strong climate coupling of terrestrial and marine environments in the miocene of northwest europe a palynological and organic geochemical record from a shallow marine paleoenvironmental setting in se netherlands documents the coupled marine and terrestrial climate evolution from the late burdigalian 17 ma through the early zanclean 4 5 ma proxy climate records show several coeval variations in both relative sea surface deduced from percent cool dinocysts and terrestrial subtropical vs cool temperate pollen temperature indices the terrestrial climatic trend is confirmed by a quantitative reconstruction of annual mean air temperature based on the distribution of fossil branched glycerol dialkyl glycerol tetraethers showing a cooling from 27 c to 14 c between 17 and 5 ma punctuated by short term variations decreases in sea surface temperature broadly correlate to inferred third order sea level variations and correspond to isotope glacial events mi 3 through mi 7 an additional strong sst decrease occurs around 8 4 ma coincident with a strong reduction and regional disappearance of subtropical pollen types this cooling phase seems associated with lowered sea levels but it has not yet been described from the deep sea 18o record 2009 elsevier b v

oil and gas developments in western canada in 1989 there were 5513 wells drilled in western canada during 1989 30 fewer than in 1988 total meterage drilled was 6 459 797 m for an average well depth of 1172 m exploratory drilling in 1989 dropped by 13 and development drilling by 40 from 1988 levels british columbia was the only area in western canada with increased activity the industry continued to acquire more acreage for less total bonus at provincial crown sales throughout western canada during 1989 3 564 827 ha were acquired for a total bonus of 484 872 000 footnote 5 although the total disposition of crown lands decreased only 4 the average bonus dropped to 136 ha down 26 from 1988 in alberta the most active exploration areas were the southern and eastern mesozoic gas play the western deep devonian gas play the oil plays on and adjacent to the peace river arch and the middle devonian carbonate oil plays in the northwest in british columbia the most active exploration areas were the mesozoic and paleozoic gas plays in the northeastern portion of the province for the first time in 5 years crown drilling rights were issued within the fraser valley in the southwest there was a focus on gas exploration in the province as pipeline reversal was implemented permitting access to canadian and california markets through the alberta transportation network in manitoba exploration and development activity continued to decline in northern canada exploratory drilling success offering of crown lands for exploration approval of gas exports and indications that many of the native lands claims may be approaching settlement all provided exploration encouragement for the next decade exploration activities occurred throughout the northwest territories from the offshore beaufort to the southern border in saskatchewan active exploration areas were shallow mesozoic gas plays in the western portions of the province and deep paleozoic oil plays in the south

organic geochemistry of oil and gas in the kuqa depression tarim basin nw china abstract the kuqa depression in the tarim basin nw china contains significant natural gas and condensate resources with only small amounts of black oil this study demonstrates that the primary reason for the accumulation of large natural gas reserves in the kuqa depression is the high maturity level of the jurassic coal bearing sequence that is currently at the peak stage of dry gas generation from the combined stable carbon isotopes and molecular biomarker data it is possible to identify two separate source rocks for the discovered hydrocarbon fluids the gases were primarily from the middle lower jurassic coals and associated clastic rocks and the oils were from the upper triassic lacustrine mudstones peak oil generation from the triassic source rocks occurred during the early miocene 23 12 ma b p these oils migrated laterally over relatively long distances 20 50 km reaching the outer periphery of the depression peak gas generation took place more recently perhaps during the past 5 ma the gases migrated mainly along faults over relatively short lateral distances resulting in accumulations adjacent to the over matured source kitchens different timings for the trap formation along the north and south margins and a late injection of gas into early oil accumulations provided favorable conditions for the formation of evaporative condensates and the preservation of gas pools in the more down dip reservoirs and oil pools in the more up dip locations

the impact of glaciation river discharge and sea level change on late quaternary environments in the southwestern kara sea sedimentary records from the southwestern kara sea were investigated to better understand the extent of the last glaciation on the eurasian arctic shelf sea level change and history of the ob and yenisey river discharge sediment core and seismic reflection data indicate that the quaternary depositional sequence in the southwestern kara sea consists of glacial glaciomarine and marine sedimentary units glaciogenic sediments in the deep novaya zemlya trough are presumably related to the last glacial maximum lgm whereas further east they may represent an earlier glaciation thus it is inferred that the southeastern margin of the lgm barents kara ice sheet was contained in the southwestern kara sea east of the novaya zemlya trough changes in mineralogical foraminiferal and stable isotopic composition of sediment cores indicate that riverine discharge strongly influenced sedimentary and biotic environments in the study area during the late weichselian and early holocene until ca 9 ka consistent with lowered sea levels subsequent proxy records reflect minor changes in the holocene hydrographic regime generally characterized by reduced riverine inputs

origin and distribution of terrestrial organic matter in the nw mediterranean gulf of lions exploring the newly developed bit index the branched and isoprenoid tetraether bit index is based on the relative abundance of nonisoprenoidal glycerol dialkyl glycerol tetraethers gdgts derived from organisms living in terrestrial environments versus a structurally related isoprenoid gdgt crenarchaeol produced by marine crenarchaeota the bit index varies between 0 and 1 representing marine and terrestrial organic matter om end members respectively hopmans et al earth planet sci lett 224 107 116 2004 in this study the applicability of the bit index to trace terrestrial om is tested in combination with other organic parameters toc c n ratio 13corg total lipid and n alkane in the gulf of lions a river dominated continental margin of the western mediterranean we analyzed a variety of soils and riverbed sediments from the continent as well as surface sediments from the shelf and canyons the bit index in soils and riverbed sediments shows high values 0 9 while it varies between 0 02 and 0 83 in marine sediments decreasing seaward from the inner shelf to the slope for marine surface sediments high bit values are associated with lower 13corg values as well as higher toc contents and higher n alkane concentrations our results confirm that the bit index can be applied in coastal marine environments in order to characterize terrestrial om as proposed by hopmans et al 2004 therefore the bit index is a useful addition to the proxies presently available for studying the origin and distribution of om in continental margins and especially valuable in multiproxy studies

a 15 ka ph record from an alpine lake in north china derived from the cyclization ratio index of aquatic brgdgts and its paleoclimatic significance abstract a well dated sediment core from an alpine lake in north china gonghai lake was used for analysis of branched glycerol dialkyl glycerol tetraether lipids brgdgts based on the cyclization ratio index cbt of the brgdgts and using different terrestrial and lacustrine cbt ph empirical relationships the reconstructed ph records over the past ca 15 ka exhibited similar trends of variation although the absolute ph values were different in order to better understand the reconstructed ph record samples of surface soils from the dust source area and the catchment of gonghai lake as well as surface sediments from the lake were collected for instrumental ph measurements and modern brgdgt analysis the instrumental ph results demonstrated that the surface soils from the dust source area were alkaline while those from the catchment of gonghai lake were acidic in addition the instrumental ph results for the surface sediments from the lake were slightly alkaline and the corresponding ph values were intermediate between those of the two surface soil source groups this may reflect the effect of the input of material from different sources on the sedimentary ph record however the results from modern brgdgts in some of the surface soils and surface sediment samples demonstrate that brgdgts in the core sediments from gonghai lake are predominantly of aquatic origin therefore the cbt derived ph record over the past ca 15 ka from the lake can be interpreted as a record of the lake water ph history which is consistent with the carbonate content record from a parallel core from the same lake in addition using the modern lacustrine calibration the cbt derived ph values for surface sediments of gonghai lake are consistent with instrumental modern lake water ph values for the lake further comparison indicates that the lake water ph is controlled mainly by the degree of humidity of the local climate which is closely related to the intensity of the east asian summer monsoon easm therefore the ph record can be used as an indicator of easm intensity our results demonstrate that on the basis of careful analysis of its origins the cbt index of aquatic brgdgts can be used for lake water ph reconstruction and subsequent paleoclimate reconstruction and that in north china the lake water ph is controlled mainly by the degree of humidity of the local climate

the importance of solar insolation on the temperature variations for the past 110 kyr on the chinese loess plateau abstract the late quaternary temperature history on the chinese loess plateau clp is little known due to the absence of suitable paleothermometers here we present a quantitative temperature record for the last 110 kyr from lantian county southern clp based on the distributions of bacterial tetraethers lantian loess temperature variations display significant correlation with the northern hemisphere insolation 35 n as well as the cave monsoon records at the precession band we attribute such correlation to both the latent heat release from the east asian summer monsoon and the direct influence of sun s sensible heat over the semi arid landscape the long term cooling during the marine isotope stage mis 3 and the modest temperature drop of 5 c from 79 to 65 ka are best explained by interactions among multiple climate forcings including insolation atmospheric co 2 concentration global ice volume and regional glacier activities the cold and modestly wet climate during mis 3 may have promoted maximum regional glacial advances whereas the minimal temperature during local lgm reduced moisture transfer and led to glacial recession the unusually early deglacial warming at 22 5 ka highlights the importance of regional climate records to decipher the complex continental climate dynamics

vertically transferred overpressures in brunei evidence for a new mechanism for the formation of high magnitude overpressure overpressures in sedimentary basins are commonly assumed to be the result of two distinct and separate mechanisms disequilibrium compaction and fluid expansion however the potential for overpressures to be redistributed or transferred to other pressure compartments over time has been seldom considered and rarely demonstrated pore pressure data and velocity effective stress plots from 61 fields across the baram delta province of brunei northwest borneo reveal that two different types of overpressure occur in stratigraphically defined sections the basal pro delta shales contain overpressures generated by disequilibrium compaction whereas the overlying sand shale deltaic sequence contains overpressures that appear to be generated by fluid expansion however the geology of the deltaic sequences and high magnitude of the pore pressures precludes the overpressures in the deltaic sequences being generated by any conventional fluid expansion mechanism such as kerogen to gas maturation or clay diagenesis the fluid expansion overpressures are located in fields that were inverted during the pliocene an event that resulted in large scale fluid migration from the pro delta shales into the deltaic sequences including charging of the numerous oil fields in the inner shelf hence we propose that the overpressures in brunei provide the first evidence for a new overpressuring mechanism whereby overpressured fluids have been vertically transferred from the pro delta shales into the deltaic sequences during basin inversion furthermore vertical transfer may be a mechanism for explaining overpressures observed in basins that have been recently uplifted or inverted

a vitrinite reflectance kinetic model incorporating overpressure retardation abstract the models currently used to predict maturation and hydrocarbon generation in petroleum basins use time and temperature as controlling parameters a small number of studies have indicated that overpressure can retard maturation although some of the published information from experimental investigations appears to be conflicting careful examination of the experimental conditions shows that both vitrinite reflectance and hydrocarbon generation are retarded by overpressures overpressure appears to result in the retention of volatiles within the molecular structure which prevents the molecular reorganisation necessary to produce higher reflectance values using a database containing vitrinite reflectance from both overpressured and normally pressured wells a kinetic model presro has been developed in which overpressure modifies the arrhenius a factor the model has been tested on two different basins south china sea and sable exhibiting a range of time temperature overpressure characteristics the results suggest that the maturity and timing of the onset of hydrocarbon generation differ significantly from those predicted by current models

a novel proxy for terrestrial organic matter in sediments based on branched and isoprenoid tetraether lipids we propose a novel tracer for terrestrial organic carbon in sediments based on the analysis of tetraether lipids using high performance liquid chromatography mass spectrometry hplc ms analysis of terrestrial soil and peats shows that branched tetraether lipids are predominant in terrestrial environments in contrast to crenarchaeol the characteristic membrane lipid of non thermophilic crenarchaeota which is especially abundant in the marine and lacustrine environment based on these findings an index was developed the so called branched and isoprenoid tetraether bit index based on the relative abundance of terrestrially derived tetraether lipids versus crenarchaeol this bit index was applied to surface sediments from the angola basin where it was shown to trace the outflow of the congo river furthermore analyses of particulate organic matter from the north sea showed relatively higher bit indices in water column particulate organic matter near large river inputs a survey of globally distributed marine and lacustrine surface sediments shows that the bit index in these environments correlates with the relative fluvial input of terrestrial organic material making this index generally applicable the new proxy allows the rapid assessment of the fluvial input of terrestrial organic material in immature sediments up to 100 ma old

