recognition of 18β h oleanane in several crudes and tertiary upper cretaceous sediments definition of a new maturity parameter abstract ekweozor et al chem geol 27 11 28 and 29 37 first discovered an unknown compound with a gc retention time very close to that of the 18 h olenane peak in oils and tertiary sediments of the nigerian delta this compound was called j several authors wang et al advances in organic geochemistry 1981 pp 108 113 wiley chichester 1983 schoelle et al ibid pp 156 163 reported the occurrence of 18 h oleanane without underlying the presence of j because of their coelution in this study the presence of j has been confirmed in more than 150 rock extracts and 19 oils from different countries and is identified as the 18 h oleanane by comparison to retention time and mass spectrum and by its coelution with an authentic standard apart from tertiary sediments the 18 h and 18 h oleananes have also been found in upper cretaceous sediments which extends the occurrence of these compounds back in age a maturity correlation has been found between the relative concentration of 18 h oleanane and 18 h oleanane in fact an increase in the 18 h 18 h oleanane ratio has been observed with increasing depth in several wells the 18 h 18 h oleanane ratio has been correlated with other classical maturity parameters i e ts tm ro and tmax

characterization of high molecular weight organic matter in marls of the salt iv formation of the mulhouse basin high molecular weight organic matter of six marl samples of the mulhouse basin has been characterized the kerogen asphaltene and polar fractions were analysed by flash pyrolysis gc ms in addition sulphur rich geomacromolecules present in the polar fractions were also desulphurized with raney ni and the released hydrocarbons were characterized by gc ms the kerogen and asphaltene pyrolysates are dominated by linear and isoprenoid alkanes and alkenes most likely derived from aliphatic biopolymers of algae algaenans and contain moderate to low amounts of alkylated thiophenes marls deposited under hypersaline conditions contain more organically bound sulphur and less isoprenoid algaenans in their kerogen asphaltene fractions than marls deposited under less saline conditions high contributions of terrestrial organic matter are not revealed by abundant alkyl phenols in the pyrolysates desulphurization of sulphur rich geomacromolecules present in the polar fractions yields hydrocarbons with distributions different from those of the free saturated hydrocarbons but the amounts released are low relative to the hydrocarbons present as such

the influence of dunes on mixing in a migrating salt wedge fraser river estuary canada dune bedforms and salt wedge intrusions are common features in many estuaries with sand beds and yet little is known about the interactions between the two flow visualization with an echosounder and velocity measurements with an acoustic doppler current profiler over areas of flat bed and sand dunes in the highly stratified fraser river estuary canada were used to examine the effect of dunes on interfacial mixing as the salt wedge migrates upstream over the flat bed mixing is restricted to the lower portion of the water column however as the salt wedge migrates into the dune field from the flat bed there is a dramatic change in the flow and large internal in phase waves develop over each of the larger dunes with water from the salt wedge reaching the surface of the estuary the friction richardson number shows that bed friction is more important in interfacial mixing over the dunes than over the flat bed and a plot of internal froude number versus obstacle dune height shows that the salt wedge flow over the dunes is mainly supercritical such bedforms can be expected to cause similar effects in interfacial mixing in other estuaries and sediment laden density currents and may thus be influential in fluid mixing and sediment transport copyright 2010 john wiley sons ltd

the microbial input in carbonate anhydrite facies of a sabkha palaeoenvironment from guatemala a molecular approach abstract nine representative rock samplesincluding four anhydrites an oil stained dolomite and a laminated mudstone source rock from a sabkha type palaeoenvironment la felicidad 1 well guatemala have been compared in order to tentatively characterize each facies by a geochemical signature each sample has been studied by using basic parameters toc rock eval pyrolysis yields and analyses of alkanes and aromatics by computerized gc ms the following families of compounds have been reviewed n alkanes branched and cyclic alkanes n alkylbenzenes benzohopanes monoaromatic steroids d ring aromatic 8 14 secohopanoids alkylnaphthalenes alkylphenanthrenes alkyldibenzothiophenes and triaromatic steroids despite close geochemical relationships of all the sample a more in depth investigation taking into account molecular patterns and semi quantitative data reveals significant differences among the samples anhydrites may be differentiated from carbonates which illustrates the efficiency of organic geochemistry in environmental palaeoreconstruction even in organiccarbon lean sediments toc 0 04 0 08 in anhydrites in these anoxic marginally mature sediments the strong predominance of triterpanes over steranes tt to st 20 associated with other molecular features leads to the conclusion that the main contribution to the organic matter of all facies is by bacteria several prominent components including novel families iso c23 and iso c27 alkanes tetracyclic terpanes d ring aromatic 8 14 secohopanoids 1 phenylpentadecane undecylnaphathalene and their mono and dimethylated counterparts have been interpreted as derived from halophilic bacteria these conclusions may be extended to all crude oils from the same area which may be considered as true bacterially derived petroleums the la felicidad 1 well data are discussed with reference to other palaeosabkha type sequences from the sw aquitaine basin france in which the bacterial input is less important however in these sabkha sequences 1 phenylpentadecane undecylnaphthalene and related structures have also been identified

