tidally modulated occurrence of megaripples in a saturated surf zone 1 an abstracted model for saturated surf zone megaripple occurrence based on the hypothesis that megaripples form and persist unless flow conditions change too rapidly or the bed passes through the swash zone correctly predicts the bed state presence or absence of megaripples for 73 of measurements over 1 year at scripps beach more than seven standard deviations above the agreement between a random model and the measurements transitions between bed states are predicted within 1 5 hours for 54 of measurements compared with 6 agreement for a random model the model is forced with a record of water depth over the beach h from offshore tide measurements and inferred changes in bed elevation assuming that changes in flow conditions and depth are determined by tide level alone in a saturated surf zone model parameter values are estimated independent of model results megaripple formation time t 2 5 hours maximum rms depth change over time t hrms 0 1 m and minimum depth averaged over time t below which megaripples are smoothed hsw 0 3 m allowing model parameters to vary increases agreement between measurements and model predictions to a maximum 82 for parameter values t 3 hours hrms 0 05 m and hsw 0 1 m neither bed state nor bed state transitions are correlated with offshore wave conditions

synoptic imaging of nearshore bathymetric patterns 1 a new technique for near real time optical imaging of surf zone morphology synoptic imaging implemented at scripps beach la jolla california permits simultaneous measurements of the time varying position of individual linear and lunate megaripples fields of bed forms rocks cobble patches beach steps and sandbars and troughs a varying threshold filter for brightness is applied to video frames sampled at 1 hz to remove pixels corresponding to surface foam and suspended bubbles or sediment remaining fragments of the video frames are averaged over time intervals generally ranging from 5 to 10 min to produce images of the surf zone sand bed to facilitate accurate measurement of the position of sand bed features these images are enhanced to increase feature visibility transformed to plan view and corrected for refraction using surveyed bathymetry and tide level contrast in the images results from differences in water depth shading variations from tilted bed surfaces and changes in bed material the surveyed positions of megaripples and sandbars correspond to the positions of persistent features in the images a ray path model quantifying sand bed contrast as a function of water depth angle of line of sight and light attenuation coefficient in water predicts that for the scripps beach field site bed forms with height as small as 0 03 0 2 m can be detected in water depths up to 2 5 m in accord with observations and that visibility can be improved by changing the line of sight toward overhead viewing bed visibility is reduced by persistent surface foam and water turbidity generated by waves with period 8 s and height exceeding 1 5 m example images showing transitions between linear and lunate megaripples location of megaripple crestlines and the interaction between sandbars bed form fields and cobble patches illustrate the potential of synoptic imaging

evidence for mixed and biodegraded crude oils in the socororo field eastern venezuela basin this work presents a geochemical study of crude oils from the socororo field socororo major area in the maturin sub basin of the eastern venezuelan basin the v ni total concentrations and v v ni ratios suggest the presence of two oil groups these oils are heavy aromatic asphaltic and according to their sulfur content api gravity and hydrocarbon compositions fall into the same two groups established from the v and ni proxies although the analyzed crude oils show evidence of biodegradation it was possible to determine based on various biomarkers parameters that the oils originated from marine organic matter in a marine carbonate or marine marl source rock deposited under anoxic to suboxic conditions the oils were generated near the peak of the oil window distributions of n alkanes isoprenoids hopanes and steranes combined with a prominent unresolved complex mixture ucm indicate that the oils are biodegraded moreover the presence of pristane and phytane along with alteration of hopanes and steranes and the presence of 25 norhopanes reveals that these oils are mixtures showing different levels of biodegradation sulfur content v and ni concentration and saturate aromatic resin and asphaltene sara composition provide additional evidence for oil mixing such mixed oils originate from several episodes of charging and biodegradation in the reservoirs the first charge was severely biodegraded and many biomarkers susceptible to degradation n alkanes acyclic isoprenoids terpanes methyl hopanes methyl steranes and steranes were extensively altered or completely removed the second oil charge was subjected to a lower degree of biodegradation and only the n alkanes show significant biodegradation both oil charges seem to come from the same source rock which was deposited under variable redox conditions moreover due to their similar maturity the generation and migration of these oils to reservoirs likely occurred close together in time

biomarker distributions in australian oils predominantly derived from terrigenous source material oils found in many australian sedimentary basins contain a relatively high input of terrigenous organic source material a study of a large number of these oils has permitted a number of biomarker distributions to be determined that appear to be characteristic for oils derived from terrigenous source material these features include the presence of sesquiterpanes absence of tricyclic terpanes relatively high concentrations of a c24 tetracyclic terpane predominance of c29 steranes presence of two unidentified c27 and c30 terpanes and virtual absence of 18 h oleanane the latter observation is significant since it appears that 18 h oleanane appears only in oils of tertiary age derived from terrigenous source material an attempt has also been made to compare the results for the australian oils with published results for oils derived from terrigenous source material in other parts of the world the number of reports in the literature for these oils is fairly limited but it appears that some of the observations for the australian oils can be extended to them this study is an initial attempt to devise a classification scheme that can be used to determine the origin of an oil unambiguously from biomarker parameters in order for this approach to be successful a relatively large number of biomarker parameters need to be assigned as characteristic of a particular type of source material

upper permian lacustrine oil shales southern junggar basin northwest china upper permian organic rich lacustrine mudstones oil shales that crop out in the southern junggar basin rank among the richest and thickest petroleum source rock intervals in the world with maximum toc values reaching 34 and rock eval pyrolytic yields s 2 up to 200 kg hc t rock lacustrine sedimentary facies define an overall transgressive regressive cycle of approximately 2000 m gross thickness which includes approximately 800 m of source rocks averaging 4 1 toc and 26 2 kg hc t rock basinal facies comprise silicic organic rich laminated lacustrine mudstones and interbedded siltstones organic matter contained in the mudstones ranges in composition from type i to type iii basinal facies were deposited in a deep oxygen deficient stratified lake lake margi facies consist of nonlaminated siliciclastic mudstones rippled dolomitic siltstones and sandstones and minor limestones maximum toc values are approximately 6 desiccation cracks are common in the marginal facies but evaporite minerals are rare or absent biomarker correlation parameters measured from rock extracts exhibit significant stratigraphic variability but strongly support the hypothesis that upper permian lacustrine oil shales charge the giant karamay field in the northwestern junggar basin karamay oils are characterized by high relative abundances of beta carotane this characteristic is restricted to desiccated facies in the outcrop sections however we therefore propose that an abundance of beta carotane indicates elevated environmental salinities during deposition of the oil shales orographic precipitation induced by a paleo tian shan range may have provided fresh water to the southern areas of the basin while more evaporative conditions prevailed to the north outcrop oil seeps confirm that the outcrop sections have attained sufficient thermal maturity to generate oil t max values range from 431 to 451 degrees c vitrinite reflectances range from 0 73 to 0 88 and sterane isomerization ratios range from 0 30 to 0 48 20s 20s 20r matoil registered trademark computer modeling of burial history and thermal maturity of the outcrop sections indicates that approximately 4 5 km of triassic jurassic cover was needed to bring the oil shales to their current maturity the major phase of hydrocarbon generation in this area appears to have preceded the creation of traps by neogene thrusting which may account for the lack of discoveries in the southern junggar basin most of the oil discovered so far is trapped in structures which originated duri g the late paleozoic or mesozoic

pore connectivity and water accessibility in upper permian transitional shales southern china abstract pore connectivity of shale controls shale gas migration and production behavior the pore connectivity and water accessibility in clay rich upper permian transitional shales remain unclear contrast matching small angle neutron scattering cm sans tests were used to determine the accessibility of water to pores in the transitional shales complementary analyses with sans gas co2 and n2 physisorption isotherm mercury intrusion capillary pressure micp helium ion microscopy him as well as field emission scanning electron microscopy fe sem were conducted to study the pore connectivity and distribution characteristics of closed pores the results show that closed pores inaccessible to nitrogen molecules and mercury are mainly distributed in pore diameters 10 nm and associated with organic pores and interlayer spaces of illite smectite mixed layer mineral the pore volume values obtained from micp and n2 adsorption underestimate the large pores pore diameters 100 nm in shales based on deuterated water cm sans tests 87 98 of the pores 2 200 nm diameters are water connected in transitional samples the low accessibility to water is at pore sizes of 5 10 nm and 20 30 nm results from in situ gas contents show that closed pores have a certain gas bearing capacity but micropores pore diameters 2 nm control the gas occurrence in transitional samples the connectivity of the organic pore network and between organic pores and surrounding interparticle pores is directly supported by fe sem and him imaging overall improving pore fracture connectivity through effective fracturing techniques is a means of mitigating the rapid decline in shale gas production

multiscale connectivity characterization of marine shales in southern china by fluid intrusion small angle neutron scattering sans and fib sem abstract an evaluation of shale pore connectivity is essential for predicting the production behavior and optimizing the development plan of shale gas to systematically investigate the multiscale connectivity characteristics and controlling factors complementary tests were conducted on four overmature marine shale samples from southern china one each from longmaxi formation and wufeng formation and two from niutitang formation with different maturity and composition the methods included mercury intrusion capillary pressure micp spontaneous imbibition with deionized water and n decane saturated diffusion distribution with seven nano sized tracers n2 physisorption small angle neutron scattering sans and focused ion beam scanning electron microscopy fib sem tomography moreover a novel repeated micp measurement technique was developed and used to evaluate the pore connectivity from the distribution behavior of residual mercury results indicate that the connectivity loss of hydrophilic pore networks owing to an increased maturity and the compaction causes pore shrinkage and bond breakage between pore networks according to the three dimensional reconstruction and pore network extraction of fib sem images pores in organic matter om have a good pore connectivity but the minerals surrounding the om reduce the overall pore connectivity of the shale matrix by evaluating the pore connectivity using different methods the hydrocarbon migration pattern in overmature marine shales was established our results imply that in addition to creating induced fracture networks effectively connecting induced fractures with preexisting microcracks or joint sets between om pore networks and transport pores can also be used to enhance overall pore connectivity microwave heating in shale reservoirs may be an effective way of further improving the production and recovery of hydrocarbons

the pleistocene and holocene records of the mazarron basin se spain abstract here we reconstructed the evolution of the mazarron basin during the pleistocene and holocene in this regard we studied 9 cores with the aim to 1 define a chronological framework 2 obtain data on the palaeoenvironment and 3 establish the relationship with recent tectonics a total of 158 samples were recovered for amino acid racemization aar dating 4 for radiocarbon dating 14c and 332 for sedimentological and palaeontological determination and 110 for determination of the mineralogical content these approaches allowed us to elucidate the evolutionary phases of the palaeo landscape of the mazarron basin a fault controlled graben affected by diverse faults mainly those of las moreras and rella the ages of the records and the facies correlation indicate that las moreras fault controlled sedimentation during marine isotope stage mis 7 whereas the rella fault was strongly active during the middle holocene during mis7 a brackish lagoon developed in the western area overlying alluvial fan deposits later the area was uplifted thereby becoming exposed to erosion the activity of the rella fault allowed sedimentation in the western part of the mazarron basin during the middle holocene while in the upper holocene sedimentation occurred in the eastern part the holocene transgression was reflected in a temporarily floodable marsh in the hinterland with changing salinity conditions from brackish to euhaline waters along the sea front the marine influence was evident but not dominant thus the mazarron basin during the holocene was brackish to highly euhaline with variable biological diversity linked to a narrow and probably discontinuous communication with the sea with restricted circulation and long flushing times which was reflected by the significant presence of halite the record ended with recent alluvial anthropic sediments

