bottom simulating reflections and geothermal gradients across the western svalbard margin seismic reflection data reveal prominent bottom simulating reflections bsrs within the relatively young 0 78 ma sediments along the west svalbard continental margin the potential hydrate occurrence zone covers an area of c 1600 km2 the hydrate accumulation zone is bound by structural tectonic features knipovich ridge molloy transform fault vestnesa ridge and the presence of glacigenic debris lobes inhibiting hydrate formation upslope the thickness of the gas zone underneath the bsr varies laterally and reaches a maximum of c 150 ms using the bsr as an in situ temperature proxy geothermal gradients increase gradually from 70 to 115 c km 1 towards the molloy transform fault anomalies only occur in the immediate vicinity of normal faults where the bsr shoals indicating near vertical heat fluid flow within the fault zones amplitude analyses suggest that sub horizontal fluid migration also takes place along the stratigraphy as the faults are related to the northwards propagation of the knipovich ridge long term disturbance of hydrate stability appears related to incipient rifting processes

geochemistry of vanadium in an epigenetic sandstone hosted vanadium uranium deposit henry basin utah the epigenetic tony m vanadium uranium orebody in south central utah is hosted in fluvial sandstones of the morrison formation upper jurassic although the deposit is mined for uranium vanadium has a higher average abundance in the ore thus the geochemistry of vanadium in the orebody was studied to characterize ore forming processes within the inferred ground water flow regime measurements of the relative amounts of v super 3 and v super 4 in ore minerals show that v super 3 is more abundant thermodynamic calculations show that vanadium was more likely transported to the site of mineralization as v super 4 the ore formed as v super 4 was reduced by hydrogen sulfide followed by hydrolysis and precipitation of v super 3 in oxide minerals e g montroseitc or paramontroseite or chlorite uranium was transported as uranyl ion u super 6 or some complex thereof and reduced by hydrogen sulfide forming coffinite detrital organic matter in the rocks served as the carbon source for sulfate reducing bacteria it was this bacteriogenic h 2 s that reduced the metals in the mineralization process possible sources for the v and u in this deposit have been identified previously vanadium most likely was derived from the dissolution of iron titanium oxides which liberated fe as well as v a zone of titanium rich remnants is observed updip and up the hydrologic gradient from the deposit m goldhaber and r l reynolds unpub data uranium probably was derived from the overlying brushy basin member of the morrison formation northrop 1982 a preliminary age date for the deposit of 115 ma k ludwig 1986 pers commun indicates that the ore formed after deposition of the brushy basin member previous studies have shown that the ore formed at the density stratified interface between a basinal brine and dilute meteoric water the mineralization processes described above occurred within the mixing zone between these two fluids stable isotope analyses of ore stage dolomite show a progressively heavier carbon and oxygen isotope signature with increasing depth through an ore horizon consistent with the two solution interface model

late glacial and deglacial palaeoceanographic changes at vestnesa ridge fram strait methane seep versus non seep environments abstract two cores from 1200 m water depth from vestnesa ridge on the western svalbard margin have been investigated for the distribution of benthic and planktic foraminiferal assemblages oxygen and carbon isotopes geochemical and sedimentological parameters including magnetic susceptibility total organic carbon toc and caco 3 content of the sediment vestnesa ridge is known for the presence of numerous pockmarks where methane gas is bubbling out from the seafloor one core was taken from a pockmark with active seepage of methane while the second core was taken just outside the seepage area for comparison the purpose of the study is to reconstruct the palaeoceanography and compare to published palaeoceanographic records from the area and evaluate if seepage of methane have had any impact on the distribution patterns of benthic foraminiferal species and the sedimentary environments through time the results indicate almost continuous presence of atlantic water throughout the last 43 000 years during the heinrich h1 interval ca 18 000 15 300 years atlantic water flowed subsurface along the bottom and the period stands out with the highest bottom water temperatures of the last 43 000 years settlement of a community of chemo synthesizing bivalves indicates increase in the release of methane beginning during h1 however in both records of seep versus non seep environments the distribution patterns of benthic foraminiferal species diversity and productivity of the specimens were the same indicating that seepage of methane had no influence on the foraminiferal faunas our results show that the palaeoceanographic development at vestnesa ridge was similar to the development over the western svalbard margin and the fram strait confirming previously published results we conclude that the benthic foraminifera at the methane seep site were mainly controlled by palaeoceanographic changes and associated changes in the sedimentary environment and palaeoproductivity overprinting any eventual influence of seepage of methane

opening of the fram strait gateway a review of plate tectonic constraints abstract we have revised the regional crustal structure oceanic age distribution and conjugate margin segmentation in and around the lena trough the oceanic part of the fram strait between the norwegian greenland sea and the eurasia basin arctic ocean the lena trough started to open after eurasia greenland relative plate motions changed from right lateral shear to oblique divergence at chron 13 times 33 3 ma earliest oligocene a new bouguer gravity map supported by existing seismic data and aeromagnetic profiles has been applied to interpret the continent ocean transition and the influence of eocene shear structures on the timing of breakup and initial seafloor spreading assuming that the onset of deep water exchange depended on the formation of a narrow oceanic corridor the gateway formed during early miocene times 20 15 ma however if the initial lena trough was blocked by terrigenous sediments or was insufficiently subsided to allow for deep water circulation the gateway probably formed with the first well developed magnetic seafloor spreading anomaly around chron 5 times 9 8 ma late miocene paleoceanographic changes at odp site 909 northern hovgard ridge are consistent with both hypotheses of gateway formation we cannot rule out that a minor gateway formed across stretched continental crust prior to the onset of seafloor spreading in the lena trough the gravity seismic and magnetic observations question the prevailing hypotheses on the yermak plateau and the morris jesup rise as eocene oceanic plateaus and the hovgard ridge as a microcontinent

effect of early pliocene uplift on late pliocene cooling in the arctic atlantic gateway despite the undisputed role of the arctic ocean in the modern and pliocene climate system the arctic has only recently attracted public awareness that ongoing fundamental change in the arctic cryosphere could be a response to global warming clarification of the arctic s role in global climate during the pliocene is however largely hampered by equivocal stratigraphic constraints from a well dated pliocene sequence from the yermak plateau off nw spitsbergen we present sedimentological and geochemical data indicating that 4 million years ago terrigenous sediment supply and sources changed abruptly in response to a regional tectonic uplift event we argue that this event together with contemporary uplift and tilting along the northwestern european continental margin preconditioned the landmasses for glacial ice build up during intensification of the northern hemisphere glaciation inhg our data further suggest that the final deepening widening of the arctic atlantic gateway the fram strait between 6 5 and 5 ma gradually caused increased deep water mass exchange which in turn likely contributed to the intensification of the north atlantic thermohaline circulation coupled to the north atlantic warm pool as a regional moisture source declining atmospheric co2 levels and other feedback mechanisms during the pliocene the regional tectonic activities in the high northern latitudes caused decreased summer ablation and thus allowed the initial build up of glacial ice both in scandinavia and the sub aerially exposed svalbard barents sea culminating in the first large scale coastline shelf edge glaciations at 2 75 ma

