late quaternary deltaic and carbonate sedimentation in the gulf of papua foreland basin response to sea level change abstract the rivers that drain the wet mountainous island of new guinea discharge about 1 5 billion tonnes yr of sediments into the adjacent seas including the foreland basin between new guinea and australia despite this huge sediment input there appears to have been only limited deposition in the gulf of papua during the holocene postglacial rise in sea level seismic and core data indicate that the transgressive systems tract in the gulf of papua is thin and patchy it is confined to regions within and north of an incised east west trending shelf valley system of the possible explanations for the absence of a significant transgressive systems tract inland storage and along and off shelf transport of the sediment are of greatest significance reef growth up to the latitude of the east west trending incised valley system in the southern gulf of papua is considered to have been facilitated by a northward flowing coastal boundary current the coral sea coastal current this current now sweeps turbid brackish waters and terrigenous sediments discharged by the rivers northwards away from the reefs an observed northward offset in transgressive sediments in relation to the axis of the shelf valleys suggests that such a northward flowing shelf current operated during the late pleistocene and early holocene the northern limit of the great barrier reef could thus be controlled by the balance between fluvial sediment supply and northward advection of suspended sediment by the coral sea coastal current this current may also be imp rtant in maintaining a supply of clear water to the eastern gulf of papua thus enabling photosynthesis and the flourishing of calcareous algae halimeda bioherms or biostromes at depths of up to 100 m over much of the middle and outer shelf directly offshore of the modern fly delta these carbonate sediments represent the exposed maximum flooding surface and condensed section modern highstand delta deposits have begun to prograde over this layer on the inner shelf

resolution analysis of tomographic slug test head data two dimensional radial case hydraulic tomography inverse problems which are solved to estimate aquifer hydraulic properties between wells are known to be ill conditioned and a priori information is often added to regularize numerical inversion of head data because both head data and a priori information have effects on the inversed solution assessing the meaningful information contained in head data alone is required to ensure comprehensive interpretation of inverse solutions whether they are regularized or not this study thus aims to assess the amount of information contained in tomographic slug tests head data to resolve heterogeneity in kh kv kh and ss therefore a resolution analysis based on truncated singular value decomposition of the sensitivity matrix with a noise level representative of field measurements is applied using synthetic data reflecting a known littoral aquifer as an approximation of the hydraulic behavior of a real aquifer system synthetic tomographic experiments and associated sensitivity matrices are generated using a radial flow model accounting for wellbore storage to simulate slug tests in a plane encompassing a stressed well and an observation well although fine scale resolution of heterogeneities is limited by the diffusive nature of the groundwater flow equations inversion of tomographic slug tests head data holds the potential to uniquely resolve coarse scale heterogeneity in kh kv kh and ss as inscribed in the resolution matrix this implies that tomographic head data can provide key information on aquifer heterogeneity and anisotropy but that fine scale information must be supplied by a priori information to obtain finer details

efficient sequestration of terrigenous organic carbon in the new britain trench abstract the fate of terrigenous organic carbon octerr in the ocean remains an enigma for four decades hadal trenches the deepest ocean realm 6 11 km deep were recently proposed to be oc depocenters but whether and how much octerr was sequestrated there remain elusive here we conducted comprehensive analyses for four sediment cores from the new britain trench nbt close to papua new guinea to assess source translocation and burial of oc the bulk and molecular radiocarbon data suggest that the nbt landward slope and axis sediments mainly receive young and biogenic rather than petrogenic oc the three endmember mixing model based on 14c 13c and oc contents reveals that sediments of the nbt axis 8225 m comprise relatively high oc contents 0 66 0 08 of which biogenic octerr accounts for 62 10 the high proportion of biogenic octerr was attributed to the selective translocation of octerr enriched coarse particles and rapid delivery of sediments supported by unique v shape feature of the trench in contrast the sediment oc at the oceanward slope is primarily of a marine origin suggesting that octerr was efficiently trapped in the trench bottom it is estimated that the burial rate is 2 75 0 32 g c m 2 yr 1 for oc and 1 69 0 41 g c m 2 yr 1 for octerr in the nbt given a fact that many trenches are close to the landmasses we propose that the hadal trenches may contribute significantly to the burial of octerr in the ocean

deposition of bomb 14c in continental slope sediments of the mid atlantic bight assessing organic matter sources and burial rates abstract as part of the ocean margins program omp organic carbon 14c measurements have been made on benthic fauna and kasten core sediments from the north carolina continental slope these analyses are used to evaluate the nature and burial flux of organic matter in the omp study area off cape hatteras despite the fact that surface sediment 14c contents ranged from 41 to 215 per mil the benthic fauna primarily polychaetes all contained significant amounts of bomb 14c body tissue 14c contents ranging from 20 to 82 per mil bomb 14c clearly is reaching the seabed on the north carolina slope and the labile planktonic material carrying this signal is a primary source of nutrition to the benthic ecosystem the enrichment of 14c in benthic faunal tissue relative to the 14c content of bulk surface sediment organic matter a difference of 150 per mil is attributed to a combination of particle selection and selective digestive processes organic carbon burial rates from 12 stations on the north carolina slope varied from 0 02 to 1 7 mol of c m 2 yr 1 with a mean value of 0 7 mol of c m 2 yr 1 the accumulation of organic matter on the upper slope accounts for

a field study of the chemical weathering of ancient sedimentary organic matter weathering profiles developed on organic carbon rich black shales were studied to examine the loss and degradation of organic matter om during weathering and its role in the geochemical carbon cycle analysis of weathered shales reveals between 60 and nearly 100 total organic carbon toc loss in highly weathered samples relative to initial unweathered toc content pyrite loss coincides with or precedes organic carbon loss elemental analysis and flash pyrolysis gas chromatography py gc of kerogen concentrates indicate that there is little or no selective enrichment or depletion of norg containing sorg containing alkylaromatic branched alkyl or long chain n alkyl moieties in most profiles during weathering kerogen o c ratios consistently increase with toc and pyrite loss infrared spectroscopy ir reveals an increase in the relative abundance of c c and c o bonds relative to alkyl c h bonds in progressively weathered samples these results suggest a two component model for kerogen weathering largely non selective oxidation and hydration followed by cleavage dissolution of oxidized kerogen fragments the extent of weathering in a given outcrop is likely limited by a combination of the rate of physical erosion and exposure of the rock to oxidizing surface waters with om type composition playing a lesser role

dispersal and transformation of organic carbon across an episodic high sediment discharge continental margin waipaoa sedimentary system new zealand abstract the rivers that drain active collisional margins of the southwest pacific deliver up to 35 of particulate organic carbon poc to the world ocean and are a key component of the global organic carbon flux however knowledge of the fate of terrestrial poc in the ocean is both limited and necessary for quantifying terrestrial and coastal ocean carbon budgets here the fate of terrestrial poc is determined off the high discharge waipaoa river sediment yield 15 mt y 1 based on a transect of seven cores from the river floodplain to the adjacent continental shelf and slope total organic carbon toc 13 c 14 c c n ratios and lipid biomarker compounds were used to determine biogeochemical characteristics of surface sediments from terrestrial source to marine sink and how these characteristics vary with river discharge complementary to surface sediments down core characteristics of three multi cores covering the shelf and slope regions were used to identify perturbations in sediment supply via major floods the presence of flood deposits allows us to compare their oc characteristics with non flood sediment thereby helping address the question of how flood events in the river catchment affect the transfer and fate of terrestrial oc through the marine environment results from this study show that as surface sediments are physically and biologically processed across the continental margin they gain a marine signature biomarker analyses of surface samples show decreases in terrigenous vascular plant sources with increasing distance offshore biomarkers also demonstrate that terrestrial oc is being transferred across the continental margin with plant sterols long chain alcohols and long chain fatty acids biomarkers indicative of vascular plants persisting as far offshore as the mid continental slope in contrast to ambient conditions represented by surface sediments rapid delivery by floods allows for more complete transfer of terrestrial carbon to the marine environment a 1 10 cm thick flood layer preserved from cyclone bola march 1988 contains a significant amount of terrestrially sourced oc which subsequently was rapidly buried by sediments delivered during less extreme conditions

a case of post depositional aerobic degradation of terrestrial organic matter in turbidite deposits from the madeira abyssal plain abstract a set of oxidized and unoxidized sediment intervals from the f turbidite identified in two piston cores from the madeira abyssal plain map was analyzed for calcium carbonate total organic carbon toc total nitrogen tn stable carbon composition of toc 13c toc total hydrolyzable amino acids thaa total neutral sugars tsug lignin phenols lig two different lipid biomarkers of marine phytoplankton origin and vascular plantwax n alkanes and n acids comparison shows changes for all properties depicting the effect of post depositional aerobic oxidation the oxidation process re mineralized approximately 80 of the toc and approximately 60 of the tn in the original deposit and left the residual organic matter depleted in 13c by 1 7 2 9 thaa and tsug account for 10 or less of the toc in all samples leaving approximately 90 of the toc chemically unidentified thaa tsug lig marine phytoplankton biomarkers and plantwax n acids were lost from the oxidized deposit to an extent as great as that for toc two non protein amino acids alanine and aminobutyric acid and plant wax n alkanes displayed much less degradation 9 37 and concentrated 3 3 4 8 times relative to toc by the oxidation process these observations show that both marine and terrestrial components contribute to the re mineralized toc fraction a binary mixing approach was used to model quantitatively the change in 13c toc and plantwax n alkane concentration results suggest that terrestrial organic carbon contributes approximately 15 to the toc content of the original turbidite its abundance increases approximately 2 4 times as a consequence of the oxidation process and approximately 40 and 90 of the terrestrial and marine component of toc in the original turbidite respectively was destroyed by the oxidation process although selective preservation of terrestrial relative to marine organic carbon is a well documented phenomenon in sedimentary processes this study represents the first attempt to assess the sensitivity of terrestrial organic matter to oxidative degradation in a sedimentary environment

