geochemistry and petrology of palaeocene coals from spitsbergen part 1 oil potential and depositional environment abundant oil prone coal type iii kerogen deposits are preserved within the high latitude middle palaeocene todalen member of the central tertiary basin spitsbergen island norwegian arctic the coals svea longyear svarteper and askeladden seams have been subjected to only minor previous geochemical characterisation focussing upon the longyear seam this paper characterises the present prospective and economic oil potential of the svalbard coals organic biomarker parameters fe s chemistry and coal maceral analysis are then applied to understand the provenance and environmental origins of this unusual source rock the upper todalen mbr coals longyear svarteper and askeladden seams have significantly more oil potential than the lower svea seams with estimated retortion yields of 170 190 kg tonne vs 24 kg tonne respectively the longyear seam exhibits relatively high hi values ca 300 400 mg g toc consistent with a hydrogen rich mixed type ii iii kerogen source greatest oil potential is shown to be favoured by formation within a fen environment with high bacterial degradation 100 g g toc hopanes marine influence 0 5 wt sulfur fe s 0 9 and the unique temperate high latitude palaeocene climate of svalbard leading to preservation of hydrogen rich organic matter via organo sulfur bond formation

organic geochemical proxies of paleoceanographic paleolimnologic and paleoclimatic processes abstract organic matter constitutes a minor fraction of marine and freshwater sediments yet its important contribution to the sedimentary record can be used to reconstruct marine and continental paleoenvironments the organic matter content of sediments is the residue of past biota the amounts and types of organic matter present in sediments consequently reflect environmental conditions that impacted ecosystems at different past times general sources of the organic matter are inferred from bulk properties such as elemental compositions carbon and nitrogen stable isotope ratios rock eval pyrolysis data and organic petrography details of organic matter origins are refined by analyses of biomarker molecular compositions source changes are proxies for fluctuations in sea level oceanic surface currents and continental climates algal paleoproductivity rates are indicated by organic carbon mass accumulation rates and carbon and nitrogen stable isotopic compositions these parameters record past availability of nutrients and therefore are proxies of surface mixing in the oceans and amount of land runoff to lakes sea surface paleotemperatures are recorded by the number of carbon carbon double bonds in lipid biomarkers produced by marine algae larger proportions of the double bonds are proxies for the cooler surface waters that accompanied periods of global glaciation and intervals of enhanced upwelling the 13c and d values of plant organic matter record past concentrations of carbon dioxide in the atmosphere and changes in delivery of atmospheric moisture respectively diagenesis which causes the concentration and composition of organic matter in sedimentary settings to differ from those of the original biologically synthesized materials can bias organic geochemical paleoenvironmental records the magnitude of this potential source of misinformation must always be considered and evaluated comparison of multiple organic geochemical proxies of past conditions helps to compensate for the effects of diagenetic alterations and thereby to improve interpretations of paleoenvironmental change

geoelectric mapping of near surface karstic fractures by using null arrays the term null array is introduced for those electrode configurations where the measured potential difference is zero above a homogeneous half space when using a measuring dipole m0n0 different types of null arrays three electrode schlumberger and dipole axial equatorial null arrays and their corresponding traditional arrays are studied it was shown in a field study carried out in a karstified limestone area covered by thin sediments that it is possible to obtain geologically meaningful results with null array techniques the main features of the null array data are as follows 1 null array data appear to be more spatially variable than the classical data the spatial variability provides information about the presence of karstic fractures in the subsurface 2 the null array anomalies caused by nearly vertical karstic fractures in the limestone basement do not decay with depth as quickly as the classical array anomalies 3 the strike direction of the fractures is much less ambiguous than that

petrological and geochemical composition of lignite from the d field kolubara basin serbia abstract the upper miocene lignite from the main coal seam in the d field kolubara basin is a typical humic coal with huminite liptinite and inertinite concentrations of up to 83 7 vol 17 2 vol and 15 5 vol respectively in the huminite group textinite and ulminite are the most abundant macerals with variable amounts of densinite and attrinite liptodetrinite and sporinite are the most common macerals of the liptinite group while inertodetrinite is the most abundant maceral of the inertinite group the mineral matter consists mostly of clay minerals the main sources of organic matter were gymnosperms conifers and microbial biomass followed by angiosperms based on composition of saturated and aromatic diterpenoids it has been established that coal forming plants belonged to the gymnosperm families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae peatification occurred in neutral to slightly acidic fresh water environment composition and distribution of biomarkers show that diagenetic changes of the organic matter were mainly governed by bacterial activity in a suboxic to oxic environment based on distribution of aromatic diterpenoids a novel diagenetic pathway for transformation of abietane type precursors under suboxic to oxic conditions is proposed variations in compositions of macerals and biomarkers are in concordance with pronounced seasonality during pontian which caused changes in the water level redox conditions during peatification and to some extent vegetation differences in the paleo plant communities

biomarkers of oligocene lacustrine source rocks beibuwan song hong basin junction offshore northern vietnam abstract highly oil prone source rocks containing sapropelic type i and mixed types i and iii kerogen are found in 233 m of the 500 m deep fully cored enreca 3 well drilled on bach long vi island located at the junction between the beibuwan and the song hong basins offshore northern vietnam the cored succession is made up entirely by oligocene deep lacustrine deposits the origin of the organic matter om in 62 samples is evaluated on the basis of gas chromatography mass spectrometry gc ms and gc ms ms om in 55 samples is sourced primarily from lacustrine organisms and contains abundant 4 methylsteranes tetracyclic polyprenoids tpp and lycopane and no markers for marine organic matter the proportion of triterpanes derived from angiosperms is low in most saturated fractions and only traces of gymnosperm diterpanes are detected in contrast all aromatic fractions have a high proportion of compounds having an origin from both gymnosperms and angiosperms very high concentrations of hopanoids in both fractions suggest significant bacterial alteration of the original om most samples have a high concentration of rare c31 diaromatic 8 14 secohopanes with a fluorene moiety low pristane phytane pr ph ratios indicate that anoxic suboxic bottom water conditions existed during om accumulation the presence of carotane gammacerane and traces of arylisoprenoids could indicate a stratified water column om in a few samples with lower than average hydrogen index hi is mainly of terrestrial origin with a higher proportion of c29 steranes diterpanes and oleanoids and lower concentrations of both saturated and aromatic hopanes higher pr ph a higher c34 isohopane ratio ihr34 and a lower homohopane index hhi indicate that this low hi om was originally deposited under more oxic conditions and subsequently transported to deeper water low sterane and hopane isomerization ratios show that no samples have reached the oil window some novel maturity parameters for immature lacustrine samples are proposed

triterpanes and ring a degraded triterpanes as biomarkers characteristic of tertiary oils derived from predominantly higher plant sources abstract a number of oils previously proposed to be derived from terrigenous source materials have been obtained from the taranaki basin new zealand niger delta beaufort mackenzie region taiwan and indonesia and their c24 tetracyclic and c30 pentacyclic terpenoid distributions examined by gc ms and gc ms ms the c24 tetracyclic terpanes are thought to be derived from their corresponding c30 hopane oleanane ursane and lupane counterparts as previously reported a mixture of at least nine c30 pentacyclic terpanes are found to be present with remarkably uniform distributions in oils from these widely separated provinces whilst definitive structures have not been proposed for these compounds information has been obtained as to whether these pentacyclic terpanes are all six membered rings or contain one or two five membered rings the presence of this mixture of tetracyclic and pentacyclic terpanes provides a good indicator for oils derived from terrigenous source materials and in the case of these basins of tertiary age

changes in bulk properties and molecular compositions within new zealand coal band solvent extracts from early diagenetic to catagenetic maturity levels abstract the bulk properties and bitumen molecular compositions of a rank series of 38 humic coals from the new zealand coal band cretaceous cenozoic have been analysed to investigate early maturation processes affecting coaly organic matter through diagenesis to moderate catagenesis rank s r 0 0 11 8 r o 0 23 0 81 the samples comprise a relatively restricted range of vitrinite rich coal types formed largely from higher land plant material under relatively oxic conditions but with a significant contribution from microbial biomass with increasing rank total organic carbon contents show a general increase whereas moisture and asphaltene contents decrease bitumen yields also decrease through the stages of diagenesis and early catagenesis rank s r r o r 5 6 r o 0 40 as indicated by the constant occurrence and gradual increase of isoprenoids e g pristane and phytane and hopanoids in their more mature configuration this early phase of catagenesis not previously recognised in new zealand coals is followed at rank s r 9 r o 0 55 by the main catagenesis phase characterised by a more rapid increase in the generation of hydrocarbons including total n alkanes isoprenoids and hopanes changes in the maturity of new zealand coals can be traced by the carbon preference index and several hopane maturity parameters including 22 s 22 s 22 r and

carbon dioxide generation from coals in taranaki basin new zealand implications for petroleum migration in southeast asian tertiary basins elevated co2 levels in gas accumulations within the onshore area of the taranaki basin can be quantitatively accounted for by decarboxylation of vitrinite rich tertiary coals over the lignite to early high volatile bituminous coal rank range the highest levels are found within sandstone reservoirs vertically adjacent to eocene coal seams that have realized approximately 50 of their co2 generative potential the gas exists as a supercritical fluid under reservoir conditions and appears to be generated in significant amounts comparable to liquid hydrocarbons co2 may aid oil expulsion from coals directly when intense co2 generation coincides with major oil generation or indirectly by creating pressure induced microfractures du ing the relatively rapid generation of large amounts of co2 prior to the main phase of oil generation for these effects to be realized the rate of co2 production relative to removal is considered critical and favorable conditions are probably restricted to basins that have experienced relatively rapid heating in this respect the taranaki basin provides a model for co2 evolution in many southeast asian tertiary basins

diagenetic trends of a tertiary low rank coal series abstract the mahakam delta kalimantan indonesia coals represent all the evolution stages between freshly deposited plant peat material lignites and bituminous coals the geochemical techniques used to study this coal series included elemental analysis extraction of humic compounds infrared spectroscopy and 13 c nuclear magnetic resonance of the total coal the main mechanisms of early maturation in this series are loss of oxygenated compounds aromatisation and condensation of the organic matter these changes which have already been suggested for other coal series and partially reported for sedimentary organic matter were confirmed and described in more detail for the mahakam coal series

