organic geochemistry of oils and condensates in the kekeya field southwest depression of the tarim basin china this study shows that the oils and condensates in the kekeya field in the tarim basin nw china belong to a single family most likely derived from marine shale source rocks deposited under oxic suboxic conditions with mixed terrigenous and algal bacterial organic inputs the maturity data clearly indicate that the paraffinic condensates were not formed by thermal cracking of oil during late catagenesis ro 1 2 both the oils and condensates were generated within the normal oil window whereas addition of gaseous hydrocarbons from a separate source resulted in migration fractionation and hence spuriously high heptane indices age specific biomarkers show that the oils and condensates were not generated from the mesozoic cenozoic strata but from the carboniferous permian sections 1d basin modeling results are consistent with this interpretation suggesting that the mesozoic eocene strata are currently immature with respect to hydrocarbon generation and expulsion deep seated faults may have provided routes for upward fluid migration at the time of active deformation during several pulses of the himalayan orogeny the favored targets for further petroleum exploration in front of the kunlun mountains include the deep structures within the carboniferous permian strata for indigenous petroleum accumulations and anticlines and stratigraphic traps within the mesozoic cenozoic sections that are cut by deep seated thrust faults where secondary petroleum accumulations most likely occurred

holocene aeolian activity in the southwestern kalahari desert southern africa significance and relationships to late pleistocene dune building events little is known about the timing of dune building episodes in the southwestern kalahari desert previously arid phases when dune activity occurred have been inferred from gaps in chronologies derived from information that attests to former humid periods to redress this optically stimulated luminescence osl dating was applied to sediment samples taken from a range of aeolian landforms in the sw kalahari four periods of dune building are identified in the late pleistocene and holocene holocene aeolian activity at 6 ka and 1 2 ka led to the construction of localised dune forms in contrast to late pleistocene times when the extensive field of linear dunes that dominates the region was emplaced late holocene aridity was however sufficient to allow rapid emplacement of the lunette dune at witpan the record of aeolian activity is evaluated in the context of humid chronologies and an ocean atmosphere model of holocene climate change with good agreement obtained it is concluded that the application of

identifying marine incursions into the paleogene bohai bay basin lake system in northeastern china abstract the extent of marine influence on the paleogene bohai bay basin in northeastern china which accumulated mainly continental e g fluvial and lacustrine facies remains under debate evidence from geochemical paleontological and lithological data have documented several marine incursions but no systematic study has been conducted to investigate their timing and frequency and their significance for understanding the paleogene tectonic evolution of northeastern china in order to address the marine influence on sediment accumulation and to identify variations in paleosalinity during deposition of the mid eocene lower es3 es3l member of the shahejie formation this study analyzed multiple paleosalinity proxies b ga sr ba and s toc in fine grained siliciclastic argillaceous sediments of the luo 69 drillcore from the dongying depression all three proxies yielded similar paleosalinity interpretations with peak salinity and marine influence i e maximum b ga sr ba and s toc values occurring at the base of the es3l member and progressively declining salinities representing a shift toward brackish conditions upsection over an interval of 185 5 m representing 2 2 myr of sedimentation this paleosalinity record suggests gradual long term variations that were probably due to changes in tectonically controlled gateways linking the bohai bay basin to the yellow sea in addition to analysis of the mid eocene es3l member published data on the stratigraphic distribution of marine fossils glauconite and elemental paleosalinity proxies are applied to evaluate the history of marine incursions into the bohai bay lake system throughout the mid to late paleogene 50 24 ma this analysis revealed four intervals of probable major marine incursions dating to the early eocene the middle eocene the early oligocene and the late oligocene

organic matter rich shales of china abstract organic matter rich shales are the main target rocks for unconventional oil and gas exploration and development across the world in china shale gas geological resources are estimated as approximately 110 1012 m3 with recoverable gas reserves of ca 20 1012 m3 recoverable shale oil reserves are estimated as ca 5 109 t a total 35 important organic matter rich shale units have been recognized from mesoproterozoic to cenozoic strata across the entire china these shales are categorized according to their origin under marine marine nonmarine transitional and lacustrine conditions shales of marine origin with ca 9 1012 m3 recoverable resources dominate china s potential in terms of total volume of organic carbon currently the most favorable marine shales for oil and gas exploration are found in the sichuan basin within the lower cambrian qiongzhusi formation and in the wufeng longmaxi formations of uppermost ordovician through lower silurian a fortuitous combination of of sea level variations of paleo productivity of tectonic activity causing development and migration of partially closed deep basin depocenters and of sediment accumulation rates controlled the extensive deposition and distribution of organic matter rich shales in these wufeng and longmaxi formations organic matter rich shales in marine nonmarine transitional facies associated with coal measures occur in north china within the carboniferous and permian and in south china within the permian these carboniferous permian organic matter rich shales are important source rocks for the gas fields in the ordos and sichuan basins abundant organic rich shales are also widely distributed within coal bearing clastics and coal measure shales of fluvial lacustrine and swamp facies in upper triassic to middle jurassic successions of many basins lacustrine organic rich shales were deposited during the permian through neogene in various freshwater to saline lake settings lacustrine organic matter rich shales are the main oil source rocks in the songliao bohai bay ordos and junggar basins lacustrine algae contributed to the rain of organic matter and the preservation of organic matter and distribution of organic rich shale was controlled by lake currents water depth and oxygen poor conditions with enhanced preservation when buried by turbidity currents algal blooms were partly induced by trace nutrients from volcanic ash falls in all of these lacustrine basins seawater intrusion into the freshwater lake of the songliao basin promoted some episodes of black shales saline lacustrine basins such as middle permian junggar basin contain organic rich dolomite mudstone that mainly formed during hot climate conditions when the lakes had high salinity and stratified water columns that deprived the bottom waters of oxygen thereby preserving massive amounts of organic matter laminated calcite rich mudstone in the saline lacustrine settings formed in more brackish waters under stable warm conditions and weak biological activity the modeling of the factors controlling the distribution of organic matter rich shales within china s basins is important for the exploration and development of unconventional oil and gas resources

dune mobility and vegetation cover in the southwest kalahari desert as part of a wider project investigating the palaeoenvironmental significance of partially vegetated linear dunes in the southwest kalahari data collected in the latter part of 1992 concerning dune movement and vegetation cover suggest that sediment transport is occurring on some dune surfaces and that the majority of surface activity occurs on the crests and upper slopes of the dunes the data suggest that the limiting variables on surface sediment movement vary on different parts of a dune on interdunes and lower dune slopes the primary limiting variable is available wind energy while on dune crests and upper slopes it is vegetation cover ground cover by litter has much greater importance in protecting the surface sediment from erosion than rooted vegetation from individual data points no evidence is found to support a threshold vegetation cover below which sediment movement occurs rather a gradient of activity is suggested whereby a reduction in vegetation cover increases the potential for sediment movement and surface change however dunes with differing amounts of mean vegetation cover display differing degrees of surface activity and at this scale a vegetation cover threshold in the region of 14 per cent may be recognized

evaluating late cretaceous oaes and the influence of marine incursions on organic carbon burial in an expansive east asian paleo lake abstract expansive late cretaceous lacustrine deposits of east asia offer unique stratigraphic records to better understand regional responses to global climate events such as oceanic anoxic events oaes and terrestrial organic carbon burial dynamics this study presents bulk organic carbon isotopes 13 c org elemental concentrations xrf and initial osmium ratios 187 os 188 os os i from the turonian coniacian qingshankou formation a 5 ma lacustrine mudstone succession in the songliao basin of northeast china a notable 13 c org excursion 2 5 in organic carbon lean qingshankou members 2 3 correlates to oae3 in the western interior basin wib of north america within temporal uncertainty of high precision age models decreases in carbon isotopic fractionation 13 c through oae3 in the wib and songliao basin suggest that significantly elevated global rates of organic carbon burial drew down pco 2 likely cooling climate despite this os i chemostratigraphy demonstrates no major changes in global volcanism or weathering trends through oae3 identification of oae3 in a lake system is consistent with lacustrine records of other oaes e g toarcian oae and underscores that terrestrial environments were sensitive to climate perturbations associated with oaes additionally the relatively radiogenic os i chemostratigraphy and xrf data confirm that the qingshankou formation was deposited in a non marine setting organic carbon rich intervals preserve no compelling os i evidence for marine incursions an existing hypothesis for generating member 1 s prolific petroleum source rocks based on our results we present a model for water column stratification and source rock deposition independent of marine incursions detailing dominant biogeochemical cycles and lacustrine organic carbon burial mechanisms