ebullition and storm induced methane release from the east siberian arctic shelf vast quantities of carbon are stored in shallow arctic reservoirs such as submarine and terrestrial permafrost submarine permafrost on the east siberian arctic shelf started warming in the early holocene several thousand years ago however the present state of the permafrost in this region is uncertain here we present data on the temperature of submarine permafrost on the east siberian arctic shelf using measurements collected from a sediment core together with sonar derived observations of bubble flux and measurements of seawater methane levels taken from the same region the temperature of the sediment core ranged from 1 8 to 0 degrees c although the surface layer exhibited the lowest temperatures it was entirely unfrozen owing to significant concentrations of salt on the basis of the sonar data we estimate that bubbles escaping the partially thawed permafrost inject 100 630 mg methane m 2 d 1 into the overlying water column we further show that water column methane levels had dropped significantly following the passage of two storms we suggest that significant quantities of methane are escaping the east siberian shelf as a result of the degradation of submarine permafrost over thousands of years we suggest that bubbles and storms facilitate the flux of this methane to the overlying ocean and atmosphere respectively

gas hydrate reservoir and active methane venting province in sediments on 20 ma young oceanic crust in the fram strait offshore nw svalbard seafloor pockmarks are common indicators for vertical fluid flow and frequently associated with methane discharge through the gas hydrate stability zone ghsz the present day flux through these degassing systems is presumably at a low level on most rifted continental margins a pockmark field on the nw svalbard passive margin is located on young ocean crust 20 ma and shows evidence of ongoing episodic degassing new geophysical data from the vestnesa ridge 79 n a mounded and elongated sediment drift in the eastern fram strait reveal a gas hydrate free gas and venting system that is exceptionally more dynamic than documented elsewhere along the northeastern north atlantic margin the prominent bottom simulating reflection bsr about 200 mbsf separates anomalously high p wave velocities in the ghsz from a remarkable underlying low velocity zone indicating the presence of gas hydrate and gas in the pore space inversion of p wave velocity data using the differential effective medium theory yields a two dimensional concentration model of methane hydrate and free gas the model predicts saturations of up to 11 in the hydrate reservoir which due to the seafloor topography forms a large anticlinal permeability barrier below in the low velocity zone i e 1350 1500 m s up to 3 of free gas is predicted across the apex of the vestnesa ridge and in the immediate vicinity of extensional faults a conservative estimate indicates that 225 kg m2 of pure methane is stored in hydrate and gas in the upper 230 m of the sedimentary column an elongated pockmark field consisting of 100 individual pockmarks up to 600 m wide systematically aligns the apex of the vestnesa ridge active vigorous degassing from the topography controlled pressure valve system was evident from a 750 m high and 150 m wide gas flare observed in the water column during a cruise with r v jan mayen in october 2008 the gas flare documents dynamic degassing through the corresponding chimney which penetrates the entire ghsz and into the underlying free gas zone cruises in 2006 and 2007 did not detect active gas venting above the pockmark field accordingly vigorous degassing may operate in an episodic mode where hydrothermal circulation systems through young ocean crust may play a significant role

abiotic methane from ultraslow spreading ridges can charge arctic gas hydrates biotic gas generation from the degradation of organic carbon in marine sediments supplies and maintains gas hydrates throughout the world s oceans in nascent ultraslow spreading ocean basins methane generation can also be abiotic occurring during the high temperature 200 c serpentinization of ultramafic rocks here we report on the evolution of a growing arctic gas and gas hydrate charged sediment drift on oceanic crust in eastern fram strait a tectonically controlled deep water gateway between the subpolar north atlantic and arctic oceans ultraslow spreading ridges between northwest svalbard and northeast greenland permit the sustained interaction of a mid ocean ridge transform fault and developing sediment drift on both young 10 ma oceanic crust since the late miocene geophysical data image the gas charged drift and crustal structure and constrain the timing of a major 30 km lateral displacement of the drift across the molloy transform fault we describe the buildup of a 2 m y long lived gas hydrate and free gas charged drift system on young oceanic crust that may be fed and maintained by a dominantly abiotic methane source ultraslow spreading sedimented ridge flanks represent a previously unrecognized carbon reservoir for abiotic methane that could supply and maintain deep water methane hydrate systems throughout the arctic

gas hydrate distribution and hydrocarbon maturation north of the knipovich ridge western svalbard margin a bottom simulating reflector bsr occurs west of svalbard in water depths exceeding 600 m indicating that gas hydrate occurrence in marine sediments is more widespread in this region than anywhere else on the eastern north atlantic margin regional bsr mapping shows the presence of hydrate and free gas in several areas with the largest area located north of the knipovich ridge a slow spreading ridge segment of the mid atlantic ridge system here heat flow is high up to 330 mw m 2 increasing towards the ridge axis the coinciding maxima in across margin bsr width and heat flow suggest that the knipovich ridge influenced methane generation in this area this is supported by recent finds of thermogenic methane at cold seeps north of the ridge termination to evaluate the source rock potential on the western svalbard margin we applied 1d petroleum system modeling at three sites the modeling shows that temperature and burial conditions near the ridge were sufficient to produce hydrocarbons the bulk petroleum mass produced since the eocene is at least 5 kt and could be as high as 0 2 mt most likely source rocks are miocene organic rich sediments and a potential eocene source rock that may exist in the area if early rifting created sufficiently deep depocenters thermogenic methane production could thus explain the more widespread presence of gas hydrates north of the knipovich ridge the presence of microbial methane on the upper continental slope and shelf indicates that the origin of methane on the svalbard margin varies spatially

