alkyldibenzofurans in terrestrial rocks influence of organic facies and maturation abstract dibenzofuran dbf dibenzothiophene dbt and phenanthrene phe have been determined along with their methyl derivatives mdbfs mdbts mps in coals carbonaceous shales and mudstones of lower cretaceous to upper carboniferous ages from the elmworth gas field canada and from the sakoa madagascar and ruhr coal germany basins the samples contained mainly terrestrial organic matter with thermal maturities in the 0 7 1 9 mean vitrinite reflectance rr range the pronounced predominance of mdbfs over mdbts in the sakoa samples is typical of plant debris deposited in lacustrine swamp environments onset of intense mdbf generation occurs at fairly low rank 0 77 rr as indicated by elevated concentrations of 50 120 g mdbfs g total organic carbon toc influences of lithology organic matter type and maturity on distributions of the target compounds were extracted from the molecular concentration data by multivariate statistical methods such as principal components analysis pca and fuzzy c means cluster analysis with nonlinear mapping nlm a specific source effect on 1 mdbt concentrations suggests that lichens contributed to the senescent coal forming forest in the sakoa coal basin alkyldibenzofurans hence are potential lichen biomarkers mdbfs can be used as maturity indicators only beyond 1 0 rr where ruhr coals displayed a distinct increase in the 1 4 mdbf ratio

variable alteration in heavy crude oils of west central saskatchewan canada heavy crude oils occurring in the mississippian bakken and lower cretaceous mannville reservoirs in west central saskatchewan display variable geochemical composition in their light c 5 c 8 and medium c 12 c 30 molecular weight fractions all oils show a depletion of normal alkanes and to a lesser extent acyclic isoprenoids which appears to increase progressively southward as biodegradation seems to be the primary control of the n alkane distributions it appears that oils produced from deeper reservoirs in the south are more biodegraded than the oils in shallower mannville reservoirs in the north however several other compositional characteristics including gasoline range and aromatic fractions are inconsistent with the trend in biodegradation defined by the relative n alkane abundance oils from the shallower northern reservoirs are enriched in cycloalkanes show lower relative concentrations of isoheptane lower paraffin indices much higher kl ratios and lower relative concentrations of lower molecular weight naphthalenes moreover some oils show a persistent presence of lower homologs of n alkanes c 5 c 8 and light aromatics such as benzene and toluene when higher c 15 homologs are not present such compositional characteristics may indicate that some of the reservoirs containing biodegraded oil were subjected to a subsequent secondary charge of lighter unbiodegraded crude or to different post generative alteration mechanisms this later charge of light hydrocarbons suggests the timing of most biodegradation to be pre eocene destructive microbial action resulting in preferential removal of n alkanes isoprenoids alkylbiphenyls and methylated naphthalenes had little effect on higher molecular weight fractions therefore despite their apparently very low gravities average api of 14 most of these oils suffered only light to moderate biodegradation although generally similar biomarker signatures indicate an overall genetic affinity and the same source rock for these oils minor but systematic variations in the biomarker compositions likely reflect regional source organic facies variation or indicate a progressive change in oil maturity

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

significant changes in land vegetation and oceanic redox across the cretaceous paleogene boundary abstract the impact of an extraterrestrial body 65 5 ma caused the so called cretaceous paleogene k pg event that resulted in a mass extinction and rapid changes in the surface environment on earth here we report changes in land vegetation and oceanic redox across the k pg boundary at caravaca southeastern spain using biomarkers the results reveal that the basal 3 mm thick layer of the k pg boundary clay is marked by a rapid increase in the concentration of terrestrial long chain n alkanes and dibenzofuran indicating the destruction of land vegetation and an increase in the supply of terrestrial organic matter into the marine environment during the deposition of the k pg boundary clay this layer also records a rapid increase in the concentration of dibenzothiophenes which indicates a change in redox conditions from oxic to anoxic euxinic conditions in the intermediate water over the seafloor the low oxygen conditions could have been caused by an increase in the influx of terrestrial organic matter into the ocean a rapid increase in the concentration of retene and retene cadalene occurred during the deposition of the upper part of the boundary clay 10 kyr after the mass extinction indicating the recovery of conifers which greatly decreased at the k pg boundary

dibenzothiophenes in solid bitumens use of molecular markers to trace paleo oil filling orientations in the lower cambrian reservoir of the moxi gaoshiti bulge sichuan basin southern china abstract the moxi gaoshiti mg bulge of the sichuan basin in southwestern china is unique because of its enormous gas field in old cambrian and proterozoic marine strata where oils in carbonate reservoirs have been nearly completely cracked to solid bitumen and natural gas because of high to post mature thermal maturity levels numerous solid bitumen bearing dolomites obtained from boreholes in the mg bulge provide an ideal opportunity to trace the major filling orientations for the lower cambrian paleo oil reservoirs biomarker analysis was conducted on solid bitumens through quantitative detection with gas chromatography mass spectrometry results show that all solid bitumen samples in the mg bulge exhibit similar compositions of molecular markers thereby implying that they belong to the same oil population and that paleo oils should be derived from the same source kitchen bed low pristane phytane and dibenzothiophene dbt phenanthrene ratios as well as the predominance of dbt among dbt dibenzofuran and fluorene are observed in the solid bitumen samples which suggest that related paleo oil reservoirs likely originated from a highly reducing marine shale environment all isopleth maps of the dbt concentrations 4 methyldbt 1 methyldbt 4 6 dimethyldbt 1 4 1 6 dimethyldbt dmdbt and 2 6 3 6 dmdbt 1 4 1 6 dmdbt ratios consistently indicate that the overall orientation of oil migration in the mg bulge is primarily from the west to east direction with the strongest filling point located at approximately the mx12 well the north to west direction is an additional filling orientation these indicators show that those paleo oils that had been cracked to pyrobitumens mainly originated from a source kitchen in the western part of the mg bulge a hydrocarbon source kitchen in the northern part of the mg bulge may also have developed but further research on this is needed the recognition of these solid bitumen molecular signatures particularly the consistent results using dbt concentrations and alkyl dbt thermal maturity indicators suggests a potential approach that can be applied to the study of paleo oil reservoirs

