stable isotope geochemistry of crude oils and of possible source rocks from new zealand 2 sulfur abstract the sulfur isotopic composition of new zealand low s crude oils and components asphaltenes absorptive filtration fractions and source rock components extracted hydrocarbons kerogen pyrite sulfates were determined oils from the taranaki basin have 34s values from 3 to 14 o the lower values possibly represent plant assimilation of fresh water sulphate higher values particularly those from the west coast basin around 20 suggest closed ocean basin conditions or fast sedimentation rate whereas negative 34s values from east coast basin suggest open ocean or low sedimentation rate conditions it is suggested than an oil source rock relation should show as a similarity in 34s values for total oil and source rock extract kerogen and pyrite shale samples analysed plot outside the corresponding oil range and cannot be considered as possible source rocks however coal samples from the maui 4 well and nelson outcrops show strong isotopic correlations with the taranaki oils

dynamics of advection driven upwelling over a shelf break submarine canyon 1 the response over a submarine canyon to a several day upwelling event can be separated into three phases an initial transient response a later much longer steady advection driven response and a final relaxation phase for the advection driven phase over realistically steep deep and narrow canyons with near uniform flow and stratification at rim depth we have derived scale estimates for four key quantities observations from 5 real world canyon studies and 3 laboratory studies are used to validate the scaling and estimate the scalar constant for each scale based on 4 geometric parameters of the canyon the background stratification the coriolis parameter and the incoming current we can estimate 1 the depth of upwelling in the canyon to within 15 m 2 the deep vorticity to within 15 and 3 the presence absence of a rim depth eddy can be determined based on laboratory data 4 the total upwelling flux can also be estimated the scaling analysis shows the importance of a rossby number based on the radius of curvature of isobaths at the upstream mouth of the canyon this rossby number determines the ability of the flow to cross the canyon isobaths and generate the pressure gradient that drives upwelling in the canyon other important scales are a rossby number based on the length of the canyon which measures the ability of the flow to lift isopycnals and a burger number based on the width of the canyon that determines the likelihood of an eddy at rim depth generally long canyons with sharply turning upstream isobaths strong incoming flow small coriolis parameter and weak stratification have the strongest upwelling response

circulation near submarine canyons a modeling study circulation near a submarine canyon is analyzed with a numerical model previous theoretical work indicated that stratification controlled the interaction of coastal flow with canyons specifically the ratio of canyon width to the internal radius of deformation a wide canyon was thought to merely steer the flow while a narrow canyon would create substantial cross shelf exchange four cases are analyzed considering two directions of alongshore flow and two choices of initial stratification the weakly stratified case has an internal radius about equal to the canyon width while the strongly stratified case has one about 3 times the canyon width the direction of the alongshore flow is shown in this study to be the more important of the two factors in particular right bounded flow flow with the coast on the right looking downstream in the northern hemisphere leads to shallow downwelling in the canyon and weak exchange across the shelf break while left bounded flow creates upwelling at the head of the canyon and strong exchange between the ocean and shelf in left bounded flow upwelling dense water is pumped onto the shelf even for strong stratification however the stratification limits the vertical extent of the topographic influence so that the alongshore flow above the canyon is only weakly affected in the strongly stratified case with any level of stratification the surface temperature density is not modified at all by the flow interaction with the submarine canyon the important dynamics involve pressure gradients and coriolis acceleration and how they interact with the bathymetric gradients but not advection of momentum advection of density is clearly important in the upwelling cases finally continued upwelling onto the shelf acts as a drag mechanism and retards the alongshore coastal flow

a field study of the behaviour of an anticyclonic eddy on the catalan continental shelf nw mediterranean abstract through the analysis of satellite thermal images mesoscale anticyclonic eddies have been observed to recurrently drift along the nw mediterranean coasts the presence of these eddies is known to cause transient inversions of the shelf slope current by means of an exhaustive analysis of sea surface temperature images a group of anticyclonic structures were monitored in september 2001 one of these eddy like features was tracked and intensely surveyed by means of conductivity temperature depth ctd casts and repeated fast surveys with n shuttle oscillating ctd and acoustic doppler current profiler adcp measurements during the et2001 oceanographic cruise a well developed anticyclonic eddy was surveyed over the catalan continental shelf 60 km north of barcelona in situ velocity data revealed that the anticyclonic motion was characterized by surface velocities of 50 cm s and a diameter of about 45 km the signal of the eddy was found down to 100 m depth well below the seasonal thermocline the passage of the eddy modified the local flow involving advection and subduction of surrounding waters

