signature of the gold cove event 10 2 ka in the labrador sea abstract one of the least known catastrophic meltwater and sediment release events of the laurentide ice sheet during the early holocene is the so called gold cove proglacial lake outbursts a drainage event through the hudson strait this event may have disturbed circulation in the labrador sea by releasing freshwater here we report data from four sediment cores and re analysis of six published records spatially covering 2000 km from the mouth of hudson strait to the northeastern sohm abyssal plain abundant detrital carbonate dc and less positive 18o values in neogloboquadrina pachyderma sinistral suggest a short lived meltwater event in the hudson strait region this discharge transported detrital carbonate rich sediment and shallow water benthic forams southward along the labrador margin mixing with the north atlantic current near the grand banks sediments associated with this event were guided through the deep labrador sea from the mouth of hudson strait and the northwest atlantic mid ocean channel namoc to the sohm abyssal plain furthermore we report less positive 13c values in the epibenthic foram cibicidoides wuellerstorfi from the southern labrador sea during this event our twenty one 14c ams dates in addition to earlier published radiocarbon dates from the labrador margin suggest that this dc event was coeval with the gold cove proglacial lake outbursts related to re advance of the laurentide ice sheet

holocene and pleistocene dissolution cycles in deep sea cores of baffin bay and davis strait palaeoceano graphic implications abstract calcium carbonate dissolution has been studied in several grab samples and piston cores from baffin bay and davis strait ranging in water depth from 200 to 2300 m the intensity of dissolution was determined from examining 1 the ratio of arenaceous to calcareous benthonic foraminifera 2 the ratio of benthonic to planktonic foraminifera 3 the relationships between the dissolution susceptible and dissolution resistant foraminifera 4 the degree of foraminiferal test fragmentation and 5 the relationships between plankton tows and the fauna in the surface sediments all core tops and grab samples from baffin bay surface sediments below 600 900 m water depth demonstrated intense dissolution of calcium carbonate sediments below 900 m were biogenic carbonate free indicating 100 foraminiferal loss due to dissolution possible causes of substantial undersaturation in calcium carbonate of baffin bay bottom water are very low temperatures and higher concentrations of carbon dioxide all cores also demonstrated intense dissolution during interglacial or interstadial isotope stages 1 3 5 7 and 9 similarities in planktonic foraminiferal assemblages suggested the presence of similar bottom water masses during these periods the preservation state of biogenic carbonate debris in glacial isotope stages 2 4 6 8 and 10 is similar to the assemblage found in the water at present

origin of oil and bitumen in the late devonian siljan impact structure central sweden organic geochemical assessment of seep oil from the upper ordovician hirnantian boda limestone and solid bitumens from the middle ordovician darriwilian limestone formations in the siljan crater sweden indicates their generation primarily from peak oil window maturity clay rich marine source rocks that contained aquatic algal organic matter and were deposited in an anoxic environment biomarkers indicate some significant differences between the seep oil and solid bitumens and their alteration by moderate to severe biodegradation the solberga quarry seep oil from the boda limestone and solberga 1 solid bitumen from the skarlov seby folkslunda limestone equivalents do not show signs of mixing and the similarity in their biomarker distributions indicates a genetic relationship however solid bitumens recovered from cavities in the underlying segerstad and holen limestones were derived predominantly from clay rich source rocks that contained mixed marine and lacustrine algal organic matter and minor inputs of prokaryotic organic matter possibly from thin beds of calcareous rocks interbedded within the main clay rich source rocks it is inferred that the siljan crater seep oil and solid bitumens were generated from the organic rich upper ordovician fjacka shale a source rock for economic accumulation of oil in the eastern baltic region and or from silurian shale units the presence of various compounds of known biological origin and existence of organic rich fjacka shale silurian shale units are consistent with the biogenic origin of siljan crater petroleum although these seep oil and solid bitumens were generated at peak oil window maturities the intense heat generated by meteorite impact caused secondary reactions resulting in unusual distributions of maturity sensitive aromatic hydrocarbon isomers and conflicting molecular maturities crown copyright c 2014 published by elsevier ltd all rights reserved less

petroleum charge history in the lunnan low uplift tarim basin china evidence from oil bearing fluid inclusions abstract the petroleum charge history in the lunnan low uplift tarim basin china was investigated by comparing the geochemical characteristics of fluid inclusion fi oils from ordovician and triassic reservoirs with crude oils from stratigraphically different reservoirs quantitative grain fluorescence qgf and total scanning fluorescence tsf were used to screen the reservoir samples so as to identify suitable samples for molecular composition of inclusion mci analysis all of the samples contain c 30 n propylcholestanes diagnostic of marine source rocks the ordovician hosted fi oils differ from the triassic hosted fi oils having higher relative abundances of c 19 tricyclic terpane c 24 tetracyclic terpane and rearranged hopanes ts and c 29 ts and higher pr ph ratios while the triassic hosted fi oils have lower pr ph ratios and higher relative abundances of c 23 tricyclic terpane arylisoprenoids 25 norhopanes and c 35 homohopane several of the crude oils are similar to the triassic hosted fi oils based on the geochemical characteristics of the fi and crude oils combined with information on the burial history of the area at least two petroleum charge episodes can be distinguished in the lunnan low uplift an early charge represented by the ordovician hosted fi oils was biodegraded as evidenced by the presence of 25 norhopanes in the triassic hosted fi oils and crude oils but not in the ordovician hosted fi oils ordovician hosted fi oils provide the only evidence for oil generated from cambrian lower ordovician source rocks triassic hosted fi oils and crude oils in the ordovician carboniferous and triassic reservoirs are mixtures of biodegraded oil from an early charge episode and more mature oil from later charge

is the central arctic ocean a sediment starved basin abstract numerous short sediment cores have been retrieved from the central arctic ocean many of which have been assigned sedimentation rates on the order of mm ka implying that the arctic basin was starved of sediments during plio pleistocene times a review of both shorter term sedimentation rates through analysis of available sediment core data and longer term sedimentation rates through estimates of total sediment thickness and bedrock age suggests that cm ka scale rates are pervasive in the central arctic ocean this is not surprising considering the physiographic setting of the arctic ocean being a small land locked basin since its initial opening during early cretaceous times we thus conclude that the central arctic ocean has not been a sediment starved basin either during plio pleistocene times or during pre pliocene times rigorous chronstratigraphic analysis permits correlation of sediment cores over a distance of 2600 km from the northwestern amerasia basin to the northwestern eurasia basin via the lomonosov ridge using paleomagnetic biostratigraphic and cyclostratigraphic data

origin nature and world climate effect of arctic ocean ice cover during the cenozoic an open water arctic ocean changed to the modern permanently ice covered condition significant world climate modification accompanied this change but the precise role of the arctic ocean in major pleistocene climate events is controversial the present ice cover averages 3 m thickness but there are theories that during the pleistocene it was antarctic like several thousand metres thick the time of origin of the ice cover is placed as young as 0 7 myr ago and as old as the middle miocene any theory concerned with origin nature and climatic response of the arctic ice cover must consider the ocean s sediment record

isotope stratigraphy sedimentation rates deep circulation and carbonate events in the labrador sea during the last 200 ka high resolution stable isotope and accelerator mass spectrometry 14c measurements in 25 box and piston cores from the labrador sea allow the reconstruction of major paleoceanographical changes during the last 200 ka in this basin and also document the links between the interior of the laurentide ice sheet and the north atlantic ocean during this interval two deep circulation regimes are indicated by contrasting sedimentation rates on the slopes i the modern situation is characterized by a gyre of the north atlantic deep water nadw components into the basin which is responsible for the high energy western boundary undercurrent this regime also prevailed during the former true interglacials and possibly during shorter warm intervals e g bolling allerod ii a more frequent nadw free situation during glacial and interstadial intervals is marked by the presence of a vertically homogeneous water mass in the basin sedimentological records also indicate that carbonate events i e pulses of

