lunar global shape and polar topography derived from kaguya lalt laser altimetry a global lunar topographic map with a spatial resolution of finer than 0 5 degree has been derived using data from the laser altimeter lalt on board the japanese lunar explorer selenological and engineering explorer selene or kaguya in comparison with the previous unified lunar control network ulcn 2005 model the new map reveals unbiased lunar topography for scales finer than a few hundred kilometers spherical harmonic analysis of global topographic data for the moon earth mars and venus suggests that isostatic compensation is the prevailing lithospheric support mechanism at large scales however simple rigid support is suggested to dominate for the moon venus and mars for smaller scales which may indicate a drier lithosphere than on earth especially for the moon and venus

modeling an exogenic origin for the equatorial ridge on iapetus abstract iapetus has a ridge along the equator that extends continuously for more than 110 in longitude parts of the ridge rise as much as 20 km above the surrounding terrains most models for the formation of this enigmatic ridge are endogenic generally requiring the formation of a fast spinning iapetus with an oblate shape due to the rotation speed many of these require specific scenarios and have constraining parameters in order to generate a ridge comparable to what is seen today an exogenic formation mechanism has also been proposed that the ridge represents the remains of an early ring system around iapetus that collapsed onto the surface thus far none of the models have conclusively identified the origin of the ridge in this study an exogenic origin for the ridge is assumed which is derived from a collapsing disk of debris around iapetus without invoking any specific model for the generation of the debris disk here we evaluate whether it is possible to generate a ridge of the size and shape as observed by simulating the impact of the collapsing debris using the cth hydrocode pi scaling calculations suggest that extremely oblique impact angles 1 10 are needed to add to ridge topography these extreme impact angles severely reduce the cratering efficiency compared to a vertical impact adding material rather than eroding it during crater formation furthermore material is likely to be excavated at low angles enhancing downrange accumulation multiple impacts from debris pieces will heighten this effect because infalling debris is predicted to impact at extremely low angles both of these effects might have contributed to ridge formation on iapetus the extreme grazing angles of the impacts modeled here decouple much of the projectile energy from the target and impact heating of the surface is not significant these models suggest that a collapsing disk of debris should have been able to build topography to create a ridge around iapetus

cassini imaging science initial results on phoebe and iapetus the cassini imaging science subsystem acquired high resolution imaging data on the outer saturnian moon phoebe during cassini s close flyby on 11 june 2004 and on iapetus during a flyby on 31 december 2004 phoebe has a heavily cratered and ancient surface shows evidence of ice near the surface has distinct layering of different materials and has a mean density that is indicative of an ice rock mixture iapetus s dark leading side cassini regio is ancient heavily cratered terrain bisected by an equatorial ridge system that reaches 20 kilometers relief local albedo variations within and bordering cassini regio suggest mass wasting of ballistically deposited material the origin of which remains unknown

coupling of thermal evolution and despinning of early iapetus abstract the cassini mission revealed two spectacular characteristics of iapetus 1 a geologically old and high equatorial ridge which is unique in the solar system and 2 a large flattening of 35 km consistent with the equilibrium figure for a hydrostatic body rotating with a period of 16 h whereas the current spin period is 79 33 days this study describes three dimensional simulations of solid state convection within an undifferentiated iapetus it investigates the implications for the evolution of the interior thermal structure and its spin rate and global shape using radially layered viscoelastic models the role of the concentration in the short lived radiogenic element 26 al just after accretion is completed is specifically addressed the first result is to show that whatever the 26 al value convection occurs as suggested by castillo rogez et al castillo rogez j matson d sotin c johnson t lunine j thomas p 2007 icarus 190 179 202 convection reduces the warming of the interior compared to the conductive evolution and therefore limits the conditions for despinning in our calculations two conceptual linear viscoelastic models are used when considering a maxwell rheology the interior temperature viscosity never reaches a value high low enough to induce despinning in order to promote dissipation at low temperature a burgers rheology which includes an additional dissipation peak is introduced for favorable parameter values this latter rheology leads to despinning however only models associated with large amounts of short lived radiogenic elements 26 al 25 ppb lead to the observed flattening this suggests that the accretion process needs to be completed shortly after the formation of cais calcium aluminum rich inclusions 4 myr for 26 al varying between 72 and 46 ppb the observed flattening is obtained only for a limited range of initial spin period between 9 5 and 10 2 h for 26 al ranging between 30 and 15 ppb initial spin rates smaller than 8 5 h are required for smaller values of 26 al the body is too cold and viscous to acquire a significant flattening even if a rotation period close to the body disruption limit is considered even with a thin lithosphere during the early stage our simulations show that iapetus never reaches the equilibrium figure for a hydrostatic body due to the non zero rigidity of the lithosphere the 35 km value of the flattening is the result of the partial relaxation of an ancient larger flattening ranging between 45 and 80 km depending on the evolution of the lithosphere thickness mainly controlled by the radiogenic content a thin lithosphere is consistent with an early building of the equatorial ridge the lithosphere thickening due to interior cooling can explain the preservation of the ridge throughout the remaining evolution of iapetus

active moribund and buried tidal sand ridges in the east china sea and the southern yellow sea shallow seismic profiles and borehole data revealed active moribund and buried tidal sand ridges in the east china sea and the southern yellow sea the ridges consist of relatively clean well sorted sands with fairly uniform sequences the microfossil assemblage exhibits a high diversity including both euryhaline and stenohaline species the ridges are huge elongated sand bodies several kilometres wide 10 60 km long and up to 20 m thick and occur in groups with a spacing of several to 10 km normally they are parallel with each other extending in the direction of the tidal currents the field of tidal sand ridges on the east china sea shelf covers an area of 57 000 km2 tidal sand ridges in the east china sea and the southern yellow sea were formed in estuarine and shallow shelf environments where strong tidal currents reworked transported and redeposited large amounts of relict sands from older deltaic and fluvial sediments the development of tidal sand ridges in estuary mouth areas is accompanied by a net sand transport from the shelf into the estuary the evolution of tidal sand ridges is closely related to transgressions active tidal sand ridges are formed during sea level rises they show distinct morphology and active migrations in a lateral as well as in a landward direction they are generally in equilibrium with present day tidal processes and their distribution patterns are related to the flow field of the tidal currents as the sea level rises further these tidal sand ridges become moribund sand bodies with less distinct morphologies their upper surfaces are covered by a thin calcareous rich layer with very high contents of foraminifera tests reflecting a submarine hiatus condition on the shelf during the highstand period during the subsequent steady fall in sea level tidal sand ridges are often buried by fine grained shelf and prodelta sediments they have therefore a good chance of being preserved in stratigraphic records the sequential buildup during a sea level rise tr tract and a subsequent sea level fall hs and ls tract would consist of estuarine channel and tidal flat facies tidal sand ridge facies shelf mud facies delta facies and fluvial facies in an ascending order tidally dominated estuary conditions may also occur when a major distributary is abandoned such as at the northern branch of the modern changjiang river mouth where the accumulation of sand from an abandoned delta lobe and the development of tidal sand ridges have been observed the observed features have important implications for the subsurface recognition of fossil tidal sand ridges for the reconstruction of the regional palaeogeography and transgressional history and for the prediction of potential reservoir sandstones

