late oligocene miocene syn late orogenic successions in western and central mediterranean chains from the betic cordillera to the southern apennines the identification of syn and late orogenic flysch deposits extending from the betic cordillera to the southern apennines assists in the reconstruction of the tectonic sedimentary evolution of the perimediterranean chains a microplate was located between the european and african plates during the late jurassic early cretaceous bordered northwards by the piemontese ocean and southwards by another north africa flysch basin or maghrebian ocean the piemontese ocean and the northern margin of the microplate were structured from the late cretaceous to the eocene to create an eo alpine chain the southern margin of the microplate was deformed in the aquitanian when the internal areas of the maghrebian ocean were characterized by syn orogenic flysch deposits this episode culminated with metamorphism 25 22 ma and nappe emplacement which destroyed the former palaeogeography and created an orogenic belt alkapeca afterwards a lower burdigalian late orogenic cycle started in the deformed area which as a result of the opening of the algero provencal basin caused the fragmentation of the alkapeca its thrusting on the flysch basin and the collision with the north africa and south iberia margins these latter were folded and thrusted the flysch units pushed over the external domain and also back thrusted langhian late orogenic deposits suture the new tectonic features finally the whole orogen was thrust onto the foredeep during the middle late miocene

neutral carbohydrate geochemistry of particulate material in the central equatorial pacific abstract neutral carbohydrate compositions were determined for particulate samples from plankton net tows shallow floating sediment traps mid depth and deep moored sediment traps and sediment cores collected along a north south transect in the central equatorial pacific ocean during the u s jgofs eqpac program total neutral carbohydrate depth profiles and patterns along the transect follow essentially the same trends as bulk and organic carbon oc fluxes attenuating with depth high near the equator and decreasing poleward oc normalized total aldose tch 2 o yields along the transect and with depth do not show any consitent patterns relative to a planktonic source neutral carbohydrate compositions in sediment trap and sediment core samples reflect preferential loss of ribose and storage carbohydrates rich in glucose and preferential preservation of structural carbohydrates rich in rhamnose xylose fucose and mannose there is also evidence for an intermediately labile component rich in galactose it appears that compositional signatures of neutral carbohydrates in sediments are more dependent upon their planktonic source than on any particular diagenetic pathway relative to other types of organic matter neutral carbohydrates are better preserved in calcareous oozes from 12 s to 5 n than in red clays at 9 n based on oc normalized tch 2 o yields due to either differing sources or sorption characteristics weight per cent glucose generally decreases with increased degradation of organic material in the central equatorial pacific region based on weight per cent glucose comparisons of samples between survey i el nion and survey ii non el nino indicate that during survey i organic material in the epipelagic zone in the northern hemisphere may have undergone more degradation than organic material in the southern hemisphere

geomorphological control of gold distribution and gold particle evolution in glacial and fluvioglacial placers of the ancocala ananea basin southeastern andes of peru abstract gold placers are formed as a result of surficial processes but glacial and fluvioglacial systems are generally considered to be unfavourable for placer genesis nevertheless some important glacial and fluvioglacial placers have been discovered and are currently being exploited in the andes of peru and bolivia in the plio pleistocene ananea ancocala basin 4300 4900 m above sea level the gold content of the various formations indicates that only glacial and fluvioglacial sediments related to the ancocala and chaquiminas glaciations middle and upper pleistocene contain gold in any notable quantity local concentrations of economic interest occur only where a glacier has cut through a primary mineralized zone glacial erosion of dispersed primary mineralizations does not produce high content placers of the kind found in fluviatile environments gold distribution in tills is more irregular than in fluviatile sediments and no marked enrichment at bedrock occurs the transition from a glacial to a fluvioglacial environment is characterized by an increase in gold content due to a relative concentration of the biggest gold flakes and by the appearance of a gold distribution pattern similar to that found in a fluviatile environment during their transport by glacial and fluvioglacial processes gold particles acquire specific features the size and morphology of a gold flake population are determined by the sedimentological and geomorphological environment in which the flakes are carried

a new mechanistic model for organic carbon fluxes in the ocean based on the quantitative association of poc with ballast minerals abstract in simulation studies of the ocean s role in the global carbon cycle predicting the depth distribution for remineralization of particulate organic carbon poc is of particular importance following sarmiento et al global biogeochemical cycles 7 1993 417 most simulation models have the power law curve of martin et al deep sea research 34 1987 267 for this purpose the martin et al curve is an empirical fit to data most of which is from shallow floating sediment traps using such a fit implies that all the information necessary for prediction is contained in the carbon flux itself so that the organic carbon flux f oc z at any depth z can be predicted from the flux of organic carbon f oc z 0 at some near surface depth z 0 here we challenge this basic premise arguing that fluxes of ballast minerals silicate and carbonate biominerals and dust determine deep water poc fluxes so that a mechanism based model of poc flux must simultaneously predict fluxes of both poc and ballast minerals this assertion is based on the empirical observation that poc fluxes are tightly linked quantitatively to fluxes of ballast minerals in the deep ocean here we develop a model structure that incorporates this observation and fit this model to us jgofs eqpac data this model structure plus the preliminary parameter estimates we have obtained can be used to explore the implications of our model in studies of the ocean carbon cycle

speciation bioavailability and preservation of phosphorus in surface sediments of the changjiang estuary and adjacent east china sea inner shelf abstract the speciation potential bioavailability and preservation of phosphorus p in surface sediments of the changjiang yangtze river estuary and adjacent east china sea ecs inner shelf were investigated through the analyses of p fractions and sediment bulk properties a sequential extraction method sedex was used to separate and quantify the following six sedimentary p reservoirs exchangeable p ex p authigenic p au p detrital p de p organic p or p refractory p re p and fe bound p fe p total p tp in surface sediments ranged from 15 0 to 21 4 mol g 1 and was highest near the changjiang river mouth the average contribution of each form of p to tp was 55 6 de p 17 8 re p 16 1 or p 5 5 au p 2 5 ex p and 2 5 fe p respectively de p showed relatively higher concentrations in the river mouth and the ecs shelf region off the changjiang estuary high concentrations of or p were found mainly in mud areas showing a similar distribution pattern with silt sediment surface area ssa and total organic carbon toc re p was mainly distributed near the estuarine area and the zhe min coast bioavailable p bap accounted for 9 5 32 0 of tp with a mean of 21 2 and showed a similar distribution pattern to that of or p de p ssa and toc ssa loadings both decreased with increasing of ssa while or p ssa loadings varied little with ssa indicating that or p may have reached an adsorption desorption equilibrium on mineral surfaces toc to total organic p top sum of re p and or p ratios less than the redfield ratio 84 in average may have indicated efficient remineralization of organic matter in mobile muds of the changjiang estuary and adjacent ecs inner shelf furthermore the relatively high toc or p ratios 72 422 with a mean of 188 likely suggest a higher degree of preferential regeneration of labile or p over toc in sediments

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

chemical and mineralogical signatures of gold formed in oxidizing chloride hydrothermal systems and their significance within populations of placer gold grains collected during reconnaissance the close association of pd with au has been previously reported in highly oxidized chloride hydrothermal systems from several regions including australia brazil poland and the united kingdom the distinctive mineralization precipitated usually as a consequence of contact with reducing environments is characterized by au alloys containing low ag pd hg cu associated with selenides tellurides antimonides arsenides placer gold grains derived from this style of mineralization inherit these chemical and physical characteristics which are shown to be distinct from those placer grains derived from other styles of mineralization the discovery of placer gold grains of this type in areas remote from known in situ mineralization initiated the present project and provided a methodology for the study of a relatively large number of occurrences data describing alloy chemistry and mineralogy of polished sections of 957 placer grains from 19 localities in the united kingdom and 1 locality in the czech republic have augmented previously published data for 303 gold grains from 10 localities in the united kingdom six generic gold alloy types have been identified based on the relative proportions of au ag pd and hg mineralogical descriptions of similar gold alloys from localities worldwide usually conform to this classification but slight deviations are noted where p t conditions differ from those previously identified in devon alloy types may occur either as discrete grains or as phases within heterogeneous grains type 1 gold defined as 99 mass au type 2 gold au pd and type 3 gold au ag alloys with selenide inclusions are the most common compositions and occur at most localities although in different proportions type 4 gold is also an au ag alloy but contains sulfide and sulfarsenide inclusions gold alloys or intermetallics containing pd hg and or pd sb alloys type 5 and cu type 6 are found only at some localities as is a variety of type 3 gold selenide inclusions which contains hg the spatial arrangement of the main alloy types within heterogeneous gold grains shows a consistent precipitation order of type 1 type 2 and type 3 independent of locality interpretation of the chemical controls on alloy precipitation indicates that o2 controls whether type 1 or type 2 gold precipitates initially the formation of type 4 gold au ag alloys with sulfide inclusions is ascribed to a fall in o2 to around the hematite magnetite buffer where hs aq replaces cl aq as the aqueous gold complex types 3 and 5 gold commonly mantle earlier alloys and show evidence for aggressive replacement of the core this texture is interpreted as evidence for influx of a more oxidizing fluid which also accounts for the abundance of selenide and telluride mineral inclusions within this gold type this approach provides a plausible explanation of the complex heterogeneity within and between gold grains from the localities and accounts for the common sequence of alloy precipitation without invoking multiple episodes of hydrothermal activity to account for different alloys however the absence of thermodynamic data describing the au cu au ag cu and au ag pd hg systems prevents interpretation of the significance of some alloy types this study has demonstrated that gold mineralization associated with oxidizing strata is more widespread than currently appreciated the methodology described here not only permits identification of gold from this style of mineralization but allows initial evaluation of the economic potential of the source through the study of the alloy types this information may be gained at an early stage in the exploration process from gold grains collected during routine reconnaissance

