provenance and depositional environments of quaternary sediments from the western north sea basin as the majority of the data on quaternary sediments from the north sea basin are seismostratigraphical we analysed the elsterian swarte bank formation the late saalian fisher formation and the late weichselian dimlington stadial bolders bank formation in order to determine genesis and provenance the swarte bank formation is a subglacial till containing palynomorphs from the moray forth and the northeastern north sea and metamorphic heavy minerals from the scottish highlands the fisher formation was sampled from the northern and central north sea in the north it is interpreted as a subglacial till with glaciomarine sediments cropping out further south these sediments exhibit a provenance signature consistent with the midland valley of scotland the eocene of the north sea basin the grampian highlands and northeast scotland the bolders bank formation is a subglacial till containing palynomorphs from the midland valley of scotland northern britain and a metamorphic heavy mineral suite indicative of the grampian highlands southern uplands and northeast scotland these data demonstrate that there was repeated glaciation of the north sea basin during the middle and late pleistocene with ice sheets originating in northern scotland there was no evidence for a scandinavian ice sheet in the western north sea basin

saalian to weichselian stratigraphy and sedimentation along the lagjaeren hogjaeren escarpment southwest norway quaternary sediments along a profile crossing the southern part of the jaeren escarpment southwestern norway have been investigated with regard to their glacial history and sea level variations deposits from at least three glaciations and two ice free periods between oxygen isotope stage 6 and the late weichselian have been identified subglacial till directly overlain by a glaciomarine regressional succession indicates a deglaciation and amino acid ratios in elphidium excavatum between 0 083 and 0 118 date this event to oxygen isotope stage 6 sea level dropped from 130 to below 110 m a s l subsequently a short lived ice advance deposited a marginal moraine and a sandur locally on the escarpment stratigraphical position and luminescence dates around 148 ka bp suggest deposition during the final stage 6 deglaciation a late weichselian till covers most of the surface of jaeren in addition to a well documented westerly ice flow glaciotectonic indications of ice flow towards the north have been found ice flow directions and a hiatus between oxygen isotope stage 6 and the weichselian indicate enhanced erosion along the escarpment and the influence of a norwegian channel ice stream copyright 1999 john wiley sons ltd

the micromorphology of last glacial maximum sediments in the southern north sea abstract the terrestrial ice limits of the last glacial maximum ice sheets are well understood but areas submerged during postglacial sea level rise have proved more difficult to accurately map fine grained diamicts in the southern north sea have been variously interpreted as glacial glacioaqueous or periglacial in origin implying different sedimentary environments this has resulted in contrasting opinions regarding the position of the last ice sheets in this area micromorphology is presented as a useful technique to aid the analysis of such sediments using systematic description of the physical characteristics of the sediments related to an interpreted seismic stratigraphy results indicate that the british ice sheet deposited glaciomarine sediments during an early advance and then advanced over an extensive part of the southern north sea as terrestrial ice

age of the pineo ridge system implications for behavior of the laurentide ice sheet in eastern maine u s a during the last deglaciation abstract the laurentide ice sheet was a major driver of global sea level change during the last deglaciation and may have impacted both atmospheric and oceanic circulation an understanding of past changes in the ice sheet is important for constraining its interaction with other components of the climate system here we present the geologic context and chronology for ice sheet fluctuations in eastern maine adjacent to the north atlantic ocean thought to be a key player in the termination of the last ice age retreat of the laurentide ice sheet through coastal maine first produced a series of lobate grounding line moraines followed by deposition of the prominent pineo ridge system which crosscut the earlier moraine set and which is characterized by extensive ice contact deltas closely spaced parallel moraines and association with eskers our new 10 be surface exposure ages indicate that the pineo ridge system which extends for more than 100 km in eastern maine and atlantic canada dates to 15 3 ka 800 years older than recent estimates our data are in accord with inboard minimum limiting radiocarbon ages of terrestrial materials which indicate deglaciation as early as 15 3 ka as well as of marine shells that are as old as 15 0 ka both the deglaciation that produced the lobate moraines and the short lived readvance that led to the pineo ridge system occurred during heinrich stadial 1 given that faunal and isotopic evidence indicates that the ocean remained cold during deglaciation of coastal maine we infer that ice recession was due to rising summer air temperatures that gave way briefly to cooling to allow minor readvance glacial deposits north of the pineo ridge system display evidence of ice stagnation and downwasting suggesting rapid ice retreat following deposition of the delta moraine complex coincident with the onset of the bolling

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

factors controlling regional spatial distribution of 53 elements in coastal sea sediments in northern japan comparison of geochemical data derived from stream and marine sediments abstract in all 53 elements were analyzed in 1406 coastal sea sediment samples collected from an area off hokkaido and the tohoku region of japan during a nationwide marine geochemical mapping project the spatial distribution patterns of the elemental concentrations in coastal seas along with the existing geochemical maps in terrestrial areas were used to define natural geochemical background variation and mass transport processes the terrestrial area is covered by mafic volcanic rocks and accretionary complexes associated with ophiolite which has small amounts of felsic volcanic rocks and granite the spatial distribution patterns of elements enriched in mafic lithologies such as fe total fe 2 o 3 and sc in marine environments are influenced by adjoining terrestrial materials the spatial distribution patterns of cr and ni concentrations which are highly abundant in ultramafic rocks on land are used to evaluate the mass transport from land to the sea and the dispersive processes caused by oceanic currents the scale of mass transport by oceanic currents occurs up to a distance of 100 200 km from the coast along the coastal areas the regional differences of elements rich in felsic lithologies such as k k 2 o nb and la in marine sediments are determined mainly by the relative proportion of minerals and lithic fragments enriching felsic materials to those associated with mafic materials the spatial distribution of elemental concentration is not always continuous between the land areas and coastal sea areas that difference is interpreted as resulting from 1 transportation of marine sediments by oceanic currents and storm waves 2 contribution of volcanic materials such as tephra 3 occurrence of shell fragments and foraminifera tests and 4 distribution of relict sediments of the last glacial age and early transgression age contamination with cu zn cd as mo sn sb hg pb and bi was not observed in marine environments because the study area has little anthropogenic activity terrestrial materials are the dominant source for these metals the mo cd sn sb hg pb and bi are abundant in silty and clayey sediments locally because of early diagenetic processes authigenic precipitation and organic substances associated with these elements the spatial distribution of as concentration shows exceptions it is concentrated in some coarse and fine sands on the shelf the enrichment is explained by adsorption of as sourced from a coal field to fe hydroxide

rates and timing of earth surface processes from in situ produced cosmogenic be 10 beryllium 10 is the longest lived of the seven known unstable isotopes of be it results mostly from the interaction of cosmic radiation primarily neutrons with a variety of target atoms by spallation the splitting of nuclei lal 1988 it can also be produced at very low levels by radio disintegration of u and th sharma and middleton 1989 although all radioactive be isotopes are produced in the atmosphere via cosmic ray reactions arnold 1956 lal and peters 1967 morris et al chapter 5 this volume in this paper we are most interested in 10be produced in rock which we refer to as in situ produced such in situ produced 10be is a cosmic ray dosimeter functioning as a quantitative monitor of near surface residence time in some geologic situations 10be can be used as a chronometer allowing one to estimate the duration of surface exposure in other settings 10be can be used as a tracer allowing one to estimate the rate distribution and behavior of earth surface processes rates of 10be production are very low in rocks exposed at earth s surface 102 atoms g 1 y 1 resulting in typical in situ produced 10be concentrations termed activities of 103 to 107 atoms g 1 the development of accelerator mass spectrometry ams in the 1980s allowed routine measurement of 10be at levels typical of rocks exposed near earth s surface elmore and phillips 1987 analytical refinements in the 1990s lowered detection limits by an order of magnitude allowing dating of exposure periods 103 years in favorable geologic and geographic situations simple exposure histories at high altitude and latitude most in situ 10be is measured in quartz mineral separates where the primary spallation target is o lal and arnold 1985

