warming of global abyssal and deep southern ocean waters between the 1990s and 2000s contributions to global heat and sea level rise budgets abyssalglobalanddeepsouthern oceantemperature trendsarequantifiedbetweenthe1990sand2000sto assesstheroleofrecentwarmingoftheseregionsin globalheatandsealevelbudgets theauthors1 compute warming rates with uncertainties along 28 full depth high quality hydrographic sections that have been occupied two or more times between 1980 and 2010 2 divide the global ocean into 32 basins defined by the topography and climatological ocean bottom temperatures and then 3 estimate temperature trends in the 24 sampled basins the three southernmost basins show a strong statistically significant abyssal warming trend with that warming signal weakening to the north in the central pacific western atlantic and eastern indian oceans eastern atlantic and western indian ocean basins show statistically insignificant abyssal cooling trends excepting the arctic ocean and nordic seas the rate of abyssal below 4000 m global ocean heat content change in the 1990s and 2000s is equivalent to a heat flux of 0 027 60 009 w m 22 applied over the entire surface of the earth deep 1000 4000 m warming south of the subantarctic front of the antarctic circumpolar current adds 0 068 60 062 w m 22 the abyssal warming produces a 0 053 60 017 mm yr 21 increase in global average sea level and the deep warming south of the subantarctic front adds another 0 093 60 081 mm yr 21 thus warmingin theseregions ventilatedprimarilyby antarcticbottomwater accounts for a statistically significant fraction of the present global energy and sea level budgets

biological markers in lower jurassic synrift lacustrine black shales hartford basin connecticut u s a abstract the east berlin formation lower jurassic hartford basin connecticut u s a is distinctive for its six cyclic units of lacustrine black shale and gray mudstone separated by playa and fluvial redbeds the black shales are each about a meter thick and were deposited in subtropical thermally strastified oligomictic lakes the youngest of which lakes 3 through 6 were large enough to flood most of the basin and attained depths of several tens of meters the saturate fractions of solvent extracts of organic rich black shales from each of the six lakes collected at fresh roadcuts near east berlin are dominated by extended homologous series of n alkanes alkylcyclohexanes and branched chain alkanes a striking feature of the black shales is the presence of a series of extended tricyclic terpanes from c20 to at least c41 hopanes are either not detectable or present only in subordinate quantities relative to the tricyclic terpanes the samples are depleted in hopanes in part because of the elevated maturity level mid to late oil window tricyclic terpane concentrations may also have been enhanced by fractionation effects related to oil expulsion out of the black shales in addition the original organic matter may have been exceptionally rich in tricyclic terpane precursors i e fossil lipids of prokaryotes present in anoxic moderately saline alkaline lakes

a predictable amo like pattern in the gfdl fully coupled ensemble initialization and decadal forecasting system the decadal predictability of sea surface temperature sst and 2 m air temperature t2m in the geophysical fluid dynamics laboratory gfdl decadal hindcasts which are part of the fifth coupled model intercomparison project experiments has been investigated using an average predictability time apt analysis comparison of retrospective forecasts initialized using the gfdl ensemble coupled data assimilation system with uninitialized historical forcing simulations using the same model allows identification of the internal multidecadal pattern imp for sst and t2m the imp of sst is characterized by an interhemisphere dipole with warm anomalies centered in the north atlantic subpolar gyre region and north pacific subpolar gyre region and cold anomalies centered in the antarctic circumpolar current region the imp of t2m is characterized by a general bipolar seesaw with warm anomalies centered in greenland and cold anomalies centered in antarctica the retrospective prediction skill of the initialized system verified against independent observational datasets indicates that the imp of sst may be predictable up to 4 10 yr lead time at 95 90 significance level and the imp of t2m may be predictable up to 2 10 yr at the 95 90 significance level the initialization of multidecadal variations of northward oceanic heat transport in the north atlantic significantly improves the predictive skill of the imp the dominant roles of oceanic internaldynamicsin decadalpredictionare furtherelucidated byfixed forcing experimentsin which radiative forcing is returned abruptly to 1961 values these results point toward the possibility of meaningful decadal climateoutlooksusingdynamicalcoupledmodelsiftheyareappropriatelyinitializedfromasustainedclimate observing system

controls of oil family distribution and composition in nonmarine petroleum systems a case study from the turpan hami basin northwestern china controls on oil family distribution in tectonically complicated nonmarine petroliferous basins are commonly difficult to isolate because of the varying ages of potential source rocks the complex assemblage of organic rich sedimentary facies and the geographic variability of burial histories the turpan hami basin of northwestern china is an oil bearing intermontane basin where stratigraphic sedimentologic and geochemical controls are sufficient to address each of these issues independently and to determine how they influence the current distribution and composition of liquid hydrocarbons source rock age is one of three major statistically significant discriminators affecting oil family composition both lower middle lower or middle jurassic and upper permian rocks are important source rocks for the basin a newly developed diterpane biomarker parameter can distinguish permian rocks and their correlative oils from jurassic coals and mudrocks and their derivative oils source facies is a second key control on petroleum occurrence and character a variety of biomarker parameters that reflect source rock depositional conditions are indexed to rock samples from interpreted depositional environments by erecting rock to oil correlation models the biomarker parameters separate oil families into end member groups group 1 oils lower middle jurassic peatland swamp facies high land plant input less reducing conditions group 2 oils lower middle jurassic profundal lacustrine facies high algal input more reducing conditions and group 3 oils upper permian lacustrine facies high algal stratified anoxic conditions burial history exercises a third major control on petroleum distribution source rock maturation modeling can demonstrate that relatively uninterrupted burial in the asymmetrically subsiding northern turpan hami area taibei depression exhausted upper permian sourced rocks by the late cretaceous which led to southward migration of upper permiansourced oils group 3 into triassic reservoirs of southern and southwestern turpan hami tainan and tokesun depressions subsequent to uplift of the central basin thrust that currently partitions taibei from tainan lower middle jurassicsourced oils were expelled in the taibei depression by paleoceneeocene time which locally charged jurassic and cretaceous reservoirs groups 1 and 2 forming turpan hami s largest oil accumulations in the basin