new age determinations for the eocene oligocene boundary sediments in the fayum depression northern egypt the fayum depression of northern egypt contains the richest collection of fossil vertebrates known from the afro arabian paleogene this fauna has been collected for over a century and yet the sediments containing the fossil localities have remained undated paleomagnetic sampling was carried out through the fossil bearing jebel qatrani formation and the underlying dir abu lifa member of the qasr el sagha foundation to determine a correlation between the paleomagnetic reversal stratigraphy and the geomagnetic reversal time scale grts a new date of 23 64 pm 0 035 ma was determined for the overlying widan el faras basalt by the laser incremental heating 40 ar 39 ar dating method the results of this study indicate that the majority of the vertebrate fossil localities occur in chrons c13 c15r late eocene to early oligocene in age these age determinations provide a minimum date for the origin of higher primates

the significance of benzo b naphtho d furans in fluids and source rocks new indicators of facies type in fluvial deltaic systems abstract the distributions of benzo b naphtho d furans bnfs in source rocks and fluids crude oil and condensate are shown to be useful indicators of facies type in fluvial deltaic systems from the dampier sub basin north west shelf of australia the stratigraphy in the dampier sub basin represents a challenging petroleum system where the organic matter is very similar in most of the triassic jurassic sequences these sections consist of a fluvial deltaic system with increasing marine influence towards the end of the jurassic period potential applications of bnfs for source rock characterisation as well as fluid source rock correlations are reported for the first time the formation of 1 2 bnf seems to be influenced by clay catalysis and the ratio 2 1 1 2 bnf can be used to describe lithofacies this ratio is much lower in sediments from fluvial deltaic systems compared to clay depleted sediments from marine environments e g carbonate sequences for this study the triassic source rocks show ratios of 0 9 1 5 with 25 w w of clay content in the rock whereas the ratios for the middle jurassic source rocks are around 1 6 2 1 with 14 w w of clay content the bnf ratio is lowest in the late jurassic samples 0 8 with 28 w w of clay minerals the ternary plot of 2 1 1 2 2 3 bnfs could be applied to fluid fluid and fluid source rock correlations however further work needs to be done on the factors controlling the abundance of the 2 3 bnf which is more abundant in source rocks compared to the fluids generated and expelled from these

fractionation of dibenzofurans during subsurface petroleum migration based on molecular dynamics simulation and reservoir geochemistry abstract dibenzofurans oxygen containing heterocyclic aromatics are ubiquitous in crude oils their geochemical implications in petroleum geochemistry have been studied in numerous previous publications here we present the distribution of dibenzofuran and its methylated homologues and calculate the polarity and solubility of methyldibenzofuran isomers based on the connolly surfaces and molecular dynamics simulation the results show that the geo chromatographic fractionation effect is evident due to absorption onto the water silica matrix carrier bed during the oil migration process two potential molecular indicators relative to dibenzofurans i e the total content of dibenzofurans and the relative abundances of 1 methyldibenzofuran to 4 methyldibenzofuran are proposed for tracing the oil migration orientation and filling pathways these two indicators were applied successfully in paleozoic marine carbonate and tertiary lacustrine sandstone reservoirs the variations of source input depositional environment and maturity for oils from same source bed kitchen appear to have no significant effect on these two indicators it suggested that these two dibenzofuran indicators are potentially effective molecular tracers for orientation and filling pathways in oil migration

abundance anomalies of aromatic biomarkers in the permian triassic boundary section at meishan china evidence of end permian terrestrial ecosystem collapse several aromatic biomarkers detected in solvent extracts and kerogen pyrolysates from samples of the global stratotype section and point gssp for the permian triassic boundary at meishan china show distinctive relative abundance anomalies that may be related to the end permian biotic crisis on land enrichment of dibenzofuran homologues across the permian triassic boundary may corroborate the concept of excessive soil erosion following loss of rooted vegetation enrichment of alkylphenol entities occurs just below the main marine mass extinction horizon and prior to the characteristic end permian 13c decline the alkylphenols were probably derived from lignin and may provide a molecular record of dieback of woody vegetation highly decreased relative abundances of dibenzothiophenes could be indicative of excessive supply of fe2 it is suggested that fe2 was land derived and may have originated from soils in addition to the permian triassic boundary interval biomarker abundance anomalies also occur around the wuchiapingian changhsingian boundary in the basal part of the meishan section

geochemical comparison of three oil families from the gippsland basin se australia abstract the biomarker and aromatic compounds including polycyclic aromatic hydrocarbons pahs in three oil families composed of 29 crude oils from the gippsland basin se australia were studied using gas chromatography mass spectrometry environment related parameters such as the pr ph ratio and the gammacerane index indicate that all the oils originated from a lacustrine fluvial deltaic environment with fresh water thermal maturity related parameters including aliphatic and aromatic maturity indicators e g c29 sterane isomerisation parameters alkylnaphthalene indices and methylphenanthrene index show that all the oils from the ga1 oil family have a similar thermal maturity in the peak late oil window however oils from the ga2 and gb families vary in thermal maturity and are interpreted to be mixtures of less mature and more mature crude oils source related biomarkers e g isopimarane labdane and phyllocladane and pahs e g retene and oleanane ursane lupane derived aromatic triterpenoids suggest that the ga1 oils were mainly derived from source rocks rich in conifer derived organic matter the organic matter source of the ga2 and gb oil families included both angiosperms and gymnosperms with a relatively stronger angiosperm contribution to the organic matter in the source rock s of the gb oils based on the pah analysis moreover higher plant derived triterpenoids can be effectively used to correlate oil families across the study area supplementing the n alkane carbon isotope and biomarker data of the three oil families reported previously

paleomagnetism of mesozoic and tertiary rocks from east el owenat area southwest egypt ten sites 310 samples from alkali syenite at east el oweinat 23 2 n 29 5 e yield a stable mean direction of magnetization d 340 3 i 19 9 with 95 12 1 k 13 4 n 10 after alternating field cleaning resulting in a pole at 67 8 n 268 8 e with a95 8 6 this pole position agrees with the other upper cretaceous pole positions of africa from seven sites 82 samples from upper cretaceous nubian sandstone at east el oweinat a mean direction d 349 9 i 27 1 with 95 10 1 k 37 8 mixed polarity was obtained after thermal demagnetization combined with previous investigations on nubian sandstone at other localities schult et al 1978 1981 this yields a pole at 80 8 n 238 9 e with a95 3 2 k 435 9 n 30 five sites from tertiary basalt yield a mean direction d 12 4 i 23 9 and 95 9 2 k 46 6 after alternating field cleaning which yield a paleopole position at 74 1 n 159 8 e with a95 6 0 k 107 8 n 5 the paleopole positions of east el oweinant rocks confirm the apparent polar wander path of africa established in previous papers hussain et al 1980 schult et al 1981 more comparisons with rotated south american and australian pole positions after proper reconstructions to africa show agreements with the present results

