depositional processes and stratigraphy of fluvially dominated lacustrine deltas mississippi delta plain abstract a geomorphic and stratigraphic investigation of lacustrine delta deposits in the atchafalaya basin louisiana revealed that lacustrine delta formation is rapid and cyclic in nature during the holocene thin coarse grained regionally extensive fluvially dominated lacustrine deltas filled interdistributary basins in the transition zone between the alluvial valley and the marine delta plain of the mississippi river one delta lake fausse pointe delta prograded 6 5 km partially filling the lake and covering more than 29 km2 in area in twelve years depositional processes in lake fausse pointe ranged from suspension settling of mud and organic matter during low sediment input to traction deposition of sand during floods hyperpycnal flow conditions set up by the introdu tion of sediment laden river water into the freshwater lake induced underflows that scoured the lake bottom and deposited upward coarsening lobes the low relief of the mississippi basin a constant large volume of fine grained sediment supply and prevalent fluvial processes have formed fluvially dominated lacustrine deltas that differ sedimentologically and stratigraphically from gilbert type and brackish water lacustrine deltas parallel laminated prodelta mud rippled to cross laminated delta front silty sand and very finegrained to medium grained distributary mouth bar sand are characteristic of rapidly deposited sediment whereas rooted and burrowed sediments signify periods of minimal deposition in a fluvially dominated setting delta geometry and sediment distribution patterns are controlled by river mouth processes basin shape and bathymetry thickest sand accumulations occur in linear dip elongate distributary m uth bar and natural levee lobes that are separated laterally by mud filled channels and interdistributary troughs lacustrine delta deposition is driven by basin subsidence regional downwarping and sediment compaction and the concomitant development of distributary channels in the interdistributary basins numerous lacustrine deltaic wedges each bounded by rooted backswamp clay are preserved multilaterally in atchafalaya basin sediments although lacustrine deltaic deposits constitute much of the basin s sedimentary fill each individual delta sequence records depositional events of only 100 years duration these deltaic deposits represent basin filling aggradational episodes that preceded the formation of marine delta complexes such as the maringouin teche la fourche and atchafalaya deltas of the mississippi river

fluctuations of caspian sea level beyond climatic variations the continued rising mode since about 1978 in the level of the caspian sea cannot be ascribed to a change in the hydrologic balance that is governed solely by runoff precipitation and evaporation such a change fails to explain some of the chemical links k cl rb cl ca cl sr cl and k rb between kara bogaz and caspian sea waters a more realistic model must include a tectono hydrodynamic factor that allows for subsurface addition of saline water to caspian sea and kara bogaz waters the subsurface water component could be akin to the coastal thermal springs in the area but must dissolve some evaporite deposits in the subsurface before addition to the waters of the inland sea a budget calculation gives an estimate of 2 to 9 subterranean addition of saline water to the seawater such an addition could cause a rise in the level of the caspian sea from 63 to as much as 225 cm within the past 20 yr

planform dynamics of the lower mississippi river this paper presents an analysis of the planform behaviour of the lower mississippi river lmr using a series of maps and hydrographic surveys covering the period 1765 1975 data allow analysis at various time and space scales using fixed and statistically defined reaches both before and after extensive channel modification previous research has interpreted planform change in relation to geomorphological or engineering regime type analyses of channel length and width for the lmr as a single system the analysis here is broadly consistent with these approaches but highlights the importance of meander geometry in the form of the radius of curvature width ratio this neglected factor helps resolve paradoxes relating to observed changes in sediment transport and channel stability when viewed over smaller time and space scales analysis of dynamics using fixed reach boundaries reveals a downstream trend in the pattern of planform behaviour which is closely related to the distribution of valley floor deposits and which also reflects neotectonic influences analysis of changes using statistically determined reach boundaries shows that over shorter time scales meander trains are continually formed and modified over a period of approximately 120 years zones of more or less dynamic behaviour thus move through the lmr the research also provides a context for 20th century engineering interventions to the river these have constrained the magnitude of planform adjustment but also altered the kind of response that is now possible in relation to changes in discharge and sediment load and as a consequence of internal feedbacks within the lmr system copyright 2006 john wiley sons ltd

the alleged early palaeolithic artefacts are in reality geofacts a revision of the site of konczyce wielkie 4 in the moravian gate south poland in this paper we show that a site konczyce wielkie 4 sw poland published in jas 2010a by foltyn et al can no longer be accepted as a reliable evidence for the oldest presence of humans in the northern part of carpathians and sudetes mountains matuyama brunhes unfortunately in the light of conducted analysis among others with peacock s method it seems that the lithics from konczyce wielkie appear to be much more similar to geofacts rather than to artefacts as a background for comparison lower paleolithic artefacts from two german sites wallendorf and wangen were used moreover the petrological determination of the finds from konczyce wielkie is also dubious issue foltyn et al suggested a long distance transport of lithics from several sources as it has been demonstrated in the paper local glacial sediments consist of rocks that are analogous to published lithic spectrum finally the geological data shown by foltyn et al seem to be incorrect authors did not take into account the results concerning the regional geology that indicate clearly much younger age of layers dated by foltyn et al 2010a at the beginning of the middle pleistocene

the origin of geothermal waters in morocco multiple isotope tracers for delineating sources of water rock interactions abstract the geochemical and isotopic strontium boron radium oxygen hydrogen variations of geothermal waters from five different regions in morocco were investigated in order to evaluate the sources of solutes and the mechanisms of water rock interaction during 2008 to 2010 twenty two geothermal water samples were collected from the southern central and northern parts of morocco the water samples were analyzed for major and trace elements stable isotopes 18 o 2 h naturally occurring radionuclides 226 ra 228 ra 224 ra and isotopes of dissolved strontium 87 sr 86 sr and boron 11 b the moroccan geothermal waters exhibited a wide range of salinity ranging from 590 to 25 000 mg l with predominance of chloride sodium sulfate calcium and bicarbonate ions integration of the geochemical and isotope data suggests that the geothermal waters in morocco originate from recharge of meteoric water and water rock interactions the predominance of chloride and sodium and the relatively low br cl ratios 3 combined with ca so 4 ratios 1 suggest that halite and sulfate gypsum anhydrite minerals are the major rock sources for mineralization of the geothermal waters the variations of 87 sr 86 sr ratios 0 7076 0 7122 and 11 b 5 3 29 3 were used to distinguish two rock sources 1 dissolution of marine sulfate carbonate rocks with sr isotope composition that correspond to the expected ratios in seawater during time of deposition and 2 non marine sources with higher 87 sr 86 sr and 11 b presumably from interactions with clay minerals and shale rocks the variations of radium isotopes indicate that the alpha recoil of the parent nuclides on the host rocks caused mobilization of the short lived 224 ra and 228 ra to the geochemical waters the low 228 ra 226 ra ratios activity ratios of 0 04 0 14 measured in the geothermal waters mimic the th u ratios in the source rocks which indicate predominance of uranium over thorium our data show that some of the geothermal waters in morocco are characterized by high salinity and in some systems also by elevated radioactivity above international drinking water standards which limits their utilization for agricultural and domestic applications adequate treatment is therefore required to use geothermal waters in morocco as an alternative or additional water source other geothermal waters with low mineralization can be utilized as alternative resource for the agricultural and domestic sectors without any restrictions

architecture and facies distribution of organic clastic lake fills in the fluvio deltaic rhine meuse system the netherlands abstract lakes are prominent features in distal zones of delta plains organic clastic lake fills may form in these lakes which include gyttja and lacustrine deltas understanding of the geometrical properties the facies distribution and the origin of organic clastic lake fills is limited knowledge of their development and composition however will improve our fundamental understanding of both sediment distribution in and evolution of distal delta plains furthermore organic clastic lake fills potentially form connectors in hydrocarbon reservoirs this study aims to describe and explain the characteristics of organic clastic lake fills and thereby to contribute to the understanding of delta evolution especially of distal delta plains a field study conducted in the schoonhoven and angstel vecht areas located in the distal part of the rhine meuse delta the netherlands indicates that organic clastic lake fills developed in peat bounded lakes after an avulsion initiated fluvial sedimentation the characteristics of organic clastic lake fills such as geometry sedimentary facies and sedimentation rates were both qualitatively and quantitatively determined by cross sections geomorphogenetic maps and logs the results show that in the angstel vecht area as much as 30 of the fluvial sand volume is stored in organic clastic lake fills this contrasts to the general notion that overbank deposits do not contain significant portions of sand further the lacustrine setting often results in vertically bounded sediment bodies that include gyttja and underlies clastic depositional facies which show a prominent coarsening upward succession it is concluded that the presence of organic clastic lake fills enlarges the reservoir capacity of ancient fluvio deltaic successions as they contribute to the reservoir volume and also can form connectors between isolated channel belt sand bodies

the co evolution of black sea level and composition through the last deglaciation and its paleoclimatic significance abstract the black sea was an inland lake during the last ice age and its sediments are an excellent potential source of information on eurasian climate change showing linkages between regionally and globally recognized millennial scale climate events of the last deglaciation here we detail changes from the last glacial maximum lgm through the transition to an anoxic marginal sea using isotopic strontium and oxygen and trace element sr ca ratios in carbonate shells which record changing input sources and hydrologic conditions in the basin and surrounding region sr isotope records show two prominent peaks between 18 and 16 ka bp cal reflecting anomalous sedimentation associated with meltwater from disintegrating eurasian ice sheets that brought black sea level to its spill point following a sharp drop in sr isotope ratios back toward glacial values two stages of inorganic calcite precipitation accompanied increasing oxygen isotope ratios and steady sr isotope ratios these calcite peaks are separated by an interval in which the geochemical proxies trend back toward glacial values the observed changes reflect negative water balance and lake level decline during relatively warm periods bolling allerod and preboreal and increasing river input less evaporation resulting in higher lake levels during the intervening cold period the younger dryas a final shift to marine values in sr and oxygen isotope ratios at 9 4 ka bp cal corresponds to connection with the global ocean and marks the onset of sedimentation on the black sea continental shelf this date for the marine incursion is earlier than previously suggested based on the appearance of euryhaline fauna and the onset of sapropel formation in the deep basin

relationship between the sr and o isotope compositions of hydrothermal fluids and the spreading and magma supply rates at oceanic spreading centers we find a first order correlation between the sr and o isotope compositions of hydrothermal fluids and spreading rate at oceanic spreading centers the isotope signatures of hydrothermal fluids at slow spreading ridges are more rock dominated than those at fast spreading ridges implying that they have undergone a greater extent of sr and o exchange with the crust the local spatial and temporal variability in sr and o isotope signatures within individual hydrothermal sites can be attributed to short term variations in the hydrothermal system in response to magmatic or tectonic events phase separation at depth and mixing with seawater in the upwelling zone however these processes cannot explain the systematic global relationship of an increasing rock signature in hydrothermal fluids with decreasing spreading rate a greater extent of sr and o exchange between rocks and the circulating fluids can be achieved by 1 a longer fluid flow pathway through the oceanic lithosphere 2 more fractured rock that exposes a greater reaction area 3 an increased residence time of the fluid due to slower hydrothermal circulation or 4 a combination of all three our preferred interpretation is that fluid flow paths are longer and depths of penetration are likely greater at slow spreading ridges