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

late glacial impacts on dispersal and colonization of atlantic canada and maine by freshwater fishes late glacial scenarios of ice retreat and biogeography databases constrain the dispersal routes of obligate freshwater fishes into atlantic canada and maine evidence indicates glacial ice covered the present day mainland and offshore islands at 18 000 14c yr before present possible refugia for extirpated freshwater fishes were the exposed outer edge of the grand banks east exposed georges bank south atlantic refugium and the mississippi refugium in the west it is improbable that the region was recolonized from the offshore refugia rather fishes recolonized from the east via the upper st lawrence river valley into the upper saint john river maine lake madawaska from 11 000 to 12 000 14c yr bp the short period of entry resulted in the low diversity of obligate freshwater species in the region lake madawaska was breached and dispersal continued into the remainder of the region after 8000 14c yr bp by 6000 14c yr bp access routes to the east along low lying coastal zones were blocked by rising sea levels which isolated prince edward island cape breton island and most probably nova scotia natural dispersal across the region appeared complete by this time

repeated advance and retreat of the east antarctic ice sheet on the continental shelf during the early pliocene warm period abstract diatom analysis of a sediment core recovered at iodp site u1358 on the continental shelf off the adelie coast indicated that the lower section of the core contained an assemblage dating back to the thalassiosira innura zone of the lower pliocene that ranges from 4 2 to 5 12 ma based on lithological descriptions at both a macro and micro scale of this early pliocene part of the core four facies were interpreted from the diamictons representing the progressive advance and retreat of the grounding line over the site facies 1a and 1b contain a distinct directional signal from the orientation of the a axis of clasts with several phases of fabric development along with both brittle and ductile deformation features that are common in sediments that have been subglacially deformed facies 1c and 1d are finely laminated and were deposited in open marine conditions the four facies within the depositional model provide for the first time direct evidence for ice advancing across the shelf adjacent to the wilkes subglacial basin on at least four occasions separated by three periods of open marine conditions indicating retreat of grounded ice inland of the site during a warmer than present early pliocene the times of open marine conditions are correlated with previous findings from the neighbouring rise sites that also indicated an oscillating ice margin this has significant implications because firstly it suggests a dynamic east antarctic ice sheet eais that is probably far more sensitive to climatic and oceanic forcing even during relatively short time periods than had previously been thought secondly it suggests that proxies used to interpret the advance and retreat of the grounding line from the rise can be linked with direct evidence of grounding line migration from the shelf it also has important implications for the future behaviour and sensitivity of the eais under present continuing warming conditions together with results from the rise this paper provides a crucial ice extent target for a new ice sheet model of this region during the pliocene

mechanisms of sediment transport and deposition sediment sequences and accumulation during the holocene on the thermaikos plateau the continental slope and basin sporadhes basin northwestern aegean sea greece abstract detailed 3 5 khz seismic reflection profiling carried out on the thermaikos plateau the slope and the basin sporadhes basin northwestern aegean has shown that during the holocene the area received fine grained sediments discharged mainly by the rivers axios aliakmon and pinios a well developed oblique sigmoid progradation pattern has been observed on the seismic profiles taken across the deltaic holocene sequences of these rivers three seismic facies have been identified within the oblique sigmoid pattern 1 dark homogeneous facies that represent fine sand deposits along the delta front topsets 2 stratified facies that represent alternating muddier or sandier horizons foresets and 3 transparent facies in which the muddy sediments predominate bottomsets the base of the holocene reflector c has been found beneath the oblique sigmoid pattern the thin homogeneous and transparent seismic facies throughout the slope and the basin has been interpreted as the holocene muddy sediment sequence in the area bottom samples from the outer thermaikos plateau have shown that it is floored by relict terrigenous sand at depths of 90 110 m the sediment and clay mineral distribution and the presence of relict sand confirm that during the holocene period the fine grained sediment dispersion and deposition was effected by the water mass circulation the majority 80 90 of the sediments dispersed from the rivers during the holocene has been captured by the extensive shelf thermaikos plateau having deposited from the near bottom nepheloid layer minor amounts 10 20 of very fine grained material have escaped and deposited from suspension hemipelagic settling in the slope and basin of the studied area

sediment yield studies of headwater catchments in sussex s e england the transport of sediment from six small 0 2 to 17 6 km2 headwater catchments is described the catchments under investigation were located in relation to predominant lithological deposits within the cretaceous rock succession two of the areas were underlain by weald clay two by sandstone ashdown sand and tunbridge wells sand and two by chalk the climate of the region under investigation is temperate with an average annual precipitation 850 mm in excess of potential evapotranspiration 450 mm the transport of suspended material from within the catchments was examined by collecting samples of the water sediment mixture draining the areas using hand held depth integrating and permanently installed stage sampling systems the results of the regularly maintained sampling programme over a two year period are described attempts were made to both measure and compute bed load transport suspended sediment concentrations are compared between catchments and related to hydrological characteristics the nature of the material in transit is examined sediment rating curves are derived for each of the headwater catchments defining the relationship in the form y axb where y suspended sediment concentration mg 1 and x water discharge m3 s annual rating curves are used to derive annual suspended sediment loads by combination with water discharge data using a log incremental computerized approach multiple regression techniques have been used to examine annual loads in terms of hydrological and morphological characteristics of the headwater catchments based on the field information available a generalized model for the relationship between suspended sediment concentration and water discharge is described finally the derived annual loads from the headwater catchments are combined with both limited observations from the larger sussex rivers and data available for other catchment investigations in the british isles to produce a series of prediction equations for catchment yield under temperate climatic conditions

geochemical and sedimentological patterns in the thermaikos gulf north west aegean sea formed from a multisource of elements surface sediment samples from thermaikos gulf were analysed for organic carbon cd pb cr cu zn mn ni co and fe and were subjected to grain size analysis the results showed that pb cu and zn had the same source of pollution in the following order of importance the sewage outfall the industrial zone and the axios river the concentration of these metals increased with decreasing mean grain size suggesting their association with the fine fraction of the sediments the clays and the organic matter cadmium was more loosely correlated with the metals of the previous group being derived from the community activities and also from the weathering of land based ophiolitic rocks iron cr ni co and mn are of natural origin the weathering of mafic and ultramafic rocks being responsible for their enrichment this was more apparent in the case of ni which was more enriched in the coarser and better sorted sediments near the delta of the river aliakmon

chemical cycles in pliocene sapropel bearing and sapropel barren eastern mediterranean sediments abstract high resolution 3 4 cm investigations of major and minor elements were carried out on sediment cores from odp leg 160 sites 964 ionian basin 969 mediterranean ridge 967 and 966 northern slope and top of eratosthenes seamount south of cyprus at site 967 element al ratios display pronounced cyclic records that are related to astronomically forced climatic variations sediments from the top of eratosthenes seamount site 966 show a similar pattern to those from site 967 but they are more disturbed by bioturbation and also strongly influenced by long term variations in sediment dispersal sediments from site 969 display similar trends to those from site 964 i e they are characterized by higher mg al slightly higher k al and lower ti al ratios during sapropel formation higher ti al ratios at site 969 compared with sediments from site 964 may be explained by a westward transport of material from a source in the east where ti al ratios are highest sites 966 and 967 elevated mg al ratios at site 969 during sapropel intervals are due to river derived material transported through the kithira strait between peloponnesus and crete from the northwestern aegean sea which originates from ultramafic rocks a change in intermediate water currents current reversal during sapropel formation may explain the enhanced supply of mg rich and the relatively diminished supply of ti rich material we propose that during deposition of the reddish intervals at site 969 a change in circulation did not occur because a drastic decrease in ti al ratios is not evident in these sediments ba peaks indicative of former sapropels are not present ba enrichments in the same sapropel barren intervals at site 967 northern slope of eratosthenes seamount suggest that during such intervals the burn down process was more effective than during the sapropel bearing intervals mn contents in all investigated pliocene sediments correlate with the carbonate contents higher mn contents of the sapropel barren sediments suggest that during time intervals of sapropel formation either mn accumulation at the margins of the permanently oxic upper water column or mn export into the western mediterranean might have occured the latter could only be explained by sub or anoxic conditions in large parts of the water column

