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

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

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

secular changes in environmental stresses and eukaryotes during the early triassic to the early middle triassic abstract the early triassic following the end permian mass extinction was an interval of severe low diversity increasing amounts of evidence demonstrate that variable environmental stresses were widespread and intense after the end permian mass extinction here we report biomarkers from lowest triassic to lower middle triassic strata in south china qingyan and chaohu sections including biomarkers for environmental stress 2 methyl hopane index and eukaryotic algae steranes and c21 n alkylbenzene ratio using the 2 methyl hopane index we detected the persistence of environmental stress during most of the early triassic using steranes and the c21 n alkylbenzene ratio we found a gradual increase in the biomass of eukaryotic algae during the early to early middle triassic a decrease in environmental stress in the qingyan section leidapo member during the early middle triassic was synchronous with the explosion of the qingyan biota which is characterized by a high abundance and diversity of invertebrate marine animals because the environmental stresses revealed by the 2 methyl hopane index encompass various factors e g ph and temperature we cannot identify the exact stresses at that time however our results reflect the amelioration of harsh environments for life during the interval of complete biotic recovery

sensitivity of the ocean state to lee wave driven mixing abstractdiapycnal mixing plays a key role in maintaining the ocean stratification and the meridional overturning circulation moc in the ocean interior it is mainly sustained by breaking internal waves two important classes of internal waves are internal tides and lee waves generated by barotropic tides and geostrophic flows interacting with rough topography respectively currently regarding internal wave driven mixing most climate models only explicitly parameterize the local dissipation of internal tides in this study the authors explore the combined effects of internal tide and lee wave driven mixing on the ocean state a series of sensitivity experiments using the geophysical fluid dynamics laboratory cm2g ocean ice atmosphere coupled model are performed including a parameterization of lee wave driven mixing using a recent estimate for the global map of energy conversion into lee waves in addition to the tidal mixing parameterization it is shown that although the global energy input in

novel tricyclic and tetracyclic terpanes in tertiary deltaic oils structural identification origin and application to petroleum correlation abstract tricyclic terpanes of the cheilanthane series in crude oils and sediments are routinely used for geochemical correlation the cheilanthanes are particularly useful to identify crude oils derived from marine clastic or carbonate source rock as well as input to the source rocks from marine algal or terrigenous organic matter however they sometimes have limitations for the correlation of oils expelled from different source rocks that received similar organic matter e g oils from source rocks dominated by terrigenous organic matter novel non cheilanthane tricyclic terpanes consisting of c21 and c25 compounds and a c27 tetracyclic terpane were identified in oils from the assam india beaufort mackenzie canada and the niger nigeria deltas nmr data reveal that all three compounds have an oleanane type structure with rings c d and e intact while rings a and b have been degraded leaving a side chain attached to ring c in the case of the tricyclics and only a degraded a ring in the tetracyclic on the basis of occurrence nmr structure and co variance with oleanane abundance these new tricyclic and tetracyclic compounds are believed to form from a ring functionalised oleanoid precursors in angiosperm flowering plants the distribution of these compounds in representative oils from the niger delta accumulations permits separation of the oils into at least three distinct source rock organofacies

oil oil and oil source rock correlations in the carpathian foredeep and overthrust south east poland abstract the chemical composition of 35 crude oils and the extracts of potential source rock samples from south east poland were studied in detail by geochemical methods in order to understand their genetic relationships twenty six oils including three seep samples were collected from cretaceous to oligocene reservoirs within the carpathian overthrust nine oils originated from carboniferous to miocene reservoirs within the carpathian foredeep the rock samples studied were selected after rock eval pyrolysis screening of a large suite of samples and consist of one lower cretaceous sample and five oligocene menilite shale samples from three different outcrop locations all within the carpathian overthrust geochemical fingerprinting indicates at least two families of crude oils the first represented only by one oil has no specific characteristics except for a light carbon isotope composition the second family is characterized by the presence of 28 30 dinor hopane oleanane and a highly branched isoprenoid c25 alkane within this latter family four subfamilies were recognized a 19 oils having the aforementioned characteristics b seven oils similar to subfamily a but with a relatively high sulphur content c one oil with high abundance of higher plant derived triterpanes and d seven oils with abundant 28 30 dinor hopane although maturity influences the relative abundance of 28 30 dinor hopane it suggested that subfamilies a b and c had an initial low 28 30 dinor hopane content whereas subfamily d an initial high 28 30 dinor hopane content only one oil of subfamily a could potentially be a high maturity counterpart of subfamily d a palaeozoic source rock is suggested for the first family and the second family including the majority of the pils from the carpathian foredeep is most likely derived from the oligocene menilite shales an oil source rock relationship with the menilite shale is supported by the presence although not in all samples studied of 28 30 dinor hopane oleanane or its precursors and the highly branched isoprenoid alkane the strong facies variations observed within this shale gave rise to the different types of crude oils in the second family

internal waves and turbulence in the antarctic circumpolar current abstractthis study reports on observations of turbulent dissipation and internal wave scale flow properties in a standing meander of the antarctic circumpolar current acc north of the kerguelen plateau the authors characterize the intensity and spatial distribution of the observed turbulent dissipation and the derived turbulent mixing and consider underpinning mechanisms in the context of the internal wave field and the processes governing the waves generation and evolution the turbulent dissipation rate and the derived diapycnal diffusivity are highly variable with systematic depth dependence the dissipation rate is generally enhanced in the upper 1000 1500 m of the water column and both the dissipation rate and diapycnal diffusivity are enhanced in some places near the seafloor commonly in regions of rough topography and in the vicinity of strong bottom flows associated with the acc jets turbulent dissipation is high in regions where internal wave energy is high consistent with the idea that i

gc ms identification of biomarkers in road asphalts and in their parent crude oils relationships between crude oil maturity and asphalt reactivity towards weathering abstract asphalt cements vacuum residues of petroleum used as binders for road construction can undergo weathering phenomena or natural oxidation to various degrees depending on their chemical structures and on their origin the first aim of this study was to determine the characteristics of the source rocks generating the parent crude oils the second aim was to correlate the chemical structures of recovered asphalt cements to the genesis data of their parent crude oils in order to predict their sensitivity towards weathering towards these ends saturated fractions of sixteen asphalt cements and their parent crude oils have been analysed by gc ms sir many linear branched and naphthenic compounds from the saturated hydrocarbon fraction have been identified hopanes m z 191 norhopanes m z 177 163 and steranes m z 217 and 218 have been selected to characterize original and weathered asphalts as well as their parent crude oils using geochemical indices t s t s t m c29 steranes etc aliphatic structures of the asphalts and corresponding crude oils could be differentiated through principal component analysis pca the selected variables involve geochemical indices and asphalt rheological characteristics results are in good agreement with the classification obtained from ftir indices linear alkanes branched aliphatics aliphatics versus aromatic structures etc moreover good correlations in geochemical indices have been found between asphalts and their parent crude oils finally it was also possible to predict some rheological properties e g stiffness at low temperature using a multilinear regression which involves geochemical indices of parent crude oils before any physical transformation distillation etc and ftir indices of corresponding asphalt cements