simulation of fluid distributions observed at a crude oil spill site incorporating hysteresis oil entrapment and spatial variability of hydraulic properties subsurface oil water and air saturation distributions were determined using 146 samples collected from seven boreholes along a 120 m transect at a crude oil spill site near bemidji minnesota the field data collected 10 years after the spill show a clearly defined oil body that has an oil saturation distribution that appears to be influenced by sediment heterogeneities and water table fluctuations the center of the oil body has depressed the water saturated zone boundary and the oil appears to have migrated laterally within the capillary fringe a multiphase cross sectional flow model was developed and used to simulate the movement of oil and water at the spill site comparisons between observed and simulated oil saturation distributions serve as an indicator of the appropriateness of using such models to predict the actual spread of organic immiscible liquids at spill sites sediment hydraulic properties used in the model were estimated from particle size data the general large scale features of the observed oil body were reproduced only when hysteresis with oil entrapment and representations of observed spatial variability of hydraulic properties were incorporated into the model the small scale details of the observed subsurface oil distribution were not reproduced in the simulations the discrepancy between observed and simulated oil distributions reflects the considerable uncertainty in model parameter estimates and boundary conditions three phase capillary pressure saturation relative permeability functions representations of spatial variability of hydraulic properties and hydrodynamics of the groundwater flow system at the study site

dense nonaqueous phase liquid dnapl source zone characterization influence of hydraulic property correlation on predictions of dnapl infiltration and entrapment dnapl source zone characterization

quantification of experimental subsurface fluid saturations from high resolution source zone images laboratory scale aquifer cells are commonly used to investigate processes governing contaminant fate and transport in heterogeneous subsurface systems in recent years dramatic improvements in image processing methods have led to increasingly refined image resolution in these experiments with these enhanced imagining methodologies system parameters such as nonaqueous phase liquid napl saturation can now be quantified at the submillimeter scale this fine level of resolution however is generally inconsistent with the typical scale of a representative elementary volume rev the averaging volume associated with property evaluation in continuum based flow and transport models such inconsistency of scales calls into question the practice of directly comparing laboratory observations with continuum based model simulations this work explores the application of alternative approaches to image data processing for characterization of napl source zone architecture in aquifer cells and examines the implications of data processing on the interpretation of experimental model comparisons the utility of two alternative upscaling methods a continuity equation based cb and discrete block based dbb approach are considered examination of the stability of point averages of saturation demonstrates that a rev length scale can be defined as 30 d50 for the thickness averaged two dimensional aquifer cell experiments examined quantification of upscaled source zone metrics including the average saturation the second spatial moment in the vertical direction and the ganglia to pool gtp mass ratio reveals that the gtp is strongly sensitive to observation scale use of gtp values computed from upscaled images is shown to improve mathematical model predictions of experimental effluent concentrations by nearly 50

thermal history model for the south central graben north sea derived using both tectonics and maturation abstract the thermal history modelling of basins is essential for petroleum systems analysis the methodology involves the derivation of the heat flow history by calibration using a kinetic model to match the predicted and observed vitrinite reflectance values in wells although this method is almost universally used by basin modellers a simple check using two independent methods with tectonic subsidence history being the second method shows that the thermal histories derived from the subsidence history do not match those predicted by the vitrinite reflectance method for any point in a basin there can only be one thermal history and the derivation of two different thermal histories indicates that there is a problem that has been ignored by geochemists and basin modellers the thermal history must predict the tectonic subsidence history and this heat flow history must also account for the maturation data e g vitrinite reflectance sediments subside under the action of forces and energy e g heat is a function of force during subsidence the downward force exceeds the upward force and the heat flow supplied to the basin must be reduced as the upward force is reduced while force and heat flow must be increased during uplift applying this relationship to the central graben north sea a heat flow history is derived that accounts for the rifting and subsequent subsidence tectonic history of two wells the british 23 26 2z and the danish lulu 1 the vitrinite reflectance predicted by this thermal history and the easy ro kinetic vitrinite reflectance model are higher than the measured values in both wells both wells are overpressured and the problem with the vitrinite reflectance calibration method is that the kinetic parameters used do not correctly account for the retardation produced by pressure le chatelier s principle without the pressure retardation effect incorporated into the kinetic parameters the modeller has to use lower temperatures to simulate retardation using the presro vitrinite reflectance model which incorporates pressure retardation as required by thermodynamics the thermal history derived from the rifting subsidence history can also be used to model the vitrinite reflectance data in the british 23 26 2z and danish lulu 1 wells this method of deriving an unknown e g thermal history using two independent models is widely used in physical sciences as an essential check on any prediction and this scientific rigor has to be followed by geoscientists modelling the thermal history of basins

permeability controls on aquathermal pressuring aquathermal pressuring refers to fluid pressures in excess of the hydrostatic which have been created by fluid thermal expansion against a less expansive sediment matrix two commonly stated objections to this mechanism are 1 hydraulic gradients and the finite but very low permeabilities now existing in the gulf of mexico are sufficient to dissipate aquathermal pressures and 2 the increasing temperatures decrease fluid viscosity at a rate so that hydraulic conductivity increases fast enough to dissipate these pressures evaluation of the momentum transport equations in the eulerian frame of reference indicates the first objection is not applicable because it treats the problem as steady flow and not transient flow furthermore existing data indicate that under no mal diagenetic conditions the decrease in intrinsic permeability caused by consolidation is greater than the viscosity effect therefore the two commonly stated objections to aquathermal pressuring do not by themselves prove the mechanism is ineffective in settings such as the gulf of mexico permeability increases by fracturing and faulting may however be sufficient to bleed off aquathermally produced excess pressures the measured very low permeabilities of gulf coast fine grained sediments indicate that aquathermal pressuring is a potentially important mechanism if the fine grained sediments do control the hydraulic response

fluxes and distribution of tetraether lipids in an equatorial african lake constraints on the application of the tex86 palaeothermometer and bit index in lacustrine settings abstract the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether gdgt lipids was studied in material from various sources in and around lake challa a crater lake on the southeastern slope of mt kilimanjaro tanzania to examine the provenance of gdgts in lake sediments and their potential application as palaeoenvironmental and palaeoclimatic proxies the study material included samples collected at monthly intervals in a sediment trap over one complete annual cycle particles suspended in the stratified water column profundal surface sediments and soils surrounding the lake the sediment trap time series revealed that crenarchaeol and related isoprenoid gdgts were predominantly produced in january and february following the locally prominent short rain season november december the tex 86 inferred temperature derived from sedimenting particles corresponded well with lake surface water temperature at this time of largest crenarchaeol flux molecular ecological analysis showed that group 1 1a and 1 1b crenarchaeota are the most likely source organisms of these gdgts gdgt 0 in the lake sediments does not only originate from lake surface dwelling crenarchaeota but seems predominantly derived from archaea residing in the deeper anoxic part of the water column the main flux of branched gdgts to the sediment was during the short rain season and is most probably derived from eroded catchment soils in surface run off however a contribution from in situ production of branched gdgts in the lake sediment or water or in groundwater cannot be fully excluded we conclude that palaeoclimatic reconstruction based on branched gdgt distributions in lake sediments should only be performed when the origin of those branched gdgts is well constrained

coupled thermal and hydrological evolution of tropical africa over the last deglaciation we analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the congo river outflow and the results enabled us to reconstruct large scale continental temperature changes in tropical africa that span the past 25 000 years tropical african temperatures gradually increased from 21 to 25 c over the last deglaciation which is a larger warming than estimated for the tropical atlantic ocean a direct comparison with sea surface temperature estimates from the same core revealed that the land sea temperature difference was through the thermal pressure gradient an important control on central african precipitation patterns

rare earth element fractionations of the northwestern south china sea sediments and their implications for east asian monsoon reconstruction during the last 36 kyr abstract rare earth elements rees fractionations in siliciclastic marine sediments are related to the parent rock properties weathering degree grain size and heavy minerals the relations between marine sediment ree compositions and regional paleoclimate are not fully understood here the rees for detrital components of a core retrieved from the northwestern south china sea scs were measured results show the ree lree hree la yb n and light ree la sm n fractionation degrees have good responses to the regional paleoclimate over the past 36 kyr sea level played a key role in ree fractionations during 36 24 kyr bp manifesting as lower ree and lree fractionation degrees correspond to the decreased sea level the entire trends for lree hree la yb n and la sm n over the past 20 5 kyr are almost in phase with the regional east asian summer monsoon easm records because rees are mainly concentrated in heavy minerals the density difference of heavy minerals is probably the main controlling factor on ree fractionations clay minerals and feldspars released during the weathering process have a high content of light rees lrees in the warm wet periods holocene optimum and bolling allerod more precipitation promoted weathering and strengthened the estuarine hydrodynamic force which respectively resulted in high content of clay minerals and feldspars and high density heavy minerals e g monazite the process led to lree enrichment because the enriched minerals contain higher contents of the lrees in contrast the dry cold climate conditions during the periods heinrich 1 younger dryas and last glacial maximum resulted in the reversed ree fractionations as the weak hydrodynamic force can only carry the low density heavy minerals e g zircon that are enriched in hrees this model does not seem to apply to 36 24 kyr bp probably because of the re transport of ancient shelf sediments the study facilitates the understanding of ree application in paleoclimate reconstruction within slope sediments

warm arctic continents during the palaeocene eocene thermal maximum the palaeocene eocene thermal maximum petm 55 5 ma is a geologically relatively brief episode of extreme warmth both deep and surface ocean temperatures increased by up to 5 c in equatorial waters and up to 8 c in mid and high latitude waters from the continents the annual mean air temperature response during the petm is still largely unknown mainly due to a lack of quantitative temperature proxies and sufficient suitable continuous high resolution records recently a new proxy for continental temperature reconstructions has been proposed based on the distribution of membrane lipids of bacteria in present day soils j w h weijers s schouten j c van den donker e c hopmans j s sinninghe damste 2007 environmental controls on bacterial tetraether membrane lipid distribution in soils geochimica et cosmochimica acta 71 703 713 and shown to reconstruct annual mean air temperature in this study we applied this new proxy in an attempt to reconstruct the air temperature in high latitude continental areas during the petm by analysis of a marine sedimentary sequence obtained from the lomonosov ridge in the central arctic ocean integrated ocean drilling program expedition 302 site 004 hole a the results indicate a warming of 8 c above background values of 17 c this warming is coincident with a similar rise in sea surface temperatures documented earlier our results thus further confirm the warm conditions in the arctic and point to a strongly reduced latitudinal temperature gradient during the petm 2007 elsevier b v all rights reserved

branched glycerol dialkyl glycerol tetraethers in arctic lake sediments sources and implications for paleothermometry at high latitudes branched glycerol dialkyl glycerol tetraethers brgdgts are analyzed in different lakes of the mackenzie canadian arctic and kolyma siberian arctic river basins to evaluate their sources and the implications for brgdgt based paleothermometry in high latitude lakes the comparison of brgdgt distributions and concentrations in the lakes with those in river suspended particulate matter riverbank sediments and permafrost material indicates that brgdgts in arctic lake sediments have mixed sources in contrast to global observations distributional offsets between brgdgts in arctic lakes and elsewhere in the catchment are minor likely due to the extreme seasonality and short window of biological production at high latitudes consequently both soil and lake calibrated brgdgt based temperature proxies return sensible temperature estimates even though the mean air temperature mat in the arctic is below the calibration range the original soil calibrated mbt cbt methylation of branched tetraethers cyclisation of branched tetraethers proxy generates mats similar to those in the studied river basins whereas using the recently revised mbt cbt calibration overestimates mat the application of the two global lake calibrations generating summer air temperatures sat and mat respectively illustrates the influence of seasonality on the production of brgdgts in lakes as the latter overestimates actual mat whereas the sat based lake calibration accounts for this influence and consequently returns more accurate temperatures our results in principle support the application of brgdgt based temperature proxies in high latitude lakes in order to obtain long term paleotemperature records for the arctic although the calibration and associated transfer function have to be selected with care