palaeomagnetic evidence for early pleistocene in the central and northern north sea the palaeomagnetic evidence presented here refutes the earlier hypothesis that most of the quaternary succession in the central north sea area is of middle to upper weichselian age a study of the quaternary seismic stratigraphy has been tied to 11 cored boreholes which are being examined for their physical properties and faunal content initial palaeomagnetic studies show a major reversely magnetized zone which can be correlated from borehole to borehole and with the seismic stratigraphy this reversely magnetized zone is thought to represent the matuyama epoch which ended 790 000 yr bp consequently this suggests the presence of early pleistocene strata in the central and northern north sea

the sedimentary signature of ice contact sedimentation and deformation at macro and micro scale a case study from nw scotland abstract studies on the genesis of subaerial debris flows and associated deposits are relatively rare in the literature especially in an ice marginal context of moraine formation the present contribution reports results from both the macro and micro scales of a subaerial depositional setting in order to contribute to closing this gap at the macroscale alternating loose stratified clast and matrix supported diamicts and finely laminated sand units indicate deposition of debris flows and fluvial units in a subaerial ice marginal setting that were stacked up to form a terrestrial ice contact fan macroscale and micromorphological analyses show that this fan displays evidence of a three phased formation a overriding and glaciotectonisation of pre existing sediments followed by retreat and burial of this core by b ice contact fan deposition dominated by water rich fluvial deposition with relatively little debris flow activity and c a switch to a gravitational sedimentation style with dominantly debris flow deposition and fewer and thinner fluvial units thin sections of both the diamict and laminated sand units show evidence of deposition of a mud and fine sand rich slurry being expelled from the tops of advancing mass flows water rich fine grained slurries appear to have been progressively overridden and deformed in response to ductile shear occurring at the base of individual flows liquefaction and remobilisation of sand within laminated deposits occurred during such basal shear events resulting in the injection of liquefied sediments into variably deformed laminated sands and clays deformation is more likely to have taken place through internal movement of the sediment due to changing porewater conditions and loading upon emplacement our approach confirms previous results that highlight the possibilities of increasing the accuracy of sedimentological investigations through combined sedimentological analyses at varying scales

modern sedimentation in the n w aegean sea abstract the area under investigation is located within 22 45 to 23 45 e and from 39 15 to 40 15 n sedimentological bathymetric and shallow geophysical data were collected from here during the 7 78 cruise of r r s shackleton twenty seven sea bed surface samples were collected using a day grab from different environments these were analysed for grain size distribution carbonate content and clay mineralogy on the basis of the bathymetric and shallow geophysical data the area has been classified into five major physiographic environments according to their bathymetry and topography 1 shelf thermaicon plateau 2 slope 3 marginal plateau 4 the canyon system and valleys and 5 sporades basin based on the sedimentological analyses the surface sediments have been classified into four major provinces as follows 1 province 1 shelf muds 2 province 2 muddy sands 3 province 3 outer margin muds and 4 province 4 outer shelf shelf break it is concluded that modern sedimentation in the n w aegean sea is dominated by the terrigenous river inputs and by the circulation of both high and low salinity masses

tunnel valleys current knowledge and future perspectives tunnel valleys are elongated incisions that are commonly interpreted as being the result of erosional processes by subglacial meltwater occurring under continental ice sheets the abundance size and the primarily coarse grained infill of these features have made tunnel valleys important hydrocarbon and groundwater reservoirs although numerous tunnel valleys have been described over the last century their formation and infill remain poorly understood this review summarizes and discusses the current knowledge of tunnel valleys providing an overview of the observations around the world morphological aspects that separate tunnel valleys from other landforms are discussed as well as the wide variety of sedimentary environments found to contribute to the infilling of these features the depth of the incision and the character of ice retreat significantly determine the final infill architecture the formational hypotheses proposed in the literature are assessed to test their wider applicability to all other tunnel valleys in order to find a generic model that helps in the prediction of the morphology and infilling of both pleistocene and pre pleistocene age a quasi steady state model with small meltwater outbursts that erode tunnel valleys near the ice margin seems compatible with most of the known valleys other proposed models require specific geographical or climatic conditions

a postglacial history of vegetation and bog formation at point escuminac new brunswick radiocarbon dating and analyses of fossils contained in peat cliffs establish the history of peatland formation and development at the northern edge of point escuminac new brunswick a 532 cm radiocarbon dated mineral sediment and peat sequence the oldest of four sections studied yielded pollen and macrofossils that record bog development from 11 000 bp the earliest landscape was open juniperus shrubland picea was the first tree to move into the area forming woodland communities by 10 200 bp and closed coniferous forests with abies by 9200 bp an early counterpart of the modern acadian forests was in place by 6500 bp and was fully developed by 2900 bp when fagus spread through the area shallow freshwater open wetland communities acted as nuclei for the development of fen near the centre of the peninsula transformation into an ombrotrophic bog started around 6500 bp and was completed by 4700 bp after which time the bog spread laterally by paludification onto higher parts of the peninsula

changes in chemical and 87sr 86sr signature distribution patterns of suspended matter and bed sediments in the upper loire river basin france abstract the mineralogy of the suspended particulate matter spm transported by the upper loire river consists mainly of quartz and k feldspar during periods of high river flow with an increase in calcite concentration during periods of low flow concurrently large fluctuations are observed in the levels of cao and fe2o3 the main oxides present in the spm along with sio2 the analysed trace elements also fluctuate significantly the bed sediments bs have a similar oxide content to the spm but lower zn and pb levels and higher zr levels fluctuations in the chemical element concentrations with river discharge are related to fluctuation in the mineral assemblages present in the spm thus k ti and rb levels increase with increasing in k feldspar abundance during high flow and ca and sr levels decrease with increasing discharge due to a decrease in calcite abundance these mineralogical and chemical variations relate to different sources of sediments under different flow conditions sources that can be distinguished by sr isotopic study the sr isotopic composition fluctuates according to the rate of river discharge i e the 87 sr 86 sr ratio increases with increasing discharge and reaches a maximum with peak flow and vice versa the 87 sr 86 sr ratio also increases with the combined increase in k feldspar abundance and decrease in calcite abundance these similarities suggest the existence of at least two particulate matter reservoirs one with detrital silicates and the other with carbonates finally the relationship between the 87 sr 86 sr ratios in the suspended and dissolved loads suggests the coexistence of authigenic calcite in the carbonate reservoir the spm flow is related to a specific mechanical erosion rate over the whole loire watershed ranging from 9 to 23 t km 2 yr 1 during the survey at orleans the spm flow of the loire river was 37 104 t yr 1 providing an estimate of the specific erosion rate of around 9 8 t km 2 yr 1 from the shift in the spm flux between the sampling point and the mouth of the loire river and the divergence in the mean annual discharge a calculation was made of the input of solid matter by the tributaries and by supplementary erosion processes along the river

a late glacial transition from picea glauca to picea mariana in southern new england abstract picea is an important taxon in late glacial pollen records from eastern north america but little is known about which species of picea were present we apply a recently developed palynological method for discriminating the three picea species in eastern north america to three records from new england picea glauca was dominant at 14 500 14 000 cal yr bp followed by a transition to picea mariana between 14 000 and 13 500 cal yr bp comparison of the pollen data with hydrogen isotope data shows clearly that this transition began before the beginning of the younger dryas chronozone the ecological changes of the late glacial interval were not a simple oscillation in the position of a single species range but rather major changes in vegetation structure and composition occurring during an interval of variations in several environmental factors including climate edaphic conditions and atmospheric co2 levels

