litho1 0 an updated crust and lithospheric model of the earth we present the litho1 0 model which is a 1 tessellated model of the crust and uppermost mantle of the earth extending into the upper mantle to include the lithospheric lid and underlying asthenosphere the model is parameterized laterally by tessellated nodes and vertically as a series of geophysically identified layers such as water ice sediments crystalline crust lithospheric lid and asthenosphere litho1 0 is created by constructing an appropriate starting model and perturbing it to fit high resolution surface wave dispersion maps love and rayleigh group and phase over a wide frequency band 5 40 mhz we examine and discuss the model with respect to key lithospheric parameters such as average crustal velocity crustal thickness upper mantle velocity and lithospheric thickness we then compare the constructed model to those from a number of select studies at regional and global scales and find general consistency it appears that litho1 0 represents a reasonable starting model of the earth s shallow structure crust and uppermost mantle for the purposes in which these models are used such as traveltime tomography or in efforts to create a 3 d reference earth model the model matches surface wave dispersion over a frequency band wider than the band used in the inversion there are several avenues for improving the model in the future by including attenuation and anisotropy as well as making use of surface waves at higher frequency

reservoir characteristics and their effects on hydrocarbon accumulation in lacustrine turbidites in the jiyang super depression bohai bay basin china abstract a great difference exists between the hydrocarbon charging characteristics of different tertiary lacustrine turbidites in the jiyang super depression of the bohai bay basin east china based on wireline log data core observation and thin section analyses this study presents detailed reservoir property data and their controlling effects from several case studies and discusses the geological factors that govern the hydrocarbon accumulation in turbidite reservoirs the lacustrine fluxoturbidite bodies investigated are typically distributed in an area of 0 5 10 km2 with a thickness of 5 20 m the sandstones of the tertiary turbidites in the jiyang super depression have been strongly altered diagenetically by mechanical compaction cementation and mineral dissolution the effect of compaction caused the porosity to decrease drastically with the burial depths especially during the early diagenesis when the porosity was reduced by over 15 the effect of cementation and mineral dissolution during the late stage diagenesis is dominated by carbonate cementation in sandstones high carbonate cement content is usually associated with low porosity and permeability carbonate dissolution secondary porosity zone and primary calcite dissolution is believed to be related to thermal maturation of organic matter and clay mineral reactions in the surrounding shales and mudstone two stages of carbonate cementation were identified the precipitation from pore water during sedimentation and secondary precipitation in sandstones from the organic acid dissolved carbonate minerals from source rocks petrophysical properties have controlled hydrocarbon accumulation in turbidite sandstones high porosity and permeability sandstones have high oil saturation and are excellent producing reservoirs it is also noticed that interstitial matter content affects the oil bearing property to some degree there are three essential elements for high oil bearing turbidite reservoirs excellent pore types low carbonate cement 15 and average permeability 10 md

anomalous density and elastic properties of basalt at high pressure reevaluating of the effect of melt fraction on seismic velocity in the earth s crust and upper mantle independent measurements of the volumetric and elastic properties of columbia river basalt glass were made up to 5 5 gpa by high pressure x ray microtomography and ghz ultrasonic interferometry respectively the columbia river basalt displays p and s wave velocity minima at 4 5 and 5 gpa respectively violating birch s law these data constrain the pressure dependence of the density and elastic moduli at high pressure which cannot be modeled through usual equations of state nor determined by stepwise integrating the bulk sound velocity as is common practice we propose a systematic variation in compression behavior of silicate glasses that is dependent on the degree of polymerization and arises from the flexibility of the aluminosilicate network this behavior likely persists into the liquid state for basaltic melts resulting in weak pressure dependence for p wave velocities perhaps to depths of the transition zone modeling the effect of partial melt on p wave velocity reductions suggests that melt fraction determined by seismic velocity variations may be significantly overestimated in the crust and upper mantle

formation of lava tubes and extensive flow field during the 1991 1993 eruption of mount etna detailed mapping during the 1991 1993 eruption of mount etna has shown that there is a relationship between tumuli ephemeral vents lava tubes and their parent lava flows during this eruption many tubes formed in stationary inflated a a lava flows ephemeral vents at the fronts of these stationary flows and above lava tubes fed secondary lava flows many of which subsequently developed new tubes the resulting complex network of tubes ephemeral vents and secondary flows was responsible for most of the widening thickening and lengthening of the 1991 1993 etna lava flow field the supply of relatively uncooled lava via tubes to distal parts of this flow field allowed lava to flow 3 km farther from the vent than the longest channel fed lava flow our observations suggest that lava tubes play a more important role in the formation of extensive a a flow fields on etna than has previously been recognized

seismic evidence for sharp lithosphere asthenosphere boundaries of oceanic plates the mobility of the lithosphere over a weaker asthenosphere constitutes the essential element of plate tectonics and thus the understanding of the processes at the lithosphere asthenosphere boundary lab is fundamental to understand how our planet works it is especially so for oceanic plates because their relatively simple creation and evolution should enable easy elucidation of the lab data from borehole broadband ocean bottom seismometers show that the lab beneath the pacific and philippine sea plates is sharp and age dependent the observed large shear wave velocity reduction at the lab requires a partially molten asthenosphere consisting of horizontal melt rich layers embedded in meltless mantle which accounts for the large viscosity contrast at the lab that facilitates horizontal plate motions

a new model for the emplacement of columbia river basalts as large inflated pahoehoe lava flow fields extensive flows of the columbia river basalt crb group in washington oregon and idaho are dominantly inflated compound pahoehoe sheet lavas early studies recognized that crb lavas are compound pahoehoe flows with textures suggesting low flow velocities but it was thought that the great thickness and extent of the major flows required very rapid emplacement as turbulent floods of lava over a period of days or weeks however small volume 1 km compound pahoehoe flows on kilauea hawai i demonstrate that such flows can thicken by at least an order of magnitude through gradual inflation and the same mechanism has been proposed for larger 10 20 km3 pahoehoe flows in iceland the vertical distribution of vesicles and other morphologic features within crb lava flows indicate that they grew similarly by inflation small pahoehoe lobes at the base and top of many crb pahoehoe lava flows indicate emplacement in a gradual piecemeal manner rather than as a single flood we propose that each thick crb sheet flow was active for months to years and that each group of flows produced by a single eruption a flow field was emplaced slowly over many years

toothpaste lava characteristics and origin of a lava structural type transitional between pahoehoe and aa toothpaste lava an important basalt structural type which illustrates the transition from pahoehoe to aa is particularly well displayed on the 1960 kapoho lava of kilauea volcano its transitional features stem from a viscosity higher than that of pahoehoe and a rate of flow slower than that of aa viscosity can be quantified by the limited settling of olivine phenocrysts and rate of flow by field observations related to the low angle slope on which the lava flowed much can be learned about the viscosity rheologic condition and flow velocity of lavas long after solidification by analyses of their structural characteristics and it is possible to make at least a semiquantitative assessment of the numerical values of these parameters

the influence of source depositional conditions on the hydrocarbon and nitrogen compounds in petroleum from central montana usa abstract the hydrocarbon and pyrrolic nitrogen compound compositions of 21 crude oils from reservoirs in the heath tyler amsden and swift morrison formations of central montana have been investigated by combined gas chromatography mass spectrometry the biomarker and aromatic hydrocarbon data enabled recognition of three composition types within the heath tyler amsden oils the swift morrison oils displayed different hydrocarbon characteristics and are classified as a separate oil group a number of geochemical parameters e g dibenzothiophene phenanthrene c 20 triaromatic steroid hydrocarbon c 20 c 28 triaromatic steroid hydrocarbons indicate strong variations in petroleum composition from north to south across the region oils from the central montana uplift with high relative c 27 diasteranes c 29 steranes and ts ts tm suggests increasing clay contribution to the source while abundant gammacerane indicates the development of hypersaline conditions with restricted circulation oils from the bull mountain basin represented by the amsden oils show relatively low c 27 diasteranes c 29 steranes and ts ts tm ratios indicating increasing carbonate contribution to the source while the decrease of a gammacerane contribution suggests decreasing salinity levels which may explain the dominance of tricyclic terpane and hence their precursors to the source organic matter while the changes recorded by the biomarker and aromatic hydrocarbon compositions show strong regional variations the nitrogen compounds do not respond so strongly however weak trends coinciding with source carbonate content were apparent in the following ratios 1 8 dimethylcarbazole 1 8 dimethylcarbazole 1 ethylcarbazole and carbazole sum of c 2 carbazoles the second parameter may be responding to variations in salinity since it co varies with the behaviour exhibited by the tricyclic terpanes the source information that can be extracted from biomarkers and aromatic hydrocarbons suggests that primary migration and compositional fractionation during expulsion has exerted little influence on this fraction of petroleum meanwhile primary migration and compositional fractionation during expulsion appear to effect the carbazole and benzocarbazole distributions thereby limiting their application as indicators for source rock facies composition

variations in the sterane carbon number distributions of marine source rock derived crude oils through geological time abstract the analysis of the sterane data of a large set of crude oils 414 derivedfrom marine carbonate 27 and siliciclastic source rocks 14 where influences of terrestrial or lacustrine derived organic matter can reasonably be excluded shows that there are increases in the relative content of c28 steranes and decreases in the relative content of c29 steranes through geological time there are no consistent variations in the relative content of c27 steranes through time with one major exception a proterozoic oil from oman palaeozolic and older crude oils are thus generally characterised by strong predominances of c29 steranes and low relative concentrations of c28 steranes significantly higher proportions of c28 steranes and lower proportions of c29 steranes occur in oils derived from jurassic and upper cretaceous source rocks these changes through time do not appear to reflect the chemical evolution of the sterols of one particular variety of marine organism the increase in c28 steranes may be related to the increased diversification of phytoplantonic assemblages in the jurassic and cretaceous possible sources of the c28 sterols necessary for the observed changes in crude oil steranes includes diatoms coccolithophores and dinoflagellates although the technique does not give an accurate means of determining the age of the source rock of a crude oil it is possible to distinguish younger crudes derived from the upper cretaceous and tertiary from palaeozoic and older crudes

evolution of the oceanic lithosphere in the equatorial atlantic from rayleigh wave tomography evidence for small scale convection from the pi lab experiment