the composition and diagenesis of interstitial solutions ii fluxes and diagenesis at the water sediment interface in the high latitude north and south atlantic studies of the major element composition of in situ sampled pore waters are reported for the north atlantic and southern ocean between africa and antarctica the pattern of diagenetic modification of pore water composition is similar throughout the entire atlantic enrichment of na ca2 and alkalinity and depletion of mg2 and k are nearly universal only siliceous oozes consistently provide very limited evidence of cation diagenesis the changes observed and the calculated fluxes across the seawater sediment interface are much the same as those reported previously for other areas of the atlantic and caribbean fluxes of the major cations across the interface continue to be indicated as a major factor in the geochemical cycling of these elements particularly na mg2 and k diagenetic modelling indicates that aerobic oxidation of organic matter and consequent dissolution of caco3 is a dominant reaction throughout the north atlantic the data indicate that o2 oxidation to at least 30 cm is prevalent at nearly all stations dissolution of caco3 in response to the introduction of metabolic co2 can lead to significant post depositional modification of the sediments the modelling also indicates a 1 1 stoichiometric relationship between na release and mg2 uptake by sedimentary components although dissolved silica concentrations in biogenic siliceous sediments are among the highest yet reported 700 m calculations demonstrate that solubility control cannot be through equilibria with the mineral sepiolite further the influence of cation silicate surface phases generally upon solubility is contraindicated by si oh 4 mg2 h relationships evaluation of the influence of fluid advection on pore water profiles indicates that at the stations studied in the north atlantic it is small a more general consideration of the potential contribution of fluid advection to shaping interstitial water profiles demonstrates that advection can be a dominant factor in such circumstances serious misinterpretation of the nature of diagenetic reactions may result from a lack of knowledge and consideration of fluid advection

transport of terrestrial organic carbon to the oceans by rivers re estimating flux and burial rates this study re estimates one important component in the global carbon cycle the modern global fluviatile organic carbon discharge and burial rates according to these results approximately 430 1012 g of terrestrial organic carbon are transported to the ocean in modern times this amount is higher than the latest estimates but takes into account new data from oceania not previously considered in global flux studies however only the minor amount of 10 or approximately 43 1012 gc year 1 is most likely buried in marine sediments this amount is similar to the burial of marine organic carbon in the coastal ocean 55 1012 gc year 1 adding both estimates gives approximately 100 1012 gc year 1 which is the value calculated by berner 1982 for terrestrial deltaic shelf sediments however the results in this study suggest that on a global scale the organic carbon content in coastal ocean sediments is not solely of terrestrial origin but a mixture of nearly equal amounts of marine and terrestrial organic carbon the major part of the terrestrial organic carbon that enters the ocean by rivers approximately 400 1012 gc year 1 seems to be either a remineralised in the ocean whereas the mechanism by which the terrestrial organic carbon is oxidised in the ocean are unknown or b is dispersed throughout the oceans and accumulates in pelagic sediments

3 d transient hydraulic tomography in unconfined aquifers with fast drainage response we investigate through numerical experiments the viability of three dimensional transient hydraulic tomography 3dtht for identifying the spatial distribution of groundwater flow parameters primarily hydraulic conductivity k in permeable unconfined aquifers to invert the large amount of transient data collected from 3dtht surveys we utilize an iterative geostatistical inversion strategy in which outer iterations progressively increase the number of data points fitted and inner iterations solve the quasilinear geostatistical formulas of kitanidis in order to base our numerical experiments around realistic scenarios we utilize pumping rates geometries and test lengths similar to those attainable during 3dtht field campaigns performed at the boise hydrogeophysical research site bhrs we also utilize hydrologic parameters that are similar to those observed at the bhrs and in other unconsolidated unconfined fluvial aquifers in addition to estimating k we test the ability of 3dtht to estimate both average storage values specific storage ss and specific yield sy as well as spatial variability in storage coefficients the effects of model conceptualization errors during unconfined 3dtht are investigated including 1 assuming constant storage coefficients during inversion and 2 assuming stationary geostatistical parameter variability overall our findings indicate that estimation of k is slightly degraded if storage parameters must bemore jointly estimated but that this effect is quite small compared with the degradation of estimates due to violation of structural geostatistical assumptions practically we find for our scenarios that assuming constant storage values during inversion does not appear to have a significant effect on k estimates or uncertainty bounds less

the role of supergene sulphuric acid during weathering in small river catchments in low mountain ranges of central europe implications for calculating the atmospheric co2 budget abstract the geochemistry of dissolved and suspended loads in river catchments of two low mountain ranges in central europe allows comparison of pertinent chemical weathering rates distinct differences in lithology i e granites prevailing in the black forest compared to palaeozoic sediments in the rhenish massif provide the possibility to examine the influence of lithology on weathering here we determine the origin of river water using the stable isotope ratio 18oh2o and we quantify the geogenic proportions of sulphate from stable isotope ratios 34sso4 and 18oso4 particularly in catchments with abundant pyrite determination of the geogenic amount of sulphate is important since oxidation of pyrite leads to acidity which increases weathering our results show that spatially averaged silicate weathering rates are higher for the river catchments acher and gutach in the black forest 10 12 t km2 yr compared to the river catchments of the mohne dam and the aabach dam in the rhenish massif 2 6 t km2 yr correspondingly the co2 consumption by silicate weathering in the black forest 334 395 103 mol km2 yr is more than twice as high as in the rhenish massif 28 151 103 mol km2 yr these higher rates for watersheds of the black forest are likely due to steeper slopes leading to higher mechanical erosion with respective higher amounts of fresh unweathered rock particulates and due to the fact that the sediments in the rhenish massif have already passed through at least one erosion cycle carbonate weathering rates vary between 12 and 38 t km2 yr in the catchments of the rhenish massif the contribution of sulphuric acid to the silicate weathering is higher in the catchments of the rhenish massif 9 16 than in the catchments of the black forest 5 7 due to abundant pyrite in the sediments of the rhenish massif three times higher long term erosion rates derived from cosmogenic nuclides compared to short term erosion rates derived from river loads in central europe point to three times higher co2 consumption during the past 103 to 104 years

organic carbon deposition on the north carolina continental slope off cape hatteras usa abstract the continental slope off cape hatteras nc is a region of high sediment accumulation and organic matter deposition sediment accumulation rates range from 3 to 151 cm kyr 1 organic carbon deposition rates are 5 13 moles c m 2 yr 1 the highest reported for the slope off the eastern us burial efficiencies are 3 40 the organic matter deposited is marine in origin and a mix of old and young particles high organic carbon deposition rates support remineralization throughout the upper 2 3 m of sediment deep bioirrigation to depths of 60 100 cm within the seabed affects the biogeochemistry of the sediments by extending the zone of sulfate reduction and by steepening dic porewater gradients through the non local exchange of porewater stable and radiocarbon isotope mixing curves for porewater dissolved inorganic carbon dic indicate that the dominant source of dic accumulating in the upper 2 3 m of the seabed is of nearly uniform 13c 21 10 and 14c 546

composition and provenance of terrigenous organic matter transported along submarine canyons in the gulf of lion nw mediterranean sea abstract previous projects in the gulf of lion have investigated the path of terrigenous material in the rhone deltaic system the continental shelf and the nearby canyon heads this study focuses on the slope region of the gulf of lion to further describe particulate exchanges with ocean s interior through submarine canyons and atmospheric inputs nine sediment traps were deployed from the heads to the mouths of lacaze duthiers and cap de creus submarine canyons and on the southern open slope from october 2005 to october 2006 sediment trap samples were analyzed by cuo oxidation to investigate spatial and temporal variability in the yields and compositional characteristics of terrigenous biomarkers such as lignin derived phenols and cutin acids sediment trap data show that the dense shelf water cascading event that took place in the months of winter 2006 january february and march had a profound impact on particle fluxes in both canyons this event was responsible for the majority of lignin phenol 55 4 and cutin acid 42 8 inputs to submarine canyons with lignin compositions similar to those measured along the mid and outer continental shelf which is consistent with the resuspension and lateral transfer of unconsolidated shelf sediment to the canyons the highest lithogenic normalized lignin derived phenols contents in sediment trap samples were found during late spring and summer at all stations i e 193 46 g vp g 1 lithogenic at deep slope station when river flow wave energy and total particle fluxes were relatively low during this period lignin compositions were characterized by elevated cinnamyl to vanillyl phenol ratios 3 at almost all stations high p coumaric to ferulic acid ratios 3 and high yields of cutin acids relative to vanillyl phenols 1 all trends that are consistent with high pollen inputs our results suggest marked differences in the sources and transport processes responsible for terrigenous material export along submarine canyons mainly consisting of fluvial and shelf sediments during winter and atmospheric dust inputs during spring and summer

sulfur and iron diagenesis in temperate unsteady sediments of the east china sea inner shelf and a comparison with tropical mobile mud belts mmbs redox cycling of iron fe and sulfur s exerts profound influences on fates of numerous elements in coastal marine sediments in this study s and fe cycling and its geochemical expressions in the east china sea ecs inner shelf a representative of temperate mobile mud belts mmbs were characterized and compared with tropical counterparts the amazon shelf and the gulf of papua fe and s speciation consistently points to the dominance of authigenic nonsulfidized fe ii phases i e poorly crystalline clays pccs and carbonates and the prevalence of fe redox cycling in the suboxic or weakly sulfidic regimes of the ecs mmbs high contents of authigenic magnetite may be a common diagenetic expression in all mmbs compared to the tropical mmbs three main differences of diagenetic expressions in the ecs mmbs are i light 34spyrite in the ecs mmb vs characteristically heavy 34spyrite in the amazon shelf mmbs ii lower total reactive fe fetr total diagenetic fe ii and ratio of fetr to total fe in the ecs mmbs iii fe ii carbonates and pccs are equally important sinks for nonsulfidized fe ii in the ecs mmbs whereas pccs are the predominant sink in the tropical counterparts these differences are ascribable to factors including low degradability of organic matter small diffusion scales less intense chemical weathering in the drainage basin and or weaker reverse weathering in the ecs mmbs despite the differences above fe and s diagenetic expressions that characterize the prevalence of fe redox cycling in the unsteady suboxic regimes are shared by the ecs and tropical mmbs