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

the postglacial history of three picea species in new england usa abstract given the difficulty of separating the three picea species p glauca p mariana and p rubens white black and red spruce in the pollen record little is known about their unique histories in eastern north america following deglaciation here we report the first use of a classification tree analysis cart to distinguish pollen grains of these species it was successfully applied to fossil pollen from eight sites in maine and one in massachusetts we focused on the late glacial early holocene 14 000 to 8000 cal yr b p and the late holocene 1400 cal yr b p to present the two key periods since deglaciation when picea has been abundant in the region the result shows a shift from a picea forest of p glauca and p mariana in the late glacial to a forest of p rubens and p mariana in the late holocene the small number of p rubens grains identified from the late glacial early holocene samples picea 1000 to 500 cal yr b p was likely the first time since deglaciation that p rubens was abundant in the region

seismic chimneys in the southern viking graben implications for palaeo fluid migration and overpressure evolution highlights 3d seismic interpretation reveals 46 large chimney structures in the svg chimneys can be subdivided in three categories based on their seismic appearance seismic appearance of chimneys enables reconstructing formation mechanisms overpressure and seal weakening by deformation control chimney formation fluid flow along chimneys represents an efficient pressure transfer mechanism abstract detailed understanding of natural fluid migration systems is essential to minimize risks during hydrocarbon exploration and to evaluate the long term efficiency of the subsurface storage of waste water and gas from hydrocarbon production as well as co2 the southern viking graben svg hosts numerous focused fluid flow structures in the shallow 1000 m subsurface the seismic expressions of vertical fluid conduits are variously known as seismic chimneys or pipes seismic pipes are known to form large clusters seismic chimneys have so far been described as solitary structures here we show that the study area in the svg hosts more than 46 large scale vertical chimney structures which can be divided in three categories implying different formation processes our analysis reveals that seal weakening formation wide overpressure and the presence of free gas are required to initiate the formation of vertical fluid conduits in the svg the presence of numerous vertical fluid conduits implies inter stratigraphic hydraulic connectivity which significantly affects the migration of fluids in the subsurface chimney structures are important for understanding the transfer of pore pressure anomalies to the shallow parts of the basin

3d seismic analysis of buried tunnel valleys in the central north sea morphology cross cutting generations and glacial history abstract this work presents the results of morpho stratigraphic analyses carried out on more than 180 buried tunnel valleys imaged in the central north sea using 3d seismic data at a variety of resolutions the buried tunnel valleys form complex networks of multiple cross cutting generations in the northern part of the study area cross cutting relationships within higher resolution 3d seismic data are used to extrapolate seven generations of tunnel valleys over an area of 14 400 km 2 three generations of cross cutting tunnel valleys are also observed within higher resolution 3d seismic data in the southern part of the study area detailed morphological measurements of individual tunnel valleys reveal average widths between 300 m and 3000 m lengths in the region of tens of kilometres and relatively straight and simple planform geometries the majority of the tunnel valleys display undulating basal profiles which provide evidence for the uphill movement of water over distances greater than 10 km and indicate formation by meltwater under pressure tunnel valley geometries vary between generations and defy a simple link between formation process and end form detailed orientation measurements for the tunnel valley generations reveal an overall ne sw trend in the northern part of the study area and a nw se directionality in the south when considered in light of palaeoglaciological models for the british and scandinavian ice sheets during the pleistocene tunnel valley orientation and distribution are consistent with the majority of tunnel valley generations forming perpendicular to a retreating british ice sheet changes in orientations between generations in both northern and southern study areas provide evidence for changes in the dynamics of the british and scandinavian ice sheets between subsequent glaciations of the central north sea

the quaternary succession in the northern north sea abstract studies of core material show that the upper 200 m of sediments deposited in central parts of the north sea span the last ca 1 ma in the norwegian trench the upper 120 m span the last ca 500 ka sedimentation in both areas was characterized by rapid rates over short intervals separated by long hiatuses in the central area fine grained shallow water sediments dominate the pleistocene sequence these sediments were redeposited transported by rivers flowing northward from the british isles and the continent during periods of low sea level through the quaternary the extreme low stands of sea level are also indicated by river channels cut in the sequence in the northern north sea in the norwegian trench thick glacial and glacial marine diamictons make up ca 80 of the record in the middle and late pleistocene sequence the northern north sea was glaciated as early as 850 ka evidence of possibly the most extensive glaciation of the north sea basin has been dated to between 200 and 450 ka in cores from the fladen area the british and scandinavian ice sheets probably did not coalesce in the north sea during the late weichselian maximum

chironomid evidence for late glacial climatic reversals in maine previously published pollen studies from maine have not identified any late glacial reversals despite evidence for them from adjacent areas the distribution and abundance of midge flies are strongly correlated with summer surface water temperatures we analyzed fossils of larval midge flies from the sediments of two ponds trout and tilley from maine each site reveals a major and a minor oscillation during which inferred summer surface water temperatures fell by 7 13 c and 2 1 2 6 c respectively we tentatively correlate these events with the younger dryas cooling and killarney oscillation reported from adjacent maritime canada where they have been ams 14c dated at 10 770 10 000 and 11 160 10 910 yr b p respectively a third oscillation occurs at the northernmost site tilley pond and may represent the effects of a local ice advance in northern maine

geochemical and micropaleontological characterisation of a mediterranean sapropel s5 a case study from core ban89gc09 south of crete several geochemical and micropaleontological proxies were studied in a well developed sapropel s5 from a core collected south of crete to investigate the causes and the mechanisms of its deposition to reconstruct the paleoenvironmental and paleoceanographical conditions at time of its formation and to detect the roles played by productivity and anoxia the geochemical proxies are also used to unravel the sediment provenance and therefore to help tracing water circulation patterns and freshwater sources the multiproxy approach reveals that the sapropel layer has high internal variability and five different depositional phases can be identified four within the visible sapropel layer an increase in temperature and the development of a deep chlorophyll maximum characterise the onset of the sapropel phase 1 with enhanced productivity being favoured by local riverine input not clearly ascribable to nile river freshwater discharge and by the shoaling of the pycnocline nutricline surface water stratification and productivity develop together with strong seafloor dysoxia anoxia phase 2 is characterised by lower stratification slightly lower temperature and or higher seasonal contrast and still high productivity phase 3 records high productivity high temperature and high stratification probably more sustained by the nile input a sudden partial re oxygenation takes place at the end of this phase changing the main features of the sapropel in the fourth phase productivity starts to decrease water stratification seems to be partially broken down and sediment oxygenation increases a transitional phase phase 5 occurs between the end of the visible sapropel and the normal pelagic post sapropel sedimentation where productivity is still high and oxygenation improves compared to the visible sapropel layer the massive occurrence of polysphaeridium zoharyi cyst of a red tide forming dinoflagellate also characterises this phase the geochemical proxies indicate that pre sapropel and post sapropel sediments are quite different from each other and the provenance shifts from a more mixed to a more markedly southern origin of sediments

