tracing seafloor methane emissions with benthic foraminifera in the baiyun sag of the northern south china sea changes in the concentrations of atmospheric greenhouse gases are an important part of the global climate forcing the hypothesis that benthic foraminifera are useful proxies of local methane emission from the seafloor has been verified on sediment cores by numerous studies the calcium carbonate caco3 content and the high resolution carbon and oxygen isotope composition of the benthic foraminifera from the core 08cf7 from the northeastern shenhu gas hydrate drilling area in the baiyun sag of the northern south china sea were analyzed and the benthic foraminifera s evidence for methane release from gas hydrate decomposition are presented here for the first time two rapid obvious carbon isotope negative excursions were observed in the oxygen isotope stage boundaries 5d 5c and 6 5e penultimate deglaciation about 130 ka of the cold to warm climatic transition period the largest negative value of 13c is about 2 95 and the whole change of carbon and oxygen isotope is strikingly similar and is in consonance with the atmospheric methane concentration recorded by the vostok ice core and the carbon isotopic record from lake baikal combining these results with the analysis of the geological conditions of the study area and the fact that gas hydrate exists in the surrounding area it can be concluded that the carbon isotope negative excursions of the benthic foraminifera in the northern south china sea are associated with methane release from gas hydrate decomposition due to deglacial climate warming by recording the episodes of massive gas hydrate decomposition closely linked with the northern hemisphere temperatures during major warming periods the new 13c record from the baiyun sag provides further evidence for the potential impact of gas hydrate reservoir on rapid deglacial rises of atmospheric methane levels

a tectonostratigraphic framework for the mid norway region abstract the tectonostratigraphic analysis presented here aims to establish a broad stratigraphic framework within which the likely distribution of both reservoir and source rock intervals within the deep water voering and more basins can be evaluated in terms of hydrocarbon potential the devonian to triassic interval can be effectively discounted by its extreme depth of burial across most of the study area the middle jurassic is interpreted to provide a potential reservoir target in the gjallar ridge area the cretaceous is seismically mappable across the region and has been divided into five tectonostratigraphic sequences late cretaceous reservoirs are considered to offer targets in the nyk high area six tectonostratigraphic sequences are described within the cenozoic succession paleocene reservoirs are interpreted to offer targets over both the ytterskallen and ormen lange areas of the more basin source rock maturity is critical for exploration success mapping shows the late jurassic earliest cretaceous spekk formation to be overmature over most of the area though the presence of possible dhis indicates the probable presence of major gas accumulations in the region only on the western flank of the vigrid syncline does the spekk shallow sufficiently to lie within the potential oil window it is concluded that the region has the potential to become a significant new hydrocarbon province for the 21st century

late cenozoic glacial history and evolution of the storegga slide area and adjacent slide flank regions norwegian continental margin abstract acoustic data and sediment cores collected from the storegga slide and its adjacent slide flanks i e the voring plateau to the north and the north sea fan to the south have been used to study the late cenozoic glacial history and geological development of this region age constrains obtained from the investigated cores show that the fennoscandian ice sheet reached the shelf edge during marine isotope stages mis 12 10 8 6 and 2 ice sheet fluctuations within each glaciation might have occurred as is evidenced for the last glacial maximum mis 2 the first extensive ice advance is identified in the early pleistocene at c 1 1 ma however between 2 6 and 0 5 ma the ice sheets were largely restricted to the fjords and inner shelf during each glacial maximum glacigenic debris flows gdfs transported basal till deposited at the shelf edge into the deep sea along the entire studied margin the most voluminous gdf sequences are found on the southern storegga slide flank north sea fan where the individual flows are found as far as 500 km from the shelf edge on the voring plateau glacimarine hemipelagic sedimentation has dominated the last c 250 000 yr during mis 2 such sediments were rapidly deposited covering the upper slope limited gdf units in this region between c 15 700 and 15 000 14c yr bp i e during the last deglaciation of the norwegian margin a presumed meltwater plume released from the disintegrating norwegian channel ice stream transported and rapidly deposited up to 20 m of fine grained sediments in the region north of the north sea fan the rapid deposition of large volumes of gdfs glacimarine and meltwater related sediments might have influenced the stability of the slope sediments in the studied region promoting conditions favorable for failure furthermore these high sedimentation rates also partly account for the high subsidence rates observed on the norwegian continental margin in the late cenozoic

composition and exhalation flux of gases from mud volcanoes in taiwan many mud volcanoes are distributed along the tectonic sutures in southern taiwan and can be divided into five zones based on their relative positions in different tectonic domains most active mud volcanoes are exhaling methane dominated gases nevertheless some gases show unusual carbon dioxide dominated and or nitrogen excess compositions this implies that there are multiple sources for the gas compositions of mud volcanoes in taiwan

factors controlling the cenozoic sequence development in the eastern parts of the north sea the causal relationship between the cenozoic sequence development in the southeastern north sea basin and sea level changes climatic fluctuations and tectonic events is unravelled by relating variations in the relative sea level and base level based on interpretations of seismic surveys to published 18 o variations and eustatic changes the latter curve is based on the earth9s orbital forcing and here informally termed as the gsi curve the analysis shows that the cenozoic sequence development in the southeastern north sea was influenced by climatically and tectonically induced sea level changes the major cenozoic sequence stratigraphic boundaries lower order are highly influenced by tectonic events e g uplift of fennoscandia and increased subsidence rates in the basin centre reactivation of mesozoic fault zones controlled the deposition of minor sand bodies transported to the centre of the basin during the late palaeocene by mass flows the location of an oligocene mound structure which constitutes part of a sequence is controlled by the overall palaeotopography of the basin and local fault related depressions correlation between i the ages of our sequences and the 18 o variations in the oligocene succession and ii the gsi curve and the base level fluctuations of the late miocene and younger sequences show that the generation of the higher order sequence boundaries were driven by glacio eustatic sea level changes a climatic control of the sequence formation due to glacio eustatic sea level changes is therefore suggested for the oligocene and pliocene sequences and probably also for the upper miocene sequences

quantifying stratigraphic uncertainties by stochastic simulation techniques based on markov random field abstract stratigraphic or lithological uncertainty refers to the uncertainty of boundaries between different soil layers and lithological units which has received increasing attention in geotechnical engineering in this paper an effective stochastic geological modeling framework is proposed based on markov random field theory which is conditional on site investigation data such as observations of soil types from ground surface borehole logs and strata orientation from geophysical tests the proposed modeling method is capable of accounting for the inherent heterogeneous and anisotropic characteristics of geological structure in this method two modeling approaches are introduced to simulate subsurface geological structures to accommodate different confidence levels on geological structure type i e layered vs others the sensitivity analysis for two modeling approaches is conducted to reveal the influence of mesh density and the model parameter on the simulation results illustrative examples using borehole data are presented to elucidate the ability to quantify the geological structure uncertainty furthermore the applicability of two modeling approaches and the behavior of the proposed model under different model parameters are discussed in detail finally bayesian inferential framework is introduced to allow for the estimation of the posterior distribution of model parameter when additional or subsequent borehole information becomes available practical guidance of using the proposed stochastic geological modeling technique for engineering practice is given