rock magnetic properties of the fine grained sediment on the outer shelf of the east china sea implication for provenance the rock magnetic properties of surface sediments from the fine grained depositional area on the outer shelf of the east china sea an area surrounded by sands were investigated with a view to providing information on the sediment provenance multiple magnetic parameters such as magnetic susceptibility anhysteretic remanent magnetization saturation remanent magnetization sirm coercivities of sirm and s ratios relative abundance of low coercivity magnetic minerals were measured for all 179 surface samples and partial representative samples were examined for their magnetic hysteresis parameters temperature dependence of magnetic susceptibility and x ray diffraction spectra our research indicates that the magnetic mineralogy is dominated by magnetite with a small amount of hematite and is primarily of a pseudo single domain to multidomain nature with a detrital origin the magnetic concentration in the study area generally decreases to the east or southeast accompanied by magnetic particle fining to the east or northeast the geographic pattern of magnetic properties is most reasonably explained by a major source of sediment jointly from the erosion of the old huanghe river deposit and the discharge of the changjiang river the rock magnetic data facilitate understanding of the transport mechanism of fine grained sediments in the outer shelf of the east china sea

source dependent biomarker properties of five crude oils from the gulf of suez egypt abstract five crude oils from some producing wells in the southern part of the gulf of suez were characterized using a variety of organic geochemical parameters the results reveal significant differences within the oils from the gulf of suez basin that suggest two oil types and one mixed type type 1 oils from ras fanar and east zeit fields show a high relative abundance of gammacerane indicating a marine saline source depositional environment another related feature of these oils is the predominance of c 35 over c 34 17 h homohopanes type 2 oils from gama and amal 9 wells show oleanane indices over 20 indicating that they originated from an angiosperm rich tertiary source rock type 3 oil from amal 10 well has geochemical characteristics intermediate between those of types 1 and 2 this may reflect mixing of oils from the sources of both types 1 and 2 the geochemical characteristics of the oils vary sufficiently to suggest multiple sources the type 1 oils possess geochemical characteristics consistent with upper cretaceous brown limestone or lower eocene thebes formation carbonate source rocks type 2 oils are very similar in geochemical character to the lower miocene rudeis formation source rocks

magnetic properties of muddy sediments on the northeastern continental shelves of china implication for provenance and transportation mud deposits are widespread in estuaries and on continental shelves and contain important information regarding interactions between terrestrial and coastal processes magnetic properties of muddy sediments from the northeastern continental shelves of china including shelves close to korean coasts were analyzed using bulk and size fractionated samples to elucidate muddy sediment sources and transport types concentration and granulometry of magnetic minerals were determined and all samples were found to be dominated by magnetite muddy sediments from the zhemin coast off the zhejiang and fujian coasts have the highest magnetic susceptibility and saturation isothermal remanent magnetization sirm values while those from the central and southeastern south yellow sea and the western korea strait have lower values reflecting lower magnetic mineral concentrations single domain ferrimagnetic grains dominate the magnetic particles in the central south yellow sea while superparamagnetic sp grains contribute significantly to the magnetic grains in the bohai sea sp and coarse multi domain md grains dominate magnetic grain assemblages in the north yellow sea and along the zhemin coast rock sediment particle size is not a major factor affecting the magnetic properties of the mud deposits in the study area rather terrigenous inputs and hydrodynamic transport processes primarily control the magnetic properties and sediments from the changjiang and huanghe rivers make the most significant contribution this observation applies to the whole study area although terrigeneous magnetic mineral concentrations decrease with increasing distance from the river mouths due to both sorting and mixing with other sediments with weak magnetic signatures bacterial magnetosomes also play a role in the central south yellow sea

delayed formation of the equatorial ridge on iapetus from a subsatellite created in a giant impact 1 the great equatorial ridge on saturn s moon iapetus is arguably the most perplexing landform in the solar system the ridge is a mountain range up to 20 km tall and sitting on the equator of iapetus and explaining its creation is an unresolved challenge models of its formation must satisfy three critical observations why the ridge 1 sits exactly on the equator 2 is found only on the equator and 3 is thus far found only on iapetus we argue that all previously proposed models fail to satisfy these observations and we expand upon our previous proposal that the ridge ultimately formed from an ancient giant impact that produced a subsatellite around iapetus the orbit of this subsatellite would then decay once iapetus itself had despun due to tides raised by saturn until tidal forces from iapetus tore the subsatellite apart the resultant debris formed a transient ring around iapetus the material of which rained down on the surface to build the ridge by sequestering the material in a subsatellite with a tidally evolving orbit formation of the ridge is delayed which increases the likelihood of preservation against the high impact flux early in the solar system s history and allows the ridge to form on thick stiff lithosphere heat flow likely 1 mw m 2 required to support this massive load without apparent flexure this mechanism thus explains the three critical observations

oil prospects of the gulf of suez egypt a case study abstract four groups of rocks having more than 0 5 of organic carbon are defined within the subsurface section of rahmi area gulf of suez the deduced types of indigenous kerogen are algal amorphous inertinite woody and herbaceous the algal amorphous kerogen of rudeis nukhul formations lower miocene eocene and pre eocene rocks is recognized as being oil prone that is having high capacity for generating oil the application of hydrocarbon liquid window concept shows that the lom values fall within the range from 8 6 to 10 8 and the thermal alteration index for the different units is not extended into oil generation window where it ranges from immature kareem formation lower miocene to moderately mature paleocene to the beginning of the thermal phase of oil generation senonian the vitrinite reflectance values indicate a low level of thermal maturity the formational temperatures increase towards the depocentral part of the basin and eastwards to the present gulf of suez the thermal maturity index increases towards ancient stratigraphic units the study of organic richness quality and maturity revealed that where the nukhul eocene and senonian rocks are buried deeper in the study area would have been excellent source rocks for oil

drainage basin weathering and major element transport of two large chinese rivers huanghe and changjiang long term records show high concentrations of dissolved major elements in the changjiang yangtze river and the huanghe yellow river the huanghe drainage basin is characterized by intense weathering and erosion of carbonates and evaporites while weathering and erosion of carbonates and silicates over the drainage basin is the main source of major elements in the changjiang the rock soil composition and tectonics of the drainage basin are more important than atmospheric precipitation in affecting major element composition of these two rivers compared with other large rivers of the world the high suspended sediment and major element loads of the changjiang and huanghe reveal intense physical and chemical erosion over the chinese continent

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

structural regime and its impact on the mechanism and migration pathways of hydrocarbon seepage in the southern gulf of suez rift an approach for finding new unexplored fault blocks abstract a natural active oil seepage occurs at the intersection of the nw oriented rift coastal fault and a ne oriented cross fault which bound the southwest dipping little zeit tilted fault block at the southwestern side of the gulf of suez egypt detailed surface geological mapping followed by subsurface mapping using aeromagnetic seismic and borehole data of ras el ush oilfield the nearest oil field to the seepage provide a reliable hydrocarbon migration pathway model of the area the proposed model suggests that hydrocarbons migrated upward at the intersection of a ne oriented and the nw oriented rift coastal faults where they found their way to the surface the nubia sandstone occurs south of ras el ush oilfield in a trap door structure and probably entrapped some of the migrating hydrocarbons while a probable oil water contact at 1000 m which resulted into the migration of hydrocarbon through the damage zone of the northeast fault the original oil in place of the predicted reservoir is estimated to be more than 47 5 mmbo which encourages the design makers for more investigation of this reservoir to increase its certainty and putting it in the plan of the future investments