late glacial fluctuations of the laurentide ice sheet in the white mountains of maine and new hampshire u s a abstract prominent moraines deposited by the laurentide ice sheet in northern new england document readvances or stillstands of the ice margin during overall deglaciation however until now the paucity of direct chronologies over much of the region has precluded meaningful assessment of the mechanisms that drove these events or of the complex relationships between ice sheet dynamics and climate as a step towards addressing this problem we present a cosmogenic 10be surface exposure chronology from the androscoggin moraine complex located in the white mountains of western maine and northern new hampshire as well as four recalculated ages from the nearby littleton bethlehem moraine seven internally consistent 10be ages from the androscoggin terminal moraines indicate that advance culminated 13 2 0 8 ka in close agreement with the mean age of the neighboring littleton bethlehem complex together these two datasets indicate stabilization or advance of the ice sheet margin in northern new england at 14 13 ka during the allerod greenland interstadial i

geochemical study of sediments from northern euboekos bay greece with regard to the presence of submarine mineral deposits abstract chemical analyses of surface sediment cores from northern euboekos bay greece show that this area is markedly enriched in metals e g ni cr mn relative to aegean shelf sediments these enrichments are partly related to the presence of an fe ni ore body on the seafloor formed by the dumping of a metal rich slag and partly to natural geological processes in a zone on the northwestern coast of euboea island considerable enrichments of ni cr and mn are attributed to weathering of mafic and ultramafic rocks present on the island and probably extended onto the continental shelf it is suggested that the geological and oceanographic conditions in this area are favourable for the formation of placer mineral deposits similar and even greater enrichments of fe ni cr mn zn and cu identified in two older geological horizons are associated with coarse sediments and may be the result of the following processes 1 the weathering of ophiolitic rocks or fe ni deposits or both extending from onshore below the seafloor 2 the production of greater amounts of metal rich weathering products in the past due to climatic changes and 3 lowering of the sea level at times when metal rich horizons were being formed closer to the continent

younger dryas climatic reversal in northeastern usa ams ages for an old problem abstract late glacial macrofossils from a 10 m core from alpine swamp new jersey were radiocarbon dated using accelerator mass spectrometry ams the arrival of the first trees to the area following deglaciation is indicated by maximum percentages of spruce pollen and a date of 12 290 440 yr b p on a single spruce needle subsequent spread of deciduous hardwoods was followed by the expansion of boreal taxa including spruce picea fir abies larch larix laricina paper birch betula papyrifera and alder alnus three ams dates on paper birch seeds and a spruce needle during this boreal expansion indicate that it took place between 11 000 and 10 000 yr b p the timing of this vegetational shift and its correlation with late glacial pollen stratigraphy from many sites in southern new england indicate that a climatic reversal correlative with the younger dryas characterized the north atlantic seaboard of the united states

pollen response surface estimates of late quaternary changes in the moisture balance of the northeastern united states abstract quantitative estimates of late quaternary climate in the northeastern united states are reconstructed from fossil pollen data to evaluate changes in the regional moisture balance inferred from water level fluctuations we use environmental response surfaces to calibrate modern pollen data for 17 different taxa to an index of effective soil moisture and mean annual precipitation we apply these response surfaces to fossil pollen data from 60 sites in the region to reconstruct changes in soil moisture and mean annual precipitation at 3000 yr intervals from 12 000 yr b p to present the mapped reconstructions of soil moisture and mean annual precipitation illustrate how the regional moisture balance of the northeast may have changed over the last 12 000 yr in response to changing climate reconstructions of annual precipitation show a gradual increase from 30 below modern values at 12 000 yr b p to near modern values by 6000 yr b p and then remain relatively constant thereafter reconstructed changes in the index of effective soil moisture however show a pattern of near modern values at 12 000 6000 and 3000 yr b p with significantly lower values estimated for 9000 yr b p the time of maximum pine pollen abundances in the northeast this pattern of change is similar to the change in regional moisture balance inferred from stratigraphic records of water level fluctuations these results confirm previous interpretations based on records of water level fluctuations that conditions in the northeast were significantly drier during the early to middle holocene than at other times during the last 12 000 yr

timing and style of deposition on humid temperate fans vermont united states fans in the once glaciated mountainous landscape of humid temperate new england preserve a long and unique record of deposition and thus of hillslope erosion by using multiple backhoe trenches and radiocarbon dating of wood and charcoal we determined the history of five small fans 1900 14 850 m 3 that range in age from historic to 13 320 calibrated cal 14 cy r

3d seismic geomorphology of a large plio pleistocene delta bright spots and contourites in the southern north sea abstract regional 2d seismic interpretation has been integrated with high resolution 3d interpretation in dutch offshore blocks a f in the southern north sea 17 horizons mmu s1 s4 s4 1 s4 2 s5 s5 1 s6 s13 and 14 seismic units were interpreted expanding upon studies by kuhlmann and wong 2008 the study presents detailed and extensive twt structure and thickness maps of key depositional units allowing paleogeographic reconstructions detailed analysis of incisional scour marks and hypothesised iceberg scours and constructional features contourites identified initially by bright spots on seismic data linked to bottom currents was undertaken paleo paleographic reconstructions of water depth emphasise the role of hypothesised tidally generated contour currents in the late stage deltaic infill of an epicontinental basin north sea

postglacial palaeophytogeography of the eastern st lawrence river watershed and the climatic signal of the pollen record abstract pollen analytical studies of the sediments of over 150 lakes and bogs in southern quebec have led to the indentification of a limited number of sequential types or temporal suites of the various pollen assemblages within each of three main stages of the postglacial development of vegetation the non arboreal stage the afforestation stage and the forest stage these sequential types within any of the three stages show distinct geographical and chronological distributions in southern quebec during the last 12 000 yr when compared in a broader geographic context they demonstrate a strong differentiation of the pollen record within and around the great lakes st lawrence river watershed during the last 15 000 yr b p amongst the most striking gradients identified stand the late glacial perichamplainian gradients ca 11 500 10 000 yr b p and the early holocene gradients the former involve seaward and northeastward clines from closed coniferous forests to tundras and the latter northeastward changes in the nature and duration of the afforestation stage the modern pattern of even the broader vegetational gradients in southern quebec was not attained before 3000 yr b p palynological reconstruction of the various regional paleoclimates highlights the interaction of local regional and global climatic forcings through time mesoscale climate modelling and palaeoclimatology should find boundary conditions in those regional reconstructions

iceberg ploughmarks illuminated by shallow gas in the central north sea 2014 the authors published by elsevier ltd this is an open access article under the cc by nc salicense http creativecommons org licenses by nc sa 3 0

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

a quaternary aminostratigraphy constraining chronology of depositional environments in the north sea basin abstract the aminostratigraphy of up to 1000 m of glacial and interglacial sediments in the north sea basin nsb is compiled from multiple boreholes sites and dated using strontium isotope sr analysis to provide a chronological framework extending throughout the quaternary the quaternary aminostratigraphy within the nsb can be divided into five amino zones az az1 youngest to az5 based on alle ile ratios which are used to correlate depositional events recorded in sedimentary facies from multiple borehole sites the new relative and absolute chronology also ties to seismostratigraphy and multi generational tunnel valley fill early pleistocene sediments produce az5 ratios with sr ages around 1 4 1 5 ma deposited in marine to glacimarine conditions sediments with az4 ratios are constrained by sr ages and magnetic polarity to 1 3 0 9 ma spanning the eccentricity to axial tilt insolation periodicity change of the mid pleistocene transition mpt some coarse grained sedimentary units with az4 ratios may be linked to ice proximal deposition during the mpt sediments with az3 ratios are poorly chronologically constrained to between 1 1 and 0 26 ma at least one episode of diminished coarse clasts and increased foraminiferal diversity during this mid pleistocene time suggests a progression from ice proximal to warmer possibly interglacial conditions furthermore the stratigraphically deepest generation of tunnel valleys cut strata with az3 ratios indicating subglacial conditions at least once during the mid pleistocene sediments with az2 ratios corresponding to mis7 5 are tied to seismic units including a thick up to 40 m deformation till suggesting glacial incursion into the nsb during mis6 followed by tunnel valley cutting of the this till thought to be an mis6 event also the geometry and cross cutting complexities of such tunnel valleys precludes further correlation of this ice extent the youngest aminostratigraphic zone az1 is recognised in all boreholes and well constrained to mis4 2 and the youngest set of tunnel valleys attributed to a single or multiple glacial advances at this time