centers of organic carbon burial and oxidation at the land ocean interface abstract continental margin systems collectively receive and store vast amounts of organic carbon oc derived from primary productivity both on land and in the ocean thereby playing a central role in the global carbon cycle the land ocean interface is however extremely heterogeneous in terms of terrigenous input marine primary productivity sediment transport processes and depositional conditions e g such as bottom water oxygen level continental margins are also highly dynamic with processes occurring over a broad range of spatial and temporal scales the rates of oc burial and oxidation are consequently variable over both space and time hindering our ability to derive a global picture of oc cycling at the land ocean interface here we review the processes controlling the fate of organic matter in continental margin sediments with a special emphasis on hot spots and hot moments of oc burial and oxidation we present a compilation of compositional data from a set of illustrative settings including fjords small mountainous river margins large deltaic systems and upwelling areas bulk oc stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of oc buried in marginal seas this primarily relates to differences in marine and terrestrial inputs the composition of the terrestrial component e g vascular plant oc soil and petrogenic oc inputs and processes modulating the fate of oc within the marine environment e g priming this widely contrasting behavior of oc among these systems illustrates that the reactivity of oc is a product of its chemical composition and regional conditions interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers e g lignin derived phenols the possibility exists to tease apart complex mixtures of terrestrial and marine inputs and to shed light on the role of the myriad of depositional and post depositional processes finally we discuss a set of hot topics that warrant further investigation such as the role of photochemistry fungi halogenation and reactive iron in dictating the fate of oc in the changing coastal ocean

sedimentary organic matter preservation a test for selective degradation under oxic conditions the authors report here a test of the hypothesis that the extent of organic matter preservation in continental margin sediments is controlled by the average period accumulating particles reside in oxic porewater immediately beneath the water sediment interface oxygen penetration depths organic element compositions and mineral surface areas were determined for 16 sediment cores collected along an offshore transect across the washington continental shelf slope and adjacent cascadia basin individual amino acid sugar and pollen distributions were analyzed for a 11 to 12 cm horizon from each core and sup 14 c based sediment accumulation rates and stable carbon isotope compositions were determined from depth profiles within a subset of six cores from representative sites sediment accumulation rates decreased and dissolved o sub 2 penetration depths increased offshore along the sampling transect as a result oxygen exposure times oet increased seaward from decades mid shelf and upper slope to more than a thousand years outer cascadia basin organic contents and compositions were essentially constant within individual sediment cores but varied consistently with location in particular organic carbon surface area ratios decreased progressively offshore and with increasing oet three independent compositional parameters demonstrated that the remnant organic matter in farther offshore sediments is more degraded both concentrationmore and compositional patterns indicated that sedimentary organic matter exhibits a distinct and reproducible oxic effect oet helps integrate and explain organic matter preservation in accumulating continental margin sediments and hence provides a useful tool for assessing transfer of organic matter from the biosphere to the geosphere less

burial of terrestrial organic matter in marine sediments a re assessment 1 calculations based on recent observations indicate that approximately one third of the organic matter presently being buried in marine sediments may be of terrestrial origin with the majority of this terrestrial organic matter tom burial occurring in muddy deltaic sediments these calculations further suggest that the remineralization of terrestrial organic matter in the oceans is also much less efficient than that of marine organic matter these two underappreciated observations have important implications in terms of our understanding of the controls on the global carbon cycle from a paleoceanographic perspective the results presented here also suggest that changes in tom burial on glacial interglacial timescales have the potential to impact the global carbon cycle i e atmospheric co2 levels

carbon burial rates in sediments and a carbon mass balance for the herbert river region of the great barrier reef continental shelf north queensland australia the largest century scale carbon reservoir in the herbert river sector of the great barrier reef continental shelf is carbonate carbon this carbonate carbon is produced by corals coralline algae and other benthic organisms and is stored on less than 13 of the area of the shelf maximum organic carbon burial rates 1 28 mol m 2 yr 1 occur within a wind protected 20 m water depth embayment 1 area of the shelf where the highest bulk sedimentation rates 1 12 kg m 2 yr 1 were determined from 210pb and137 cs profiles in 1 4 m cores sediment organic carbon oc and carbonate carbon cc accumulation rates are very low in the great barrier reef lagoon shelf and slope where most annual productivity 8 15 mol oc m 2 yr 1 is decomposed by algal and microbial respiration a carbon mass balance indicated that approximately 1 of combined river and marine organic carbon production was preserved in across shelf sedimentation but 3 of river and mangrove organic carbon input was preserved in this small wind protected embayment an across shelf carbon mass balance model predicted average shelf organic matter respiration correctly and the ratio of organic carbon fixation to respiration corrected for burial losses was 1 06

pathways and processes associated with the transport of groundwater in deltaic systems summary rivers are considered to be the primary means driving hydrological and geochemical fluxes between the continents and the ocean however it is unclear how well surface water fluxes represent total fluxes or whether more diffuse subterranean fluxes of river water to the coastal ocean occur this question is important in light of research demonstrating that submarine groundwater discharge sgd is important for geochemical and hydrological fluxes here we examine the pathways and potential magnitude of the role that sgd plays in the mississippi river delta mrd the largest delta in north america we present multiple independent lines of evidence demonstrating a hydrological connection between the mississippi river mr and the mrd evidence includes hydrological budgets demonstrating downstream water losses from the mr which are unexplained and are of the same magnitude as water sources to adjacent coastal bays of the mrd well data indicating a correlation between groundwater height and the stage of the mr and excess 222 rn inventories exceeding that expected from in situ production implying an advective i e groundwater source to coastal bays sgd likely flows from the mr to its delta via paleochannels and other buried sand bodies seismic data indicates that such features are common whereas resistivity data suggest the intrusion of low salinity water to coastal bays adjacent to the river these results may be applicable to other deltas worldwide as many of the world largest rivers have deltas with numerous abandoned distributaries that could act as conduits for groundwater

reconstructing organic matter sources and rain rates in the southern west pacific warm pool during the transition from the deglaciation period to early holocene abstract transient features in the organic carbon content of deep sea sediment cores resulting from changes in the flux and or quality of sedimentary organic matter are not uncommon we examined the geochemical characteristics of sediments retrieved with a gravity corer from the northwestern solomon sea 3908 m water depth southern west pacific warm pool wpwp 13c and 15n of sedimentary organic matter together with toc tn data suggest that the organic material is characterized by a mixture of marine and terrestrial origins with a higher contribution from marine algae the data were analyzed with an inverse non steady state reaction transport model to examine the variability and magnitude of particulate organic carbon poc flux to the seafloor during the transition between the deglaciation period and early holocene measured poc content and porewater no3 nh4 dic and so42 concentrations were used to constrain the model hindcast results revealed that poc flux decreased from 75 to 37 5 g cm 2 yr 1 during the deglaciation early holocene transition the rate of poc degradation in the present setting is slightly lower compared to that in the pre holocene setting the synchronous decline in the relative contribution of terrestrial organic matter input and rapid sea level rise during this transition suggest that sea level rather than surface productivity is the dominant factor controlling the poc deposition flux in the solomon sea this is conceivable because the sampling site is proximal to high relief islands with high rainfall a well developed submarine canyon system and narrow and steep continental margins consequently we suggest that deep water basins in proximity to similar high relief mountainous islands in the tropical pacific may represent important sinks for terrestrial organic material especially during sea level lowstands

a field assessment of high resolution aquifer characterization based on hydraulic travel time and hydraulic attenuation tomography 1 in this study the potential of an inversion approach based on hydraulic travel time and hydraulic attenuation tomography was assessed both hydraulic travel time and hydraulic attenuation tomography are based on the transformation of the transient groundwater flow equation into the eikonal equation using an asymptotic approach the eikonal equation allows the calculation of pressure propagation and attenuation along trajectories which is computationally efficient the attenuation and travel time based inversion approaches are naturally complementary hydraulic travel times are determined by the hydraulic diffusivity a combination of hydraulic conductivity and specific storage whereas the attenuation is determined solely by specific storage the potential of our hydraulic tomographical approach was investigated at a well characterized sand and gravel aquifer located in the leine river valley near gottingen germany the database for the hydraulic inversion consists of 392 cross well slug interference tests performed between five wells in which the positions of the sources injection ports and the receivers observation ports isolated with double packer systems were varied between tests the results have shown that the combination of hydraulic travel time and hydraulic attenuation tomography allows the reconstruction of the diffusivity and storage distribution in two and three dimensions with a resolution and accuracy superior to that possible with type curve analysis

the persistence of memory the fate of ancient sedimentary organic carbon in a modern sedimentary system the cycle of organic carbon burial and exhumation moderates atmospheric chemistry and global climate over geologic timescales the burial of organic carbon occurs predominantly at sea in association with clay sized particles derived from the erosion of uplifted continental rocks it follows that the history of the fine grained particles on land may bear on the nature of the organic carbon buried in this study the evolution of clay associated organic matter was followed from bedrock source to the seabed in the eel river sedimentary system of northern california using natural abundance 13c and 14c tracers approximately half of the fine grained organic carbon delivered to the shelf is derived from ancient sedimentary organic carbon found in the uplifted mesozoic tertiary franciscan complex of the watershed the short residence time of friable soils on steep hill slopes coupled with rapid sediment accumulation rates on the shelf slope act to preserve the ancient organic carbon a comparable quantity of modern organic carbon is added to particles in the watershed and on the shelf and slope the bimodal mixture of ancient and modern c in soils and sediments may be characteristic of many short mountainous rivers if the eel river chemistry is typical of such rivers more than 40 tg of ancient organic c may be delivered to the world s oceans each year a flux of that magnitude would have a significant influence on marine and global c cycles

