revisiting the use of seismic attributes as soft data for subseismic facies prediction proportions versus probabilities geostatistical modeling originated within the mining industry to estimate average minable ore grade from large support volumes given samples measured on small volume support in petroleum geostatistics the goal is more equivocal due to several different scales of support of input data which are often incongruent with the desired prediction scale more specifically the goal is to utilize indirect measurements e g seismic data from a scale larger than the prediction scale for fine scale spatial distributions of facies and petrophysical properties grounded by undersampled point data e g well log data note volume support is a geostatistical term that describes the size or resolution of the sample or measurement

226ra in marine barite new constraints on supported 226ra abstract following the pioneering work of paytan et al a paytan et al geochim cosmochim acta 60 1996 4313 4319 new investigations have been undertaken on marine barite separated from central and western equatorial pacific sediments these investigations are designed to achieve a better quantification of supported 226 ra activities in the separated samples enabling the use of excess 226 ra 226 ra ex in marine barite as a tool for dating holocene sediments instrumental neutron activation analysis allowed first to measure significant 238 u activities in the separated samples attributable to highly insoluble minerals that like barite are resistant to the chemical treatment used in this study tio 2 minerals zircon monazite within these u rich minerals 226 ra activities are in secular equilibrium with 238 u second the study of the 226 ra signal in old barite samples that do not contain any residual 226 ra ex activities provided accurate constraints on the amount of 226 ra produced by unsupported 230 th the remaining 226 ra activities corrected for the 238 u contribution appeared to decrease with depth with a slope comparable to that defined by the bulk 230 th ex activities the consistency of this deep trend allowed its extrapolation upwards to the sediment top in order to obtain an estimate of the 226 ra activities produced by unsupported 230 th in the holocene barite samples the total correction for supported 226 ra in the holocene barite samples used in this study therefore consists of the sum of 226 ra activities in secular equilibrium with 238 u within minerals and 226 ra activities produced by unsupported 230 th thus estimated the resulting correction is low for samples separated from central equatorial pacific sediments compared with both the total 226 ra activities measured in barite and results of previous studies the magnitude of the correction is nevertheless higher for samples from western equatorial pacific sediments which display a lower barite purity the corrected 226 ra in barite profiles are in agreement with the general trend observed for long half life radionuclides with a similar mixed layer in the sediment top thus adding confidence in the use of this tool below the mixed layer the exponential decay of 226 ra ex activities in barite allowed the determination of sedimentation rates that agree with the estimates for the two investigated sites ultimately one of the main uses for the 226 ra in barite dating method will be its application to holocene sediments from the southern ocean where dating is often problematic

radium isotopes in the chesapeake bay 228ra and 226ra are enriched in waters of chesapeake bay through fluxes from the bottom sediments and desorption from particles entering the estuary the activity ratio of 228ra 226ra increases from 1 5 in the susquehanna river to 3 4 in waters of 15 20 salinity apparently much of the 228ra is supplied by diffusion from sediments within the bay while desorption from particles entering the bay is more important for 226ra because of the multiple inputs and long residence time of water in the bay no curvature is obvious in a plot of radium isotope concentration vs salinity

on suspended barite and the oxygen minimum in the southern ocean particulate ba profiles were measured in the indian sector of the southern ocean the largest fraction 80 of this barium is present as barite microcrystals the profiles of total barium are characterized by a subsurface maximum between 200 and 500 m depth in the vicinity of the oxygen minimum highest barium values are found just south of the polar front while lowest values occur close to the antarctic divergence between the divergence and the polar front a tight inverse relationship is observed between oxygen in the oxygen minimum and barium in the barium maximum this relationship disappears north of the polar front since suspended barite is known to be of biological origin the correlation of barite with oxygen suggests that the observed decrease of oxygen in the oxygen minimum between the divergence and the polar front is due to local consumption of oxygen it is proposed that deep low oxygen water is advected towards the divergence where upwelling occurs and where this water subsequently partly spreads out to the north north east as entrained by the antarctic circumpolar current oxidation of locally produced organic matter with which barite crystals are associated consumes oxygen and sets free individual discrete barites as a result oxygen decreases and barite increases away from the divergence with barite integrating former biological processes

