facies and architectural element analysis of a meandering fluvial succession the permian warchha sandstone salt range pakistan abstract the 30 to 155 m thick early permian artinskian warchha sandstone of the salt range pakistan is a conglomerate sandstone and claystone succession within which seven lithofacies types gt st sp sr sh fl and fm occur in a predictable order as repeated fining upward cycles common sedimentary structures in the conglomerates and sandstones include planar and trough cross bedding planar lamination soft sediment deformed bedding compound cosets of strata with low angle inclined bounding surfaces and lags of imbricated pebbles structures in the finer grained facies include desiccation cracks raindrop imprints caliche nodules and bioturbation groups of associated facies are arranged into nine distinct architectural elements channels gravel bars sandy bedforms downstream and laterally accreting barforms sand sheets crevasse splays levees floodplain units and shallow lakes which is consistent with a fluvial origin for the succession the types of architectural elements present and their relationship to each other demonstrate that the warchha sandstone preserves a record of a meandering river system that drained the northern margin of gondwanaland the dominance of fine grained floodplain facies over gravel grade channel base facies and the widespread occurrence of large scale lateral accretion elements supports the interpretation of a high sinuosity meandering fluvial system in which channel bodies accumulated via the lateral accretion of point bars but in which the active channels covered only a small part of a broad floodplain at any time instant although the regional and temporal distribution of these deposits is complex in broad terms the lower part is dominated by stacked multistorey channel bodies whereas single storey channel elements isolated in abundant fine grained floodplain deposits dominate the middle and upper parts of the formation

basinwide sedimentation and the continuum of paleoflow in an ancient river system kayenta formation lower jurassic central portion colorado plateau abstract utilizing detailed documentation of alluvial architecture to reconstruct the continuum of paleoflow perennial intermittent ephemeral a basinwide study of the kayenta formation lower jurassic reveals that the northern half of the basin is characterized by sandy low sinuosity fluvial systems which exhibit perennial assoc 1 to intermittent assoc 2 discharge indicators the rivers had headwaters east of the uncompahgre highlands western colorado and flowed southwest across the basin depositing a braidplain of channel sands with well preserved 3 dimensional macroforms one significant aspect of the macroform architecture is documentation of macroform climb in both an upstream and downstream direction the macroforms aggrade vertically by climbing maximum 10 dip in an upstream direction and migrating over the backs upstream ends of underlying macroforms the process of macroform climb records a minimum water depth of 8 m and a maximum of 16 m which places the kayenta perennial waterways assoc 1 within a mesothermal hydrologic regime the southern portion of the basin contains intermittent assoc 2 to ephemeral assoc 3 fluvial deposits extensive floodplain preservation and eolian dune and interdune sandsheet deposition assoc 4 a tributary drainage pattern to the northwest was established by smaller low to moderately sinuous streams eolian dune and interdune deposits migrated across this more arid windswept portion of the basin the range of alluvial architecture present in the kayenta attests to the diversity that can be found in a small continental sedimentary basin

on the spatial properties of ambient noise in the tonga trench including effects of bathymetric shadowing in september 2012 the free falling deep diving instrument platform deep sound iii descended to the bottom of the tonga trench where it resided at a depth of 8515 m for almost 3 h recording ambient noise data on four hydrophones arranged in a vertical l shaped configuration the time series from each of the hydrophones yielded the power spectrum of the noise over the frequency band 3 hz to 30 khz the spatial coherence functions along with the corresponding cross correlation functions were recovered from all available hydrophone pairs in the vertical and the horizontal the vertical coherence and cross correlation data closely follow the predictions of a simple theory of sea surface noise in a semi infinite ocean suggesting that the seabed in the tonga trench is a very poor acoustic reflector which is consistent with the fact that the sediment at the bottom of the trench consists of very fine grained material having an acoustic impedance similar to that of seawater the horizontal coherence and cross correlation data are a little more complicated showing evidence of a bathymetric shadowing of the noise by the walls of the trench and b highly directional acoustic arrivals from the research vessel supporting the experiment

particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump a synthesis of global sediment trap programs since 1983 particulate organic carbon poc is vertically transported to the oceanic interior by aggregates and their ballasts mainly caco3 and biogenic opal with a smaller role for lithogenic aerosols through the mesopelagic zone diel migrating zooplankton communities effect vertical transport and remineralization of poc in the upper layers of the ocean below 1 5 km the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport we normalized the fluxes of poc caco3 and biogenic opal from data published on samples collected at 134 globally distributed bottom tethered time series sediment trap ts trap stations to annual mole fluxes at the mesopelagic bathypelagic boundary m b at 2 km and defined them as fm bcorg fm bcinorg and fm bsibio using this global data set we investigated 1 the geographic contrasts of poc export at m b and 2 the supply rate of co2 to the world mesopelagic water column fm bcorg varies from 25 pacific warm pool to 605 divergent arabian sea mmolc m 2 yr 1 fm bcinorg varies from 8 high latitude polar oceans or 15 pacific warm pool to 459 divergent arabian sea mmolc m 2 yr 1 and fm bsibio the most spatially temporally variable flux ranges from 6 north atlantic drift to 1118 pacific subarctic gyre mmolsi m 2 yr 1 the oceanic region exhibiting the highest poc flux over a significantly large region is the area of the north pacific boreal gyres where the average fm bcorg 213 fm bcinorg 126 and fm bsibio 578 mmol m 2 yr 1 fm bcorg and fm bcinorg are particularly high in large upwelling margins including the divergent arabian sea and off cape verde one of the data sets showing the lowest flux over a significant region basin is fm bcorg 39 fm bcinorg 69 and fm bsibio 22 mmol m 2 yr 1 in the north pacific subtropical tropical gyres pan atlantic average fluxes are similar except fm bsibio fluxes are even lower where corg cinorg and sibio cinorg are 1 defines the carbonate ocean and where these ratios are 1 defines the silica ocean the carbonate ocean occupies about 80 of the present world pelagic ocean between the two major oceanographic fronts the north pacific polar front and the antarctic polar front and the silica ocean is found on the polar sides of these fronts the total global annual fluxes of fm bcorg fm bcinorg and fm bsibio at m b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar 36 2 33 8 and 34 6 teramol yr 1 120 112 and 114 mmol m 2 yr 1 respectively resulting in a near uniform binary ratio between the above three elements of about one the global ternary ratios estimated from 152 ts trap samples of the three elements are 35 32 33 from our global fm bcorg and a published model estimate of the global export production we estimate the regeneration rate of co2 through the mesopelagic zone by the biological pump is 441 teramolc yr 1 based on our global fm bcinorg and recently estimated global primary production of pic 36 86 teramolc yr 1 of pic is assumed to be dissolved within the upper 2 km of the water column

depth dependence of wind driven broadband ambient noise in the philippine sea in 2009 as part of philsea09 the instrument platform known as deep sound was deployed in the philippine sea descending under gravity to a depth of 6000 m where it released a drop weight allowing buoyancy to return it to the surface on the descent and ascent at a speed of 0 6 m s deep sound continuously recorded broadband ambient noise on two vertically aligned hydrophones separated by 0 5 m for frequencies between 1 and 10 khz essentially all the noise was found to be downward traveling exhibiting a depth independent directional density function having the simple form cos where 90 is the polar angle measured from the zenith the spatial coherence and cross spectral density of the noise show no change in character in the vicinity of the critical depth consistent with a local wind driven surface source distribution the coherence function accurately matches that predicted by a simple model of deep water wind generated noise provided that the theoretical coherence is evaluated using the local sound speed a straightforward inversion procedure is introduced for recovering the sound speed profile from the cross correlation function of the noise returning sound speeds with a root mean square error relative to an independently measured profile of 8 2 m s

ephemeral fluvial deposits integrated outcrop and simulation studies reveal complexity ephemeral fluvial sandstones form the main reservoirs in many oil and gas fields production histories and development difficulties suggest these deposits are more complex than is commonly supposed in the petroleum industry there is inadequate published information to account for this observation relevant sedimentological literature on such deposits is qualitative and unsuitable for detailed reservoir characterization studies therefore integrated sedimentological petrophysical and fluid flow simulation studies have been conducted on outcrop analogs in the southwestern united states our key objectives were to define flow units and to find areas of sensitivity inherent both in the sediments and in the analytical and statistical procedures used to describe and model s ch systems we report results of integrated studies on the lower jurassic kayenta formation in southeastern utah the kayenta formation is a relatively proximal sand rich succession dominated by channel fill sandstones sedimentological analysis identified eight main genetic units in contrast reservoir simulations based on probe permeameter data collected at outcrop show that six of the main genetic units have uniform flow behavior intraformational mudclast conglomerates are the dominant permeability barriers both because of the clasts themselves and because they act as sites of preferential cementation stochastic permeability models conditioned to the outcrop data produce results little different from models based on averaged values for each facies the most sensitive feature of the mode s concerns the assumptions made about the mudclast conglomerates the model results show that only by integrating analytical approaches can we understand the full character of an outcrop analog in such a way that we can use it predictively

palaeoenvironment of braided fluvial systems in different tectonic realms of the triassic sherwood sandstone group uk abstract fluvial successions comprising the fills of sedimentary basins occur in a variety of tectonic realms related to extensional compressional and strike slip settings as well as on slowly subsiding passive basin margins a major rifting phase affected nw europe during the triassic and resulted in the generation of numerous sedimentary basins in the uk much of the fill of these basins is represented by fluvial and aeolian successions of the sherwood sandstone group additionally regions that experienced slow rates of mesozoic subsidence unrelated to triassic rifting also acted as sites of accumulation of the sherwood sandstone group one well exposed example being the eastern england shelf the fluvial depositional architecture of deposits of the sherwood sandstone group of the eastern england shelf a shelf edge basin is compared with similar fluvial deposits of the st bees sandstone formation eastern irish sea basin a half graben the two studied successions represent the preserved deposits of braided fluvial systems that were influenced by common allogenic factors climate sediment source delivery style differences in preserved sedimentary style principally reflect their different tectonics settings analysis of lithofacies and architectural elements demonstrates that both studied successions are characterized by amalgamated channel fill elements that are recorded predominantly by downstream accreting sandy barforms the different tectonic settings in which the two braided fluvial systems accumulated exerted a dominant control on preserved sedimentary style and long term preservation potential on the eastern england shelf the vertical stacking of pebbly units and the general absence of fine grained units reflect a slow rate of sediment accommodation generation 18 19 4 m myr in this shelf edge basin successive fluvial cycles repeatedly reworked the uppermost parts of earlier fluvial deposits such that only the lowermost channel lags tend to be preserved by contrast in the eastern irish sea basin of west cumbria the rate of sediment accommodation generation was substantially greater 119 m myr such that space was available to preserve complete fluvial cycles including silty drape units that cap the channelized deposits