a contraction model for the flattening and equatorial ridge of iapetus others have explained the excess flattening of iapetus by a model in which the moon formed at a high spin rate achieved isostatic equilibrium by very rapid interior heating caused by short lived radioactive isotopes slri and subsequently cooled locking in the excess flattening with respect to an equilibrium shape at its present spin rate here we propose an alternate model that does not require an unusually high initial spin rate or the slri the initial formation of iapetus results in a slightly oblate spheroid with porosity 10 radioactive heating by long lived isotopes warms the interior to about 200 k at which point it becomes ductile and the interior compacts by 10 while the 120 km thick exterior shell remains strong the shell must deform to match the reduced volume of the ductile interior and we propose that this deformation occurs along the equator perhaps focused by a thinner equatorial shell the final shape of the collapsed sphere matches the observed shape of iapetus today described as an oblate ellipse except along the equator where strain concentration forms a broad ridge to maintain this non equilibrium shape the thickness of the shell must exceed 120 km testing the equatorial focusing hypothesis will require a model that includes non linear processes to account for the finite yield strength of the thick lithosphere nevertheless we show that the stress in the lithosphere generated by the contraction of the interior is about 3 times greater than the stress needed to deform the lithosphere so some type of lithospheric deformation is expected

a review on the provenance discrimination of sediments in the yellow sea the yellow sea has been extensively studied for the understanding of dispersal patterns and limits of sediments from neighboring countries including china and korea although sedimentological mineralogical and geochemical approaches have been tried to solve the problems especially including the identification of sediment sources in and around the yellow sea the published results are not enough for understanding them suggestions on sediment origins budgets sediment accumulation rates mineralogical and geochemical compositions are not coincident to each other and sometimes even controversial for example conflicts on the distribution patterns of smectite and calcium carbonate the provenance of the southeastern yellow sea mud and sedimentation rates in there the ratios of v al and mn al in korea and china river sediments the origin of ba and pb in sandy sediments of the northeastern yellow sea and so on various geochemical indicators from the literature for the provenance discrimination in the yellow sea are reviewed here in depth and corresponding discussions are described separately research topics for the future study also are suggested for the proper access to the understanding of the origin and dispersal patterns of the yellow sea sediments especially focusing on the geochemical approaches d 2003 elsevier science b v all rights reserved

the provenance of the southeastern yellow sea sediments constrained by detrital zircon u pb age abstract u pb ages of detrital zircon grains collected from sandy sediments in the southeastern yellow sea were analyzed to infer their provenance the zircon age spectra show e w direction differences with a wide age range from early cenozoic to late archean the western samples were dominated by paleozoic to neoproterozoic zircons whereas the eastern samples by paleoproterozoic zircons this age distribution suggests diversity of age populations in the source terranes and changes in sediment supply to the sample locations comparison of these results with the basement rock geology and detrital zircon ages of river sediments in the surrounding land areas indicates that the eastern and western parts of the southeastern yellow sea sandy sediments were mainly supplied from the korean peninsula and southern china along with now submerged shelf bedrocks respectively with a mixing zone in the middle differences in zircon age populations resulted from the change of proportions in sediment supply from two dominant provenances due to sea level rising and associated reworking during the holocene transgression

world wide delivery of river sediment to the oceans new data and new estimates from old data show that rivers with large sediment loads annual discharges greater than about 15 times 10 6 tons contribute about 7 times 10 9 tons of suspended sediment to the ocean yearly extrapolating available data for all drainage basins the total suspended sediment delivered by all rivers to the oceans is about 13 5 times 10 9 tons annually bedload and flood discharges may account for an additional 1 2 times 10 9 tons about 70 of this total is derived from southern asia and the larger islands in the pacific and indian oceans where sediment yields are much greater than for other drainage basins

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

holocene development of the yellow river s subaqueous delta north yellow sea high resolution seismic profiles from the north yellow sea reveal a 20 40 m thick subaqueous clinoform delta that wraps around the eastern end of the shandong peninsula extending into the south yellow sea this complex sigmoidal oblique clinoform containing an estimated 400 km 3 of sediment overlies prominent relict transgressive surfaces the nearshore topset of the clinoform 50 m contain less than 1 m of holocene sediment with low sedimentation rates 1 mm year in contrast to other clinoforms the shandong clinoform appears to be a compound subaqueous deltaic system with what we interpret to be proximal and distal phases of clinoform development the underlying proximal sequence formed proximally between f11 and 9 2 ka in response to a temporary pause in the rapid postglacial sea level rise after the meltwater pulse 1b mwp 1b and increased discharge from the yellow river to the north yellow sea due to intensification of the summer monsoon a flooding surface appears to separate the proximal and distal phases corresponding to the next rapid sea level rise 9 5 9 2 ka bp mwp 1c since 9 2 ka bp an overlying distal sedimentary sequence has accumulated reflecting the backstepping and shifting river mouth westward to the gulf of bohai some inputs from coastal erosion and nearby small streams may be locally important along shore transport cross shelf advection and upwelling in the north yellow sea have reworked post lgm sediment and have helped maintain the morphology of the clinoform in the shandong mud wedge d 2004 elsevier b v all rights reserved

mesozoic detrital zircon u pb ages of modern river sediments in korea implications for migration of arc magmatism in the mesozoic east asian continental margin terra nova 24 156 165 2012 abstract u pb ages of detrital zircons collected from the sediments of seven major south korean rivers were analysed to infer the temporal and spatial distribution of mesozoic arc magmatism related to the subduction of the palaeo pacific plates mesozoic detrital zircon u pb ages indicate continuous arc magmatic activity in the korean peninsula throughout the mesozoic era 249 72 ma except for a magmatic gap during 120 162 ma with nw se spatial migration of the arc magmatic centres trenchward migration in both the triassic and the cretaceous periods and inland directed migration in the jurassic period a comparison of these results with the magmatic ages in the adjacent regions such as northeastern china and southwestern japan suggests that subduction modes of the palaeo pacific plates were changed in the mesozoic east asian continental margin due to buoyancy differences caused by the subduction of the farallon izanagi plate ridge or oceanic plateaus and their subducting location shifting with time

sediment distribution dispersal and budget in the yellow sea abstract information on the surface sediment distribution in the yellow sea is newly compiled based on all available data produced by chinese and korean workers and is used to refine the dispersal patterns and budget of sediments derived from the adjoining landmass the central yellow sea is largely covered with fine grained sediments originating from the huanghe river 2 2 10 8 t yr about 20 of the total discharge thick sediment accumulation exceeding 5 mm yr occurs in the gulf of bohai and around the shandong peninsula about two thirds of the total huanghe river discharge the old huanghe delta suffers from reworking by strong tides and waves and forms a mud patch southwest of cheju island accumulation rate 2 10 7 t yr more than half of the sediments derived from the changjiang river are deposited along the coast of the east china sea the remainder accumulate on the inner shelf off the river mouth in the southeastern yellow sea the keum river dominates sediment discharge forming a holocene mud belt along the southwestern coast of korea accumulation rate 5 10 6 t yr turbid water plumes occur nearshore throughout the year and their suspended sediments are transported along the tip of the peninsula to the western coastal embayments in the south sea the nakdong river discharge of 1 10 7 t yr is responsible for the eastern nearshore mud of the south sea relict sands occur in the northern part of the yellow sea in the northern east china sea and in the korea strait

rifted margin source rock deposition a carbon isotope and biomarker study of a west african lower cretaceous lacustrine section lower cretaceous passive margin sections penetrated in wells peripheral to the deep basinal development of pre salt sediments of the liawenda ponta vermelha troughs in the lower congo coastal basin revealed sustained source potential kerogen type kinetic ea a and carbon isotopic data plus rock extract biomarker signatures confirmed large systematic organofacies variations within these rift phase sediments an inverse correlation between 25 28 30 trisnorhopane and gammacerane abundances suggested three major depositional regimes reflecting salinity and water depth control 13c depleted basal sediments showing strong gammacerane 4 methyl sterane signatures were segregated by a major isotopic excursion this event represented the transition between saline playa lake to deeper water stratified conditions supporting a high level of anoxia for these intermediate sediments sterane and tricyclic diterpane abundances plus sterane hopane ratios had marine connotations and could be interpreted as the result of intermittent marine incursions fore shadowing irreversible oceanic ingression a resurgence of gammacerane abundance in the uppermost sediments typified littoral shallow marine depositional conditions recognition of a possible non ubiquity in lacustrine depositional conditions during the opening of a rifted margin provides further insight into the complexity and attendant controls on hydrocarbon generation in such habitats