early diagenesis in differing depositional environments the response of transition metals in pore water the cycling of fe mn ni co cu cr v and mo during early diagenesis was investigated in sediments from five different depositional environments in the california borderland dissolved o2 no3 no2 and so4 were also measured at each site to establish the position of redox boundaries pertinent to this study sites were chosen to allow the comparison of several parameters of potential importance to the cycling of these metals bottom water o2 concentration sediment redox conditions cycling of metal oxide carrier phases and the relative contribution of biogenic and terrigenous material to the detrital metal flux at 10 m oxygen and above the sequence of terminal electron acceptor utilization was typical of pelagic sediments differing only in scale under these conditions the recycling of mn oxides resulted in an enriched layer near the interface at bottom water 02 concentrations 5 m mn oxides are not recycled under these conditions fe oxides and so42 are important oxidants the depth of the zone of manganese oxidation with respect to the interface affects the efficiency of metal scavenging by manganese oxides trapping and recycling of ni and co with mn oxides results in remobilization from reducing sediments and enrichment in oxic sediments scavenging of these metals is favored by a deep oxic zone in the sediments in contrast cr v and mo appear to be transported to the sediments as reduced species and are released from the sediments by oxidation the source of the reduced species is assumed to be biogenic material the accumulation of these metals is favored by reducing conditions in the sediments cu is enriched in the sediments by transport with detrital biogenic material followed by adsorption onto sediment solids cu is released at the interface and rapidly removed onto the solids at all sites except the one pelagic site at the base of the slope the magnitude of cu released in the slowly accumulating pelagic sediment exceeds the cu binding capacity of the solids resulting in pore water cu concentrations in excess of 100 nm in general metal cycling associated with the early diagenesis of sediments was observed to decouple transport processes from burial processes for the transition metals measured in this study

geochemical and isotopic evidence for paleoredox conditions during deposition of the devonian mississippian new albany shale southern indiana the upper part of the new albany shale is divided into three members in ascending order these are 1 the morgan trail member a laminated brownish black shale 2 the camp run member an interbedded brownish black and greenish gray shale and 3 the clegg creek member also a laminated brownish black shale the morgan trail and camp run members contain 5 to 6 total organic carbon toc and 2 sulfide sulfur isotopic composition of sulfide in these members ranges from 5 0 to 20 0 c s plots indicate linear relationships between abundances of these elements with a zero intercept characteristic of sediments deposited in a non euxinic marine environment formation of diagenetic pyrite was carbon limited in these members the clegg creek member contains 10 to 15 toc and 2 to 6 sulfide sulfur isotopic compositions of sulfide range from 5 0 to 40 the most negative values occur in the uppermost clegg creek member and are characteristic of syngenetic pyrite formed within an anoxic water column abundances of carbon and sulfur are greater and uncorrelated in this member consistent with deposition in as euxinic environment in addition dop degree of pyritization values suggest that formation of pyrite was generally iron limited throughout clegg creek deposition but sulfur isotopes indicate that syngenetic water column pyrite becomes an important component in the sediment only in the upper part of the member at the top of the clegg creek member a zone of phosphate nodules and trace metal enrichment coincides with maximal toc values during euxinic deposition phosphate and trace metals accumulated below the chemocline because of limited vertical circulation in the water column increased productivity would have resulted in an increased flux of particulate organic matter to the sediment providing an effective sink for trace metals in the water column phosphate and trace metals released from organic matter during early diagenesis resulted in precipitation of metal rich phosphate nodules

methane generated pockmarks on young thickly sedimented oceanic crust in the arctic vestnesa ridge fram strait acoustic backscatter imagery in the fram strait between greenland and spitzbergen reveals a 1 3 km wide 50 km long belt of 50 pointlike backscatter objects decorating the 1300 m deep crest of vestnesa ridge a 1 2 km thick sediment drift possibly underlain by a transform parallel oceanic basement ridge crustal ages 3 14 ma a 3 5 khz seismic reflection profile indicates that at least some objects are pockmarks 100 200 m in diameter and 10 20 m deep the pockmarks possibly also mud diapirs may have been formed by evolution of methane generated by the decomposition of marine organic matter in the vestnesa ridge sediment drift the ridge may be underlain by an anticlinal carapace of methane hydrate calculated to be 200 300 m thick comparable to the hydrate thickness measured just to the south the rising methane would collect in the ridge crest trap intermittently escaping to the sea floor this hypothesis is supported by multichannel evidence for bright spots and bottom simulating reflectors in the area the pockmark belt may also be located above a transcurrent fault sediment slumps on the flanks of vestnesa ridge and northeast of molloy ridge may have been triggered by plate boundary earthquakes and facilitated by methane hydrates

an integrated view of the methane system in the pockmarks at vestnesa ridge 79 n accepted manuscript version published version available at https doi org 10 1016 j margeo 2017 06 006 accepted manuscript version licensed cc by nc nd 4 0

the plio pleistocene glaciation of the barents sea svalbard region a new model based on revised chronostratigraphy based on a revised chronostratigraphy and compilation of borehole data from the barents sea continental margin a coherent glaciation model is proposed for the barents sea ice sheet over the past 3 5 million years ma three phases of ice growth are suggested 1 the initial build up phase covering mountainous regions and reaching the coastline shelf edge in the northern barents sea during short term glacial intensification is concomitant with the onset of the northern hemisphere glaciation 3 6 2 4 ma 2 a transitional growth phase 2 4 1 0 ma during which the ice sheet expanded towards the southern barents sea and reached the northwestern kara sea this is inferred from step wise decrease of siberian river supplied smectite rich sediments likely caused by ice sheet blockade and possibly reduced sea ice formation in the kara sea as well as glacigenic wedge growth along the northwestern barents sea margin hampering entrainment and transport of sea ice sediments to the arctic atlantic gateway 3 finally large scale glaciation in the barents sea occurred after 1 ma with repeated advances to the shelf edge the timing is inferred from ice grounding on the yermak plateau at about 0 95 ma and higher frequencies of gravity driven mass movements along the western barents sea margin associated with expansive glacial growth

liquid immiscibility in the caf2 granite system and trace element partitioning between the immiscible liquids abstract the recent discoveries of ca fluoride melt in magmatic systems especially in peralkaline granites with rare earth element enrichment has raised questions about the presence and nature of liquid immiscibility in caf2 granite systems as well as the partitioning behavior of trace elements between such immiscible liquids we have experimentally explored the immiscibility in this system using natural granite fluorite starting materials at fast and slow cooling rates temperatures from 500 c to 1200 c and 1 atmosphere pressure our experiments confirm the presence of a miscibility gap in the caf2 granite system over a wide range of temperatures the two immiscible liquids are a mafic fluorosilicate melt fm with high cao and f and a felsic oxysilicate melt sm with high sio2 and alkalis immiscibility is encountered when the bulk f content exceeds approximately 4 4 wt at 1200 c and then rapidly decreases to only 0 75 wt at low temperature below 900 c this indicates that calcic magmas are able to evolve to the liquid immiscibility domain by the residual enrichment of fluorine resulting from fractional crystallization and that liquid immiscibility should be common the peritectic reaction fm sm fluorite removes the fluorosilicate liquid around 600 c and could explain the absence of fluorosilicate observations in natural granites the compositions of the liquids in fast cooling experiments show a significantly larger miscibility gap which is characterized by compared to slow cooling runs similar sm compositions but higher ca and f content in fm this difference is caused by suppression of fluorite nucleation and is interpreted as a metastable extension of the high temperature liquid immiscibility immiscibility results in strong fractionation of trace elements which is primarily governed by melt structure and the ionic potential z r of the elements the behavior of trace elements can be categorized into three groups 1 network formers si al ga pb b partition into the oxysilicate melt 2 the partitioning of the alkalis and alkali earths is strongly dependent on the ionic potential with the partitioning coefficients d fm sm in the order dcs

