early diagenetic transformation of higher plant triterpenoids in deep sea sediments from baffin bay abstract a sediment sequence of early miocene to holocene from ocean drilling program site 645 in central baffin bay was found to contain abundant triterpenoids of higher plant origin including monodesmethyl derivatives and other oxidative degradation products 24 nor triterpenoids of the oleanene ursene and lupane series were found in the nonaromatic hydrocarbon and alcohol fractions of the sediment extracts other diagenetic transformation products included 24 28 dinor olean 17 ene and 24 nor urs 12 en 1 1 one as well as their tentatively identified des a counterparts the identification of these novel degradation products was confirmed by synthesis of a suite of reference compounds the simple reaction sequence applied to obtain 24 nor urs 12 ene from 3 acetoxyurs 12 en 24 oic acid is likely to happen in a similar manner during early diagenesis of organic matter in nature these results have implications for the understanding of the diagenetic reaction sequence leading to the formation of other demethylated triterpenoids of terrigenous origin e g 24 28 dinor lupanes 28 30 dinor 17 hopane is sometimes the dominant hydrocarbon in the most deeply buried samples its co occurrence with higher plant triterpenoids and the low abundance of other regular hopanoids is not considered an indication however that 28 30 dinor 17 hopane is derived from a higher plant precursor molecule it is suggested that two independent sedimentary processes are responsible for the presence of the two types of demethylated triterpenoids observed in baffin bay sediments

biomarker and carbon isotope variation in coal and fossil wood of central europe through the cenozoic abstract carbon isotope analyses of terrigenous organic matter are often used to reconstruct changes in the isotopic composition of upper ocean and atmospheric carbon reservoirs carbon isotope values from tree rings fossil wood and coal matrices have been related to climatic change e g temperature humidity via water use efficiency of land plants in this study we report on carbon isotope analyses on low rank coal deposits of the alpine realm and middle german lignite district covering the early eocene to pliocene time interval fossil wood and extracted wood cellulose from gymnosperms and angiosperms respectively are used for paleoenvironmental reconstructions the trend in 13c is parallel to the carbon isotope record obtained from benthic foraminifera because both data sets sample a common reservoir in the atmosphere the evaluation of the magnitudes of 13c variations of coal caused by environmental change requires the correction of the 13c data due to the effects of different contents of lipids in the organic matter differences in biogeochemical carbon cycling varying contributions of gymnosperms versus angiosperms to peat formation and differences in 13c of atmospheric co2 the resulting carbon isotope record of coal generally co varies with the estimated variability in mean annual temperatures during the tertiary based on paleobotanical data changes in humidity and pco2 may be responsible for deviations between the isotopic trend and the paleotemperature curve during the miocene the obtained temperature coefficient for 13c of c3 plants of about 0 3 c is in agreement with the results of previous studies

early diagenesis of terrigenous triterpenoids and its implications for petroleum geochemistry abstract the distribution of triterpanes in sediments and crude oils is commonly used for oil oil and oil source rock correlation in petroleum geochemistry while isomer ratios of such compounds are applied as maturity parameters the triterpane pattern in terrestrially influenced geological samples is however remarkably less diverse than the triterpenoid skeletons occurring in the extant higher plant biosphere natural observations laboratory experiments and molecular mechanics calculations have revealed that acid catalysed double bond isomerization and skeletal rearrangement reactions of terrigenous triterpenoids during early diagenesis are the key to understanding the triterpane patterns in more matured geological materials examples studied in detail are the double bond isomerization of oleanenes and the subsequent hydrogenation of the products into oleanane and 18 oleanane and the transformation of taraxer 14 ene and lup 20 29 ene into oleanenes although the reactions are likely to be kinetically controlled the main products formed and ultimately preserved are the thermodynamically most stable ones the experimental results and natural observations have significant implications for the use of terrigenous triterpenoid compounds in petroleum geochemistry

petrography palynology and depositional environments of the early miocene oberdorf lignite seam styrian basin austria abstract an early miocene ottnangian lignite seam up to 36 m thick occurs in the oberdorf trough at the northwestern margin of the styrian basin it forms part of the fluvial koflach voitsberg formation petrographic and palynologic data together with ash yield and sulphur content of samples from two boreholes and two surface profiles have been used to study vertical and horizontal coal facies variations numerous partings and a high ash yield show that the lignite originated in a topogenous mire petrographic indices and palynological data suggest a wet forest swamp paleo environment a fluvial main parting with channel sediments at the eastern margin of the oberdorf trough and overbank sediments in its central part splits the lignite into a lower and an upper seam the lower seam consists of a lower high ash part with frequent splittings and a higher low ash part the upward decrease in number and thickness of silty clayey partings interpreted as crevasse splay deposits reflects the withdrawal of the fluvial sediment source coal composition is characterized by an upward increase in detro xylitic coal and in tissue preservation a good correlation between tissue preservation and percentages of taxodiaceae cupressaceae pollen suggests that this is mainly a result of an increasing contribution of decay resistant gymnosperms conifers the upper seam is also ash rich abundant inertinite at the eastern margin of the oberdorf trough is related to fire episodes inside or outside the mire main features of the upper seam in the central basin are an upward increase in tissue preservation and in percentages of taxodiaceae cupressaceae pollen high sulphur contents in the fresh water lignite are a result of a concentration of sulphate rich waters above the impermeable floors of the lower and upper seams carbonate rich surface waters from the graz palaeozoic and raasberg sequence raised the ph value and controlled sulphur and ash contents in those parts of the lower seam which are uninfluenced by the basal sulphur enrichment palynomorph spectra are dominated by taxodiaceae cupressaceae pollen and pollen from plants living in a mixed mesophytic forest pollen from aquatic and reed plants are rare the ratio between arctotertiary and paleotropic pollen is close to one and supports the early miocene age of the lignite the detected pollen spectra point to warm temperate subtropic and humid conditions

petrological and organic geochemical investigation of recent peats with known environments of deposition abstract a series of recent peat samples from tropical sub tropical and temperate locations were investigated using coal petrographical and organic geochemical techniques maceral and biomarker compositions were examined to see if they correlated or diverged from the known environment of deposition of the peats the proportion of humotelinite was related to the water depth and the frequency of dry periods the ph and trophic level have a modifying influence on the preservation of tissues furthermore the proportions of sclerotinite in the peats seem to reflected the oxygen status in the mire which was also mirrored in the abundance of humic and fulvic acids a facies diagram was calculated for the peat samples to see how maceral indices would fare in interpreting their known environments of deposition the results proved to be generally unsuccessful as the herbaceous and woody peats did not always give the predicted high humodetrinite and humotelinite compositions respectively the aliphatic hydrocarbon fraction from the extracts of the peat samples show that mainly odd numbered n alkanes are present diterpenoids triterpenoids and hopanoids were found in most samples and were mainly unsaturated in nature the relative proportion of hopanoids in pears appears to be related to bacterial activity in acidic environments de a triterpenoids were also detected in the peat stage of diagenesis in an angiosperm dominated peat type mariscus polycyclic aromatic triterpenoids were present in the aromatic fraction of the extract their occurrence and proportion appears to be related to the degree of humification in a taxodium peat mono di and triaromatic diterpenoids were detected the presence of these aromatic biomarkers indicate the rapid formation of these compounds in the peat stage mainly mediated by microbial activity

three dimensional modeling study of the low permeability petroleum system of the bakken formation the bakken formation of the williston basin is a prime example of an unconventionally produced petroleum system with a low permeability reservoir that requires application of advanced technologies for commercial production a three dimensional model of the williston basin was constructed to integrate and assess the parameters that influence the generation and migration of hydrocarbons in the bakken formation this study tests the applicability of available basin and petroleum system modeling technology on an unusually low permeability petroleum system the model is based on nine surfaces constructed from log tops of thousands of wells in the study area and additional depth and isopach maps of the bakken formation members these were integrated with the established basin evolution in line with published research temperature and thermal maturity were calibrated during model construction from well temperature and geochemistry data the resulting heat flow map supports the existence of a heat flow anomaly along longitude 103w discussed controversially in the literature furthermore the results indicate that the invasion percolation migration approach best describes the distribution of petroleum accumulation and the saturated areas in the bakken members the volume of generated hydrocarbons was calculated and the extent of the highly saturated accumulation beyond the area of the high mature source was mapped furthermore it was demonstrated that petroleum accumulations beyond the high saturation zones have to be related to stratigraphic pinch outs lateral variability in permeability of the bakken members or smaller structural influences that were lost because of the resolution applied in the model