upper oligocene lacustrine source rocks and petroleum systems of the northern qaidam basin northwest china our organic geochemical study of oils from the northern qaidam basin defines a family of genetically related oils that contain biomarkers indicative of source rocks deposited in tertiary hypersaline anoxic lacustrine settings although cenozoic outcrop samples from northern qaidam are too organic lean to be of source quality dark laminated upper oligocene mudstones containing gypsum crystals and pyrite from the shi 28 well yield total organic carbon toc and rock eval data indicative of fair to good source rocks organic matter is derived from algae and bacteria and there apparently was little contribution from terrestrial material biomarker data provide a good correlation between the produced oils and the upper oligocene shi 28 core samples hydrocarbons derived from these source rocks are contained in upper oligocene miocene and pliocene reservoirs although eight of the oil samples are from the northwest corner of the basin one sample in this genetic family of hypersaline oils comes from northeast qaidam an area previously believed to only produce oils derived from jurassic freshwater lacustrine source rocks this sample thus indicates the presence of an unidentified and undocumented source rock in the northeast part of the basin hypersaline oils and the associated source rocks have low biomarker maturity parameters thermal modeling indicates that hydrocarbon generation probably occurred in northwestern qaidam within the last 3 million years

population age structure techniques and ostracods applications in coastal hydrodynamics and paleoenvironmental analysis abstract ostracods are microcrustaceans that grow by moulting eight to nine instars in most cases and consequently studies of its populations need the application of some special techniques the population age structure techniques whatley in ostracoda in the earth sciences 1988 pp 245 256 are a simple statistical method to estimate paleoenvironmental conditions in fossil recent populations of ostracods for its application it is necessary to determine the percentages of each instar present in the samples studied in order to analyze the different types of population age structure histograms and their paleo environmental interpretations some potential applications are the paleo energy levels or the sedimentation rates in this paper these special techniques are applied to recent populations of the ostracod pontocythere elongata collected in littoral sediments of southwestern spain in this area the relative percentages of this species and the adult percentages are closely related with depth and consequently this species was used as a bathymetrical tracer in shallow neogene areas of the guadalquivir basin in addition a first three step multivariate analysis permits the definition of three groups closely related to the theoretical models proposed by whatley a group 1 structure or biocoenosis present either in recent low to medium energy environments located in erosional coastal stretches and neogene fair weather conditions b group 2 structure or high energy thanatocoenosis observed either in recent river mouths with groynes and neogene storm and post storm conditions and c group 3 structure or low energy thanatocoenosis characteristic of recent progradational coastal areas and present in the recent neogene deeper areas analyzed in this paper 30 40 m depth this separation is mainly controlled by intrinsic factors i e the natural growth of this species whereas the extrinsic factors i e the hydrodynamic levels are only a minor cause of the distribution of this species in the area studied

geochemical investigation of oils and source rocks from qianjiang depression of jianghan basin a terrigenous saline basin china abstract six oils and seven suspected source rocks from the jianghan saline basin in the central eastern part of china have been examined using a variety of geochemical techniques the results from this study show that oils from the third and fourth sections of the qianjiang formation eocene are derived from similar source materials but have a different source from the oils of xingouzui formation eocene in the same basin the oils of the xingouzui formation eocene are more mature and probably have a greater input of terrigenous source material and in all probability have migrated greater distances than the qianjiang oils oils from these sections are derived from an environment characterized as being extremely anoxic strongly reducing and highly saline the suspected source rocks examined in the study were from the qianjiang formation and were generally mature except for the shallowest sample the biomarker distributions in the suspected source rocks examined from the qianjiang formation were very different from those of the oils present in the same sections it is proposed that oils from the qianjiang formation have sources in addition to or exclusive of the suspected source rocks examined in this study

molecular isotopic characterisation of hydrocarbon biomarkers in palaeocene eocene evaporitic lacustrine source rocks from the jianghan basin china immature organic matter in lacustrine source rocks from the jianghan basin eastern china was studied for distributions and stable carbon isotopic compositions 13 c of hydrocarbon biomarkers all of the bitumens contain isorenieratane 13 c ca 17 indicating the presence of chlorobiaceae and thus periods of euxinic conditions extended into the photic zone aliphatic hydrocarbon fractions are dominated by pristane and phytane and contain relatively low amounts of 4a and 4 methylsteranes c 30 13 c ca 16 believed to originate from 4 methylsterols in dinoflagellates 13 c values of gammacerane ca 24 and c 30 17 21 h hopane ca 23 are consistent with an origin from bacterivorous ciliates that fed on chlorobiaceae the bitumens contain low relative amounts of organo sulphur compounds one rock contains c 37 and c 38 n alkanes 13 c ca 36 derived from alkadienes and alkenones of prymnesiophytes the distributions of hydrocarbon biomarkers suggest that they were initially sulphurised during early diagenesis and later released during early thermal maturation

the effect of wave breaking on surf zone turbulence and alongshore currents a modeling study the effect of breaking wave generated turbulence on the mean circulation turbulence and bottom stress in the surf zone is poorly understood a one dimensional vertical coupled turbulence k and mean flow model is developed that incorporates the effect of wave breaking with a time dependent surface turbulence flux and uses existing published model closures no model parameters are tuned to optimize model data agreement the model qualitatively reproduces the mean dissipation and production during the most energetic breaking wave conditions in 4 5 m water depth off of a sandy beach and slightly underpredicts the mean alongshore current by modeling a cross shore transect case example from the duck94 field experiment the observed surf zone dissipation depth scaling and the observed mean alongshore current although slightly underpredicted are generally reproduced wave breaking significantly reduces the modeled vertical shear suggesting that surf zone bottom stress cannot be estimated by fitting a logarithmic current profile to alongshore current observations model inferred drag coefficients follow parameterizations manning strickler that depend on the bed roughness and inversely on the water depth although the inverse depth dependence is likely a proxy for some other effect such as wave breaking variations in the bed roughness and the percentage of breaking wave energy entering the water column have a comparable effect on the mean alongshore current and drag coefficient however covarying the wave height forcing and dissipation and bed roughness separately results in an alongshore current drag coefficient only weakly strongly dependent on the bed roughness because of the competing effects of increased turbulence wave forcing and orbital wave velocities

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

nanometre sized pores in coal variations between coal basins and coal origin abstract we have used small angle neutron scattering sans to investigate the differences in methane and hexane penetration in pores in bituminous coal samples from the u s canada south africa and china and maceral concentrates from australian coals this work is an extension of previous work that showed consistent differences between the extent of penetration by methane into 10 20 nm size pores in inertinite in bituminous coals from australia north america and poland in this study we have confirmed that there are differences in the response of inertinite to methane and hexane penetration in coals sourced from different coal basins inertinite in permian australian coals generally has relatively high numbers of pores in the 2 5 250 nm size range and the pores are highly penetrable by methane and hexane coals sourced from western canada had similar penetrability to these australian coals however the penetrability of methane and hexane into inertinite from the australian illawarra coal measures also permian is substantially less than that of the other australian coals there are about 80 fewer 12 nm pores in illawarra inertinite compared to the other australian coals examined the inertinite in coals sourced from south africa and china had accessibility intermediate between the illawarra coals and the other australian coals the extent of hexane penetration was 10 20 less than cd4 penetration into the same coal and this difference was most pronounced in the 5 50 nm pore size range hexane and methane penetrability into the coals showed similar trends with inertinite content the observed variations in inertinite porosity between coals from different coal regions and coal basins may explain why previous studies differ in their observations of the relationships between gas sorption behavior permeability porosity and maceral composition these variations are not simply a demarcation between northern and southern hemisphere coals

petroleum systems in the jiangling dangyang area jianghan basin china source related geochemical data define at least four petroleum systems in the jiangling dangyang area of the jianghan basin eocene paleocene anoxic evaporitic lacustrine source rocks generated most of the crude oils in the area eocene qianjiang rock from the sha 13 well 1322 m contains fast reacting sulfur rich type is organic matter and its extract is most similar to the sha 13 oil sand bitumen qianjiang reservoir lower eocene paleocene xingouzhui rocks from the xin 73 well 842 and 862 m contain slow reacting low sulfur type i organic matter and their extracts are most similar to the sha 26 oil sand bitumen eocene jinsha reservoir and the ling 2 sha 24 and tuo 3 oils xingouzhui reservoirs two unidentified middle triassic or older marine carbonate evaporite source rocks or different facies of the same source rock generated the daxiakou oil triassic jialingjiang formation outcrop xingshan county and the moderately biodegraded tianwan seep oil permian changxing outcrop chengxi county respectively one or more unidentified marine source rocks which could include the lower permian qixia or the upper sinian doushantuo formations generated the miaoshi and yanmenkuo seep oils permian qixia outcrops the jingshan seep oil ordovician baota outcrop probably is related to these oils but could represent another petroleum system different kinetics for hydrocarbon generation among eocene qianjiang and lower eocene paleocene xingouzhui formation source rocks and chemical differences among the related oils are caused by organic facies variations high salinity and low eh enhanced the preservation of oil prone organic matter in these lacustrine settings and facilitated incorporation of sulfur into the organic matter anoxia and the unusual presence of abundant sulfate as gypsum resulted in the microbial reduction of sulfate to sulfide and incorporation of this sulfur into the kerogen for example biomarkers show that source rock in the sha 13 well 1322 m was deposited under more saline lower eh conditions than that in the ling 80 well 1808 m although both are from the qianjiang formation the sha 13 rock sample is more organic rich 6 62 vs 1 27 wt toc and has a higher hydrogen index 794 vs 501 mg hc g toc and faster reaction kinetics than the ling 80 sample kerogen from the sha 13 sample is type is because it has a high hydrogen index and an atomic s c ratio 0 074 in the range of sulfur rich fast reacting kerogens of the monterey formation s c 0 040 organic rich lower jurassic coaly rocks from outcrops at daxiakou contain immature to mature gas prone organic matter that is not related to any oils in the study several organic rich upper sinian to permian samples could have been source rocks in the past but are now highly mature based on high tmax 464 540 c and estimated vitrinite reflectance ro values mass balance calculations were used to estimate the original toc toc c in these samples prior to maturation these samples could not be correlated with the oils using biomarkers because of high maturities and low extract yields however stable carbon isotope type curves suggest that the miaoshi yanmenkuo permian qixia formation and the jingshan ordovician baota formation seep oils originated from source rocks in the lower permian qixia 3 00 wt toc or upper sinian doushantuo formations 5 96 wt toc lack of triaromatic dinosteroids in the miaoshi and yanmenkuo seep oils supports but does not prove a permian source rock very negative stable carbon isotope ratios for kerogens from the lower cambrian shuijintuo formation 33 5 to 33 6 8 85 16 64 wt toc show that they are not related to any of the analyzed oils