controls on phosphorus concentration and accumulation in oceanic sediments understanding phosphorus p sedimentation in the ocean is important both for quantifying outputs in the marine phosphorus cycle and for determining the controls on phosphogenesis the authigenic formation of carbonate fluorapatite and phosphorite deposition large accumulations of p rich sediments on continental margins in this study i have compiled literature data on sedimentary p concentrations and sedimentation rates from continental margins phosphogenic continental margins and open ocean environments i have also calculated p accumulation rates the product of p concentration sediment density and sedimentation rate in these settings sedimentary p concentrations exhibit a similar range in a wide variety of oceanic environments and sedimentation rate conditions for example p concentrations in continental margin sediments range from 8 to 108 mol p g 1 with sedimentation rates from 80 to 8 000 m my 1 in open ocean sediments the p concentration range is similar 7 307 mol p g 1 even though sedimentation rates are generally about 100 times lower 2 50 m my 1 the exception to this are phosphogenic environments where p concentrations are exceptionally high 580 3 700 mol p g 1 while sedimentation rates are relatively low 20 310 m my 1 phosphorus accumulation rates appear to be controlled by sedimentation rate in ocean sediments although p concentrations generally exhibit similar ranges the large difference in sedimentation rates between various environments results in p accumulation rates that are several orders of magnitude higher in continental margins 90 8 000 mol p cm 2 kyr 1 compared to open ocean sediments 2 75 mol p cm 2 kyr 1 in the case of phosphogenic environments low sedimentation rates result in p accumulation rates 80 6 300 mol p cm 2 kyr 1 that are surprisingly similar to those of non phosphogenic continental margin sediments

slow science the value of long ocean biogeochemistry records sustained observations sos have provided invaluable information on the ocean s biology and biogeochemistry for over 50 years they continue to play a vital role in elucidating the functioning of the marine ecosystem particularly in the light of ongoing climate change repeated consistent observations have provided the opportunity to resolve temporal and or spatial variability in ocean biogeochemistry which has driven exploration of the factors controlling biological parameters and processes here i highlight some of the key breakthroughs in biological oceanography that have been enabled by sos which include areas such as trophic dynamics understanding variability improved biogeochemical models and the role of ocean biology in the global carbon cycle in the near future sos are poised to make progress on several fronts including detecting climate change effects on ocean biogeochemistry high resolution observations of physical biological interactions and greater observational capability in both the mesopelagic zone and harsh environments such as the arctic we are now entering a new era for biological sos one in which our motivations have evolved from the need to acquire basic understanding of the ocean s state and variability to a need to understand ocean biogeochemistry in the context of increasing pressure in the form of climate change overfishing and eutrophication

upper ocean export of particulate organic carbon and biogenic silica in the southern ocean along 170 w abstract upper ocean fluxes of particulate organic carbon poc and biogenic silica bsi are calculated from four us jgofs cruises along 170 w using a thorium 234 based approach both poc and bsi fluxes exhibit large variability vs latitude during the seasonal progression of diatom dominated blooms poc fluxes at 100 m of up to 50 mmol c m 2 d 1 are found late in the bloom and farthest south near the ross sea gyre biogenic si fluxes also peak late in the bloom as high as 15 mmol si m 2 d 1 but this flux peak occurs at a different latitude just south of the antarctic polar front apf which is centered around 60 s along this cruise track the ratios of both poc and bsi export relative to their production rates are large suggesting an efficient biological pump at these latitudes the highest relative bsi poc flux ratios at 100 m are found just south of the apf coincident with a bsi poc flux peak seen in 1000 m traps during this same program by deep sea research ii honjo et al deep sea research ii 47 3521 3548 these data suggest that efficient export at these latitudes can support the high accumulation rates of bsi found in the sediments under and south of the apf despite the generally low biomass and productivity levels in this region

recent sedimentation on the new jersey slope and rise radiocarbon dating and sedimentological studies of closely spaced cores indicate movement during the holocene of sediments on the new jersey continental slope and upper rise between wilmington and lindenkohl canyons the uneven time stratigraphic thickness of the late quaternary sediment sections between cores and the nonuniform deposition rate at any given core site and among core sites show that the sediment blanket in canyon and intercanyon areas has been affected by downslope gravity driven pocesses during the holocene to the present the reduced rate of deposition on the slope and upper rise between the late pleistocene and the present is largely due to decreased off shelf transport in response to the eustatic rise in sea level very old radiocarbon dates at core tops result from emplacement of older reworked materials from upslope or from truncation of sections by mass wasting processes exposing older material at the sea floor these processes also account for an irregular sequence of dated sections within cores and stratigraphic irregularities of the surficial cover from core to core marked variability in deposition rates on the slope and upper rise is largely a function of topographic configuration proximity and accessibility to sediment source and transport processes seaward of the shelf break moreover higher accumulation rates on the upper rise are attributed primarily to slope bypassing bypassing prevalent during the late pleistocene has continued periodically to the present

factorial correspondence analysis a useful tool in palaeogeographical reconstructions example from late cretaceous calciturbidites of the northwestern external rif morocco

crystalline placer gold from the rio neuquen argentina implications for the gold budget in placer gold formation recent fluvial sediments of the rio neuquen argentina contain variable amounts of placer gold in addition to rounded detrital placer gold the sediments also contain pristine crystalline gold type 1 gold which occurs as overgrowths on detrital placer gold cores type 1 gold is locally rimmed by gold with a wormlike or crystalline texture type 2 gold the chemistry of the primary cores indicates variable intragrain and intergrain compositional heterogeneity this is interpreted to indicate a multisource origin type 1 gold is composed of virtually pure gold 98 at au and type 2 gold is an au hg amalgam 4 9 at hg both varieties are authigenic in origin the formation of the virtually pure type 1 gold is interpreted to be due to the addition of au from an external source rather than by the removal of ag and other metals the auhgag type 2 gold is interpreted to be due to hg contamination from historic mining type 1 gold is interpreted to be analogous to the ag poor rims present on many placer gold grains the evidence presented in this study supports the view that the ag poor rims on placer gold grains are the result of au addition and not ag removal this study also has implications for both quantitative morphological and paragenetic studies of placer gold grains

association of sinking organic matter with various types of mineral ballast in the deep sea implications for the rain ratio 1 we compiled and standardized sediment trap data below 1000 m depth from 52 locations around the globe to infer the implications of the armstrong et al 2002 ballast model to the ratio of organic carbon to calcium carbonate in the deep sea the rain ratio we distinguished three forms of mineral ballast calcium carbonate opal and lithogenic material we concur with armstrong et al 2002 that organic carbon sinking fluxes correlate tightly with mineral fluxes based on the correlations seen in the trap data we conclude that most of the organic carbon rain in the deep sea is carried by calcium carbonate because it is denser than opal and more abundant than terrigenous material this analysis explains the constancy of the organic carbon to calcium carbonate rain ratio in the deep sea today and argues against large changes in the mean value of this ratio in the past however sediment trap data show variability in the ratio in areas of high relative calcium carbonate export mass caco3 mass ratio 0 4 unexplainable by the model leaving open the possibility of regional variations in the rain ratio in the past

role of increased marine silica input on paleo pco2 levels changing the supply of silica to the ocean may alter pco2 levels the increase in dust delivered to the ocean during glacial times increased the availability of silica for biological uptake the increased silica levels shifted species composition diatom populations increased and coccolith populations decreased decreasing the population of coccoliths decreased the flux of calcite to the sediments which in turn lowered pco2 levels enough to explain the glacial interglacial pco2 transition furthermore the contemporary increase in dust delivered to the ocean s mixed layer may be removing significant amounts of carbon dioxide from the atmosphere at present to set the stage this silica hypothesis is compared with the iron fertilization and nitrogen fixation hypotheses

glacial versus interglacial sedimentation rates and turbidite frequency in the bahamas the southern tongue of the ocean is a 1300 m deep flat floored basin in the bahamas that receives large amounts of sediment from the carbonate platforms surrounding it on three sides we have examined five 8 13 m long piston cores and determined bulk sedimentation rates turbidite frequency and turbidite accumulation rates for the past two glacial and interglacial periods the mean of bulk sedimentation rates is four to six times higher in interglacial periods average accumulation rates of recognizable turbidites are higher by a factor of 21 to 45 and interglacial turbidite frequency is higher by a factor of 6 to 14 sediment composition indicates that increased interglacial rates are due to higher accumulation of platform derived material additional data from other bahamian basins as well as published material from the caribbean strongly suggest that highstand shedding is a general trend in pure carbonate depositional systems carbonate platforms without a siliciclastic component export more material during highstands of sea level when the platform tops are flooded and produce sediment the response of carbonate platforms to quaternary sea level cycles is opposed to that of siliciclastic ocean margins where sediment is stored on the inner shelf during highstands and passed on to continental rises and abyssal plains during lowstands of sea level

crystallinity and diagenesis of sedimentary apatites the crystallinity of sedimentary apatites was determined by fourier transform infrared spectroscopy ft ir using the splitting of a triply degenerate antisymmetric bending vibration of orthophosphate the crystallinity indices of recent marine apatites are low 3 0 3 6 while those of onland ancient apatites are high 4 5 7 8 indicating post depositional recrystallization the infrared spectra reveal that recrystallization is associated with a decrease in carbonate content substituting for po43 and an increase in fluoride order within the apatite structure the relationship between the crystallinity index and po43 18o suggests alteration of the primary isotopic composition by exchange reactions between po43 oxygens and surrounding waters the monterey samples have a large range of crystallinity index that reflects a set of complex and highly variable diagenetic conditions this demonstrates the use of ft ir criteria for differentiating between pristine and altered apatites and as a consequence for relating geochemical markers to formation or diagenetic environments it is suggested that only those samples that have low crystallinity indices c i 3 8 should be considered as pristine apatite spectra of fish remains indicate that differences in rare earth element ree patterns correspond to variations in crystallinity carbonate content and f order in the apatite lattice the fact that crystallinity is not correlated with geologic age suggests that environmental factors such as accumulation rate and pore water chemistry govern the recrystallization process in general sr content decreases and 18op exhibits high variability with increasing crystallinity