facies and fluvial architecture of a high energy braided river the upper proterozoic seglodden member varanger peninsula northern norway abstract the seglodden member late proterozoic as studied in two areas of the varanger peninsula northern norway is dominated by sand rich braided river deposits a quantitative summary of described facies emphasises the dominance of structures deposited under high energy conditions and a general absence of fine grained deposits and visible small scale sedimentary structures the sigmoidal and concave up cross stratified planar horizontally stratified and massive sandstone facies represent 80 95 of the total vertical thicknesses of the measured sections architectural elements are defined as sheet sandstone bodies and channel forms and fills and comprise simple bars transitional simple bar dune complexes dune complexes downstream accretion complexes and various types of channel deposits the seglodden fluvial system was operating in a non vegetated setting with well exposed sediment sources probably of a sedimentary origin this situation gave a very erratic discharge system with rapid runoff high denudation rate and very high sediment discharge increased flow within channels was compensated for by a broadening of the channels and it is inferred that the channels were very wide and shallow relative to their depths bounding surfaces of at least six different orders 0th 5th are interpreted within the studied successions with the third order surface as the lowest order surface that bound architectural elements as defined in this study the highest order surface 5th order is probably the result of channel belt switching due to a combination of sedimentary processes and tectonic subsidence of the basin the east and northeasterly palaeocurrent trend in the seglodden area compared to the southeasterly trend in the smellror area indicates that the axis of the depositional system changed significantly in direction basinwards over the 15 20 km distance between the two study areas the controlling mechanisms for this may be autocyclic as well as allocyclic processes although the tectonic influence on sedimentation was probably significant

southern ocean control of silicon stable isotope distribution in the deep atlantic ocean the fractionation of silicon si stable isotopes by biological activity in the surface ocean makes the stable isotope composition of silicon delta si 30 dissolved in seawater a sensitive tracer of the oceanic biogeochemical si cycle we present a high precision dataset that characterizes the delta si 30 distribution in the deep atlantic ocean from denmark strait to drake passage documenting strong meridional and smaller but resolvable vertical delta si 30 gradients we show that these gradients are related to the two sources of deep and bottom waters in the atlantic ocean waters of north atlantic and nordic origin carry a high delta 30 sisignature of 1 7 parts per thousand into the deep atlantic while antarctic bottom water transports si with a low delta si 30 value of around 1 2 parts per thousand the deep atlantic delta si 30 distribution is thus governed by the quasi conservative mixing of si from these two isotopically distinct sources this disparity in si isotope composition between the north atlantic and southern ocean is in marked contrast to the homogeneity of the stable nitrogen isotope composition of deep ocean nitrate delta n 15 no3 we infer that the meridional delta si 30 gradient derives from the transport of the high delta si 30 signature of southern ocean intermediate mode waters into the north atlantic by the upper return path of the meridional overturning circulation moc the basin scale deep atlantic delta si 30 gradient thus owes its existence to the interaction of the physical circulation with biological nutrient uptake at high southern latitudes which fractionates si isotopes between the abyssal and intermediate mode waters formed in the southern ocean

iron isotope constraints on fe cycling and mass balance in oxygenated earth oceans the fe isotope composition of proterozoic to modern clastic sedimentary rocks and aerosols defines a range ind 56 fe values that is only slightly more variable than the range of fe isotope com positions measured in terrestrial igneous rocks indicating that chemical weathering sedimentary transport and diagenesis play only a minor role in producing fe isotope variations in environ ments where fe redox conditions have been controlled by current levels of atmospheric oxygen in contrast the fe isotope composi tions of hot fluids 300 8c from mid ocean ridge mor spread ing centers define a narrow range that is shifted to lower d 56 fe values by 0 2 0 5 as compared to igneous rocks these new data allow a conceptual model for the fe isotope composition of the oxic oceans that predicts large ranges in fe isotope composition under conditions of changing aerosol and mor fe fluxes such as during periods of major worldwide glaciation

a role for scavenging in the marine biogeochemical cycling of zinc and zinc isotopes zinc zn and cadmium cd are important biologically active trace metals in the ocean to date the marine distributions of these elements have been understood primarily in terms of biological assimilation by growing phytoplankton and regeneration of sinking biological material initial studies of zn and cd concentrations and stable isotope ratios 66zn and 114cd have therefore focused on their use as simple tracers of assimilation and regeneration in the oceans however these two processes are insufficient to explain new data on the marine distribution of zn and 66zn here using the first high resolution paired marine depth profiles of zn cd 66zn and 114cd we suggest that scavenging of zn onto organic matter plays a major yet largely unconsidered role in the marine cycling of zn this hypothesis is supported by culture experiments which show that zn released from degrading phytoplankton is rapidly scavenged back onto organic matter and that adsorbed zn is isotopically heavier than the dissolved phase by 0 58 in contrast very little cd or phosphate was scavenged and cd isotopes were not significantly fractionated during degradation our hypothesis is further supported by one dimensional modeling which reproduces observed marine 66zn profiles with 1 of zn adsorbed to particles understanding how zn cycling in the oceans is a balance between assimilation scavenging and regeneration is necessary in order to investigate 66zn as a tracer of marine productivity we anticipate that paired analyses of 66zn and 114cd will prove to be valuable new tools in constraining patterns of global primary productivity providing key information for the marine carbon cycle during periods of past and present global climate change

physical and biogeochemical controls on the distribution of dissolved cadmium and its isotopes in the southwest pacific ocean abstract cadmium stable isotope ratios 114cd have become a useful tool for oceanographers investigating the biogeochemical and physical processes that affect the nutrient like distribution of the bioactive trace metal cadmium cd throughout the oceans here we present a meridional transect of dissolved cd and 114cd from japanese geotraces section gp19 along 170 w from 64 s in the southern ocean to the equatorial pacific along the gp19 section the deep ocean 1500 m shows small variability in dissolved cd 0 75 0 9 nmol kg 1 and a homogeneous 114cd signature 0 26 0 06 2sd n 60 relative to nist srm 3108 adding these data to previously published work allows us to calculate a deep pacific and southern ocean 1500 m mean 114cd of 0 26 0 10 2sd n 436 higher in the water column depth profiles of cd along the gp19 section exhibit a strong vertical gradient from a maximum up to 0 9 nmol kg 1 at 1500 2000 m up to depleted surface waters overall the distribution of cd and 114cd along the gp19 section is remarkably well explained by large scale mixing of water mass endmembers with defined 114cd signatures emphasizing the importance of surface southern ocean processes for the distribution of trace metals such as cd in the subsurface southwest pacific at the regional scale however two other processes may overprint this mixing relationship first by comparison with the nearby southeast pacific gp16 section we find that the 114cd signature of equatorial intermediate water masses shows little zonal variation across the equatorial pacific despite becoming enriched in dissolved cd due to remineralization we propose that this uniformity is explained by complete utilization of cd in the surface tropical pacific and remineralization of cd with an isotopic signature similar to intermediate waters therefore conserving the southern sourced isotopic signature similarly the observed increase of about 30 in deep ocean cd concentrations from the south to the north pacific is associated with a near constant 114cd signal these observations enable us to constrain the net 114cd of cd added by remineralization to the deep ocean with the caveat that such a signal is integrated over the entire pacific and that remineralization under different oceanic regimes such as hnlc areas may add cd with different isotopic compositions to deep waters second at gp19 stations close to the equator subtle cd depletion relative to phosphate is observed associated with low oxygen subsurface waters consistent with other studies from the north pacific discerning the effects of such processes on cd isotopic distributions is an important step to a more detailed understanding of the biogeochemical cycling of cd in the modern ocean and the application of 114cd as a tracer of past deep water circulation this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

unconfined flow deposits in distal sectors of fluvial distributary systems examples from the miocene luna and huesca systems northern spain abstract thin sheet sandstone beds in a continental succession may be the products of unconfined overbank flow or deposition in lacustrine environments in the distal parts of fluvial distributary systems these two settings may be intercalated recording fluctuations in lake level in response to climatic changes field studies of the luna and huesca fluvial distributary systems in the miocene of the ebro basin spain are here used to characterise sheet sandstone deposited in distal fluvial and lake margin environments in this study we document the facies and relationships between 322 individual sandbodies deposited in both alluvial settings as sheetfloods and in lacustrine settings as deltaic lobes the alluvial sandstone sheets were deposited from lateral and frontal sheetflood events when unconfined flow replaced channelised flow as the main transport mechanism the term sheetflood is used here to refer to sub aerial unconfined turbulent flow events that undergo expansion thinning and deceleration with increasing radial distance from source the depositional process is similar to modern floodouts and terminal splays of the channel country and lake eyre central australia such a process was thought to be the dominant depositional mechanism during lake lowstands the sheets formed in the lacustrine setting are interpreted as deltaic sediments deposited in a shallow gradient lake similar to the modern day volga delta caspian sea shallow water friction dominated deltaic processes are thought to have been the primary depositional mechanism in the distal sectors of the fluvial systems during lake highstands

architecture of a sandstone uranium reservoir and the spatial distribution of its internal carbonaceous debris a case study of the zhiluo formation eastern ordos basin northern china abstract the sandstone of the middle jurassic zhiluo formation in the eastern ordos basin provides the opportunity for conducting a critical case study of the architecture and internal carbonaceous debris cd distribution of a sandstone uranium reservoir located in a field outcrop in shiwan the 16 24 m thick outcrop section is a sandstone dominated subaqueous distributary channel succession in which six lithofacies types se st sm sp sh and fl occur in a predictable order of repeated fining upward cycles these facies emphasize that the dominant structures had been deposited under lower flow regime conditions various groups of associated facies have been identified as six distinct architectural elements intrachannel units longitudinal bar transverse bar diagonal bar dune complex and abandoned channel deposits within a framework of five orders of bounding surfaces these elements with specific lithofacies associations and spatial relationships indicate that the subaqueous distributary channel had involved in four stages of formation channel occurring channel flooding channel waning and channel abandonment moreover as one of the most significant reductants in the sandstone succession the cd occurs in the form of channel lags and is concentrated in the middle and lower parts of the lag deposit zones the spatial distribution of cd within the studied succession is controlled by the sandstone architecture and the cd rich zones are preserved exclusively upon the basal surfaces of intrachannel units longitudinal and transverse bars this study can be helpful for exploring the distribution of metallogenic flow field as well as the restriction of the reductants on interlayer oxidation

the cycling of iron zinc and cadmium in the north east pacific ocean insights from stable isotopes abstract dissolved stable isotope ratios of the transition metals provide useful information both for understanding the cycling of these bioactive trace elements through the oceans and tracing their marine sources and sinks here we present seawater dissolved fe zn and cd concentration and stable isotope ratio 56fe 66zn and 114cd profiles from two stations in the pacific ocean the safe station 30 n 140 w in the subtropical north east pacific from the geotraces ic2 cruise and the marginal san pedro basin 33 8 n 118 4 w within the south california bight these data represent to our knowledge the first full water column profiles for 66zn and 56fe from the open ocean north pacific and the first observations of dissolved 66zn and 114cd in a low oxygen marginal basin at the safe station 56fe is isotopically lighter throughout the water column 0 6 to 0 1 relative to irrm 014 compared to the north atlantic suggesting significant differences in fe sources or fe cycling between these two ocean basins a broad minimum in 56fe associated with the north pacific oxygen minimum zone omz