lower middle jurassic nonmarine source rocks and petroleum systems of the northern qaidam basin northwest china the qaidam basin is a nonmarine petroliferous basin on the northeastern margin of the tibet plateau potential source rocks are reported from tertiary saline lacustrine deposits and jurassic freshwater lacustrine or terrestrial strata the jurassic source rock is similar in terms of depositional system lithology age and organic geochemistry to nonmarine jurassic rocks that are thought to be potentially significant hydrocarbon sources in many basins of central asia including the tarim junggar and other important petroleum producing basins these jurassic source rocks were deposited in freshwater lacustrine systems in intracontinental foreland style basins during the early and middle jurassic these lacustrine strata are associated with coals and coaly mudstones with possible secondary importance as hydrocarbon source rocks oils from the northern qaidam basin can be divided into two groups based on molecular indicators of depositional environment and age diagnostic biomarkers those derived from this jurassic freshwater lacustrine source rock and those derived from a tertiary hypersaline lacustrine source rock the correlation of some qaidam oils to a jurassic source establishes a petroleum system involving these nonmarine jurassic source rocks oils of this petroleum system have been produced from tertiary and mesozoic reservoirs in anticlinal and thrust related traps in northeastern qaidam maturation modeling of the jurassic source rock indicates that these oils were generated and expelled during the miocene pliocene in much of northern qaidam the geological context of the basin suggests that drainage within the basin primarily was vertical probably mainly along faults until evaporite or overpressured shale seals were encountered in the overlying cenozoic section documentation of this petroleum system suggests other exploration targets remain underevaluated in northern and southwestern qaidam furthermore the northern qaidam petroleum system is a useful analog to interpret the role of similar jurassic source rocks in other sparsely documented basins of central asia

bedform geometry on a barred sandy shore abstract an instrumented sled was used to repeatedly measure nearshore profiles and bedform height length and asymmetry on a double barred beach at mangawhai northland new zealand the 6 week experiment measured cross shore profiles at 30 m intervals to 12 m water depth and 500 m alongshore bedform response to changing wave conditions that included both fairweather swell and storm waves was sampled bedform geometry is closely tied to large scale morphology with alternating bands of flat bed and lunate megaripples lmr 0 3 m 2 9 m on the longshore bars a transition in bedform morphology occurs on the seaward face of the outer bar with symmetrical vortex ripples 0 04 m 0 7 m replaced by lmr within the transition zone increases relative to so that increases onshore with a shift to increasingly 3 dimensional forms bedforms reconfigured to the fairweather swell 2 weeks after a storm at the start of the experiment this was shown by a substantial reduction in longshore and cross shore variability in average bedform size and steepness wave measurements made on the ripple field seaward of the longshore bars at 5 2 and 6 9 m mean sea level msl indicate that sand mobilisation was episodic under fairweather swell skin friction shields parameter w 0 35 by comparison w 2 under storm waves indicates that the entire nearshore bed was active at least to 6 9 m msl this is consistent with the presence of lmr on storm deposits to 6 m msl lunate megaripples dominate bed roughness when parameterised by 2 they persist seaward of the longshore bars for weeks after storms because substantial sand transport is required to reconfigure the bed to fairweather conditions the natural variability in bedform geometry will need to be accounted for if realistic morphodynamic models are to be realised

geochemical and biological marker assessment of depositional environments using brazilian offshore oils abstract a combined geochemical and molecular characterization of a wide selection of oils from the major brazilian offshore basins has been undertaken the elemental sulphur nickel and vanadium and bulk oapi and 13c properties of each sample been considered together with its molecular composition determined using liquid and gas chromatography and quantitative biological marker investigations using gas chromatography mass spectrometry for alkanes the results reveal significant differences in the chemical features of the various oils which enable them to be divided into five groups the distinction of the groups appears to reflect differences in the depositional environment of the source rocks of the oils each group is correlated tentatively with source rocks laid down in a specific depositional regime namely lacustrine freshwater lacustrine saline water marine evaporitic marine carbonate or marine deltaic the diagnostic features that allow this classification are the relative abundance and carbon number distributions of n alkanes pristane phytane ratios sulphur nickel and vanadium contents carbon isotope data the absolute concentrations of hopanes and steranes and their abundance relative to 4 methylsteranes and also the occurrence and abundance of several specific biological markers including 18 h oleanane gammacerane carotane tricyclic terpanes higher acyclic isoprenoids 28 30 bisnorhopane and 25 28 30 trisnorhopane this investigation shows the value of a combined geochemical and molecular approach in the assessment of the palaeoenvironment of deposition of the source rocks which gave rise to the oils

rotary sidescan images of nearshore bedform evolution during a storm abstract high resolution acoustic images are presented of bedform development on the crest of a nearshore bar during a storm the images were obtained using a 2 25 mhz rotating sidescan sonar the sonar system provides a continuous record of the evolution of the bedform field through time within a 10 m diameter field of view the images document the occurrence of ripples cross ripples and megaripples during the waning stages of the storm transitions among ripple types occurred on time scales of 1 3 h beginning with flat bed and culminating in highly 3 d short crested ripples

expelled oils and their impacts on rock eval data interpretation eocene qianjiang formation in jianghan basin china abstract source rock samples can be contaminated by expelled oils from nearby mature source rocks or from the organic rich laminae within the same source rock units the contaminations on the rock eval samples could produce a false high s1 peak a high production index pi a suppressed tmax and other anomalies identifying the samples affected by expelled oils assessing and correcting the impacts are crucial in source rock study for shale oil shale gas resource evaluation this study analyzes the rock eval 6 results of 43 core samples from two recent shale oil exploration wells of the eocene qianjiang formation a confined source rock unit embedded with salt intervals formed in a hypersaline lacustrine setting in central china the geochemical anomalies of the affected samples are shown through the available samples in this study criteria for identifying the affected samples are discussed and impacts on the conventional rock eval parameters and subsequent estimation of kinetic parameters presented this study provides insights into rock eval data interpretation particularly in source rock evaluation for estimating shale oil resources

porosity of coal and shale insights from gas adsorption and sans usans techniques two pennsylvanian coal samples spr326 and spr879 in1 and two upper devonian mississippian shale samples mm1 and mm3 from the illinois basin were studied with regard to their porosity and pore accessibility shale samples are early mature stage as indicated by vitrinite reflectance ro values of 0 55 for mm1 and 0 62 for mm3 the coal samples studied are of comparable maturity to the shale samples having vitrinite reflectance of 0 52 spr326 and 0 62 spr879 in1 gas n2 and co2 adsorption and small angle and ultrasmall angle neutron scattering techniques sans usans were used to understand differences in the porosity characteristics of the samples the results demonstrate that there is a major difference in mesopore 2 50 nm size distribution between the coal and shale samples while there was a close similarity in micropore 2 nm size distribution micropore and mesopore volumes correlate with organic matter content in the samples accessibility of pores in coal is pore size specific and

peculiarities of salt lake sediments as potential source rocks in china abstract hypersaline lake sediments are widely distributed in china and can be good sources for petroleum the palaeogene sediments of the jianghan basin in eastern china are a typical example composed of salt lake evaporite clastic facies in fault subsided basins their organic matter is variable but is dominated by type ii kerogen the biological marker characteristics of core extracts and oils from the jianghan basin include i low oep values for n alkanes and occasionally an even odd predominance ii a high concentration of phytane iii a relatively high gammacerane 17 h 21 h hopane ratio and iv abundant mainly nickel porphyrins sample guang 33 k 33 is typical of the immature oils found in the jianghan basin geological and geochemical data both indicate that it was generated from source rocks in the maturity range r 0 0 45 0 55 its characteristics are similar to those of immature source rocks with high concentrations of phytane steranes triterpanes and nickel porphyrins and for an oil extremely low values for molecular parameters of maturity such as c 29 20s 20s 20r 14 h 17 h steranes c 32 22s 22s 22r 17 h 21 h hopanes and dpep dpep etio porphyrins

geochemical characterization of the upper mississippian goddard formation noble ranch group and related oils in the anadarko basin of oklahoma the woodford shale is anecdotally assumed to be the major source of oil for plays in the anadarko basin including the stacked oil and condensate play in the southcentral oklahoma oil province scoop however there is little published geochemical work to confirm this assumption this study set out to identify a characteristic geochemical fingerprint for the goddard formation another potential source rock in the scoop to determine if the goddard is contributing to oil accumulations within the scoop the upper mississippian goddard formation has been a target for unconventional production in scoop since 2012 published geochemical interpretations for the goddard formation are still limited and this study represents the first detailed oil source rock correlation for the goddard in the scoop area the most characteristic geochemical signature of the goddard extracts is a predominance of tricyclic terpanes relative to the hopanes in the mass to charge ratio 191 chromatogram possibly related to enrichment via thermal stress or a unique source signature additional distinctive signatures were also identified for the triaromatic steroid hydrocarbons sesquiterpenoids and steranes the biomarker fingerprints of scoop oils are nearly identical with those of the goddard extracts in this study oils in the scoop therefore appear to originate from a mississippian source such as the goddard rather than the woodford this observation demonstrates the value of oil source rock correlation studies and suggests that there may be effective source rocks in the anadarko basin that have been overlooked in the past and should be re evaluated in detail

comparative ecological analysis of the ostracod faunas from low and high polluted southwestern spanish estuaries a multivariate approach abstract the distribution and abundance of both living and total ostracod populations from the estuaries of the southwestern spanish coast are discussed a total of 68 species were obtained from 120 bottom samples collected in the channels channel margins and salt marshes four assemblages were recognized in this area a urocythereis oblonga assemblage with marine species well represented in sandy substrates located near the mouths b loxoconcha rhomboidea assemblage mainly developed in the quiet tidal channels conected with the main channels of the marine domains c loxoconcha elliptica assemblage enclosing the most cosmopolitan and euryhaline species very abundant in muddy sediments and low to moderate hydrodynamic conditions and d leptocythere porcellanea assemblage only observed in the clayey silty channel margins of the most protected ebb channels in these transitional environments very unfavorable conditions for the ostracod development were found in a the erosional channels and channel margins b most of the salt marsh samples with high subaerial exposure and c sectors with high metallic pollution levels and acidic waters

sand bed roughness in the nearshore 1 measurements made using sonar altimeters mounted on an amphibious surveying vehicle are analyzed for root mean square rms bedform roughness observations for 22 days over a 500 m 700 m area are used to quantify the cross shore distribution of roughness and its variability large bedforms with amplitudes 5 50 cm occur frequently in shallow water 2 m water depth however the patchiness of these bedforms is also largest in shallow water this is likely owing to the spatial and temporal variability of the waves and currents of the sediment grain size distributions and of the large scale nearshore morphology large bedforms were observed to exist only for mobility numbers 150 above this threshold the rms roughness was 2 cm and the bed was interpreted to have transitioned to sheet flow conditions however the state of the bed e g large ripples small ripples flat bed was not predictable for mobility numbers between about 30 and 150 existing models for orbital ripples do not predict the observed large bedforms and have little predictive skill for these data

the relationship between ostracod distribution and sediment grain size abstract sediment samples from an area seaward of the river crouch in the thames estuary have been analysed for their particle size distribution and later picked over for ostracods the sediments were classified into sediment types and three depositional sub environments were recognised viz intertidal flat sandbank and tidal channel study of the ostracods showed that three distinct faunas characterise the same three environments log grain size probability plots have been used to show a relationship between ostracod distribution and sediment grain size