a simple mathematical model to predict sea surface temperature over the northwest indian ocean abstract a novel and simple mathematical model was developed in this study to enhance the capacity of a reduced order model based on eigenvectors rmev to predict sea surface temperature sst in the northwest portion of the indian ocean including the persian and oman gulfs and arabian sea developed using only the first two of 12 416 possible modes the enhanced rmev closely matched observed daily optimum interpolation sst doisst values spatial distribution of the first mode indicated the greatest variations in doisst occurred in the persian gulf also the slightly increasing trend in the temporal component of the first mode observed in the study area over the last 34 years properly reflected the impact of climate change and rising doisst given its simplicity and high level of accuracy the enhanced rmev can be applied to forecast doisst in oceans which the poor forecasting performance and large computational time of other numerical models may not allow

structure and significance of c30 4 methyl steranes in lacustrine shales and oils abstract the structure of the abundant c 30 4 methyl steranes of ancient freshwater lacustrine sediments and derived oils is of interest as their precursors the 4 methyl and in particular 4 23 24 trimethyl sterols dinosterols are reported to be specific to dinoflagellates this study employs a novel liquid crystal gc phase combined with gc ms and gc ms ms to separate and characterise mixtures of c 30 4 methyl sterane standards not resolvable on non polar phases this technique is then applied to identify the c 30 4 methyl steranes in an ancient freshwater sediment a freshwater lacustrine and a marine derived oil a comparison is also made with the 4 methyl steranes in marine sediments containing varying amounts of dinoflagellate cysts the c 30 4 methyl steranes of the freshwater lacustrine samples have been shown to possess a 4 methyl 24 ethylcholestane structure while both 4 methyl 24 ethylcholestanes and 4 23 24 trimethyl 5 h cholestanes dinosteranes were found in the marine dinoflagellate rich sediments while still indicative of dinoflagellates 4 methyl 24 ethyl sterols are generally not the major dinoflagellate sterol and alternative explanations for the abundance of 4 methyl 24 ethylcholestanes in ancient lacustrine sediments should be considered possibly ancient freshwater dinoflagellates synthesised principally the 4 methyl 24 ethyl form alternatively a source from an unrecognized algal class is possible while a source from bacteria which are known to synthesise certain 4 methylsterols is discussed

upper ocean singular vectors of the north atlantic climate with implications for linear predictability and variability the limits of predictability of the meridional overturning circulation moc and upper ocean temperatures due to errors in ocean initial conditions and model parametrizations are investigated in an idealized configuration of an ocean general circulation model gcm singular vectors optimal perturbations are calculated using the gcm its tangent linear and adjoint models to determine an upper bound on the predictability of north atlantic climate the maximum growth time scales of moc and upper ocean temperature anomalies excited by the singular vectors are 18 5 and 13 years respectively and in part explained by the westward propagation of upper ocean anomalies against the mean flow as a result of the linear interference of non orthogonal eigenmodes of the non normal dynamics the ocean dynamics are found to actively participate in the significant growth of the anomalies an initial density perturbation of merely 0 02 kg m 3 is found to lead to a 1 7 sv moc anomaly after 18 5 years in addition northern hemisphere upper ocean temperature perturbations can be amplified by a factor of 2 after 13 years the growth of upper ocean temperature and moc anomalies is slower and weaker when excited by the upper ocean singular vectors than when the deep ocean is perturbed this leads to the conclusion that predictability experiments perturbing only the atmospheric initial state may overestimate the predictability time interestingly optimal moc and upper ocean temperature excitations are only weakly correlated thus limiting the utility of sst observations to infer moc variability the excitation of anomalies in this model might have a crucial impact on the variability and predictability of atlantic climate the limit of predictability of the moc is found to be different from that of the upper ocean heat content emphasizing that errors in ocean initial conditions will affect various measures differently and such uncertainties should be carefully considered in decadal prediction experiments copyright c

the impact of multidecadal atlantic meridional overturning circulation variations on the southern ocean the impact of multidecadal variations of the atlantic meridional overturning circulation amoc on the southern ocean so is investigated in the current paper using a coupled ocean atmosphere model we find that the amoc can influence the so via fast atmosphere teleconnections and subsequent ocean adjustments a stronger than normal amoc induces an anomalous warm sst over the north atlantic which leads to a warming of the northern hemisphere troposphere extending into the tropics this induces an increased equator to pole temperature gradient in the southern hemisphere sh upper troposphere and lower stratosphere due to an amplified tropical upper tropospheric warming as a result of increased latent heat release this altered gradients leads to a poleward displacement of the sh westerly jet the wind change over the so then cools the sst at high latitudes by anomalous northward ekman transports the wind change also weakens the antarctic bottom water aabw cell through changes in surface heat flux forcing the poleward shifted westerly wind decreases the long term mean easterly winds over the weddell sea thereby reducing the turbulent heat flux loss decreasing surface density and therefore leading to a weakening of the aabw cell the weakened aabw cell produces a temperature dipole in the so with a warm anomaly in the subsurface and a cold anomaly in the surface that corresponds to an increase of antarctic sea ice opposite conditions occur for a weaker than normal amoc our study here suggests that efforts to attribute the recent observed so variability to various factors should take into consideration not only local process but also remote forcing from the north atlantic