geosynthesis of dibenzothiophene and alkyl dibenzothiophenes in crude oils and sediments by carbon catalysis sediment extracts and crude oils have been shown to contain methyl substituted biphenyls and dibenzothiophenes with isomer distributions suggesting a geochemical relationship between the two compound classes laboratory simulation experiments have shown that carbon catalyses the reaction between surface adsorbed sulfur and biphenyl to form dibenzothiophene similarly the methyl substituted biphenyls reacted to yield corresponding methyl dibenzothiophenes we suggest that the widespread distribution of dibenzothiophene and alkylated dibenzothiophenes in sediments and crude oils is the result of a catalytic reaction of biphenyl ring systems and surface adsorbed sulfur on the surface of carbonaceous material

the siljan deep well helium isotope results the siljan ring impact structure in sweden is the scene of current deep drilling exploration for methane trapped in a crustal reservoir the initial hole drilled to a depth of 6100 m through precambrian granite has been augmented by three branching side track holes beginning at 4700 m that have extended the drilled depth to 6957 m forty four gas samples extracted from the circulating drilling fluid have been analyzed for he ne and 3he4he ratios granite chips recovered from the well and eight natural gas seeps from the siljan ring and other localities in sweden have also been analyzed to provide ambient helium comparisons the 3he4he ratios in the well gases are mixtures of three components 1 atmospheric helium dissolved in recirculated drilling fluid 2 carrier he used for well site gas chromatography that contaminated some of the samples taken for he isotope analysis and 3 a crustal radiogenic component from the granite with a 3he4he ratio of 0 015 times the atmospheric ratio 1 40 10 6 although helium concentrations are generally low throughout the hole up to 4800 ppm hydrofracturing at the termination of drilling in side track hole 3 yielded gas with 23 100 ppm of helium and the crustal isotope ratio for siljan granite fluids isotope ratios in the gas seeps are in agreement with the deep crustal value but the granite itself has lower 3he4he ratios due to preferential extraction of 3he from li bearing micas no evidence of a mantle helium component is observed in the isotopic data an upper limit calculation based on the difference between he isotope ratios in the granite and in the formation waters gives a maximum of 0 15 of more helium in the well gas helium

shock barometry of the siljan impact structure sweden the siljan impact structure in sweden is the largest confirmed impact structure in western europe despite this the structure has been poorly studied in the past and detailed studies of shock metamorphic features in the target lithologies are missing here we present the results of a detailed systematic search for shock metamorphic features in quartz grains from 73 sampled localities at siljan at 21 localities from an area approximately 20 km in diameter located centrally in the structure the orientations of 2851 planar deformation feature sets in 1179 quartz grains were measured observations of shatter cones outside of the zone with shocked quartz extend the total shocked area to approximately 30 km in diameter the most strongly shocked samples recording pressures of up to 20 gpa occur at the very central part of the structure and locally in these samples higher pressures causing melting conditions in the affected rocks were reached pressures recorded in the studied samples decrease outwards from the center of the structure forming roughly circular envelopes around the proposed shock center based on the distribution pattern of shocked quartz at siljan the original transient cavity can be estimated at approximately 3238 km in diameter after correcting for erosion we conclude that the original rim to rim diameter of the siljan crater was somewhere in the size range 5090 km less

hydrocarbons and inorganic gases in the gravberg 1 well siljan ring sweden abstract hydrocarbons and inorganic gases have been analyzed in the drilling fluid of the gravberg 1 well siljan ring sweden which represents the first commercial exploration for mantle derived methane hydrocarbons detected to a depth of 6 6 km have been in trace amounts dissolved in the drilling fluid low concentrations of hydrocarbons from granite intervals are rich in unsaturated hydrocarbons and may result from abiogenic synthesis from inorganic carbon species in the granite or may be synthesized during drilling operations from organic precursors in the drilling fluid below 5 km higher hydrocarbon concentrations in granite intervals are correlated with two different lubricants added to the drilling fluid these gases are characterized by distinctive suites of hydrocarbons especially in the c4 c6 range the effects of hydrocarbon production from these and other additives are particularly pronounced in this well due to the low concentration of indigenous hydrocarbons the highest concentrations of methane were enriched in 13c 13 c 26 and were associated with several dolerite intrusions in the granite rocks this methane was present in both a core and cuttings and is similar to methane isolated from dolerite in a well recently drilled in massachusetts u s a the methane may have a deep upper mantle origin or may be a product of abiogenic synthesis in crustal rocks significant quantities of h2 and he occurring deeper than 6 km appear to have a low temperature crustal origin there is no evidence of significant amounts of upper mantle he in the gravberg 1 gases

understanding potential pressure regimes in undrilled labrador deep water by use of global analogues in recent years new deepwater seismic based exploration work has resulted in the revision of existing basin boundaries and identification of new potentially oil bearing basins in the deepwater labrador region the petroleum potential in this deepwater area has also been encouraged by the identification of slick and seepage locations using 2d seismic data and satellite imagery the importance is that surface slicks possibly are related to subsurface hydrocarbon migration thus all recent data collated together show strong evidence for an active petroleum system in deep water many of the wells in shallow water have been drilled with low mud weights suggestive of low pore pressures however where thick shale packages are present significant overpressure is observed by significant kicks clearly there is a close association between thick and deep shale packages and high pore pressure thus one of the key risks in developing the deepwater potential is to understand the pressure regime the success of this approach has been highlighted recently by successful discoveries such as

geophysical well log motifs lithology stratigraphical aspects and correlation of the ordovician succession in the swedish part of the baltic basin the geophysical characteristics of the carbonate dominated ordovician succession is described using wire line logging data from exploration wells located within the swedish part of the baltic basin both offshore and from the island of gotland the petrophysical properties and log motifs are compared and correlated with the lithology of cores from the hamra 10 skals 1 and grotlingbo 1 wells on southern gotland the 80 125 m thick ordovician succession is divided into five log stratigraphic units o a o e which are correlated throughout the study area the proposed log stratigraphy and wire line log characteristics are evaluated and compared with the established ordovician stratigraphy from the adjacent areas of oland ostergotland and south estonia the newly established log stratigraphy is also linked to the existing seismic stratigraphic framework for the study area and exemplified with a selection of interpreted seismic type sections from gotland and the south baltic sea the presented characterization division and correlation provide a basis for understanding the lateral and vertical variation of the petrophysical properties which are essential in assessing the sealing capacity of the ordovician succession in conjunction with storage of co 2 in the underlying cambrian sandstone reservoir

decorrugation and removal of directional trends of magnetic fields by the wavelet transform application to archaeological areas the problem of removing directional trends frequently occurs in the processing of magnetic data and also in the subsequent steps of data interpretation the so called corrugations are typical directional trends occurring in levelled data which may be removed in several ways classical techniques are based on high pass filtering of the data and successively filtering these transformed data with directional cosine filters other linear features are due to real sources such as pipelines in shallow surveys or dike swarms in regional surveys they should nevertheless be considered as noise due to the fact that their effect is strong and tends to hide the field features related to structures of more interest we deal with both kinds of problem presenting the results of a study in an archaeological area of southern italy decorrugation of magnetic field anomalies is performed using a method based on the excellent space frequency localization properties of wavelet bases allowing a very sharp filtering of the field along a selected direction we compare this technique with the classical one in a synthetic case and find that the wavelet decorrugation is simpler and produces low distortion maps besides the field decorrugation the wavelet approach was also shown to be useful in the subsequent enhancement of the measured field in fact we show that the wavelet analysis offers a unique framework where various filtering problems directional isotropic global or local as well may be easily solved as regards the archaeological case strong noisy effects from elongated sources pipelines were successfully removed in a sharp and local way