fluid flow in and around a mud volcano field seaward of the barbados accretionary wedge results from manon cruise a field of mud diapirs and mud volcanoes situated in the barbados trench at 13 50 n and extending along an old oceanic fracture zone mercurus was investigated during the manon cruise using both surface ship and nautile submersible sampling and measurements the entire zone from 13 50 n up to 14 20 n has an anomalously high heat flow which implies that fluids are drained into it from a segment of the accretionary wedge a few hundred kilometers wide two structures interpreted as diatremes atalante and cyclops expell large amounts of water and methane we propose that they were formed from the release of a light fluid when gas hydrates were dissociated in the sediment as the result of the circulation of warm fluid in the area however they expell only a small fraction of the incoming fluid implying that disperse flow is the dominant mode of expulsion in this area the chemoautotrophic communities on the surface of the structures rely mostly on sulfides submersible observations temperature measurements in the sediment and the chemistry of the pore fluid indicate that convection of seawater occurs within the first few meters of sediment through high permeability channels such as cemented carbonate conduits we propose that this convection is driven by the density difference between the pore fluid and seawater but fresh water released by the dissolution of shallow hydrates may also contribute this shallow convection may be a frequent process in cold seep environments

australian offshore natural hydrocarbon seepage studies a review and re evaluation abstract surprisingly few natural hydrocarbon seeps have been identified in australia s offshore basins despite studies spanning thirty years early studies of natural hydrocarbon seepage around the australian margin were generally based on the geochemical analysis of stranded bitumens water column geochemical sniffer sampling synthetic aperture radar or airborne laser fluorosensor later studies involved the integration of these remote sensing and geochemical techniques with multi channel and shallow seismic a review of these earlier studies indicates that many seepage interpretations need to be re evaluated and that previous data sets when placed in a global context often represent normal background hydrocarbon levels low recent burial and subsidence rates are not favourable for high rates of seepage there are also difficulties in proving seepage on high energy shallow carbonate shelves where seabed features may be rapidly re worked and modern marine signatures are overprinted on authigenic seep carbonates thus the relatively few sites of proven natural hydrocarbon seepage in australia s offshore sedimentary basins can be reconciled relative to their geological occurrences and the dominantly passive margin setting active thermogenic methane seepage on the yampi shelf the only proven documented occurrence in australia is driven by deposition of a thick late tertiary carbonate succession and late miocene tectonic reactivation therefore to increase the success of detecting and correctly interpreting natural hydrocarbon seepage data need to be analysed and integrated within the context of the local geological setting and with an understanding of what is observed globally

evidence for sediment eruption on deep sea floor gulf of mexico a large crater has been discovered on the sea floor gulf of mexico in a water depth of 2176 meters deep tow high resolution imagery shows that the crater is cut into a low hill surrounded by near surface concentric faults approximately 2 million cubic meters of ejected sediment forms a peripheral debris field the low hill and faults may be related to mud diapirism or intrusion of gas hydrates into near surface sediments a recent eruption evacuated sediments from the crater apparently because of release of overpressured petrogenic gas

neotectonic implications and regional stress field constraints on mud volcanoes in offshore southwestern taiwan abstract recently discovered numerous mud volcanoes mvs and mud diapirs mds in sw taiwan both onshore and offshore show eruption lineaments suspected to be related to neotectonic processes spatial and temporal distribution of the mvs eruption events shows an obvious switch of the lineament orientation from nne ne n s nw and e w trending in n s direction the mud volcanoes have experienced multi stage eruptions and should have occurred

plio pleistocene foraminiferal stratigraphy and correlation in the central north sea abstract a detailed foraminiferal stratigraphy is presented for the plio pleistocene sequence of the central north sea region these results are based on investigations carried out on seven boreholes and a detailed foraminiferal stratigraphy is presented here for the josephine borehole 30 13 2 x the pliocene pleistocene boundary is placed at the last common occurrence of cibicides grossa in the josephine hole at a depth of 700 m cassidulina teretis is the dominant species in the pliocene and it continues with decreasing frequencies into the early pleistocene the boundary between early and middle pleistocene occurs at a depth of about 210 m in the borehole correlation from west to east in the central north sea reveals an extremely thick pliocene 400 m and early pleistocene 500 m sequence at the josephine site this sequence thins out both to the west and to the east this together with the palaeoenvironmental evidence present at the josephine site indicates that continuous tectonic subsidence occurred during the pliocene and early pleistocene in the central graben variations in the thickness of the middle and late pleistocene units in the region is probably due to pronounced glacial chanelling

hydrocarbon seeps in petroliferous basins in china a first inventory abstract natural hydrocarbon seepage is a widespread phenomenon in sedimentary basins with important implications in petroleum exploration and emission of greenhouse gases to the atmosphere china has vast petroleum oil and gas bearing sedimentary basins but hydrocarbon seepage has rarely been the object of systematic studies and measurements based on the available chinese literature we report a first inventory of 932 hydrocarbon seeps or seepage zones 710 onshore seeps and 222 offshore seeps including 81 mud volcanoes 449 oil seeps 215 gas seeps and 187 solid seeps bitumen outcrops the seeps are located within the main 20 mesozoic cenozoic petroliferous sedimentary basins especially along the marginal regional and local faults the type of manifestations oil gas or mud volcano reflects the type and maturity of the subsurface petroleum system and the sedimentary conditions of the basin oil seeps are particularly abundant in the junggar basin gas seeps mostly developed in the lunpola basin in smaller basins of the eastern guizhou and yunnan provinces onshore taiwan and in the offshore yinggehai basin mud volcanoes developed in basins junggar qaidam qiangtang onshore and offshore taiwan that experienced rapid sedimentation which induced gravitative instability of shales and diapirism in comparison to available global onshore seep data bases china results to be the country with the highest number of seeps in the world the massive gas seepage in china could represent a considerable natural source of methane to the atmosphere and a key process that may drive future hydrocarbon exploration

rare earth elements in cold seep carbonates from the southwestern dongsha area northern south china sea the circulation of methane rich fluids at cold seeps often leads to the precipitation of seep carbonates close to the seafloor along continental margins which can be used as records of past fluid seepage rare earth element ree concentrations in seep carbonates have been used to trace fluid sources and provide information on associated biogeochemical processes at cold seeps the ree concentrations of a series of carbonates collected from cold seeps in the southwestern dongsha area of the northern south china sea are analyzed in this study the total ree contents sigma ree of the seep carbonates analyzed show a wide variation from 17 ppm to 523 ppm with an average sigma ree value of 54 ppm which are higher than the carbonates from other cold seep areas a positive correlation between fe mn content and sigma ree was observed these results suggest that the seep carbonates of this study were primarily controlled by the methane derived fluid from which they precipitated the fe rich dolomite and siderite which are the main components of the carbonates are responsible for the enrichment of the ree a slight positive ce anomaly observed in the shale normalized ree patterns of the studied seep carbonates suggests that they formed in anoxic conditions and the correlations between ce ce and la n sm n ce ce and dy n sm n ce ce and sigma ree further reveal that the ree characteristics of most seep carbonate samples preserve the original redox conditions in which they precipitated and late diagenesis has had little effect on the ree however the ree characteristics of sub samples ds2 2b ds1 6a and ds1 7a are very different from those of the other sub samples indicating a greater impact of late diagenesis and post oxidation favored ree enrichment c 2014 elsevier ltd all rights reserved