identification and significance of 3β ethyl steranes in sediments and petroleum abstract 3 ethyl steranes 5a c occur in ancient sediments and petroleum particularly those of paleozoic and proterozoic age this newly recognised modification to the sterane ring system has no known direct counterpart in the steroid metabolism of extant organisms when they are present in a sample the pattern of side chain substitution and some aspects of the isomer distributions of co occurring 3 ethyl steranes 5a c 3 methyl steranes 3a c 2 methyl steranes 2a c and desmethyl steranes 1a c are similar this suggests that these ring a alkylated steranes are not synthesised de novo by their source organism s but arise via microbial modifications to sedimentary sterenes during the early stages of diagenesis

geochemical characterisation of early cretaceous lacustrine sediments of bima formation yola sub basin northern benue trough ne nigeria organic matter input preservation paleoenvironment and palaeoclimatic conditions the bima formation is the oldest lithogenetic unit occupying the base of the cretaceous successions in the yola sub basin of the northern benue trough it is differentiated into lower b1 middle b2 and upper b3 bima members integrated organic and inorganic geochemical studies were applied on the lacustrine sediments of the bima formation with the aim of reconstructing the palaeodepositional environment and organic matter input in response to climate and tectonism the analysed sediments were deposited in a freshwater lacustrine environment with a low salinity stratified water column and suboxic to relatively anoxic conditions as indicated by the bulk geochemical parameters the biomarkers provide evidence for a contribution of aquatic algae and microorganisms with a significant amount of terrigenous organic matter input the preservation of the organic matter is possibly attributed to the stratified water column with low salinity and suboxic to relatively anoxic conditions based on the geochemistry of major and trace elements the sediments were deposited during semi arid climatic conditions within passive continental margin setting this agrees with the tectonic events in the west and central african rift system wcars during the early cretaceous period

feti oxide mineralogy and the origin of normal and reverse remanent magnetization in dacitic pumice blocks from mt shasta california detailed mineralogical analyses and rock magnetic experiments have made it possible to directly identify the fe ti oxide phases responsible for the normal and reverse magnetic components of two dacitic pumice blocks from mt shasta california both samples contain a normal component carried by 100 m size multi domain md titanomagnetite usp11 24 one sample also contains a second normal component carried by 10 m size pseudo single domain psd or single domain sd ti free magnetite usp1 found in the dacitic glass the md titanomagnetite and psd or sd magnetite dominate the strong field magnetic signal but only the psd or sd magnetite has any influence on the remanence signal unlike the strong field signal the remanence signal of both samples is dominated by a reverse nrm component this reverse component is carried by 100 m size ferrian ilmenite ilm53 65 the compositions of the ilmenites in both samples are within the range of compositions ilm50 75 known to have the ability to acquire self reversing thermoremanent magnetizations trm the results of the lowric fuller test indicate that the remanence signal is dominated by psd or sd carriers because one sample contains only large md titanomagnetite and no sd ti free magnetite in addition to ferrian ilmenite the ferrian ilmenite must be a psd or sd carrier oxide and pyroxene geothermometry indicate the fe ti oxides in the pumice crystallized at temperatures between 880 and 945 c this temperature range is within the disordered region of the ilmenite hematite phase diagram for ilm53 65 previous work on synthetic ilm70 and ilm80 has shown that cooling through the order disorder transition into the ordered region develops a transformation induced microstructure consisting of cation ordered domains with disordered domain boundaries an ilm58 59 grain from one of the mt shasta samples was examined in the transmission electron microscope and was found to contain 100 200 a diameter cation ordered domains these domains arose during cooling through the transition temperature which is estimated at 800 c for ilm58 59 the presence of the disordered domain boundaries provides an explanation for the magnetic behavior of the ferrian ilmenite 1 the disordered boundaries are the higher curie point phase necessary for the operation of the self reversal mechanism 2 the disordered domain boundaries either inhibit the formation of magnetic domain walls or restrict magnetic domain wall movement accounting for the psd or sd behavior of the ferrian ilmenite

complex patterns of steroidal biomarkers in tertiary lacustrine sediments of the biyang basin china gas chromatography gc gas chromatography mass spectrometry gc ms and gas chromatography mass spectrometry mass spectrometry gc ms ms with co injected synthetic standards were used to analyse the biomarker patterns of some tertiary lacustrine clayey dolomites from the biyang basin china the lithology low pr ph ratio and high gammacerane content of these sediments indicated that high salinity prevailed during their deposition the distributions of steroidal hydrocarbons were particularly unusual and several pseudohomologous series including regular steranes c27 c29 4 methyl steranes c28 c30 including dinosteranes 3b ethyl steranes c29 c31 lanostanes c30 c32 and a variety of other 3b alkylated steranes were identified 3b n propylcholestane 3b n propylstigmastane and 4 4 dimethylcholestane were identified using authentic standards and this is the first time these compounds have been unambiguously characterised in sediments crown copyright 2001 published by elsevier science ltd all rights reserved