impacts of the tectonic stress field on natural gas migration and accumulation a case study of the kuqa depression in the tarim basin china stress fluid and temperature are three of the major factors that impact natural gas migration and accumulation in order to study the influences of tectonic stress field on natural gas migration and accumulation in low permeability rocks we take the kuqa depression as an example and analyze the evolution of the structure and tectonic stress field at first then we study the influences of tectonic stress field at different tectonic episodes on fractures and fluid potentials through the numerical simulation method on the section across the kl2 gas field we summarize two aspects of the impact of the tectonic stress field on natural gas migration and accumulation firstly under the effects of the tectonic stress field the rock dilation increases with the added stress and strain and when the shear stress of rock exceeds its shear strength the shear fractures are well developed on one hand the faults which communicate with the hydrocarbon source rocks become the main pathways for natural gas migration on the other hand these positions where fractures are well developed near faults can become good reservoirs for natural gas accumulation secondly because fluid potentials decrease in these places near the faults where fractures are well developed natural gas can migrate rapidly along the faults and accumulates the impact of tectonic stress fields on natural gas migration and accumulation allows for hydrocarbon migration and accumulation in the low permeability rocks in an active tectonic compressive setting

sources and distributions of tetraether lipids in surface sediments across a large river dominated continental margin glycerol dialkyl glycerol tetraether gdgt based proxies are increasingly used in modern carbon cycling and palaeoenvironmental investigations it is therefore crucial to examine the robustness sources transport and degradation of all gdgt based proxies in continental margins where sedimentation rates and extent of carbon cycling are high we have analyzed the distributions of gdgts in surface sediments from the lower yangtze river and east china sea ecs shelf the results revealed multiple sources and complex shelf processes that govern the distributions the isoprenoid gdgt inferred sea surface temperatures ssts are robust and reflect the satellite derived annual mean ssts on the shallow ecs shelf confirming an origin from surface water column dwelling crenarchaeota the input from methanogen sourced isoprenoid gdgts is significant in the river surface sediments but they are almost absent from the ecs shelf branched gdgts are also abundant in the river sediments but ca 95 are degraded in the yangtze estuary a much greater extent than observed for other terrigenous organic matter om proxies there is also evidence for production of branched gdgts in the oxic ecs shelf water column and the anoxic sediments waters of the lower yangtze river as a result branched gdgt based proxies in the lower river and ecs surface sediments do not reflect the catchment environmental conditions the effective degradation in the estuary and widespread aquatic contributions of branched gdgts improves our understanding of how to use branched gdgt based proxies in marginal seas

impact of riverine suspended particulate matter on the branched glycerol dialkyl glycerol tetraether composition of lakes the outflow of the selenga river in lake baikal russia branched glycerol dialkyl glycerol tetraethers brgdgts are bacterial membrane lipids found in several environments including soils rivers and lakes whose distribution varies with temperature and ph although this dependence is apparently not the same for the different environments mixing of brgdgt sources may thus complicate palaeoenvironmental reconstruction the extent to which brgdgts in a lake outflow reflect the distribution delivered by upstream rivers was studied for lake baikal russia one of the largest freshwater lakes worldwide fifteen brgdgts in suspended particulate matter spm of the selenga river and its outflow from the lake were quantified the river and lake spm had rather different distributions the riverine distribution was still apparent in the spm of the lake surface water 5 km from the river mouth but shifts in the distribution were already apparent in the spm of the surface water after 1 km based on the brgdgt distributions of the spm of the selenga outflow and that of the lake conservative mixing between the river and the lake brgdgt distributions could not fully explain the observed shifts in distributions both preferential degradation and in situ production of brgdgts in the surface and especially bottom water of the river outflow were potentially responsible this implies that a riverine lipid distribution delivered to a lake can be modified prior to being transported downstream the lacustrine brgdgt distribution that possibly could have reflected a mixture of mountainous and selenga river spm was not recognized in downstream yenisei river spm the watershed of lake baikal thus does not seem to contribute to the brgdgts transported to the marine system as many large rivers have major lakes in their watershed this has implications for palaeoclimate reconstruction from river fan sediments globally

distributions of branched gdgts in soils and lake sediments from western uganda implications for a lacustrine paleothermometer bacterially produced branched glycerol dialkyl glycerol tetraethers gdgts are ubiquitous in soils and lake sediments and can potentially be used to reconstruct past temperatures in lakes however it is still unclear if these compounds are derived from eroded soils or if they are produced in situ to better understand environmental controls on the distributions of these compounds and the sources of branched gdgts to lake sediments we compare branched gdgt distributions and concentrations in lake sediments and catchment soils within a 3600 m altitudinal transect in western uganda reconstructed mean annual air temperature maat determined from the degree of methylation mbt and cyclisation cbt of branched gdgts in soils decreases with increasing altitude as is expected from the air temperature gradient in our transect however we observe significant offsets between observed and reconstructed temperatures in soils from wet high elevation soils but not in most dry low elevation soils branched gdgt distributions differ significantly between lake sediments and soils at all elevations with greater differences at low elevations than at high elevations these data support previous hypotheses that branched gdgts are produced in situ in lakes and suggest that the abundance of water in soil environments may play a role in controlling the distribution of branched gdgts while branched gdgts in lacustrine sediments can be used to reconstruct temporal temperature variations in lakes we urge caution in utilizing this proxy in lacustrine systems with high soil loadings especially if there is evidence of changing clastic fluxes through time

constraints on the application of the mbt cbt palaeothermometer at high latitude environments svalbard norway abstract branched glycerol dialkyl glycerol tetraethers gdgts are membrane lipids of unknown bacteria that are ubiquitous in soil and peat two indices based on the distribution of these lipids in soils the cyclization of branched tetraethers cbt and the methylation of branched tetraethers mbt indices have been shown to correlate with soil ph and mean annual air temperature mat and soil ph respectively and can be used to reconstruct mat in palaeoenvironments to verify the extent to which branched gdgts in marine sediments reflect the distribution pattern on land and whether these proxies are applicable for palaeoclimate reconstruction in high latitude environments with a mat of

quantitative estimation of overpressure caused by oil generation in petroliferous basins abstract oil generation can be the dominant overpressure mechanism in low permeability source rocks because of the volume increase upon conversion of organic matter to less dense oil during the petroleum generation process to quantitatively express the relationship between oil generation and overpressure in source rocks an equation for the pressure change due to oil generation was derived to quantitatively estimate the overpressure generated in the source rock by considering of the episodic fluid expulsion and parameters such as the residual oil coefficient source rock porosity transformation ratio toc total organic carbon hydrogen index the compressibility of type i kerogen oil and pore water the equation was then calibrated with the results from physical simulation experiments in a closed pyrolysis system sensitivity analyses on the residual oil coefficient toc and hydrogen index were performed to investigate the dominant parameters controlling overpressure due to oil generation a good correlation was achieved between measured overpressure from the physical simulation experiments and the calculated data using the derived equations for the pressure change due to oil generation suggesting that the equation can be used to quantitatively estimate overpressure caused by oil generation in source rocks many parameters can affect overpressure caused by oil generation including residual oil coefficient source rock porosity toc hydrogen index and transformation ratio sensitivity analyses indicate that the most effective parameter on the pressure change due to oil generation in the source rocks is the residual oil coefficient implying that the internal pressure seal for the source rock is the most important parameter for overpressure development caused by oil generation overpressure cannot be generated from oil generation if the residual oil coefficient is less than 0 75 source rock toc and hydrogen index have moderate effects on the pressure change caused by oil generation overpressure can be generated when the toc content is as low as 0 5 provided the source rocks have a good internal pressure seal

major changes in glacial and holocene terrestrial temperatures and sources of organic carbon recorded in the amazon fan by tetraether lipids the amazon basin is a major component of the global carbon and hydrological cycles a significant natural source of methane and home to remarkable biodiversity and endemism reconstructing past climate changes in the amazon basin is important for a better understanding of the effect of such changes on these critical functions of the basin using a novel biomarker proxy based on the membrane lipids of soil bacteria with a new regional calibration we present a reconstruction of changes in mean annual air temperatures for the amazon catchment during the last 37 kyr b p biomarkers were extracted from ocean drilling program sediment core odp942 recovered from the amazon fan the amazon fan is a major depository for terrestrial sediments with the advantage that the terrestrial material captured reflects a regional integration of the whole river catchment the reconstructed tropical amazonian temperatures were similar to 5 degrees c cooler at the last glacial maximum similar to 21 degrees c compared to modern values similar to 26 degrees c this is in agreement with previous estimates of tropical continental temperatures in the tropical amazon basin and tropical africa during the last glacial maximum moreover we also illustrate how the soil bacterial membrane lipid record reveals major changes in basin dynamics and sediment provenance during the glacial holocene transition impacting the biomarker reconstructions from similar to 11 kyr onward

distributions of bacterial and archaeal membrane lipids in surface sediments reflect differences in input and loss of terrestrial organic carbon along a cross shelf arctic transect enhanced climate warming affecting the arctic region could have a dramatic impact on the terrigenous organic carbon terroc stored in the eurasian permafrost and could increase the amount of oc remobilized to the arctic shelves an improved understanding of the fate of this remobilized soil oc is essential for better understanding of the consequences for the arctic and global carbon cycle in this study glycerol dialkyl glycerol tetraethers gdgts and bacteriohopanepolyols bhps in surface sediments along a 500 km cross shelf transect from the mouth of the kolyma river to the middle of the vast east siberian sea were analysed to assess their potential and that of the associated branched and isoprenoid tetraether bit and r 0 soil indices for tracing terroc in arctic systems both bhp and gdgt contributions indicated the greatest contribution of terroc close to the river mouth while the associated indices showed declining trends in an offshore direction supporting an increasing marine oc input and or a decrease in terroc however while the bhps indicated a dominance of terroc at the start of the transect the gdgts suggested a much larger almost 50 marine oc input at this point in addition the bit index displayed an exponential decline controlled mainly by a substantial contribution of marine gdgts while

decoupled warming and monsoon precipitation in east asia over the last deglaciation our understanding of the continental climate development in east asia is mainly based on loess paleosol sequences and summer monsoon precipitation reconstructions based on oxygen isotopes delta o 18 of stalagmites from several chinese caves based on these records it is thought that east asian summer monsoon easm precipitation generally follows northern hemisphere nh summer insolation however not much is known about the magnitude and timing of deglacial warming on the east asian continent in this study we reconstruct continental air temperatures for central china covering the last 34 000 yr based on the distribution of fossil branched tetraether membrane lipids of soil bacteria in a loess paleosol sequence from the mangshan loess plateau the results indicate that air temperature varied in phase with nh summer insolation and that the onset of deglacial warming at similar to 19 kyr bp is parallel in timing with other continental records from e g antarctica southern africa and south america the air temperature increased from is c at the onset of the warming to a maximum of 27 degrees c in the early holocene similar to 12 kyr bp in agreement with the temperature increase inferred from e g pollen and phytolith data and permafrost limits in central china comparison of the tetraether membrane lipid derived temperature record with loess paleosol proxy records and stalagmite 5180 records shows that the strengthening of easm precipitation lagged that of deglacial warming by ca 3 kyr moreover intense soil formation in the loess deposits caused by substantial increases in summer monsoon precipitation only started around 12 kyr bp ca 7 kyr lag our results thus show that the intensification of easm precipitation unambiguously lagged deglacial warming and nh summer insolation and may contribute to a better understanding of the mechanisms controlling ice age terminations

hierarchies of overpressure retardation of organic matter maturation case studies from petroleum basins in china the effects of overpressure on different aspects of organic matter maturation have been examined in three basins using multiple parameters overpressure in the yinggehai basin has retarded kerogen maturation hydrocarbon generation and thermal cracking of long chain normal hydrocarbons as well as evolution of isoprenoid hydrocarbons overpressure in the dongpu depression bohai bay basin seems to have retarded the maturation of bulk kerogens reflected by rock eval tmax the thermal cracking of long chain normal hydrocarbons and the evolution of isoprenoid hydrocarbons but seems to have had no detectable effects on vitrinite reflectance overpressure in the qiongdongnan basin has had no detectable retardation effects on all aspects of organic matter maturation the observed phenomena suggest differential retardation of organic matter maturation that is different organic matter maturation reactions and different maturity parameters have been retarded by overpressure to different degrees in the same overpressured system and four hierarchies of overpressure retardation hierarchy i retardation is defined as the state where the overpressure has retarded all aspects of organic matter maturation and is proposed to have been caused by the combination of high formation pressure and excess pressure a high water organic matter ratio and strong retention of reaction products in an early developed strong persistent overpressured system hierarchy ii retardation refers to the case in which all aspects of organic matter maturation except the maturation of hydrogen poor kerogens especially vitrinite have been retarded and seem to have been caused by early developed moderate to strong persistent overpressure hierarchy iii retardation refers to the situation where overpressure has retarded only the thermal cracking of liquid hydrocarbons but has had no detectable effect on the maturation of both hydrogen rich and hydrogen poor kerogens and is proposed to have been caused by moderate to strong persistent overpressures that began to develop around peak oil generation hierarchy iv retardation is defined as the situation where overpressure has had no detectable retardation on all aspects of organic matter maturation and may have been caused by cases wherein the overpressure developed too late the intensity of the overpressure was too low the duration of the overpressure was too short or overpressured fluids had been expelled frequently resulting from both the diversities of organic matter maturation reactions and the complexities of overpressure generation and development the hierarchies of overpressure retardation in different basins may be quite different and it is necessary to use multiple parameters to understand the evolution of the petroleum systems in overpressured basins