geochemistry and water dynamics of a medium sized watershed the herault southern france abstract the aim of this study of the herault watershed is to constrain the river groundwater relations with a global geochemical investigation major and trace elements radiogenic isotopes sr pb and stable isotopes oxygen deuterium among the six sampling campaigns in high and low flows this paper focuses on the first one march 1995 sampled during a low flow period for major and trace elements and sr isotopes on both dissolved and particulate loads a companion paper will focus on the river karst relations in a dynamical scheme over a complete hydrological cycle the objective of this paper is to constrain the spatial organisation of the different water reservoirs to show the relations between surficial and groundwaters and to assess the mechanical and chemical weathering in this low flow period the herault main stream successively drains a palaeozoic basement a karstified mesozoic cover and a tertiary and quaternary alluvial plain the different tributaries also drain these lithologies this watershed is also impacted by ancient mining and agricultural activities especially in the southern part major element concentrations generally reflect the drained lithologies the chemistry of the herault main stream is mainly controlled by silicate and carbonate endmembers whereas the karstic springs show clearly a mixture of limestones and dolomitic limestones major elements point out some specific characteristics of some karstic springs and sr isotopes are used to check previous underground circulation hypotheses and sometimes reveal strong connections with overlying surface waters mixing phenomena between the herault river and its tributaries can be quantified in the 87 sr 86 sr vs 87 rb 86 sr diagram based on a simple two component scheme and agree within 10 with the real discharge measurements as in large basins the suspended matter presents more variable and more radiogenic 87 sr 86 sr than the dissolved load due to the more important contribution of silicate particles which are less soluble than carbonate dissolved ca fluxes were estimated to be 36 51 and 38 kg km 2 day 1 in the palaeozoic basement the mesozoic cover and the alluvial plain respectively this implies a chemical erosion estimated to be 20 m year in the palaeozoic basement and 58 m year in the mesozoic cover similar to values calculated for large basins

depth distributions of alkalinity tco2 and δ13ctco2 at seats time series site in the northern south china sea abstract in this study measurements of titration alkalinity ta total dissolved carbon dioxide tco2 and 13c of tco2 13 c tco 2 throughout the water column at the southeast asian time series study seats site were investigated in order to understand better the fundamental processes controlling their vertical distributions in the south china sea scs the linear correlations between ta and salinity in the shallow waters as identified by the mixing line between the surface water and salinity maximum water suggested the predominant control of physical mixing on the variability of ta in contrast tco2 and 13 c tco 2 showed the non conservative behavior in the respective tco2 and 13 c tco 2 vs salinity plot due to the effect of biological production a stoichiometric model further showed that the depth profile of nta ta salinity 35 largely reflects the increase of preformed nta in the shallow waters whereas carbonate dissolution was responsible for the continuous increase of nta in the deep waters a one dimensional diffusion advection model further revealed that the carbonate dissolution could account for 28 of ntco2 tco2 salinity 35 increase in deep waters and the remaining 72 of ntco2 was from organic decomposition calculation of excess ta further showed that it emerged well above the aragonite and calcite saturation depths at 600 and 2500 m respectively indicating that some biologically chemically and physically mediated processes must be involved to provide excess ta into the shallow waters the decrease in 13 c tco 2 with depth primarily resulted from organic decomposition the influence of anthropogenic co2 throughout the water column was assessed with the carbon chemistry and the isotope based approach in this study both methods obtained nearly the same results in which the signal of anthropogenic co2 decreased exponentially with depth and its penetration depth were found to be at 1000 m the inventory of anthropogenic co2 in the water column was estimated to be 16 6 mol c m 2 which was less than that reported in the northwest pacific at the same latitude presumably due to the enhanced upwelling in the scs such an anthropogenic co2 penetration had led to decreases of the saturation levels of aragonite and calcite by 17 and 14 respectively in the surface water and an upward migration of aragonite saturation depth by 100 m since industrial revolution

has the atmospheric supply of dissolved calcite dust to seawater influenced the evolution of marine 87sr 86sr ratios over the past 2 5 million years 1 by analyzing the geochemistry of chinese loess this study examines if the flux of calcite dust from the chinese loess plateau to the north pacific influenced the evolution of marine 87sr 86sr ratios between 2 5 million years ago ma and the present calcite comprises 10 wt of chinese loess and contains 1 104 nmol of sr g with an 87sr 86sr ratio of 0 711 a compilation of literature data suggests that the calcite dust flux emanating from eastern asia has averaged either 2 1013 or 1 1014 g yr since the onset of northern hemisphere cooling 2 5 ma the factor of 5 difference between the estimates reflects discrepancies inherent to methods for determining dust fluxes to seawater at present these discrepancies remain unresolved calcite dust is completely dissolved during transport in the atmosphere and ocean thus the marine sr input from eolian calcite dissolution has averaged either 2 108 or 1 109 mol yr a mass balance model demonstrates that the lower estimate has very little influence on seawater 87sr 86sr ratios whereas the higher estimate has possibly elevated seawater 87sr 86sr ratios by 18 since 2 5 ma when combined with previously reported effects of northern hemisphere glaciation on the riverine sr flux this shift is sufficient to reproduce the entire plio pleistocene marine sr record while more research is required to constrain dust flux estimates these findings suggest that the atmospheric supply of eolian calcite to seawater may represent a previously overlooked process linking climate change to the marine sr cycle

groundwater recharge and salinization in the arid coastal plain aquifer of the wadi watir delta sinai egypt abstract the quaternary coastal plain aquifer down gradient of the wadi watir catchment is the main source of potable groundwater in the arid region of south sinai egypt the scarcity of rainfall over the last decade combined with high groundwater pumping rates have resulted in water quality degradation in the main well field and in wells along the coast understanding the sources of groundwater salinization and amount of average annual recharge is critical for developing sustainable groundwater management strategies for the long term prevention of groundwater quality deterioration a combination of geochemistry conservative ions cl and br and isotopic tracers 87 86 sr 81 br 37 cl in conjunction with groundwater modeling is an effective method to assess and manage groundwater resources in the wadi watir delta aquifers high groundwater salinity including high cl and br concentrations is recorded inland in the deep drilled wells located in the main well field and in wells along the coast the range of cl br ratios for shallow and deep groundwaters in the delta 50 97 fall between the end member values of the recharge water that comes from the up gradient watershed and evaporated seawater of marine origin which is significantly different than the ratio in modern seawater 228 the 87 86 sr and 81 br isotopic values were higher in the recharge water 0 70 723 87 86 sr 81 br 87 86 sr 81 br 37 cl isotopic values were lower in the recharge water 0 48 37 cl 37 cl a three dimensional variable density flow and transport seawat model was developed using groundwater isotopes 87 sr 86 sr 37 cl and 81 br and calibrated using historical records of groundwater level and salinity 18 o was used to normalize the evaporative effect on shallow groundwater salinity for model calibration the model shows how groundwater salinity and hydrologic data can be used in seawat to understand recharge mechanisms estimate groundwater recharge rates and simulate the upwelling of deep saline groundwater and seawater intrusion the model indicates that most of the groundwater recharge occurs near the outlet of the main channel average annual recharge to delta alluvial aquifers for 1982 to 2009 is estimated to be 2 16 10 6 m 3 yr the main factors that control groundwater salinity are overpumping and recharge availability

the transport of osmium and strontium isotopes through a tropical estuary abstract we have determined the concentration and isotopic composition of os and sr in the estuarine waters from the godavari delta in peninsular india additionally we have obtained the concentration and isotopic composition of os and al concentration in selected suspended particulate matter recovered on 0 45 m filters the na k mg and ca concentrations of water samples obtained along salinity gradients from two distributary channels in the delta display a general two component mixing between river and sea water the data also reveal that al behaves non conservatively and is affected by interactions with suspended particulates the 87 sr 86 sr ratio of the riverine end member is 0 716303 and shows a linear decrease with salinity to seawater value and sr isotope systematics indicate that its behavior is conservative in the estuary the 187 os 188 os ratio of the godavari river end member is 1 24 and within error of the average eroding upper continental crust the concentration and isotopic composition of os through the two salinity transects shows that its behavior in the godavari estuary is complex and non conservative by comparing the al os ratios and os isotopes in the waters with those of the suspended particulate we find that both os gains and losses occur in the water column however in one of the distributaries vasishta the os concentration of suspended load increases and that of dissolved load decreases with increasing salinity towards the bay of bengal end member we infer that there is removal of seawater os at higher salinities the estimated mean residence time of os in the oceans is 37 14 2 kyr a comparison of the os concentration of the bay of bengal and the indian ocean waters indicates that the rainout rate of os in bay of bengal is 30 faster than that in the open ocean and suggests that the observed discrepancy between the mean residence time calculated from mass balance considerations and that estimated from the relaxation of the os isotopic ratio in marine record may not be real as the relaxation time experiments likely estimate the residence time for a basin sub basin and not for the entire ocean

geochemical mass balance for lithium boron and strontium in the gulf of papua papua new guinea project tropics a mass balance has been calculated for the elements li b and sr in the gulf of papua from sampling undertaken during 1993 to 1999 parameters measured included fly kikori and purari river inputs of dissolved and particulate phases removal flux to sediment traps at the base of the continental shelf slope and century scale accumulation rates in shelf and slope sediments derived from excess 210pb profiles in sediment cores about 91 of river input li was in particulate form and there was conservative behavior of dissolved li in the salinity gradient of the estuaries li accumulation rate in inner shelf sediments was slightly less than river inputs suggesting that more than 90 of li river inputs were trapped in rapid aluminosilicate mud accumulation zones of the inner shelf 50 m depth li removal rate to sediment traps at the base of the slope at 1000 m water depth was an order of magnitude smaller than the inner shelf sedimentation export of li to deep water coral sea was estimated to be 1 2 108 mol yr 1 and this amount is equivalent to the riverine dissolved li annual supply rate about 66 of river input of b was in the particulate phase and low dissolved b concentrations in freshwater were conservatively mixed with higher concentrations of b in seawater across the salinity gradient removal of b to inner shelf sediments was about 83 of the total river input indicating a small export of b 1 2 108 mol yr 1 to the coral sea about half of the dissolved b input from rivers is sorbed to particles and trapped in inner shelf sediments only 24 of river input of sr was in particulate form and low freshwater concentrations of dissolved sr were conservatively mixed with higher concentrations of sr in seawater across the salinity gradient only 20 of total river inputs of sr were buried in shelf sediments and there was a large export 7 3 108 mol yr 1 of sr off the shelf to the coral sea a sediment core from a rapidly accumulating mud deposition zone of the inner shelf shows twofold sympathetic variations in li b and sr ca supply rates over 200 to 1000 yr time intervals

natural tracer approach to characterize groundwater in the coastal sahel of oualidia morocco a natural tracer approach is applied to study the processes of salinization of the coastal carbonate aquifers in the sahel of oualidia morocco analyses of chloride sulfate bromide strontium and nitrate confirm the existence of seawater intrusion and reveal an evaporitic contamination and an anthropogenic pollution affecting both surficial and deep aquifers the evaporitic contamination is explained by the washing away of the gypsum marl of the basement of the limestone of dridrate and also by the rise of evaporitic waters from deep gypsum formations anthropogenic pollution is induced by excessive use of fertilizers in agriculture enrichment by chloride originating from the surface could also be invoked on the other hand to explain chloride content in the surficial aquifer the possible existence of connections between the layers of the aquifer system can be demonstrated by this study

high fluxes of radium and barium from the mouth of the ganges brahmaputra river during low river discharge suggest a large groundwater source the annual flux of sediment from the ganges brahmaputra river is among the highest in the world the desorption of226ra and ba from this sediment produces a major point source of226ra and ba input to the ocean highest226ra and ba fluxes are expected to occur during high river flow june september when most of the sediment is discharged surprisingly during low discharge of the ganges brahmaputra river fluxes of226ra and ba to the northern bay of bengal are comparable to expected river derived fluxes during peak river discharge a large non riverine source of ra and ba is required to explain the high fluxes during low river discharge i suggest that this source is submarine discharge of groundwater containing high concentrations of226ra and ba total annual fluxes of226ra and ba to the ocean from this system are significantly greater than estimated previously

reply to comment by d nývlt on development of the topography controlled upper odra ice lobe scandinavian ice sheet in the fore mountain area of southern poland during the saalian glaciation