pyrolytic assessment of oil generation and expulsion from a suite of vitrinite rich new zealand coals abstract pyrolysis gas chromatography py gc of tara 1 coals great south basin new zealand suggests a mean paraffinic oil potential of 85 kg t c range 70 130 kg t c based on n alkane alkene generation in the c6 c31 range and typical proportions of these compounds in related oils from new zealand this maximum in the depth trend of pyrolysate yield is reached at 0 75 0 80 r0 comparable to the previously reported maximum in hydrogen index hi thermal extraction gc te gc provided higher yields than rock eval s1pyrolysis but without the uniform trend exhibited by s1 c below the 3 0 km below sea floor 0 75 0 80 r0 onset of expulsion in addition the saturates aromatics ratio in the thermal extract decreased with depth indicating preferential retention of aromatics which may affect the expulsion efficiency of paraffins thermal extracts suggest that at most 15 kg t c of paraffinic oil is retained within the tara coals which is lower than previous estimates of saturation threshold however it is likely to be adversely affected lowered by loss of the least volatile components during recovery and storage of cuttings and incomplete recovery of high molecular weight components particularly c40 paraffins using te gc isopimarane generation appears to be restricted to the depth zone corresponding to the early oil window although it is unclear whether this is directly related to the maturity range required for such generation or that only the latest cretaceous coals in tara 1 exhibit particularly high abundances of such gymnosperm derived diterpanes

a reappraisal of kerogen formation abstract comparative microscopical and chemical studies of recognizable entities in kerogen and their extant counterparts suggest a new and simple mechanism of kerogen formation which clarifies the interrelationships between extant biomass kerogen and fossil fuels

potential source rocks organic geochemistry and thermal maturation in the southern depocenter kipourio grevena of the mesohellenic basin central greece abstract the study area is the southern depocenter depth 4200 m of the mesohellenic basin which extends between kipourio and grevena central greece the mesohellenic basin is a middle tertiary intramontane basin developed within the hellenide orogen previous studies have focused on the depositional environments configuration and hydrocarbon potential of the basin in this paper we present additional geochemical and petrographic data from outcrop samples of the basin s southern depocenter which is considered the most promising area in terms of hydrocarbon prospectivity a total number of thirty six samples were analysed rock eval pyrolysis maceral analysis vitrinite reflectance and thermal alteration index bitumens extraction liquid chromatography and gc ms the samples were collected from deltaic deposits and submarine fan sediments of late eocene to late oligocene age the toc values of the analysed samples range between rich and very rich and the organic matter consists mainly of type iii kerogen and the organic matter consider to be predominately gas prone the thermal maturity assessed from tmax and vitrinite reflectance shows an immature stage of the organic matter along with the presence of layers having reached the very early mature stage vitrinite reflectance measurements and maturity calculations applying the lopatin modeling reveal that the lower part of the depocenter sediments falls within the oil window the extractable organic matter eom mg bitumens g toc indicate the existence of samples from deltaic deposits with high ratio of transformation eom 100 mg bitumen g toc the gc and gc ms analyses of the biomarkers indicate mainly the occurrence of terrestrial organic matter reflecting oxidizing conditions and both immature and very early mature stages the results of the rock eval pyrolysis and the distribution of the isoprenoids support the assumption of the input of an organic matter mixture

petrographical and organic geochemical study of the kovin lignite deposit serbia abstract the origin of the organic matter om and the characteristics of the depositional environment of lignites from the upper miocene kovin deposit hosting three coal seams of serbia were evaluated based on petrographic data bulk organic geochemical parameters biomarker analysis and stable isotope geochemistry 13c of individual biomarkers samples were collected from four boreholes gd 601 and gd 603 the a field and kb 79 and kb 91 the b field representing different parts of coal seams i ii and iii investigated lignites are typical humic coals the om of lignites is derived from woody vegetation and herbaceous peat forming plants with prevalence of the former in most samples peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by a low amount of angiosperms lignite forming plants mostly belonged to the gymnosperm families cupressaceae taxodiaceae phyllocladaceae and pinaceae slight input of ferns fungi and aquatic macrophyta to lignite om is also evident distributions of hopanoids and isotopic compositions of these biomarkers reflect the activity of various microbial populations represented by methanotrophic chemoautotrophic and heterotrophic bacteria during diagenesis prominent c28 28 30 bisnorneohop 13 18 ene was observed for the first time in the lignite extracts according to the 13c value it was probably derived from chemoautotrophic bacteria c28 28 30 bisnorneohop 13 18 ene could be one of the possible precursors of a series of orphan aromatic hopanoids bearing an ethyl group at c 21 via progressive aromatization peatification proceeded in a fresh water environment under variable redox conditions from anoxic to slightly oxic all three coal seams are heterogeneous the lower parts of the coal seams represent a topogenous fresh water peat mire with open water areas which was subjected to inundations the upper parts of coal seams represent a wet forest swamp with relatively stable conditions despite the observed variations in all three coal seams the mean values of petrographic and organic geochemical parameters suggest general increasing of wetness and establishment of more stable conditions from seam iii to seam i maceral and biomarker data indicate that rapid flooding of the bogs stopped peat growth in all three coal seams relatively frequent variations in all three coal seams followed by repetition of lignite characteristics depict well the pronounced seasonality e g short term cycles of the climate during late miocene in investigated area

exceptional preservation of hopanoid and steroid biomarkers in ediacaran sedimentary rocks of the east european craton abstract thermally unstable hopanes with a biological 17 21 h configuration hopanes hopenes hopanoic acids and hopanols were identified as important constituents of ediacaran to cambrian sedimentary rocks of the east european craton relatively high abundances of hopanes in relation to hopanes were identified in the petersburg area and eastern belarus while in volyn samples these compounds were found in traces in addition polar hopanoids including hopanols and hopanoic acids were found in most of the petersburg and some belarus and volyn sedimentary rocks the estimated equivalent of vitrinite reflectance for samples of lower maturity measured based on c31 s r ratio is in the range 0 28 0 49 rr while for those of higher thermal maturity this parameter corresponds to 0 41 0 57 rr the values of the c31 22s s r ratio are in agreement with above data and are in the range of 0 1 0 3 for the belarus and petersburg samples of 0 3 0 4 for volyn and of 0 4 0 5 for lithuania where hopanes and hopanols were not detected or are present as traces moreover there is good correlation r2 0 8 between c31 s r and c31ene h ene ratio values defined as ratio of c31 hopenes to hopanes which proves that less stable hopanes and hopenes are enriched in the same immature sedimentary rocks the remarkable occurrence of a significant portion of sedimentary hopanes retaining the biological stereochemical configuration confirms that exceptionally immature precambrian rocks can be found in some instances when these strata have undergone only a mild burial temperature history

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

guidelines for assessing the petroleum potential of coaly source rocks using rock eval pyrolysis abstract coaly source rocks are sufficiently different from marine and lacustrine source rocks in their organic matter characteristics to warrant separate guidelines for their assessment using rock eval pyrolysis the rank threshold for oil generation is indicated by the increase in bi s1 toc at rank sr 9 10 tmax 420 430 c ro 0 55 0 6 and the threshold for oil expulsion is indicated by the peak in qi s1 s2 toc at rank sr 11 12 5 tmax 430 440 c ro 0 65 0 85 the pronounced rank related increase in hi s2 toc prior to oil expulsion renders the use of immature samples inappropriate for source rock characterisation a more realistic indication of the petroleum generative potential and oil expulsion efficiency of coaly source rocks can be gained from samples near the onset of expulsion alternatively effective hi values i e his near the onset of expulsion can be estimated by translating the measured his of immature samples along the maturation pathway defined by the new zealand or other defined coal band coaly source rocks comprise a continuum of coaly lithologies including coals shaly coals and coaly mudstones determination of the total genetic potential of coaly source rock sequences is best made using lithology based samples near the onset of expulsion

influence of floral assemblage facies and diagenesis on petrography and organic geochemistry of the eocene bourgas coal and the miocene maritza east lignite bulgaria abstract numerous differences in the petrography and organic geochemistry of two tertiary low rank coal deposits of bulgaria formed within comparable depositional environments are outlined different floral assemblages are indicated as the main sources of organic matter for the eocene bourgas sub bituminous coals a warm climate plant community dominated by angiosperms is reflected in the biomarker composition whereas a coniferous flora was the main source of the resinous organic matter of the miocene maritza east lignite the results are in agreement with palaeobotanical data these differences in the peat forming vegetation of the paleogene compared to the neogene of bulgaria are attributed to decreasing temperature during the tertiary the abundance of resinous compounds relative to lipids from plant waxes long chain n alkanes as well as the preservation of plant tissue are mainly controlled by gymnosperm angiosperm ratios pristane phytane and diasterenes sterenes ratios reflect variations in redox conditions and the ph of the depositional environments caused by eustatic sea level changes freshwater inflow or varying ground water table changing eh and ph values are associated with differences in microbial activity controlling the extent of gelification of plant tissue bacteria most probably contributed to the aromatisation of triterpenoids in the mire enhanced thermal maturation of organic matter during diagenesis is reflected in higher contents of n alkanes and the presence of alkyl naphthalenes in the bourgas coals alkyl naphthalenes are thought to have been formed from pentacyclic triterpenoids rather than from resinous compounds

use of lipid biomarker patterns as a proxy of environmental variability in the coastal sedimentary record from the gulf of cadiz sw spain use of lipid biomarker patterns as proxies of environmental variability in coastal sedimentary record from the gulf of cadiz sw spain