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

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

a submarine canyon as the cause of a mud volcano liuchieuyu island in taiwan abstract in this paper based on 3 5 khz uniboom and conventional seismic data we propose a model for the creation of liuchieuyu island a near shore mud volcano off the southwestern coast of taiwan in support of this model we also discuss the relationship between a nearby submarine canyon kaoping submarine canyon and the mud diapirs and mud volcanoes in the region seismic data suggest that liuchieuyu was originally a mud diapir with a thick continuous accumulation of sediments on its upper surface this sediment load or overburden prevented unconfined growth of the underlying mud diapir while simultaneously acting as a seal that trapped gas and formed a high pressure zone however kaoping paleo canyon eroded these overlying sediments and the overburdening pressure was reduced in consequence the mud diapir rose up to the sea floor to become a mud volcano the uppermost part of which is present day liuchieuyu island the formation of this island in the path of the paleo canyon also diverted the channel of the canyon to its present location

cenozoic erosion and sedimentation in the western barents sea abstract seismic reflection data and well logs are used to interpret cenozoic sedimentary environments in the south western barents sea using volumetric calculations and compaction trend analysis the cenozoic erosion and sedimentation rates have been quantified marine environments ranging from neritic to bathyal water depths dominated the southern barents sea during the late palaeocene at the palaeocene eocene boundary a southwards progradation commenced along the uplifted and eroded loppa and stappen highs during the early eocene to mid miocene sedimentation continued in the intracratonic basins as well as along the newly established continent ocean boundary in the embryonic northern norwegian greenland sea substantial erosion occurred on the westernmost margin particularly on the stappen high during this time interval in the mid miocene during a period of relative lowstand of sea level a system of lowstand fans was deposited west of the stappen high later a pronounced progradation of the shelf edge commenced during the mid miocene to late pliocene the shelf edge prograded between 20 and 40 km during the mid pliocene to early pleistocene the barents sea and adjacent land areas were uplifted a fluvial glaciofluvial drainage system developed on the continental shelf resulting in pronounced erosion there and very high sedimentation rates on the continental margin during the last 0 8 ma several large glaciations on the barents sea shelf proper have resulted in overdeepened troughs and high sedimentation rates at the continental shelfbreak and on the continental slope the overall cenozoic erosion varies spatially as well as temporally in the svalbard area close to 3 km of rocks have been eroded since the oligocene the same amount or more was eroded from the stappen high during the palaeocene and early neogene in the south western areas during the eocene mid miocene erosion occurred along the margin in addition the loppa high and adjacent areas served as sediment source areas during the late pliocene and pleistoncene the average erosion in the south western barents sea amounted to about 600 m erosion was greater in the south east than to the west and north and was more extensive where the former glacial ice streams had flowed

pleistocene glacial history of the nw european continental margin abstract in this paper new and previously published data on the pleistocene glacial impact on the nw european margin from ireland to svalbard between c 48 n 80 n are compiled the morphology of the glaciated part of the european margin strongly reflects repeated occurrence of fast moving ice streams creating numerous glacial troughs channels that are separated by shallow bank areas end moraines have been identified at several locations on the shelf suggesting shelf edge glaciation along the major part of the margin during the last glacial maximum deposition of stacked units of glacigenic debris flows on the continental slope form fans at a number of locations from 55 n and northwards whereas the margin to the south of this is characterised by the presence of submarine canyons glaciation curves based primarily on information from the glacial fed fan systems that depict the pleistocene trends in extent of glaciations along the margin have been compiled these curves suggest that extensive shelf glaciations started around svalbard at 1 6 1 3 ma while repeated periods of shelf edge glaciations on the uk margin started with mis 12 c 0 45 ma the available evidence for mis 2 suggest that shelf edge glaciation for the whole margin was reached between c 28 and 22 14 c ka bp and maximum positions after this were more limited in some regions north sea and lofoten the last glacial advance on the margin has been dated to 15 13 5 14 c ka bp and by c 13 14 c ka bp the shelf areas were completely deglaciated the younger dryas loch lomond advance reached the coastal areas in only a few regions

factors influencing methane derived authigenic carbonate formation at cold seep from southwestern dongsha area in the northern south china sea this paper carried out mineral and geochemical studies on a profile through a diagenetic methane derived authigenic carbonate sample that was collected from southwestern dongsha area of the northern south china sea five samples locating in the cross sectional middle mainly consist of dolomite and quartz and two samples close to the surface have a small amount of mg calcite the delta c 13 values of the samples vary between 30 59 and 0 30 vpdb with delta o 18 values ranging from 3 07 to 3 59 vpdb delta ca 44 40 values ranging from 1 35 to 1 47 srm915a indicating a contribution of methane to the carbon pool where the precipitation of authigenic carbonates occurred based on the isotope values alone it can not be distinguished if the carbon source is thermogenic gas or a mixture of biogenic methane and marine dissolved inorganic carbon the delta o 18 values are in general consistent with dolomite precipitation from a fluid similar to present seawater the observed small variation might be related to the oxygen isotope composition of seep fluid the relative small range in calcium isotope values suggests that relatively constant growth conditions and precipitation from seawater the central part of the carbonate nodule formed under the strong influence of methane seepage and the external part is less influenced by methane either due to reduced methane flux to the surface or caused by erosional exhumation of the carbonate nodule from greater depth to the sediment surface

cenozoic margin development and erosion of the barents sea core evidence from southwest of bjornoya abstract five stratigraphic boreholes at the western barents sea margin reveal an evolution from a palaeocene normal shelf setting to a complex late cenozoic offshore marginal marine system influenced by mass flows and finally a glacially influenced shelf environment palaeocene epeiric sea sedimentation was sourced by erosion at the stappen high earliest eocene extension associated with volcanism was followed by rapid subsidence of the vestbakken volcanic province which became filled by sediments from an uplifted stappen high by the middle eocene siliciclastic shelf sediments were deposited and the infill had reached a balance with subsidence tectonic movements at this time may have caused local uplift which restricted the ventilation of local basins west of the stappen high but marine conditions existed in the area until early oligocene times when subaerial exposure was caused by tectonic uplift and probably also a fall in eustatic sea level pronounced oligocene and pliocene unconformities reflect major events of uplift and erosion at the margin and abundant fossil reworking indicates erosion of the uplifted cretaceous and tertiary strata the oligocene erosion had its associated depocentre to the south and west of the study area and was less important regionally than the pliocene pleistocene phase the pliocene uplift first led to local erosion along the margin subsequent subsidence may initially have had a thermal component this was followed by extensive downwarping under the load of largescale deposition sourced by regional erosion in the barents shelf region an eocene volcanic phase was probably related to the initiation of seafloor spreading isotopically dated volcaniclastic intervals in one of the cores give evidence of a late pliocene volcanic phase this event was associated with local tectonic movements which may be part of a regional uplift in the western northwestern part of the barents sea glaciations caused by the neogene climatic deterioration became enhanced by uplift and this led to extensive regional glacial erosion the main depocentre was offset to the south by ice flow curving around the uplifted area