hydrocarbon biomarkers of different lithofacies of the salt iv formation of the mulhouse basin france forty nine samples from an 11 m section of the salt iv formation of the tertiary mulhouse basin alsace france covering six different lithotypes marl nodular lenticular laminated and massive anhydrite halite were analysed for hydrocarbon biomarkers the hydrocarbon biomarker assemblages are dominated by acyclic isoprenoids especially phytane 0 13 pr ph 0 52 n alkanes with specific distribution patterns and steranes large differences in their distributions indicate significant changes in the palaeoenvironment the largest changes observed are those in the desmethyl and methylsterane distributions and are probably linked to an occasional reconnection of the evaporite basin with the sea leading to an input of dinoflagellate algae 3 methylsteranes are present in all samples studied and their carbon number distribution mimics that of the 5 desmethylsteranes in line with previous suggestions that they are diagenetic products of sterols with a sugar unit at c 3 biosynthesized from dietary sterols the increase in relative abundance of the 3 methylsteranes during periods of marine incursions suggests that these precursors are biosynthesized by marine organisms variations in biomarker composition between the different lithofacies are minor probably because the organic matter is mainly associated with the marl and all lithotypes contain a marl component detailed subsampling of two marl layers and subsequent analysis indicated that the changes on a small time scale are minor to those on a larger time scale

how to find high quality petroleum source rocks in saline lacustrine basins a case study from the cenozoic qaidam basin nw china abstract despite having made significant contributions to global hydrocarbon occurrences source rocks in saline lacustrine basins show great mineralogical and organic geochemical heterogeneity and the controlling mechanism is weakly studied here we use the cenozoic qaidam basin as an example to compare the organic and inorganic parameters of fine grained sediments in different lacustrine facies and to figure out the characterization and distribution of effective petroleum source rocks in saline lacustrine systems organic inorganic database of six selected boreholes show that in the bench margin high gradient lacustrine system fine grained sediments in sublittoral brackish mesosaline zones containing low chlorides

polar constituents of organic matter rich marls from evaporitic series of the mulhouse basin abstract a suite of marl samples from the evaporitic series of the mulhouse basin france lower oligocene was studied for its biomarker content in particular its polar constituents novel series of 3 carboxyalkyl steranes and 15 oxo triaromatic ketones were identified by synthesis the 3 carboxyalkyl steranes probably originate from highly polar precursors yet unreported in living organisms our data suggest that micro algae could be the major source of these compounds which seem to be indicators of high algal input rather than characteristic of evaporitic environments the 15 oxo triaromatic ketones could be oxidation products of triaromatic steroid hydrocarbons formed during diagenesis although their formation during work up procedure could not be excluded

impact of dia and catagenesis on sulphur and oxygen sequestration of biomarkers as revealed by artificial maturation of an immature sedimentary rock hydrous pyrolysis of an immature ro 0 25 sulphur rich marl from the gessoso solfifera formation messinian in the vena del gesso basin was carried out at 160 c t 330 c for 72 h to study the effect of progressive diagenesis and early catagenesis on the abundance and distribution of sulphur containing and sulphur and oxygen linked carbon skeletons in low molecular weight and high molecular weight fractions e g kerogen to this end compounds in the saturated hydrocarbon fraction monoaromatic hydrocarbon fraction polyaromatic hydrocarbon fraction alkylsulphide fraction and ketone fraction were quantified as well as compounds released after desulphurisation of the polar fraction and hilialh4 treatment of the desulphurised polar fraction sulphur bound phytane and 20r 5 14 17 h and 20r 5 14 17 h c27 c29 steranes in the polar fraction become less abundant with increasing maturation temperature whereas the amount of their corresponding hydrocarbons increases in the saturated hydrocarbon fraction carbon skeletons that are bound in the kerogen by multiple bonds e g c38n alkane and isorenieratane are first released into the polar fraction and then as free hydrocarbons these changes occur at relatively low levels of thermal maturity ro 0 6 as evidenced by the immature values of biomarker maturity parameters such as the c35 hopane ratio and the 22s 22s 22r 17 21 h c35 hopane ratio sulphur and oxygen bound moieties present in the polar fraction are not stable with increasing thermal maturation however alkylthiophenes ketones 1 2 di n alkylbenzenes and free n alkanes seem to be stable thermal degradation products of these sulphur and oxygen bound moieties thus apart from free n alkanes which are abundantly present in more mature sedimentary rocks and crude oils alkylthiophenes 1 2 di n alkylbenzenes and ketones can also be expected to occur the positions of the thiophene moiety and the carbonyl group coincide with the original positions of the functional groups of their precursors thus important information about palaeobiochemicals is retained throughout the sequestration degradation process