paleoreconstruction by biological markers abstract during diagenesis and conversion of the original lipid fraction of biological systems to petroleum hydrocarbons the following four basic events needed for paleoreconstruction can be monitored by biological markets 1 sourcing 2 maturation 3 migration and 4 biodegradation actual cases of applying biological markers to petroleum exploration problems in different parts of the world are demonstrated cretaceous and phosphoria sourced oils in the wyoming thrust belt can clearly be distinguished from one another by high quality source fingerprinting of biomarker terpanes using gas chromatography mass spectrometry identification of recently discovered biological markers head to head isoprenoids allows subtle source differentiation between oils from sumatra the degree of crude oil maturation in basins from california alaska russia wyoming and louisiana can be assessed by specific novel biomarker ratios 20s 20r sterane epimers field evidence from such interpretation is confirmed by laboratory pyrolysis of the rock an example of immature sumatra rock is given extensive migration is documented by biomarkers in several oils the effect of biodegradation on biomarker steranes and terpanes is exemlified in a california basin all biological marker results are consistent with the geological setting and add a new dimension in assisting the petroleum explorationist toward paleo reconstruction

application of 24 norcholestanes for constraining source age of petroleum abstract two c26 sterane ratios the 24 nordiacholestane ratio ndr and the 24 norcholestane ratio ncr are useful for assessing petroleum source age values for these parameters generally increase in the cretaceous when diatoms were rapidly radiating and further in the oligo miocene due to widespread high latitude deposition of diatomaceous sediments sources with shale lithologies tend to exhibit the highest ratios while carbonate and terrigenous rich lithologies generally show lower ratios on the north slope of alaska elevated ratios are observed for cretaceous hrz oils and mixed oils containing cretaceous input compared to older triassic and jurassic derived oils tertiary sourced oils from romania and bulgaria have much higher ratios relative to jurassic sourced oils in the black sea region oleanane was observed in comparable levels in some black sea tertiary and jurassic oils and source rocks ndr and ncr coupled with other age diagnostic indicators such as oleanane and dinosterane provide powerful tools for differentiating age of source and organic facies for oils from the black sea and sub andean basins of peru and ecuador respectively oils derived from sources deposited in low tropical latitudes tend to have little diatom input and as a consequence do not display high values regardless of age

extended 3β alkyl steranes and 3 alkyl triaromatic steroids in crude oils and rock extracts abstract in oils and precambrian to miocene age source rocks from varying depositional environments we have conclusively identified several novel 3 alkyl sterane and triaromatic steroid series including 1 3 n pentyl steranes 2 3 isopentyl steranes 3 3 n hexyl steranes 4 3 n heptyl steranes 5 3 4 dimethyl steranes 6 3 butyl 4 methyl steranes 7 triaromatic 3 n pentyl steroids and 8 triaromatic 3 isopentyl steroids we have also tentatively identified additional homologs with 3 alkyl substituents as large as c11 the relative abundances of these compounds vary substantially between samples as indicated by 1 the ratio of 3 n pentyl steranes to 3 isopentyl steranes and 2 the ratio of 3 n pentyl triaromatic steroids to 3 isopentyl triaromatic steroids these data suggest possible utility for these parameters as tools for oil source rock correlations and reconstruction of depositional environments although no 3 alkyl steroid natural products are currently known several lines of evidence suggest that 3 alkyl steroids result from bacterial side chain additions to diagenetic 2 sterenes

southern ocean sector centennial climate variability and recent decadal trends abstractevidence is presented for the notion that some contribution to the recent decadal trends observed in the southern hemisphere including the lack of a strong southern ocean surface warming may have originated from longer term internal centennial variability originating in the southern ocean the existence of such centennial variability is supported by the instrumental sea surface temperatures ssts a multimillennial reconstruction of tasmanian summer temperatures from tree rings and a millennial control integration of the kiel climate model kcm the model variability was previously shown to be linked to changes in weddell sea deep convection during phases of deep convection the surface southern ocean warms the abyssal southern ocean cools antarctic sea ice extent retreats and the low level atmospheric circulation over the southern ocean weakens after the halt of deep convection the surface southern ocean cools the abyssal southern ocean warms antarctic sea ice expands and the low leve

multi centennial variability controlled by southern ocean convection in the kiel climate model a quasi oscillatory multi centennial mode of open ocean deep convection in the atlantic sector of the southern ocean in the kiel climate model is described the quasi periodic occurrence of the deep convection causes variations in regional and global surface air temperature southern hemisphere sea ice coverage southern ocean and north atlantic sea surface height the antarctic circumpolar current and the atlantic meridional overturning circulation amoc the deep convection is stimulated by a strong built up of heat at mid depth when the heat reservoir is virtually depleted a coincidental strong freshening event at the sea surface shuts down the convection the heat originates from relatively warm deep water formed in the north atlantic the several decades lasting recharge process of the heat reservoir depends on the amoc and the weddell gyre and sets a minimum delay for the deep convection to recur while the strength of the amoc increases the weddell gyre weakens during the non convective regime convection onset and shutdown also depend on the stochastic occurrence of favorable sea surface conditions which contributes to the multi centennial period of the phenomenon the shutdown triggers a century long deviation in amoc strength caused by significant reductions in bottom water formation and surface salinity in the southern ocean s atlantic sector additional numerical experimentation reveals that sea ice has an important effect on the frequency of occurrence and intensity of the deep convection further we find intriguing similarities to the weddell polynya observed during the 1970s