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

eruption constraints on tube fed planetary lava flows we examine the role of pressure and gravity as driving forces in planetary lava tubes for newtonian and power law rheologies the tubes are assumed to have been filled with lava that was emplaced in constant diameter circular tubes in the laminar flow regime and had constant density heat capacity thermal conductivity and viscosity our model provides relationships between tube dimensions driving forces and effusion rates and rheology parameters in general the pressure term in the driving force dominates for very small slopes but the gravity term eclipses the pressure term as the slope increases applying the model to alba patera tube flows suggests effusion rates somewhere between 2 and 105 m3 s and viscosities between 102 and 106 pa s with tighter constraints 2 to 4 orders of magnitude for specific tube sizes and travel times these effusion rate results are lower and the viscosity ranges are higher than those found in previous studies this allows eruptions that are closer in style to terrestrial basaltic eruptions although the flows are still considerably larger in scale than the hawaiian tube flows we find that very low lava viscosities are not essential for alba patera lava tubes and that tube formation may be a better indicator of the steadiness of the eruption and the presence of low slopes than it is of low viscosities e g 102 pa s in addition this analysis suggests that the tube systems on the steep flanks of olympus mons are fundamentally different from those at alba patera the olympus mons flows could not have roofed over been continuously full or maintained a continuous lava tube transport system in the assumed full steady and fully developed conditions

upper mantle water stratification inferred from observations of the 2012 indian ocean earthquake postseismic recordings of the moment magnitude 8 6 indian ocean earthquake of 2012 combined with the characteristics of olivine creep provide constraints on the water content of the asthenosphere sylvain barbot and colleagues infer that observed transient deformation in the aftermath of the 2012 indian ocean earthquake as recorded by continuous geodetic stations in the region requires a minimum olivine water content of about 0 01 per cent by weight in the oceanic asthenosphere the earthquake ruptured conjugate faults throughout the entire overlying oceanic lithosphere down to great depths compatible with dry olivine in the upper layer the authors explain the rheological contrast by dehydration across the lithosphere asthenosphere boundary presumably by buoyant melt migration that formed the oceanic crust elsewhere in this issue of nature yan hu et al use observations of postseismic deformation following this earthquake to constrain the structure of oceanic mantle rheology water the most abundant volatile in earth s interior preserves the young surface of our planet by catalysing mantle convection lubricating plate tectonics and feeding arc volcanism since planetary accretion water has been exchanged between the hydrosphere and the geosphere but its depth distribution in the mantle remains elusive water drastically reduces the strength of olivine1 and this effect can be exploited to estimate the water content of olivine from the mechanical response of the asthenosphere to stress perturbations such as the ones following large earthquakes here we exploit the sensitivity to water of the strength of olivine2 the weakest and most abundant mineral in the upper mantle and observations of the exceptionally large moment magnitude 8 6 2012 indian ocean earthquake3 to constrain the stratification of water content in the upper mantle taking into account a wide range of temperature conditions and the transient creep of olivine we explain the transient deformation in the aftermath of the earthquake that was recorded by continuous geodetic stations along sumatra as the result of water and stress activated creep of olivine this implies a minimum water content of about 0 01 per cent by weight or 1 600 h atoms per million si atoms in the asthenosphere the part of the upper mantle below the lithosphere the earthquake ruptured conjugate faults down to great depths4 compatible with dry olivine in the oceanic lithosphere we attribute the steep rheological contrast to dehydration across the lithosphere asthenosphere boundary presumably by buoyant melt migration to form the oceanic crust

spongy pahoehoe in hawaii a study of vesicle distribution patterns in basalt and their significance a well defined pahoehoe lava type that is very common medially and distally in hawaii is characterized by a high concentration and fairly uniform distribution of spherical or near spherical vesicles measurements of vesicle sizes and concentrations have been made on ten of these spongy pahoehoe lava flow units the vesicles increase in size toward the middle accompanied by a moderate increase in lava porosity the close approach to bilateral symmetry on either side of the horizontal median plane and the common occurrence of a median gas blister shows that no significant upward movement of vesicles occurred suggesting that the lava possessed a yield strength and was more or less static olivine phenocrysts when present are however concentrated in the lower half of the same flow units showing that the lava previously lacked a significant yield strength the vesicles are regarded as early inherited from the vent but the size characteristics of the vesicle population are a late formed feature vesicles grew in static lava mostly by coalescence and it is postulated that coalescence was promoted by the presence of abundant diktytaxitic voids which punctured the walls of contiguous vesicles zones in which the vesicle concentration is lower and the vesicles are larger and strongly deformed interrupt the symmetry of some spongy pahoehoe units and gas blisters higher than the median plane occur in many examples these zones are interpreted to result from late stage shearing and point to a mechanism by which vesicles may be eliminated from a lava

the character and origin of lacustrine source rocks in the lower cretaceous synrift section congo basin west africa lower cretaceous synrift lacustrine shales from the congo basin west africa have been analyzed with sedimentological and geochemical techniques to characterize source rock quality and identify triggers for deposition of intervals richest in organic carbon the sequence includes a lower active rift section deposited during active faulting and subsidence overlain by an upper late rift section deposited during reduced faulting and subsidence total organic carbon toc averages 2 3 wt throughout the active rift siliciclastic shale section 6 in marls in the lower part of the late rift section and 1 2 in deltaic shales in the upper part of the late rift section organic matter consists of mixed types i and iii kerogen in the active rift shales pure type i kerogen in the late rift marls and a type i and iii mixture in the late rift deltaic shales redox proxies indicate that the deep lake was relatively reducing throughout deposition of the active rift and lower late rift sections therefore enhanced anoxia did not trigger deposition of the richest source rocks decreased sedimentation rates in the late rift do not account for the full increase in toc nor the shift on organic matter type the richest source rocks are associated with high rates of organic productivity and chemical sedimentation indicating that flux of dissolved components to the rift lake including nutrients for algae growth was critical we propose that reduced topography associated with the late rift was necessary for efficient cycling of plant derived carbon into soil carbonate and ultimately the rift lake and for enhancing chemical weathering and nutrient flux

crystal mush compaction and the origin of pegmatitic segregation sheets in a thick flood basalt flow in the mesozoic hartford basin connecticut

oceanic lithosphere asthenosphere boundary from surface wave dispersion data abstract according to different types of observations the nature of lithosphere asthenosphere boundary lab is controversial using a massive data set of surface wave dispersions in a broad period range 15 300 s we have developed a three dimensional upper mantle tomographic model first order perturbation theory at the global scale this is used to derive maps of the lab from the resolved elastic parameters the key effects of shallow layers and anisotropy are taken into account in the inversion process we investigate lab distribution primarily below the oceans according to different kinds of proxies that correspond to the base of the lithosphere from the shear velocity variation at depth the amplitude radial anisotropy and the changes in azimuthal anisotropy g orientation the estimations of the lab depth based on the shear velocity increase from a thin lithosphere 20 km in the ridges to a thick old ocean lithosphere 120 130 km the radial anisotropy proxy shows a very fast increase in the lab depth from the ridges from 50 km to the older ocean where it reaches a remarkable monotonic subhorizontal profile 70 80 km the lab depths inferred from the azimuthal anisotropy proxy show deeper values for the increasing oceanic lithosphere 130 135 km the difference between the evolution of the lab depth with the age of the oceanic lithosphere computed from the shear velocity and azimuthal anisotropy proxies and from the radial anisotropy proxy raises questions about the nature of the lab in the oceanic regions and of the formation of the oceanic plates

the deep water counterpart of the messinian lower evaporites in the apennine foredeep the fanantello section northern apennines italy abstract a possible deep water non evaporitic unit equivalent of the messinian lower evaporites has been recognised in the northern apennine foredeep this unit whose existence is implicitly admitted in the two step model of the mediterranean messinian salinity crisis is documented here for the first time it occurs throughout the apennine foredeep basin below a thick horizon of resedimented gypsum deposits usually ascribed to the lower evaporites actually the lower evaporites of the apennine foredeep basin include both shallow water in situ precipitated facies and deep water resedimented facies deposited in distinct depocenters the usually envisaged coeval nature of the two deposits has been recently challenged in several works based on a physical stratigraphic considerations about the downbasin correlation of the messinian erosional surface cutting on top the in situ evaporites with the sharp base of the resedimented evaporites unit and b the common occurrence of a barren unit below the resedimented evaporites which has no obvious equivalents in pre evaporitic successions underlying the in situ precipitated evaporites in this work a multidisciplinary study has been carried out on a 140 m thick composite section fanantello section to definitely assess the age and palaeoenvironmental characteristics of the unit underlying the resedimented gypsum deposits the topmost part of the section comprises a 60 m thick succession of barren euxinic shales falling entirely within a reversed polarity chron and characterised by a the complete disappearance of foraminifera b the occurrence of high salinity tolerant thecosomatous pteropods creseis sp c the abundance peaks of the calcareous nannofossil sphenolithus abies interpreted as related to highly stressed likely hyperhaline conditions d the appearance of hyperhaline and or stratified water molecular indicators gammacerane based on a multidisciplinary integrated stratigraphic approach this barren interval is here proposed to be a deeper water time equivalent of the in situ primary lower evaporites thus allowing to assess the events connected to the onset and the first phase of the messinian salinity crisis from a basinal perspective these data lend support to the hypothesis that the resedimented evaporite deposits of the apennine foredeep basin postdate the in situ evaporites thus implying that the term lower evaporites actually comprises rock bodies with different origins and separated in time and space by the messinian erosional surface and its correlative conformity this could be true also for other mediterranean basins where the stratigraphy of deep water successions should be carefully re examined