analysis of linear sand dune morphological variability southwestern kalahari desert abstract linear dunes are the most common desert dune form usually occurring in extensive dunefields rather than as isolated individuals as part of a wider project investigating the dynamics and environmental significance of linear dunes the extensive linear dunefield of the southwestern kalahari desert southern africa was investigated for planimetric pattern variability considerable intradunefield variability was identified through aerial photograph analysis of a 4000 km 2 area leading to the development of a five class classification scheme this scheme was validated statistically utilising data for key planimetric pattern variables y junctions termini orientation range and wavelength the application of the classification scheme thoughout the dunefield permits the identification of trends in planimetric patterns this provides a basis for first attempts to explain aspects of planimetric variability in terms of the behaviour of linear dunes and their responses to key environmental variables

stable isotopic evidence for climate and basin evolution of the late cretaceous songliao basin china abstract because of the need to understand the links and feedbacks of the carbon cycle during times of global greenhouse conditions numerous studies have focused on the cretaceous climate much of what we know about this warm period in earth s history comes from the study of ocean sediments recovered from both ocean drill cores and marine sediments exposed at the earth s surface in contrast there are few studies of cretaceous terrestrial sediments the songliao basin located in northeast china offers a unique opportunity to understand cretaceous paleoclimate of terrestrial settings because it contains a nearly complete record of lacustrine sediments deposited throughout the cretaceous and there is an active drilling program to recover core from this paleolake we present carbon oxygen and strontium isotopic data from ostracods collected from two drill cores sk 1 n and sk 1 s that cover a time interval that extends from the turonian through the maastrichtian these data record robust isotopic trends with numerous carbon and oxygen isotope shifts that are both rapid and long term we tentatively interpret this record to reflect changes in both global climate and regional basin evolution in the turonian and coniacian qingshankou formation we observe several carbon isotope shifts that appear to be correlative to marine isotopic records based upon timing and magnitude of the isotopic changes we suggest that the carbon isotope record in the songliao basin reflect the decrease in carbon isotope ratios following the strong positive excursion at the cenomanian turonian boundary a positive isotope excursion in the late turonian and the negative isotope shift that occurs at the turonian coniacian boundary upward in the section however the marine and songliao isotopic records diverge as sediment sources shift from the southwest east and north to more northerly strontium isotopes record the change in source region as they increase markedly between the coniacian santonian yaojia and santonian campanian nenjiang formations as this is the first isotopic record of the songliao basin we are cautious about many of our interpretations of these isotopic data yet it is clear that with tighter age constraints and focused sampling centered on many of the isotope excursions presented here will allow for a deeper understanding of the terrestrial response to changing climate and the hydrologic response to basin evolution

relationship between petroleum composition and depositional environment of petroleum source rocks crude oils of nonmarine source can be distinguished from those of marine shale source and from oils originating in marine carbonate sequences by using a battery of geochemical parameters as demonstrated with a sample suite of nearly 40 oils a novel parameter based on the presence of c30 steranes in the oil was found to be a definitive indication of a contribution to the source from marine derived organic matter a second novel parameter based on monoaromatized steroid distributions was effective in helping to distinguish nonmarine from marine crudes and can be used to gauge relative amounts of higher plant input to oils within a given basin sterane distributions were similarly useful for detecting higher plant input but were less effective than monoaromatize steroid distributions for making marine versus nonmarine distinctions concentrations of high molecular weight paraffin can also be effective nonmarine indicators but are influenced by maturation and biodegradation processes certain algal derived nonmarine oils may show little high molecular weight paraffin response oils from carbonate sources with a few exceptions can be distinguished by having low pristane phytane ratios low carbon preference indexes and high sulfur contents gammacerane indexes and carbon isotope ratios of the whole crude are not effective in distinguishing these types of environmental differences on a global basis

extended 3β methylhopanes up to c45 in source rocks from the upper cretaceous qingshankou formation songliao basin northeast china abstract 3 methylhopanes methylated at the c 3 position of the a ring have been detected ubiquitously in sedimentary rocks with carbon numbers of c28 and c30 c36 these compounds have been attributed to aerobic methanotrophs due to their strongly 13c depleted compositions here we report 3 methylhopanes with carbon numbers up to c45 in source rocks from the first member of the upper cretaceous qingshankou formation songliao basin northeast china the extended homologues up to c45 might be derived from long chain alkyl bacteriohopanetetrols by consecutive enzymatic additions of a c5 sugar extremely 13c depleted compositions combined with a high 3 methylhopane index suggest an intense ch4 cycle induced by blooms of aerobic methanotrophs in the songliao paleo lake

paleoenvironmental reconstruction of the late santonian songliao paleo lake the late cretaceous is often characterized as having a variable greenhouse climate however the relatively few continental sites preserving geologic records from this time exist limiting information on terrestrial climate and environments worldwide the songliao basin slb of northeastern china is one of the largest cretaceous age continental rift basins thus this well preserved lacustrine deposit provides a unique record of terrestrial paleoenvironmental conditions during the cretaceous here we report organic geochemical data from late cretaceous age lacustrine deposits lower nenjiang formation from the eastern side of the slb outcrop samples were collected from the houjingou section and the following analyses were performed 1 total organic carbon toc content and isotopic composition 2 biomarker distribution including the identification and determination of relative amounts of both aliphatic and aromatic hydrocarbons and steranes and 3 compound specific stable carbon and hydrogen isotopic compositions of n alkanes the biomarker distribution and stable carbon isotopic values 13c of the toc indicate organic matter om from the uppermost section of the first member of the nenjiang formation upper k2n1 was mainly sourced from aquatic macrophytes and land plants in the lower part of the second member of the nenjiang formation lower k2n2 the biomarker distribution and 13c of both the toc and n alkanes indicate that om was sourced from a mixture of algae bacteria and higher plants as a result of marine transgression seawater incursions indicated by the presence of 24 n propyl cholestanes and 24 iso propyl cholestanes occurred episodically in lower k2n2 the negative hydrogen isotopic composition 2h of short chain n alkanes in lower k2n2 indicates an extremely humid environment and it is likely that an influx of freshwater caused large scale flooding of the songliao paleo lake high resolution biomarker and stable isotope records from the houjingou section demonstrate abrupt environmental changes in the songliao paleo lake following seawater incursions during the late cretaceous

rock magnetic records of the qingshankou formation of sk 1 south borehole in songliao basin northeast china and their paleoclimate implications abstract the south borehole sk 1s of the china cretaceous continental scientific drilling project songke 1 penetrated the late cretaceous lacustrine sediments in the central depression of the songliao basin northeast china in order to reveal the terrestrial records of the cretaceous climate changes high resolution rock magnetic records were obtained on the qingshankou formation k 2 qn of sk 1s the results indicate that detrital magnetite is the main remanence carrier of the k 2 qn formation while both magnetite and paramagnetic minerals including clay minerals and pyrite dominantly contribute to magnetic susceptibility although reductive diagenesis may have more or less effect on the magnetic signals of the k 2 qn formation they recorded ancient lake level changes well resulting both from the tectonic development of the basin and from the milankovitch astronomical paleoclimatic changes the first order vertical trends of the rock magnetic records were controlled by the shallowing upwards of the lake level caused by the tectonic uplift of the basin the short term variations of the rock magnetic records were controlled by the lake level periodical drift caused by the fluctuations of the rainfall of the catchment area of the basin which were controlled by astronomical orbital forcing in addition the magnetic records also distinguished two most anoxic periods during the lacustrine anoxic event 1 lae1 the sections of 1758 1761 m and 1769 1771 5 m which may suggest the two most active periods of surface productivity of the lake