upwelling induced by the frictional stress curl and vertical squeezing of the vortex tube over a submerged valley in the east china sea we conducted a process oriented modeling study to investigate the characteristics and dynamics of the prominent upwelling over a vast submerged valley in the east china sea ecs the valley is inversely funnel shaped with the west bank and the east bank oriented in the north south direction a cross bank upward transport occurred along the west bank it intensified northward and peaked around the head of the valley an along bank southward pressure gradient force pgf formed the cross bank geostrophic transport for the upwelling over the valley the pgf reached its maxima at the head of the valley our momentum and vorticity dynamic analyses revealed that a bottom stress curl mainly contributed the pgf along the west bank at the same time both the bottom stress curl and the nonlinear vorticity advection contributed to the pgf around the head the bottom stress curl was due to the bottom shear vorticity of the coastal current and the curvature vorticity around the head the nonlinear vorticity advection formed because of the vertical squeezing of vortex tube as the current flowed over the valley the nonlinearity mainly affected the pgf around the head whereas the bottom stress curl contributed to the pgf over the entire valley the ratio of the nonlinear to frictional contributions to the pgf increased as the coastal current intensified our study demonstrates that the pgf that drives the upwelling over the valley is the combined result of the nonlinearity due to vertical squeezing of vortex tube and bottom frictional effects

numerical simulation of barotropic jets over a sloping bottom comparison to a laboratory model of the northern current 1 in order to study the role of a sloping bottom on the mesoscale variability of the northern current a series of barotropic laboratory experiments was performed on a rotating table setup the present work is devoted to a numerical model which aims to simulate these laboratory conditions in order to further investigate aspects which are difficult to treat in the laboratory the onset of instabilities the influence of the velocity profile the relative position of the jet over the slope and the influence of the jet width on the resulting instabilities are discussed the robustness and the origin of a shelf break topographic rossby wave detected in our westward laboratory flows is also discussed the barotropic model for westward currents such as the northern current with rossby numbers in the range ro 0 1 0 2 predicts wavelengths of 50 75 km similar to those observed in sst images the periods associated with the model instabilities 3 3 3 8 days would be close to a 3 5 day band of mesoscale activity recorded from current meter devices in the gulf of lions which lies out of the traditionally considered baroclinic instability theory other particularities such as the up slope migration of the northern current and the increasing mesoscale activity for increasing jet velocities can also be explained through the present model these results would point out barotropic instability as a factor to consider apart from the traditional idea of baroclinic instability in order to partially explain the northern current mesoscale variability

where large deep ocean waves break underwater topography like seamounts causes the breaking of large internal waves with associated turbulent mixing strongly affecting the redistribution of sediment here ocean turbulence is characterized and quantified in the lowest 100 m of the water column at three nearby sites above the slope of a deep ocean seamount moored high resolution temperature sensors show very different turbulence generation mechanisms over 3 and 5 km horizontal separation distances at the steepest slope turbulence was 100 times more energetic than at the shallowest slope where turbulence was still 10 times more energetic than found in the open ocean away from topography the turbulence on this extensive slope is caused by slope steepness and nonlinear wave evolution but not by bottom friction critical internal tide reflection or lee wave generation

numerical study of the circulation in a steep canyon off the catalan coast western mediterranean we use a limited area fine resolution primitive equation model to carry out a case study of the circulation in the steep and narrow blanes canyon located off the catalan coast western mediterranean this area is characterized by a permanent along slope density driven current and strong northerly and easterly wind bursts in autumn in a first step the slope current is allowed to adjust to the bottom topography leading to a stationary circulation pattern which presents large vertical variations related to the canyon geometry in the surface layer the strong stratification allows the current to flow straight over the canyon rim ignoring bottom topography in the intermediate layer the canyon is wide and waters are isolated in a geostrophic anticyclonic eddy maintained by friction at the edge of the slope current in the deep layer the canyon is narrow and a topographic upwelling lifts bottom waters toward the canyon head in a second step the circulation is forced by easterly along shore with the coast on its right and northerly seaward 1 day wind bursts which induce significant vertical and cross shore motions steered by the bottom slope this ageostrophic circulation is substantially amplified in the canyon where the flow pattern presents large amplitude oscillations characterized by a downwelling upwelling during the easterly northerly wind burst followed by a rebound upwelling downwelling as the wind relaxes the upwelling induced by the northerly wind burst is capable of renewing waters trapped in the canyon eddy our results appear to be in fairly good agreement with in situ physical and biogeochemical data collected in blanes canyon and comparable canyons of the world ocean the three dimensional features obtained in this study can explain some of the observed patterns of larvae distribution and exchanges between the coastal zone and the open sea