global contraction of antarctic bottom water between the 1980s and 2000s abstracta statistically significant reduction in antarctic bottom water aabw volume is quantified between the 1980s and 2000s within the southern ocean and along the bottom most southern branches of the meridional overturning circulation moc aabw has warmed globally during that time contributing roughly 10 of the recent total ocean heat uptake this warming implies a global scale contraction of aabw rates of change in aabw related circulation are estimated in most of the world s deep ocean basins by finding average rates of volume loss or gain below cold deep potential temperature surfaces using all available repeated hydrographic sections the southern ocean is losing water below 0 c at a rate of 8 2 2 6 106 m3 s 1 this bottom water contraction causes a descent of potential isotherms throughout much of the water column until a near surface recovery apparently through a southward surge of circumpolar deep water from the north to the north smaller losses of bottom waters are see

interannual to decadal predictability of tropical and north pacific sea surface temperatures abstract a multivariate empirical model is used to show that predictability of the dominant patterns of tropical and north pacific oceanic variability el nino southern oscillation enso and the pacific decadal oscillation pdo is mostly limited to little more than a year despite the presence of spectral peaks on decadal time scales the model used is a linear inverse model lim derived from the observed simultaneous and 1 yr lag correlation statistics of july june averaged sst from the hadley centre global sea ice and sea surface temperature hadisst dataset for the years 1900 2002 the model accurately reproduces the power spectra of the data including interannual and interdecadal spectral peaks that are significant relative to univariate red noise eigenanalysis of the linear dynamical operator yields propagating eigenmodes that correspond to these peaks but have very short decay times and thus limited predictability longer term predictability does exist however due to two stationary eigen

petroleum geochemistry and depositional setting of lacustrine source rocks abstract lacustrine sequences are increasingly being recognised as hosts for commercial reserves of petroleum petroleum source rocks in lacustrine sequences have organic carbon contents ranging from 20 and kerogen types range from type i to type iii the organic matter can be of land plant algal or bacterial origin most undegraded lacustrine oils are extremely paraffinic and waxy but a few are asphaltic and rich in sulphur the crude oils and source rocks contain a wide diversity of biological marker compounds reflecting different source inputs the diversity of chemistries displayed by lacustrine source rocks and crude oils reflect the wide variety of organic source materials and depositional conditions operative in lakes lacustrine sequences preserved in the geological record represent sediments deposited in fluvial lakes on humid flood plains and tectonic lakes in humid semi arid and arid environments preservation of organic matter in lakes is dependent on the formation of anoxic or micro oxic bottom waters this is favoured by stratification of lake waters brought about by temperature and salinity contrasts organic material preserved in oligotrophic lakes is largely of land plant origin which has been extensively modified by bacteria under mildly oxidizing conditions and supplemented by the bacterial remains source rocks of this type are found in 1 fluvial lacustrine settings e g jurassic of eromanga basin australia and 2 the oligotrophic phase of larger tectonic lakes e g early stages of green river formation uinta basin usa as these freshwater lakes become productive algal remains are contributed to the sediment and anoxic bottom waters can become more firmly established the green algae pediastrum and botryococcus appear to be particularly important although land plant detritus is still significant e g cretaceous source rocks songliao basin china saline lakes conditions tend to restrict the diversity of the source biota although preservation may be enhanced through anoxia brought about by salinity stratification and inhibition of bacterial decay e g later stages green river formation uinta basin usa sulphate rich and hypersaline lacustrine systems result in the formation of sulphur rich sources and oils e g jianghan basin china because of the diversity of organic matter types maturation criteria for hydrocarbon generation in lacustrine sequences also vary however in most cases higher maturation levels are required for significant hydrocarbon generation at present it is uncertain the extent to which algal and bacterial organic matter contribute to the source for the waxy hydrocarbons which are characteristic of lacustrine oils organic rich rocks formed in large freshwater and saline lakes are the most productive type of lacustrine source rock although sources formed in lakes of flood plains and deltas are also widespread

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

petroleum isotopic and biomarker composition related to source rock organic matter and depositional environment abstract a multivariate approach has been developed that separates oils derived from organic matter in nonmarine shales marine shales and marine carbonates some or all of the following analyses were completed on 43 oils from known source rocks 1 c30 sterane and monoaromatic steroid biomarker ratios and 2 stable carbon and hydrogen isotope compositions of whole oil saturates and aromatics three group discriminant analysis of the 28 oils whereall biomarker and isotopic data are available results in no misclassifications at a significance level of 99 using only carbon and hydroogen isotopic data for whole oils saturates and aromatics results in correct classifications of 82 for oils derived from marine shale organic matter and 100 for oils from the other two sources triangular plots probabilities can be used to distinguish oils derived from the three source rock organic matter end members several publications describe classifications of marine vs nonmarine oils using stable carbon isotope ratios of the whole oil or the saturate and aromatic fractions our results confirm that these methods do not completely differentiate oils by source

unusual polycyclic alkanes in lower cretaceous ostracode sediments and related oils of the western canada sedimentary basin several series of unusual polycyclic alkanes ranging from tricyclic to heptacyclic have been identified as major components in extracts of lower cretaceous ostracode zone sediments of the western canada sedimentary basin these compounds appear to be specific markers for the ostracode zone sourced oils in the lower mannville group reservoirs of the provost area and may represent a new class of molecules whose natural distribution and biological significance remains to be determined the stable carbon isotopic data of the tri tetra and pentacyclic alkanes appear to be related to pristane and phytane yet the significant isotopic depletion observed in the hexacyclic compounds suggests that they may be derived from different groups of organisms or different biosynthetic routes