origin of nama basin bitumen seeps petroleum derived from a permian lacustrine source rock traversing southwestern gondwana abstract biodegraded bitumens associated with quartz and calcite veins in the cambrian fish river subgroup sediments of the nama group of southern namibia have a geochemical signature diagnostic for organic matter that was deposited in a saline lacustrine palaeoenvironment in particular they contain abundant gammacerane carotane and 3 methylhopanes while 24 isopropyl cholestanes and dinosteroids are not detectable sealed tube hydrous pyrolysis of asphaltene and polar fractions yielded saturated hydrocarbons amenable to c isotopic analysis and these analyses show unusually low 13 c values these combined characteristics are also present in immature bitumens from the permian irati formation of brazil and a saline lacustrine facies of the whitehill formation in the karoo basin south africa we conclude that the bitumens originated from whitehill equivalent strata of the kalahari basin deposited in what was an extensive saline lacustrine basin in southwestern gondwana during the early permian in southern africa source rocks of the whitehill formation are generally immature for petroleum generation and it is therefore likely that the nama bitumens were expelled by contact metamorphism during emplacement of karoo dolerite sills and dykes in the jurassic

shear thickening dilatancy in crystal rich flows abstract rheological models of molten rock are mostly based on behaviours in which viscosity is constant with respect to strain rate e g newtonian bingham plastic or viscosity decreases with increasing strain rate pseudo plastic or shear thinning rheological models in which viscosity increases with increasing strain rate shear thickening or dilatant models have rarely been used yet such behaviour is common in particulate systems whereas magmas with low crystal content may be appropriately modelled by the former behaviours greater crystal content may lead to particle interactions resulting in shear thickening behaviour the effect is illustrated using a powdered rhyolitic rock mixed with water which exhibits extreme shear thickening behaviour caused by particles moving apart as they move past each other the expansion of the grain fabric during flow is opposed by the applied loads such that dilatancy is invariably associated with shear thickening rheology crystal rich lava may exhibit shear thickening dilatancy a proposition supported by observations of glass rich microscopic shear zones disrupting crystal fabrics plutonic crystal mush may also exhibit shear thickening dilatancy which can explain synplutonic intrusion involving brittle fracture followed by ductile disruption in general strain rate is an important contributor to the transition from ductile to brittle behaviour in crystal rich igneous rocks

vesiculation of basaltic magma during eruption vesicle size distributions in vent lavas from the pu9u9o9o kupaianaha eruption of kilauea volcano are used to estimate nucleation and growth rates of h 2 o rich gas bubbles in basaltic magma nearing the earth9s surface 120 m depth by using well constrained estimates for the depth of volatile exsolution and magma ascent rate nucleation rates of 35 9 events cm 3 s 1 and growth rates of 3 2 x 10 4 cm s are determined directly from size distribution data the results are consistent with diffusion controlled growth as predicted by a parabolic growth law this empirical approach is not subject to the limitations inherent in classical nucleation and growth theory and provides the first direct measurement of vesiculation kinetics in natural settings in addition perturbations in the measured size distributions are used to examine bubble escape accumulation and coalescence prior to the eruption of magma

geochemistry of crude oils from eastern indonesia high resolution geochemistry shows genetic relationships among 27 crude oils from eastern indonesia and suggests the ages and paleoenvironments of their source rocks oils inferred to originate from tertiary and triassic jurassic source rocks in the study occur north and south of 2is latitude respectively twenty oils mainly from irian jaya and sulawesi originated from tertiary marine marlstone source rocks that contained type ii iii kerogen deposited under suboxic conditions probably the upper miocene klasafet formation these low sulfur oils show high oleanane c26 24 nordia cholestane and pristane phytane ratios and 13c rich carbon isotope compositions high oleanane and 24 nordiacholestane ratios are diagnostic of tertiary oils and source rocks these oils account for about 16 of the estimated ultimate recoverable reserves in eastern indonesia

geochemical characterisation and genetic origin of oils and condensates in the south viking graben norway abstract geochemical analysis of oil and condensate samples from all major fields and discoveries in the norwegian south viking graben as well as source rock extracts of upper and middle jurassic source horizons was carried out to characterise reservoired hydrocarbons and establish genetic relationships the south viking graben is in a mature phase of exploration and this study aims at unravelling regional trends to improve predictions in exploration and will show the significance of the play models in the area seven hydrocarbon families have been identified based on interpretation of molecular and isotopic characteristics and multivariate analysis of biomarker data these families can be linked to three source horizons three families originate from different facies of the draupne formation and are characterised by pr ph ratios below 2 dominance of c 27 regular steranes over the c 29 homologues and carbon isotopic values for saturate and aromatic fraction lighter than 28 and 27 respectively the upper jurassic heather formation and the middle jurassic vestland group each source one group of hydrocarbons typical for heather sourced hydrocarbons are elevated pr ph ratios between 2 35 and 3 08 low ratios of c 27 c 29 regular steranes and average isotopic values of 28 4 13 c sat and 26 8 13 c aro hydrocarbons from a middle jurassic source are characterised by very heavy isotopic composition highest pr ph ratios of the data set and dominance of c 29 regular steranes over the c 27 homologues among other factors the two remaining families represent mixtures from upper and middle jurassic sources and are mainly encountered in the greater sleipner area the available data in this study allowed characterisation of 84 of the recoverable oil resources which proved that the main source rock in the area is the upper jurassic draupne formation the play concept including a draupne source and tertiary reservoir proves to be most prolific with 239 10 6 s m 3 of recoverable oil equalling 88 of the total characterised oil resources oils in these tertiary reservoirs are however likely to be affected by biodegradation based on the available data the zone of biodegradation in the south viking graben appears to be limited to depths above 2140 m and temperatures below 70 c

application of tetracyclic polyprenoids as indicators of input from fresh brackish water environments abstract c30 tetracyclic polyprenoids tpp are most prominently observed in samples derived from low salinity i e fresh to brackish lacustrine environments and are generally present in low levels in samples derived from saline i e marine and saline lacustrine environments a near shore facies of the chonta formation peru that has no marine palynomorphs but abundant chlorococcalean green algal nonmarine palynomorphs has high levels of tpp suggesting green algae or chlorophyta are a possible source for the tpp compounds the ratio between a c30 tpp compound and 27 norcholestanes is useful for assessing this nonmarine algal input moderate elevations of tpp above what is common in marine derived samples were found in ostensibly marine source rocks and oils from certain basins of western and northern south america middle magdalena colombia maracaibo venezuela and trinidad basins this is likely due to transport from the nonmarine to the marine environment because of an influx of fresh water into the near shore marine environment alternatively oils from these basins may have inputs from near shore shallow marine algae with chemistry similar to that found in lacustrine settings the tpp ratio in conjunction with other environmental indicators such as 4 methyl steranes or hopane sterane ratio is useful for differentiating marine and nonmarine influences in pre salt oils and source rocks of west africa the tpp ratio used with other environmental indicators gammacerane c29 steranes c30 steranes and age diagnostic biomarkers dinosteranes 4 methylsteranes can be useful in differentiating among nonmarine source facies for example in the turpan hami basin china permian saline lacustrine and jurassic lacustrine deltaic facies can be discriminated

mechanisms of petroleum accumulation in the bozhong sub basin bohai bay basin china part 1 origin and occurrence of crude oils the origin of the fourteen major oil fields in the bozhong sub basin bohai bay basin was studied based on the results of rock eval pyrolysis on more than 700 samples and biomarker analysis on 61 source rock samples and 87 oil samples the three possible source rock intervals have different biomarker assemblages and were deposited in different environments the third member of the oligocene dongying formation e3d3 32 8 30 3 ma in age is characterized mainly by high c19 c23 tricyclic terpane 0 75 high c24 tetracyclic terpane c26 tricyclic terpane 2 5 low gammacerane c30 hopane 0 15 and low 4 methyl steranes c29 steranes 0 15 ratios and was deposited in sub oxic to anoxic environments with significant terrigenous organic matter input the first e2s1 35 8 32 8 ma and third e2s3 43 0 38 0 ma members of the eocene shahejie formation have low c19 c23 tricyclic terpane and low c24 tetracyclic terpane c26 tricyclic terpane ratios and were deposited in anoxic environments with minor terrestrial organic matter input but have different abundances of 4 methyl steranes and gammacerane the hydrocarbon generating potential and biomarker associations of these three source rock intervals were controlled by tectonic evolution of the sub basin and climate changes three oil families derived from e2s3 e2s1 and e3d respectively and three types of mixed oils have been identified all large oil fields in the bozhong sub basin display considerable heterogeneities in biomarker compositions and originated from more than one source rock interval which suggests that mixing of oils derived from multiple source rock intervals or multiple generative kitchens and or focusing of oils originated from a large area of a generative kitchen is essential for the formation of large oil fields in the bozhong sub basin e2s3 and e2s1 derived oils experienced relatively long distance lateral migration and accumulated in traps away from the generative kitchen e3d3 derived oils had migrated short distances and accumulated in traps closer to the generative kitchen such a petroleum distribution pattern has important implications for future exploration there is considerable exploration potential for dongying derived oils in the bozhong sub basin and traps close to or within the generative kitchens have better chance to contain oils generated from the dongying formation