sandstone type uranium deposits in the ordos basin northwest china a case study and an overview abstract this paper provides a comprehensive review on studies of sandstone type uranium deposits in the ordos basin northwest china as the second largest sedimentary basin the ordos basin has great potential for targeting sandstone type u mineralization the newly found and explored dongsheng and diantou sandstone type uranium deposits are hosted in the middle jurassic zhilou formation a large number of investigations have been conducted to trace the source rock compositions and relationship between lithic subarkose sandstone host rock and uranium mineralization an optical microscopy study reveals two types of alteration associated with the u mineralization chloritization and sericitization some unusual mineral structures with compositional similarity to coffinite have been identified in a secondary pyrite by sem these mineral phases are proposed to be of bacterial origin following high resolution mapping of uranium minerals and trace element determinations in situ moreover geochemical studies of ree and trace elements constrained the mechanism of uranium enrichment displaying lree enrichment relative to hree trace elements such as pb mo and ba have a direct relationship with uranium enrichment and can be used as index for mineralization the source of uranium ore forming fluids and related geological processes have been studied using h o and c isotope systematics of fluid inclusions in quartz veins and the calcite cement of sandstone rocks hosting u mineralization both h and o isotopic compositions of fluid inclusions reveal that ore forming fluids are a mixture of meteoric water and magmatic water the c and s isotopes of the cementing material of sandstone suggest organic origin and bacterial sulfate reduction bsr providing an important clue for u mineralization discussion of the ore genesis shows that the greenish gray sandstone plays a crucial role during processes leading to uranium mineralization consequently an oxidation reduction model for sandstone type uranium deposit is proposed which can elucidate the source of uranium in the deposits of the ordos basin based on the role of organic materials and sulfate reducing bacteria we discuss the mechanism of uranium deposition responsible for the genesis of these large sandstone type uranium deposits in this unique sedimentary basin

reconstructing the architecture and sequence stratigraphy of the preserved fluvial record as a tool for reservoir development a reality check driven in part by the need for better information about fluvial systems for the purpose of nonmarine reservoir evaluation and development much valuable work is now being conducted on modern rivers and their deposits aided by such techniques as ground penetrating radar however studies of modern and recent systems cannot address the question of the long term preservability of the present day deposits only studies of the rock record itself can explore this issue two separate studies of ancient fluvial systems illustrate some of the problems a study of the hawkesbury sandstone triassic sydney basin australia highlighted the difficulty in interpreting the dimensions of large sand bodies from comparisons with a modern analog even when very large outcrops are available a seismic time slice study of pliocene pleistocene fluvial systems in the gulf of thailand revealed major changes in channel size and fluvial style over short vertical intervals braided and meandering systems meander belt widths 4 to 10 km 2 5 to 6 mi are separated by a few tens of meters of section or less and are interbedded with the deposits of much smaller rivers showing straight meandering and anastomosed patterns incised valleys and underfit streams are also present these variations can be interpreted in terms of a sequence model but they indicate the problems that could arise from the use of a single suite of dimensional variables as input into numerical reservoir heterogeneity and flow models most numerical simulation models make use of sets of equations relating such parameters as channel width depth and sinuosity but most such equations are generalized across the whole spectrum of fluvial styles and can be conditioned to the reality of individual reservoirs only with difficulty the application of the principles of sequence stratigraphy to fluvial deposits is rendered difficult by the complex response to allogenic forcing that characterizes fluvial systems episodes of aggradation and degradation that may be used to define sequences and their bounding unconformities in the stratigraphic record may be the result of the complex interplay of several allogenic mechanisms governing varying stream power and sediment supply mechanisms that may be operating at different time scales and may be out of phase with each other in developing practical solutions for reservoir development numerical modeling and simulation may provide generalized starting points for the analysis history matching commonly demonstrates inaccuracies in many initial models further progress may be made by direct study of the reservoir itself using three dimensional 3 d seismic and surveillance techniques there is a continuing role for the study of ancient analogs as providing a realistic database on the long term preservation styles of fluvial reservoir deposits

dissolved cadmium in the southern ocean distribution speciation and relation to phosphate we report isotope dilution analyses of dissolved cadmium cd and electrochemical cd speciation measurements in the atlantic sector of the southern ocean bioavailable inorganic cd is 100 times higher in near surface waters south of the polar front compared to the subantarctic zone because of upwelling and reduced complexation by organic cd ligands to trace local changes in the relation between cd and p we examine the deviations from a linear deep water cd vs p relation cd and find that changes in cd coincide with the position of frontal systems and covary with primary productivity and total dissolved mn and fe concentrations these covariations agree with potential local changes in phytoplankton cd uptake rates resulting from differences in the availability of cd zn mn and fe a band of negative cd values is associated with formation of subantarctic mode water samw and antarctic intermediate water aaiw in contrast to samw which may export low cd p ratios from the southern ocean the cd p ratios in aaiw increase by mixing with underlying upper circumpolar deep water before being exported from the southern ocean deep waters show constant cd p ratios and both elements behave conservatively with end member mixing between deep waters of the weddell gyre the antarctic circumpolar current and inflowing north atlantic deep water overall our results support the hypothesis that the kink in the global cd vs p relation is largely caused by high cd p uptake ratios in the trace nutrient limited southern ocean

an excellent fossil wood cell texture with primary uranium minerals at a sandstone hosted roll type uranium deposit nw china abstract a fossil wood cell texture with pitchblende and coffinite found at a sandstone hosted roll type uranium deposit xinjiang nw china is first reported here for the country in the mineralized sandstone detrital grains consisting of quartz feldspar rock fragments carbonaceous trashes mica and accessory minerals were deposited in early turassic time and were cemented by clays and minor authigenic calcite and quartz pitchblende and minor coffinite are principal ore minerals at the deposit and selectively replaced carbonized fossil wood remnants or filled fossil wood cells an excellent fossil wood cell texture with primary uranium minerals formed replacement of organic debris by primary uranium minerals may be due to a local reducing environment resulting from the production of ch 4 h 2 s or h 2 so 3 in its decomposition and a biochemical reaction indicated by the common presence of framboidal pyrite

the depth dependence of rain noise in the philippine sea during the philippine sea experiment in may 2009 deep sound a free falling instrument platform descended to a depth of 5 1 km and then returned to the surface two vertically aligned hydrophones monitored the ambient noise continuously throughout the descent and ascent a heavy rainstorm passed over the area during the deployment the noise from which was recorded over a frequency band from 5 hz to 40 khz eight kilometers from the deployment site a rain gauge on board the r v kilo moana provided estimates of the rainfall rate the power spectral density of the rain noise shows two peaks around 5 and 30 khz elevated by as much as 20 db above the background level even at depths as great as 5 km periods of high noise intensity in the acoustic data correlate well with the rainfall rates recovered from the rain gauge the vertical coherence function of the rain noise has well defined zeros between 1 and 20 khz which are characteristic of a localized source on the sea surface a curve fitting procedure yields the vertical directional density function of the noise which is sharply peaked accurately tracking the storm as it passed over the sensor station

total dissolved zinc in the upper water column of the subarctic north east pacific abstract total dissolved zn concentrations are reported for winter and summer along the e w line p transect and for summer along s n line z transect extending from ocean station papa osp 50 n 145 w to the respective shelf waters surface water 10 m concentrations ranged from 0 04 nm in the open ocean to 0 9 nm at the canadian shelf station a clear gradient is evident with dissolved zn concentrations decreasing with increasing distance from shore along the e w transect in both summer and winter no consistent trend was observed along the s n transect low concentrations of zn 0 05 0 07 nm were observed in near surface water at osp in winter the vertical distribution of dissolved zn is oceanographically consistent showing a silicon like vertical profile concentrations of silicic acid and dissolved zn at depth are higher than those at equivalent depths in the atlantic as expected from deep water circulation patterns and build up in concentration of these elements dissolved zn si ratios in the upper 200 m indicate a trend of decreasing with distance from shore which infers a decoupling between dissolved zn and silicic acid in the upper ocean we hypothesise that the silicon like profile of dissolved zn is a result of recycling from relatively biologically resistant organic particulate phases that leads to profiles very similar to those of dissolved silicon other than at two stations where there is very high primary production there is no apparent horizontal relationship between total dissolved zn and chlorophyll a or production

hydrogeochemical characteristics of the sandstone hosted uranium mineralization in northern ordos basin china abstract the northern ordos basin is one of the biggest uranium resource production areas in china however the hydrogeochemical mechanism for the formation of uranium deposits remains poorly understood despite that interlayer oxidation hydrothermal fluid mineralization and gas reduction were proposed in order to provide a more comprehensive knowledge on their formation mechanism the investigation was carried out by analyzing hydrogeochemistry and environmental isotopes of waters from river lakes shallow private wells boreholes over the period from 2015 to 2016 the results showed that the analysed samples exhibited a hydrochemical heterogeneity confirmed by a large range of ph eh main cation and anion concentrations and uranium concentration in surface water quaternary shallow groundwater cretaceous confined water and jurassic confined water the piper and durov diagrams highlighted that hydrochemical facies changed with groundwater flow from shallow to deep with hco3 ca mg and hco3 ca in quaternary shallow groundwater hco3 cl ca na in cretaceous confined water and cl na and hco3 na in jurassic confined water aqueous geochemistry indicated that the jurassic ore bearing confined waters originated from the cretaceous confined waters involving both leaching processes and desulfidation nonetheless the cretaceous confined waters originated from quaternary shallow groundwater and mainly have experienced leaching processes gibbs plot indicated that with an accumulation of ions in the groundwater during runoff calcite and uraninite minerals would be oversaturated and precipitation tended to occur the variation of tds along depth indicated desulfurization occurrence in ore bearing aquifer and a decrease in migrating ability of uo22 leading to u precipitation isotopic results showed that the ore bearing confined waters were depleted in 18o and d and were located along the global meteoric water line gmwl most ore bearing confined waters plotted on or near the meteoricwater line showing their deep circulating meteoric origin uranium species study indicated that dissolved uranium was dominated by uo2 oh 3 and uo2 co3 34 which have a high migrating ability saturation index of uraninite in all water samples were determined to be below 0 indicating that this uranium deposit was currently not under mineralization the ph and eh values of the samples were located in the migration area suggesting that uranium is in a migration state under current groundwater conditions only when ph 5 8 and eh

biogeochemical cycling of dissolved zinc along the geotraces south atlantic transect ga10 at 40 s the biogeochemical cycle of zinc zn in the south atlantic at 40 s was investigated as part of the uk geotraces program to date there is little understanding of the supply of zn an essential requirement for phytoplankton growth to this highly productive region vertical zn profiles displayed nutrient like distributions with distinct gradients associated with the water masses present surface zn concentrations are among the lowest reported for the world s oceans 2 0 97 n 460 our results suggest that the use of a global zn si relationship would lead to an underestimation of dissolved zn in deeper waters of the south atlantic by utilizing si and a new tracer zn our data indicate that the preferential removal of zn in the southern ocean prevented a direct return path for dissolved zn to the surface waters of the south atlantic at 40 s and potentially the thermocline waters of the south atlantic subtropical gyre the importance of zn for phytoplankton growth was evaluated using the zn soluble reactive phosphorus srp relationship we hypothesize that the low zn concentrations in the south atlantic may select for phytoplankton cells with a lower zn requirement in addition a much deeper kink at 500m in the zn srp ratio was observed compared to other oceanic regions key points dissolved zinc biogeochemical cycle investigated in the south atlantic ocean 2014 american geophysical union all rights reserved