spatial heterogeneity of sources of branched tetraethers in shelf systems the geochemistry of tetraethers in the berau river delta kalimantan indonesia abstract the bulk organic matter composition total organic carbon toc content and 13ctoc and composition of isoprenoid and branched glycerol dialkyl glycerol tetraethers gdgt in surface sediments from 43 stations in the berau river delta east kalimantan indonesia including two coast shelf transects and stations within the river mouth were examined to reveal the spatial heterogeneity in these parameters in order to assess the impact of a tropical river loaded with suspended matter on the sedimentary organic matter in the shelf system the high resolution study showed that despite the extensive transport of eroded soil material by the river to the sea terrestrial organic matter and brgdgts are only deposited on a relatively small part of the shelf the concentrations of brgdgts are highest up to 120 g g 1 toc in sediments deposited in and close to the mouth of the berau river and their distribution indicates that they represent a mixture of soil derived and river in situ produced brgdgts crenarchaeol concentrations reach 700 g g 1 toc in sediments deposited on the outer shelf due to thaumarchaeotal production in shelf waters this results in a strong gradient 0 93 0 03 in the bit index with high values in the river mouth and low values on the shelf the decline in the bit index is caused by both decreasing concentrations of the brgdgts and increasing concentrations of crenarchaeol the bit index shows a highly significant but non linear relationship with 13ctoc on the shelf in the area not under the direct influence of the berau river cyclic brgdgts become relatively dominant most probably due to in situ production in the alkaline pore waters of the surface sediments the spatial heterogeneity of sources of brgdgts on the berau shelf complicates the use of brgdgts as temperature proxies application of the global soil calibration to sedimentary mixtures of brgdgts in the river influenced area of the shelf results in a severe underestimation of mean annual air temperature mat by 6 c this is due to the mixed origin of the brgdgts which are not only derived from soil erosion but likely also from riverine production as has been observed for other river systems comparison of the berau shelf other shelf systems indicates that in situ production of brgdgts in shelf sediments is a widespread phenomenon that is especially pronounced at water depths of ca 50 300 m it is hypothesized that this is so because benthic in situ production of heterotrophic brgdgt producing bacteria is fueled by the higher delivery of fresh organic matter to these sediments as the consequence of higher primary productivity in shelf waters and a decreased mineralization due to the relatively short settling times of particles on the shelf for palaeoclimatic studies of marine shelf sediments the application of brgdgts as proxies is severely complicated by the heterogeneity of sources of brgdgts comparison of the brgdgt composition of soils with those of shelf sediments may assist in deciding if sedimentary brgdgts are predominantly derived from soil erosion several methods to do so are discussed

seasonal variability of branched glycerol dialkyl glycerol tetraethers brgdgts in a temperate lake system quantitative climate reconstructions are crucial for understanding the magnitude of and mechanisms behind natural and anthropogenic climate change yet there are few proxies that can reliably reconstruct terrestrial temperature branched glycerol dialkyl glycerol tetraethers brgdgts are bacterial membrane lipids that are increasingly used to reconstruct paleotemperature from lake sediments but despite their potential we have a poor understanding of 1 autochthonous vs allochthonous sources of brgdgts in lakes and 2 the seasonality of and environmental controls on brgdgt production within lakes to investigate these factors we examined water column suspended particulate matter spm and settling particles from a sediment trap collected on a biweekly to monthly basis over a period of three years at lower king pond a small kettle lake in northern vermont usa we also compared the concentration and fractional abundances of brgdgts in spm and settling particles with those of catchment soils river sediments and lake surface sediments to constrain the relative importance of brgdgts derived from the landscape versus brgdgts produced within the lake itself we find significant differences in concentrations and fractional abundances of brgdgts between soil and river sediment samples from the catchment and lake sediments indicating a mostly autochthonous source for lacustrine brgdgts brgdgt concentrations fluxes and fractional abundances in spm vary over the annual cycle indicating that brgdgts are produced throughout the year and respond to changes within the water column the total annual flux of brgdgts settling through the water column is comparable to the brgdgt accumulation rates in surface sediments indicating that in this lake brgdgts are mostly produced within the water column not in the sediment itself while brgdgts are produced in all seasons within the water column the flux to the sediments is highest during periods of spring and fall isothermal mixing potentially biasing paleotemperature reconstructions towards mixing season temperature because the seasonal timing and frequency of lake mixing varies as a function of regional climate lacustrine brgdgt calibrations should be regional in nature and comprise lakes with similar mixing regimes

branched gdgt signals in fluvial sediments of the danube river basin method comparison and longitudinal evolution abundances and distributional changes of branched glycerol dialkyl glycerol tetraethers brgdgts in fluvially influenced sediments are used in various paleoclimate studies to reconstruct variations in soil export continental air temperature and soil ph in corresponding river basins for accurate interpretation of these records it is important to understand the provenance and the evolution of biomarker signals as they move through the river system here we investigate the brgdgt composition of modern river sediments of the danube river the second largest river in europe brgdgt based mean annual air temperature and soil ph parallel the actual values of air temperature and soil ph from the upper to the lower basin showing that signals predominantly reflect local as opposed to basin wide environmental conditions furthermore data generated using the recently developed method with improved chromatography separating the 6 methyl isomers from the 5 methyl isomers was compared with that resulting from the conventional method we show that the temperatures and ph values reconstructed using the data obtained by improved chromatography best resemble the local environmental conditions throughout the danube river basin our results highlight the importance of in depth studies within river systems to better understand the provenance of biomarker signals in fluvially derived sedimentary archives

geochemical evidence for coal derived hydrocarbons and their charge history in the dabei gas field kuqa thrust belt tarim basin nw china abstract large to middle scale thrust structures are important reservoir plays for coal derived hydrocarbons in the foreland basins of nw china with both gas and some accompanying oil in the dabei gas field of the kuqa thrust however the oil and gas pools are vertically distributed in a quite unique way 1 liquid oil and some dissolved gas are present in the dawanqi anticline with the reservoir at 300 700 m depth forming the only oil field in the kuqa thrust 2 gas and minor accompanying oil are found in the deep reservoir of the dabei 1 and dabei 2 thrust traps around 5000 6000 m depth 3 an extremely dry gas pool is found in the dabei 3 thrust trap where the depth of the reservoir is over 7000 m geochemical data suggest that the hydrocarbons in the dawanqi anticline and the dabei thrust traps originated from a similar source i e the underlying jurassic coal measures with some contribution from jurassic lacustrine shales the jurassic source rocks did not start to generate oil until the miocene around the kangcun stage and extended into the pliocene the kuche stage with the main gas generation period in the pliocene the kuche stage and the quaternary because the traps formed relatively early the dabei 1 and dabei 2 thrusts could trap some of the early generated oils but most of the early charged oil was redistributed to the shallower dawanqi anticline during the kuche stage the dabei 3 thrust trap formed concurrently with major gas generation and thus could not trap liquid hydrocarbons the difference in the vertical distribution of the hydrocarbon accumulations in the dabei gas field resulted from a complex interplay of source variability structural evolution of the basin and thermal maturation

petroleum geology of kela 2 the most productive gas field in china abstract the kela 2 gas field located in the kuqa depression of tarim basin is the most productive gas field in china based on per unit surface acreage the gas trap is a subsurface anticline formed along an e w trending thrust belt in front of the southern tianshan mountains the gas pay zones are located in fine grained sandstones of a fan delta front facies in the lower cretaceous bashijiqik formation k l bs and eogene evaporitic rocks serve as regional cap rocks the gases were derived primarily from over mature jurassic coal measures peak gas generation and final shaping of the kela 2 structure occurred relatively late in the late himalayan orogeny 5 0 ma thrust faulting appears to have played a significant role in the hydrocarbon generation migration accumulation and preservation in this foreland basin detailed delineation of the kela 2 gas field indicates that high quality regional cap rocks are essential for the formation of the super rich abnormally pressured giant gas fields while buried anticlines under the overthrust zone are the favorable gas habitat late gas accumulation is considered to be decisive for the conservation of the giant gas fields

effects of early petroleum charge and overpressure on reservoir porosity preservation in the giant kela 2 gas field kuqa depression tarim basin northwest china kela 2 is a giant gas field with a proven reserve of 597 tcf in the kuqa depression northern tarim basin widespread overpressures have been encountered in the eocene and cretaceous sandstone reservoirs of the field with pressure coefficients up to 2 1 from drill stem tests and well log data analysis disequilibrium compaction associated with horizontal tectonic compression may be the dominant overpressure mechanism in the sandstone reservoirs because the overpressured sandstone with a maximum burial depth over 6000 m 19 685 ft displays anomalously high porosity and low density the causes for sandstone reservoirs with anomalously high porosity in the kela 2 gas field were studied based on an integrated investigation of sandstone reservoir characteristics paleo oil water contact petroleum charge history and overpressure evolution collective evidence indicates that early oil charge had retarded the porosity reduction of the reservoir sandstone and resulted in disequilibrium compaction from overburden rocks and overpressure from disequilibrium compaction and horizontal tectonic compression at the beginning of the rapid subsidence and deposition in the kela 2 gas field again contributed to the preservation of the reservoir porosity 1 overpressured mudstones in the kela 2 gas field are characteristic of normal compaction and overpressure was generated by horizontal tectonic compression instead of disequilibrium compaction 2 the reservoir sandstones with high porosity and permeability are associated with high paleo oil saturation as indicated by quantitative grain fluorescence qgf responses and anomalous qgf on extract intensity 3 sandstone units below the paleo oil water contact have very low porosity and permeability and 4 three episodes of oil and one episode of gas charge are identified in the sandstone reservoirs of the kela 2 gas field and the later two episodes of oil charge occurred circa 5 5 4 5 ma which corresponds to the beginning of the rapid tectonic subsidence and deposition in the kuqa depression the initially charged oil in the sandstone reservoirs was subsequently displaced by gas at circa 3 2 ma through fault activation at the edge of the anticline trap the overpressure evolution for the k1bs reservoir sandstone in the kela 2 gas field indicates that the apparent overpressure development in the sandstone reservoir began at 5 ma following the major oil charge and has been maintained to the present overpressure development from 5 ma in the sandstone reservoirs of the kela 2 gas field is believed to be the dominant cause of the porosity preservation