applications of petroleum geochemistry to exploration and reservoir management abstract petroleum geochemistry improves exploration efficiency by accounting for many of the variables that control the volumes of crude oil and natural gas available for entrapment including source rock distribution richness and quality thermal maturity and the timing of generation migration accumulation relative to trap formation it is most powerful when used with other disciplines such as seismic sequence stratigraphy and reservoir characterization four key technology milestones form the basis for most modern applications of geochemistry to exploration these are the concepts and applications of 1 petroleum systems and exploration risk 2 biomarkers stable isotopes and multivariate statistics for genetic oil oil and oil source rock correlation 3 calibrated three dimensional thermal and fluid flow modeling and 4 controls on petroleum composition by secondary processes petroleum geochemistry offers rapid low cost evaluation tools to aid in understanding development and production problems some technology milestones in reservoir geochemistry include 1 assessment of vertical and lateral fluid continuity 2 determination of proportions of commingled production from multiple zones and leaky casing 3 prediction of oil quality in reservoir zones and 4 prediction of gas oil and oil water contact locations as described in the conclusions future research will continue a trend toward predictive geochemistry examples of predictive tools that draw major research support include piston core surveys to assess deepwater petroleum systems prior to drilling and three dimensional basin modeling to predict the regional timing of generation migration and accumulation of petroleum among other research objectives models are needed to better predict the distribution and quality of petroleum in reservoirs

lacustrine source rock deposition in response to co evolution of environments and organisms controlled by tectonic subsidence and climate bohai bay basin china three paleogene syn rift intervals from the bohai bay basin the most petroliferous basin in china were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions the third es3 and first es1 members of the eocene shahejie formation and the oligocene dongying formation ed display widely variable total organic carbon contents hydrogen indices and visual kerogen compositions suggesting changes in organic facies from deep to marginal sediments carefully selected deep lake facies samples from any interval however display fairly uniform biomarker composition these three intervals have distinctly different biomarker assemblages which indicate weakly alkaline freshwater lakes with a moderately deep thermocline during es3 deposition alkaline saline lakes with shallow chemocline during es1 deposition and acidic freshwater lakes with deep unstable thermocline during the deposition of the dongying formation such environmental changes corresponded to changes in subsidence rate and paleoclimate from rapid subsidence and wet climate during es3 deposition through slow subsidence and arid climate during es1 deposition to rapid subsidence and wet climate during ed deposition and resulted in synchronous changes in terrigenous organic matter input phytoplankton community and primary productivity the co evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn rift evolutions the models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins

anomalous oceanic lithosphere formed in a leaky transform fault evidence from the western limassol forest complex cyprus detailed studies in the western limassol forest complex cyprus have revealed plutonic and structural histories that differ markedly from the penrose type ophiolite of the troodos massif to the north a tectonized harzburgite of upper mantle origin acts as host to multiple mafic and ultramafic intrusions forming a plutonic core complex mafic and picrite dykes cut and are cut by e w trending shear zones demonstrating syn tectonic magmatism a retrogressive metamorphic and progressive cooling history of the intrusive suite indicates uplift of the host mantle harzburgite while in a sea floor setting it is suggested here that the geological evolution of the western limassol forest complex indicates formation of anomalous oceanic lithosphere in the active domain of an upper cretaceous leaky transform fault

heterogeneity of oil composition within a reservoir as a reflection of accumulation history abstract the unaltered petroleums of a small oil field in the f r germany reveal pronounced spatial heterogeneities in bulk and molecular composition over most of the field area the oil in high porosity high permeability sand intervals bears a higher proportion of saturated hydrocarbons and has a higher maturity chemical signature as compared to oils occupying lower porosity lower permeability zones for all sands with less than about 13 porosity a regular relationship was observed between oil composition and porosity permeability with a decrease of the latter petrophysical properties increasingly lower chemical maturities and increasingly different bulk chemical compositions lower proportions of saturated hydrocarbons and higher proportions of nso compounds were recorded maximum contrasts measured for chemical maturities are e g 0 63 versus 0 82 vitrinite reflectance equivalents rc values calculated on the basis of the methylphenanthrene index according to radke and welte 1983 0 31 versus 0 84 for the ratio of triaromatic to mono plus triaromatic steroid hydrocarbons and 0 38 versus 0 47 for the 20s 20s 20r ratio of c29 5 h 14 h 17 h steranes these spatial heterogeneities in the composition of the oils are interpreted to reflect 1 i successive stages of trap filling due to episodes of increasing burial and maturation of the relevant source rocks in combination with 2 ii low rates of in reservoir mixing of these individual oil charges by convection or diffusion recognition of compositional heterogeneities within the oil column of individual fields may not only provide a basis for the reconstruction of reservoir filling history but may also have important implications for improving petroleum production

anelasticity and viscosity of partially molten rock analogue toward seismic detection of small quantities of melt 1 anelasticity and diffusion creep viscosity of partially molten rock analogue were measured experimentally at various melt fractions 0 0025 0 04 the presence of even a small quantity of melt phase causes a significant increase in attenuation and dispersion and decrease in viscosity melt effect similar changes are additionally caused by the presence of a secondary solid component chemical effect the similitude that was observed in the anelasticity of melt free systems when scaled by the maxwell frequency for temperature and grain size effects was observed too in that of melt bearing systems when scaled by the maxwell frequency for melt and chemical effects the combined melt and chemical effects on anelasticity offer a potential means of identifying small quantities of melt with seismic velocity perturbations

the internal structure of lava flows insights from ams measurements ii hawaiian pahoehoe toothpaste lava and a ā abstract we studied the anisotropy of magnetic susceptibility ams of 22 basaltic flow units including s type pahoehoe p type pahoehoe toothpaste lava and a emplaced over different slopes in two hawaiian islands systematic differences occur in several aspects of ams mean susceptibility degree of anisotropy magnetic fabric and orientation of the principal susceptibilities among the morphological types that can be related to different modes of lava emplacement ams also detects systematic changes in the rate of shear with position in a unit allowing us to infer local flow direction and some other aspects of the velocity field of each unit a flows are subject to stronger deformation than pahoehoe and also their internal parts behave more like a unit according to ams the central part of pahoehoe commonly reveals a different deformation history than the upper and lower extremes probably resulting from endogenous growth

a seismic reflection image for the base of a tectonic plate a high resolution image for the base of an oceanic plate that is subducting beneath north island new zealand reveals a channel which is interpreted as a sheared zone of ponded partial melts or volatiles this low viscosity channel decouples the plate from mantle flow beneath allowing plate tectonics to work tim stern and co authors use explosion generated seismic waves to form a high resolution image of the base of an oceanic plate that is subducting beneath north island new zealand they find an abrupt seismic wave speed transition less than a kilometre thick at a depth of 100 km dipping at an angle of 15 the presence of a parallel 10 km deeper reflection event shows that the decrease in compressional wave speed is confined to a channel at the base of the plate which the authors interpret as a sheared zone of ponded partial melts or volatiles they conclude that this is independent evidence for a low viscosity channel at the lithosphere asthenosphere boundary that decouples plates from mantle flow beneath and allows plate tectonics to take place plate tectonics successfully describes the surface of earth as a mosaic of moving lithospheric plates but it is not clear what happens at the base of the plates the lithosphere asthenosphere boundary lab the lab has been well imaged with converted teleseismic waves1 2 whose 10 40 kilometre wavelength controls the structural resolution here we use explosion generated seismic waves of about 0 5 kilometre wavelength to form a high resolution image for the base of an oceanic plate that is subducting beneath north island new zealand our 80 kilometre wide image is based on p wave reflections and shows an approximately 15 dipping abrupt seismic wave speed transition less than 1 kilometre thick at a depth of about 100 kilometres the boundary is parallel to the top of the plate and seismic attributes indicate a p wave speed decrease of at least 8 3 per cent across it a parallel reflection event approximately 10 kilometres deeper shows that the decrease in p wave speed is confined to a channel at the base of the plate which we interpret as a sheared zone of ponded partial melts or volatiles this is independent high resolution evidence for a low viscosity channel at the lab that decouples plates from mantle flow beneath and allows plate tectonics to work