silver isotope analysis of gold nuggets an appraisal of instrumental isotope fractionation effects and potential for high resolution tracing of placer gold abstract we describe a technique for high precision analysis of 109ag 107ag ratios in natural and archaeological gold 1 0 120 mg g ag with particular emphasis on the control of ag yield and effects of instrumental mass bias after dissolution of mg sized gold samples in aqua regia and conversion to chlorides a miniature column filled with the anion exchange resin ag 1 x8 was used for removal of au from the sample solutions in a second miniature column made of the triskem tbp resin ag was converted from the chloride to the nitrate form isotopic analyses on the mc icp ms employed the combination of pd doping and standard bracketing and considering the measurements of replicate dissolutions and chromatographic separations for srm978a and cezag reference solutions the combined analytical uncertainty 2 s of the analytical method is better than 0 016 a solution prepared from several gold nuggets was characterised isotopically cezag with 109ag 0 043 0 015 for use as a silver in gold reference material in ag isotope studies of natural and processed gold results for gold nuggets from three continents indicate a wide variation in ag concentrations 5 to 123 mg g and this is matched by an equally wide range in isotopic compositions 109ag 0 58 to 0 83 this is larger than the variation found so far in in native gold from primary deposits 0 42 to 0 5 although small isotopic effects to lower 109ag during strong ag loss are possible within a single grain most analysed nuggets are internally isotopically homogeneous this suggests preservation of the primary 109ag in the supergene environment and that gold was sourced from several distinct gold deposits in the catchment recent studies however indicate that even single primary deposits may be isotopically heterogeneous implying that ag isotope fractionation is caused by numerous deposition dissolution cycles in hydrothermal systems fine grained detrital gold from three placers along the rhine river in germany show only small differences in 109ag 0 005 0 047 to 0 124 0 007 despite being distributed along 480 km of river length this may indicate thorough mixing of gold grain populations during transport the small sample size required for ag isotope work on gold opens the way for detailed micro sampling approaches these may be used to further examine the potential for within grain isotopic variability related to fluviatile processing and can be used to correlate the composition of the placers with that of grains from primary sources

the in vitro growth of gold grains gold colloids octahedral platelets and foils directly and indirectly formed from the reduction of soluble au i thiosulfate and au iii chloride complexes by iron oxidizing bacteria cyanobacteria and sulfate reducing bacteria were combined in an experimental system this system represented simplified biogeochemical conditions occurring within a fluvial environment in which placer au could occur in this study biofilm formation and physical aggregation i e sedimentation processes were critical for the accumulation of nanometer to micrometer sized au particles into grains 4 5 mm in size characterization of grain surface textures by scanning electron microscopy in association with monitoring soluble au concentrations over time suggested that dissolution and reprecipitation processes were occurring at the au grain fluid interface this laboratory model demonstrates that the biogeochemical cycling of au can contribute to the formation of anomalous enrichments such as placer au deposits

mineral ballast and particle settling rates in the coastal upwelling system off nw africa and the south atlantic the ocean off nw africa is the second most important coastal upwelling system with a total annual primary production of 0 33 gt of carbon per year carr in deep sea res ii 49 59 80 2002 deep ocean organic carbon fluxes measured by sediment traps are also fairly high despite low biogenic opal fluxes due to a low supply of dissolved silicate from subsurface waters the ocean off nw africa is characterized by predominantly carbonate secreting primary producers i e coccolithophorids these algae which are key primary producers since millions of years are found in organic and chlorophyll rich zooplankton fecal pellets which sink rapidly through the water column within a few days particle flux studies in the mauretanian upwelling area cape blanc confirm the hypothesis of armstrong et al deep sea res ii 49 219 236 2002 who proposed that ballast availability e g of carbonate particles is essential to predict deep ocean organic carbon fluxes the role of dust as ballast mineral for organic carbon however must be also taken into consideration in the coastal settings off nw africa there high settling rates of larger particles approach 400 m day 1 which may be due to a particular composition of mineral ballast an assessment of particle settling rates from opal production systems in the southern ocean of the atlantic sector in contrast provides lower values consistent with the assumptions of francois et al global biogeochem cycles 16 4 1087 2002 satellite chlorophyll distributions particle distributions and fluxes in the water column off nw africa as well as modelling studies suggest a significant lateral flux component and export of particles from coastal shelf waters into the open ocean these transport processes have implications for paleo reconstructions from sediment cores retrieved at continental margin settings

the morphology mineralogy and behavior of u fine grained gold from placer deposits of alberta sampling and implications for mineral exploration the morphology of a large number of gold grains from stream sediments of the north saskatchewan river and the athabasca river was studied together with the partitioning of the placer gold between various size fractions two major morphological varieties of gold were observed 1 flaky scaly gold with folded and hammered edges and with crystals or crystal faces still visible on the surface and 2 sandwiched droplike particles sometimes toroidal about 5 of both types of gold were found to be coated with new secondary gold the size of the majority of the gold grains studied varies between 0 500 and 0 010 mm the most frequent size range in the north saskatchewan river is 0 125 0 250 mm whereas in the athabasca river it is 0 063 0 125 mm an important fraction of the gold from both rivers is smaller than 0 063 mm the average corey shape factor csf of the gravity recovered gold increases as the particle size decreases whereas the gold grains lost to the tailings indicate very low average sha

the deposition of elemental gold from gold i thiosulfate complexes mediated by sulfate reducing bacterial conditions the role of sulfate reducing bacteria in the precipitation of elemental gold through a geologic stratum was investigated using column experiments the mixed culture dominated by sulfate reducing bacteria was isolated from the driefontein consolidated gold mine witwatersrand basin republic of south africa bacterially mediated gold precipitation from the gold i thiosulfate complex was more efficient than the corresponding abiotic experiments in the bacterial systems sulfate reducing bacteria i e desulfovibrio sp deposited gold inside the cells as spherical nanoparticles over time these nanoparticles of gold were released from the cells and deposited at cell surfaces and in the bulk solutions ultimately these nanoparticles of gold contributed to the formation of micrometer scale octahedral gold crystals occasional framboidlike structures 1 5 m diam and millimeter scale gold foils typically surrounding the silicate grains spherical gold particles 1 m diam were precipitated in the abiotic experiments and the formation of octahedral gold framboidlike structures and gold foils were not observed in these experiments the reduction and enrichment of elemental gold by sulfate reducing bacteria occurred without the concomitant death of the bacteria suggesting that in natural systems this process could go on over geologic time scales as long as nutrients and gold i thiosulfate were provided to the system

middle eocene to early oligocene paleoceanography from agulhas ridge southern ocean ocean drilling program leg 177 site 1090 1 the agulhas ridge off the tip of africa between the atlantic and indian oceans is ideally located to capture the evolution of paleogene early neogene circulation patterns associated with global cooling multiproxy records of productivity biogenic barium baex opal caco3 mass accumulation rates mars nutrient and organic carbon burial reactive phosphorus pr mars and redox state of deep waters u enrichment from ocean drilling program odp site 1090 reflect hydrographic shifts in this region between the middle eocene and early oligocene 39 33 ma several peaks in increased export productivity and burial of organic matter occurred within the late eocene 36 5 34 and 33 7 ma which along with surface hydrologic conditions favoring opaline organisms over calcareous organisms could have aided in the draw down of pco2 to a threshold level that facilitated large ice sheet development on antarctica in the earliest oligocene our multiproxy approach illustrates the importance of vertical as well as spatial hydrographic reorganization in amplifying or driving climatic cooling of the middle eocene to early oligocene by facilitating increases in the relative or absolute burial of organic carbon

glacially derived shallow marine gold placers of the cape yakataga district gulf of alaska abstract economic gold bearing coastal sediment of holocene age 10 ka occurs along the gulf of alaska coastal margin from cape yakataga in the west to icy bay in the east a distance of 50 km deposits have been worked since 1898 and total production since then is about 15 000 ounces gold is recovered from discontinuous sheets of ruby garnet rich beach sand exposed at low tide along the high energy storm dominated coastline similar auriferous sand facies are also present within raised marine terraces cut across outwash fans along the narrow mountainous coastal margin the area has been uplifted by glacio isostatic rebound following the last glacial maximum and by high magnitude earthquakes the area lies along the collision zone between the north american and pacific plates study of uplifted and well exposed late cenozoic strata the glaciomarine yakataga formation that outcrop along the coastal margin confirms this succession as the source of placer gold the yakataga formation records the rapid accumulation of over 6 km of gold bearing glaciomarine sediments in a rapidly subsiding forearc basin these strata have in turn been uplifted as coastal mountains and eroded by glaciers the white river glacier and yakataga glacier drainage basins can be identified as the principal source of detrital gold along the yakataga coastline auriferous beach sediment is the product of westward reworking of glacial outwash from the white and yakataga rivers and is accompanied by a well defined downcurrent reduction in the size and number of gold particles

ichnofabrics of a pleistocene slope succession new jersey margin relations to climate and sea level dynamics abstract trace fossil and sedimentologic data were collected at 10 cm intervals throughout a virtually continuous 520 m thick upper pleistocene siliciclastic succession recovered at odp site 1073 new jersey margin these data were examined in the context of isotopic seismic and palynologic proxies to document depositional and ichnologic responses to quaternary climate and sea level dynamics in an upper slope setting two broad texturally defined sedimentary facies assemblages are recognized the clay rich assemblage reflects relatively rapid deposition in part from turbidity currents and suspended plumes and appears to be linked to cooler sea level fall and lowstand phases the sand rich assemblage reflects overall slower sedimentation by offshelf spillover and periodic winnowing and erosion under the influence of contour and other bottom currents during warmer transgressive highstand phases facies of the sand rich assemblage muds sandy muds muddy sands and sands are completely bioturbated and are characterized by high densities of biogenic structures including distinct burrow forms in contrast the clay rich assemblage includes facies that exhibit limited biogenic disruption laminated clay silty clay and graded silt or fine sand to clay couplets and on the whole is characterized by lower densities of biogenic structures most of which are diffuse burrow mottles these ichnofabric trends reflect changes in ecological and taphonomic parameters e g substrate stability and consistency residence time of sediments in the benthic boundary layer and degree of inter and intrabed textural variability many of which were governed by variations in sedimentation rate as mediated by glacio eustacy recurring identifiable ichnofossils are most common in facies of the sand rich assemblage in the upper half of the pleistocene succession finer grained components of this assemblage e g muds and sandy muds representing quieter phases of highstand deposition are characterized by a low diversity distal cruziana ichnofacies assemblage dominated by schaubcylindrichnus and phycosiphon anconichnus both of which represent the work of deposit feeding worms narrow facies transitions that correspond to phases of rapid transgression are marked by occurrences of thalassinoides these crustacean burrow systems were excavated in coarser grained higher energy facies sands and muddy sands and in closely associated firmground substrates produced by exhumation of consolidated muds by bottom currents and or mass wasting processes the association of firmground ichnofabrics with marine flooding events in an upper slope setting demonstrates that the sequence stratigraphic utility of the glossifungites ichnofacies extends beyond shelf depositional sequences to deeper water deposits the distribution of texturally defined facies and general ichnofabric parameters e g degree of bioturbation appears to respond to glacio eustatic cycles through the entire pleistocene record however the schaubcylindrichnus phycosiphon assemblage and thalassinoides are rare or absent altogether in the lower half of the succession indicating that biological responses to and the ichnologic record of climate and sea level dynamics may be strongly dependent on margin physiographic and bathymetric evolution