tracing early charged oils and exploration directions for the wenchang a sag western pearl river mouth basin offshore south china sea the wenchang a sag is the largest petroleum producing sub depression in the western pearl river mouth basin offshore south china sea the eocene wenchang formation and the early oligocene enping formation are the two major source rocks in the sag the oil discoveries in this region mainly originated from the enping fm how to objectively estimate the petroleum potential of the wenchang fm and trace the wenchang oils has long been the focus of research and exploration in this region in this paper inclusion oils obtained from reservoir sandstones as well as typical reservoir oils and potential source rocks were investigated by systematic geochemical methods oil oil and oil source rock correlations indicate that inclusion oils in the central and marginal areas of the wenchang a sag had similar geochemical characteristics and mainly originated from the wenchang source rocks the reservoir oils in the central area are derived mainly from the enping source rocks while in the marginal areas they have mixed characteristics of both the enping and wenchang formations combining the tectonic sedimentary evolution and petroleum generation histories it is concluded that the two source rocks in the wenchang a sag have generated oils but in the central areas the main stage of oil generation of the wenchang fm was much earlier than the formation time of the traps resulting in the dissipation of most of the early generated wenchang sourced oils in the marginal areas the main stage of oil generation of the wenchang fm was later and the wenchang oils not only could be captured as fluid inclusions in the reservoir quartz grains but also migrated and accumulated into oil pools in which they mixed with the enping sourced oils the early lithological and structural traps in the central and marginal areas of the wenchang a sag especially in the northern part of the shenhu uplift are the most prospective areas for further exploration of the sag

hydrocarbon reserves of gachsaran oilfield sw iran geochemical characteristics and origin abstract biomarkers and carbon isotope data were used to depict geochemical properties and to delineate source of the crude oils from asmari and bangestan reservoirs of the giant gachsaran oilfield sw iran despite the distinct horizons of the reservoirs and severe petrophysical heterogeneity inside each reservoir all oil samples show an identical level of thermal maturity furthermore similar source related parameters reflect identical source rock for both reservoirs they indicate carbonate marl source deposited in a marine environment under anoxic suboxic conditions strong marine organic matter signatures of predominantly algal origin along with evidence of a terrigenous angiosperm plant contribution were detected geochemical evidence suggests that the gachsaran field asmari and bangestan oils being sourced from a mix of organic rich kazhdumi and pabdeh source rocks of albian and middle eocene early oligocene ages respectively carbon isotope composition and v ni ratio signatures indicate kazhdumi formation as the main source rock meanwhile significant presence of oleanane and less than unity values of c 29 c 30 hopanes ratio demonstrate a partial contribution of pabdeh formation this contradiction could be explained by two scenarios 1 incorporating very immature non expelled pabdeh oils into the mature kazhdumi oils during migration or 2 partial charge form low maturity pabdeh oils that is insufficient to impact a typical mixed signature over the geochemical fingerprint of the reservoired oils additionally geochemical similarities give rise to an assumption of reservoir and trap inter connection for this giant field

spatial and temporal variability of paleocene miocene organofacies of the kura basin eastern azerbaijan and implications for basin evolution and petroleum generation abstract fine grained paleocene miocene strata of eastern azerbaijan record the evolution of the kura basin from an open marine system connecting the south caspian basin to the paratethys of eastern europe to an isolated epicontinental sea tectonic uplift associated with the greater caucasus mountains in azerbaijan resulted in exposure of these strata over much of the northeastern part of the basin allowing detailed observation and sampling over a broad area four hundred paleocene miocene samples collected in eastern azerbaijan demonstrate spatial and temporal geochemical heterogeneity within the predominately mudstone succession indicating a complex evolution of this elongate basin through detailed organic geochemical analysis of samples trends can be seen in the distribution of total organic carbon toc pyrolysis characteristics and biomarker results from a subset of twenty four samples in addition to confirming the well documented regional basin restriction during the oligocene to early miocene deposition of the maikop series heterogeneity of these geochemical indicators across the study area shows spatial variability in oxicity and terrestrial organic input within the basin on a sub regional scale observed geochemical variability suggests a complex evolutionary history of the kura basin during the paleocene miocene and this has important implications for hydrocarbon prospectivity in the region within the 400 collected samples total organic carbon toc values range from 0 3 to 6 3 with oligocene miocene samples showing average values of 1 4 compared to lower toc values found in paleocene eocene strata average 0 3 rock eval pyrolysis shows that the majority of strata are organic lean immature and mixed oil gas to gas prone type ii iii to type iii with a smaller group of latest eocene early miocene samples having better oil prone source potential gas chromatography and biomarker analysis of 24 samples reinforces the immaturity of most samples shows varying levels of terrestrial input in all samples suggests well oxygenated waters prevailed with periodic suboxic to dysoxic anoxic events highlights gross differences between the paleocene eocene and oligocene miocene stratigraphic intervals and shows generally good lateral correlation between samples these interpretations reinforce what is seen through inorganic geochemical evaluation of trace metals bulk composition and stable isotopic ratios and offer more detail as to the evolution of this basin and the implications for oil and gas prospectivity of the region

abyssal circulation driven by near boundary mixing water mass transformations and interior stratification the emerging view of the abyssal circulation is that it is associated with bottom enhanced mixing which results in downwelling in the stratified ocean interior and upwelling in a bottom boundary layer along the insulating and sloping seafloor in the limit of slowly varying vertical stratification and topography however boundary layer theory predicts that these upslope and downslope flows largely compensate such that net water mass transformations along the slope are vanishingly small using a planetary geostrophic circulation model that resolves both the boundary layer dynamics and the large scale overturning in an idealized basin with bottom enhanced mixing along a midocean ridge we show that vertical variations in stratification become sufficiently large at equilibrium to reduce the degree of compensation along the midocean ridge flanks the resulting large net transformations are similar to estimates for the abyssal ocean and span the vertical extent of the ridge these results suggest that boundary flows generated by mixing play a crucial role in setting the global ocean stratification and overturning circulation requiring a revision of abyssal ocean theories

global ocean meridional overturning abstract a decade mean global ocean circulation is estimated using inverse techniques incorporating air sea fluxes of heat and freshwater recent hydrographic sections and direct current measurements this information is used to determine mass heat freshwater and other chemical transports and to constrain boundary currents and dense overflows the 18 boxes defined by these sections are divided into 45 isopycnal neutral density layers diapycnal transfers within the boxes are allowed representing advective fluxes and mixing processes air sea fluxes at the surface produce transfers between outcropping layers the model obtains a global overturning circulation consistent with the various observations revealing two global scale meridional circulation cells an upper cell with sinking in the arctic and subarctic regions and upwelling in the southern ocean and a lower cell with sinking around the antarctic continent and abyssal upwelling mainly below the crests of the major bathymetric ridges