geomorphic tectonic control of sediment discharge to the ocean the importance of small mountainous rivers analysis of data from 280 rivers discharging to the ocean indicates that sediment loads yields are a log linear function of basin area and maximum elevation of the river basin other factors controlling sediment discharge e g climate runoff appear to have secondary importance a notable exception is the influence of human activity climate and geology on the rivers draining southern asia and oceania sediment fluxes from small mountainous rivers many of which discharge directly onto active margins e g western south and north america and most high standing oceanic islands have been greatly underestimated in previous global sediment budgets perhaps by as much as a factor of three in contrast sediment fluxes to the ocean from large rivers nearly all of which discharge onto passive margins or marginal seas have been overestimated as some of the sediment load is subaerially sequestered in subsiding deltas before the proliferation of dam construction in the latter half of this century rivers

source diagenesis and fluxes of particulate organic carbon along the western adriatic sea mediterranean sea article i nfo in this study we investigated the modern organic carbon oc cycling along the clinoform shaped deposit that developed after the attainment of the modern sea level in the adriatic sea 5 5 kyr cal bp newly acquired data were combined with published results to characterize the i origin ii diagenesis and iii fluxes of oc along the adriatic clinoform 13 c 14 c and lignin phenols were used to constrain the composition of oc accumulating in surface sediments sediment cores collected at different water depths were used to describe the early diagenesis during burial in different regions in addition on the basis of an extensive number of accumulation rates and oc data we assessed the flux of oc to the seabed and its burial our results showed that terrigenous oc is the dominant oc source in the po prodelta mainly in the form of pre aged soil derived oc and vascular plant fragments along the clinoform both 14c and the concentration of lignin derived phenols decreased with increasing distance from the po prodelta indicating the influence of an additional pool of aged oc that gradually becomes more important because of its selective preservation during the sediment transport as a result degradation rates k decreased along the clinoform as a function of the sediment oxidative history the calculated half life of reactive oc t1 2 was 14 6 yrs in the po prodelta whereas topset forest deposits south of this region exhibited higher values 100 yrs indicating the presence of refractory material in the distal bottomset region the t1 2 was particularly high ranging from 255 to 912 yrs because of the significant southward component of the sediment transport the oc deposition in the southern surface sediments exceeded the local oc input via rivers ratio deposition input 1 2 conversely the northern adriatic was characterized by a marked imbalance ratio deposition input 0 3 0 5 according to our calculations the oc flux to the seabed along the clinoform was 309 gg of c per year whereas the oc burial was 180 gg of c per year corresponding to an overall burial efficiency of 59

interdiffusion of h2o and co2 in metamorphic fluids at 490 to 690 c and 1 gpa interdiffusion coefficients have been determined for h 2o co2 mixtures by quantifying the flux of co2 between two fluid filled chambers in a specially designed piston cylinder cell the two chambers which are maintained at 1 0 gpa and at temperatures differing by 100 c each contain the xco2 buffering assemblage calcite quartz wollastonite in h2o the positive dependence of xco2 on temperature results in a down temperature steady state flux of co 2 through a capillary tube that connects the two chambers this flux drives the wollastonite calcite quartz equilibrium to the right in the cooler chamber producing a measurable amount of calcite that is directly related to co2 h2o interdiffusion rates diffusivities calculated from seven experiments range from 1 0 10 8 to 6 1 10 8 m 2 s for mean capillary temperatures between 490 and 690 c the data set can be approximated by an arrhenius type relation d 4 7 10 6 exp 4560 t m 2 s t in k which yields values within a factor of 2 of but slightly lower than diffusivities estimated by application of the stokes einstein relation because rates of h2o and co2 interdiffusion approach within 1 to 2 orders of magnitude rates of heat conduction in rocks rapid co2 h2o interdiffusion should be expected in deep seated fluids wherever gradients in xco2 are imposed by contrasting mineral assemblages considering the small scale heterogeneity of the crust strong gradients in xco2 are probably quite common particularly where different carbonate bearing assemblages are juxtaposed or where they are interlayered with carbonate absent rocks cross layer diffusive mass transfer of co2 and h2o may play an important role in driving dehydration and decarbonation reactions even in the absence of fluid flow copyright 2004 elsevier ltd

origin of remineralized organic matter in sediments from the rhone river prodelta nw mediterranean traced by δ14c and δ13c signatures of pore water dic rivers are important links between continents and oceans by transporting terrestrial particulate organic matter pom to continental shelf regions through estuaries or deltas and the mediterranean basin is a good example of this strong linkage in the vicinity of river mouths an important fraction of the terrestrial pom settles on the seafloor sometimes mixed with marine pom where both can be recycled or buried in the rhone river prodelta previous studies have investigated the origin of the pom in the sediments they pointed at the large fraction of terrestrial pom in the sediments and the transition to older pom fractions in offshore direction these studies suggested that terrestrial pom could be an important food source for benthic heterotrophic organisms in this area in this study the 13c and 14c signatures of dissolved inorganic carbon dic and dic nh4 ratio in sediment pore water have been measured along a nearshore offshore transect the data were compared with available datasets concerning isotopic signature and c n of the pom in bottom waters and suspended particles from the rhone river and sediments from its delta in order to determine which fraction of the pom is actually mineralized our results show that a fraction of terrestrial pom corresponding to riverine plankton is preferentially mineralized indeed 13c depleted riverine pom 13c 25 to 27 which is enriched with 14c 14c 400 to 500 and shows a c n 8 gets mostly mineralized this isotopic signature differs from that of sediment pom which highlights the selective mineralization already observed in other river deltas in the mediterranean context with large human influence in river watersheds such as dam building our results highlight the importance of riverine primary production versus eroded organic matter in coastal carbon budgets

a long square barrel gravity corer for sedimentological and geochemical investigation of fine grained sediments abstract large volume undisturbed sediment cores 3 m long are obtained using a modified gravity corer the corer is square in cross section 12 7 12 7 cm and is designed to facilitate acquisition and subsampling of fine grained sediments sedimentological and geochemical data demonstrate that the modified gravity corer obtains undisturbed cores and preserves the sediment water interface

sensitivity and resolution of tomographic pumping tests in an alluvial aquifer 1 various investigators have proposed hydraulic tomography the simultaneous analysis of responses to multiple well tests as a means to obtain a high resolution characterization of aquifer flow properties this study assesses the information content of drawdown records from a set of tomographic pumping tests in an alluvial aquifer comparing the parameter sensitivity and resolution associated with transient and steady shape formulations of the objective function for the parameter estimation problem the steady shape approach takes advantage of the rapid establishment of constant gradients within the region surrounding a pumping well comparing observed drawdown differences within this region with drawdown differences predicted by a steady state model both the transient and steady shape approaches resolve k variations only within a limited distance of the pumping intervals and observation points relative to the transient approach the steady shape approach reduces the influence of poorly resolved property variations including k variations outside the region of investigation and storage coefficient variations throughout the model domain

early diagenetic remineralization of sedimentary organic c in the gulf of papua deltaic complex papua new guinea net loss of terrestrial c and diagenetic fractionation of c isotopes oceania supplies 40 of the global riverine flux of organic carbon approximately half of which is injected onto broad continental shelves and processed in shallow deltaic systems the gulf of papua on the south coast of the large island of new guinea is one such deltaic clinoform complex it receives 4 mt yr 1 particulate terrestrial organic carbon with initial particle corg loading 0 7 mg m 2 corg loading is reduced to 0 3 mg m 2 in the topset upper foreset zones of the delta despite additional inputs of mangrove and planktonic detritus and high net sediment accumulation rates of 1 4 cm yr 1 carbon isotopic analyses 13c 14c of co2 and corg demonstrate rapid 100 yr remineralization of both terrestrial 13c 28 6 and marine corg 13c 20 5 ranging in average age from modern bomb 14c 60 to 1000 yr 14c 140 efficient and rapid remineralization in the topset upper foreset zone is promoted by frequent physical reworking bioturbation exposure and reoxidation of deposits the seafloor in these regions particularly 20 m apparently functions as a periodically mixed suboxic batch reactor dominated by microbial biomass although terrestrial sources can be the primary metabolic substrates at inshore sites relatively young marine corg often preferentially dominates pore water co2 relative to bulk corg in the upper foreset thus a small quantity of young rapidly recycled marine organic material is often superimposed on a generally older less reactive terrestrial background whereas the pore water co2 reflects both rapidly cycled marine and terrestrial sources terrestrial material dominates the slower overall net loss of corg from particles in the topset upper foreset zone i e recycled marine corg leaves little residue preferential utilization of corg subpools and diagenetic fractionation of c isotopes supports the reactive continuum model as a conceptual basis for net decomposition kinetics early diagenetic fractionation of c isotopes relative to the bulk sedimentary corg composition can produce changes in 14c activity independent of radioactive decay in the gulf of papua topset upper foreset 14c of pore water co2 averaged 300 greater than corg sediment between 1 3 m depth in deposits diagenetic fractionation and decomposition aging of sedimentary corg compromises simple application of 14c for determination of sediment accumulation rates in diagenetically reactive deposits