silicon and zinc biogeochemical cycles coupled through the southern ocean zinc is vital for the physiology of oceanic phytoplankton the striking similarity of the depth profiles of zinc to those of silicate suggests that the uptake of both elements into the opaline frustules of diatoms and their regeneration from these frustules should be coupled however the zinc content of diatom opal is negligible and zinc is taken up into and regenerated from the organic parts of diatom cells thus since opaline frustules dissolve deep in the water column while organic material is regenerated in the shallow subsurface ocean there is little reason to expect the observed close similarity between zinc and silicate and the dissimilarity between zinc and phosphate here we combine observations with simulations using a three dimensional model of ocean circulation and biogeochemistry to show that the coupled distribution of zinc and silicate as well as the decoupling of zinc and phosphate can arise in the absence of mechanistic links between the uptake of zinc and silicate and despite contrasting regeneration length scales our simulations indicate that the oceanic zinc distribution is in fact a natural result of the interaction between ocean biogeochemistry and the physical circulation through the southern ocean hub our analysis demonstrates the importance of uptake stoichiometry in controlling ocean biogeochemistry and the utility of global scale elemental covariation in the ocean in understanding these controls zinc and silicon distributions co vary in much of the global oceans observations and numerical modelling suggest that this co variation can arise in the absence of mechanistic links between the uptake of zinc and silicate

compressional and shear wave properties of marine sediments comparisons between theory and data according to a recently developed theory of wave propagation in marine sediments the dispersion relationships for the phase speed and attenuation of the compressional and the shear wave depend on only three macroscopic physical variables porosity grain size and depth in the sediment the dispersion relations also involve three real parameters assigned fixed values representing microscopic processes occurring at grain contacts the dispersion relationships are compared with extensive data sets taken from the literature covering the four wave properties as functions of all three physical variables with no adjustable parameters available the theory matches accurately the trends of all the data sets this agreement extends to the compressional and shear attenuations in that the theory accurately traces out the lower bound to the widely distributed measured attenuations the theory predicts the intrinsic attenuation arising from the irreversible conversion of wave energy into heat whereas the measurements return the effective attenuation which includes the intrinsic attenuation plus additional sources of loss such as scattering from shell fragments and other inhomogeneities in the medium provided one wave or physical property is known say the compressional speed or the porosity all the remaining sediment properties may be reliably estimated from the theory

the subarctic frontal zone in the north pacific characteristics of frontal structure from climatological data and synoptic surveys the subarctic front is a thermohaline structure across the north pacific separating colder fresher water to the north from warmer saltier water to the south levitus s 1982 data and 72 conductivity temperature depth salinity temperature depth sections are used to show the spatial and seasonal variations of the climatological frontal zone and the characteristics of the frontal structure in synoptic surveys the temperature gradient in the mean frontal zone is stronger in the western pacific and decreases eastward while the salinity gradient has less variation across the pacific the temperature gradient also has larger seasonal variation with a maximum in spring than the salinity gradient the synoptic surveys show that the frontal zone is narrower and individual fronts tend to be stronger in the western pacific than in the eastern pacific density gradients tend to be more compensated at the strongest salinity fronts than at the strongest temperature fronts a horizontal minimum of vertical stability is found south of the subarctic halocline outcrop the northern boundary of the north pacific intermediate water merges with the frontal zone west of 175 w and is north of the northern boundary of the subarctic frontal zone in the eastern pacific the shallow salinity minima start within the subarctic frontal zone in the eastern pacific

estimation of the roll angle in a triplet towed array using oceanic surface generated ambient noise this paper proposes a roll angle estimation method for the triplet towed array using the oceanic ambient noise recorded in the mid frequency range of 1 to 10 khz here the dominance of oceanic surface generated noises such as wind driven and shipping noises is expected the ratio between the approximated phase parts of the noise coherence function regarding the triplet hydrophones is used for the roll estimation advantage of this technique is that explicit input regarding the oceanic environment is not required especially for an ocean with an azimuthally uniform noise field or dominant noise sources at the end fire direction of the horizontal array in other cases a roll angle bias occurs depending on the horizontal directionality this proposed technique is applied to ocean ambient noise measurements that were collected in the east sea of korea during august 2015 the roll angles of the triplet array are estimated from the measurements and compared with roll sensor measured data the estimated roll angles agree with the measured ones within the root mean square error of 10 and their difference tends to decrease with increasing wind speed

the relationship between zinc its isotopes and the major nutrients in the north east pacific abstract trace metal micronutrients play key roles in photosynthesis by oceanic phytoplankton though they are required in much smaller amounts than the major nutrients p n si their bioavailable forms are also present in the seawater solution at much lower levels relationships between the dissolved chemistry of the nutrient type trace metals their stable isotope variations as well those of the major nutrients have highlighted the importance of biological and physical processes in the southern ocean in controlling their oceanic biogeochemistry however the first order southern ocean processes are overprinted by vertical cycling in other parts of the ocean particularly upwelling regions remote from the southern ocean with the north pacific standing out in particular here we present new zinc zn concentration and isotope as well as major nutrient data for the ne pacific and couple these new data with a compilation of published data from across the region with the objective of better understanding the impact of this important region on oceanic biogeochemical cycles the new zn isotope data for two stations along line p p04 and p26 show a large range in 66 zn in the upper ocean 0 4 up to 1 associated with a very small isotope fractionation but extreme depletion of the dissolved pool during photic zone biological uptake and the regeneration of this cellular zn at very shallow depths 50 m beneath this the two profiles approach the 66 zn value of 0 5 seen throughout the deep ocean by about 500 m the minimum 66 zn resulting from regeneration is associated with very high zn concentrations particularly at the marginal p04 station where diatoms dominate the phytoplankton ecology combining the new data with published zn and major nutrient concentrations from across the north pacific emphasises the role of vertical biological cycling in controlling regional biogeochemistry in the north pacific resulting in the partial overprinting of biogeochemical signatures transported out of the southern ocean by the ocean circulation zinc isotope data document the uptake of this metal into diatoms and the co regeneration of zn with phosphate in the upper water column silica in contrast is regenerated at greater depth resulting in a decoupling of the zn si correlation that is set in the southern ocean and that dominates the atlantic previous work has suggested that the decoupling of zn and si in the subarctic north pacific results from removal of zn and other metals to water column particulate sulphide in our dataset and in the compilation of data documenting relationships between zn and the major nutrients across the north pacific this decoupling is clearly due to the different lengthscales of regeneration for organic matter zn and p and diatom opal si

pervasive sources of isotopically light zinc in the north atlantic ocean abstract in this study we report seawater dissolved zinc zn concentration and isotope composition 66 zn from the geotraces ga01 geovide section in the north atlantic across the transect three subsets of samples stand out due to their isotopically light signature those close to the reykjanes ridge those close to the sediments and those pervasively in the upper ocean similar to observations at other locations the hydrothermal vent of the reykjanes ridge is responsible for the isotopically light zn composition of the surrounding waters with an estimated source 66 zn of 0 42 this isotopically light zn is then transported over a distance greater than 1000 km from the vent sedimentary inputs are also evident all across the trans atlantic section highlighting a much more pervasive process than previously thought these inputs of isotopically light zn ranging from 0 51 to 0 01 may be caused by diffusion out of zn rich pore waters or by dissolution of sedimentary particles the upper north atlantic is dominated by low 66 zn a feature that has been observed in all zn isotope datasets north of the southern ocean using macronutrient to zn ratios to better understand modifications of preformed signatures exported from the southern ocean we suggest that low upper ocean 66 zn results from addition of isotopically light zn to the upper ocean and not necessarily from removal of heavy zn through scavenging though the precise source of this isotopically light upper ocean zn is not fully resolved it seems possible that it is anthropogenic in origin this view of the controls on upper ocean zn is fundamentally different from those put forward previously

abundance of zinc isotopes as a marine biogeochemical tracer 1 the zn isotopic compositions of ferromanganese nodules sediment trap samples sediments and organic reference samples have been analyzed by multiple collector inductively coupled plasma mass spectrometry icp ms the range of isotopic variations 1 for 66zn 64zn is significant with respect to the analytical precision 0 04 at the 95 confidence level marine argillaceous sediments show rather constant values consistent with those of continental shales and loess and with the value of a basalt from reunion island we infer that the depletion of the light zn isotopes in marine particles and in ferromanganese nodules presumably equilibrated with seawater results from biological activity in the upper water column the 66zn values of sediment trap samples collected near the upwelling off the coast of mauritania central atlantic show a seasonal isotopic fluctuation consistent with biological pumping during the high productivity period higher values of 66zn in nodules appear to be associated with the amplitude of seasonal variations rather than with the mean values of the biological productivity

processes controlling the distributions of cd and po4 in the ocean depth profiles of dissolved cd and po4 from a global data compilation were used to derive the cd p of particles exported from the surface layer and the results indicate lowest values in the north atlantic 0 17 0 05 highest in the southern 0 56 0 24 and intermediate in the south indian 0 31 0 14 and north pacific 0 36 0 08 ocean basins the cd p of exported particles in high nutrient low chlorophyll hnlc regions is twice that for particles exported in non hnlc regions as is the fractionation effect during biological uptake of cd and po4 and these trends primarily determine the spatial trends of dissolved cd po4 observed in the surface ocean in deep waters the lowest dissolved cd po4 of 0 23 0 07 is found in the north atlantic ocean and the result primarily of low cd po4 of north atlantic deep water 0 23 in contrast deep waters in the southern ocean have significantly higher dissolved cd po4 0 30 0 06 which is a result of the cd po4 of upwelled deep water from the south pacific and south indian 0 28 and the high cd p of degrading particles a multibox model that accounts for the impacts of particle degradation and thermohaline circulation in the deep sea yields dissolved cd and po4 interbasin trends close to observations model experiments illustrate the dependence of the dissolved cd po4 of the deep sea on the extent of hnlc conditions in the southern ocean and the impact on reconstructing paleo po4 concentrations from a cd proxy

new aspects of deformed cross strata in fluvial sandstones examples from neoproterozoic formations in northern norway abstract extensive 20 200 m long exposures of tabular cross sets in neoproterozoic fluvial sandstone in northern norway demonstrate that deformed cross strata in the form of recumbently folded cross strata with associated massive sand are localized features passing in both up and down current direction into undeformed concave upward or sigmoidal cross strata the deformation occurs in down current inclined tangential wedge shaped zones beneath reactivation surfaces and less commonly as flat topped lenticular zones the localized nature of the sediment deformation is attributed to local liquefaction below the top of the bed in the case of the flat topped lenses and at the dune front in the case of the more common tangential wedges the position of the flat topped lenses suggests deformation by the shear stress of high velocity suspension laden currents although liquefaction of the dune front implies the action of gravity forces it is argued that the fluvial currents were the main driving force at the instant of bed liquefaction post folding gravitational shearing probably enhanced the deformation within the upper part of the wedges with their long flat lying toeset resulting from redeposition of downslope moving liquefied sand the down current alternation of deformed tangential wedges and undeformed cross strata suggests that the mechanism that triggered the liquefaction of the dune lee side was related to the fluvial system itself and hence was of autokinetic origin the tabular cross sets have previously been interpreted as a product of the dune upper stage plane bed flow regime in this flow context it can be speculated that the liquefaction and deformation occurred when the flow conditions approached the plane bed phase probably inducing a highly differential turbulent pattern and pressure fluctuations sufficient to liquefy the fine medium sand the small flat topped deformation lenses also suggest liquefaction by cyclic loading whereas the solitary nature of the large lenses may alternatively be the result of impulsive loading from bank collapse in less well exposed fluvial successions the auto or allokinetic origin of recumbently folded cross strata may be difficult to determine however the common occurrence of recumbent folds in cross stratified fluvial sandstones and their virtual absence in marine cross stratified deposits suggests strongly that in the majority of cases the deformation was autokinetic resulting from flow phenomena typical of river channels this kind of deformation structure should thus not be attributed to an allokinetic seismic triggering mechanism unless independent evidence of fault activity can be documented