the origins of petroleum in the northern gulf of mexico abstract the distribution and chemistry of oils in the northern gulf of mexico and the adjacent onshore can be explained by multiple sources fades variations maturation and post generation alteration genetic families include jurassic smackover flexure trend upper cretaceous and paleogene oils smackover oils have high sulfur contents pristane phytane ratios c 35 c 34 hopane ratios 1 0 and c 30 c 29 hopane ratios usuall 1 0 flexure trend oils are similar and contain abundant extended hopanes high sulfur contents and v ni v 0 5 these oils are inferred to be sourced in upper jurassic lower cretaceous strata upper cretaceous oils contain a distinctive suite of tricyclic and nonhopanoid triterpanes oleanane is low or absent paleogene oils can be recognized by the presence of 18 h oleanane and a lack of extended hopanes these oils occur from south texas to southern and offshore louisiana two subfamilies can be recognized based on the relative abundance of triterpanes and steranes these oils have a presumed paleogene source mixing of oil types is quite prevalent at the geographic boundaries of oil types the initial control on the distribution of oil and gas in the northern gulf of mexico is provided by the areal extent of source rocks secondary control is due to cenozoic deposition which provides the thermal stress to generate as well as destroy oil salt tectonics provide conduits for migrating fluids to escape the zone of thermal destruction mesozoic source strata again become important in the deep gulf of mexico where cenozoic sediments thin

hydrocarbon source rock potential in the southwestern gulf of suez graben insights from organic geochemistry and palynofacies studies on well samples from the ras el bahar oilfield abstract palynological and biomarker characteristics of organic facies recovered from cretaceous miocene well samples in the ras el bahar oilfield southwest gulf of suez and their correlation with lithologies environments of deposition and thermal maturity have provided a sound basis for determining their source potential for hydrocarbons in addition to palynofacies analysis toc rock eval pyrolysis kerogen concentrates bitumen extraction carbon isotopes and saturated and aromatic biomarkers enable qualitative and quantitative assessments of sedimentary organic matter to be made the results obtained from rock eval pyrolysis and molecular biomarker data indicate that most of the samples come from horizons that have fair to good hydrocarbon generation potential in the study area the upper cretaceous paleocene lower eocene samples contain mostly type ii to type iii organic matter with the capability of generating oil and gas the sediments concerned accumulated in dysoxic anoxic marine environments by contrast the miocene rocks yielded mainly type iii and type ii iii organic matter with mainly gas generating potential these rocks reflect deposition in a marine environment into which there was significant terrigenous input three palynofacies types have been recognized the first a consists of type iii gas prone kerogen and is typical of the early middle miocene belayim kareem and upper rudeis formations the second b has mixed oil and gas features and characterizes the remainder of the rudeis formation the third association c is dominated by amorphous organic matter classified as borderline type ii oil prone kerogen and is typical of the matulla turonian santonian and wata turonian formations rock eval t max pi hopane and sterane biomarkers consistently indicate an immature to early mature stage of thermal maturity for the whole of the studied succession

tidal dissipation surface heat flow and figure of viscoelastic models of io abstract the distribution of hot spots on io s surface and io s figure constrain models of io s interior voyager observations indicate that most hot spots and volcanic plumes are close to the equator recently however it has been proposed that a large low albedo feature in the south polar region may be the source of 40 of the surface heat flow we calculate spatial distributions of the dissipation rate surface heat flow and the figures of three and four layer maxwell rheology models of io by using the correspondence principle the models are required to satisfy the observed surface heat flow constraint and are consistent with the composition of a dehydrated c2 chondrite they consist of an inviscid fe fes core and viscoelastic silicate mantle and lithosphere layers a comparison of the calculated equilibrium figure with the observed figure of io supports the chosen core radius of 980 km in addition the four layer model has a partially molten asthenosphere a few tens of kilometers thick the preferred three layer model has a mantle shear modulus of 10 10 pa and a viscosity of 2 10 16 pa s consistent with rock properties the tidal dissipation rate for this model is largest along the polar axis integration of the dissipation rate over radius gives a surface heat flow with maxima at the poles and minima near the sub jovian and anti jovian points in contrast the dissipation rate in a molten or partially molten incompressible asthenosphere has maxima near the equator and is close to zero at the poles the asthenosphere dissipation rate is mainly a function of asthenosphere viscosity and thickness the thinner the asthenosphere the smaller is the required viscosity a 50 km thick asthenosphere requires a viscosity of about 10 8 pa s a strong south polar hot spot if it can be confirmed by infrared observation favors dissipation in the mantle but does not exclude dissipation in a partially molten asthenosphere equatorial hot spots and the concentration of prometheus type plumes near the equator favor asthenosphere heating but do not rule out deep mantle dissipation both asthenosphere and deep mantle heating may contribute to io s surface heat flow the properties of magma transport through the lithosphere and the planform of mantle convection might exert a control on the surface expression of heating at greater depth

ridge formation and de spinning of iapetus via an impact generated satellite abstract we present a scenario for building the equatorial ridge and de spinning iapetus through an impact generated disk and satellite this impact puts debris into orbit forming a ring inside the roche limit and a satellite outside this satellite rapidly pushes the ring material down to the surface of iapetus and then itself tidally evolves outward thereby helping to de spin iapetus this scenario can de spin iapetus an order of magnitude faster than when tides due to saturn act alone almost independently of its interior geophysical evolution eventually the satellite is stripped from its orbit by saturn the range of satellite and impactor masses required is compatible with the estimated impact history of iapetus

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

the effect of sea level climate and shelf physiography on the development of incised valley complexes a modern example from the east china sea abstract analysis of high resolution seismic reflection and sonar data from the east china sea ecs continental shelf reveals the presence of an extremely broad 330 km and deep maximum incision of 72 m incised valley complex whose development and subsequent fill is constrained to the end of the last glacial cycle 20 000 yr bp to present results from this study indicate that sea level change climate controlled discharge and sediment supply and shelf physiography were important factors in the development and subsequent fill of the ecs incised valley complex for example wet climatic conditions during the initial marine oxygen isotope stage mis 2 fall of sea level promoted fluvial erosion of the exposed shelf however the trend toward drier conditions during the mis 2 fall of sea level slowed the overall development of the incised valley complex to the point where only minor incision occurred during the maximum lowstand furthermore the low gradient morphology of the exposed outer shelf diminished the ability of fluvial systems to incise instead fluvial systems migrated laterally creating a shallow 300 km incised valley system on the outer shelf during the late mis 2 rise of sea level accommodation was generated within the flooded reaches of the valley complex however arid climatic conditions that prevailed at this time resulted in minor sediment delivery to the transgressive shoreline via the incised valley complex thus the upper part of the drowned lowstand fluvial deposits were exposed at the sea floor and reworked into a valley wide tidal bar and tidal sheet complex wetter climatic conditions during middle to late mis 1 resulted in abundant sediment delivery to the drowned parts of the valley complex estuary and buried lowstand fluvial deposits below the depth of tidal ravinement where they remained undisturbed current sequence stratigraphic models can be applied to the late quaternary stratigraphic secession of the ecs however these models are too simplistic because they rely largely on rates and directions of sea level change to explain stratal architectures although the extent and rate of sea level change is extremely important this study shows that high frequency climate change and shelf physiography also play important roles in the development of stratigraphic architectures these factors are particularly important for the development of incised valleys where they directly influence incised valley morphology and facies distributions