reworked calcareous nannofossils as ocean dynamic tracers the guadiana shelf case study sw iberia for most micropalaeontological studies the presence of reworked specimens is usually considered as a disturbing factor where palaeoenvironmental or biostratigraphic interpretations are to be made however reworking of microfossils such as calcareous nannofossils can be used as an additional parameter in routine micropalaeontological work providing useful information on erosion transport processes acting on silty clay sized particles deriving from areas surrounding the sedimentary basin under study most of the reworked calcareous nannofossils found in the guadiana estuary water column september 2001 adjacent shelf surface sediments and a slope section of the gulf of cadiz were mainly of upper cretaceous age campanian to maastrichtian being dominated by biscutum spp cribrosphaerella ehrenbergii prediscosphaera cretacea and watznaueria barnesae since there are no upper cretaceous outcrops in the guadiana s hydrographic basin or southern portugal the source of this material must be located elsewhere matrix breccias from mud volcanoes discovered in deeper water southern portuguese and western moroccan margins of the gulf of cadiz during the ttr 10 cruise in july august 2000 as well as silty clay sediments from its slopes revealed similar calcareous nannofossil assemblages as those found on the algarve continental shelf and inside the guadiana s estuary this may indicate that most of the reworked nannofossils have their origin in deepwater areas of the gulf of cadiz the good preservation of most of the reworked cretaceous nannofossils suggest that shortly after resuspension swift transport occurred from the source area to the coastal region of the guadiana s river mouth implicating a northward change in the deep mediterranean water direction within the gulf of cadiz which reaches the upper southwest iberia slope the mediterranean outflow is therefore the major mechanism accountable for transporting upper cretaceous material to the southwest iberian margin and the atlantic inflow together with longitudinal coastal currents is the probable responsible for carrying and spreading eastward these reworked silty clay sized particles over the portuguese and spanish continental shelf this case study is a clear example of the potential importance of calcareous nannofossils as ocean dynamic tracers for particles within the silty clay fraction

palaeoenvironmental change in the gulf of carpentaria australia since the last interglacial based on ostracoda throughout the last glacial cycle the region between australia and new guinea which is today known as the gulf of carpentaria has oscillated from open shallow marine conditions to a large land locked freshwater lake including periods of subaerial exposure ostracod faunal assemblages and variations in the valve morphology preserved in the sediments of the gulf record these changes a 14 8 m long core md972132 extracted from near the centre of the modern gulf of carpentaria spanning the last 130 ka bp provides the basis of this study environmental facies were determined by r and q mode cluster analysis of the ostracod assemblage data including 72 species and comparison with modern analogues from both the gulf of carpentaria and southeast asian region using these methods six clearly distinct biofacies were identified i open shallow marine facies including bairdiids pectocytherinids and cytherettids ii shallow marine facies dominated by cytherella and hemikrithe iii marginal marine facies including xestoleberis and praemunita iv tidal channel facies dominated by loxoconcha v estuarine assemblage comprising venericythere and leptocythere vi non marine facies a brackish lagoon lake facies dominated by cyprideis and leptocythere b freshwater facies including ilyocypris with cyprinotus and cypretta in addition morphological variation of valves of the more plastic species in particular cyprideis australiensis and leptocythere hartmanni was observed and related to environmental variables including salinity and solute composition these two species occur through more than half of the length of the core and show significant variability c australiensis with irregularshaped sieve pores is associated with heavily reticulated valves of l hartmanni around 90 70 ka bp indicating increased salinity and carbonate limited environments conversely c australiensis with round sieve pores occurs with finely reticulated valves of l hartmanni from around 50 ka bp in fresher carbonate rich environments the preservation of valves was also noted so as to infer post depositional effects revealing shoreline features channel activity and subaerial exposure combined ostracod biofacies and morphological analysis reveals a fluctuating marine environment through marine isotope stage mis 5 terminating in a restricted lagoon around 90 ka bp followed by an extensive period of subaerial exposure in this

the drag coefficient bottom roughness and wave breaking in the nearshore the bottom drag coefficient in the nearshore has been suggested to depend on bottom roughness bedforms or alternatively on wave breaking the hypothesis that bottom drag coefficient depends on bottom roughness is tested with 2 months of field observations collected on a sandy ocean beach during the duck94 field experiment both the drag coefficient estimated from alongshore momentum balances and bottom roughness estimated from fixed altimeters are larger within the surfzone than in the region farther seaward although the drag coefficient increases with roughness seaward of the surfzone no relationship was found between the drag coefficient and roughness related quantities within the surfzone these results suggest that breaking wave generated turbulence increases the surfzone drag coefficient

observations of bedform migration and bedload sediment transport in combined wave current flows bedload transport is an important mechanism for sediment flux in the nearshore yet few studies examine the relationship between bedform evolution and net sediment transport our work contributes concurrent observations of bedform mobility and bedload transport in response to wave dominant current dominant and combined wave current flows in the nearshore bedload sediment flux from migrating bedforms during combined wave current conditions accounted for at least 20 more bedload transport when compared with wave dominant flows and at least 80 more than current dominant flows bedforms were observed to transport the most sediment during periods with strong currents with high energy skewed waves and while bedform orientation and transport direction were aligned regardless of flow type bedform migration rates were directly proportional to the total kinetic energy contained in the flow field eleven bedload transport models formulated to be used in combined flows both shear and energetics based were compared with sediment flux estimated from measured bedform migration an energetics based sediment transport model was most representative for our data

undertow over a barred beach the spatial distribution of the mean cross shore flow undertow over a barred beach is examined with field data obtained on three energetic wave days during the duck94 experiment the vertical structure of the undertow is modeled using a turbulent eddy viscosity closure and includes the important effects of wave breaking described using the roller concept and convective acceleration of the current other than a more realistic description of observed turbulence variations a depth dependent eddy viscosity compared with a constant does not improve the agreement between predicted and observed undertow profiles the effect of using different boundary conditions is investigated by extending the formulations of stive and wind 1986 and svendsen et al 1987 to include random waves by ensemble averaging over the wave height distribution the contribution of breaking wave rollers to the surface mass flux can be of the same order or greater than the contribution associated with the organized wave motion the largest discrepancies between model predictions and observations occur over the sandbar where the mass transport of the breaking waves appears to be underestimated

application of biological markers in the recognition of palaeohypersaline environments the hydrocarbon fractions of a marl sample from a messinian basin in the northern appenines and four oils rozel point oil utah and three seep oils from sicily were studied

biological markers in lacustrine chinese oil shales s u m m a r y a major objective in molecular organic geochemistry is the assessment and characterization of sedimentary depositional environments from the occurrence of specific biological marker compounds related to particular source organisms the aliphatic hydrocarbon distributions of petroleums and or sediments from chinese freshwater and hypersaline lacustrine environments are described and contrasted in the search for diagnostic features among their biological marker distributions the eocene maoming oil shale which crops out in guangdong province shows major differences in hydrocarbon composition through its stratigraphic succession these variations reflect changes in lithology and in the origins of the sedimentary organic matter as seen from petrographic examination the lower lignite and vitrinite layers contain significant contributions of biological markers from bacterial sources plus components derived from terrigenous higher plants such as c29 steroids in contrast the overlying shales show a dominance of dinoflagellate derived 4methylsteroids and culminate in an horizon with botryococcane homologues as their dominant alkanes thus the geochemical profile suggests that a swampy environment in which peats accumulated deepened to support populations of dinoflagellate and finally blooms of botryococcus green algae the aliphatic hydrocarbons of a series of sediments and petroleums from the eocene hypersaline sequence of the jianghan basin in southern hubei province shows various features that may be typical of such facies these include a dominance of even numbered n alkanes high amounts of phytane and gammacerane and an abundance of c35 hopanes similar characteristics are observed in shales from the eocene green river formation and in rozel point crude oil a petroleum thought to originate from sediments deposited under hypersaline conditions the same features also appear in a lower tertiary evaporitic mudstone from south of the renqui oil field in hebei province together with 4 methylsteranes fl carotane and 18c h oleanane a marker for terrigenous higher plants these data illustrate the potential of biological markers in the differentiation of different lacustrine environments and suggest that such characteristics may provide signatures for environmentally similar but geographically distant deposits

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

formation and evolution of nonmarine petroleum in songliao basin china in large lake basins source rocks containing sapropelic kerogen have a high transformation ratio and a high potential for petroleum and they offer the material basis for the formation of a large nonmarine oil field on the basis of geologic and geochemical data and the results of thermal simulation of kerogen it is confirmed that the maturation sequence of kerogen is type i type ii and type iii

relationships between hydrocarbon evolution and the geochemistry of solid bitumen in the guanwushan formation nw sichuan basin abstract recently the devonian guanwushan formation in the northwestern sichuan basin gained industrial attention when solid bitumen was discovered in reservoirs and outcrops this discovery initiated the exploration and development of the devonian natural gas devonian in the northwestern sichuan basin is a new stratum for the exploration and development of paleozoic marine natural gas in sichuan basin however the unclear recognition on the genesis the sources and the hydrocarbon evolution history of solid bitumen and natural gas seriously restricted further exploration and development based on the solid bitumen reflectance carbon isotopes saturated hydrocarbon chromatography and solvent extract bitumen biomarkers combined with the component and carbon isotopes of natural gas comprehensive analyses have been performed on the origin of the solid bitumen and the accumulation and evolution of the natural gases the results showed that the outcrop solid bitumen is derived from biodegraded oil from the lower cambrian source rocks and is characterised by low bitumen reflectance low saturated aromatic hydrocarbon ratios seriously damaged normal alkanes and severe migration of the gas chromatographic baseline the reservoir bitumen formed through thermal cracking of oil from lower cambrian and lower permian source rocks and is characterised by high bitumen reflectance high saturated aromatic hydrocarbons and complete normal alkanes the differences of tectonic evolution take control of the two different genesis bitumen the longmen mountain strata in the northwestern sichuan basin were uplifted sharply after the jurassic and the early generated crude oil was biodegraded during uplifting and formed the outcrop bitumen however strata in well shuangtan 3 st3 continued to subside and the paleo reservoir thermal cracked during deep burial into dry gas and heavy components gathered to form reservoir bitumen revealing the devonian hydrocarbon evolution in sichuan basin is of highly significance and is meaningful to guide further researches on the gas source correlation of natural from paleo strata it is of great significance to reveal the devonian hydrocarbon evolution in sichuan basin and to guide further researches on the gas source correlation of natural gas from paleo strata

fingerprint of hydrocarbon generation in the southern georgina basin australia revealed by small angle neutron scattering small angle neutron scattering sans and ultra small angle neutron scattering usans are used to directly detect the processes of hydrocarbon generation in the 10 nm to 10 m size pores in middle cambrian carbonate and siliciclastic rocks which contain no land plant material suitable for conventional maturity determination by vitrinite reflectance the method takes advantage of the pore size specific variation of neutron scattering contrast between the solid rock matrix and pore space content with depth which is caused by thermal maturation of organic matter through the oil and gas generation windows sans and usans measurements were performed on bedding plane orientated core slices extracted from a series of 10 to 12 depth intervals for three wells ckad0001 macintyre 1 and baldwin 1 in the southern georgina basin central australia the depth intervals intersecting the organic rich basal hot shales of the middle cambrian arthur creek formation were selected based on rock eval pyrolysis data sans and usans results indicate that oil generation has occurred in the past in nanometer sized pores in rocks that are now at depths of around 538 4 m in ckad0001 and 799 3 m in macintyre 1 furthermore in the ckad0001 well the oil wet pores extend into the larger pore size range at least up to 10 m due to the efficient expulsion of oil at around 880 m in baldwin 1 the influence of pyrobitumen reverts pore space from gas wet to oil wet these hydrocarbons have remained in situ since the devonian when the neoproterozoic to paleozoic section was exhumed in the alice springs orogeny and subsequently eroded preserving only remnants of the once extensive basin sediments keywords hydrocarbon generation hydrocarbon expulsion sans usans georgina basin cambrian arthur creek formation