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

pedogenesis of a catena of the farmdale sangamon geosol complex in the north central united states abstract the farmdale sangamon geosol pedocomplex consists of the sangamon geosol and the overlying farmdale geosol which form the most extensive terrestrial record of the last interglacial to glacial transition in the midwest united states the geosol complex formed for upwards of 100 ka extending from the end of mis 6 through 4 for the sangamon geosol then the farmdale geosol for during a brief episode at the end of mis 3 following slow accumulation and pedogenic modification of eolian silt deposited on top of the sangamon geosol our study site consists of a buried paleo hillslope transect that forms a catena enabling evaluation of slope effects on interglacial scale soil formation the sangamon geosol is formed in calcareous and illitic glaciogenic sediment along the catena the sangamon geosol profiles display some morphological changes namely in terms of colors that we interpret as indicators of differences in drainage most thickness and horizonation characteristics are similar all along the transect with intact upper sola horizons ae and e horizons that overlie clay enriched bt horizons the bt horizons contain abundant clay that exists as illuvial clay coatings matrix infills and as mosaic speckled domains the clay originated both by in situ weathering and through illuviation from the clay depleted upper sola slope does not appear to affect bt characteristics beyond redder hues of the matrix and clay coatings in the upper slope position with depth effects of carbonate leaching and infilling of clay in the matrix decrease and clay coatings are restricted to walls of voids adjacent to aggregates clay mineralogy shows illite depletion but no interstratified kaolinite expandable minerals indicating the degree of weathering is not as great as is typical of sangamon geosol profiles formed in loess or in glaciogenic sediment of the central illinois type area clay mineralogy is also stratified with depth coincident with particle size which probably indicates sorting of layers of illitic dolomite and shale variation of horizon and profile characteristics appears to largely be a function of particle size variability and stratification than topographic position in the catena the influence of hillslope position on soil redistribution during formation of the sangamon geosol appears negligible given the uniformity of upper solum horizon thickness and sandy particle size characteristics so we conclude that a bioturbation and rainwash origin of the upper solum and the texture contrast in these profiles is not the best process model explanation we suggest that the base rich nature of these soils led to ecosystem characteristics that discouraged erosion and encouraged infiltration and a lessivage type origin of the texture contrast no convincing evidence of mis 6 through mis 4 loess occurs at this site the farmdale geosol formed in the robein silt which is roxana silt mis 3 loess that was redistributed downslope the robein silt is thicker and finer in the topographic low and indicates the cooler and forested environmental conditions during mis 3 were conducive to downslope movement of soil and also produced greater differences in drainage induced soil morphological changes in the farmdale geosol

criteria for the recognition of salt pan evaporites layered evaporites can accumulate in 1 ephemeral saline pans 2 shallow perennial lagoons or lakes and 3 deep perennial basins criteria for recognizing evaporites deposited in these settings have yet to be explicitly formulated the characteristics of the ephemeral saline pan setting have been determined by examining eight holocene halite dominated pans salt pans and their deposits marine and non marine from the u s mexico egypt and bolivia these salt pans are typified by alternating periods of flooding resulting in a temporary brackish lake evaporative concentration when the lake becomes saline and desiccation which produces a dry pan fed only by groundwater the resulting deposits consist of alternating layers millimetres to decimetres of halite and mud the layers of halite are characterized by 1 vertical and horizontal cavities rounded crystal edges and horizontal truncation surfaces due to dissolution during flooding 2 vertical chevrons and cornets grown syntaxially on the bottom during the saline lake stage 3 halite cements overgrowths and euhedral cavity linings and disruption of layering into metre scale polygons produced during the desiccation stage the muddy interbeds are characterized by displacive growth of halite during the desiccation stage immediately below the surface of the pan the halite layers are matured by repeated episodes of dissolution and diagenetic crystal growth this results in porous crusts with patches of chevron and cornet crystals truncated by dissolution clear diagenetic halite cement and internal sediment these layers of mature halite closely resemble the patchy cloudy and clear textures of ancient halite deposits holocene salt pans are known to cover thousands of square kilometres and cap halite deposits hundreds of metres thick so they are realistic models for ancient evaporites in scale e g permian salado formation of new mexico texas which preserves many primary salt pan features

organic matter of the mulhouse basin france a synthesis the lower oligocene evaporite sequence of the mulhouse basin france contains organic matter rich marl deposits these marls display an overall cyclic variation of sedimentation rate organic carbon content hydrogen index and selected molecular parameters over a 30 m thick stratigraphic interval the integration of all sedimentological and geochemical parameters has allowed the reconstruction and characterization of the paleoenvironment of deposition the marls were deposited in a perennial lake that was at times connected to the sea two organic facies end members could be assigned to a lake stage with a marine connection and a lake stage that received dominantly continental water input the overall stratigraphic variation in the organic matter content is interpreted to reflect the adaptation of the oligocene flora to the changing paleoclimate and environmental conditions

variations in abundances and distributions of isoprenoid chromans and long chain alkylbenzenes in sediments of the mulhouse basin a molecular sedimentary record of palaeosalinity abstract the abundances and distribution patterns of mono di and trimethylated 2 methyl 2 4 8 12 trimethyltridecyl chromans mttcs and long chain alkylbenzenes in extracts of marl 66 samples anhydrite 15 and halite 1 strata of the salt iv formation of the oligocene mulhouse basin are reported the distributions of the methylated mttcs indicate salinity changes of the upper part of a density stratified water column of the basin these variations are explained by a tectonically or climatically induced change in the supply of water of relative lower salinity to form a layer overlying the deeper water brine hence it is suggested that mesohaline 3 5 15 conditions in the surface waters were established as a result of periodic incursions of marine water and subsequent evaporation conversely during periods when the surface water was derived mainly from fresh water from the hinterland lower average salinity in the surface layer resulted the distributions of long chain alkylbenzenes also appear to record these changes

