investigation of the catalytic effects of indigenous minerals in the pyrolysis of aleksinac oil shale substrates steranes triterpanes and triaromatic steroids in the pyrolysates abstract evidence for catalytic effects of indigenous minerals in the pyrolysis of aleksinac oil shale kerogen was found by investigating the liquid products obtained in the micro activity test mat pyrolysis of raw shale and its demineralized substrates by comparing the corresponding fragmentograms of a demineralized sample with those of a substrate containing only silicate minerals differences in the side chain isomerisation of the steranes and triterpanes and in the side chain cleavage of the triaromatic steroids were observed these findings corroborated the previous conclusion based on mat parameters and tg weight losses that the catalytic effect of the indigenous mineral components during the pyrolysis of aleksinac oil shale kerogen is very low

shape sorting of flood transported synthetic clasts in a gravel bed river abstract an experiment was set up in a gravel bed river to test shape sorting of gravel size clasts synthetic clasts representing four shape types were used spheres were entrained in larger numbers than the other shapes and travelled furthest rods and blades were intermediate in mobility discs moved the shortest distance and in the least numbers the angle of repose and therefore the pivotability of clasts in combination with lift and drag forces exerted on the clast will determine if a clast will be entrained or not as well as the shear stress needed for the clast to maintain motion a sphere projects relatively higher than the other shape types of equal volume and will induce a higher degree of flow separation in its wake than other shape types therefore larger components of lift and drag forces exerted by water flow will be present to set this shape type in motion or to maintain motion the prolate clasts have a small angle of repose compared to discoid clasts and will roll much more readily the imbricated orientation assumed by discoid and sometimes blade shaped clasts is a very stable position very high applied shear stress will be needed to dislodge imbricated discs

pacific equatorial subsurface countercurrent velocity transport and potential vorticity concurrent shipboard adcp and ctd sections are used to calculate the mean velocity transport and potential vorticity fields associated with the pacific equatorial subsurface countercurrents sccs averaged in stream coordinates the core eastward velocity of the sccs is a factor of 2 higher than previously reported means but the estimated transports are unchanged the meridional profile of zonal velocity along isopycnals is sharply peaked and nearly linear on each flank of the current the sharp and strong reversal of relative vorticity over a distance of 20 km at the jet core sharpens the coincident potential vorticity front this front separates a region of very low homogeneous potential vorticity on the equatorward side from a homogeneous high potential vorticity region on the poleward side each potential vorticity pool extends well beyond the edges of the scc into regions of westward flow on the equatorward sides of the sccs this westward flow is the equatorial intermediate current in the western pacific but in the central and eastern parts of the basin it is off the equator in deep extensions of the south equatorial current in the central and eastern regions the net westward transport in an isopycnal layer between the sccs exceeds the combined eastward scc transport in that layer the net zonal transport between the scc cores is highly divergent in the east and convergent in the west this pattern together with downstream changes in scc density indicates that neither they nor the westward return flows are simple inertial recirculations strong diapycnal processes must be involved

correlative geochemical study of crude oils from southeastern and southern parts of the pannonian basin abstract several crude oils from the southeastern yugoslav part of the pannonian basin are correlated for the first time on the basis of many bulk and specific parameters the investigations involved 15 oils from oil gas fields a and b and oil field c from the banat depression and oil field d from south backa depression and four oils from recently discovered oil shows e the kostolac depression on the basis of structural group analysis and other bulk parameters such as api gravity contents of asphaltenes and sulfur as well as content of n alkanes and pristane to phytane ratio the examined oils are classified into four groups however the distributions and relative abundances of n alkanes isoprenoids c19 c20 steranes tricyclic terpanes and pentacyclic triterpanes obtained by capillary gc and computerized gc ms analysis suggest classification of the examined oils into only two genetic types a d and e1 e4 the oils are of relatively high maturity they are not biodegraded except for both oils from field d and the oil a9

equatorial subthermocline currents across the pacific recent sections crossing the equator at nine longitudes from 146 e to 86 w show zonal currents below 400 m similar to those found in a 16 month mean section on 159 w from the pacific equatorial ocean dynamics pequod program in 1982 1983 most of the new measurements were made with a lowered acoustic doppler current profiler eastward current extrema north and south intermediate countercurrents are found in all sections about 2 from the equator in the depth range 500 1500 m with the possible exceptions of 146 e where topography complicates the picture south of the equator and 150 e where the sections extend only from 1 s to 2 n poleward of the intermediate countercurrents westward flow is found near 3 from the equator in most of the sections on the equator from 250 500 m depth a westward equatorial intermediate current is found in many but not all of the sections similarly it is present in the pequod mean but not in all synoptic sections below the intermediate currents and countercurrents an eastward current near 3000 m was found at and south of the equator in the pequod mean and in the new sections from 150 e to 110 w near 4000 m there is westward flow south of the equator in the pequod mean and near the equator in the new sections from 179 e to 135 w geostrophic currents calculated from an 8 year mean hydrographic section at 165 e also resemble the pequod mean although not conclusive the evidence presented here indicates that these currents are basin scale components of the general circulation perhaps involving vigorous horizontal recirculation in a set of basin wide elongated gyres within a few degrees of the equator

origin of crude oils in the jinhu depression of north jiangsu south yellow sea basin eastern china abstract the chemical compositions of 20 crude oils and the extracts of potential source rocks from the jinhu depression of the north jiangsu south yellow sea basin eastern china were studied in detail by geochemical methods in order to understand their genetic relationship the oil samples were collected from the major producing fields in the western slope ws and the biandong yangjiaba minqiao uplift belt bmy the rock samples studied selected after rock eval pyrolysis screening of a large suite of samples consist of 20 shale samples in the e 2 f 2 member of the paleocene funing formation from the oilfield areas ws and bmy and the sanhe sag all within the jinhu depression geochemical characteristics indicate only one single family of oils a number of biomarker features support deposition of the source rocks for these oils under conditions of enhanced salinity stratified water columns a wide thermal maturity range for the oils as indicated by sterane isomerization ratios was not substantiated by other maturity parameters the genetic relationships between the oils and the e 2 f 2 member of the paleocene funing formation present in the deeper parts of the sanhe and longgang sags were suggested using a wide range of molecular parameters variation in the sterane concentrations in source rocks with different maturity suggests that migrational contamination and or in situ extractions of organic matter from caprocks or intra reservoir shales by mature oils could potentially produce oils with apparent immaturity at the molecular level secondary alteration e g biodegradation of oils in the reservoir could also have a similar effect on the bulk oil compositions although we do not discount the possible presence of minor amounts of immature oils exploration focus in the jinhu depression as well as many other rift basins in eastern china should be on mature oils derived from the deep source kitchens

modification of clast shape in high arctic glacial environments abstract clast shape data from a range of different glacial environments at several high arctic valley glaciers in svalbard are presented these data add to the growing body of reference information about clast shape in modern glacial environments and is used to explore the role of lithology in clast morphogenesis and to evaluate the different methodological approaches to the analysis of clast shape data the following conclusions are drawn 1 it is possible to distinguish clasts transported subglacially from those moved supraglacially 2 it is not possible to differentiate among different types of subglacial sediment or to distinguish them collectively from glaciofluvial samples 3 lithology has some influence on clast shape although not as much as previously suggested and 4 covaria t plots of the ra percentage of angular and very angular clasts versus c40 percentage of clasts with c to a axial ratio 0 4 index give superior data visualization and discriminate more effectively among different glacial sediments than sphericity and roundness plots

the pacific subsurface countercurrents and an inertial model abstract the tsuchiya jets or subsurface countercurrents extend across the pacific ocean carrying 7 2 106 m3 s 1 eastward on each side of the equator mean meridional sections of potential temperature salinity neutral density anomaly and the square of buoyancy frequency are presented for the western central and eastern tropical pacific ocean these sections are used together with maps of depth and salinity on isopycnals as well as thickness between isopycnals to describe the evolution of the tsuchiya jets as they flow from west to east an inertial jet model is formulated in which conservation of the bernoulli function and potential vorticity combine with the eastward shoaling of the tropical pycnocline to dictate the jet structure this model jet is consistent with a number of features of the tsuchiya jets their roughly constant volume transports their advection of properties such as salinity and oxygen over long zonal distances their rapidity and narrowness their poleward shift from we

geochemistry of petroleum systems in the niuzhuang south slope of bohai bay basin part 1 source rock characterization detailed mapping of the tertiary strata of the dongying depression bohai bay basin reveals that oil shales and dark mudstones in the es4 and es3 members of the eocene oligocene shahejie formation have excellent potential as petroleum source rocks regional distributions of total organic carbon content kerogen type and thermal maturation indicate that abundant mature source rocks are present in the niuzhuang sag whereas source rocks along the niuzhuang south slope are currently immature or marginally mature for the generation of conventional oils this study examined the molecular characteristics for a number of biomarker compound classes and related these to either source facies change or different burial and thermal maturation an important observation made during this study is the significant variation in the relative distributions and absolute concentrations of a wide range of aliphatic and aromatic hydrocarbon markers in the rock extracts as a function of burial depth this variation may potentially explain the uncertainty associated with the maturity assessment and genetic modeling for so called immature oils that are usually defined on the basis of alkane biomarker isomerization ratios and the presence of biomarkers with biological configurations