global energy conversion rate from geostrophic flows into internal lee waves in the deep ocean a global estimate of the energy conversion rate from geostrophic flows into internal lee waves in the ocean is presented the estimate is based on a linear theory applied to bottom topography at o 1 10 km scales obtained from single beam echo soundings to bottom stratification estimated from climatology and to bottom velocity obtained from a global ocean model the total energy flux into internal lee waves is estimated to be 0 2 tw which is 20 of the global wind power input into the ocean the geographical distribution of the energy flux is largest in the southern ocean which accounts for half of the total energy flux the results suggest that the generation of internal lee waves at rough topography is a significant energy sink for the geostrophic flows as well as an important energy source for internal waves and the associated turbulent mixing in the deep ocean

overturning circulation driven by breaking internal waves in the deep ocean a global estimate of the water mass transformation by internal wave driven mixing in the deep ocean is presented the estimate is based on the energy conversion from tidal and geostrophic motions into internal waves combined with a turbulent mixing parameterization we show that internal wave driven mixing in the deep ocean can sustain 20 30 sv of water mass transformation one third or more of this transformation is attributed to lee waves generated by geostrophic motions flowing over rough topography primarily in the southern ocean while these results are uncertain due to many assumptions poorly constrained parameters and data noise that enter in the calculation the result that lee wave driven mixing plays an important role in the abyssal ocean circulation is likely robust the implication is that lee wave driven mixing should be represented in ocean and climate models but currently it is not citation nikurashin m and r ferrari 2013 overturning circulation driven by breaking internal waves in the deep ocean geophys res lett 40 doi 10 1002 grl 50542

unusual biomarker maturation ratio changes through the oil window a consequence of varied thermal history abstract saturated and aromatic biomarker ratios continue to change systematically through the oil window and into the gas condensate window to high vitrinite reflectances r o 1 16 in mature marine and lacustrine mesozoic clastic samples from a south african basin two of the ratios reverse above r o 0 9 these unusual maturation effects result from isolated periods of high rates of maturation increase the basin cooled regionally after the break up of gondwana but high heating rates prevailed during the late cretaceous early tertiary as africa moved across a hotspot and again in the late tertiary as a result of a possible hotspot and hydrothermal event

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

spatial variability of turbulent mixing in the abyssal ocean ocean microstructure data show that turbulent mixing in the deep brazil basin of the south atlantic ocean is weak at all depths above smooth abyssal plains and the south american continental rise the diapycnal diffusivity there was estimated to be less than or approximately equal to 0 1 x 10 4 meters squared per second in contrast mixing rates are large throughout the water column above the rough mid atlantic ridge and the diffusivity deduced for the bottom most 150 meters exceeds 5 x 10 4 meters squared per second such patterns in vertical mixing imply that abyssal circulations have complex spatial structures that are linked to the underlying bathymetry

the influence of facies and depositional environment on the occurrence and distribution of carbazoles and benzocarbazoles in crude oils a case study from the gulf of suez egypt abstract two major hinge zones separate the gulf of suez gos of egypt into three tectonic sub provinces namely the northern central and southern sectors based on bulk and molecular parameters the crude oils from the gos can be subdivided into three groups according to their geographical origin from the three sectors the geochemical characteristics of the oils are consistent with inferred depositional environments of anoxic marine carbonate facies in the central sector compared to a more oxic environment that has received an increased proportion of clastic input in the southern sector while the northern is intermediate in character most of the oils cover a relatively narrow maturity range 0 86 0 98 r c in the peak oil window the biomarker parameter ts ts tm is controlled by variations of facies and depositional environment but not by maturity concentrations of pyrrolic nitrogen compounds in the gos crude oils are in general relatively low but show a large range of variability in crude oils of the northern sector a strong predominance of c 4 and c 5 carbazoles over the lower homologues is observed towards the south the relative abundance of carbazole and the methylcarbazoles increases successively variations within the methylcarbazoles and c 2 carbazoles are rather small and therefore are not useful for a straightforward classification of oil families however atypical patterns in some of the oils particularly from the northern sector give evidence for contributions from yet unidentified local sources which might not be of general importance in the gos petroleum province benzo b carbazole is near or even below detection limit in the gos crude oils the benzocarbazole a a c ratio shows a consistently positive correlation with api gravity pr ph and ts ts tm and a negative correlation with the sulphur content based on these observations it is inferred that facies and depositional environment of the relevant source rocks are the major factors influencing the benzocarbazole distributions in the central sector of the gos in which oils are predominantly sourced from carbonates deposited under strongly reducing conditions a a c values are mainly below 0 5 in the southern sector where source rocks were deposited under less reducing conditions and received significant clastic input as well as in the northern sector the a a c values are mainly above 0 5

a toy model for the response of the residual overturning circulation to surface warming abstracta simple model for the deep ocean overturning circulation is presented and applied to study the ocean s response to a sudden surface warming the model combines one dimensional predictive r

widespread intense turbulent mixing in the southern ocean observations of internal wave velocity fluctuations show that enhanced turbulent mixing over rough topography in the southern ocean is remarkably intense and widespread mixing rates exceeding background values by a factor of 10 to 1000 are common above complex bathymetry over a distance of 2000 to 3000 kilometers at depths greater than 500 to 1000 meters this suggests that turbulent mixing in the southern ocean may contribute crucially to driving the upward transport of water closing the ocean s meridional overturning circulation and thus needs to be represented in numerical simulations of the global ocean circulation and the spreading of biogeochemical tracers

complex series of pentacyclic triterpanes in a lacustrine sourced oil from korea bay basin abstract gc ms analysis was undertaken of a waxy paraffinic low sulphur oil from korea bay basin apparently deriving mainly from bacterially reworked terrestrial organic matter deposited in a lacustrine environment in addition to the regular c27 35 hopanes a number of pentacyclic triterpanes was identified in the range c29 c32 these components appeared to be members of at least two homologous series one of which has been previously postulated to be 18 h neohopanes a further previously unreported series is characterized by a relatively intense molecular ion response during gc ms analysis a bacterial origin is suggested for these pentacyclic triterpane series the presence of which may reflect a particular set of sedimentological conditions