stereochemical studies of acyclic isoprenoids xii lipids of methanogenic bacteria and possible contributions to sediments abstract abundant volatile lipids of methanobacterium thermoautotrophicum and methanosarcina barkeri include isoprenoid hydrocarbons c30 and c15 c20 and c25 isoprenoid alcohols m barkeri contains 2 6 10 15 19 pentamethyleicosane whose relative stereochemistry is the same as found in marine sediments indicating that it is a marker of methanogenic activity the c20 c30 and c25 alkenes in m thermoautotrophicum also have a preferred sterochemistry the latter have the 2 6 10 14 18 pentamethyleicosanyl skeleton suggesting that the alkane in marine sediments may derive from methanogens the stereochemistry of squalane in a marine sediment is also compatible with an origin in methanogens in contrast the stereochemistry of pristane in m thermoautotrophicum indicates a fossil fuel contaminant origin suggesting that this and certain other alkanes reported in archaebacteria might also be of contaminant origin there is therefore little evidence at present that the pristane in immature marine sediments originates in methanogens the c15 and c20 saturated alcohols in m thermoautotrophicum have mainly the all r configuration if this is generally true for methanogens the c20 alcohol in the messel shale may originate mainly from methanogens whereas that in the green river shale may originate mainly from photosynthetic organisms

characterization of organic rich material in an evaporitic environment the lower oligocene of the mulhouse basin alsace france evaporitic sediments from the max borehole mulhouse potash basin southern rhine graben were studied over an interval of about 40 m in the vicinity of sylvite beds total organic carbon toc analyses of 450 samples showed that marly layers interbedded within the evaporites have toc values that fluctuate in a rhythmic manner the highest values are found near the top of the clay anhydrite layers and the lowest values are recorded near the top of the halite rich beds geochemical elemental analysis of kerogen gas chromatography of bitumen and palynological studies of 26 samples showed that the organic matter is mainly of algal origin a and b groups a third category of organic material c group may have been derived from a mixture of continental supply and in situ bacterial productivity

geochemical study of macromolecular organic matter from sulfur rich sediments of evaporitic origin messinian of sicily by chemical degradations abstract selective chemical degradations have been performed on sulfur rich macromolecular organic matter from sediments of the messinian of sicily upper miocene italy the biomarkers released upon different desulfurization experiments are much more abundant than the free lipids and display completely different distributions which reflect the selective trapping of poly functionalized molecules by inorganic sulfur species at an early stage of diagenesis the bound biomarker distributions reveal a dominant phytoplanktonic input originating from an upper oxic water layer and a moderate bacterial reworking of the organic matter a contribution from cyanobacteria to the organic matter cannot be excluded the presence of carotenoids typical from photosynthetic sulfur bacteria attests to a stratified water body where an anoxic photic zone occurred lialh4 hydrogenolysis of sulfur rich macromolecules revealed that polysulfide bridges contribute to a large extent in the cross linking the results of deuterium labelling experiments are discussed in terms of sulfur incorporation on functionalized lipids

geological and geochemical modeling an approach for understanding organic cyclic sedimentation in evaporitic sequences application to the mulhouse basin france in the upper eocene to lower oligocene mulhouse basin france upper rhine graben an organic rich evaporitic series has been deposited first and second order cyclicities can be defined at the scale of the study a short period cyclicity corresponding to an alternation of marl and evaporitic layers a long period cyclicity corresponding to an evolution of the evaporitic layers from an anhydritic to halitic or sylvitic composition the characteristics and abundance of organic matter in the marl also show cyclic variations in amount and origin a geological scenario based on numerical modeling served for testing relationships between the environmental evolution including state of stratification of the basin sea level change and water balance variations and the organic sedimentation phytoplankton productivity as well as terrestrial organic matter input have been simulated and compared to the organic data the model results account for the distribution of organic matter in the basin and are in agreement with the geological and geochemical data they serve to place the paleo environment elaborated by hofmann et al 1993 within a more dynamic sedimentological framework this work demonstrates the benefit of numerical modeling in tentatively identifying the respective influence of eustasy and climate on the organic sedimentation in an evaporitic basin

the foreslope hills large scale fine grained sediment waves in the strait of georgia british columbia abstract the foreslope hills are a set of 20 m high 5 km long ridges at 230 350 m water depth in the south central strait of georgia occupying a 60 km 2 area at the base of the fraser river delta foreslope they are composed of clay silt and fine sand previous authors have interpreted them as 1 a single mass slide deposit 2 mud diapirs 3 in situ rotational failures and 4 creep deformation features but collaborative evidence for these interpretations is lacking seafloor surface morphological renders derived from recent multibeam sonar bathymetry data show linear evenly spaced symmetrical ridges with ridge bifurcation resembling wave ripples but on a much larger scale detailed multichannel and single channel seismic reflection data show sinusoidal internal reflections suggesting upslope migration the ridges occur within the uppermost portion of the holocene section in a very high sedimentation rate environment consequently they are probably less than 3000 years old moored current meter records for the region show reversing currents largely oriented normal to the ridge crests averaging 10 cm s with a maximum of 50 cm s this evidence combined with increasing documentation of large scale sedimentary bedforms in slope and rise environments suggests that the foreslope hills should be re interpreted as sediment waves upslope migration is typical of many large scale fine grained sediment waves the preferred physical interpretation for the creation and maintenance of the foreslope hills as sediment waves is the lee wave model requiring a phase shift in density stratified flow as it passes over the wavy topography maximum measured bottom currents are easily strong enough to entrain silt and clay delivered to the site by turbidity currents or by sediment plume fallout from fraser river outflow either strong flood tides or severe biannual density intrusions due to their intense stratification may be susceptible to lee wave formation and the creation of sediment waves leading to the observed pattern of upslope migration