paleomagnetism of late neoproterozoic african dike swarms from the south eastern desert and the paleo neoproterozoic dataset from egypt paleomagnetic analysis has been carried out on late neoproterozoic dike swarms from two areas along the red sea coast 13 dikes 87 samples close to the um rus gold mine and eight dikes 59 samples at sadi salem rock magnetic experiments indicate that the main carrier of magnetization of these dikes is titanomagnetite and or magnetite most samples display a component of magnetization ca that is in agreement with previously published paleo late neoproterozoic poles from other dikes and from one ore complex but they cluster around the cenozoic 0 60 ma portion of torsvik s gondwana apparent polar wander path apwp when plotted in southern african coordinates we suggest two causes of this behavior remagnetization related to the opening of the red sea or later emplacement of the dikes along pre existing paleo late neoproterozoic fractures will have to be tested with new reliable paleomagnetic data on carefully dated rocks a second component cb seen in many of our samples but which is difficult to estimate is in agreement with late neoproterozoic granite poles and a dike supposed to be triassic in age however all these poles plot on the jurassic cretaceous portion 80 200 ma of torsvik s path these results as well as the cambro carboniferous sediments from sinai and the late neoproterozoic dokhan volcanic formation that cluster around the late paleozoic portion 280 300 ma of torsvik s apwp are tentatively interpreted as global viscous remagnetizations acquired respectively during the cretaceous normal and the kiaman reverse superchrons

palaeomagnetism of some cenozoic sediments cairo fayum area egypt abstract the palaeomagnetic and rock magnetic characteristics of some cenozoic rocks from the cairo fayum area have been investigated a total number of 259 oriented core samples were collected at 32 sites located in rocks of eocene 13 sites oligocene 11 sites and pliocene 9 sites ages most of these rocks carry a weak but stable remanent magnetisation that is principally carried by hematite goethite and magnetite are also found in some samples as subordinate constituents careful thermal demagnetisation successfully enabled the isolation of the characteristic remanent magnetisation normal and reversed polarities that passed a reversal test have been recorded in the three age groups this magnetisation is probably of primary origin and reflects the ages of the rocks the resultant palaeomagnetic poles are considered reliable and represent a good contribution to the african palaeomagnetic database and should help in further refining of the cenozoic apwp for africa

origin and geochemical implication of relatively high abundance of 17α h diahopane in yabulai basin northwest china abstract relatively high abundance of 17 h diahopane has been detected in source rock extracts in the yabulai basin a lacustrine basin in northwest china gas chromatography mass spectrometry gc ms x ray diffraction xrd and field emission environment scanning electron microscope imaging fe esem were used in combination with conventional geochemical parameters to unravel the enrichment mechanisms significant variations of 17 h diahopane concentrations detected in the xinhe formation with similar maturity inferred that thermal evolution is not the unique factor inducing the compound generating the sedimentation of samples rich in 17 h diahopane usually occur under suboxic conditions results of mineralogy analysis suggested that samples with high content of 17 h diahopane are rich in carbonate minerals about 20 wt which might deposit in brackish saline water depositional environment relatively high content of gammacerane is also consistent with the experimental results of xrd based on the viewpoint of moldowan et al 1991 the regular hopanes may be the precursor of the rearranged hopanes with the wagner meerwein rearrangement as the mechanism in this reaction the critical factor of methyl migration is the production of carbocation starting with dehydroxylation we suggested a general scheme for the generation of 17 h diahopane in this study in lacustrine sediments suboxic and brackish environment could catalyze the methyl migration accompanied by carbonate deposit its geochemical implication can be used to reconstruct lacustrine paleoenvironment and contribute to a better understanding on oil oil correlation oil source rock correlation and petroleum system study

a spike of woody plant biomarkers in the deep sea iridium layer at the cretaceous paleogene boundary abstract at the cretaceous paleogene k pg boundary 66 million years ago the chixulub impact resulted in significant environmental changes and a mass extinction of dinosaurs and marine invertebrates such as ammonites here we report that accumulation of woody plant biomarkers in the deep water occurred in the iridium anomaly at 700 km from the impact crater the results reveal that the concentration of terrestrial organic molecules derived from woody plants namely biphenyl and dibenzofuran shows synchronized changes and increases abruptly in the red layer fine ejecta which has an iridium spike above tsunami like coarse deposits indicating a significant increase in the influx of woody plant fragments into the ocean a few years after the impact long chain n alkanes and cadalene derived from land vegetation in the tsunami like coarse deposits prior to the transportation of trees were also transported to the deep sea this implies that transportation of grass to the deep sea started within a few days of the bolide impact transportation of trees then began a few years later a rapid increase in the concentration of dibenzothiophenes also occurs in the red layer indicating that low dissolved oxygen conditions had expanded in the bathypelagic zone over the seafloor an increase in the influx of terrestrial organic matter into the deep ocean could have resulted in the low dissolved oxygen conditions furthermore the stratigraphic distribution of planktonic foraminifera at beloc shows that cretaceous planktonic foraminifera became extinct as the result of an asteroid impact

comprehensive geochemical correlation between surface and subsurface hydrocarbon occurrences in the batman mardin şirnak area se turkey abstract southeast turkey is the main oil producing region of the country located at the northwestern part of the zagros basin in this study we investigated the geochemical characteristics of both surface and subsurface hydrocarbon occurrences in the batman mardin irnak area in southeast turkey to determine whether a genetic relationship exists between the two for this thirty solid bitumens from twenty two different veins along with ten heavy oils and thirteen oil seepage samples from nearby oilfields and seeps were studied using diverse geochemical tools firstly each of the different hydrocarbon types was considered individually with respect to source organofacies level of thermal maturity and degree of biodegradation the results obtained from the source related parameters demonstrate a marine algal source for all investigated samples also lithology determination based on various diasterane tricyclic terpane hopane and homohopane parameters suggests a carbonate source for all samples except for the dadas and iskar seeps clastic thereafter considering the influences caused by thermal and biological alteration processes all heavy oils less mature solid bitumens as well as the less biodegraded seep oils were selected to be correlated using selected additional parameters homohopane distributions reveal that solid bitumens compared to heavy oils and seeps are highly enriched in c31 and depleted in higher homologues possibly due to cracking of high molecular weight homologues to lower ones during and or after solidification processes furthermore the similarities observed for the relative abundances of six series of aromatic hydrocarbons and their alkylated counterparts substantiate strong genetic affinities within the sample set finally compound specific stable carbon isotopes of individual components show that solid bitumens are more enriched in 13c than the heavy oils which is mainly attributed to the preferential removal of light isotopes 12c during solidification our results strongly confirm that turkish solid bitumens are genetically related to the nearby heavy oils thereby providing new information on the petroleum system in this part of the southeast anatolia