coupled isotopic evidence for elevated pco2 and nitrogen limitation across the santonian campanian transition abstract the santonian campanian s c transition notably coincides with the termination of the cretaceous normal superchron a positive carbon isotope anomaly and the enhanced preservation of organic matter associated with an oceanic anoxic event at ca 84 ma the driving factors for the oaes should include global warming widely believed to be from volcanic sources the delivery of nutrients to surface oceans from the continents anoxic sediments and atmosphere and variations in the configuration of ocean basins to further investigate this phenomenon and evaluate whether there was a teleconnection between the marine and continental realm we have studied a lacustrine succession in northeastern china the songliao basin which is 3 the size of lake superior that preserves two thick horizons of oil shales and a positive carbon isotope anomaly recorded in ostracode carbonate near the s c boundary this freshwater basin is one of the many that formed as a consequence of mesozoic extensional tectonics in eastern asia the stratigraphic trends illustrate broad excursions in the isotopic compositions of carbonate total organic carbon including black carbon and total nitrogen the carbon isotope data suggest that maximal fractionation etoc at the s c boundary is caused by enhanced burial of organic carbon and inputs from anoxygenic photoautotrophs and chemoautotrophs or from the buildup of co2 in a lake environment on the other hand the nitrogen isotope data suggest that the lake became limited in nitrogen immediately before the deposition of the younger oil shale resulting in the addition of new nitrogen to the system likely as the result of diazotrophy or ammonium assimilation to some extent all of the features we described from the songliao basin have been recognized in jurassic and cretaceous oaes insofar as climatically sensitive lakes are typically supersaturated with co2 relative to the atmosphere we speculate that nutrient driven primary productivity in massive lake systems may have released enough greenhouse gas co2 ch4 and n2o into the atmosphere and therefore played a role in enhancing global temperatures and driving widespread anoxia in the mesozoic oceans

isotopic analysis of equid teeth from wonderwerk cave northern cape province south africa abstract stable carbon and nitrogen isotope ratios have been determined from equid teeth from a well dated sequence of holocene deposits at wonderwerk cave situated in a summer rainfall area of the northern cape province of south africa stable carbon isotope ratios confirm the existence of a c 4 grassland habitat throughout the holocene nitrogen isotope ratios are assessed in relation to data from modern equid samples from southern africa temporal variability in both carbon and nitrogen isotope ratios of holocene equid samples from wonderwerk appears to be analogous to spatial variability of such ratios determined for faunal samples from modern environments relationships between isotope ratios and data from modern environments are used to obtain rainfall indices

response of the benthic nepheloid layer to near inertial internal waves in southern lake michigan 1 time series measurements of water transparency water temperature and current velocity were made at a station located in 58 m of water in southern lake michigan during the summer of 1995 currents generated by near inertial internal waves are correlated with variations in the thickness and in the vertical distribution of suspended sediment in the benthic nepheloid layer although a direct causal link between internal wave action and changes in the nepheloid layer could not be established the data suggest that local resuspension by shoaling internal waves maintains the layer during the stratified period the origin and maintenance of the benthic nepheloid layer is most likely the result of local resuspension due to a combination of internal wave action and longer term processes

late cretaceous climate changes recorded in eastern asian lacustrine deposits and north american epieric sea strata abstract cretaceous climate data of the long lived cretaceous songliao basin sb in eastern asia is correlated and compared with the western interior seaway wis on the northern american plate in order to understand better the dynamics of the earth s past greenhouse climates nearly continuous late cretaceous terrestrial deposition in the songliao basin is represented by two cores totaling 2431 m in length the turonian maastrichtian age of the section is based on integrated stratigraphy and is comparable in age with upper cretaceous strata in the wis being consistent with global trends the dynamic late cretaceous climates of both the sb and wis gradually cooled from the warmest albian cenomanian time to the end of the maastrichtian with several intervening warm periods as did the global climate however regional differences existed the songliao basin climate was humid to semi humid warm temperate subtropical and the western interior seaway was in the humid warm temperate zone and experienced only moderate climatic changes the shifts of oxygen isotope data in the songliao basin were frequent and abrupt whereas wis records more gradual change affected mainly by fresh water runoff mixing with southern tethyan and northern arctic waters sedimentary cycles of eccentricity obliquity and precession bands are recorded in both the sb and wis basins the sedimentary cycles in the wis and sb are interpreted to be related to variations of the wet dry runoff cycles which indicate that orbital forcing played an important role in global climate change in late cretaceous the most favorable condition for organic carbon burial in both the sb and wis basin was bottom water anoxia regardless of the cause of the anoxia but the organic carbon burial rate was usually much higher in the songliao lake than in the wi epeiric sea suggesting that giant lakes may serve as important sinks of atmospheric co 2 in both basins organic rich deposits formed during a rise in water level and incursion of saline waters the integration of paleoclimate data from cretaceous marine deposits and terrestrial sedimentary record will promote our understanding of the cretaceous greenhouse climate change and may provide insights for a future greenhouse world

lateral migration thermoluminescence chronology and colour variation of longitudinal dunes near birdsville in the simpson desert central australia the longitudinal dunes of the simpson desert in the vicinity of birdsville have been reworked largely during the holocene from dunes deposited up to 80000 years ago or earlier the widespread asymmetry of these roughly northward trending dunes with steeper eastern faces and more gentle western faces supports wind rose data showing sand transporting winds from the southwest obliquely intersecting the dunes while this suggests a change in the wind pattern since the dune field was oriented it does not indicate that the dunes are necessarily shifting leeward eastward as a consequence it is hypothesized that the direction of migration is controlled by the extent to which the dunes are vegetated relatively well vegetated dunes can accrete sand on their gentle stoss slopes and erode on their lee slopes causing them to shift westward and hence obliquely into the wind a condition that probably prevails in wetter regions and during episodes of relatively humid climate in contrast in very dry areas or during arid phases sand can move unimpeded up a sparsely vegetated stoss face and over the crest to form an avalanche or slip face on the lee side thereby causing the dunes to shift eastward despite evidence that longitudinal dune crests can shift laterally to some extent the dunes in the western part of the simpson desert have not migrated either westward or eastward more than 100m or so from their pleistocene cores aeolian transport and partial or complete removal of iron cutans from around quartz grains results in dunes of widely varying colour yet of similar age

palaeoenvironmental conditions during deposition of the upper cretaceous oil shale sequences in the songliao basin ne china implications from geochemical analysis abstract excellent hydrocarbon source rocks oil shales containing type i organic matter om were deposited in the continental songliao rift basin during the late cretaceous a major contribution of aquatic organisms dinoflagellates green algae botryococcus and minor input from macrophytes and land plants to om accumulation is indicated by n alkane distribution steroid composition and 13 c values of individual biomarkers microbial communities included heterotrophic bacteria cyanobacteria and chemoautotrophic bacteria as well as purple and green sulfur bacteria the presence of methanotrophic bacteria is indicated by 13 c depleted methyl hopane the sediments were deposited in a eutrophic alkaline palaeolake highly reducing saline bottom water conditions and a stratified water column existed during om accumulation of the qingshankou formation and member 1 of the nenjiang formation this is indicated by low pristane phytane gammacerane index and mttc ratios and the presence of carotane and aryl isoprenoids however an abrupt change in environmental conditions during deposition of member 2 of the nenjiang formation is indicated by significant changes in salinity and redox sensitive biomarker ratios a freshwater environment and suboxic conditions in the deep water prevailed during this period higher input of terrigenous om occurred during deposition of the upper nenjiang formation good oil to source rock correlation was obtained using biomarker fingerprints of oil stained sandstone from the quantou formation and oil shales from the qingshankou formation based on the extent of isomerisation of c 31 hopanes the oil was most probably derived from oil shales of the qingshankou formation in deeper parts of the basin