facies probabilities from multidimensional crossplots of seismic attributes application to tight gas mamm creek field piceance basin colorado crossplots are commonly used in the geosciences to gain qualitative insight about relationships between different variables typically three for two dimensional colored crossplots on rare occasions the relationships among four variables are explored by using three dimensional colored crossplots the variable used to color the crossplot is usually related to the property of interest sand or pay for instance in these cases crossplots can be used in a quantitative sense by selecting drawing a region in the crossplot where most of the property of interest lives drawing a polygon in a 2d crossplot to separate good from bad areas is the extension to 2d of simple cutoffs commonly applied to 1d well log data to separate scenarios of interest one drawback of this approach is that it works best only when there is no overlap between the region occupied by the property of interest and the region occupied by the background another drawback is that it is difficult to extend to three dimensional crossp

226ra in the black sea and sea of marmara water column distributions of226ra were determined at stations in the sea of marmara and the black sea as part of the 1988 joint u s turkish black sea expedition black sea surface water226ra concentrations were a factor of three to four lower than measurements made 20 years earlier the most likely cause is increased removal of226ra and ba 35 due to increased surface biological activity a secondary effect is decreased fluvial discharge and related dimunition of inputs by desorption from fluvial suspended sediments the amount of226ra missing from the surface waters of the black sea over this period is accounted for in the high porosity surficial fluff sediment layer throughout the black sea depth profiles of226ra exhibited pronounced maxima of approximately 25 dpm 100 l at about 16 2 16 3 in the vicinity of a bacterial maximum but slightly shallower than the total dissolved mn and fe maxima 16 4 16 5 reported by lewis and landing 38 while the226ra maximum may in part be linked to the cycling of mn and fe oxyhydroxides near theo2h2s interface its distribution appears to be more plausibly explained as a result of the microbial breakdown of particulate organic matter and the subsequent release and partial dissolution of associated barite in this region a simple steady state two model has been used to obtain a semiquantitative understanding of the behavior of226ra in the black sea by incorporating reasonable estimates for the input and removal of226ra in the black sea an excellent agreement between predicted and observed 1988 226ra concentrations was achieved the model suggests that the dominant variables controlling the distribution of226ra in the black sea are riverine input and cycling with ba

the behavior of u and th series nuclides in the estuarine environment rivers carry the products of continental weathering and continuously supply the oceans with a broad range of chemical constituents this erosional signature is however uniquely moderated by biogeochemical processing within estuaries estuaries are commonly described as complex filters at land sea margins where significant transformations can occur due to strong physico chemical gradients these changes differ for different classes of elements and can vary widely depending on the geographic location u and th series nuclides include a range of elements with vastly different characteristics and behaviors within such environments and the isotopic systematics provide methods for investigating the transport of these nuclides and other analog species across estuaries and into the coastal ocean there are numerous types and definitions of estuaries see dyer 1973 in this paper it is simply considered to be a region where freshwater and seawater mix to emphasize the chemical focus of the issues involved here this region can either be contained within a river channel or extend onto the shelf with effects often extending well into an adjoining ocean basin fairbridge 1980 these are complex ecological biogeochemical and hydrodynamic systems with strong gradients in the concentrations and composition of micro and macro particulate matter as well as dissolved organic and inorganic species particle reactive radionuclides and trace elements being transported across estuaries are subject to partitioning between the dissolved colloidal and particulate phases the variable chemical nature of the u and th series radionuclides is evident in their distributions in an estuarine environment such radionuclides can effectively serve as tracers to identify the sources fate and transport of particles and colloids as well as other pollutants that behave similarly to these nuclides these nuclides also have a wide range of half lives that can be used to examine processes over various time scales for example th and ra daughter isotopes have

hyperpycnal plume formation from riverine outflows with small sediment concentrations a series of laboratory experiments has been conducted in order to elucidate the sediment induced mixing processes accompanying riverine outflows specifically the discharge of a warm fresh particle laden fluid over a relatively dense cool brine in a parameter regime analogous to recently acquired field measurements hypopycnal surface plumes were subject to a convective instability driven by some combination of heat diffusing out of the warm fresh sediment laden plume and particle settling within it convection was robust in the presence or absence of intense turbulence at sediment concentrations as low as 1 kg m 3 and took the form of millimetre scale sediment laden fingers descending from the base of the surface plume a consequence of the convective instability of the original hypopycnal plume is the generation of a hyperpycnal bottom riding flow the experiments presented here indicate that natural river outflows may thus generate hyperpycnal plumes when sediment concentrations are 40 times less than those required to render the outflow heavy relative to the oceanic ambient the resulting hyperpycnal plumes may play an important role in transporting substantial quantities of sediment to the continental slope and beyond