the stable carbon isotopic composition of oil from the taranaki basin of new zealand abstract the average stable carbon isotope ratio of 21 oils from the taranaki basin of new zealand suggests that the source rocks date from the cretaceous period when sedimentation in this basin began stable carbon isotope ratios also confirm the grouping of these oils into the genetic families which were previously suggested by the correlation of source related biomarkers stahl isotope type curves for the oils also reflect the correctness of these relationships a plot of the saturate versus aromatic 13c values for the new zealand oils is particularly valuable for oil correlation in this basin and clearly demonstrates that the ahuroa and stratford oils while separated from the mckee field by some 30 km probably originate from the same oil source formation as do the oils of the mckee field the plot also indicates that the kaimiro mangahewa pukearuhe and waihapa oils are discrete in situ accumulations of petroleum which do not have the characteristics of oils from adjacent fields these conclusions are further supported by the values of the sofer canonical variable for all of the oils additionally the sofer plot provides clear evidence of the predominantly terrigenous origin of the oils in the taranaki basin consideration of the data for these oils leads to a hypothesis that three independent sources of organic material microbes gymnosperms and angiosperms gave rise to the oils in this region

prediction of the location of future rupture surfaces of a slowly moving loess landslide by electrical resistivity tomography a slowly moving loess landslide along the river danube in south hungary was studied using electrical resistivity tomography our aim was to determine the fracture system of the study site due to the homogeneous composition of the loess it seems to be the only possibility to get information about the landslide and its further evolution the applicability of the electrical resistivity tomography technique for such a supposedly dense fracture system was studied by numerical modelling and the results have been verified in the field the dip of the fractures could not always been observed and they could not be explored deeply however it was possible to map their surface projection to get the desired information about the structure of the landslide fracture zones could have been especially well localized enabling the prediction of the positions of future rupture surfaces and thus the delineation of the endangered zone although the area outside of the already subsided one is not endangered yet the area which has already started to move is going to break into two parts of the about 5 m wide blocks at the front of the landslide may fall or slide down anytime a large area was assumed to move as one unit most of our predictions have been verified by the mass movements that occurred about one and half years after the measurements the electrical resistivity tomography method proved to be a good tool to characterize the fracture system of such a landslide area enabling the prediction of future rupture surfaces and also delineation of the endangered area its use is therefore highly recommended to monitor landslides to provide early risk warnings to avoid damage to constructions or endangering human life

source rock potential of lignite and interbedded coaly shale of the ogwashi asaba formation anambra basin as determined by sequential hydrous pyrolysis abstract outcrops in the anambra basin in southern nigeria contain paleogene imo shale marine the neogene paralic ogwashi asaba and the continental benin formations representing equivalents of the subsurface successions in the niger delta basin thirty three samples of lignite and the interbedded coaly shale of the ogwashi asaba formation were investigated petrologically before rock eval screening two selected samples of lignite and coaly shale were subjected to sequential hydrous pyrolysis hp at 330 c for 72 h and at 355 c for 72 h to characterize their oil and gas potential the lignite sample has a rock eval hydrogen index hi of 481 mg g toc and a mean vitrinite reflectance of 0 36 rom the total amount of expelled oil generated in the sequential hp experiments is 259 mg g of original total organic carbon tocorig this expelled waxy oil has abundant high molecular weight n alkanes and an extremely high pristane phytane ratio of 6 5 typical of crude oils generated from coals as observed in some onshore and shallow offshore accumulations of the niger delta the overlying coaly shale has a lower hi of only 191 mg g toc the total amount of expelled oil generated in the sequential hp experiments is only 15 mg g tocorig this oil is not waxy and has a pristane phytane of 2 6 which is more typical of a marine source rock these results are contrary to the idea that coaly shale associated with coal is the main source of oil the greater yields of expelled oil from the coal relative to the coaly shale are attributed to the higher liptinite content in the former and the possibility that the organic matter in the latter was oxidized prior to deposition 13c of the methane generated at 355 c for 72 h is 39 5 for the lignite and 35 0 for the coaly shale this suggests different methane precursors in these two lithologies the data set reveals remarkable differences in the characteristics of the two types of source rocks in the ogwashi asaba formation and their potential to contribute a mixture of hydrocarbons derived from intervals that are stratigraphically only meters apart these results suggest that coal and coaly shale within the thermally mature stratigraphic levels of the agbada formation in the sub surface are potential source rocks for liquids and gaseous hydrocarbons in the niger delta

artificial maturation of an immature sulfur and organic matter rich limestone from the ghareb formation jordan abstract an immature r o 0 39 s rich s org c 0 07 organic matter rich 19 6 wt toc limestone from the ghareb formation upper cretaceous in jordan was artificially matured by hydrous pyrolysis 200 220 300 c 72 h to study the effect of progressive diagenesis and early catagenesis on the amounts and distributions of hydrocarbons organic sulfur compounds and s rich geomacromolecules the use of internal standards allowed the determination of absolute amounts with increasing thermal maturation large amounts of alkanes and alkylthiophenes with predominantly linear carbon skeletons are generated from the kerogen the alkylthiophene isomer distributions do not change significantly with increasing thermal maturation indicating the applicability of alkylthiophenes as biomarkers at relatively high levels of thermal maturity for a given carbon skeleton the saturated hydrocarbon alkylthiophenes and alkylbenzo b thiophenes are stable forms at relatively high temperatures whereas the alkylsulfides are not stable the large amount of alkylthiophenes produced relative to the alkanes may be explained by the large number of monosulfide links per carbon skeleton these results are in good agreement with those obtained previously for an artificial maturation series of an immature s rich sample from the gessoso solfifera formation

tracing the origin of thermogenic hydrocarbon signals in pockmarks from the southwestern barents sea abstract the glacially influenced southwestern barents sea is a promising area for petroleum exploration the present study area which is located in the loppa high region exhibits extensive pockmark fields covering an area of several square kilometers and containing thousands of pockmarks in high density to investigate whether the pockmark formation was driven by petroleum leakage to the surface acting thus as indicators for an active petroleum system gravity cores from selected pockmark and reference sites were investigated using an organic geochemical approach various biomarkers indicative of thermogenic hydrocarbons such as short chain n alkanes with a low carbon preference index alkylcyclohexanes hopanes steranes and diasteranes mixed with biomarkers representing immature organic matter were detected in the pockmark but also in reference cores outside of the pockmark and even from a non pockmark area the abundance and level of thermal maturity of the thermogenic hydrocarbons are comparable between the pockmark and reference sites additionally their distribution with depth is quite similar to those of the immature biomarkers these observations support the conclusion that the thermogenic hydrocarbon signal in the pockmarks is the result of reworked eroded mature material mixed with immature organic matter distributed across the entire area rather than the result of seepage events of thermogenic hydrocarbons through the pockmark system the data show that in the loppa high region the pure presence of petroleum derived hydrocarbons in pockmark areas cannot be used to indicate the presence or leakage of deeper petroleum systems

main oil generating macerals for coal derived oil a case study from the jurassic coal bearing turpan basin nw china abstract this paper examines the geochemical characteristics of pyrolysates from macerals such as the alginite sporinite cutinite collotelinite and collodetrinite isolated from jurassic coals and investigates their relative contributions to oil potential in respect to the jurassic coal measures in the turpan and other basins of northwest china the alginite pyrolysate has the lightest carbon isotopic composition followed by the sporinite and cutinite while the collotelinite and collodetrinite pyrolysates show comparatively heavy carbon isotopic compositions pyrolysates from the alginite sporinite and cutinite demonstrate much lower pr ph ratios than those from the collotelinite and collodetrinite regarding the distributions of regular biomarkers such as steranes and hopanes the alginite pyrolysate is comparatively rich in c 27 steranes followed by pyrolysates from the sporinite and cutinite whereas pyrolysates from the collotelinite and collodetrinite contain little or undetectable c 27 steranes furthermore the pyrolysates from different kinds of macerals have remarkably different gammacerane concentrations the gammacerane concentrations in pyrolysates from the alginite and cutinite are higher than that from the sporinite though these macerals were separated from the same coal whereas the collotelinite and collodetrinite pyrolysates have almost no gammacerane the experimental results suggest that liptinite content in one given coal e g alginite sporinite and cutinite controls the biomarker distributions in the coal derived oils mass balance calculations of carbon isotopic compositions from the maceral pyrolysates show that the carbon isotopic composition of liquid hydrocarbons generated by organic matter in mudstone is very similar to that of most of the oils in the jurassic coal bearing basins of northwest china while liquids from coal are much heavier than that of the oils this indicates that the mudstone is likely to be the major source rocks of the oils and coals likely to be the subordinate source rocks mass balance calculation based on the maceral contents and hydrocarbon generative potential suggests that liptinites in mudstone in the jurassic coal measures of the turpan basin generate about 70 of oils while the vitrinites produce about 30 of the oils therefore the hydrogen rich liptinites alginite sporinite and cutinite are the main oil generating macerals while vitrinites collotelinite and collodetrinite are secondary oil generating macerals in the jurassic coal bearing turpan basin and other jurassic basins of northwest china

evidence of electrical anisotropy in limestone formations using the rmt technique azimuthal resistivity surveys are often applied to complement hydrological information or to improve the location of observation boreholes in pump tests symmetric electrode configurations cannot distinguish anisotropy from lateral changes or dipping layers but asymmetric arrays e g the offset wenner array can tensor radiomagnetotellurics rmt is presented as an alternative method in studies of electrical anisotropy in the shallow subsurface the electromagnetic and geomagnetic transfer functions provide information about the dimensionality of the data these transfer functions can also be used to find the directions of anisotropy data with an anisotropic signature can be inverted for a one dimensional 1d azimuthal anisotropy model the method is faster than the azimuthal resistivity method a 380 m long profile of tensor rmt data 12 7 243 khz from limestones that overlie shale on the island of gotland sweden is used to show the merits of the method the data have a clear anisotropic signatur