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography application to the southern ocean abstract recent estimates from observations and inverse models indicate that turbulent mixing associated with internal wave breaking is enhanced above rough topography in the southern ocean in most regions of the ocean abyssal mixing has been primarily associated with radiation and breaking of internal tides in this study it is shown that abyssal mixing in the southern ocean can be sustained by internal waves generated by geostrophic motions that dominate abyssal flows in this region theory and fully nonlinear numerical simulations are used to estimate the internal wave radiation and dissipation from lowered acoustic doppler current profiler ladcp ctd and topography data from two regions in the southern ocean drake passage and the southeast pacific the results show that radiation and dissipation of internal waves generated by geostrophic motions reproduce the magnitude and distribution of dissipation previously inferred from finescale measurements in the region suggesting that it is one of the

oleanane or lupane reappraisal of the presence of oleanane in cretaceous tertiary oils and sediments nonpolar gc columns are normally used for gc ms analysis of saturate fractions from crude oils under these conditions lupane coelutes with oleananes and some minor c30 compounds of non terrigenous origin having lupane like mass spectra because any peak eluting fractionally earlier than 17 21 h hopane in the m z 191 mass chromatogram is routinely assigned to oleanane the presence of lupane may sometimes have been overlooked lupane and oleananes are easily separated using reverse phase hplc triterpane concentrates from 10 crude oils known to contain oleananes were hplc separated lupane was unambiguously identified in six of the oils by full scan gc ms analysis of fractions having the hplc retention time of authentic lupane gc separation of lupane and oleananes is possible using polar gc columns having a polyethylene glycol stationary phase organic geochemistry 23 1995 21 allowing estimation of the lupane lupane oleanane ratio high ratios were measured in the marraat oil west greenland 0 8 and the amauligak oil from the beaufort mackenzie delta 0 26 the results suggest that lupane may be more frequently occurring than previously thought and that this compound is preferably associated with high latitude samples high concentrations of 28 nor and 24 28 bisnortriterpanes oleananes lupanes and taraxastanes were detected in the marraat oil

late cenozoic genus fupingopollenites development and its implications for the asian summer monsoon evolution an extinct palynomorph fupingopollenites was used as the basis for a discussion of the late cenozoic asian summer monsoon asm evolution and its possible driving forces based on the spatial and temporal variations in its percentages across inner and east asia we found that fupingopollenites mainly occurred in east asia with boundaries to the ne of ca 42 degrees n 135 degrees e and nw of ca 36 degrees n 103 degrees e during the early miocene ca 23 17 ma this region enlarged westwards reaching the eastern qaidam basin ca 36 degrees n 97 5 degrees e during the middle miocene ca 17 11 ma before noticeably retreating to a region bounded to the nw at ca 33 degrees n 105 degrees e during ca 11 5 3 ma the region then shrank further in the pliocene with the ne boundary shrinking southwards to about 35 degrees n 120 degrees e the area then almost disappeared during the pleistocene 2 6 0 ma the flourishing and subsequent extinction of fupingopollenites is indicative of a narrow ecological amplitude with a critical dependence on habitat humidity and temperature most likely mean annual precipitation map 1000 mm and mean annual temperature mat 10 degrees c therefore the fupingopollenites geographic distribution can indicate the humid asm evolution during the late cenozoic revealing that the strongest asm period occurred during the middle miocene climate optimum mmco similar to 17 14 ma after which the asm weakened coincident with global cooling we argue that the global cooling played a critical role in the asm evolution while the tibetan plateau uplifts made a relatively small contribution c 2015 international association for gondwana research published by elsevier b v all rights reserved

global rate and spectral characteristics of internal gravity wave generation by geostrophic flow over topography the rate of generation of internal gravity waves in the lee of small length scale topography by geostrophic flow in the world ocean was estimated using linear theory with corrections for finite amplitude topography several global data sets were combined for the calculation including an ocean circulation model for the near bottom geostrophic flow statistics over 500 abyssal current meter records historical climatological data for the buoyancy frequency and two independent estimates of the small scale topographic statistical properties the first topography estimate was based on an empirically derived relationship between paleo spreading rates and abyssal hill roughness with corrections for sedimentation the second estimate was based on small scale 100 km roughness of satellite altimetry derived gravity field using upward continuation relationships to derive estimates of abyssal hill roughness at the seafloor at scales less than approximately 20 km the lee wave generation rate was found to be between 0 34 to 0 49 tw the southern hemisphere produced 92 of the lee wave energy with the southern ocean dominating strength of the bottom flow was the most important factor in producing the global pattern of generation rate except in the indian ocean where extremely rough topography produced strong lee wave generation despite only moderate bottom flows the results imply about one half of the mechanical power input to the ocean general circulation from the extra equatorial wind stress of the world ocean results from abyssal lee wave generation topographic length scales between 176 m and 2 5 km horizontal wavelengths between 1 and 16 km accounted for 90 of the globally integrated generation

origin and occurrence of 25 norhopanes a statistical study abstract the alkane fraction of more than 200 rocks biodegraded oils and non biodegraded oils have been analysed by means of computerized gc ms in order to investigate the effect of natural biodegradation on the occurrence of demethylated hopanes i e 17 25 norhopanes the results obtained indicate that 25 norhopanes are preexisting biomarkers the concentration of which is enhanced by selective biodegradation of more readily degradable homologs i e regular hopanes rather than by demethylation of hopanes in reservoirs however the use of 25 norhopane enrichment as a palaebiodegradation indicator in apparently non biodegraded oils is still valuable providing the initial background content in the corresponding source rocks is known furthermore 25 norhopanes appear to be diagnostic of specific environmental conditions marine and lacustrine source rocks dysoxic and not very hypersaline lastly one other novel bacterially resistant rearranged hopanoic compound namely a c29 neohopane is applicable for both biodegradation and maturation evaluation

the jurassic petroleum system north and west of britain a geochemical oil source correlation study abstract recent significant oil discoveries have focused exploration attention on the atlantic margin areas north and west of britain in particular the west of shetlands area these discoveries the foinaven and schiehallion fields each have reserves of 250 to 500 million barrels 39 8 to 79 5 106 m3 of 24 27 api oil while an earlier heavy oil discovery the clair field is the largest undeveloped oil discovery on the u k continental shelf with resources estimated in the range 3 5 billion barrels 477 to 795 106 m3 other discoveries include suilven the very heavy oil in well 204 28 1 and the quadrant 205 strathmore and solan fields potential source rocks in areas adjacent to the west of shetlands include the upper jurassic kimmeridge clay formation equivalent the middle and lower jurassic and the middle devonian the results of geochemical studies of the oils reservoir core extracts and source rocks from released wells from these west of shetlands discoveries show them to be genetically related to north sea oils sourced from the kimmeridge clay formation equivalent detailed geochemical analysis biomarkers source rock reaction kinetics compound specific isotope analysis and fluid inclusion crush leach analysis of the clair field and foinaven complex oils showed that at least two episodes of charging from different source facies within the kimmeridge clay formation took place with an intervening biodegradation event oil charging from middle jurassic lacustrine source rocks is also indicated in the foinaven complex oils the source rocks are shown to exhibit variations in organic facies from very oil prone to mixed oil and gas with a corresponding range of kinetic parameters this complex generation migration and trapping scenario is directly linked with the tectonic evolution of the west of shetlands with major oil generation from very oil prone kimmeridge clay and middle jurassic lacustrine facies into shallow buried reservoirs biodegradation of the oils appears to have occurred shortly after migration into the traps followed later by a second charge of unaltered oil this appears to have been from a different source facies with more terrestrial slower reacting type ii iii kerogens similar to those seen in the kimmeridge clay formation or heather formation in wells on the basin margins kinetics studies show the middle and upper jurassic kerogens to be fast reacting and very oil prone with little potential for later gas generation this finding appears crucial in the understanding of the west of shetlands petroleum system as it explains the lack of large gas accumulations in a basin of such high thermal maturity

