periodicities raising the question of what the ultimate cause of the postulated cooling may have been

water flow in a hummocky landscape in central saskatchewan canada i distribution of water and soils abstract water flow in a hummocky landscape is highly variable in time and space the purpose of the study is to use a classification system based on landscape surface form to delineate areas with similar hydrologic properties the study was conducted in a hummocky landscape with a closed drainage pattern in the black soil zone of saskatchewan the sites consisted of three closed drainage basins 80 150 m across surrounding individual temporary sloughs the distribution of water in the landscape was inferred from in situ electrical conductivity and soil morphological properties including thickness of a and eluviated horizons and depth to calcium carbonate in situ electrical conductivity was strongly correlated with the depth of water in the top 1 2 m of the soil the sites were divided on the basis of landscape surface form into lower slope upper slope and saddle positions which accounted for 30 50 and 20 of the cultivated areas of the basins respectively the lower slope positions were well leached of soluble salts and had high water contents thick a horizons gleyed and or eluviated horizons and thick zones of calcium carbonate depletion the upper slope positions had limited leaching of soluble salts low water contents thin a horizons lacked eluviated horizons and calcium carbonate was present either at shallow depths or at the soil surface the properties of the saddle positions were intermediate between the upper and lower slope positions the spatial distribution of water in the landscape persisted over time due to the redistribution of water in the landscape by topography

morphology and origin of smaller scale mass movements on the continental slope off northern norway abstract little attention has been paid to smaller scale mass movements on continental slopes even though they occur much more frequently than their large scale counterparts swath bathymetry side scan sonar sub bottom profiler and seismic data from the continental slope offshore the lofoten islands northern norway reveal evidence of repetitive smaller scale translational sliding involving spreading and multi phase retrogression in water depths between 1100 and 2500 m three styles of failure have been identified occurring in close proximity style 1 is characterized by a 4 7 km wide and up to 100 m deep amphitheater shaped headwall a relatively deep glide plane 130 mbsf detached sediment ridges and a run out area with rafted sediment blocks style 2 consists of a staircase pattern of secondary escarpments caused by the activation of several glide planes between 30 and 110 mbsf headwalls and secondary escarpments have a height of up to 30 and 70 m respectively the run out area shows an almost complete sediment evacuation style 3 is more subtle as it is only identified on the side scan sonar data due to its higher spatial resolution this style shows different phases of on going evolution illustrating the gradual disintegration of a slab of sediments moving over a shallow glide plane at 13 mbsf zones with sediment slabs are up to several hundreds of meters wide and are sharply delineated by shear margins or escarpments the spatial variation in the failure style is inferred to have been caused by the activation of different glide planes which is probably a result of the thinning of contouritic sediments towards the south west in the north east the mounded contouritic sediments contain more potential glide planes and higher slope angles the smaller scale mass movements are suggested to have been triggered by undercutting and removal of support at the foot of the slope due to large scale mass movements that have occurred immediately south of the study area such as the traenadjupet or nyk slides the geophysical data indicate that relatively recent mass movement processes have taken place in this area through the formation of shallow cracks and graben structures by the movement of 13 m thick slabs of sediments style 3 which could have severe implications for offshore infrastructure

digital elevation model networks demon a model of flow over hillslopes for computation of contributing and dispersal areas current algorithms for computing contributing areas from a rectangular grid digital elevation model dem use the flow routing model of o callaghan and mark 1984 which has two major restrictions 1 flow which originates over a two dimensional pixel is treated as a point source nondimensional and is projected downslope by a line one dimensional moore and grayson 1991 and 2 the flow direction in each pixel is restricted to eight possibilities we show that large errors in the computed contributing areas result for any terrain topography divergent convergent or planar we present a new model called digital elevation model networks demon which avoids the above problems by representing flow in two dimensions and directed by aspect demon allows computation of both contributing and dispersal areas demon offers the main advantage of contour based models e g moore et al 1988 the representation of varying flow width over nonplanar topography while having the convenience of using rectangular grid dems

a record of fluctuating bottom currents on the slopes west of the porcupine bank offshore ireland implications for late quaternary climate forcing abstract both local and regional controls on slope sedimentation west of porcupine bank are assessed using an array of 25 gravity cores integrated with shallow seismic tobi side scan and high resolution bathymetry data the cores were retrieved from an area of smooth distally steepened slope between 52 and 53 n in water depths of 950 to 2750 m the slope here is unmodified by gravity failures and is swept by bottom currents that flow from s to n along the margin the cores reveal a coherent shallow stratigraphy that can be traced along and between transects at upper mid and lower slope levels ams 14 c dating oxygen isotopes and carbonate profiles suggest the cored record could extend as far back as 500 ka in the longest cores with most cores providing details of the slope response to the last interglacial last glacial and holocene forcing the facies indicate deposition was dominated by a combination of bottom currents ice rafting and hemipelagic settling with carbonate prone deposits during interglacials and siliciclastic deposits during glacials inferred contourites imply that strong currents operated during interglacials with weaker current reworking during glacial conditions a pair of erosion surfaces record significant mid and upper slope scouring during marine isotope stage mis 3 and in the early holocene the lateral facies distribution implies stronger currents at shallower levels on the slope although there is evidence that the core of the current migrated up and down the slope and that sand might locally have spilt down slope the bathymetry influenced both the wider geometry of the condensed contourite sheet and the local thickness and facies variation across the slope a significant result of the study is the identification of a pair of thin sand mud contourite couplets that record enhanced bottom current reworking corresponding to periods of interstadial warming during mis 3 the couplets can be correlated to the terrestrial records onshore ireland and imply that the ne atlantic margin oceanographic and onshore climate records are strongly coupled at interstadial level