the biogeochemical cycling of zinc and zinc isotopes in the north atlantic ocean zinc zn is a marine micronutrient with an overall oceanic distribution mirroring the major macronutrients especially silicate seawater zn isotope ratios 66zn are a relatively new oceanographic parameter which may offer insights into the biogeochemical cycling of zn to date the handful of published studies of seawater 66zn show the global deep ocean to be both remarkably homogeneous approximately 0 5 and isotopically heavier than the marine sources of zn 0 1 to 0 3 here we present the first high resolution oceanic section of 66zn from the u s geotraces ga03 north atlantic transect from lisbon to woods hole throughout the surface ocean biological uptake and release of isotopically light zn together with scavenging of heavier zn leads to large variability in 66zn in the ocean below 1000 m 66zn is generally homogeneous 0 50 0 14 2 sd though deviations from 0 5 allow us to identify specific sources of zn the mediterranean outflow is characterized by 66zn of 0 1 to 0 3 while margin sediments are a source of isotopically light zn 0 5 to 0 8 which we attribute to release of nonregenerated biogenic zn mid atlantic ridge hydrothermal vents are also a source of light zn close to 0 5 though zn is not transported far from the vents understanding the biogeochemical cycling of zn in the modern ocean begins to address the imbalance between the light 66zn signature of marine sources and the globally homogeneous deep oceans 66zn of 0 5 on long timescales with overall patterns pointing to sediments as an important sink for isotopically light zn throughout the oceans

the seismic signature of rain abstractrain has long been a problem for land seismic surveys in terms of its effect on the condition of the surface and near surface and also due to the seismic noise it creates when raindrops hit the ground i measured the seismic signature of rainfall using water dripped from height using a pipette and natural rain in winchester england over a three month period my results indicated that rain noise is concentrated at frequencies of greater than 80 hz with a detectable range of less than 1 m drops of water landing directly on a geophone result in events with amplitudes nearly 30 times larger than those landing next to the geophone items placed on the surface of the ground such as cables absorb the energy of the impact and reduce the level of the resulting seismic noise burying geophones results in attenuation of rain noise by between 7 7 and 8 6 db 0 1 m but given the effort required to bury geophones it is likely that data processing algorithms or the placement of vibration absorbent ma

cadmium isotope variations in the southern ocean abstract cadmium concentrations and isotope compositions were determined for 47 seawater samples from the high nutrient low chlorophyll hnlc zone of the atlantic sector of the southern ocean the samples include 13 surface waters from a transect of the weddell gyre and 3 depth profiles from the weddell sea and drake passage the southern ocean mixed layer samples from this study and abouchami et al 2011 define a clear but broad hnlc trend in a plot of e cd 114 110 versus cd which is primarily a consequence of isotopic fractionation associated with biological uptake e cd 114 110 is the deviation of the 114cd 110cd ratio of a sample from nist srm 3108 cd in parts per 10 000 the trend is especially apparent in comparison to the large range of values shown by a global set of seawater cd data for shallow depths the southern ocean samples are also distinguished by their relatively high cd concentrations typically 0 2 to 0 6 nmol kg and moderately fractionated e cd 114 110 generally between 4 and 8 that reflect the limited biological productivity of this region detailed assessment reveals fine structure within the hnlc trend which may record differences in the biological fractionation factor different scenarios of closed and open system isotope fractionation and or distinct source water compositions southern ocean seawater from depths 1000 m has an average e cd 114 110 of 2 5 0 2 2se n 16 and together with previous results this establishes a relatively constant e cd 114 110 value of 3 0 0 3 2se n 27 for global deep waters significant isotopic variability was observed at intermediate depths in the southern ocean seawater from 200 m to 400 m in weddell sea has high cd concentrations and e cd 114 110 as low as 1 presumably due to remineralization of cd from biomass that records incomplete nutrient utilization antarctic intermediate water which was sampled at 150 to 750 m depth in the drake passage features a distinct cd isotope signature of e cd 114 110 4 which reflects biological isotope fractionation at the surface and subsequent mixing into the ocean interior taken together our results demonstrate that coupled cd isotope and concentration data provide valuable insights into the distribution and biological cycling of cd in the water column the highly systematic nature of cd isotope signatures may furthermore prove to be of utility for future research in marine geochemistry and paleoceanography

architecture and origin of an amalgamated fluvial sheet sand lower castlegate formation book cliffs utah abstract amalgamated fluvial sheet sandstones in the stratigraphic record are often interpreted as the deposits of braided rivers alluvial sequence stratigraphic models show these sheet sandstones overlying sequence boundaries and deposited during low rates of base level rise and fall since sequence stratigraphic models rely on the balance between creation destruction of accommodation and sediment supply is the sheet like nature of these units controlled by channel style by aggradation rates tied to base level changes or a combination of both the lower member of the castlegate formation in the book cliffs of eastern utah u s a was selected to answer these questions regarding the origin and architecture of amalgamated sheet sandstones the lower castlegate is 60 m thick and is underlain by a regional sequence boundary delineation of the alluvial architecture utilized a combination of outcrop photography measured sections and paleochannel dimension estimation at two outcrops in the type area architectural components within the outcrops were defined and include 1 basal thalweg fill units 2 inclined sandy or heterolithic barform deposits and 3 overbank siltstone and mudstone thalweg fill units represent deposition in the topographically lowest part of the channel and are preferentially preserved thalweg units exist as single units or as a composite of multiple thalweg units overlying thalweg units inclined barform deposits are in places preserved and genetically linked to an underlying thalweg fill unit bar accretion directions when combined with paleocurrent indicators show that lateral downstream and upstream accretion all occur in the lower castlegate overbank deposits are rarely preserved but where present they typically overlie bar deposits the architectural components stack to form a threefold cyclic hierarchy of 1 channel bar systems 2 12 m thick 2 channel belts 2 16 m thick and 3 stacked channel belt complexes 17 40 m thick complete channel bar systems are rarely preserved and occur locally as a succession of multiple stacked thalweg fill units the lack of barforms within a composite thalweg unit suggests that channel migration is the dominant process controlling preservation within channel bar systems possibly associated with a component of local avulsion channel belts are composed of stacked channel bar systems capped by a barform the barform is preserved due to a regional avulsion moving the active channel to another location within the floodplain isolating it from potential reworking stacked channel belt complexes are characterized by alternations of thalweg dominated and barform dominated channel belts the mechanism responsible for deposition at the stacked channel belt complex scale may be creation destruction of accommodation associated with base level changes paleochannel reconstructions show that channel flow depths using bar and underlying thalweg thickness were up to 7 6 m channel depth estimates utilizing a cross bed set thickness of 26 cm averaged 4 6 7 7 m these values were used to calculate channel widths which were estimated at 143 365 m up to a maximum of approximately 1 km regional paleoflow within the lower castlegate was dominantly southeast directed the architectural components paleochannel characteristics and paleocurrent data suggest the lower castlegate member was deposited in low to intermediate sinuosity rivers influenced by autocyclic processes at smaller scales and allocyclic processes at the larger outcrop scale

zn isotope fractionation during uptake into marine phytoplankton implications for oceanic zinc isotopes abstract the extreme scarcity of zinc zn in the euphotic zone coupled to deep enrichments is consistent with biological uptake at the surface and regeneration at depth in the context of a nutrient type depth profile so clearly shaped by uptake into phytoplankton the growing dataset for zn isotopes presents a challenge these data either show very minor isotope effects associated with extreme depletion or enrichment of the light isotopes in the upper ocean in contrast culturing of eukaryotes in the laboratory suggests that light zn isotopes are preferentially taken up into diatoms and coccoliths implying that zn depletion at the surface should be associated with extremely heavy residual dissolved signals here we present the first zn isotope measurements for cultured marine cyanobacteria and compare these data to those for eukaryotic diatoms grown under identical conditions of the four cyanobacteria cultured belonging to the genera synechococcus and prochlorococcus three preferentially take up light zn into the cell with a variability that is not fundamentally different between pro and eukaryotic phytoplankton we also observe only very subtle differences between zn p and fe p uptake ratios for these three cyanobacteria groups relative to diatoms grown under the same conditions a fourth strain exhibits preferential uptake of heavy zn isotopes and very high zn p ratios overall we speculate that the observed variability among cyanobacteria may be related to the molecular structure of their photosynthetic light harvesting apparatus adapted to significantly different light niches these new and published culture data support the hypothesis that cellular 66zn in culture might largely be controlled by the organic ligands that bind zn in the medium given that the zn binding ligands in the ocean have thermodynamic stability constants that are orders of magnitude smaller than the edta used in culture media the surprisingly subtle zn isotope variability in some parts of the surface ocean may be reconciled with culture data by the lesser near zero preference of these weaker complexes for heavy zn isotopes this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

the isotopic composition of some common forms of anthropogenic zinc abstract anthropogenic sources account for much of the zinc zn in the environment constraining the isotopic composition of anthropogenic zn is therefore essential to understanding the environmental biogeochemical cycling of zn isotopes this study examines the isotopic variability in several different categories of anthropogenic zn pure zn metal and zn dust are the raw materials used in many zn containing products we have measured 66 zn for zn dust purified by thermal distillation electrochemically purified zn metal and us pennies which are made from the most common grade of zn metal special high grade zn in galvanized steel and electroplated hardware was studied because this is a common use of zn and zn in these products may be easily released into the environment through corrosion vitamins were studied because they are more highly purified than typical zn metals and are made from processed chemical compounds such as zn oxide or zn gluconate the isotopic composition of samples measured in this study are as follows reported as 66 zn compared to lyon jmc zn laboratory standards seven samples 9 15 to 0 17 zn metal dust purified by thermal distillation three samples 0 09 to 0 19 zn metal shot purified by electrochemically one sample 0 22 special high grade zn as represented in us pennies six samples 0 14 to 0 31 galvanized steel three samples 0 12 to 0 58 electroplated hardware three samples 0 56 to 0 20 and health products five samples 0 09 to 0 24 based on these results we suggest that the isotopic composition of common anthropogenic zn products ranges from 0 1 to 0 3 all samples studied here had 66 zn values within this range except four laboratory standards all electroplated hardware samples and a single galvanized steel sample the isotopic range for common anthropogenic zn is much smaller than the total 66 zn range found in zn ore field hydrothermal samples demonstrating the effects of zn isotope homogenization during ore processing and purification laboratory standards may have anomalously light 66 zn values because they undergo extra purification steps and zn recovery during these steps is not quantitative electroplated hardware was also isotopically light consistent with previous studies showing that lighter isotopes are electroplated more quickly than heavy isotopes our results suggest that isotopically heavy zn may be incorporated into the waste stream during the electroplating process by defining the range of 66 zn values that is typical for some common zn products and discovering some kinds of products that fall outside this range we will be better able to use zn isotopes to trace different anthropogenic zn sources