magmatic history of the east rift zone of kilauea volcano hawaii based on drill core from soh 1 abstract deep drilling has allowed for the first time an examination of most of the shield stage of a hawaiian volcano when it is centered over the hotspot and most of its volume is produced we determined the lithologies ages geochemical characteristics and accumulation rates of rocks from the continuously cored 1 7 km deep scientific observation hole soh 1 which was drilled into kilauea s east rift zone the uppermost 750 m of this hole contain relatively unaltered subaerially quenched lavas the lower portion is a mixture of weakly to moderately altered hyaloclastites and massive basalts intruded by dikes unspiked k ar dating was attempted on 14 lavas but only four yielded geologically reasonable ages the oldest age is 351 12 ka for a sample from 1541 m eighty xrf major and trace element analyses of lavas from throughout the section demonstrate that these lavas have the same compositional range as historical kilauea lavas and that there was no systematic geochemical variation for the volcano over the last 350 ka kilauea s average yearly magma supply during this period was probably 0 05 01 km 3 which is identical to its average historical magma supply rate thus kilauea s overall source and melting conditions have remained remarkably constant for the last 350 ka despite its having drifted 42 km over the hawaiian plume these results require that the portion of the plume being melted to produce kilauea magmas be relatively large and well mixed which is inconsistent with models that place this source on the margin of a radially zoned plume

water table fluctuation owing to time varying recharge pumping and leakage this paper presents an analytical solution of a 2 d linearized boussinesq equation to predict water table variation in a horizontal aquifer induced by time varying recharge and or withdrawal from any number of recharge basins pumping wells and leakage sites of different dimensions the rate of time varying recharge or withdrawal is approximated by series of line elements of different lengths and slopes depending on the nature of variation of recharge or withdrawal rate advantage of this approximation scheme is that any complex nature of recharge and or withdrawal rates for any number of recharge basins pumping wells and leakage sites and for any number of these operations can be approximated with more accuracy application of the solution in the prediction of water table variation in the presence of time varying recharging pumping and leakage is demonstrated with the help of an example problem the present analytical solution is validated by comparing its results with the corresponding numerical results obtained from modflow for the same example problem

factors controlling reservoir properties and hydrocarbon accumulation of lacustrine deep water turbidites in the huimin depression bohai bay basin east china abstract lacustrine deep water turbidite plays are a novel area for exploration in the huimin depression bohai bay basin turbidites in the shang 847 block a typical turbidite play in the huimin depression provide an opportunity to study the factors controlling the reservoir properties and hydrocarbon accumulation in lacustrine turbidite sandstones the reservoir quality of turbidite sandstones very fine grained moderately to well sorted mainly lithic arkose in this study area are mainly controlled by the distribution patterns of carbonate cements and pseudomatrix significant inverse relationships exist between the volume of carbonate cement and both porosity and permeability of the turbidite sandstones carbonate cement is located preferentially near the margins of the sandstone bodies sandstones with distance from the sandstone mudstone contact surface less than 0 7 m or with thickness less than 1 2 m are commonly tightly cemented carbonate cement 15 with low porosity and permeability lower than 10 and 0 1 md respectively the source of carbonate cement was most likely external probably derived from the surrounding mudstone most pore filling carbonate cements occurred during late diagenesis at burial depths greater than 2200 m the petrophysical properties of turbidites have a positive relationship with the content of kaolinite and chlorite but have a negative relationship with the content of illite 2 d and 3 d reconstructions of non oil bearing and oil bearing layers indicate that dissolution of carbonate cement feldspars and unstable rock fragments was more developed in oil bearing layers than in non oil bearing layers and hance oil bearing layers have higher porosity and larger pore sizes petrophysical property appears to have a significant effect on the hydrocarbon accumulation in the turbidite sandstones sandstones with porosities lower than 9 and or permeabilities lower than 0 78 md are not prone to contain oil

age spreading rates and spreading asymmetry of the world s ocean crust we present four companion digital models of the age age uncertainty spreading rates and spreading asymmetries of the world s ocean basins as geographic and mercator grids with 2 arc min resolution the grids include data from all the major ocean basins as well as detailed reconstructions of back arc basins the age spreading rate and asymmetry at each grid node are determined by linear interpolation between adjacent seafloor isochrons in the direction of spreading ages for ocean floor between the oldest identified magnetic anomalies and continental crust are interpolated by geological estimates of the ages of passive continental margin segments the age uncertainties for grid cells coinciding with marine magnetic anomaly identifications observed or rotated to their conjugate ridge flanks are based on the difference between gridded age and observed age the uncertainties are also a function of the distance of a given grid cell to the nearest age observation and the proximity to fracture zones or other age discontinuities asymmetries in crustal accretion appear to be frequently related to asthenospheric flow from mantle plumes to spreading ridges resulting in ridge jumps toward hot spots we also use the new age grid to compute global residual basement depth grids from the difference between observed oceanic basement depth and predicted depth using three alternative age depth relationships the new set of grids helps to investigate prominent negative depth anomalies which may be alternatively related to subducted slab material descending in the mantle or to asthenospheric flow a combination of our digital grids and the associated relative and absolute plate motion model with seismic tomography and mantle convection model outputs represents a valuable set of tools to investigate geodynamic problems

the 40ar 39ar and k ar dating of lavas from the hilo 1 km core hole hawaii scientific drilling project mauna kea lava flows cored in the hilo hole range in age from 200 ka to about 400 ka based on 40ar 39ar incremental heating and k ar analyses of 16 groundmass samples and one coexisting plagioclase the lavas all subaerially deposited include a lower section consisting only of tholeiitic basalts and an upper section of interbedded alkalic transitional tholeiitic and tholeiitic basalts the lower section has yielded predominantly complex discordant 40ar 39ar age spectra that result from mobility of 40ar and perhaps k the presence of excess 40ar and redistribution of 39ar by recoil comparison of k ar ages with 40ar 39ar integrated ages indicates that some of these samples have also lost 39ar nevertheless two plateau ages of 391 40 and 400 26 ka from deep in the hole combined with data from the upper section show that the tholeiitic section accumulated at an average rate of about 7 to 8 m kyr and has a mean recurrence interval of 0 5 kyr flow unit samples from the upper section yield relatively precise 40ar 39ar plateau and isotope correlation ages of 326 23 241 5 232 4 and 199 9 ka for depths of 415 7 m to 299 2 m within their uncertainty these ages define a linear relationship with depth with an average accumulation rate of 0 9 m kyr and an average recurrence interval of 4 8 kyr flow unit the top of the mauna kea sequence at 280 m must be older than the plateau age of 132 32 ka obtained for the basal mauna loa flow in the corehole the upward decrease in lava accumulation rate is a consequence of the decreasing magma supply available to mauna kea as it rode the pacific plate away from its magma source the hawaiian mantle plume the age depth relation in the core hole may be used to test and refine models that relate the growth of mauna kea to the thermal and compositional structure of the mantle plume

deformation and structural evolution of mantle peridotites during exhumation on transform faults a forced transition from ductile to brittle regime abstract the exhumation of peridotite rocks in oceanic transform zones passes by the rheological transition between the ductile and brittle deformation until the complete emplacement in the oceanic lithosphere the sao pedro and sao paulo archipelago spspa in the equatorial atlantic records the deformational products of ductile brittle and the rocks fluid interaction generating specific structures in each domain the deformational stages are related to the transpressional and transtensional geodynamics of sao paulo transform fault firstly during transpression exhumation occurs associated with the ductile domain causing intense mylonitization in temperatures between 700 and 800 c defined by olivine and orthopyroxene recrystallization the interaction with fluids initially originated from the mantle generates amphibole and oxide rich layers marking the passage to a semi brittle deformation the continuation of peridotite exhumation associated with an nw se shortening and transpressional led to a higher availability of hydrothermal fluids as a consequence four serpentinization episodes are recorded which are associated with semi brittle to brittle transition under temperatures between 300 and 400 c finally the complete exhumation and establishment of brittle mechanisms led to carbonatation phase near the surface with temperatures ranging from 300 to 150 c the active nw se tectonic stress generated e w strike slip faults that were filled by carbonates recording the final exhumation stage

textural evidence for dilatant shear thickening rheology of magma at high crystal concentrations investigation of the rheology of magmas at high crystal concentrations by experimental means has proved problematic an alternative approach is to study textures of igneous rocks that not only preserve evidence of the kinematics of magma flow such as flow direction but can also preserve evidence of rheology flow textures in multiply intruded trachyte dykes on fraser island eastern australia record evidence of dilatant flow during solidification this conclusion is reached by interpretation of microscopic ductile shear zones that disrupt the groundmass of aligned feldspar laths detailed three dimensional investigation demonstrates that the dihedral angle between conjugate micro shear zones is approximately 65 this conjugate angle is equivalent to that observed in dilatant granular materials such as sand dilatant behaviour is synonymous with shear thickening rheology indicating that the magma flow is time dependent and resists high flow rates some of the dykes contain autobrecciation fragments that may represent localities where the ductile flow rate threshold was exceeded newtonian or pseudoplastic shear thinning rheology of crystal poor magmas must progressively give way to shear thickening rheology during cooling and increasing crystal concentration

water table fluctuation in soils overlying semi confined aquifers in response to time varying replenishment abstract the water table height in drained agricultural land depends on time varying replenishment that is due to the vertical downward recharge from irrigation or rainfall and in some cases to the upward vertical leakage from a semi confined aquifer the downward recharge may be assumed to vary exponentially with time whereas the upward leakage may be expressed as a function of the unknown water table height furthermore the rising of the water level in the field drainage system that may cause an inverse flow from the drains towards the soil is introduced through a properly defined boundary condition a non homogeneous form of the boussinesq equation that is used to describe this particular drainage problem is solved for three different initial conditions the same drainage problems were solved numerically by using the finite element method comparison between analytical and numerical solutions shows satisfactory agreement from the analytical solutions we obtain the non dimensional water table height at the midpoint between the drains and the non dimensional discharge of the drains per unit drained area as functions of non dimensional time and constants describing the aforementioned drainage conditions variation of these functions has also been illustrated graphically in non dimensional diagrams these can be used to show the sensitivity to various sets of parameter values and to calculate easily the water table height and the drain discharge in practical problems