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

the stardalur magnetic anomaly revisited new insights into a complex cooling and alteration history abstract this study provides new rock magnetic and magneto mineralogical data including mossbauer spectroscopy of basaltic drill cores from the stardalur volcanic complex iceland in order to better understand the strong magnetic anomaly which is caused by an extraordinary high natural remanent magnetization nrm nrm and magnetic susceptibility display a positive linear correlation r 2 0 81 and reach very high values up to 121 a m and 148 10 3 si although a curie temperature of 580 c and a verwey transition at about 160 c is indicative of magnetite t heating experiments in argon and air atmosphere and thermal demagnetization measurements of nrm revealed a slight cation deficiency according to induced remanent magnetization experiments the remanence is carried solely by this low coercive phase minor titanomaghemite with a t c at about 340 c only occurs in samples with larger oxide grains 20 80 m high vesicle abundances and the exsolution texture of fe ti oxides suggest subaerial extrusion of the lava a high oxygen fugacity probably above the nno buffer and a low ti ti fe ratio of the basaltic melt are suggested as a precondition for high concentration of magnetic minerals and therefore high primary trm during high temperature oxidation ilmenite exsolution lamellae developed in titanomagnetite and symplectic magnetite pyroxene formed by the breakdown of olivine this secondary magnetite grown at temperatures above the curie temperature increases the primary trm early stage hydrothermal alteration below about 375 c led to maghemitization of titano magnetite clearly indicated by shrinkage cracks and irreversible t curves during later stage hydrothermal alteration nrm intensity increased slightly due to the growth of secondary magnetite at lower temperatures about 250 300 c this hydrothermally formed magnetite acquired only a low crm but increased magnetic susceptibility significantly according to our results it is suggested that hydrothermal alteration does not necessarily lower remanent magnetization but contributes to an increase in magnetization the interplay of the three factors melt composition small grain sizes of secondary magnetite due to decomposition of silicates and new formation under hydrothermal conditions caused the strong magnetic anomaly at the surface

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

heterocyclic aromatic hydrocarbon distributions in petroleum a source facies assessment tool abstract this study reports a novel source facies assessment application from distributions of heterocyclic aromatic hydrocarbons in petroleum i e dibenzothiophene dbt dibenzofuran dbf and fluorene f to illustrate the approach initially a large set of crude oils from global petroleum basins are geochemically characterized based on source facies organic matter type and environment of deposition variation petroleum bulk properties and molecular distributions of isoprenoids terpanes steranes and related parameters are applied to demonstrate the source facies and maturity of the entire oil suite and to delineate the oil suite into marine carbonate marine shale marine shale with terrigenous organic matter om coaly and lacustrine source facies families from within this interpretive context the relative percentages of hetercyclic aromatic hydrocarbons are reported and discussed from each of these source facies families a triplot drawn from the percentages of dbt dbf and f is shown to effectively differentiate the oils source facies classifications marine carbonate oils show highest dbt plotted in the dbt vertex freshwater lacustrine sourced oils positioned near to 100 f vertex coaly sourced oils revealed highest dbf the marine shale and marine shale with terrigenous om oil families plotted away from three vertices and represent a distinctive position with in the triplot these results establish an effective source facies assessment tool triplot based on heterocyclic aromatic hydrocarbon distributions these novel signatures which are derived from variations in the chemical composition of source rocks hence kerogen lead to the occurrence of kerogen catalysis in sedimentary reaction like carbon catalysis for the formation of heterocyclic aromatic hydrocarbons

biomarker signatures of upper cretaceous latrobe group petroleum source rocks gippsland basin australia distribution and geological significance of aromatic hydrocarbons abstract aromatic hydrocarbons extracted from upper cretaceous maastrichtian and campanian latrobe group coaly shales and shales from the gippsland basin were investigated by gas chromatography mass spectrometry a variety of 2 ring to 6 ring aromatic hydrocarbons were identified including both higher plant derived and combustion derived polycyclic aromatic hydrocarbons pahs these aromatic compounds indicate that the upper cretaceous coaly shales and shales were deposited in a fluvial deltaic environment with significant higher plant input and are at a relatively low thermal maturity stage higher plant parameters and angiosperm gymnosperm indices based on aromatic components suggest that higher land plants including both angiosperms and gymnosperms were an important part of the palaeovegetation in the upper cretaceous the aromatic angiosperm gymnosperm index that includes chrysene and picene type pahs is not as reliable for evaluation of relative angiosperm and gymnosperm contributions as the aliphatic indices due to input of combustion derived pahs and the complexity of burning conditions altering the relative contributions however combustion derived pahs and aromatic angiosperm gymnosperm indices supplement the information from aliphatic hydrocarbons and provide further evidence to support the hypothesis that palaeoclimate cooled from the campanian to the maastrichtian

two phases of cretaceous tertiary magmatism in the eastern desert of egypt paleomagnetic chemical and k ar evidence abstract paleomagnetic and radiometric data confirm the existence of two phases of igneous activity in the late mesozoic and cenozoic history of eastern egypt in the mid to late cretaceous the earlier and more extensive episode produced the wadi natash alkaline basalts and numerous small trachytic intrusions the ring complexes of abu khrug and gebel el kahfa were also emplaced at this time the mean paleopole position for the intrusive rocks is at 65 3 n 111 2 w a 95 11 4 31 sites chemical analyses of the trachytes show that they are enriched in nb zr and y and depleted in sr ba cr and ni suggesting either prolonged fractionation or limited partial fusion the second phase of activity during oligo miocene time is represented by small tholeiitic basalt flows on the red sea coast and along the nile valley the mean paleopole position for the flows is at 68 2 n 101 5 e a 95 27 8 3 sites the wide scatter is interpreted as reflecting secular variation the chronological and chemical data are used with studies of sedimentary formations coeval with the igneous rocks to apply a general model of continental rifting to the northern red sea the earlier alkaline phase of igneous activity is related to regional uplift while the second tholeiitic phase is associated with widening of the rift valley