chemostratigraphy of the posidonia black shale sw germany i influence of sea level variation on organic facies evolution abstract during the toarcian widespread deposition of organic rich mudrocks black shales occurred across europe linked to a 3rd order sea level rise we provide a high resolution multi proxy chemostratigraphic study of the dotternhausen sections in sw germany embedded in a stratigraphic and palecological framework chemostratigraphy and paleoenvironmental reconstruction is based on rock eval and elemental analysis of bulk organic matter and biomarker analysis of aliphatic hydrocarbon fractions aliphatic biomarker ratios applied to reconstruct the facies development include pristane phytane and pristane phytane n c 17 n c 18 ratios carbon preference index c 27 c 29 sterane and hopane sterane distribution results show that sea level change exerted the major control on the composition of primary produced organic matter and on its redox controlled preservation changes in primary production and in the ratio of terrestrially versus marine derived organic matter take place drastically at the onset of black shale deposition the relative proportion of terrestrial versus marine biomass accumulation is independently assessed by highly correlative bulk organic matter properties hi values and biomarker ratios cpi the terrestrially derived end member yields hi values of 50 100 mg hc toc and cpi values of 1 4 2 0 whereas the marine end member has hi values of 600 700 mg hc toc and cpi values of 0 95 1 05 correspondingly the shift in plant versus bacteria derived biomass is discriminated by hi values and hopane sterane ratios data were grouped according to their position in the lowstand lst lower and upper transgressive tst highstand systems tract hst and maximum flooding surface mfz of the sequence stratigraphic framework occurrence of organic matter with a significant bacterial contribution is restricted to the lst and lowermost tst and shows hopane sterane ratios of 0 25 0 5 marine phytoplanktonic matter dominates the upper tst hst and mfz with organic matter giving hopane sterane ratios between 0 5 and 1 7 samples from the hst yield hi values between 450 and 500 mg hc toc which is consistently lower by 150 mg hc toc when compared to the tst the lower quality of the organic matter deposited in the hst is due to its longer settling times through a thicker oxygenated water column a strong correlation with relative sea level stand and the c 27 c 29 sterane ratio is observed lst exhibits c 27 c 29 sterane ratios of 0 7 during transgression values increase to 1 0 reaching a maximum at 1 4 during sea level highstand thus reflecting decreasing terrigenous input and shifts in near shore versus open marine algal communities episodic fluctuation of anoxia is discussed on the basis of a monsoonal climate model which infers significant surface run off during summer monsoon providing high nutrient supply and associated high primary productivity in combination with a density stratified water column excellent preservation conditions for organic matter were established dry winter conditions with inversion of the surface water flow regime led to seasonal export of bottom waters and episodic establishment of dysoxic conditions variations in the extent of annual flushing of sub basins on the toarcian shelf controlled long term organic matter accumulation rate paleoclimate variability and its connection with sea level stand is thus of paramount importance for different modes of organic matter accumulation and redox system stability

bitumen molecular maturity parameters in the ikpikpuk well alaskan north slope abstract several bitumen molecular maturity parameters alkylnaphthalene ratios mnr enr dnr methylphenanthrene indices mpi 1 mpi 2 dpi n c 17 pristane pristane phytane c 15 alkane distributions and gc ms analyses of triterpanes steranes diasteranes triaromatic steroids and monoaromatic steroids for samples of the ikpikpuk well alaskan north slope are reported the molecular maturity parameters are compared and contrasted with previous data for lower molecular weight c 1 c 7 hydrocarbons production index vitrinite reflectance and thermal alteration index bitumen maturation indices c 15 alkane distributions and distributions of steranes diasteranes triterpanes triaromatic and monoaromatic steroids agree with kerogen maturation indices in the kingak section of ikpikpuk well bitumen maturation indices and distributions of steranes diasteranes triterpanes triaromatic and monoaromatic steroids diverge from vitrinite maturation profiles for the shublik section of ikpikpuk indicating either a major influence of changes in kerogen type or the presence of residues of expulsion migration in the shublik the data are consistent with the shublik being a source and or conduit of migration of oil

hopane derived triterpenoids in soils the occurrence distribution and degradation pathways of hopanoid triterpenes have been studied in thirteen soil samples with varying degrees of biological activity hopanoids were shown to occur in all samples suggesting that they are not only ubiquitous in subaquatic sediments but also in soils hop 22 29 ene was generally predominant in the hydrocarbons whereas the 17 h 21 h bishomohopanoic acid c32 was the major component in the acids the concentrations of hopanes were usually rather low except in acidic peat the distribution in carbon number of hopanes and hopanoic acids showed great similarities with those of moderately oxic subaquatic sediments intact bacteriohopane tetrol widespread in microorganisms and the main precursor of geohopanoids was identified in substantial amounts in a peat exposed to groundwater oscillations

palaeoenvironmental implications of coal formation in dobrudzha basin bulgaria insights from organic petrological and geochemical properties abstract the dobrudzha basin in northeast bulgaria contains 86 coal seams distributed within three coal bearing formations of late carboniferous age this study presents the organic petrological and geochemical characteristics of coals from the makedonka and krupen formations containing some of the most prominent coal seams these were characterized by means of proximate and rock eval analyses vitrinite reflectance measurements organic petrography and gcms analysis in order to establish variations in vegetation and depositional settings based on random vitrinite reflectance avg 0 7 r r and toc contents avg 80 daf the coals can be classified as low rank bituminous high volatile b c low tmax values avg 430 c further indicate a low degree of organic matter maturity the low to moderately high ash yields together with the presence of shaly partings and generally low sulfur contents are consistent with peat formation in a fluviatile sedimentary environment petrographic analysis reveals complex maceral composition with abundant liptinite and inertinite the predominance of detrovitrinite and the almost complete lack of strongly gelified macerals argue for enhanced humification of the plant tissues and peat formation in relatively dry environments above water table the distributions of n alkanes diterpenoids and steranes indicate that the organic matter originated from terrestrial vascular plants the high pristane phytane ratios point to peat deposition under oxic conditions low concentrations of hopanes argue for limited bacterial degradation of the organic matter possibly due to low ph conditions during peatification the presence of tetracyclic diterpanes and their aromatic counterparts is attributed to pre gymnosperm cordaitean input the existence of cordaiteans although as minor component of the palaeovegetational communities is further evidenced by the presence of trace amounts of aromatic arborane fernane derivatives in almost all studied samples the occurrence of combustion derived pahs in all studied samples is consistent with the abundant inertinite and indicates frequent forest fires during peat formation

isometamorphic variations in the reflectance and fluorescence of vitrinite a key to depositional environment abstract petrographic investigations of serial ply samples from five high to medium volatile bituminous coal seams from australia 4 and canada 1 reveal substantial in seam variations in the reflectance and monochromatic microfluorescence intensities of the maceral subgroup telovitrinite the variations consist of one case of reflectance enhancement and fluorescence suppression and four cases of reflectance suppression and fluorescence enhancement the single case of reflectance enhancement and fluorescence suppression is due to the oxidation of the vitrinite nuclei at the sequence boundary between the bayswater and upper wynn seams in new south wales the four cases of reflectance suppression and fluorescence enhancement result from the syn and epigenetic absorption by the vitrinite nuclei of hydrogen donated by presumably anaerobic bacteria generated lipids two of the coals are marine influenced the liskeard seam from the bowen basin by combined syngenetic and epigenetic effects and the greta seam from the sydney basin mainly by epigenetic contact with sea water for both coals the results are strong vitrinite reflectance suppression and fluorescence enhancement the remaining two coals the bulli seam from the sydney basin and a coal seam from the gates formation in british columbia show moderate epigenetic effects on the optical properties of telovitrinite by fresh water in the bulli seam which was studied in two adjacent localities the reflectance suppression and fluorescence enhancement of telovitrinite are stronger under sandstone roof than under shale roof in some cases the epigenetic effects are superimposed on syngenetic telovitrinite reflectance and fluorescence variations resulting from the cogeneration and mixing of different telovitrinite precursors for example autochthonous roots and hypautochthonous or allochthonous shoots a measure of the degree of dispersal and mixing is the coefficient of variation of telovitrinite reflectance and or fluorescence this coefficient correlates well with detrital minerals and dispersed macerals e g inertodetrinite and to a lesser extent sporinite some comments are made on slitted so called pseudovitrinite which is regarded as a telovitrinite that was subjected to very weak post coalification desiccation and possibly oxidation without losing much of its thermoplastic properties

geochemical characteristics of carboniferous coaly source rocks and natural gases in the southeastern junggar basin nw china implications for new hydrocarbon explorations abstract the upper carboniferous coaly source rocks are verified to be developed in the southeastern junggar basin which is lithologically composed of carbonaceous mudstones and mudstones according to the geochemical total organic carbon rock eval and biomarker fingerprints and organic petrology analyses the carboniferous source rocks are primarily gas prone characterized by kerogen type iii and were deposited in an oxidized sub oxidized brackish environment significantly contributed by terrigenous higher plants carbonaceous mudstones are generally more oil prone in comparison with the mudstones the measured vitrinite reflectance t max and sterane isomers indicate that the source rocks are at immature early gas generation stage and have not entered the peak gas generation stage natural gases are coal type gases derived from the carboniferous source rock the maturities of them are highly inconsistent with those of source rock samples based on 2 d basin modeling natural gases were generated from the highly mature coaly source rocks in the fukang depression and migrated upward to the uplift via the p c regional inconformity

geochemical characteristics of tertiary coal bearing source rocks in xihu depression east china sea basin abstract this study aims at investigating hydrocarbon generation potential and biological organic source for the tertiary coal bearing source rocks of pinghu formation middle upper eocene in xihu depression east china sea shelf basin another goal is to differentiate coal and mudstone with respect to their geochemical properties the coal bearing sequence has a variable organofacies and is mainly gas prone the coals and carbonaceous mudstones in comparison with mudstones have a higher liquid hydrocarbon generation potential as reflected by evidently higher hi values averaging 286 mg hc g c and h c atomic ratios round 0 9 the molecular composition in the coal bearing sequence is commonly characterized by unusually abundant diterpenoid alkanes dominant c29 sterane over c27 and c28 homologues and high amount of terrigenous related aromatic biomarkers such as retene cadalene and 1 7 dimethylphenanthrene indicating a predominantly terrigenous organic source the source rocks show high pr ph ratios ranging mostly from 3 5 to 8 5 and low mdbts mdbfs ratios