geochemical composition and provenance of muddy shelf deposits in the east china sea abstract textural and geochemical compositions of shelf sediments in the east china sea were measured and compared with those of riverine sediments the sediments were primarily composed of mud and sandy mud with an average mean grain size of 6 1 contents of caco3 varied from 3 9 to 11 5 averaging 7 6 elemental ratios of sc al zr ti cr th and nb co can be treated as powerful geochemical indices for sediment sources because these elements behave conservatively under marine environments and the ratios show large variations between different end members of potential sediment sources comparative analysis between elemental sc al zr ti cr th nb co ratios and sr isotopic 87sr 86sr ratios strongly suggest that sediments in the northern part of the east china sea primarily originate from the huanghe river whereas the muddy deposits in the western part of the east china sea originate from the changjiang river the difference in 87sr 86sr ratios between the two regions appears to indicate varied sources

formation of iapetus extreme albedo dichotomy by exogenically triggered thermal ice migration the striking appearance of saturn s moon iapetus half black and half white has puzzled astronomers for over three centuries now spencer and denk p 432 1 published online 10 december present an explanation for this asymmetry a thermally controlled runaway migration of water ice triggered by exogenic deposition of dark material on the moon s leading darker side which faces the direction of motion of the moon in its orbit around saturn this mechanism is unique to iapetus because it rotates slowly enough to allow large temperature variations to arise it is small enough to allow long range migration of water and there is a source of dust to trigger the process in a related paper denk et al p 435 2 published online 10 december present data derived from the cassini imaging science subsystem that reveal that both dark and bright materials on the leading side of iapetus are redder than their trailing side counterparts this asymmetry results from the deposition of dust and debris from other moons in the saturnian system the very same process that initiates the thermal segregation proposed above 1 lookup doi 10 1126 science 1177132 2 lookup doi 10 1126 science 1177088

testing models for the formation of the equatorial ridge on saturn s moon iapetus via crater counting abstract iapetus s equatorial ridge visible in global views of the moon is unique in the solar system the formation of this feature is likely attributed to a key event in the evolution of iapetus and various models have been proposed as the source of the ridge by surveying imagery from the cassini and voyager missions this study aims to compile a database of the impact crater population on and around iapetus s equatorial ridge assess the relative age of the ridge from differences in cratering between on ridge and off ridge and test the various models of ridge formation this work presents a database that contains 7748 craters ranging from 0 83 km to 591 km in diameter the database includes the study area in which the crater is located the latitude and longitude of the crater the major and minor axis lengths and the azimuthal angle of orientation of the major axis analysis of crater orientation over the entire study area reveals that there is no preference for long axis orientation particularly in the area with the highest resolution comparison of the crater size frequency distributions show that the crater distribution on the ridge appears to be depleted in craters larger than 16 km with an abruptly enhanced crater population less than 16 km in diameter up to saturation one possible interpretation is that the ridge is a relatively younger surface with an enhanced small impactor population finally the compiled results are used to examine each ridge formation hypothesis based on these results a model of ridge formation via a tidally disrupted sub satellite appears most consistent with our interpretation of a younger ridge with an enhanced small impactor population

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

botryococcane in a new class of australian non marine crude oils there are few documented examples of source specific hydrocarbons in non marine petroleum and most of these are related to land plant precursors1 3 one such biological marker of algal origin is botryococcane c34h70 a geologically rare acyclic alkane derived from the freshwater green alga botryococcus braunii4 5 first discovered in several sumatran crude oils6 7 and here identified in a suite of coastal bitumens from 10 different stranding sites between kingston south australia and portland victoria table 1 figs 1 2 biological marker and carbon isotope analyses of these bitumens provide evidence for a new class of australian non marine crude oils the bitumens are inspissated waxy residues of paraffinic and paraffinic naphthenic crude oils that emanate from submarine seeps in the western otway basin8 12 and are characterized by high concentrations of botryococcane unlike other high wax australian oils13 14 the coastal bitumens contain up to 2 6 sulphur and seem to be primarily of algal origin their geochemistry can be used to predict the occurrence of extensive organic rich source beds that were deposited in deep meromictic lakes along australia s southern continental margin

on a ring origin of the equatorial ridge of iapetus 1 most recent cassini observations by the imaging science subsystem iss showed that the third largest saturnian satellite iapetus has a curious ridge system exactly aligned with its equator porco et al 2005 because iapetus has a large hill sphere for the trapping of circum satellitary material a ring system might have been present during its formation a scenario is proposed to describe how the equatorial ridge system could have been produced by the collisional accretion of a ring remnant subsequent to the formation of the proto iapetus

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

geology and habitat of oil in ras budran field gulf of suez egypt deminex as operator for its partners british petroleum and shell discovered ras budran oil field in 1978 discovery well ee 85 1 was drilled in approximately 140 ft 42 m of water 2 5 mi 4 km off the sinai coast of the gulf of suez appraisal drilling wells ee 85 2 85 3 and 85 4 confirmed the presence of a major field with an estimated 700 million bbl of oil in place the field developed from three wellhead platforms has been producing since april 1983 to date 20 development wells have been drilled the ras budran structure at the deepest mappable seismic reflector the top of the kareem formation middle miocene is a broad northeast southwest trending anticlinal feature with an anomalous strike nearly at right angles to the main gulf of suez trend at deeper pre miocene producing levels the structure is complex and consists of a northeast dipping flank 14 15 broken into several blocks by northwest trending longitudinal faults and nearly north south trending cross faults the ras budran is limited to the south and west by major bounding faults oil is produced from three units of nubian formation sandstone from a depth of 11 000 12 000 ft 3 352 3 657 m the lower unit of paleozoic age averages 10 porosity and has up to 200 md in situ permeability wells completed in this unit produce up to 2 000 bopd in contrast the sands of the upper two units of the early cretaceous have 15 20 porosity and up to 700 md permeability wells completed in this unit produce 6 000 8 000 bopd the ras budran structure was formed primarily during an intra rudeis tectonic phase lower miocene oil migration for accumulation in the structure started in the late miocene or pliocene when the santonian brown limestone and the eocene thebes formation the main source beds in the gulf of suez reached the threshold of oil generation at a burial depth of approximately 10 000 ft 3 048 m at this depth the organic matter in the source beds had a high transformation ratio 0 10 to 0 15 high yields of c15 soluble organic matter and c15 saturated hydrocarbons vitrinite reflectance ro of 0 62 and a time temperature index tti value of 15 oil migration from mature source beds in adjoining lows into low potential nubian reservoirs is easily explained by fault planes that acted as conduits for oil migration