an organic geochemical investigation of crude oils from shanganning jianghan chaidamu and zhungeer basins people s republic of china abstract eighteen oils from four different oil producing basins in china have been characterized using a variety of organic geochemical techniques the source materials for these oils were deposited under a variety of environmental conditions and this study investigates the use of geochemical parameters in differentiating the resultant oils the parameters discussed are based on relative amounts and distributions of both individual and groups of biomarkers including organosulphur compounds and the carbon isotopic composition of the aliphatic and aromatic fractions examination of the oils showed that those from the zhungeer basin thought to be derived from source rocks formed in a brackish lacustrine environment possessed high concentrations of tricyclic terpanes relative to pentacyclic hopanes and a predominance of 24 methyl and 24 ethylcholestanes c28 and c29 respectively over cholestanes c27 which were virtually absent oils believed to be derived from source rocks deposited in the saline depositional environment of the jianghan basin were characterized by a large amount of gammacerane relative to 17 21 30 homohopanes c31 22r and 22s in general those oils considered to be derived from source rocks deposited in fresh water lacustrine environments shanganning and chaidamu basins had small amounts of tricyclic terpanes relative to pentacyclic hopanes the presence of an unknown c30 pentacyclic terpane small amounts of extended hopanes c31 c35 relative to 17 21 hopane and relatively large amounts of 24 ethylcholestanes 20r and 20s relative to total stearanes it appears therefore that the distribution of biomarkers may be used to differentiate oils derived from different lacustrine environments

vertical flow structure during sandy duck observations and modeling abstract observations of the vertical distribution of time averaged cross shore and alongshore flows during the sandy duck field experiment are compared with model predictions to assess the parameters governing the flow behaviour the measurements were obtained with a vertical stack of eight two component current meters with the lowest and highest sensor at respectively o 0 1 and o 2 7 m above the bed observations under breaking wave conditions within the surfzone show that the maximum return flow velocities occur in the lower part of the water column consistent with laboratory observations under non breaking conditions outside the surfzone the maximum return flow velocities are observed closer to the water surface again in line with laboratory results analogous to previous observations the measured longshore current velocity profiles are logarithmic under non breaking conditions and become more depth uniform under breaking conditions the model description of the vertical structure of the flow includes the presence of wind stresses wave stresses pressure gradients turbulent eddy viscosity and a wave boundary layer the model utilizes parabolic shape functions to describe the vertical distribution of the turbulent eddy viscosity in the middle layer and within the bottom boundary layer eddy viscosity is enhanced in regions where turbulence is produced i e near the surface in the case of breaking waves and within the bottom boundary layer estimates of the wave breaking induced turbulent eddy viscosity and bottom friction are obtained by minimizing the model measurement discrepancies predictions utilizing calibrated expressions for both the turbulent eddy viscosity and bottom friction are in general agreement with the observations provided the wave transformation and associated mass flux are modeled correctly and a parabolic eddy viscosity distribution is used using a piecewise constant eddy viscosity distribution generally results in a degrading of the agreement between measurements and model results

the occurence of unusual c27 and c29 sterane predominances in two types of oman crude oil abstract two types of oman crude oils reveal unusual sterane distributions type a which is the more common 74 examples is characterised by a predominance of c 29 iso and normal steranes and generally none or only very low relative concentrations of rearranged steranes the triterpanes are characterised by the predominance of the c 29 17 h 21 h norhopane over the c 30 17 h 21 h hopane and non predominant c 20 c 30 tricyclic terpanes the c 29 steranes of this type of crude were not derived from the c 29 sterols of land plant origin frequently proposed as the source of c 29 steranes since there is good geological evidence that these crudes were generated from a pre cambrian source rock a geological period when land plants did not exist the type b crude oil 11 known examples is characterised by a strong predominance of c 27 iso normal and rearranged steranes relatively lower concentrations of 17 h 21 h hopanes and relatively high concentrations of c 20 c 30 tricyclic terpanes the remarkably different biomarker characteristics of these crude oils imply that the organisms active in the depositional environment of the respective source rocks were significantly different

properties and shale oil potential of saline lacustrine shales in the qianjiang depression jianghan basin china abstract the geochemical and petrographic characteristics of saline lacustrine shales from the qianjiang formation jianghan basin were investigated by organic geochemical analysis x ray diffraction xrd scanning electron microscopy sem and low pressure nitrogen adsorption analysis the results indicate that the saline lacustrine shales of eq3 member with high oil content are characterized by type i and type ii oil prone kerogen variable toc contents 1 0 10 0 wt and an early maturity stage ro ranges between 0 41 and 0 76 the mineral compositions of eq3 saline shale show strong heterogeneity brittle intervals with high contents of quartz and carbonate are frequently alternated with ductile intervals with high glauberite and clay contents this combination might be beneficial for oil accumulation but may cause significant challenges for the hydraulic stimulation strategy and long term production of shale oil the interparticle pores and intraparticle pores dominate the pore system of eq3 shale and organic matter hosted pores are absent widely distributed fractures especially tectonic fractures might play a key role in hydrocarbon migration and accumulation the pore network is contributed to by both large size inorganic pores and abundant micro factures leading to a relatively high porosity 2 8 30 6 and permeability 0 045 6 27 md within the saline shale reservoir which could enhance the flow ability and storage capacity of oil the oil content s1 100 toc mg hc g toc and s1 mg hc g rock and brittleness data demonstrate that the eq33x section has both great potential for being a producible oil resource and hydraulic fracturing considering the hydrocarbon generation efficiency and properties of oil the mature shale of eq3 in the subsidence center of the qianjiang depression would be the most favorable zone for shale oil exploitation

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

small angle neutron scattering signature of oil generation in artificially and naturally matured hydrocarbon source rocks abstract we have demonstrated for the first time the application of a small angle neutron scattering sans technique for the precise determination of the onset of hydrocarbon transport primary migration in shaly source rocks we used a sequence of rocks pyrolysed in the laboratory under nitrogen at temperatures in the range 310 370 c these rocks contained several percent of dispersed marine type ii organic matter geochemical analysis indicated a peak of the hydrocarbon generation in the middle of the temperature range at 340 c we observed a sharp decrease of sans intensity in a narrow maturity range within the geochemically determined region of the onset of hydrocarbon generation this decrease was a direct consequence of the sans contrast variation caused by the invasion of the pore space by bitumen during the primary migration of hydrocarbons a similar phenomenon was observed for a natural maturity sequence of source rocks originating from the same location

organic geochemical characteristics and organic matter enrichment of mudstones in an eocene saline lake qianjiang depression hubei province china abstract the qianjiang depression is a typical eocene hypersaline lake basin developing good source rocks in the qianjiang formation which have recently been identified as a potential target for saline lacustrine shale oil exploration previous studies have only focused on estimates of source rock potential and reservoir quality however studies on organic matter enrichment mechanisms in evaporative environments are limited based on organic geochemical and mineralogical data as well as sedimentological analyses we researched the factors controlling differences in organic matter enrichment in the basin the results show that total organic carbon toc contents are closely associated with lithofacies with distinct variations three main lithofacies associations las were identified 1 glauberite rich la1 with medium toc 2 carbonate rich la2 with high toc and 3 anhydrite rich la3 with low toc the distribution of biomarkers from 14 samples indicate both higher land plants and aquatic organisms were involved in the organic matter accumulations combining experimental results on gammacerane c30 hopane extended tricyclic terpane ratio etr sr ba v ni and sedimentary characteristics we analyzed the sedimentary environments of the three las la1 was deposited in a salinity stratified waterbody with strong evaporation la2 was deposited in a still stratified deep waterbody whereas la3 was deposited in a disturbed saline waterbody sedimentary environments not only controlled the formation of the lithofacies but also influenced the organic matter sources and preservation relatively low salinity strong anoxic condition without physical disturbance appropriate nutritional terrigenous material inputs and algal blooms produced the best organic matter enrichment in the saline lake system

geochemistry of oils from the junggar basin northwest china the junggar basin of northwestern china is a structural basin containing a thick sequence of paleozoic pleistocene rocks with estimated oil reserves of as much as 5 billion bbl analyses of 19 oil samples from nine producing fields and two oil stained cores in the junggar basin revealed the presence of at least five genetic oil types the geochemistry of the oils indicates source organic matter deposited in fresh to brackish lake and marine environments including coaly organic matter sources the volumetrically most important oil type discovered to date is produced from late carboniferous middle triassic reservoirs in the giant karamay field and nearby fields located along the northwestern margin of the junggar basin oil produced from the mahu field located downdip in a depression east of the karamay field is from a different source than karamay oils unique oil types are also produced from an upper permian reservoir at jimusar field in the southeastern part of the basin and from tertiary oligocene rocks at dushanzi field and lower jurassic rocks at qigu field both located along the southern margin of the basin previous studies have demonstrated the presence of upper permian source rocks and the possibility of mesozoic or tertiary sources has been proposed but not tested by geochemical analysis although analyses of some possible jurassic coal source rocks have been reported our findings indicate that several effective source rocks are present in the basin including local sources of mesozoic or younger age for oil accumulations along the southern and southeastern margins of the basin future exploration or assessment of petroleum potential of the basin can be improved by considering the geological relationships among oil types possible oil source rocks and reservoirs

geochemical study on a well in the western canada basin relation of the aromatic distribution pattern to maturity of organic matter abstract thirty one rock samples from a western canada basin well have been analysed for aromatics using glass capillary gas chromatography with simultaneous flame ionization and sulfur selective flame photometric detection a uniform aromatic distribution pattern with a marked predominance of di and tricyclic aromatic hydrocarbons was observed throughout a depth interval of 3000 meters comprising cretaceous and jurassic sediments the very high relative abundance of sulfur aromatics at two narrow intervals in the triassic and mississippian is attributed to a major change in facies gradual changes with increasing depth have been observed for a series of compound ratios which had been calculated from the isomers of methyl and dimethylphenanthrene and their parent compounds these changes reflect the increasing thermal maturation of the sedimentary organic matter a methylphenanthrene index mpi has been introduced which exhibited a very good correlation with vitrinite reflectance data the mpi is the first maturity parameter which is based on a series of aromatic hydrocarbons this hydrocarbon internal maturity parameter permits the recognition and definition of maturity levels in extracts which can be compared to the maturity e g vitrinite reflectance of source rocks

unusual triterpane distributions in lacustrine oils abstract a series of diahopanes and a second unknown early eluting series of triterpanes are reported in lacustrine oil samples from three different basins we suggest that these compounds together with 18 h 30 norneohopane show distributions which vary with the salinity of the depositional environment