the middle eocene markushegy subbituminous coal hungary paleoenvironmental implications from petrographical and geochemical studies abstract samples from two coal seams of the markushegy underground mine hungary were investigated for variations in maceral composition petrography based facies indicators and various geochemical parameters using three seam profiles both seams originate from a topogenous mire and evolved within a peneplaned coastal area covered with eutrophic swamps the presence of foraminifera and marine algae in the marly layers is indicative of marine ingressions coal facies characterisation from these parameters is combined with the results from biomarker analyses of soluble organic matter in order to reconstruct the depositional environment and to relate petrography based indicators to the molecular composition the contents of macerals of the liptinite group are positively correlated with soluble organic matter som yields and hydrogen index hi consistent with maceral composition and high hi values enhanced proportions of n alkanes of intermediate molecular weight n c21 25 which are predominantly found in macrophytes are obtained from samples of the marly shales the final drowning of the mire is reflected by decreasing pristane phytane ratios due to the rise of the ground water table and the establishment of anaerobic conditions the observed positive correlation between pristane phytane ratios and inertinite percentages suggests that at least in the markushegy deposit both parameters reflect variations in redox conditions of the mire the predominance of angiosperms in the peat forming vegetation of the markushegy coal is evidenced by the high relative proportions of angiosperm derived triterpenoids the influence of the relative proportion of fossil wood on tissue preservation tpi is indicated by the positive relationship of the concentration of land plant derived terpenoid hydrocarbons and tpi the degree of gelification of plant tissue gi is governed by the microbial activity in the mire as indicated by a negative relationship between gi and the steroids hopanoids concentration ratios the variation of the 13c values of coal is obviously governed by the relative contribution of plant lipids to the biomass the obtained negative relationship between 13c of the coal and gi is explained by the effect of cellulose decomposition and microbial activity on the isotopic composition of the organic matter

the relationship between coal petrography and depositional environments from selected coal basins in canada abstract this paper reviews current research in canada relating to the sedimentology of coal bearing sequences and the petrographic character of contained seams from selected intermontane and foreland basin settings the intermontane cumberland and stellarton basins of nova scotia contain westphalian coal bearing strata of different character coal seams that formed in fluvial dominated depositional environments of the springhill coalfield cumberland basin commonly brighten upward and laterally display distinct areal zones a piedmont zone formed by interfingering of mire and distal fan sheetflow deposits an inner mire zone largely devoid of partings and a riverine zone with large scale seam splits about multistorey sandstone bodies maceral based groundwater influence and vegetation indices combined with miospore analyses indicate that the peat precursors of the no 3 seam of the inner mire zone accumulated from a groundwater influenced rheotrophic to mesotrophic forest mire swamp fen both the gelification of lignin derived maceral precursors and the domination of mire vegetation by lycopsid trees reflect this groundwater influence coal that formed from the frequently flooded paleomires of the stellarton basin is generally dull microbanded and mineral rich the location of mires within the basin was largely determined by basin subsidence rates when subsidence rates were high mires developed around the margin of a central basin lake coal seams that formed from these mires e g mcleod seam thicken toward basin margins and grade into sapropelic shale near the basin centre petrographic analyses of the mcleod seam suggest development from limnic to wet forest swamp conditions and a return to a limnic environment at the top of the seam thick coal e g foord seam developed near the basin centre during periods of lower subsidence rates and grades into red beds and paleosols toward the basin margin the foord seam of the basin centre is characterized by low mineral matter contents and a high proportion of degraded vitrinite macerals in the central parts of the seam interpreted to reflect prolonged peat accumulation with very limited clastic input the top and the base of the seam in contrast were subjected to significant clastic input as indicated by microbanding associated with significant amounts of detrital minerals and macerals coal seams of the lower cretaceous gates formation in the western canada basin formed in depositional settings ranging from coastal swamps strandplains to the upper delta plain strandplain coal is characterized by great lateral continuity and substantial thickness whereas coal of the upper delta plain is thin and discontinous the strandplain coal is characterized by variable lithotype sequences oscillatory brightening up dulling up maceral based facies parameters indicate a wide range of mire facies for these lithotype successions open moor forest moor herbaceous and or shrubby marshes and slightly raised mires results from megafossil and phyteral analyses suggest that the coastal plain mires were dominated by taxodiaceous conifers whereas ferns angiosperms and herbaceous lycopods are thought to have occupied the more marshy and or marginal stream lake side environments

observations on the nature and origin of fusain abstract evidence for a wildfire origin of fusain is examined charcoal produced by natural fires and artificial charring resembles fossil fusain both in physical size and shape and in optical reflectance artificially charred leaves and naturally burnt wood are illustrated using the sem reflectance studies on modern charcoals suggest that much semifusinite may be produced by pyrolysis the ecological implications of a wildfire origin of fusain are discussed and it is concluded that fires have been a feature of terrestrial ecosystems from at least the late devonian

self boring pressuremeter study of san francisco bay mud discussion and closure the discussers comment on the use of s sub u p ratios from the laboratory uu and vane tests and on the comparisons with similar ratios from cu triaxial tests the second discusser notes that the instrument used by the authors the cambridge type self boring pressuremeter is now considerably improved recent work has also shown that it is possible to be more certain in the initial setting of the cutter this coupled with cutter geometry have meant that it is no longer a procedure of trial and error to determine the correct cutter setting it is also possible even in stiff clay to attain driving rates up to a meter of drilling in ten minutes the authors comment on the issues raised the authors observe that the self boring pressuremeter offers promise as a means to define the properties of soft clay soil the device is useful because it not only can determine the shear strength of a soil but also the stress strain and pore pressure response and the lateral stress in the ground

some mass balance and geological constraints on migration mechanisms oil and gas are not at rest in the sedimentary mantle of the earth they are not in equilibrium whether they are finely dispersed in a potential source rock or whether they are concentrated in a trap in a reservoir rock a wide variety of possible escape mechanisms exists these include diffusion continuous single phase flow solution of oil in gas or gas in oil and solution in water derived from compaction clay diagenesis or meteoric sources the problem is to quantify the possible mechanisms and to rank their relative importance under a given set of physical chemical and geologic conditions the quantitative importance of the various proposed mechanisms can vary by orders of magnitude depending on the physical chemical and geologic conditions during the past decade oil to source correlations have become reliable and the timing of peak generation and concomitant migration has been sufficiently quantified to allow the geologist geochemist to make estimates of when and how much petroleum moved from one location to another combined with a knowledge of the physical chemical and geologic conditions at the time of migration such quantitative descriptions of subsurface petroleum transfer permit an empirical test of the applicability of the various proposed migration mechanisms the application of this technique to selected areas suggests that most of the major commercial oil accumulations of the world left their source rock in a continuous oil phase when bitumen concentrations in the rock are too low for continuous phase flo to exist other migration mechanisms which always are operative will increase in both absolute and relative intensity solution of oil in gas may become significant in thick tertiary delta systems and meteoric water may be a surprising asset in some very specific geologic settings however it is unlikely that solution of oil in water derived from compaction or from dehydration of clay has much to do with the origin of many of the major oil accumulations of the world

chemical characteristics of liptinite macerals in humic and sapropelic coals abstract according to previous studies alginite does not occur in humic coals however in coals from the saar district f r germany alginite was identified by fluorescencemicroscopy in addition high amounts of an undeterminable liptinite maceral were found and tentatively explained as an alteration product of alginite therefore organic geochemical methods were used to characterize and identify this unknown liptinite maceral organic geochemical parameters such as cpi pristane phytane ratio and methylphenanthrene index show not only a dependence from coal rank but also yield additional information about the type of organic matter input and the depositional environment of the coals a series of coals of different origins around 0 8 vitrinite reflectance were investigated to determine how far the geochemical parameters reflect change in facies the samples included cannel boghead and resinite rich coals as well as isolated durain bands with increasing amounts of alginite in the coal the cpi pristane phytane and c 4 naphthalene phenanthrene ratios of the extracts decrease as illustrated by two representatives samples some resinite and sporinite rich coals show a primarily naphthalene derived aromatic composition whereas some alginite rich coals of the same rank show phenanthrene and its derivatives to be dominant with respect to technological properties most coals from the saar district correspond with a higher rank than indicated by reflectance measurements those coals in general show lower values of the aforementioned ratios in comparison with ruhr coals of similar vitrinite reflectance values