morphogenesis and composition of native gold in the chelopech volcanic hosted au cu epithermal deposit srednogorie zone bulgaria native gold is an important economic component of the complex ores of the chelopech high sulphidation volcanic hosted epithermal au cu deposit bulgaria the ore consists of pyrite chalcedonic silica chalcopyrite enargite luzonite tennantite bornite sphalerite galena and numerous other sulphide arsenide and telluride minerals gold is paragenetically associated with most of the arsenic bearing and base metal sulphide minerals the chemistry and morphology of gold grains which were separated from disintegrated ores were systematically studied by scanning electron microscopy sem and electron probe microanalysis epma the gold is characterised by high fineness 950 and a mean composition of 94 1 wt au 5 27 wt ag 0 53 wt cu and 0 10 wt fe gold grains show variable morphology subhedral flakes irregular grains euhedral isometric crystals elongated rods wires and fine fibrous crystals 111 twins fine dendrite like formations spongy gold and polycrystalline grains the densest faces 111 are morphologically the most important morphometric measurements show a pronounced flatness of the gold particles the mean value of the corey factor a measure of flatness from 0 to 1 spherical is 0 14 and the mean length to width value is 1 64 it is suggested that crystal growth of gold took place in small voids fine cracks and intergranular space the geometry of which have controlled the highly variable grain shapes no direct correlation between the size and composition of gold grains exists but larger grains tend to be of higher fineness

the relationship between placer gold particle shape rimming and distance of fluvial transport as exemplified by gold from the klondike district yukon territory canada a semiquantitative study of various physical features of approximately 2 700 gold particles from 21 lode deposits and 36 placer deposits in the klondike district yukon territory canada was undertaken the shape parameters of roundness and flatness were determined using a classification method there appears to be a systematic variation between these parameters and between the parameters and the distance of transport of the particle these relationships were confirmed by quantitative measurements on critical samples rim characteristics were also estimated they show a systematic relationship between one another with the particle shape and less clearly with the distance of transport gold particle shape data shows a smooth well defined relationship to distance of transport from the lode source of the gold both roundness and flatness show a rapid increase within the first 5 km from the lode source and a slower more linear increase beyond this relationship seems to apply worldwide the relationship between the shape of a gold particle and the rim characteristic supports the conclusion that rims are formed by the removal of ag hg and cu and not by the precipitation of au thus rim thickness and the associated high fineness is probably the result of the dynamic process of ag removal in stagnant sediments to create the rim and abrasion in active sediments to remove the rim the composition of the rims represents the stable composition of gold in normal surficial environments together these observations place limits on the occurrence of new gold hammering is the main cause of shape change in fluvially transported gold particles its principal effect is to flatten particles abrasion has its most marked effect on surface texture hammering and abrasion both decrease the mass size and increase the roundness of the gold particles it is therefore possible to make a connection between hydraulic conditions during gold particle transport and its shape change

characteristics and origin of coarse gold in late pleistocene sediments of the cariboo placer mining district british columbia canada the cariboo placer mining district 1000 km2 sited in the interior plateau of central british columbia canada is the premier placer gold mining district of the province gold is recovered from three late pleistocene sedimentary facies postglacial fluvial gravels 25 ka this study reports the morphology size roundness sphericity of 1636 gold grains ranging in size from 0 25 to 17 mm recovered from 19 placer mines older gravels contain the smallest gold grains mean grani size 1 53 mm grains of intermediate size occur in till 2 23 mm and the coarsest gold occurs in postglacial gravels 2 34 mm with a mean of 1 93 mm for the mining district as a whole the most common grain shapes are sub rounded discoidal 14 73 of the grain population sub angular discoidal 10 88 and sub rounded sub discoidal 9 59 the most angular grains occur in postglacial gravels in situ growth of coarse angular grains is indicated by a composite grain structure consisting of aggregates of gold particles welded together by high grade ag 2 filamentous gold in situ coarsening may be reliant on organic complexing agents produced below a dense forest cover an evolutionary sequence of grain form from angular aggregates to rounded pumpkin seed grains is suggested rounded grains commonly show a crystalline structure which may result from the cold hammering of gold during transport fracturing along crystal boundaries is common gold grains may undergo cycles of coarsening rounding diagenesis and breakup in response to repeated recycling through pleistocene sedimentary environments

societal need for improved understanding of climate change anthropogenic impacts and geo hazard warning drive development of ocean observatories in european seas society s needs for a network of in situ ocean observing systems cross many areas of earth and marine science here we review the science themes that benefit from data supplied from ocean observatories understanding from existing studies is fragmented to the extent that it lacks the coherent long term monitoring needed to address questions at the scales essential to understand climate change and improve geo hazard early warning data sets from the deep sea are particularly rare with long term data available from only a few locations worldwide these science areas have impacts on societal health and well being and our awareness of ocean function in a shifting climate substantial efforts are underway to realise a network of open ocean observatories around european seas that will operate over multiple decades some systems are already collecting high resolution data from surface water column seafloor and sub seafloor sensors linked to shore by satellite or cable connection in real or near real time along with samples and other data collected in a delayed mode we expect that such observatories will contribute to answering major ocean science questions including how can monitoring of factors such as seismic activity pore fluid chemistry and pressure and gas hydrate stability improve seismic slope failure and tsunami warning what aspects of physical oceanography biogeochemical cycling and ecosystems will be most sensitive to climatic and anthropogenic change what are natural versus anthropogenic changes most fundamentally how are marine processes that occur at differing scales related the development of ocean observatories provides a substantial opportunity for ocean science to evolve in europe here we also describe some basic attributes of network design observatory networks provide the means to coordinate and integrate the collection of standardised data capable of bridging measurement scales across a dispersed area in european seas adding needed certainty to estimates of future oceanic conditions observatory data can be analysed along with other data such as those from satellites drifting floats autonomous underwater vehicles model analysis and the known distribution and abundances of marine fauna in order to address some of the questions posed above standardised methods for information management are also becoming established to ensure better accessibility and traceability of these data sets and ultimately to increase their use for societal benefit the connection of ocean observatory effort into larger frameworks including the global earth observation system of systems geoss and the global monitoring of environment and security gmes is integral to its success it is in a greater integrated framework that the full potential of the component systems will be realised highlights societies increasingly depend on timely information on ecosystems and natural hazards data is needed to improve climate related uncertainty and geo hazard early warning observatory networks coordinate and integrate the collection of standardised data ocean observatories provide opportunity for ocean science to evolve

sediment carbon nitrogen and phosphorus cycling in an anoxic fjord effingham inlet british columbia sediment geochemistry as well as benthic exchange of nutrients was investigated in effingham inlet a fjord located on the west coast of vancouver island in barkley sound the effect of bottom water oxygenation on sediment carbon nitrogen and phosphorus cycling was compared at sites overlain by oxic and anoxic bottom waters the sites separated by only 3 kilometers were similar in terms of key diagenetic parameters including mass accumulation rate and bulk sediment organic carbon content thus allowing a focus on diagenetic effects attributable to depositional oxygen availability benthic flux chamber incubations sulfate reduction rate measurements measurements of solid phase and pore water chemical profiles were compared for the sites these comparisons reveal that diagenetic processes in the site overlain by oxic waters act to retain more phosphorus in the sediment relative to the anoxic site differences in phosphorus benthic fluxes and burial between the two sites most likely result from differences in organic matter cycling under aerobic versus anaerobic conditions and are not strongly influenced by cycling of p associated with metal oxide phases

westerly derived early cretaceous gold paleoplacers in the western canada foreland basin southwestern alberta tectonic and economic implications albian aged early cretaceous igneous pebble to cobble conglomerates fill multiple northeast southwest oriented subparallel channels in the upper blairmore group upper beaver mines and mill creek formations of the rocky mountain foreland basin southwestern alberta and southeastern british columbia paleocurrent data show that the conglomerate was derived from the west clast petrography implies a provenance that includes granitoids mafic volcanics low grade metamorphic rocks and shallow level ca 7 km depth postmetamorphic quartz veins formed from meteoric fluids the conglomerate was probably derived from the southern omineca belt of british columbia prior to the rise of the rocky mountains the conglomerate contains detrital gold grains up to 150 m in diameter and chemical analyses indicate widespread anomalous gold concentrations up to 910 ppb au in conglomerate matrix gold content in these igneous clast conglomerates excedes that reported from the richest modern placers in alberta les

influence of boundary scavenging and sediment focusing on 234th 228th and 210pb fluxes in the santa barbara basin abstract sediment trap samples were collected from the santa barbara basin to examine the flux of 234 th 228 th and 210 pb mean ratios of measured to predicted fluxes are 2 10 and 21 for 234 th 228 th and 210 pb respectively boundary scavenging may supply a portion of all three radionuclides however sediment focusing supplies additional 228 th and 210 pb but little 234 th sediment temporarily deposited on the shelf around the basin contains little excess 234 th due to its short half life 228 th and 210 pb fluxes to the sediments in the santa barbara basin are several times greater than predicted from their supply in the overlying water column these enhanced fluxes require lateral transport of 228 th and 210 pb to the basin through boundary scavenging and sediment focusing 234 th flux is poorly correlated with 228 th and 210 pb fluxes because individual radionuclide sources to the basin differ i e water column production boundary scavenging and or sediment focusing correlations between 228 th and 210 pb fluxes are high due to the strong influence of sediment focusing on both radionuclides there is a strong correlation between both the 228 th and 210 pb flux and total mass flux and lithogenic flux but a weak correlation with the other major sediment components e g organic carbon carbonate and biogenic opal in the santa barbara basin a large fraction of the total mass flux is lithogenic material 50 80 hence the strong correlation between 228 th and 210 pb fluxes and both total mass and lithogenic fluxes 234 th flux is poorly correlated with total mass and major sediment component fluxes