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

magnetostratigraphic results from impact crater lake el gygytgyn northeastern siberia a 300 kyr long high resolution terrestrial palaeoclimatic record from the arctic summary a 12 7 m long sedimentary record recovered from lake el gygytgyn located in a meteorite impact crater created 3 6 ma in late cretaceous igneous rocks on chukotka peninsula northeast siberia has been analysed for its palaeo and rock magnetic properties continuous high resolution 1 mm measurements of magnetic susceptibility yielded successions of pronounced lows and highs analyses of the rock magnetic properties by low and high temperature runs of magnetic susceptibility determination of hysteresis parameters as well as irm acquisition experiments yielded a dominance of psd pseudo single domain magnetite in intervals of high magnetic susceptibility whereas due to selective magnetite dissolution associated with anoxic lake water and or pore water conditions during times of enhanced deposition of organic matter haematite dominates within low susceptibility intervals in terms of mass percentage here however magnetic properties are still dominated by magnetite five ams accelerator mass spectromentry 14 c ages eight irsl infrared stimulated luminescense ages together with preliminary pollen data suggest that variations in magnetite content reflect climatic variability of the last 300 ka with low high susceptibilities representing cold warm climates this pattern caused by a complex system of deposition preservation or decomposition of organic matter and or magnetic minerals in turn can be correlated in detail to global climate archives such as the oxygen isotope records from greenland ice cores and marine sediments respectively thus the sedimentary sequence recovered from lake el gygytgyn represents the longest continuous terrestrial climate record now available from the arctic

lower paleozoic petroleum from southern scandinavia implications to a paleozoic petroleum system offshore southern norway petroleum occurring in lower paleozoic rocks is known to be present in southern scandinavia northern poland and the baltic states oil has been produced from lower paleozoic reservoirs in sweden northern poland and the baltic countries lithuania latvia and the russian exclave area of kaliningrad the sources for this petroleum are marine organic rich muds deposited in the cambrian ordovician and silurian this article concerns geochemical analysis of oils extracted from sandstones and carbonates from the norwegian oslo graben rift and locations in sweden and describes in addition insoluble bitumens collected from lower paleozoic rocks in the oslo graben locations in sweden and from upper paleozoic rocks in a norwegian north sea well the oils in this study have several geochemical characteristics shared with oils from the baltic states and northern poland and the maturities of the oils are in general low the occurrences of bitumen and migrated petroleum in the oslo graben lead us to believe that petroleum also has been generated and expelled in the related offshore skagerrak graben indicating that a paleozoic petroleum system operated in the skagerrak graben this potential petroleum system has not suffered the degree of uplift erosion and destruction of reservoirs experienced by the onshore oslo graben making preservation of any petroleum accumulations in the skagerrak graben more plausible although speculative these considerations should interest anyone involved in petroleum exploration in the skagerrak and the norwegian danish basin not the least because of the proximity of skagerrak and major energy markets in europe

relationship between rank and composition of aromatic hydrocarbons for coals of different origins distributions of di and tricyclic aromatics were determined for upper carboniferous to oligocene coals of various origins in addition to upper carboniferous ruhr coals wealden lower creataceous coals from north west germany lower cretaceous coals from western canada and tertiary coals from japan and colombia were studied the coals ranged from sub bituminous to anthracite in rank and showed vitrinite reflectance from 0 4 to 4 9 rm the previously established relationship between the rank of coal in terms of vitrinite reflectance and the distribution patterns of individual aromatic hydrocarbon isomers has been verified and refined it is demonstrated how the above relationships can be used to calculate vitrinite reflectance from the methylphenanthrene index mpi 1 the chemical rank levels of coals can now be defined in terms of the calculated vitrinite reflectance rc

quaternary dinoflagellate cysts in the arctic ocean potential and limitations for stratigraphy and paleoenvironmental reconstructions abstract the arctic ocean is a siliciclastic depositional environment which lacks any rock forming biogenic calcareous and siliceous components during large parts of its quaternary history these hemipelagic sediments are nevertheless suitable for the study of organic walled microfossils of which the fossil remains of dinoflagellates dinoflagellate cysts are the most important group dinoflagellate cysts have become an important tool in paleoceanography of the high northern latitudes but their potential for quaternary biostratigraphy has remained largely unexplored dinoflagellate cysts are the dominant marine palynomorph group which is more continuously present in the marginal seas e g barents sea bering sea than in the arctic ocean itself throughout the quaternary most species have long stratigraphic ranges are temporary absent and show abundance variations on glacial interglacial timescales of the more than 30 taxa recorded only habibacysta tectata and filisphaera filifera became extinct in the pleistocene the highest persistent occurrence of h tectata at ca 2 0 ma and the top of f filifera acme at ca 1 8 ma can be used for supra regional stratigraphic correlation between the arctic ocean and adjacent basins these events corroborate a slow sedimentation rate model for the quaternary section on the central lomonosov ridge but a combination of different methods will have to be applied to provide a detailed chronostratigraphy the occurrence of cysts of phototrophic dinoflagellates in certain stratigraphic intervals on lomonosov ridge supports published evidence of episodic opening of the multiyear arctic sea ice cover during the quaternary probably related to a stronger inflow of atlantic water this contradicts the hypothesis of a permanently ice covered central arctic ocean in the quaternary

baffin bay present day analog of the central arctic during late pliocene to mid pleistocene time olive green and olive gray glacial marine sandy clays with rare planktonic foraminifera dominated by a euryhaline and eurytherm species blanket the northern baffin bay floor today these sediments are analogous to those of the central arctic basin deposited between 3 and 0 9 m y ago while today the central arctic is covered with perennial sea ice during part of the gauss and most of the matuyama epochs unit ii hydrological conditions were very similar to those in northern baffin bay today generally ice free year round these data lend support to the hypothesis of an ice free arctic during late pliocene to mid pleistocene time

pollen distribution in recent marine sediments eastern canada analysis of 90 samples from coastal and continental shelf areas off eastern canada between 42 and 69 n shows that quaternary pollen and spores are present in recent marine muds throughout this region pollen and spore concentrations range from 50 000 to 100 grains per cm3 and they decrease both offshore as a function of distance from vegetation sources and northwards as a function of lower vegetation density north of the summer arctic frontal zone isopercentage contours show that maximum relative abundances of most palynomorphs occur in marine sediments adjacent to their regions of highest vegetation representation onshore however pinus and picea pollen tend to increase in percentage abundance with distance offshore presence of these tree pollen in marine sediments off baffin island implies that wind transport is an important pathway by which bisaccate pollen types enter the ocean in addition to fluvial transport q mode factor analysis shows that four major factors account for 89 of the variance amo

late cretaceous early tertiary palaeoclimates of northern high latitudes a quantitative view analyses of plant community structure vegetational and leaf physiognomy and growth rings and vascular systems in wood provide qualitative and quantitative data that can be combined to define non marine palaeoclimatic parameters with better resolution than is available from other principally sedimentological methods application of these techniques to cenomanian through paleocene floras from high palaeolatitudes 75 85 n indicates a polar light regime similar to that of the present plant data suggests cenomanian sea level mean annual air temperatures mats of 10 c and mats of 13 c 5 c and 6 7 c in the coniacian maastrichtian and paleocene respectively evapotranspirational stresses at sea level were low and precipitation was in most part uniform throughout the growing season in the cenomanian with possible seasonal drying occurring by the maastrichtian maastrichtian winter freezing was likely but periglacial conditions did not exist at sea level permanent ice was likely above 1700 m at 75 n in the cenomanian and above 1000 m at 85 n in the maastrichtian these near polar data provide critical constraints on global models of late cretaceous to early tertiary climates