measurement of equivalent doses in quartz from contemporary water lain sediments using optically stimulated luminescence the single aliquot technique and its derivatives are very attractive for the measurement of the very small doses found in young materials because they inherently avoid concerns about low dose non linearity and can offer high precisions a modification is outlined to the single aliquot regeneration and added dose sara protocol mejdahl and botter jensen 1994 quaternary geochronology quaternary science reviews 13 551 5541 to permit its application to sedimentary quartz using the optically stimulated luminescence signal this revised protocol is then used to determine the doses found in several contemporary fluvial sediments and one coastal beach sand thought to be deposi ted by recent wave action two over bank river deposits were both homogeneously well bleached with doses of 0 4 gy although most of the grains in three channel deposits from a range of catchment sizes were also well bleached contamination by a small proportion of very poorly bleached quartz grains prevented the measurement of the dose in the majority the beach deposit was homogeneously bleached and contained a dose of about 0 02 gy it is concluded that over bank sites may provide accurate dates for samples older than a few hundred years but that the heterogeneity of the channel sites limits the accuracy of dates less than a few thousand years

organic matter accumulation in the upper cretaceous qingshankou and nenjiang formations songliao basin ne china implications from high resolution geochemical analysis abstract the songliao basin is well known as one of most prolific petroleum basins in china information regarding upper cretaceous organic matter om accumulation within black shales of the qingshankou and nenjiang formations fm can be obtained by geochemical analyses two oil shale successions at the bottom of the qingshankou fm first member k2qn1 and nenjiang fm second member k2n2 are investigated in high resolution to reveal the factors that govern om accumulation within the two target profiles combined petrological and geochemical results indicate that om accumulation can be divided into two phases i a lower phase characterized by high primary productivity enhanced input of terrigenous om and anaerobic conditions of om deposition toc maximum 18 25 wt and ii an upper phase of lower primary productivity and anoxic to dysoxic conditions in bottom water toc maximum 9 45 wt alternations of warmer and wetter climatic conditions provided the nutrients and fluctuations in lake level are suggested to be responsible for differences in redox conditions and bioproductivity between the two phases marine ingressions enhanced om preservation by promoting bottom water salinity e g anaerobic conditions with brackish saline water within k2qn1 lower phase the identification of different om accumulation mechanisms by high resolution geochemical analyses are expected to improve the prediction of high quality source rocks within uniform depositional environments

oil shale formation in the upper cretaceous nenjiang formation of the songliao basin ne china implications from organic and inorganic geochemical analyses abstract two oil shale layers are present in the upper cretaceous nenjiang formation of the songliao basin representing excellent hydrocarbon source rocks their biomarker compositions provide evidence for a major contribution by aquatic organisms within the photic zone of the water column phytoplankton blooms were promoted by warm humid climate and lake eutrophication salinity stratification and anoxic bottom water conditions are indicated in the lower oil shale layer whereas decreased salinity and partial oxygenation of the water column are evident in the upper oil shale layer moreover an increase in sizes of alginite from the lower to the upper oil shale layer and enhanced telalginite concentrations is detected therefore a stratified water column with high salinity and anoxic bottom water conditions contributes to organic matter om preservation in the lower oil shale layer in contrast high bioproductivity in combination with om preservation favored by enhanced algae sizes and telalginite concentrations are suggested as the om enrichment mechanisms in the upper oil shale layer in addition factors such as clay minerals microbial activity and detrital matter input cannot be ignored for their influence on om enrichment in this study a preservation model within the lower oil shale layer and a productivity model within the upper oil shale layer are established the models imply that excellent preservation is the major controlling factor for om enrichment in the lower oil shale layer whereas the high bioproductivity is the major controlling factor for om enrichment in the upper oil shale layer however the combination of both factors for oil shale deposition must be considered

a biomarker study of depositional paleoenvironments and source inputs for the massive formation of upper cretaceous lacustrine source rocks in the songliao basin china abstract the abundance and composition of total organic carbon aliphatic and aromatic hydrocarbons including biomarkers and the 13c composition of total organic matter and individual compounds in core samples of the nenjiang formation from the sk 1 borehole of the songliao basin provide information on the paleoenvironmental conditions of lacustrine sediments formed during the upper cretaceous the distribution of n alkanes and their 13c composition and 4 methylsteranes and dinosteranes in the first member of the nenjiang formation k2n1 indicate that the organic matter largely originated from algal organisms and is dominated by types i and ii kerogen the occurrence of gammacerane aryl isoprenoids isorenieratane and low pristane phytane and diasterane sterane ratios further suggest a salinity stratified water column associated with anoxic bottom waters as well as possible photic zone oxygen depletion conditions during major source rock deposition of the k2n1 the organic geochemical data also indicate significantly different depositional environments for the second member of the nenjiang formation k2n2 sediments which are interpreted to have been deposited under a uniform salinity non stratified oxic water column consequently although the organic matter in the k2n2 sediments was largely derived from algal and bacterial sources the kerogen types are dominantly iib and iii due to the oxidative degradation of organic matter combined with a gradual increase in land plant input furthermore the occurrence and shift of two saw toothed distribution patterns of the 13c composition of c29 to c33 n alkanes with w and m patterns being isotopically heavy odd and even numbered alkanes respectively is suggestive of organic input shift or an unknown mechanism of carbon uptake or isotopic fractionation in particular the heavy even carbon numbered high molecular weight n alkanes is rare and needs further investigation

new chronological evidence for the nature and timing of linear dune development in the southwest kalahari desert abstract the age of the linear dunes in the southwest kalahari desert has not previously been directly established by applying the optical dating method to samples from the dunefield a number of questions relating to the timing and nature of linear dune development are addressed the last major period of simple linear dune development occurred 17 000 10 000 years ago probably from the reworking of earlier aeolian sediments dune emplacement occurred under more arid probably windier conditions than those prevailing today which are only responsible for episodic surficial dune sand movement as well as simple linear dunes the dunefield also contains more complex linear dune patterns samples from one area in the eastern dunefield demonstrate that multi phase development is more probable for complex dune patterns as opposed to single phase evolution under a complex wind regime

paleoenvironmental implications of fixed dune systems in southern africa extensive systems of fixed linear dunes occur in the kalahari region of southern africa from 28 s to 16 30 s they provide evidence for large scale expansion of arid climates in the subcontinent during the quaternary on the basis of differing dune morphologies and alignments three periods of upper pleistocene aridity are recognised patterns of dune alignments reflect paleosand flow regimes and permit deduction of past winds and circulation patterns leading to the conclusion that arid episodes were associated with and probably caused by greater strength and persistence of the south african anticyclone a tentative chronology of the arid periods tends to support the hypothesis that subtropical aridity was contemporaneous with glacial conditions in high latitudes

compound specific carbon isotope study on the hydrocarbon biomarkers in lacustrine source rocks from songliao basin abstract stable carbon isotopic composition of organic matter 13 c org and compound specific 13 c values of biomarkers from 15 lacustrine source rocks were analyzed to identify the original paleoenvironment and source organisms the 13 c values of hopanes 13 c hop ranged from 68 7 to 32 and exhibit strongly 13 c depleted values in the lower part of member 1 of the nenjiang formation k 2 n 1 up to 68 7 suggesting an origin from predominantly methanotrophic bacteria 13 c enriched 13 c ga values and significantly 13 c depleted 13 c hop in k 2 n 1 which coincide with water stratification and an intermittent anoxic photic zone represents a shallow chemocline the presence of an intermittent anoxic photic zone which means that the anoxia expanded into the euphotic zone is beneficial for om preservation and results in high values of toc and hi in this section however the absence of gammacerane and 13 c enrichment of 13 c hop in member 2 of nenjiang formation k 2 n 2 reflect a deeper chemocline corresponding to relatively oxidizing conditions and low values of toc and hi moreover the negative correlation of toc vs 13 c org and hi vs 13 c org reflects the control of om formation by sedimentary environments rather than productivity in the water column thus the depth of the chemocline not only controls the abundance of om but also affects the development of the microbial community such as chemoautotrophic bacteria in the deep chemocline and chemoautotrophic and methanotrophic bacteria in the shallow chemocline moreover 13 c ga and 13 c values for 4 methyl steranes are related to water salinity with a higher salinity accompanied by 13 c enrichment in gammacerane and 4 methyl steranes