the effects of boundary turbulence on canyon flows forced by periodic along shelf currents previous laboratory experiments and associated numerical models of laminar flows forced by oscillatory along shelf background currents are extended to include some of the effects of boundary generated turbulence the experiments are conducted in the 13 m diameter rotating flow facility in grenoble france two pairs of case studies one at a large forcing velocity designated as fast for which the boundary layers are fully turbulent during part of the flow cycle and one at relatively smaller forcing slow for which transitional boundary layers are operative at the higher speeds of the background flow are conducted smooth and artificially roughened boundaries are considered respectively for each of these pairs phase averaged and time mean velocity vertical vorticity and horizontal divergence fields are found to be qualitatively similar to those of previous laminar experiments the similarities in the time mean fields are that i within the canyon they are dominated by cyclonic vorticity with maxima centered near the shelf break ii within and in the vicinity of the canyon the general circulation pattern includes a net transport into the canyon through its mouth a net upwelling in the canyon interior a transport away from the canyon over the shelf break along both sides of the canyon and by inference a return flow to the deep ocean and iii the interior time mean flow is characterized by a well defined coastal current whose axis follows the shelf in the vicinity of the shelf break with the coast on the right it is found that the measurements of the characteristic speed of the residual or time mean flow within the canyon for the transitional and fully turbulent experiments do not follow the scaling law derived earlier for laminar experiments an alternative scaling analysis for large reynolds number flows is thus derived although sufficient numbers of experiments are not available to test the hypothesis fully the measurements available for the fully turbulent flows are consistent with the theory advanced

the behavior of jet currents over a continental slope topography with a possible application to the northern current abstract the northern current is a slope current in the northwest mediterranean that shows high mesoscale variability generally associated with meander and eddy formation a barotropic laboratory model of this current is used here to study the role of the bottom topography on the current variability for this purpose a source sink setup in a cylindrical tank placed on a rotating table is used to generate an axisymmetric barotropic current to study inviscid topographic effects experiments are performed over a topographic slope and also over a constant depth setup the latter being used as a reference for the former with the aim of obtaining a fully comprehensive view of the vorticity balance at play the flow may be forced in either azimuthal direction leading to a westward prograde current similar to the northern current or an eastward retrograde current for slow flows eastward and westward currents showed similar patterns dominated by kelvin helmholtz type instabilities for high speed flo

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

circulation over a submarine canyon in the nw mediterranean 1 the circulation in blanes canyon an interruption in the nw mediterranean continental shelf north of barcelona was investigated the study employs data from oceanographic surveys carried out in the summer and fall of 2003 velocity data show that in the vicinity of the shelf break the flow is deflected along the canyon walls a cyclonic mean flow can be seen over the canyon mouth owing to vortex stretching of fluid parcels advected across the shelf break field observations are in qualitative agreement with fundamental fluid dynamic considerations based on potential vorticity conservation and friction effects at lateral boundaries evidence is given that upwelling is found near the shelf break inside the canyon in the two field experiments this upwelling extends vertically from the seasonal thermocline at about 100 m to the shelf slope front at about 200 m there is no evidence that upwelled water can reach the continental shelf

deep flow variability in a deeply incised mediterranean submarine valley blanes canyon abstract deep flow variability in blanes canyon is analyzed by means of a unique dataset in which the canyon was instrumented at its axis and at the two canyon walls from march 2003 to july 2004 the mean intensity of deep currents range between 3 5 cm s 1 at the canyon axis 1500 m and 5 4 cm s 1 upstream canyon wall 900 m a wavelet analysis shows that the energy is concentrated in the 2 30 day band and it is mainly associated to single not periodical not wave related events uncoupled at the different canyon sites an empirical orthogonal function analysis shows two main patterns of current variability explaining 65 of the total variance the first mode represents intensifications of the typical along bathymetry pattern of currents over the canyon the second mode corresponds to near bottom upwelling events along the canyon axis with water exiting the canyon through the canyon head after discussing possible forcing mechanisms it is here suggested that such deep upwelling events are associated to offshore displacements of the northern current namely the interaction of the current with the particular shape of the canyon topography at large depths 1800 m would be responsible for the observed deep upwelling events