iapetus geophysics rotation rate shape and equatorial ridge iapetus has preserved evidence that constrains the modeling of its geophysical history from the time of its accretion until now the evidence is a its present 79 33 day rotation or spin rate b its shape that corresponds to the equilibrium figure for a hydrostatic body rotating with a period of 16 h and c its high equatorial ridge which is unique in the solar system this paper reports the results of an investigation into the coupling between iapetus thermal and orbital evolution for a wide range of conditions including the spatial distributions with time of composition porosity short lived radioactive isotopes slri and temperature the thermal model uses conductive heat transfer with temperature dependent conductivity only models with a thick lithosphere and an interior viscosity in the range of about the water ice melting point can explain the observed shape short lived radioactive isotopes provide the heat needed to decrease porosity in iapetus early history this increases thermal conductivity and allows the development of the strong lithosphere that is required to preserve the 16 h rotational shape and the high vertical relief of the topography long lived radioactive isotopes and slri raise internal temperatures high enough that significant tidal dissipation can start and despin iapetus to synchronous rotation this occurred several hundred million years after iapetus formed the models also constrain the time when iapetus formed because the successful models are critically dependent upon having just the right amount of heat added by slri decay in this early period the amount of heat available from short lived radioactivity is not a free parameter but is fixed by the time when iapetus accreted by the canonical concentration of 26al and to a lesser extent by the concentration of 60fe the needed amount of heat is available only if iapetus accreted between 2 5 and 5 0 myr after the formation of the calcium aluminum inclusions as found in meteorites models with these features allow us to explain iapetus present synchronous rotation its fossil 16 h shape and the context within which the equatorial ridge arose

lunar accretion from an impact generated disk although the mechanism by which the moon was formed is currently unknown several lines of evidence point to its accretion from a circumterrestrial disk of debris generated by a giant impact on the earth theoretical simulations show that a single large moon can be produced from such a disk in less than a year and establish a direct relationship between the size of the accreted moon and the initial configuration of the debris disk

oil window in the gulf of suez basin egypt petroleum in the gulf of suez is multisourced mainly by restricted marine cretaceous to eocene beds the campanian carbonates of the sudr formation and the turonian shales of the abu qada formation are high quality sources other proven sources are carbonate and shale intervals within other sub miocene formations geothermal modeling calibrated by maturation measurements suggests that the organic rich lower miocene marls may not be mature enough to expel hydrocarbons north of the morgan amal fields area but are mature to the south this could be related mainly to a gradual increase in thermal gradient from north to south 20 55 degree c km a few anomalies do exist however thermal gradients are generally higher in areas where oil accumulated the depth of peak generation ranges between 5 200 m to the north and 3 300 m to the south the geographic variations in heat flow maturation depths and age of source rocks are not reflected in the timing of hydrocarbon migration during the middle miocene a short lived salinity crisis resulted in the deposition of massive thick evaporites that form the ultimate seal in the gulf the accompanying rapid burial of the underlying sub miocene potential source intervals caused them all to sequentially enter the oil window within a verymore short time soon after the evaporites accumulated this timing was perfect for hydrocarbon preservation after seal deposition and major disturbing regional tectonic events the almost simultaneous migration from all the source beds resulted in mixed multisourced hydrocarbon accumulations less

the topography of iapetus leading side abstract we have used cassini stereo images to study the topography of iapetus leading side a terrain model derived at resolutions of 4 8 km reveals that iapetus has substantial topography with heights in the range of 10 km to 13 km much more than observed on the other middle sized satellites of saturn so far most of the topography is older than 4 ga neukum g wagner r denk t porco c c 2005 lunar planet sci xxxvi abstract 2034 which implies that iapetus must have had a thick lithosphere early in its history to support this topography models of lithospheric deflection by topographic loads provide an estimate of the required elastic thickness in the range of 50 100 km iapetus prominent equatorial ridge porco c c and 34 colleagues 2005 science 307 1237 1242 reaches widths of 70 km and heights of up to 13 km from their base within the modeled area the morphology of the ridge suggests an endogenous origin rather than a formation by collisional accretion of a ring remnant ip w h 2006 geophys res lett 33 doi 10 1029 2005gl025386 l16203 the transition from simple to complex central peak craters on iapetus occurs at diameters of 11 3 km the central peaks have pronounced conical shapes with flanking slopes of typically 11 and heights that can rise above the surrounding plains crater depths seem to be systematically lower on iapetus than on similarly sized rhea which if true may be related to more pronounced crater wall slumping which widens the craters on iapetus than on rhea there are seven large impact basins with complex morphologies including central peak massifs and terraced walls the largest one reaches 800 km in diameter and has rim topography of up to 10 km generally no rings are observed with the basins consistent with a thick lithosphere but still thin enough to allow for viscous relaxation of the basin floors which is inferred from crater depth to diameter measurements in particular a 400 km basin shows up domed floor topography which is suggestive of viscous relaxation a model of complex crater formation with a viscoplastic bingham rheology melosh h j 1989 impact cratering oxford univ press new york of the impact shocked icy material provides an estimate of the effective cohesion viscosity at 0 04 0 01 mpa 0 6 0 2 gpa s the local distribution of bright and dark material on the surface of iapetus is largely controlled by topography and consistent with the dark material being a sublimation lag deposit originating from a bright icy substrate mixed with the dark components but frost deposits are possible as well

tidal current ridges in the southwestern yellow sea abstract large tidal current ridges tidal sand banks in the southwestern yellow sea are located offshore of northern jiangsu province china these ridges radiate to a depth of 20 30 m the dimensions of the ridge system are about 200 km long and 90 km wide their morphology indicates the strong influence of tidal currents the ridges are composed of well sorted fine sands size range is 2 4 the grain size distributions of the sands show that the sands are transported and deposited by tidal currents the ridge system formed on the abandoned yellow river and ancient yangtze river deltas has an abundant sand supply from the former deltas of particular importance is the existence of two tidal wave systems in the yellow sea the rotary ti al wave system in the southern yellow sea and the pacific progressive tidal wave system propagated into the southern ridge area of the southwestern yellow sea under the interaction of the two tidal wave systems the huge tidal current system in the southwestern yellow sea has formed

topographic constraints on the origin of the equatorial ridge on iapetus abstract saturn s moon iapetus has an equatorial ridge system which may be as high as 20 km that may have formed by endogenic forces such as tectonic and convective forces or exogenic processes such as debris infall we use high resolution topographic data to conduct a topographic analysis of the ridge which suggests a predominantly triangular morphology with some ridge face slopes reaching 40 allowing for an exogenic formation mechanism

despinning and shape evolution of saturn s moon iapetus triggered by a giant impact abstract iapetus possesses two spectacular characteristics i a high equatorial ridge which is unique in the solar system and ii a large flattening a c 34 km inconsistent with its current spin rate these two main characteristics have probably been acquired in iapetus early past as a consequence of coupled interior rotation evolution previous models have suggested that rapid despinning may result either from enhanced internal dissipation due to short lived radioactive elements or from interactions with a sub satellite resulting from a giant impact for the ridge formation different exogenic and endogenic hypotheses have also been proposed but most of the proposed scenarios have not been tested numerically in order to model simultaneously internal heat transfer tidal despinning and shape evolution we have developed a two dimensional axisymmetric thermal convection code with a deformable surface boundary coupled with a viscoelastic code for tidal dissipation the model includes centrifugal and buoyancy forces a composite non linear viscous rheology as well as an andrade rheology for the dissipative part by considering realistic rheological properties and by exploring various grain size values we show that in the absence of additional external interactions despinning of a fast rotating iapetus is impossible even for warm initial conditions t 250 k alternatively the impact of a single body with a radius of 250 350 km at a velocity of 2 km s may be sufficient to slow down the rotation from a period of 6 10 h to more than 30 h by combining despinning due to internal dissipation and an abrupt change of rotation due to a giant impact we determined the parameters leading to a complete despinning and we computed the corresponding shape evolution we show that stresses arising from shape change affect the viscosity structure by enhancing dislocation creep and can lead to the formation of a large scale ridge at the equator as a result of rapid rotation change for initial rotation periods of 6 h