pyrite morphology in the first member of the late cretaceous qingshankou formation songliao basin northeast china abstract the study of sedimentary pyrite morphological characteristics provides useful information on depositional environments and early diagenic processes and can be used as an indicator of redox conditions in ancient lake bottom waters the results of this study in the songliao basin in northeastern china show that euhedral crystals and framboids are the dominant pyrite forms in the mudstones of the first member of the qingshankou formation k2qn1 the framboidal size distribution indicates that during the deposition of k2qn1 redox conditions in the bottom water fluctuated from oxic dysoxic to euxinic anoxic to oxic dysoxic the presence of euxinic anoxic bottom water suggests that an anoxic event developed in the songliao ancient lake and continued for 196 ka the development of an anoxic bottom environment was the most important factor in hydrocarbon source rock formation in the songliao basin

spatial variability and hydrologic evolution of australian lake basins analogue for pleistocene hydrologic change and evaporite formation abstract processes evident in basins across hydrologic gradients from humid to arid regions today provide analogues for systems that may have operated in some individual basins during periods of past hydrologic change thus lakes in humid regions today with low salinity sedimentary facies and with morphology controlled largely by wave action may closely resemble past lacustral pluvial phases experienced in zones which today are relatively arid and saline conversely playas controlled today by groundwater and in some cases subject to defletion may resemble those arid and dune building stages experienced by basins in sub humid regions today as they underwent glacial age desiccation in any such sequence of spatial or temporal gradients from humid to more arid conditions the frequency of basin filling and drying modulates the rate of evaporitive loss of interstitial waters from the exposed basin surface this in turn controls the salinity evolution of the interstitial and local groundwaters the notion of closed systems for terminal lakes while satisfactory for analysis of surface water budgets is quite inapplicable to the evolution of brines where surfacewater groundwater exchange during the high salinity drying stages becomes a controlling factor affecting all salt budgets in these systems evaporites may only be preserved when the sub surface waters have evolved to salinites near saturation for the salts concerned if sub surface waters are frequently diluted by surfacewater groundwater exchange evaporites will not be preserved in the record even though the surface system appears hydrologically closed the process of interstitial water evolution which controls efflorescence deflation and salt weathering exerts a dominating influence on basin geomorphic expression as well as on hydrochemical fractionation

high resolution geochemical analysis of organic matter accumulation in the qingshankou formation upper cretaceous songliao basin ne china abstract in the well known continental songliao basin the oil shale successions of the cretaceous qingshankou formation are excellent source rocks for oil the oil shale layers with high toc total organic carbon contents developed at the bottom of the formation they are divided into the lower oil shale toc up to 18 3 and the upper oil shale layer toc up to 14 4 the oil shale layers and accompanying mudstones are investigated by high resolution analyses of drill cores by pyrolysis organic petrology organic and inorganic geochemistry the results demonstrate the predominance of type i kerogen derived from algal microbial mats i e lamalginite however increased proportions of plant derived organic matter are indicated by rock eval parameters and the presence of vitrinite in the upper oil shale as evidenced from lower concentrations of hopanes higher sinking rates of organic matter om are suggested to have been responsible for a lower extent of microbial degradation during accumulation of the lower oil shale unit the environmental conditions are characterized by anoxic saline bottom water overlain by an extended zone of freshwater favorable for om production and preservation under these preconditions oil shale thickness and quality are governed by primary productivity related to accommodation space and nutrient supply redox conditions within the water column are the key factor controlling organic matter preservation

basin evolution and oil shale deposition during upper cretaceous in the songliao basin ne china implications from sequence stratigraphy and geochemistry abstract the controlling factors of oil shale formation within the upper cretaceous qingshankou and nenjiang formations of the songliao basin are investigated by petrological and geochemical methods sediment deposition was balanced by basin subsidence resulting in the accumulation of cretaceous strata of high thickness global sea level fluctuations have been related to periods of oil shale deposition within the basin the results indicate a comparable depositional environment during oil shale formation within the two upper cretaceous strata with respect to palaeotectonic and palaeoclimate but differences in the accommodation space during accumulation of the two formations the larger accommodation space during deposition of the nenjiang formation resulted in the higher thickness and wider distribution of the oil shale members total thickness 11 2 32 m distribution area 4 48 103 km2 within the basin as compared to the oil shale of the qingshankou formation total thickness 2 19 3 m distribution area 1 3 103 km2 further differences exist with regard to the palaeoenvironment of oil shale formation and primary productivity deposition of the qingshankou formation 1st member and nenjiang formation 1st member took place within a saline brackish lake under anoxic conditions in the bottom water preservation of organic matter is suggested to have been less favorable during deposition of the nenjiang formation 2nd member higher primary productivity is believed to be the responsible factor for the accumulation of organic rich sediments in the qingshankou formation 1st member the interplay of these two factors i e preservation productivity leads to the formation of oil shale in the qingshankou formation average toc 8 32 tocmax 13 52 average oil yield 5 57 with better hydrocarbon source rock potential and slightly higher oil yield during pyrolysis as in the nenjiang formation average toc 7 76 tocmax 9 7 average oil yield 5 54 primary productivity is suggested as the main controlling factor on differences in oil shale quality and source rock potential between the two formations whereas the variations in quality within each formation mainly depend on the preservation of organic matter the high thickness wide spatial distribution and excellent hydrocarbon potential of the upper cretaceous oil shales in the songliao basin are suggested to have been the result of large accommodation space stable palaeoenvironmental conditions and high primary productivity

sulfur rich petroleum derived from lacustrine carbonate source rocks in bohai bay basin east china abstract crude oils produced from the zhanhua depression bohai bay basin are high in sulfur and differ from most lacustrine oils in this basin and elsewhere physical properties biomarker ratios and aromatic hydrocarbon assemblages reveal that they are derived from carbonate source rock horizons representative source rock samples with abundant organic matter toc 1 and s 2 5 mg hc g rock were selected for further correlation and their high bitumen contents indicated their indigenousness to saline or carbonate depositional environments the results of oil source rock correlation suggest that these sulfur rich heavy oils originate from es 3 4 carbonates and marls limited to the bonan sag maturity assessments with burial history showed that they were expelled at the early oil generation window high levels of 20s 5 14 17 and 5 14 17 steranes together with low values for the ts ts tm ratio and two methylated aromatic ratios mdr and mpi 1 were observed in these oils sulfur associated with evaporite and carbonate environments is a significant factor not only in controlling the occurrence of biomarker isomers but also for petroleum formation at abnormally low thermal stress levels

the floating astronomical time scale for the terrestrial late cretaceous qingshankou formation from the songliao basin of northeast china and its stratigraphic and paleoclimate implications abstract the upper cretaceous qingshankou formation k 2 qn in the songliao basin slb of northeast china consists of up to 550 m thick lacustrine mudstone and shale that constitute one of the most important source rocks of the daqing oil field a high resolution cyclostratigraphic analysis of the natural gamma ray logging from 10 wells of the qingshankou formation k 2 qn reveals orbital cycles of precession 20 ka obliquity 40 ka and eccentricity 100 ka and 405 ka providing strong evidence for astronomically driven climate changes in the late cretaceous terrestrial environments floating astronomical time scales ats are established for all sections which demonstrate variable durations of k 2 qn across the basin 1 09 ma 5 20 ma and strong diachroneity of the lacustrine strata four periods of high depositional rates can be identified in the central parts of the basin possibly recording deposition during times of sustained wet climate and high chemical weathering an ats established from well m206 in the central depression zone of the basin where the most complete and stable milankovitch cycles are present suggests that the maximum duration of the k 2 qn is 5 20 ma from 94 27 ma to 89 07 ma late cenomanian to early coniacian the lacustrine anoxic event 1 lae1 at the cenomanian turonian boundary lasted 210 310 ka during which the most prolific petroleum source rocks in slb were deposited the onset 94 21 94 18 ma and duration 210 310 ka of lae1 in slb are comparable to those of the oceanic anoxic event 2 oae2 onset at 94 21 ma and duration of 320 900 ka suggesting that the same trigger mechanism such as increased atmospheric co 2 from large scale igneous activity may have initiated high primary productivity and organic carbon burial in both marine and terrestrial systems