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

sedimentary facies of glacial interglacial cycles in the norwegian sea during the last 350 ka sediment fluxes were highest in the norwegian sea during late glacial early deglacial periods i e at oxygen isotope transition 43 below transition 65 at various levels within stage 6 and below stage 9 dark diamictons deposited at these times reflect intense iceberg rafting in surface waters fed by surges along the front of the marine based parts of the continental ice sheets in the southeastern sector of the norwegian sea the high organic carbon content 0 5 1 3 in these layers reflects input from erosion of terrigenious matter rich sediments outcropping on the shelves partial oxidation of organic matter and decreased deep water renewal may explain the strong carbonate dissolution observed during these periods interglacial environments were strongly variable throughout the last 350 ka circulation patterns of stage 5e best resemble modern conditions while stage 7 and 9 sediments record a much weaker norwegian current

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

the barra fan a bottom current reworked glacially fed submarine fan system abstract on the basis of sedimentary structures textures and ichofauna seven depositional facies have been recognised in cores from the barra fan region of the hebrides slope sedimentary facies are combined into three genetic groups a c that represent their primary mode of deposition a sandy to muddy contourite facies a a1 and a2 which represent an overall coarsening upward sequence caused by an increase in bottom current velocity over time b disorganised glaciomarine deposits including the glaciomarine dumpstone of facies b and facies b1 deposited as a result of ice rafting and glaciomarine sedimentation and c hemipelagite facies c and c1 which are the result of normal marine hemipelagic settling it is most likely that all contourite facies a a2 identified in this study are holocene in terms of its diverse morphological elements and varied facies this high latitude submarine fan is truly composite in nature however a broad three stage glacial to post glacial evolutionary system is recognised during which different processes and process combinations were dominant during the last glacial period low stand system tract downslope processes including debris flows and minor turbidity currents sculpted an irregular slope topography little in the way of bottom current activity was evident staged deglaciation was accompanied by rising sea level and high sedimentation rates across the region this created an unstable margin prone to extensive sliding and slumping that masked any effects of an incipient alongslope current the present high stand system tract is dominated by a strong slope current that became fully active during the early part of the holocene low sedimentation rates diminished sediment supply and strong bottom current activity led to development of the sandy contourite sheeted drift system across the mid slope region little downslope movement is evident during this period so that the slope topography is being slowly smoothed and remoulded by active bottom currents

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

the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

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

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

evidence from fram strait 78 n for early deglaciation recent syntheses of the history of the last northern hemisphere glaciation and deglaciation illustrate that understanding of the mechanisms and timing of deglaciation before approximately 12 000 years bp1 5 is limited after 12 000 yr bp however there is sufficient evidence from radiocarbon dated moraines raised beaches varved lake sediments and pollen records to provide a reasonable temporal and geographic picture of the decay of the ice sheets here we report on the first oxygen isotope record from the norwegian greenland sea that is radiocarbon dated directly by accelerator mass spectrometry a significant light oxygen isotope event is recorded at approximately 15 000 years bp which suggests that the marine based barents shelf ice sheet disintegrated rapidly at this time recent studies6 7 have estimated that the decay of this ice sheet could have contributed as much as 15 metres to eustatic sea level rise the decay of the barents shelf ice sheet is the earliest major deglacial event yet dated and may have triggered subsequent deglacial events through eustatic sea level effects

soil nutrient dynamics during podzol development under lowland temperate rain forest in new zealand abstract the haast chronosequence on the west coast of the south island of new zealand consists of a series of coastal dune ridges formed by periodic earthquake disturbance over the last 6500 years it approximates an ideal chronosequence because soils are under the same climate and vegetation have similar topography and are developed in the same parent material we assessed soil development and the changes in nutrients at eleven sites along the sequence to determine rates of nutrient transformations and the potential for limitation of biological activity by nitrogen and phosphorus availability soils develop rapidly to podzols spodosols under the super humid climate involving acidification and depletion of base cations in the first few hundred years development of a bleached eluvial horizon under a thick organic horizon within 2000 years and formation of a continuous cemented iron pan within 4000 years soil phosphorus concentrations decline markedly in the first few hundred years in both the organic and upper mineral soil horizons with rapid depletion of primary mineral phosphate and the accumulation of organic phosphorus to 80 of the total phosphorus in the upper mineral soil these changes lead to an increasing degree of phosphorus limitation along the sequence as indicated by an increase in c p and n p ratios and a decline in available phosphate the rates of soil development and phosphorus depletion are more rapid than at the nearby franz josef post glacial chronosequence where glacial moraine derived from graywacke contains a relatively high phosphorus concentration and weathers into fine textured soils the haast chronosequence therefore provides an important additional example of soil development linked to long term depletion of soil phosphorus under a perudic moisture regime