particulate organic carbon fluxes compilation of results from the 1995 us jgofs arabian sea process study by the arabian sea carbon flux group abstract organic carbon fluxes in the arabian sea were measured as a function of depth season and distance from the coast of oman we present here a compilation of measurements of primary production water column export flux and sediment accumulation of organic carbon over a full annual monsoon cycle on a 1500 km transect from the coast of oman toward the central arabian sea this represents an integration of measurements spanning one day primary production to 1000 yr sediments and gives a broad overview of organic carbon removal and remineralization in the highly productive seasonally varying region of the northern indian ocean organic carbon fluxes decreased from the surface to the sediments by a factor of 500 10 000 with the largest rates of change in the upper ocean and at the sediment seawater interface organic carbon fluxes generally decreased with distance offshore with the largest gradient between surface and seafloor being at the offshore station sediment accumulation rates of organic carbon differed by a factor of 40 between nearshore and offshore while primary productivity varied only by a factor of 2 the decrease in carbon flux with depth that occurs between the deepest traps and the sediment becomes a greater proportion of the total loss with increasing distance from shore thus the influence of processes at the sediment water interface on the proportion of primary productivity preserved in the sediment increases offshore relative to upper water column processes carbon fluxes changed greatly with season with highest fluxes during the southwest monsoon export fluxes varied more with season than primary productivity or mid water fluxes

the south pyrenean eocene carbonate megabreccias revisited new interpretation based on evidence from the pamplona basin abstract the south pyrenean foreland basin contains numerous units of eocene carbonate megabreccias intercalated with siliciclastic turbidites and derived by resedimentation of shallow marine carbonate platforms previous studies were limited mainly to the foreland eastern part known as the jaca basin the present study from the pamplona basin a western part of the foreland trough sheds new light on the origin and regional significance of these south pyrenean eocene carbonate megabreccias specms the number of the specm units in the foreland basin is higher than previously recognized and their age is somewhat older than originally assumed the specm units appear to occur as time stratigraphic clusters which can be correlated with the relative sea level lowstands and linked with phases of tectonic activity the megabreccias were derived from a carbonate platform system hosted by the foreland basin s southern passive margin the episodic instability and mass wasting were triggered by phases of structural steepening forebulge uplift accompanied by high magnitude earthquakes with the former causing platform emergence increased load stresses and excess pore water pressure in the carbonate ramp the specm deposits were emplaced by cohesive debris flows evolving into high density turbidite currents an ideal specm unit consists of 1 an immature homogeneous debrite in the proximal part 2 a differentiated bipartite debrite and turbidite in the medial part and 3 an incomplete base missing debrite overlain by turbidite or a turbidite alone in the distal part the debrite component volumetrically predominates in the specm units and the original terms megaturbidite and seismoturbidite thus seem to be inappropriate for these deposits

phosphorus speciation and its bioavailability in sediments of the jiaozhou bay abstract phosphorus p is an important macronutrient that can limit primary productivity in coastal marine ecosystems in this study four sediment cores were collected in the jiaozhou bay to study the phosphorus forms and their bioavailability including exchangeable or loosely sorbed p ex p iron bound p fe p authigenic p ca p detrital p de p and organic p op which were separated and quantified using a sequential extraction method sedex the results showed that the concentration of total p tp in core sediments ranged from 6 23 to 10 46 mol g and inorganic p ip was the dominated p form fe p and de p were the main chemical forms of ip in core sediments the profile variation of op presented the most significant among the phosphorus forms whereas the concentrations of ex p fe p and ca p varied slightly with depth indicating that the transformation of ex p fe p ca p and op could occur during sedimentary p burial moreover the distribution of p species was influenced by many factors including terrigenous input biological processes organic matter degradation and increasing human activities high total organic carbon toc op ratio occurred in the jiaozhou bay ranging from 73 to 472 average 180 81 in core sediments which was caused by the increasing terrestrial organic matter the ratio of toc p reactive ranged from 24 to 101 average 46 15 in core sediments lower than the redfield ratio implying a surplus of sedimentary reactive p compared with toc potential bioavailable p bap accounted for about 28 2 60 8 average 47 1 7 4 of tp in core sediments and presented an increasing trend since 1980s which might be responsible for the shift of phytoplankton community composition during these decades

particulate organic carbon fluxes along upwelling dominated continental margins rates and mechanisms 1 time series sediment trap samples were used to examine the rates and mechanisms of particulate organic carbon poc flux at three continental margin locations santa barbara basin cariaco basin and guaymas basin marked by seasonal upwelling and high primary production the mean poc flux in santa barbara basin 0 096 g m 2 d 1 is nearly twice that of cariaco basin and 4 times higher than that in guaymas basin with all three sites having poc fluxes significantly higher than the open ocean average 0 007 g m 2 d 1 in cariaco basin the only site with available primary production numbers there is no significant relationship between poc flux and monthly primary production rather poc fluxes in all three areas strongly correlate with mineral carbonate opal and lithogenic material fluxes this supports the mineral ballast hypothesis where it has been suggested that higher density minerals enhance the flux of organic matter to the deep ocean on the basis of multiple regression analysis the three mineral components explain 72 of the total variance in poc fluxes at the three study sites with biogenic carbonate particles being the most effective transport mineral

factors controlling the flux of organic carbon to the bathypelagic zone of the ocean 1 particle fluxes measured with time series sediment traps deployed below 2000 m at 68 sites in the world ocean are combined with satellite derived estimates of export production from the overlying water to assess the factors affecting the transfer of particulate organic matter from surface to deep water multiple linear regression is used to derive an algorithm suggesting that the transfer efficiency of organic carbon defined as the settling flux of organic carbon normalized to export production increases with the flux of carbonate and decreases with water depth and seasonality the algorithm predicts 80 of the organic carbon transfer efficiency variability in diverse oceanic regions the influence of the carbonate flux suggests that the ballasting effect of this biogenic mineral may be an important factor promoting export of organic carbon to the deep sea by increasing the density of settling particles however the lack of a similar effect for biogenic opal suggests that factors other than particle density also play a role the adverse effect of increasing seasonality on the transfer efficiency of carbon to the deep sea is tentatively attributed to greater biodegradability of organic matter exported during bloom events in high latitude opal dominated regions with high f ratios and seasonality while a higher fraction of net production is exported a higher fraction of the exported organic matter is remineralized before reaching bathypelagic depths on the other hand in warm low latitude carbonate dominated regions with low f ratios and seasonality a higher fraction of the exported organic matter sinks to the deep sea

genesis of late cretaceous toe of slope breccias in the bakony mts hungary abstract toe of slope megabreccia deposits of an upper cretaceous rudist platform were studied in the bakony mountains during the turonian early senonian tectogenesis an articulated basin came into being in the area of the bakony depressions and highs were formed roughly parallel with the structural strike of the mountains inundation of the highs led to the evolution of carbonate platforms the investigated platform shows an asymmetric architecture in contrast to its gentle northern slope a steep erosional slope bounded the platform to the south with large low angle aprons the site of deposition of megabreccias the breccia accumulation occurred within a single 3rd order cycle commencing in the early highstand and reaching its climax in the late highstand

authigenic apatite formation and burial in sediments from non upwelling continental margin environments abstract evidence for precipitation of authigenic carbonate fluorapatite cfa in long island sound and mississippi delta sediments suggests that formation of cfa is not restricted to environments of active coastal upwelling we present porewater data suggestive of cfa formation in both these areas application of a sequential leaching procedure designed specifically to separate authigenic carbonate fluorapatite from other phosphorus containing phases including detrital apatite of igneous or metamorphic origin provides strong supporting evidence for authigenic apatite formation in these sediments the size of the authigenic apatite reservoir increases with depth indicating continued formation of cfa during early diagenesis this depth increase is mirrored by a decrease in solid phase organic p at both sites suggesting that cfa is forming at the expense of organic p mass balance considerations application of diagenetic models to interstitial water nutrient data and the saturation state of the interstitial water are consistent with this interpretation diagenetic redistribution of phosphorus among the different solid phase reservoirs is observed at both sites and results in near perfect retention of p by these sediments over the depth intervals sampled formation of cfa in continental margins which do not conform to the classically defined regions of phosphorite formation renders cfa a quantitatively more important sink than has previously been recognized including this reservoir as a newly identified sink for reactive p in the ocean the residence time of p in the modern ocean must be revised downward the implication for ancient oceans of cfa formation in continental margin sediments other than phosphorites is that phosphorite formation may be less a representation of episodicity in removal of reactive p from the oceans than of localized concentration of cfa in phosphatic sediments by secondary physical processes

spatial distribution vertical and horizontal and partitioning of dissolved and particulate nutrients c n and p in the campos basin southern brazil abstract tropical oceans are characterized by low amounts of dissolved nutrients and high amounts of particulates in the biogenic layer and by increased dissolved nutrients and reduced particulates in the water masses of the biolytic layer in this study the hydrochemistry of the area included in the campos basin was evaluated at 72 sampling sites and six depths surface a second depth and the cores of deep water masses up to 2300 m during the summer and winter seasons of 2009 the vertical distribution of dissolved and particulate nutrients had patterns typical of permanently stratified tropical waters and greater values were found on the continental shelf than on the slope as expected these results confirm that the continent is an important source of the materials found in the studied water masses additionally the spatial variations observed are likely related to the south atlantic central water sacw intrusion into the continental shelf in the cabo frio region and to eddies formation in the cabo de sao tome region where higher concentrations of dissolved and particulate nutrients were found despite the n p ratio indicates limitation of primary producers by inorganic nitrogen the particulated and dissolved organic n p indicate a strong depletion of p relative to n suggesting preferential degradation of that