sediment deposition and sources into a mississippi river floodplain lake catahoula lake louisiana floodplain lakes are important wetlands on many lowland floodplains of the world but depressional floodplain lakes are rare in the mississippi river alluvial valley one of the largest is catahoula lake which has existed with seasonally fluctuating water levels for several thousand years but is now in an increasingly hydrologically altered floodplain woody vegetation has been encroaching into the lake bed and the rate of this expansion has increased since major human hydrologic modifications such as channelization levee construction and dredging for improvement of navigation but it remains unknown what role those modifications may have played in altering lake sedimentation processes profiles of thirteen 137cs sediment cores indicate sedimentation has been about 0 26 cm y 1 over the past 60 years and has been near this rate since land use changes began about 200 years ago 210pb and 14c in tedford 2009 carbon sequestration was low 10 4 g m 2 y 1 likely because annual drying promotes mineralization and export elemental composition high zr and ti and low ca and k and low ph of recent 60 y or surface sediments suggest gulf coastal plain origin but below the recent sediment deposits 51 of sediment profiles showed influence of mississippi river alluvium rich in base cations such as k ca2 and mg2 the recent shift to dominance of coastal plain sediments on the lake bed surface suggests hydrologic modification has disconnected the lake from sediment bearing flows from the mississippi river compared to its condition prior to hydrologic alterations that intensified in the 1930s catahoula lake is about 15 cm shallower and surficial sediments are more acidic although these results are not sufficient to attribute ecological changes directly to sedimentological changes it is likely the altered sedimentary and hydrologic environment is contributing to the increased dominance of woody vegetation

geographic and hydrodynamic characteristics of shallow coastal lagoons abstract coastal lagoons can be conveniently separated based on geomorphology into leaky restricted or choked systems this subdivision orders coastal lagoons hydrodynamically according to water exchange with the coastal ocean leaky systems have the shortest turnover time restricted lagoons have a longer turnover time and choked lagoons have the longest turnover time in leaky coastal lagoons oscillating tidal currents account for most of the flow variance and mask residual currents due to wind and freshwater induced density gradients in restricted lagoons tides winds and freshwater runoff drive components of the circulation winds are usually dominant in causing circulation and mixing in choked lagoons and water exchange with the coastal ocean largely depends on the hydrologic cycle coastal lagoons are usually well mixed but can exhibit significant horizontal gradients due to freshwater runoff and vertical gradients due to solar radiation or surface cooling in general river inflow and heat balance induce stratification in coastal lagoons whereas winds and tides cause mixing coastal lagoons usually trap inorganic sediment and organic matter thus serving as material sinks on a geologic time scale they are short lived landscape features with an existence intrinsically linked to filtering efficiency and relative sea level change as a result of glacioeustatic cycles and local tectonic activity

analysis of the seismic origin of landslides examples from the new madrid seismic zone by analyzing two landslides in the new madrid seismic zone we develop an approach for judging if a landslide or group of landslides of unknown origin was more likely to have formed as a result of earthquake shaking or in aseismic conditions the two landslides analyzed are representative of two groups of land slides that previous research on the geomorphology and regional distribution of landslides in this region indicates may have been triggered by the 1811 1812 new madrid earthquakes slope stability models of aseismic conditions show that neither landslide is likely to have formed aseismically even in unrealistically high ground water conditions dynamic stability analysis using newmark s method shows that both slides probably would have experienced large inertial displacements during earthquake shaking similar to that which occurred in 1811 1812 these displacements are large enough that catastrophic failure is highly probable thus the stability analyses are consistent with other lines of evidence that these landslides formed as a result of strong earthquake shaking during the 1811 1812 earthquakes our analysis yields a general relationship between newmark landslide displacement earthquake shaking intensity and the critical acceleration of a landslide using this relationship we estimate the minimum shaking intensities required to trigger the types of landslides studied an mb 5 8 or m 5 9 earthquake is the lower bound threshold at zero epicentral distance that could trigger catastrophic movement of typical block slides in the new madrid seismic zone for earth flows mb 5 4 or m 5 3 is the threshold earthquake

high precision radiogenic strontium isotope measurements of the modern and glacial ocean limits on glacial interglacial variations in continental weathering existing strontium radiogenic isotope 87sr 86sr measurements for foraminifera over quaternary glacial interglacial climate cycles provide no evidence for variations in the isotope composition of seawater at the 9 13 ppm level of precision however modelling suggests that even within this level of uncertainty significant up to 30 variations in chemical weathering of the continents are permitted accounting for the longer term rise in 87sr 86sr over the quaternary and the apparent imbalance of sr in the oceans at the present day this study presents very high precision 87sr 86sr isotope data for modern seawater from each of the major oceans and a glacial interglacial seawater record preserved by planktic foraminifera from ocean drilling program odp site 758 in the north east indian ocean strontium isotope 87sr 86sr measurements for modern seawater from the atlantic pacific and indian oceans are indistinguishable from one another 87sr 86sr 0 7091792 0 0000021 n 17 at the level of precision obtained in this study 4 9 ppm 2 this observation is consistent with the very long residence time of sr in seawater and underpins the utility of this element for high precision isotope stratigraphy the 87sr 86sr seawater record preserved by planktic foraminifera shows no resolvable glacial interglacial variation 87sr 86sr 0 7091784 0 0000035 n 10 and limits the response of seawater to variations in the chemical weathering flux and or composition to 4 9 ppm or less calculations suggest that a variation of 12 around the steady state weathering flux can be accommodated by the uncertainties obtained here the new data cannot accommodate a short term weathering pulse during de glaciation although a more a diffuse weathering pulse accompanying protracted ice retreat is permissible however these results still indicate that modern weathering fluxes are potentially higher than average over the quaternary and such variations through glacial cycles can also account for the longer term rise in 87sr 86sr over this time interval the very high precision measurements made for the marine 87sr 86sr record in this study place clear limits on the magnitude and timing of changes in the chemical weathering flux during glacial interglacial cycles further constraints must be sought from even higher precision measurement or elements with shorter residence times in the ocean such as osmium os that have the capacity to respond to short term variations in input

dynamically and observationally constrained estimates of water mass distributions and ages in the global ocean abstracta data constrained ocean circulation model is used to characterize the distribution of water masses and their ages in the global ocean the model is constrained by the time averaged temperature salinity and radiocarbon distributions in the ocean as well as independent estimates of the mean sea surface height and sea surface heat and freshwater fluxes the data constrained model suggests that the interior ocean is ventilated primarily by water masses forming in the southern ocean southern ocean waters including those waters forming in the antarctic and subantarctic regions make up about 55 of the interior ocean volume and an even larger percentage of the deep ocean volume in the deep north pacific the ratio of southern ocean to north atlantic waters is almost 3 1 approximately 65 of interior ocean waters make first contact with the atmosphere in the southern ocean further emphasizing the central role played by the southern ocean in the regulation of the earth s climate results of the a

strontium and oxygen isotopic composition of east greenland rivers and surface waters implication for palaeoenvironmental interpretation abstract isotopic composition of strontium and oxygen and strontium concentrations from 4 hydrographic sites in scoresby sund fjord and 6 rivers draining the adjacent jameson land have been investigated schuchert flod the major river on jameson land erodes a large celestite srso4 deposit dissolved sr in schuchert flod has 87sr 86sr 0 7137 and is responsible for most of the continental sr flux to the fjord the sr isotope data have been used to construct a mixing model for the surface water in scoresby sund fjord salinity s and sr concentrations csr of brackish water from the fjord show conservative mixing between river water and seawater results of the 87sr 86sr salinity mixing model of seawater and fresh water were used to interpret the isotopic composition of sr 87sr 86sr and oxygen 18oc of recent and interglacial eemian 120 ka shallow water bivalve shells from the coast of jameson land because of the high csr in some of the rivers draining jameson land a correlation exists between 87sr 86sr and 18oc of recent and interglacial shallow water bivalve shells from the coast of jameson land higher than seawater 87sr 86sr values in shells from the langelandselv interglaciation can be explained only if the shells were formed close to a sr rich fresh water source which is not present in the langelandselv area today these results suggest that there was a different river and drainage system on the jameson land peninsula during the last interglacial the 87sr 86sr values indicate that shell formation took place in waters with salinities between 20 and 31 in a fjord with less glacial melt water than seen today

seawater paleotemperature and paleosalinity evolution in neritic environments of the mediterranean margin insights from isotope analysis of bivalve shells the first step of ice sheet build up on antarctica at the eocene oligocene boundary was followed by a phase of climate instability culminating during the miocene with a warming event called the middle miocene climate optimum mmco that ended with a marked cooling phase identified as the middle miocene climate transition mmct while numerous benthic foraminifera 18o and mg ca data have been used to capture the global climate evolution during this interval of climate and ice sheet instability geochemical records from shallow water carbonates still remain scarce yet such records are crucial to capture the diversity of regional environmental responses to global climate changes and thus to better understand the behavior of our climate system during this critical interval in this work we test the potential of a multi proxy approach 18o clumped isotope 47 strontium isotopes 87sr 86sr applied to bivalves recovered from the liguro provencal basin and rhodano provencal basin northwestern of the mediterranean sea to reconstruct the evolution of shallow seawater temperature and salinity in this region over the latest oligocene to middle miocene interval 10 myrs our results highlight a local cooling in the northwestern mediterranean sea during the mmco that contrasts with the warming observed in other regions with seawater temperatures inferred from 47 analyses in the 13 18 c range these cool seawater temperatures recorded in the studied region during the mmco are much cooler than those recorded in the open oceans but are in agreement with the proliferation of bryozoan observed in the castillon du gard area during this interval low bivalve 18o values 3 24 in average are recorded during this episode are interpreted to reflect enhanced freshwater inputs lowering local salinity and seawater 18o such enhanced freshwater inputs point to a phase of enhanced hydrological cycle in the studied region possibly linked to the global mid miocene warming event bivalve 87sr 86sr data mostly fall within the global seawater sr isotope reference curve but remain compatible with enhanced freshwater inputs during the aquitanian and during the langhian as these inputs were probably not important enough to induce a large departure from the seawater curve at a regional scale

discrepancy between sr isotope and biostratigraphic datings of the upper middle and upper miocene successions eastern north sea basin denmark abstract one hundred and fifty six 87sr 86sr analyses have been performed on 129 samples from 18 outcrops and boreholes in oligocene miocene deposits from jylland denmark these analyses were mainly conducted on mollusc shells but foraminiferal tests bolboforma and one shark tooth were also analysed the main purpose of the study is to compare the ages of the danish succession suggested by the biostratigraphic zonation on dinoflagellate cysts dybkjaer and piasecki 2010 with the ages based on analyses of the 87sr 86sr composition of marine calcareous fossils in the same succession analyses of samples from the danish brejning vejle fjord klintinghoved arnum odderup hodde ornhoj and gram formations gave ages between 25 7 my late oligocene and 10 3 my late miocene the sr isotope ages from the lower part of the succession i e brejning to odderup formations agree with the age estimates based on biostratigraphy however the 87sr 86sr ratios of fossil carbonates from the middle upper miocene hodde to gram succession consistently indicate ages older than those recorded by biostratigraphy post depositional processes as an explanation for this offset are inconsistent with good preservation of shell material and little reworking a palaeoenvironmental cause for the observed mismatch is therefore indicated search for geological events that could explain the older ages obtained by sr isotope compositions have not led to any conclusions and we had recognised the same problem in earlier reports and communications we conclude that this is a general and possibly global middle late miocene problem that has to be reconsidered and explained geologically