distribution and sources of particulate organic matter in the water column and sediments of the fly river delta gulf of papua papua new guinea suspended particles from surface and bottom waters and surficial sediments from the seabed were collected throughout the fly river subaqueous delta region during the monsoon season in january 2003 because of the unusually low river discharge associated with a strong el nino water column salinities were relatively high 10 to 32 throughout most of the delta with brackish salinities 4 wt relatively high organic carbon nitrogen molar ratios oc n 20 mol mol and quite depleted stable isotopic compositions of organic carbon 13coc 27 in contrast surface sediments in the seabed displayed spatially uniform compositions that were characterized by markedly lower oc contents 1 1 0 8 wt lower oc n ratios 17 9 mol mol and relatively enriched 13coc compositions 25 5 1 1 the radioisotopic compositions of oc from a selected set of seabed samples 14coc of 408 82 indicate om in surface sediments is old 14c ages of 2800 to over 6000 years before present the ratios of organic carbon to mineral surface area exhibited by these sediments are within the typical mono layer equivalent ranges characteristic of shelf sediments and do not reflect the preferential removal of terrigenous om overall these compositions indicate that while water column pom appears to be derived mainly from terrigenous vascular plant debris and riverine estuarine phytoplankton the source of most of the sedimentary pom is aged soil oc ultimately derived from c3 vegetation we speculate that the concentrations and sources of suspended pom in the water column of the fly river delta region reflect the conditions of low river discharge low wave energy and neap tides encountered at the time of sampling in contrast pom compositions in surface sediments are consistent with the transport and deposition of old mineral bound oc most likely eroded from the upland regions of the fly river watershed which is characterized by steep slopes high precipitation and c3 tropical forests and grasslands

a temporal sampling strategy for hydraulic tomography analysis 1 this paper investigates optimal sampling times of drawdowns for the analysis of hydraulic tomography ht survey the investigation was carried out by analyzing the spatial and temporal evolution of cross correlations between the head responses at an observation well and transmissivity t and storage coefficient s properties during a pumping test in homogeneous and heterogeneous aquifers the analysis shows that the cross correlation between the head and s values is limited to the region between the observation and the pumping well in the aquifers it reaches the highest value near the early time tm and decays to zero afterwards the time tm is approximately equal to the time t0 at which the extrapolated drawdown from the first straight line portion of an observed drawdown log time plot becomes zero at early times the high cross correlation between the head and t is confined to the region between the observation and the pumping well this region then evolves into two humps one on each side of the circular region encompassing the observation well and the pumping well the size of the two humps expands and their values reach the maximum as flow reach steady state as a consequence we hypothesize that pairs of head data at t0 and those at either the steady state or a late time during an ht survey could yield the best estimates of the heterogeneous t and s fields results from numerical experiments have verified this hypothesis and demonstrated that this sampling strategy is generally applicable even when the boundary condition is unknown we therefore recommend in principle that 1 carrying out pumping tests of ht surveys for sufficiently long period of time such that drawdown reaches the entire area of interest and 2 using a constant head or zero drawdown for all boundaries during the inverse modeling analysis

evolution of organic matter degradation in cretaceous black shales inferred from authigenic barite a reaction transport model abstract a reaction transport model was used to infer the long term evolution of anaerobic organic matter degradation in cretaceous black shales from the distribution of authigenic barite in sediments drilled at demerara rise odp leg 207 site 1258 in these sediments sulfate reduction and methanogenesis are the major pathways of organic matter decomposition and the depth distribution of authigenic barite serves as an indicator for the temporal evolution of the sulfate methane transition zone smtz the strength of the biogenic methane flux and ultimately the organic matter reactivity in the black shales over geological timescales organic matter degradation is described according to the reactive continuum model approach and parameters values are determined by inverse modeling based on present day porewater and authigenic barite profiles fully transient simulations were performed over a period of 100 myrs and indicate that important features of the biogeochemical dynamics are associated to changes in the boundary forcing hiatuses in sediment accumulation rate result in quasi steady state conditions and lead to distinct accumulations of authigenic barites in the smtz the inversely determined parameters reveal that the reactivity of the organic matter was already low apparent first order rate constant k 10 4 year 1 10 6 year 1 at the time of its deposition in the cretaceous the geochemical characteristics of sediments drilled at demerara rise as well as the presence of specific biomarkers suggest that this low reactivity is most likely due to the euxinic palaeo conditions which favored the sulfurization of the organic matter simulation results predict average initial organic carbon contents between 8 1 and 9 5 wt implying a high preservation efficiency of the organic matter between 79 and 89 calculated mass accumulation rates between 0 43 and 0 5 g c m 2 year 1 compare well with estimations for the western basin of the cretaceous southern north atlantic simulation results thus indicate that the enhanced preservation of organic matter under euxinic conditions may have been the main cause for the formation of organic rich cretaceous black shales at demerara rise

composition and fate of terrigenous organic matter along the arctic land ocean continuum in east siberia insights from biomarkers and carbon isotopes abstract climate warming is predicted to translocate terrigenous organic carbon terroc to the arctic ocean and affect the marine biogeochemistry at high latitudes the magnitude of this translocation is currently unknown so is the climate response the fate of the remobilized terroc across the arctic shelves represents an unconstrained component of this feedback the present study investigated the fate of permafrost carbon along the land ocean continuum by characterizing the terroc composition in three different terrestrial carbon pools from siberian permafrost surface organic rich horizon mineral soil active layer and ice complex deposit and marine sediments collected on the extensive east siberian arctic shelf esas high levels of lignin phenols and cutin acids were measured in all terrestrial samples analyzed indicating that these compounds can be used to trace the heterogeneous terrigenous material entering the arctic ocean in esas sediments comparison of these terrigenous biomarkers with other terroc proxies bulk 13c 14c and hmw lipid biomarkers highlighted contrasting across shelf trends these differences could indicate that terroc in the esas is made up of several pools that exhibit contrasting reactivity toward oxidation during the transport in this reactive spectrum lignin is the most reactive decreasing up to three orders of magnitude from the inner to the outer shelf while the decrease of hmw wax lipid biomarkers was considerably less pronounced alternatively degradation might be negligible while sediment sorting during the across shelf transport could be the major physical forcing that redistributes different terroc pools characterized by different matrix association despite the marked decrease shown by lignin the fingerprint of lignin phenols such as the acid aldehyde ratio of vanillyl and syringyl phenols showed a lack of any across shelf trends and exhibited an extremely wide range of values in all terrestrial samples by contrast the 3 5 dihydroxybenzoic vanillyl phenols ratio exhibited a clear across shelf trend suggesting either increasing degradation with distance from the coast or terroc sorting along the sediment dispersal system the ratio of syringyl vanillyl phenols indicated that gymnosperm tissues are more important than angiosperm tissues in surface sediments in particular off the lena river mouth consistent with the vegetation in its watershed conversely the fingerprint of p hydroxybenzenes suggests lack of substantial input of moss derived material finally autochthonous lipid and protein derived cuo reaction products displayed a strong along shelf gradient likely reflecting the inflow of nutrient rich pacific waters from the bering strait that stimulate primary productivity in the eastern esas in particular short chain fatty acids showed a clear frontal transition zone between pacific influenced and river influenced waters approximately along the 160 e longitude considering the labile nature of phytoplankton priming and co metabolism processes might stimulate degradation of terroc in the easternmost region of the siberian shelf this study demonstrated the need to consider multiple terroc proxies at isotopic molecular levels to differentiate the fate for different allocthonous components in arctic sediments and the need to assess how these terroc pools are distributed in different density size and settling fractions to better discriminate between the extent of hydrodynamic sorting versus degradation

diverse origins and pre depositional histories of organic matter in contemporary chinese marginal sea sediments abstract marginal seas are estimated to account for up to 90 of organic carbon oc burial in marine sediments and thus play an important role in global carbon cycle however comprehensive assessments of carbon budgets for marginal sea systems are challenging due to their inherent complexity with spatial and temporal variability in carbon inputs and dispersal processes we examine the bohai sea and yellow sea bs ys in order to further our understanding of sedimentary oc delivery translocation and accumulation in a shallow marginal sea system bulk properties and the content and isotopic compositions 14c 13c of source specific plant wax n alkyl lipid biomarkers were determined for a suite of surficial sediment samples variable 13c values 25 1 to 28 5 and contemporary radiocarbon ages of short chain n fatty acids fas c16 c18 reflect modern autochthonous marine and or fresh terrestrial plant input in contrast extremely depleted 14c values 932 to 979 of short chain n alkanes c16 c18 suggest a predominant input from sedimentary rocks petrogenic oc or petroleum abundance weighted average 13c and 14c values of long chain leaf wax lipids c26 28 30 n fas c24 26 28 n alkanols c27 29 31 n alkanes are 29 1 1 1 to 30 2 0 3 and 286 150 to 442 119 respectively illustrating that terrestrial oc delivery is dominated by pre aged 3000 5000 14c yrs c3 vegetation sources a coupled carbon isotopic mixing model based on the bulk and compound specific biomarker 13c and 14c values is used to partition the bs ys sedimentary oc into three components that reflect both origins and transport processes for all sampling sites 31 64 is modern contemporary oc 24 49 is pre aged terrestrial oc and 7 26 is fossil oc the latter likely derived from both physical erosion of ancient sedimentary rocks and fossil fuel sources pre aged soil oc is most prominent in front of the modern and old huanghe yellow river delta 48 and 49 and fossil oc is most significant north of the old huanghe mouth 26 significant pre aged soil contributions 33 are also evident for sites further offshore where transport and deposition of eolian dust supply may be important for the three major deposition areas of the bs ys system bohai basin sub aqueous huanghe delta and central south ys basin we estimate that about 3 02 mt yr of refractory plant derived pre aged soil oc and 0 98 mt yr of 14c depleted fossil oc accumulates in surface sediments corresponding to 35 and 11 of sediment toc respectively compared with estimates for fluxes from corresponding sources the burial efficiency is close to 100 for pre aged soil oc and 70 for fossil oc implying efficient oc burial in delta and shelf environments re burial of these two pools of terrigenous oc only affects carbon cycling on millennial and longer timescales respectively and exerts little influence on the modern carbon cycle

role of river suspended material in the global carbon cycle the reaction of ca derived from silicate weathering with co2 in the world s oceans to form carbonate minerals is a critical step in long term climate moderation ca is delivered to the oceans primarily via rivers where it is transported either as dissolved species or within suspended material the relative importance for climate moderation of riverine dissolved ca vs suspended ca transport stems from the total ca flux and its climate dependence data in the literature suggest that within uncertainty global riverine dissolved ca flux is equal to suspended material ca flux to determine how these fluxes depend on temperature and rainfall a 40 yr field study was performed on 4 catchments