multiple deglaciations of the hudson bay lowlands canada since deposition of the missinaibi last integlacial formation abstract the stratigraphic record in the james and hudson bay lowlands indicates that the sequence of glacial events at the geographical center of the 12 6 10 6 km 2 laurentide ice sheet may have been more complex than hitherto imagined isoleucine epimerization ratios of in situ and transported shells recovered from till and associated marine and fluvial sediments cluster into at least 4 discrete groups two alternative explanations of the data are offered of which we strongly favor the first hypothesis 1 setting the age of the last interglacial marine incursion the bell sea at 130 000 yr b p results in a long term average diagenetic temperature for the lowlands of 0 6 c using this temperature enables us to predict the age of shells intermediate in age between the last interglaciation and the incursion of the tyrrell sea 8000 yr ago between these two interglacial marine inundations hudson bay is predicted to have been free of ice along its southern shore about 35 000 75 000 and 105 000 yr ago based on amino acid ratios from shells occurring as erratics in several superimposed tills and fluvial sediments these results suggest 1 that traditional concepts of ice sheet build up and decay must be reexamined 2 that high sea levels may have occurred during the wisconsin glaciation and 3 that a critical reappraisal is required of the open ocean 18 o record as a simple indicator of global ice volume an alternative hypothesis 2 is also examined it is based on the assumption that the 35 000 yr old deposits calculated on the basis of hypothesis 1 date from the last interglaciation this in effect indicates that the missinaibi formation commonly accepted as sediments of the last interglaciation are about 500 000 yr old and that the effective diagenetic temperature in the lowlands during approximately the last 130 000 yr has been close to 6 c we argue for rejection of this alternative hypothesis

optically stimulated luminescence dating supports central arctic ocean cm scale sedimentation rates 1 this paper presents new results from optically stimulated luminescence osl dating on a sediment core raised from the crest of the lomonosov ridge in the central arctic ocean there has been much debate about dating sediment cores from the central arctic ocean and by using an independent absolute dating technique we aim to test whether or not relatively fast cm scale ka sedimentation rates were typical of arctic s pleistocene depositional mode on the basis of mainly paleomagnetic reversal stratigraphy many previous studies suggest mm scale ka sedimentation rates a common feature in these studies is that the first down core paleomagnetic negative inclination is consistently interpreted as the brunhes matuyama boundary at about 780 ka our osl dating results indicate that this assumption is not generally valid and that the first encountered negative inclination represents younger age excursions within the brunhes chron implying reinterpretation of many published core studies where paleoenvironmental reconstructions have been made for the central arctic ocean our dating results furthermore corroborates a correlation of the uppermost 2 3 m of the lomonosov ridge cores to a well dated core located off the barents kara sea margin that in turn is correlated to cores in the fram strait valuable information on the paleoceanographical evolution in the arctic ocean from mis 6 to the holocene is given through this correlation of records from the central arctic ocean to records off the eurasian continental margin

oceanic mechanisms for amplification of the 23 000 year ice volume cycle situated adjacent to the largest northern hemispher ice sheets of the ice ages the mid latitude north atlantic ocean has an important role in the earth s climate history it provides a significant local source of moisture for the atmosphere and adjacent continents forms a corridor that guides moisture bearing storms northward from low latitudes and at times makes direct contact along its shorelines with continental ice masses evidence of major ice ocean air interactions involving the north atlantic during the last 250 000 years is summarized outflow of icebergs and meltwater initially driven by summer insolation over the ice sheets affects midlatitude ocean temperatures summer heat storage winter sea ice extent and global sea level these oceanic responses in turn influence the winter moisture flux back to the ice sheets as well as ablation of land ice by calving spectral data indicate that the oceanic moisture and sea level feedbacks in part controlled by glacial melt products amplify milankovitch insolation forcing of the volumetrically dominant mid latitude ice sheets at the 23 000 year precessional cycle

palynostratigraphy and chronostratigraphy of baffin bay deep sea cores climatostratigraphic implications abstract palynostratigraphic considerations and 14c dates ams accelerator mass spectrometry on foraminifera samples from piston cores suggest sedimentation rates as high as ca 8 11 cm ka in deep baffin bay during the late pleistocene throughout this interval baffin bay experiences rigorous conditions and probably the extension of a dense sea ice cover unfavourable to phytoplanktonic productivity the dinocyst microflora indicates only brief episodes of higher productivity related to arctic conditions and to moderately low salinites ca 30 31 the abundance of reworked pre quaternary palynomorphs in the deposits is interpreted as a response to glacial and glacio marine activity in the northernmost areas surrounding baffin bay the dinocyst stratigraphy spanning approximately over the last ice age ca 100 ka reveals that baffin bay constituted a confined basin isolated from the north atlantic ocean prior to the present interglacial

hydrocarbon migration and entrapment in the baltic syneclise abstract based on the data concerning the type quantity and thermal maturity of the organic matter several petroleum source rock complexes have been distinguished in the paleozoic succession of the baltic syneclise maturity of organic matter varies from immature in the ne part of the baltic syneclise to peak generation in the central part and postmature stage towards the teisseyre tornquist zone the isolated local postmature areas are most likely related to the occurrence of sills the oils of the baltic region have moderate gravities 26 42 api that decrease with present reservoir depth reflecting the thermal maturity quantitative modeling of the oil and gas migration and entrapment was performed by the means of the 3d software semi this confirmed that oil generation and migration was most intense during late silurian early devonian time based on modeling the major cambrian traps accumulated oil expelled from different stratigraphic source rock units the cambrian ordovician and silurian organic rich shales

organic geochemical characterisation of depositional palaeoenvironments of source rocks and oils in brazilian marginal basins abstract an investigation of bulk isotopic and molecular features of a wide selection of source rocks and oils from brazilian marginal basins ranging from lower cretaceous to tertiary in age provides a number of organic geochemical criteria that characterise and distinguish their depositional palaeo environments the methods employed include evaluation of organic carbon contents rock eval pyrolysis vitrinite reflectance measurements determination of carbon isotope ratios elemental and visual kerogen analysis assessment of oils and solvent extracts by liquid and gas chromatography and quantitative biological marker investigations using gc ms for aliphatic hydrocarbons and uv vis spectrophotometry for metalloporphyrins selected data were evaluated using principal component analysis the results enable the recognition and differentiation of seven depositional regimes lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate marine deltaic marine highly anoxic with a predominance of calcareous mudstone lithology and marine anoxic with predominance of siliciclastic lithology diagnostic features in the biological markers from these depositional environments include the carbon number distributions of n alkanes pristane phytane ratios absolute concentrations of carotane higher acyclic isoprenoids c 30 hopane and steranes and the abundance of the latter relative to 4 methylsteranes the occurrence and abundance of particular biological markers such as gammacerane tricyclic and tetracyclic terpanes 18 h oleanane 28 30 bisnorhopane and 25 28 30 trisnorhopane and the relative abundances of nickel and vanadyl porphyrins

development of oil formation theories and their importance for peak oil this paper reviews the historical development of both biogenic and non biogenic petroleum formation it also examines the recent claim that the so called abiotic oil formation theory undermines t