new appraisal of radium 226 as a large scale oceanic mixing tracer radium 226 and ba data in the eastern and central indian ocean collected during the geochemical ocean sections study geosecs expeditions are reviewed and used to delineate the geochemical cycle of both species the data show that although particulate uptake of 226ra and ba occurs in the surface ocean their regeneration may largely take place near or below the sediment water interface therefore over much of the deep ocean save close to the bottom 226ra can be regarded as being chemically conservative taking advantage of this geochemical aspect of 226ra enables us to compute the vertical z and horizontal meridional x eddy diffusivities kz and kx and advective velocities vz and vx and their variability in the eastern and central parts of the indian ocean the absolute magnitudes of these mixing parameters are calibrated against the decay rate of 226ra the computation is done by numerically solving the mass continuity equations for three properties 226ra total salt and mass of seawater the grid size used in the calculations in which the advective transport is taken to be along the isopycnal surface has dimensions of x 700 km and z 400 m the model calculation shows that in the eastern and central indian ocean along the geosecs traverses values of diapycnal diffusivity kz of 1 10 cm2 s 1 are found near the surface and the bottom minima occur in the thermocline region where kz falls to about 10 2 cm2 s 1 below kz has values largely in the range 0 1 1 cm2 s 1 and increases downward the horizontal isopycnal diffusivity varies between 104 and 108 cm2 s 1 mainly in the range 106 107 cm2 s 1 upwelling velocities are mostly in the lower end of the range 1 10 m yr 2 whereas downwelling unlike upwelling which tends to be localized occurs with velocities of 0 1 1 m yr 2 the meridional component of subsurface currents is in the range of 0 01 0 1 cm s 1 mostly toward the south and not restricted to a particular depth interval the current field deduced in the study area provides a broad picture of the strength and pattern of return flows of the deep water introduced from the south and thought to be principally transported northward via the relatively narrow intense currents along the western boundaries of the basins the present study as well as recent developments in the high precision and high sensitivity mass spectrometric analysis of 226ra suggests that this naturally occurring isotope warrants further exploitation as a rate tracer for large scale ocean circulation and mixing processes

remobilization of transition metals in surficial pelagic sediments from the eastern pacific abstract the top thirty centimeters of sediment at two sites in the eastern equatorial pacific contain evidence of post depositional remobilization of mn fe co ni cu and zn remobilization takes place as mn and fe oxyhydroxides are released to the pore water during the microbially mediated decomposition of organic matter precipitation of the dissolved metals in near surface more oxic strata controls the solid phase distribution of mn fe and zn the solid phase redistribution of co and ni requires only suitable material for readsorption comparison of pore water fluxes with solid phase metal distributions in the solid sediment indicates no loss of dissolved metal to the overlying water column at the present time loss of mn during the quaternary is indicated by the composition of the sediments however leaching experiments suggest that portions of the mobile mn fe co ni and cu are fixed by incorporation in authigenic smectite in the surficial sediments

double diffusive convection in this paper we present a rather personal view of the important developments in double diffusive convection a subject whose evolution has been the result of a close interaction between theoreticians laboratory experimenters and sea going oceano graphers more recently applications in astrophysics engineering and geology have become apparent in the final section we attempt to draw some general conclusions and suggest that further progress will again depend on a close collaboration between fluid dynamicists and other scientists

observational and modeling evidence of seasonal trends in sediment derived material inputs to the chukchi sea author posting american geophysical union 2020 this article is posted here by permission of american geophysical union for personal use not for redistribution the definitive version was published in journal of geophysical research oceans 125 5 2020 e2019jc016007 doi 10 1029 2019jc016007