distribution of tetraether lipids in the 25 ka sedimentary record of lake challa extracting reliable tex86 and mbt cbt palaeotemperatures from an equatorial african lake the distribution of isoprenoid and branched glycerol dialkyl glycerol tetraether gdgt lipids was studied in the sedimentary record of lake challa a permanently stratified partly anoxic crater lake on the southeastern slope of mt kilimanjaro kenya tanzania to examine if the gdgts could be used to reconstruct past variation in regional temperature the study material comprised 230 samples from a continuous sediment sequence spanning the last 25 ka with excellent age control based on high resolution ams c 14 dating the distribution of gdgts showed large variation through time in some time intervals i e from 20 4 to 15 9 ka bp and during the younger dryas 12 9 11 7 ka bp crenarchaeol was the most abundant gdgt whereas at other times i e during the early holocene branched gdgts and gdgt 0 were the major gdgt constituents in some intervals of the sequence the relative abundance of gdgt 0 and gdgt 2 was too high to be derived exclusively from lacustrine thaumarchaeota suggesting a sizable contribution from methanogens and other archaea this severely complicated application of tex86 palaeothermometry in this lake and limited reliable reconstruction of lake water temperature to the time interval 25 13 ka bp i e the last glacial maximum and the period of post glacial warming the tex86 inferred timing of this warming is similar to that recorded previously in two of the large african rift lakes while its magnitude is slightly or much higher than that recorded at these other sites depending on which lake based tex86 calibration is used application of calibration models based on distributions of branched gdgts developed for lakes inferred temperatures of 15 18 degrees c for the last glacial maximum and 19 22 degrees c for the holocene however the mbt cbt palaeothermometer reconstructs temperatures as low as 12 degrees c for a lateglacial period centred on 15 ka bp variation in down core values of the bit index are mainly determined by the varying production rate of crenarchaeol relative to in situ produced branched gdgts the apparent relationship of the bit index with climatic moisture balance can be explained either by the direct influence of lake level and wind strength on nutrient recycling or by influx of soil nutrients promoting aquatic productivity and nitrification this study shows that gdgts can aid in obtaining climatic information from lake records but that the obtained data should be interpreted with care

distributions of branched gdgts in a tropical lake system implications for lacustrine application of the mbt cbt paleoproxy branched glycerol dialkyl glycerol tetraether gdgt lipids are abundant and ubiquitous in lake sediments potentially allowing for a paleolimnological application of the so called mbt cbt proxy methylation index of branched tetraethers cyclization ratio of branched tetraethers to investigate the origin and characteristics of these compounds in lacustrine environments we examined the distributions of gdgts in soils river sediments and lake sediments from lake towuti on the island of sulawesi indonesia we found significant differences in the degree of methylation and cyclization expressed by way of the mbt and cbt indices between the soil samples and the aquatic samples suggesting that there may be in situ production of gdgts in the aquatic environment based on these findings we urge caution in the application of the mbt cbt paleoproxy to lake sediments and encourage more rigorous study of these compounds in freshwater environments

onset of long term cooling of greenland near the eocene oligocene boundary as revealed by branched tetraether lipids the eocene oligocene e o boundary interval is considered to be one of the major transitions in earth s climate witnessing the fi rst major expansion of the east antarctic ice sheet however the extent of the associated climatic cooling especially for high northern latitude continental landmasses is poorly constrained in this study we reconstruct the fi rst mean annual air temperature maat for the greenland landmass during the late eocene and early oligocene by applying a new proxy based on the distribution of branched tetraether lipids derived from soil bacteria preserved in a marine sediment core from the greenland basin the temperature estimates are compared with a composite continental temperature record based on bioclimatic analysis of pollen assemblages both proxies reveal comparable late eocene maats of 13 15 c and a gradual long term cooling of 3 5 c starting near the e o boundary these data are in agreement with other maat reconstructions from northern midlatitude continents and suggest a general cooling of the northern hemisphere during the e o transition

the c 32 alkane 1 15 diol as a tracer for riverine input in coastal seas long chain alkyl diols are lipids that occur ubiquitously in marine sediments and are used as a proxy for sea surface temperature sst using the long chain diol index ldi and for upwelling intensity high nutrient conditions the distribution of 1 13 and 1 15 diols has been documented in open marine and lacustrine sediments and suspended particulate matter but rarely in coastal seas receiving a significant riverine and thus continental organic matter input here we studied the distribution of diols in four shelf seas with major river outflows the gulf of lion the kara sea the amazon shelf and the berau delta covering a wide range of climate conditions the relative abundance of the c32 1 15 diol is consistently higher close to the river mouth and particularly in the suspended particulate matter of the rivers suggesting a terrigenous source this is supported by statistical analysis which points out a significant positive correlation between the c32 1 15 diol and the branched and isoprenoid tetraether index a proxy reflecting soil and riverine input in marine environments however the c32 1 15 diol was not detected in soils and is unlikely to be derived from vegetation suggesting that the c32 1 15 diol is mainly produced in rivers this agrees with the observation that it is a dominant diol in most cultivated freshwater eustigmatophyte algae we therefore suggest that the relative abundance of the c32 1 15 diol can potentially be used as a proxy for riverine organic matter input in shelf seas our results also show that long chain alkyl diols delivered by rivers can substantially affect ldi reconstructed ssts in coastal regions close to river mouths

change in provenance of branched glycerol dialkyl glycerol tetraethers over the holocene in the baltic sea and its impact on continental climate reconstruction abstract the baltic sea is an enclosed basin that experienced a number of different salinity phases during the holocene corresponding to the establishment of a connection with the north sea branched glycerol dialkyl glycerol tetraethers brgdgts in surface sediments and holocene sedimentary successions from the gotland and arkona basins were analyzed to examine their potential applicability as indicators for soil organic matter input as well as their suitability for paleoclimate reconstructions our results show a marked change in brgdgt distributions and the branched and isoprenoid tetraether bit index the transition of the ancylus lake fresh to the littorina sea brackish phase is revealed by a large drop in the bit index and an increase in the mbt 5me which reveals a large shift in provenance of the sedimentary brgdgts during the lake phase brgdgts are presumed to be primarily produced by in situ production in the water column during the brackish phase in situ brgdgt production in the alkaline pore waters of the surface sediments as revealed by their high degree of cyclization was predominant although there was evidence of occasional input of soil derived brgdgts the predominant aquatic autochthonous production of brgdgts does not allow the use of brgdgts for continental air temperature reconstructions but they can be used for bottom water and lake temperature reconstructions during some intervals the results from this study demonstrate that geological changes and concomittant salinity variations can be revealed by the provenance of brgdgts

in situ produced branched glycerol dialkyl glycerol tetraethers in suspended particulate matter from the yenisei river eastern siberia abstract soil derived branched glycerol dialkyl glycerol tetraethers brgdgts in marine river fan sediments have a potential use for determining changes in the mean annual temperature mat and ph of the river watershed soils prior to their incorporation in marine sediments the compounds are transported to the marine system by rivers however emerging evidence suggests that the brgdgts in freshwater systems can be derived from both soil run off and in situ production the production of brgdgts in the river system can complicate the interpretation of the brgdgt signal delivered to the marine system therefore we studied the distribution of brgdgt lipids in suspended particulate matter spm of the yenisei river chromatographic improvements allowed quantification of the recently described hexamethylated brgdgt isomer characterized by having two methyl groups at the 6 6 instead of the 5 5 positions in an environmental dataset for the first time this novel compound was the most abundant brgdgt in spm from the yenisei its fractional abundance correlated well with that of the 6 methyl isomer of the hexamethylated brgdgt that contains one cyclopentane moiety the yenisei river watershed is characterized by large differences in mat 11 c as it spans a large latitudinal range 46 73 n which would be expected to be reflected in brgdgt distributions of its soils however the brgdgt distributions in its spm show little variation furthermore the reconstructed ph values are high compared to the watershed soil ph we therefore hypothesize that the brgdgts in the yenisei river spm are predominantly produced in situ and not primarily derived from erosion of soil this accounts for the absence of a change in the temperature signal as the river water temperature is more stable using a lake calibration the reconstructed temperature values agree with the mean summer temperatures mst recorded the brgdgts delivered to the sea by the yenisei river during this season are thus not soil derived possibly complicating the use of brgdgts in marine sediments for palaeoclimate reconstructions

simulation of three dimensional flow of immiscible fluids within and below the unsaturated zone this paper presents a two phase flow model based on a three dimensional finite difference formulation as three dimensional simulations can require substantial computer effort a numerical technique that takes advantage of vector and parallel processing computer architecture is developed the model is posed in terms of water saturation and nonwetting fluid pressure it uses three phase capillary pressure and relative permeability relationships to permit simulation within or below the unsaturated zone a modified formulation of slice successive overtaxation an iterative matrix solution technique is introduced this technique is designed to use parallel processing capabilities of new computers the model is applied to immiscible fluid flow at two chemical waste landfills near niagara falls new york at both sites denser than water nonaqueous liquids napls are present in the groundwater regimes in relatively large quantities the model applications address several technical concerns at the two sites including the effectiveness of clay as a geologic barrier to napl migration owing to capillary pressure forces the three dimensional aspects of dense napl flow and the sensitivity of napl recovery in pumping wells due to various hydrogeologic and fluid properties the results of the applications show that 1 even under a downward hydraulic gradient natural differences in capillary pressure relationships for different lithologies can prevent downward migration of napl 2 without any lithologic capillary barrier an upward hydraulic gradient induced by a de watering system can prevent downward migration of napl 3 napl recovery at wells is sensitive to relative permeability a relationship that requires field calibration in many settings and 4 the three dimensional aspects of two phase flow and hydrogeologic heterogeneity require explicit treatment in many settings

sources and distributions of branched and isoprenoid tetraether lipids on the amazon shelf and fan implications for the use of gdgt based proxies in marine sediments branched glycerol dialkyl glycerol tetraethers brgdgts in river fan sediments have been used successfully to reconstruct mean annual air temperature maat and soil ph of the congo river drainage basin however in a previous study of amazon deep sea fan sediments the reconstructed maats were ca 10 c colder than the actual maat of the amazon basin in this study we investigated this apparent offset by comparing the concentrations and distributions of brgdgts in amazon river suspended particulate matter spm and sediments to those in marine spm and surface sediments the riverine brgdgt input was evident from the elevated brgdgt concentrations in marine spm and surface sediments close to the river mouth the distributions of brgdgts in marine spm and sediments varied widely but generally showed a higher relative abundance of methylated and cyclic brgdgts than those in the river since this difference in brgdgt distribution was also found in intact polar lipid ipl derived brgdgts which were more recently produced the change in the marine brgdgt distribution was most likely due to marine in situ production consequently the maats calculated based on the methylation of branched tetraethers mbt and the cyclisation of branched tetraethers cbt were lower and the cbt derived ph values were higher than those of the amazon basin however spm and sediments from stations close to the river mouth still showed mbt cbt values that were similar to those of the river therefore we recommend caution when applying the mbt cbt proxy it should only be used in sediment cores that were under high river influence the influence of riverine derived isoprenoid gdgt isogdgt on the isogdgt based tex86 temperature proxy was also examined in marine spm and sediments an input of riverine isogdgts from the amazon river was apparent but its influence on the marine tex86 was minor since the tex86 of spm in the amazon river was similar to that in the marine spm and sediments

dense nonaqueous phase liquid dnapl source zone characterization influence of hydraulic property correlation on predictions of dnapl infiltration and entrapment 1 the influence of aquifer property correlation on multiphase fluid migration and entrapment was explored through the use of correlated and uncorrelated porosity permeability and capillary pressure saturation pc sat parameter fields in a cross sectional numerical multiphase flow model data collected from core samples in a nonuniform sandy aquifer were used to generate three dimensional aquifer parameter fields porosity was assumed to be uniform or simulated using sequential gaussian simulation sgs permeability k was modeled independently of porosity using sgs as well as simulated geostatistical indicator classes derived from measured grain size distribution curves retention characteristics were assigned employing leverett scaling of a representative pc sat curve to the geostatistical k fields or alternatively on the basis of simulated indicator classes and porosity values ensemble dense nonaqueous phase liquid dnapl infiltration and entrapment behavior for a hypothetical tetrachloroethylene pce spill was simulated in four sets of two dimensional profiles extracted from these realizations comparisons of saturation profiles and spatial moments from point source dnapl infiltration simulations suggest that choices involving the geostatistical algorithm used to model k and the incorporation of variable versus uniform porosity have a smaller influence than choices involving the scaling of capillary retention properties to k from these simulations it is apparent that the degree of spatial correlation in pc sat parameters exerts a controlling influence on predicted dnapl spreading and redistribution in saturated aquifers the resultant distribution of mass within a dnapl source zone will have implications for dnapl recovery and subsequent mass fluxes in remediation operations