spatial and temporal variability of meiobenthic density in the blanes submarine canyon nw mediterranean abstract meiofaunal density distribution was studied from 400 m to 1500 m depth inside blanes submarine canyon nw mediterranean and on the eastern open slope in autumn 2003 and spring 2004 our multidisciplinary approach allowed to study the hydrodynamics and sedimentary processes in the blanes canyon that characterize it as highly heterogeneous environment inside the canyon area particle fluxes were higher than on the slope area increased from autumn to spring and mostly consisted of lithogenic material moreover the canyon s locations experienced more intense bottoms currents and sediment disturbance being reflected in a greater variability of meiobenthic densities both between stations and sampling times than on the open slope no clear trends e g declining densities associated with increasing depths were observed contrary in the open slope current velocities were relatively lower compared with the canyon area and showed lower temporal variability at the same time the nutritional quality of the particle fluxes at deeper grounds were higher probably allowing the meiofaunal densities not to change over time in conclusion the meiobenthos in our system apparently showed a higher temporal variability inside the canyon area strongly affected by particle fluxes or erosive and sediment mixing processes linked to current modifications induced by the canyon topography

northern current variability and its impact on the blanes canyon circulation a numerical study a high resolution 1 2 km 3d numerical model was used to analyze the interaction of the northern current a right bounded flow with the blanes submarine canyon bc nw mediterranean although it refers to a climatological simulation the model properly suites our purpose since it simulates the northern current nc mesoscale variability as well as its seasonal variability model results were validated with satellite sea surface temperature and current meter data the simulated nc tends to be faster and deeper in winter and slower and shallower in summer according to our results nc meanders and eddies are recurrent in the bc area and produce highly fluctuating three dimensional circulation patterns within the canyon we found that nc meanders and anticyclonic eddies propagating along the current pathway tend to be deep and consequently their effects extend down to the deeper part of the bc we also found that the meandering of the nc plays a key role in enhancing vertical motions inside the bc upwelling and downwelling events occurring on timescales of 4 20 days are associated with nc meanders crests and troughs passing over the bc net upwelling downwelling events are accordingly influenced by the nc seasonality they are more predominant in winter while damped in summer our results show the importance of nc meanders in creating local net upwelling downwelling and strengthen the evidence that continuous right bounded downwelling favorable flows can also produce net upwelling inside submarine canyons

patterns of flow in the canyons of the northern gulf of alaska abstract the continental shelf around kodiak island is incised with numerous submarine canyons which play an important role in the cross shelf transport of heat salt and nutrients and the transport of ichthyoplankton of deep spawning fish from the slope region into the shallow nursery grounds surrounding kodiak island to explore the pathways and variability of flow and the extent of tidal mixing within the canyons moorings were placed in the chiniak barnabas and amatuli troughs and off the shelf from resurrection bay seward line and the kenai peninsula gore point in the troughs intensified flow was evident near the trough walls and flow was directed by bathymetry with inflow along the upstream northern side and outflow along the downstream southern side the presence of mesoscale eddies in the gulf had no unique influence on currents or salinity in the troughs tidal mixing was strongest in chiniak trough and this introduced cold nutrient rich bottom waters into the upper water column intensified bottom flow associated with the alaskan coastal current was evident along the seward line and gore point and directed toward the kennedy stevenson entrances which are also regions of strong tidal mixing observations of tidal mixing were consistent with model results and satellite images showing cooler phytoplankton rich water in summer in the nursery grounds that surround kodiak island patterns of flow within the troughs and in shelikof strait were consistent with the springtime advance of ichthyoplankton across the shelf

multiscale variability in the balearic sea an altimetric perspective 1 the present day availability of an 18 year record of 1 8 merged mediterranean sea sea level anomaly sla data enables a contemporary description of long term mesoscale activity in the balearic sea sla data from satellite altimetry are used to study the variability of sea level and surface geostrophic circulation at different spatial and temporal scales within this complex and relatively understudied region in the western mediterranean wmed we find that the mean northern current along the iberian slope is strongest in autumn although higher variability in winter leads to stronger peaks in kinetic energy the balearic current which flows along the northern slopes of the balearic islands also has its maximum expression in autumn across the two balearic channels ibiza and mallorca key locations that partly regulate meridional exchange in the wmed observed seasonal variability in geostrophic velocity anomalies conforms rather well to prior descriptions suggesting cautious confidence in the use of the mediterranean merged altimeter product in nearshore regions circulation through the channels is maximum in winter the channel data support the hypothesis that the channel circulation may be hindered by the intermittent presence of the western intermediate water mass which sometimes forms in winter in the gulf of lions this is the first time that an analysis of variability in the balearic channels has been performed using altimetric data