oxygen tongues and zonal currents in the equatorial atlantic 1 equatorial zonal currents and associated oxygen distributions are studied using shipboard hydrographic data trajectories from isopycnic floats drifting at about 300 m depth and velocity time series from the upper 1100 m obtained at two equatorial moorings located at 35 w and 23 w mean profiles of zonal velocity measured by moored acoustic doppler current profilers yielded a westward flowing equatorial intermediate current eic below the equatorial undercurrent euc at both locations the eic consists of two westward current cores at about 250 and 450 m the upper core of the eic deepens by about 30 m from 23 w where it has a mean velocity of 6 2 cm s 1 to 35 w where the mean is 5 3 cm s 1 the lower core of the eic is about twice as strong with 12 1 cm s 1 at 23 w and 9 2 cm s 1 at 35 w the flow below the euc is characterized by substantial interannual variability from may to december 2005 a strong zonally coherent eastward jet occurred at 300 to 350 m depth found to be an expression of shallow stacked jets superimposed on the mean eic shipboard hydrographic observations in june july 2006 revealed the existence of a high oxygen tongue that can be traced from 35 w to 10 w in the depth range of the eastward jet prevailing during the preceding year on the basis of an advection diffusion balance it is suggested that the oxygen decrease from 35 w to 10 w within the oxygen tongue is mainly balanced by lateral eddy diffusivity and oxygen consumption with diapycnal turbulent diffusivity playing only a minor role

middepth circulation of the eastern tropical south pacific and its link to the oxygen minimum zone there is an incomplete description of the mid depth circulation and its link to the oxygen minimum zone omz in the eastern tropical south pacific subsurface currents of the omz in the eastern tropical south pacific are investigated with a focus at 400 m depth close to the core of the omz using several acoustic doppler current profiler sections recorded in january and february 2009 five profiling floats with oxygen sensors were deployed along 85 50 w in february 2009 with a drift depth at 400 m their spreading paths are compared with the model flow field from a 1 10 tropical pacific model tropac01 and the simple ocean data assimilation soda model overall the mean currents in the eastern tropical south pacific are weak so that eddy variability influences the flow and ultimately feed oxygen poor water to the omz the center of the omz is a stagnant area so that floats stay much longer in this region and can even reverse direction in one case of one float deployed at 8 s returned to the same location after 15 month on the northern side of the omz in the equatorial current system floats move rapidly to the west most current bands reported for the near surface layer exist also in the depth range of the omz a schematic circulation flow field for the omz core depth is derived which shows the northern part of the south pacific subtropical gyre south of the omz and the complicated zonal equatorial flow field north of the omz

distance of movement of coarse particles in gravel bed streams distributions of distance of bedload particle movement were examined in two gravel bed streams using several hundred magnetically tagged cobbles and pebbles the compound poisson model of einstein hubbell sayre and a simple gamma function model were compared with observed distributions of moved particles and of all particles both models fit the data reasonably well for small mean displacements but notable misfits occurred in an event with large mean displacement when mean particle travel distance approaches the scale of bar spacing trapping in the bars interrupts particle progress and the dispersion process the data remain very noisy so definitive discrimination of suitable models will require trials with more than 103 particles

pebble shape and size abstract the mathematical technique of r mode factor analysis was applied to the long intermediate and short axes of one synthetic random data set and three sets of natural pebbles to extract the three fundamental factors related to these parameters one factor corresponds to size which is best described by the mean of the axes two further factors correspond to shape sphericity and disc rodness these factors are revealed whether synthetic data or natural pebble samples are analyzed extending the factor analysis to include shape indices revealed which indices are equivalent which are most useful and which should be discarded sphericity is best described with the corey shape index s il and disc rodness is best described with the disc rod index l i l s accordingly the most effective shape diagram is a triangular plot of these two shape indices the three end members of shape are spheres discs and rods shape is best investigated using this shape diagram a 2 d technique such as contouring point density on this diagram should be used to determine the mean and standard deviation of shape while others ask themselves what is there to do i ask myself what is there that i can avoid doing masanobu fukuoka one straw revolution

organic geochemical and petrographical characteristics of coal bearing oligo miocene sequence in the oltu narman basin erzurum ne turkey abstract in the oltu narman erzurum tertiary basin coals occur in the oligo miocene lacustrine sequence in this study n alkane isoprenoid and saturated aromatic biomarker distributions of coals in the sutkans region are found in association with pyrolysis and petrographic data and detailed organic geochemical characteristics depositional environments and hydrocarbon potential of the coals are propounded huminite is the dominant maceral type in coals 51 84 telohuminite is in lesser abundance detrohuminite especially densinite and gelohuminite gelinite are in higher abundance groundwater influence index gwi and gelification index gi are quite high for the studied coals whilst tissue preservation index tpi and vegetation index vi are found to be extremely low according to the results of pyrolysis coal coaly claystone and clayey coal samples contain type ii kerogen although sutkans coals have high ash content 6 28 44 60 average 27 99 their calorific value is quite high 3947 7583 kcal kg random huminite reflectance values of coals vr are 0 4 048 average 0 44 indicating sub bituminous b rank tmax values of coal coaly claystone and clayey coal samples are between 413 and 437 c 20s 20r 20s sterane 22s 22r 22s homohopane ma i ma i ii ta i ta i ii and c28ta c29ma c28ta steroid mpi mpr and mdr ratios which reflect the maturity of coals are very low mpi 1 is intermediate and moretane hopane ratio is high according to petrographical palynological and geochemical data the coal sequence was formed in an environment changing in character from lacustrine to fluvial and coals were accumulated in a swamp area with high water level high ph and intense microbial activity represented by suboxic anoxic conditions

homogenization of potential vorticity in planetary gyres the mean circulation of planetary fluids tends to develop uniform potential vorticity q in regions where closed time mean streamlines or closed isolines of mean potential vorticity exist this state is established in statistically steady flows by geostrophic turbulence or by wave induced potential vorticity flux at the outer edge of the closed contours the expelled gradients of q are concentrated beyond this transition lies motionless fluid or a different flow regime in which the planetary gradient of q may be dominant the homogenized regions occur where direct forcing by external stress or heating within the closed isoline is negligible upon the potential density surface under consideration in the stably stratified ocean such regions are found at depths greater than those of direct wind induced stress or penetrative cooling in channel models of the atmosphere we again find constant q when mesoscale eddies cause the dominant potential vorticity flux in the real atmosphere the results here can apply only where internal heating is negligible the derivations given here build upon the prandtl batchelor theorem which applies to non rotating steady two dimensional flow supporting evidence is found in numerical circulation models and oceanic observations

geochemistry and possible origin of petroleum in palaeozoic reservoirs from halahatang depression abstract the halahatang depression in the tabei uplift of the tarim basin is an active exploration area because it has substantial reservoir potential and contains or is near to many commercial oil fields geochemical analysis indicates that halahatang oils were derived from marine carbonate source rocks deposited under anoxic reducing conditions the maturities for halahatang oils are corresponding to the peak of the oil window and slightly higher than the neighboring tahe oils the halahatang oils feature low pr ph c 21 c 23 tricyclic terpane and c 28 c 29 sterane ratios high c 29 c 30 hopane and c 35 c 34 hopane ratios a v shape in the distribution of c 27 c 28 c 29 steranes and light carbon isotope ratios similar to the tahe oils and correlate well with the middle upper ordovician source rock however some source related biomarker parameters imply a more reducing source organofacies with more zooplanktonic contribution than that for the tahe oils

the origin of the pacific equatorial 13 c water abstract examination of the vertical distributions of temperature salinity oxygen and nutrient salts in the thermostad of the equatorial 13 c water in the eastern pacific ocean indicates that local vertical mixing is unimportant in creating the thermostad and the characteristics of the 13 c water maps are presented that show the oceanwide distributions of depth geostrophic flow salinity oxygen phosphate silica and nitrate on the 160 cl t 1 isanosteric surface which nearly coincides with the core of the 13 c water the maps suggest that the original characteristics of the 13 c water are acquired in the surface and thermocline layers to the northeast of new zealand and in the tasman sea by winter convection and vertical mixing the acquired characteristics are advected to the thermostad in the eastern pacific via a long route starting from the source region the flow is first eastward in high latitudes and then returns westward in low latitudes around the anticyclonic subtropical gyre of the sout

bedload entrainment travel lengths step lengths rest periods studied with passive iron magnetic and active radio tracer techniques this paper reports results from bedload transport investigations with active radio and passive iron magnetic tracers in the lainbach a step pool mountain river in bavaria southern germany the spatial distributions of the iron tracers after flood events can be best described by exponential or gamma distributions there is some indication of a tendency of size selective transport of the iron tracers but there is also a considerable amount of scatter in the correlations between weight size and travel length owing to the masking influence of other variables such as the shape of the particles and different positions in the river bed the experiments with artificial magnetic tracers showed that elongated pebbles rods had the longest mean transport distance platy ones discs remained relatively close to the starting points the particles from the pool showed the greatest transport lengths and a 100 per cent chance of being eroded the pebble transmitter system petsy consists of transmitters implanted into individual pebbles a computerized receiver a stationary antenna system with an antenna switchboard and a data logging system the particles do not move continuously but in a series of transport steps and non movement intervals a single value for a given size class is not adequate to describe the critical conditions of entrainment under natural circumstances a probability approach is much more suitable the critical unit discharges total discharge divided by active channel width along the measuring reach are dependent on river bed morphology in the steps bedload needs higher unit discharges to be entrained once entrained the transport of bedload is stochastic in nature and the single particle transport is controlled by the step lengths and the duration of rest periods the distributions of both parameters can be approximated by exponential functions applying the stochastic concept proposed by einstein the mean values of the random variables step length and duration of rest period measured with the petsy technique were used for the simulation of spatial distributions of bedload particles from point sources more field and laboratory data are needed to include varying flow and roughness conditions with tracers representing different particle characteristics