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

application of biological markers in the recognition of palaeohypersaline environments the hydrocarbon fractions of a marl sample from a messinian basin in the northern appenines and four oils rozel point oil utah and three seep oils from sicily were studied

microanalysis of primary fluid inclusions in halite constraints for an evaporitic sedimentation modeling application to the mulhouse basin france the chemistry of the waters from which the evaporitic minerals crystallized in the lower part of the salt iv unit of the mulhouse basin france has been investigated the lithological and fluid inclusion data have been compared to the output data of the mass transfer program newequi which simulates the change in brine composition during its evaporation advancement the results show that the evolution of the composition of the brine is compatible with the calculated sequence of evaporation of a parent water corresponding to a seawater modified by cacl2 rich hydrothermal water in the studied sequence fluid inclusion data provide useful constraints for reconstructing the paleoenvironment controlling the evaporitic sedimentation they also provide data on the water stratification in the basin and on its connectivity with the open sea and important parameters controlling the productivity possible sources for the nutrients and the preservation of organic matter in the sediment

the deep thermal field of the upper rhine graben abstract the upper rhine graben has a significant socioeconomic relevance as it provides a great potential for geothermal energy production the key for the utilisation of this energy resource is to understand the controlling factors of the thermal field in this area we have therefore built a data based lithospheric scale 3d structural model of the upper rhine graben and its adjacent areas in addition 3d gravity modelling was performed to constrain the internal structure of the crystalline crust consistent with seismic information based on this lithosphere scale 3d structural model the present day conductive thermal field was calculated and compared to measured temperatures our results show that the regional thermal field is mainly controlled by the configuration of the upper crust which has different thermal properties characteristic for the variscan and alpine domains temperature maxima are predicted for the upper rhine graben where thick insulating cenozoic sediments cause a thermal blanketing effect and where the underlying crustal units are characterised by high radiogenic heat production the comparison of calculated and measured temperatures overall shows a reasonable fit while locally occuring model deviations indicate where a larger influence of groundwater flow may be expected

a paleoweathering profile from griqualand west south africa evidence for a dramatic rise in atmospheric oxygen between 2 2 and 1 9 bybp a core drilled near wolhaarkop in griqualand west south africa intersected highly oxidized kuruman iron formation below red beds of the gamagara formation the lateral equivalents of the kuruman iron formation in this drill hole consist largely of siderite ankerite magnetite greenalite and quartz the oxidation of the kuruman iron formation in wol 2 occurred almost certainly during weathering prior to the deposition of the gamagara formation the date of this weathering episode is bracketed between about 2 2 and 1 9 bybp by the age of the ongeluk lavas in the transvaal sequence below the unconformity and by the age of the hartley lavas in the olifantshoek group above the unconformity the ratio of iron to sio2 in the several facies of the weathered kuruman iron formation in wol 2 is nearly the same as that in their unweathered equivalents since sio2 loss during weathering was almost certainly minor the similarity of the fe sio2 ratio in the weathered and unweathered bif indicates that nearly all the feo in the kuruman iron formation was oxidized and retained as feo3 during weathering such a high degree of iron retention is best explained by an o2 content of the atmosphere or 0 03 atm at the time of weathering such an o2 pressure is very much greater than that suggested by the composition of paleosols developed on basalt or 2 2 bybp but is consistent with the highly oxidized nature of the 1 85 by flin flon paleosol the new data suggest that po2 rose dramatically from about 1 percent pal present atmospheric level to or 15 percent pal between 2 2 and 1 9 bybp

graben width controlling syn rift sedimentation the palaeogene southern upper rhine graben as an example eocene to early oligocene syn rift deposits of the southern upper rhine graben urg accumulated in restricted environments sedimentation was controlled by local clastic supply from the graben flanks as well as by strong intra basinal variations in accommodation space due to differential tectonic subsidence that in turn led to pronounced lateral variations in depositional environment three large scale cycles of intensified evaporite sedimentation were interrupted by temporary changes towards brackish or freshwater conditions they form three major base level cycles that can be traced throughout the basin each of them representing a stratigraphic sub unit a relatively constant amount of horizontal extension l in the range of 4 5 km has been estimated for the urg from numerous cross sections the width of the rift lf however varies between 35 and more than 60 km resulting in a variable crustal stretching factor between the bounding masterfaults apart from block tilting tectonic subsidence was therefore largely controlled by changes in the initial rift width l0 the along strike variations of the graben width are responsible for the development of a deep trough like evaporite basin potash basin in the narrowest part of the southern urg adjacent to shallow areas in the wider parts of the rift such as the colmar swell in the north and the rhine bresse transfer zone that delimits the urg to the south under a constant amount of extension the along strike variation in rift width is the principal factor controlling depo centre development in extensional basins

dunes and associated sand transport in a tidally influenced sand bed channel fraser river british columbia dunes form annually on the sand bed of the tidally influenced south arm of fraser river british columbia bathymetric surveys along the center of the main channel throughout a snow melt freshet provided measurements of dune geometry and migration dune length height and steepness all increase with river discharge however lag between the highest flow conditions and development of the largest steepest dunes reflects the influence of antecedent flow conditions on dune geometry population averages of dune height and steepness ratio change more rapidly than dune length whilst coefficients of variation of dune height length and steepness ratio indicate high variability in dune geometry within the estuarine reach during periods of dune growth and decay unlike dune geometry dune migration rates display little lag with flow conditions the largest coefficients of variation for dune migration occur during periods of rapid change in discharge and tidal fall corresponding to the onset of rapid change in