organic geochemical and paleoenvironmental characterization of the brown shale formation kiliran sub basin central sumatra basin indonesia abstract the central sumatra basin csb formed during the late eocene to early oligocene is the most prolific hydrocarbon basin in indonesia the brown shale formation of the pematang group is the sole known source rock for the tens of billions of barrels of oil located in the csb samples analyzed in this study were from the karbindo coal mine in the kiliran graben of the kiliran sub basin located on the western side of the csb this study incorporates advanced organic geochemical and petrographical data of samples from the brown shale formation as well as interpretations from previous studies at this location to construct a detailed paleoenvironment model for this tertiary lake the lacustrine source rock was deposited under fresh water conditions with subtle changes in the environment that resulted in significant changes in ecologies based on new data from organic petrography biomarkers microscale sealed vessel pyrolysis and characterization of the polyaromatic hydrocarbons the organic matter in the brown shale formation was determined to be sourced primarily from lacustrine organisms with a small amount of terrestrial plant input 4 methylsterane concentrations and n alkane distributions indicate that non marine dinoflagellates and botryococcus braunii a race were likely a significant portion of the local biosphere

changes in biomarker abundances and sulfur isotopes of pyrite across the permian triassic p tr schuchert dal section east greenland abstract in this study we report on biomarker abundances through parts of the permian triassic boundary ptb of schuchert dal east greenland that contains rich marine faunal records and excellent terrestrial palynological records biomarker abundances and sulfur isotopes are used to correlate the series of events including changes in element cycling and associated redox conditions of the ocean surrounding the collapse of the marine and terrestrial ecosystems through this record of a major crisis of life on earth during a mass extinction episode the upper schuchert dal formation contains a low diversity palynological assemblage ascribed to arborescent cordiaite conifer pteridosperm vegetation samples from this pre collapse interval are characterised by high abundances of dibenzofuran dbf dibenzothiophene dbt and biphenyl since these compounds have similar base structures and show comparable abundance curves it is plausible that they probably derive from a common source we propose that phenolic compounds of lignin of the woody plants present during this period could be the source for dbf dbt and biphenyl the redox conditions during this period of time also support the formation of dbf and dbt just above the extinction interval there is a dramatic decrease in the abundances of dbf and dbt which occurs at the same time as a sudden change in the stable sulfur isotopic composition 34s of pyrite indicating a change in redox conditions from oxic to anoxic euxinic conditions 34s values leading up to the extinction are highly depleted in the heavy sulfur isotope about 40 vs vcdt whilst shortly after the extinction interval much more positive isotope values are observed about 25 an inferred change in the biogeochemical sulfur cycle is supported by facies evidence from similar neighbouring sections it is suggested that two processes are operating closely here 1 changes in redox conditions and 2 extinction and or transgression accounting for the absence of woody material

aliphatic and aromatic biomarkers from carboniferous coal deposits at dunbar east lothian scotland palaeobotanical and palaeoenvironmental significance carboniferous visean coals from dunbar east lothian scotland contain well preserved miospore and megaspore assemblages suggesting a lycopod dominated forest ecosystem with some ferns sphenopsids and pteridosperms the low rank of the coals and the well defined microflora permit assessment of the palaeoenvironmental significance of lipid biomarkers during the early carboniferous rock eval petrographic and lipid analyses indicate a fully terrestrial depositional environment although we also present and discuss a wide diversity of other lipid biomarkers alkanes hopanoids steroids we focus on the terrestrial derived biomarkers combustion derived pahs pyrene fluoranthene benzo a anthracene chrysene and triphenylene indicate the occurrence of forest fires in the study areas during early carboniferous times alkyldibenzofurans are considered to derive from lichen biomass retene cadalene simonellite tetrahydroretene and kaurane are poorly specific and can derive from a variety of early palaeozoic land plants abietane phyllocladane ent beyerane and 4 h eudesmane as well as bisnorsimonellite diaromatic totarane diaromatic sempervirane and 2 methylretene however as yet had only been reported from conifers which do not appear in the fossil record until the late carboniferous within the lower carboniferous forest ecosystem arborescent lycopsids and pteridosperms are proposed as alternative sources for these compounds

a forest fire and soil erosion event during the late devonian mass extinction abstract the late devonian mass extinction occurred in a stepwise manner and culminated close to the frasnian famennian f f boundary 372 million years ago organic molecular indices from marine sedimentary rocks at the sinsin section belgium indicate that the sequence of combustion of land vegetation soil erosion and anoxia euxinia occurred close to this boundary the increased concentrations of biomarkers indicating forest fire and soil erosion measured in the sinsin section suggest that fire became widespread at this time leading to various damaging consequences increased runoff and oceanic anoxia that caused marine extinctions magnetic susceptibility data in the sinsin section indicate a relatively dry climate spanning the f f boundary which would have encouraged forest fires the study of organic biomarkers presents several lines of evidence to link forest fire and soil erosion to the late devonian mass extinction

high resolution estimates of nubia somalia plate motion since 20 ma from reconstructions of the southwest indian ridge red sea and gulf of aden

the potential role of redox reactions for the distribution of alkyl naphthalenes and their oxygenated analogues in terrestrial organic matter of late palaeozoic age abstract the occurrence and distribution of alkyl naphthalenes and alkyl phenanthrenes in 39 late palaeozoic coal and sediment samples containing predominantly terrestrial organic matter is related to thermal maturity and biological source input this study investigates the relationship between aromatic hydrocarbons and the corresponding aldehydes ketones carboxylic acids and dicarboxylic acids based on the naphthalene skeleton it is suggested that alkyl naphthalenes are oxygenated in the sediments the behaviour of alkyl phenanthrenes and their oxygenated analogues is discussed in this context alkyl naphthalenes and phenanthrenes were abundant in all samples the low polarity nitrogen sulfur and oxygen compound fraction was characterised by the presence of alkyl naphthaldehydes and naphthyl ketones for the majority of the samples the presence of naphthalene carboxylic acids and anthracene phenanthrene carboxylic acids was restricted to samples of relatively enhanced maturity vitrinite reflectance rr 0 67 1 26 with one exception the correlations between the different classes of compounds based on the naphthalene skeleton led to the hypothesis that within the maturity range investigated aldehydes and ketones were readily formed from the corresponding aromatic hydrocarbons while the carboxylic acids were formed at elevated maturity for alkyl naphthalene dicarboxylic acids two formation pathways are suggested because of two different distribution patterns a direct correlation of these dicarboxylic acids with the occurrence of other compounds having a naphthalene skeleton was not apparent