detection of gas hydrates in faults using azimuthal seismic velocity analysis vestnesa ridge w svalbard margin accepted for publication in journal of geophysical research solid earth copyright 2020 american geophysical union further reproduction or electronic distribution is not permitted

near surface hydrocarbon anomalies in shelf sediments off spitsbergen evidences for past seepages 1 as global warming occurs the dissociation of bound methane on arctic shelves due to ocean current temperature changes may become a major contributor to the global methane budget and thus contribute to strong positive climate feedback mechanisms however little is known about the magnitude and fate of methane emissions from shallow submarine sediments to the atmosphere in the peculiar area in this paper we present one of the first direct evidences for seepage on the northwestern barents sea shelf by studying the molecular and isotopic signatures of low molecular weight hydrocarbons in seawater near surface sediment pore space and the sediment matrix at 26 locations we provide a detailed view on the partitioning of gaseous hydrocarbons in the sediment water interface off spitsbergen in the free gas phase low concentration of methane 28 ng g wet sediment paired with constantly high isotopic values 65 is consistent with high impact of methane oxidation on the isotopic composition in contrast high concentrations of adsorbed ch4 up to 5292 ng g wet 63 m and c2 ethane through pentane up to 1724 ng g wet 63 m in the sediment matrix suggest that the adsorbed gas is reasonably well protected against microbial degradation moreover the isotopic and molecular signatures of adsorbed ch4 38 60 100 5300 ng g wet 63 m and c2h6 20 36 30 1700 ng g wet 63 m indicate an integrated but strongly varying signal of historic thermally derived hydrocarbon plumes plus in situ adsorbed gas of biological origin this suggests a minimal exchange and unlike histories of free and adsorbed gas the majority of gaseous hydrocarbons in the adsorbed pool may be the result of past seepages past upward flow of thermogenic gas and impregnation with mature hydrocarbons was particularly strong along tectonic lineaments active petroleum source rocks along the continental margin and migration of gaseous hydrocarbons at re activated fault systems might explain the anomalies along these conduits

thermal cracking of kerogen in open and closed systems determination of kinetic parameters and stoichiometric coefficients for oil and gas generation abstract the purpose of the study is to compare artificial maturation of kerogens representative of the main types of organic matter kerogen types i ii ii s and iii in open and anhydrous closed pyrolysis systems the generated compounds are fractionated according to their thermal stability into six chemical classes c 1 c 2 c 5 c 6 c 14 c 15 saturates c 15 aromatics and nsos which include resins and asphaltenes in both systems primary cracking of kerogen can be described by two main reactions oil generation together with early gas generation followed by late gas production mass balances obtained in the two pyrolysis systems are reasonably similar although some secondary cracking of the nsos and underestimation of methane potential due to incomplete pyrolysis may occur in the open system kinetic parameters of thermal cracking are derived from experiments in the open system using an optimization procedure which determines a unique frequency factor and a weight distribution of chemical classes for a discrete series of activation energies the resultant frequency factors are checked with those obtained for specific molecular tracers such as n c 12 and n c 24 alkanes generated from kerogens in open and closed systems under isothermal conditions the results show that using a unique frequency factor as determined by optimization is correct for type i ii and ii s kerogens this factor is more questionable however when the distribution of activation energies is very broad such as for type iii coals based on this study a strategy for determination of kinetic parameters on any new source rock sample is proposed

geological controls on fluid flow and gas hydrate pingo development on the barents sea margin vista a basic research program in collaboration between the norwegian academy of science and letters and equinor

role of large particles in the transport of elements and organic compounds through the oceanic water column abstract during the past decade data from a variety of sources have been obtained which show conclusively that the relatively rare large particles sinking through the water column are responsible for the majority of the downward vertical mass flux in the sea this finding has important implications for understanding the transfer distribution and fate of elements and organic compounds in marine waters the large 100 m detrital particles responsible for vertical flux are primarily biogenic and range in size and composition from small discrete fecal pellets and plankton hard parts to large amorphous aggregates or snow which contain both organic and inorganic constituents depending on size shape and density these particles sink at rates ranging from 1000 m day 1 several methods have been developed for sampling these particles of which in situ sediment trapping has probably furnished the most comprehensive qualitative and quantitative information on the role large particles play in material transport flux studies have highlighted the importance of marine heterotrophs in packaging fine suspended particulate matter into large rapidly sinking particles which accelerate the movement of incorporated materials to depth large particle production via biological packaging is not restricted to the euphotic zone but can occur at all depths and information is now accruing on rates of production of large particles in the water column chemical analyses of sedimenting particles collected in sediment traps and those sampled by other means have allowed quantifying vertical fluxes and residence times of elements radionuclides and organic compounds natural and anthropogenic in various oceanic regimes pertinent studies dealing with the above aspects are reviewed and several areas for future research are suggested

modelling persistent methane seepage offshore western svalbard since early pleistocene abstract recent observations of extensive methane release into the oceans and atmosphere have raised concern as to whether rising temperatures across the arctic could drive rapid destabilization of gas hydrate reservoirs here we report modelling results from hydrate modulated methane seepage from vestnesa ridge offshore western svalbard suggesting that continuous leakage has occurred from the seafloor since the early pleistocene up until today sustained by modelled deep subsurface thermogenic sources of miocene age large scale hydrocarbon fluid migration started 6 million years ago and reached the seafloor some 4 million years later the modelling results indicate that widespread methane seepage offshore western svalbard commenced in earnest during early pleistocene significantly older than late holocene as previously reported we propose that the onset of vertical hydrocarbon migration is the response of rapid burial of potential hydrocarbon sources induced by increased sediment deposition following the onset of northern hemisphere glaciations 2 7 million years ago from the modelling results we propose that source rock intervals capable of generating hydrocarbons and hydrocarbon reservoirs buried kilometers deep have continuously fueled the gas hydrate system off western svalbard for the past 2 million years it is this hydrocarbon system that primarily controls the thermogenic methane fluxes and seepage variability at the seabed over geological times