influence of in situ bitumen on the generation of gas and oil in new zealand coals new zealand coals of peat to high volatile bituminous rank have been studied in order to assess the effect of in situ bitumen soluble in a methanol acetone chloroform azeotrope on petroleum potential during progressive maturation both non extracted and extracted coals as well as the extracted bitumen itself were analyzed using rock eval and pyrolysis gas chromatography the difference in yields between non extracted and extracted coals attributable to the influence of bitumen were compared with direct measurements made on the bitumen itself major compositional changes in pyrolysis products were seen when the bitumen was finely dispersed throughout the kerogen matrix notably second order reactions between kerogen and bitumen during pyrolysis reduce primary gas yield and enhance both oil yield and potential secondary gas yield the stabilization of free radicals and prevention of recombination repolymerization processes have been attributed to the presence of the dispersed in situ bitumen these results demonstrate that petroleum formation in coals likely proceeds via intermolecular interactions and not simply first order cracking the common procedure of employing solvent extraction prior to pyrolysis is clearly not appropriate when assessing the petroleum potential of coal

extended hopanoids in peat environments abstract detailed results are presented for the distributions of triterpenoid alkanes acids and alcohols of the hopane family in ten samples of peat from three environments and of contributing organisms in the case of lyne of skene scotland extended hopanoids of the and configuration appear at the very earliest stage of diagenesis such environments appear to be characterised by particular distributions of c 32 hopanoid acids and alcohols and a high preponderance of the c 31 hopane

petroleum generation and migration in coal seams of the carboniferous ruhr basin northwest germany a series of 64 coal and clastic rock samples of westphalian age was taken from five narrow 3 m depth intervals between 1200 and 1530 m depth and studied by geochemical and petrological methods maturity increases regularly with increasing depth as indicated by several maturity parameters the influence of organic facies is evident in the uppermost coal seam 0 70 rr where a hand picked vitrinite contains less total extract and less saturated long chain hydrocarbons than a directly adjacent sporinite rich coal extracts from deeper and more mature coals are less affected by facies changes probably due to enhanced petroleum redistribution in the seams total yield and gross composition of extracts in the deepest seam 0 92 rr which is directly overlain by sandstone seem to be influenced by the preferential expulsion of saturated hydrocarbons

multi proxy approach on the hydrocarbon generation perspective of barjora basin india abstract barjora basin in india is a small basin characterized by a high organic richness of early mature nature the present study aims to find the source of organic matter om and hydrocarbon generation potential of barjora basin systematically collected coal and shale samples from r ii seam of the basin were used for proximate and ultimate analyses rock eval pyrolysis along with total organic carbon toc content organo micropetrographic framework thermal maturity carbon isotopic signature biomarker composition functional group studies and estimation of relative aliphaticity and aromaticity through fourier transform infrared spectroscopy ftir the novelty of the present work lies in the application of multiple proxies such as stable isotope ratio of organic carbon 13c biomarker signatures thermal maturity parameters organo micropetrography and estimation and quantification of functional groups for palaeoenvironmental reconstruction and to assess the hydrocarbon productivity of the basin a dominant terrestrial om input in barjora basin is indicated by the toc to total nitrogen ratio c n 13c and biomarker compositions high gelification index gi tissue preservation index tpi and carbon preference index cpi values indicate that coals are deposited in wet swamp forest regime under high rainwater conditions and shales are formed in upper delta plain regime under high groundwater activity in addition large liptinite content tpi and gi designate short transportation of the om before burial leading to organic richness of the barjora basin moreover high liptinite content type ii iii admixed kerogen input s2 s3 ratio tpi and index for hydrocarbon generation ihg signify higher potential of the basin for hydrocarbon generation

thermal stability of thiophene biomarkers as studied by hydrous pyrolysis abstract an immature r o 0 25 sulphur rich calcareous shale from the gessoso solfifera formation messinian in the vena del gesso basin northern italy was artificially matured by hydrous pyrolysis at constant temperatures ranging from 160 to 330 c for 72 h to study the applicability of alkylthiophenes as molecular indicators during progressive diagenesis and early catagenesis artificial maturation at temperatures up to 330 c generated large amounts of alkylthiophenes from the thermal degradation of kerogen the importance of the kerogen in the production of alkylthiophenes is supported by the observation that the isomer distributions of alkylthiophenes at high temperatures coincide with the isomer distributions of alkylthiophenes in the curie point pyrolysate of the isolated kerogen of the original sample the generation profiles of the thiophenes with a phytane carbon skeleton and the 3 4 di n alkylthiophenes suggest that continuous degradation of alkylthiophenes is also taking place so that the overall effect is alkylthiophene concentrations with intermediate values the structural isomer distribution of linear alkylthiophenes does not change significantly when these compounds are generated at different temperatures this implies that important information regarding the original positions of functionalities in the precursor molecules is retained and thus that alkylthiophenes are useful biomarkers at relatively high levels of thermal maturity up to r o 0 95 1 1

sesquiterpanes diterpanes and other higher terpanes in oils from the taranaki basin of new zealand abstract the bi tri and tetracyclic terpenoids in crude oils from the taranaki basin of new zealand have been studied the distribution of c14 c15 and c16 bicyclanes was essentially invariant amongst the various fields a suggestion is made that the proportion of rearranged to total drimanes may be related to maturity and the ratio of homodrimane to drimane may be related to depositional environment mass spectra are reported for a number of unidentified sesquiterpanes including possibly norbisabolane and bisabolane the distribution of bi tri and tetracyclic diterpanes was very similar to that of crude oils from the gippsland basin of south east australia the occurrence of rimuane was confirmed 8 h labdane was identified and 4 h 18 norisopimarane was tentatively identified isopimarane dominated the diterpane distribution of oils from the maui field in the south west of the basin and its abundance gradually diminished in a north westerly direction until it became a minor component of oil from the new plymouth field this trend coincided with an increase in the complexity of the triterpane distribution and with the oleanane content of the oils these northwards trends also followed the evolution of coal deposits in the region the diterpanes in these oils had the same structure as those which occur in extant trees of the araucariaceae and podocarpaceae which flourish in new zealand today and did so even more extensively in the past coal measures formed from forests of such trees are probably the source of the diterpanes a situation analogous to that in the gippsland basin of south eastern australia tricyclanes of the cheilanthane series were not detected in any of the taranaki oils lending support to the view that these tricyclanes occur most abundantly in oils derived from marine sources c24 tetracyclanes secotriterpanes occurred abundantly in all the oils as they do in terrigenous oils from other parts of the world

a thermal and chemical degradation approach to decipher pristane and phytane precursors in sedimentary organic matter a thermal and chemical degradation approach was followed to determine the precursors of pristane pr and phytane ph in samples from the gessoso solfifera ghareb and green river formations hydrous pyrolysis of these samples yields large amounts of pr and ph carbon skeletons indicating that their precursors are predominantly sequestered in high molecular weight fractions however chemical degradation of the polar fraction and the kerogen of the unheated samples generally does not release large amounts of pr and ph additional information on the precursors of pr and ph is obtained from flash pyrolysis analyses of kerogens and residues after hydrous pyrolysis and after chemical degradation multiple precursors for pr and ph are recognised in these three samples the main increase of the pr ph ratio with increasing maturation temperature which is associated with strongly increasing amounts of pr and ph is probably due to the higher amount of precursors of pr compared to ph and not to the different timing of generation of pr and ph

predicting the quantities of oil and gas generated fromaustralian permian coals bowen basin using pyrolyticmethods abstract the aim of the study was to establish kinetic parameters for gas and oil generation and totest the applicability of the kinetic models to petroleum generation through comparisons withnatural maturity coal sequences 433 c t max ro ro ro modelled ro calculated ro calculated

recognition of paleobiochemicals by a combined molecular sulfur and isotope geochemical approach study of organic matter in immature sediments from a messinian evaporitic basin shows that consideration of structures modes of occurrence and carbon isotopic compositions of free and sulfur bound carbon skeletons allow identification of biochemical precursors detailed information concerning biotic communities present during deposition of sediments can be retrieved in this way moreover unprecedented biochemicals were recognized these extend the horizon of biomarker geochemistry

isolation and structural characterisation of isopimarane in some new zealand seep oils abstract isopimarane a tricyclic diterpane was isolated from some new zealand late cretaceous seep oils and coals in which it occurs in abundance the structure and absolute stereochemistry of this terrigenous oil biomarker were determined by nmr spectroscopy cd and synthesis

paleoenvironment of eocene lignite bearing succession from bikaner nagaur basin western india organic petrography palynology palynofacies and geochemistry abstract lignite and associated shale samples from the matasukh mine of western india have been studied by petrographic palynofacies palynological and organic geochemical parameters the objective is to understand the floral organic composition and palaeo depositional conditions ecology and climate of the lignite bearing sequence petrographically the low rank b lignites are dominantly composed of huminite macerals followed by moderate liptinite and low inertinite macerals the predominance of detrohuminite attrinite densinite with respect to telohuminite textinite ulminite suggests that the woody vegetation has undergone higher degree of degradation during the peat accumulation as is also indicated by the frequent occurrence of funginite the tpi gi gwi and vi indices point towards limno telmatic condition of the palaeomire during the deposition of lignite forming peat under mesotrophic to rheotrophic basin conditions the reducing conditions in the depositional site are evident from the frequent pyrite content the studied samples had a high organic matter yield which showed a co dominance of phytoclasts and aom this nexus is indicative of a marginal marine depositional environment also evident from tyson s app diagram the palynofloral assemblage is dominated by angiosperm pollen especially those having affinity with the family arecaceae the presence of palynomorphs of the family dipterocarpaceae indicates the existence of rain forest vegetation in the vicinity of the depositional site the degradation products of oleanane and 23 norlupane in the sediment extracts also suggest that the angiosperm dominant higher plants served as the source for the peat forming biomass the presence of hopanes indicates high microbial activity during the formation of lignites the high cpi and tar values also indicate the large input of terrigenous higher plant materials