temporal variability in composition and fluxes of yellow river particulate organic matter this study examines temporal variations of the abundance and carbon isotopic characteristics of particulate organic carbon poc and specific source compounds in the context of hydrological variability in the yellow river the content and bulk carbon isotopic characteristics 13c and 14c of poc were relatively uniform over the hydrologic seasonal cycle we attribute these temporally invariant geochemical characteristics to the dominant contribution of loess material to the suspended particulate matter spm in contrast molecular level signals revealed that hydrologic conditions exert a significant influence on the proportional contributions of petrogenic and especially fresh plant derived oc while pre aged soil oc is mobilized via deeper erosion processes e g gully erosion mudslides and is independent of hydrodynamics and surface runoff a coupled biomarker isotope mixing model was applied to estimate the time varying supply of contemporary modern biomass pre aged soil and fossil oc components to chinese marginal seas from the yellow river we found that natural e g precipitation and human induced e g water and sediment regulation variations in hydrological regime strongly influence the flux with the magnitude of the corresponding annual fluxes of poc ranging between 0 343 0 122 mt yr 1 and 0 581 0 213 mt yr 1 but less strongly infleunce proportions of the different oc constituents inter annual differences in pre aged soil and fossil oc fluxes imply that extreme climate events e g floods modulate the exhumation and export of old carbon to the ocean but the oc homogeneity in the pre aged mineral soil dominated watersheds facilitates robust predictions in terms of oc transport dynamics in the past sediment cores and in the future

protection of organic matter by mineral matrix in a cenomanian black shale abstract three types of pathways degradation recondensation natural sulphurization and selective preservation are commonly considered for the formation of kerogen dispersed in sedimentary rocks a fourth pathway has been recently put forward however from studies on recent marine sediments the so called sorptive protection mechanism this pathway is based on the adsorption of otherwise labile organic compounds onto minerals thus preventing their diagenetic degradation and promoting their subsequent condensation into kerogen the main results of the present study are derived from a combination of microscopic and pyrolytic methods applied on a cenomanian kerogen they provide i evidence on an ancient material for a crucial role of the mineral matrix both in organic matter om preservation during kerogen formation and in kerogen stability once formed ii indications that the dominant protective process likely involves physical protection by minerals resulting from alternation of organic and clay nanolayers of approximately 100 nm in thickness rather than om adsorption as molecular monolayers and iii observations of the relatively poor stability of an isolated kerogen contrary to the inertness commonly assumed for fossil macromolecular organic matter

widespread dispersal and aging of organic carbon in shallow marginal seas the occurrence of pre aged organic carbon oc in continental margin surface sediments is a commonly observed phenomenon yet the nature sources and causes of this aged oc remain largely undetermined for many continental shelf settings here we present the results of an extensive survey of the abundance and radiocarbon content of oc in surface sediments from the northern chinese marginal seas pre aged oc is associated with both coarser 63 m and finer 63 m sedimentary components measurements on specific grain size fractions reveal that it is especially prevalent within the 20 63 m fraction of inner shelf sediments we suggest that organic matter associated with this sortable silt fraction is subject to protracted entrainment in resuspension deposition loops during which it ages is modified and is laterally dispersed most likely via entrainment within benthic nepheloid layers this finding highlights the complex dynamics and predepositional history of organic matter accumulating in continental shelf sediments with implications for our understanding of carbon cycling on continental shelves development of regional carbon budgets and interpretation of sedimentary records

the radiocarbon age of calcite dissolving at the sea floor estimates from pore water data abstract we measured the radiocarbon content and stable isotopic composition of pore water and bottom water co2 sedimentary organic carbon and caco3 at two sites on the ceara rise one underlying bottom water that is supersaturated with respect to calcite site b the other underlying undersaturated bottom water site g the results were combined with pore water o2 co2 and ca2 profiles martin and sayles 1996 to estimate the radiocarbon content of the caco3 that is dissolving in the sediment mixed layer at site g the caco3 that is dissolving in the upper 2 cm of the sediments is clearly younger richer in 14c than the bulk sedimentary caco3 indicating that nonhomogeneous caco3 dissolution occurs there the case for nonhomogeneous dissolution is much weaker at the site underlying supersaturated bottom water the results indicate that nonhomogeneous dissolution occurs in sediments underlying undersaturated bottom water that the dissolution is rapid relative to the rate of homogenization of the caco3 in the mixed layer by bioturbation and that the dissolution rate of caco3 decreases as it ages in the sediment mixed layer the results support the hypothesis based on solid phase analyses that the preferential dissolution of young i e radiocarbon rich caco3 leads to a pattern of increasing radiocarbon age of mixed layer caco3 as the degree of undersaturation of bottom water increases keir 1984 broecker et al 1991

late pleistocene and holocene sedimentation organic carbon delivery and paleoclimatic inferences on the continental slope of the northern pandora trough gulf of papua 1 we investigated sediment and organic carbon accumulation rates in two jumbo piston cores mv 54 mv 51 retrieved from the midslope of the northeastern pandora trough in the gulf of papua papua new guinea our data provide a first assessment of mass fluxes over the past 33 000 14c years b p and variations in organic carbon sources core sediments were analyzed using a suite of physical properties organic geochemistry and micropaleontological measurements mv 54 and mv 51 show two periods of rapid sediment accumulation the first interval is from 15 000 to 20 400 cal years b p mv 51 1 09 m ka 1 and 81 2 g cm 2 ka 1 and the second occurs at 32 000 14c years b p 2 70 m ka 1 and 244 g cm 2 ka 1 extremely high accumulation rates 3 96 m ka 1 428 g cm 2 ka 1 characterize 15 800 17 700 cal years b p in mv 54 and likely correspond to early transgression when rivers delivered sediments much closer to the shelf edge a benthic foraminiferal assemblage in mv 51 from 18 400 to 20 400 cal years b p indicates a seasonally variable flux of organic carbon possibly resulting from enhanced contrast between monsoon seasons the oldest sediments 32 000 14c years b p contain toc fluxes 200 g cm2 ka 1 with 50 of it derived from c3 vascular plant matter magnetic susceptibility values are 2 to 3 times higher and benthic foraminiferal accumulation rates are 6 times higher during this interval than at any younger time indicating a greater influence of detrital minerals and labile organic carbon the ms data suggest more direct dispersal pathways from central and eastern png rivers to the core site

a travel time based hydraulic tomographic approach 1 hydraulic tomography is a method to identify the three dimensional spatial distribution of hydraulic properties in the subsurface we propose a tomographic approach providing the inversion of travel times of hydraulic or pneumatic tests conducted in a tomographic array the inversion is based on the relation between the peak time of a recorded transient pressure curve and the diffusivity of the investigated system the development of a transformation factor enables the inversion of further travel times besides the peak time of a transient curve as the early travel times of the curve are mainly related to preferential flow features while the inversion based on late travel times are reflecting an integral behavior it can be assumed that the different inversion results reflect the properties of the overall system by comparing the different reconstructions the system interpretation therefore becomes more comprehensive and reliable furthermore the similarity of the proposed hydraulic tomographic approach to seismic travel time tomography allows us to apply the inversion algorithms which are used for seismic tomography we therefore apply the method of staggered grids which enables to refine the grid resulting in a higher nominal resolution to data from a set of interference tests arranged in a tomographic array the tests were conducted in an unsaturated fractured sandstone cylinder in the laboratory the three dimensional reconstructions of the diffusivity distribution are found to be highly reliable and robust in particular the mapped fracture of the sandstone cylinder coincides with our reconstructed diffusivity distribution

impact of hurricane katrina 2005 on shelf organic carbon burial and deltaic evolution 1 sediment cores from the continental shelf adjacent to the mississippi river delta immediately after the passage of hurricane katrina were used to examine the magnitude and implications for the carbon budget of sediment and particulate organic carbon poc remobilized by the storm on the river dominated continental shelf poc was sourced from incision of the innermost continental shelf 5000 ybp poc eroded from the seafloor has major implications for the remineralization versus burial of poc in deltas the scale of erosional deflation of the shelf in water depths beyond seasonal wave current conditions suggests that over millennia tropical cyclones may be responsible for partly removing prodeltaic strata from the geologic record in low to mid latitude deltas

disentangling marine soil and plant organic carbon contributions to continental margin sediments a multi proxy approach in a 20 000 year sediment record from the congo deep sea fan abstract a 20 kyr long sediment sequence from the congo deep sea fan core geob 6518 1 one of the world s largest deep sea river fans has been analysed for bulk and molecular proxies in order to reconstruct the marine soil and plant organic carbon oc contributions to these sediments since the last glacial maximum the bulk proxies applied c n ratio and 13 c org ranged from 10 to 12 5 and from 24 5 to 21 vpdb respectively as molecular proxies concentrations of marine derived alkenones and terrestrial derived odd numbered n alkanes were used which varied between 0 2 and 4 g g dry weight sediment in addition the branched vs isoprenoid tetraether bit index a proxy for soil organic matter input was used which varied from 0 3 to 0 5 in this core application of binary mixing models based on the different individual proxies showed estimates for terrestrial oc input varying by up to 50 due to the heterogeneous nature of the oc application of a three end member mixing model using the 13 c org content the c n ratio and the bit index enabled the distinction of soil and plant organic matter as separate contributors to the sedimentary oc pool the results show that marine oc accounts for 20 to 40 of the total oc present in the deep sea fan sediments over the last 20 kyr and that soil oc accounts for about half 45 on average of the oc present this suggests that soil oc represents the majority of the terrestrial oc delivered to the fan sediments accumulation rates of the plant and soil oc fractions over the last 20 kyr varied by a factor of up to 5 and are strongly related to sediment accumulation rates they showed an increase starting at ca 17 kyr bp a decline during the younger dryas peak values during the early holocene and lower values in the late holocene this pattern matches with reconstructions of past central african humidity and congo river discharge from the same core and revealed that central african precipitation patterns exert a dominant control on terrestrial oc deposition in the congo deep sea fan marine oc accumulation rates are only weakly related to sediment accumulation rates and vary only little over time compared to the terrigenous fractions these variations are likely a result of enhanced preservation during times of higher sedimentation rates and of relative small fluctuations in primary production due to wind driven upwelling