vanadium accumulation in carbonaceous rocks a review of geochemical controls during deposition and diagenesis abstract published data relevant to the geochemistry of vanadium were used to evaluate processes and conditions that control vanadium accumulation in carbonaceous rocks reduction adsorption and complexation of dissolved vanadium favor addition of vanadium to sediments rich in organic carbon dissolved vanadate v v species predominate in oxic seawater and are reduced to vanadyl ion v iv by organic compounds or h 2 s vanadyl ion readily adsorbs to particle surfaces and is added to the sediment as the particles settle the large vanadium concentrations of rocks deposited in marine as compared to lacustrine environments are the result of the relatively large amount of vanadium provided by circulating ocean water compared to terrestrial runoff vanadium rich carbonaceous rocks typically have high contents of organically bound sulfur and are stratigraphically associated with phosphate rich units a correspondence between vanadium content and organically bound sulfur is consistent with high activities of h 2 s during sediment deposition excess h 2 s exited the sediment into bottom waters and favored reduction of dissolved v v to v iv or possibly v iii the stratigraphic association of vanadiferous and phosphatic rocks reflects temporal and spatial shifts in bottom water chemistry from suboxic phosphate concentrated to more reducing euxinic conditions that favor vanadium accumulation during diagenesis some vanadium organic complexes migrate with petroleum out of carbonaceous rocks but significant amounts of vanadium are retained in refractory organic matter or clay minerals as carbon in the rock evolves toward graphite during metamorphism vanadium is incorporated into silicate minerals

paleo methane emissions recorded in foraminifera near the landward limit of the gas hydrate stability zone offshore western svalbard we present stable isotope and geochemical data from four sediment cores from west of prins karls forland ca 340 m water depth offshore western svalbard recovered from close to sites of active methane seepage as well as from shallower water depths where methane seepage is not presently observed our analyses provide insight into the record of methane seepage in an area where ongoing ocean warming may be fueling the destabilization of shallow methane hydrate the 13c values of benthic and planktonic foraminifera at the methane seep sites show distinct intervals with negative values as low as 27 8 that do not coincide with the present day depth of the sulfate methane transition zone smtz these intervals are interpreted to record long term fluctuations in methane release at the present day landward limit of the gas hydrate stability zone ghsz shifts in the radiocarbon ages obtained from planktonic foraminifera toward older values are related to methane derived authigenic carbonate overgrowths of the foraminiferal tests and prevent us from establishing the chronology of seepage events at shallower water depths where seepage is not presently observed no record of past methane seepage is recorded in foraminifera from sediments spanning the last 14 ka cal bp 14c ams dating 13c values of foraminiferal carbonate tests appear to be much more sensitive to methane seepage than other sediment parameters by providing nucleation sites for authigenic carbonate precipitation foraminifera thus record the position of even a transiently stable smtz which is likely to be a characteristic of temporally variable methane fluxes

depositional environment and source rock potential of miocene strata from the central fram strait introduction of a new computing tool for simulating organic facies variations abstract organic rich sediments were recognized in early miocene strata from the norwegian greenland sea during odp leg 151 three organic geochemical subunits were distinguished in hole 909c using detailed organic geochemical and microscopic analyses toc up to 3 wt hi up to 200 mg hc g toc and 13corg values 24 26 indicate the predominance of terrestrial type iii organic matter in subunit 3 18 16 2 ma biomarker and vitrinite reflectance values r0 0 5 point to rather fresh immature terrestrial organic matter supplied by river discharge from adjacent vegetated coastal areas although the sediments of subunit 3 have a fair to good source rock potential they are insufficiently mature to generate significant amounts of oil or gas to test if the moderate generation potential and source rock quality of subunit 3 are applicable to the entire area the computer software of mod was applied several modelling runs testing the most probable depositional scenarios result even under conservative assumptions in the formation of good to excellent source rocks towards the basin margins

middle miocene ice sheet expansion in the arctic views from the barents sea 1 revised core data from ocean drilling program odp leg 151 hole 909c and preglacial paleorelief and bathymetric reconstructions in the barents sea and the arctic gateway region indicate that large scale glaciations were already developed in the northern barents sea during the middle miocene climate transition mmct 15 14 million years ago our findings show that subsequent to an ice free period during the miocene climate optimum mco 17 15 ma glacially eroded materials from the uplifted northern barents sea were transported by iceberg flotillas toward the fram strait the simultaneous opening of the north atlantic arctic gateway provided pathways for iceberg transport from the north the expansive ice growth is probably induced by both large scale changes in ocean circulation due to enhanced flow of atlantic water into the arctic ocean during opening of the gateway and concurrent global cooling during the mmct

anoxia and high primary production in the paleogene central arctic ocean first detailed records from lomonosov ridge 1 except for a few discontinuous fragments of the late cretaceous early cenozoic climate history and depositional environment the paleoenvironmental evolution of the pre neogene central arctic ocean was virtually unknown prior to the iodp expedition 302 arctic ocean coring expedition acex drilling campaign on lomonosov ridge in 2004 here we present detailed organic carbon oc records from the entire ca 200 m thick paleogene oc rich section of the acex drill sites these records indicate euxinic black sea type conditions favorable for the preservation of labile aquatic marine algae type oc occur throughout the upper part of the early eocene and the middle eocene explained by salinity stratification due to freshwater discharge the superimposed short term milankovitch type variability in amount and composition of oc is related to changes in primary production and terrigenous input prominent early eocene events of algae type oc preservation coincide with global 13c events such as the petm and elmo events the elmo 13c event has been identified in the arctic ocean for the first time

rifting in the northern norwegian greenland sea thermal tests of asymmetric spreading the analysis of heat flow seismic and topographic data collected in the northern norwegian greenland sea reveals an asymmetric evolution of the eurasian and north american plates these data are compared to predictions from three kinematic models of extension which produce asymmetry about the knipovich ridge 1 uniform asymmetric pure shear 2 lithospheric simple shear and 3 rift ridge jumping the data are consistent with a range of deformation scenarios from one ridge jump occurring at about 25 m y after the initiation of spreading to continuous asymmetric extension the simple shear model can match the data only when a detachment fault dips more steeply than 45 under svalbard tectonic and heat flow evidence suggests that asymmetry may have evolved from a combination of all three models when the mohns ridge propagating to the east encountered the preexisting northward trending spitsbergen shear zone the direction of ridge propagation shifted to the north being influenced by the abrupt change in the regional stress field at the shear zone ridge axis intersection as a result the nascent knipovich ridge entered into and propagated along the shear zone consequently formerly active shear faults became the new detachment surfaces along which new crust is minted and asymmetrically extended the high level of deviatoric stress about the mohns and knipovich ridge intersection may cause a gradual eastward migration of the knipovich ridge resulting in multiple zones of magma intrusion off axial bands of high heat flow and volcanism located along the barents sea and svalbard margin along the yermak plateau and on continental svalbard just southeast of the yermak plateau may be evidence for this migration propagation from the nansen ridge may have entered the same shear zone from the north explaining the creation of the small molloy ridge and off axis volcanism on the yermak plateau