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

investigation on the lignite deposits of surkha mine saurashtra basin gujarat western india their depositional history and hydrocarbon generation potential abstract an integrated approach is adopted to study the lignite deposits of surkha mine associated with the khadsaliya clays formation eocene of saurashtra basin western india the compilation of detailed investigation includes organic petrographical palynofacies and geochemical analyses the type and amount of organic matter and its relation to palaeoenvironmental conditions have been determined and discussed along with its significance as hydrocarbon source the macerals of huminite group show dominance av 61 over the liptinite and inertinite groups the petrographical indices gi tpi gwi vi indicate wood dominated precursors of peat were deposited in limno telmatic to telmatic regime under mesotrophic hydrological conditions in palynofacies analysis it is observed that the particulate organic matter is dominated by the phytoclasts group av 69 followed by the amorphous organic matter aom and palynomorphs the biomarker signatures show angiosperm and gymnosperm source vegetation the presence of sesquiterpenoids indicate the occurrence of dipterocarpaceae flora suggesting the existence of rain forest vegetation in the vicinity of depositional site the kaurane type of diterpenoids suggest the presence of conifers among the source flora the extrapolation of organic matter data on tyson s app diagram along with the pr n c 17 vs ph n c 18 plot indicate that the deposition took place in dysoxic suboxic conditions with intermittent shifting of the environment in proximal settings the huminite reflectance values av 0 31 r r show a good correlation with gross calorific values av 3917 cal g and average t max value 416 c of the lignites furthermore the abundance of thermally unstable hop 17 21 ene and hopane indicate immature stage of lignites these lignites contain high toc av 35 wt and low ash yields the volatile matter carbon and oxygen contents are relatively high whereas sulphur content is moderate and hydrogen and nitrogen contents are comparatively low in all the lignite samples the hydrogen index values vary between 53 and 538 mg hc g toc the atomic values of h c range from 0 47 to 1 04 and of o c from 0 20 to 0 29 overall the lignite bearing sequence is characterized by type ii iii admixed kerogens organic matters and has potential to generate hydrocarbons upon maturation

maturity related compositional changes in the low molecular weight hydrocarbon fraction of toarcian shales abstract compositional changes in the light hydrocarbon content of sedimentary rocks and petroleum are known to reflect their maturation history the present contribution comprises the study of the low molecular weight hydrocarbon fraction in core samples of lower toarcian age posidonia shale lias the samples series collected by shallow borehole drilling in the hils syncline lower saxony basin northern germany represents an excellent petroleum source rock type ii kerogen of a wide maturity range mean vitrinite reflectance rm between about 0 5 and 1 5 about 30 compounds in the c2 c7 molecular range were determined quantitatively using a combined thermovapourization capillary gas chromatography method both quantity and composition particularly of the c7 hydrocarbon fraction are discussed in relation to vitrinite reflectance values measured at five locations rm 0 48 0 66 0 68 0 88 and 1 45 correlations between rm and paraffin naphthene concentration ratios are described also the isomer concentration ratios of 2 methylhexane 3 methylhexane and of trans to cis 1 2 dimethylcyclopentane are clearly related to the maturity of the organic matter

origin and composition of organic matter in tidal flat sediments from the german wadden sea abstract two sediment cores of up to 550 cm length from an intertidal flat of the german wadden sea near the island of spiekeroog were investigated for the quantity and composition of fossil organic matter om the lowermost parts of the cores are dominated by grey mud of a salt marsh facies containing mainly terrestrial om estimated to account for 60 75 of the total om based on 13 c values and the ratio of short to long chain n alkanols the terrigenous origin of the dominant fraction is indicated among others by high proportions of c 29 sterols and long chain n alkanes typical of plant waxes coarse shell beds overlying the grey mud at 2 2 5 m depth represent a flooding and erosion event possibly related to heavy storm floods in the middle ages within the intertidal sand dominated sediments in the upper parts of the cores total organic carbon toc contents are generally low ranging from 0 1 to 0 5 and correlate well with the amount of mud fraction r 2 0 90 at the surface marine om has not undergone intense diagenetic alteration and so is the dominant fraction eroded peat particles are common throughout most of the sequence and values of the phragmites peat indicator ppi 5 indicate an origin from reed peat due to a high relative abundance of the n c 24 alkane changes in the composition of microbial communities over the depth interval investigated are documented by varying compositions of unsaturated fatty acids with 16 and 18 carbons eicosapentaenoic acid epa was detected along the entire cores and indicates the presence of epa producing bacterial strains

novel side chain methylated and hexacyclic hopanes identification by synthesis distribution in a worldwide set of coals and crude oils and use as markers for oxic depositional environments abstract novel side chain methylated and hexacyclic hopanes have been identified in coals and oils from around the world extended hopanes c 32 with an additional methyl in the side chain isohopanes were identified by comparison with synthetic standards the major c 33 c 35 isohopanes are 31 methylbishomohopanes 32 methyltrishomohopanes and 33 methyltetrakishomohopanes extended hopanes methylated at c 29 were not detected the 17 h 21 h 31 methyltrishomohopanes show four peaks on gas chromatography because of the extra asymmetric carbon at c 31 like regular hopanes the isohopanes extend beyond c 35 low concentrations of novel hexacyclic hopanes having 35 or more carbons were also detected in oils and coal extracts the c 35 hexacyclic hopanes were identified as 29 cyclopentylhopanes isohopanes are released from the kerogen by hydrous pyrolysis and hydropyrolysis the 22s 22s 22r ratio for 31 methylbishomohopanes and other isohopanes is around 0 60 at equilibrium in geological samples they isomerize slightly more slowly than regular c 33 hopanes isohop 17 21 enes 2 methylisohopanes and two series of rearranged isohopanes were tentatively identified isohopanes can be biodegraded to form the corresponding 25 norhopanes when 25 norhopanes are not formed the isohopanes are much more resistant to biodegradation than regular hopanes in biodegraded oil seeps from greece 30 norisohopanes were tentatively assigned the composition and relative abundance of c 33 and c 34 isohopanes in a worldwide set of coals and crude oils was determined isohopanes are abundant in coal and coal generated oils where they can account for more than 5 of all extended hopanes and low in abundance in oils from source rocks deposited under anoxic conditions

comparative study of serbian miocene coals insights from biomarker composition abstract the origin of the organic matter om and the characteristics of the paleoenvironment of serbian brown coals covering a time span from the lower to the upper miocene were evaluated and compared based on comprehensive petrological and biomarker analyses investigated coals are typical humic coals peat forming vegetation is characterized by abundant decay resistant gymnosperm coniferous plants followed by variable amount of angiosperms coal forming plants belonged to the gymnosperm families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae peatification proceeded in fresh water environment under variable eh settings from anoxic to slightly oxic condition upper miocene lignites were formed in neutral to slightly acidic environment whereas lower and middle miocene coals were deposited under neutral to slightly alkaline and more reductive conditions which is the result of calcium rich surface waters derived from the surrounding jurassic to cretaceous calcareous country rock and higher water column level diagenetic changes of the om were governed by bacterial activity rather than thermal alteration biomarker pattern does not significantly differ in serbian coals of different ages the main differences between upper middle and lower miocene coals are expressed by higher gelification index gi proxy ratio p aq n c 23 n c 27 n c 31 and pimarane 16 h phyllocladane ratio as well as lower relative abundance of c 31 r hopane of the latter one om of lower miocene coals is more mature corresponding to immature early mature stage huminite vitrinite reflectance 0 45 whereas om of upper miocene lignites is in immature diagenetic phase huminite reflectance 0 3 consequently higher gelification of lower miocene coals is probably an effect of higher rank however high humidity wet climate and low acidity within the mire could not be excluded a good correlation between biomarker parameters and paleoclimate data is observed indicating that biomarker patterns represent a valuable tool that reflect even slight paleoclimate changes in serbia during miocene

petrological and organic geochemical properties of lignite from the kolubara and kostolac basins serbia implication on grindability index abstract the influence of different coal lithotypes on grindability has been investigated using lignite from two of the most important upper miocene lignite basins in serbia kolubara and kostolac yellow xylite rich types demonstrated the most negative impact on hardgrove grindability index hgi all different types of xylite rich coal as well as total xylite rich coal from the kolubara basin have a negative influence on the grindability properties while only the yellow type of xylite rich coal from the kostolac showed a negative impact on hgi matrix coal does not show a clear effect on hgi a negative correlation between textinite content and hgi is observed in both basins whereas contents of other macerals do not show influence on grindability properties content of total organic carbon demonstrated the negative impact on hgi correlation analysis indicates that the negative impact of the yellow type of xylite rich coal and the sum of total xylite rich coal on the grindability properties partly can be related to content of total organic carbon and high amount of soluble organic matter matrix lithotype does not show any significant correlation with bulk geochemical parameters in both basins the peat forming vegetation of all samples from both basins were dominated by decay resistant gymnosperm coniferous plants belonging to one or several of the families taxodiaceae podocarpaceae cupressaceae araucariaceae phyllocladaceae and pinaceae lignite from the kolubara basin is characterized by a higher contribution of angiosperm vegetation than coal from the kostolac basin peatification of the kolubara coal occurred under more oxic conditions than the kostolac one analysis of biomarkers indicated that the negative impact of all types of xylite rich coal from the kolubara on hgi can be related to the higher proportion of angiosperms abundance of mid chain n alkanes and sesquiterpenoids aromatization of non hopanoid triterpenoids and hopanoids and intense degradation of wood tissues in a more oxic environment the positive impact of matrix coal on hgi in the kolubara samples can be attributed to elevated content of non aromatic hopanoids and low amounts of aromatic non hopanoid triterpenoids and sesquiterpenoids which seems to hinder the grindability properties