high resolution seismic profile through a late cenozoic delta complex in the southern north sea abstract a digitally recorded and processed multichannel seismic profile between cromer england and sylt germany has provided the first continuous section through the miocene to middle pleistocene delta complex of the southern north sea basin the profile depicts the progressive westward expansion of deltaic sedimentation that eventually filled in this gently subsiding epicontinental basin significant basinward shifts in seismic facies occur above all but one of 14 seismic sequence boundaries that punctuate the deposition of up to 830 m of deltaic sediments on the profile these sequence boundaries and the morphology of prodelta delta front delta top and fluvio deltaic seismic facies record the interaction between subsidence cyclic fluctuation in sediment supply to and cyclic change of relative sea level within the basin two submarine slides were developed within delta front facies in the pliocene section and the profile has intersected a swarm of elsterian middle pleistocene glacial palaeovalleys that have been incised into the upper part of the delta complex

chronology of tertiary fan deposits off the western barents sea implications for the uplift and erosion history of the barents shelf abstract a combined biostratigraphic and seismic study was performed on three holes drilled in the western barents sea two holes penetrate the thick sedimentary wedge which forms a large fan located off a trough on the barents sea shelf the bjornoyrenna fan the study shows that the fan was built over a short time span in the late pliocene pleistocene mainly due to glacial erosion of the barents shelf region this contrasts earlier age assignments which concluded that fan deposition started in the oligocene the results have a major impact on the understanding of trough mouth fan formation and has important bearing on the history of the sedimentary basins of the barents shelf

significance of mud volcanism 1 mud volcanism and diapirism have puzzled geoscientists for 2 centuries they have been described onshore and offshore in many places on earth and although they occur in various tectonic settings the majority of the features known to date are located in compressional tectonic scenarios this paper summarizes the main thrusts in mud volcano research as well as the various regions in which mud volcanism has been described mud volcanoes show variable geometry up to tens of kilometers in diameter and several hundred meters in height and a great diversity regarding the origin of the fluid and solid phases gas predominantly methane water and mud may be mobilized at subbottom depth of only a few meters but in places can originate from several kilometers depth with minor crustal or mantle input the possible contribution of mud extrusion to global budgets both from quiescent fluid emission and from the extrusive processes themselves is important in regions where mud volcanoes are abundant such as the collision zones between africa and eurasia fluid flux through mud extrusion exceeds the compaction driven pore fluid expulsion of the accretionary wedge also quiescent degassing of mud volcanoes may contribute significantly to volatile budgets and hence to greenhouse climate

high frequency sequence stratigraphy of upper cenozoic deposits in the central and southeastern north sea areas abstract during late cenozoic times southwestward prograding deposits filled in the central and southern part of the epicontinental north sea basin the ringkobing fyn high acted as a topographical high partly separating the central and southeastern north sea into two embayments which were connected towards the west by a deeper seaway located in the central graben area the stratal geometry deduced from seismic sections indicates different basin physiography subsidence rates and sediment influx between the two embayments eustatic sea level cycles of several frequencies interacted with low subsidence rates in the southern embayment to generate composite relative sea level cycles each composed of relative sea level cycles of higher frequencies forty five upper cenozoic sequences are identified in the southern embayment whereas only 21 sequences are recognized in the northern embayment major hiati and intervals of starved sedimentation may therefore be present in the northern embayment the sequences stack into nine composite sequences each reflecting a depositional cycle representing lowstand succeeded by transgressive highstand conditions in general a composite sequence is characterized by a period of increasing sediment accumulation rates

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

seven million years of glaciation in greenland glacial till glaciomarine diamictites and ice rafted detritus found in marine cores collected off the shore of southeast greenland record multiple late cenozoic glaciations beginning in the late miocene distinct rock assemblages and seismic stratigraphic control correlate the diamictites with glaciation of the southeast greenland margin glaciers advanced to the sea during several intervals in the pliocene and pleistocene north atlantic glaciation may have nucleated in southern greenland rather than further north because of the high mountains and the high levels of precipitation in this region

pleistocene geochemical stratigraphy of the borehole 1317e iodp expedition 307 in porcupine seabight sw of ireland applications to palaeoceanography and palaeoclimate of the coral mound development stable isotopes and element compositions of the fine grained matrix were measured for iodp expedition 307 hole u1317e drilled from the summit of challenger mound in porcupine seabight northeast atlantic to explore the palaeoceanographic and palaeoclimatic background to development of the deep water coral mound the 155 m long mound section was divided into two units by an unconformity at 23 6 mbsf unit m1 2 6 1 7 ma and unit m2 1 0 0 5 ma results from 519 specimens show a difference in 13c value between unit m1 0 6 to 5 0 and unit m2 1 0 to 1 0 but such a distinct difference was not seen in 18o values 1 0 2 5 caco3 content 40 60 wt sr ca ratio 2 0 8 0 mmol mol 1 and mg ca ratio 10 0 20 0 mmol mol 1 through the mound positive 18o and negative 13c shifts at the mound base are consistent with the oceanographic changes in the northeast atlantic at the beginning of the quaternary the positive 13c regression in unit m2 suggests a linkage to the mid pleistocene intensified glaciation in the northern hemisphere warm mediterranean upper core water of mediterranean outflow water eastern north atlantic water and cold labrador sea water of north atlantic deep water are key oceanographic features that cause spikes and shifts in stable isotope and element composition however the stable isotope values of the sediment matrix could not primarily record the glacial interglacial eustatic temperature change but indirectly indicate current regimes of the intermediate oceanic layer where the coral mound grew similarly elemental ratios and caco3 content may not represent the productivity and temperature of surface sea water respectively but superpose the fractions from both surface and bottom water it is concluded that palaeoceanographic change coupled to the pleistocene glacial interglacial cycles is a key control on the geochemical stratigraphy of the matrix sediments of the carbonate mound developed in porcupine seabight copyright 2011 john wiley sons ltd

bayesian identification of soil strata in london clay identification of soil strata in the london clay formation lcf is of practical significance as it allows geotechnical property data within the same soil strata to be compared or used effectively the soil strata in lcf are generally determined based on their lithological characters and fossil contents with which geotechnical engineers are less familiar to assist geotechnical engineers in identifying the soil strata in lcf this paper aims to develop bayesian approaches to identification of soil strata in lcf using water content data equations are derived for the proposed bayesian approaches and the approaches are illustrated using a water content profile at st james s park london the proposed bayesian approaches are shown to correctly identify the soil strata in lcf in addition a sensitivity study is performed to explore the effect of data quantity i e both the measurement interval and number of measurements at the same depth in a water content profile and provide guidance on the water conten

mud ridge on the crest of the outer swell off japan trench abstract a small mound of sediment was found on the deep ocean floor by a swath mapping survey associated with 3 5 khz subbottom profiling on the outer swell east off the japan trench at a depth of 5220 m it is 130 m high oblately elongated and situated on a ne sw trending normal fault no evidence of active seepage of deep methane rich water such as biological communities and an anomalous sediment color has been found by direct observation of the bottom using a deep towed television system the superficial and surrounding characteristics suggest that this mound is a type of mud volcano and be best called a mud ridge it would be the first diapir discovered in the deep floor oceanward of a trench the origin of this mound may be the injection of fluidized sediment expelled by highly compressed pore water through a normal fault plane associated with an earthquake shock generated by extensional forces caused by downward bending of the oceanic lithosphere near the trench