controls over the strontium isotope composition of river water abstract strontium concentrations and isotope ratios have been measured in river and ground waters from the ganges orinoco and amazon river basins when compared with major element concentrations the data set has allowed a detailed examination of the controls over the strontium isotope systematics of riverine input to the oceans in the following environments 1 1 typical drainage basins containing limestones evaporites shales and alumino silicate metamorphic and igneous rocks 2 2 shield terrains containing no chemical or biogenic sediments and 3 3 the floodplains that constitute the largest areas of many large rivers the strontium concentration and isotope composition of river waters are largely defined by mixing of strontium derived from limestones and evaporites with strontium derived from silicate rocks the strontium isotope composition of the limestone endmember generally lies within the phanerozoic seawater range which buffers the 87 sr 86 sr ratios of major rivers a major exception is provided by the rivers draining the himalayas where widescale regional metamorphism appears to have led to an enrichment in limestones of radiogenic strontium derived from coexisting silicate rocks the strontium isotope systematics of rivers draining shield areas are controlled by the intense transportlimited nature of the weathering reactions and thereby limits variations in the strontium flux from these terrains floodplains are only a minor source of dissolved strontium to river waters and precipitation of soil salts in some floodplains can reduce the riverine flux of dissolved strontium to the oceans the most effective mechanisms for altering the isotope ratio and flux of riverine strontium to the oceans are increased glaciation and large scale regional metamorphism of the type produced during continental collision both mechanisms provide a means for increasing the 87 sr 86 sr ratio of the global riverine flux

origin of groundwater salinity current seawater vs saline deep water in a coastal karst aquifer based on sr and cl isotopes case study of the la clape massif southern france origin of groundwater salinity current seawater vs saline deep water in a coastal karst aquifer based on sr and cl isotopes case study of the la clape massif southern france a b s t r a c t in this study a typical coastal karst aquifer developed in lower cretaceous limestones on the western med iterranean seashore la clape massif southern france was investigated a combination of geochemical and isotopic approaches was used to investigate the origin of salinity in the aquifer water samples were collected between 2009 and 2011 three groundwater groups a b and c were identified based on the hydrogeological setting and on the cl a concentrations average and maximum cl a concentrations in the recharge waters were calculated cl ref and cl ref max to be 0 51 and 2 85 mmol l respectively group a includes spring waters with cl a concentrations that are within the same order of magnitude as the cl ref concentration group b includes groundwater with cl a concentrations that range between the cl ref and cl ref max concentrations group c includes brackish groundwater with cl a concentrations that are significantly greater than the cl ref max concentration overall the chemistry of the la clape groundwater evolves from dominantly ca hco 3 to nacl type on binary diagrams of the major ions vs cl most of the la clape waters plot along mixing lines the mixing end members include spring waters and a saline component current seawater or fossil saline water based on the br cl molar ratio the hypothesis of halite dissolution from triassic evaporites is rejected to explain the origin of salinity in the brackish groundwater groundwaters display 87 sr 86 sr ratios intermediate between those of the limestone aquifer matrix and current mediterranean seawater on a sr mixing diagram most of the la clape waters plot on a mixing line the end members include the la clape spring waters and saline waters which are similar to the deep geo thermal waters that were identified at the nearby balaruc site the 36 cl cl ratios of a few groundwater samples from group c are in agreement with the mixing hypothesis of local recharge water with deep saline water at secular equilibrium within a carbonate matrix finally phreeqc modelling was run based on cal cite dissolution in an open system prior to mixing with the balaruc type saline waters modelled data are consistent with the observed data that were obtained from the group c groundwater based on several trac ers i e concentrations and isotopic compositions of cl and sr calculated ratios of deep saline water in the mixture are coherent and range from 3 to 16 and 0 to 3 for groundwater of groups c and b respectively with regard to the la clape karst aquifer the extension of a lithospheric fault in the study area may favour the rise of deep saline water such rises occur at the nearby geothermal balaruc site along another lithospheric fault at the regional scale several coastal karst aquifers are located along the gulf of lion and occur in mezosoic limestones of similar ages the 87 sr 86 sr ratios of these aquifers tend toward values of 0 708557 which suggests a general mixing process of shallow karst waters with deep saline fossil waters the occurrence of these fossil saline waters may be related to the introduction of seawater during and after the flandrian transgression when the highly karstified massifs invaded by seawater formed islands and peninsulas along the mediterranean coast

low temperature alteration of basalt by interstitial seawater mururoa french polynesia chemical and isotopic analysis of interstitial fluids and secondary phases in two drill cores from the volcanic pile of the mururoa atoll french polynesia permits documentation of the lowtemperature alteration by seawater of basalt and secondary minerals as a function of rock water ratio r w up to 110 g l as r w increases in this system up to 70 g l the interstitial waters exhibit an almost total removal of mg and k a net decrease of ph and eh a marked enrichment in ca sr and si and depletion of 18o and d with further increases in r w above 70 g l a reversal of mg ca exchange is observed mg accumulates in the fluid while ca is removed in addition the enrichment of 18o and d is also observed in the fluids at these high r w these chemical and isotopic reversals are shown to result from the transformation of early precipitated mg rich saponite into ca na saponite chemical and isotopic reactions take place at two separate solid solution interfaces 1 1 an interface at the surface of the fresh basalt that leads to the formation of a hydrated amorphous layer which progressively crystallizes into clay and 2 2 a second interface between the interstitial bulk fluid and the resultant clay layer consequently geochemical codes which fail to account for both aqueous diffusion in altered layers and the existence of multiple reaction interfaces cannot accurately describe alteration at high rock water ratios

paleoceanography of the late cretaceous maastrichtian western interior seaway of north america evidence from sr and o isotopes abstract well preserved fossils of the late cretaceous western interior seaway wis of north america have been analyzed for sr concentration and sr and o isotopes in order to decipher paleosalinities and paleotemperatures the samples are from four biofacies within the seaway late maastrichtian offshore interior pierre shale nearshore interior fox hills formation brackish reduced salinity fox hills formation and freshwater hell creek formation samples were also obtained from the severn formation of maryland considered to be representative of the open ocean all biofacies except the freshwater are demonstrably within the jeletzkytes nebrascensis ammonite zone 87 sr 86 sr ratios show significant and systematic decreases from marine mean 1 s d 0 707839 0 000024 to brackish facies mean 1 s d 0 707677 0 000036 consistent with dilution by freshwater with a lower 87 sr 86 sr ratio than seawater such variation disallows using the 87 sr 86 sr ratios of fossil shell material to assign ages to fossils from the late cretaceous wis without knowledge of the salinity in which the organism grew the sr isotope ratios for scaphitid ammonites within a single biofacies are similar to each other and different from those for scaphites in other biofacies implying that these organisms are restricted in their distribution during life the 87 sr 86 sr values of freshwater unionid mussels range widely and are not compatible with the freshwater endmember 87 sr 86 sr ratio required by the trend in 87 sr 86 sr vs biofacies established from the other samples paleosalinities for the biofacies are estimated to range from 35 in the open marine to a minimum of 20 in the brackish based on the presence of cephalopods in all four facies and the known salinity tolerance of modern cephalopods producing reasonable 87 sr 86 sr values for the freshwater endmember of a 87 sr 86 sr vs 1 sr plot requires a sr concentration 0 2 0 5 that of seawater for the dominant freshwater input to the wis such high sr concentrations relative to seawater are not observed in modern rivers and we suggest that the brackish environment in the wis arose through the mixing of freshwater and seawater in a nearshore aquifer system reactions of the solution with aquifer solids in this subterranean estuary moore mar chem 65 1999 111 125 produced brackish water with the sr concentration and isotopic composition recorded in the brackish biofacies 18 o values of the fossils show decreases from the marine to brackish biofacies consistent with increasing temperatures from 13 to 23 c or if temperatures were relatively constant to a decrease in the 18 o of the water in which the shell formed the latter interpretation is consistent with less than fully marine salinities in the nearshore biofacies but both changes in temperature and the isotopic composition of the water may have occurred in this environment

processes affecting groundwater chemistry in a zone of saline intrusion into an urban sandstone aquifer abstract samples have been collected from inflows into railway tunnels in the triassic sandstone aquifer beneath liverpool and the mersey estuary england u k these provide a profile through a saline freshwater mixing zone analyses were made of major anions and cations 34s and 18o in so4 13c in dissolved inorganic c and 87sr 86sr the data demonstrate that the presence of a low permeability fault exerts a strong control on the local groundwater chemistry on the estuary side of the fault groundwater chemistry is dominated by mixing of intruding estuary water which is modified by so4 reduction and calcite dissolution with fresh groundwater the environment of so4 reduction in the tidal estuary is one of repeated reduction and re oxidation of s in an open system and has resulted in virtually no change in s isotopic composition but an enrichment in residual so4 18o of 1 5 groundwater chemistry on the landward side of the fault is primarily the result of recharge in an urban environment there is also evidence that saline water has been present in this region of the aquifer in the past and that this has now been flushed by fresh groundwaters this saline water was either transported along the landward side of the fault from nearer the estuary or more probably transmitted across the fault both mechanisms would have been driven by large landward head gradients caused by heavy industrial abstraction earlier this century this has produced a zone of groundwaters depleted in ca and radiogenic sr and enriched in na as a result of ion exchange between the fresh groundwaters and the aquifer previously occupied by more saline water sulphur isotopic composition however shows no variation since so4 does not undergo significant ion exchange a tracer test from a borehole to the tunnels showed multiple breakthroughs to some locations indicating a number of different flow paths through the aquifer the maximum flow velocity recorded in this test was 140 m d suggesting flow along fractures

occurrence and mobilization of radium in fresh to saline coastal groundwater inferred from geochemical and isotopic tracers sr s o h ra rn abstract salinization in groundwater systems can induce water rock interaction including the release of naturally occurring trace elements of health significance such as radium ra with possible implications for the usability of water resources in addition to the increase of dissolved solids tds concentrations in general radium mobility is limited by chemical removal mechanisms including adsorption onto clays and or mn and fe oxides exchange processes and coprecipitation with secondary barite in order to examine the effect of aquifer salinity gradients on the distribution of naturally occurring ra in fresh to saline groundwater and the relationship to water rock interaction and ra removal mechanisms two contrasting systems were investigated the shallow unconfined coastal aquifer in agadir southwestern morocco and the confined cretaceous cape fear and pliocene yorktown aquifers of the atlantic coastal plain north carolina usa geochemical and isotopic indicators of salinity sources e g cation ratios 18o 2h br cl 34 s so 4 2 18 o so 4 2 were used to identify the relative contributions of seawater and other saline waters and subsequent geochemical modification by water rock interaction radium activities 224ra 226ra 228ra radon 222 alkaline earth metal mg ca sr ba concentrations and ratios and 87sr 86sr ratios were analyzed to identify water rock interaction processes affecting alkaline earth metals including ra the morocco coastal aquifer is generally oxic exhibits a range of salinity and water types cl 163 2120 mg l median 932 mg l and exhibits ca na ratios above the seawater value typical of monovalent divalent cation exchange base exchange reactions in coastal aquifers in contrast the atlantic coastal plain aquifers are anoxic sulfate reducing cover a wider salinity range cl 5 9890 mg l median 800 mg l representing a transition between na hco 3 and na cl waters and exhibit ca na ratios below that of modern seawater typical of reverse base exchange reactions possible salinity sources in the morocco coastal aquifer include seawater intrusion mesozoic evaporites other natural saline waters and or wastewater whereas the atlantic coastal plain is primarily affected by old seawater present in the aquifer system radium activities are generally low and vary significantly within each aquifer for example 226ra ranges from 1 8 27 7 mbq l in the morocco coastal aquifer median 8 1 mbq l and 1 9 214 mbq l in the atlantic coastal plain median 18 9 mbq l the highest ra activities were observed in the most saline wells sampled in the atlantic coastal plain at total dissolved solids tds concentrations above an apparent threshold of 5000 mg l radium activities increase in a generally linear fashion with salinity in the atlantic coastal plain broadly comparable to previous studies indicating a threshold range of 3000 10 000 mg l at lower tds concentrations water rock interaction processes that vary with local aquifer conditions appear to control ra distribution rather than merely salinity in the morocco coastal aquifer adsorption of ra and coprecipitation with secondary barite are apparently favorable to control ra levels in groundwater radium removal in the anoxic atlantic coastal plain aquifers appears to be associated with adsorption and or exchange processes with the additional possibility of barite precipitation in the cape fear aquifer indicated by barite saturation overall the locally variable factors that can control ra sources and mobility in fresh to brackish groundwater at near neutral ph include variation in solid phase radioactivity redox state affecting adsorption sites availability of competing divalent cations and barite saturation