the response of a steep sided narrow canyon to time variable wind forcing abstract the response of a relatively narrow 7 km wide and deep 450 m deep steep sided up to 45 bottom slope submarine canyon to strong wind forcing is explored using data from an 18 element moored array as well as ctd surveys in the vicinity of astoria submarine canyon the data are used to describe spatial patterns and phase relationships between lateral velocity vertical velocity temperature relative and stretching vorticity alongshelf wind and the flow incident on the canyon upwelling within the canyon is simultaneous and spatially uniform to zero order and vertical velocity is highly correlated and in phase with alongshelf wind vertical velocity within the canyon is not related to flow incident on the canyon except during strong upwelling above the canyon temperature rather than vertical velocity time rate of change of temperature is in phase with wind estimated vertical velocities within the canyon were as great as 50 m d 1 upward during upwelling and 90 m d 1 downward du

a two dimensional tidal model for the mediterranean sea the tidal propagation in the mediterranean sea is described through a high resolution two dimensional hydrodynamic model forced by the equilibrium tide and the incoming tide at the strait of gibraltar the four most significant constituents m2 s2 k1 and o1 are included in the model good agreement with a set of 63 coastal gauges is achieved the significance of the equilibrium tide and the forcing at the open boundary is investigated the incoming wave from the strait of gibraltar is important in tuning the tides in the whole of the mediterranean for the north aegean sea the solution without the forcing at gibraltar results in a doubling of the amplitudes of the semidiurnal tides the estimated energy dissipation due to bottom friction is 8 8 108 w the major area of dissipation is the gulf of gabes energy fluxes through the major straits are calculated

sulfur isotopic variations in low sulfur coals from the rocky mountain region abstract the isotopic composition of organic sulfur and disseminated and massive pyrite has been determined in vertical sections from eight low sulfur coals paleocene and cretaceous in age in four coal fields of wyoming and colorado the 34 s values of organic sulfur from five sites in the anderson wyodak coal paleocene of the eastern powder river basin wyoming are more negative than expected for low sulfur coals 18 7 to 3 9 suggesting that organic sulfur was derived from a combination of original plant sulfur and secondary 34 s depleted sulfur the 34 s depleted sulfur was probably produced from bacterial reduction of sulfate which infiltrated from the top and bottom during the peat stage the 34 s of organic sulfur in a paleocene coal from the hanna basin wyoming ranges from 1 6 to 13 1 vertical variation in 34 s here suggests bacterial reduction in a partially closed system of sulfate which infiltrated from the top of the seam a paleocene and a cretaceous coal from the green river coal region in wyoming and colorado both yield 34 s values of organic sulfur 2 4 to 8 1 consistent with what would be expected for original plant sulfur 34 s values of pyrite at all sites varies widely 52 6 to 34 6 the isotope composition of the disseminated pyrite correlates with that of the organic sulfur implying a similar mode and timing of incorporation 34 s of the massive pyrite shows no such correlation

tidal motions and tidally induced fluxes through la linea submarine canyon western alboran sea detailed observations from two mooring lines deployed in la linea submarine canyon western alboran sea are presented this is a narrow canyon in the sense that its width is always less than the internal radius of deformation tidal currents within the canyon are polarized in the along canyon direction according to its narrow nature they have considerable amplitude values of around 0 5 m s are often observed and are forced by the internal pressure gradients associated with the baroclinic tide that is generated in the surroundings subsequent amplification of onshore baroclinic currents within the canyon accounts for the large amplitude observed cross shelf exchange through the canyon due to tidal motions is different from zero despite the close to zero mean of tidal currents the explanation is based on the asymmetry of water properties flowing up canyon and down canyon some sort of tidal rectification regarding the energy flux the canyon seems to be an adequate conduit to carry energy to the shore estimations made from our observations indicate that energy input onto the shelf per unit length parallel to the shore at the canyon head is enough to maintain mixing on the shelf at intermediate depths

carbon isotope composition of lower palaeozoic kerogen effects of maturation abstract the carbon isotope composition of type i kerogen from a marine organic rich black shale deposit of late cambrian age the alum shale formation of southern scandinavia varies from 28 to 30 pdb the thermal maturity is rated by hi oi index t max pi and vitrinite reflectance values and published conodont alteration data the results range from immature conditions with regard to oil generation in central sweden to overmature and submetamorphic conditions in southern sweden denmark and norway in the immature areas the shale is found to be extremely hydrogen rich and oil prone hydrocarbon potential up to 85 kg per ton rock the observed 13 variations are not correlated with maturity it is therefore concluded that thermal maturation processes have no influence on the isotopic composition of a purely marine kerogen the observed range in lower palaeozoic 13 kerogen values 27 to 31 is in accordance with published results from other sedimentary basins