probabilistic analysis and design of stabilizing piles in slope considering stratigraphic uncertainty abstract the uncertainty involved in the interpreted geological model may be categorized as the stratigraphic uncertainty and the properties uncertainty note that although the influence of the properties uncertainty on the behavior or performance of the geotechnical system and the geotechnical design has been extensively reported in the literature the studies that address the stratigraphic uncertainty are limited this paper presents a study regarding the influence of the stratigraphic uncertainty on the behavior of the geotechnical system and the geotechnical design in which the uncertainty in the stratigraphic configuration is characterized using the stochastic markov random field based approach with a large number of potential stratigraphic realizations with these stratigraphic realizations as inputs the influence of the stratigraphic uncertainty on the behavior of the geotechnical system is evaluated in a probabilistic manner then the design of the geotechnical system is formulated as a bi objective optimization based problem that considers the design safety and the cost simultaneously to demonstrate the effectiveness of the proposed probabilistic analysis and design approach the problem of designing stabilizing piles in a slope consisting of multiple strata is studied the parametric study is further conducted to analyze how the probabilistic analysis results are influenced by the pile parameters and how the probabilistic design results are influenced by the additional boreholes

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

mud volcanoes along the chishan fault in southwestern taiwan a release bend model abstract both land and offshore mud volcanoes have been investigated thoroughly in southwestern taiwan in terms of morphological expression spatial distribution composition and evasion flux of extruded material the interactive relationship between mud volcanoes and their associated structures however has rarely been examined this study proposes a release bend model that explains the spatial distribution and relative activity of mud volcanoes along the chishan fault southwestern taiwan the surface movement of the chishan fault and mud volcano activity were monitored by gps stations and gas flux measurements respectively the resistivity sub structure of strata across the fault was investigated by the magnetotelluric mt method and resistivity image profiling rip analytical results support the contention that extensional activity at the release bend provides openings to fissures associated with the chishan fault thereby increasing the potential for a mud volcano the proposed model may facilitate future exploration of mud volcanoes

relicts of mud diapirism of the emerged wedge top as an indicator of gas hydrates destabilization in the manila accretionary prism in southern taiwan hengchun peninsula abstract due to oblique collision of the luzon volcanic arc and eurasian passive margin in taiwan we observe southward progression of mountain building processes consequently the southernmost tip of taiwan represents the most recently emerged part of the orogen the hengchun peninsula the area shows evidence of a trench slope basin that emerged in the holocene with landforms that bear submarine characteristics in the late pleistocene lagoonal sediments blanket the basin however the deeper deposits maanshan formation can be found on the surface in several areas we document that the maanshan formation was brought to the surface through upwelling structures mud diapirs as a consequence of fast and overpressured sedimentation from the emerging orogen although fast erosional processes continuously reorganize the new landscape we are able to capture relicts of fast eroding inactive mud volcanoes these unique features are preserved on the surface due to shielding by coral terraces during the shallowing and the lagoonal period of the basin stable carbon 13c and oxygen 18o isotope analysis performed on samples of carbonate blocks of cold vents collected on the outcrops of the maanshan formation confirm classic seep carbonates origins we also identify a mud core anticline below the study area acting as the main source for the mud volcanoes and a possible cause of the uplift of the trench slope basin two multichannel seismic profiles from marine surveys along with a synthesis of several previous surveys helped construct a model of the characteristics of mud diapirism in southeastern offshore taiwan

cold seep systems in the south china sea an overview abstract three decades after the discovery of cold seep systems various sites of hydrocarbon seepage have been found in the south china sea scs over the past decade these sites have become model systems for understanding the variability of hydrocarbon seepage and associated biogeochemical processes in this review we describe the cold seep systems of the scs with an emphasis on seafloor manifestations fluid sources biogeochemical processes and macroecology seafloor features associated with seeps include mud volcanoes pockmarks and carbonate deposits a common characteristic of cold seeps is the occurrence of authigenic i e in situ precipitated carbonate minerals these carbonates commonly exhibit low 13c and high 18o values suggesting the incorporation of methane derived carbon and oxygen derived from gas hydrate water biogeochemical processes such as sulfate driven anaerobic oxidation of methane sd aom the key process at seeps have been studied in detail with the aim of establishing geochemical proxies to trace these processes into the geological past we also detail the features characterizing seep ecosystems understanding the impact of decomposing methane hydrate on the marine carbon budget remains challenging and requires additional seafloor observations as well as models predicting how gas hydrate responds to changing conditions such as temperature increase sea level rise and episodic mass wasting

distribution of the neogene utsira sand and the succeeding deposits in the viking graben area north sea abstract the sandy quartzose parts of the utsira formation the middle miocene to mid pliocene utsira sand extends north south along the viking graben near the uk norwegian median line for more than 450 km and 75 130 km east west the utsira sand is located in basin restricted seismic depocentres east of and below prograding sandy units from the shetland platform area with hutton sands the utsira sand reaches thicknesses up to ca 300 m in the southern depocentre and 200 m in the two northern depocentres with sedimentation rates up to 2 4 cm ka succeeding plio pleistocene is divided into seismic units including base upper pliocene shale drape prograding complex and pleistocene the units mainly consist of clay but locally minor sands occur especially at toes of prograding clinoforms bottom set sands and in the pleistocene parts and the total thickness covering the utsira sand is in most places more than 800 m but thins towards the margins

improved chronostratigraphic reference curve of late neogene seawater 87sr 86sr we present a reference curve of seawater 87 sr 86 sr variation through the past 7 m y based on 455 samples of planktonic foraminifera from ocean drilling program odp site 758 in the indian ocean this single site curve is superior to extant curves because of several features 1 a continuous sedimentary section free of disturbances 2 a well determined and precise chronostratigraphy that is calibrated to numeric age on the basis of continuous magnetostratigraphy and a refined astronomical time scale 3 a high temporal resolution sample interval averages 15 ka 4 an improved analytical reproducibility and 5 a uniformly high sample quality the gross structure of the site 758 curve is generally similar to that observed in previous work but the increased temporal resolution and decreased analytical scatter of the curve provide improved chronostratigraphic resolution at the 95 confidence level uncertainties on age estimates range from 0 60 m y in the lower pleistocene and upper miocene to 2 03 m y in the middle pliocene moreover this detailed record identifies two periods of steplike increases in seawater 87 sr 86 sr 6 10 to 5 80 ma and 1 46 to 1 13 ma that are characterized by rates of change of 150 10 6 m y these features if verified at other sites indicate abrupt changes in the sr mass balance of the ocean and may be used as precise event markers in late neogene marine sections