very high resolution side scan sonar mapping of biogenic reefs of the tube worm lanice conchilega reefs of the tube building polychaete lattice conchilega are known to represent hotspots of biodiversity within inter and subtidal soft sediments of the north sea however because of their patchy distribution point sampling does not appropriately map their subtidal spatial distribution this study evaluated the feasibility to detect l conchilega reefs by very high resolution side scan sonar imagery a subtidal very high resolution 410 khz side scan survey combined with grab sampling revealed high densities of l conchilega up to 1979 ind m 2 to coincide with a higher reflectivity patchy and grainy acoustic facies from the side scan sonar imagery individual reefs were estimated to reach a maximum size of 15 m 2 to ground truth the acoustic facies the distribution of intertidal l conchilega reefs was mapped at low tide and side scan sonar imagery was recorded during the following high tide intertidal l conchilega reefs had a patch size of 0 8 m 2 up to 11 6 m 2 elevated 7 5 to 11 5 cm above the surrounding seafloor and covered approximately 10 of the selected area the very high 445 khz resolution side scan sonar imagery revealed a similar acoustic facies as in the subtidal lower resolution 132 khz side scan sonar imagery was less efficient to detect physically less developed l conchilega reefs we conclude that 1 there are no major technical restrictions to map l conchilega reefs using side scan sonar 2 the developmental stage of l conchilega reefs impacts the detectability of the reefs and 3 very high resolution side scan sonar imagery is considered a necessity when mapping small scale structures such as l conchilega reefs c 2008 elsevier inc all rights reserved

warm humid paleoclimate control of salinized lacustrine organic rich shale deposition in the oligocene hetaoyuan formation of the biyang depression east china abstract lacustrine organic rich shales are widely developed within the oligocene biyang depression in the nanxiang basin in east china and across southeast asia these shales have been proven as hydrocarbon source rocks of crude oil as well as sources and reservoirs of shale oil understanding the deposition of these shales is essential to reconstruct the paleoenvironment and paleoclimate during the oligocene in east china as well as target the potential shale oil resources based on x ray diffraction organic and inorganic petrologic organic and inorganic geochemical and stable isotopic analyses paleoenvironment paleoclimate and hydrocarbon potential of the lacustrine organic rich shales in the oligocene hetaoyuan formation were investigated the mineral composition of hetaoyuan formation organic rich shales is dominated by clay minerals followed by quartz plagioclase calcite dolomite pyrite and gypsum six lithotypes are identified including siltstone silty shale clay shale calcareous shale dolomite shale and massive mudstone the organic matter om of the organic rich shales is dominated by type i kerogen lamalginite maturity parameters tmax biomarker ratios and calculated vitrinite reflectance suggest that the om enters the oil window maturity high toc and generative potential together with high contents of brittle minerals including quartz plagioclase and carbonates reveal the oligocene hetaoyuan formation hold good to very good potential of shale oil exploitation six organic rich shale layers have been identified in the hetaoyuan formation shale layer 1 to 6 from top to bottom among them shale layers 5 and 3 hold the best shale oil potential and therefore be investigated in the present paper shale layer 5 was deposited in a semi deep lacustrine environment under the moderately warm humid paleoclimate further dividing into lower middle and upper units relatively low toc contents av 2 6 wt in the lower unit are probably caused by high sedimentation rate high bioproductivity under favorable preservation conditions led to relatively high toc contents av 3 6 wt in the middle unit less reducing conditions together with moderate low bioproductivity resulted in relatively low toc contents av 2 6 wt in the upper unit warm humid paleoclimate prevailed during deposition of shale layer 3 deepened water depth and formed a deep lacustrine environment the stratified water column led to stable anoxic condition and photic zone euxinia in the saline deep lacustrine environment which enabled the accumulation of high amounts of om av 4 9 wt toc under excellent preservation av hi 710 mg hc g toc the results of core scanning analysis indicate that formation of the laminated shales probably controlled by seasonal fluctuations of paleoclimate

porphyrin distributions in crude oils from the jianghan and biyang basins china abstract a number of oils tar sands and extracts of suspected source rocks from the jianghan and biyang basins of china have been studied to investigate their porphyrin content the results obtained suggest that these distributions are controlled to a large extent by the nature of the depositional environment and the maturity levels of the sediments it is proposed that the predominance of ni porphyrins in the sediments of these basins is caused mainly by the high ni content of the groundwater the relatively high content of a c32 porphyrin isomer with a five membered ring with a methyl substituent is indicative of environments with very high salinity the porphyrin distributions have been affected through thermal maturation with the major changes being dealkylation alkylation within etio porphyrins the instability of ni dpep porphyrins is suggested as a major reason for the rarity of dpep porphyrins in chinese oils the ratios of dpep etio or dpep etio dpep c 31 etio a c 28 etio b and etio a c 31 c 30 are useful as thermal maturity parameters and the results also indicate that the percentage of dpep porphyrins decreases through migration

mineral controlled nm μm scale pore structure of saline lacustrine shale in qianjiang depression jianghan basin china abstract the pore structure of the saline lacustrine shales in the eq3 unit of the qianjiang formation was characterized for pore space of m nm scales through a combined study of mercury injection capillary pressure micp and small ultra small angle neutron scattering sans and usans x ray diffraction xrd and total organic carbon toc content tests as well as field emission scanning electron microscopy fe sem imaging are also employed to obtain the mineralogical composition organic richness as well as the general pore types and sizes of the selected qianjiang shale samples in these samples three major rock types are identified 1 silica rich carbonate mudstone 2 carbonate siliceous mudstone and 3 salt the porosity as well as pore size and pore throat size distributions generated from both sans usans and micp techniques indicate a porous rock matrix and well connected pore networks in the two mudstone rock types meanwhile an averaged toc of around 3 5 wt for eq3 unit exhibits a good quality for oil generation potential this study primarily provides new insights into the pore structure of the qianjiang shales across a wide measurable range for both pore and pore throat sizes and correlates the pore structure and mineral compositions at different scales

life in the sublittoral zone of long lived lake pannon paleontological analysis of the upper miocene szak formation hungary life and depositional environments in the sublittoral zone of lake pannon a large brackish paratethyan lake from the late miocene were reconstructed from fossils and facies of the szak formation this formation is exposed in several roughly coeval 9 4 8 9 ma outcrops located along strike of the paleo shelf break in northwestern hungary the silty argillaceous marl of the formation was deposited below storm wave base at 20 30 to 80 90 m water depth the abundance of benthic organisms indicates that the bottom water was usually well oxygenated interstitial dysoxia however may have occurred immediately below the sediment water interface as evidenced by occasional preservation of trace fossils such as diplocraterion the fauna comprised endemic mollusks including brackish cockles of the subfamily lymnocardiinae dreissenid mussels congeria and highly adapted uniquely large sized deep water pulmonate snails planorbids and lymnaeids ostracods were dominated by endemic species and in some cases endemic genera of candonids leptocytherids cypridids and loxoconchids fish remnants include a sciaenid otolith and the oldest skeletal occurrence of perca in europe the phytoplankton comprised exclusively endemic coccolithophorids mostly endemic dinoflagellates prevailingly spiniferites and cosmopolitan green algae the late miocene fauna and flora of lake pannon were in many ways similar to the modern caspian biota and in particular cases can be regarded as its precursor

biomarker characterisation of an oil and its possible source rock from offshore korea bay basin abstract comparison of biomarker distributions in an oil and in sedimentary rock samples from an offshore well in korea bay basin indicates that an upper jurassic 500 m thick mudstone zone could form the source rock for the oil the organic material in this zone appears to be h rich and of sufficient abundance from pyrolysis measurements to generate oil it seems to derive primarily from bacterial lipids as reflected in high levels of bacterial hopanoids and predominance of amorphous kerogen macerals a higher plant wax contribution to the organic matter is indicated by an oep in n akanes c 20 and there may also be an autochtonous algal contribution sedimentological and biomarker evidence is consistent with input from a river delta prograding into a deep freshwater lake biomarker distributions suggest that pronounced bacterial reworking of allochthonous higher plant material had occurred in probably anoxic conditions high heat flows in a rapidly subsiding extensional basin probably account for the observed extensive aromatisation of monoaromatic steroidal hydrocarbons at a relatively early stage of sterane isomerisation

vertical profiles of longshore currents and related bed shear stress and bottom roughness the vertical structure of the mean wave driven longshore current over a barred beach is examined on three strong current days during the duck94 experiment and it is found that the bottom boundary layer is well described by a logarithmic profile mean correlation coefficient for all 22 profiles 0 98 the logarithmic profile fits better in the trough where turbulent bottom boundary layer processes predominate than over the bar where breaking wave induced turbulence generated at the surface modifies the profile the surface layer in the presence of waves is well described by adjusting the logarithmic profile for the intermittent presence of water and adding the alongshore component of the mass transport velocity slope of the least squares linear regression between model predictions and observations 1 005 and root mean square rms error of 7 bed shear stresses calculated from logarithmic velocity profiles are equated to a quadratic bottom shear stress formulation the associated bed shear stress coefficients vary by more than an order of magnitude across the surf zone 0 0006 0 012 bottom roughness was measured throughout the nearshore using a sonic altimeter mounted on a moving platform the bed shear stress coefficients are positively correlated with bottom roughness linear correlation coefficient 0 6 a higher linear correlation coefficient 0 8 is obtained by subtracting skin friction from the total bed shear stress

ripex observations of a rip current system rip current kinematics and beach morphodynamics were measured for 44 days at sand city monterey bay ca using 15 instruments composed of co located velocity and pressure sensors acoustic doppler current profilers and kinematic gps surveys the morphology consisted of a low tide terrace with incised quasi periodic rip channels representative of transverse bars offshore 17 m depth significant wave height and peak period ranged 0 20 3 0 m and 5 20 s the mean wave direction was consistently near 08 resulting in rip channel morphology which evolved in response to the changing wave characteristics an inverse relationship between sediment accreting on the transverse bar and eroding in the rip channel was found the spatial distribution of sediment is reflected in the background rip current flow field the mean velocity magnitudes within the rip channel transverse bars increased offshore onshore with decreasing tidal elevations and increased with increasing sea swell energy eulerian averaged flows were predominantly shoreward on the transverse bars and seaward within the rip channel throughout the experiment resulting in a persistent cellular circulation except during low wave energy the rip current spacing to the rip channel width was less than or equal to two which suggests that the rip currents are influenced by each other and that no two dimensional bar return flow should be present the vertical velocity profile on the bar indicated that the flow was predominantly shoreward the flow field within the surf zone was depth uniform except for significant shear occurring near the surface owing to stokes drift the wave induced transport hypothesis is evaluated d 2005 elsevier b v all rights reserved

small scale morphology across the surf zone small scale 5 m horizontal length nearshore morphologic height variations were measured by combining crab surveys with bed elevations acquired with a 1 mhz sonic altimeter mounted on the crab during the october phase of the duck94 experiment bedform plan views were recorded simultaneously using a 500 khz side scan sonar mounted on the crab waves and currents were measured at the same time significant temporal and spatial variations in the small scale morphology were measured in response to changing waves and currents during the 2 weeks examined three cases are examined in detail 1 mild waves and weak longshore currents resulting in wave ripples throughout the study area 2 storm waves with strong longshore currents resulting in lunate and straight crested mega ripples in the trough of the barred beach and 3 narrow band normally incident waves with a strong rip current resulting in a planar bed except in the throat of the rip where mega ripples were measured wavenumber spectra of the bed were generally broad indicating newly formed ripples coexisted with residual ripples from the past to form complex multi scaled ripple patterns