bacterial and algal hydrocarbons in sediments from a saline antarctic lake ace lake capillary gas chromatography mass spectrometry c gc ms and iatroscan thin layer chromatography flame ionisation detection tlc fid were used to study hydrocarbon distributions in a sediment core from ace lake a saline meromictic lake in the vestfold hills of antarctica hydrocarbons were abundant in most core sections up to 125 g g dry wt particularly in near surface samples and the distributions were very complex major constituents were identified as phytane 2 6 10 15 19 pentamethyleicosane tetrahydrosqualene a mixture of phytenes cholesta 3 5 diene and fern 7 ene smaller amounts of sterenes and hopenes were also present the predominance of the first 3 acyclic isoprenoids in sediments buried less than 30 cm is consistent with high populations of methanogenic bacteria known to be present phytenes were abundant in all core sections and there was no relationship between their abundance and that of phytane which suggests that they were not derived from methanogenic bacteria phytadienes were minor constituents at all depths studied an unusual feature of some distributions was the high concentrations of fern 7 ene which was the major hydrocarbon in the 20 25 cm core section this alkene was only abundant in sediments which contained high concentrations of methanogen markers suggesting that it may also be indicative of anoxic depositional environments a possible source might be from purple non sulphur bacteria high concentrations of straight chain c29 and c34 alkenes were also found in these sediments but their origin has not been determined major changes in the hydrocarbon distributions with depth indicate that the depositional environment in the lake has altered dramatically since the lake was formed less than 8000 years ago the present condition of permanent anoxic bottom waters probably developed only in the last 1000 years

a sequence stratigraphic investigation of a miocene formation supported by coal seam quality parameters central paratethys n hungary abstract a stratigraphic investigation of the coal bearing miocene siliciclastic succession in structurally dissected basins of northern hungary was performed based on log correlations and is supported by coal petrology and sulphur data the succession represents the karpatian lower order global eustatic cycle of the paratethys and was dissected into six higher order sedimentary sequences sq 1 sq 6 the coal bearing strata in the nograd basin sq 1 sq3 represent a lowstand systems tract lst prior to the karpatian relative sea level rise the transgressive systems tract tst starts with the oncophora beds sq 4 accumulated above a regional unconformity and containing coal beds in the borsod basin the tst is superimposed by tectonically forced higher order lowstand systems tracts sq 5 sq 6 containing coal beds only in the relatively elevated east borsod basin to support the sequence stratigraphic model the average maceral and sulphur content of coal seams was also interpreted the low sulphur 0 47 content in sq 1 reflects the lowstand environment determined by continental derived freshwater input transitional sulphur contents 0 66 1 02 in the late lowstand sq 2 and sq 3 indicate occasional saline invasions related to relative sea level rises high 2 3 2 6 sulphur contents in the tst sq 4 were caused by regular seawater inundations into the lagoon while decreasing sulphur contents in sq 5 and sq 6 2 28 2 09 reflect the increasing rate of freshwater income in association with the stepwise basinward shifts of the shoreline and the lagoonal facies within the lower to middle miocene salgotarjan lignite formation the analysis of coal seams contributed to the interpretation of relative sea level changes and the sequence stratigraphic context facilitated both the interpretation of sulphur content in coals and the reliable correlation of coal seams

the petrology organic geochemistry and palynology of tertiary age eureka sound group coals arctic canada abstract tertiary age lignites from arctic canada were analysed by petrographical palynological and organic geochemical methods results from petrographic analyses indicate the predominance of wood derived macerals humotelinite group in seams from the strathcona and stenkul fiord areas whereas in the bache peninsula area many seams are characterized by the predominance of detrital macerals humodetrinite and have also higher inertinite contents palynological assemblages are dominated by taxodiaceae pollen whereas pinaceae pollen and pteridophyte spores are less common angiosperm derived pollen contents are quite variable organic geochemical results indicate that norisopimarane and pimarane are the most abundant diterpenoids cadalene was present in the aromatic fractions of all samples with other components such as simonellite and retene in variable abundance rock eval data obtained from stenkul fiord area samples indicate low petroleum generation potential for this predominantly woody material the depositional environment at strathcona and stenkul fiords was that of a forested swamp which formed in a lagoonal alluvial plain setting palynomorph assemblages petrographic indices and the abundance of diterpenoids suggest that the mire flora was dominated by gymnosperms although locally angiosperms may also have been abundant as indicated by the occurrence of tetra and pentacyclic aromatic hydrocarbons at bache peninsula the mire was less forested as indicated by palynological assemblages typical for a marsh environment and petrographic characteristics such as low tissue preservation and the abundance of detrial macerals

algal and bacterial hydrocarbons in particulate matter and interfacial sediment of the cariaco trench particulate matter samples 53 m size fractions and sediment from the sediment water interface were collected in the cariaco trench an anoxic marine basin on the continental shelf of venezuela and analyzed for hydrocarbons concentrations of hydrocarbons were highest 10 20 ng 1 in oxic surface waters 0 150 m and at the top of the anoxic zone 350 600 m and were low 3 4 ng l in the low oxygen zone above the oxic anoxic interface 150 250 m and anoxic bottom waters 600 1150 m branched c25 trienes and tetraenes dominated the hydrocarbon distributions in 53 m particles particle size and depth distributions of the hydrocarbons demonstrate the importance of algal hydrocarbons in surface waters coupled with increased abundances of bacterial hydrocarbons especially in the 53 m particles in the anoxic zone these observations illustrate the importance of oxic anoxic interfaces even in the oceanic water column as zones of intense microbial alteration of organic matter and as sources of some of the organic compounds found in sediments

organic geochemistry of the lower miocene oberdorf lignite styrian basin austria its relation to petrography palynology and the palaeoenvironment abstract in the oberdorf trough at the northwestern margin of the styrian basin austria an up to 36 m thick lower miocene ottnangian lignite seam occurs within the fluvial koflach voitsberg formation previous results indicate that the lignite originated in a topogenous mire within a wet forest swamp palaeoenvironment differences in soluble organic matter som yield of borehole samples from the lignite seam are related to free lipids present in plant waxes or resins and the presence of thermally labile polymers indicated by the contents of liptinite macerals i e resinite suberinite and liptodetrinite the n alkane distribution patterns are dominated by high molecular weight lipids with marked odd over even predominance originating from plant waxes a contribution of algae to the even numbered short chain lipids observed in considerable amounts in the footwall sediments is proposed terpenoid biomarkers characteristic for conifers and angiosperms were detected consistent with palynomorphic spectra which are dominated by forest swamp pollen taxodiaceae cupressaceae and pollen from plants living in a mixed mesophytic forest excellent relationships between higher plant biomarker composition and palynologic data indicate that the organic geochemical results reflect the varying inputs of coniferales vs angiosperms the data further imply that cuparene may be used for taxonomical differentiation of coniferales families organic geochemical data provide evidence that the content of land plant derived biomarkers is controlled by the input of resin rich conifers concentrations of hopanoids dominated by hop 17 21 ene generally increase towards the top of the lignite a section characterised by high extents of aromatisation of triterpenoid biomarkers the results suggest that the aromatisation of angiosperm derived biomarkers may be governed by the activity of anaerobic rather than by aerobic bacteria however changes in the depositional environment and palynologic facies during peat formation probably influenced the origin and fate of angiosperm derived triterpenoids the results indicate how biomarker composition may contribute to the evaluation of environmental changes cross correlations of organic geochemical parameters with palynological data and petrography based facies indicators will provide further insights in the peat forming vegetation and biogeochemical activities in the mire