fused spectral decomposition seismic attributes and forward seismic modelling to predict sand bodies in meandering fluvial reservoirs abstract understanding the hierarchical architectural elements of fluvial sand bodies is important for planning their development strategy and to enhance oil recovery red green blue rgb blending of multiple seismic attributes and forwarding seismic modelling are commonly used in the analysis of compound sand bodies however rgb blending of multiple seismic attributes can only qualitatively describe the boundaries and thickness of sand bodies the forward seismic modelling techniques previously documented in the literature are not effective when depicting the geometry of and stacking relationships between sand bodies i e reservoir compartmentalisation hence we propose in this work a new workflow that combines fused spectral decomposition seismic attributes sdsas and forwarding seismic modelling to quantitatively predict sand thickness and to characterise stacking relationships between sand bodies first we employ a support vector machine svm algorithm to fuse high middle and low frequency components attributes of seismic data so as to quantitatively predict the thickness of sand bodies second we define the seismic waveform response patterns corresponding to the typical conceptual stacked sand bodies with the constraints of waveform patterns and predicted sand thickness fused sdsas the geometry and stacking relationships of the sand bodies are characterised by forward seismic modelling to illustrate the effectiveness of our proposed workflow we apply it to the neogene minghuazhen formation nm of the qhd 32 6 oil field bohai bay basin china we define five architectural elements of a meandering fluvial reservoir by analysing the hierarchy of sand bodies using our workflow the predicted sand bodies in this workflow were further proven by horizontal drilling and production data

ba ra th and u in marine mollusc shells and the potential of 226ra ba dating of holocene marine carbonate shells the geochemistry of ba ra th and u and the potential of using 226 ra ba ratios as an alternative dating method are explored in modern and holocene marine mollusc shells five modern shells of the antarctic scallop adamussium colbecki collected from the present day beach and six radiocarbon dated specimens from holocene beach terraces of the ross sea region antarctic between 700 and 6100 calibrated yr bp old have been analysed by mass spectrometry in clean shells 226 ra concentrations and 226 ra ba ratios show a clear decrease with increasing age suggesting the possibility of 226 ra dating limiting factors for such dating are ba and 226 ra present in surface contaminants and ingrowth of 226 ra from u present within the shell surface contamination is difficult to clean off entirely but moderate levels of residual contamination can be corrected using 232 th sub samples from the same shell with different proportions of contamination form a mixing line in a 226 ra ba 232 th ba graph and the 226 ra ba of the pure shell can be derived from the intercept on the 226 ra ba axis contaminant corrected 226 ra ba ratios of late holocene 14 c dated samples fall close to that expected from simple 226 ra excess decay from seawater 226 ra ba values 226 ra ingrowth from u incorporated into the shell during the lifetime of the mollusc can be corrected for however the unknown timing of post mortem u uptake into the shell makes a correction for 226 ra ingrowth from secondary u difficult to achieve in the a colbecki shells 226 ra ingrowth from such secondary u becomes significant only when ages exceed 2500 yr in younger shells 226 ra ba ratios corrected for surface contamination provide chronological information if evidence for a constant oceanic relationship between 226 ra and ba in the ocean can be confirmed for that time scale the 226 ra ba chronometer may enable the reconstruction of variability in sea surface 14 c reservoir ages from mollusc shells and allow its use as a paleoceanographic

plume dispersed hydrothermal particles a time series record of settling flux from the endeavour ridge using moored sensors abstract settling particles collected with moored sediment traps near an area of active hydrothermal venting in the northeast pacific ocean provide information about the deep sea distribution of hydrothermal material results of an 8 day near field single trap experiment and a 340 day multi instrument 5 trap deployment two kilometers from the endeavour ridge vent field show variability in the quantity and composition of the plume to sediment particle flux over time with depth and with distance from the vent field hydrothermal elemental fluxes vary by a factor of two among the four sampling intervals of the longer experiment a factor of three variation in fe s among these periods reflects temporal changes in phase composition changes in flux with depth for example a 200 fold increase in cu and zn between above and below plume traps are evidence of hydrothermal input comparison of fluxes determined in the near and far field experiments reveals the spatial influence of vent effluent near field particle flux exceeds that measured two kilometers away by a factor of 10 to 20 and is relatively enriched in fe cu and organic carbon but depleted in mn calculations of the residence time of the plume with respect to settling indicate that more than 90 percent of the particulate material is transported farther than two kilometers from the vent field interpretation of elemental mineralogical and grain size analyses suggest that chemical precipitation kinetics other physical and biological particle forming processes changes in vent output and lateral transport of hydrothermal material by abyssal currents are tenable explanations for our observations our findings suggest that these rate interdependent processes be included in realistic models of hydrothermal particle flux