on the shapes of natural sand grains 1 digitized outlines of sand grains from a dozen locations including deserts beaches and seabeds have been acquired using an optical microscope linked to a desktop computer fourier analysis of the outlines returns the normalized power spectrum of each sample averaged over several hundred grains regardless of the origin of the samples these power spectra all exhibit essentially the same inverse power law dependence on the harmonic number n varying as n 10 3 for 2 n 20 this universal spectrum provides the basis of a numerical technique for synthesizing the irregular outline of a sand grain the outline is represented as a random pulse train in which identically shaped microasperities with normally distributed amplitudes are randomly superimposed on the perimeter of a circle by identifying the spectrum of the microasperities with the observed inverse power law dependence derived from the optical images the synthetic outlines are constrained to show the same statistical properties as the outlines of the real grains the synthesized and real outlines are qualitatively similar in that visually it is difficult to distinguish between them the new numerical technique for synthesizing irregular outlines of sand grains has potential for investigating the random packing of realistically rough particles through computer simulation

modulation of the southern ocean cadmium isotope signature by ocean circulation and primary productivity article i nfo article history the high nutrient low chlorophyll hnlc southern ocean plays a key role in regulating the biological pump and the global carbon cycle here we examine the efficacy of stable cadmium cd isotope fractionation for detecting differences in biological productivity between regions our results show strong meridional cd isotope and concentration gradients modulated by the antarctic fronts with a clear biogeochemical divide located near 56 s the coincidence of the cd isotope divide with the southern boundary of the antarctic circumpolar current acc together with evidence for northward advection of the cd signal in the acc demonstrate that cd isotopes trace surface ocean circulation regimes the relationships between cd isotope ratios and concentrations display two negative correlations separating the acc and weddell gyre into two distinct cd isoscapes these arrays are consistent with rayleigh fractionation and imply a doubling of the isotope effect due to biological consumption of cd during water transport from the weddell gyre into the acc the increase in magnitude of cd isotope fractionation can be accounted for by differences in the phytoplankton biomass community composition and their physiological uptake mechanisms in the weddell gyre and acc thus linking cd isotope fractionation to primary production and the global carbon cycle 2011 elsevier b v all rights reserved

zinc and nickel isotopes in seawater from the indian sector of the southern ocean the impact of natural iron fertilization versus southern ocean hydrography and biogeochemistry abstract the southern ocean is the site of 20 of global ocean carbon export and the origin of water masses that significantly impact the chemistry of the global ocean much of the southern ocean is a high nutrient low chlorophyll hnlc region iron is the primary limiting nutrient for phytoplankton growth and may also be an important control on the biogeochemistry of the water masses emanating from the southern ocean here we investigate the response of zn and ni and their isotopes to natural fe fertilization from southern ocean islands using samples collected during the keops 2 oct nov 2011 program in the early austral spring near the kerguelen plateau indian sector of the southern ocean zinc and ni concentrations show depth distributions and relationships to major nutrients that are very similar to published data from the atlantic sector of the southern ocean away from island fertilization as in the atlantic sector and other regions outside the southern ocean there is a slight minimum in 66zn at about 100 150 m depth and a slightly heavier value at the surface at the keops 2 sites the light sub surface zn isotopes occur at the depth level where measured chl a has declined to near zero the heaviest zn isotope values in either the atlantic or indian sectors occur in bottom waters are associated with samples that show high dissolved si relative to zn these latter represent possible evidence for a heavy input directly to deep water or from sediment and the zn si 66zn systematics are consistent with a source in diatom opal nickel concentrations show much less variation than those of zn with the most depleted surface value only 15 20 lower than those in upwelled deep water in the southern ocean these small variations in ni concentration are associated with no significant variability in ni isotopes as also previously observed in the atlantic sector overall the key feature of the dataset is the apparent absence of any significant impact of natural fe fertilization on the distribution of zn and ni with the dominant control being the station location relative to the polar front in both the atlantic and indian sectors zinc and ni isotopes are invariant in surface waters whether inside or outside the fertilized zone and whether south or north of the polar front this article is part of a special issue entitled cycles of trace elements and isotopes in the ocean geotraces and beyond edited by tim m conway tristan horner yves plancherel and aridane g gonzalez

origin of the carbonaceous debris and its implication for mineralization within the qianjiadian uranium deposit southern songliao basin abstract appearance and coal petrology of the carbonaceous debris cd from the qianjiadian uranium deposit southern songliao basin are illustrated in order to reveal the relationship between the cd and uranium mineralization response of the cd and uranium mineralization to diabase dikes and origin of the cd three types of cd have been identified in the yaojia formation cd serving as trapped sediments cd serving as laminae of cross bedding and cd occurring in lumpy sandstones with an average content of 91 2 in the cd organic macerals are primarily composed of homoeollinite desmocollinite and inertinite inorganic macerals of the cd mainly include pyrite with an average content of 8 8 average contents of the desmocollinite inertinite and pyrite from the cd in the ore bearing section are higher than that in the non ore bearing section respectively the study demonstrates that the cd rich in inertinite and desmocollinite facilitates uranium mineralization uranium is frequently adsorbed in the desmocollinite and inertinite and coffinite is embedded in the inertinite inferring that roles of the cd in uranium mineralization are both adsorption and reduction vitrinite reflectance vr of the cd ranges from 0 24 to 0 513 with an average value of 0 335 the vr of the cd in the ore bearing section is generally larger than that in the non ore bearing section uranium mineralization and enlargement of the vr are both attributed to the diabase dikes the cd originated from the late cretaceous wildfire related woody plants and it has been transported into fluvial channels and preserved in sandstones

the relationship between cadmium and phosphate in the atlantic ocean unravelled abstract cadmium cd is not generally considered a nutrient element but behaves like a nutrient in the oceans and might play an important role in ocean biology after all the relationship between cd and the nutrient phosphate po4 has been studied for over 40 yrs but the debate on the driving mechanism and reason behind the kink a change in the steepness of the slope is ongoing using new data of high accuracy and spatial resolution covering the west atlantic ocean from north to south in combination with a robust extended optimum multiparameter eomp water mass model we show that mixing between different water masses is the dominant factor explaining the observed correlation and its kink regeneration of cd via remineralisation explains the smaller scale variability notably in the surface ocean observations imply the availability of cd in surface waters determines the cd uptake and thus the cd po4 remineralisation ratio this ratio is variable between different ocean regions notably between the northern and southern high latitude oceans due to their role in deep water formation both the northern and southern high latitude oceans are a driving factor in the atlantic and global cd and po4 relation outside the atlantic ocean the classical kink is not expected but the relationship is by no means linear most likely this is due to the interaction between low latitude surface waters and subsurface waters from high latitude origin but more data are required to assess this in detail

a model of the iron cycle in the ocean the ironex ii in situ fertilization experiment showed decisively that availability of iron limits the growth of phytoplankton in equatorial pacific surface waters high nutrient low chlorophyll hnlc surface waters potentially iron limited are also found in the north pacific and the southern ocean a model of seawater iron geochemistry has been incorporated into a global ocean circulation and carbon cycle model and tuned to match the observed ocean fe distribution the model reproduces the observed hnlc areas in the equatorial pacific and southern ocean but predicts nutrient depletion in the north pacific a region of high dust fluxes from asia the model is based on the idea that the concentrations of organic iron binding ligands in seawater control the subsurface fe concentration and predicts that a majority 70 80 of the global carbon export production can be sustained by upwelling of dissolved iron in seawater rather than by atmospheric deposition the ocean iron cycle increases the efficiency of iron utilization in the biological pump buffers new production against interannual fluctuations in iron deposition and contributes several new intrinsic timescales to the ocean carbon cycle several hundred years for the ocean iron concentration and perhaps several thousand for the concentration of ligand in the deep sea ocean recycling of fe appears to play a major role in determining the strength of the biological pump in the ocean and the pco2 of the atmosphere

reservoir and aquifer characterization of fluvial architectural elements stubensandstein upper triassic southwest germany this paper aims at a quantitative sedimentological and petrophysical characterization of a terminal alluvial plain system exemplified by the stubensandstein south german keuper basin the study follows the outcrop analogue approach where information derived from outcrops is collected in order to enhance interpretation of comparable subsurface successions quantitative data on sandbody geometries porosities and permeabilities are presented in order to constrain modelling of subsurface sandbodies and permeability barriers for sedimentological characterization the method of architectural element analysis miall a d 1996 the geology of fluvial deposits springer berlin was used and modified to include poroperm facies a special photo technique with a precise theodolite survey was developed to create optically corrected photomosaics for outcrop wall maps from up to 20 000 m2 large outcrops nine architectural elements have been classified and quantified bedload mixed load and suspended load channel fills are separated the petrophysical characterization of the architectural elements integrated porosity and permeability measurements of core plugs with gamma ray measurements along representative sections it could be demonstrated that certain architectural elements show a characteristic poroperm facies four scales of sedimentary cycles have been recognized in the stubensandstein cyclic sedimentation causes changing lithofacies patterns within the architectural elements depending on their position in the sedimentary cycle stratigraphic position exerts only some paleogeographic position exerts significant influence on porosity and permeability of the sandbodies the highest poroperm values were found in proximal areas of the alluvial plain and in middle parts within sedimentary macrocycles the strong internal heterogeneity on the alluvial plain system is important for its reservoir and aquifer characteristics compartments of bedload channel sandstones in medial positions of a stratigraphic cycle represent very good reservoirs or aquifers the seals or aquicludes are formed by extensive floodplain claystones lacustrine sediments paleosols and suspended load deposits strongly cemented zones of sandstones represent aquitards

biogeochemical cycling of zinc and its isotopes in the southern ocean abstract we report zn concentration and isotope data for seawater samples from the atlantic sector of the southern ocean collected during the ipy geotraces ant xxiv iii cruise along the greenwich zero meridian data are reported for the full depth range of the water column at three stations as well as a transect of surface samples using a new analytical approach that is presented in detail here zn concentrations increase with depth though due to proximity to upwelling sites surface concentrations are not as low as in some parts of the ocean such as further northward into the sub antarctic zone for two depth profiles south of the polar front zone the physical stratification of the upper water column is reflected in sudden near surface changes in zn concentration with depth in contrast beneath 100 300 m zn concentrations barely change with depth zn isotopic data beneath 1000 m for the southern ocean data presented here as well as published data from the north atlantic and north pacific are strikingly homogeneous with an average 66zn 0 53 0 14 2sd 2se 0 03 n 21 the surface southern ocean is more variable with 66zn ranging from 0 07 to 0 80 between the two is a thin horizon at 40 80 m which in the southern ocean as well as the north atlantic and north pacific is characterised by distinctly light isotopic signatures with 66zn about 0 3 lower than surface waters strong correlations between si and zn concentrations seen here and elsewhere coupled to the lack of any systematic relationship between si and zn isotopes in the southern ocean suggest that the removal of zn associated with diatom opal involves little or no isotopic fractionation regeneration of this zn also explains the homogeneous zn isotopic composition of the global deep ocean so far sampled however the low zn content of opal requires that deep ocean zn does not directly come from the opal phase itself but rather from associated organic material external to the diatom frustule during growth experimental data are consistent with little or no fractionation during incorporation of zn into this material on the other hand the light zinc at 40 80 m is most consistent with the regeneration of an intra cellular pool that both culturing experiments and field data suggest will be isotopically light the data thus imply two processes by which zn is taken up in the surface ocean that these pools have very different regeneration lengthscales and that physical mixing of the oceans cannot eradicate their isotopic signatures finally the deep 66zn ocean value is significantly higher than the current best estimate of the input to the oceans the most obvious candidate for the required light sink is the survival of some of the cellular zn to be buried in sediment