calculated volume and pressure changes during the thermal cracking of oil to gas in reservoirs 1 the rising temperature that accompanies increasing burial depth converts oil in a reservoir into thermal gas a consideration of hydrogen balance during this cracking shows that approximately 3000 cubic ft 85 cubic meters of gas at standard temperature and pressure is generated from each barrel of oil in addition a graphitic residue is precipitated if the volume relationships among oil thermal gas and the graphitic residue are combined with data for gas solubility in pore water and gas nonideality z factor then pressure can be calculated for any degree of thermal cracking these calculations show that in an effectively isolated system pressures would become very high and could considerably exceed the rock load so that fracturing must occur causing pressure b eed off and loss of gas the lithostatic gradient 1 0 psi ft or 22 6 kpa m is reached after only about 1 0 of the oil is cracked if the reservoir system remains open i e at hydrostatic pressure and is initially filled with oil that is subsequently cracked to gas then roughly 75 of the gas will be lost or the reservoir volume must effectively increase in size for example by moving the gas water contact downward

drastic changes in the distribution of branched tetraether lipids in suspended matter and sediments from the yenisei river and kara sea siberia implications for the use of brgdgt based proxies in coastal marine sediments abstract the distribution of branched glycerol dialkyl glycerol tetraethers brgdgts in soils has been shown to correlate with ph and mean annual air temperature because of this dependence brgdgts have found an application as palaeoclimate proxies in coastal marine sediments based on the assumption that their distribution is not altered during the transport from soils to marine systems by rivers to study the processes acting on the brgdgt distributions we analysed the full suite of brgdgts including the recently described 6 me brgdgts in both the suspended particulate matter spm of the siberian yenisei river and the spm and sediments of its outflow in the kara sea the brgdgt distribution in the spm of the yenisei river was fairly constant and characterized by high abundances of the 6 me brgdgts reflecting their production at the neutral ph of the river water however the brgdgt distribution showed marked shifts in the marine system firstly in the yenisei river mouth the fractional abundance of the 6 me brgdgts decreases sharply the brgdgt signature in the yenisei river mouth possibly reflects brgdgts delivered during the spring floods that may carry a different distribution also coastal cliffs were shown to contain brgdgts and to influence especially those sites without major river inputs e g khalmyer bay further removed from the river mouth in situ production of brgdgts in the marine system influences the distribution however also the fractional abundance of the tetramethylated brgdgt ia increases resulting in a distribution that is distinct from in situ produced signals at similar latitudes svalbard we suggest that this shift may be caused by preferential degradation of labile riverine in situ produced brgdgts and the subsequent enrichment in less labile soil material the offshore distribution indeed agrees with the brgdgt distribution encountered in a lowland peat this implies that the offshore kara sea sediments possibly carry a soil dominated signal indicating potential for palaeoclimate reconstructions at this site both in the river system and coastal cliffs brgdgts were much more abundant than crenarchaeol an archaeal isoprenoid gdgt resulting in high 0 93 branched and isoprenoid tetraether bit index values moving downstream in the marine sediments a decrease in brgdgt concentrations coeval with an increase in crenarchaeol resulted in decreasing bit index values this decrease correlates with changes in bulk proxies for terrigenous input 13corg c n confirming the use of the bit index to trace the delivery of river transported and coastal cliff derived terrigenous organic matter

tracing soil organic carbon in the lower amazon river and its tributaries using gdgt distributions and bulk organic matter properties abstract in order to trace the transport of soil organic carbon oc in the lower amazon basin we investigated the distributions of crenarchaeol and branched glycerol dialkyl glycerol tetraethers gdgts by analyzing riverbed sediments and river suspended particulate matter spm collected in the solimoes amazon river mainstem and its tributaries the branched and isoprenoid tetraether bit index a proxy for river transported soil oc into the ocean was determined from the distributions of these gdgts the gdgt derived parameters were compared with other bulk geochemical data i e c n ratio and stable carbon isotopic composition the gdgt derived and bulk geochemical data indicate that riverine spm and riverbed sediments in the lower amazon river and its tributaries are a mixture of c3 plant derived soil oc and aquatic derived oc the branched gdgts in the spm and riverbed sediments did not predominantly originate from the high andes soils 2500 m in altitude as was suggested previously however further constraint on the soil source area of branched gdgts was hampered due to the deficiency of soil data from the lower montane forest areas in the andes our study also revealed seasonal and interannual variation in gdgt composition as well as soil oc discharge which was closely related to the hydrological cycle by way of a simple binary mixing model using the flux weighted bit values at obidos the last gauging station in the amazon river we estimated that 70 80 of the poc pool in the river was derived of soil oc however care should be taken to use the bit index since it showed a non conservative behaviour along the river continuum due to the aquatic production of crenarchaeol further investigation using a continuous sampling strategy following the full hydrological cycle is required to fully understand how soil derived gdgt signals are transformed in large tropical river systems through their transport pathway to the ocean

distribution of branched gdgts in surface sediments from the colville river alaska implications for the mbt cbt paleothermometer in arctic marine sediments significant climate fluctuations in the arctic over the recent past and additional predicted future temperature changes highlight the need for high resolution arctic paleoclimate records arctic coastal environments supplied with terrigenous sediment from arctic rivers have the potential to provide annual to subdecadal resolution records of climate variability over the last few millennia a potential tool for paleotemperature reconstructions in these marine sediments is the revised methylation index of branched tetraethers mbt cyclization ratio of branched tetraethers cbt proxy based on branched glycerol dialkyl glycerol tetraethers brgdgts in this study we examine the source of brgdgts in the colville river alaska and the adjacent simpson lagoon and reconstruct temperatures from simpson lagoon sediments to evaluate the applicability of this proxy in arctic estuarine environments the colville catchment soils fluvial sediments and estuarine sediments contain statistically similar brgdgt distributions indicating that the brgdgts throughout the system are soil derived with little alteration from in situ brgdgt production in the river or coastal waters temperatures reconstructed from the mbt cbt indices for surface samples show good agreement with regional summer june through september temperatures suggesting a seasonal bias in arctic temperature reconstructions from the colville system in addition we reconstruct paleotemperatures from an estuarine sediment core that spans the last 75 years revealing an overall warming trend in the twentieth century that is consistent with trends observed in regional instrumental records these results support the application of this brgdgt based paleotemperature proxy for subdecadal scale summer temperature reconstructions in arctic estuaries containing organic material derived from sediment laden episodic rivers

new evidence on the neogene uplift of south tianshan constraints from the u th he and aft ages of borehole samples of the tarim basin and implications for hydrocarbon generation we identified a neogene rapid uplift denudation event of the south tianshan based on apatite u th he and apatite fission track aft ages in tertiary rocks of the tarim basin using borehole samples the u th he thermochronology can be used to reveal the tectono thermal events with lower temperature than that of aft thermochronology and has not been used previously to study the uplift of the tianshan mountain using these data we show the relationship between the uplift of the south tianshan and the subsidence deposition of the northern tarim basin during the neogene the apatite helium ages reveal the migration of uplift erosion and deposition in the northern tarim basin a rapid uplift of the south tianshan during the miocene and a corresponding rapid subsidence in the northern tarim basin occurred however in the pliocene the kuqa depression and south tianshan uplifted and eroded at the same time and in turn provided the detrital source rocks for the northern uplift of the tarim basin in contrast to earlier studies we arrive at the conclusion that the south tianshan experienced rapid uplift in the miocene based on u th he data of apatite obtained from borehole samples collected in the tarim basin itself and not from the bordering mountain chain combined apatite u th he and fission track thermochronometry enables reconstruction of thermal histories of sedimentary rocks between 40 and 120 c and this has implications for the generation of liquid hydrocarbon in the 65 120 c range in the basin thermal and burial histories of typical samples were also modelled to show the rapid uplift in our study our works not only provide a new evidence for the south tianshan uplift but also indicate that there is a coupling between uplift and subsidence in the south tianshan and adjacent northern part of the tarim basin which controlled hydrocarbon accumulation in the kuqa depression and northern uplift of the tarim basin

selective preservation of soil organic matter in oxidized marine sediments madeira abyssal plain in ocean margin sediments both marine and terrestrial organic matter om are buried but the factors governing their relative preservation and degradation are not well understood in this study we analysed the degree of preservation of marine isoprenoidal and soil derived branched glycerol dialkyl glycerol tetraethers gdgts upon long term oxygen exposure in om rich turbidites from the madeira abyssal plain by analyzing gdgt concentrations across oxidation fronts relative to the anoxic part of the turbidites ca 7 20 of the soil derived branched gdgts were preserved in the oxidized part while only 0 2 3 of the marine isoprenoid gdgt crenarchaeol was preserved due to these different preservation factors the branched isoprenoid tetraether bit index a ratio between crenarchaeol and the major branched gdgts that is used as a tracer for soil derived organic matter substantially increases from 0 02 to 0 4 split flow thin cell splitt separation of turbidite sediments showed that the enhanced preservation of soil derived carbon was a general phenomenon across the fine particle size ranges 38 m calculations reveal that despite their relatively similar chemical structures degradation rates of crenarchaeol are 2 fold higher than those of soil derived branched gdgts suggesting preferential soil om preservation possibly due to matrix protection

identification and carbon isotope composition of a novel branched gdgt isomer in lake sediments evidence for lacustrine branched gdgt production branched glycerol dialkyl glycerol tetraethers brgdgts are bacterial membrane lipids that occur ubiquitously in soils and lacustrine sediments and have great potential as proxy indicators for paleotemperature and ph reconstructions initially brgdgts in lakes were thought to originate from soils of the watershed the composition of the lacustrine brgdgt pool however often differs substantially from that in catchment soils complicating the application of the brgdgt paleothermometer to lake sediments this suggests that terrigenous brgdgt signals in lacustrine sedimentary archives may be affected by aquatic in situ production in sediments of a swiss mountain lake we detected a novel hexamethylated brgdgt which elutes between the known 5 and 6 methyl brgdgt isomers during hplc ms analysis this novel isomer accounted for 8 5 of the total brgdgts most remarkably this brgdgt was not detected in soils collected from the catchment of the lake providing circumstantial evidence for an in situ brgdgt source in the lake s water column or sediments isolation of the compound by preparative hplc and subsequent gc ms analysis of the alkyl chains revealed that the novel brgdgt comprises two structural isomers one possesses a 5 13 16 and a 6 13 16 trimethyloctacosanyl moiety and constitutes 84 of the new brgdgt the second contains a 13 16 dimethyloctacosanyl and a 5 13 16 23 tetramethyloctacosanyl moiety the 13c values of both the alkyl chains derived from the novel brgdgt 46 and all other major brgdgts 43 to 44 were significantly lower than those of brgdgt derived alkanes in catchment soils 27 to 28 further attesting to in situ production of brgdgts in the studied lake

persistent near tropical warmth on the antarctic continent during the early eocene epoch the warmest global climates of the past 65 million years occurred during the early eocene epoch about 55 to 48 million years ago when the equator to pole temperature gradients were much smaller than today1 2 and atmospheric carbon dioxide levels were in excess of one thousand parts per million by volume3 4 recently the early eocene has received considerable interest because it may provide insight into the response of earth s climate and biosphere to the high atmospheric carbon dioxide levels that are expected in the near future5 as a consequence of unabated anthropogenic carbon emissions4 6 climatic conditions of the early eocene greenhouse world however are poorly constrained in critical regions particularly antarctica here we present a well dated record of early eocene climate on antarctica from an ocean sediment core recovered off the wilkes land coast of east antarctica the information from biotic climate proxies pollen and spores and independent organic geochemical climate proxies indices based on branched tetraether lipids yields quantitative seasonal temperature reconstructions for the early eocene greenhouse world on antarctica we show that the climate in lowland settings along the wilkes land coast at a palaeolatitude of about 70 south supported the growth of highly diverse near tropical forests characterized by mesothermal to megathermal floral elements including palms and bombacoideae notably winters were extremely mild warmer than 10 c and essentially frost free despite polar darkness which provides a critical new constraint for the validation of climate models and for understanding the response of high latitude terrestrial ecosystems to increased carbon dioxide forcing

characteristics and origin of natural gases in the kuqa depression of tarim basin nw china abstract significant gas condensate as well as some black oils have been discovered in the kuqa depression of tarim basin nw china dry gases with high 13 c values occur in the kelasu structural belt wet isotopically light gases in the yiqikelik belt whereas condensates are distributed mainly in the front uplift area kinetic modeling results show that the variation of methane and ethane isotopes with increasing vitrinite reflectance is independent of heating rates for a given source rock two maturity trends have been observed on a c 2 c 1 13 c 1 plot one for thermogenic gases associated with coal another for oil associated gases with minor contribution from biogenic gas it is most likely that the gases in the kelasu belt and front uplift area were derived from the jurassic coal measures and triassic lacustrine shales respectively with those in the yiqikelik belt being the mixtures of gases from the two sources both jurassic coals and triassic lacustrine shales appear to have contributed to the gases in the kela 2 kl2 and dina 2 dn2 the two largest gas fields in the tarim basin