spatial distribution of sedimentation rate increases in blanes canyon caused by technification of bottom trawling fleet abstract a detailed study of 15 sediment cores from blanes canyon and its immediate surroundings nw mediterranean sea was conducted to compare historic sedimentation rates and evaluate the possible impact of bottom trawling intensification on the sedimentary regimes over the past 50 years the canyon axis and flanks as well as the adjacent open slope were sampled at water depths ranging from 300 m to 2200 m grain size dry bulk density and 210pb concentration profiles were measured to assess possible changes in sedimentation rates over the last century and their temporal and spatial relationship to bottom trawling effort sedimentation rates in the upper canyon axis 900 1200 m had the highest rates of 0 9 2 1 cm yr 1 quantified since the 1970s farther downcanyon sedimentation rates increased two to five times after the 1970s from 0 1 0 2 cm yr 1 to 0 2 0 8 cm yr 1 which coincides with a rapid growth of the total engine power of the fishing fleet operating in the study area the enhanced sedimentation rates occur downslope of the main fishing grounds and decrease downcanyon as the distance from trawling grounds increases these results highlight the ability of bottom trawling to resuspend bottom sediments leading to net erosion of the canyon rims and flanks in turn large volumes of sediment are advected towards the canyon s interior ultimately increasing sediment deposition along the canyon axis natural sedimentation rates at similar along canyon distance from shore in the untrawled continental slope 900 1500 m and in the lower canyon axis 1500 2200 m are comparable 0 08 0 20 cm yr 1 suggesting distance from coastal sediment sources as the main control on regional sedimentation in deeper parts of the margin while submarine canyons have been regarded as preferential cross margin conduits for sediment dispersal they can also potentially function as modern depocenters for trawling induced sedimentation

shelf slope exchanges associated with a steep submarine canyon off calvi corsica nw mediterranean sea a modeling approach a three dimensional unsteady nonlinear high resolution model is used to investigate the impact of the calvi canyon nw corsica steep topography on the shelf slope exchanges as well as on the circulation in the calvi bay in homogeneous winter and early spring conditions a double coordinate system is considered in order to represent adequately the high depth gradients within the canyon the studied region is under the influence of the west corsica current flowing northeastward along the nw corsican coast right bounded flow model results show that the circulation in the calvi bay is determined by flow modifications in the canyon area the mean horizontal flow is deviated southwestward upstream of the canyon to form an anticyclonic gyre in the western part of the calvi bay within the canyon the circulation is cyclonic leading to an offshore flow downstream of the canyon around the canyon rim the cross shelf currents become important indicating that this region acts as a transition zone of high exchange between nearshore and offshore areas furthermore the canyon topography generates high downwelling upwelling and downsloping upsloping velocities responsible for an intense vertical transport of material in the area numerical runs are performed for typical prevailing wind conditions the wind is responsible for a drastic increase of cross shore transports between the bay and the canyon area 3 4 times larger than in the no wind case sw winds induce a further enhancement of cross shelf exchanges whereas the effect of n ne winds is to reduce exchange at the shelf break apart from the canyon head where an intense offshore flow occurs within the canyon high vertical velocities are shown to be associated with high cyclonic vorticity which is enhanced reduced by the n ne sw wind event a comparison between model results and measured distributions of nitrate and chlorophyll a concentrations in the area shows the role played by this specific hydrodynamics as a strong constraint on the coastal pelagic ecosystem

the stable isotope geochemistry of australian coals abstract d h 13 c 12 c 18 o 16 o and 34 s 32 s ratios in the organic matrix and organic solvent extracts of australian coals and in the fluids and minerals associated with these coals are reported and reviewed against similar isotopic data for coals from other regions where coals are immature original isotopic differences between macrolithotypes and between solvent extracts lipid concentrates and insoluble residues are largely preserved however with increasing maturity these characteristic differences particularly those between macrolithotypes are rapidly erased conversely where as indicated by low total sulfur contents coals of cretaceous to permian age were deposited under essentially freshwater conditions 34 s values for the organically bound sulfur remain remarkably constant at 4 3 relative to meteoritic sulfur in similar younger tertiary coals the organic sulfur is markedly enriched in 34 s five distinctive isotopic patterns which may be interpreted in terms of the environment of sulfate reduction can be recognized from 34 s 32 s ratio measurements on the various forms of sulfur in australian coals isotopic studies of seam gas hydrocarbons collected in situ show these to be unexpectedly strongly depleted in the heavier isotopes of hydrogen and carbon relative to natural gases from proposed humic sources furthermore no pronounced increase in the 13 c content in methane with increase in rank of the parent coal was observed in addition several sources of associated carbon dioxide have been delineated including normal maturation processes invasion of the seams by magnetic carbon dioxide and interaction of the coal with intrusive magma isotopic exchange between free seam gases is not accepted as an explanation for some unusual isotopic fractionations seen rather the data suggest that these gases may be formed in a state approaching isotopic equilibrium this argument also satisfactorily explains the isotopic compositions of primary siderite and secondary calcite associated with bituminous coal seams however where seams are invaded and permeated with externally derived carbon dioxide usually of magnetic origin carbonates are frequently absent presumably as a result of the action of carbonic acid