biomarker and micropetrographic investigations of coal from the krepoljin brown coal basin serbia abstract we investigated early diagenetic processes of the extractable organic matter from the miocene freshwater sequence which consists of coal fragments in clays sandstones and shales alternating with continuous brown coal layers we examined eight coals thirteen sediments and three non coaly underground layers the molecular assemblages of the identified aliphatic hydrocarbons in the krepoljin basin reflect the abundance of plant taxa as precursors or participants in the early diagenetic stage the data provide insight into the conditions prevailing in the lakes and bogs during early diagenesis the dominance of diterpanes indicates that the prevalent of the organic matter was of gymnosperous origin the hopanoid contents are considered to reflect microbial activity that the organic matter in the miocene krepoljin coal basin is immature was confirmed by the presence of biolipids such as hopanes c 27 17 h trisnorhopan saturated and aromatized abietanes pimaranes and phyllocladanes the most abundant compounds in all samples indicate a predominantly higher plant input related to the coniferous group but identification of the individual plant families was not possible amyrin and other triterpenoid derived triaromatic and triaromatic c ring cleaved hydrocarbons with triterpenoid structures are thought to be characteristic for angiosperms unsaturated compounds 2 triterpanes early intermediaries in the diagenetic transformation of angiosperms also indicate a low degree of sediment maturity

the organic geochemistry of coal from plant materials to coal coalification is a process that transforms plant remains under the influence of time temperature and possibly pressure to a black generally lustrous solid organic fossil fuel having a very complex chemistry although much has been learned in the past two centuries on coal chemistry we still have little knowledge of the way plant materials undergo these transformations the problem has been the existence of adequate characterization tools the advent of some new tools for structural elucidation of macromolecules has led to some revised thinking on coalification originally thought to be a process involving the full degradation of plant remains and subsequent reconstitution of these remains the general consensus today is that the process involves a selective preservation of certain resistant plant components followed by some minor reorganization of the biopolymers that survive the major components of plants do degrade and the resistant ones often constitute only a small fraction of the original mass of the plant materials this paper examines the most recent literature concerning coalification and focuses on the chemistry associated with coalification of certain recognizable plant remains that have been at the center of research activity for the past two decades thus we examine the recent knowledge of the chemistry of resistant biopolymers in extant and fossil wood cuticles resins spores and algae knowledge that has been assembled to establish the reaction pathways towards coal macromolecules

characterization of depositional conditions for lacustrine oil shales in the eocene jijuntun formation fushun basin ne china abstract the strike slip fushun basin hosts a lacustrine oil shale interval of ca 50 300 m in the eocene lutetian jijuntun formation the oil shale deposits consist of the lower lean oil shale unit losu and the upper rich oil shale unit rosu in outcrop areas the identified depositional cycles of ca 8 10 m and 5 8 m in thickness record the stacking of massive and non laminated oil shales in the losu and fine and coarse laminated oil shales in the rosu respectively depositional conditions in the paleo jijuntun lakes were synoptically reconstructed based on sedimentary features trace element and organic geochemical proxies oxic to suboxic fresh water conditions were prevailing in the paleo jijuntun lakes during deposition of the losu and then evolved into oxygen deficient fresh to mildly brackish water conditions during deposition of the rosu as revealed by the concentrations of redox and salinity sensitive trace elements e g v ni v cr ni co and sr ba ratios and boron content in the oil shales warm to cool and humid to arid climate represented by e g sr cu and rb sr ratios could result in the deepening of water column from ca 20 30 m to ca 100 m and saline stratification superposed on pre existing thermal stratification in the paleo jijuntun lakes a systematical decrease approximately one order of magnitude in the concentrations of most trace elements except for boron and co in the coaly oil shale in the lowermost losu relative to those in the other oil shales in the jijuntun formation indicates the significant change of organic matter om input from higher plant especially coaly materials to aquatic plankton this is partly consistent with the variations of om input from terrestrial higher plant and aquatic organisms type ii kerogen in the losu to lacustrine algae type i kerogen in the rosu as revealed by biomarkers the slight to significant enrichment or depletion of few trace elements i e mn and mo in these immature to low mature oil shale deposits may be associated with low to moderate productivities of aquatic plankton and or incompletely oxygen free conditions in the paleo jijuntun lakes

strain rate effects in self boring pressuremeter tests in clay a method is proposed for assessing the effect of strain rate on pressuremeter test results in clay the approach takes into account the strain rate used to expand the cavity and its variation within the soil mass both of which influence the value of the undrained shear strength deduced from the pressuremeter expansion curve the method is applied to quantify strain rate effects in idealized materials and in model pressuremeter test results the pressuremeter deduced stress strain curve is also used to predict the total pressure radial strain relationship observed in one of the model tests key words pressuremeter test clays strain rate idealized materials model tests

determination of organic matter content of appalachian devonian shales from gamma ray logs the organic matter content of the devonian shale of the appalachian basin is important for assessing the natural gas resources of these rocks and patterns of organic matter distribution convey information on sedimentary processes and depositional environment in most of the western part of the appalachian basin the organic matter content of the devonian shale can be estimated from gamma ray wire line logs using the equation phgro ggrb ggr 1 378a where phgro is the organic matter content of the shale fractional volume ggr the gamma ray intensity api units ggrb the gamma ray intensity if no organic matter is present api units and a the slope of the crossplot of gamma ray intensity and formation density api units g cm3 the quantities a and ggrb vary regionally and are mapped using data from gamma ray and formation density wire line logs organic matter contents estimated using this equation are compared with organic matter contents determined from direct laboratory analyses of organic carbon for 74 intervals of varying thickness from 12 widely separated wells the organic matter content of these intervals ranges from near zero to about 20 by volume excluding the cleveland member of the ohio shale and the lower part of the olentangy shale the distribution of the differences between volume percent organic matter content determined from core samples and estimated from gamma ray logs has a mean of 0 44 and a standard deviation of 1 98 which indicates that the accuracy of the gamma ray method is adequate for most geologic applications the gamma ray intensity of the cleveland member of the ohio shale and the lower pa t of the olentangy shale is anomalously low compared to other devonian shales of similar richness so that organic matter content computed for each of these units from gamma ray logs is likely to be too low wire line methods for estimating organic matter content have the advantages of economy readily available sources of data and continuous sampling of the vertically heterogenous shale section the gamma ray log in particular is commonly run in the devonian shale its response characteristics are well known and the cumulative pool of gamma ray logs forms a large and geographically broad data base the quantitative computation of organic matter content from gamma ray logs should be of practical value in studies of the appalachian devonian shale the general approach described here may also be applicable to other formations with physical and geochemical characteristics similar to the appalachian devonian shale

characterization of organic matter and depositional environment of tertiary mudstones from the sylhet basin bangladesh abstract the sylhet basin of bangladesh is a sub basin of the bengal basin it contains a very thick up to 22 km tertiary stratigraphic succession consisting mainly of sandstones and mudstones the sylhet succession is divided into the jaintia paleocene late eocene barail late eocene early miocene surma middle late miocene tipam late miocene pliocene and dupitila groups pliocene pleistocene in ascending order the origin of the organic matter om and paleoenvironment of deposition have been evaluated on the basis of c n s elemental analysis rock eval pyrolysis and gas chromatography mass spectrometry gc ms analysis of 60 mudstone samples collected from drill core and surface outcrops total organic carbon toc content ranges from 0 11 to 1 56 sulfur content is low in most samples toc content in the sylhet succession varies systematically with sedimentation rate with low toc caused by clastic dilution produced by high sedimentation rates arising from rapid uplift and erosion of the himalaya the om in the succession is characterized by systematic variations in pristane phytane pr ph oleanane c30 hopane n c29 n c19 alkane tm ts 17 h 22 29 30 trisnorhopane 18 h 22 29 30 trisnorhopane and sterane c29 c27 c28 c29 ratios during the middle eocene to pleistocene based on biomarker proxies the depositional environment of the sylhet succession can be divided into three phases in the first middle eocene to early miocene deposition occurred completely in seawater dominated oxic conditions with abundant input of terrestrial higher plants including angiosperms the second phase middle to late miocene consisted of mainly freshwater anoxic conditions along with a small seawater influence according to eustasic sea level change with diluted om derived from phytoplankton and a lesser influence from terrestrial higher plants oxygen poor freshwater conditions prevailed in the third phase post late miocene planktonic om was relatively abundant in this stage while a high angiosperm influx prevailed at times tmax values of ca 450 c vitrinite reflectance ro of ca 0 66 and methylphenanthrene index mpi 3 of ca 1 indicate the om to be mature the lower part middle eocene to early miocene of the succession with moderate toc content and predominantly terrestrial om could have generated some condensates and oils in and around the study area