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

organic geochemical characterisation of sediments from the sakoa coalfield madagascar abstract eleven coals and five mudstones of the sakoa coalfield southwest madagascar have been characterised by microscopy rock eval pyrolysis and detailed analysis of c 12 aromatic and c 15 saturated hydrocarbon fractions of the organic extracts average vitrinite reflectance of 0 77 r r and t max of 439 c indicate moderate thermal evolution of the organic matter corresponding to the beginning of catagenesis which is confirmed by molecular indicators based on aromatic hydrocarbons and saturated biological markers the average methylphenanthrene index mpi 1 of 0 69 corresponding to a calculated vitrinite reflectance r c of 0 81 is in agreement with an isomerisation of selected steranes and triterpanes having not yet reached equilibrium maceral compositions and molecular distributions of saturated and aromatic hydrocarbons are typical of organic matter mainly derived from terrestrial higher plants with significant contributions of bacteria and a minor input of algae the hydrocarbon potential in terms of hydrogen index hi values of the coal samples varies between 83 and 284 mg hydrocarbons hc g c org i e in approximately the same range as that commonly observed for high volatile bituminous coals carbon normalised concentrations of c 12 aromatic and c 15 saturated hydrocarbons generally are higher in the coals than in the mudstones thus suggesting expulsion of heavier hydrocarbons was relatively ineffective in sakoa coals

aliphatic and aromatic biomarkers from gondwanan sediments of late ordovician to early devonian age an early terrestrialization approach abstract twenty one core samples of late ordovician to early devonian age from sections in southern tunisia north african platform gondwana and containing marine and terrestrial organic matter with microbial input were investigated to link the aliphatic and aromatic hydrocarbon distributions with the terrestrial and marine palynomorph content e g acritarchs prasinophytes chitinozoans cryptospores and trilete spores in addition to several biomarkers of algal bacterial origin long chain n alkanes that might be derived from land plants as well as the terrestrial diterpane norabietane were found several land plant derived biomarkers such as retene cadalene simonellite tetrahydroretene and c19 isohexylalkyl naphthalene were observed in the aromatic fractions while these terrestrial biomarkers could be clearly recognized in the middle silurian lower devonian samples their presence in the upper ordovician lower silurian sediments is more doubtful because of much lower relative abundances the land plant biomarkers show a fairly good correlation with the occurrence and abundance of cryptospores and trilete spores derived from bryophytes and tracheophytes which covered the emerged areas around the ghadamis basin during the silurian and devonian the early tracheophytes e g cooksonia lycophytes and zosterophylls are therefore suggested as a new terrestrial source for most of the saturated and aromatic biomarkers found in sediments of middle silurian to early devonian age

biomarker distributions in crude oils and source rocks from different sedimentary environments abstract the saturated and aromatic hydrocarbons from a significant number of oils and source rocks derived from terrestrial and marine organic matter have been analysed by gc and gc ms results show that certain classes of biomarkers including bicyclic sesquiterpanes tricyclic terpanes pregnanes methylsteranes rearranged steranes hopane sulfides benzohopanes long chain alkylbenzenes and pentacyclic triterpanes can be used to distinguish differences in source input and or depositional environments variations in the distributions of the naphthalenes phenanthrenes fluorenes dibenzofurans dibenzothiophenes naphthobenzothiophenes and triaromatic steroid hydrocarbons may also reflect disparities in source input or sedimentary environments

interpreting lake isotope records of holocene environmental change in the eastern mediterranean oxygen isotope records from lake sediment archives are becoming an increasingly common tool for palaeoenvironmental reconstruction we discuss their interpretation in the eastern mediterranean region with particular reference to three records zeribar van and eski acigol during the holocene the latter two records have been interpreted as controlled by changes in the precipitation to evaporation ratio and the first due to changes in precipitation seasonality in light of recent isotope work in the region and comparison with other proxy data from the same lakes we show both of these initial interpretations to be oversimplified careful interpretations of complex lake isotope systems are therefore required in order that palaeoclimatic inferences are drawn correctly

age and origin of the well preserved organic matter in internal sediments from the silesian cracow lead zinc deposits southern poland the molecular and petrographic characteristics of organic matter in internal sediments from the mississippi valley type lead zinc deposits in southern poland reveal immature and well preserved organic matter huminite reflectance values of organic matter in all internal sediments are low with a mean value of 0 29 corresponding to a lignite range of coalification most organic compounds in the organic matter e g cadalene retene simonellite perylene and sitosterol and its transformation products stigmastanol and stigmasta 3 5 dien one as well as lignin degradation compound products e g benzoic acid vanillin 4 benzaldehyde benzenedicarboxilic acids and hydroxybenzoic acids are of terrestrial origin monosaccharides with dominant and glucose were identified as possible remnants of cellulose degradation products suggesting an excellent state of organic matter preservation given that monosaccharides are preserved only under conditions of limited oxygen after sedimentation resulting from the rapid accumulation of internal sediments in meteoric paleokarst cavities followed by insignificant diagenesis petrologic and palynological data on internal sediments clearly indicate a middle triassic age for organic matter and for the development of a triassic meteoric karst system immediately after anisian carbonate sedimentation

oleananes in oils and sediments evidence of marine influence during early diagenesis abstract the oleananes as markers for the angiosperms provide valuable source and age information when present in an oil nevertheless they are not quantitatively related to the land plant input and indeed their presence reflects only a small leak in diagenetic processes leading primarily to aromatic oleanoids because they are minor products the abundance of oleananes in terrigenous oils and sediments may be highly sensitive to changes in early diagenetic conditions here we present evidence that contact of plant matter with seawater during early diagenesis enhances the expression of oleananes in a mature sediment or oil oleananes are absent or present at very low concentrations in samples from the base of an eocene coal seam affected by postdepositional seawater intrusion however their abundance increases toward the top of the seam in correlation with organic sulphur dibenzothiophene phenanthrene and the homohopane index similarly in deltaic sediments from the south sumatra basin oleanane hopane is strongly correlated with indicators of marine influence such as c 27 c 29 steranes and the homohopane index in each case increasing oleanane abundance is accompanied by a reduction in the extent of aromatisation and for the south sumatra basin the proportion of a ring contracted oleananes an angiosperm derived miocene coal from the philippines deposited under freshwater conditions shows abundant aromatic oleanoids but no oleananes these results show that oleananes need to be used with caution as age and source markers in fluvio deltaic and lacustrine petroleum systems on the other hand their sensitivity to early diagenetic conditions may make them useful in locating effective source rocks in such systems