carbon isotope geochemistry of paleozoic oils from big horn basin abstract twenty crude oils from paleozoic reservoirs in the big horn basin wyoming were fractionated into light hydrocarbons saturates monoaromatics diaromatics polyaromatics and polars and asphaltenes amounts and isotopic composition of each fraction were found to be internally consistent with the degree of maturation of the oil confirming the established single source origin for these oils a variation of approximately three per mil in the carbon isotopic composition of the whole oil and individual fraction was explained as being caused by maturation the isotope type curves for these oils the variations in isotopic composition as a function of compound group type were not found to be as simple as commonly believed other alteration processes such as migration and deasphalting might have influenced the pattern of the isotope distributions among fractions the conservative nature of mass balance and subsequent isotope flows among various fractions of crude oil showed that the maturation of crude oil consists of consecutive processes leading from larger and more polar components into smaller and less polar components culminating in natural gas calculations were made to project the amount of condensates associated with the crude oils and the amount of natural gas which had been generated from crude oils of a given maturity

the influence of a narrow transverse canyon on initially geostrophic flow the interaction of a geostrophic current with a transverse submarine canyon is considered with an analytical two level model of a homogeneous fluid on an f plane the dynamical hypothesis is that the flow in the canyon is forced by the pressure gradient due to a sloping free surface the interaction of flow in the canyon with the overlying fluid is through the vertical velocity forced by divergence in the canyon the mathematical problem considers a flat bottom ocean with an infinitely long canyon having a rectangular cross section and uniform depth the dynamics are rotationally modified shallow water equations for each level the initial time behavior of the model is considered with a power series solution which shows that flow in the canyon responds quickly in about 0 1 of the inertia period to an imposed surface pressure gradient the time dependent model is solved by means of a laplace transform in time in three spatial domains over the canyon and on either side for a canyon of arbitrary width the flow over the canyon is composed of standing waves while radiating waves exist on either side of the canyon in the absence of friction the oscillations continue indefinitely since there are standing gravity modes in the canyon in steady state there is no net flow of water across the canyon so such submarine features should act as barriers to barotropic geostrophic flow the limit of a narrow canyon is considered arguments are presented to show that a canyon is narrow if its width is less than half of the smaller of the radius of deformation or the width scale of the overlying current for a forcing current with a width about equal to the radius of deformation the oscillations in the canyon have periods of about 0 1 up to 1 times the inertia period such oscillations have been observed in most canyons for which current meter observations exist

flow near submarine canyons driven by constant winds circulation over coastal submarine canyons driven by constant upwelling or downwelling wind stress is simulated and analyzed with a primitive equation ocean model astoria canyon on the west coast of north america is the focus of this study and model results are consistent with most major features of mean canyon circulation observed in astoria canyon near surface flow crosses over the canyon while a closed cyclone occurs within the canyon upwelling prevails within the canyon and is larger than wind driven upwelling along the adjacent shelf break water rises from depths reaching 300 m to the canyon rim and subsequently onto the adjacent shelf onshore flow within the canyon is driven by the onshore pressure gradient force due to the free surface slope created by the upwelling wind and is enhanced by the limitation to alongshore flow by the canyon topography density gradients largely compensate the surface slope with realistic stratification but continual upwelling persists near the edges of the canyon within the upper canyon 50 150 m below the canyon rim a cyclone is created by flow turning into the canyon mouth separating from the upstream edge and advecting toward the downstream rim below this layer the cyclone is created by vortex stretching due to the upwelling downwelling winds create nearly the opposite flow in which compression and momentum advection create a strong anticyclone within the canyon momentum advection is found to be important both in creating strong circulation within the canyon and in allowing the surface flow to cross the canyon undisturbed model results indicate that astoria like submarine canyons produce across shore transport of sufficient volume to flush a continental shelf in a few 2 5 years