210pb 226ra 230th systematics in very low sedimentation rate sediments from the mendeleev ridge arctic ocean this article is one of a series of papers published in this special issue on the theme polar climate stability network geotop publication 2008 0031 u series isotope behaviour in subsurface sediment of the arctic ocean is investigated based on high resolution measurements of natural radionuclides 210pb 226ra 230th and a few analyses of anth

constraining 3d facies modeling by seismic derived facies probabilities example from the tight gas jonah field seismic reservoir characterization is usually based on the interp retation of seismic attributes that relate to the geological feature or reservoir property of interest if we are interested in fault geometries a variety of geometric attributes can be used to map the details of fault distributions and constrain discontinuities and flow barriers in geological and flow simulation models if we are interested in reservoir properties however the usual approach is to estimate seismic attributes that are qualitatively related to such properties the interpretation of the attribute focuses on the identification of good and bad areas depending on how the attribute relates to the property of interest

fluxes of 226ra and barium in the pacific ocean the importance of boundary processes abstract the 226 ra ba ratio in particles collected in sediment traps decreases with depth fluxes of ba and al increase with depth these observations cannot be explained by simple vertical processes instead they require a component to the deep flux which originates at the ocean margins we suggest that the deep traps are enriched in ba through the advection of barite originally precipitated in biologically productive regions of the ocean margin this source is less important for 226 ra because some is lost by radioactive decay between the precipitation of barite on the margin and outward transport the boundary flux is an important source of material to the deep sea from 226 ra fluxes in the upper 1000 m of the water column we estimate that the residence time of 226 ra in the upper ocean is 400 years the removal of 226 ra in the particle flux is approximately balanced by the upwelling of waters enriched in 226 ra

228ra 226ra and 226ra ba ratios in the western mediterranean sea barite formation and transport in the water column 226ra 228ra and ba distributions as well as 228ra 226ra and 226ra ba ratios were measured in seawater suspended and sinking particles at the dyfamed station in the western mediterranean sea at different seasons of year 2003 in order to track the build up and fate of barite through time the study of the 228raex 226raex ratios raex ra activities corrected for the lithogenic ra of suspended particles suggests that baex baex ba concentrations corrected for the lithogenic ba mostly barite formation takes place not only in the upper 500 m of the water column but also deeper i e throughout the mesopelagic layer temporal changes in the 228raex 226raex ratios of sinking particles collected at 1000 m depth likely reflect changes in the relative proportion of barite originating from the upper water column with a high 228ra 226ra ratio and formed in the mesopelagic layer with a low 228ra 226ra ratio 228raex 226raex ratios measured in sinking particles collected in the 1000 m trap in april and may suggest that barite predominantly formed in the upper water column during that period while barite found outside the phytoplankton bloom period february and june appears to form deeper in the water column combining ratios of both the suspended and sinking particles provides information on aggregation disaggregation processes high 226raex baex ratios were also found in suspended particles collected in the upper 500 m of the water column because celestite is expected to be enriched in ra bernstein r e byrne r h and schijf j 1998 acantharians a missing link in the oceanic biogeochemistry of barium deep sea res ii 45 491 505 acantharian skeletons may contribute to these high ratios in shallow waters the formation of both acantharian skeletons and barite enriched in 226ra may thus contribute to the decrease in the dissolved 226ra activity and 226ra ba ratios of surface waters observed between february and june 2003 at the dyfamed station