origins of metals and organic matter in the mecca quarry shale member and stratigraphically equivalent beds across the midwest samples of the middle pennsylvanian age mecca quarry shale member and stratigraphically equivalent beds from indiana illinois missouri and kansas have been analyzed for both inorganic and organic constituents trends for mo values reported by coveney and martin 1983 who found the highest tenors to be associated with the ancient shoreline in indiana have been confirmed regionally across the midwest similarly it has been found that cd v u se and sb are most concentrated near the shoreline whereas constituents such as ca and sr are richest offshore e g kansas organic matter analyses including pyrolysis gas chromatography show the eastern samples to be richest in total organic carbon and also in terrestrial organic matter unbuffered aqueous solutions containing powdered organic rich shales from indiana equilibrate to acid ph values ph 4 6 where mo is readily retained by organic matter laboratory experiments show the shales retain a capacity to fix mo from dilute solutions correlations between organic matter type and metal values such as those existing between mo and v and terrestrial organic matter in shale samples generally fit with the syngenetic model for metal fixation in near shore brackish waters proposed by coveney and martin 1983 however other evidence including the remnant activity of organic matter rich samples to fix metals suggests that nonsyngenetic agents such as basinal brines or meteoric fluids have probably augmented the metal contents of the deposits subsequent to sedimentation and diagenesis

the thermal evolution of sedimentary basins and its effect on the maturation of hydrocarbons summary the maturation of hydrocarbon source rocks depends on a range of factors including the primary rock type and its original content of organic matter kerogens the history of sedimentation and burial depth the local geothermal gradient temperature and duration of sedimentation time the standard approach to modelling this process assumes an evolving burial history but in a basin with a steady state geotherm both in the sediment column and in the underlying basement rocks this first order approach neglects any evects of changes in the geothermal profile resulting from the timing and history of the particular mechanism that formed the sedimentary basin and hence may lead to systematic overestimation or underestimation of hydrocarbon maturation in such rocks this systematic evect may be small when sedimentation rates are low but can be significant in basins with sedimentation rates that are rapid when compared with the rate of heat transport and re equilibration in the system here we describe two analytical 1 d mathematical models for divusive heat transport during sediment deposition which is rapid compared with the thermal relaxation rate the two models describe sedimentary events that can be considered either evectively instantaneous sudden or continuous in both cases we calculate a time dependent geothermal profile and the resulting maturation index of particular source rocks given the combined evects of the thermal and burial histories the models take account both of the transient cooling evect of the cold sediment blanket and of the steady state warming from the underlying basement after calibration with borehole data the method allows a reconstruction of the initial geothermal gradient at the start of the sedimentation event the model has been applied to data derived from two wells drilled in two diverent tectonic settings the pannonian basin and the central north sea in both cases there is a good agreement between the model predictions of the maturation index and empirical observations based on the vitrinite reflectance technique applied to borehole samples of actual source rocks in contrast the steady state geotherm models give a systematic overestimation of both the maximum temperature and the degree of maturation reached by the sediments by the end of the sedimentary event this overestimation is particularly evident for the case of the pannonian basin such systematic evects could have significant implications both for the interpretation of past thermotectonic events and for oilfield appraisal

dissolved vanadium in rivers and estuaries abstract new measurements of dissolved vanadium in a variety of rivers and estuaries are presented here the data indicate that the average concentration of dissolved vanadium in major rivers entering the ocean is 15 nmol kg weathering rate and type of source rock rather than solution chemistry or anthropogenic influences appear to be the important factors in determining fluvial dissolved vanadium concentrations laboratory experiments suggest that in oxic waters vanadium is found predominantly in its most oxidized anionic form v v complexation with organic matter and formation of large colloidal species appear to be unimportant adsorption also appears to be a less important influence for vanadium than for some other trace elements such as zinc in estuaries vanadium behaves as a bioactive element showing a close correspondence with the distribution of phosphate the extent of estuarine vanadium removal is presently uncertain but may be low due to rapid remineralization of this element based on the river flux the oceanic residence time for dissolved vanadium is estimated to be 100 000 years

deciphering late cenozoic development of the western svalbard margin from odp site 986 results abstract the present work is based on sedimentological data from odp site 986 drilled off western svalbard the data include grain size distribution bulk mineralogy clay mineralogy total carbon total organic carbon and carbonate determinations from over 500 samples the results show interesting trends across the seismic sequence boundaries defined earlier and can be related to changes in climate and depositional styles the interpretation of these results together with the seismic observations and interpretations made earlier have shed new light on the timing of the onset of major glaciations and sedimentary processes on the svalbard margin during plio pleistocene the estimate for the timing of the first major glacial advance is revised to 1 6 ma from the earlier estimate of 2 3 ma barents sea was the likely source for the sediments in the 2 3 1 6 ma interval followed by svalbard as the main sediment source in the post 1 6 ma interval it is also suggested that in view of their morphology and proposed sedimentary processes the sedimentary wedges off svalbard barents sea margin are better described as slope aprons than in terms of glacial fans or trough mouth fans used earlier in the literature

constraints on gas hydrate distribution and morphology in vestnesa ridge western svalbard margin using multicomponent ocean bottom seismic data source at https doi org 10 1029 2018jb016574 2019 american geophysical union all rights reserved

crustal fingering facilitates free gas methane migration through the hydrate stability zone widespread seafloor methane venting has been reported in many regions of the world oceans in the past decade identifying and quantifying where and how much methane is being released into the ocean remains a major challenge and a critical gap in assessing the global carbon budget and predicting future climate c ruppel j d kessler rev geophys 55 126 168 2017 methane hydrate ch 4 5 75 h 2 o is an ice like solid that forms from methane water mixture under elevated pressure and low temperature conditions typical of the deep marine settings 600 m depth often referred to as the hydrate stability zone hsz wide ranging field evidence indicates that methane seepage often coexists with hydrate bearing sediments within the hsz suggesting that hydrate formation may play an important role during the gas migration process at a depth that is too shallow for hydrate formation existing theories suggest that gas migration occurs via capillary invasion and or initiation and propagation of fractures fig 1 within the hsz however a theoretical mechanism that addresses the way in which hydrate formation participates in the gas percolation process is missing here we study experimentally and computationally the mechanics of gas percolation under hydrate forming conditions we uncover a phenomenon crustal fingering and demonstrate how it may control methane gas migration in ocean sediments within the hsz