geomorphic evidence for the geometry and slip rate of a young low angle thrust fault implications for hazard assessment and fault interaction in complex tectonic environments abstract we present surface evidence and displacement rates for a young active low angle 20 reverse thrust fault in close proximity to major population centers in southern california usa the southern san cayetano fault sscf active faulting along the northern flank of the santa clara river valley displaces young landforms such as late quaternary river terraces and alluvial fans geomorphic strain markers are examined using field mapping high resolution lidar topographic data 10be surface exposure dating and subsurface well data to provide evidence for a young active sscf along the northern flank of the santa clara river valley displacement rates for the sscf are calculated over 103 104 yr timescales with maximum slip rates for the central sscf of 1 9 1 0 0 5 mm yr 1 between 19 7 ka and minimum slip rates of 1 3 0 5 0 3 mm yr 1 since 7 ka uplift rates for the central sscf have not varied significantly over the last 58 ka with a maximum value of 1 7 0 9 0 6 mm yr 1 for the interval 58 19 ka and a minimum value of 1 2 0 3 mm yr 1 since 7 ka the sscf is interpreted as a young active structure with onset of activity at some time after 58 ka the geometry for the sscf presented here with a 20 north dip in the subsurface is the first interpretation of the sscf based on geological field data our new interpretation is significantly different from the previously proposed model derived geometry which dips more steeply at 45 60 and intersects the surface in the middle of the santa clara river valley we suggest that the sscf may rupture in tandem with the main san cayetano fault additionally the sscf could potentially act as a rupture pathway between the ventura and san cayetano faults in large magnitude multi fault earthquakes in southern california however given structural complexities including significant changes in dip and varying holocene displacement rates along strike further work is required to examine the possible mechanism likelihood and frequency of potential through going ruptures between the ventura and san cayetano faults confirmation of the sscf in a previously well studied area such as southern california demonstrates that identification of young faults is critical for accurate seismic hazard assessment we suggest that many young active faults remain undetected in other structurally complex and tectonically active regions globally and that significant seismic hazards can be overlooked

application of rank sr a maturity index based on chemical analyses of coals abstract the rank sr classification of suggate nz j geol geophys 43 2000 521 which uses data from standard coal industry chemical analyses is illustrated on interdependent diagrams with axes of atomic o c and h c and of calorific value and volatile matter the rank sr scale which is compensated for coal type is linear with depth under conditions of linear geothermal gradients so that the depth value for each unit increase in rank depends on the geothermal gradient at the time of maximum temperature normally that of maximum burial a general relation is established between rank sr and the temperature of attainment of rank temp c 10 rank sr 15 significant oil generation begins at rank sr 9 10 and expulsion at rank sr 11 5 12 5 a clear general relation exists between rank sr and vitrinite reflectance but rank sr is somewhat more accurate over the range from peat to the end of the oil window in the paleogene buller coalfield new zealand the use of rank sr aids interpretation of the geological history coals in the carboniferous nottinghamshire yorkshire coalfield in england probably contributed hydrocarbons including oil to the adjoining east midlands hydrocarbon fields vertical and lateral variations in rank sr in the coalfield and the rank sr values in coal measures at the base of the permian require a thick mesozoic tertiary cover in the oilfields of the mahakam delta indonesia and the taranaki basin new zealand rank sr depth gradients imply surface values that are close to zero where little or no cover has been eroded from above the wells and inferred temperatures that are reasonably close to present temperatures

a geochemical appraisal of oil generation in the taranaki basin new zealand from a basin wide evaluation of organic geochemical data it has been possible to characterize and differentiate various source rock units and to establish the genetic relationships of oils most of the oils are primarily terrestrially sourced and it is possible to recognize varying contributions from source rocks within the paleogene kapuni group and late cretaceous pakawau group this distinction is attributable to the rise to dominance of angiosperms over gymnosperms in coastal plain swamp communities by the eocene apart from the maui family i e maui field maui 4 and moki 1 oils the inferred relative contributions from the main source rock types generally correlate with the relative proportions of suitably thick and mature units near reservoirs given that mos cretaceous sourced oil appears to have escaped prior to trap development maui family oils do appear to be primarily sourced by rakopi formation late cretaceous coals in the northern part of the taranaki peninsula where heat flows are highest mangahewa kaimiro formation eocene coals are the chief sources of oils farther south in the kapuni and kupe south fields farewell formation paleocene coals appear to be the main oil source rocks biomarkers suggest that the onset of oil expulsion from coals occurs at a maturity level corresponding to a vitrinite reflectance of ca 0 8 ro and may be aided by the evolution of large volumes of carbon dioxide the terrestrial influence on paleogene source rocks diminishes to the north northwest of the basin and increasing marin contributions to oils are observed a late paleocene marine black shale is the source of oil in the kora volcanic structure it is possible that shales interbedded with coals reflecting periodic marine incursions of coastal flood plains also contribute to oil generation throughout much of the basin

maturity related variation in the bulk transformation kinetics of a suite of compositionally related new zealand coals abstract bulk hi transformation kinetics were determined by open system pyrolysis for a suite of compositionally related late cretaceous to paleocene coals from tara 1 well great south basin new zealand these coals span a maturity range encompassing the onset of significant oil generation and expulsion kinetic parameters were also obtained for one of the immature samples following artificial maturation by hydrous pyrolysis kinetic models were based on three modes of optimisation of kinetic parameters discrete e act distribution with single variable a value discrete e act distribution with fixed a 10 14 s 1 and gaussian e act distribution with single variable a value hi transformation rate vs temperature envelopes for the naturally matured coals exhibited an abrupt jump to higher temperature near rank s r 12 5 apparently coinciding with the onset of significant paraffinic oil expulsion for all optimisation modes the artificially matured sample does not predict this shift in transformation envelopes which suggests that certain of the reactions that occur under natural maturation do not occur during laboratory pyrolysis the structural rearrangements occurring up to the expulsion threshold some or all of which are responsible for the increase in hi up to rank s r 11 are not manifested in changes in hi transformation rate envelopes however the presence of adsorbed bitumen may mask the influence of structural rearrangements during optimisation of the kinetic data which could explain the behaviour of the transformation rate envelopes in the rank s r 11 0 12 5 range obtained from the discrete e act free a optimisation this behaviour involves a regression in transformation rate envelopes to lower temperatures as the amount of retained bitumen increases prior to expulsion the almost perfect nesting of transformation rate envelopes subsequent to oil expulsion suggests either that any further structural rearrangement does not produce a significant change in the a and e act distributions of hydrocarbon generating bonds or that the expulsion drastically reduces the degree of further rearrangements involving hydrocarbon generating moieties within the kerogen it follows that kinetic parameters for immature coals should not be considered ideal for modelling the whole phase of hydrocarbon generation nevertheless the kinetic parameters for the least mature tara coal rank s r 8 5 reproduced the normalised hi trend for the entire suite of coals with reasonable accuracy over the maturity range considered rank s r 8 5 15 0 only slightly underestimating conversion at the lower maturity levels and overestimating it slightly at the higher levels

organic geochemistry of semianthracite from the gequan mine xingtai coalfield china abstract eighteen semianthracite samples of the no 9 coal seam in the gequan mine xingtai coalfield china were investigated primarily by microscope and organic geochemical methods the petrological results showed that the vitrinite random reflectance r o is 2 36 and the maceral group was dominated by vitrinite the gas chromatograms gc of the saturates display a monomodal or bimodal outline of n alkane peaks generally from n c 10 to n c 31 resulting in two ranges of c 1 c 21 c 22 c 34 values most of the coal samples exhibit consistently similar parameters such as pristane n c 17 and phytane n c 18 ratios whereas samples with different pr ph values may have been the result of varied redox depositional conditions the distributions of the polycyclic aromatic compounds pacs identified in the aromatics were generally similar due to the similar high rank of the coal samples under the high thermal maturity the pacs with greater thermodynamic stabilities including 2 methylnaphthalene 2 6 and 2 7 dimethylnaphthalenes 2 and 3 methylphenanthrenes and 2 6 and 2 7 dimethylphenanthrenes were present at higher concentrations than those of less thermodynamically stable pacs a portion of these pacs most likely originated from a secondary generation the generally higher contents of dibenzothiophenes and benzonaphthothiophenes were most likely generated under the control of hydrothermal fluids however the coal forming environment may also have played a role for higher contents of dibenzothiophenes and benzonaphthothiophenes

changes in hydrocarbon maturity indices with coal rank and type buller coalfield new zealand abstract the buller coalfield south island new zealand is an inverted late paleogene basin that contains middle eocene bituminous coals which exhibit considerable variation in both coal rank across basin and coal type in seam twenty two fractionated bitumen extracts of brunner coal measures coal samples from 12 drillholes were analyzed by gc and gc ms to characterize the effect of coal rank and type on conventional hydrocarbon maturity indices at the beginning and end of the oil window 0 56 1 26 ro max the carbon preference index pristane phytane and isoprenoid n alkane ratios evolve throughout the high volatile bituminous b rank stage while other biomarker ratios 18 h 22 29 30 trisnorneohopane 17 h 22 29 30 trisnorhopane ts tm 18 h 21 h 30 norneohopane c 29 ts 17 h 21 h 30 norhopane and c 30 diahopane hopane do not show appreciable change in value until medium volatile bituminous rank various aromatic based ratios appear to be more effective in delineating rank throughout the entire oil window in particular the methylphenanthrene index and vitrinite reflectance are positively correlated over the entire bituminous rank range however subtle changes in depositional conditions variable coal type complicate these rank estimates within a given coal seam variation in cpi isoprenoid n alkane and hopane sterane ratios appear to be related to the hydrogen content of the coal while the homohopane index and the oleanane hopane ratio covary with sulfur content as with depressed vitrinite reflectance values mpi is similarly lowered in the perhydrous samples the mechanisms that control these hydrocarbon parameters during deposition and diagenesis are complex and convoluted however changes in bacterial activity and community with marine incursion appear to play an important role due to these anomalies none of the hydrocarbon maturity indices calculated can be singularly used to constrain coal rank