sulfur isotope ratios in petroleum research and exploration williston basin the three major types of crude oil in the williston basin the type i oils of the winnipeg red river system the type ii oils of the bakken madison system and the type iii oils of the tyler pennsylvanian system can be distinguished by their sulfur isotope compositions they have characteristic dgr34s values of 5 8 1 2 parts per thousand ppt 2 8 0 8 ppt and 4 0 0 7 ppt respectively highly mature oils have less typical values type ii oils which have migrated over a distance of some 150 km beyond the region of generation have maintained their characteristic dgr34s values even though sulfur may have been lost this indicates little or no interaction with reservoir sulfates under normal circumstances on the periphery of the basin type ii oils altered by water washing and biodegradation have altered dgr34s values which increase from 2 9 to 9 4 ppt with the increasing degree of crude oil degradation the bakken shales source of the type ii oils have dgr34s distribution patterns in the reduced sulfur typical of marine sediments the dgr34s values for the type ii oils match most closely the dgr34s value of organic sulfur in the black bituminous shales of the lower bakken

shelf slope exchanges by frontal variability in a steep submarine canyon abstract we study the dynamics of a frontal jet and its short timescale variability generated by the interaction with a submarine canyon using a limited area fine resolution three dimensional coastal ocean model the focus is on the steep and narrow palamos canyon located off the northeast catalan coast northwestern mediterranean that is characterized by the presence of a permanent along slope density driven current first we analyse the stationary circulation induced with different jet locations and show a deflection of the flow in the vicinity of the canyon significant vertical motions develop as a result of these current adjustments the general pattern such as downwelling upstream of the canyon and upwelling downstream are always observed second we analyse the circulation and exchanges associated with an onshore displacement of the jet thus produces a meander propagating with the flow that interacts with the canyon we find that the resulting three dimensional patterns present an oscillation characterized by an intense downwelling followed by upwelling as a result of this interaction shelf slope exchanges and vertical motions are enhanced in the area compared with the passing of a meander above a shelf that is not indented by a submarine canyon the resulting horizontal transports through the palamos canyon represent up to 10 of the along shore fluxes on the shelf and appear to be sufficient to exchange the shelf water of the gulf of lions and catalan sea in 2 5 years considering the number of canyons existing in the area we can estimate an exchange of all the shelf waters in less than 3 months

reproductive biology and recruitment of the deep sea fish community from the nw mediterranean continental margin abstract temporal patterns in deep sea fish reproduction are presently unknown for the majority of deep continental margins a series of seasonal trawling surveys between depths of 300 to 1750 m in the blanes submarine canyon and its adjacent open slope nw mediterranean were conducted the bathymetric size distributions and reproductive cycles of the most abundant species along the nw mediterranean margin were analyzed to assess the occurrence of i temporal patterns in reproduction i e spawning season along a bathymetric gradient and ii preferential depth strata for recruitment the fish assemblages were grouped in relation to their bathymetric distribution upper slope middle slope and lower slope species middle slope species i e 800 1350 m showed short i e highly seasonal reproductive activity compared to the upper 300 800 m and lower 1350 1750 m ones our results together with those previously published for megabenthic crustacean decapods in the area suggest a cross phyla depth related trend of seasonality in reproduction in the middle and lower slope species the reproductive activity reached a maximum in the autumn winter months and decreased in the spring the observed seasonal spawning patterns appear to be ultimately correlated with changes in the downward transport of organic particles and with seasonal changes in the physicochemical characteristics of the surrounding water masses the distribution of juveniles was associated with the bathymetric stratum where intermediate nepheloid layers interact with the continental margins indicating that this stratum acts as a deep sea fish nursery area

flow modification and shelf slope exchange induced by a submarine canyon off the northeast spanish coast we present results from a study of the modifications induced by the short timescale response of a shelf break baroclinic jet to the presence of a downstream canyon the field site was the canyon of palamos located in the northeastern edge of spain to determine the short time scale variability of the area three intensive surveys were carried out at approximately 10 day intervals data indicate that the jet s location usually over the slope is subjected to significant onshore offshore displacements analysis of the data has shown the importance of a small scale temporal variability induced by river runoff and the climatology of the area this variability generates on off shore displacements of the jet which interacts with the head mouth of the canyon the different interactions with the canyon induced by these displacements produce different regimes of shelf slope exchange in the canyon domain that strongly modify the biomass patterns in the area