wavelet analysis of well logging data from oil source rock egret member offshore eastern canada wavelet analysis is a sensitive method for automatically detecting and distinguishing abrupt discontinuities i e faults unconformities cyclicity and gradual changes in sedimentation rate by transforming depth related sedimentary signals i e gamma rays into wavelengths at distinct depth intervals we used wavelet analysis for evaluation of the spatio temporal distribution of oil source rocks and for estimating accumulation rates in a sedimentary basin having high resolution the method was applied to 16 gamma ray logs from the jurassic egret member an oil source rock succession 55 m to 227 m in thickness offshore eastern canada dominant gamma ray cycles having wavelengths varying from 2 8 m western margin of the basin to 24 m eastern part of the basin have been detected by wavelet analysis the coincidence of the ratio of predominant gamma ray cycles with the ratio of milankovitch spectra about 400 100 40 20 k y suggests that climatic cycles are an important factor controlling sedimentary cyclicity in the egret member dominant wavelengths likely represent 100 k y eccentricity giving accumulation times of 1 9 m y for stratigraphically complete sections having 19 successive 2 8 m gamma ray cycles and giving accumulation times of 600 k y for incomplete successions having only 6 cycles up to four discontinuities occur in gamma ray log cyclicity and separate the egret member into subunits we interpret the discontinuities as unconformities or faults and as related to sediments having low petroleum potential the stratigraphic completeness of the egret member is correlated to total mass of organic carbon and decreasing thickness of non source rock intervals having correlation coefficients of r 0 8 and r 0 76 respectively

the geology and coal petrology of a miocene lignite profile at meliadi mine katerini greece abstract the present study describes vertical variations in petrographic composition of a miocene lignitebearing succession from the moschopotamus basin greece the lignite beds are described megascopically in terms of lithotypes and microscopically by maceral contents examination of lithotype variations within the seams and the distribution of facies critical macerals such as humotelinite and humodetrinite and the relatively low inertinite contents suggest a formation of the miocene lignites as reed marsh to wet forest type swamps in a lower delta plain depositional setting reflectances measured on the maceral type eu ulminite b range from 0 36 to 0 42 r random placing the meliadi coals into a transition zone from lignite to subbituminous coal

lithotype maceral composition and variation as correlated with paleo wetland environments gates formation northeastern british columbia canada abstract lithotype samples collected from mid albian gates formation coal seams in northeastern british columbia were analysed in order to gain a better understanding of coal facies variation compositional boundaries between lithotypes are gradational from bright to dull coals there is a progressive decrease in vitrinite and increase in inertinite liptinite is negligible

determination of the total organic carbon toc based on conventional well logs using artificial neural network abstract total organic carbon toc is the measure of the amount of carbon available in an organic compound and is often used as an essential factor for unconventional shale resources evaluation previous models for toc determination based on density log data considered the presence of organic matter is proportional to the formation bulk density also model those based on resistivity log sonic or density logs as well as the formation level of maturity lom were used to determine the toc these models assumed linear relation between resistivity and porosity logs previous correlations showed very low coefficient of determination of the estimated toc compared to the actual laboratory data the objective of this paper is to develop an empirical correlation to determine the toc for barnett and devonian shale formations based on conventional logs using artificial neural network ann core toc data 442 data points and well logs resistivity gamma ray sonic transit time and bulk density from barnett shale were used to develop the ann model for the first time an empirical correlation for toc was developed based on the weights and biases of the ann model the developed correlation was then applied to estimate toc for devonian shale the developed ann model predicted the toc based on conventional well log data with high accuracy the average absolute deviation aad and coefficient of determination r2 for the predicted toc compared with the measured toc for barnett shale are 0 91 wt and 0 93 respectively the developed model outperformed the previous available models in estimating toc for devonian shale as well with aad of 0 99 wt and r2 of 0 89 compared to aad of 1 16 wt or more and r2 of 0 65 or less for the available correlations the developed empirical correlation was used to estimate the toc with high accuracy for barnett shale and devonian shale formations the developed correlation will help the geological and reservoir engineers predict the toc using well logs without the need to measure toc in the laboratory

biogeochemistry of the miocene lacustrine deposit at clarkia northern idaho u s a abstract the lipid preservation observed in the sediments from clarkia reflects an extremely immature thermal history many biomarkers have still retained functionality even after 17 20 million years the soluble components are predominantly higher plant and algal derived lipids and the original sources for these compounds are still preserved in the sediment thus biogeochemical data are in agreement with the associated palaeontological evidence chemical changes noted in the lipids preserved in these sediments are similar to those observed in modern fresh water mesotropic or eutrophic lacustrine sediments therefore it can be inferred that the processes that operate in modern lacustrine sediments are similar to those that took place within the sediments at clarkia 17 20 million years ago

effect of strain rate on undrained strength derived from pressuremeter tests a method is presented for evaluating the effect of strain rate on pressuremeter tests it can analyse the combined effects of higher strain rate and variation of strain rate across the soil mass on the undrained strength derived from pressuremeter tests the results of a parametric study using this method indicate that the stress strain curves derived from the pressuremeter curves differ from the true material stress strain curves and that the undrained strength is overestimated these differ ences are quantified l article presente une methode pour evaluer i effet du taux de deformation sur les essais pressiometriques en utilisant la mkthode il est possible d analyser les effects combines d un taux de deformation plus eleve et d une variation dans le taux de deformation a travers la masse du sol sur la resistance non drainee obtenue a partir d essais pressiometriques les resultats d une etude parametrique utilisant cette methode indiquent que les courbes de contrainte deformation obtenues a partir des

the sources and deposition of organic matter in the late quaternary pigmy basin gulf of mexico abstract the concentration and carbon isotopic composition 13c of sedimentary organic carbon corg n c ratios and terrigenous and marine 13corg endmembers form a basis from which to address problems of late quaternary glacial interglacial climatic variability in a 208 7 m hydraulic piston core dsdp 619 from the pigmy basin in the northern gulf of mexico while interpretations of sedimentary 13corg time series records are often not unique paired analyses of 13corg and n c are consistent with the hypothesis that the corg in the pigmy basin is a climatically determined mixture of c3 photosynthetic terrigenous and marine organic matter confirming the earlier 13corg model of sackett 1964 a high resolution 1 4 2 9 ka sample 13corg record shows that sedimentary organic carbon in interglacial oxygen isotope sub stages 1 and 5a b are enriched in 13c average 1 values are 24 2 1 2 o and 22 9 0 7 o relative to pdb respectively while glacial isotope stage values 2 are relatively depleted 25 6 0 5 concentrations of terrigenous and marine sedimentary organic carbon are calculated for the first time using 13corg and corg measurements and empirically determined terrigenous and marine 13corg endmembers the net accumulation rate of terrigenous organic carbon is 4 3 2 6 times higher in isotope stages 2 4 than in sub stages 1 and 5a b recording higher erosion rates of terrigenous organic material in glacial times the concentration and net accumulation rates of marine and terrigenous corg suggest that the nutrient bearing plume of the mississippi river may have advanced and retreated across the pigmy basin as sea level fell and rose in response to glacial interglacial sea level change

stable carbon isotopes of amorphous kerogens from phanerozoic sedimentary rocks amorphous kerogens from phanerozoic sedimentary rocks may be divided into two groups on the basis of their 13c values h amorphous kerogens have isotopic values in the range of 24 to 20 per mil and l amorphous kerogens have isotopic values in the range of 35 to 26 per mil the occurrence of amorphous kerogens in the intermediate isotopic range from one rock unit in the data set suggests a weak continuum may exist between these two groups phytoplankton and to a lesser extent zooplankton and bacteria are considered to be the precursors for both kerogen types a plausible explanation for this dichotomy may be found in the source of co2 utilized by phytoplankton which is considered to be controlled by environmental factors h amorphous kerogens are expected to occur in silled basins that are overlain by expansive well circulated deep 500 m water where the prevailing source of carbon in the photic zone is atmospheric derived co2 conversely l amorphous kerogens are expected to occur in restricted basins that are overlain by stratified shallow 200 m water where the prevailing source of carbon in the photic zone may be organic derived co2