compositional variations and morphological evolution in platinum beach placers southern new zealand morphologies of placer platinum group minerals pgm are more variable and resistant to modification during transport than placer gold grains this study documents morphological evolution of pgm placer grains during up to 120 km of transport in beach placers after river transport from inferred sources up to 200 km inland pgm morphological changes are calibrated with changes in morphology of associated placer gold most of the pgm are pt fe alloy and have been fed into the beach placer system from a large river at the western end of the beaches on the south coast of new zealand the incoming fluvial pgm suite includes os ir and ru alloys which may have been derived from distal ophiolitic sources more proximal sources have ural alaskan affinities and these contributed cooperite and braggite or sperrylite locally as well as pt fe alloy grains some pgm may have been recycled through cretaceous quaternary fluvial sediments before entering the modern placer system recycled placer pgm grains have also been derived from elevated quaternary beaches near the coastline pgm grains entering beach placers have rough surfaces with remnants of crystal faces and these evolve to smooth flakes with progressive long shore transport pgm flakes have slightly thickened rims caused by impacts by saltating sand on windy beaches and the most distal beach placers contain flakes with incipient toroidal shapes these pgm incipient toroids are poorly developed compared to accompanying well formed toroidal gold that has developed in nearly all beach placers including those on elevated quaternary beaches typical pgm and gold placer grain size decreases with increasing distance of transport from fluvial grain size of 400 1 000 to 200 microns on the most distal beaches accompanied by eastward loss of equant pgm grains and associated increase in proportion of flakes although net transport distance is 120 km in the beach placer complex frequent aeolian transport of grains from beach to dunes and subsequent recycling by storm surges substantially increased total transport distance in a dynamic windy tectonic environment

high production and highstand shedding from deeply submerged carbonate banks northern nicaragua rise abstract because the shallow isolated carbonate banks on the northern nicaragua rise the nicaragua honduras and southern jamaica carbonate shelves and many other modern carbonate banks worldwide are covered by an average of 20 to 30 m of water and by a thin blanket of coarse carbonate sediments other carbonate sedimentologists have considered these banks good examples of incipiently drowned or even drowned carbonate banks however based on recent research on the northern nicaragua rise we can demonstrate that these banks currently are healthy producers of large volumes of periplatform sediments fine aragonite and magnesian calcite which are exported almost entirely to the deep surrounding slopes these sediments which were deposited during the past 9000 10 000 years form peripl tform wedges on the middle and upper slopes which are seen clearly on 3 5 khz seismic profiles radiocarbon ages of the wedge surface sediment range between 230 and 610 ybp and provide clear evidence for the contemporaneous production of sediments on the shallow bank and shelf and their instantaneous export to the upper slopes for the last 5000 years sedimentation rates ranged from 2000 mm ky off pedro bank to 1300 mm ky off jamaica these rates are somewhat lower than but of the same order of magnitude as sedimentation rates on the western leeward slopes of great bahama bank deposition of the metastable carbonate sediments discussed in this paper occurred as soon as sea level rose to flood the bank and shelf which flank walton basin following the last glacial lowstand they com rise a wedge shaped package of transgressive and highstand sediments on the upper and middle slopes of pedro bank and the southern jamaica shelf

carbonate turbidite sequences deposited in rift basins of the jurassic tethys ocean eastern alps switzerland syn rift sediments in basins formed along the future southern continental margin of the jurassic tethys ocean comprise in the eastern alps of switzerland up to 500 m thick carbonate turbidite sequences interbedded with bioturbated marls and limestones in the fault bounded troughs no submarine fans developed in contrast the fault scarps acted as a line source and the asymmetric geometry as well as the evolution of the basin determined the distribution of redeposited carbonates the most abundant redeposits are bio and lithoclastic grainstones and packstones with sedimentary structures indicating a wide range of transport mechanisms from grain flow to high and low density turbidity currents huge chaotic megabreccias record catastrophic depositional events their main detrital components are upper triassic shallow water carbonates and skeletal debris from nearby submarine highs after an event of extensional tectonism sedimentary prisms accumulated in the basins along the faults each prism is wedge shaped with a horizontal upper boundary and consists of a thinning and fining upward megacycle within each megacycle six facies associations are distinguished at the base of the fault scarp an association of breccias was first deposited by submarine rockfall and rockfall avalanches a narrow approximately 4000 m wide depression along the fault was subsequently filled by the megabreccia association in which huge megabreccias interfinger with thin bedded turbidites and hemipelagic limestones the thick bedded turbidite association covered the megabreccias or formed farther basinward the base of the sedimentary column within the thick bedded turbidites thinning and fining upward cycles are common the overlying thin bedded turbidite association shows nearly no cyclicity and the monotonous sequence of fine grained calciturbidites covers most of the basin area with continuous filling and diminishing sediment supply a basin plain association developed comprising fine grained and thin bedded turbidites intercalated with bioturbated marls and limestones on the gentle slopes opposite the fault escarpment redeposited beds are scarce and marl limestone alternations as well as weakly nodular limestones prevail

magnitude and composition of sinking particulate phosphorus fluxes in santa barbara basin california examined particulate p cycling in the santa barbara basin sbb off the coast of southern california using a 520 m deep moored sediment trap deployed from 1993 2006 and a sediment core collected in 2005 directly beneath the sediment trap at 590 m total particulate p tpp particulate inorganic p pip and particulate organic p pop were quantified using a 5 step sequential extraction method sedex that chemically separates pip into loosely bound oxide bound authigenic and detrital p phases pop fluxes while similar in magnitude to other coastal regions 22 10 mmol m 2 d 1 were a small component of the tpp pool 15 seasonal trends revealed significant increases in pop fluxes during upwelling due to increased biological production in surface waters by organisms that increased mineral ballast high particulate organic carbon poc to pop ratios 337 18 further indicated rapid and efficient remineralization of pop relative to poc as particles sank through the oxic water column however further reduction of pop ceased in the deeper anoxic waters loosely bound oxide bound and authigenic p dominated the tpp pool with pip fluxes substantially higher than those measured in other coastal settings strong correlations between oxide associated authigenic and detrital p fluxes with lithogenic material indicated a terrestrial source associated with riverine discharge furthermore more than 30 of the loosely bound and oxide bound p was remineralized prior to burial with the magnitude of dissolution far exceeding that of pop these results highlight the dynamic nature of the particulate p pool in coastal ecosystems and how changes in p source can alter the composition and lability of p that enters coastal waters

phosphorus cycling in marine sediments advances and challenges abstract phosphorus p is a critical macronutrient for all living cells as it provides the phosphate ester backbone of nucleic acids plays a crucial role in the transmission of chemical energy by the atp molecule and is also a structural constituent in many cell components while p cycling in the marine water column has been the subject of many studies and reviews many aspects of the sedimentary p cycling remain poorly understood this is mainly due to low p concentrations in sediments and analytical difficulties associated with isolating distinct p forms from sediment samples the aim of this review is to highlight the advances made in our understanding of p cycling in marine sediments as a result of improved instrumentation and novel approaches some of these techniques range from sediment sequential extractions sedex to spectroscopic techniques 31p nmr and innovative isotope tracer experiments stable oxygen ratios in phosphate radioactive p isotopes while our understanding of p cycling has considerably improved numerous aspects of sedimentary p cycling including the fate of organic p in sediments as a function of redox conditions organic matter content and burial depth as well as turnover rates of different sedimentary p compounds remain poorly constrained the techniques presented in this review along with yet to be utilized innovative approaches used in soil and lacustrine sediment p research will play an important role in addressing these important questions and in furthering our understanding of this critical component of the p global biogeochemical cycle

transgressive regressive facies cycles in late cretaceous calciturbidites from the mauretanian series beni ider thrust sheet northwestern external rif morocco application of the facies tract facies sequence concept

evidence for long term instability in the storegga slide region off western norway abstract shallow seismic surveys around the storegga slide off western norway have allowed greater understanding of the development of this part of the european margin the northern flank of the scarp is formed of seismically well layered hemipelagic and distal glaciomarine deposits in which a variety of luid escape structures probably due to gas are locally abundant there is evidence of slides that substantially pre date the earliest slide previously recognized surveying on the north sea fan to the southwest of the storegga slide shows the markedly different nature of the autochthonous sediments on the southern flank of the storegga slide there is a predominance of glacigenic debris flows in the upper part of the sequence lesser maximum slopes and an apparent absence of interstitial gas and or hydrates this contrast has had considerable effect on slope stability and has influenced the position of the southwestern storegga slide boundary the north sea fan succession includes at least three major buried slides termed the vigra more and tampen slides all of which substantially pre date the storegga event and probably pre date predominantly glacigenic margin sedimentation post late weichselian slope failure is locally significant the region has a long but as yet chronologically poorly defined history of instability in which seismic triggering is considered to have been important

gold nugget growth during tectonically induced sedimentary recycling otago new zealand abstract an alluvial fan 5 km wide and 3 5 km long has been derived over the past 65 000 years from an actively rising schist mountain range dunstan range in central otago new zealand the fan can be locally subdivided into four distinctive consecutively formed gravel sequences the earliest of which has been deformed along the range margin these gravels are pre dated by miocene mature fluvial sediments manuherikia group which have been recycled into the alluvial fan gravels during uplift all these sedimentary sequences contain gold which has been mined sporadically manuherikia gold grains up to 13 wt ag are well rounded and typically 300 m across typical grain size of gold becomes progressively coarser with each gravel sequence in the alluvial fan and nuggets up to 2 cm occur in younger gravel sequences gold grain size increase is due to addition of authigenic gold on to pre existing grains authigenic gold occurs as a cement between earlier detrital grains 1 4 wt ag as amorphous coatings and protrusions 0 1 wt ag and as overgrowths of lattice intergrowths 0 1 wt ag gold nuggets formed in the gravels have overgrown detrital minerals and authigenic clay minerals chemical accretion of nuggets may be still continuing today in parts of the alluvial fan

regional correlations across the internides externides front northwestern rif belt morocco during the late cretaceous early burdigalian times palaeogeographical and palaeotectonic implications