morphology and weathering trends of the sangamon soil complex in south central indiana in relation to paleodrainage abstract three paleodrainage groups are proposed for profiles of the farmdale sangamon soil complex in south central indiana the groups good intermediate and poor are differentiated on the basis of matrix colors and color patterns genetic support for the groupings is provided by morphological trends still evident following 100 000 yr of pedogenesis and burial by late wisconsinan loess depth of carbonate leaching solum thickness and argillic horizon thickness all decrease with poorer drainage clay mineralogy also reflects paleodrainage illite degradation is intense in all profiles but profiles with good drainage have poorly crystalline interstratified expandable minerals while well crystalline smectites dominate in profiles with poor drainage remanent aggregation in former a horizons is stronger in more poorly drained profiles while the effects of structural overprinting from the modern soil increase with better modern drainage soil morphology mineralogy and parent material paleolandscape position of sangamon profiles are all internally consistent with color development under soil hydrological conditions during the last interglacial to glacial transition the occurrence frequency of each drainage group indicates that the sangamon soilscape was better drained than now and morphology and clay mineral evidence suggests that areas with poor drainage did not experience the extreme seasonal groundwater shifts that the modern landscape experiences

comparison of fixed and moving vessel flow measurements with an adp in a large river a comparison of three dimensional flow velocity measurements made with an acoustic doppler profiler adp from fixed and moving vessels at cross sections of the parana river argentina was performed the purpose was to design a rapid and reliable procedure for quantifying the velocity field and related parameters such as bed shear velocity and the identification of secondary circulations in large rivers using an adp the fixed vessel measurements were performed over a period of 10 min at three vertical profiles along two of the sections these data were then compared with the results of ten moving vessel repeat transects made at each of the sections and which intersected the fixed vessel sampling locations using a number of different adp setup configurations from the velocity profiles obtained with both fixed and moving vessel measurements total bed shear velocity values were computed by applying the law of the wall the results indicate there can be significant differences between velocities obtained using the moving vessel method and fixed vessel measurements averaged over 10 min these differences in horizontal velocity can be significantly reduced by averaging five or more moving vessel transects with corresponding shear velocities calculated from five transect averages showing differences ranging between 10 and 15 dependent on the adp configuration location of the at a point vertical velocity profile in relation to large scale bed roughness may also be an influential factor and ideally the bed morphology should be quantified together with the adp derived velocities when using the adp to identify secondary flow cells it was found that although one cross section transect can provide a reasonable overall picture an average of five cross sections is necessary to resolve the finer details of flow the implications for applications that use moving vessel techniques for measurement and analysis of three dimensional flow structures including secondary flows are highlighted

a molecular stratigraphic approach to palaeoenvironmental assessment and the recognition of changes in source inputs in marls of the mulhouse basin alsace france principal components analysis pca has been used to investigate changes in concentrations of the components of the hydrocarbon fractions extracted from 71 marl samples selected to cover two total organic carbon toc maxima in the lower part of the salt iv formation a lower oligocene evaporitic sequence from the mulhouse basin france the analysis indicates that the fractions can be ascribed as lying between two end member distributions the changes in these distributions are gradual suggesting that they resulted from fairly gradual changes in the depositional palaeoenvironment these changes are related to increased algal productivity associated with the evolution of a restricted lacustrine environment through to one with a greater marine influence systematic variations in the concentrations of selected components relative to the toc profile point to a repeated sequential evolution in the biological assemblage during deposition of the sequence

photochemical sulfurization of sedimentary organic matter a widespread process occurring at early diagenesis in natural environments abstract the possibility of light induced formation of sedimentary organo sulfur compounds has been investigated with simulation experiments these experiments using mono and diunsaturated hydrocarbons and reduced sulfur species in particular h 2 s and elemental sulfur were conducted under mild conditions sunlight low temperature likely to occur in the photic zone of anoxic environments these experiments showed an efficient sulphurization of the organic matter under sunlight conditions leading to the formation of organo sulfur compounds such as thiophenes and sulfur cross linked macromolecules very similar to those occurring in sediments deposited in anoxic environments these results show the potential for photochemically induced sulfurization of organic matter in environments with photic zone anoxia such a process would be especially favored in evaporitic environments with a shallow anoxic boundary extending well into the photic zone