effects of weathering on organic matter abstract bulk geochemical petrographical mineralogical and molecular compositions of unweathered weathered and transitional zones of a middle jurassic fossil wood were analyzed to trace changes caused by oxidative weathering of the immature terrestrial organic matter om the occurrence of such zones was confirmed by the mineral composition showing replacement of siderite and pyrite by goethite vitrinite reflectance analysis of weathered and unweathered fossil wood samples revealed that weathering elevated the vitrinite reflectance values by ca 0 1 which should be taken into account during modeling of low maturity terrestrial om in the weathered part of the wood most of the biomarkers and biomolecules were totally removed or the concentration decreased significantly the concentration of most of the polynuclear aromatic hydrocarbons pahs decreased by 50 80 being 90 for the more reactive and less stable benzo a pyrene and perylene on the other hand several aromatic compounds like phenanthrene and its methyl derivatives phenyl naphthalenes fluoranthene and oxygen containing aromatic compounds increased in concentration in the weathered zone this results from processes such as formation of phenyl derivatives of pahs and their cyclization as well as aromatization of diterpenoids and incorporation of oxygen into aromatic structures weathering should always be considered in studies of fossilized terrestrial om especially in the case of thermal maturation modeling because it significantly decreases the om content and total sulfur content changes vitrinite reflectance values and alters the extract composition as a result of organic compound degradation

global plate motion frames toward a unified model 1 plate tectonics constitutes our primary framework for understanding how the earth works over geological timescales high resolution mapping of relative plate motions based on marine geophysical data has followed the discovery of geomagnetic reversals mid ocean ridges transform faults and seafloor spreading cementing the plate tectonic paradigm however so called absolute plate motions describing how the fragments of the outer shell of the earth have moved relative to a reference system such as the earth s mantle are still poorly understood accurate absolute plate motion models are essential surface boundary conditions for mantle convection models as well as for understanding past ocean circulation and climate as continent ocean distributions change with time a fundamental problem with deciphering absolute plate motions is that the earth s rotation axis and the averaged magnetic dipole axis are not necessarily fixed to the mantle reference system absolute plate motion models based on volcanic hot spot tracks are largely confined to the last 130 ma and ideally would require knowledge about the motions within the convecting mantle in contrast models based on paleomagnetic data reflect plate motion relative to the magnetic dipole axis for most of earth s history but cannot provide paleolongitudes because of the axial symmetry of the earth s magnetic dipole field we analyze four different reference frames paleomagnetic african fixed hot spot african moving hot spot and global moving hot spot discuss their uncertainties and develop a unifying approach for connecting a hot spot track system and a paleomagnetic absolute plate reference system into a hybrid model for the time period from the assembly of pangea 320 ma to the present for the last 100 ma we use a moving hot spot reference frame that takes mantle convection into account and we connect this to a pre 100 ma global paleomagnetic frame adjusted 5 in longitude to smooth the reference frame transition using plate driving force arguments and the mapping of reconstructed large igneous provinces to core mantle boundary topography we argue that continental paleolongitudes can be constrained with reasonable confidence

geochemical and petrophysical source rock characterization of the vaca muerta formation argentina implications for unconventional petroleum resource estimations abstract the vaca muerta formation is currently regarded as the most prolific source rock interval for unconventional petroleum exploration in argentina in this study we integrate recent ct scanner nuclear magnetic resonance nmr t1 t2 and rock eval shale play analytical techniques combined with classical geochemical petrological and petrophysical methods to characterize vaca muerta source rocks along a vertical profile the proposed analytical workflow was tested here on 4 samples derived from one core the lje 1010 borehole drilled in the lowermost jurassic vaca muerta member neuquen basin argentina to evaluate the unconventional hydrocarbon potential and pore network attributes first entire rock samples were analyzed by dual energy ct scanner to evaluate possible heterogeneities this also helped in the selection of representative samples then the organic matter properties were investigated by open system pyrolysis techniques organic petrography and biomarker analyses as a function of the core depth a comparative approach between open system pyrolysis methods e g rock eval basic bulk rock shale play methods vs source rock analyzer is also illustrated in this work finally petrophysical characteristics and pore network attributes in shale were estimated by gas permeability steady state method corrected for klinkenberg effect porosity and nmr methods the investigated samples have oil window maturity and are characterized by a network of solid bitumen based on new rock eval shale play data the potentially producible oil present in the rock samples was estimated using the modified oil saturation index osi sh0 sh1 peaks 100 toc results indicate that the oil crossover effect and potential productive oils occur within intervals showing higher toc values 3 to 8 wt we also illustrated here that for unconventional shale play perspectives rock eval shale play parameters sh0 sh1 allow to obtain both a better quantification of free and retained hydrocarbons in source reservoir rock samples and correct original oil in place ooip estimations in early exploration campaign for shale oil and shale gas assessment for vaca muerta rock samples ooip estimations range from 60 to 160 bbl oil acre ft approximately we also demonstrated that the solid bitumen oil and organic matter are clearly distinguished in the studied samples using advanced nmr t1 t2 maps obtained at different temperatures the solid bitumen was clearly evidenced as a peak with t1 t2 ratio 14 on nmr t1 t2 maps concerning the matrix bulk rock permeability the obtained results showed that the most deep sample is characterized by a permeability of about 140 nanodarcy nd whereas the shallower sample containing also higher amounts of organic matter is more permeable 213 nd indicating that toc values play a main control on vaca muerta poromechanical characteristics the maximum total porosity values range between 6 5 and 21 8 and were calculated in this work integrating nmr and helium porosity values finally global interpretations of these obtained results suggest that the vaca muerta formation could be considered as a prolific shale play interval for unconventional petroleum exploration in the near future