origin of petroliferous bitumen from the buyuk menderes gediz geothermal graben system denizli saraykoy western turkey abstract the kb 5 well is located at the intersection of the geothermally active menderes and gediz graben systems in western turkey significant volumes of petroleum like material plm with its associated thermal water 120 c erupted onto the surface during drilling from a depth of 120 132 m i e from the claystone and marl rich early to middle pliocene kolonkoya formation the purpose of this paper is 1 to characterize this plm 2 to assess the source characteristics from which the plm was likely generated and 3 to recognize the generation mechanism considering the geothermal gradual versus the hydrothermal rapid processes analytical organic geochemistry using thin layer chromatographic separation followed by gas chromatography mass spectrometry gc ms was carried out the plm is composed primarily of polar nso compounds asphaltenes 77 this feature is similar to hydrothermal petroleums e g calcite springs yellowstone national park wyoming the plm shows n alkanes ranging from n c 19 to n c 38 i e with a maximum at n c 30 but n alkanes are depleted in n c 19 an absence of acyclic isoprenoids pristane and phytane and considerably large ucm unresolved complex mixture indicate that the plm has been subjected to a moderate degree of alteration possibly by the accompanying hot geothermal waters the source specific biomarkers i e low c 29 nh c 30 h ratio presence of gammacerane and 18 h oleanane high c 35 c 34 homohopane ratio and c 29 sterane concentration n c 28 n c 27 n c 29 c 28 27 29 r steranes c 29 r c 27 r suggest that the plm is a petroleum and was most likely generated from a tertiary source rock with a carbonate clay rich lithology the source organic matter was predominantly terrestrial and bacterial detritus deposited in relatively saline anoxic environmental conditions maturity sensitive biomarker parameters i e t m t s c 29 sterane 20 s 20 s 20 r 0 35 c 32 hopane 22 s 22 s 22 r 0 57 low diasterane regular sterane ratio correspond to a maturity level of approximately 0 50 0 60 r o this level of maturation could not be reached by such a young upper miocene lower pliocene and shallow sedimentary column max 600 m in the absence of instantaneous hydrothermal activity pahs are not detectable but series of alkylbenzenes alkyltoluenes alk 1 enes and triaromatic steranes are present the lack of organic richness and maturity in the drilled section of the kb 5 well indicates that the petroleum was generated in the deeper sections of the formation the temperature profile of the well and composition of the hydrocarbons in the petroleum suggest that the temperature of the hydrothermal activity during hydrocarbon generation was

modelling of water table variation in response to time varying recharge from multiple basins using the linearised boussinesq equation a mathematical model is presented to describe the variations of the water table in an unconfined aquifer due to time varying recharge applied from four rectangular basins the model is developed by solving the linearised boussinesq equation using the extended finite fourier cosine transform the time varying recharge rate is approximated by a number of piecewise linear elements of different lengths and slopes depending on the nature of the variation in recharge rate application of this model for the prediction of water table fluctuations and in the sensitivity analysis of various controlling parameters on the aquifer response is demonstrated in an example

relationship between plagioclase crystallization and cooling rate in basaltic melts rock textures commonly preserve a record of the near surface crystallization history of volcanic rocks under conditions of simple cooling without convection or mixing textures will reflect sample cooling rate the temperature at which crystallization was initiated and the distribution of mineral phase precipitation across the crystallization interval compilation of plagioclase size and number density data on natural dike sill and lava lake and experimental samples suggests that 1 growth and nucleation rates of plagioclase in natural basaltic samples are a predictable function of cooling rate and 2 the observed crystallization rate dependence on cooling rate is similar to that observed in experiments initiated at subliquidus temperatures comparison of natural and experimental samples thus suggests that most basalts crystallize under conditions of heterogeneous nucleation with the number density of preexisting nucleii partially controlling textural responses to cooling rate changes time scales of crystallization and cooling in magmatic systems are intimately linked through a balance between heat removal from the system and heat evolved through crystallization evaluation of textural data in the context of recent numerical models of crystallization in simple one and two component systems provides new insight into regularities in the crystallization behavior of basaltic magmas for example the rate of change in crystal size and number density as dictated by mass balance has been used as a measure of the relative importance of time scales of crystallization and cooling in numerical models of crystallizing systems in natural samples plagioclase size scales with the length scale of cooling such that a logarithmic plot of grain size as a function of normalized distance across the dike has a slope that appears approximately independent of dike width solidification time comparison with available textural data for other phenocryst phases suggests that the same may be true for pyroxene and magnetite crystallization with each phase having a characteristic slope probably controlled by the thermodynamic properties of the crystallizing phase measured crystal size distributions are unimodal and show maximum frequencies in the smaller size classes distributions broaden and the grain size at peak frequency increases with increasing crystallization times decreasing cooling rates in contrast partially crystallized makaopuhi lava lake samples have crystal size distributions that decrease exponentially with increasing crystal size measured size distributions in dikes can be explained by late stage modification of makaopuhi type distributions through loss of small crystals possibly the consequence of growth without nucleation finally this compilation of the textural response of basaltic magmas to changes in cooling rate suggests that empirical calibrations of crystallization rate dependence on cooling rate from natural samples provide a reasonable model for plagioclase crystallization in near surface basaltic systems predicted growth rates will be slow and relatively constant 10 10 10 11 cm s for crystallization times expected in most shallow volcanic systems 1000 years

crystal size distribution csd in rocks and the kinetics and dynamics of crystallization ii makaopuhi lava lake crystal size distribution csd theory has been applied to drill core samples from makaopuhi lava lake kilauea volcano hawaii plagioclase and fe ti oxide size distribution spectra were measured and population densities n were calculated and analyzed using a steady state crystal population balance equation n n0 exp l g slopes on ln n versus crystal size l plots determine the parameter g a product of average crystal growth rate g and average crystal growth time the intercept is j g where j is nucleation rate known temperature depth distributions for the lava lake provide an estimate of effective growth time allowing nucleation and growth rates to be determined that are independent of any kinetic model plagioclase growth rates decrease with increasing crystallinity 9 9 5 4 10 11 cm s as do plagioclase nucleation rates 33 9 1 6 10 3 cm3 s ilmenite growth and nucleation rates also decrease with increasing crystallinity 4 9 3 4 10 10 cm s and 15 2 2 10 3 cm3 s respectively magnetite growth and nucleation rates are also estimated from the one sample collected below the magnetite liquidus g 2 9 10 10 cm s j 7 6 10 2 cm3 s moments of the population density function were used to examine the change in crystallization rates with time preliminary results suggest that total crystal volume increases approximately linearly with time after 50 crystallization a more complete set of samples is needed for material with 50 crystals to define the entire crystallization history comparisons of calculated crystallization rates with experimental data suggests that crystallization in the lava lake occurred at very small values of undercooling this interpretation is consistent with proposed thermal models of magmatic cooling where heat loss is balanced by latent heat production to maintain equilibrium cooling

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

molecular organic geochemistry of the tarim basin northwest china we conducted organic geochemical analyses on the largest suite of oils and source rock extracts from the tarim basin northwest china currently available statistical cluster analysis of the entire suite of tarim oils distinguishes at least seven genetic groups of oils the largest group of oils was collected from the tazhong and tabei uplifts and originated from marine middle upper ordovician anoxic marls that mark slope facies at the margins of structural uplifts two other genetic groups most likely originated from marine middle upper ordovician source rocks but of distinct facies with one an oxic shale rich source west of the bachu uplift and the other an anoxic shale source at tazhong

water table fluctuation in aquifers overlying a semi impervious layer due to transient recharge from a circular basin summary an analytical solution of a linearised form of boussinesq equation is presented in this paper to describe the water table fluctuation in unconfined aquifers overlying a semi impervious layer in response to transient recharge this solution does not require the common assumption of an impervious formation underlain the unconfined aquifer on the contrary it shows that even when the hydraulic conductivity of the semi impervious layer is several orders of magnitude less than the aquifer hydraulic conductivity downward leakage can be important and can lead to large overestimations of water table heights if it is ignored the rate of recharge is considered to decrease exponentially with time during a single cycle of recharge while two cycles of time varying recharge are approximated by continuous elements described by nth degree polynomials numerical solution of the non linear boussinesq equation was implemented to validate the applied linearisation

three long lava flows in north queensland the kinrara toomba and undara basaltic lava flows are from 55 to 160 km long and range in age from 13 to 190 ka the lavas were emplaced down low gradients 0 2 to 0 4 with volumes ranging up to 30 km3 they were not unusually hot at eruption 1130 1160 nor unusually fluid gentle topography controlled the flows and shallow drainage lines captured them lava tubes operated in places and some drained to form caves injection under surface crust was widespread producing inflation features ranging from tumuli and low plateaus to extensive ridges sustained eruption was essential for the development of the long flows but each is composite with pauses between successive pulses that partially covered the earlier longer flows the lava structures are mainly pahoehoe but some a a lavas are present of the three volcanoes involved undara is a simple low angle lava cone with a 200 m wide crater toomba is a low angled cone with several eruption centers and kinrara has a deep crater with evidence of strong fountaining effusion rates are not known but may have been relatively low similar to those observed in hawaiian volcanoes lava tubes most of which remained undrained are believed to have been of major importance in flow emplacement given the evidence of successive flows and the time needed to develop widespread inflation it is suggested that the two long flows over 100 km involved many decades of eruption