conceptual model for origin of abnormally pressured gas accumulations in low permeability reservoirs the largest gas fields in the rocky mountain region occur in abnormally pressured reservoirs these gas accumulations are different from more conventional gas accumulations in that they are commonly located in basin center positions they occur downdip from water bearing rocks and they are in overpressured or underpressured low permeability reservoirs we suggest that overpressured and underpressured gas accumulations of this type have a common origin in basins containing overpressured gas accumulations rates of thermogenic gas accumulation exceed gas loss causing fluid gas pressure to rise above the regional hydrostatic pressure within the overpressured gas generation zone free water in the larger pores is forced out of the gas generation zone into overlying and updip normally pressured water bearing rocks the remaining tightly bound water at irreducible saturation levels cannot remove dissolution products precluding significant permeability and porosity enhancement thus while other diagenetic processes continue a pore network with very low permeability develops as a result gas accumulates in these low permeability reservoirs at rates higher than it is lost in basins containing underpressured gas accumulations rates of gas generation and accumulation are less than gas loss these basins have typically experienced significant uplift and erosion and or temporal variations of paleotemperature despite these modifications the basin center gas accumulation persists but because of changes in the basin dynamics the overpressured accumulation evolves into an underpressured system

branched glycerol dialkyl glycerol tetraethers and crenarchaeol record post glacial sea level rise and shift in source of terrigenous brgdgts in the kara sea arctic ocean this study evaluates the glycerol dialkyl glycerol tetraether gdgt distribution and provenance in sediments spanning a minimum of 13 3 ka from the st anna trough northern kara sea the site has experienced extensive fluctuation in the delivery of river derived organic matter om caused by a eustatic change in sea level this is in line with the record of the concentration of the isoprenoid gdgt crenarchaeol produced by marine thaumarchaota which was low at the bottom of the core increasing gradually in the most shallow unit the concentration of branched br gdgts showed an opposite trend and a marked shift in distribution the deepest sediments 10 ka with a distribution currently encountered in surface sediments in front of the yenisei river are characterized by terrigenous brgdgts whereas the distribution in the shallowest unit 10 ka is strongly influenced by marine in situ brgdgts during the shift from terrigenous to marine sourced brgdgts there was one horizon where a pronounced shift in the brgdgt distribution was observed and the brgdgt concentration significantly decreased as the brgdgts delivered to the current kara sea system are derived from several sources we postulate that a temporary change in the relative importance of the brgdgt sources happened during this interval both in situ production and changing brgdgt provenance have implications for paleoclimate reconstruction using brgdgts in situ production of marine brgdgts results in a higher reconstructed ph however these in situ produced brgdgts did not influence the reconstructed mean annual air temperature mat when the matmrs calibration was used changes in the relative contribution of brgdgt sub pools were shown however to influence both soil ph reconstruction and mat reconstruction

occurrence of tetraether lipids in stalagmites implications for sources and gdgt based proxies lipid biomarkers in stalagmites have potential in palaeoenvironmental reconstruction but glycerol dialkyl glycerol tetraethers gdgts in stalagmites have rarely been investigated we report the occurrence of archaeal isoprenoid gdgts and bacterial branched gdgts in heshang cave stalagmites in central china the archaeal component crenarchaeol dominated bacterial branched gdgts in the stalagmites and on the weathered parent rock surface collected inside the cave in contrast the distribution of gdgts in the overlying soil shows that branched gdgts dominated archaeal gdgts hence the majority of archaeal gdgts in stalagmites may be produced by crenarchaeota inhabiting the cave rather than being inherited from the overlying soil bacterial branched gdgt distributions expressed as mbt and cbt indices showed remarkable differences between stalagmite and soil samples implying that most branched gdgts may also be produced in situ in the cave the tex86 or tex86 values were found to increase with more depleted 18o values representing much stronger monsoon and therefore usually higher temperatures in the study region however the mbt cbt index in stalagmites may be influenced by a variety of factors besides palaeotemperature

the influence of pressure on petroleum generation and maturation as suggested by aqueous pyrolysis because fluid pressures are transient in sedimentary basins over geologic time the effect of increasing fluid pressure on organic matter metamorphism is difficult to determine and conflicting opinions exist concerning its influence properly performed aqueous pyrolysis experiments can closely simulate hydrocarbon generation and maturation in nature and thus offer an excellent way to study the influence of pressure such experiments carried out on the retort phosphatic shale member of the lower permian phosphoria formation type ii s organic matter at different constant temperatures demonstrated that increasing pressure significantly retards all aspects of organic matter metamorphism including hydrocarbon generation maturation and thermal destruction this conclusion results from detailed quantitative and qualitative analyses of all products from hydrocarbon generation from the c1 to c4 hydrocarbon gases to the asphaltenes and also from analyses of the reacted rocks we have documented that our aqueous pyrolysis experiments closely simulated natural hydrocarbon generation and maturation thus the data taken as a function of pressure have relevance to the influence of normal and abnormal fluid pressures as related to 1 depths and temperatures of mainstage hydrocarbon generation 2 the thermal destruction of deposits of gas or light oil or their preservation to unexpectedly high maturation ranks and 3 the persistence of measurable to moderate concentrations of c15 hydrocarbons in fine grained rocks even to ultra high maturation ranks

bacteriohopanepolyol distribution in yenisei river and kara sea suspended particulate matter and sediments traces terrigenous organic matter input abstract bacteriohopanepolyols bhps are ubiquitous bacterial membrane lipids encountered in soils river and marine suspended particulate matter spm and sediments their abundance and distribution provides a direct means to identify bacterial inputs and can be used to trace soil derived bacterial organic matter om and in some cases the presence of bacterial groups and their activities in aquatic systems we have studied the bhp distribution in the spm of a major siberian river yenisei river that crosses a large latitudinal gradient draining a large part of mongolia and siberian russia the yenisei river is the main river to flow into the kara sea a shelf sea of the arctic ocean we show that the bhp distribution and concentration of spm and surface sediments of the yenisei outflow in the kara sea allow to trace soil marker bhps and evaluate the performance of the r soil index a proxy developed to trace bacterial soil derived om soil marker bhps are present in the yenisei river and their concentration decreases from the yenisei river outflow into the offshore marine sediments the r soil correlates well with an independent proxy for bacterial om the bit index r2 0 82 and has a moderate correlation with the 13corg values a bulk om proxy for terrigenous input r2 0 44 consequently the r soil index performs well in the kara sea strengthening its application for tracing bacterial om in the arctic ocean both in modern and downcore sediments furthermore a suite of bhps that are characteristic for methanotrophic bacteria i e 35 aminobacteriohopane 30 31 32 33 34 pentol aminopentol and 35 aminobacteriohopane 31 32 33 34 tetrol aminotetrol is encountered in the yenisei outflow sediments these components are partly sourced from terrigenous sources but are likely also produced in situ in the marine sediments the distribution of the pentafunctionalized cyclitol ether bhp in the marine systems is noteworthy and indicates that it can possibly be applied as a marker for cyanobacterial biomass in marine sediments

constraining the applicability of organic paleotemperature proxies for the last 90 myrs abstract we evaluated changes in the distributions of long chain alkenones long chain diols and gdgts lipids commonly used for paleothermometry over the last 90 myrs for sediments deposited on the new jersey shelf the bass river site and assessed potential effects of different ancestral producers and diagenesis on their distributions and their impact on the associated temperature proxies as reported before the paleogene distributions of alkenones are generally similar to those in modern haptophytes but unusual alkenone distributions characterized by a dominant di unsaturated c40 alkenone are observed for late cretaceous sediments suggesting different ancestral source organisms for alkenones in this interval the isoprenoid gdgt distributions remained comparable to modern day distributions suggesting that tex86 can be applied up to ca 90 ma the miocene long chain diol distributions are similar to modern day distributions but the older sediments reveal unusual distributions dominated by the c28 1 12 and c26 1 13 diols suggesting different source organisms before 30 ma accordingly the ldi does not match other paleotemperature proxies suggesting its applicability might be compromised for sediments older than the miocene our results indicate that of the three proxies the tex86 seems to be the most applicable for deep time temperature reconstructions

quantitative fluorescence techniques for detecting residual oils and reconstructing hydrocarbon charge history abstract two new fluorescence techniques quantitative grain fluorescence qgf and quantitative grain fluorescence on extract qgf e can detect palaeo oil zones and current residual oil zones in petroleum wells respectively qgf and qgf e measure the fluorescence emission spectra of trace fluorescence from reservoir grains and their extracts qgf is measured on dry disaggregated reservoir grains after a cleaning procedure involving solvent hydrogen peroxide and acid whereas qgf e is measured on the solvent extract from the qgf cleaned grains palaeo oil zones have distinct qgf spectra with spectral peaks between 375 and 475 nm and elevated fluorescence intensities compared with spectra for rocks that have always been water saturated current and residual oil zones have distinct qgf e spectra with spectral peaks at around 370 nm and elevated qgf e intensities compared with that for current water zones both qgf and qgf e responses increase upwards from the palaeo oil water and residual oil water contacts respectively an oil producing well from timor sea nw australia was investigated in detail using the qgf and qgf e techniques to illustrate how they can be used to reconstruct hydrocarbon migration history

the application of fluid inclusions to migration of oil and diagenesis in petroleum reservoirs abstract fluid inclusions can be used to interpret thermal history and petroleum maturation and migration relative to burial history temperature pressure and composition data collected from fluid inclusions are used to determine the environment of diagenesis and the timing of cementation and migration cements in petroleum reservoirs contain both oil and aqueous fluid inclusions fluorescence spectroscopy is used to identify oil inclusions and to determine the maturity of entrapped oil the lifetime of fluorescence induced by a pulsed laser is related to the api gravity of entrapped oil interpretation of fluid inclusion data depends on knowing the origin of fluid inclusions and the probability that they survive in the burial environment those aspects of fluid inclusion study are investigated by synthesizing oil and aqueous inclusions in calcite crystals in laboratory experiments examples of how fluid inclusions are used to determine the physico chemical environments of diagenesis in petroleum reservoirs and the timing of cementation and migration are given for the wealden basin england the mishrif formation dubai the smackover formation gulf coast u s a and jurassic sandstones offshore norway in the wealden basin temperature data from fluid inclusions are used to determine that oil migration occurred in the cretaceous and that the reservoir rocks have been uplifted to varying degrees at a time after migration distribution of oil inclusions indicates that generation and migration of oil was principally in the western part of the basin the geochemistry of oil inclusions in calcite cements from the mishrif formation dubai are used to determine the type and maturity of entrapped oil temperature data from oil and water inclusions are used to relate reservoir diagenesis to burial history and the migration of oil in deep smackover reservoirs oil contains h 2 s the origin of the h 2 s is examined by study of fluid inclusions containing h 2 s in jurassic sandstones offshore norway fluid inclusion studies show that silica cementation is related to burial depth whereas a later calcite cementation originated from invasion of a hot fluid

using tetraether lipids archived in north sea basin sediments to extract north western european pliocene continental air temperatures the pliocene is often regarded as a suitable analogue for future climate due to an overall warmer climate 2 3 c coupled with atmospheric co2concentrations largely similar to present values 400 ppmv numerous pliocene sea surface temperature sst records are available however little is known about climate in the terrestrial realm here we generated a pliocene continental temperature record for northwestern europe based on branched glycerol dialkyl glycerol tetraether brgdgt membrane lipids stored in a marine sedimentary record from the western netherlands the total organic carbon toc content of the sediments and its stable carbon isotopic composition 13corg indicate a strong transition from primarily marine derived organic matter om during the pliocene to predominantly terrestrially derived om after the transition into the pleistocene this trend is supported by the ratio of branched and isoprenoid tetraethers bit index the marine terrestrial transition indicates a likely change in brgdgt sources in the core which may complicate the applicability of the brgdgt paleotemperature proxy in this setting currently the application of the brgdgt based paleothermometer on coastal marine sediments has been hampered by a marine overprint here we propose a method to disentangle terrestrial and marine sources based on the degree of cyclizationof tetramethylated brgdgts rings using a linear mixing model based on the global soil calibration set and a newly developed coastal marine temperature transfer function application of this method on our brgdgt record resulted in a corrected terrestrial temperature record matterr this latter record indicates that continental temperature were 12 14 c during the early pilocene and 10 5 12 c during the mid pilocene pollen based terrestrial temperatures estimate from nortern and central europe furthermore two colder 5 7 c periods in the pilocene maytterr record show that the influence of pilocene glacials reached well into nw europe