oligocene sequence stratigraphy and basin development in the danish north sea sector based on log interpretations abstract five sequences are defined in the oligocene succession of the danish north sea sector two of the sequences 4 1a and 4 3 have been identified onshore denmark two types of prograding lowstand deposits are recognized sand dominated deposits occur proximally comprising sharp based forced regressive deposits covered with prograding low stand deposits clay dominated prograding lowstand deposits occur distally in the sequences the highstand deposits are proximally represented by thick prograding sandy deposits and distally by thin and condensed intervals the main sediment input direction was from the north and the northeast a succession oif lithofacies from shallow marine facies dominated by sand to outer shelf facies dominated by clay is mapped in each of the sequences an overall southward progradation of the shoreline took place during the oligocene interrupted only by minor shoreline retreats

high resolution dating of cenozoic sediments from northern north sea using 87sr 86sr stratigraphy we demonstrate the potential of sr isotope stratigraphy as a tool in basin analysis by dating bioclastic carbonate and phosphate fragments from eight seismic units in cenozoic sedimentary rocks along two east west profiles in the northern north sea the dates which agree well with available rb sr glauconite dates have precisions in the range 0 5 to 3 m y thereby providing important chronostratigraphic information for sediments that otherwise are difficult to date basinward southwest in this area the most important seismic sequence boundaries are dated at approximately 53 ma 33 ma 22 ma 8 ma and 2 ma northeastward toward the basin margin these boundaries represent important periods of erosion or nondeposition deep water sedimentation predominated from he paleocene until the early oligocene 33 ma a time of high global sea levels close to the basin margin local tectonic activity contributed turbiditic clastic sediments an important sequence boundary at 30 ma involves erosion in the northern area and correlates with a sharp eustatic drop in sea level post early oligocene seismic sequence boundaries are controlled mainly by basin margin tectonics related to uplift events in fennoscandia and in the shetland platform area

quantifying spatial uncertainty in rock through geostatistical integration of borehole data and a geologist s cross section abstract in order to increase understanding of spatial uncertainty in subsurface conditions for problems in geological and geotechnical engineering this study develops a geostatistical approach for incorporating a geologist s interpreted cross section to quantify spatial uncertainty of lithology in this work the sequential indicator cosimulation cosism algorithm and the information theory concept of entropy are utilized to generate uncertainty models a sensitivity analysis is used to study how both borehole data and the cross section are incorporated into the algorithm which is quantified using entropy as a metric for uncertainty in geologic unit boundary locations a verification methodology is then developed to identify the most appropriate combination of input parameters for combining these two data types recommendations from the verification methodology are made by comparing the calculated entropy to accuracy at the global scale on a point by point basis this methodology is then used to investigate how calibrated input parameters vary due to differences in the input cross section based on different levels of understanding of the subsurface geology by iteratively providing a geologist with additional borehole data after a cross section is developed results show that two of the parameters variogram range and the number of conditioning data can be used to most directly reflect geologist understanding in the simulations finally this study provides guidelines for incorporating a geologist s understanding of a geological environment into this modeling framework as results show cross sections that are locally accurate are better represented by different parameters than cross sections that are not locally accurate but are globally accurate these guidelines are intended to aid geologists and engineers in understanding how to incorporate a geologist s interpretation of the subsurface lithology or categorical geotechnical parameters at a particular worksite into a structured geostatistical framework

three dimensional site characterization with borehole data a case study of suzhou area abstract due to the inherent spatial variation of the site information and the limited number of boreholes which could be afforded in a specified project the geotechnical and geological information at a site could not be fully characterized which imposes a significant challenge to the analysis design and construction of the geotechnical system of concern indeed the issue of site characterization has long puzzled engineers this paper presents a three dimensional site characterization in the urban area of suzhou where plenty of borehole explorations have been undertaken with the borehole database established the relationship between the shear wave velocity and the depth is analyzed this relationship can be captured by regression based models and then a sequence extrapolation method that is based upon the linear relationship between the time average shear wave velocities is developed for the prediction of the shear wave velocity along the depth next a three dimensional characterization and visualization of the stratigraphic model in the urban area of suzhou are presented the characterization of the stratigraphic model in this paper is realized through the characterization of the elevations of the interfaces between adjacent strata in the sequence stratigraphic structure the sequence stratigraphic structure is derived with a method that is based upon the one by one comparison and updating of the borehole data and then the best unbiased estimator of the elevations of the interfaces between adjacent strata at the concerned site is predicted with the kriging based interpolation method with the aid of arcgis engine a three dimensional visualization of the characterized stratigraphic model is made possible

quaternary stratigraphy of the draugen area mid norwegian shelf abstract lithostratigraphic biostratigraphic and chronostratigraphic studies on a 130 m long core from haltenbanken mid norwegian shelf dr 88 30 shows sequences of short episodic glacigenic sedimentation and periods of more continuous marine sedimentation the sediment sequence is dated by palaeomagnetism as well as the amino acid and the strontium isotope methods back to ca 1 1 ma previous seismostratigraphic interpretations placed the regional pliocene pleistocene boundary at ca 90 m depth at the core site this level was dated to be of brunhes matuyama age the study area has been covered by grounded glaciers at least five times during the last 1 1 ma the first expansion of the scandinavian ice sheet was at ca 1 1 ma depositing a diamicton these sediments are overlain by a long sequence of normal marine sediments deposited during both glacial and interglacial conditions two interglacial periods from this sequence have been given an informal interglacial notation except for the glaciation at ca 1 1 ma the glacials during the early pleistocene which are identified in the core were relatively limited a transition to more extensive glaciations occurs in the early middle pleistocene during these more extensive glacial phases major erosion took place along the inner continental shelf this erosional phase resulted in overdeepening of the inner shelf which during the middle and late pleistocene influenced the depositional dynamics in the central and the outer part of the shelf in the study area the middle and late pleistocene periods are dominated by glacigenic sediments with only very thin interglacial sediments occasionally preserved one interglacial period from the middle pleistocene has been given an informal interglacial notation the core has been correlated to cores from the north sea basin on the basis of amino acid stratigraphy and palaeomagnetism the lithological and the foraminiferal stratigraphy indicates a synchronous appearance of the major lithological units and of the fauna assemblages in these areas

high frequency depositional sequences and stratal stacking patterns in lower pliocene coastal deltas mid norwegian continental shelf extensive deltaic and coastal progradation occurred along the mid norwegian continental shelf during the early pliocene thirty eight well developed high frequency fourth order sequences are identified within the deltaic complex on multifold seismic data the fourth order sequences are arranged in four oblique progradational and two sigmoid progradational sequence sets deposition of the high frequency sequences and their stacking patterns probably were in response to high frequency cycles of relative changes in sea level cycles produced by variable rates of subsidence and uplift superimposed on high frequency eustatic cycles within a lower frequency eustatic system the mixed aggrading prograding sequence sets are interpreted to represent increased space added accommodation rates and deposition within third order highstand systems tracts conversely the progradational sequence sets are interpreted to represent decreasing space added accommodation rates and deposition within the third order lowstand systems tracts the recognition of multiple sequence sets likely reflects the effect of long term relative fall in sea level tectonic uplift superim osed on high frequency eustatic cycles the terminal sequence boundaries of the sequence sets are formed by conjunction of third and fourth order falling inflection points on the relative sea level curve these sequence boundaries represent the timing of maximum subaerial erosion and may represent times of greatest potential for the deposition of reservoir sands