crystallization history of the 1984 mauna loa lava flow during a 3 week eruption in 1984 mauna loa produced vent lavas that increased in crystallinity from 1 to 30 and 27 km long flows that increased in crystallinity as they moved downstream we examined the crystallization history of these lavas using crystal size distribution csd analysis to study the rates of crystallization viscosity increase and latent heating typical average growth and nucleation rates were 5 10 9 cm s 1 and 5 cm 3 s 1 for microphenocrysts 20 to 500 m size crystals nucleated in the rift zone and 5 10 8 cm s 1 and 5 104 cm 3 s 1 for microlites 1 to 20 m size crystals nucleated in the channel these crystallization rates are high compared with those found in other csd studies of igneous rocks probably due to highly nonequilibrium conditions brought on by rapid degassing in the rift zone and cooling in the lava channel growth and nucleation rates decreased with time at the vent and with distance downstream the maximum downstream total crystallinity measured is 39 25 microlites 14 microphenocrysts in a quenched sample 14 km from the vent growth and nucleation rates cannot be calculated for postemplacement samples but they place upper limits of 53 58 on the amount of crystallization in the channel 9 20 km from the vent crystallization could have been mostly responsible for the 105 fold downstream increase in apparent viscosity although degassing and increasing incorporation of solid lava fragments also contributed another effect of crystallization on the lava flow was the sizeable latent heating 0 01 j g 1 s 1 over the first half of the flow length if the crystallinity of downstream quench samples is representative of the hot fluid core which may have been counteracted by entrainment of cooler material measurements of crystallization are shown to be crucial in the study of lava flow emplacement dynamics

application of biomarkers to petroleum migration in the linyi fault area huimin depression bohai bay basin china a geochemical investigation was carried out on 32 crude oil samples to investigate the origin of the oil and to trace the migration direction in the linyi fault area huimin depression bohai bay basin china the oils which were characterized by low gammacerane content and a dominance of c27 over c29 regular steranes originated from the source rock of the third member of the shahejie formation es3 in the linnan sag a sequential charge of low and high maturity oils from the es3 source rocks resulted in a decrease in oil maturity in the migration direction the petroleum migration direction in the footwall of the linyi fault was northward away from the fault and the migration direction at the southwest end in the hanging wall of the linyi fault was westward along the fault as evidenced by lateral gradients of biomarker parameters of various maturity density and viscosity

a unified continental thickness from seismology and diamonds suggests a melt defined plate thick rigid continents move over the weaker underlying mantle although geophysical and geochemical constraints on the exact thickness and defining mechanism of the continental plates are widely discrepant xenoliths suggest a chemical continental lithosphere 175 kilometers thick whereas seismic tomography supports a much thicker root 250 kilometers and a gradual lithosphere asthenosphere transition consistent with a thermal definition we modeled ss precursor waveforms from continental interiors and found a 7 to 9 velocity drop at depths of 130 to 190 kilometers the discontinuity depth is well correlated with the origin depths of diamond bearing xenoliths and corresponds to the transition from coarse to deformed xenoliths at this depth the xenolith derived geotherm also intersects the carbonate silicate solidus suggesting that partial melt defines the plate boundaries beneath the continental interior

composition and microstructure of magma bodies from effective medium theory summary the extent and seismic properties of magma bodies beneath the subsurface are normally ascertained via seismic methods the seismic properties of such bodies depend on the composition and microstructure of both melt and crystals using effective medium theory we assess the effect of microstructure geometry and orientation of melt and crystals on the seismic properties namely p and s wave velocities and anisotropy we find that s wave velocity and anisotropy are key observables in determining the composition and microstructure of magma bodies

predictions and observations for the oceanic lithosphere from s to p receiver functions and ss precursors the ocean lithosphere is classically described by the thermal half space cooling hsc or the plate models both characterized by a gradual transition to the asthenosphere beneath scattered waves find sharp seismic discontinuities beneath the oceans possibly from the base of the plate active source studies suggest sharp discontinuities from a melt channel we calculate synthetic s to p receiver functions and ss precursors for the hsc and plate models and also for channels we find that the hsc and plate model velocity gradients are too gradual to create interpretable scattered waves from the base of the plate subtle phases are predicted to follow a similar trend as observations flattening at older ages therefore the seismic discontinuities are probably caused by a thermally controlled process that can also explain their amplitude such as melting melt may coalesce in channels although channels 10 km thick should be resolvable by scattered wave imaging

development of the 1990 kalapana flow field kilauea volcano hawaii the 1990 kalapana flow field is a complex patchwork of tube fed pahoehoe flows erupted from the kupaianaha vent at a low effusion rate approximately 3 5 m3 s these flows accumulated over an 11 month period on the coastal plain of kilauea volcano where the pre eruption slope angle was less than 2 the composite field thickened by the addition of new flows to its surface as well as by inflation of these flows and flows emplaced earlier two major flow types were identified during the development of the flow field large primary flows and smaller breakouts that extruded from inflated primary flows primary flows advanced more quickly and covered new land at a much higher rate than breakouts the cumulative area covered by breakouts exceeded that of primary flows although breakouts frequently covered areas already buried by recent flows lava tubes established within primary flows were longer lived than those formed within breakouts and were often reoccupied by lava after a brief hiatus in supply tubes within breakouts were never reoccupied once the supply was interrupted during intervals of steady supply from the vent the daily areal coverage by lava in kalapana was constant whereas the forward advance of the flows was sporadic this implies that planimetric area rather than flow length provides the best indicator of effusion rate for pahoehoe flow fields that form on lowangle slopes

a matlab toolbox and excel workbook for calculating the densities seismic wave speeds and major element composition of minerals and rocks at pressure and temperature to interpret seismic images rock seismic velocities need to be calculated at elevated pressure and temperature for arbitrary compositions this technical report describes an algorithm software and data to make such calculations from the physical properties of minerals it updates a previous compilation and excel spreadsheet and includes new matlab tools for the calculations the database of 60 mineral end members includes all parameters needed to estimate density and elastic moduli for many crustal and mantle rocks at conditions relevant to the upper few hundreds of kilometers of earth the behavior of and quartz is treated as a special case owing to its unusual poisson s ratio and thermal expansion that vary rapidly near the transition the matlab tools allow integration of these calculations into a variety of modeling and data analysis projects

water rich sublithospheric melt channel in the equatorial atlantic ocean the lithosphere asthenosphere boundary is the most extensive boundary on earth separating the mobile plate above from the convecting mantle below but its nature remains a matter of debate using an ultra deep seismic reflection technique here we show a systematic seismic image of two deep reflectors that we interpret as the upper and lower limits of the lithosphere asthenosphere boundary beneath a 40 70 million year old oceanic lithosphere in the atlantic ocean these two reflections correspond to 1 260 c and 1 355 c isotherms and bound a low velocity channel suggesting that the lithosphere asthenosphere boundary is thermally controlled we observe a clear age dependency of this sublithospheric channel its depth increases with age from 72 km where it is 40 myr old to 88 km where it is 70 myr old whereas its thickness decreases with age from 18 km to 12 km we suggest that partial melting facilitated by water is the main mechanism responsible for the low velocity channel the required water concentration for melting increases with age nevertheless its corresponding total mass remains relatively constant suggesting that most of the volatiles in the oceanic sublithospheric channel originate from a horizontal flux near the ridge axis

hawaiian lava flows in the third dimension identification and interpretation of pahoehoe and a a distribution in the kp 1 and soh 4 cores 1 hawaiian lava flows are classified as pahoehoe or a a by their surface morphology as surface morphology reflects flow emplacement conditions the surface distribution of morphologic flow types has been used to study the evolution and eruptive history of basaltic volcanoes we extend this analysis to the third dimension by determining the distribution of flow types in two deep drill cores the scientific observation hole 4 soh 4 core drilled near kilauea s east rift zone erz and the pilot hole kahi puka 1 kp 1 for the hawaiian scientific drilling project hsdp drilled through distal flows from mauna loa and mauna kea flows are classified using both internal structures and groundmass textures with the latter useful when identification based on mesoscopic flow features e g surface morphology and vesicle content and distribution is ambiguous we then examine the temporal distribution of pahoehoe and a a flows in proximal soh 4 and distal kp 1 settings sequence analysis shows that the two flow types are not randomly distributed in either core but instead are strongly clustered the proximal soh 4 core is dominated by thin pahoehoe flows 60 by volume consistent with the common occurrence of surface fed pahoehoe flows in near vent settings the distal kp 1 core has a high proportion of a a 58 by volume although the proportion of pahoehoe and a a varies dramatically throughout the mauna kea sequence thick inflated pahoehoe flows dominate when the drill site was near sea level consistent with the numerous inflated pahoehoe fields on the current coastal plains of kilauea and mauna loa a a flows are abundant when the site was far above sea level as slope increases from the coastal plains to mauna kea s flank this correlation may reflect the combined effect of long transport distances and increased slopes on flow emplacement these results demonstrate that flow type and thickness variations in cores provide valuable information about both vent location and local site environment observed variations in flow type within the kp 1 core raise interesting questions about feedback between volcano evolution and flow morphology and suggest that flow type is an important variable in models of volcano growth and related models for lava flow hazard assessment