deep petroleum occurrences in the lower kura depression south caspian basin azerbaijan an organic geochemical and basin modeling study abstract high sedimentation rates as much as 2500 m ma during pliocene pleistocene with a resultant undercompacted section as thick as 10 000 m and lower than normal geothermal gradients are the main characteristics which have created all the means for generation and preservation of oil at deep layers in the lower kura depression oils collected from eight different oil fields for analyses seem to have originated from a common source rock which probably is clastic deposited in relatively subanoxic to suboxic transitional marine environment receiving low to moderate input of terrestrial organic matter oils from shallow a computer aided basin modeling study has been carried out to outline the spatial variation of the oil window and thus help in further identification of possible source rocks for the reservoired oil in the lower kura depression results suggest that the potential hydrocarbon source horizons of the miocene and pliocene red bed series of the so called productive succession are even at depocenter areas immature with respect to oil generation and thus are very unlikely to have been source rocks for the reservoired oils however the oligocene lower miocene maykop rocks are marginally mature to mature depending on locality and the eocene and older rocks are mature with respect to oil generation at all representative field locations oil generation commenced at the end of pliocene and continues at present at depths between 6000 and 12 000 m an unusually deep 10 000 m oil window in the depocenter areas has been caused by the depressed isotherms due to extremely high sedimentation rates up to 3000 m ma for the last two million years the main phase of oil generation is taking place at depths greater than what most of the wells in the study are have reached

biomarker and n alkane isotope profiles for tertiary oils relationship to source rock depositional setting abstract biomarker and n alkane isotope profiles have been measured for 29 late cretaceous tertiary oils from se asia china papua new guinea new zealand and the u s a the results are interpreted with respect to six kinds of source rock depositional setting fluvio deltaic fd freshwater transitional tr lacustrine lac saline lacustrine sal marine deltaic md and marine carbonate mc a comparison of biomarker and n alkane isotope results suggests that parameters such as the oleanane hopane ratio may overestimate the higher plant contribution to marine oils the abundance of bicadinanes is much more variable than that of oleanane probably because of a specific association with the highly resinous dipterocarp hardwoods of se asia however traces do occur in an oil from outside the paleogeographic range of the dipterocarp family confirming that there is also a more general angiosperm source the bicadinane isomeric distribution is shown to depend on maturity leading to new maturity parameters which are resistant to even very heavy biodegradation retention indices based on the regular hopane series are provided for the main bicadinane and methyl bicadinane isomers and for a group of oleanane related triterpanes of unknown structure the presence of the latter compounds may indicate locally deposited as opposed to transported higher plant matter in the source source rock depositional setting is the primary control on the shape of the n alkane isotope profile with negatively sloping curves being characteristic of fd and tr oils and flat or positively sloping curves typical of marine oils the difference is probably related to the bacterial reworking of higher plant matter in the fd environment a slight isotopic anomaly at n c 17 correlates with the abundance of algal derived steranes and may indicate a minor marine contribution to the source of an fd oil

generation of internal waves in the deep ocean by tides 1 a direct computation of the tidal generation of internal waves over the global ocean is presented it is based on linear wave theory and high resolution data for the bottom topography the geographical distribution of the energy flux from tides to internal waves is determined with a spatial resolution of a few kilometers the total flux over the area with a depth greater than 500 m is found to be 1 2 tw the greatest uncertainties of the computation are due to unresolved topography and to nonlinear effects caused by supercritical bottom slope

a mechanism for local dissipation of internal tides generated at rough topography abstract fine and micro structure observations indicate that turbulent mixing is enhanced within o 1 km above rough topography enhanced mixing is associated with internal wave breaking and in many regions of the ocean has been linked to the breaking and dissipation of internal tides the generation and dissipation of internal tides are explored in this study using a high resolution two dimensional nonhydrostatic numerical model which explicitly resolves the instabilities leading to wave breaking configured in an idealized domain with a realistic multiscale topography and flow characteristics the control simulation chosen to represent the brazil basin region produces a vertical profile of energy dissipation and temporal characteristics of finescale motions that are consistent with observations results suggest that a significant fraction of mixing in the bottom o 1 km of the ocean is sustained by the transfer of energy from the large scale internal tides to smaller scale internal waves by nonlin

organofacies variation control on hydrocarbon generation a lower congo coastal basin angola case history abstract a group of lower congo coastal basin angola carbonate platform petroleums all determined to be of lower cretaceous pre salt bucomazi fm neocomian aptian rift phase provenance showed considerable internal diversity recognised in terms of biomarker abundances and waxiness this variation was particularly evident in their carbon isotopic compositions which ranged from 26 4 to 29 7 ppt although not exclusive to all oils many contained an abundance of an unusual triterpane tentatively characterised as 25 30 bisnorhopane using a combination of kerogen type i ii iii and kinetic data ea and a plus kerogen pyrolysate isotopic signatures a conspicuous variation in organofacies was observed over the vertical and lateral development of this lacustrine source unit in a series of control wells three oil prone organofacies were recognised two of which could be individually characterised as type i 13c depleted and type ii 13 c enriched assemblages a third assemblage of type ii iisuperior character and intermediate isotopic signature not dependent upon mixing of the above end members was similarly recognised significantly the 25 30 bisnorhopane marker observed in many of the oils was found to be exclusively associated with the type ii 13c enriched organofacies on this basis rationalisation of crrde oil character and genera was possible in terms of phased co generation from these limiting organofacies with subsequent co mingling of the resultant oils although dissimilar end member oils could be isotopically matched to source facies representative of the more labile type ii lower ea to the less labile type i higher ea candidates most oils showed a mixed character reflecting their aggregate compostion definition of organofacies make up and variation is crucial to the fine tuning of contemporary modelling practises in their application to the study of hydrocarbon productive habitats

the impact of finite amplitude bottom topography on internal wave generation in the southern ocean direct observations in the southern ocean report enhanced internal wave activity and turbulence in akilometer thicklayeraboveroughbottomtopographycollocatedwiththedeep reachingfrontsoftheantarctic circumpolar current linear theory corrected for finite amplitude topography based on idealized twodimensional numerical simulations has been recently used to estimate the global distribution of internal wave generation by oceanic currents and eddies the global estimate shows that the topographic wave generation is a significant sink of energy for geostrophic flows and a source of energy for turbulent mixing in the deep ocean however comparison with recent observations from the diapycnal and isopycnal mixing experiment in the southern ocean shows that the linear theory predictions and idealized two dimensional simulations grossly overestimate the observed levelsof turbulent energy dissipation thisstudypresentstwo and three dimensional realistic topography simulations of internal lee wave generation from a steady flow interacting with topography with parameters typical of drake passage the results demonstrate that internal wave generation at threedimensional finite bottom topography is reduced compared to the two dimensional case the reduction is primarilyassociatedwithfinite amplitudebottomtopographyeffectsthatsuppressverticalmotionsandthusreduce the amplitude of the internal waves radiated from topography the implication of these results for the global leewave generation is discussed