plant lipids and fossil hydrocarbons in embalming material of roman period mummies from the dakhleh oasis western desert egypt abstract embalming material contained in four mummies from the roman period 4th century ad excavated in the dakhleh oasis western desert of egypt were analysed for the soluble lipid components according to the distribution patterns of n alkanes steroid hydrocarbons polycyclic terpane hydrocarbons n fatty acids diterpenoid acids and wax esters the embalming material mainly consists of plant material including coniferous resins and possibly beeswax in addition fossil bitumen was present in all samples but of different composition in samples from the cranial cavities and the thorax the bitumen in the thorax samples closely resembles the composition of dead sea asphalt

geochemistry of alkaline earth elements mg ca sr ba in the surface sediments of the yellow sea abstract the concentrations of alkaline earth elements were measured in the surface sediments of the yellow sea in an attempt to establish their sources from horizontal distributions the maximum concentrations of mg are found in the central yellow sea and its horizontal distribution is mainly controlled by quartz dilution the concentrations of ca and sr increase toward the southeastern yellow sea region the relatively higher enrichment of ca and sr in the southeastern yellow sea with sr ca ratios of 0 0053 suggests the presence of carbonates which are comprised of foraminifera and or coccoliths like deep sea carbonates on the other hand the concentrations of ba increase toward the northeastern yellow sea the higher ba enrichment in the sandy region of the northeastern yellow sea is associated with the presence of feldspar as evidenced by excellent correlations among ba mg al mg and sr ca ratios our results suggest that the transgressive and relict sand occurring in the eastern parts of the yellow sea contains al sr and ba enriched feldspars which originated from arprock river korea and thus can be distinguished from sand occurring in the western parts of the yellow sea which originated from yellow and yangtze rivers

source to sink transport in the oligocene huagang formation of the xihu depression east china sea shelf basin abstract the huagang formation is the most important hydrocarbon reservoir in the xihu depression of the east china sea shelf basin reconstructing the provenance and transport pathways of its main sand bodies is of great significance to oil and gas exploration previous provenance studies were mainly based on heavy mineral analyses and showed multiple source areas but so far quantitative estimates on provenance are lacking detrital zircon u pb dating combined with heavy mineral analysis is an effective tool to quantitatively investigate sediment provenance in this paper we use the la icp ms method for u pb dating of detrital zircons of 18 samples from 13 drill cores in the xihu depression to determine the sediment provenance of the oligocene huagang sandstones the u pb zircon dating results show three different age groups in which precambrian ages dominate 60 and paleozoic and mesozoic ages each account for 20 the precambrian zircons are mainly derived from the hupijiao uplift which indicates a dominant and long distance north to south transport direction the provenance of the paleozoic zircons is mainly from the diaoyu islands folded uplift belt in the east while the haijiao and yushan uplifts in the west are the main source region for the mesozoic zircons the northern provenance transport pathway is dominated by axial channels incised valleys are observed in the western source and a transfer zone dominates the eastern provenance the integration of all data results in a new schematic model of source to sink transport in the huagang sandstones demonstrating the complexity of multiple source rocks and sediment transport pathways in the oligocene xihu depression

the factors controlling the abundance and migration of heavy versus light oils as constrained by data from the gulf of suez part i the effect of expelled petroleum composition pvt properties and petroleum system geometry abstract in the gulf of suez gos petroleum systems the main factors which control the abundance and migration of heavy vs light oils are a the composition and pvt properties of the expelled fluids b the geometry of the petroleum systems and c reservoir flow processes compositional and pvt modeling of the expelled petroleum fluids from the brown limestone and the thebes formation carbonate source rocks show the following the fluids expelled below a transformation ratio of 0 5 are heavy oils stock tank api gravity 10 20 have a low gor and contain 20 25 asphaltenes these fluids are formed from source rocks which have mainly low to intermediate sulfur content and normal thermal stability the further expelled fluids up to a transformation ratio of around 0 97 are bubble point behaving fluids oils with stock tank api from 20 50 and gor 300 800 scf bbl and display a progressive decrease in asphaltene content the latest 3 expelled fluids represent dew point behaving fluids gas condensates the heavy low gor oils expelled below a transformation ratio of 0 5 have a very low saturation pressure and are not prone to asphaltene precipitation unless they are mixed with higher gor fluids the pvt properties of these early expelled oils permit their efficient migration this is consistent with an overabundance of low maturity asphaltenes in the gos discovered heavy oils the tendency for asphaltene precipitation is increased for the fluids expelled above a transformation ratio of 0 5 due to both a decrease in their asphaltene content and an increase in gor geometrically imposed mixing of fluids with large maturity induced compositional differences and reservoir flow processes have a significant effect on the pvt behavior of the migrating fluids on asphaltene precipitation and on the distribution of heavy vs light oils

development of depositional systems in the southeastern yellow sea during the postglacial transgression this study focuses on the development of depositional systems in the southeastern yellow sea during the postglacial transgression based on the analysis of closely spaced high resolution seismic profiles chirp and piston cores transgressive deposits comprise the paralic component of estuarine channel fills seaward prograding wedge and along shore prograding mound and the marine component of sand veneer mud blanket and offshore ridge these transgressive deposits were developed through three distinctive stages in terms of possible sea level position during the early stage tidal sand ridges and sand veneer formed south of jeju island resulting from shoreface erosion associated with a relatively slow transgression the following transgression in the middle stage inundated subaerially formed interfluves along the central part of the sea and affected development of estuarine environments with increasing tidal regime in the eastern part of the sea combined with the strong tidal reworking insufficient sand supply enhanced the formation of erosional ridges short period increase in fluvial discharge affected the deposition of coastal wedge in the western part fine grained sediments from either fluvial discharge or tidal reworking were dispersed seaward to form mud blanket the late stage was characterized by the deposition of veneered sands off the jiangsu coast which was due to relatively slow rise in sea level further offshore along shore prograding mound was constructed by huanghe derived sediment influx and subsequently eroded and redeposited by wave and tide activities thus detached from the proximal source the depositional processes and variability of the transgressive deposits in the southeastern yellow sea were largely controlled by changes in rate of sea level rise during the transgression most likely related to the global flooding events triggered by melt water pulses the changes in shoreline configuration and oceanographic regime have also influenced the distribution and morphology of the transgressive deposits a short period increase in riverine discharge caused the temporal sediment progradation off the jiangsu coast

provenance of upper miocene to quaternary sediments in the yinggehai song hong basin south china sea evidence from detrital zircon u pb ages abstract the yinggehai song hong y sh basin located on the northwestern shelf of the south china sea is one of the world s largest pull apart basins in order to identify the provenance of the upper miocene to quaternary sediments of the basin ten sediment samples were collected from drill cores in the dongfang gas field u pb dating of detrital zircon grains extracted from the ten samples using a laser ablation inductively coupled mass spectrometer la icp ms yields ages ranging from the archean to cenozoic 2898 46 ma to 26 1 ma the zircon u pb age spectra of the upper miocene to quaternary show a similar pattern with major peaks clustered at ca 32 ma ca 99 ma ca 160 ma ca 247 ma ca 422 ma and three broad age groups 600 1000 ma 1700 2100 ma and 2200 2800 ma suggestive of a wide range of igneous rock ages in the source areas the detrital zircon ages provide diagnostic criteria for identification of the various source areas and reveal that the detritus was derived from multiple sources comparison of the results with the rock types and their ages surrounding the potential source areas indicates that the clastic material was derived from three dominant age sources 1 yangtze craton 2 hainan island and 3 indochina block the yangtze craton was a major and continuous source area contribution to the basin comparing the age characteristics and its source areas since 10 ma the largely stable provenance also suggests that if the red river capture ever existed it should have happened before the late miocene