a concept of maximum stream depletion rate for leaky aquifers in alluvial valleys 1 existing analytical models for evaluating stream depletion by wells in alluvial aquifers are based on the assumption that stream depletion supplies 100 of groundwater withdrawals analysis of specific hydrostratigraphic conditions in leaky aquifers indicates that stream depletion may range from 0 to 100 a new concept of maximum stream depletion rate msdr is introduced and defined as a maximum fraction of the pumping rate contributed by the stream depletion several new analytical solutions indicate that the msdr is determined by aquifer hydrostratigraphic conditions geometry of recharge and discharge zones and locations of pumping wells

transient solution for stream unconfined aquifer interaction due to time varying stream head and in the presence of leakage summary this paper presents new analytical solutions of a linearized boussinesq equation characterizing groundwater flow in a stream unconfined aquifer system due to transient seepage the aquifer is underlain by a horizontal leaky bed and interacts with an adjoining stream of varying water level through a semipervious vertical stream bank close form analytical expressions are derived to predict water head distribution flow rate and volumetric exchange of water in response to time dependent rise or drop in the stream water level comparison between analytical and numerical results shows satisfactory agreement the effects of the finite and semi infinite lengths of the domain are considered in detail certain asymptotic situations such as sudden rise or drop in the stream water level no flow condition at the aquifer s base and absence of vertical stream bank can be dealt with as limiting cases of main results an illustration of the new analytical approach is used to quantify the accretion recession of the bank storage due to variation in various aquifer parameters

two dimensional modelling of water table fluctuation in response to localised transient recharge abstract an analytical solution of the linearised boussinesq equation is presented and used to predict the spatio temporal variation of the water table in a finite aquifer system in response to a transient recharge from an overlying rectangular basin the boundary conditions of the finite aquifer are taken as fixed heads which would apply when the aquifer system is surrounded by open water bodies application of the solution is illustrated with the help of a numerical example the results would also have applications in studying stream aquifer interaction in the presence of transient recharge

models of hawaiian volcano growth and plume structure implications of results from the hawaii scientific drilling project the shapes of typical hawaiian volcanoes are simply parameterized and a relationship is derived for the dependence of lava accumulation rates on volcano volume and volumetric growth rate the dependence of lava accumulation rate on time is derived by estimating the eruption rate of a volcano as it traverses the hawaiian plume with the eruption rate determined from a specified radial dependence of magma generation in the plume and assuming that a volcano captures melt from a circular area centered on the volcano summit the timescale of volcano growth is t 2 r plate where r is the radius of the melting zone of the circular plume and plate is the velocity of the pacific plate the growth progress of a volcano can be described by a dimensionless time t t plate 2r where t 0 is chosen to be the start of volcano growth and t 1 approximates the end of shield growth using a melt generation rate for the whole plume of 0 2 km 3 yr a plume diameter of 50 km and a plate velocity of 10 cm yr we calculate that the lifetime of a typical volcano is 1000 kyr for a volcano that traverses the axis of the plume the standard dimensions are a volume of 57 000 km 3 a summit thickness of 18 km a summit elevation of 3 6 km and a basal radius of 60 km the volcano first breaches the sea surface at t 0 22 when it has attained only 5 of its eventual volume 80 of the volume accumulates between t 0 3 and t 0 7 typical lava accumulation rates start out over 50 m kyr in the earliest stages of growth from the seafloor and level out at 35 m kyr from t 0 05 until t 0 4 from t 0 4 to t 0 9 the submarine lava accumulation rates decrease almost linearly from 35 m kyr to 0 subaerial accumulation rates are about 30 lower the lava accumulation rate is a good indicator of volcano age a volcano that passes over the plume at a distance 0 4r off to the side of the plume axis is predicted to have a volume of about 60 of the standard volcano a lifetime about 8 shorter and lava accumulation rates about 15 20 smaller the depth age data for mauna kea lavas cored by the hawaii scientific drilling project are a good fit to the model parameters used given that mauna kea appears to have crossed the plume about 15 20 km off axis the lifetime of mauna kea is estimated to be 920 kyr mauna loa is predicted to be at a stage corresponding to t 0 8 kilauea is at t 0 6 and loihi is at t 0 16 the model also allows the subsurface structure of the volcanoes the interfaces between lavas from different volcanoes to be modeled radial geochemical structure in the plume may be blurred in the lavas because the volcanoes capture magma from a sizeable cross sectional area of the plume this inference is qualitatively born out by available isotopic data the model predicts that new hawaiian volcanoes are typically initiated on the seafloor near the base of the next older volcano but generally off the older volcano s flank

seismic crustal structure and morphotectonic features associated with the chain fracture zone and their role in the evolution of the equatorial atlantic region oceanic transform faults and fracture zones fzs represent major bathymetric features that keep the records of past and present strike slip motion along conservative plate boundaries although they play an important role in ridge segmentation and evolution of the lithosphere their structural characteristics and their variation in space and time are poorly understood to address some of the unknowns we conducted interdisciplinary geophysical studies in the equatorial atlantic ocean the region where some of the most prominent transform discontinuities have been developing here we present the results of the data analysis in the vicinity of the chain fz on the south american plate the crustal structure across the chain fz at the contact between 10 and 24 ma oceanic lithosphere is sampled along seismic reflection and refraction profiles we observe that the crustal thickness within and across the chain fz ranges from 4 6 5 9 km which compares with the observations reported for slow slipping transform discontinuities globally we attribute this presence of close to normal oceanic crustal thickness within fzs to the mechanism of lateral dike propagation previously considered to be valid only in fast slipping environments furthermore the combination of our results with other data sets enabled us to extend the observations to morphotectonic characteristics on a regional scale our broader view suggests that the formation of the transverse ridge is closely associated with a global plate reorientation that was also responsible for the propagation and for shaping lower order mid atlantic ridge segmentation around the equator

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

the gutenberg discontinuity melt at the lithosphere asthenosphere boundary the lithosphere asthenosphere boundary lab beneath ocean basins separates the upper thermal boundary layer of rigid conductively cooling plates from the underlying ductile convecting mantle the origin of a seismic discontinuity associated with this interface known as the gutenberg discontinuity g remains enigmatic high frequency ss precursors sampling below the pacific plate intermittently detect the g as a sharp negative velocity contrast at 40 to 75 kilometer depth these observations lie near the depth of the lab in regions associated with recent surface volcanism and mantle melt production and are consistent with an intermittent layer of asthenospheric partial melt residing at the lithospheric base i propose that the g reflectivity is regionally enhanced by dynamical processes that produce melt including hot mantle upwellings small scale convection and fluid release during subduction

modelling of aquifer response to time varying recharge and pumping from multiple basins and wells this paper deals with the development of an analytical solution of two dimensional linearized boussinesq equation to predict water table variation in response to time varying recharge and pumping from any number of basins and wells the rates of time varying recharge and pumping are approximated by series of line elements of different lengths and slopes depending on the nature of variation of the recharge and or pumping rates advantage of this approach is that any complex nature of recharge and pumping rates for any number of basins and wells and for any number of these operations can be approximated with more accuracy application of the solution in the prediction of water table variation is demonstrated with the help of an example problem also the results of the analytical solution are compared with those obtained from modflow both results are found to be in good agreement

pahoehoe and aa lavas a discussion and continuation of the model of peterson and tilling abstract the graphical method of peterson and tilling for representing the behaviour of a lava flow is considered in terms of simple rheological theory assuming that a lava may be approximately described as a bingham fluid this approach helps resolve an apparent anomaly in the original treatment of peterson and tilling with respect to the representation of the pahoehoe to aa transition it also suggests further methods for quantitatively defining the limits of the pahoehoe and aa fields and the transition threshold zone

the evolution of lava flows from ephemeral vents at mount etna insights from vesicle distribution and morphological studies abstract lava flow units from ephemeral vents at mount etna are characterized by a cross flow subdivision into zones with different surface morphology symmetrically distributed with respect to the centerline of the flow these zones are 1 a central zone cp zone with a relatively smooth surface near the vent 2 a lateral zone lp zone covered by a carpet of clinkers overlying the massive lava body and 3 a lateral levee zone ll zone in many cases the cp and lp zones are separated by an inward dipping groove and the cp zone is from some decimeters up to more than 1 m thicker than the adjacent lp zone in sections perpendicular to the flow direction the vesicles corresponding with the cp zone are systematically distributed in a ring like region and are characterized by a sub elliptical shape with their minor axes along a direction radial to the center of such region vesicles corresponding with the lp zone are still elliptical and their major axes tend to be parallel to the nearest cooling surface vesicularity is the lowest at the center of the ring like region where vesicles approach a spherical shape in the upper part of the ring like region vesicle accumulation and coalescence below the crust produces one or more gas rich layers which act as levels of preferential detachment for the formation of lava tubes the observed morphological characteristics and reconstructed vesicle distribution patterns are consistent with a radial distribution of velocity within the lava flow unit and suggest the existence of an inner plug flow region where the velocity gradient is zero a simple evolution scheme is proposed in which a lava flow unit from ephemeral vent invariably evolves to a lava tube through the downward migration of the plug flow region the progressive reduction of the cross flow section due to cooling produces a pressure increase within the flowing lava body and the thickening of the active central portion of the lava flow unit in order to satisfy mass conservation