suboxic trace metal geochemistry in the eastern tropical north pacific abstract we analyzed al ti fe mn cu ba cd u mo v and re in water column settling particulate and sediment 0 to 22 cm samples from the intense oxygen minimum zone omz of the eastern tropical north pacific near mazatlan mexico the goal was to determine how the geochemistry of these elements was influenced by suboxic water column conditions and whether the sediments have a unique suboxic geochemical signature the water column was characterized by a mn maximum reaching 8 nmol kg 1 at 400 m concentrations of cu ba cd mo re u and v were unaffected by the low o2 conditions and were comparable to those of the open ocean sinking particles were composed of lithogenic particles of detrital origin and nonlithogenic particles of biogenic origin al ti and fe were mostly at least 79 lithogenic about 75 of the mn was nonlithogenic significant amounts at least 58 of cu ba cd and mo were nonlithogenic sediment geochemistry varied across the continental shelf and slope cadmium u and re have prominent maxima centered at 310 m with 12 3 ppm 10 9 ppm and 68 3 ppb respectively at the core top high values of mo averaging 6 8 ppm and v averaging 90 ppm are seen in omz surface sediment additional down core enrichment occurs for all redox sensitive elements in the top 10 cm for u mo v and re surface sediments are a poor indicator of metal enrichment comparison of the nonlithogenic composition of sediments with sinking particles suggests that direct input of plankton material enriched in metals makes a significant contribution to the total composition especially for cd u and mo we evaluated re mo and cd u ratios as tracers for redox environments rhenium and mo concentrations and re mo ratios do not lead to consistent conclusions concurrent enrichments of re and mo are an indicator of an anoxic depositional environment in contrast high re mo ratios are an indicator of suboxic conditions cadmium is enriched in surface sediments while u has considerable down core enrichment the concentrations of cd and u and the cd u ratio do not follow patterns predicted from thermodynamics though the water column is suboxic these four redox sensitive elements indicate that the sediments are anoxic the implication for paleostudies is that a trace metal sediment signature that indicates anoxic conditions is not necessarily attributable to an anoxic water column

advective excess ba transport as shown from sediment and trap geochemical signatures abstract we report the results of a geochemical study of sediment and trap material major and trace elements zr ba rare earth elements and th were analyzed on bulk sedimentary material collected along the ne atlantic margin our aim is to test the widespread use of ba barite as a proxy for paleoproductivity in a continental margin area this environment is of great interest because atmospheric oceanic exchanges are important in sediments the geochemical signatures remain close to an upper crust reference with flat shale normalized rare earth elements patterns and constant elementary ratios the calculated biogenic fraction of ba or excess ba 20 45 remains lower than the excess ba record in trap material 80 99 the evolution of the geochemical signature along the margin reflects variable dilution of a detrital post archean australian shale like component by a biogenic carbonaceous seawater derived component the trap material displays a wide range of variation in its trace element content e g ba 150 3000 ppm zr 2 100 ppm except for the abyssal site which is characterized by constant signature in the two other sites all of the trace element contents increase with water depth and present pronounced seasonal changes at each sampled water depth the amount of excess ba also increases in the deepest traps and its evolution throughout the year mimics the change of the other analyzed trace elements in contrast its relationships with particulate organic carbon are not obvious in term of fluxes two periods of enhanced excess ba fluxes are observed 1 excess ba flux increases with the detrital like elements like th especially during winter and 2 excess ba flux is enhanced without any change for the other trace elements during spring to explain the first case a supply through lateral advection is proposed such transient input of significant excess ba flux will have a great impact on the yearly averaged estimation of the export production indeed only the second case reflects a bloom in the biological productivity of the water column and must be taken into account in a mean calculation of the export production finally a normalization of the excess ba by detrital like element like th will help to discriminate between a real increase of the excess ba due to local productivity change high excess ba and high excess ba th ratio 10 000 and any input due to advection process high excess ba but low excess ba th ratio

barium accumulation in the arabian sea controls on barite preservation in marine sediments in this study a new sequential extraction technique is used to investigate the particulate barium ba phases in sediments from the arabian sea to determine the processes controlling ba accumulation in marine sediments the total solid phase ba concentration in arabian sea surface sediments increases with water depth from 200 ppm at 500 meters below sea surface mbss to 1000 ppm at 3000 mbss the sedimentary ba composition consists of three major fractions barite ba incorporated in aluminosilicates and ba associated with mn fe oxides accumulation of barite which is the most important ba fraction in sediments located below 2000 mbss increases gradually with water depth the ba al ratio of the terrigenous fraction varies significantly across the arabian basin as the result of differences in grain size and provenance of the terrigenous sediment ba associated with mn oxides is a relatively minor fraction compared with bulk ba concentrations and it only accumulates in well oxygenated sediments below the present day oxygen minimum zone the water depth dependent accumulation of barite in the arabian sea is not related to the continuous formation of barite in settling organic particles or ba scavenging by mn oxyhydroxides but is primarily controlled by differences in ba preservation upon deposition a good correlation between the barite saturation index and the barite accumulation rate in the upper 2000 m of the water column may indicate that the degree of barite saturation of the bottom water is the main environmental factor regulating the burial efficiency of barite organic matter degradation bioturbation diagenetic mn cycling and the crystallinity of the accumulating barite may play additional roles copyright 2001 elsevier science ltd