maturity assessment of oils from the sakhalin oil fields in russia phenanthrene content as a tool a correlation analysis of maturation parameters was carried out on 14 crude oil samples from nine oil fields on sakhalin island russia the oils were taken from reservoir rocks of miocene age at depths ranging from 73 to 2841 m on the basis of gc analysis of the alkane fraction n alkanes and the isoprenoid alkanes pristane and phytane as well as on the basis of the abundance of demethylated hopanes gc ms analysis m z 177 it is assumed that the oils are either biodegraded or are a mixture of biodegraded and nonbiodegraded oils therefore their maturation is assessed on the basis of the distribution and abundance of tricyclic aromatic hydrocarbons that are more resistant to biodegradation than alkane type biological markers the oils may be classified into three groups on the basis of the well established maturation parameter mpi 3 highly mature group i moderately mature group ii and immature group iii the correlation analysis shows that the percentage of phenanthrene p in the tricyclic aromatic fraction of the oils of the sakhalin oil fields can be used as a maturation parameter the highly mature oils group i were found to have a p value of more than 14 the moderately mature oils group ii have values of 7 14 and the immature oils group iii a value of less than 7 the very good correlation between mpi 3 and p also indicates that parallel to methylphenanthrene isomerization dealkylation also occurs in the reservoir rocks by correlation analysis it is shown that these reactions are to a great extent determined by the depth of the reservoir rocks

generation of the north equatorial undercurrent jets by triad baroclinic rossby wave interactions abstractformation processes responsible for the north equatorial undercurrent neuc jets that appear across the tropical north pacific ocean near 9 13 and 18 n are explored both theoretically and using numerical models with different complexities analyses of an eddy resolving global ocean general circulation model output reveal that the neuc jets have a mode 1 baroclinic vertical structure and are spatially persistent on the interannual and longer time scales this ogcm simulated vertical structure prompts the authors to adopt the simpler nonlinear layer reduced gravity model as well as the baroclinic rossby wave triad interaction theory to unravel the essential processes underlying the neuc jets the seed for the neuc jets originates in annual baroclinic rossby waves driven by the large scale surface wind stress forcing emanating from the ocean basin s eastern boundary these wind forced primary waves are subject to nonlinear triad interactions and break down offshore where the e folding tim

an evaluation of shape indices as palaeoenvironmental indicators using quartzite and metavolcanic clasts in upper cretaceous to palaeogene beach river and submarine fan conglomerates

subthermocline and intermediate zonal currents in the tropical pacific ocean paths and vertical structure abstractthe mean subthermocline and intermediate zonal circulation in the tropical pacific is investigated using a compilation of shipboard adcp measurements and absolute geostrophic velocities constructed from a high resolution 0 2000 m argo climatology referenced to a 1000 m velocity field derived from argo float drifts this reference field is dominated by basinwide alternating zonal jets with a meridional wavelength of about 3 in regions where the sampling of sadcp data is sufficient the consistency between the two independent datasets is striking using the argo drift reference is crucial to capture the current structures two apparently distinct systems of alternating westward and eastward zonal jets are seen in both datasets equatorward of 10 a series of low latitude subthermocline currents llscs below the thermocline extending from about 200 to 800 m including the eastward tsuchiya jets and a series of low latitude intermediate currents llics extending from about 700 to at least 2000

movement of lithics by trampling an experiment in the madjedbebe sediments northern australia understanding post depositional movement of artefacts is vital to making reliable claims about the formation of archaeological deposits human trampling has long been recognised as a contributor to post depositional artefact displacement we investigate the degree to which artefact form shape and size attributes can predict how an artefact is moved by trampling we use the zingg classification system to describe artefact form our trampling substrate is the recently excavated archaeological deposits from madjedbebe northern australia madjedbebe is an important site because it contains early evidence of human activity in australia the age of artefacts at madjedbebe is contentious because of the possibility of artefacts moving due to trampling we trampled artefacts in madjedbebe sediments and measured their displacement as well as modelling the movement of artefacts by computer simulation artefact elongation is a significant predictor of horizontal distance moved by trampling and length width thickness and volume are significant predictors of the vertical distance the explanatory power of these artefact variables is small indicating that many other factors are also important in determining how an artefact moves during trampling our experiment indicates that trampling has not contributed to extensive downward displacement of artefacts at madjedbebe

quasi stationary north equatorial undercurrent jets across the tropical north pacific ocean 1 subthermocline circulation in the tropical north pacific ocean 2 n 30 n is investigated using profiling float temperature salinity data from the international argo and the origins of the kuroshio and mindanao current okmc projects three well defined eastward jets are detected beneath the wind driven westward flowing north equatorial current dubbed the north equatorial undercurrent neuc jets these subthermocline jets have a typical core velocity of 2 5 cms 1 and are spatially coherent from the western boundary to about 120 w across the north pacific basin centered around 9 n 13 n and 18 n in the western basin the neuc jet cores tend to migrate northward by 4 in the eastern basin vertically the cores of the southern central and northern neuc jets reside on the 26 9 27 2 and 27 3 surfaces respectively and they tend to shoal to lighter density surfaces by about 0 2 as the jets progress eastward

oxygen minimum zone in the north atlantic south and east of the cape verde islands the open ocean oxygen minimum zone omz south and east of the cape verde islands is studied from ctd hydrography adcp velocities argo float trajectories and historical data with a focus on the zonal supply and drainage paths the strongest oxygen minimum is located north of the north equatorial countercurrent necc at about 400 to 500 m depth just above the boundary between central water and antarctic intermediate water aaiw it is shown that the necc the north equatorial undercurrent at 4 to 6 n and a northern branch of the necc at 8 to 10 n are the sources for oxygen rich water supplied to the omz in summer and fall a weak eastward necc at 200 m depth also exists in winter and spring as derived from argo floats drifting at shallow levels historical oxygen data from 200 m depth confirm this seasonality showing high low oxygen content in summer and fall spring within the supply paths compared to the strong oxygen supply at 150 to 300 m depth the ventilation of the omz at 300 to 600 m depth is weaker westward drainage of oxygen poor water takes place north of the guinea dome i e north of 10 n most pronounced at 400 to 600 m depth in july 2006 the total eastward transport of both necc bands above 27 1 kg m 3 at 23 w was about 13 sv 1 sv 106 m3 s 1 about half of this water volume circulates within the guinea dome or recirculates westward north of the guinea dome

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

studies on settling traction and entrainment of larger benthic foraminiferal tests implications for accumulation in shallow marine sediments settling and traction velocities were measured on optimally preserved tests of larger foraminifera using a settling tube and flume tank within larger foraminifera with porcelaneous tests the peneroplids peneroplis antillarum p planatus p pertusus and dendritina cf d zhengae are distinguished by low test densities ca 1 2 that do not change with growth buoyancy is high because of low reynolds numbers and increases in large individuals because of the allometric change of test shape the fusiform alveolinella quoyi with test densities ca 1 6 is characterized by high reynolds numbers inducing the weakest buoyancy within porcelaneous larger foraminifera the highest buoyancy was recorded for the three soritids parasorites orbitolitoides sorites orbiculus and amphisorus hemprichii because of their low test densities ca 1 25 and the extremely flat biconcave plate like shape flat tests however reduce traction and entrainment from smooth surfaces within hyaline larger foraminiferat the amphisteginids show thick lenticular amphistegina lobifera a radiata to thin lenticular tests a bicirculata a papillosa influencing buoyancy here high test densities ca 1 8 decrease with growth in a lobifera a lessonii and a bicirculata and remain constant in a radiata and a papillosa minimum velocities required for entrainment are lower for thick lenticular tests and higher for thin lenticular tests test densities remain constant with growth in the calcarinid baculogypsina sphaerulata 1 78 and decrease slightly in calcarina gaudichaudii and neorotalia calcar starting at 1 85 all living under extreme hydrodynamic conditions density decreases the most in baculogypsinoides spinosus starting at 1 8 resulting in higher buoyancy through low reynolds numbers traction is promoted in spherical tests of baculogypsina and baculogypsinoides within nummulitids the thick lenticular palaeonummulites venosus test density decreasing with size starting at 1 78 is less buoyant expressed in high reynolds numbers but easily entrained thick lenticular juveniles and extremely flat adults distinguish operculinella cumingii heterostegina depressa and the giant cycloclypeus carpenteri test densities increase during growth starting from ca 1 6 and attaining a maximum of 1 8 buoyancy is low in small tests and high in large tests while entrainment velocities are reduced as the tests flatten high buoyancy is also a characteristic of the entirely flat tests in operculina ammonoides from deeper regions and planostegina operculinoides which is expressed in the lowest reynolds numbers within larger foraminifera