dibenzothiophenes and benzo b naphthothiophenes molecular markers for tracing oil filling pathways in the carbonate reservoir of the tarim basin nw china abstract dibenzothiophenes dbts and benzo b naphthothiophenes bnts are the main sulfur containing heterocyclic aromatic compounds in crude oils and sedimentary rock extracts because of the relatively higher electronegativity and an unshared pair of electrons in the outer shell orbital of the sulfur atom hydrogen bonds can be formed between the sulfur and hydrogen atoms of the surrounding medium in carrier beds therefore dbts and bnts are potential geochemical markers for tracing oil filling pathways a correlation of oils in the halahatang oilfield of the tabei uplift in the tarim basin nw china shows that the molecular marker compositions of all oils are quite similar implying that these oils have been sourced from the same source kitchen and belong to a same oil family using molecular indicators relative to dbts and bnts namely 4 1 mdbt 4 1 methyldibenzothiophene 4 6 1 4 1 6 dmdbt 4 6 1 4 1 6 dimethyldibenzothiophene 2 6 3 6 1 4 1 6 dmdbt 2 6 3 6 1 4 1 6 dimethyldibenzothiophene and 2 1 bnt 2 1 bnt 1 2 bnt benzo b naphtho 2 1 d thiophene benzo b naphtho 2 1 d thiophene benzo b naphtho 1 2 d thiophene this paper traces the oil migration orientation and filling pathways in this oilfield the isopleth maps of these molecular indicators unequivocally reveal an overall oil migration filling points and preferred filling pathways orientation from south to north based on this a potential source kitchen is predicted in the southern part of the halahatang depression most probably at the manxi shuntuoguole low uplift just between the awati and manjiaer depressions the southern part of the halahatang depression along the oil charging pathways is predicted to be the most promising region for oil exploration

cenozoic to cretaceous paleomagnetic dataset from egypt new data review and global analysis abstract different phases of igneous activity took place in egypt during the mesozoic and the cenozoic and oriented samples were collected from three cenozoic localities baharya oasis in the western desert abu had in the eastern desert and quseir along the red sea coast and four cretaceous localities toshki abu simbel south of aswan and shalaten abu shihat along the red sea coast rock magnetic properties of the samples indicate magnetite and titanomagnetite as the main carrier of the remanent magnetization following stepwise demagnetization characteristic remanent directions were identified only for 62 of the samples a fairly low rate for that type of samples and 8 new paleomagnetic poles were calculated all our cenozoic poles fall clearly off master polar wander paths proposed for south africa therefore all paleomagnetic results previously published for egypt were compiled from cretaceous to quaternary the published poles largely overlap blurring the egyptian apparent polar wander path a new analysis at the site level was then carried out only poles having a kappa larger than 50 were selected and new pole positions were calculated by area and by epoch when at least 3 sites were available even though the selection drastically reduced the number of considered poles it allows definition of a reliable cenozoic apparent polar wander trend for egypt that differs from the south african master polar wander path by about 10 15 if the cretaceous igneous poles are in good agreement with the rest of the african data the sedimentary poles plot close to the cenozoic portion of the south african master polar wander path a discrepancy that could be related either to inclination flattening and or error on age and or remagnetization in the cenozoic

oxygen containing aromatic compounds in a late permian sediment in northern italy the base of the tesero oolite horizon represents the lithological boundary between the bellerophon and werfen formations and marks one of the most dramatic environmental perturbations in phanerozoic time the marl which directly underlies the tesero horizon contains many indicators of environmental change during the end permian mass extinction at vigo meano near trento the marl is relatively thermally immature and contains abundant terrestrially sourced oxygen containing aromatic compounds such as xanthones dibenzofurans and dibenzo p dioxin as well as abundant alkylated naphthalenes

active concomitant counterclockwise rotation and northwards translation of africa during the albian campanian time a paleomagnetic study on the wadi natash alkaline volcanic province 104 78ma south eastern desert egypt abstract africa was a key tectonic unit in the geologic evolution of the tethyan realm in the middle late cretaceous during the rifting of the south equatorial atlantic ocean this research sheds light on the tectonic evolution of africa during the albian campanian time the two end members of the wadi natash alkaline volcanic province wnavp 104 78 ma in the south eastern desert of egypt were studied paleomagnetically the wnavp 24 5 n 34 25 e is made up of a thick succession of differentiated lava flows grading from alkali olivine basalt aob followed by hawaiite mugearite and benmoreite flows with abundant sandstone interbeds all intruded by a large number of trachyte phonolite tr ph circular lava domes and ring dykes forming conspicuous landmarks in the province the oldest flows of the aob 104 7 ma and the youngest tr ph plugs and ring dykes 86 78 ma as well as the interbedded turonian taref sandstone formation previously known as nubian sandstone were sampled all over the province which covers more than 500 km 2 the isothermal remanent magnetization irm study pointed to magnetite family as the major remanence in wadi natash volcanics with little contribution from goethite hematite minerals on the other hand goethite and or hematite are the dominant remanence carriers in the interbedded taref sandstone after the progressive stepwise thermal demagnetization of all samples the characteristic remanence chrm direction for each rock type was visually isolated and its best fit line was calculated followed by the site means rock unit means and the paleomagnetic poles this paleomagnetic study revealed that 1 in the tilt corrected coordinates the mean chrm of the oldest aob flows n 12 sites was dec inc 340 10 k 54 95 6o yielding a north pole at 55 n 250 e the chrm of the youngest tr ph ring dykes and plugs n 10 sites was dec inc 354 3 5 k 60 95 6 3o yielding a north pole at 66 5 n 229 e 2 on the other hand the site mean chrms of the taref sandstone interbeds n 8 sites in the present day in situ coordinates are clustered around the present day geomagnetic field with a mean dec inc 3 33 k 37 95 9 3 yielding a north pole at 83 n 191 e the two paleomagnetic poles of the aob and the tr ph are in accordance with albian campanian poles from africa including madagascar and those rotated from the main cratons such as the north american craton europe including greenland and iberia south america and india using the published plate kinematics and paleomagnetic euler pole pep rotation parameters paleogeographically the two obtained poles of wadi natash volcanics place the african plate at two different azimuths and paleolatitudes during albian cenomaniam and santonian middle campanian tectonically these two paleomagnetic poles point to an active synchronous northwards translation associated with a counterclockwise rotational convergence of africa towards eurasia during the albian campanian time between the time of the aob eruption 104 7 ma and the intrusion of the tr ph 86 78 ma africa concomitantly rotated counterclockwise about 14 and translated northwards towards eurasia about 6 of latitude