towards incorporating uncertainty of structural data in 3d geological inversion abstract all geological models are subject to several kinds of uncertainty these can be classified into three different types data imprecision and quality inherent randomness and incomplete knowledge with our approach we address uncertainties introduced by input data quality in complex three dimensional 3d models of subsurface structures geological models as input data we consider parameters of geological structures i e formation and fault boundary points and orientation measurements our method consists of five steps construction of an initial geological model with an implicit potential field method assignment of probability distributions to data positions and orientation measurements simulation of several input data sets construction of several model realisations based on these simulated data sets and finally the visualisation and analysis of the uncertainties we test our approach in two generic models a simple graben setting and a complex dome structure the first model shows that our approach can evaluate uncertainties from different structures and their interaction furthermore it indicates that the final uncertainty of the model is not simply the sum of all input data uncertainties but complex interactions exist the second example demonstrates that our approach can handle full three dimensional settings with overturned surfaces results of the uncertainty simulation can be visualised and analysed in several ways ranging from borehole histograms to uncertainty maps for complex 3d visualisation and analysis we use indicator functions when we apply these we can treat the visualisation of uncertainties in complex settings in a self consistent manner with our simulation method it is possible to analyse and visualise the uncertainties directly introduced by imprecision in the input data our approach is intuitive and straight forward and suitable in both simple and complex geological settings it enables detailed insights into the model quality even for the non expert in cases where a geological model is the basis for geophysical simulation it opens up the way to geological data driven ensemble modelling and inversion

seep carbonates and preserved methane oxidizing archaea and sulfate reducing bacteria fossils suggest recent gas venting on the seafloor in the northeastern south china sea seep carbonates formed by the synergistic metabolism of methane oxidizing archaea moa and sulfate reducing bacteria srb have been found in many places worldwide but have not been found to date in the south china sea mud volcanoes and shale diapirs have been reported in the south china sea however and microscope and geochernical analysis of carbonates dredged where bottom simulating reflectors bsr suggest the presence of gas hydrate on the northeastern continental slope of the south china sea suggest that the carbonates are hydrocarbon seep related carbonates the carbonates we dredged are chimney like and preserve moa srb fossils their very light carbon isotopic compositions 51 25 to 51 76 parts per thousand suggest that their carbon was derived from microbial methane oxidization these seep carbonates and their preserved moa srb fossils imply gas venting has occurred recently on the seafloor in the northeastern continental slopes in the south china sea c 2005 elsevier ltd all rights reserved

glacial geology of outer bjornoyrenna southwestern barents sea the upper cenozoic glacigenic succession in outer bjornoyrenna bear island trough southwestern barents sea is investigated utilizing data from six shallow boreholes 143 m below sea bed and seismic profiling overdeepened troughs in the lowermost part of a large plio pleistocene wedge at the shelf margin are interpreted as glacial erosion forms this suggests that the overlying succession which basinward attains a thickness of several km was deposited during a period with glaciations large scale possible sand ridges in the stratigraphic lower part of this succession are confined to two north south trending zones parallel to the present shelf break they probably formed in a continental shelf coastal environment with exceptionally high sediment supply and fluctuating relative sea level related to glaciations a core from a channel fill in the lower part of the succession consists of possibly glaciofluvial gravelly sand intercalated with till most of the other cores are dominated by middle and upper pleistocene muddy massive partly fissile diamictons interpreted to be mainly tills undrained shear strength of these cores ranges from about 20 kn m 2 to more than 300 kn m 2 and both underconsolidated intervals compared to the present burial depth are found an underconsolidated interval comprising eemian interglacial biourbated marine sediments overlain by laminated weichselian glaciomarine sediments on the outher shelf is covered by 50 100 m of muddy diamicton this diamicton is suggested to be mainly till deposited by a late weichselian ice sheet which was grounded to more than 500 m below present sea level earlier weichselian ice expansions did not reach the outer shelf based on the stratigraphy in the shallow cores and seismic interpretation we suggest that there have been five major expansions of grounded ice to the shelf break since ca 440 ka the present study suggests that glacial erosion was a major process in the late cenozoic denudation of the barents sea and in large areas perhaps as much as 200 250 m of preexisting strata could have been eroded by glaciers since about 440 ka

the history of quaternary sedimentation in the uk sector of the north sea basin reconnaissance seismic and sampling surveys have shown that up to 500 m of lower and early middle pleistocene deltaic sediments are preserved in the uk sector of the north sea the distributions of delta related facies record the progressive expansion of peripheral delta systems northwards across the southern north sea during the early pleistocene a late middle pleistocene unconformity is present throughout the uk sector and sedimentation above the unconformity was dominated by glacial erosional and depositional processes a complex system of deeply incised valleys was eroded during each of three regional middle and upper pleistocene glaciations and the valleys have been filled or partially filled by glaciolacustrine or glaciomarine and interglacial marine sediments the valleys of the earliest elsterian glaciation are up to 400 m deep in the southern north sea the saalian and weichselian valleys are commonly more than 100 m deep they are eroded through their contemporary tills nearshore but occur well beyond the limits of these tills offshore the origins of these valleys are attributed to a combination of fluvial subglacial and periglacial processes

activation of gas bubble emissions indicated by the upward decreasing lead 210 activity at a submarine mud volcano ty1 offshore southwestern taiwan abstract a submarine mud volcano mv known as ty1 is one of the largest conical structures found offshore southwestern taiwan active gas bubble emissions at the flat crest of the mud volcano disperse sediment particles into the water column changes in the mud volcanism of ty1 were revealed by radiograph and grain size analysis of the sediment cores 210 pb geochronology was applied to the near seafloor sediments to reveal the detailed mud volcanism from the deposition rate in a 58 cm long sediment core taken from the northern margin of the crest known as ty1 n 170 the size and frequency of the mud clasts decrease upward the clasts are smaller than 8 mm above a sediment depth of 34 cm below the sea floor cmbsf sediments between 0 and 19 cmbsf are massive and particles larger than 2 mm are absent an enrichment of coarse silt sized particles in the massive sediment unit and the restricted distribution of the unit suggest that the massive unit was generated by re deposition of sediment particles that were dispersed into the water column by gas bubble emission these characteristics suggest that during the last mud volcanism of ty1 there was a decrease in mud eruption energy and gas bubble emission became the main activity in core ty1 s 440 taken from the southern slope a massive sediment unit enriched with coarse silt sized particles is intercalated between mud breccia structures this suggests repeated mud breccia flows caused by ty1 the excess 210 pb activity present in the massive sediment unit of ty1 n 170 suggests activation of gas bubble emission in the massive unit a decrease in excess 210 pb activity appears upward toward the seafloor the highest value is 3 1 dpm g at 19 8 cmbsf 26 4 g cm 2 in cumulative mass values lower than 1 0 dpm g are distributed 2 8 6 8 cmbsf 3 6 8 8 g cm 2 the upwardly decreasing trend is opposite that of the reference core from which a reasonable areal sedimentation rate was obtained using a constant flux constant sedimentation model the anomalous depth profile at the massive unit indicates an increasing rate of sediment deposition which originated from the activation of gas bubble emission