internal waves and mixing near the kerguelen plateau abstractin the stratified ocean turbulent mixing is primarily attributed to the breaking of internal waves as such internal waves provide a link between large scale forcing and small scale mixing the internal wave field north of the kerguelen plateau is characterized using 914 high resolution hydrographic profiles from novel electromagnetic autonomous profiling explorer em apex floats altogether 46 coherent features are identified in the em apex velocity profiles and interpreted in terms of internal wave kinematics the large number of internal waves analyzed provides a quantitative framework for characterizing spatial variations in the internal wave field and for resolving generation versus propagation dynamics internal waves observed near the kerguelen plateau have a mean vertical wavelength of 200 m a mean horizontal wavelength of 15 km a mean period of 16 h and a mean horizontal group velocity of 3 cm s 1 the internal wave characteristics are dependent on regional dynamics suggesting tha

oceanography mountain waves in the deep ocean internal lee waves are a player in ocean dynamics that may make an important contribution to deep ocean mixing they warrant serious consideration for inclusion in the next generation of climate models

mixing of a tracer in the pycnocline a patch of sulfur hexafluoride was released in may 1992 in the eastern north atlantic on an isopycnal surface near 300 m depth and was surveyed over a period of 30 months as it dispersed across and along isopycnal surfaces the diapycnal eddy diffusivity k estimated for the first 6 months was 0 12 0 02 cm2 s while for the subsequent 24 months it was 0 17 0 02 cm2 s the vertical tracer distribution remained very close to gaussian for the full 30 months as the root mean square rms dispersion grew from 5 to 50 m lateral dispersion was measured on several scales the growth of the rms width of the tracer streaks from less than 100 m to approximately 300 m within 2 weeks implies an isopycnal diffusivity of 0 07 m2 s at scales of 0 1 to 1 km larger than expected from the interaction between vertical shear of the internal waves and diapycnal mixing teasing of the overall patch initially about 25 km across into streaks with an overall length of 1800 km within 6 months supports predictions of exponential growth by the mesoscale strain field at a rate of 3 0 5 10 7 s 1 the rms width of these streaks estimated as 3 km and maintained in the face of the streak growth indicates an isopycnal diffusivity of 2 m2 s at scales of 1 to 10 km much greater than expected from internal wave shear dispersion the patch was painted in albeit streakily by 12 months confirming expectations from analytical and numerical models homogenization of the patch continued during the subsequent 18 months while the patch continued to spread with an effective isopycnal eddy diffusivity on the order of 1000 m2 s acting at scales of 30 to 300 km

isoarborinol through geological times evidence for its presence in the permian and triassic abstract optical rotation measurements and hplc chiral separations using a cyclodextrin phase performed on aromatic hydrocarbons isolated from diverse geological sources and belonging to the arborane or fernane triterpenoid series have shown that isoarborinol one of the possible biological precursors was abundantly present at the time of deposition of permian and triassic sediments this fact considerably reinforces the hypothesis that arborane derivatives in sediments often found in abundance in lacustrine or lagoonal environments must originate from microorganisms such as aerobic bacteria or algae rather than from angiosperms a group of higher plants whose evolution dates from the cretaceous and currently believed to be the principal source of isoarborinol

molecular fossils in coastal bitumens from southern australia signatures of precursor biota and source rock environments abstract weathered waxy crude oil and black asphaltite tar are regularly washed ashore along the coastlines of south australia and western victoria these bitumens generally strand on medium to high energy sandy beaches in west or southwest facing bays some very weathered bitumens have been discovered in holocene dune deposits up to 200 m from the present day coastline differences in the sulphur content and carbon hydrogen and sulphur isotopic compositions of the coastal bitumens suggest that they belong to at least four oil families one of which may be emanating from submarine seeps along australia s highly faulted southern continental margin the remainder appear to be flotsam carried south from s e asia possibly sumatra the waxy bitumens families 1 3 range from paraffinic to aromatic intermediate in bulk composition and contain up to 2 6 s their density 13 38 api dictates that they are near surface drifters they have low pristane phytane ratios pr ph 2 abundant 4 methyl steranes c 30 with 24 ethyl substitution and in most cases high concentrations of botryococcane this biomarker assemblage indicates accumulation of freshwater algal source material including the remains of botryococcus sp and dinoflagellates under anoxic to suboxic conditions the additional presence of 28 30 bisnorhopane dinosterane and 24 n propylcholestane among the molecular fossils in family 3 bitumens suggests derivation from a lacustrine organic facies subject to marine incursions or alternatively mixing in the reservoir of two end member lacustrine and marine oil types trace amounts of oleanane and isomeric bicadinanes in the waxy bitumens constrain the age of their source rocks late cretaceous or younger and also preclude their local derivation an indonesian origin is considered likely implying long distance transport by surface ocean currents the family 4 bitumens 5 api are bottom drifters these sulphur rich 3 6 s aromatic asphaltic crudes have molecular signatures that include pr ph 1 c 27 c 29 c 28 c 30 desmethyl steranes dinosterane dominant over 4 methyl 24 ethylcholestane an enhanced concentration of 28 30 bisnorhopane relative to hopane and the absence of 2 or 3 methylhopanes a distal anoxic marine facies of the late cretaceous belfast mudstone in the eastern otway basin or its lithostratigraphic equivalent in the duntroon basin are possible local sources of the asphaltic bitumens

hydrocarbon traces in the tertiary basalts of the faeroe islands abstract hydrocarbons in the form of gases oils and waxes have been observed in the basalts of the faeroe islands in the north atlantic gases and traces of oil were observed in the outflowing water of the deep lopra 1 well drilled in 1981 the hydrocarbon gas was fairly dry with stable isotopic ratios of 13c1 3 41 4 32 4 26 5 respectively typical of a thermogenic gas high temperature gas chromatography of the oil showed that it consisted mostly of c13 60 n alkanes biomarker distribution observed by gc ms indicates that the oil was derived from a mature source rock deposited in an anoxic environment this suggests that the source rock must lie beneath the known basalts waxes exhibiting bright yellow fluorescence under uv light were observed as coatings on zeolite minerals widely distributed on the faeroe islands the waxes consist predominantly of higher n alkanes shown by htgc the fluorescence indicates the presence of aromatic compounds biomarker distribution indicated that the waxes were derived at least in part from a source rock containing some terrestrial organic matter astestified by the low amounts of oleanane present the waxes were probably deposited from traces of oil present in deeply circulating waters in fractures within the basalts coals which had been suspected to generate some of the hydrocarbons observed in the faeroese basalts were also examined vitrinite values of ro 0 5 as well as gc ms analyses of the suduroy coal extracts showed that these coals are immature and have not generated significant hydrocarbons