the early miocene onset of a ventilated circulation regime in the arctic ocean deep water formation in the northern north atlantic ocean and the arctic ocean is a key driver of the global thermohaline circulation and hence also of global climate1 deciphering the history of the circulation regime in the arctic ocean has long been prevented by the lack of data from cores of cenozoic sediments from the arctic s deep sea floor similarly the timing of the opening of a connection between the northern north atlantic and the arctic ocean permitting deep water exchange has been poorly constrained this situation changed when the first drill cores were recovered from the central arctic ocean2 here we use these cores to show that the transition from poorly oxygenated to fully oxygenated ventilated conditions in the arctic ocean occurred during the later part of early miocene times we attribute this pronounced change in ventilation regime to the opening of the fram strait a palaeo geographic and palaeo bathymetric reconstruction of the arctic ocean together with a physical oceanographic analysis of the evolving strait and sill conditions in the fram strait suggests that the arctic ocean went from an oxygen poor lake stage to a transitional estuarine sea phase with variable ventilation and finally to the fully ventilated ocean phase 17 5 myr ago the timing of this palaeo oceanographic change coincides with the onset of the middle miocene climatic optimum3 although it remains unclear if there is a causal relationship between these two events

clay mineral sedimentation in high northern latitude deep sea basins since the middle miocene odp leg 151 naag high resolution clay mineralogical investigations and their comparison with other sedimentological data from odp sites 908 and 909 central fram strait were used to reconstruct the paleoclimate and paleoceanography in the high northern latitudes since the middle miocene ice rafting has probably occurred since 15 ma the comparison of sand sized components and clay mineral distribution demonstrate that both were not delivered by the same transport process the input of the clay fraction is related to transport through sea ice and or oceanic currents a provenance change at 11 2 ma is indicated by variations within clay mineral distribution and increased accumulation rates this is interpreted as a result of an increase in water mass exchange through the fram strait decreases of the smectite to illite and chlorite ratio at site 909 suggest a middle miocene cooling phase between 14 8 and 14 6 ma and a further cooling phase between 10 and 9 ma the intensification of glaciation in the northern hemisphere is documented by an increase of illite and chlorite from 3 4 to 3 3 ma which is synchronous to the onset of major northern hemisphere glaciation as indicated by oxygen isotope data

contourites in the fram strait abstract multichannel seismic reflection profiles from the fram strait show many features that can be attributed to bottom current influence on the sediments by comparison with well known contourite sequences elsewhere a greater than 2 km thick contourite drift with a smooth internal reflection pattern is observed northwest of svalbard the currents here have probably been controlled by local topography we interpret sequences with abundant diffractions in the broader basins to be current related probably deposited during periods of intensified circulation the continental slopes on the svalbard side have fairly continuous sequences whereas the younger sequences on the greenland lower slope onlaps the lowermost one this can be attributed to differences in current regime sediment supply or margin subsidence the contourites of the lower slope in the northeastern part of the strait about 1000 m water depth can be explained by long term influence of the west spitsbergen current but current influenced patterns down to 3000 m water depth are not compatible with the weak deep water circulation observed at present the oldest contourites west of svalbard are estimated to be of late miocene to pliocene age between 10 and 3 ma based on correlation to the dsdp site 344 and inferred basement ages near the present plate boundary hiatuses may be present beneath the contourites the onset of currents may be related to opening of the gateway between greenland and svalbard to climatic cooling and to palaeogeographic changes outside the fram strait contourite deposition has continued through the late neogene and quaternary but vertical changes in the pattern suggest that current intensities have decreased through time

history and geochemistry of a metalliferous sediment core from the mid atlantic ridge at 26 n fourteen thousand years of hydrothermal deposition are recorded in a metalliferous sediment core recovered from the trans atlantic geotraverse tag hydrothermal field on the mid atlantic ridge at 26 n an estimated 26 to 96 of the sediment at this core site is hydrothermally derived as determined from the caco3 al and fe data layers of essentially pure vent precipitates contain 3 caco3 and 0 5 al with high concentrations of fe 43 cu 4 1 zn 1 2 mn 1 1 v 480 ppm pb 175 ppm cd 32 ppm and hg 3 8 ppm sediment accumulation rates vary from 1 to 30 g cm2 1000 y throughout the core a function of the intensity of hydrothermal inputs distinct hydrothermal events are recorded at 6000 and 8500 y b p in layers containing 90 vent derived material vertical metal profiles and interelement relationships in the core result from variable deposition of oxides and sulfides oxidation and dissolution of sulfide phases and scavenging of metals from seawater

potential serpentinization degassing and gas hydrate formation at a young 20 ma sedimented ocean crust of the arctic ocean ridge system 1 global assessment of methane must consider the role of mid ocean ridges fluids from serpentinized mantle and gabbro material are noteworthy on ocean ridges although they are not very well understood only a few sedimented ocean ridges exist worldwide and they may document past and ongoing serpentinization driven migration of gas rich fluids this study is based on two multichannel reflection seismic profiles acquired across a sedimented segment of the ultraslow spreading knipovich ridge offshore nw svalbard seismic data allow suggesting a potential link between inferred areas of serpentinization transfer of carbon from the deep seated host rocks through the sediments above by diapirism and methane capture within the gas hydrate stability zone at the eastern flank of the knipovich ridge the origin of sediment remobilization features can be related to intrusions and the degassing process from mantle serpentinization these disturbances in sediments overlying the oceanic crust can be observed in seismic data and are interpreted as diapirs in shallower sediments at the predicted base of the gas hydrate stability zone the seismic data show a bright spot with all the characteristics of a gas hydrate related bottom simulating reflector bsr such as enhanced reflection amplitude phase reversal relative to the seabed reflection and crosscutting of sedimentary strata the bsr occurs at about 200 ms two way time within a sequence of marine sediments two dimensional concentration models of methane hydrate using the differential effective medium theory predict saturations of up to 26 of methane hydrate in the pore space of sediments in the gas hydrate reservoir

active gas venting through hydrate bearing sediments on the vestnesa ridge offshore w svalbard abstract gas hydrate systems offshore western svalbard are extensive and include the whole vestnesa ridge an elongated sediment drift north of the molloy transform and just east of the molloy ridge one of the shortest segments of the slow spreading north atlantic ridge system the crest of the vestnesa ridge at water depth between 1200 1300 m is pierced with fluid flow features seafloor pockmarks vary in size up to 700 m in diameter pockmarks are generally larger at the eastern start of the vestnesa ridge than at its western termination a recent cruise with r v jan mayen discovered methane flares in the water column above the pockmark field at the onset of the vestnesa ridge over a period of two days at least 3 pockmarks were continuously active and methane flares in the water column reached a height of approximately 800 m it is still unclear what has triggered the increase in gas expulsion from seafloor sediments high resolution 3d seismic data acquired in 2007 and 2010 show significant differences of the subseafloor expression of these fluid leakage systems at the western end of the vestnesa ridge sub seafloor fluid flow features resemble well described chimney structures however the seismic expression of the active fluid flow features is much broader much more chaotic dome shaped and is not very similar to a typical chimney structure the vestnesa ridge gas hydrate and free gas system occurs within few kilometers of a mid oceanic ridge and transform fault which makes this gas hydrate system unique on earth the close proximity to the spreading center and its hydrothermal circulation system affects the dynamics of the gas hydrate and free gas system the high heat flow together with the high tectonic activity of this region a thick sedimentary cover a shallow maturation window and an accelerated rate of biogenic and thermogenic gas production cause substantial disturbance to the free gas system leading to high variability in gas supply gas migration and gas hydrate build up and dissociation