a high resolution biomarker study of different lithofacies of organic sulfur rich carbonate rocks of a kimmeridgian lagoon french southern jura the upper jurassic calcaires en plaquettes formation southern jura france which was deposited in a lagoonal setting reveals three lithofacies limestones with fine scale parallel laminations limestones with undulated stromatolite type laminations and massive limestones it was examined at the millimetre scale if the lithological differences are accompanied by differences in the composition of organic matter om and if microbial mats played a role in the preservation of om as suggested previously four types of laminae light parallel dark parallel light undulated dark undulated and a massive limestone sample were analysed the om in all facies is characterised by a high hydrogen index 870 970 and a variable 13c content 23 5 or to 28 1 the molecular composition of om appeared similar in all samples e g i extractable biomarkers are dominated by n alkane and hopanoid carbon skeletons predominantly in a sulfur bound form ii isorenieratene derivatives indicating anoxic conditions in the photic zone are present in relatively large amounts iii kerogen pyrolysates are dominated by organic sulfur compounds notwithstanding the overall similarity in om composition some significant differences were observed e g i low molecular weight sulfur bound hopanoids and steroids are relatively more abundant in toc lean light coloured samples than in toc rich dark coloured samples this is probably related to differences in the degree of intermolecular sulfur cross linking of the om ii the concentrations and distributions of several biomarkers in the light coloured undulated sample differ from those in the other samples these differences are attributed to the periodic occurrence of microbial mats our data indicate that om in the calcaires en plaquettes formation is predominantly composed of sulfur bound lipids formed at times that bottom waters were euxinic a periodic deepening of the oxic anoxic interface and of the light penetration depth to below the sediment surface allowed microbial mats to develop organic remains of the mats however are swamped by sulfur bound planktonic lipids

diagnosis of decadal predictability of southern ocean sea surface temperature in the gfdl cm2 1 model abstractthe average predictability time apt method is used to identify the most predictable components of decadal sea surface temperature sst variations over the southern ocean so in a 4000 yr unforced control run of the gfdl cm2 1 model the most predictable component shows significant predictive skill for periods as long as 20 years the physical pattern of this variability has a uniform sign of sst anomalies over the so with maximum values over the amundsen bellingshausen weddell seas spectral analysis of the associated apt time series shows a broad peak on time scales of 70 120 years this most predictable pattern is closely related to the mature phase of a mode of internal variability in the so that is associated with fluctuations of deep ocean convection the second most predictable component of so sst is characterized by a dipole structure with sst anomalies of one sign over the weddell sea and sst anomalies of the opposite sign over the amundsen bellingshausen seas this component has sig

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

a decadal prediction case study late twentieth century north atlantic ocean heat content an ensemble of initialized decadal prediction dp experiments using the community climate system model version 4 ccsm4 shows considerable skill at forecasting changes in north atlantic upper ocean heat content and surface temperature up to a decade in advance coupled model ensembles were integrated forward from each of 10 different start dates spanning from 1961 to 2006 with ocean and sea ice initial conditions obtained from a forced historical experiment a coordinated ocean ice reference experiment with interannual forcing core ia which exhibits good correspondence with late twentieth century ocean observations from the north atlantic subpolar gyre spg region north atlantic heat content anomalies from the dp ensemble correlate highly with those from the core ia simulation after correcting for a drift bias in particular theobservedlarge rapid rise in spgheatcontentin themid 1990sis successfullypredicted in the ensemble initialized in january of 1991 a budget of spg heat content from the core ia experiment sheds light on the origins of the 1990s regime shift and it demonstrates the extent to which low frequency changes in ocean heat advection related to the atlantic meridional overturning circulation dominate temperature tendencies in this region similar budgets from the dp ensembles reveal varying degrees of predictive skill in the individual heat budget terms with large advective heat flux anomalies from the south exhibiting the highest correlation with core ia the skill of the dp in this region is thus tied to correct initialization of ocean circulation anomalies while external forcing is found to contribute negligibly and for incorrect reasons to predictive skill in this region over this time period

impact of the antarctic bottom water formation on the weddell gyre and its northward propagation characteristics in gfdl cm2 1 model

a molecular and carbon isotope biogeochemical study of biomarkers and kerogen pyrolysates of the kimmeridge clay facies palaeoenvironmental implications abstract structures and carbon isotopic compositions of biomarkers and kerogen pyrolysis products of a dolomite a bituminous shale and an oil shale of the kimmeridge clay formation kcf in dorset were studied in order to gain insight into i the type and extent of water column anoxia and ii changes in the concentration and isotopic composition of dissolved inorganic carbon dic in the palaeowater column the samples studied fit into the curve of increasing 13 c of the kerogen 13 c toc with increasing toc reported by huc et al 1992 their hypothesis that the positive correlation between toc and 13 c toc is the result of differing degrees of organic matter om mineralisation in the water column was tested by measuring the 13 c values of primary production markers these 13 c values were found to differ on average by only 1 among the samples implying that differences in the extent of om mineralisation cannot fully account for the 3 difference in 13 c toc the extractable om in the oil shale differs from that in the other sediments due to both differences in maturity and differences in the planktonic community these differences however are not likely to have significantly influenced 13 c toc either all three sediments contain abundant derivatives of isorenieratene indicating that periodically euxinia was extending into the photic zone the sediments are rich in organic sulfur as revealed by the abundant sulfur compounds in the pyrolysates the prominence of c 1 c 3 alkylated thiophenes over n alkanes and n alkenes is most pronounced in the pyrolysate of the sediment richest in toc this suggests that sulfurisation of om may have played an important role in determining the toc 13 c toc relationship reported by huc et al 1992