development of the topography controlled upper odra ice lobe scandinavian ice sheet in the fore mountain area of southern poland during the saalian glaciation abstract during the saalian drenthe glaciation the upper odra ice lobe constituted the most southern part of the scandinavian ice sheet in central europe the lobe was situated in an area with varied topography in the foreland of a mountain range the ice lobe had a complex form because it was subdivided into several smaller sublobes the primary factors that controlled the lobe were investigated it was found that the ice lobe development depended largely on the topography but the lithology of the ice sheet substratum was also highly important the topography controlled the main movement direction of the ice and caused a concentration of the ice flow in the axial part of the silesian lowland between subglacial morphological barriers which thereby formed a corridor of relatively fast flowing ice which was probably streaming and which supplied the lobe the topography also determined the ice flow within the lobe which strongly matched the valley system the presence of sediments with relatively low permeability at the base of the lobe the quaternary deposits are underlain by neogene clays caused high pore water pressure in the subglacial zone and triggered the basal movement of the ice sheet which promoted a rapid flow of the ice and favoured the development of the lobe the basal tills deposited from the active and passive ice and extant till patches without a fluvioglacial cover atop some parts of the studied area indicate spatially varying ice flow dynamics especially in the later stage of glaciation certain parts of the lobe underwent stagnation while in other parts the ice was probably still active the varied behaviour of the ice within the lobe was determined primarily by the topography and lithology of the substratum which produced spatially varied marginal compression and basal friction a model of the development of the lobe is proposed

sources of ree in sediment cores from the rainbow vent site 36 14 n mar a geochemical investigation was carried out on two sediment cores collected at 2 and 5 km from the rainbow hydrothermal vent site bulk sediment compositions indicate that these cores record clear enrichments in fe cu mn v p and as from hydrothermal plume fallout cave et al 2002 cave r r german c r thomson j nesbitt r w 2002 fluxes to sediments underlying the rainbow hydrothermal plume at 36 14 n on the mid atlantic ridge geochim cosmochim acta 66 11 1905 1923 sequential dissolution of the bulk sediments has been used to discriminate between a leach biogenic and oxy hydroxide component and a residual phase detrital and sulphide sulphate fractions major element data al fe ti mn mg ca si and index reveal that the hydrothermal input as recorded in the leach phase is much stronger than apparent from bulk sediment analyses alone ree patterns for the leach phase record contributions from both biogenic carbonate mimicking seawater ree patterns and hydrothermal oxy hydroxides with the latter exhibiting positive eu anomalies hydrothermal derived and negative ce anomalies seawater derived based on major element and ree data the residue contains contributions from aeolian dust input local morb material and a hydrothermal component ternary ree mixing calculations indicate that most of the ree within the residual fraction 80 is derived from hydrothermal material while detrital contributions to the ree budget as deep sea clay and volcanic debris are

interaction of dense shelf water cascading and open sea convection in the northwestern mediterranean during winter 2012 the winter of 2012 experienced peculiar atmospheric conditions that triggered a massive formation of dense water on the continental shelf and in the deep basin of the gulf of lions multiplatforms observations enabled a synoptic view of dense water formation and spreading at basin scale five months after its formation the dense water of coastal origin created a distinct bottom layer up to a few hundreds of meters thick over the central part of the nw mediterranean basin which was overlaid by a layer of newly formed deep water produced by open sea convection these new observations highlight the role of intense episodes of both dense shelf water cascading and open sea convection to the progressive modification of the nw mediterranean deep waters

abu dhabi sabkha persian gulf revisited application of strontium isotopes to test an early dolomitization model a study of brines and diagenetically altered minerals from coastal sabkha of abu dhabi persian gulf was undertaken to test the flood recharge evaporative pumping model for early dolomitization using strontium isotopes as a tracer the sup 87 sr sup 86 sr ratio of the sabkha brines defines a pattern of both horizontal and vertical mixing of coastal seawater and continental ground water consistent with a previously proposed model the sup 87 sr sup 86 sr ratio of the diagenetic dolomites indicates early dolomitization by marine recharge waters the sup 87 sr sup 86 sr ratio of gypsum from the dolomitization area 1 4 to 4 4 km from high tide mark and seaward reflects precipitation from marine brines but more landward 6 to 9 km gypsum and anhydrite record a continental signal in the minerals suggests a paragenetic evaporative sequence dolomite yields gypsum yields anhydrite the dolomitizing fluid is evaporated seawater that recharges the sabkha aquifer during supratidal flooding and is afterward pumped upward through the saturated zone by evaporative processes

sulfate dependent anaerobic oxidation of methane at a highly dynamic bubbling site in the eastern sea of marmara cinarcik basin abstract during the marsitecruise expedition in november 2014 on board the rv pourquoi pas multidisciplinary sampling was carried out with the rov victor 6000 in order to investigate biogeochemical processes taking place at cold seep environments in the sea of marmara pore water bottom water sediment and authigenic carbonate samples were collected from two short push cores mrs dv5 pc04 8 cm mrs dv5 pc01 12 5 cm at an active methane bubbling site in the southeastern part of the cinarcik basin sulfate sulfur and oxygen isotope data as well as sulfide isotope data indicate that sulfate dependent anaerobic oxidation of methane is the dominant process in the sediments this is confirmed by archaeal lipids diagnostic for anaerobic methane oxidizers detected with strong 13c depletions the available data even allows to distinguish the dominant aom assemblages specific lipid patterns are consistent with a dominance of anme 2 archaea within the microbial community abundant authigenic carbonates mostly aragonite found at all depths show a narrow range in 13c values between 27 69 and 33 40 the carbon isotopic composition of the dissolved inorganic carbon as well as strontium and calcium isotopes confirm that the current reaction zone sulfate methane transition zone starts at the bottom of the core all shallower carbonates are witnesses of paleo seepage activity u th dating of four pure aragonite samples show the short time span that is preserved in core mrs dv5 pc01 235 60 yr b p two major earthquakes of 1766 ce and 1754 ce in the cinarcik basin might potentially have triggered the increased seepage of methane at this location

morphology of fluvial levee series along a river under human influence maros river hungary abstract the development and morphometry of fluvial levees reflect the connection between channel and overbank processes which can be altered by various human activities the aims of this study are to investigate the morphology and spatial characteristics of fluvial levees and evaluate the role of some local and catchment scale human activities on their medium term 150 years development this study applies lidar data along a 53 km long reach of the maros river in hungary six fluvial levee types are identified based on the beginning and end of their evolution these levee types were generated by local nineteenth century channel regulation works cutoffs and mid twentieth century channel narrowing which was caused by gravel mining and water impoundment in the upstream sections however other human activities also influenced the development of active fluvial levees because their horizontal evolution could have been limited by embanked flood protection levees or the widening of low lying floodplain benches that were generated by channel narrowing additionally revetment constructions influenced their vertical parameters as higher fluvial levees developed along the fixed banks generally the older active fluvial levees are wider while the younger active levees are narrower with steeper slopes but not always lower on the low lying floodplain levels benches the youngest fluvial levees evolved quite rapidly and consist of coarser material currently only 9 8 to 38 year return period floods could cover the fluvial levees contributing to their evolution this fact and the development of fluvial levee series with two three members reflect a gradual decoupling of the channel from the floodplain

the fidelity of oxygen and strontium isotope values from shallow shelf settings implications for temperature and age reconstructions abstract the oxygen and strontium isotopic ratios of marine carbonates are widely employed to derive paleotemperature and age respectively while open ocean samples are the standard source for these measures shelf settings can also provide detailed records however the implementation of shelf data for these purposes has been hindered by the perception that local environmental conditions such as freshwater influx confound regional and global signals here we directly evaluate this concern by assessing the spatial variability in the isotopic composition of biogenic carbonate precipitated along the depositional strike of an inner shelf environment data are derived from mollusc shells collected from a stratigraphically restricted transgressive unit in the early eocene 55 ma of the us gulf coastal plain gcp lithofacies and fossil assemblages suggest that an estuary was present in the westernmost study region whereas more typically marine facies predominated elsewhere isotopic composition varies predictably with paleoenvironmental setting shells from the estuary have 18o values and 87sr 86sr ratios that reflect high freshwater input specimens in the eastern gcp however from within and between outcrops separated by up to 400 km all yield similar results serial microsampling reveals congruence not only in mean 18o values but also in winter and summer extremes estimated paleotemperatures mean annual temperature of 26 c agree well with proxy and model evidence for the early eocene and the gcp and 87sr 86sr ratios are consistent with the established early eocene seawater ratio the fidelity of isotopic values relative to environment indicates that shallow shelf records have much to contribute to studies of ancient climate and ocean chemistry

quantifying the impact of riverine particulate dissolution in seawater on ocean chemistry the quantification of the sources and sinks of elements to the oceans forms the basis of our understanding of global geochemical cycles and the chemical evolution of the earth s surface there is however a large imbalance in the current best estimates of the global fluxes to the oceans for many elements in the case of strontium sr balancing the input from rivers would require a much greater mantle derived component than is possible from hydrothermal water flux estimates at mid ocean ridges current estimates of riverine fluxes are based entirely on measurements of dissolved metal concentrations and neglect the impact of riverine particulate dissolution in seawater here we present 87sr 86sr isotope data from an icelandic estuary which demonstrate rapid sr release from the riverine particulates we calculate that this sr release is 1 1 7 5 times greater than the corresponding dissolved riverine flux if such behaviour is typical of volcanic particulates worldwide this release could account for 6 45 of the perceived marine sr budget imbalance with continued element release over longer timescales further reducing the deficit similar release from particulate material will greatly affect the marine budgets of many other elements changing our understanding of coastal productivity and anthropogenic effects such as soil erosion and the damming of rivers

the sedimentary texture structure and framework of lacustrine deltaic deposits in the atchafalaya basin abstract the lacustrine deltaic deposits in six mile lake have been defined sedimentologically in terms of sedimentary texture structure and framework data sources include color infrared photography vibracore samples and field studies six mile lake is interconnected with grand lake on its northern end and both lakes are interdistributary lakes in south central louisiana the lakes lie between the former teche mississippi river meander belt and the la fourche modern mississippi river meander belt lacustrine deltaic deposition has been accelerated since grand and six mile lakes were included in the atchafalaya basin floodway in 1928 the sedimentary sequence of the deltaic deposits in six mile lake is built on approximately 120 to 160 feet of early holocene backswamp deposits sedimentological analyses describe a lacustrine sub environment with a lacustrine and fluvio lacustrine facies and a lacustrine deltaic sub environment with a subaqueous and subaerial bar facies a purpose sedimentaological model was designed from sedimentological data and field studies the model includes four phases of development of the lacustrine deltaic deposits of grand and six mile lake the first phase is the southward translation of subaqueous bars over quiet water lacustrine deposits and fluvio lacustrine deposits in phase two vertical and lateral accretion deposits of fine sand silt and clay increase the size of the subaqueous bar and it becomes subaerial and stabilized in the lake basin natural levee swales develop on the subaerial bars along with dense growths of vegetation in phase three subaerial bars merge and coalesce by leteral accretion processes to form lacustrine deltaic lobes the bar components are outlined in color infrared photography by abandoned distributary channel sutures the abandoned interdistributary sutures add to the complexity of the subaerial bar sedimentology the model is completed by phase four where the subaerial bars and lobes eventually coalesce through continued lateral and vertical accretion until all of the original lacustrine area fills with the deposits and overbank sedimentation from the main atchafalaya river channel the resultant landform will resemble a floodplain or well drained swamp