paleoenvironmental implications from biomarker and stable isotope investigations on the pliocene velenje lignite seam slovenia a pliocene lignite seam up to 160 m thick occurs in the velenje basin slovenia the seam originated in a topogenous mire and evolved within a non marine transgressive setting differences in soluble organic matter yield and hydrocarbon content of borehole samples from the lignite are related to differences in the composition of free lipids of microbial origin and or hydrocarbons derived from the biogeochemical degradation of plant tissue variations of the redox conditions within the mire are reflected by pristane phytane ratios the abundance of terpenoid biomarkers indicates the predominance of gymnosperms over angiosperms which is consistent with palynomorphic spectra dominated by pollen of the sequoia taxodium metasequoia plant community rather than by angiosperms evidence is also provided that the content of land plant derived biomarkers and the preservation of plant tissue is controlled by the input of resin rich decay resistant conifers sections of the seam characterized by a high degree of gelification of humotelinite gelification index show high contents of hop 17 21 ene but low hopane concentrations the results suggest that the gelification of plant tissue may be governed by the activity of anaerobic rather than aerobic bacteria despite the minor variation in the proportions of gymnosperms versus angiosperms in the peat forming vegetation a general influence of the floral assemblage on carbon isotopic composition of the coals 13c 25 3 to 27 0 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is assumed to affect the 13c value of the lignite petrographic and geochemical data of gelified and ungelified fossil wood provide evidence that gelification may be governed by microorganisms e g anaerobic bacteria different from those responsible for decreasing cellulose contents during early diagenetic aerobic degradation of wood based on the molecular composition of terpenoid biomarkers the wood fragments are identified as derived from gymnosperms the relative proportions of saturated versus aromatic hydrocarbon fractions of fossil gymnosperms display a general tendency towards lower values in gelified wood remains this indicates that bacteria involved in gelification of plant tissue may also be involved in aromatisation of diterpenoid hydrocarbons the chemotaxonomical classification of the macrofossils as gymnosperms is corroborated by the mean carbon isotopic compositions of the macrofossils 13c 24 5 and the extracted cellulose 13c 22 0 the higher isotopic difference of about 2 5 between cellulose and fossil wood compared to that found in modern trees can most probably be explained by the smaller effect of 13c discrimination for cellulose when compared with wood during decomposition chem geol 158 1999 121 compared with the coals the 13c values of wood and extracted cellulose are affected to a minor extent by microbial activity

assessment of self boring pressuremeter tests in sensitive clay the present paper analyzes field test results obtained by means of the cambridge self boring pressuremeter sbpm in a sensitive champlain clay of quebec it is shown that although the undrained shear strengths deduced from the sbpm tests are higher than the values obtained with the field vane the observed discrepancy is reduced by taking into account progressive failure effects it is not the sbpm test that overestimates the undrained shear strength but rather the vane test that underestimates it in this sensitive clay total and effective field stress paths are inferred from the sbpm tests and it is shown that the effective stress paths approach the tension zone of the mohr coulomb failure diagram before heading towards the large strain failure envelope of the clay the pressuremeter interpretation has been thoroughly worked through for various uncertainties like undrained test conditions plane strain conditions and disturbance basing the final judgment on a comparison of the effective stress adj

paleoenvironment of the upper oligocene trbovlje coal seam slovenia abstract in the trbovlje region slovenia an upper oligocene coal seam up to 30 m thick developed in a topogenous mire and evolved within a transgressive setting the lower ash rich part of the seam unit i accumulated in a forest swamp strongly influenced by fluvial activity palynomorph spectra are dominated by taxodiaceae cupressaceae pollen ash yields decrease in the middle unit ii and upper part of the seam unit iii indicating decreasing fluvial activity an increase in cao contents reflects increasing amounts of inflowing water from an alkaline lake which progressively controlled peat hydrology in units ii and iii high sulfur contents in the nonmarine coal are a result of the carbonate rich water abundant pollen and spores from myricaceae and polypodiaceae indicate that unit ii represents a bush moor during deposition of unit iii this environment was replaced by a reed moor sapropelic coal unit iv and sapropelic shale unit v accumulated in a relatively large lake which was established by another water table rise the interpreted environmental changes are confirmed by biomarker data pristane phytane ratios reflect variations of the redox conditions within the mire and reach a minimum in the sapropelic unit iv the abundances of gymnosperm and angiosperm derived terpenoid hydrocarbons testify the predominance of gymnosperms over angiosperms during early peat stages unit i and increasing proportions of angiosperms during deposition of units ii and iii highest contents of diterpenoids coincide with maxima in the preservation of plant tissue tpi within unit i wet forest swamp suggesting that tpi is partly controlled by the input of resin rich decay resistant conifers sections of the seam characterized by advanced gelification show low steroids hopanoids ratios the results imply that gelification of plant tissue is related to increased microbial activity evidence is provided that the hopanes could be used as a measure for the activity of aerobic bacteria whereas for the hop 17 21 ene a microbial origin from anaerobic iron reducing bacteria is assumed a general influence of the floral assemblage and of varying contributions of algal biomass on carbon isotopic composition of the organic matter 13 c 24 0 to 28 1 is proposed carbon cycling during biogeochemical decomposition of plant tissue by bacteria is assumed to affect the 13 c values of the coal fossil wood collected from the seam is identified as derived from gymnosperms based on the molecular composition of terpenoid hydrocarbons this chemotaxonomical classification is corroborated by the mean carbon isotopic compositions of the fossil wood 13 c 24 0 and by the 13 c value 21 8 of the extracted cellulose from one macrofossil the low cellulose content of the sample 2 7 together with the slightly higher isotopic difference of 1 6 between cellulose and fossil wood compared to that found in modern trees can most probably be explained by the possible reversal in 13 c discrimination for cellulose when compared with wood in highly degraded samples

a practical model for organic richness from porosity and resistivity logs a practical method the delta log r technique for identifying and calculating total organic carbon in organic rich rocks has been developed using well logs the method employs the overlaying of a properly scaled porosity log generally the sonic transit time curve on a resistivity curve preferably from a deep reading tool in water saturated organic lean rocks the two curves parallel each other and can be overlain since both curves respond to variations in formation porosity however in either hydrocarbon reservoir rocks or organic rich non reservoir rocks a separation between the curves occurs using the gamma ray curve reservoir intervals can be identified and eliminated from the analysis the separation in organic rich intervals results from two effects the orosity curve responds to the presence of low density low velocity kerogen and the resistivity curve responds to the formation fluid in an immature organic rich rock where no hydrocarbons have been generated the observed curve separation is due solely to the porosity curve response in mature source rocks in addition to the porosity curve response the resistivity increases because of the presence of generated hydrocarbons the magnitude of the curve separation in non reservoirs is calibrated to total organic carbon and maturity and allows for depth profiling of organic richness in the absence of sample data this method allows organic richness to be accurately assessed in a wide variety of lithologies and maturities using common well logs

sulphur and carbon isotopic composition of power supply coals in the pannonian basin hungary abstract the present work is an attempt to establish the stable isotope database for mesozoic to tertiary coals from the pannonian basin hungary maceral composition proximate analysis sulphur form sulphur isotopes organic and pyritic and carbon isotopes were determined this database supports the assessment of the environmental risks associated with energy generation the characterization of the formation and the distribution of sulphur in the coals used the maceral composition the sulphur composition the c s isotopic signatures and some of the geological evidences published earlier show that the majority of these coals were deposited in freshwater and brackish water environments despite the relatively high average sulphur content however the upper cretaceous eocene and lower miocene formations also contain coal seams of marine origin as indicated by their maceral composition and sulphur and carbon chemistry the majority of the sulphur in these coals occurs in the organic form all studied sulphur phases are relatively rich in 34s isotopes 34sorganic 12 74 34spyrite 10 06 on average this indicates that marine bacterial sulphate reduction played a minor role in their formation in the sense that isotopic fractionation was limited it seems that the interstitial spaces of the peat closed rapidly during early diagenesis due to a regime of high depositional rate leading to a relative enrichment of the heavy sulphur isotopes