improved understanding of mixed oil in nigeria based on pyrolysis of asphaltenes abstract crude oil from reservoirs in the onshore niger delta is a mixture of low and high maturity charge aromatic biomarkers in these oils such as alkylphenanthrenes and alkylnaphthalenes show relatively high thermal maturity whereas the saturated sterane and hopane biomarkers indicate lower maturity close to the peak of the oil window the high predicted maturity of the crude oils based on alkylphenanthrene and alkylnaphthalene indices is probably caused by mixing of high maturity condensate with less mature black oil this correlates with the gas washing phenomenon of studied nigerian oils caused by migrating condensate stream the results of our study indicate that asphaltenes can be used to infer the organofacies of the low maturity petroleum charge in mixed crude oils compositional characteristics of the asphaltene pyrolysates indicate an origin of the related oils from type ii iii or type iii source rock kerogen the n alkyl chain length distributions of the asphaltene pyrolysates predict source rocks that generated high wax paraffinic naphthenic aromatic oils or paraffinic oils the n alkyl chain length of asphaltene pyrolysates changes in proportion to oxicity and the relative input of terrigenous organic matter to the source rock

coastal bitumens from western australia long distance transport by ocean currents abstract samples of weathered bitumens were collected from granite rocks and quartz sand beaches near the high water mark along the west and south coasts of western australia samples were subjected to analysis using gc and gc ms techniques the proportions of n alkanes and branched and cyclic compounds in the samples were variable and the variation was attributed to differences in sample weathering more detailed analysis of the bitumens for biomarkers revealed the presence of botryococcane 4 methylsteranes bicadinanes and oleanane the occurrence of these compounds has also been observed in crude oils from the s e asian region the presence of bicadinanes has been attributed to a source contribution from an angiosperm currently confined to tropical regions and indicates that the source rocks from which the bitumens were derived were deposited after late cretaceous times the absence of late cretaceous and tertiary sediments deposited in lower latitudes in the northwest and western offshore basins of australia suggests a non local source of the bitumens a mechanism involving the leeuwin current has been proposed to account for transport of these bitumens which are presumably sourced from locations in s e asia

geochemical evaluation of the besikli oil field kahta adiyaman turkey abstract mesozoic source rocks and crude oils from the besikli oil field adiyaman turkey havebeen characterized by a variety of organic geochemical techniques the potential source rocksinvestigated include the karababa a b and c members and the karabogaz formations thekarababa a member and the karabogaz formation of clayey limestone and limestone areimportant source rocks in the basin the crude oils examined in this study were obtained fromreservoir formations of the same age throughout the oil field the source rock screening analysisindicates that the karababa a member and the karabogaz formation have substantialoil generation potential the karababa b and c members have no source potential because theydo not contain sufficient amount of total organic matter content 0 12 0 24 toc wt selectedsource rock and oil samples were characterized in detail and distributions and concentrations both relative and absolute concentrations of biomarkers at different oils were examined thebiomarker characteristics were combined with other geochemical and geological data to interpretthe sources depositional environments and the age of the oils oil source rock correlations weremade between source rocks and crude oils based on qualitative and quantitative biomarkerdistributions petrographic descriptions and vitrinite reflectance measurements were used toevaluate petrographic properties of source rocks and maturity levels of the formations thesource rocks for the oil from the karababa a member and karabogaz formation are not matureenough and therefore oil should have migrated from the outside of the study area

radiation and dissipation of internal waves generated by geostrophic motions impinging on small scale topography theory abstract observations and inverse models suggest that small scale turbulent mixing is enhanced in the southern ocean in regions above rough topography the enhancement extends o 1 km above the topography suggesting that mixing is supported by the breaking of gravity waves radiated from the ocean bottom in this study it is shown that the observed mixing rates can be sustained by internal waves generated by geostrophic motions flowing over bottom topography weakly nonlinear theory is used to describe the internal wave generation and the feedback of the waves on the zonally averaged flow vigorous inertial oscillations are driven at the ocean bottom by waves generated at steep topography the wave radiation and dissipation at equilibrium is therefore the result of both geostrophic flow and inertial oscillations differing substantially from the classical lee wave problem the theoretical predictions are tested versus two dimensional high resolution numerical simulations with parameters representative of

oleanane parameter verification by quantitative study of the biomarker occurrence in sediments of the niger delta abstract the variation of the absolute concentration of oleananes in three selevted sedimentary columns of the tertiary niger delta is paralleled by the corresponding oleanane parameter op profile thereby confirming that the latter can be utilized for estimating the relative contribution of terrigenous organic matter it is shown that op features a dynamic range especially at the oil generative window ogw and can precisely delimit the top of the ogw which for the niger delta is shown to coincide approximately with the 80 c isotherm and ro 0 55 this study provides the first direct evidence of the inadequacy of vitrinite reflectance as a maturity parameter for type iii kerogen furthermore based on the new findings an alternative model for oleanene oleanane interconversions in the geosphere is proposed

bicadinanes in oils from the surma basin bangladesh abstract bicadinanes c 30 pentacyclic triterpanes have only been reported in crude oils and sediment extracts from s e asia the present investigation indicates that they are also widely present in land plant derived tertiary oils from the surma basin of n e bangladesh oleanane is also abundant in these oils though its distribution does not correlate with those of the bicadinanes this is consistent with separate specific land plant sources for these two classes of triterpanes and with the formation of bicadinanes during maturation of polymerised angiosperm tree resin

idealized solutions for the energy balance of the finescale internal wave field abstract recent fine and microstructure observations indicate enhanced finescale shear and strain in conjunction with bottom intensified turbulent dissipation above rough bathymetry in the brazil basin such observations implicate the bottom boundary as an energy source for the finescale internal wave field simple analytical and numerical solutions to an equation governing the spatial and temporal evolution of the finescale wave field are described here the governing equation implicitly treats the effects of wave breaking on the vertical propagation of internal waves through a flux representation of nonlinear transports associated with internal wave wave interactions these solutions identify the rate of dissipation of turbulent kinetic energy with downscale energy transports at high vertical wavenumber resulting in an estimate of dissipation versus depth the sensitivity of the turbulent dissipation depth profile to various environmental parameters is examined observed dissipation profiles and shear