oil shales evaporites and ore deposits abstract the relationships between oil shales evaporites and sedimentary ore deposits can be classified in terms of stratigraphic and geochemical coherence oil shale and black shale deposition commonly follows continental red beds and is in turn followed by evaporite deposition this transgressive regressive sequence represents an orderly succession of depositional environments in space and time and results in stratigraphic coherence the amount of organic carbon of a sediment depends on productivity and preservation both of which are enhanced by saline environments work on great salt lake utah allows us to estimate that only 5 of toc originally deposited is preserved inorganic carbonate production is similar to toc production but preservation is much higher oil shales and black shales commonly are enriched in heavy metals through scavenging by biogenic particles and complexation by organic matter ore deposits are formed from such rocks through secondary enrichment processes establishing a geochemical coherence between oil shales and ore deposits the permian kupferschiefer of n europe is used as an example to define a kupferschiefer type kst deposit here oxygenated brines in contact with red beds become acidified through mineral precipitation and acquire metals by dissolving oxide coatings oxidation of the black shale leads to further acid production and metal acquisition and eventually to sulfide deposition along a reducing front in order to form ore bodies the stratigraphic coherence of the red bed black shale evaporite succession must be joined by the geochemical coherence of the ore body evaporite black shale association the cretaceous cu zn deposits of angola the zambian copperbelt as well as the creta oklahoma deposits are other kst examples in the zambian copperbelt evaporites are indicated by the carbonate lenticles thought to be pseudomorphs after gypsum anhydrite nodules mvt deposits are also deposited by acid brines but at more elevated temperatures and with carbonates as principal host rocks the pine point deposits are cited for their close association with evaporites alkaline metal rich brines are postulated for the hyc deposit of mcarthur river australia such brines are known from the green river formation and deposits formed from such brines constitute the grt class they can be recognized by the presence of magadi type cherts and zeolite analcime k spar tuffs the cu co ore bodies of outokumpu finland might also belong to this type a new classification of sedimentary ore deposits is proposed based on their geochemical environment kst and mvt are formed from acid ore fluids while grt and ct creede type are derived from basic ore fluids ph of the fluids is best evaluated not from the ores themselves but from their effect on the host rocks

isotopically heavy carbon in the c21 to c25 regular isoprenoids in halite rich deposits from the sdom formation dead sea basin israel abstract a series of miocene pliocene halite deposits with extremely low organic carbon contents from the sdom formation dead sea basin israel have been studied distributions and 13c contents of biomarkers have been determined using gc ms and irm gcms analyses respectively the hydrocarbon fractions consist mainly of pristane phytane and c21 to c25 regular isoprenoids the predominance of c21 regular isoprenoids in the dead sea halites and other hypersaline deposits indicate that these components could be derived from ether bound membrane lipids of halophilic archaea the lack of intact ether bound lipids in the polar fractions indirectly infers that such components have already been released at early stages of diagenesis their 13c contents are enriched in 13c by up to 7 compared to the biomarkers of presumed phytoplanktonic origin i e steranes and hopanes within the same sediment sample in agreement with a source other than algae and cyanobacteria thus tentatively assigned as halophilic archaea based on biomarker distributions 13c contents and mineral compositions these sediments appear to have been deposited in a salinity stratified water body with a bottom water brine continual evaporation and deposition of the higher salts i e carnallites are favourable conditions for the growth of halophilic archaeal communities

dinosterane and other steroidal hydrocarbons of dinoflagellate origin in sediments and petroleum abstract the steroidal alkanes of a selection of sediments and oils have been examined by gc ms with multiple metastable reaction monitoring specific 4 methyl sterane isomers have been identified by comparison with isomers synthesized from sterols isolated from dinoflagellates an immature marine oil shale and two mature marine oils of triassic to early cretaceous age contained high concentrations of c30 steranes comprising desmethyl 24 ethyl 4 methylcholestane and 4 23 24 trimethylcholestane dinosterane isomers an immature non marine oil shale and two non marine oils of cretaceous to eocene age contained stereoisomers of 24 ethyl 4 methylcholestane as the dominant c30 steranes reaction monitoring analyses in gc ms are particularly suited to unravelling complex distributions of homologous and stereoisomeric steroids encountered in oils and their source rocks

palaeoclimate controlled accumulation of organic matter in oligocene evaporite sediments of the mulhouse basin abstract marl beds of a 30 m thick interval of the oligocene evaporites of the mulhouse basin display a cyclic variation in their organic carbon content that is related to changes in sedimentation rate the construction of a time scale suggests a duration of 58 000 30 yr for the interval studied calculated accumulation rates for organic matter of aquatic origin are used to assess the fluctuation of palaeoproductivity of the system the observed variation of the accumulation rates of terrigenous organic matter throughout the studied interval is most likely linked to variations in palaeoclimate

use of organic carbon content as a chronostratigraphic tool abstract in the mulhouse potash basin france the lithology and the organic carbon content reveal an extended succession of recurrent sequences variation in lithology shales anhydrite halite reflects variations in depositional environment organic matter exclusively present in the shaly horizons shows variations in content and origin these changes highlight small variations of their depositional environment which are not detected in the lithology of the shales on the other hand when these variations increase and are large enough they are recorded by the lithology in homogeneous facies i e shaly facies analysis of the distribution of the organic content in sediments thus appears to be an interesting method for determining small variations of the depositional environment the organic carbon signal showsvariations of sedimentation rates over time and can be interesting for small scale geochronology quite a similar duration for each cycle lasting an average of 13 000 3400 yr has been calculated this time span based on biostratigraphy is in agreement with results obtained by lamination counts this duration can be criticized due to the lack of precision of the dating methods but is significantly different from the well known periodicities of milankovitch

the mulhouse basin evidence from porphyrin distributions for water column anoxia during deposition of marls abstract marls from the evaporitic mulhouse basin oligocene alsace france contain alkyl porphyrins dominated by nickel complexed species the presence in high relative abundance of a range of components with carbon numbers up to c 37 indicates that anaerobic photosynthetic bacteria made a significant contribution to the photosynthetic community in the palaeoenvironment and in turn that anoxic conditions extended into the photic zone of a stratified water column further evidence is given by the assignment by hplc coinjection with a standard of a c 34 component with the same carbon skeleton as one of the bacteriochlorophylls d of such bacteria significant differences in the nickel and vanadyl porphyrin distributions in one of the samples examined appear to result from changes in the depositional environment which are recorded with a stratigraphic resolution below that sampled or indicate derivation of these two porphyrin pools from different parts of the water column