reassessing the stable δ88 86sr and radiogenic 87sr 86sr strontium isotopic composition of marine inputs the stable strontium isotope system 88 86sr has recently been suggested to be a suitable proxy for determining variations in the strength of the marine carbonate system the principal output flux of oceanic sr however in order to be able to interpret carbonate driven variations in 88 86srseawater a robust understanding of 88 86srinput is required surprisingly only a limited amount of 88 86sr data currently exists for rivers and hydrothermal fluids thus this study assesses the variability of 88 86sr and 87sr 86sr in global rivers hydrothermal fluids and porewaters as well as minor marine sr sources such as continental dust rainwater and glacial ice our analyses broadly confirm the findings of krabbenhoft et al 2010 and reveal flux weighted 88 86srriverine and 87sr 86srriverine compositions of 0 32 and 0 71299 respectively the hydrothermal fluids analysed in this study are consistent with an end member 88 86srhydrothermal composition that is the same as the oceanic crust at 0 24 although three samples that display 88 86sr compositions offset from the seawater hydrothermal mixing trend suggest that the precipitation of alteration phases such as anhydrite may drive 88 86srhydrothermal to higher values porewater fluids obtained from sediment cores in the atlantic and pacific oceans have 88 86sr compositions within error of seawater 0 39 implying that the diagenetic flux of sr may not significantly affect the 88 86sr composition of seawater continental loess samples have 88 86sr compositions that are consistently lighter than or equal to terrestrial silicates with their tendency to lower values thought to reflect the preferential removal of heavier sr isotopes into solution during weathering finally rainwater and glacial ice samples have 88 86sr compositions that are also isotopically lighter than their associated water sources a factor that may be attributed to interaction with isotopically light loess and additional sr contributions from the bedrock together the principal marine inputs define flux weighted oceanic 88 86srinput and 87sr 86srinput compositions of 0 32 and 0 71161 these values are consistent with an elevated supply of riverine sr to the oceans due to increased post glacial weathering but require the enhanced weathering of exposed carbonate shelves during glacial periods or significant changes in the rate of carbonate burial to match observed changes in the 87sr 86sr ratio of seawater our results confirm that providing a diagenetically robust proxy can be found the 88 86sr and 87sr 86sr isotope systems should provide a useful proxy for investigating changes in the marine carbonate system through time

strontium neodymium and lead isotope variations of authigenic and silicate sediment components from the late cenozoic arctic ocean implications for sediment provenance and the source of trace metals in seawater proven ance changes of silicate sediment deposited during the late cenozoic 5 0 ma on the alpha ridge central arctic ocean are determined from variations in strontium lead and neodymium isotope compositions whereas strontium and lead isotope compositions are relatively invariant from 5 to 1 7 ma end values start to increase at 3 ma subsequently s7sr 86sr and 2 6pb z 4pb ratios progressively increase and end values progressively decrease from 1 7 ma to the present day from these isotope variations three different endmember compositions for sediment source regions are defined the two endmember compositions defined by sediment that was deposited by sea ice from 5 to 1 7 ma are consistent with a significant component being derived from the east siberian shelf the progressive change in isotope compositions from 1 7 to 0 ma correlates with an increase in coarse detritus deposited by icebergs over this time period the isotope data are consistent with a progressive increase in the proportion of sediment that was deposited in the central arctic ocean since 1 7 ma having been derived from the northern canada or queen elizabeth island region changes in the strontium neodymium and lead isotope compositions of arctic seawater are determined by analyzing the oxide fractions of fe mn micronodules strontium isotope compositions of the microno dule oxide fractions are similar to published late cenozoic seawater data and indicate that 97 of the sr is seawater derived but minute contributions of sr from silicate detritus prohibit using the hydrogenous fractions for chronostratigraphic purposes neodymium and lead isotope compositions of the micronodule oxide fractions which reflect those of arctic seawater follow the isotope variations of the silicate components throughout the late cenozoic these relations indicate that river water can not be the primary source of rare earth elements and pb to the dissolved reservoir in arctic seawater and that ice rafted detritus by dissolution or exchange processes is an important source of trace elements to seawater in ice covered oceans copyright 1997 elsevier science ltd

strontium isotope stratigraphy as a constraint on the age of condensed levels examples from the jurassic of the subbetic zone southern spain condensed levels are often characterized by reworked fossils that may lead to incorrect age assessments strontium isotope stratigraphy is an important chronostratigraphic tool that can be used to verify the biostratigraphic information from condensed beds this paper describes a study of the 87sr 86sr isotope ratios of 56 belemnite samples collected from 28 stratigraphic sections of the boundary between the upper member of the gavila n formation and the zegri formation pliensbachian subbetic zone the petrographic and geochemical data d18o d13c concentrations of fe mn and mg and the sr mn ratio suggest that the belemnites have preserved their original marine geochemical composition after plotting the samples in diagrams of 87sr 86sr values against time according to their biostratigraphic age four different groups a b c and d were obtained with respect to the reference curve in groups a and b the age deduced from the sr isotope ratio is in total or partial agreement respectively with the biostratigraphic age therefore the 87sr 86sr ratio is a good method for the dating correlation and assessment of biostratigraphic results in groups c and d the sis age and the biostratigraphic age do not coincide a graphic procedure is presented as a suitable methodology to constrain the age of the samples showing an sis age that differs from the relative age deduced by biostratigraphy or stratigraphic correlation for the bed they were collected in these situations are interpreted as being the result of reworking of the belemnites group c or ammonites group d that are included in condensed levels these condensed levels formed during the maximum flooding event that led to the drowning of the gavila n carbonate platform the methodology supplied in this paper represents a valuable tool in identifying reworking processes improving correlation and constraining biochronostratigraphic results the values of 87sr 86sr represent a new contribution to the data set of 87sr 86sr ratios for the pliensbachian

investigation of a dynamic seawater intrusion event using strontium isotopes 87sr 86sr summary a seawater intrusion experiment was carried out in a shallow coastal unconfined aquifer at skansehage denmark the aquifer consists of 6 10 m of postglacial holocene eolian and marine sands and gravels resting on pleistocene glacial sequence of tills and glacio fluviatile sediments on a basement of palaeocene danian limestone stable isotopes 18 o and 2 h strontium isotopes 87 sr 86 sr and the elements sr and cl were measured to delineate the mixing of seawater and groundwater in the shallow aquifer and to determine the contribution from different water sources along the flow paths the stable isotopes reflect recharge conditions and mixing between groundwater and seawater the 87 sr 86 sr isotope ratios are controlled by aquifer matrix chemistry the 87 sr 86 sr ratio distribution and sr content reveal a ternary mixing system in the shallow aquifer encompassing brackish seawater fresh shallow groundwater and deep groundwater from the underlying limestone aquifer as end members a mixing analysis is performed using the cl contents and the 87 sr 86 sr ratios the mixing analysis indicates a zone with leakage of deep groundwater from the limestone aquifer into the lower part of the shallow sandy aquifer through the pleistocene sedimentary sequence the upper part of the sandy aquifer is thoroughly dominated by mixing processes between infiltrating fresh groundwater and brackish seawater from isefjord prior to the intrusion experiment there appeared to be limited mixing between the upper and lower part of the water body in the shallow sandy aquifer the leakage of deep groundwater increased during the intrusion experiment as a result of the large abstraction of groundwater following the ceasing of the groundwater pumping the interface went from being vertical to being predominantly horizontal due to density flow as a consequence the deep groundwater from the limestone aquifer was pushed by the seawater into the upper part of the aquifer to mix with the upper fresh groundwater

the sources and transport of sr and nd isotopes in the baltic sea we have determined the concentration and isotopic composition of sr and nd in waters from the baltic sea the baltic sea is an intracontinental stratified brackish water estuarine like system and the rivers emptying into it drain a suite of terranes ranging from proterozoic archean in the north to phanerozoic in the south the sampled brackish waters range in salinity from seawater sw at 35 289 to a minimum of 2 460 at the surface in the innermost part of the gulf of bothnia the sr concentrations show generally conservative behavior indicating a simple two component mixing however small deviations 3 70 from a perfect mixing line reveal that the imprints from rivers with different sr concentrations are preserved in the blending strontium concentrations from a depth profile across the redoxcline in the baltic proper indicate that vertical particle transport alters the sr concentration in the water our estimated concentration of sr in the average freshwater input to the baltic is 0 03 ppm which is only about 0 4 of the sw concentration the sr isotopic data range from e sr sw 0 in seawater to e sr bw sw 7 8 in the least saline baltic water bw sample in the gulf of bothnia the isotopic composition of sr versus 1 sr in the baltic sea follows an almost perfect mixing line which shows that seawater sr is mixed with much more radiogenic components calculated end member values of e sr sw for each sample show that the riverine input into the gulf of bothnia has e sr sw 120 200 and 10 50 e units in the baltic proper these values are in general agreement with direct measurements of river waters in each region however the calculated values in the gulf of bothnia are lower than the measured river water input in this region which indicates the presence of less radiogenic sr presumably originating from the river waters draining the southern part of the basin which are partially transported northward and mixed with sr from the gulf of bothnia rivers the nd concentration in the baltic sea is not conservative varying between 5 and 45 ppt with the highest concentrations in the bottom waters due to vertical particulate transport a plot of e nd o in baltic water yields a good correlation with the calculated freshwater end member e sr sw the data show that it is possible to unravel the different freshwater sources into the baltic and to identify the zones of particulate removal of both non conservative species such as the ree and of quasi conservative species such as sr the use of isotopic tracers in this estuarine environment may provide a much better insight into mixing and element transport it should also be possible to trace lateral movements of freshwater inputs

assessing the role of submarine groundwater discharge as a source of sr to the mediterranean sea abstract submarine groundwater discharge sgd has been identified as an important source of sr to the ocean and the sgd driven sr flux to the global ocean has been recently re evaluated beck et al 2013 however the uncertainty of this value is still high because of the uncertainties related to the determination of sgd flow rates and the paucity of 87 sr 86 sr data in sgd end members as carbonates have high sr concentrations and are subjected to intense heightened weathering they might significantly influence the sgd input of sr to the ocean here we present data on sr concentrations and 87 sr 86 sr ratios in three carbonate dominated sites of the western area of the mediterranean sea a semi enclosed basin characterized by abundant coastal carbonates the 87 sr 86 sr ratios in groundwater were lower compared to modern seawater 0 70916 as expected for areas dominated by carbonate lithologies concentrations of sr and 87 sr 86 sr ratios in groundwater showed conservative mixing in the studied subterranean estuaries by using sgd flow rates reported in the literature for the study areas a flow weighted fresh sgd end member characterized by a sr concentration of 27 30 m and a 87 sr 86 sr ratio of 0 707834 0 708020 was calculated for the eastern coast of the iberian peninsula integrating these sr data with literature data i e values of sr concentration and 87 sr 86 sr ratio from other lithologies as well as sgd flow rates we also calculated the fresh sgd driven sr flux to the entire mediterranean sea obtaining a value of 0 34 0 83 10 9 mol y 1 with a 87 sr 86 sr of 0 7081 0 7086 thus for the entire mediterranean basin sgd is globally a source of sr less radiogenic compared to seawater the sgd sr flux to the mediterranean sea represents 5 6 of the sgd sr flux to the global ocean and the mediterranean sgd end member has higher sr concentration 5 12 m than the global sgd end member 2 9 m this confirms the significant role of carbonate lithologies on sgd driven sr fluxes to seawater the fresh sgd driven sr flux to the mediterranean sea is about 20 50 of the riverine sr input and significantly higher than the input through atmospheric dust deposition therefore sgd should be considered as an important continental source of sr to the basin