detailed record of the neogene sr isotopic evolution of seawater from dsdp site 590b a detailed study of strontium isotope variations in neogene marine carbonate sediments from deep sea drilling project site 590b using techniques that allow the 87sr 86sr ratio to be determined to better than 0 00001 gives a high resolution record of the sr isotopic evolution of seawater the data show that the rate of change of the marine 87sr 86sr ratio has varied significantly even on time scales as short as 1 m y periods of particularly rapid growth appear to follow major marine regressions and probably reflect an increase in the delivery of radiogenic sr from the continents coupled with a decreased submarine carbonate dissolution rate greater carbonate compensation depth periods of relatively slowly changing 87sr 86sr follow major marine transgressions on the basis of correlations with the marine oxygen isotope record and the times of major continental glacier growth it is inferred that the effects of sea level variations are modified by climatic factors that affect the intensity of continental weathering and runoff the effects of sea floor generation rate variations are not discernible for the neogene the maximum attainable stratigraphic resolution using sr isotopes is between 0 1 and 2 m y for this time period

interstadial conifer wood from northern maine abstract conifer wood probably spruce picea sp of middle wisconsinan age 29 200 500 yr b p was recovered from late glacial lake sediments from upper south branch pond maine if the wood was derived from a local source deglaciation of part of northern new england is suggested for this time the occurrence also has implications for understanding the problem associated with radiocarbon dating of bulk lake sediment containing small amounts of organic matter

geochemistry and mineralogy of the nw aegean sea surface sediments implications for river runoff and anthropogenic impact abstract surface sediments of the nw aegean sea were analyzed for clay mineral composition 94 samples organic c and carbonate content and major and minor elements 112 samples illite is the most abundant clay mineral followed by smectite chlorite and kaolinite clay minerals are preferentially deposited within the continental shelf and slope environment due to the prevailing cyclonic circulation and the formation of flocs in the rivers pro delta areas the spatial distribution of major lithogenic elements si al ti fe is substantially biased by the presence of relict sands located in the central eastern part of the thermaikos gulf continental shelf biogenic elements ca sr are noticeably pronounced on the northern flank of the north sporades islands organic c content and minor elements cu zn as and pb are enriched markedly over the thessaloniki bay and gulf suggesting substantial human impact deriving largely from untreated or partly treated domestic and industrial effluents the terrigenous component of the elements is preferentially contributed from the axios river zn and pb the aliakmon river cr co ni cu and as and to a lesser extent from the pinios river v co ni and cu a considerable part of the metals originates in ultra mafic and volcanic formations which are abundant in the rivers catchment basins carbonate content exhibits great variability with the highest values observed in biogenic sediments of the sporades basin in the latter area mn and fe oxides and hydroxides were found as coatings on calcite the coatings were enriched in cr co ni zn as mo and pb due to adsorption or ion exchange during early diagenesis the combined influence of the river systems the thessaloniki metropolis and the diverse sedimentological background generates great patchiness in the distribution of major and minor elements

geomorphic implications of subglacial drainage configuration rates of basal sediment evacuation controlled by seasonal drainage system evolution abstract although basal sediment evacuation by subglacial meltwater is widely assumed to dominate the sediment budget of most temperate glaciers and ice caps its potential influence for glacial geomorphic processes and landforms has largely been overlooked in the glacial literature data collected at haut glacier d arolla switzerland during the 1998 ablation season are used to test theoretical predictions that subglacial drainage configuration should exert a primary control on rates of basal sediment evacuation by subglacial meltwater seasonal evolution of the subglacial drainage system enables observation of sediment evacuation from both distributed and channelised drainage systems daily suspended sediment load exhibits an extreme nonlinear increase with respect to discharge between winter and summer periods which correspond to periods of predominantly distributed and channelised subglacial drainage respectively these results suggest that subglacial drainage configuration should significantly impact upon a rates of subglacial erosion and debris production b the nature of debris transport and the proportion of sediment in glacial versus fluvioglacial transport pathways and c rates and styles of ice marginal sedimentation in contrast to their distributed counterparts channelised drainage configurations are predicted to encourage subglacial erosion through the removal of basal sediment from the ice bedrock interface and with the exception of supraglacial transport will discourage sediment transport by alternative glacial mechanisms direct sedimentation at the glacier margin may therefore be reduced resulting in smaller moraines despite an overall increase in sediment production an appreciation of the coupling between glacier hydrology and geomorphic processes suggests new frameworks for the understanding of rates and styles of glacial erosion sediment transfer and deposition and the complex geomorphology of ice marginal environments

recent evolution of a mediterranean deltaic coastal zone human impacts on the inner thermaikos gulf nw aegean sea the inner thermaikos gulf is located in the northwestern aegean sea receiving water and sediment fluxes from the axios aliakmon gallikos and loudias rivers the geomorphological and sedimentological evolution of the system is reconstructed for the last 150 years 1850 2000 on the basis of detailed analysis of historical bathymetric charts late holocene history is considered within the context of changing riverine sediment supply and human activities three evolutionary stages are identified stage i 1850 1916 corresponds to a natural phase of rapid deltaic progradation and sea floor deposition with an average sediment accumulation rate of 6 5 10 6 m 3 a 1 during stage ii 1916 1956 human interference e g artificial changes in river delta plains realignment of channels and land reclamation schemes to the deltaic system increased sediment delivery to the coastal waters by a factor of three this in turn enhanced the progradation of the active river mouth areas in contrast stage iii 1956 2000 is characterized by significant coastline deltaic retreat and erosion of the adjacent sea floor net loss of 2 5 10 6 m 3 a 1 this was as a result of extensive river damming which trapped a significant part of the sediment moving seaward furthermore these human impacts have affected the character of the surficial sea bed sediments of the gulf by reducing the proportion of mud the response of the deltaic margin of the inner thermaikos gulf to various anthropogenic interventions seems to be analogous to that of other deltas in the mediterranean region where large drainage projects the development of irrigation networks and dam construction have taken place within their river basins

morphology sedimentary infill and depositional environments of the early quaternary north sea basin 56 62 n abstract the north sea basin has been subsiding during the quaternary and contains hundreds of metres of fill seismic surveys 170 000 km2 provide new evidence on early quaternary sedimentation from about 2 75 ma to around the brunhes matuyama boundary 0 78 ma we present an informal seismic stratigraphy for the early quaternary of the north sea and calculate sediment volumes for major units early quaternary sediment thickness is 1000 m in the northern basin and 700 m in the central basin total about 40 000 km3 northern north sea basin fill comprises several clinoform units prograding westward over 60 000 km2 architecture of the central basin also comprises clinoforms building from the southeast to the west an acoustically layered and mounded unit unit z was deposited remaining accommodation space was filled with fine grained sediments of two central basin units above these units an upper regional unconformity equivalent uru records a conformable surface with flat lying units that indicate stronger direct glacial influence than on the sediments below on the north sea plateau north of 59 n the upper regional unconformity uru is defined by a shift from westward to eastward dipping seismic reflectors recording a major change in sedimentation with the shetland platform becoming a significant source a model of early quaternary sediment delivery to the north sea shows sources from the scandinavian ice sheet and major european rivers clinoforms prograding west in the northern north sea basin representing glacigenic debris flows indicate an ice sheet on the western scandinavian margin in the central basin sediments are generally fine grained suggesting a distal fluvial or glacifluvial origin from european rivers ploughmarks also demonstrate that icebergs derived from an ice sheet to the north drifted into the central north sea basin by contrast sediments and glacial landforms above the uru provide evidence for the later presence of a grounded ice sheet