aspects of generation and migration of hydrocarbons from coal bearing strata of the hitra formation haltenbanken area offshore norway abstract the haltenbanken area situated 150 200 km offshore mid norway is a proven gas condensate and oil producing province with continuing exploration potential in this structurally and stratigraphically complex area with multiple source rock possibilities we have examined the upper triassic lower jurassic hitra formation to determine its possible contribution to the hydrocarbon pools in the area the 400 m thick hitra formation consists of interbedded shales siltstones sandstones and coal seams in this study conventional cores of the hitra formation from depths varying from 2 4 and 4 6 km have been examined with the objective to obtain a better understanding of hydrocarbon generation migration and expulsion processes in these coals as function of variation in facies and maturity in addition to basic geochemical measurements toc rock eval and gc analysis of c15 saturated hydrocarbons microscopic studies normal and uv reflected light were carried out to determine the abundance and initial distribution of hydrogen rich macerals including fluorescent mobile phases such as exsudatinities geochemical and microscopal evidence was obtained suggesting that some of the interbedded sandstones show indications of impregnation by migrated hydrocarbons some bitumen filled micro fractures were observed extending from the coals towards the adjacent sands a preliminary interpretation of these data is that these fractures represent conduits carrying hydrocarbons from the coal seams towards the sandstones the role of the kerogen type variations on the amount of hydrocarbons generated and the mechanism and efficiency of hydrocarbon expulsion from the coals is discussed

chemostratigraphic evidence of higher plant evolution in the taranaki basin new zealand correlation between palynological and biomarker records of higher plant development during the cretaceous and paleogene in taranaki basin new zealand is good gymnosperms particularly podocarps were the chief members of coastal plain swamp flora during the late cretaceous and contributed significant quantities of diterpanes often dominated by isopimarane to organic rich sediments angiosperms increased in relative abundance through the paleocene and became the dominant higher plants in the eocene their contributions to coaly sediments are characterized by various triterpanes particularly 18 h oleanane and its c24 a ring degraded counterpart this change in dominance of higher plant groups can be followed by the use of an angiosperm gymnosperm index agi based on the relative concentrations of selected triterpanes and diterpanes in mz 191 and mz 123 mass chromatograms plant biomarker distributions do not provide as precise age indications as do pollen assemblages but they may be more representative of the vegetation growing in a particular area of a peat swamp

biomarker maturity parameters the role of generation and thermal degradation abstract the effects of burial maturation upon seven molecular maturity parameters and the concentrations of individual biomarkers employed in these parameters have been studied in a well in the barents sea the depth interval between 1400 and 3000 m comprises homogenous eocene claystones with effectively uniform organic carbon content 0 4 0 6 and kerogen type hi of 100 200 mg hc g toc the quantitative biomarker data thus contain minimal interference from organic facies hydrocarbon expulsion effects and the presence of migrated hydrocarbons bulk geochemical data define the hydrocarbon generation threshold or oil window at around 2300 m molecular maturity parameters proceed to equilibrium and in some cases demonstrate inversion at high maturity these molecular changes are associated with major changes in biomarker concentrations the hopane 22 s c 31 hopane and 20 s c 29 sterane parameters proceed as a result of the balance between the relative rates of generation and thermal degradation of the different isomers increased concentrations of the individual isomers are interpreted to be the result of biomarker generation from the kerogen mainly and other macromolecular polar fractions the c 29 sterane parameter and the three parameters involving rearranged hopanes ts 29ts and diahopane operate at higher maturity levels and proceed as a result of the relative rates of thermal degradation of the compound pairs isomerisation in the bitumen may also influence the operation of the parameters involving stereoisomers but must be a relatively minor contribution

organic geochemical evaluation of cretaceous shale samples from the orange basin south africa abstract organic geochemical evaluation of thirty two aptian to campanian shale samples from seven wells drilled on the shelf of the orange basin southwestern atlantic margin was carried out in order to determine their origin depositional environment thermal maturity and hydrocarbon potential the shale samples selected to represent highstand lowstand and transgressive systems tracts were analysed by rock eval pyrolysis for total organic c characteristics and by gas chromatography gc and gas chromatography mass spectrometry gc ms for n alkanes aliphatic isoprenoid hydrocarbons and biomarkers steranes hopanes and tricylic terpanes for most of the shale samples rock eval data hydrogen hi and oxygen index oi point to mainly type iii terrigenous organic matter only a few samples of turonian age reveal a higher proportion of marine organic matter being classified as type ii iii or type ii biomarker parameters suggest that the samples are deposited under suboxic to oxic environmental conditions rock eval data and biomarker maturity parameters assign for most of the samples a maturity level at the beginning of the oil window with some more mature samples of aptian albian and cenomanian age the hydrocarbon generation potential is low for most of the shelf shales as indicated by the s2 s3 ratio and hi values exceptions are some samples of turonian and aptian age

alternative theory for signal contribution sections and depth of investigation characteristics in electrical prospecting we present an alternative to roy s theorem for direct current regimes with the aim of validating the theoretical basis of signal contribution sections in electrical prospecting roy s theorem establishes that the electrical potential at a point can be expressed as an integral over all space of the electric field weighted by the gradient of inverse distance the integrand is interpreted to represent elementary contributions to the potential that can be analyzed to compare different electrode arrays signal contribution sections and depth of investigation characteristics can be beautifully illustrated with important practical applications however the electric potential being the solution of a boundary value problem cannot be uniquely decomposed into elementary contributions there is no guarantee for the integrand of a given integral to be meaningful in all situations in the case of roy s theorem the concept has been severely criticized by respected scholars who challenged the scientific legitimacy of his approach if we are going to keep the concept of elementary contributions alive we need to go beyond roy s theorem in this paper we develop an alternative theorem and show that it merges with the concept of sensitivity which is unique and mathematically sound and is also open to physical validation this prevents any possible contradictions in the future and equally important eliminates the dichotomy between sensitivity and elementary contributions

organic geochemical and stable carbon isotopic investigation of coals formed in low lying and raised mires within the eastern alps austria abstract up to 16 m thick coal seams formed in miocene pull apart basins within the eastern alps in low lying and raised mires despite similar rank sub bituminous stage coal quality differs significantly coals from low lying mires e g fohnsdorf are characterized by significantly higher ash yields and sulfur contents than coals from raised mires e g leoben organic geochemical and carbon isotope investigations were performed to assess the differences in facies the fohnsdorf coals are characterized by higher yields of soluble organic matter som slightly higher proportions of hydrocarbons in the som generally lower pristane phytane ratios and the occurrence of high corg normalized n alkane concentrations only n alkane patterns in the leoben samples show a marked odd over even predominance these differences are indicative of a more intensive dys to anaerobic biochemical degradation of plant material within the fohnsdorf mire terpenoid biomarkers characteristic of conifers and angiosperms were detected in the leoben coals whereas the latter are missing in the fohnsdorf samples in the leoben coals higher saturated to aromatic diterpenoid ratios were detected than in the fohnsdorf coals because of similar rank enhanced aromatisation in the fohnsdorf basin is probably related to microbial activity despite this the fohnsdorf coals are characterized by lower hopane concentrations the results imply that the aromatisation of terpenoid biomarkers is governed by the activity of anaerobic rather than aerobic bacteria an overall negative correlation between 13c of organic matter and the degree of aromatisation of diterpenoid biomarkers is observed it is suggested that the carbon isotopic composition results from different extents of microbial degradation of the biomass the fohnsdorf coals are rich in sulfur high contents of coalbed methane were encountered during mining suggesting high activities of anaerobic bacteria in a nearly neutral sulfate bearing brackish environment of the low lying mire and methanogenesis during or after coalification sulfate reduction and methanogenesis are known to increase 13c values of residual organic matter

hopanoid hydrocarbon maturation by an igneous intrusion abstract the thermal effects of an igneous intrusion 0 9 m thick dyke upon the abundance and composition of hopanes and hopenes are reported for a suite of samples within a single sedimentary horizon a carbonate concretion 1 6 m in diameter from the jurassic dun caan shale member bearreraig bay isle of skye scotland the conventional hopane maturity parameters show normal trends towards the dyke and through the oil window approximately 22 45 cm from the dyke i e 25 50 dyke thickness with the exception of the ts ts tm parameter which shows a progressive fall with increasing maturity until the middle of the oil window when it increases markedly molecular abundances demonstrate that the observed changes in the hopane maturity parameters result from the combined effects of generation presumed to be from kerogen and degradation of individual compounds with isomerization in the free phase being minimal or unimportant the unexpected behaviour of ts ts tm results from the minimal generation of ts compared with tm our data indicate that the ts skeleton is not present in the kerogen and at least under the elevated heating associated with an igneous intrusion may be derived from 18 h 22 29 30 trisnorneohop 13 18 ene in the bitumen thermally induced modifications to hopane carbon number distributions are also reported and show that oil source rock correlations between samples of different maturity must consider the effects of generation degradation of kerogen bound hopanes

vegetation differences and diagenetic changes between two bulgarian lignite deposits insights from coal petrology and biomarker composition abstract during the miocene numerous sedimentary basins formed on the territory of bulgaria as a result of the extensional tectonic settings related to the post orogenic development of the late alpine orogen in this study we review the petrographic composition and biomarker assemblage of two adjacent basins in western bulgaria i e beli breg and staniantsi basins both contain lignite formed during late miocene c 6 ma despite similar tectonic settings and depositional environments the lignite seams possess different petrographic and organic geochemical characteristics reflecting differences in the peat forming palaeo communities and facies variations the peat forming vegetation in beli breg basin was dominated by decay resistant coniferous plants as indicated by abundant fossil wood remains very good tissue preservation and a biomarker assemblage dominated by diterpenoids in contrast staniantsi lignite is poor in fossil wood and contains a significant amount of triterpenoid biomarkers suggesting the predominance of angiosperm plants in the swamp the results of the biomarker analyses are consistent with palaeobotanical and palynological data from the literature the lignite seams in both basins formed under frequently changing eh conditions as indicated by the severe degradation of the non gymnosperm tissues the low gelification index values and the variations in pristane phytane ratio probably as a result of seasonal drying of the swamps and changes of the ground water table hopanoid contents in beli breg lignite are very low and are consistent with the abundance of decay resistant vegetation in contrast bacterial activity was obviously higher in the staniantsi swamp however resulting only in slightly enhanced gelification of plant tissues the geochemical data suggest that the diagenetic changes of the organic matter were mainly governed by thermal degradation rather than bacterial activity