integrated facies modeling in unconventional reservoirs using a frequentist approach example from a south texas field abstractmodeling of rock types or facies in unconventional reservoirs presents numerous challenges that are not encountered in conventional reservoirs because the exploitation of unconventional reservoirs frequently relies on the use of large numbers of long data poor horizontal wells routine tasks in conventional reservoirs such as petrophysical analyses and rock physics diagnostics become problematic in unconventional reservoirs due to insufficient data similarly the inability to generate synthetic seismograms in the horizontal section of the wells makes seismic well ties and time depth conversions more difficult our approach for facies modeling in unconventional reservoirs attempts to overcome these challenges by using the abundant log information available along the vertical pilot well to extract discrete facies indicators facies flags from logging while drilling information along the horizontals after performing a time depth conversion constrained by geosteering information we estimate fa

early diagenesis impact on precise u series dating of deep sea corals example of a 100 200 year old lophelia pertusa sample from the northeast atlantic deep sea coral has proved useful for paleoceanographic reconstructions and for documenting 14 c ages of water masses using 230 th ages however for precise and accurate u series dating further information on coral age structure growth rate and diagenetic evolution is still needed to document such processes we used u th 226 ra systematics in a 40 cm diameter lophelia pertusa specimen collected in 1912 from the eastern atlantic sea of the hebrides external parts of the specimen are thought to have been alive when collected whereas more internal parts were likely dead the live collected and dead parts of the skeleton were sampled and analyzed for their 230 th 232 th 234 u 238 u 226 ra and ba contents by thermal ionization and multicollector inductively coupled plasma mass spectrometry 230 th 234 u ratios in the most recent parts yielded ages of 86 6 a and 92 9 a in agreement with the date of recovery the older parts yielded 230 th ages ranging from 169 15 to 211 10 a n 5 but had a 31 higher u content than more recent parts of the skeleton this raises concerns about the possibility of secondary diagenetic u uptake although an environmentally controlled u ca shift between coral growth stages cannot be ruled out 226 ra ba measurements were made and model 226 ra ba ages averaging 250 12 yr were calculated for the older part assuming a constant initial 226 ra ba ratio in bottom waters these ages are slightly older than 230 th ages suggesting either that 226 ra ba ratios of ambient seawater changed over time or that a diagenetic phenomenon have affected the u series system or both scanning electron microscope observations revealed bioerosion and secondary biomineralization in the older part of the coral skeleton supporting the hypothesis that diagenetic processes may have influenced the ages obtained by the u series toolbox modeled u series ages for such an open system are discussed however a comparison between 14 c and 230 th ages performed on both pristine and bioeroded parts of the coral gives coherent values ca 450 a for the preindustrial 14 c reservoir age of north atlantic waters it remains to be determined however whether diagenesis occurs rapidly over a short period of time or whether it continues for longer periods in the latter case diagenetic processes would hamper paleoceanographic interpretations as well as the precise calculation of 14 c ages of deep water masses based on comparative u th and 14 c chronologies copyright 2005 elsevier ltd

228ra 226ra and 226ra ba ratios to track barite formation and transport in the water column abstract we measured 228 ra ex 226 ra ex and 226 ra ex ba ex ratios in suspended and sinking particles collected at the oceanic flux program ofp time series site in the western sargasso sea and compared them to seawater ratios to provide information on the origin and transport of barite baso 4 in the water column the 228 ra ex 226 ra ex ratios of the suspended particles down to 2000 m are nearly identical to those of seawater at the same water depth these ratios are much lower than expected if suspended barite was produced in surface waters and indicate that barite is produced throughout the mesopelagic layer the 228 ra ex 226 ra ex activity ratios of sinking particles collected at 1500 and 3200 m varied mostly between 0 1 and 0 2 which is intermediate between the seawater ratio at these depths ex ba total ba lithogenic considered to be mainly barite present in the sinking flux is a mixture of crystals formed recently in the upper water column formed several years earlier in the upper water column or formed recently in deeper waters we observe a sizeable temporal variability in the 228 ra ex 226 ra ex ratios of sinking particles which indicates temporal variability in the relative proportion of barite crystals originating from surface with a high 228 ra ex 226 ra ex ratio and mesopelagic with a low 228 ra ex 226 ra ex ratio sources however we could not discern a clear pattern that would elucidate the factors that control this variability the 226 ra ba ratios measured in seawater are consistent with the value reported from the geosecs expeditions 2 3 dpm mol 1 below 500 m depth but are significantly lower in the upper 500 m high 226 ra ex ba ex ratios and elevated sr concentrations in suspended particles from the upper water column suggest preferential uptake of 226 ra over ba during formation of srso 4 skeletons by acantharians which must contribute to barite formation in shallow waters deeper in the water column the 226 ra ex ba ex ratios of suspended particles are lower than those of seawater since 228 ra ex 226 ra ex ratios demonstrate that suspended barite at these depths has been produced recently and in situ their low 226 ra ex ba ex ratios indicate preferential uptake of ba over ra in barite formed in mesopelagic water