carbonates and relative changes in sea level abstract in the geologic record some of the most accurate gauges of changes in sea level are the sediment type geometry and diagenesis of carbonate shelves and platforms this is because carbonates frequently occur at or very near sea level and are usually less compacted than siliciclastics world wide changes in relative sea level the sum of eustatic sea level changes sedimentation and crustal movements have occurred repeatedly and cyclicly through geologic time producing characteristic responses in carbonates 1 1 relative rises in sea level usually caused by the cumulative effect of tectonic subsidence and eustatic rise may result in the following 1 1 a drowned carbonate reefs or platforms here carbonate growth potential is exceeded by relative sea level rise and is characterized by shallow water sediments overlain by hardgrounds and or deep water sediments some of which may be condensed sequences 1 2 b platforms where only the fast growing rim and patches of the interior are able to match sea level rise while the remainder of the platform is drowned temporarily 1 3 c platforms which keep up and maintain a flat top at sea level and contain shallow water sediments whose thickness at the least matches the height of the sea level rise if terrigenous supply is limited prograding sheets of shelf carbonate occur frequently capped by supratidal evaporites with prograding shelf margin carbonate clinoforms and turbidites if terrigenous supply is high the shelf carbonates encroach on deltaics 2 2 relative drops in sea level caused by crustal uplift or by subsidence being outpaced by a eustatic drop in sea level cause karst and soil development over shelves and platforms deposition of deep water evaporites in adjacent semi enclosed basins and in open marine basins the deposition of deltaic and aeolian clastics that bypassed the shelf falls are accompanied by platform wide fresh water diagenesis during relative sea level rises marine diagenesis is common in the subtidal portions of the shoaling upward carbonates and fresh water diagenesis and dolomitization and sulphate deposition is common in their intertidal and supratidal portions the stratigraphic significance of these reponses to relative sea level change is that many are tied to eustatic events and so are predictable within a basin of deposition

particle fluxes to the interior of the southern ocean in the western pacific sector along 170 w abstract an array of five bottom tethered moorings with 19 parflux time series sediment trap at three depths 1 and 2 km below the surface and 0 7 km above the sea floor was deployed in the western pacific sector of the southern ocean along 170 w the five stations were selected to sample settling particles in the main hydrological zones of the southern ocean the sampling period spanned 425 days november 28 1996 january 23 1998 and was divided into 13 or 21 synchronized time intervals a total of 174 sequential samples were recovered and analyzed to estimate fluxes of total mass tmf organic carbon carbonate biogenic silica and lithogenic particles the fluxes of biogenic material were higher than anticipated challenging the notion that the southern ocean is a low productivity region organic carbon fluxes at 1 km depth within the polar frontal zone and the antarctic zone were relatively uniform 1 7 2 3 g m 2 yr 1 and about twice the estimated ocean wide average ca 1 g m 2 yr 1 carbonate fluxes were also high and uniform between the subantarctic front and ca 64 s 11 13 g m 2 yr 1 a large fraction of the carbonate flux in the antarctic zone was due to the presence of pteropod shells coccoliths were found only to the north of the polar front and calcium carbonate became the dominant phase in the subantarctic zone in contrast carbonate particles were nearly absent near 64 s latitudinal variations in biogenic silica fluxes were substantial the large opal flux 57 g m 2 yr 1 measured in the antarctic zone suggests that opal productivity in this region has been previously underestimated and helps to explain the high sedimentary opal accumulation often found south of the polar front unlike biogenic material fluxes of lithogenic particles were among the lowest measured in the open ocean 0 12 0 05 g m 2 yr 1 reflecting a very low dust input

morphological and compositional analysis of alluvial gold the fresnedoso gold placer spain abstract the fresnedoso creek gold placer fgp in the moraleja basin w iberian massif has been investigated in terms of morphological textural and compositional evolution of gold particles a mixture of two populations has been identified being coherent with primary sources located at a proximal 2 5 10 km and distal 20 50 km range shape and compositional evidences suggest recycling of paleoplacers tertiary has to be considered to some extend primary laminar morphologies point to lode deposits in small flat veins hosted in the metasediments of the schist greywacke complex all these features suggest the fresnedoso creek gold placer is a deposit constituted by with mono and polycyclic particles transport distance flattening indexes cfi shilo models have been tested and result in useful information for exploration of undiscovered deposits even with a limited dataset compositional analysis of gold particle morphotypes has revealed that the fresnedoso gold is a auag bimetallic alloy textural and compositional groups include type 1 au1 au88 94ag12 6 type 2 au2 au99 ag1 and type 3 au3 au99ag1 variations in composition of type 1 particle s cores could reflect differences in primary composition spatial dispersion of sources or secondary processes but fit within the compositional range of orogenic gold deposits secondary processes have been explored to explain compositional heterogeneity in the particles gold type 2 rim and 3 micro aggregates represents two different de alloying stages from initial ag leaching at the rim and or through grain boundaries and microfractures au2 to complete resetting of primary chemical imprint pervasive porous texture and au re precipitation with fe ooh and clays au3 a model is proposed which combines ag de alloying enhanced in a cl fe rich environment lateritic and the deformation recrystallization processes related to mechanical cold work in the river load bed during transport

phosphorus composition of sinking particles in the guaymas basin gulf of california phosphorus p composition and fluxes were measured in samples collected using a moored sediment trap located at 500 m in depth in the center of guaymas basin gulf of california from february 1991 through september 1997 p composition was measured using a sequential extraction technique that chemically separates the particulate inorganic p pip pool into exchangeable oxide bound authigenic and detrital phases pip comprised 69 6 15 of the total particulate p pool with significantly higher concentrations during the rainy summer strong relationships between authigenic and detrital p fluxes with lithogenic material r2 0 85 indicate that a significant component of pip is terrestrially derived and varies with large scale changes in regional climate particulate organic p pop fluxes were significantly higher during the winter as a result of stimulation of biological production during upwelling average particulate organic carbon poc pop ratios also varied seasonally with higher ratios in the summer 221 vs the winter 158 the fact that poc fluxes remained relatively constant throughout the year indicates that in winter fresher less degraded organic material was more effectively transported to depth strong correlations between pop and opal fluxes r2 5 0 63 further support a ballast mechanism whereby enhanced sinking rates reduce the time during which organic matter is subjected to water column degradation compared to trap concentrations pop is preferentially remineralized over pip in concert with an increase in the authigenic p pool this signifies rapid diagenetic transformations of sedimentary p between the sediment trap and underlying sediments

benthic phosphorus regeneration net primary production and ocean anoxia a model of the coupled marine biogeochemical cycles of carbon and phosphorus we examine the relationships between ocean ventilation primary production water column anoxia and benthic regeneration of phosphorus using a mass balance model of the coupled marine biogeochemical cycles of carbon c and phosphorus p the elemental cycles are coupled via the redfield c p ratio of marine phytoplankton and the c p ratio of organic matter preserved in marine sediments the model assumes that on geologic timescales net primary production in the oceans is limited by the upwelling of dissolved phosphorus to the photic zone the model incorporates the dependence on bottom water oxygenation of the regeneration of nutrient phosphorus from particulate matter deposited at the water sediment interface evidence from marine and lacustrine settings modern and ancient demonstrates that sedimentary burial of phosphorus associated with organic matter and ferric oxyhydroxides decreases when bottom water anoxia dysoxia expands steady state simulations show that a reduction in the rate of thermohaline circulation or a decrease of the oxygen content of downwelling water masses intensifies water column anoxia dysoxia and at the same time increases surface water productivity the first effect reflects the declining supply of oxygen to the deeper parts of the ocean the second effect is caused by the enhanced benthic regeneration of phosphorus from organic matter and ferric oxyhydroxides sedimentary burial of organic carbon and authigenic calcium phosphate mineral francolite on the other hand is promoted by reduced ocean ventilation according to the model global scale anoxia dysoxia leads to a more efficient recycling of reactive phosphorus within the ocean system consequently higher rates of primary production and organic carbon burial can be achieved even when the continental supply of reactive phosphorus to the oceans remains unchanged

genesis of limestone megabreccias and their significance in carbonate sequence stratigraphic models a review a re appraisal of the factors controlling the deposition of carbonate megabreccias and their sequence stratigraphic significance is presented based on an examination of the mechanisms for instigating carbonate seafloor slope instability and a review of the depositional settings of these distinctive rock deposits limestone megabreccias have classically been interpreted as formed by the catastrophic collapse of high angle metastable oversteepened carbonate platform margins however a review of megabreccia occurrence shows that these deposits formed on a broad range of carbonate slope angles and that metastable oversteepened slopes are not necessary for their genesis a re evaluation constructed from first principles of mechanisms promoting submarine gravitational instability indicates that pore water overpressure of confined aquifer horizons beneath the seafloor rather than slope oversteepening is the critical control on megabreccia deposition catastrophic release of overpressure may initiate gravitational instability of previously kinematically stable slopes the relative importance of endogenic processes intrinsically linked to the depositional system and exogenic processes operating independently in generating megabreccias is assessed two particularly important mechanisms in generating megabreccias are endogenic processes causing overpressure at discrete hydrologically confined horizons beneath the seafloor during relative sea level falls and increases in stress as pore fluid drains from the sediment when the platform top becomes subaerially exposed during relative lowstands of sea level the increased likelihood of megabreccia genesis during relative sea level falls is supported by an empirical trend identified from a review of the stratigraphic distribution of documented megabreccias exogenic causes of gravitational instability with inherently random periodicity especially seismicity may account for the small number of documented megabreccias that do not conform to this underlying trend the proposed endogenic pattern favouring megabreccia deposition during relative sea level falls is important in a sequence stratigraphic context megabreccia deposits may build volumetrically significant toe of slope wedges and aprons during relative lowstands of sea level partially compensating for the decrease loss in the supply of fresh granular sediment as the platform top carbonate factory contracts lowstand wedges and aprons in carbonate systems therefore generally differ in composition from equivalent highstand deposits in being composed not of calciturbidite deposits but of megabreccias cannibalized from the upper slope

particle settling rates increase with depth in the ocean abstract time and depth scales of particulate organic carbon degradation and caco3 and biogenic opal dissolution are critical to understanding the depth distribution of co2 and dissolved nutrients in the ocean the speed at which particles sink and the factors that control sinking speed are of primary importance to the distribution of oceanic nutrient concentrations and to the preservation of biogenic material in the sediment record sequencing sediment trap collectors deployed at us jgofs sites in the equatorial pacific and arabian sea provided a time series of particle fluxes from which particle settling rates were estimated a comparison of settling velocities obtained from 100 500 m pilskaln et al deep sea research 45 1998 1803 to settling velocities obtained for depths between 1000 and 3500 m indicate an increase of a factor of 2 10 between 100 and 2000 m and an increase of 15 60 between 2000 and 3500 m the increase in settling velocity in the deep ocean is generally correlated with the loss of corg with depth lithogenic content does not appear to impact particle settling rate variability in particle settling rate is systematically related to physical forcing of the surface ocean in the equatorial pacific but not in the arabian sea the increase in particle settling rate with depth likely influences the delivery of caco3 to the sea floor