intermediate zonal jets in the tropical pacific ocean observed by argo floats abstractargo float data in the tropical pacific ocean during january 2003 august 2011 are analyzed to obtain lagrangian subsurface velocities at their parking depths maps of mean zonal velocities at 1000 and 1500 m are presented at both depths a series of alternating westward and eastward zonal jets with a meridional scale of 1 5 is seen at the basin scale from 10 s to 10 n these alternating jets with mean speeds about 5 cm s 1 are clearly present in the western and central parts of the basin but weaken and disappear approaching the eastern coast they are stronger in the southern hemisphere along the equator at both 1000 and 1500 m a westward jet is seen the jets closer to the equator are remarkably zonally coherent across the basin but the jets farther poleward appear broken in several segments in the western half of the basin the 1000 m zonal jets appear to slant slightly poleward from east to west at the western boundary in the south east of solomon islands and papua new guinea the al

radio tracking gravel particles in a large braided river in new zealand a field test of the stochastic theory of bed load transport proposed by einstein hans a einstein initiated a probabilistic approach to modelling sediment transport in rivers his formulae were based on theory and were stimulated by laboratory investigations the theory assumes that bed load movement occurs in individual steps of rolling sliding or saltation and rest periods so far very few attempts have been made to measure stochastic elements in nature for the first time this paper presents results of radio tracing the travel path of individual particles in a large braided gravel bed river the waimakariri river of new zealand as proposed by einstein it was found that rest periods can be modelled by an exponential distribution but particle step lengths are better represented by a gamma distribution einstein assumed an average travel distance of 100 grain diameters for any bed load particle between consecutive points of deposition but larger values of 6 7 m or 150 grain diameters and 6 1 m or 120 grain diameters were measured for two test particle sizes together with other available large scale field data a dependence of the mean step length on particle diameter relative to the d50 of the bed surface was found during small floods the time used for movement represents only 2 7 of the total time from erosion to deposition the increase in percentage of time being used for transport means that it then has to be regarded in stochastic transport models tracing the flow path of bed load particles between erosion and deposition sites is a step towards explaining the interactions between sediment transport and river morphology copyright 2001 john wiley sons ltd

rare earth element input and transport in the near surface zonal current system of the tropical western pacific abstract continental sources and current transport play a major role in rare earth element ree and other trace element input and distribution in the tropical western pacific here we present spatially highly resolved distributions of dissolved ree concentrations ree along three transects in the zonal extra equatorial current system and the solomon strait of the tropical western pacific we use seawater ree in combination with direct physical oceanographic observations e g current velocity data to characterize the geochemical composition origin and pathways of the complex surface and upper layer currents of the tropical western pacific and to quantify the input fluxes of rees we identify papua new guinea png volcanic rocks sediments and or river particles as the key source adding trace elements to the equatorial eastward zonal currents of the tropical western pacific our and published data indicate temporal and spatial variability of this input and transport in the png source area and the equatorial eastward currents the westward currents on the other hand lack this ree input signal suggesting lateral transport of preformed seawater ree at the transition between these zonal eastward and westward currents our data indicate lateral mixing of eastern and western pacific source waters

three dimensional dynamics of the subsurface countercurrents and equatorial thermostad part ii influence of the large scale ventilation and of equatorial winds sensitivity tests are performed to assess the respective influences of the large scale ventilation and of the near equatorial winds on the dynamics of the the subsurface countercurrents sccs and thermostad they show that the intensity of the inertial jets is a function of the potential vorticity pv values at subduction and that stronger jets are favored by low pv injection forced in the authors framework either by a deep mixed layer at subduction and or by an injection of pv at lower latitudes such circumstances lead to a strong meridional shoaling of the thermocline near the equator the resulting inertial jets occur at about 3 8n in the western part of the basin and are the poleward limit of a near 0 pv region and of an equatorial thermostad a necessary condition for the existence of inertial jets is that the equatorial wind fetch is large enough otherwise only weak time mean eastward currents are produced by a nonlinear rectification of instability waves farther away from the equator the presence of a north equatorial countercurrent does not constitute a barrier for equatorward motions within the lower thermocline and inertial jets are still controlled by the meridional slope of the sscs layer setup through the establishment of tropical pv pools predicted by ventilation theory

aeolian silt transport processes as fingerprinted by dynamic image analysis of the grain size and shape characteristics of chinese loess and red clay deposits abstract this study applied dynamic image analysis dia sympatec qicpic to characterize the grain size and shape of chinese aeolian sediments in order to fingerprint their transportation processes this is the first time this technique has been applied to late neogene and quaternary silt particles 2 63 m from the chinese loess plateau clp we selected four well studied quaternary loess palaeosol sequences along a north south transect across the clp and compared their grain size distribution obtained by dia with that yielded by laser diffraction particle size analysis ld fritsch analysette 22 and sympatec helos kr this comparison demonstrated that dia is successfully able to differentiate loess units from palaeosols and to characterize clearly spatiotemporal variations in the grain size records of loess palaeosol sequences formed during the last two glacial and interglacial periods this is consistent with grain size results obtained using ld dia is also able to characterize spatial variations in the more fine grained aeolian red clay deposits underlying the quaternary loess and allows the quantification of the fluvial contribution to red clay sequences dia of the characteristics of grain shapes in loess palaeosol sequences and red clay deposits revealed a systematic pattern whereby the aspect ratio decreased with increasing grain size indicating that systematic shape sorting occurred during the aeolian transportation of these dust particles it could be inferred from our study that particles in a certain grain size range correspond to a specific aspect ratio range and may in turn be aerodynamically distinguishable from each other and further correlated with the wind velocity strength also evident from analysis of our dia data was a subtle but systematic downwind decrease in the aspect ratio of the particles in the loess units this observation suggests that elongated and or flat particles with a low aspect ratio were transported further downwind than more symmetrically shaped particles with a high aspect ratio this study indicates that dia of grain size and shape characteristics can be an additional powerful tool for identifying grain size and shape sorting trends determining the dominant mode of transport and reconstructing transport pathways of silt sized aeolian sediments

upper and intermediate circulation in the western equatorial pacific ocean in october 1999 and april 2000 1 the upper and intermediate circulation 0 1200 m in the western equatorial pacific ocean is examined thanks to lowered acoustic doppler current profiler ladcp measurements carried out during two cruises in october 1999 and april 2000 several new features of the equatorial circulation are discussed it is shown that the secondary south subsurface countercurrent ssscc laying at 6 s 400 m depth had a deep extension at 165 e with a maximum core velocity around 5 s 1000 m furthermore the equatorial intermediate current eic and the lower eic leic displayed a strong temporal variability between 165 e and 180 as these two westward currents were replaced by eastward flow along the equator on the second cruise finally during the april 2000 cruise the zonal velocity profile carried out at the equator east of the gilbert island around 175 e broke into small vertical scales possibly reflecting topographic effect and or destabilization mechanism that leads to the formation of long zonal jet like structures

basin wavelength equatorial deep jet signals across three oceans equatorial deep jets edjs are equatorially trapped stacked zonal currents that reverse direction every few hundred meters in depth throughout much of the water column this study evaluates their structure observationally in all three oceans using new high vertical resolution argo float conductivity temperature depth ctd instrument profiles from 2010 to 2014 augmented with historical shipboard ctd data from 1972 to 2014 and lower vertical resolution argo float profiles from 2007 to 2014 the vertical strain of density is calculated from the profiles and analyzed in a stretched vertical coordinate system determined from the mean vertical density structure the power spectra of vertical strain in each basin are analyzed using wavelet decomposition in the indian and pacific oceans there are two distinct peaks in the power spectra one kelvin wave like and the other entirely consistent with the dispersion relation of a linear first meridional mode equatorial rossby wave in the atlantic ocean the first meridional mode rossby wave signature is very strong and dominates in all three ocean basins rossby wave like signatures are coherent across the basin width and appear to have wavelengths the scale of the basin width with periods of about 5 yr in the indian and atlantic oceans and about 12 yr in the pacific ocean their observed meridional scales are about 1 5 times the linear theoretical values their phase propagation is downward with time implying upward energy propagation if linear wave dynamics hold

environmental influence on the biohopanoid composition of recent sediments abstract bacteriohopanepolyols are the biological precursors of extended hopane biomarkers which are ubiquitous in the geosphere the abundance and composition of these biohopanoids were determined for modern sediments from eight depositional environments by gc ms analysis of hopanols derived from a side chain cleavage reaction periodic acid and sodium borohydride of the bacteriohopanepolyols we report quantitative data for bacteriohopanetetrol bht composite tetrafunctionalised biohopanoids pentafunctionalised biohopanoids and hexafunctionalised biohopanoids bht was found in concentrations higher than previously reported up to ca 1500 g g toc but comprised only a relatively small proportion 0 26 of the total biohopanoids in all except one sample composite tetrafunctionalised biohopanoids were the dominant group of bacteriohopanepolyols in all other sediments and are likely to be a major source of the geologically occurring extended hopanes hexafunctionalised biohopanoids were most abundant in lake sediments particularly two small highly productive stratified lakes where they comprised 20 40 of total biohopanoids this feature is interpreted to be due to greater contribution to the organic matter of these sediments from type i methanotrophic bacteria which produce dominantly hexafunctionalised biohopanoids consistent with the environmental settings in the marine environments where sulphate reduction is dominant hexafunctionalised biohopanoids are relatively minor constituents 2 6 of total biohopanoids these data comprise the first clear demonstration that bacteriohopanepolyols vary in composition between depositional environments and have the potential to preserve specific bacterial source information in sedimentary organic matter