application of biological markers in the assessment of paleoenvironments of chinese non marine sediments abstract in this study we employ molecular organic geochemical data for 22 representative sediment samples from chinese non marine sedimentary basins in an attempt to characterize and assess the non marine depositonal paleoenvironments the samples investigated include oilshale shale mudstone and sodium sulphate rich sediments ranging in age from cretaceous to tertiary it is evidenced by geological and geochemical data that those sediments studied originate from lacustrine environments ranging from freshwater brackish fresh water to hypersaline the aliphatic fractions of the sediment extracts were analyzed by gc and gc ms and relative abundance of compounds and compound classes of normal acyclic and cyclic alkanes were measured from mass chromatograms the results reveal significant differences in the chemical features of the various sample groups which enable them to be characterized and identified in terms of source and or environment related parameters the diagnostic parameters that allow this assessment are the relative abundances of n alkanes acyclic isoprenoid alkanes and 4 methyl steranes hopane sterane ratio gammacerane and homohopane indexes etc in this study data interpretation was also assisted by pattern recognition through principal component analysis the results show that the sample groups of different environmental origin could be unambiguously distinguished on scores plot

prediction of source rock characteristics based on terpane biomarkers in crude oils a multivariate statistical approach abstract the distributions of eight tricyclic and eight pentacyclic terpanes were determined for 216 crude oils located worldwide with subsequent simultaneous rq mode factor analysis and stepwise discriminate analysis for the purpose of predicting source rock features or depositional environments five categories of source rocks are evident nearshore marine i e paralic deltaic deeper water marine lacustrine phosphaticrich source beds and ordovician age source rocks the first two factors of the rq mode factor analysis describe 45 percent of the variation in the data set the tricyclic terpanes appear to be twice as significant as pentacyclic terpanes in determining the variation among samples lacustrine oils are characterized by greater relative abundances of c 21 diterpane and gammacerane nearshore marine sources by c 19 and c 20 diterpanes and oleanane deeper water marine facies by c 24 and c 25 tricyclic and c 31 plus c 32 extended hopanes and ordovician age oils by c 27 and c 29 pentacyclic terpanes although thermal maturity trends can be observed in factor space the trends do not necessarily obscure the source rock interpretations also since bacterial degradation of crude oils rarely affects tricyclic terpanes biodegraded oils can be used in predicting source rock features the precision to which source rock depositional environments are determined might be increased with the addition of other biomarker e g steranes and stable isotope data using multivariate statistical techniques

reducing marine and warm climate conditions during the late cretaceous and their influence on organic matter enrichment in the oil shale deposits of north jordan abstract late cretaceous oil shales located in the yarmouk sub basin north jordan were analysed using techniques of organic and inorganic geochemistry coupled with a microfossil study results of this study were used to reconstruct the paleoenvironmental and paleoclimatic conditions during the late cretaceous and to investigate their influence on organic matter enrichment of the oil shale deposits the analysed oil shales have high toc and s total content values in the ranges of 2 11 12 85 wt and 1 83 8 81 wt respectively the high s total content and its relation with toc values indicate that the sulfur is associated with organic matter and that the oil shales were deposited in a marine environment under reducing conditions this is shown by petrographic observation and supported by biomarker distributions the microscopic investigation indicated that the oil shales contain abundant liptinitic materials i e alginite and amorphous organic matter and planktonic foraminifera the presence of these sapropelic materials and planktonic foraminifera assemblages further suggests a marine origin biomarker distributions are also known to reflect dominantly marine plankton algal and microorganisms source input water column stratification and low oxygen reducing conditions are indicated by narrow pr ph values relatively high v ni elemental ratios and the presence of gammacerane reducing conditions contribute to preservation of organic matter warm water periods during the late cretaceous are also indicated by dominant occurrences of warm water index microfossil taxa the warm climate combined with elevated phosphorus p are the major causes of excessive algae growth and led to enhanced biological productivity within the photic zone of the water column during deposition of the oil shale deposits this increased bio productivity in combination with good preservation of organic matter are the main mechanisms of organic matter enrichment within the late cretaceous oil shales in the north jordan

tetracyclic polyprenoids indicators of freshwater lacustrine algal input because of the great variety of lacustrine source depositional characteristics and biological consortia identification of a universally applicable indicator of freshwater or brackish water organic input for crude oils and rock extracts has proven elusive tetracyclic polyprenoid compounds tpp are present in relatively high concentrations in oils and associated source rocks deposited under freshwater or brackish water conditions but typically are present in relatively low concentrations in samples from marine or coal forming depositional environments a tpp ratio constructed from the gas chromatography tandem mass spectrometry peak areas of a c30 tetracyclic polyprenoid divided by the sum of the peak areas of the c26 27 norcholestanes revealed great specificity in identifying freshwater or brackish water algal input particularly in crude oils

depositional environment and maturity of devonian pimenteira formation in the sao luis basin brazil abstract we carried out a detailed organic facies study on shale cutting samples from the devonian pimenteira formation in the sao luis basin northwest brazil to reconstruct the depositional paleoenvironment and origin of the organic matter samples were collected from the stratigraphic well 2 anp 5 ma and were analyzed for total organic carbon toc total sulfur s insoluble residue ri spore coloration index sci vitrinite reflectance ro palynofacies and biomarkers the toc values of the analyzed sediments range from 0 19 to 0 51 s from 0 17 to 0 85 and the total carbonate caco3 is low