comparative hydrodynamics of 10 mediterranean lagoons by means of numerical modeling a comparison study between 10 mediterranean lagoons has been carried out by means of the 3 d numerical model shyfem the investigated basins are the venice and marano grado lagoons in the northern adriatic sea the lesina and varano lagoons in the southern adriatic sea the taranto basin in the ionian sea the cabras lagoon in sardinia the ganzirri and faro lagoons in sicily the mar menor in spain and the nador lagoon in morocco this study has been focused on hydrodynamics in terms of exchange rates transport time scale and mixing water exchange depends mainly on the inlet shape and tidal range but also on the wind regimes in the case of multi inlet lagoons water renewal time which is mostly determined by the exchange rate is a powerful concept that allows lagoons to be characterized with a time scale in the case of the studied lagoons the renewal time ranged from few days in the marano grado lagoon up to 1 year in the case of the mar menor the analysis of the renewal time frequency distribution allows identifying subbasins the numerical study proved to be a useful tool for the intercomparison and classification of the lagoons these environments range from a leaky type to a choked type of lagoons and give a representative picture of the lagoons situated around the mediterranean basin mixing efficiency turns out to be a function of the morphological complexity but also of the forcings acting on the system

constraining the marine strontium budget with natural strontium isotope fractionations 87sr 86sr δ88 86sr of carbonates hydrothermal solutions and river waters we present strontium sr isotope ratios that unlike traditional 87sr 86sr data are not normalized to a fixed 88sr 86sr ratio of 8 375209 defined as 88 86sr 0 relative to nist srm 987 instead we correct for isotope fractionation during mass spectrometry with a 87sr 84sr double spike this technique yields two independent ratios for 87sr 86sr and 88sr 86sr that are reported as 87sr 86sr and 88 86sr respectively the difference between the traditional radiogenic 87sr 86sr normalized to 88sr 86sr 8 375209 and the new 87sr 86sr values reflect natural mass dependent isotope fractionation in order to constrain glacial interglacial changes in the marine sr budget we compare the isotope composition of modern seawater 87sr 86sr 88 86sr seawater and modern marine biogenic carbonates 87sr 86sr 88 86sr carbonates with the corresponding values of river waters 87sr 86sr 88 86sr river and hydrothermal solutions 87sr 86sr 88 86sr hydend in a triple isotope plot the measured 87sr 86sr 88 86sr river values of selected rivers that together account for not vert similar18 of the global sr discharge yield a sr flux weighted mean of 0 7114 8 0 315 8 the average 87sr 86sr 88 86sr hydend values for hydrothermal solutions from the atlantic ocean are 0 7045 5 0 27 3 in contrast the 87sr 86sr 88 86sr carbonates values representing the marine sr output are 0 70926 2 0 21 2 we estimate the modern sr isotope composition of the sources at 0 7106 8 0 310 8 the difference between the estimated 87sr 86sr 88 86sr input and 87sr 86sr 88 86sr output values reflects isotope disequilibrium with respect to sr inputs and outputs in contrast to the modern ocean isotope equilibrium between inputs and outputs during the last glacial maximum 10 30 ka before present can be explained by invoking three times higher sr inputs from a uniquely glacial source weathering of shelf carbonates exposed at low sea levels our data are also consistent with the weathering peak hypothesis that invokes enhanced sr inputs resulting from weathering of post glacial exposure of abundant fine grained material

sr concentrations and isotope ratios as tracers of ground water circulation in carbonate platforms examples from san salvador island and long island bahamas abstract the depth to which seawater and fresh water circulate through modern carbonate platforms may be estimated with 87 sr 86 sr isotope ratios of dissolved sr 2 that is enriched through carbonate mineral dissolution and recrystallization in 23 water samples from onshore san salvador island and long island bahamas carbonate mineral dissolution and aragonite to calcite transformations elevate sr 2 concentrations to twice seawater values in water with near seawater salinity and to about 130 times the expected value for seawater that has been mixed with fresh water carbonate mineral dissolution enriches ca 2 concentrations to around 30 times seawater concentrations only in the mixed waters water with seawater salinity has approximately seawater ca 2 concentrations assuming two end member mixing between seawater sr 2 and mineral derived sr 2 model estimates indicate that mineral derived sr 2 of 19 samples have 87 sr 86 sr ratios equivalent to modern seawater within error of the measurement indicating alteration of shallow buried late pleistocene to holocene carbonate minerals four samples have mineral derived sr 2 with 87 sr 86 sr ratios lower than modern seawater value these low ratios reflect alteration of carbonate minerals that were deposited around 1 mybp although the measured 87 sr 86 sr values could reflect ages as great as 4 6 ma considering the analytical uncertainty of the measurements these estimated ages are likely to be minimum values because alteration of modern carbonate minerals at the surface would provide an unknown but probably large amount of sr 2 with modern seawater isotope signatures thereby overprinting any low 87 sr 86 sr ratios of non modern mineral derived sr 2 three of the four samples with low 87 sr 86 sr ratios have high salinities and were collected from the interior of the islands they reflect seawater flow paths at least tens of meters deep may link the ocean to water several kilometers inland the fourth sample is from the fresh water lens below a pleistocene beach ridge 125 ka only 100 m from the shore line this sample suggests the lens may be thicker than expected based on estimates of recharge hydraulic conductivity and size of the ridge

fluvial geomorphic features of the lower mississippi alluvial valley abstract the lower mississippi valley lmv has been one of the most intensively studied alluvial valleys in the world in terms of it s geological and geomorphic framework and history a brief outline of the history of the major geological and geomorphological investigations of the lmv is provided the results of these investigations are discussed in terms of the fluvial geomorphic framework of the valley and the apparent significant changes in the regime of the mississippi river during the late wisconsinan and holocene stages the lmv occupies the broad deep synclinal trough of the mississippi embayment which extends from cairo illinois to the gulf of mexico in a slightly sinuous north south trend the embayment is filled with a north to south thickening wedge of non marine and marine sediment ranging in age from jurassic to holocene the major landscapes of the lmv may be considered in four regions 1 a narrow active meander belt in a broad valley of late pleistocene valley train in the northern third 2 a wide mosaic of interwoven holocene meander belts in the middle third 3 a relatively narrow valley of the atchafalaya basin bounded on each side by narrow meander belts in the upper part of the lower third and 4 the broad distributary wedge of the deltaic plain in the southernmost region of the valley the valley trains vary in age and landform with the oldest occurring as slightly dissected low ridges and the youngest as broad flats separated by shallow interwoven former braided channels meander belts formed throughout the holocene are comprised of low natural levee ridges flanking abandoned courses and bordered by crescent shaped oxbow lakes and ridge and swale topography in the middle third of the valley meander belts are separated by expansive backswamps of very little relief the deltaic plain is also exceptionally flat interrupted by the low natural levee ridges of the abandoned deltaic distributaries the floodplain of the lmv is a complex mosaic of fluvial features and landscapes within the four landscape regions included in this mosaic are abandoned channels and courses lateral accretion topography of ridges and swales natural levees crevasses and crevasse channels distributary channels backswamps and rimswamps alluvial fans and aprons valley trains braided stream terraces lakes and lacustrine deltas terraces and the alluvial valley bluff changes in the hydraulic regime of the lower mississippi river lmr since the late pleistocene have played a major role in the development of the landscape of the valley the most important regime change was the diminishment of the influence of wisconsinan glaciation in the upper midwest and the resultant evolution of the mississippi river from a broad braided outwash channel to a more narrow but sinuous meandering channel at the end of the pleistocene during the holocene the mississippi river undoubtedly responded to major climatic changes rising sea level tributary stream influence and possibly tectonism diapirism and subsidence through the growth and evolution and abandonment of it s meander belts and deltas

neodymium isotopes in the mediterranean sea comparison between seawater and sediment signals nine depth profiles of dissolved nd concentrations and isotopic ratios epsilon nd were obtained in the levantine basin the ionian the aegean the alboran seas and the strait of gibraltar thirteen core top sediments and nile river particle samples were also analyzed leached with 1 n hcl acetic acid or hydroxylamine hydrochloride the seawater epsilon nd values become more radiogenic during the eastward circulation in the mediterranean sea the relationship between salinity and the seawater epsilon nd shows that the nd isotopic signature is more conservative than salinity in the mediterranean sea the water mass with the highest epsilon nd 4 8 is found at about 200 m in the easternmost levantine basin the average epsilon nd value for deep waters is 7 0 in the eastern basin 2 5 epsilon units higher than in the western basin by examining the sensitivity of seawater epsilon nd to nd inputs from the nile we conclude that the most significant radiogenic nd source is partially dissolved nile river particles the nd flux from the nile river water has a minor influence on the mediterranean seawater end except for the easternmost levantine basin the leachate epsilon nd values are consistent with the seawater values in the easternmost levantine basin the leachate end values obtained with hcl leaching are systematically higher than the seawater values the relationship between leachate and residual epsilon nd values indicates that the hcl leaching partially dissolves lithogenic nd so the dissolution of nile river particles is the cause of the observed shift some end values obtained with hydroxylamine hydrochloride leaching are higher than those obtained with hcl leaching although the reason for this shift is not clear sr 87 sr 86 successfully detects the presence of a nonmarine component in the leachate our results suggest that leaching performance may vary with the mineralogy of marine sediments at least in the case of the mediterranean sea copyright c 2004 elsevier ltd

spatial and temporal variability of downward particle fluxes on a continental slope lessons from an 8 yr experiment in the gulf of lions nw mediterranean abstract a long term experiment of downward particle fluxes and currents has been initiated in 1993 on the continental slope of the gulf of lions nw mediterranean and pursued within the frame of several french and european projects pnec euromarge nb mtp ii mater eurostrataform sediment traps and current meters were deployed at several locations on this slope deeply incised by numerous canyons with an extensive spatial coverage for the first 2 years canyons at the entrance middle and exit of the gulf with respect to the general along slope circulation head and mid canyon depths adjacent open slope from late 1995 onwards this design was reduced to the two mid canyon moorings at the entrance and exit of the gulf monthly fluxes and hourly temperatures and currents were recorded at 500 m 30 m above bottom mab in the canyon heads at 500 and 1000 m respectively 530 and 30 mab nominal depths at the mid canyon sites and at 750 m 30 mab open slope this study aims at describing the spatial seasonal and interannual variability of flux intensity and composition of settling particles and at analyzing the role of diverse forcings in the control of particle exchange across the margin results from the first 8 years 1993 2001 show that total mass fluxes in the 101 104 mg m 2 d 1 range increase along slope particularly for the near bottom traps between the ne planier canyon and the sw lacaze duthiers canyon limits of the gulf of lions indicating an increased shelf export of particulate matter in the western part of the system bulk chemical composition organic matter carbonate opal and lithogenic fraction remained rather stable during the course of the experiment tending towards values typical of superficial shelf sediments at higher mass fluxes first order calculations using a simple two component mixing model suggest a decreasing contribution of primary particles settling out of the overlying waters to the total flux from the entrance towards the exit of the system particulate material transferred to the deeper slope in the southwestern part of the gulf of lions appears therefore to predominantly originate in resuspended shelf and or upper slope sediment downward particle fluxes and potential forcing parameters exhibit a high seasonal variability with higher values from late autumn to early spring furthermore unprecedented winter flux peaks observed in 1999 dominated the interannual differences which otherwise were quite limited correlations between sources of particulate material on the shelf i e river and atmospheric inputs phytoplankton biomass and sediment resuspension cross slope exchange mechanisms derived from in situ temperature and current records and flux data indicate a predominant effect of dense cold water cascading on the exchange of particulate matter between the shelf and the slope