geochemistry origin and accumulation of continental condensate in the ultra deep buried cretaceous sandstone reservoir kuqa depression tarim basin china abstract a continental condensate field with the deepest burial depth 7084 m so far in china was recently discovered from the cretaceous sandstone reservoir in the bozi area of the kuqa depression tarim basin in this paper we report general features of this field including geochemistry of the condensates their origin and migration and accumulation general geochemistry of the condensate reflects that it is an over pressured condensate reservoir analytical results by newly developed high resolution gc gc tofms method indicate that the condensate is rich in n alkanes from nc 3 to nc 34 and in diamondoid hydrocarbons with a high content of adamantanes the condensate has a high abundance of aromatic hydrocarbons the gas 13 c 2 values in these are 23 3 which is characteristic of coal derived gases compared with the contents of conventional condensate oils the bz1 well has a high content of aromatic hydrocarbons suggesting that the condensate is in a stage of highly mature cracking analyses of oil biomarkers carbon isotopes gas compositions etc revealed that the condensate is dominantly sourced from the highly mature coals of the jurassic qiakemake formation in the western kuqa depression this set of coal source sequences has generated large quantities of condensate since 3 ma when the study area was subjected to a rapid subsidence with sediments over 2000 m and consequently attained at the condensate generating stage such condensates then migrated vertically into the cretaceous traps along faults therefore the bozi condensate field is a typical case of large scale oil gas field characterized by late stage accumulation multiple elements favor the formation of this large scale condensate field the timing of trap formation accords with that of the condensate generation since 3 ma the traps and source rocks are stacked vertically faults connect the source rock sequences and the reservoirs the hydrocarbon charge is strong and efficient thick paleogene gypsum beds act as an excellent cap rock favoring the accumulation and preservation of the condensate

an interlaboratory study of tex86 and bit analysis of sediments extracts and standard mixtures two commonly used proxies based on the distribution of glycerol dialkyl glycerol tetraethers gdgts are the tex86 tetraether index of 86 carbon atoms paleothermometer for sea surface temperature reconstructions and the bit branched isoprenoid tetraether index for reconstructing soil organic matter input to the ocean an initial round robin study of two sediment extracts in which 15 laboratories participated showed relatively consistent tex86 values reproducibility 3 4 degrees c when translated to temperature but a large spread in bit measurements reproducibility 0 41 on a scale of 0 1 here we report results of a second round robin study with 35 laboratories in which three sediments one sediment extract and two mixtures of pure isolated gdgts were analyzed the results for tex86 and bit index showed improvement compared to the previous round robin study the reproducibility indicating interlaboratory variation of tex86 values ranged from 1 3 to 3 0 degrees c when translated to temperature these results are similar to those of other temperature proxies used in paleoceanography comparison of the results obtained from one of the three sediments showed that tex86 and bit indices are not significantly affected by interlaboratory differences in sediment extraction techniques bit values of the sediments and extracts were at the extremes of the index with values close to 0 or 1 and showed good reproducibility ranging from 0 013 to 0 042 however the measured bit values for the two gdgt mixtures with known molar ratios of crenarchaeol and branched gdgts had intermediate bit values and showed poor reproducibility and a large overestimation of the true i e molar based bit index the latter is likely due to among other factors the higher mass spectrometric response of branched gdgts compared to crenarchaeol which also varies among mass spectrometers correction for this different mass spectrometric response showed a considerable improvement in the reproducibility of bit index measurements among laboratories as well as a substantially improved estimation of molar based bit values this suggests that standard mixtures should be used in order to obtain consistent and molar based bit values

timing and stepwise transitions of the african humid period from geochemical proxies in the nile deep sea fan sediments large fluvial systems such as the nile river allow a basin scale integrated view of climatological and environmental changes in this study we reconstructed the nile discharge history for the last 20 ka using molecular ratios of glycerol dialkyl glycerol tetraethers gdgts and neodymium nd radiogenic isotopes by characterizing both the organic and inorganic fractions we assessed the relevance of the gdgt based proxies in deltaic environments as tracers of terrigenous origin a large increase in nile discharge is documented from 14 8 to 8 4 ka bp reflecting enhanced physical erosion and transport processes from the ethiopian traps we confirmed the primary control of insolation on precipitation on north east africa through the last 20 ka the centennial time resolution reached on the sedimentary sequence revealed a step wise onset and termination of the african humid period ahp starting at 14 8 ka and ending at 8 4 ka bp respectively our centennial millennial records allowed furthermore pinpointing the abrupt periods of arid conditions corresponding to the younger dryas these data illustrate the linkage between low and high latitude hydrological variability

molecular records of continental air temperature and monsoon precipitation variability in east asia spanning the past 130 000 years our current understanding of past changes in east asian summer monsoon easm precipitation intensity derives from several loess paleosol sequences and oxygen isotope 18o records of well dated stalagmites although temperature is generally presumed to have had minimal impact on easm records past air temperature dynamics over east asia are so far relatively poorly understood mainly due to the lack of tools to reconstruct continental paleotemperatures here we report a high resolution record of east asian air temperature over the past 130 000 years based on soil bacterial lipid signatures preserved in a loess paleosol sequence from the mangshan loess plateau in china we find that maximum local insolation is the main driver of air temperature although greenhouse gas concentrations and southern hemisphere climate may influence temperature at times when insolation is weak causing a decoupling with easm precipitation intensity direct comparison of our temperature record with precipitation induced changes in past soil ph derived from the same suite of lipids confirms this decoupling subsequent cross spectral analysis of the two molecular proxy records reveals that variations in monsoon precipitation consistently lag those in air temperature throughout the whole record at the dominant precession band the length of this lag is variable however and increases as glaciation develops this observation is consistent with an increasing influence of northern hemisphere ice sheets on the modulation of easm response to insolation forcing during ice ages

signatures of tetraether lipids reveal anthropogenic overprinting of natural organic matter in sediments of the thames estuary uk intertidal foreshore sediments from a 110 km stretch of the thames estuary were analysed for glycerol dialkyl glycerol tetraethers gdgts to track soil organic matter om input and evaluate the impact of coastal urbanisation on their distribution concentration of branched br gdgts ranged from 1 to 15 g g organic carbon oc and crenarchaeol ranged from 0 6 to 19 g g oc an overall decrease in brgdgts was observed from the inner thames brentford to the outer thames isle of grain suggesting a drop in soil om input towards the sea in contrast crenarchaeol concentration was highest around east london rather than towards the open sea such elevated crenarchaeol concentration occurred in the section of the river most influenced by anthropogenic pollution such as discharge points for london s major sewage treatment plants docks and power plants the non systematic spatial distribution of crenarchaeol was also reflected in the branched isoprenoid tetraether bit index the highest bit values occurred upstream and in close proximity to salt marshes 0 8 1 whereas the lowest values 0 3 0 5 were towards the sea however unusually low values 0 4 were observed in the river section that had high crenarchaeol concentration in contrast bulk 13c values were insensitive to london s anthropogenic influence this suggests that the natural systematic decrease in bit index in the estuary is overprinted by london s anthropogenic activity between deptford creek and tilbury we therefore advise caution when interpreting the bit index for sediments in close proximity to megacities discharging industrial and municipal waste that can become incorporated into the near surface sedimentary record

comparison of two dimensional and three dimensional simulations of dense nonaqueous phase liquids dnapls migration and entrapment in a nonuniform permeability field 1 the influence of reduced dimensionality two dimensional 2 d versus 3 d on predictions of dense nonaqueous phase liquid dnapl infiltration and entrapment in statistically homogeneous nonuniform permeability fields was investigated using the university of texas chemical compositional simulator utchem a 3 d numerical multiphase simulator hysteretic capillary pressure saturation and relative permeability relationships implemented in utchem were benchmarked against those of another lab tested simulator the michigan vertical and lateral organic redistribution m valor simulation of a tetrachloroethene spill in 16 field scale aquifer realizations generated dnapl saturation distributions with approximately equivalent distribution metrics in two and three dimensions with 2 d simulations generally resulting in slightly higher maximum saturations and increased vertical spreading variability in 2 d and 3 d distribution metrics across the set of realizations was shown to be correlated at a significance level of 95 99 neither spill volume nor release rate appeared to affect these conclusions variability in the permeability field did affect spreading metrics by increasing the horizontal spreading in 3 d more than in 2 d in more heterogeneous media simulations the assumption of isotropic horizontal spatial statistics resulted on average in symmetric 3 d saturation distribution metrics in the horizontal directions the practical implication of this study is that for statistically homogeneous nonuniform aquifers 2 d simulations of saturation distributions are good approximations to those obtained in 3 d however additional work will be needed to explore the influence of dimensionality on simulated dnapl dissolution

influence of hydraulic property correlation on predicted dense nonaqueous phase liquid source zone architecture mass recovery and contaminant flux 1 organic liquid saturation distributions resulting from a simulated tetrachloroethene pce spill were generated with alternative models of spatially varying aquifer properties for a statistically homogeneous nonuniform sand aquifer the distributions were analyzed to quantify dnapl source zone characteristics and then incorporated as initial conditions for simulated pce recovery using surfactant enhanced aquifer remediation sear the predicted evolution of the spatial distribution of dnapl saturations or source zone architectures and associated remediation efficiencies are strongly influenced by the spatial correlation of aquifer parameters and multiphase flow constitutive relationships model predictions suggest that removal of 60 to 99 of entrapped pce can reduce dissolved contaminant concentration and mass flux under natural gradient conditions by approximately two orders of magnitude aqueous phase contaminant flux however does not vary consistently as a function of the percentage of dnapl removed and notable differences in flux evolution were observed for models incorporating correlated versus uncorrelated capillary entry pressure and permeability fields simulation results demonstrate that the application of alternative models of aquifer parameter spatial variability can influence predicted dnapl infiltration entrapment and recovery even for relatively homogeneous aquifers of the type investigated here results also demonstrate potential benefits in the form of reduced mass flux accruing from partial mass removal that may not be readily predicted from analyses relying on simplified conceptual models for dnapl source zone architecture or aquifer flow fields index terms 1829 hydrology groundwater hydrology 1832 hydrology groundwater transport 1831 hydrology groundwater quality keywords contamination mass flux dnapl remediation dnapl source zone heterogeneity nonuniformity

source settling and degradation of branched glycerol dialkyl glycerol tetraethers in the marine water column abstract branched glycerol dialkyl glycerol tetraethers branched gdgts are commonly found in distal marine sediments however their presence in the water column source and delivery process are not fully understood in this study we examined seasonal and depth variation in the flux of branched gdgts in sinking particles and underlying sediment at 39 n 147 e in the mid latitude nw pacific from november 1997 to august 1999 branched gdgts showed synchronous variation in their sinking flux at different depths and the variation was similar to that of lithogenic material of eolian dust origin their degrees of cyclization and methylation were nearly constant and bear some resemblance to those of alkaline soils this suggests that westerly winds transport branched gdgts to the study site via the atmosphere from continental asia the sinking flux of branched gdgts was higher in 1999 than in 1998 presumably reflecting changes in the migration path of asian dust in response to the el nino southern oscillation synchronous variation in branched gdgt concentrations at different depths implies rapid vertical transport of branched gdgts to deep water with a sinking velocity exceeding 260 m d 1 the sinking flux of the branched gdgts decreased with increasing depth but the rate of decrease was much smaller than those of other compounds the preservation efficiency of branched gdgts was 3 5 6 4 of surface inputs at the water sediment interface which is much higher than those of isoprenoid gdgts 1 0 1 3 and other compounds the branched and isoprenoid tetraether bit index values were extremely low i e