eastern pacific oxygen minimum zones supply paths and multidecadal changes the supply of oxygen rich water to the oxygen minimum zones omzs of the eastern north and south pacific via zonal tropical currents is investigated using shipboard acoustic doppler current profiler and hydrographic section data near the equator the equatorial undercurrent euc northern and southern subsurface countercurrents sccs and the northern and southern intermediate countercurrents iccs all carry water that is oxygen richer than adjacent westward flows thereby providing a net oxygen supply to the eastern pacific omzs the synoptic velocity weighted oxygen concentration difference between eastward and westward flows is typically 10 50 mol kg 1 subthermocline zonal oxygen fluxes reflect decreasing oxygen concentrations of the euc the sccs and the iccs as they flow eastward approximately 30 year time series in well sampled regions of the equatorial pacific show oxygen content decreasing as rapidly as 0 55 mol kg 1 yr 1 in the major oxygen supply paths of the omzs for a 200 700 m layer and similar trends for a density layer spanning roughly these depths this finding is in gross agreement with climate models which generally predict expanding omzs

geochemistry of petroleum systems in the niuzhuang south slope of bohai bay basin part 2 evidence for significant contribution of mature source rocks to immature oils in the bamianhe field the chemical compositions of 28 representative crude oils and oil sand samples collected from the bamianhe region of the bohai bay basin eastern china were studied in detail in order to understand their genetic relationships biodegradation ranking and thermal maturity level molecular geochemical parameters indicate the presence of one single oil family in the cenozoic reservoirs a number of biomarker features support deposition of the source rocks for these oils under conditions of enhanced salinity stratified water columns the extremely low maturity levels of these immature oils as indicated by sterane isomerization ratios were not supported by other maturity parameters the genetic relationship between the oils and the es4 and es3 members of the eocene oligocene shahejie formation present in the deeper part of the niuzhuang sag but not those along the niuzhuang south slope was suggested using a wide range of molecular parameters variation in the sterane concentrations observed from potential source rocks with different maturity levels in the study area suggests a high probability of migration contamination of mature oils by immature bitumens along migration pathways or from intra reservoir shales variation in the level of oil biodegradation could also create anomalies in the use of gross oil compositions as an indicator of oil maturity although the recent rapid subsidence of the bohai bay basin and the saline depositional environment of one of the potential source rocks favor oil generation at relatively low maturity levels most of the economic oils discovered in the bamianhe region appear to have derived from conventionally mature source rocks but contain lower maturity fluids admixed with them

seasonal patterns of coarse sediment transport on a mixed sand and gravel beach due to vessel wakes wind waves and tidal currents direct measurements of coarse sediment gravel transport are presented and analyzed from a mixed sand and gravel beach on bainbridge island puget sound wa that is exposed to wind waves vessel wakes and tidal currents in order to quantify the relative role of different forcing mechanisms and the corresponding time scales of morphological response radio frequency identification rfid passive integrated transponder pit technology is implemented in two coincident yearlong tracking studies of sediment particles and complemented with beach profile surveys and meteorological and hydrodynamic measurements the sampling of the gravel tracers provides sufficient resolution to reveal the dominant seasonal transport patterns which include a range of wave climates during winter storms the predominant transport is due to wind waves in an alongshore uni directional process whereas tides and wakes play a relatively minor role in non storm intervals transport is brought about by the combination of vessel wakes and tidal currents although tidal currents are not sufficient to initiate sediment movement alone the combination of tidal currents and vessel wakes generate significant transport and provide a mechanism for post storm recovery re distributing sediment onshore morphologic response occurs as a seasonal fluctuation of the upper beach profile from steep to flat and in sediment composition from gravel to coarse sand between non storm and storm conditions respectively these results which are unique in their duration suggest that mixed sand and gravel beaches experience different modes of behavior over the range of forcing conditions observed during a typical year they point to the need for including grain composition in modeling mixed sand and gravel beach response and the need for long term observations of both forcing and response

temporal and spatial structure of the equatorial deep jets in the pacific ocean abstract the spatial and temporal structure of the equatorial deep jets edjs in the pacific ocean is investigated using ctd station data taken on the equator from 1979 through 2001 the edjs are revealed in profiles of vertical strain z estimated from the ctd data in a stretched vertical coordinate system the majority of synoptic meridional sections were occupied over an 8 yr span west of the date line two decade equatorial time series are available at both 110 w and 140 w analysis shows the expected equatorial trapping of z but yields little new detailed information about the edj meridional structure analysis of the equatorial data yields novel results the edjs are most easily seen in the eastern pacific at and east of 140 w there they may be isolated from the influence of higher frequency rossby waves generated by surface forcing spectral analysis of equatorial z profiles shows a significant and coherent peak at 400 sdbar vertical wavelength with no 1 56 10 3 s 1 from 95 w to 142

results from a velocity transect along the equator from 125 to 159 w abstract during march april 1980 a velocity and ctd transect was made in the pacific along the equator from 110 to 180 w the horizontal baroclinic pressure gradient was observed to be primary confined between 160 and 130 w direct velocity profiles between 125 and 159 w showed the equatorial undercurrent to be a continuous feature maximum eastward transport per unit width in the undercurrent was 2 5 108 cm2 s 1 at 150 w and decreased both westward and eastward to about 1 5 108 cm2 s 1 at 159 w and at 125 w despite these variations the maximum speeds along the transect remained 150 cm s 1 beneath the undercurrent the velocities decreased and were of the order of 25 cm s 1 they exhibited small scale variation in the vertical as has recently been observed at other equatorial locations above 1600 m the vertical wavelength of these variations in the zonal component was 300 m small scale features in these zonal velocities were identifiable over 10 of longitude 1000 km the small vertical an

an evaluation of shape indices as palaeoenvironmental indicators using quartzite and metavolcanic clasts in upper cretaceous to palaeogene beach river and submarine fan conglomerates the feasibility of using quantitative shape measurements to discriminate between clast populations from different depositional settings was evaluated using samples from 11 fluvial six submarine fan and four beach conglomerates from south west california these origins had been established previously by facies analysis quartzite and metavolcanic clasts were characterized by the following indices modified wentworth roundness rw maximum projection sphericity p oblate prolate index opi and long l intermediate i and short s axial ratios these indices were compared with those documented previously for modern gravels the results show that certain indices are useful palaeoenvironmental indicators despite inherited differences in shape due to texture provided that multiple sites are sampled and a statistical approach is used statistically the most effective shape indices are p and s l which give good results with the zingg classification i l vs s i better results are also obtained using quartzite clasts the opi is useful for discriminating between beach and river conglomerates which consist largely of oblate and prolate clasts respectively the relative abundance of blade shaped clasts is a useful index of sediment maturity being greatest for river clast samples and smallest for submarine fan clast samples the latter are dominated by spherical particles no correlation between palaeoenvironment and rw is observed hence the abundance of disc shaped clasts in the beach conglomerates studied is attributed to selective transport in suspension and sediment by passing during fluvial transport prior to deposition in the surf zone selective transport of rollers spheres and rods by traction in a shallow marine setting prior to redeposition by mass transport may be responsible for the dominance of spherical particles in submarine fan conglomerates

oxygen minimum zones in the eastern tropical atlantic and pacific oceans within the eastern tropical oceans of the atlantic and pacific basin vast oxygen minimum zones omz exist in the depth range between 100 and 900 m minimum oxygen values are reached at 300 500 m depth which in the eastern pacific become suboxic dissolved oxygen content 4 5 mol kg 1 with dissolved oxygen concentration of less than 1 mol kg 1 the omz of the eastern atlantic is not suboxic and has relatively high oxygen minimum values of about 17 mol kg 1 in the south atlantic and more than 40 mol kg 1 in the north atlantic about 20 40 of the north pacific volume is occupied by an omz when using 45 mol kg 1 or 90 mol kg 1 respectively as an upper bound for omz oxygen concentration for ocean densities lighter than 27 2 kg m 3 the relative volumes reduce to less than half for the south pacific 7 and 13 respectively the abundance of omzs are considerably smaller 1 and 7 for the south atlantic and only 0 and 5 for the north atlantic thermal domes characterized by upward displacements of isotherms located in the northeastern pacific and atlantic and in the southeastern atlantic are co located with the centres of the omzs they seem not to be directly involved in the generation of the omzs omzs are a consequence of a combination of weak ocean ventilation which supplies oxygen and respiration which consumes oxygen oxygen consumption can be approximated by the apparent oxygen utilization aou however aou scaled with an appropriate consumption rate aour gives a time the oxygen age here we derive oxygen ages using climatological aou data and an empirical estimate of aour averaging oxygen ages for main thermocline isopycnals of the atlantic and pacific ocean exhibit an exponential increase with density without an obvious signature of the omzs oxygen supply originates from a surface outcrop area and can also be approximated by the turn over time the ratio of ocean volume to ventilating flux the turn over time corresponds well to the average oxygen ages for the well ventilated waters however in the density ranges of the suboxic omzs the turn over time substantially increases this indicates that reduced ventilation in the outcrop is directly related to the existence of suboxic omzs but they are not obviously related to enhanced consumption indicated by the oxygen ages the turn over time suggests that the lower thermocline of the north atlantic would be suboxic but at present this is compensated by the import of water from the well ventilated south atlantic the turn over time approach itself is independent of details of ocean transport pathways instead the geographical location of the omz is to first order determined by i the patterns of upwelling either through ekman or equatorial divergence ii the regions of general sluggish horizontal transport at the eastern boundaries and iii to a lesser extent to regions with high productivity as indicated through ocean colour data