thermogenic methane injection via bubble transport into the upper arctic ocean from the hydrate charged vestnesa ridge svalbard we use new gas hydrate geochemistry analyses echosounder data and three dimensional p cable seismic data to study a gas hydrate and free gas system in 1200 m water depth at the vestnesa ridge offshore nw svalbard geochemical measurements of gas from hydrates collected at the ridge revealed a thermogenic source the presence of thermogenic gas and temperatures of similar to 3 3 degrees c result in a shallow top of the hydrate stability zone thsz at similar to 340 m below sea level mbsl therefore hydrate skinned gas bubbles which inhibit gas dissolution processes are thermodynamically stable to this shallow water depth this was confirmed by hydroacoustic observations of flares in 2010 and 2012 reaching water depths between 210 and 480 mbsl at the seafloor bubbles are released from acoustically transparent zones in the seismic data which we interpret as regions where free gas is migrating through the hydrate stability zone hsz these intrusions result in vertical variations in the base of the hsz bhsz of up to similar to 150 m possibly making the shallow hydrate reservoir more susceptible to warming such arctic gas hydrate and free gas systems are important because of their potential role in climate change and in fueling marine life but remain largely understudied due to limited data coverage in seasonally ice covered arctic environments

the paleocene eocene thermal maximum petm in svalbard clay mineral and geochemical signals abstract for the first time the paleocene eocene thermal maximum petm interval has been identified in drillcores and field outcrops from the paleogene central basin in svalbard based on mineralogical and geochemical information grumantbyen and frysjaodden formations a more than 300 m thick paleogene interval representing deltaic delta influenced marine shelf and deep water slope environments the petm has been recognized in the deepest and most distal deposits in the lower parts of the frysjaodden formation here this global event is displayed in clay mineralogical distributions as significantly increased kaolinite abundances reflecting a period with intensified chemical weathering in the land areas surrounding this paleogene basin the period was characterized by dominantly reducing sea floor conditions as seen in the th u distribution and the well developed parallel lamination in the pyrite rich shales all to be expected during an interval with increased temperature and precipitation

bottom simulating reflector dynamics at arctic thermogenic gas provinces an example from vestnesa ridge offshore west svalbard the vestnesa ridge comprises a 100 km long sediment drift located between the western continental slope of svalbard and the arctic mid ocean ridges it hosts a deep water 1000 m gas hydrate and associated seafloor seepage system near seafloor headspace gas compositions and its methane carbon isotopic signature along the ridge indicate a predominance of thermogenic gas sources feeding the system prediction of the base of the gas hydrate stability zone for theoretical pressure and temperature conditions and measured gas compositions results in an unusual underestimation of the observed bottom simulating reflector bsr depth the bsr is up to 60 m deeper than predicted for pure methane and measured gas compositions with 99 methane models for measured gas compositions with 4 higher order hydrocarbons result in a better bsr approximation however the bsr remains 20 m deeper than predicted in a region without active seepage a bsr deeper than predicted is primarily explained by unexpected spatial variations in the geothermal gradient and by larger amounts of thermogenic gas at the base of the gas hydrate stability zone hydrates containing higher order hydrocarbons form at greater depths and higher temperatures and contribute with larger amounts of carbons than pure methane hydrates in thermogenic provinces this may imply a significant upward revision up to 50 in the case of vestnesa ridge of the amount of carbon in gas hydrates

evaluation and modelling of tertiary source rocks in the central arctic ocean abstract with the recently recovered organic rich sediments of early tertiary age from the lomonosov ridge by the integrated ocean drilling program iodp expedition 302 the first data collection directly from source rocks of the central basins of the arctic ocean is now available using the results of seismic interpretations and published sedimentological and organic geochemical data from expedition 302 the framework for the first quantitative assessment of source rock quality and distribution of the palaeogene sediments was modelled in the central arctic ocean the modelling results suggest that an approximately 100 m thick early to middle eocene sedimentary sequence of good to very good source rocks exists along a 75 km long transect across the lomonosov ridge in situ generation of hydrocarbons is unlikely because the overburden 200 250 m and consequently the thermal maturity are too low burial history and thermal modelling reveal that an additional overburden of at least 1000 m is necessary to start hydrocarbon generation along the ridge however source rock modelling results show that good source rock potential may exist in correlative units in the adjacent amundsen basin simulated organic carbon contents of 1 5 5 coupled with an overburden of 1000 1200 m and heat flow anomalies 117 and 100 mw m 2 due to the vicinity to the gakkel ridge spreading centre indicate that necessary conditions for hydrocarbon expulsion are already reached and point to viability of a potential petroleum system our results support the hypothesis that deposition of a potentially good hydrocarbon source rock occurred across the entire arctic basin and adjacent margins during the early tertiary

a new 6 myr stratigraphic framework for the atlantic arctic gateway abstract a comprehensive stratigraphic framework for the atlantic arctic gateway has been established for the last 6 myr on the yermak plateau nw svalbard based on new paleomagnetic and biostratigraphic sampling and correlation of high resolution seismic data between ocean drilling program odp holes 911a 910c and 912a the new results indicate a late miocene age for the base of both holes 911a and 910c providing the first complete late neogene record for the marginal arctic ocean and extending the previously published age model by several million years during the late miocene pleistocene the southern yermak plateau was dominated by contourite deposition from the intensification of the northern hemisphere glaciation at 2 7 ma glacial fans from nw svalbard prograded onto the southernmost yermak plateau this indicates that the ice sheet on nw svalbard reached the shelf break at 2 7 ma much earlier than on the western barents sea svalbard margin 1 5 ma simultaneous with the first shelf break glaciation on the western barents sea svalbard margin at 1 5 ma we observe the first signs of extensive glacial erosion on the yermak plateau indicating a regional glacial intensification at this time for the whole barents sea svalbard region our results agree well with the widening deepening of the fram strait and the opening of the atlantic arctic gateway during the middle miocene