iron sources and dissolved particulate interactions in the seawater of the western equatorial pacific iron isotope perspectives this work presents iron isotope data in the western equatorial pacific marine aerosols and top core margin sediments display a slightly heavy fe isotopic composition 56 fe of 0 33 0 11 2sd and 0 14 0 07 respectively samples reflecting the influence of papua new guinea runoff sepik river and rabaul volcano water are characterized by crustal values in seawater fe is mainly supplied in the particulate form and is found with a 56 fe between a0 49 and 0 34 0 07 the particulate fe seems to be brought mainly by runoff and transported across continental shelves and slopes aerosols are suspected to enrich the surface vitiaz strait waters while hydrothermal activity likely enriched new ireland waters dissolved fe isotopic ratios are found between a0 03 and 0 53 0 07 they are almost systematically heavier than the corresponding particulate fe and the difference between the signature of both phases is similar for most samples with 56 fe dfe pfe 0 27 0 25 2sd this is interpreted as an equilibrium isotopic fractionation revealing exchange fluxes between both phases the dissolved phase being heavier than the particles suggests that the exchanges result in a net nonreductive release of dissolved fe this process seems to be locally significantly more intense than fe reductive dissolution documented along reducing margins it may therefore constitute a very significant iron source to the ocean thereby influencing the actual estimation of the iron residence time and sinks the underlying processes could also apply to other elements

architectural elements and bounding surfaces in fluvial deposits anatomy of the kayenta formation lower jurassic southwest colorado abstract three well exposed outcrops in the kayenta formation lower jurassic near dove creek in southwestern colorado were studied using lateral profiles in order to test recent regarding architectural element analysis and the classification and interpretation of internal bounding surfaces examination of bounding surfaces within and between elements in the kayenta outcrops raises problems in applying the three fold classification of allen 1983 enlarging this classification to a six fold hierarchy permits the discrimination of surfaces intermediate between allen s second and third order types corresponding to the upper bounding surfaces of macroforms and internal erosional reactivation surfaces within the macroforms examples of the first five types of surface occur in the kayenta outcrops at dove creek the new classifications is offered as a general solution to the problem of description of complex three dimensional fluvial sandstone bodies the kayenta formation at dove creek consists of a multistorey sandstone body including the deposits of lateral and downstream accreted macroforms the storeys show no internal cyclicity neither within individual elements nor through the overall vertical thickness of the formation low paleocurrent variance indicates low sinuosity flow whereas macroform geometry and orientation suggest low to moderate sinuosity the many internal minor erosion surfaces draped with mud and followed by intraclast breccias imply frequent rapid stage fluctuation consistent with variable seasonal monsonal ephemmeral flow the results suggest a fluvial architecture similar to that of the south saskatchewan river through with a three dimensional geometry unlike that interpreted from surface studies of that river

architectural analysis of fluvial sequences in the northwestern part of kyongsang basin early cretaceous se korea abstract the northwestern part of kyongsang basin early cretaceous largely comprises interbedded sandstones and mudstones of fluvial depositional environments with local basin margin conglomeratic deposits of alluvial fan systems these non marine successions are divided into 5 successive stratigraphic units each of which is unique in facies assemblages and architecture of sandstone bodies one stratigraphic unit sinpyong anpyong unit is documented in this paper with detailed architectural analysis of sandstone bodies the deposits of the sinpyong anpyong unit are divided into three major components thick sandstone thin sandstone and mudstone dominated bodies the thick sandstone bodies 2 47 m thick comprise stacked element groups bounded by laterally persistent erosional surfaces probably representing superposition of channel belts within individual element groups elements are laterally superposed indicating growth and superposition of bars and movement of associated channels the thickness of bar deposits and dip angles of laterally inclined strata suggest that channels were a few to 10 m in depth and 9 m to several tens of meters in width paleocurrent data indicate southward or southeastward draining channel systems the thin sandstone bodies generally the thick sandstone bodies formed in major channels and channel belts are characterized by lateral superposition of numerous bar and channel deposits limited extent of individual lateral accretion sets and the presence of mid channel bar deposits suggesting deposition in braided rivers detailed reconstruction of bars and channels reveals a range of processes including growth coalescence and erosion of bars and migration switching and filling of channels lateral accretion of bars and the associated channel migration might have been principal processes in the sinpyong anpyong river systems bars were commonly coalesced by lateral superposition forming large bar complexes

cadmium isotope fractionation in seawater a signature of biological activity investigations of cadmium isotope variations in the oceans may provide new insights into the factors that control the marine distribution and cycling of this element here we present the results of cd isotope and concentration analyses for 22 seawater samples from the atlantic southern pacific and arctic oceans the results reveal for the first time large and well resolved cd isotope fractionations in the marine environment the majority of the seawater samples display an inverse relationship between dissolved cd contents and isotope compositions which range from e114 110cd 3 0 5 for cd rich waters 0 8 1 0 nmol kg to e114 110cd 38 6 for surface water with a cd concentration of only 0 003 nmol kg all e114 110cd data are reported relative to the jmc cd munster standard this suggests that the cd isotope variations reflect kinetic isotope effects that are generated during closed system uptake of dissolved seawater cd by phytoplankton a few samples do not follow this trend as they exhibit extremely low cd contents 0 008 nmol kg and nearly un fractionated cd isotope compositions such complexities which are not revealed by concentration data alone require that the cd distribution at the respective sites was affected by additional processes such as water mass mixing atmospheric inputs of cd and or adsorption uniform isotope compositions of e114 110cd 3 3 0 5 1 s d were determined for seawater from 900 m depth despite of cd concentrations that display the expected increase along the global deep water pathway from the atlantic 0 3 nmol kg to the pacific ocean 0 9 nmol kg this indicates that the biomass which is remineralized in the deeper ocean is also characterized by a very constant cd isotope composition this observation is in accord with the interpretation that the cd distribution in surface waters is primarily governed by rayleigh fractionation during near quantitative uptake of dissolved seawater cd

on the origin of the marine zinc silicon correlation abstract the close linear correlation between the distributions of dissolved zinc zn and silicon si in seawater has puzzled chemical oceanographers since its discovery almost forty years ago due to the apparent lack of a mechanism for coupling these two nutrient elements recent research has shown that such a correlation can be produced in an ocean model without any explicit coupling between zn and si via the export of zn rich biogenic particles in the southern ocean consistent with the observation of elevated zn quotas in southern ocean diatoms here we investigate the physical and biological mechanisms by which southern ocean uptake and export control the large scale marine zn distribution using suites of sensitivity simulations in an ocean general circulation model ogcm and a box model ensemble these simulations focus on the sensitivity of the zn distribution to the stoichiometry of zn uptake relative to phosphate po4 drawing directly on observations in culture our analysis reveals that ogcm model variants that produce a well defined step between relatively constant high zn po4 uptake ratios in the southern ocean and low zn po4 ratios at lower latitudes fare best in reproducing the marine zn si correlation at both the global and the regional southern ocean scale suggesting the presence of distinct zn biogeochemical regimes in the high and low latitude oceans that may relate to differences in physiology ecology or micro nutrient status furthermore a study of the systematics of both the box model and the ogcm reveals that regional southern ocean zn uptake exerts control over the global zn distribution via its modulation of the biogeochemical characteristics of the surface southern ocean specifically model variants with elevated southern ocean zn po4 uptake ratios produce near complete zn depletion in the si poor surface subantarctic zone where upper ocean water masses with key roles in the global oceanic circulation are formed by setting the main preformed covariation trend within the ocean interior the subduction of these zn and si poor water masses produces a close correlation between the zn and si distributions that is barely altered by their differential remineralisation during low latitude cycling we speculate that analogous processes in the high latitude oceans may operate for other trace metal micronutrients as well splitting the ocean into two fundamentally different biogeochemical and thus biogeographic regimes

outcrop architecture of a fluvio lacustrine succession upper triassic yanchang formation ordos basin china abstract although several studies have considered the sedimentary facies of the upper triassic yanchang formation in terms of their hydrocarbon potential in the petroliferous ordos basin such studies have mostly interpreted subsurface data and few have systematically examined the detailed outcrop based anatomy of this succession this study characterizes a series of well exposed outcrop sections along an 80 km long e w oriented series of road cuttings in the southeast ordos basin to reconstruct the sedimentary architecture of a fluvio lacustrine succession and determine the principal controls that governed the style of accumulation and preservation the yanchang formation is divided into 10 depositional units chang 10 base to chang 1 top that record the sedimentary evolution of a series of large scale fluvial systems that constructed delta front and pro delta bodies as they entered a large interior draining lake detailed analysis of the internal architectures of the delta front bodies records the mechanism of growth of a large scale shallow water delta succession lacustrine subaqueous distributary channels are composed of 3 15 m thick sandstone fills such channelized bodies are highly elongate and many can be traced several kilometres such bodies can be shown to be commonly associated with thin bedded mouth bar and subaqueous interdistributary bay deposition the progradational architecture of the delta front elements is difficult to recognize on outcrop scale deposits of the chang 10 to 1 units record 4 major lacustrine transgressive regressive cycles during the late triassic transgressive events are signified by the widespread occurrence of 10 20 m thick oil shale prone intervals regressive events are signified by the progradational stacking towards the basin centre of sandstone prone facies associations mainly accumulated in fluvial channel delta plain and upper delta front environments the uppermost chang 1 interval records late stage filling of the lacustrine basin the transgressive regressive cycles equate to sequences that can be correlated across the region development of which was controlled by a combination of changes in the rate of tectonic subsidence the rate of sediment delivery from the basin margin hinterland and climate factors that were themselves influenced by intracontinental growth of the neighbouring qinling orogen

genetic and grade and tonnage models for sandstone hosted roll type uranium deposits texas coastal plain usa abstract the coincidence of a number of geologic and climatic factors combined to create conditions favorable for the development of mineable concentrations of uranium hosted by eocene through pliocene sandstones in the texas coastal plain here 254 uranium occurrences including 169 deposits 73 prospects 6 showings and 4 anomalies have been identified about 80 million pounds of u 3 o 8 have been produced and about 60 million pounds of identified producible u 3 o 8 remain in place the development of economic roll type uranium deposits requires a source large scale transport of uranium in groundwater and deposition in reducing zones within a sedimentary sequence the weight of the evidence supports a source from thick sequences of volcanic ash and volcaniclastic sediment derived mostly from the trans pecos volcanic field and sierra madre occidental that lie west of the region the thickest accumulations of source material were deposited and preserved south and west of the san marcos arch in the catahoula formation by the early oligocene a formerly uniformly subtropical climate along the gulf coast transitioned to a zoned climate in which the southwestern portion of texas coastal plain was dry and the eastern portion humid the more arid climate in the southwestern area supported weathering of volcanic ash source rocks during pedogenesis and early diagenesis concentration of uranium in groundwater and movement through host sediments during the middle tertiary era abundant clastic sediments were deposited in thick sequences by bed load dominated fluvial systems in long lived channel complexes that provided transmissive conduits favoring transport of uranium rich groundwater groundwater transported uranium through permeable sandstones that were hydrologically connected with source rocks commonly across formation boundaries driven by isostatic loading and eustatic sea level changes uranium roll fronts formed as a result of the interaction of uranium rich groundwater with either 1 organic rich debris adjacent to large long lived fluvial channels and barrier bar sequences or 2 extrinsic reductants entrained in formation water or discrete gas that migrated into host units via faults and along the flanks of salt domes and shale diapirs the southwestern portion of the region the rio grande embayment contains all the necessary factors required for roll type uranium deposits however the eastern portion of the region the houston embayment is challenged by a humid environment and a lack of source rock and transmissive units which may combine to preclude the deposition of economic deposits a grade and tonnage model for the texas coastal plain shows that the texas deposits represent a lower tonnage subset of roll type deposits that occur around the world and required aggregation of production centers into deposits based on geologic interpretation for the purpose of conducting a quantitative mineral resource assessment