tectonic and climate control of oil shale deposition in the upper cretaceous qingshankou formation songliao basin ne china oil shales were deposited in the songliao basin ne china during the upper cretaceous period representing excellent hydrocarbon source rocks high organic matter om contents a predominance of type i kerogen and a low maturity of om in the oil shales are indicated by bulk geochemical parameters and biomarker data a major contribution of aquatic organisms and minor inputs from terrigenous land plants to om input are indicated by n alkane distribution patterns composition of steroids and organic macerals strongly reducing bottom water conditions during the deposition of the oil shale sequences are indicated by low pristane phytane ratios high c14 aryl isoprenoid contents homohopane distribution patterns and high v ni ratios enhanced salinity stratification with mesosaline and alkaline bottom waters during deposition of the oil shales are indicated by high gammacerane index values low mttc ratios high carotene contents low toc s ratios and high sr ba ratios the stratified water column with anoxic conditions in the bottom water enhanced preservation of om moderate input of detrital minerals during the deposition of the oil shale sequences is reflected by titanium concentrations in this study environmental conditions in the paleo lake leading to om accumulation in the sediments are related to sequence stratigraphy governed by climate and tectonics the first member of the qingshankou formation k2qn1 in the songliao basin containing the oil shale sequence encompasses a third order sequence that can be divided into three system tracts transgressive system tract tst highstand system tract hst and regressive system tract rst enrichment of om changed from low values during tst i to high moderate values during tst ii iii and hst i ii low om enrichment occurs during rst i and rst ii therefore the highest enrichment of om in the sediments is related to stages of mid late tst and early hst

sulfur isotope constraints on marine transgression in the lacustrine upper cretaceous songliao basin northeastern china abstract organic rich cretaceous source rocks of the petroliferous songliao basin in northeast china are considered to be lacustrine in origin but paleontological and organic geochemical evidence suggest episodic marine incursions as a test of this hypothesis we applied time series measurements of elemental and isotopic abundances on core and cutting samples to evaluate fluctuations in the sulfur and carbon cycles across the santonian campanian transition preserved in the upper yaojia and lower nenjiang formations the data reveal a spike in pyrite sulfur abundance and a marked negative excursion in 34s at the base of the nenjiang formation when the basin expanded to its maximal extent the elemental and isotopic data suggest that flooding was associated with rapid marine transgression that enhanced sulfate concentrations which promoted microbial sulfate reduction in anoxic bottom waters that were episodically euxinic subsequent restriction of the basin and a decline in marine influence is supported by progressive upsection 34s enrichment up to 30 in nenjiang member i which are interpreted to reflect the distillation of sulfate through enhanced pyrite burial followed by a gradual return to lacustrine conditions that prevailed in overlying strata

structural and sedimentary evolution of the southern songliao basin northeast china and implications for hydrocarbon prospectivity the southern songliao basin manifests itself as a wide rift system that developed in northeast china from the late jurassic to early cretaceous individual basins in the system experienced marked rift subsidence but the postrift subsidence was insignificant in most of the basins contrasting strikingly with the tectonic subsidence history of the northern songliao basin two types of rift basins are defined according to whether the basins underwent prominent postrift subsidence type 1 basins are characterized by thick postrift accumulations type 2 basins although experiencing minor postrift subsidence represent most of the southern songliao basin and can be subdivided in accordance with bounding fault geometry and areal extent basins bounded by high angle faults type 2a basins bounded by low angle faults type 2b and basins with limited spatial area type 2c many rift basins are expressed as narrow belts in map view and are composed internally of several segments linked through different types of transfer zones depositional processes and facies architecture of the basins are controlled primarily by dips and migration of active bounding faults synrift depocenters occur close to high angle bounding faults and deep lake deposition commonly persists through much of the synrift subsidence lacustrine deposition can be enhanced by the backward or toward the footwall stepping of active bounding faults depocenters controlled by low angle bounding faults in contrast tend to shift basinward through time and deep lake facies commonly develop in the middle stage of rifting at the end of the cretaceous basin inversion was evident in type 1 basins such as the shiwu basin on the north but other basins appear to have mostly escaped the contractional deformation gravitational collapse of the previously thickened crust is considered the cause for the generation of the rift basins and lateral flow of the ductile lower crust may explain the significantly induced postrift subsidence of type 2 basins effective plays occur in basins bounded by high angle faults and therefore type 1 and type 2a basins are suggested to be the main targets of future oil exploration synrift source rock maturation might be partially attributed to the heating of early cretaceous magmatism because shallower burial alone could not elevate temperatures high enough for petroleum generation

late quaternary paleoenvironments in the southwestern kalahari abstract landforms of the southwestern kalahari in southern africa include linear dune systems pans and associated lunette dunes and the valleys of ephemeral rivers present day climates in the region are transitional from arid to semi arid making the area sensitive to climatic change the linear dunes are part of an extensive system of fixed dunes developed in the surface kalahari sands the dunes were in existence prior to 32 000 yr b p but have been reactivated on a number of occasions since then in conditions of increased wind velocities more nw winds and reduced rainfall especially in northern and eastern parts of the region periods of dune activity probably occurred at 19 000 17 000 10 000 6000 and 4000 3000 yr b p the development of pans in the region has been strongly influenced by changes in groundwater conditions deflation from pans and formation of lunettes occurred in periods when groundwater levels were higher and fluctuated seasonally more than they do today such periods probably occurred 25 000 20 000 yr b p around 10 000 yr b p and just prior to 1000 yr b p still higher groundwater discharges promoted by increased regional rainfall resulted in the formation of spring tufas and seasonal or permanent lakes in the pans which were also fed by surface runoff during the intervals between 33 000 28 000 23 000 21 000 17 000 15 000 and 12 000 11 000 yr b p the headwaters of the major ephemeral streams lie outside the region but within the same climatic zone increased flow in the molopo river occurred prior to 19 000 and between 15 000 and 13 000 yr b p

depositional environment thermal maturity and shale oil potential of the cretaceous qingshankou formation in the eastern changling sag songliao basin china an integrated organic and inorganic geochemistry approach abstract the changling sag in the petroliferous songliao basin has produced large amounts of conventional petroleum but studies on unconventional resources are rare a suite of core samples from the cy 1 well drilled in the eastern changling sag was analysed employing a series of micropetrographic geochemical and pyrolysis techniques to reveal the shale oil potential of the lower k2qn1 and middle k2qn2 qingshankou formation in this area for the first time from the lower k2qn1 upwards the sampled section the ratio of k al delineates an increasing palaeo temperature trend but still within a warm climate based on element ratios al2o3 toc and tio2 toc the highest terrestrial matter and nutrient supply on average occurred in the lower k2qn1 triggering bioproductivity toc ts and fe mn show that bottom water anoxia prevailed in the upper k2qn1 and lower k2qn2 providing excellent conditions for organic matter om preservation as compared to the lower k2qn1 high maturity of the studied layers is implied by e g vitrinite reflectance vrr of 1 03 1 09 tmax values over 445 c and molecular organic geochemical indices which correlate very well with vrr kinetic data on petroleum generation from open system pyrolysis were implemented in a numerical 1d basin and petroleum system model the k2qn1 has generated and expelled large amounts of petroleum 78 and 36 transformation of kerogen to petroleum based on kinetics of the low mature qingshankou shale om consisted originally of type i ii kerogen but has lost more than half of its original hydrocarbon generation potential upon maturation oil saturation index osi and s1 suggest that the studied layers show fair shale oil potential but are regarded as good conventional petroleum source rocks a newly proposed shale oil potential index sopi takes also thickness into account application to the qingshankou formation implies that the lower k2qn2 holds the highest shale oil potential

calibration of the c 14 timescale over the past 30 000 years using mass spectrometric u th ages from barbados corals uranium thorium ages obtained by mass spectrometry from corals raised off the island of barbados confirm the high precision of this technique over at least the past 30 000 years comparison of the u th ages with 14c ages obtained on the holocene samples shows that the u th ages are accurate because they accord with the dendrochronological calibration before 9 000 yr bp the 14c ages are systematically younger than the u th ages with a maximum difference of 3 500 yr at 20 000 yrbp the u th technique thus provides a way of calibrating the radiocarbon timescale beyond the range of dendrochronological calibration