chemical molecular and isotopic differentiation of organic facies in the tertiary lacustrine duaringa oil shale deposit queensland australia abstract total organic matter extractable organic matter bitumen and pyrolysates released on low temperature sealed tube pyrolysis of kerogen were analysed chemically and isotopically based on bulk bitumen and biomarker parameters the sediments are immature to a depth of approx 1300 m within the terrestrial and lacustrine depositional environments of the tertiary duaringa basin various organic facies have been classified according to inorganic input and maceral abundances of organic matter derived from land plant and algal sources the latter derived mainly from pediastrum and with a varying botryococcus content the lacustrine upper lamosite is chemically and isotopically distinct from the lower lamosite due to a changing algal community relative contributions from allochthonous land plants and for the lower lamosite a slightly more saline and restricted lake environment the lower lamosite is associated with the highest concentrations of c 28 c 30 4 methylsteranes and 13 c depletion in toc in the upper lamosite there is a strong positive correlation between botryococcus content and 13 c enrichment the organically lean claystones have sources nearly identical to the lamosites but the organic matter is diluted due to rapid influx of siliciclastics the terrestrial facies the cannel coal and carbonaceous shales are mainly distinguished from the lacustrine facies by higher relative proportions of c 29 steranes c 30 4 methylsteranes and 13 c values for the pyrolysed hydrocarbons intermediate between the two lamosite facies the carbonaceous oil shale has a composite geochemical signature intermediate between the two end members lamosite and cannel coal oleanane and ring a degraded triterpanes derived from lupane arborane and oleanane skeletons are distributed throughout all organic facies representing both autochthonous and allochthonous higher plant inputs higher concentrations of oleanane and des a lupane are associated with the terrestrial facies hopanes dominate over steranes in all organic facies and their concentration ranges are independent of facies for the lamosites the aliphatic biopolymer algaenan is implicated as the dominant source for n alkanes from analysis of their yields homologue abundances and individual 13 c values in the terrestrial facies resinites are paraffinic and are a major source for the n alkanes released on pyrolysis compound specific analysis of extractable and pyrolysate hydrocarbons allowed deconvolution of different source inputs to free lipids and kerogen for the lamosites low molecular weight n alkanes in the bitumen are derived mainly from a pediastrum source while botryococcus is associated with waxy n alkanes however the situation is reversed in the kerogen pediastrum algeanan has a longer average alkyl chain length than botryococcus algaenan the magnitude of the isotopic differences between single n alkanes released at different temperatures is useful in determining multiplicity of sources

organic geochemical study of the w oil gas field in the yugoslav part of the pannonian basin the naphthenic crude oil from the w oil gas field differs from almost all other paraffinic base oils discovered until now in the yugoslav part of the pannonian basin in order to explain this difference some geological and organic geochemical investigations were carried out on the basis of the bulk and biomarker parameters determined in oil samples taken from 13 producing wells located at different parts of the field it is concluded that the crude oil throughout the field has an almost uniform composition however some differences in alkane content due to biodegradation and or water washing were found in the northeast part of the field where a tilted oil water layers shows an active hydrodynamism and where the temperatures are the lowest and pressure gradients the highest the isoprenoids pristane and phytane were detected in trace amounts indicating the most intensive biodegradation in the central part where a hydrocarbon accumulation exists in a miocene reservoir somewhat lower biodegradation was observed the crude oil from this field has probably a mixed terrestrial marine origin and is derived from argillaceous source rocks sedimented in marine delta or brackish lakes specific maturation parameters confirmed that the w crude oil has reached a quite uniform and significant thermal maturation considering maturation parameters such as ratios c30 moretane hopane and c29 20s 20s 20r steranes as well as the presence of oleanane it could be proposed that the w oil originates from a pre tertiary source rock at least an upper cretaceous one unlike most pannonian basin oils which are tertiary in age

baccharane 18 19 secolupane a rare triterpenoid skeleton widespread in triassic sediments and petroleum from the adriatic basin abstract baccharane 18 19 secolupane 1 a triterpenoid skeleton seldom encountered in living organisms has been characterized together with 17 h des e lupane 2 one of its minor degradation products in italian triassic sediment and crude oil samples from the adriatic basin by synthesis of standards reports of baccharane derived triterpenoids in the field of natural products are scant and up to now restricted to terrestrial plants angiosperms and ferns in this regard sedimentary baccharane derivatives may indicate a continental contribution ferns to fossil organic matter but they may also represent a contribution of as yet undetermined marine microorganisms as has been proposed for dammarenes and dammaranes alternatively they could be the bio geochemical transformation products of biosynthetically closely related precursors such as lupane or dammarane type triterpenoids the apparently restricted occurrence of baccharane derivatives in geological samples up to now detected only in triassic sediments of the adriatic basin confers upon these compounds great value as correlation parameters and possibly as source indicators

oceanic transport of fossil dammar resin the chemistry of coastal resinites from south australia abstract fragments of resin and fossilised resin resinites occasionally wash ashore along the southern australian coast chemical and isotopic analyses were carried out on a suite of coastal and reference resinites to determine the likelihood of a local as opposed to a distant origin all of the coastal resinites were found to contain a polymer based on the sesquiterpenoid cadinene skeleton and were markedly different to the diterpenoid resinites found in local victorian coals the coastal resinites closely resemble both fossil and recent dammar resin a material associated primarily with the tropical angiosperm hardwoods of southeast asia and one which has no known australian source minor variations in the composition of our resinite samples are attributed to differences in their thermal history these findings confirm the viability of long distance oceanic transport not only for the resinites but also for the waxy bitumens that strand along the same coastline analytical data on the coastal resinites also help to clarify the role of dammar resin in generating bicadinanes a class of source and age specific triterpanes found commonly in the cainozoic oils and sediments of southeast asia

geochemical composition and origin of tertiary oils in the yinggehai and qiongdongnan basins offshore south china sea abstract this study comprehensively characterizes the geochemical compositions of tertiary crude oils in the yinggehai and qiongdongnan basins offshore south china sea and differentiates their source properties using chemical and isotopic data the oils in the two basins have distinct source characteristics the majority of the oils from the yacheng yc field in the qiongdongnan basin are commonly marked by high pr ph ratios mostly from 4 5 to 7 0 unusually abundant angiosperm derived compounds and a domination of c29 in diasteranes suggesting a predominantly terrigenous organic source in contrast the oils from the dongfang df and ledong ld fields in the yinggehai basin have relatively lower pr ph values 2 5 5 5 and a low amount of bicadinanes moreover some oils in this basin contain abundant 4 methylsteranes and detectable c30 desmethyl steranes the difference in the molecular composition is also apparent with regard to the aromatic hydrocarbons the former oils contain more abundant biphenyls fluorenes and 2 phenylnaphthalene than the latter ones the oils from the qiongdongnan basin are relatively depleted in 13c and have 13c values of the whole oil in the range of 24 9 to 26 9 consistent with the great terrigenous input in contrast the yinggehai oils are isotopically heavier with 13c values from 21 6 to 23 6 typical of a marine isotope signature correspondingly their n alkane isotopes have different 13c ranges and exhibit distinct distribution profiles based on the oil source rock correlation the oils in the yc field were generated from the coastal plain swamp and shallow marine strata of the oligocene in the qiongdongnan basin while the yinggehai oils were sourced from the miocene shallow marine mudstones in the basin

a theory of deep stratification and overturning circulation in the ocean abstract a simple theoretical model of the deep stratification and meridional overturning circulation in an idealized single basin ocean with a circumpolar channel is presented the theory includes the effects of wind eddies and diapycnal mixing predicts the deep stratification in terms of the surface forcing and other problem parameters makes no assumption of zero residual circulation and consistently accounts for the interaction between the circumpolar channel and the rest of the ocean the theory shows that dynamics of the overturning circulation can be characterized by two limiting regimes corresponding to weak and strong diapycnal mixing the transition between the two regimes is described by a nondimensional number characterizing the strength of the diffusion driven compared to the wind driven overturning circulation in the limit of weak diapycnal mixing deep stratification throughout the ocean is produced by the effects of wind and eddies in a circumpolar channel and maintained even in the