the occurrence of petroleum in sedimentary rocks of the meteor impact crater at lake siljan sweden abstract during the devonian large parts of sweden were covered by sandstones shales and limestones of precambrian to upper silurian age at the end of the devonian 360 m yr b p a meter struck causing a large impact crater at lake siljan with a diameter of 50 60 km annular depression was formed which is still preserved today this depression contains undisturbed as well as tilted paleozoic rocks numerous sedimentary occurrences of asphalts and seep oils are reported from quarries in the sedimentary rocks and some shallow boreholes contain a thin layer of free oil floatingon arterian groundwater a representative set of paleozoic shales and limestones found in the siljanarea was analyzed with respect to organic richness type and thermal maturity three intervals of organic rich and oil prone source rocks 2 10 toc were distinguished and extracts of these rocks were geomically compared with the seep oils using stable carbon isotopes and terpenoid biomarkers even though these low maturity oils were altered by biodegradation a correlation with ordovician source rocks was established all the analyzed organic rich rocks are on the verge of oil generation as determined by 20s 20r 5 h c 29 sterane ratios in addition burial history indicates insufficient overburden available for oil generation the seep oils however are more mature and within the oil window yet below peak generation levels thus it appears that the heat effect of meteor impact locally matured the source rock allowing for geologically instantaneous hydrocarbon generation and expulsion resulting in the formation of seep oils

application of aromatic compounds as maturity indicators in source rocks and crude oils concentration ratios of aromatic compounds such as naphthalenes phenanthrenes and dibenzothiophenes are at present attracting increasing attention as maturity indicators in sedimentary rocks and crude oils generally these indicators rely either on an increase with maturity in the degree of alkylation of a given parent compound or a shift in the isomer distribution of alkyl aromatic homologues towards thermally more stable isomers a combination of both concepts in the methylphenanthrene index mpi resulted in an excellent maturity parameter as demonstrated for rock extracts by an improved correlation with mean vitrinite reflectance rm between 0 65 and 1 4 i e in the zone of oil formation in cases that rm measurements were ambiguous this empirical relationship has proved useful in the calculation of theoretical vitrinite reflectance rc values from the mpi on the other hand for potential petroleum source rocks reaching maturity at relatively low temperatures the influence of the organic matter type on the aromatic distributions cannot be neglected consequently organic facies effects should be taken into account in the interpretation of aromatic distributions of such source rocks and related crude oils since the impact of the organic facies is strongly reduced with increasing maturity aromatic maturity parameters are particularly useful in the maturity evaluation of post mature crude oils and condensates in contrast to biological markers substantially higher concentrations of the key alkyl aromatics persist at elevated maturation levels thus aromatic maturity parameters should be considered as versatile tools in organic maturation studies and can complement established maturity indicators based on steranes and terpanes

laser argon dating of melt breccias from the siljan impact structure sweden implications for a possible relationship to late devonian extinction events in earlier studies the 6575 km diameter siljan impact structure in sweden has been linked to the late devonian mass extinction event the siljan impact event has previously been dated by kar and ar ar chronology at 342368 ma with the commonly quoted age being 362 7 2 2 ma 2 recalculated using currently accepted decay constants until recently the accepted age for the frasnian famennian boundary and associated extinction event was 364 ma which is within error limits of this earlier siljan age here we report new ar ar ages extracted by laser spot and laser step heating techniques for several melt breccia samples from siljan interpreted to be impact melt breccia the analytical results show some scatter which is greater in samples with more extensive alteration these samples generally yield younger ages the two samples with the least alteration yield the most reproducible weighted mean ages one yielded a laser spot age of 377 2 2 5 ma 95 confidence limits and the other yielded both a laser spot age of 376 1 2 8 ma 95 confidence limits and a laser stepped heating plateau age over 70 6 39ar release of 377 5 2 4 ma 2 our conservative estimate for the age of siljan is 377 2 ma 95 confidence limits which is significantly different from both the previously accepted age for the frasnian famennian f f boundary and the previously quoted age of siljan however the age of the f f boundary has recently been revised to 374 5 2 6 ma by the international commission for stratigraphy which is within error the same as our new age however the currently available age data are not proof that there was a connection between the siljan impact event and the f f boundary extinction this new result highlights the dual problems of dating meteorite impacts where fine grained melt rocks are often all that can be isotopically dated and constraining the absolute age of biostratigraphic boundaries which can only be constrained by age extrapolation further work is required to develop and improve the terrestrial impact age record and test whether or not the terrestrial impact flux increased significantly at certain times perhaps resulting in major extinction events in earths biostratigraphic record

application of tetracyclic polyprenoids as indicators of input from fresh brackish water environments abstract c30 tetracyclic polyprenoids tpp are most prominently observed in samples derived from low salinity i e fresh to brackish lacustrine environments and are generally present in low levels in samples derived from saline i e marine and saline lacustrine environments a near shore facies of the chonta formation peru that has no marine palynomorphs but abundant chlorococcalean green algal nonmarine palynomorphs has high levels of tpp suggesting green algae or chlorophyta are a possible source for the tpp compounds the ratio between a c30 tpp compound and 27 norcholestanes is useful for assessing this nonmarine algal input moderate elevations of tpp above what is common in marine derived samples were found in ostensibly marine source rocks and oils from certain basins of western and northern south america middle magdalena colombia maracaibo venezuela and trinidad basins this is likely due to transport from the nonmarine to the marine environment because of an influx of fresh water into the near shore marine environment alternatively oils from these basins may have inputs from near shore shallow marine algae with chemistry similar to that found in lacustrine settings the tpp ratio in conjunction with other environmental indicators such as 4 methyl steranes or hopane sterane ratio is useful for differentiating marine and nonmarine influences in pre salt oils and source rocks of west africa the tpp ratio used with other environmental indicators gammacerane c29 steranes c30 steranes and age diagnostic biomarkers dinosteranes 4 methylsteranes can be useful in differentiating among nonmarine source facies for example in the turpan hami basin china permian saline lacustrine and jurassic lacustrine deltaic facies can be discriminated

geochemical application of sterane and triterpane biomarkers to a description of oils from the taranaki basin in new zealand abstract the distributions of sterane and terpane biomarkers in a suite of 25 oils from onshore and offshore regions of the taranaki basin of new zealand have been determined by gc ms features of these distributions include the presence of relatively high concentrations of a number of c 24 tetracyclic terpanes the virtual absence of tricyclic terpanes a predominance of c 29 normal iso and dia steranes and the presence of a number of non hopanoid triterpanes in one member of the suite urenui 18 h oleanane is the most abundant component m z 191 ion chromatogram of the terpane class of biomarkers based upon the distributions of 18 h oleanane the mckee and moturoa families of oils can be delineated these terpane distributions are qualitatively similar to those encountered in crude oils from a number of far eastern basins and from the handil field of the mahakam delta indonesia the taranaki oils are of approximately the same thermal maturity maturity parameters calculated from the distributions of c 29 steranes and of 17s h 21 h and 17 h 21s h hopanes confirm recent findings of incomplete nuclear isomerisation in oils derived from tertiary sediments an attempt has been made to correlate the mckee 1 and maui 4 crude oils with potential source rocks from depths of 3708 m and 3825 m respectively the rocks studied have attained insufficient maturity to have been the sources of these oils