palynological analysis of hyrax middens from southern africa abstract hyrax middens in relatively dry parts of africa preserve plant material which includes pollen the bottoms of two stratified hyrax dung middens from blydefontein basin in the karoo shrubland of south africa were dated by radiocarbon to ca 300 yr b p and ca 1130 yr b p comparison of midden pollen spectra with pollen from alluvial sediments near one of the hyrax middens and in modern surface samples indicates that middens contain pollen which reflects local vegetation and that diet probably does not have a major influence on pollen spectra changes in pollen composition probably reflect climatic conditions during the early history of the older midden profile grass dominated spectra suggest moist conditions existed between 1200 and 300 yr b p and an interval of slightly more shrubby karoid vegetation possibly points to a minor dry spell at 1000 yr b p a sharp increase of karoid shrub vegetation and a decrease of grass since 300 yr b p is reflected in both middens the change was apparently triggered by relatively dry conditions and later during the last 150 years it was enhanced by overgrazing from european domestic stock

marine transgressional events in the gigantic freshwater lake songliao paleontological and geochemical evidence abstract the fossil remains of euryhaline organisms in the mesozoic cenozoic non marine sedimentary records of eastern china may have resulted from either marine transgressions or inland hypersaline lacustrine environments paleontological and organic geochemical results of this study have provided new evidence for marine transgressional events in the gigantic freshwater lake songliao during the late cretaceous

optical dating of young modern sediments using quartz results from a selection of depositional environments abstract equivalent dose ed evaluations for quartz grains extracted from a number of modern or young samples collected from a range of depositional environments are reported the signal used was optically stimulated luminescence osl with an argon ion laser tuned to 514 nm as a light source typical equivalent dose values were 0 05 0 3 gy for the given samples which is substantially less than equivalent doses expected for similar sediments by conventional thermoluminescence tl the non zero equivalent dose exhibited by the samples may be a product of relict osl from incompletely bleached traps sample pre treatment procedures or due to signal recuperation following bleaching during antiquity the potential significance of each are discussed a number of modifications to sample pre treatment and processing are also described

continental scientific drilling project of cretaceous songliao basin scientific objectives and drilling technology abstract the continental scientific drilling project at the cretaceous age songliao basin is a drilling initiative under the framework of the international continental scientific drilling program to recover a nearly complete cretaceous terrestrial sedimentary record in the songliao basin northeastern china the recovered cores will provide unique opportunities for the geosciences community to advance the understanding of climate change in the cretaceous greenhouse world and provide a documentation of geological events relevant to the carbon cycle during this time period this drilling project will address significant geological questions such as the identification of important stratigraphic boundaries and the marine terrestrial correlations of stratigraphy the reasons for the biotic response to the terrestrial environmental changes the terrestrial response to the cretaceous oceanic anoxic events the formation of terrestrial petroleum source rocks and the mechanisms for the cretaceous magnetic normal superchron cns in the first stage of this drilling project the ski drilling rock cores of 2485 89 m in total length were recovered and the recovery ratio reached 96 46 a series of drilling and coring technologies including regular confined directional and sealed coring were utilized to ensure a higher recovery ratio for the core and will be described at the end of this paper well loggings were conducted right after coring core handling and storage were arranged in such a way that the scientific research was conducted on half of each core whereas the other half of each core was preserved for long term storage the upcoming second stage the skii drilling will combine with data from the existing ski to provide complete high resolution climate records of the terrestrial environment for the whole cretaceous time period

present day lunette sediment cycling at witpan in the arid southwestern kalahari desert abstract witpan is a pan depression in the southwestern kalahari desert the pan fringing lunette dune has a number of notable characteristics a highly active crest the lower lunette pediment is cemented and the lower lunette supports a highly developed and active gully system geomorphological and sedimentological considerations are used to evaluate the interaction of wind and water in shaping contemporary lunette processes it is considered that like other pans in the area groundwater activity influences pan floor sediment availability and transport that the present highly sea sonal climatic regime permits the interaction of aeolian transport of sediment to the dune and its return to the pan floor by water during storm events creating a cycling process favoured by sedimentary properties that promote surface runoff

depositional environment of the late santonian lacustrine source rocks in the songliao basin ne china implications from organic geochemical analyses abstract the songliao basin slb located in northeastern china is one of the largest cretaceous continental sedimentary basins in the world the slb is filled with sediments deposited in the upper jurassic the lower cretaceous and the upper cretaceous epochs the nenjiang formation k2n is subdivided into five members where member 2 k2n2 was deposited in the late santonian in the lower part of the nenjiang formation this member is characterized by a thick succession of organic rich source rocks however the complexity of the depositional environment raises questions about the specific factors that drove this accumulation of organic material here we present data on the total organic carbon toc contents and their stable carbon isotope values 13corg as well as biomarker data from 50 outcrop samples collected from the yuewangcheng ywc section in the southeastern slb according to the variations of the bulk organic parameters toc and 13corg and biomarker indices the profile could be divided into three stages stages i iii the distribution of biomarkers n alkanes steranes and hopanes and 13corg values indicate that the organic matter om in the lower k2n2 is derived largely from algae and macrophytes with a minor input from bacteria and land plants the water column was stratified as indicated by the presence of gammacerane variations in the pristane phytane pr ph and aryl isoprenoids relative to phenanthrene ratio a i p suggest that bottom waters were anoxic during stage i 31 5 26 0 m and stage ii 26 0 16 3 m with the anoxic layer impinging on the euphotic zone and a relative oxic environment at stage iii 16 3 0 m this brackish environment persisted in the water over the interval represented by the section as reflected by methytrimethyltridecyl chromans mttcs index mttci and mttc mttc ratios marine transgressions with subsequent seawater incursions can be detected with the presence of 24 n propyl cholestanes and 24 isopropyl cholestanes in the lower k2n2 sediments especially during stage i these seawater incursions are closely correlated with anoxic conditions and the deposition of organic rich source rocks

optical dating of holocene dune sands in the ferris dune field wyoming abstract optical dating of late quaternary quartz dune sands from the clear creek portion of ferris dune field wyoming demonstrates the considerable potential of the technique as a chronostratigraphic tool a sequence of radiocarbon dated holocene interdune strata permit optical dating of the intercalated dune sand to be tested the concordance is good the optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at clear creek peaked during two relatively short phases at ca 8500 and 4000 yr b p the dates indicate that aeolian accumulation maxima at least in the clear creek area may not be synchronous with previously defined phases of marked aridity

aryl isoprenoids and diaromatic carotenoids in paleozoic source rocks and oils from the western canada and williston basins abstract aryl isoprenoids in the range c13 c31 have been identified in source rock bitumens and oils from several paleozoic age petroleum systems in the western canada and williston basins the principal compounds possess the 2 alkyl 1 3 4 trimethyl substitution pattern characteristic of diaromatic carotenoids found in the chlorobiaceae family of photosynthetic sulfur bacteria two c40 perhydrodiaromatic carotenoids which are structurally related to the presumed precursors of the aryl isoprenoids have also been identified in oils and source rock bitumens of the duvernay late devonian petroleum system pyrolysis gas chromatograms of kerogens isolated from several paleozoic source rocks show an unusual abundance of 1 2 3 4 tetramethylbenzene it is proposed that this compound arises from cleavage of diaromatic carotenoid moieties which have been incorporated into the kerogen structure with increasing maturation concentrations of the aryl isoprenoids in duvernay source rock bitumens increase to a point whereas the c40 perhydrodiaromatic carotenoids decrease steadily previous studies have suggested that aryl isoprenoids may be indicators of enhanced salinity environments this is not supported by the present work which shows high concentrations in source rocks associated with presumed normal marine salinities there is however a general association with intervals of condensed clastic or mixed clastic carbonate sedimentation within carbonate depositional systems from the association found and from parallels to modern habitats of photosynthetic bacteria it can be inferred that these biomarkers indicate prolific bacterial growth in a stratified water column at and below the oxic anoxic boundary layer in sub tropical to tropical marine environments