stratigraphy pollen history and geochronology of tidal marshes in a gulf of maine estuarine system climatic and relative sea level impacts abstract sedimentologic and stratigraphic characteristics of five tidal marshes in great bay estuary new hampshire which is located on the western boundary of the gulf of maine were assessed from 20 vibracores detailed descriptions of surficial environments pollen analyses and radiocarbon dating modern marsh sequences in great bay estuary initiated with a time transgressive basal peat that formed at the upland brackish marsh boundary the oldest basal peat deposit sampled during this study was dated at 4560 cal yr b p based on an age of 4060 40 14 c yr b p the original tidal marshes that formed in great bay estuary apparently were unable to accrete at a high enough rate to allow seaward expansion resulting in a transgressive sequence of low marsh or mudflat sediments overlying the basal peat the transgressive tidal marsh sequence is capped by high marsh sediments that corresponded to a slowing of relative sea level rsl rise in the region and regressive seaward expansion of the tidal marshes however significant variations from these transgressive regressive sequences occur in the great bay tidal marshes as a result of more recent marsh expansion and tidal channel migrations detailed pollen analyses of a vibracore taken in a tidal marsh along squamscott river with a sedimentary record spanning the last 3900 cal yr b p exhibit five well documented marker horizons including 1 an increase of tsuga hemlock 2 the appearance of picea spruce 3 tsuga and fagus beech declines 4 an increase in ambrosia ragweed coupled with a sudden decrease in quercus oak and 5 the castanea chestnut decline using published ages for these pollen horizons and a calibrated 14 c age obtained during this study for a basal peat accretion rates for this marsh system over five time intervals were calculated 1 0 4 to 0 5 mm yr 1 from 3900 to 2850 cal yr b p 2 0 6 mm yr 1 from 2850 to 1960 cal yr b p 3 0 8 mm yr 1 from 1960 to 580 cal yr b p 4 0 7 to 0 8 mm yr 1 from 580 to 210 cal yr b p and 5 0 8 to 0 9 mm yr 1 over the last 210 years the long term accretion rate for the entire sequence based on the calibrated 14 c age of the basal peat was 0 6 to 0 7 mm yr 1 this result agrees with accretion rates determined from calibrated 14 c ages from two other tidal marsh systems in great bay estuary with accretion rates between 0 6 to 0 8 mm yr 1 higher accretion rates were obtained at a nearby tidal marsh with 1 2 mm yr 1 for just the marsh and 1 3 mm yr 1 for the marsh and underlying subtidal sediment the results of this study indicate that the sedimentology and stratigraphy of moderate size tidal marshes in rocky glaciated coasts are highly variable and are strongly influenced by complex interactions among rsl climatic variations and anthropogenic influences for instance the early development of many of the marshes in the great bay estuary area were likely driven by changes in rates of rsl resulting in transgressive onlap boundaries subsequently overlain by regressive intertidal marsh sequences however more recent changes in tidal marsh sediment composition deposited during a relatively slow steady rsl rise likely result from other forcings such as changes in minerogenic and orogenic sediment inputs due to anthropogenic effects tidal channel migrations major storms causing erosion of the marsh or climatic changes causing shifts in sediment delivery or vegetation

sedimentologic and palynologic records of the last deglaciation and holocene from ballston lake new york continuous pollen and sediment records from two 8 5 m long cores document late pleistocene and holocene sedimentation and vegetation change in the ballston lake basin eastern new york state pebbles at the base of both cores and the geomorphology of the watershed reflect the presence of the mohawk river in the basin prior to 12 900 70 cal yr b p ballston lake formed at the onset of the younger dryas yd by an avulsion of the mohawk river the transition from clay to gyttja with low magnetic susceptibility ms low bulk density and high organic carbon indicates rapid warming and increased lake productivity beginning 11 020 cal yr b p ms measurements reveal that the influx of magnetic particles associated with pre holocene clastic sedimentation ceased after 10 780 cal yr b p the pollen record is subdivided into six zones bl1 12 920 to 11 020 cal yr b p is dominated by boreal forest pollen bl2 11 020 to 10 780 cal yr b p by pine pinus forest pollen bl3 10 780 to 5290 cal yr b p by hemlock tsuga and mixed hardwood pollen bl4 5290 to 2680 cal yr b p by mixed hardwood pollen bl5a 2680 cal yr b p to 1030 cal yr b p by conifer and mixed hardwood pollen and bl5b 1030 cal b p to present by increasing ragweed ambrosia pollen a 62 decrease in spruce picea pollen in 320 cal years during bl1 reflects rapid warming at the end of the yd holocene pollen zones record more subtle climatic shifts than occurred at the end of the yd one of the largest changes in the holocene pollen spectra began 5300 cal yr b p and is characterized by a marked decline in hemlock pollen this has been noted in other pollen records from the region and may record preferential selection of hemlock by a pathogen or parasites

glacioisostasy and lake level change at moosehead lake maine abstract reconstructions of glacioisostatic rebound based on relative sea level in maine and adjacent canada do not agree well with existing geophysical models in order to understand these discrepancies better we investigated the lake level history of 40 km long moosehead lake in northwestern maine glacioisostasy has affected the level of moosehead lake since deglaciation ca 12 50014c yr b p lowstand features at the southeastern end and an abandoned outlet at the northwestern end of the lake indicate that the lake basin was tilted down to the northwest toward the retreating ice sheet by 0 7 m km at 10 00014c yr b p water level then rose rapidly in the southeastern end of the lake and the northwestern outlet was abandoned indicating rapid relaxation of landscape tilt lowstand features at the northwestern end of the lake suggest that the lake basin was tilted to the southeast at ca 875014c yr b p possibly as the result of a migrating isostatic forebulge after 800014c yr b p water level at the southeastern end was again below present lake level and rose gradually thereafter we found no evidence suggesting that postglacial climate change significantly affected lake level the rebound history inferred from lake level data is consistent with previous interpretations of nearby relative sea level data which indicate a significantly steeper and faster moving ice proximal depression and ice distal forebulge than geophysical models predict

analysis of multiple cosmogenic nuclides constrains laurentide ice sheet history and process on mt mansfield vermont s highest peak abstract constraining glacial history and process on mt mansfield the highest peak in vermont 1339 m a s l provides insight into how the laurentide ice sheet shaped the underlying landscape when latest pleistocene ice retreated and how upland and lowland glacial histories relate here we quantify in situ cosmogenic 10be in 20 bedrock and boulder surfaces as well as in situ cosmogenic 14c in three of those surfaces to assess subglacial erosion and exposure history isotopic concentrations indicate that mt mansfield s lower elevations 400 1200 m a s l were deeply eroded by at least several meters during the last glaciation and then deglaciated rapidly 10be ages across this elevation span are indistinguishable and average 13 9 0 6 ka n 15 suggesting that 800 m of ice thinning occurred within at most about a millennium conversely the higher elevations 1200 m a s l preserve a more complex geomorphic history mt mansfield s summit surfaces contain 10be from previous periods of exposure indicating that the mountaintop landscapes were likely preserved beneath cold based weakly erosive glacial ice exposure ages from the shorter lived isotope 14c are younger 9 7 and 11 7 ka suggesting that mt mansfield s summit was covered until the early holocene perhaps by snowfields ice carapaces and or till our findings in context of previous work suggest that thinning laurentide ice flowed through the valleys for at most hundreds of years following deglaciation of the uplands but that the summit remained shielded by ice or sediment for millennia after the valleys became ice free