surf zone megaripple orientation measurements and models 1 two existing models for bed form orientation are tested against measurements of megaripple crest line orientation from scripps beach optical time averaged images of the surf zone sand bed at 10 min intervals are processed with an automatic crest line tracing algorithm flow measurements concurrent with images of the sand bed collected during 3 7 april and 17 23 july 1999 are used as input to the gross bed form normal transport model bed forms align to maximize gross transport across crests predicting steady state crest orientation and the defect model bed forms reorient at a rate proportional to the differential velocity of crest line ends or defects predicting a time dependent orientation generally poor agreement was found between predictions and measurements of crest line orientation the gross bed form normal transport model predicted crest line normal orientation within 20 of measured orientation for 38 of records with increased agreement coinciding with longitudinal and oblique bed forms the defect model predicted crest line normal orientation within 20 of measurements for 22 of records when the ratio between defect and transport event timescales is assumed 1 and 14 of the records for the ratio 1 although migration and mean sediment transport direction are assumed to coincide in both models rms deviation in bed form migration direction from the calculated 30 min mean sediment transport direction was found to be 38 additionally rms deviation of megaripple migration direction from crest line normal orientation was 39

relationship of biomarker distribution to depositional environment phosphoria formation montana u s a from biomarker distributions it is possible to distinguish extracts from four different members facies meade peak rex retort and tosi of the permian phosphoria formation at little sheep creek montana these distributions relfect changes in floral and faunal distribution in response to a changing depositional environment and suggest that the retort and tosi members the second cycle of deposition were deposited under more anoxic conditions and at higher salinity than meade peak and rex members the first cycle correlations between biomarker indicators of anoxia and salinity suggest that anoxia was in part the result of a chemocline separating normal marine waters above from more saline bottom waters anoxia and salinity in the bottom waters increased with time making conditions in the basin progressively more hostile to benthic organisms development of extreme environmental conditions in continental shelf habitats such as those suggested by biomarker parameters at little sheep creek may have compounded spatial problems created by continental suturing suggested to be a cause of permian extinctions factor analysis indicates that four factors for 75 3 of the variance in biomarker ratios these factors are suggested to be source organisms types of eukaryotic plankton salinity eh and mineralogy the grandeur member of the phosphoria which is a typical reservoir rock for phosphoria derived oils yields an extract containing a novel c30 nitrogen containing steroid this unique steroid is not abundant in any other known extracts or oils which along with the extremely low porphyrin maturity parameter of all the extracts pmp 0 01 confirms the absence of migrated oils in the phosphoria at little sheep creek the biomarker ratios c29 ga a steranes ts ts tm triaromatic triaromatic monoaromatic steroids short long short chain monoaromatic steroids and short long short chain triaromatic steroids are commonly used to determine the thermal maturity of oils and source rock extracts however these ratios show considerable variation in core extracts of the same thermal maturity from different facies in contrast the thermal maturity parameters c29 20s 20s 20r steranes and porphyrin maturity parameter pmp show little variation indicating that these parameters are less affected by changes in depositional environment and may be most useful for thermal maturation determinations of phosphoria related oils and source rocks this study supports previous work suggesting environmental effects must be considered if correct determination of thermal maturity of an oil or extract is to be made this is especially true of oils and extracts from source rocks with high sulfur concentrations and or those deposited at elevated salinities

bed level changes on intertidal wetland in response to waves and tides a case study from the yangtze river delta short term bed level variability in tidal wetlands has important implication both for ecology and engineering in this study we combined in situ measurements with model simulations to quantify short term bed level changes on a meso macrotidal wetland in the yangtze river delta on the middle flat we observed erosion during neap to mean tides under onshore moderate to strong winds and bed recovery during subsequent spring tides when winds were both offshore and weaker suggesting that winds can overturn the neap spring cyclicity of bed level changes even on meso macrotidal mudflats the magnitude of bed level changes was smaller on both sides of the middle flat while the smallest changes occurred on the salt marsh observed bed level changes were reconstructed using a single point bed level change model which incorporates in situ measured parameters of hydrodynamics waves and currents suspended sediment concentrations and bed sediment properties we conclude that the relative importance of waves and tides in intertidal wetland erosion and accretion can vary temporally due to changes in balance between wave and tidal energies and spatially because of changes in elevation and vegetation in the cross shore profile our study also reflects the advantage of combination of in situ measurement with simulation in detecting short term variability of tidal flats

a geochemical investigation of crude oils and source rocks from biyang basin china abstract china has a number of petroliferous lacustrine sedimentary basins of varying salinity and age mainly eocene a geochemical investigation has been undertaken on several oils and source rocks from the eocene lacustrine biyang basin the distributions of n alkanes isoprenoids steranes and terpanes have been studied and used to characterize the sedimentary environment of deposition maturity biodegradation and undertake possible correlations the ratios of c 30 hopane gammacerane 4 methyl steranes regular steranes steranes hopanes c 21 tricyclic c 30 hopane are proposed to be indicative of the depositional environment whereas s carotane appears to be a source related indicator the geochemical data obtained in this study suggest that the major source rocks in the biyang basin were deposited in a saline hypersaline depositional environment

response of sand ripples to change in oscillatory flow ripples take time to evolve to a new equilibrium state in response to a change in wave generated oscillatory flow the paper presents results from flow tunnel experiments designed to examine oscillatory flow transient ripple processes under controlled full scale laboratory conditions the experiments include study of the growth of ripples from flat bed and the evolution of existing ripples to new equilibrium ripples in response to a step change in the flow in general ripples evolve through a combination of two main processes i from a flat bed or from a bed consisting of ripples that are smaller than the equilibrium ripples through a combination of slide and merge ii from a bed consisting of ripples that are larger than the equilibrium ripples through a combination of split and merge the experimental results show that equilibrium ripple geometry is independent of initial bed morphology while the time to reach equilibrium is largely independent of the initial bed and the equilibrium ripple size the time to reach equilibrium depends strongly on the mobility number and a new empirical equation relating mobility number and the number of flow cycles to equilibrium is proposed this equation is combined with a simple exponential function for ripple height growth or decay to produce a new empirical model for ripple height evolution which gives a reasonably good overall agreement with the measurements the model is based on experiments involving one sediment size only and further work is needed to develop the model for other sand sizes

geometry and dynamics of wave ripples in the nearshore zone of a coarse sandy beach 1 extensive measurements of ripple characteristics and dynamics along with associated suspended sediment fluxes and hydrodynamic conditions were made in the shoaling and surf zones of a macrotidal coarse grained beach at sennen cove cornwall england median grain diameter 0 69 mm suborbital vortex ripples were observed during the majority of the study period with height 5 cm and length 35 cm the scale and shape of the ripples did not vary significantly as the bed shear stress increased during wave shoaling and breaking however ripple migration rates onshore directed were strongly dependent on their location relative to the breakpoint increasing from 0 1 cm min 1 under shoaling waves to 2 cm min 1 in the outer surf zone during low energy conditions farther inside the surf zone ripples persisted but migration rates slowed probably owing to the presence of the offshore directed mean flow which impedes landward migration of the ripples under low wave conditions during which measured sediment fluxes peaked around the outer surf zone and decreased through the saturated surf zone bed form transport rates under shoaling waves were of the same magnitude as net suspended sediment fluxes but at least an order of magnitude smaller in the outer surf zone under high energy conditions during which suspended sediment fluxes in the surf zone were offshore directed owing to the presence of the seaward directed mean flow bed form transport rates were several orders of magnitude smaller than suspended fluxes

estimating nearshore bedform amplitudes with altimeters abstract estimates of the heights of large 0 1 0 4 m heights and 1 10 m horizontal lengths migrating bedforms on a sandy beach made with fixed single point altimeters are similar to heights estimated from profiles across the bedforms made with altimeters mounted on an amphibious vehicle that traversed the surf zone unlike many profiling systems the robust fixed altimeters can measure bedforms in bubbly sediment laden surf zone waters nearly continuously including during storms thus allowing investigation of the relationships between bedform heights and near bottom velocities to be extended to a wide range of wave conditions the fixed altimeter observations of migrating bedforms suggest a sandy surf zone seafloor is not always smooth during energetic conditions with strong mean currents and large wave orbital velocities

monitoring tectonically controlled marine to lacustrine transitions using organic facies ridge basin california u s a abstract ridge basin is an elongate intermontane basin filled with upper miocene pliocene clastics located 80 km north northwest of downtown los angeles over 13 km of marine lacustrine and fluvio deltaic sandstones and shales are present because of southeastward depocenter migration throughout basin development no more than 4 5 km of vertical section are present in any one location this has resulted in an ideal situation to study organic facies variability namely a thick thermally immature stratigraphic succession with only minor variations in maturity level in this paper we use molecular isotopic and petrographic data to help identify systematic variability in organic facies in the castaic ridge route and peace valley fms all late miocene and relate these variations to the paleolimnology tectonic history and oil source rock potential of the basin as strike slip movement continued along the san gabriel fault during the late miocene the sedimentation regime changed from a marine dominance to one controlled by lacustrine and fluvio deltaic processes this transition results in changes in the organic facies within the basin as reflected in a a systematic decrease in organic carbon isotope ratios b an increase in relative yields of phenolic and n aliphatic structures in the kerogen pyrolysate c an increasing occurrence of perhydro carotene indicating episodic development of a halocline in the water column and d decreasing pristane phytane and c 29 c 28 sterane ratios unusual patterns of kerogen maceral distribution and a ring sterane methylation are also observed these geochemical data support the existence of a marine embayment in the early late miocene yielding to a lacustrine and fluvio deltaic setting which experienced considerable variation in bathymetry salinity and oxicity low levels of thermal maturity preclude the occurrence of hydrocarbon source rocks although source rock potential is present in sporadic localities optical and molecular maturity indicators show no systematic variation with stratigraphic succession this lack of variation is consistent with the known tectonic development in the basin and the shingled sedimentation pattern resulting from a migrating depocenter internal variability in the sterane and hopane epimer ratios may eventually be useful in estimating the uneven extent of overburden in the peace valley and ridge route fms leading to applications elsewhere in intermontane lacustrine basins with tectonically migrating depocenters

plant landscape and environmental changes recorded in marginal marine environments the ancient roman harbour of portus rome italy abstract the interpretation of past environment changes in coastal marshes river mouths and drainage channels connecting fresh to salt water bodies is a difficult task since several factors must be considered such as the variable influence of climate sea level changes coastline variations and changes in the river discharge it is even more difficult if this attempt is carried out in basins and channels of an ancient harbour used for centuries connected to the sea and to a river this is the case of the ancient harbour of rome located in the tiber delta area which had a prominent role during the imperial age in the mediterranean a town named portus arose in the vicinity and although sacked many times by barbarians was still very important during medieval times the romans managed the harbour the city and the surroundings and the impact on the environment must have been very strong a multi proxy approach was used to characterize and date environment and landscape changes in the ancient port of rome area from the 1st century to the 15th century ad plant macrofossil results have been integrated not only with pollen and microcharcoal but also with the tiber river bi millennial record available in literature this integration used to improve the chronological framing of the cores was carried out using ostracod analyses micro crustaceans commonly occurring in marginal marine environments and widely used for palaeoenvironmental reconstructions in particular the ability of some species to live within specific salinity ranges has been a precious tool to identify the hydrological setting of the depositional environment the cores recovered allowed recognition of two different sedimentary sequences the older shows the silting of the harbour during the first centuries and the younger records the sedimentation that occurred between the 4th and the 15th century ad this multi proxy approach applied to the study of plant remains indicates that 1 the human impact was lower during the first centuries ad than during late antiquity and middle ages or that 2 clues of human presence were easier to detect in a closed marshy area than in an open harbour the correlations between macroremains pollen percentage and concentration freshwater brackish water and salt water ostracods and the frequencies of tiber river floods during a 1500 year time span link some environmental changes and the silting of the harbour to the variations in hydrological regime of the tiber river