late quaternary stratigraphy and paleoecology of northwest labrador sea abstract sedimentological study of 20 piston cores from the northwestern labrador sea shows that thin bedded distal turbidites are important constituents of the quaternary strata on the continental slope and rise sedimentation on the outer shelf ca 500 900 m is dominated by ice rafting and hemipelagic deposition detailed study of two outer shelf cores reveals a stratigraphic record extending to oxygen isotopic stage 9 studies of foraminifera and dinoflagellates show that subarctic surface waters penetrated into the northern labrador sea during the early middle glacial stages and pollen data indicate that northward advection of warm air masses occurred at the same time microfossil data indicate that late glacial stages were characterized by year around sea ice cover and arctic surface water and by the dominance of cold dry arctic air masses transitions from glacial to interglacial stages are marked by the presence of low salinity melt water these data support models which postulate that open water in the labrador sea played an important role in supplying moisture to laurentide and greenland ice sheets

correlation of marine and continental glacial and interglacial events arctic ocean and banks island correlation of marine and continental glacial and interglacial events arctic ocean and banks island

magnetostratigraphy and palynology demonstrate at least 4 million years of arctic ocean sedimentation it has long been recognized1 2 that the arctic ocean has a major role in regulating the timing of northern hemisphere glaciations global heat exchange and ocean circulation several recent studies3 7 have attempted to interpret the palaeoclimatic record in sediment cores from the arctic ocean but conflicting ages have been reported for palaeoclimatic events dated by different methods3 6 to establish a consistent chronology for cores from the central arctic ocean we performed detailed palaeomagnetic and palynological studies of three cores collected7 near the crest of the alpha ridge and obtained radiocarbon dates from planktonic foraminifers isolated from 1 cm thick intervals magnetic inclination values for these cores clearly record normal and reversed polarity intervals that apparently correspond to the brunnes and matuyama magnetochrons the longest core also includes polarity intervals typical of the gauss and gilbert magnetochrons this chronology is confirmed by the first and last occurrences of pollen and dinoflagellate species that can be correlated with european8 9 and dsdp10 12 chronostratigraphies dated by standard biochronological methods micromass radiocarbon dates for foraminifers indicate a sedimentation rate of 1 mm per 1 000 yr we believe that these data confirm a long 4 myr chronology for the alpha ridge cores the lithostratigraphy of which can be correlated over extensive areas of the western arctic ocean2 7 and more important provide dinoflagellate and palynomorph data that indicate the validity of early chronology

a 1 0 myr record of glacial north atlantic intermediate water variability from odp site 982 in the northeast atlantic changes in the intermediate water structure of the north atlantic were reconstructed using benthic foraminiferal 13c at ocean drilling program odp site 982 for the past 1 0 myr during most terminations of the late pleistocene melting of icebergs and low salinity surface waters caused production of glacial north atlantic intermediate water to cease resulting in decreased ventilation of the middepth north atlantic poor ventilation of intermediate water masses lasted well into some interglacial stages until upper north atlantic deep water nadw production resumed under full interglacial conditions the magnitude of benthic 13c minima and ice rafted debris maxima at terminations at site 982 generally match the degree of glacial suppression of nadw inferred from site 607 these processes may be related and controlled by the spatial and seasonal extent of sea ice cover during glaciations in the nordic seas

central arctic ocean paleoceanographic interpretations based on late cenozoic calcareous dinoflagellates abstract four calcareous dinoflagellate morphotypes interpreted to represent a single species thoracosphaera arctica n sp occur in upper miocene to holocene sediments of the central arctic ocean the calcareous fossils generally are rare except during one interval that of the latest pliocene to late pleistocene during this interval the fossil dinoflagellates were alternately abundant and rare in approximate coordination with greater and lesser times of foraminifera productivity dinoflagellates and foraminifera generally are rare during times of accumulation of abundant coarse textured ice rafted sediment during this interval the life cycle of the dinoflagellate that produces the arctic ocean calcareous fossil is unknown but the fossils probably are either resting cysts motile vegetative cells or hypnozygotes a vegetative cell origin better explains the co occurrence of foraminifera as well as the negative correlation with ice rafting this tentative interpretation leads to the conclusion that during the interval 2 0 to 0 7 m y b p the arctic ocean had relatively productive surface waters with very thin or even periodic absence of pack ice alternating with conditions more like that of the present during periods before 2 0 m y and since 0 7 m y the arctic ocean probably was ice covered with oceanographic conditions similar to that of the modern ocean these conclusions differ from previous interpretations that the arctic was continually ice covered had no surface productivity or was covered by a giant antarctic like ice cap

pleistocene calcite lysocline and paleocurrents of the central arctic ocean and their paleoclimatic significance most previous references to the depth of the arctic ocean calcite lysocline have been based on comparison with the known north atlantic carbonate compensation depth foraminifera from cores taken at depths ranging from 2316 to 3956 m provide the first firm calcite lysocline constraints for the central arctic ocean these data suggest progressive lowering of the calcite lysocline to at least 3956 m during the past 1 5 m y interrupted by 300 m rises of the lysocline level that apparently correspond with interglacial and early glacial climate conditions most cores from less than 2450 m indicate variable foraminifera abundance but continual presence of foraminifera for the past 1 5 m y low abundances commonly occur in coarse textured sediment and are interpreted to represent low productivity during major deglaciations within certain equivalent lithostratigraphic units representing the past 1 5 m y there is an absence of foraminifera in cores from depths greater than 2450 m this absence of foraminifera is interpreted to be due to dissolution dissolution intervals are associated with fine grain sediments interpreted to represent interglacial and early glacial climate conditions the interpretation of a rise in the lysocline level during interglacials is in apparent disagreement with studies reported from lower latitudes in the atlantic ocean but is complementary with the hypothesis that formation of norwegian greenland sea deep water ngdw and cold canada basin deep water occurs during interglacials paleocurrent data from the lomonosov ridge and the adjacent makarov basin are interpreted to indicate that during periods of increased glacial ice influx into the arctic ocean system there was reduced current activity in the bottom and intermediate water masses relative to periods when little glacial ice was present this is in accord with the idea that ngdw affects intermediate and deep water circulation in the central arctic ocean and hence the calcite lysocline level

the ratios of dibenzothiophene to phenanthrene and pristane to phytane as indicators of depositional environment and lithology of petroleum source rocks abstract the ratio of dibenzothiophene to phenanthrene and the ratio of pristane to phytane when coupled together provide a novel and convenient way to infer crude oil source rock depositional environments and lithologies such knowledge can significantly assist in identifying the source formation s in a basin thereby providing valuable guidance for further exploration the ability to infer this information from analysis of a crude oil is especially valuable as frequently the earliest samples in a new area may be shows and or drill stem test samples from exploratory wells which are characteristically drilled on structural highs stratigraphically remote from the source formation s a cross plot of dibenzothiophene phenanthrene versus the pristane phytane ratios measured on seventy five crude oils from forty one known source rocks ranging in age from ordovician to miocene consistently classified the oils into the following environment lithology groups marine carbonate marine carbonate mixed and lacustrine sulfate rich lacustrine sulfate poor marine and lacustrine shale and fluvial deltaic carbonaceous shale and coal the dibenzothiophene phenanthrene ratio alone is an excellent indicator of source rock lithology with carbonates having ratios 1 and shales having ratios the dibenzothiophene to phenanthrene and the pristane to phytane ratios can also be used to classify source rock paleodepositional environments the classification scheme is based on the premise that these ratios reflect the different eh ph regimes resulting from the significant microbiological and chemical processes occurring during deposition and early diagenesis of sediments the dibenzothiophene phenanthrene ratio assesses the availability of reduced sulfur for incorporation into organic matter and the pristane phytane ratio assesses the redox conditions within the depositional environment interpretation of these ratios has been aided by quantitative biomarker analysis and by carbon isotope data for pristane and phytane obtained by gas chromatography isotope ratio mass spectrometry