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

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

correlation ofbolboforma zonation and nannoplankton stratigraphy in the neogene of the north atlantic dsdp sites 12 116 49 408 81 555 and 94 608 abstract the neogene bolboforma zones established in the north atlantic have been correlated with the calcareous nannoplankton stratigraphy obtained by investigation of the same samples from dsdp sites 12 116 44 samples 49 408 76 samples 81 555 43 samples and 94 608 103 samples the absolute ages for the zonal boundaries were determined by the paleomagmetic record of site 94 608 this correlation and the age determinations are additional useful tools to develop a precise biostratigraphy of neogene sediments in the northern atlantic

application of bayesian kriging to subsurface characterization a large number of geologic environments are composed of different layers of contrasting grain sizes an accurate description of the locations of these stratigraphic units is necessary for defining

mud diapirism fan sedimentation and strike slip faulting caribbean colombian margin abstract a closely spaced seismic survey carried out during the diapicar cruise off the caribbean coast of colombia permitted study of the interaction between thick deltaic sedimentation and tectonic stress the consequence of these combined tectonic and sedimentary processes is the formation of large mud diapirs the colombian accretionary wedge is divided into two parts by a more than 100 km long lateral ramp this observation replaced in a plate tectonic framework indicates that the northern south america is divided in several blocks which move to the northwest these blocks may overthrust the caribbean oceanic crust but we exclude the formation of a true subduction zone

reconstruction of glaciation over the past 6 myr from ice borne deposits in the norwegian sea it is well known that a significant intensification of northern hemisphere glaciation occurred 2 5 myr ago in contrast to the much earlier onset 35 myr of glaciation in antarctica1 3 much less is known about the behaviour of the climate before 2 5 myr and it has remained unclear when sizeable glaciers first started to develop in the northern hemisphere here we deduce the history of high northern latitude glaciation over the past 6 myr from records of ice borne deposits in deep sea sediments of the norwegian sea we find that glaciers large enough to reach sea level were present in the norwegian sea area as early as 5 5 myr three million years before the intensification of glaciation at 2 5 myr fluctuations in ice volume can be deduced from the oxygen isotope record but this provides only a global average which may not reflect the history of ice sheet growth in specific regions from a comparison of the oxygen isotope records with the record of ice rafted material we derive an estimate of the relative contributions of southern and northern hemisphere glaciation to global variations in ice volume

cenozoic differential subsidence of north sea the structural evolution of the central north sea has been dominated by subsidence throughout the last 65 m y which occurred at different rates in various segments of the basin the bulk of the tertiary sediments accumulated in a relatively narrow elongate basin in the central north sea the base of the tertiary today is deeper than 3 250 m in the axis of the central graben the overall shape of the basin is well defined by contours decreasing in depth northward to the norwegian sea and landward in all other directions different rates of subsidence of the various subbasins are evident by comparison of isopach maps during the paleocene and eocene the main depocenter was located in the northwest part of the north sea the viking graben whereas the oligocene and miocene depocenters are observed to have been in the southern part of the central graben in addition two ancillary depocenters have been identified for other intervals of the tertiary the moray firth and the central jutland portion of the danish subbasin

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

deep seismic transects across the sheared western barents sea svalbard continental margin abstract we have used recently acquired deep seismic reflection and refraction profiles together with a large amount of conventional mcs data to study the 1000 km long sheared western barents sea svalbard margin with the objective of determining its crustal structure and tectonic history the margin developed from a megashear zone which linked the norwegian greenland sea and the eurasia basin during the eocene opening the margin is composed of two large shear segments and a central rifted margin segment associated with volcanism the continent ocean boundary is confined within a narrow zone 10 20 km at the sheared margin segments but is more obscure and partly masked by volcanics at the rifted margin the crustal structure and tectonic history differ significantly between the three margin segments in the north across the hornsund fault zone the crustal thickness changes abruptly from more than 30 km thick continental crusy on the svalbard platform to 6 8 km thick oceanic crust in the greenland sea this margin segment experienced oblique continent continent and partly continent ocean shear with both transtensional and transpressional component during eocene time while post eocene extension caused crustal stretching west of svalbard the volcanic province at the central rifted margin segment probably comprises an outer part of thick oceanic crust and an inner part of thinned continental crust covered by a mixture of volcanics and sediments this formed at a releasing bend in the margin in response to eocene oligocene extension and two phases of volcanism in the south the crustal thinning occurs over a wider area landward of the senja fracture zone here the margin bounds a basinal province in which as much as 18 20 km of sediments cover a highly attenuated crystalline crust the senja fracture zone evolved due to eocene transtensional continent continent shear followed by continent ocean shear and has been passive since earliest oligocone time we conclude that the first order crustal structure along the margin and its tectonic development is mainly the result of three controlling parameters 1 1 the pre breakup structure 2 2 the geometry of the plate boundary at opening and 3 3 the direction of relative plate motion the interplay between the direction of plate motion and the geometry of the plate boundary gave rise to striking differences in the structural development of the different margin segments

morphology and extension of the evaporitic structures of the liguro provencal basin new sea beam data abstract a multi beam echo sounder sea beam and continuous seismic profiling in the liguro provencal basin were used to determine the distribution and morphology of the salt domes in this region several areas were mapped on the scale of 1 25 000 having 10 m distant contour lines an analysis of the sea beam and seismic profile data has enabled a better understanding of the hypotheses concerning the phenomenon of halokinesis i e the influence of the sedimentary overload and the influence of tectonic activities in the area it will be demonstrated that the sediment cover in the delta regions of the rhone and var rivers has a negative influence on halokinesis in these areas no piercement structures can be seen deep level tectonic activity and the faulting of the area have a primary role in the halokinesis observed in the studied zones observed diapiric features are characteristic of the underlying layer and can be used as guides for geodynamic study of the basin

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

cenozoic sequence stratigraphy of the central and northern north sea basin tectonic development sediment distribution and provenance areas the cenozoic succession in the central and northern north sea has been investigated to establish a regional sequence stratigraphic framework changes in sediment distribution indicate a complex pattern of regional vertical movements along older palaeozoic and mesozoic structures in cenozoic times these vertical movements mainly related to tectonic processes along the continental margin to the north and north west were responsible for the generation and removal of provenance areas for sediments delivered to the north sea basin through cenozoic time during the early through middle palaeogene sediments were mainly sourced from areas in the west and from the atlantic margin in the north uplift in the northern north sea in the late eocene was in the earliest oligocene followed by marked basin subsidence and tectonic uplift of southern norway a similar pattern of tectonic movements resulted in subaerial exposure of the northern north sea in the early miocene followed by significant tectonic subsidence in the basin and along the atlantic margin in late miocene pliocene times at the same time southern norway was uplifted and became a major sediment source after the miocene pliocene subsidence uplift events glacial processes in southern norway and fluvial processes in a large drainage area east and south east of the north sea were responsible for the main sediment influx to the north sea the cenozoic depositional sequences in the north sea developed in close interaction with regional tectonic movements and changes in provenance areas tectonic movements in north west europe overprinted global sea level changes so that the generation of depositional sequences and sequence boundaries apparently occurred independently of the rate of eustatic sea level change