shallow gas off the rhone prodelta gulf of lions sediment cores acquired in 2004 off the rhone prodelta show consistent anomalous methane concentrations of up to 87 440 ppm methane compositional and isotopic data support a biogenic origin although there are a few sites that show strongly depleted delta c 13 values 53 o pdb suggesting a mixed source for the gas biogenic and thermogenic anomalous methane concentrations samples with more than 90 ppm are discussed and integrated with organic carbon data sedimentary rates and adcp profiles highest gas concentrations were found directly off the river mouth 20 40 m water depth and where the ifremer models point to the thickest accumulation 2 m in response to the rhone flood event in areas unaffected by the high flux of organic matter and rapid thick flood deposition or in between flood events the conditions for methanogenesis and gas accumulation have not been met in these areas the physical and biological reworking of the surficial sediment may effectively oxidize and mineralize organic matter and limit bacterial methanogenesis in the sub surface we propose that in the rhone prodelta flood deposits deliver significant amounts of terrigenous organic matter that can be rapidly buried effectively removing this organic matter from aerobic oxidation and biological uptake and leading to the potential for methanogenesis with burial c 2006 elsevier b v all rights reserved

early diagenetic cycling incineration and burial of sedimentary organic carbon in the central gulf of papua papua new guinea 1 the clinoform complex of the gulf of papua represents a major deltaic system in oceania two seasons largely control seafloor dynamics and sedimentary c cycling the relatively quiescent nw monsoon and the se trades characterized by remobilization and reoxidation of topset deposits surface sediments 20 cm are reactive with co2 production fluxes 35 42 mmol m 2 d 1 at mangrove channel and topset sites during the monsoon and 10 20 mmol m 2 d 1 on the foreset bottomset 40 m fluxes decrease by a factor of 0 3 on the topset during the transition period and trades the 13 14c isotopic compositions of pore water co2 reveal diagenetic fractionation with dominant utilization of young 14c 1 4 31 1 terrestrial c substrates inshore channels topset 13c 29 to 25 and a progressive increase of young marine c sources seaward outer topset foreset bottomset 13c 22 2 to 19 5 remineralization patterns of terrestrial and marine corg demonstrate cross shelf exchange multiple tracers show that a suboxic mobile mud layer 10 60 cm thick usually 10 30 cm characterizes the central gulf topset and umuda valley off the fly river and unconformably overlies methanic deposits releasing old co2 14c 159 to 229 residual terrestrial corg delivered to the bioturbated foreset continues to be remineralized slowly generating co2 having net 14c 270 within sediments deposited 100 200 years ago the reactivity of corg below 0 5 m in the foreset is 10 20 times lower than expected based on accumulation rates reflecting loss of 50 of sedimentary corg on the topset which functions as a suboxic incinerator

aging of marine organic matter during cross shelf lateral transport in the benguela upwelling system revealed by compound specific radiocarbon dating organic matter accumulation and burial on the namibian shelf and upper slope are spatially heterogeneous and strongly controlled by lateral transport in subsurface nepheloid layers much of the material deposited in depo centers on the slope ultimately derives from the shelf supply of organic matter from the shelf involves selective transport of organic matter we studied these selective transport processes by analyzing the radiocarbon content of co occurring sediment fractions here we present radiocarbon data for total organic carbon as well as three tracers of surface ocean productivity phytoplankton derived alkenones membrane lipids of pelagic crenarchaeota crenarchaeol and calcareous microfossils of planktic foraminifera in core top and near surface sediment samples the samples were collected on the namibian margin along a shelf slope transect 85 to 1040 m at 24 s and from the upper slope depo center at 25 5 s in core top sediments alkenone ages gradually increased from modern to 3490 radiocarbon years with distance from shore and with water depth crenarchaeol while younger than alkenones also increased in age with distance offshore it was concluded that the observed ages were a consequence of cross shelf transport and associated aging of organic matter radiocarbon ages of preserved lipid biomarkers in sediments thus at least partially depend on the relative amount of laterally supplied pre aged material present in a sample highlighting the importance of nepheloid transport for the sedimentation of organic matter over the namibian margin

organic matter origin and distribution in suspended particulate materials and surficial sediments from the western adriatic sea italy abstract in this study organic carbon oc total nitrogen tn stable carbon isotopic 13 c oc and cuo reaction product compositions were used to identify the sources of organic matter om and to quantify the relative importance of allochthonous and autochthonous contributions to the western adriatic sea italy suspended particulate material 195 samples and surficial sediments 0 1 cm 70 samples from shallow cross shelf transects were collected in february and may 2003 respectively vertical water column profiles were acquired along the same transects data include depth potential temperature salinity density and chlorophyll fluorimetry along the western adriatic shelf in the near shore region the phytoplankton growth was influenced by dynamics of the buoyant plumes from the po and appennine rivers a small amount of very fine terrigenous material remained suspended within the coastal current and was exported southward along the shelf to the slope high variability in the bulk composition was detected in the po prodelta surficial sediments whereas the western adriatic shelf although a larger area exhibited a narrower range of values a significant decoupling was observed between suspended particles in the water column and surficial deposits the organic material collected in the water column was compositionally heterogeneous with contributions from marine phytoplankton riverine estuarine phytoplankton and soil derived om frequent physical reworking of surficial sediments likely leads to the efficient oxidation of marine oc resulting in the observed accumulation and preservation of refractory soil derived oc delivered by the po and appennine rivers

spatial variability in the abundance composition and age of organic matter in surficial sediments of the east china sea 1 understanding the sources and fate of organic matter om sequestered in continental margin sediments is of importance because the mode and efficiency of om burial impact the carbon cycle and the regulation of atmospheric co2 over long time scales we carried out molecular lignin derived phenols from cuo oxidation elemental isotopic 13c 14c and sedimentological grain size and mineral surface area analyses in order to examine spatial variability in the abundance source age of surface sediments of the east china sea higher terrigenous organic matter values were found in the main accumulating areas of fluvial sediments including the changjiang yangtze estuary and zhejiang fujian coastal zone isotopic and biomarker data suggest that the sedimentary om in the inner shelf region was dominated by aged 14c 423 42 but relatively lignin rich om 0 94 0 57 mg 100 mg oc associated with fine grained sediments suggesting important contributions from soils in contrast samples from the outer shelf while of similar age 14 c 450 99 are lignin poor 0 25 0 14 mg 100 mg oc and associated with coarse grained material regional variation of lignin phenols and om ages indicates that om content is fundamentally controlled by hydrodynamic sorting especially sediment redistribution and winnowing and in situ primary production selective sorption of acid to aldehyde in clay fraction also modified the ratios of lignin phenols the burial of lignin in east china sea is estimated to be relatively efficient possibly as a consequence of terrigenous om recalcitrance and or relatively high sedimentation rates in the changjiang estuary and the adjacent zhejing fujian mud belt

shallow gas and flood deposition on the po delta abstract sediment cores acquired on the po delta northwestern adriatic sea in water depths of 10 to 25 m yielded anomalous concentrations of methane up to 41 300 ppm of the 19 unique sites analyzed 5 sites 9 cores had more than 90 ppm of ch 4 and of those 3 sites 4 cores had more than 13 800 ppm methane compositional and isotopic analyses of the gas support a bacterial origin anomalous methane concentrations were found in kasten gravity and box cores where more than one core type was acquired at a single location all cores contained anomalous methane despite the regional high productivity in the adriatic all of the highest gas concentrations were found in the region associated with the thickest accumulation of recent flood deposits off the most active channel of the po delta po di pila cores acquired in this region contain primary sedimentary structures that indicate rapid burial of thick 10 cm flood deposits and a relative lack of bioturbation down to the base of the flood layer we propose that in the po delta flood deposits deliver significant amounts of terrigenous organic matter that can be rapidly buried on the prodelta effectively removing this organic matter from aerobic oxidation and biological uptake and leading to the potential for methanogenesis with burial in areas unaffected by this high flux of organic matter and rapid thick flood deposition or in between flood events our data indicate that the conditions for methanogenesis and gas accumulation have not been met we suggest that in these areas the physical and biological reworking of the surficial sediment between flood events may effectively oxidize and mineralize organic matter derived from both marine and terrestrial sources and limit bacterial methanogenesis in the subsurface

river plumes coral reefs and mixing in the gulf of papua and the northern great barrier reef abstract the mean annual freshwater discharge in the gulf of papua principally from the fly kikori and purari rivers is estimated to be 13000 m 3 s 1 water from these rivers forms a low salinity surface layer in the gulf where it has a residence time of about two months and flows generally eastward a small fraction of this water intrudes through bligh entrance on the great barrier reef continental shelf horizontal patchiness and mixing of these intruding waters with shelf waters are considerably enhanced by secondary circulation wakes around coral reefs the wakes shapes visible in enhanced landsat imagery are similar to those around cylinders and plates in laboratory experiments at low reynolds numbers topographically enhanced mixing may explain why the cross shelf gradients of temperature and of the structure of fish communities are smaller in the northern region than in the central region of the great barrier reef