amino acid epimerization in planktonic foraminifera suggests slow sedimentation rates for alpha ridge arctic ocean interpretations of the palaeoclimatic and palaeooceanographic histories of the arctic ocean1 2 have been hampered by conflicting chronologies obtained using different dating methods magnetostratigraphic and micropalaeontological data1 4 have suggested a sedimentation rate of 1 mm kyr 1 whereas the rate indicated by amino acid epimerization analyses on foraminifera5 is an order of magnitude higher to establish a firm chronology for cores from the alpha ridge arctic ocean and to help resolve the controversy between the ages assigned by different dating methods we have carried out detailed amino acid epimerization analyses on planktonic foraminifera neogloboquadrina pachyderma sinistral from a long gravity core assuming that the temperature in the arctic ocean did not exceed 3 c during the past 1 myr the alloisoleucine isoleucine alle ile ratios obtained from this core suggest a sedimentation rate of 1 mm kyr 1 supporting previous magnetostratigraphic and micropalaeontological studies

surface oceanographic changes in the eastern labrador sea nannofossil record of the last 31 000 years abstract calcareous nannofossils in two ams 14c dated piston cores from the eastern labrador sea yield oceanographic information of the last 31 kyr moderate nannofossil productivity and abundance of north atlantic warm water taxa in the southern labrador sea core 91 045 094p suggest cool surface ocean condition between 31 and 26 thousand years ago ka the irminger current was absent in this interval thus we attribute this cool condition to weak advection of north atlantic water from the southeast we found evidence of cold and or seasonally ice covered surface conditions between 26 and 13 ka in the southern labrador sea and between 31 and 12 6 ka in the northeastern labrador sea core 90 013 013p increase of nannofossil productivity and abundance of north atlantic taxa at about 10 7 ka in core 91 045 094p suggests that the southern labrador sea was influenced by warm north atlantic surface water the polar water of the labrador current had little or no influence on the surface ocean in this area before 9 ka the labrador current started to flow or intensify after 9 ka and became strong by 8 4 ka the northeastern labrador sea remained cold until 8 4 ka perhaps because of discharge of cold meltwater from the greenland ice sheet at this time productivity increased sharply and the assemblage of nannofossils changed these suggest a significant improvement in surface ocean conditions and the establishment of the warm irminger current which marked the onset of the modern circulation pattern characterized by warm west greenland current and strong labrador current

tetracyclic polyprenoids indicators of freshwater lacustrine algal input because of the great variety of lacustrine source depositional characteristics and biological consortia identification of a universally applicable indicator of freshwater or brackish water organic input for crude oils and rock extracts has proven elusive tetracyclic polyprenoid compounds tpp are present in relatively high concentrations in oils and associated source rocks deposited under freshwater or brackish water conditions but typically are present in relatively low concentrations in samples from marine or coal forming depositional environments a tpp ratio constructed from the gas chromatography tandem mass spectrometry peak areas of a c30 tetracyclic polyprenoid divided by the sum of the peak areas of the c26 27 norcholestanes revealed great specificity in identifying freshwater or brackish water algal input particularly in crude oils

elements d une climatostratigraphie du pleistocene moyen et tardif dans l est du canada par l analyse palynologique et isotopique du forage 84 030 003 mer du labrador the piston and gravity cores 84 030 003 collected in the southern labrador sea have been sampled for detailed palynological and isotopic analyses the 18o record on foraminifera neogloboquadrina pachyderma left coiling indicates a stratigraphy spanning isotopic stages 8 to 1 i e over ca 300 000 years the isotopic record allows the calculation of a mean sedimentation rate of approximately 5 cm ka the pollen and spore contents of the sediments are low the low pollen influxes generally less than 1 grain cm2 per year and the dominance of pinus suggest aeolian transport over long distances with southwest northeast to south southwest north northeast trends dinoflagellate cyst concentrations are relatively low indicating a low regional phytoplanktonic productivity the assemblages are however diversified they reflect influences from the north atlantic drift and from the labrador current the occurrence of warm temperate to tropical impagidinium species in deposits suggests an almost permanent

30 norhopanes their occurrence in sediments and crude oils abstract sediments and crude oils have been analysed using gc ms techniques and shown to contain two homologous series of hopanes namely 30 nor 17 h hopanes and 25 30 bisnor 17 h hopanes as well as the common 17 h hopanes homologues c28 to c34 of the 30 nor 17 h hopane series have been identified in crude oils associated with carbonate source rocks the abundances of these hopanes relative to the 17 h hopanes in the soluble organic matter from carbonate sediments has been shown to depend upon sample maturity the more mature samples having higher relative abundances of these norhopanes a comparison of the relative abundances of the norhopanes in the soluble organic matter of sediments and in the hydrocarbon fraction released when the extracted sediments were pyrolysed showed that the 30 nor 17 h hopanes were more abundant in the pyrolysis product these observations indicate that the proportion of norhopanes relative to normal 17 h hopanes in bound form in the kerogen is greater than that present in the soluble form and so kerogen cracking proceeds with increased maturity of the sediments and a relative enrichment of these norhopanes occurs in the soluble fraction the series of 25 30 bisnor 17 h hopanes has been identified in a severely biodegraded crude oil from a putative carbonate source this observation together with the reported occurrence of enriched 25 norhopanes in severely biodegraded crude oils suggests that 25 30 bisnor 17 h hopanes may be biomarkers for severely biodegraded crude oils from carbonate rich source rocks

organic geochemical characteristics of black shales across the ordovician silurian boundary in the holy cross mountains central poland abstract black shales in the holy cross mountains area of poland provide a record of environmental change across the ordovician silurian boundary the changing depositional conditions have generated a variation in organic matter contents above and below the boundary investigating the organic constitution of these black shales has the potential to reveal how their organic matter contents were generated and how suitable these rocks and their lateral equivalents may be for exploitation as shale gas reservoirs one outcrop at the holy cross mountains with a continuous section across the ordovician silurian boundary occurs near the village of bardo stawy in the kielce region and contains sandy silty mudstones as well as grey and black shales organic geochemical analyses of samples at bardo stawy reveals low total organic carbon toc contents for ordovician samples and higher toc values for silurian samples organic biomarkers indicate that the ordovician rocks were deposited in a shallow marine shelf setting while the silurian rocks were deposited in a deeper marine environment the progressive increase in toc from the uppermost ordovician to the lowermost silurian rocks reflects increasingly oxygen poor depositional conditions during the post glacial transgression following the deposition and preservation of organic matter in the ordovician and silurian rocks these rocks were buried and subjected to thermal maturation rock eval and biomarker thermal maturity parameters all indicate that the organic matter is mature and lies within the oil window the ordovician and silurian shales have direct relevance to recent attempts to discover and exploit shale gas reservoirs in poland our data and interpretations suggest that the relatively low toc values

trimethylnaphthalenes in crude oils and sediments effects of source and maturity abstract three sedimentary sequences and a number of crude oils have been analysed for trimethylnaphthalenes tmns using gas chromatography the sediments were found to contain enhanced relative abundances of 1 2 5 tmn and 1 2 7 tmn in samples of cretaceous age and younger this was especially pronounced in lower maturity sediments containing type iii organic matter older samples containing type iii organic matter were found to contain enhanced relative abundances of 1 2 5 tmn and lower relative abundances of 1 2 7 tmn 1 2 7 tmn appears to be derived directly from the structural degradation of oleanane type triterpenoids present in angiosperms and as such is proposed as a marker for this class of plant and indirectly therefore also for samples deposited since the early cretaceous the crude oils have been classified according to their trimethylnaphthalene compositions this classification enables crudes of higher plant origin to be identified and to be further classified according to whether the organic matter pre dated or post dated the evolution of angiosperms