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

sediment transport processes in pool riffle sequences this paper reviews the published data for sediment transport in pool riffle sequences which suggests that a velocity or shear stress reversal hypothesis does not explain all of the published evidence of sediment transport this conclusion is explored in more detail using observations of sediment transport from the regulated river north tyne sediment transport rates at discharges of 30 per cent bankfull are initially highest on riffles as discharge increases sediment transport rates in pools rise sharply and values locally exceed those on riffles tracing experiments using a combination of magnetic and painted tracers are used to show the downstream dispersal of fine and coarse sediments through the pool riffle sequence coarser particles experience longer transport paths and faster virtual rates of travel in pools during bankfull floods analysis of entrainment data reveals evidence for additional restraint operating on riffles and causing higher dimensionless entrainment thresholds an appraisal of the possible mechanisms controlling sediment entrainment transport and deposition in pool riffle sequences is made which reveals evidence for the operation of a combination of hydraulic sedimentological and interactive processes a descriptive model of sediment transport processes in pool riffle sequences is presented

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

interannual variability of the subsurface high salinity tongue south of the equator at 165 e abstract a 14 yr time series of salinity at thermocline level was constructed from repeated meridional ctd sections averaging about 110 days apart spanning the equator along 165 e during 1984 97 a tongue of high salinity water extends along the isopycnal t 24 5 from its surface outcrop in the southeast pacific to 175 m depth near 5 10 s along the section at 165 e in the west the tongue moves vertically with the thermocline mostly as part of the enso cycle while salinity in the tongue varied interannually over a range of 0 4 psu most of this variability was due to zonal advection along the isopycnal tongue with similar changes observed at other longitudes in the west and central pacific part of the interannual salinity signal can be attributed to changes in the near zonal flow of the south equatorial current associated with el nino but a general 0 3 psu rise occurring during the 1990s probably starting even earlier was not apparently consistent with this explanation an attempt was made to

ventilation of the equatorial atlantic by the equatorial deep jets equatorial deep jets edjs are a prominent flow feature of the equatorial atlantic below the equatorial undercurrent down to about 3000 m here we analyze long term moored velocity and oxygen observations as well as shipboard hydrographic and current sections acquired along 23 degree sign w and covering the depth range of the oxygen minimum zones of the eastern tropical north and south atlantic the moored zonal velocity data show high baroclinic mode edj oscillations at a period of about 4 5 years equatorial oxygen observations which do not resolve or cover a full 4 5 yr edj cycle nevertheless reveal large variability with oxygen concentrations locally spanning a range of more than 60 mol kg 1 we study the effect of edjs on the equatorial oxygen concentration by forcing an advection diffusion model with the velocity field of the gravest equatorial basin mode corresponding to the observed edj cycle the advection diffusion model includes an oxygen source at the western boundary and oxygen consumption elsewhere the model produces a 4 5 yr cycle of the oxygen concentration and a temporal phase difference between oxygen concentration and eastward velocity that is less than quadrature implying a net eastward oxygen flux the comparison of available observations and basin mode simulations indicates that a substantial part of the observed oxygen variability at the equator can be explained by edj oscillations the respective role of mean advection edjs and other possible processes in shaping the mean oxygen distribution of the equatorial atlantic at intermediate depth is discussed key points equatorial deep jets strongly affect oxygen distribution variability mean oxygen ditribution in the equatorial atlantic at intermediate depth gravest equatorial basin mode forces an advection diffusion model

assessing automated image analysis of sand grain shape to identify sedimentary facies gran dolina archaeological site burgos spain abstract gran dolina is a cave sierra de atapuerca spain infilled by a 25 m thick sedimentary record divided into 12 lithostratigraphic units that have been separated into 19 sedimentary facies containing early and middle pleistocene hominin remains in this paper an automated image analysis method has been used to study the shape of the sedimentary particles since particle shape is interpreted as the result of sedimentary transport and sediment source this study can provide valuable data about the sedimentological mechanism of sequence formation the shape of the sand fraction in 73 samples from gran dolina site and sierra de atapuerca was analyzed using the malvern morphologi g3 an advanced particle characterization tool in this first complete test we used this method to the published sequence of gran dolina defined previously through field work observations and geochemical and textural analysis the results indicate that this image analysis method allows differentiation of the sedimentary facies providing objective tools to identify weathered layers and measure the textural maturity of the sediments channel facies have the highest values of circularity and convexity showing the highest textural maturity of particles on the other hand terra rossa and debris flow samples show similar values with the lowest particle maturity

estimation of the kinetics of geochemical reactions with geophysical models of sedimentary basins and applications abstract the configurational isomerisation and aromatisation reactions which affect the steroid and triterpenoid hydrocarbons present in most organic rich sedimentary rocks are good indicators of the thermal histories of these rocks the extents to which these reactions have occurred can be assessed by gas chromatography mass spectrometry analysis of the organic extracts of the sediment samples we have assumed the reactions can be described as first order and used the model of sedimentary basin formation by extension of the lithosphere to provide thermal histories for the integration of the relevant arrhenius and rate equations governing the reaction rates the activation energies and frequency factors of the reactions were derived by comparing the reaction extents predicted by the model with geochemical observations from basins northern north sea and pannonian basin formed by lithospheric extension which have not experienced major uplift these values were then used to test the thermal consequences of the lithospheric stretching model for nova scotian continental shelf to calculate the amount of uplift and erosion experienced by lower jurassic sediments in the paris and lower saxony basins and the geographical variation in heat flow in a sedimentary basin formed by lithospheric flexure in the foreland basin of alberta in all cases the figures so calculated appear geologically reasonable and receive support from other independent techniques for their estimation the calculated activation energies of all reactions and the frequency factor for aromatisation are chemically sensible the relative values of the frequency factors for the isomerisation reactions could be expected the more sterically hindered c 20 site in a sterane has a lower frequency factor than that for isomerisation at the less hindered c 22 site in hopanes however both values are very low 0 006 and 0 016 s 1 respectively for the back reactions and imply an entropy change of 282 and 271 j mol 1 c 1 respectively the transition states are therefore much more ordered than the reactants this could be the case if catalysis was important no significant variation in catalytic activity can yet be demonstrated in the rocks investigated here

annual reversal of the equatorial intermediate current in the pacific observations and model diagnostics abstract a large reversal of zonal transport below the thermocline was observed over a period of 6 months in the western pacific ocean between 2 s and the equator from 26 2 sv 1 sv 106 m3 s 1 eastward in october 1999 to 28 6 sv westward in april 2000 to document this reversal and assess its origin an unprecedented collection of adcp observations of zonal currents 2004 06 together with a realistic ogcm simulation of the tropical pacific was analyzed the results of this study indicate that this reversal is the signature of intense annual variability in the subsurface zonal circulation at the equator at the level of the equatorial intermediate current eic and the lower equatorial intermediate current l eic in this study the eic and the l eic are both shown to reverse seasonally to eastward currents in boreal spring and winter for the l eic over a large depth range extending from 300 m to at least 1200 m the peak to peak amplitude of the annual cycle of subthermocline zonal currents at

secondary alteration of ancient shuntuoguole oil reservoirs tarim basin nw china abstract multiple tectonic movements and charge episodes have occurred in the tazhong uplift of the tarim basin nw china contributing to widespread solid bitumen heavy oil normal oil condensate and gas in the shuntuoguole high especially in the lower silurian kepingtage formation a detailed investigation of cores and fluid inclusions from different intervals i e s1k3 3 s1k3 1 s1k1 has been carried out using petrographic analysis gas chromatograph mass spectrometry and micro fourier transform infrared spectroscopy three hydrocarbon charge events in the kepingtage formation have been recognized associated with the late caledonian late hercynian and himalayan orogenies in the late caledonian oils were charged into the s1k3 3 s1k3 1 and s1k1 intervals but evolved to solid bitumen due to biodegradation and water washing as the silurian strata have experienced both strong uplift and erosion during the early hercynian orogeny and the influence of igneous intrusions during the permian hydrocarbons associated with the caledonian contain no regular steranes diasteranes hopanes or extended tricyclic terpanes due to in reservoir thermal cracking the second charge period occurred in the late hercynian which has experienced severe biodegradation and water washing hydrocarbons of this period are characterized by an obvious chromatographic hump of the unresolved complex mixture ucm coupled with petroleum inclusions that fluoresce light blue and yellow possibly indicating variable maturity whether or not high maturity oil charged during this period into the s1k1 interval has commercial production value needs further investigation the third change occurred during the himalayan orogeny highly mature hydrocarbons were emplaced into the s1k3 3 s1k3 1 and s1k1 intervals with the s1k1 interval as being the most significant biodegradation water washing and igneous intrusion had no impact on hydrocarbons charged during this period resulting in higher potential for economic production

deep currents and their interpretation as equatorial waves in the western pacific ocean abstract vertical profiles of current and density made within 5 latitude of the equator along longitudes 168 and 179 e the vicinity of the gilbert islands reveal multiple deep current reversals which are confined to the equator these current jets have amplitudes of roughly 5 20 cm s 1 vertical scales of order hundreds of meters and time scales longer than the one month of measurements during the cruise spectral analysis of profiles indicates that 1 meridional trapping varies roughly as the square root of the vertical scale 2 both east and north currents are coherent over meridional separations of 0 45 within roughly 1 30 of the equator and 3 zonal current lags vertical displacement by 4 in depth within 0 45 of the equator zonal coherence scales are smaller than the smallest separation of 3 30 along the equator kinetic energy decreases near the island chain current meter records taken over nearly two years near the islands suggest strong quasi annual variability in deep currents near t