an organodiagenetic model for marinoan age cap carbonates abstract the nuccaleena formation cap carbonate is the global stratotype for the marinoan glaciation and ediacaran gssp a designation that emphasises the importance of cap carbonates to our current understanding of global neoproterozoic biogeochemistry sedimentology and stratigraphy however to date there is no agreed depositional model for cap carbonates and there remains minimal detailed paragenetic data for developing process based depositional models here an early diagenetic organodiagenetic dolomite cementation model for marinoan cap carbonate formation is hypothesised and explored it is demonstrated how this process based model can explain the three main atypical sedimentary structures that are the basis for correlation of marinoan age cap carbonates giant tepee like structures sheet veins and tubestones these features are interpreted to be products of fluid overpressure deformation induced by organodiagenetic expansive cementation giant tepee like structures the hallmark of marinoan cap carbonates conform to a simple structural analysis that is consistent with the predicted stress field induced by expansive cementation driven fluid overpressure the undeformed to highly deformed gradient of deformation features in cap carbonates is consistent with the range of rheologies in a shallowly buried cementing carbonate modification of matrix textures and bedding surfaces also conforms to the range of expected textures within this model overall it is hypothesised that the aggradational condensed section architecture of cap carbonates was the primary control over the generation of these atypical sedimentary features the available paragenetic analysis suggests that the geochemical data particularly the c isotopic data can be reinterpreted as supportive of the organodiagenetic model and that the neoproterozoic ocean was perhaps similar to that of today the proposed model indicates that the current criteria for the placement of the ediacaran gssp are non unique and potentially non isochronous perhaps the most important aspect of this model is that it is testable and is a call for focused research on the much overlooked paragenesis of cap carbonates

significance to hydrocarbon exploration of terrestrial organic matter introduced into deep marine systems insights from the lower cretaceous in the levant basin abstract oil shows from wells in the levant basin and egypt are suggestive of potential economic discoveries within unpenetrated mesozoic reservoirs in the eastern mediterranean analysis of some of these oils indicate a non marine source of mixed deltaic terrestrial or lacustrine origin for the organic matter data from barremian aptian sediments from the mnuph 1 core in northern israel opens a window on potential importance of terrestrial sourced kerogen deposited in source rocks in a marine depositional environment core analyses of the barremian nabi sa id fm demonstrate the occurrence of a gas prone immature source rock of 77 m gross thickness averaging 4 6 toc peaking at 37 toc rock eval pyrolysis biomarker n alkane sterane and tricyclic terpane indices atomic c n ratios and 13corg ranges indicate mixed terrestrial marine organic source rocks for the barremian while higher up the aptian hidra fm contains source rocks with organic matter derived dominantly from carbohydrate rich land plants the interval at mnuph 1 includes abundant evidence for off shelf mass transport of terrestrial and proximal marine sediments into the deep marine basin these features are used to explain the anomaly of a terrestrial source for organic matter in this setting mass transport and consequent mixing of distal marine proximal marine and land derived sediment is in fact the norm at the foot of continental slopes globally the dominantly type iii source rocks described here would be unlikely to expel oil but might produce thermogenic gas thermogenic gas identified in similar marine settings might wrongly be interpreted as having been generated from marine organic matter misleadingly indicative of a prospective oil source when prospecting for deep rooted hydrocarbon accumulations in offshore marine settings an alternative system dominated by basinward sediment transport of gas prone terrestrial source rocks into strategically positioned toe of slope marine settings is supported here and could well be producing gas in the levant basin

14c excess in deep sea sediments porewater driven by diffusionߞsoutheast mediterranean core profiles in the deep se mediterranean sea revealed a significant 14 c excess in the total dissolved inorganic carbon dic of porewater as compared to the 14 c of the sediments below the bioturbation zone down to core bottom 2 m the main observation was that the age difference between porewater and sediments as calculated from the excess was not constant but rather increasing with depth the porewater apparent age was younger by 10 than the age of the sediment at the core top and gradually became younger by about 70 at the bottom of the core flux calculations and mass balances of the chemical and isotopic data suggest that this 14 c excess stems from a downward diffusive flux of 95 15 atoms of 14 c dic m 2 s 1 from the bioturbation zone and overlying bottom water into the sediment the 14 c dic flux is opposite in direction to the dic flux out of the sediment it is suggested here that the 14 c dic flux may severely interfere with age determination of small submarine brine lakes formed in the deep mediterranean in addition the 14 c excess should show up in authigenic carbonate phases precipitating within the sediment and hence may serve as a tool to identify the extent and duration of authigenic carbonate precipitation

preservation of organic matter and alteration of its carbon and nitrogen isotope composition during simulated and in situ early sedimentary diagenesis abstract the carbon and nitrogen isotope composition of organic matter has been widely used to trace biogeochemical processes in marine and lacustrine environments in order to reconstruct past environmental changes from sedimentary organic matter it is crucial to consider potential alteration of the primary isotopic signal by bacterial degradation in the water column and during early diagenesis in the sediments in a series of oxic and anoxic incubation experiments we examined the fate of organic matter and the alteration of its carbon and nitrogen isotopic composition during microbial degradation the decomposition rates determined with a double exponential decay model show that the more reactive fraction of organic matter degrades at similar rates under oxic and anoxic conditions however under oxic conditions the proportion of organic matter resistent to degradation is much lower than under anoxic conditions within three months of incubation the 13c of bulk organic matter decreased by 1 6 with respect to the initial value the depletion can be attributed to the selective preservation of 13c depleted organic compounds during anoxic decay the 15n values continuously decreased to about 3 below the initial value the decrease probably results from bacterial growth adding 15n depleted biomass to the residual material in the oxic experiment 15n values increased by more then 3 before decreasing to a value indistinguishable from the initial isotopic composition the dissimilarity between oxic and anoxic conditions may be attributed to differences in the type timing and degree of microbial activity and preferential degradation in agreement with the anoxic incubation experiments sediments from eutrophic lake lugano are on average depleted in 13c 1 5 and 15n 1 2 with respect to sinking particulate organic matter collected during a long term sediment trap study

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

po river plume on the adriatic continental shelf dispersion and sedimentation of dissolved and suspended matter during different river discharge rates abstract suspended matter and dissolved nutrients were studied in the prodelta of the po river northern adriatic sea immediately after one of the greatest floods of the last century which occurred in october 2000 and in four successive seasonal conditions hydrology total suspended matter tsm particulate organic carbon poc and particulate nitrogen pn content organic carbon stable isotopes 13 c poc particle grain size spectra phytoplankton and dissolved inorganic nutrients i e nitrate nitrite ammonium phosphate and silicate were measured in different discharge conditions to describe processes occurring in the po river delta the main effect of high river discharge was a large volume of low salinity water at the surface that extended over the entire study area the concentration of most sampled variables decreased along a dilution gradient from the po river distributaries mouths to the offshore for tsm at the surface riverine input and dilution were the main factors affecting its distribution at the bottom however increased tsm in the nearshore was due to rapid sinking of suspended matter at the river mouth while resuspension and advection dominated the transport of near bottom sediments offshore at 15 20 m depth in the offshore where resuspension was active an increase in ammonium and decrease in oxygen supported the presence of regeneration processes occurring at the bottom during the october 2000 flood event high nutrient concentrations promoted new production triggering an algal bloom in the southern region of the study area the origin of particulate organic carbon in the river delta was then estimated from a mixing model based on 13 c poc values and carbon nitrogen c n molar ratios and as the contribution of three distinct sources of organic carbon were determined i e marine riverine and terrestrial the riverine end member accounted for 50 of the surface poc and generally decreased towards the offshore the terrestrial carbon contribution was generally the least abundant 20 28 at the surface and at depth respectively and exhibited peak values 30 40 during the october 2000 flood last the marine contribution was the most abundant at the bottom 40 and generally increased offshore during the october 2000 flood the fluvial contribution of particulate organic carbon that is the terrestrial and riverine fractions represented approximately 80 of the total particulate organic carbon in the po river delta

loss of organic matter from riverine particles in deltas abstract in order to examine the transport and burial of terrigenous organic matter along the coastal zones of large river systems we assessed organic matter dynamics in coupled river delta systems using mineral surface area as a conservative tracer for discharged riverine particulate organic matter pom most pom in the rivers studied n 6 is tightly associated with suspended mineral material e g it is sorbed to mineral surfaces average organic loadings in the amazon river 0 67 0 14 mg c m 2 the river for which we have the largest dataset are approximately twice that of sedimentary minerals from the amazon delta 0 35 mg c m 2 stable carbon isotope analysis indicate that approximately two thirds of the total carbon on the deltaic particles is terrestrial the combined surface normalized isotope distinguished estimate is that 70 of the amazon fluvial pom is not buried in the delta consistent with other independent evidence aller et al 1996 losses of terrestrial pom have also been quantified for the river delta systems of columbia in the usa fly in new guinea and huange he in china if the losses of riverine pom observed in these river delta systems are representative of rivers worldwide then the surface constrained analyses point toward a global loss of fluvial pom in delta regions of 0 1 x 1015 g c y 1

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

an evaluation of 14c age relationships between co occurring foraminifera alkenones and total organic carbon in continental margin sediments 1 radiocarbon age relationships between co occurring planktic foraminifera alkenones and total organic carbon in sediments from the continental margins of southern chile northwest africa and the south china sea were compared with published results from the namibian margin age relationships between the sediment components are site specific and relatively constant over time similar to the namibian slope where alkenones have been reported to be 1000 4500 years older than co occurring foraminifera alkenones were significantly similar to 1000 years older than co occurring foraminifera in the chilean margin sediments in contrast alkenones and foraminifera were of similar age within 2 sigma error or better in the nw african and south china sea sediments total organic matter and alkenone ages were similar off namibia age difference toc alkenones 200 700 years chile 100 450 years and nw africa 360 770 years suggesting minor contributions of preaged terrigenous material in the south china sea total organic carbon is significantly 2000 3000 years older owing to greater inputs of preaged terrigenous material age offsets between alkenones and planktic foraminifera are attributed to lateral advection of organic matter physical characteristics of the depositional setting such as seafloor morphology shelf width and sediment composition may control the age of co occurring sediment components in particular offsets between alkenones and foraminifera appear to be greatest in deposition centers in morphologic depressions aging of organic matter is promoted by transport age offsets are correlated with organic richness suggesting that formation of organic aggregates is a key process