heinrich event 0 dc 0 in sediment cores from the northwest labrador sea recording events in cumberland sound layers of ice rafted limestone debris rich sediment were deposited in the northwest labrador sea and the north atlantic during the last glacial period 10 80 ka these sediments were deposited by heinrich events h events which record catastrophic collapses of the laurentide ice sheet in the region of the hudson strait these intervals of detrital carbonate rich sediments are referred to as detrital carbonate layers dc in the northwest labrador sea accelerator mass spectrometry ams 14c dates provide a strong constraint on the timing for these events h 1 dc 1 and h 2 dc 2 dc 0 also known as h 0 correlative to the younger dryas cooling event is not as distinct a sediment unit in the northwest labrador sea as dc 1 and dc 2 an analysis of sediments from two cores hu75009 iv 055 and hu75009 iv 056 off the mouth of the hudson strait in the northwest labrador sea basin sheds new light on the missing dc 0 sediment unit timing for the dc 0 event in cores 055 and 056 is bracketed between 11

upper cenozoic history of the labrador sea baffin bay and the arctic ocean a paleoclimatic and paleoceanographic summary foraminifera palynomorphs and stable isotopes in planktonic foraminifera have been studied in piston cores from the northern labrador sea southern baffin bay and the alpha ridge region of the central arctic ocean foraminifera in cores from the labrador sea and southern baffin bay show glacial interglacial 18o values similar to those reported from the norwegian and greenland seas in contrast to the eastern north atlantic ocean however peaks of subarctic foraminifera and dinoflagellates in the western north atlantic cores show that relatively warm atlantic surface water continued to flow into the northern labrador sea during the early glaciation growth phases of isotopic stages 2 4 6 and 8 boreal and subarctic pollen suggest that warm atlantic air flowed into the northern labrador sea and baffin bay during the ice sheet growth phases the advection of warm air masses and the presence of open waters during the summer probably provided moisture for the growth of the laurentide innuitian and greenland ice sheets isotopic and microfossil records in arctic cores can also be tentatively correlated with major high latitude north atlantic glacial interglacial events magnetostratigraphic palynological and amino acid dating however shows that sedimentation on the alpha ridge has been very slow during the past 0 73 m y therefore events of less than 20 000 years duration cannot be clearly discerned interpretation of pre pleistocene paleoenvironments is further limited by the sparseness of calcareous and siliceous microfossils

palaeoclimate of baffin bay from 300 000 year record of foraminifera dinoflagellates and pollen several different models1 5 have attempted to relate quaternary marine and terrestrial records of ice sheet growth in the north atlantic region the models are derived from either discontinuous terrestrial records including marine fossils in raised shorelines1 2 or from deep sea calcareous microfossils3 4 this study correlates arctic marine and terrestrial data directly by comparing 18o foraminiferal dinoflagellate and pollen records from a core taken in baffin bay the core contains an almost continuous sequence of sediments deposited during isotope stages 1 10 subarctic foraminifera and atlantic dinoflagellates in early isotope stages 2 4 6 and 8 show that subarctic water entered southern baffin bay before the glacial maxima boreal subarctic pollen suggest that atlantic air flowed into baffin bay during the ice sheet growth phases these data support models which postulate that open water in the labrador sea had an important role in supplying moisture to laurentide and greenland ice sheets

report of 1st discussion group the last interglacial in high latitudes of the northern hemisphere terrestrial and marine evidence abstract the paleoclimatic informations preserved at some selected sites from high northern latitudes correlative with the last interglacial maximum of isotopic substage 5e have been compiled on a hemisphere scale the mapped compilation reveals much warmer climate conditions on average than present in both terrestrial and marine environments and indicates a northward shift of subpolar and boreal bioclimatic zones the data also suggest that temperature and precipitation gradients were significantly different than those of the holocene with particularly efficient latitudinal and eastward transport of warm air masses the paleoenvironmental and paleoclimate trends through the last interglacial sensu lato isotopic stage 5 are more difficult to assess because the chronostratigraphical framework is poorly constrained nevertheless the data suggest important regionalism in the climatostratigraphical trends in particular the large amplitude climatic cyclicity that characterizes the last interglacial of europe is barely observed elsewhere moreover by the end of the last interglacial isotopic substage 5a conditions slightly cooler than present are recorded in western europe while relatively warm conditions similar to today apparently prevailed in circumpolar regions adjacent to the north atlantic despite the onset of ice growth the last interglacial provides paleosynoptic situations unlike those of the present that may contribute to understanding interactions within the environmental system on a hemispheric scale there is however an imperative need for uniformization of data sets and for more accurate chronological control on regional scales

the occurence of unusual c27 and c29 sterane predominances in two types of oman crude oil abstract two types of oman crude oils reveal unusual sterane distributions type a which is the more common 74 examples is characterised by a predominance of c 29 iso and normal steranes and generally none or only very low relative concentrations of rearranged steranes the triterpanes are characterised by the predominance of the c 29 17 h 21 h norhopane over the c 30 17 h 21 h hopane and non predominant c 20 c 30 tricyclic terpanes the c 29 steranes of this type of crude were not derived from the c 29 sterols of land plant origin frequently proposed as the source of c 29 steranes since there is good geological evidence that these crudes were generated from a pre cambrian source rock a geological period when land plants did not exist the type b crude oil 11 known examples is characterised by a strong predominance of c 27 iso normal and rearranged steranes relatively lower concentrations of 17 h 21 h hopanes and relatively high concentrations of c 20 c 30 tricyclic terpanes the remarkably different biomarker characteristics of these crude oils imply that the organisms active in the depositional environment of the respective source rocks were significantly different

a new interpretation of the sedimentary cover in the western siljan ring area central sweden based on seismic data abstract two new reflection seismic profiles over the paleozoic successions of the western part of the siljan ring impact structure show a contrasting seismic signature the more southerly c 10 km long mora profile reveals a highly disturbed structure with only a few kilometers of relatively horizontally layered structures observed however interpretations of refracted arrivals in the data that can be correlated to reflections indicate the silurian clastic rocks to be about 200 m thick in the central part of the profile weak reflections from about 600 m depth suggest a 400 m thick ordovician limestone sequence to be present cores from the area show a mainly shale lithology for the silurian and only a thin sequence of ordovician strata suggesting a rapid thickening of the ordovician towards the north on the more northern c 12 km orsa profile clear reflections from the paleozoic successions are seen along the entire profile except on the southernmost few kilometers based on interpretations of refracted arrivals the silurian succession appears to be considerably thinner here and possibly absent at some locations the ordovician is also interpreted to be thinner in this area with a maximum thickness of about 200 300 m along most of the profile a deeper reflection from about 2 km within the crystalline basement may represent a dolerite sill the lack of clear basement reflections on the mora profile can be attributed to near surface conditions and the acquisition geometry the seismic data and recent coring in the area suggest the presence of a deeper paleo basin towards the southwest with significantly more shales being deposited and the paleozoic successions being severely disturbed the shallow coring and seismic data will help form the basis for locating future boreholes for deeper drilling to study impact processes and the paleozoic evolution of central sweden

reflection seismic investigations of the siljan impact structure sweden reflection seismic measurements were carried out during 1985 in the area of the siljan impact structure of sweden a total profile length of 80 km was shot to get a clearer picture of the subsurface geometry of impact structures and the processes that formed them than could be obtained from surface observations or theoretical modeling studies standard stacked sections have been interpreted in terms of current impact models the transient crater diameter is found to be approximately 22 km considerably smaller than current estimates based on interpretation of surface geology the structural uplift is estimated to be 3 km at the 5 to 8 km level and the material flow necessary to support the uplift is mainly horizontal rather than vertical