late quaternary evolution of the yellow east china sea tidal regime and its impacts on sediments dispersal and seafloor morphology the evolution of a tidal current field in the yellow sea and east china sea yecs in response to the sea level rise since the last glacial maximum lgm was investigated using a two dimensional tidal model with special attention to changes in the sedimentary environment of the continental shelf region it was found that tidal currents on the yecs shelf have generally been semi diurnal throughout the post glacial stages with f ratio index of diurnal inequality and s2 m2 ratio index of spring neap cycle remaining similar to present on the other hand the spatial distribution of the tidal bottom stress associated with m2 and m4 tidal currents changed greatly during the transgression as the sea level rose two core regions showing high bottom stress values migrated shoreward from cheju island toward the west coast of korea and along the retreat path of the paleo changjiang estuary distribution of extremely intense tidal bottom stress suggested that intense tidal reworking may have occurred at sea levels from 90 to 45 m in the southeast yellow sea and at 75 to 60 m off the paleo changjiang estuary the latter of which agreed with the timing of a large terrigenous organic c flux observed on the shelf slope distribution of slightly weaker bottom stress indicated that the sand ridges off the changjiang estuary and in the southeast yellow sea also might have formed at during those periods on the other hand when the sea level was between 45 and 15 m the tidal bottom stress was generally not strong enough to invoke significant reworking even though the stress intensity may be stronger than present correlation with modern and relict sedimentary features suggested that the tidal process have played a significant role on the reworking and deposition of sediments on the yecs shelf

reappraisal of the ages of neoproterozoic strata in south china no connection with the grenvillian orogeny the jiangnan fold belt separates the yangtze and cathaysia blocks in south china and has long been considered grenvillian in age in order to place south china in central rodinia it consists of deformed early neoproterozoic strata that are unconformably overlain by undeformed late neoproterozoic strata and intruded by undeformed and unmetamorphosed granitic plutons zircons from the early neoproterozoic strata yield u pb ages as young as 830 ma and one granitic pluton has a zircon u pb age of ca 827 ma the 830 ma mafic rocks along the southeastern margin of the yangtze block have arc affinity geochemical characters whereas mafic rocks younger than 830 ma have typical ocean island basalt oib like compositions thus we suggest that the early neoproterozoic strata were deposited on an active continental margin prior to amalgamation of the yangtze and cathaysia blocks at ca 830 ma the overlying late neoproterozoic strata were deposited in the intracontinental rifted nanhua basin at 820 730 ma and probably reflect backarc spreading above the long lived 950 735 ma oceanic subduction zone along the northern and western margin of the yangtze block this model is consistent with the secular tectonic evolution of south china during the neoproterozoic the jiangnan fold belt is therefore not a grenvillian feature as previously suggested and there is no evidence to place south china in central rodinia instead we believe that south china was located in a marginal position relative to this supercontinent

geochemistry of surface sediments off the southern and western coasts of korea abstract the continental shelf off the southern and western side of the korean peninsula is part of a modern epicontinental sea and is an effective sediment trap for clastic material derived from china and korea we have analyzed 179 surface sediment samples from this shelf for al fe na k mg ca ti p mn sr ba v cr co ni cu zn organic carbon and calcium carbonate in order to determine the geochemical characteristics of these sediments results showed a wide range of element contents which are mainly related to the textural variability of sediments exceptions to this were found in the contents of ca k sr and ba the ca and sr contents were largely determined by the amounts of carbonate present the k content on the other hand appeared to be influenced by both the contents of illite and feldspar and ba of potassium feldspar for muds i e sediments deposited under present day conditions it is possible to distinguish those in the central yellow sea from those in the keum estuary the former are characterized by high contents of fe na k mg ca and v and the latter by high contents of mn ba and co these differences become more apparent when these elements are normalized relative to al in order to minimize grain size effects the distribution of v al ratios is different from that of other elements the highest v al values occur in muds from the central yellow sea derived from the huanghe the yellow river in china whereas the highest values of mn al are found in the nearshore area adjacent to the korean peninsula based on these results it is suggested that the sources of fine sediments in the yellow and south seas can be distinguished from the geochemical characteristics of the surface sediments in the yellow sea two different sources of fine grained sediments can be seen the huanghe and the keum river the former is characterized by higher v contents and the latter by higher mn contents using the v al ratio as an end member component of the two source materials the dispersal patterns of the fine sediments 6o were also derived

control of extensional transfer zones on syntectonic and post tectonic sedimentation implications for hydrocarbon exploration the gulf of suez red sea rift system exhibits superb outcrop examples of extensional transfer zones and displays the control of these zones on syntectonic and post tectonic sedimentation hard and soft linkage transfer zones were identified at variable scales hard linkage transfer zones form inward and outward fault kinks whereas soft linkage transfer zones form relay ramps between overlapping rift parallel faults the two types of transfer zones invariably exerted fundamental control on the deposition of syn and post tectonic sediments flow direction of drainage systems and locations of sediment entry points as well as the intensity of erosion patterns of the structurally high sediment source areas this study highlights the close relationship between the transfer zones and hydrocarbon accumulations in clastic syntectonic reservoirs in rift basins

effects of source thermal maturity and biodegradation on the distribution and isomerization of homohopanes in petroleum abstract the distributions of c31 c35 17 21 h homohopanes in marine petroleums can be used to describe redox conditions in the source rock depositional environment for example high c35 homohopane indices c35 c31 c35 are typical of petroleums generated from source rocks deposited under anoxic marine conditions where the c35 backbone of the precursor bacteriohopanetetrol is preferentially preserved homohopane distributions have been used to distinguish petroleums from different organic facies of the same source rock homohopane distributions are altered by secondary processes for example the c35 homohopane index decreases with increasing api gravity and thermal maturity of related oils from the monterey formation offshore california similar decreases in the homohopane index are observed for expelled oils from monterey source rock during hydrous pyrolysis biodegradation can result in selective loss of high or low molecular weight homologs apparently depending on the bacterial population in the reservoir bacterial demethylation of homohopanes appears necessary to explain 25 norhopanes in at least one biodegraded oil hydrous pyrolysis studies of the phosphatic and siliceous members in the monterey formation show that identical heating conditions result in different homohopane c 22 epimer ratios furthermore a reversal in the trend of the epimer ratio at high experimental temperatures is observed for the phosphatic but not for the siliceous lithology this could be caused by the combined effects of isomerization and differential thermal destruction of epimers at high temperatures possibly mediated by rock mineralogy

development of stratigraphy and sediment distribution in the northeastern yellow sea during holocene sea level rise abstract a succession of holocene deposits in the northeastern yellow sea were interpreted in a sequence stratigraphic context and sedimentology of each deposit was characterized based on analyses of high resolution seismic profiles and sediment cores taken along a transect thin 3 m transgressive sediments that accumulated through shoreface erosion during the rapid sea level rise in the early holocene overlie a subaerially eroded low gradient late pleistocene platform on the present day inner shelf region cores reveal marine sands over tidal estuarine sandy muds with an intervening rather indistinct ravinement surface in the deepest shelf area these early holocene tidal estuarine deposits remain exposed at the seabottom in the mid o late holocene two contrasting deposits of the highstand type deltaic clayey mud and tidal sand ridges began to accumulate in response to slower rates of sea level rise a series of tidal sand ridges in the nearshore area migrated offshore over the transgressive sand sheet and a deltaic watery mud prograded discordantly over consolidated tidal estuarine deposits in the central shelf the transgressive facies relationships present a model for macrotidal epicontinental sea settings subject to low wave energy and reduced sediment supply