seawater 87sr 86sr ratios along continental margins patterns and processes in open and restricted shelf domains abstract to better constrain the sr isotope budget in marginal domains without any fluvial inputs we analyzed the chemical composition and 87sr 86sr ratio of waters and shells from four locations two coastal lagoons one hemipelagic platform and one open marine shelf our results highlight homogeneous 87sr 86sr ratios typical of oligotrophic oceanic waters oow i e 0 709172 0 000023 in the pacific tatakoto atoll and along a mediterranean shore to offshore transect 25 km off banyuls sur mer bsm this attests that oceanic inputs from oligotrophic areas remain the main sr source in open shelf areas compared with submarine groundwater discharges sgd or particulate dissolution influences in bsm only foreshore data are more radiogenic possibly due to rainwater mixing local groundwater springs or more efficient particle dissolution in the intertidal zone in restricted areas we report variable 87sr 86sr ratios between the salses leucate france and oualidia morocco lagoons the first one has homogeneous 87sr 86sr ratio typical of oow except close to sgd in oualidia 87sr 86sr ratios decrease by 1 2 10 3 from oow values close to the atlantic inlet to progressively less radiogenic ones upstream within the interior of the lagoon these differences depend on several factors including the leaky restricted or choked morphology of lagoons modulating the oceanic sr inputs but also sgd fluxes whose 87sr 86sr ratios and sr concentrations are highly variable according to the nature of rocks leached in karstic aquifer in oualidia the low 87sr 86sr ratios correspond to high sr concentrations up to 150 mol l 1 issued from the dissolution of mesozoic evaporites leading to sgd fluxes accounting for 60 of the local sr budget through data compilation we show that similar 87sr 86sr gradients and processes prevail at the whole mediterranean scale finally we postulate that high coastal water retention times can also account for anomalous coastal 87sr 86sr ratios and that the combination of water mass restriction sgd bioadsorption and early diagenetic processes could decrease seawater sr concentrations in some marginal areas

87sr 86sr of brines from the fennoscandian shield a synthesis of groundwater isotopic data from the baltic sea region high salinity ca na cl brines occur in sweden and finland the complex geological history of the fennoscandian shield is reflected by the wide range of saline waters whose chemical compositions have been explained by local water rock interaction simple evolution of relict sea water or freezing of sea water during glacial periods this study deals with the present knowledge of sr isotopes in groundwater from the fennoscandian shield to better constrain the origin of their deep saline component two different mixing trends are seen between aspo island groundwater and the baltic sea the first trend links the north sea to rivers through various dilution levels in the baltic the second trend is a simple linear relationship through aspo groundwaters agreeing with a binary mixing between a baltic end member and a highly sr concentrated fluid strontium isotope compositions are presented for precipitation in finland and sweden the baltic sea and the river waters draining the fennoscandian shield and for g

preservation of seawater sr and nd isotopes in fossil fish teeth bad news and good news abstract we analyzed 87sr 86sr ratios in foraminifera pore fluids and fish teeth for samples ranging in age from eocene to pleistocene from four ocean drilling program sites distributed around the globe site 1090 in the cape basin of the southern ocean site 757 on the ninetyeast ridge in the indian ocean site 807 on the ontong java plateau in the western equatorial pacific and site 689 on the maud rise in the southern ocean sr isotopic ratios for dated foraminifera consistently plot on the global seawater sr isotope curve for sites 1090 757 and 807 sr isotopic values of the pore fluids are generally less radiogenic than contemporaneous seawater values as are values for fossil fish teeth in contrast pore fluid 87sr 86sr values at site 689 are more radiogenic than contemporaneous seawater and the corresponding fish teeth also record more radiogenic values thus sr isotopic values preserved in fossil fish teeth are consistently altered in the direction of the pore fluid values furthermore there is a correlation between the magnitude of the offset between the pore fluids and the seawater curve and the associated offset between the fish teeth and the seawater curve these data suggest that the hydroxyfluorapatite of the fossil fish teeth continues to recrystallize and exchange sr with its surroundings during burial and diagenesis therefore sr chemostratigraphy can be used to determine rough ages for fossil fish teeth in these cores but cannot be used to fine tune age models in contrast to the sr isotopic system our nd concentration data combined with published isotopic and rare earth element data suggest that fish teeth acquire nd during early diagenesis while they are still in direct contact with seawater the concentrations of nd acquired at this stage are extremely high relative to the concentrations in surrounding pore fluids as a result nd isotopes are not altered during burial and later diagenesis therefore fossil fish teeth from a variety of marine environments preserve a reliable and robust record of deep seawater nd isotopic compositions from the time of deposition

methane derived carbonates and authigenic pyrite from the northwestern black sea abstract methane seeps in the northwestern black sea are accompanied by carbonate and pyrite precipitates sediments were sampled at locations on the romanian 120 m depth and ukrainian 180 200 m depth shelf and slope layered carbonate crusts are formed of i carbonate cemented siliciclastic sediment containing dreissenoid bivalves ii microcrystalline high mg calcite or aragonite and iii aragonitic cement the dreissena sediment is subrecent and was deposited during the freshwater phase of the black sea it has been affected by seepage of methane rich fluids which induced intergranular precipitation of authigenic carbonates the microcrystalline carbonates exhibit an intense autofluorescence high mg calcite contains 11 14 mol mgco3 the aragonitic cement 8300 9500 ppm sr forms either isopachous layers or botryoids microbial filaments about 10 20 m in diameter and up to 900 m in length are preserved within and on carbonate crusts the carbonates are depleted in 13c microcrystalline carbonate ranges from 27 to 41 pdb and botryoidal aragonite ranges from 26 to 38 pdb the 13c depletion indicates that the carbonates predominantly derive from the microbial oxidation of methane carbonate deposits do not project up into the oxic water column they are restricted to the anoxic water column and to anoxic sediments revealing the crucial role of anaerobic methane oxidation for carbonate precipitation 14c contents give apparent radiocarbon ages of 20 640 180 a bp for a sample of botryoidal aragonite and 19 110 180 a bp for a sample of microcrystalline carbonate compatible with minimum ages of carbon derived from a fossil hydrocarbon source the 18o values of methane derived carbonates show a narrow range from 1 2 to 0 2 pdb 87sr 86sr ratios of microcrystalline carbonate mean 0 70927 and aragonitic cement mean 0 70918 are indistinguishable from ambient seawater mean 0 70917 and thus indicate a shallow sr source higher 87sr 86sr ratios of the dreissena sediment mean 0 71005 are probably caused by sr derived from detrital mica carbonates are accompanied by blocks and crusts composed of pyrite the framboidal sulphide exhibits a palisade like fabric with framboids arranged to parallel pillars sulphur isotopic ratios 34s ranging from 16 8 to 19 7 cdt indicate that the sulphur derives not from the 34s depleted h2s of the water column or the uppermost sediment layers most likely pyrite formed in the lacustrine sediments after the first incursion of mediterranean seawater

spatial variations in vent chemistry at the lucky strike hydrothermal field mid atlantic ridge 37 n updates for subseafloor flow geometry from the newly discovered capelinhos vent

sr and 87sr 86sr in estuaries of western india impact of submarine groundwater discharge abstract dissolved sr and 87sr 86sr are measured in the narmada tapi and the mandovi estuaries linked to the eastern arabian sea the concentration of dissolved sr and 87sr 86sr in the river water endmembers show significant differences reflecting the lithologies they drain the distribution of sr in all these estuaries shows a near perfect two endmember mixing between river water and seawater suggesting that there is no discernible net addition removal of sr from the estuarine waters in contrast 87sr 86sr shows non conservative behaviour in all these estuaries its distribution exhibits significant departure from the theoretical mixing lines a likely mechanism for this difference in the behaviour between dissolved sr and its 87sr 86sr is the discharge of submarine groundwater sgd which can modify the 87sr 86sr of the estuarine waters by exchange with sediments without causing measurable changes in sr concentration the impact of such an exchange process on the 87sr 86sr of the estuaries and therefore on the sr isotope composition of dissolved sr entering the arabian sea differs among the three estuaries and also between seasons in the narmada the non conservative behaviour of 87sr 86sr provides a handle to estimate the quantum of sgd to these estuaries the sr concentration 87sr 86sr ratio and salinity of the submarine groundwater and estimate of its fluxes to the narmada estuary have been made using inverse model calculations the model derived sgd flow rates are 5 and 280 cm day during pre monsoon and monsoon respectively the more radiogenic sr isotope composition of sgd relative to the seawater suggests that sgd acts as an additional source of 87sr to the arabian sea

seawater strontium and sr ca variability in the atlantic and pacific oceans abstract seawater sr and sr ca exhibit spatial gradients of 2 3 globally with the deep ocean more enriched relative to the surface in latitudinal transects the highest surface values are found at high latitudes and associated with areas of upwelling a pronounced upper ocean vertical sr gradient is attributable to the production of celestite skeletons by surface dwelling acantharia coupled to a shallow dissolution cycle the upper ocean residence time of sr with respect to celestite cycling is much shorter than its global oceanic residence time although the magnitude of seawater sr ca variability is relatively small it is significant with respect to high precision paleoceanographic applications sr ca gradients in the contemporary ocean also complicates evaluating quaternary changes in seawater sr ca that may have resulted from other processes such as aragonite recrystallization during sea level low stands

strontium isotope variations in middle jurassic late bajocian callovian seawater implications for earth s tectonic activity and marine environments abstract strontium isotope ratios of well preserved belemnite rostra and ammonite shells are presented from stratigraphically well dated upper bajocian callovian sediments of the polish jura chain in central poland nekto benthic belemnites show a narrow trend of changes of 87 sr 86 sr ratio that are interpreted to record secular variations in the strontium isotope composition of seawater a new fit of the seawater strontium isotope curve for the late bajocian callovian is presented based on current and literature data the data show a gradual decrease of seawater 87 sr 86 sr ratio throughout the late bajocian earliest middle callovian lowest 87 sr 86 sr ratios 0 706850 and the flat minimum of the curve were reached in the latest middle and the late callovian the middle jurassic decrease in seawater 87 sr 86 sr ratio is interpreted to have been a result of the increased volcanic activity of the seafloor studied nektonic ammonites are considered to have lived in surface or shallow near coastal waters of the polish jura chain basin and been affected by the freshwater influx a slight enrichment of ammonite shells in 87 sr isotope is linked to a change in strontium isotope composition of the surface or near coastal waters due to the riverine strontium input

nonhomogeneous seawater sr isotopic composition in the coastal oceans a novel tool for tracing water masses and submarine groundwater discharge here we present high precision 2 3 ppm 87sr 86sr measurements in coastal waters together with salinity to evaluate water mass mixing and the influence of submarine groundwater discharge sgd in coastal waters and marginal seas nonhomogeneous sr isotopic variations in water columns were documented in the southern okinawa trough sot south china sea and kao ping canyon kpc where seawater 87sr 86sr varied up to 70 ppm seawater sr isotopic composition changes only slightly in the upper 200 m of the sot but was detectable and highly correlated with salinity indicating a mixing between radiogenic north pacific tropical water high 87sr 86sr and high salinity at 100 150 m and a less radiogenic component with low 87sr 86sr and low salinity at 200 m vertical profiles of seawater 87sr 86sr along the kpc show significant variations suggesting dynamic mixing affected by continental inputs i e river runoff and sgd in this region these results highlight the potential use of seawater sr isotopes as a powerful tracer for determining mixing ratios and the dynamic mixing of oceanic water masses especially in coastal and marginal seas