unifying large and small wave generated ripples 1 frequently in field and laboratory studies of wave generated bed forms on beds of sandy sediments both large and small wave generated ripples lwrs and swrs are observed and in some situations may be superimposed upon one another the present paper examines relationships between measured wave conditions and the geometry of lwrs and swrs and shows that existing empirical equations used to predict the dimensions of swrs perform badly for lwrs to address this problem relationships found between ripple geometry and the wave reynolds number are used as the basis for new expressions for prediction of ripple height wavelength and steepness that improve the accuracy of existing approaches for both lwrs and swrs the present results indicate strongly that swrs and lwrs are related and their superposition in certain conditions reflects the time lag between the response of the bed to changing hydrodynamic conditions they must be considered therefore when estimating the total bed roughness in a range of practical engineering and numerical modeling applications

sedimentology organic geochemistry and petroleum potential of jurassic coal measures tarim junggar and turpan basins northwest china lower and middle jurassic coal bearing strata occur widely throughout central asia and are well developed in northwestern china where their thicknesses in the southern junggar northern tarim and turpan basins exceed 2500 2300 and 1500 m respectively examination of these strata along 13 transects across basin margin outcrop belts indicates that they are entirely nonmarine meandering fluvial deposits with local development of braided fluvial and lacustrine deltaic facies chinese subsurface data suggest that regional jurassic lacustrine facies are present down depositional dip consistent with predictions from global circulation modeling of early and middle jurassic monsoonal precipitation laboratory analyses of coals and organic rich shales show a dominance of terrestrial higher plant components visual kerogen analysis indicates that vitrinite inertinite and exinite are the dominant macerals and elemental analysis characterizes most kerogens as type iii rock eval analyses yield moderate hydrogen index values 50 300 and very low oxygen index values 20 jurassic source rock extracts are characterized by odd over even normal alkane distributions high pristane phytane and high hopane sterane ratios dominance of c29 sterane homologs local abundance of diterpenoid compounds and low abundance of tricyclic terpanes geochemical correlation with four petroleums from the junggar tarim and turpan basins strongly suggests that the jurassic coaly deposits and their lacustrine equivalents downdip are petroleum source rocks sterane and hopane distributions of petroleums and extracts of their putative jurassic source rock are similar and can be easily distinguished from published distributions of these compounds in other source rock layers additional correlation parameters include high pristane phytane low abundance or lack of tricyclic terpanes but similar distributions where present and lack of gammacerane with one exception and carotanes compounds that characterize permian and ordovician source rocks and their respective petroleums pyrolysis gas chromatography of selected jurassic samples s ggests that they possess potential for liquid hydrocarbon generation expulsion of c15 hydrocarbons from jurassic source rocks appears likely despite the traditional view that bituminous coals are incapable of expelling long chain hydrocarbons end page 929

stereo video observation of nearshore bedforms on a low energy beach abstract a new technique utilising underwater stereo video was tested for its ability to measure nearshore bed morphology at high frequency and high resolution a stereo video system was used to monitor small scale ripple morphology wavelengths 0 05 0 10 m heights 5 mm in the nearshore of a low energy beach in southwestern australia waves currents and suspended sediment concentrations were also monitored bed morphology could be measured with a mean accuracy of 2 mm with the stereo video system measurements in the field were limited to ripple crest positions since targets over the entire ripple profiles could not be identified in both the left and right stereo images this limitation could be overcome in the future by use of laser stripes to illuminate the profiles and the generation of epipolar lines within the analysis software to match corresponding targets in each of the images ripple crest positions were measured at 1 hz and the relationship between ripple movement and near bed hydrodynamics was investigated to test the applicability of the stereo video system to make high frequency bedform observations ripple crests were found to oscillate at the same frequency as the swell waves the magnitude of the ripple movement at swell wave frequencies was an order of magnitude greater than ripple movement at wind wave frequencies net onshore migration of the ripples corresponded to onshore wave asymmetry very weak mean cross shore currents and net onshore suspended sediment flux measured at an elevation of 0 05 m

ephemeral sand waves in the hurricane surf zone abstract airborne bathymetric lidar observations along the florida panhandle after hurricane dennis 2005 show the first unequivocal observations of surf zone sand wave trains these are found in depths of 5m along the trough of the hurricane bar where hindcasts show strong longshore currents only during severe storms the waves extend over tens of kilometers of coast after dennis but are absent from the same area in four other datasets observed wavelength to water depth ratios are comparable to river dunes and tidal sand waves but height to depth ratios are smaller with the largest wave heights around 0 1 times the water depth the sand wave generation mechanism is hypothesized to be from wind and wave induced longshore currents which were hindcast to be large during dennis with destruction from water wave orbital velocities

performance of a sonar altimeter in the nearshore abstract a 1 mhz sonar altimeter with automatic gain control is shown to provide accurate estimates of the distance between the instrument and the seafloor laboratory experiments indicate that distance estimates degrade slightly when the bottom is rough or sloped and when sediment is suspended in the water column results from field tests both within and seaward of the surf zone show some degradation owing to a combination of suspended sediment and bubbles bed undulations and perhaps the dynamic nature of the sand bottom under waves seaward of the surf zone the bottom can be located within 2 cm nearly continuously whereas inside the surf zone the bottom can be located only intermittently and the accuracy decreases to 3 cm a 300 m long cross shore transect of 16 altimeters was deployed from the shoreline to about 4 m depth for 3 months in summer fall 1994 near duck nc results show that the altimeters are robust and can usually provide estimates of the seafloor position every few minutes even in the surf zone during large storms

geochemical characteristics of tertiary saline lacustrine oils in the western qaidam basin northwest china abstract based on the systematic analyses of light hydrocarbon saturate aromatic fractions and c isotopes of over 40 oil samples along with related tertiary source rocks collected from the western qaidam basin the geochemical characteristics of the tertiary saline lacustrine oils in this region was investigated the oils are characterized by bimodal n alkane distributions with odd to even c11 c17 and even to odd c18 c28 predominance low pr ph mostly lower than 0 6 high concentration of gammacerane c35 hopane and methylated mttcs reflecting the high salinity and anoxic setting typical of a saline lacustrine depositional environment mango s k1 values in the saline oils are highly variable 0 99 1 63 and could be associated with the facies dependent parameters such as pr ph and gammacerane indexes compared with other tertiary oils the studied tertiary saline oils are marked by enhanced c28 sterane abundance 30 or more of c27 c29 homologues possibly derived from halophilic algae it is noted that the geochemical parameters of the oils in various oilfields exhibit regular spatial changes which are consistent with the depositional phase variations of the source rocks the oils have uncommon heavy c isotopic ratios 24 to 26 and a flat shape of the individual n alkane isotope profile and show isotopic characteristics similar to marine organic matter the appearance of oleanane and high 24 24 27 norcholestane ratios 0 57 0 87 in the saline oils and source rocks confirm a tertiary organic source

biological marker compounds as indicators of the depositions history of the maoming oil shale abstract the eocene maoming oil shale from guangdong province occurs as a laterally uniform stratigraphic section typically 20 25 m thick from which the aliphatic hydrocarbon constituents of six representative samples were investigated using gc and c gc ms the sediments evaluated included the basal lignite a vitrinite lens from the overlying claystone and four intervals from the massive oil shale bed as expected the lignite and vitrinite differ markedly from the oil shales the lignite is dominated by bacterial hopanoids and components of higher plant origin including c 29 steroids and triterpenoids such as oleanenes visually the oil shale samples show corroded and degraded phytoclasts spores wispy particles of fluorescent organic material attributable to dinoflagellates and especially in the uppermost sample colonial algal bodies the distributions of biological markers in the oil shales show many features in common notably a dominance of dinoflagellate derived 4 methylsteroids and a significant proportion of higher plant derived n alkanes with marked odd over even carbon number predominance overall they exhibit several features that resemble characteristics of the messel shale the hydrocarbons of the lowest shale horizon suggest that there may have been a gradual transition between deposition of the original peat and the subsequent oil shales the aliphatic hydrocarbons of the uppermost shale are dominated by a number of c 31 and c 33 botryococcane homologues and other unusual branched alkanes possibly derived from green algae all of the samples are immature overall molecular and microscopic examination of the stratigraphic succession of the maoming oil shale suggests a shallow lacustrine environment within which peats were deposited this lake subsequently deepened to support abundant algal populations especially dinoflagellates culminating in a dominance of botryococcoid algae

geochemical study of crude oils from the xifeng oilfield of the ordos basin china abstract the xifeng oilfield is the largest newly discovered oilfield in the ordos basin in order to determine the possible source crude oils collected systematically from the oilfield and an adjacent oilfield have been examined isotopically and molecularly the predominance of long chain n alkanes high abundance of c29 sterane lower ratios of c25 c26 tricyclic terpane and c25 tricyclic terpane c24 tetracyclic terpane and high c24 tetracyclic terpane c24 tetracyclic terpane c26 tricyclic terpanes ratio in the studied oils suggest generation from a source with mixed terrigenous and algal bacterial organic matter the presence of diterpenoid hydrocarbon with abietane skeletons is characteristic of the main contribution of higher land plants to the oils the biomarker distributions in the oils show that they were formed under a weakly reducing freshwater environment molecular maturity parameters indicate that the crude oils are mature the oil source rock correlation and oil migration investigation suggest that the oils in the xifeng oilfield originated from the source rocks of the yanchang formation deposited in a shallow to deep freshwater lacustrine environment especially chang 7 source rocks the data from the distribution of pyrrolic nitrogen compounds indicate that the charging direction of the chang 8 crude oils is mainly from the zhuang 12 well northeast of the oilfield toward the southwest this direction of oil migration is consistent with that indicated by regional geological data

wave formed sand ripples at duck north carolina a recently developed acoustic multiple transducer array was utilized to measure small scale bed forms in the nearshore and inner shelf regions at duck north carolina two populations of wave formed ripples were observed short wave ripples swr with heights ranging from 3 mm to 2 cm and lengths ranging from 4 to 25 cm and long wave ripples lwr with heights ranging from 3 mm to 6 cm and lengths ranging from 35 to 200 cm the swr were only present sometimes and their presence or absence was determined by a critical value of the near bed mobility number the swr were highly dynamic sometimes flattening during wave groups and reforming over several incident wave periods the lwr in contrast were almost always present they were longer and lower relief than predicted by models or generally observed previously both swr and lwr were often observed to migrate shoreward but were rarely observed to migrate seaward the dimensions of the swr when they were present were predictable by the nielsen 1981 model or the wiberg and harris 1994 model to within approximately a factor of 2