climate driven variability in the southern ocean carbonate system abstractseasonal and interannual variability in the southern ocean carbonate system is investigated using output from a historically forced 1948 2007 ocean general circulation model with embedded biogeochemistry atmospheric co2 is fixed at preindustrial levels to investigate carbonate system variability in the absence of an anthropogenic co2 perturbation it is found that nearly a quarter of interannual variability in southern ocean pacific sector surface carbonate ion concentration can be explained by variability in enso with pacific sector surface decreasing by 0 43 mmol m 3 per standard deviation decrease in the enso 3 4 index enso related variability in vertical advection of dissolved inorganic carbon dic drives this relationship between enso and surface it is also found that positive phases of the southern annular mode sam are associated with decreased southern ocean surface an association driven by sam related variability in vertical advection of dic despite the influence of the sam on

feedbacks between oceanic redox states and marine productivity a model perspective focused on benthic phosphorus cycling a new model for the marine cycles of particulate organic carbon poc oxygen nitrate and phosphorus has been developed and applied to explore the controls and constraints on marine productivity and nutrient inventories the coupled benthic pelagic model uses a new approach for the simulation of the reactive phosphorus turnover preac corresponding to the sum of organic p authigenic p and adsorbed phosphate in marine sediments the simulated poc preac burial ratio in shelf slope and rise and deep sea sediments increases under strongly reducing conditions in agreement with field observation the model runs revealed that the spread of anoxia in bottom waters may enhance the productivity of the global ocean by one order of magnitude if sufficient nitrate is provided by n2 fixation thus anoxic bottom waters promote eutrophic conditions and vice versa additional model runs showed that the productivity and nutrient inventory of the glacial ocean were probably enhanced due to the falling sea level marine regression induced a narrowing of the depositional areas on the continental shelves and thereby an increase in the fraction of poc exported to the deep ocean the accelerated poc delivery in turn decreased the oxygen contents of the deep water and thus favored the release of phosphate from deep sea and rise sediments enhanced recycling of phosphate at the seafloor promoted further poc export in a positive feedback loop

phosphorus imbalance in the global ocean the phosphorus budget of the pre human modern ocean is constrained applying the most recent estimates of the natural riverine eolian and ice rafted input fluxes the phosphorus burial in marine sediments and the hydrothermal removal of dissolved phosphate from the deep ocean this review of current flux estimates indicates that the phosphorus budget of the ocean is unbalanced since the accumulation of phosphorus in marine sediments and altered oceanic crust exceeds the continental input of particulate and dissolved phosphorus the phosphorus mass balance is further tested considering the dissolved phosphate distribution in the deep water column the marine export production of particulate organic matter rain rates of phosphorus to the seafloor benthic dissolved phosphate fluxes and the organic carbon to phosphorus ratios in marine particles these independent data confirm that the phosphate and phosphorus budgets were not at steadystate in the pre human global ocean the ocean is losing dissolved phosphate at a rate of 11 6 x 1010 mol yr 1 corresponding to a decline in the phosphate inventory of 4 5 kyr 1 benthic data show that phosphate is preferentially retained in pelagic deep sea sediments where extended oxygen exposure times favor the degradation of particulate organic matter and the up take of phosphate in manganese and iron oxides and hydroxides enhanced c p regeneration ratios observed in the deep water column 400 m water depth probably reflect the preferential burial of phosphorus in pelagic sediments excess phosphate is released from continental margin sediments deposited in low oxygen environments the dissolved oxygen threshold value for the enhanced release of dissolved phosphate is 20 m benthic phosphate fluxes increase drastically when oxygen concentrations fall below this value

phosphorus burial and diagenesis in the central bering sea bowers ridge iodp site u1341 perspectives on the marine p cycle abstract to reconstruct the cycling of reactive phosphorus p in the bering sea a p speciation record covering the last 4 ma was generated from sediments recovered during integrated ocean drilling program iodp expedition 323 at site u1341 bowers ridge a chemical extraction procedure distinguishing between different operationally defined p fractions provides new insight into reactive p input burial and diagenetic transformations reactive p mass accumulation rates mars are 20 110 mol cm2 ka which is comparable to other open ocean locations but orders of magnitude lower than most upwelling settings we find that authigenic carbonate fluorapatite cfa and opal bound p are the dominant p fractions at site u1341 an overall increasing contribution of cfa to total p with sediment depth is consistent with a gradual sink switching from more labile p fractions fish remains fe oxides organic matter to stable authigenic cfa however the positive correlation of cfa with al content implies that a significant portion of the supposedly reactive cfa is non reactive detrital contamination by eolian and or riverine cfa in contrast to cfa opal bound p has rarely been studied in marine sediments we find for the first time that opal bound p directly correlates with excess silica contents this p fraction was apparently available to biosiliceous phytoplankton at the time of sediment deposition and is a long term sink for reactive p in the ocean despite the likelihood for diagenetic re mobilisation of this p at depth indicated by increasing ratios of excess silica to opal bound p average reactive p mars at site u1341 increase by 25 if opal bound p is accounted for but decrease by 25 if 50 of the extracted cfa fraction based on the lowest cfa value at site u1341 is assumed to be detrital combining our results with literature data we present a qualitative perspective of terrestrial cfa and opal bound p deposition in the modern ocean riverine cfa input has mostly been reported from continental shelves and margins draining p rich lithologies while eolian cfa input is found across wide ocean regions underlying the northern hemispheric dust belt opal bound p burial is important in the southern ocean north pacific and likely in upwelling areas shifts in detrital cfa and opal bound p deposition across ocean basins likely occurred over time responding to changing weathering patterns sea level and biogenic opal deposition

widespread influence of resuspended sediments on oceanic particulate organic carbon insights from radiocarbon and aluminum contents in sinking particles globally widespread also a strong correlation is found to exist between d 14 c values of organic carbon and aluminum content in sinking particles that is consistent over a range of oceanic settings together these findings imply that aged organic carbon associated with lithogenic material from sediment resuspension is responsible for the observed low d 14 c values as opposed to other processes such as incorporation of dissolved inorganic carbon or dissolvedorganiccarbonintopocatdepth anestimatebasedonpocflux weightedd 14 c values shows that about 35 of sinking poc at the locations studied is derived from resuspended sediment our results suggest that resuspension of sediment and its subsequent lateral transport is an important component of the oceanic carbon cycle and should be considered in models of oceanic carbon export and burial

surface area control of organic carbon accumulation in continental shelf sediments the relationship between organic carbon oc and grain size found in most continental shelf sediments is here reinterpreted in terms of the surface area of the sediments cores from many north american shelf environments show downcore decreases in oc to similar refractory background concentrations if expressed relative to the surface area of the sediments this consistent concentration is 0 86 mg oc m 2 which is equivalent in concentration to a monolayer of organic matter coating all mineral surfaces a more global collection of sediment water interface samples show that this relationship is even more extensive with exceptions occurring in areas of very high riverine sediment input organic pollution or low oxygen water columns density separations indicate that organic matter is largely adsorbed to mineral grains the microtopography of surfaces was examined with n2 sorption and most surface area was found to be inside pores of 10 nm width these data lead to a hypothesis that organic matter is protected by its location inside pores too small to allow functioning of the hydrolytic enzymes necessary for organic matter decay such protection would likely work in concert with other protection mechanisms such as humification this consistent surface area correlation with oc concentration may explain control of spatial and temporal variations in oc burial rates by sedimentation rates the pore protection hypothesis provides a causal mechanism for this observed control

compositions and transport of lipid biomarkers through the water column and surficial sediments of the equatorial pacific ocean abstract a systematic investigation of fluxes and compositions of lipids through the water column and into sediments was conducted along the u s jgofs egpac transect from l2 n to l5 s at 140 w fluxes of lipids out of the euphotic zone varied spatially and temporally ranging from 0 20 0 6 mmol lipid c m 2 day 1 lipid fluxes were greatly attenuated with increasing water column depth dropping to 0 002 0 06 mmol lipid c m 2 day 1 in deep water sediment traps sediment accumulation rates for lipids were 0 0002 0 00003 mmol lipid c m 2 day 1 lipids comprised 11 23 of corg in net plankton 10 30 in particles exiting the euphotic zone 2 4 particles in the deep egpac and 0 1 1 in sediments lipids were in general selectively lost due to their greater reactivity relative to bulk organic matter toward biogeochemical degradation in the water column and sediment qualitative changes in lipid compositions through the water column and into sediments are consistent with the reactive nature of lipids fatty acids were the most labile compounds with polyunsaturated fatty acids pufas being quickly lost from particles branchedchain c15 and c17 fatty acids increased in relative abundance as particulate matter sank and was incorporated into the sediment indicating inputs of organic matter from bacteria long chain c39 alkenones of marine origin and long chain c20 c30 fatty acids alcohols and hydrocarbons derived from land plants were selectively preserved in sediments compositional changes over time and space demonstrate the dynamic range of reactivities among individual biomarker compounds and hence of organic matter as a whole a thorough understanding of biogeochemical reprocessing of organic matter in the oceanic water column and sediments is thus essential for using the sediment record for reconstructing past oceanic environments

on the proportion of ballast versus non ballast associated carbon export in the surface ocean the role of biominerals in driving carbon export from the surface ocean is unclear we compiled surface particulate organic carbon poc and mineral ballast export fluxes from 55 different locations in the atlantic and southern oceans substantial surface poc export accompanied by negligible mineral export was recorded implying that association with mineral phases is not a precondition for organic export to occur the proportion of non mineral associated sinking poc ranged from 0 to 80 and was highest in areas previously shown to be dominated by diatoms this is consistent with previous estimates showing that transfer efficiency in such regions is low however we propose that rather than the low transfer efficiency arising from diatom blooms being inherently characterized by poorly packaged aggregates which are efficiently exported but which disintegrate readily in mid water it is due to such environments having very high levels of unballasted organic c export