the ocean general circulation near 1000 m depth abstractthe mean ocean circulation near 1000 m depth is estimated with 100 km resolution from the argo float displacements collected before 1 january 2010 after a thorough validation the 400 000 or so displacements found in the 950 1150 dbar layer and with parking times between 4 and 17 days allow the currents to be mapped at intermediate depths with unprecedented details the antarctic circumpolar current acc is the most prominent feature but western boundary currents and their recirculations and alternating zonal jets in the tropical atlantic and pacific are also well defined eddy kinetic energy eke gives the mesoscale variability on the order of 10 cm2 s 2 in the interior which is compared to the surface geostrophic altimetric eke showing e folding depths greater than 700 m in the acc and northern subpolar regions assuming planetary geostrophy the geopotential height of the 1000 dbar isobar is estimated to obtain an absolute and deep reference level worldwide this is done by solving num

water masses and currents in the upper tropical northeast atlantic off northwest africa recent current measurements in the tropical eastern north atlantic reproduce the components of the large scale flow field however the observations as well as the 1 12 flame model computations indicate that a lot of eddy scale variability is superimposed on the mean flow field despite of the disturbance by variability the signature of the guinea dome is well present in november 2002 the guinea dome transport from direct observations was about 2 8 sv above 25 8 kg m3 and 4 sv between 25 8 and 27 1 kg m3 the oxygen minimum in the shadow zone comprises the central water and the antarctic intermediate water aaiw layers and is located between the equatorial current system and the north equatorial current the north equatorial counter and undercurrents at 3 to 6 n are major oxygen sources for the central water layer of the low oxygen regions in the northeastern tropical atlantic a second northern north equatorial countercurrent nnecc band exists at 8 to 10 n the nnecc carries oxygen rich water from the southern hemisphere eastward but with an admixture of water from the northern hemisphere a float at 200 m depth was spreading eastward in the north equatorial undercurrent neuc at 28 w it shifted northward into the nnecc and then was trapped in the guinea dome region for more than 3 years the model indicates the region 22 to 32 w as the area of exchange between the necc neuc and the nnecc bands in the aaiw layer the northern intermediate countercurrent acts as oxygen source for the oxygen minimum zone

monitoring the 1979 1985 equatorial pacific current transports with expendable bathythermograph data geostrophic transports of the major equatorial currents including the equatorial undercurrent and the south equatorial current have been estimated on a bimonthly basis in the central and western pacific over the 1979 1985 period this was made possible by a collection of carefully checked expendable bathythermograph xbt data and a few hydrocast and conductivity temperature depth data this collection considerably improved the number and quality of temperature profiles of the original institut francais de recherche scientifique pour le developpement en cooperation orstom scripps institute of oceanography tropical pacific xbt ship of opportunity program the temperature profiles were first grouped independently of longitude in regions around mean xbt tracks dynamic heights were then calculated relative to 400 db through a t s relationship deduced from the climatological levitus file geostrophic currents were calculated along the roughly south north oriented fiji hawaii and new caledonia japan mean xbt tracks using a specific technique this technique which combines fourier filtering in the meridional direction and in time also ensures the continuity across the equator between geostrophic currents deduced from the first and second derivatives of the meridional pressure field the filter coefficients in the meridional direction were determined through an adjustment of geostrophic currents to directly measured currents using the mean of data collected along 165 e during six tropical ocean and global atmosphere toga orstom cruises finally transports of the main equatorial currents were computed in a subjective way between 20 n and 20 s 0 400 m using monthly charts of geostrophic currents along the two mean xbt tracks the transports in the central pacific were compared to the transports derived from the semicontinuous direct current measurements taken during the hawaii tahiti shuttle experiment in 1979 1980 and during the line island profiling project pacific equatorial ocean dynamics experiment in 1982 1983 reasonable agreement demonstrates that it is possible to use xbt data for transport indexes of the major equatorial currents in the central and western pacific

number of tracers required for the measurement of longshore transport distance on a shingle beach the aim of this study was to identify a method for determining the number of tracer particles required to define the mean longshore transport distance of indigenous littoral shingle with a particular level of precision a method is presented which can be applied to existing tracer data to determine both the precision of the measurements collected and the number of tracers required to achieve a particular level of precision the method which utilises well established statistical relationships is demonstrated by applying it to archive tracer data the study demonstrates the sensitivity of the number of tracers to the variance of the transport distances of indigenous particles at the site and the precision with which the investigator wishes to define the mean it is anticipated that application of the method by other practitioners in the future will allow a dataset to develop which can be used alongside the method presented here to allow the number of tracers required for a study to be estimated prior to entering the field results are presented to initiate the development of this dataset and a look up chart derived using the method is given to aid its application

channel flow competence and sediment transport in upland streams in southeast australia bedload transport data from planebed and step pool reach types are used to determine grain size transport thresholds for selected upland streams in southeast australia morphological differences between the reach types allow the effects of frictional losses from bedforms microtopography and bed packing to be incorporated into the dimensionless critical shear stress value local sediment transport data are also included in a regime model and applied to mountain streams to investigate whether empirical data improve the delineation of reach types on the basis of dimensionless discharge per unit width q and dimensionless bedload transport q b instrumented planebed and step pool sites are not competent to transport surface median grains d50s at bankfull discharge qbf application of a locally parametrized entrainment equation to the full range of reach types in the study area indicates that the majority of cascades cascade pools step pools and planebeds are also not competent at qbf and require a 10 year recurrence interval flood to mobilize their d50s consequently the hydraulic parameters of the regime diagram which assume equilibrium conditions at bankfull are ill suited to these streams and provide a poor basis of channel delineation modifying the diagram to better reflect the dominant transported bedload size equivalent to the d16 of surface sediment made only slight improvements to reach delineation and had greatest effect on the morphologies with smaller surface grain sizes such as forced pool riffles and planebeds likewise the corey shape factor was incorporated into the regime diagram as an objective method for adjusting a base dimensionless critical shear stress c50b to account for lithologically controlled grain shape on bed packing and entrainment however it too provided only minor adjustments to reach type delineation

three dimensional dynamics of the subsurface countercurrents and equatorial thermostad part i formulation of the problem and generic properties a fully three dimensional primitive equation simulation is performed to reunite the local equatorial dynamics of the subsurface countercurrents sccs and thermostad with the large scale tropical ventilated ocean dynamics it captures i the main characteristics of the equatorial thermostad the sccs location and their eastward evolution and the potential vorticity budget with its equatorial homogenization to zero values and ii the largescale meridional shoaling of the thermocline equatorward it supports the idea that the two dimensional hadley cell mechanism proposed by marin et al is a candidate able to operate in a fully three dimensional ocean the main difference between the 2d hadley cell mechanism and the oceanic 3d case is that for the 3d case the large scale meridional velocity at zeroth order is geostrophic while the cell mechanism is a next order smallscale mechanism a detailed budget of the zonal momentum equation is provided for the ageostrophic dynamics at work in the sccs the mean meridional advection and the coriolis term dominate discounting the possibility that lateral eddies play a major role for the sccs creation a 3 layer idealized ventilation model calibrated to the three dimensional simulation parameters is able not only to capture the tropical density structure but also to isolate the main controlling factors leading to the triggering of the equatorial secondary cells with its associated jet and thermostad namely the shoaling of the equatorial thermocline because of low potential vorticity injection at distant subduction latitudes it is also shown that equatorial recirculation gyres play a quantitative role that may be of the same order of magnitude as ventilation from higher latitudes

deep circulation in the equatorial atlantic ocean in the atlantic ocean the northward export of warm surface water is compensated by a southward flow of cold north atlantic deep water nadw the nadvv is transported southward along the american continental margin within the deep western boundary current dwbc some tracer and float observations have shown that part of the dwbc water flows eastward along the equator here we present three meridional velocity sections which give an instantaneous image of the lop to bottom zonal circulation along the equatorial atlantic they reveal the presence of equatorial deep jets edjs between 1 30 n and 1 30 s alternating eastward westward currents with short vertical scale surrounded by columns of eastward currents the extra equatorial jets or eejs at 2 n and 2 s in addition to direct velocity measurements tracer distributions give indications of water mass feeding of the edjs and eejs by the dwbc

equatorward energy cascade critical latitude and the predominance of cyclonic vortices in geostrophic turbulence geostrophic turbulence exhibits features similar to those observed in the oceans a movement of energy toward the equator a critical latitude below which are alternating zonal flows and above which the flow is largely isotropic and a predominance of cyclonic vortices above the critical latitude these features arise in geostrophic turbulence when the latitude dependence of the deformation radius is taken into account with the aid of a quasigeostrophic one layer numerical model this paper proposes physical mechanisms giving rise to these features