wind energy variations in the southwestern kalahari desert and implications for linear dunefield activity the southwestern kalahari linear dunefield which displays marked morphological variability possesses a partial but temporally and spatially variable vegetation cover and has frequently been described as a palaeodunefield palaeo status has been ascribed on the basis of several criteria including the presence of vegetation but also because dunes are thought to be out of alignment with modern resultant potential sand moving wind directions and because present day wind energy is regarded as low for the period 1960 1992 wind data from eight dunefield meteorological stations are analysed in detail to examine these assertions potential sand transport directions including spatial and temporal variations and potential drift directions for the windiest three month periods are calculated and explained it is concluded that the present day potential sand transport environment is markedly variable from year to year and from place to place while periods of low sand transport energy do occur it is also noted that the 1980s possessed considerable potential for sand transport in the dunefield directional variability is also relatively high perhaps exceeding that under which linear dunes can be expected to form because linear dune aeolian activity has a number of states however the present day wind environment may allow dune surface aeolian activity to occur which does not alter the overall pattern of the dunes

experimental study on the gas generation processes of lacustrine and marine shales in north china source implications for shale gas abstract using a high pressure semi closed thermal simulation system two organic rich lacustrine and marine immature shales from north china were investigated to probe the dynamic processes and potential for the gas generation throughout the oil gas window the results identified at least two processes during gas generation as revealed by changes of the gas dry coefficient c1 c1 5 and carbon isotopic composition of methane 13cmethane the first process is associated with kerogen thermal degradation and occurs during the main phase of oil generation showing an increasing trend of the dry coefficient and 13cmethane the second process begins during the late phase of oil generation accompanied by increasing yields of wet gas components and 13c depleted methane due to the lack of aliphatic carbon in kerogen in the highly to over mature stage as demonstrated by ftir analyses the second process is mainly related to the cracking of kerogen generated bitumen which is retained in the shale the hydrogen content a key parameter for petroleum generation is then used to quantitatively evaluate the gas generation potential from kerogen thermal degradation and retained bitumen cracking mass balance calculations show that kerogen generated bitumen that is retained in lacustrine and marine shales is estimated to contribute 30 of the total gas yields at the stage of 1 5 2 0 ro this result is consistent with the theoretical calculations from xia et al 2013 and has important implications for the shale gas sources and further the shale gas resource assessments before exploration in shale gas petroleum systems

methodological considerations in the optical dating of quartz abstract the optically stimulated luminescence from quartz grains extracted from sediments at two archaeological sites has been studied the sites were the upper palaeolithic site at hengistbury head dorset u k and the upper aterian site at chaperon rouge morocco problems associated with the technique of optical dating are discussed particularly the thermal treatment that is necessary to remove thermally unstable charge following artificial irradiation and the extrapolation of growth curves to estimate the equivalent dose the technique used is described and some preliminary dates are presented

marine incursion events in the late cretaceous songliao basin constraints from sulfur geochemistry records abstract songliao basin in ne china developed the most productive oilfield in the world sourced from terrestrial rocks the main source rock of the basin includes member 1 of the qingshankou k2qn1 and members 1 and 2 of the nenjiang formation k2nj1 2 however the exact reasons for the formation of the source rock especially the k2qn1 are still controversial former paleontological and organic geochemical research suggested that organic matter was deposited during marine incursion events of k2qn1 but further geochemical evidence is needed this paper explores the distinct sulfate levels that distinguish marine from fresh waters of the songliao paleo lake we undertook a systematic investigation the sulfur geochemistry of the sediments from top of member 4 of the quantou formation k1q4 to top of member 1 of the qingshankou k2qn1 the ratio of organic carbon to the pyrite sulfur toc pys proved the previously suggested saline conditions during the deposition of k2qn1 and the pyrite sulfur isotope indicated that marine incursion may not only have occurred for k2qn1 but also for top of k1q4 the exact time for the beginning of marine incursion is to be determined the marine incursion within k2qn1 is not strong and partially controlled by the fluctuation of paleo lake level the present study will be helpful for understanding the contribution of marine incursion events to the burial of organic carbon in the songliao paleo lake although further studies are still needed

superheavy pyrite in the upper cretaceous mudstone of the songliao basin ne china and its implication for paleolimnological environments abstract the widely developed dark mudstone in the upper cretaceous nenjiang formation of the songliao basin is a natural archive for reconstructing the palaeoenvironment a time series sulfur isotope study on the nenjiang formation reveals that authigenic pyrite from the paleo lake is enriched in 34s relative to coeval marine sulfate in the lower nenjiang member i and basal nenjiang member ii the occurrence of 34s enriched pyrite must be explained to understand the paleolimnological environment and the sulfur cycling during this period for which several explanations can be advanced based on a comparison of various mechanisms for superheavy pyrite formation we consider the presence of an anaerobic sulfate minimum zone smz in the paleo lake as the most likely scenario in this zone sulfate was enriched in 34s through microbial sulfate reduction msr and this heavy sulfate became the source for pore water or bottom water from which superheavy pyrite was produced the conceptual model for formation of the superheavy pyrite in the nenjiang formation indicates that the distribution range of the smz was variable in the different sedimentary stages of the nenjiang formation these variations were likely related to successive inputs of sulfate from continental weathering which led to partial mixing of sulfate and attenuation of the smz in the basal nenjiang member ii

optical dating of sediments a new method for dating sediments is proposed which determines the time since the sediment was last exposed to sunlight an argon ion laser is used to excite electrons from thermally stable light sensitive traps and the subsequent luminescence used as a measure of the past radiation dose two sample sequences spanning the periods 0 700 kyr and 0 6 kyr show steadily increasing luminescence with age an age of 62 8 kyr is obtained for a silt radiocarbon dated at 58 8 0 3 kyr problems were found with two much younger samples

dinosteranes 4 23 24 trimethylsteranes and other biological markers in dinoglagellate rich marine sediments of rhaetian age abstract alkane biological marker distributions and concentrations have been determined in 18 samples from a section of rhaetian age from the bristol trough and a quantitative micropalaeontological analysis carried out taking into account previous geological investigations of the sequence three end member depositional settings have been recognised from changes in total organic carbon content the biological markers and the micropalaeontological composition these depositional environments are attributed as follows the first which occurs in the lower part of the section corresponds to deposition in a supratidal sabkha type setting with the major organic input being of allochthonous origin the second also in the lower part of the section indicates the occurrence of periods of marine incursion with enhanced salinity resulting from evaporation in the upper part of the section marginal marine conditions are apparent with higher organic carbon biological marker and amorphous organic matter contents at the top suggesting the establishment of more stable conditions of oxygen depletion some sediments in the sequence are notable for containing an abundance of cysts of rhaetogonyaulax rhaetica one of the oldest marine dinoflagellates comparison of microfossil abundances with hydrocarbon abundances extends the circumstantial evidence for the dinophyceae being the major biological source of dinosteranes 4 23 24 trimethylcholestanes and some other 4 methyl steranes in marine sediments the presence of dinosteranes and their 24 ethyl counterparts extends the stratigraphic range of occurrence of such components back to the rhaetian c 31 methyl steranes in the sediments from the second depositional setting are tentatively assigned a 4 22 23 24 tetramethyl sterane skeleton and a dinoflagellate origin

sea surface temperature fluctuations during the holocene off the south coast of africa implications for terrestrial climate and rainfall models of southern african palaeoclimate implicate surface atmospheric circulation anoma lies as forcing large scale changes during the late quaternary the available proxy data are insufficient to test the models since they provide information about temperature and rainfall rather than surface circulation a conceptual model is proposed which links coastal ocean temperatures with atmospheric circulation and allows a history of surface circulation to be inferred from sea temperature data a holocene sea surface temperature sst record was constructed by measuring the oxygen isotope composition of marine mollusc shells preserved in an archaeological cave deposit on the coast of the eastern agulhas bank southern africa radiocarbon dating of individual shells allowed definition of the timing and timespan of events in the record by serially sampling along the growth axis of each shell information was obtained about intra annual variability as well as millennial scale trends during the early holocene th