source rock potential of evaporitic environment examination of modern saline lakes solar evaporation ponds and lagoons shows that the evaporitic environment can be very productive of organic matter few species survive in the brines but those that do commonly exist in great profusion in a marine evaporitic embayment the flow of surface currents is persistently toward regions of highest salinity so that there is a continual supply and concentration of nutrients prolific growth of phytoplankton may be similar to that in areas of upwelling in modern oceans only carbonates precipitate in the mesosaline part 4 to 12 salinity of such an evaporitic environment and no great dilution of organic matter by clastic or biogenic sediments occurs because stratification of brine may occur and reducing conditions may be a sociated with the bottom waters much of the organic matter produced can be preserved upon maturation the result may be a rich carbonate source rock frequently unrecognized in the geologic column in the middle east mesosaline conditions are known to have occurred many times from the triassic to cretaceous and may be responsible for the vast reserves of petroleum in the area evaporitic conditions may also have played a part in the petroleum productivity of many other areas including the michigan and paradox basins

organic geochemical studies of a messinian evaporitic basin northern apennines italy ii isoprenoid and n alkyl thiophenes and thiolanes abstract series of n alkyl and isoprenoid thiophenes and thiolanes most of which have not been previously reported have been identified in an extract from a messinian upper miocene marl layer deposited under hypersaline euxinic conditions the identifications were based on mass spectra and chromatographic data of synthesized reference compounds and on comparison of mass spectra relative retention times and response on the fpd their specific structures and their distribution patterns show similarities with those of the alkanes inorganic sulphur is therefore considered to be incorporated into specific lipid moieties from archae bacterial and or algal input during diagenesis a biosynthetic origin of these compounds is also possible however the organic sulphur compounds encountered are thought to be indicators of a hypersaline depositional environment

stable isotope δ13c and δ15n based interpretation of organic matter source and paleoenvironmental conditions in al azraq basin jordan abstract this study examines the stable isotopes of carbon and nitrogen from cored lacustrine sediments of the al azraq an arid lake basin on the jordan plateau lacustrine sediments contain valuable records of paleoenvironmental conditions recording local and regional responses to environmental change previous paleo reconstructions on the jordan plateau are based on archaeology pollen mineralogy and stratigraphy the application of organic geochemistry analyses to these lake sediments identifies multiple sources of organic matter biological production and contributes to understanding the paleoenvironments of the al azraq basin during the mid pleistocene period organic carbon concentration corg provides an overview of the organic matter distribution carbon isotopic composition 13corg and nitrogen isotopic composition 15n are indicators of organic matter sources and paleoproductivity magnetic susceptibility mgsus measured the concentration of ferromagnetic minerals and indicated aeolian inputs organic geochemistry differentiated five paleoenvironmental zones with specific sources of organic matter both aquatic and terrestrial it identified a long period of climate wetter than the present punctuated by a short intense period of aridity diagenesis plays an important role in the decomposition of organic matter and studies indicate this degradation can alter the isotopic signals of organic matter analyses of the isotopic signals and statistical analyses demonstrate diagenesis is not a factor in the al azraq sediments in all but zone 4 of the paleoenvironmental zones this zone is defined by less negative carbon isotopic composition and the presence of thick primary gypsum layers in addition to the influx of high peaks of aeolian sediment as reflected in the magnetic susceptibility data stable isotope geochemistry provides detailed information on the paleoenvironments of lake sediments and is applicable to typically challenging arid basin sediments

dinosteranes 4 23 24 trimethylsteranes and other biological markers in dinoglagellate rich marine sediments of rhaetian age abstract alkane biological marker distributions and concentrations have been determined in 18 samples from a section of rhaetian age from the bristol trough and a quantitative micropalaeontological analysis carried out taking into account previous geological investigations of the sequence three end member depositional settings have been recognised from changes in total organic carbon content the biological markers and the micropalaeontological composition these depositional environments are attributed as follows the first which occurs in the lower part of the section corresponds to deposition in a supratidal sabkha type setting with the major organic input being of allochthonous origin the second also in the lower part of the section indicates the occurrence of periods of marine incursion with enhanced salinity resulting from evaporation in the upper part of the section marginal marine conditions are apparent with higher organic carbon biological marker and amorphous organic matter contents at the top suggesting the establishment of more stable conditions of oxygen depletion some sediments in the sequence are notable for containing an abundance of cysts of rhaetogonyaulax rhaetica one of the oldest marine dinoflagellates comparison of microfossil abundances with hydrocarbon abundances extends the circumstantial evidence for the dinophyceae being the major biological source of dinosteranes 4 23 24 trimethylcholestanes and some other 4 methyl steranes in marine sediments the presence of dinosteranes and their 24 ethyl counterparts extends the stratigraphic range of occurrence of such components back to the rhaetian c 31 methyl steranes in the sediments from the second depositional setting are tentatively assigned a 4 22 23 24 tetramethyl sterane skeleton and a dinoflagellate origin