sr ba in barite a proxy of barite preservation in marine sediments abstract the observation by bertram and cowen j mar res 55 1997 577 593 that the strontium content of marine barite decreased from the water column to the deep sea floor suggested that the sr ba ratio in barite was sensitive to barite dissolution following this observation we have investigated the potential of using the sr ba ratio in barite as a proxy of barite preservation by separating barite crystals from sediment cores collected at different water depths in the equatorial pacific and in the southern ocean our investigations do not reveal significant downcore variations in the sr ba ratios during the holocene period in the two basins and up to a few hundred thousand years in the equatorial pacific however a comparison of the mean sr ba ratios in individual cores suggests that the sr ba ratios in barite decrease with increasing water depth a feature that could be related to dissolution of barite crystals during settling to the deep sea floor and or at the sediment water interface if confirmed the sr ba ratios in barite could be used to infer the intensity of barite dissolution and the state of preservation of barite crystals in sediments such information could be employed usefully in paleoproductivity reconstructions for the purpose of distinguishing between productivity and dissolution signals affecting barite distributions in marine sediments

a major helium 3 source at 15 s on the east pacific rise an extensive plume of water enriched with helium 3 has been discovered in the deep pacific ocean at latitude 15 s on the east pacific rise in the core of the plume at a depth of 2500 meters over the ridge crest the helium 3 helium 4 ratio is 50 percent higher than the ratio in atmospheric helium indicating a strong injection of mantle or primordial helium at the spreading center axis through local hydrothermal systems the helium 3 plume is completely absent east of the rise but it can be traced over 2000 kilometers to the west above a newly observed physical feature a density discontinuity here caled the ridge crest front the injected plume provides a unique deep sea tracer with an asymmetric distribution which shows that the deep circulation across the rise is from east to west the striking intensity and lateral extent of this helium 3 anomaly compared to observations at known oceanic hydrohrmal sites suggest that the largest hydrothermal fields in the ocean are yet to be discovered and that they will be found near 15 s on the east pacific rise

the water column distributions of thorium isotopes in the western north pacific abstract four vertical profiles of 230 th and 228 th were determined using large volume water samples in the western north pacific an almost linear increase of 230 th with depth was observed for all of the profiles for which the unidirectional first order scavenging model was difficult to explain we developed a model which included a dissolved particulate transformation as well as parameters of the scavenging model application of the model to the vertical distributions of total and the geosecs particulate th isotopes 230 th and 234 th yielded the residence time of dissolved th with respect to adsorption to particles and the turnover time of particulate th to be 235 days and 57 days respectively the th isotopes appeared to be carried down the water column by fine particles with a mean settling velocity of 1 m day which continually release th into sea water as well as pick up th from the water along their journey to the bottom for 228 th a large excess over 232 th was observed throughout the water column with pronounced high concentrations in surface and bottom waters suggesting that the 228 th was derived from 228 ra diffused out of sediments the vertical distributions of 228 th seemed to be significantly influenced by lateral mixing along isopycnals

submarine groundwater discharge revealed by 228 ra distribution in the upper atlantic ocean submarine groundwater discharge estimated from a 228ra inventory across the upper atlantic ocean provides a flux of 2 4 1013 m3 yr 1 equivalent to 80 160 of the influx from rivers into the atlantic ocean