stable isotopic and elemental characteristics of pale and dark layers in a late pliocene lignite deposit basin in yunnan province southwestern china implications for paleoenvironmental changes abstract the carbon and nitrogen stable isotopic compositions and elemental characteristics of pliocene pale and dark lignites in the jinsuo basin yunnan province southwestern china were investigated these data were used to develop paleoenvironmental models and to discuss possible geological driving forces for the formation of pale and dark layers the 13c values of fossil wood av 24 79 and fusain samples av 24 19 are generally higher than the values obtained from bulk pale av 27 01 and dark av 26 38 lignite samples in contrast the 15n values of fossil wood av 0 63 and fusain samples av 1 29 are lower than the average values of bulk pale lignites av 2 17 and dark lignites av 1 79 the difference in the carbon isotopic values between pale and dark lignites can be explained by the very high amount of liptinite and strong degradation of woody material by bacterial activity in pale lignites which resulted in depletion of 13c in pale lignites and the wet humid depositional conditions contributed to the relatively heavy stable carbon isotope compositions of dark layers the higher 13c values in the fossil wood and fusain samples can be explained by the general enrichment of 13c in woody material compared to leaves the weakly negative correlation between the 15n and 13c values indicates that besides bacterial degradation the liptinite content could also influence the carbon and nitrogen compositions of lignites the influence of the original plant community gymnosperms angiosperms on the carbon and nitrogen isotopic compositions of bulk lignites is insignificant in the jinsuo basin the paleoenvironmental model suggests deposition of pale layers under relatively dry cold conditions supporting the expansion of gymnosperms such as pinus yunnanensis the slight stepwise uplift of the tibetan plateau and the approximate co occurrence of the more intense asian monsoon might have supported short periods of a locally dry cold climate resulting in the lowering of water table which was favorable for the formation of pale layers the low 13c values in pale layers further support this the relatively high sio2 al2o3 ratios higher values of the average detrital authigenic index and high levels of tio2 and zr in pale layers suggest an increased detrital input relative to dark layers the dark layers however formed in a tropical subtropical warm humid climate that favored angiosperm dominance of the vegetation the long term geologically stable conditions together with the regionally warm humid climate resulted in a rise in the water table in the basin which led to the formation of dark layers until the subsequent slight uplift of the tibetan plateau this conclusion is also supported by the high 13c values in dark layers and the thickness differences between pale thin and dark thick layers and the changes in major elements and minerals changes between the two types of layer

strain rate effects in model pressuremeter testing a series of one eighth scale strain controlled model pressuremeter tests were performed using an automated flexible wall calibration chamber testing system undrained model pressuremeter tests were performed with and without the internal pore water pressure measuring piezometer needles at radial strain rates ranging from 1 to 8 min in a controlled laboratory setup in beds of kaolin clay prepared with known stress histories reference strength and deformation properties were determined using one dimensional consolidation isotropically consolidated undrained compression and k sub 0 consolidated undrained compression laboratory tests and comparisons were made with the interpreted values from the pressuremeter test data interpretations of the undrained shear strength initial shear modulus shear stress radial strain variation limit pressure and horizontal stress for each net pressuremeter curve were evaluated via various interpretation procedures using the marquardt levenberg algorithm based on the laboratory test data and the analytical interpretations several conclusions were made regarding the effects of the rate of probe expansion on the deduced shear modulus undrained shear strength and limit pressure in the pressuremeter testing of clays

organic carbon in bakken formation united states portion of williston basin the upper and lower members of the mississippian and devonian bakken formation in the united states portion of the williston basin are black shales that are extremely rich in organic matter and are the source of much of the oil found in the basin organic carbon values are calculated from formation density logs using the equation toc 154 497 rgr 57 261 where toc is organic carbon content wt and rgr is formation density g cm3 test calculations comparing this equation to laboratory organic carbon analyses from 39 wells in north dakota show an average absolute difference of 1 1 in organic carbon content organic carbon content calculated at 159 locations in north dakota and 107 in montana averages 12 1 for the upper member of the bakken formation and 11 5 for the lower member there is a regional depletion of organic carbon paralleling present day isotherms that reflects the conversion of organic matter to oil and subsequent expulsion of the oil from the formation the mass of organic carbon in the bakken formation is approximately evenly divided between the upper and lower members and it totals about 126 1012 kg in the study area of which 102 1012 kg are in the thermally mature region the assumption that 167 mg hc g toc have migrated out of the mature bakken shales leads to a tentative estimate that hydrocarbons equivalent to 132 billion bbl of 43 api gravity oil have been expelled from the united states portion of the upper and lower members of the bakken formation

a paleoclimatic and paleoatmospheric record from peatlands accumulating during the cretaceous paleogene boundary event western interior basin canada petrological and 13 c analyses were undertaken on contiguous specimens of coal and intercalated minor organic rich clastic sediments collected from coal seams spanning the cretaceous paleogene boundary in the alberta and saskatchewan portions of the western interior basin the generally high smectite content of the coal suggests that the original mires were largely small disconnected and rheotrophic readily receiving abundant waterborne detrital clastic material of largely volcanic origin nevertheless using the distinctive claystone that marks the cretaceous paleogene boundary as a regional datum it is possible to correlate cycles in the vitrinite and inertinite composition of the coals over 500 km estimates of peat accumulation rates suggest that the cycles in vitrinite and inertinite composition represent regional cyclic fluctuations in wildfire and oxidation of the peatlands and overlying canopy at a frequency of hundreds to thousands of years the likely causes of these fluctuations were cyclic regional scale changes in temperature the cretaceous paleogene boundary event occurred early during a phase of gradually increasing temperature and or decreasing rainfall but peak wildfire and desiccation of peat occurred up to 14 000 yr later than the cretaceous paleogene boundary and the mires did not experience significant water stress in the immediate aftermath of the extinction event a persistent 1 5 3 0 negative 13 c excursion occurs across the cretaceous paleogene boundary but it cannot be readily separated from four further negative excursions later in the earliest danian the negative carbon isotope excursion linked to the cretaceous paleogene boundary began a few hundred years before the event itself and recovery occurred within 21 k y and possibly in as little as just a few thousand years consistent with recently calibrated shallow marine 13 c records hence the atmospheric and surface ocean carbon pools were coupled at this time the absence of evidence for catastrophic change in the climatic regime at the time of the cretaceous paleogene extinction in these mires supports the notion that the negative shift in atmospheric 13 c was brought about by changes in the 13 c composition of the surface ocean this is consistent with the greater magnitude of extinction experienced by marine fauna relative to the terrestrial realm

the nature and influence of fire in carboniferous ecosystems fusain occurs widely in carboniferous coals and sediments it is now recognised to represent charcoal and be the product of wildfire the occurrence of fire is partly constrained by atmospheric oxygen levels availability and nature of fuel and by aspects of climate rainfall and seasonability in particular the majority of fires in the carboniferous were probably started by lightning strikes or by volcanic activity experiments on the charring of modern plants has shown that the reflectance of charcoal and hence fusain is directly related to temperature of formation different fire types may yield fusain assemblages of differing reflectance spectrums but it may be significant that many modern charcoal assemblages yield only semifusinites as seen by reflectance microscopy the significance of these findings is assessed in relation to the use of fusinites and semifusinites as depositional indicators as interpreted from coal petrology fires may have a dramatic effect on ecosystems not only causing changes in vegetational succession but also severe erosion can occur following a major fire which can be traced in depositional systems in this paper we document three major carboniferous sedimentary systems affected by fire clastic sedimentary systems using extensive fusain deposits in mid lower carboniferous near shore sediments in donegal ireland volcanic systems using late early carboniferous volcaniclastic sequences in the midland valley of scotland and coal and coal bearing sequences in the upper carboniferous westphalian b of the pennine basin england in the later settings the influence of fire in peat formation and succession is assessed in addition data on the vegetational composition of charcoal assemblages is considered it is concluded that fire plays a major role in many carboniferous ecosystems