grain shape analysis a new method for determining representative particle shapes for populations of natural grains abstract the size sorting and shape sorting of gravel bedload by running water often is investigated using identifiable tracer grains that represent the grains within the riverbed a new robust and reproducible method is described for the objective selection of three dimensional shapes that are representative of the variety of shape within any whole sample widespread adoption of the method would ensure comparability between the shape sorting results of different experiments the approach identifies average and extreme grain shapes from natural gravel samples importantly tracer dimensions are derived that form shapes with equal volume thus ensuring that the shape of the tracers is the only transport variable the method is tested on seven gravel samples from a range of fluvial beach and scree slope environments as well as different sieve sizes initially measurements of the short s intermediate i and long l orthogonal axes of clasts are made from selected sieve intervals that represent the spread in the size distribution of the natural gravel shapes are identified to be within the realms of the observed shapes of the sampled population four extreme shapes are identified a blade a rod a spheroid and a discoid as well as a median form the starting points of the analysis are the zingg ratios s i and i l however these quantities require polar coordinate transformation to be useful in shape selection the polar coordinate quantities form a joint probability density function that is the product of the marginal distributions of the new shape indices and the axes of the shape diagram utilizing and combining extreme percentiles of these latter distributions identifies the required shapes a reverse transformation returns these selected quantities back into zingg indices finally using the intermediate axial dimensions and the volume ratio the final tracer dimensions are found

observed tracer fields structuration by middepth zonal jets in the tropical pacific abstractthe middepth ocean circulation in the tropical pacific is dominated by sets of alternating eastward and westward jets the origin and transport properties of these flow features remain in m

organic geochemical study of the w oil gas field in the yugoslav part of the pannonian basin the naphthenic crude oil from the w oil gas field differs from almost all other paraffinic base oils discovered until now in the yugoslav part of the pannonian basin in order to explain this difference some geological and organic geochemical investigations were carried out on the basis of the bulk and biomarker parameters determined in oil samples taken from 13 producing wells located at different parts of the field it is concluded that the crude oil throughout the field has an almost uniform composition however some differences in alkane content due to biodegradation and or water washing were found in the northeast part of the field where a tilted oil water layers shows an active hydrodynamism and where the temperatures are the lowest and pressure gradients the highest the isoprenoids pristane and phytane were detected in trace amounts indicating the most intensive biodegradation in the central part where a hydrocarbon accumulation exists in a miocene reservoir somewhat lower biodegradation was observed the crude oil from this field has probably a mixed terrestrial marine origin and is derived from argillaceous source rocks sedimented in marine delta or brackish lakes specific maturation parameters confirmed that the w crude oil has reached a quite uniform and significant thermal maturation considering maturation parameters such as ratios c30 moretane hopane and c29 20s 20s 20r steranes as well as the presence of oleanane it could be proposed that the w oil originates from a pre tertiary source rock at least an upper cretaceous one unlike most pannonian basin oils which are tertiary in age

morphodynamics of a boulder beach putuo island se china coast the role of storms and typhoon abstract in this paper we examine the sedimentological properties and morphodynamic evolution of a boulder beach at huayanpeng cape on putuo island off the southeast china coast focus is given to the formation of the boulder beach 256 2000 mm diameter and resulting morphology in relation to high energy storms and seasonal typhoon holocene sea level rise to the present position at ca 7000 6000 yrs bp provides a long term window for the formation of the beach the beach is primarily characterized from east to west by 1 the convex to concave beach morphology 2 reduced longest axis of the skeleton boulders 3 decreased flatness of the skeleton boulders and 4 greater sphericity of the skeleton boulders infilling cobbles pebbles in the beach demonstrate a bi modal distribution corresponding to dominant sizes of 100 250 mm and 50 100 mm in diameter on the eastern beach and western beach respectively this reflects changed intensity of storm waves alongshore multiple peaks of the distributions of infilling clasts for the western beach supratidal probably reflect storm and calm weather sedimentation statistically both the skeleton boulders and infilling clasts follow a distribution reflecting the high energy control of beach formation and the dominance of crushing in boulder size reduction a boulder transport model applied in the present study further reveals that boulders with an a axis length of 500 1000 mm the dominant component on the beach move under a wide range of wave conditions depending on wave height and wave period with a cluster of critical wave heights in the range 2 6 m and wave periods of 5 15 s

estimating the 3d shape of volcanic ash to better understand sedimentation processes and improve atmospheric dispersion modelling abstract the sedimentation rate of volcanic ash through the atmosphere influences its travel distance with important implications for aviation and health the fall velocity of a particle depends on its size and density but also shape and volcanic ash is not spherical to capture the sedimentation of ash atmospheric dispersion models use empirical drag equations calibrated using geometric shape descriptors however particle shape data are scarce and there is no standard method of shape measurement in addition shape measurements are not always available during an eruption when dispersion models are used operationally to forecast ash hazard we assess the variability in the shape of volcanic ash from icelandic eruptions using x ray computed tomography to consider how good different drag equations and shape descriptors are at representing the sedimentation of volcanic ash we compare calculated fall velocities to measured fall velocities of volcanic ash in air in a settling column we then suggest the best drag equations and shape descriptors for use in atmospheric dispersion models we find that shape dependent drag equations produce more accurate results than a spherical approximation however accurate drag calculations based on the shape descriptor sphericity which is a function of surface area require the imaging resolution to be within the range of 102 105 voxels per particle where a voxel is a volumetric pixel as surface area is sensitive to imaging resolution we suggest that the large scale form of the particle impacts sedimentation more than small scale surface roughness shape descriptors based on ratios between principal axis lengths are more practical as they are less variable among particle size classes and much less sensitive to imaging resolution finally we use particle shape data from this study and literature sources to make recommendations on default values for use with atmospheric dispersion models where no shape data are available

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

an organic geochemical study of cenomanian turonian sediments from the western interior seaway canada abstract bulk geochemical and biomarker data were collected for three cenomanian turonian late cretaceous sections in the western canada sedimentary basin western interior seaway canada rock eval and biomarker analyses indicate an east west thermal maturity trend due to progressive deeper burial associated with the tectonic flexure of the foreland basin the source of extractable organic matter is dominantly marine with a minor terrestrial contribution a pseudohomologous family of 2 2 dimethylalkanes 2 2 dmas in the c 16 c 28 range with an even number of carbon atoms exclusively was tentatively identified from mass spectral data in samples from the pasquia hills region easternmost section the specific origin of 2 2 dimethylalkanes remains unclear the presence of isorenieratene derivatives indicates that the northern part of the western interior seaway experienced photic zone euxinic events throughout the transgressive highstand and regressive phases of the greenhorn cycle the differential occurrence of isorenieratane between the canadian sections and the united states transect at maximum sea level high stand indicates that the water column of the northern part of the wis was less oxygenated whereas the water column in the southern wis was more dynamic and well mixed

major role of the equatorial current system in setting oxygen levels in the eastern tropical atlantic ocean a high resolution model study understanding the causes of the observed expansion of tropical ocean s oxygen minimum zones omzs is hampered by large biases in the representation of oxygen distribution in climate models pointing to incorrectly represented mechanisms here we assess the oxygen budget in a global biogeochemical circulation model focusing on the atlantic ocean while a coarse 0 5 configuration displays the common bias of too large and too intense omzs the oxygen concentration in an eddying 0 1 configuration is higher and closer to observations this improvement is traced to a stronger oxygen supply by a more realistic representation of the equatorial and off equatorial undercurrents outweighing the concurrent increase in oxygen consumption associated with the stronger nutrient supply the sensitivity of the eastern tropical atlantic oxygen budget to the equatorial current intensity suggests that temporal changes in the eastward oxygen transport from the well oxygenated western boundary region might partly explain variations in the omzs

characterizing block geometry in jointed rockmasses the intersection of discontinuities in a jointed rockmass creates in situ blocks of variable three dimensional 3d geometry the size and shape of rock blocks in a rockmass assembly have a dominant influence on the engineering properties of a rockmass and control for example the failure geometry of a rock face and the optimum associated support and surface restraint strategy the distribution of block volumes within a rockmass can be effectively analyzed and communicated using a cumulative volume distribution curve integrated with this analysis a methodology has been developed to characterize the shape and volumetric shape distribution of rock blocks in 3d models of jointed rockmasses the proposed block shape characterization method takes into account two factors the first describes the shortening of the minor principal axis of the block while describes the elongation of the major axis when merged with the block volume distribution the block shape characterization method can effectively describe and classify both the size and shape distributions of any jointed rockmass and is not limited to orthogonal blocks or hexahedra this methodology can classify any polyhedra and has been developed and calibrated based on synthetic joint data and simulated block assemblies a demonstration is given of its effectiveness in characterizing block geometries in the field using mapped fracture data

evaluation of the effects of native minerals on the organic matter of aleksinac oil shale based on the composition of free and bound bitumens abstract in order to evaluate the adsorption and catalytic effects of indigenous carbonates and silicates on the organic matter of aleksinac oil shale the free and the bound bitumens were isolated and analyzed by organic geochemical methods the differences in the gross compositions indicated an adsorption effect of both the carbonates and silicates in the examined oil shale the maturation parameters based on n alkanes and isoprenoid alkanes pristane and phytane indicated that bitumen 3 was of the highest and bitumen 1 of the lowest apparent maturity the silicates were shown to have had a thermocatalytic effect on the organic matter of this sediment clay minerals had a catalytic effect primarily on sterane aromatization rearrangement of steranes into diasteranes and their 20r 20s isomerization all evidence obtained by analysis of steranes and aromatic steroids suggested that the differences in bitumen compositions should be explained by the effect of clay minerals rather than by variations in the origin of the precursor biomass