pleistocene stratigraphy in the devils hole area central north sea foraminiferal and amino acid evidence a detailed study of the foraminiferal assemblages from the 229 1 m deep core 81 34 in the central north sea has been combined with a series of measurements of the isoleucine epimerisation of foraminiferal tests a total of 17 foraminiferal zones have been established and both the faunal compositions and the amino acid values suggest that a major part of the sequence represents deposits of early and middle pleistocene age only the uppermost zone is referred to the late pleistocene the sequence mainly comprises a series of marine zones from cold periods but with some barren possibly non marine intervals in between only two of the foraminiferal zones can be referred to interglacial periods the oldest one of these defined here as the devils hole interglacial may belong to the latter part of the cromerian complex while the upper warm interval is correlated with the holsteinian of northwest europe on the basis of its amino acid values a detailed stratigraphical correlation between core 81 34 and the neighbouring core 81 29 is suggested on the basis of their foraminiferal content palaeomagnetic evidence and amino acid measurements from both cores a characteristic feature of both sequences is that most of the quaternary record is missing similar episodic patterns of deposition and erosion have been reported previously from the north sea area

the hillsborough new brunswick mastodon and comments on other pleistocene mastodon fossils from nova scotia this is the first detailed description of the remains of a young adult american mastodon mammut americanum found in 1936 in peaty silt and clay underlying till in gypsum karst near hillsborough new brunswick it documents 312 fossils comprising a partial skull with molar teeth and tusks a neck vertebra and much of the right postcranial skeleton an individual age of 15 18 years and a weight of 8 3 t are estimated for this mastodon associated spheroids containing cut wood fragments and an unusually high clay content are interpreted to be mastodon coprolites radiocarbon ages are 13 600 200 bone 37 200 1 310 coprolite wood 51 500 1 270 coprolite carbonate cement and 43 000 bp peat pollen in the coprolites and associated sediment indicates a coniferous forest nine other mastodon fossils from nova scotia include a femur from middle river which dates 31 300 500 bp and contains pollen representing boreal forest tundra and three molars from offshore georges bank all ages are

associated terrestrial and marine fossils in the late glacial presumpscot formation southern maine usa and the marine reservoir effect on radiocarbon ages article i nfo excavations in the late glacial presumpscot formation at portland maine uncovered tree remains and other terrestrial organics associated with marine invertebrate shells in a landslide deposit buds of populus balsamifera balsam poplar occurred with twigs of picea glauca white spruce in the presumpscot clay tree rings in picea logs indicate that the trees all died during winter dormancy in the same year ring widths show patterns of variation indicating responses to environmental changes fossil mosses and insects represent a variety of species and wet to dry microsites the late glacial environment at the site was similar to that of today s maine coast radiocarbon ages of 14 tree samples are 11 907 31 to 11 650 50 14 c yr bp wiggle

late quaternary vegetational dynamics and community stability reconsidered abstract defining the spatial and temporal limits of vegetational processes such as migration and invasion of established communities is a prerequisite to evaluating the degree of stability in plant communities through the late quaternary the interpretation of changes in boundaries of major vegetation types over the past 20 000 yr offers a complementary view to that provided by migration maps for particular plant taxa north of approximately 43 n in eastern north america continual vegetational disequilibrium has resulted from climatic change soil development and species migrations during postglacial times between 33 and 39 n stable full glacial vegetation was replaced by a relatively unstable vegetation during late glacial climatic amelioration stable interglacial vegetation developed there after about 9000 yr b p late quaternary vegetation has been in dynamic equilibrium with a relatively constant flora south of 33 n on upland interfluves along the northern gulf coastal plain peninsular florida and west central mexico

a middle pleistocene glacial interglacial succession in the inner silver pit southern north sea abstract benthic foraminiferal data from the depth interval between 42 0 and 30 5 m in the inner silver pit core 81 52a in the southern north sea has revealed a glacial interglacial succession comprising a 5 m thick interglacial deposit the foraminiferal assemblages initially indicate ice proximal conditions zone 52 1 from a deglaciation period a transitional zone zone 52 2 with faunal indication of relatively deeper water and slightly higher but still subarctic temperature conditions is followed by a true interglacial succession called the inner silver pit interglacial with increased faunal diversity and with a high content of warm water species zone 52 3 a decrease in water depth is registered towards the top of the interglacial succession the assemblage in the topmost sample zone 52 4 indicates a return to high arctic glacial marine conditions foraminiferal faunas in three vibrocores obtained from the slopes of the neighbouring inner silver pit valley are correlated with the interglacial assemblages in zone 52 3 and with the succeeding glacial marine zone 52 4 of the inner silver pit core 81 52a based on the degree of isoleucine epimerisation in benthic foraminifera the interglacial deposit is referred to the middle pleistocene and a correlation with oxygen isotope stage 9 is suggested

midges and palaeotemperature reconstruction the north american experience abstract the development of midge based palaeoclimatology in north america is reviewed with a focus on lateglacial and holocene climatic change although relatively few sites have been studied midge inferred palaeotemperatures reveal detailed records of lateglacial climate oscillations and more subtle holocene temperature changes holocene climate changes are often at or near the detection limit using current palaeotemperature inference models interference from other environmental variables including water depth and oxygen concentration changes are discussed as well as the challenges inherent to developing better models the isotopic signature of chitin preserved in midge head capsules has opened new avenues for midge palaeotemperature inference through coordinated research efforts national and international collaborations will provide opportunities to reconstruct holocene palaeoclimate at continental and hemispheric scales

cosmogenic exposure age evidence for rapid laurentide deglaciation of the katahdin area west central maine usa 16 to 15 ka abstract katahdin the highest peak in maine and part of the second highest mountain range in new england provides an opportunity to assess the timing and style of continental ice sheet surface lowering during deglaciation we collected 14 samples from boulders on the adjacent basin ponds moraine from bedrock and boulders on the upper part of the mountain and from boulders in the surrounding area to estimate the age at which they were exposed by deglaciation of the laurentide ice sheet measurements of in situ produced 10be which are consistent with measurements of 26al indicate that the katahdin edifice became exposed from under ice by 15 3 2 1 ka n 6 an age indistinguishable from the adjacent basin ponds moraine 16 1 1 2 ka n 5 a boulder in the lowlands several km south of the moraine dates to 14 5 0 8 ka and a boulder deposited at pineo ridge about 170 km se of katahdin dates to 17 5 1 1 ka these data show that samples collected over an elevation range of 1 6 km and a distance of 170 km all have exposure ages that are indistinguishable within uncertainties together these data suggest that the laurentide ice sheet surface dropped rapidly and the ice sheet margin retreated quickly across maine between about 16 and 15 ka perhaps influenced by calving of the marine based ice sheet in the st lawrence lowlands to the north and the penobscot basin to the south

late glacial and early holocene landscapes in northern new england and adjacent areas of canada abstract the landscapes of northern new england and adjacent areas of canada changed greatly between 14 000 and 9000 yr b p deglaciation occurred sea levels and shorelines shifted and a vegetational transition from tundra to closed forest took place data from 51 14 c dated sites from a range of elevations were used to map ice and sea positions physiognomic vegetational zones and the spread of individual tree taxa in the region a continuum of tundra woodland forest passed northeastward and northward without major hesitation or reversal an increased rate of progression from 11 000 to 10 000 yr b p suggests a more rapid warming than in the prior 2000 3000 yr elevational gradients controlled the patterns of deglaciation and vegetational change the earliest spread of tree taxa was via the lowlands of southern vermont and new hampshire and along a coastal corridor in maine only after 12 000 yr b p did the taxa spread northward through the rest of the area different tree species entered the southern part of the area at different times and continued their spread at different rates the approximate order of arrival follows poplars 13 000 12 000 yr b p in the south spruces paper birch and jack pine followed by balsam fir and larch and possibly ironwood ash and elm and somewhat later by oak maple white pine and finally hemlock 10 000 9000 yr b p in the south