novel families of tetra and hexacyclic aromatic hopanoids predominant in carbonate rocks and crude oils two novel families of monoaromatic geomarkers related to hopanoids have been separated and characterized in sediments and crude oils the benzohopanes c32 c35 1 and the ring d aromatized 8 14 secohopanoids c27 c35 4 and 5 both series are particularly abundant in many carbonate samples where they amount to approximately 100 p p m per component in some crude oils but can also be detected in other environments the benzohopanes have been separated as pure compounds by high performance liquid chromatography and identified by x ray diffraction the structure of the 8 14 secohopanoids mostly relies on spectroscopic data nmr and ms and comparison with synthetic analogs both families must be formed in the subsurface from bacterial c35 hopanoid precursors but the benzohopanes seem to occur at an earlier stage of sedimentation the two series appear in varying distributions in the different samples and may therefore be potentially useful as geochemical correlation parameters

environmental history of the german lower rhine embayment during the middle miocene as reflected by carbon isotopes in brown coal stable carbon isotope investigations have been carried out on miocene brown coal from the garzweiler seam of the german lower rhine embayment material studied included fossil wood from seven different taxa and brown coal matrix isotope results from macrofossil analysis show variations of more than 6 within individual samples and reveal a general isotopic difference between angiosperm and gymnosperm wood specimens according to mean carbon isotope values found for gymnosperms angiosperms and brown coal matrix 23 3 26 0 and 25 8 the peat forming vegetation of the garzweiler seam was dominated by angiosperm taxa results from brown coal matrix establish a continuous high resolution depth profile of carbon isotope variations during the late middle miocene they show a significant and characteristic isotope pattern with distinct medium and short term cycles high frequency variations in the two main units of garzweiler seam locally split into three units the medium term 13c variations are most likely caused by varying proportions of gymnosperms within the peat forming vegetation while high frequency oscillations seem to be a direct signal of environmental changes a long term decline of carbon isotope values observed within the complete garzweiler seam from base to top is presumably due to a cooling trend in the miocene

sulfur isotope ratios in petroleum research and exploration williston basin the three major types of crude oil in the williston basin the type i oils of the winnipeg red river system the type ii oils of the bakken madison system and the type iii oils of the tyler pennsylvanian system can be distinguished by their sulfur isotope compositions they have characteristic dgr34s values of 5 8 1 2 parts per thousand ppt 2 8 0 8 ppt and 4 0 0 7 ppt respectively highly mature oils have less typical values type ii oils which have migrated over a distance of some 150 km beyond the region of generation have maintained their characteristic dgr34s values even though sulfur may have been lost this indicates little or no interaction with reservoir sulfates under normal circumstances on the periphery of the basin type ii oils altered by water washing and biodegradation have altered dgr34s values which increase from 2 9 to 9 4 ppt with the increasing degree of crude oil degradation the bakken shales source of the type ii oils have dgr34s distribution patterns in the reduced sulfur typical of marine sediments the dgr34s values for the type ii oils match most closely the dgr34s value of organic sulfur in the black bituminous shales of the lower bakken

parameters determining the carbon isotopic composition of coal and fossil wood in the early miocene oberdorf lignite seam styrian basin austria abstract petrographical and geochemical data of gelified and ungelified fossil wood from the early miocene oberdorf lignite seam styrian basin austria provide evidence that the early diagenetic aerobic degradation of wood by fungi may be followed by further decomposition under reducing conditions by the activity of anaerobic bacteria based on the molecular compositions of terpenoid hydrocarbons the wood fragments in the lignite are identified as gymnosperms this result is corroborated by the mean isotopic composition 13c 24 2 of the macrofossils the isotopic difference between fossil wood and extracted cellulose of most samples 3 9 2 5 is higher than in modern trees which can be explained by the smaller effect of 13c discrimination during decomposition of cellulose when compared with wood the mean carbon isotope values found for gymnosperms and coals 24 2 and 24 7 respectively confirm the results from biomarker analyses indicating that the peat forming vegetation of the oberdorf seam was dominated by gymnosperm taxa minor variation in the relative contributions of gymnosperms and angiosperms to coal deposition is of negligible influence on the isotopic composition of the coals cross correlations between 13c of the coals soluble organic matter yield and the proportions of liptinite macerals of higher plant origin imply that the carbon isotopic composition may be affected by the contents of plant lipids because of their 13c values ranging from 5 to 10 less than whole plant tissue values an isotopic shift of the coals towards more negative values due to the activity of prokaryotes i e anaerobic bacteria in organic matter degradation is proposed the results obtained from the early miocene oberdorf lignite indicate that the carbon isotope ratios of the coals are primarily affected by varying contributions of different parts of whole plant tissue due to their different isotopic and molecular compositions e g epicuticular leaf waxes resins wood and their different decay resistance against the early diagenetic changes involved in organic matter decomposition carbon cycling during anoxic decomposition of plant derived organic matter is assumed to affect the 13c values of coal 13c values of wood and extracted cellulose are affected only to a minor extent

statistical model for source rock maturity and organic richness using well log data bakken formation williston basin united states geologic notes a study of the bakken formation the proposed source rock for much of the hydrocarbons generated in the williston basin was done using bulk density neutron porosity and resistivity logs and formation temperatures principal components cluster and discriminant analyses indicate that the present day distribution of organic matter controls much of the variability in the log values present day total organic carbon values are high in the central part of the basin near northeastern montana and along the east edge of the basin and low in the area of the nesson anticline and along the southwest edge of the basin using a regression of density on temperature and the analysis of residuals from this regression hydrocarbon maturity effects were partially separated from depos tional effects these analyses suggest that original concentrations of organic matter were low near the limits of the bakken and increased to a high in northeastern montana the pre maturation distribution of total organic carbon and the present day total organic carbon distribution as determined by statistical analyses of well log data agree with the results of geochemical analyses the distributions can be explained by a relatively simple depositional pattern and thermal history for the bakken

petrographic composition and depositional environments of the pliocene velenje lignite seam slovenia abstract a pliocene lignite seam up to 160 m thick occurs in the velenje depression in northern slovenia it forms part of a non marine transgressive sequence petrographic data together with ash and sulphur content of samples from two boreholes one located in the central and the other in the marginal part of the seam have been used to study vertical and lateral coal facies variations in the central part the lignite seam overlies fluvial sediments facies critical macerals and petrographic indices suggest that the lower ash rich part of the seam unit i accumulated in a wet forest swamp in an alluvial plain setting later this environment was replaced by a dry telmatic forest swamp unit iia according to our interpretation a decrease in tree density in units iib and iic reflects a change to a bush moor the transition from unit ii to unit iii is characterized by a rapid water table rise which resulted in the establishment of a wet limnotelmatic forest swamp within unit iii the tree density decreases and the degree of gelification increases towards the top of the seam suggesting a transition to a fen type environment another rapid water table rise ended peat formation in the eutrophic topogenous mire and established open lacustrine conditions a calcium rich environment resulted in high ph values and is responsible for high sulphur lignites up to 4 on a dry basis in the upper part of the seam the ph values were controlled by the amount of the inflowing lacustrine water only thin ash rich topotelmites accumulated along the northern margin of the mire there the seam originated in a wet forest swamp and was separated by limnic and fluvial sediments from other organic rich horizons due to its closer vicinity to the pre tertiary carbonates the depositional environment was probably even more alkaline therefore the lignite shows a higher degree of gelification and is even more sulphur rich up to 5 5 on a dry basis

petrographical and organic geochemical investigation of the oberpfalz brown coal deposit west germany abstract a detailed macro and micropetrographical investigation coupled with gc and gc ms analysis of the alkane fraction of tertiary brown coal samples from the oberpfalz region of bavaria west germany was undertaken distinctive petrographical and organic geochemical facies differences were evident in the coal seams investigated which came from two neighbouring open cast mines the lower seam was of a limnic nature while the upper seam in the neighbouring mine showed the more typical characteristics of terrestrial depositon both seams were generally characterized by high ash contents and extract yields microlayering and framboidal pyrite the predominance of texto ulminite a combined with relatively high resinite contents suggested that gymnosperms were the main peat forming plants additionally the coal extracts were characterized by the presence of the diterpane phyllocladane which made up to 60 of the alkane fraction in some samples bacterial activity in the coal swamp was marked by the presence of hopanes mainly 17a h 21 h homohopane and biodegradation of the n alkanes