the pacific south american modes and tropical convection during the southern hemisphere winter abstract atmospheric circulation features and convection patterns associated with two leading low frequency modes in the southern hemisphere sh are examined in multiyear global reanalyses produced by ncep ncar and nasa dao the two leading modes referred to as the pacific south american psa modes are represented by the first two eof patterns the two patterns are in quadrature with each other and are dominated by wavenumber 3 in midlatitudes with large amplitudes in the pacific south american sector in the pacific anomalies in the subtropics and in the midlatitudes are opposite in phase taken together the two psa modes represent the intraseasonal oscillation in the sh with periods of roughly 40 days the evolution of the psa modes shows a coherent eastward propagation a composite analysis was conducted to study the evolution of tropical convection and the corresponding circulation changes associated with the psa modes outgoing longwave radiation olr anomaly composites during the mature phase

stable carbon isotope compositions of crude oils application to source depositional environments and petroleum alteration the carbon isotopic composition of the c15 saturate and aromatic hydrocarbon fractions and the gas chromatographs of the c15 saturate fraction of 339 oils were geochemically and statistically evaluated results of this study show that the average isotopic compositions of the c15 aromatic hydrocarbon fractions of oils sourced from terrigenous or marine organic matter are identical the average isotopic composition of the c15 saturate fraction of oils derived from terrigenous organic sources is slightly more negative 0 9 pmil than the average for marine oils but this difference is insufficient to be used as a reliable source indicator reports in the literature stating that marine oils are isotopically more positive than te rigenous oils and that the difference can be utilized to distinguish between the two are therefore not supported by this study the isotopic differences between oils sourced from terrigenous and marine organic matter do not manifest themselves in the range of absolute values of one oil fraction but rather in the isotopic relationship between the saturate and aromatic hydrocarbon fractions the isotopic relationship is the following oils of terrigenous organic source dgr13caro 1 12 dgr13csat 5 45 oils of marine organic source dgr13caro 1 10 dgr13csat 3 75 the difference between the two equations was evaluated statistically and a statistical parameter cv the canonical variable cv 2 53 dgr13csat 2 22 dgr13caro 11 65 was used to distinguish between marine and terrigenous oils cv values larger than 0 47 indicate predominantly a terrigenous organic source for the oil whereas cv values smaller than 0 47 indicate mostly a marine organic source thermal maturity differences in oils and isotopic variations in the source beds can cause as much as 2 pmil variations in the isotopic composition of one family of oils finally stable carbon isotopes can in some situations help correlate biodegraded oils to their nondegraded counterparts

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

global teleconnections in response to freshening over the antarctic ocean abstract in this paper coupled ocean atmosphere responses to freshening over the antarctic ocean are investigated in a fully coupled model with a series of sensitivity experiments in the model 1 0 sv 1 sv 106 m3 s 1 of freshwater flux is uniformly imposed over the antarctic ocean for 400 yr while the ocean and atmosphere remain fully coupled both locally and elsewhere the model explicitly demonstrates that a freshening of the antarctic ocean can induce a significant local cooling coupled with an intensification of the westerly winds and expansion of sea ice furthermore the cooling can extend to the entire southern extratropical and tropical oceans coupled with an intensification of southeasterly trades and the equatorial trade winds some modest warm anomalies also occur in the northern extratropical oceans forming a sharp interhemispheric sst contrast a series of sensitivity experiments are conducted to understand the mechanisms responsible for transmitting the southern high latitude cooling

chemometric differentiation of crude oil families in the southern dongying depression bohai bay basin china abstract fifty seven crude oil samples from the southern dongying depression were selected for detailed geochemical analysis high c26 c25 tricyclic terpanes 0 81 1 26 and low c31 homohopane r c30 hopane 0 15 0 26 ratios indicate that the oils are from lacustrine source rocks the presence of c30 4 methyl 24 ethylcholestanes and c30 tetracyclic polyprenoids imply the contribution of microalgal organic matter large variations of depositional environment related biomarker parameters suggest differences in organofacies and water environment four genetically distinct oil families were differentiated by chemometrics of hierarchical cluster and principal component analyses using the parameter dataset of three isotope ratios and 15 molecular parameters all related to source and depositional environment family i is mature and does not match any available source rocks the inferred source rock contains microalgal material that could produce large quantities of wax c29 steranes and tricyclic terpenoids in a reducing salinity stratified water column family ii is characterized by a strong phytane dominance relatively high gammacerane and c35 homohopanes and low diasterane and 4 methyl sterane contents it has high values of sterane hopane s h 1 67 4 14 c35 c34 homohopane c35h c34h 0 81 1 66 and gammacerane c30 hopane g c30h 0 57 1 13 and low pristane phytane pr ph 0 30 0 59 suggesting that the inferred source rock is the upper es4 interval family iii has characteristics distinct from families i and ii low s h 0 15 0 27 c35h c34h 0 39 0 49 and g c30h 0 03 0 12 ratios and high pr ph 0 48 1 90 c30 4m c29 20r 0 54 1 18 and c30 tetracyclic polyprenoid 0 54 0 66 ratios suggesting that the source rock is the lower es3 interval the family iv oils are compositionally in between the ranges of families ii and iii oils and in line with them in plots of geochemical parameters we suggest that family iv consists of mixed oils derived from the upper es4 and lower es3 intervals family ii has a relatively low thermal maturity and the inferred source rock may be located in the niuzhuang sag and or the southern gentle slope zone family iii is mature and its inferred source rock may be situated in the lijin and boxing sags the upper es4 and lower es3 source rocks in the three sags contribute the crude oils of family iv that occurs in the middle and eastern parts of the southern dongying depression