assessment on tight oil resources in major basins in china abstract large scale commercial development of shale gas and tight oil resources in north american and continuous discoveries of tight oil in china lead to the recognition of the importance of assessment on tight oil resources based on the characteristics of china s tight oil reservoirs and exploration status this paper discusses a workflow focusing on in place resource evaluation in the workflow a resource richness analogy approach rr aa is proposed for assessment of tight oil resources in less explored areas a genesis statistics assessment approach gs aa for lacustrine tight oil resources with strong heterogeneity and regions where more delicate assessment is required and an eur analogy approach eur aa for assessment on recoverable tight oil by fully using available eur data of production wells after analyzing the geological characteristics of the formation of tight oil in the ordos bohai bay songliao junggar sichuan and other major basins the distributions of essential parameters such as reservoir thickness area and porosity have been defined and the parameter evaluation criteria have been established finally the tight oil resource potentials in the major basins in china have been evaluated using one of the three methods and the prospective areas of high resource abundance are outlined in each of basins the results from this study show that china s tight oil resources have a large potential and good exploration future the estimated in place tight oil resources are 12 580 109 tons mainly distributed in the ordos songliao bohai bay and junggar basins 15 most favorable zones are proposed having in place resources of 5 296 109 tons

deep ocean biogeochemistry of silicic acid and nitrate 1 observations of silicic acid and nitrate along the lower branch of the global conveyor belt circulation show that silicic acid accumulation by diatom opal dissolution occurs at 6 4 times the rate of nitrate addition by organic matter remineralization the export of opal and organic matter from the surface ocean occurs at a si n mole ratio that is much smaller than this almost everywhere cf sarmiento et al 2004 the preferential increase of silicic acid over nitrate as the deep circulation progresses from the north atlantic to the north pacific is generally interpreted as requiring deep dissolution of opal together with shallow remineralization of organic matter broecker 1991 however sarmiento et al 2004 showed that the primary reason for the low silicic acid concentration of the upper ocean is that the waters feeding the main thermocline from the surface southern ocean are depleted in silicic acid relative to nitrate by implication the same southern ocean processes that deplete the silicic acid in the surface southern ocean must also be responsible for the enhanced silicic acid concentration of the deep ocean we use observations and results from an updated version of the adjoint model of schlitzer 2000 to confirm that this indeed the case

organic matter enrichment of the late triassic yanchang formation ordos basin china under dysoxic to oxic conditions insights from pyrite framboid size distributions abstract pyrite framboids are spherical or ellipsoidal compact aggregates of submicron pyrite microcrystals the various lithologies in the chang 7 member of the upper triassic yanchang formation contain abundant pyrite framboids which provide an opportunity to understand the fluctuation in paleoredox conditions and relative sedimentation rates during deposition the measured diameters of the pyrite framboids in the chang 7 member are characterized by large mean diameters 9 7 16 6 m with a wide distribution range that plots in the area indicative of dysoxic to oxic paleoredox conditions during deposition of the chang 7 sediments based on correlation analysis the strong correlation between paleoredox sensitive trace elements ratios v cr u th and cu zn and the mean size of framboids indicate that the latter can serve as a reliable indicator of paleoredox conditions the results of the framboid size distribution can also be interpreted through crystal size distribution theory csdt according to csdt the relative sedimentation rate of the chang 7 member fluctuated during deposition in parallel with fluctuation in lacustrine levels furthermore the strongly positive correlation between total organic carbon toc and paleoredox conditions indicates that although relatively high sedimentation rate may have contributed to the dysoxic oxic conditions that were harmful to the preservation of organic matter but it may also have brought nutrients to increase productivity similarly the correlation between toc and relative sedimentation rates suggests that the relative sedimentation rates can affect organic matter enrichment in several ways a high sedimentation rate is favourable for the preservation of organic matter which can be prevented from oxidation but large amounts of sediments can dilute the organic matter which reduces the organic matter abundance in a potential source rock

the vertical distribution of iron stable isotopes in the north atlantic near bermuda seawater dissolved iron isotope ratios 56 fe have been measured in the north atlantic near bermuda in a full depth profile seawater dissolved 56 fe is isotopically heavy compared to crustal values throughout the water column 56 fe irmm 014 0 30 to 0 71 iron isotope ratios are relatively homogenous in the upper water column between 0 30 to 0 45 above 1500 m and 56 fe increases below this to a maximum of 0 71 at 2500 m decreasing again to 0 35 at 4200 m the 56 fe profile is very different from the iron concentration profile in the upper water column fe is variable while 56 fe is relatively constant and in the deeper water column 56 fe varies while fe remains relatively constant the 56 fe profile is also not well correlated with other hydrographic tracers in the north atlantic such as temperature salinity or the concentrations of oxygen phosphate silica and cfc 11 the dissimilarity between 56 fe profiles and profiles of fe and other hydrographic tracers shows that fe isotope ratios provide a unique sort of information about ocean chemistry and they suggest that fe isotopes may therefore be a valuable new tool for tracing the global sources sinks and biogeochemical cycling of fe

fluvial facies architecture in small scale river systems in the upper dupi tila formation northeast bengal basin bangladesh abstract the late stage basin fill history of the fluvial dupi tila group plio pleistocene is described these rocks have been deposited in the sylhet trough a sub basin of the bengal basin in a foreland basin setting this outcrop study carried out in sylhet bangladesh presents the first detailed facies analysis of the upper dupi tila formation four facies have been identified trough cross bedded sandstone st ripple cross laminated sandstone sr finely laminated mud with ripples fl and massive mud with rootlets fm facies analysis supplemented with embedded markov chain analysis reveals small scale fining upward cycles average 4 5 m thick facies architectural elements include channel ch lateral accretion la sandy bedforms sb and overbank fines of with limited vertical and lateral connectivity of the sand bodies the average channel depth and width is 5 and 30 m respectively sand body geometry ranges from tabular to sheet to shoestring with a 0 45 net to gross ratio this study shows that the upper dupi tila formation is composed of small scale mudstone reach meandering river deposits in bangladesh the dupi tila formation is the main aquifer presently being utilized understanding of facies architecture and sand body geometry of this formation is crucial in examining the issue of arsenic and other contaminations of ground water in bangladesh

architectural units and heterogeneity of channel reservoirs in the karamay formation outcrop area of karamay oil field junggar basin northwest china reservoirs of the karamay formation occur as oil sandstones in outcrop in the karamay oil field two types of high quality reservoirs are present in this field low sinuosity channel sandstones and distributary channel sandstones each having different sediments bounding surfaces and architectural units the low sinuosity channel has coarse grained sediments a smaller scale and relatively simple architectural units composed of intrachannel units and lithofacies that occur in a vertically stacked pattern the distributary channel has fine grained sediments a larger scale and relatively complex architectural units which are reflected in the following three ways 1 the distributary channels have three multiorder architectural units an intrachannel unit a macroform accretion unit and a lithofacies unit 2 isolated barrier beds whose permeability is lower occur near third order and fifth order surfaces 3 the evolution of the distributary channels has two stages in the flooding stage the sediments were coarse grained and the intrachannel units were in a vertically stacked pattern in the waning stage the sediments were fine grained and the intrachannel units were in a laterally stacked pattern reservoir heterogeneity of distributary channel sandstones is revealed in the following three scales 1 in a microscale range the growth of pores is associated directly with lithofacies the pore diameter and the throat width both increase with the coarsening of the grain size in the sediments the anisotropic pore structure is reflected in the variation of permeability the horizontal permeability parallel to the paleocurrent is the largest the horizontal permeability perpendicular to the paleocurrent is intermediate and the vertical permeability is the smallest 2 at a channel scale the fluid flow units are demarcated according to the isolated barrier bed and porosity and permeability inside the distributary channel the fluid flow unit distributed mainly in the middle lower interval of the distributary channel or the intrachannel unit is associated closely with third order or fifth order surfaces the porosity and permeability inside the fluid flow unit decrease gradually from its center to the margin and upper interval depending on the spatial distribution of lithofacies in this kind of lithofacies which is characterized by a low matrix content and by coarse grained sediments with large trough cross beds high porosity and permeability are commonly found 3 in a lacustrine delta system the distributary channel sandstone has the best porosity and permeability and is the best reservoir

heavy nickel isotope compositions in rivers and the oceans abstract nickel is a biologically active trace metal whose dissolved concentration depth profiles in the ocean show nutrient like behaviour if the pronounced removal of nickel from the dissolved phase in the surface ocean and its return in the deep is associated with an isotopic fractionation nickel isotopes may be able to yield constraints on the precise biogeochemical processes involved here we present the first nickel isotope data for seawater along with data for the dissolved phase of rivers one of the principal sources of nickel to the oceans the dissolved phase of rivers exhibits substantial variability in both ni concentration and 60 ni from 2 2 to 35 nmol kg 1 and 0 29 to 1 34 respectively the most striking result from the nickel isotope analyses of rivers is that they are substantially heavier by up to 1 for 60 ni than the range for silicate rocks on the continents a finding that is analogous to that for other transition metal isotope systems if the data presented here are close to representative of the global riverine flux they suggest an annual input of ni to the oceans of 3 6 10 8 moles and a discharge and concentration weighted 60 ni average of 0 80 the relationship between ni isotopes and concentrations shows similarities with those for other transition metal isotope systems where the main control has been suggested to be isotopic partitioning between the dissolved phase and particulates either in the weathering environment or during transport in stark contrast to the rivers the dataset for seawater is very homogeneous with 2sd of the entire dataset being only twice the analytical reproducibility the second main feature is that seawater is distinctly heavier in ni isotopes than rivers the average 60 ni is 1 44 0 15 2sd and only 2 of the 29 seawater analyses have a ni isotopic composition that is lighter than the heaviest river the lack of an isotopic shift associated with the drawdown of nickel concentrations in the surface ocean suggests that the cycling of nickel between the surface and deep ocean is not associated with a pronounced isotopic fractionation the isotopic data also present a mass balance problem the main output of nickel from the oceans sorption to fe mn oxides appears to be similar in isotopic composition to the dissolved phase yet the riverine input is lighter than the dissolved pool this observation either requires other inputs that are isotopically heavy or an output that is isotopically light further large inputs over and above the dissolved riverine source appear to be required by what we know of the elemental budget but the isotopic mass balance suggests that such an input needs to be isotopically much heavier than both the riverine dissolved load and the lithogenic isotopic composition of nickel