oxygen isotope and geochemical variations in the missouri river oxygen isotope ratios in streamflow of the missouri river basin vary geographically due to differences in source precipitation and the integration of waters from upstream regions average 18o values in the missouri river main stem systematically increase from less than 17 in the headwaters to about 9 in the lower basin seasonal variations at a given location result from fluctuations in meteoric precipitation residence time in reservoirs and groundwater systems evaporation and snowmelt average water chemistry values are successfully predicted for the upstream stations of two reaches on the lower missouri river based on changes in discharge along each reach and water quality measurements collected at the downstream stations source regions for some dissolved ions found in the lower missouri river are also identified sodium and sulfate originate predominantly from the basin above sioux city iowa while nitrate is largely derived from agricultural regions below sioux city

surface area control of shallow cratonic to deep marine carbonate accumulation sites of calcium magnesium carbonate accumulation have been shifting from shallow shelf to deep marine settings since the late cretaceous during this time total area of flooded epicratonic shelf has decreased about 50 and areas of shelf carbonate deposition have declined from 27 106 km to present areas of 1 4 106 km while the maximum extent of platform carbonate accumulation has decreased from about 50 to 28 north latitude in terms of cratonic carbonate this decrease in tropical shelf area has resulted in a sixfold reduction in shoal water limestone accumulation from a cretaceous rate of 0 6 km m y to a present value of about 0 1 106 km m y over the same time period the global carbonate compensation depth has deepened by about 1 5 km attendant with a threefold areal increase of calcite ooze depositionn 40 to 130 106 km this expansion has resulted in an eightfold increase in pelagic limestone accumulation from a cretaceous rate of 0 05 106 km m y to a present rate of about 0 4 106 km m y transfer of accumulation from shallow cratonic to deep marine depositional settings records the central role of sedimentary environment surface area in predicating the differential partitioning of finite carbonate fluxes to phanerozoic global oceans

elevated arsenic in deeper groundwater of the western bengal basin india extent and controls from regional to local scale the deeper groundwater depending on definition of the bengal basin ganges brahmaputra delta has long been considered as an alternate safe drinking water source in areas with as enrichment in near surface groundwater the present study provides the first collective discussion on extent and controls of elevated as in deeper groundwater of a regional study area in the western part of the bengal basin deeper groundwater is defined here as non brackish potable cl 250 mg l groundwater available at the maximum accessed depth similar to 80 300 m the extent of elevated as in deeper groundwater in the study area seems to be largely controlled by the aquifer aquitard framework arsenic enriched deeper groundwater is mostly encountered north of 22 75 degrees n latitude where an unconfined to semi confined aquifer consisting of holocene to early neogene age gray sand dominates the hydrostratigraphy to 300 m depth below land surface aquifer sediments are not abnormally enriched in as at any depth but sediment and water chemistry are conducive to as mobilization in both shallow and deeper parts of the aquifer s the biogeochemical triggers are influenced by complex redox disequilibria results of numerical modeling and profiles of environmental tracers at a local scale study site suggest that deeper groundwater abstraction can draw as enriched water to 150 m depth within a few decades synchronous with the advent of wide scale irrigational pumping in west bengal india

groundwater flow dynamics and arsenic source characterization in an aquifer system of west bengal india numerical groundwater flow modeling reverse particle tracking and environmental tracers are used to locate the source of geogenic as affecting an aquifer in west bengal the aquifer is hosted by point bar sands deposited in a meandering fluvial environment wells tapping the aquifer exhibit as concentrations up to 531 g l high as groundwaters are recharged in ponds marking an abandoned river channel the source of as is traced to the underlying fine grained channel fill sediments arsenic release within these sediments is accompanied by a concomitant release of br and doc indicating that these species may be decay products of natural organobromines codeposited along with as mass transfer of as to the dissolved phase and its flushing from source sediments are described using a simplified reactive solute transport model based on this model a characteristic reaction time for mass transfer is estimated at 6 7 years average groundwater residence times in the source are estimated to have declined from 16 6 to 6 6 years with the advent of intensive irrigation pumping the ratio of residence and reaction times a damkohler number has declined correspondingly from 2 49 to 0 99 indicating a shift from transport to reaction rate limited as mobilization greater insight into the as problem in se asia may be achieved by shifting the focus of field investigations from aquifers to potential contamination sources in aquitards

arsenic enrichment in groundwater of west bengal india geochemical evidence for mobilization of as under reducing conditions abstract the mechanism of as release and source s of as has been investigated in a small part of a watershed in the murshidabad district of west bengal analyses include major ion and trace element concentrations as well as o h and s isotope ratios of groundwater surface water and a thermal spring the results indicate that all water samples belong to the ca hco 3 type except for the thermal spring which is of the na hco 3 type shallow and deeper groundwaters have distinct hydrochemical features high as contents were registered only in the deeper groundwater horizon factor analysis and the distribution pattern of major and trace elements indicate that as is present in the aquifer as a scavenged phase by fe iii and to a lesser extent by mn iv phases the release of as into the groundwater occurs gradually in successive stages corresponding to the actual redox state in the aquifer the main stage of as release is related to the bacterial reduction of fe iii to fe ii i e to the simultaneous dissolution of fe oxyhydroxides low redox conditions in highly polluted areas are indicated by low so 4 concentration and high 34 s values during bacterial so 4 reduction residual so 4 in groundwater is depleted in the lighter s isotope 32 s however the cause of the gradual decrease of the redox state in the groundwater is still not well understood

the tectonic history of drake passage and its possible impacts on global climate this study provides an integrated review of plate tectonic models of the evolution of the antarctica patagonia connection compared to geological records collected on land in patagonia and tierra del fuego and offshore along the northern edge of the scotia sea a temporal framework for the sedimentary and tectonic events of the north scotia ridge and tierra del fuego is constructed with additional data compiled from entire patagonia and the austral basin this review provides robust correlations of seaways and tectonic events along the scotia and south america plates and indicates that the opening of the drake passage was not steady state since ca 30 ma rather the regions forming the present day northern limit of this gateway experienced important paleogeographic changes from deep marine basins to shallow ridges and emerged regions during the late oligocene and early middle miocene time our compilation of geological data shows that emergence along the north scotia ridge and tierra del fuego was achieved at 23 22 ma and has been followed by elimination of the patagoniano sea in patagonia starting at 22 23 ma and achieved at 20 ma this transition towards more continental sedimentation in southern south america is correlated with more shallow marine conditions in the austral basin this succession of events had a strong influence on the general geometry of the drake passage corresponding to a constriction of its northern limit starting in the window 29 22 ma and achieved at 21 ma this period of active deformation in southern south america also corresponds to a period of the global climate having two anomalies well known from the isotopic records the late oligocene warming around 26 ma and the mid miocene climatic optimum which ended between 15 and 14 ma the possible effects of the post oligocene tectonic evolution of the drake passage region on general oceanic circulation are discussed causes for the synchronicity between tectonic events and these global warming events are examined

contrasting dissolved organic matter quality in groundwater in holocene and pleistocene aquifers and implications for influencing arsenic mobility abstract the discontinuous nature of elevated arsenic as in drinking water wells of west bengal and other regions in the bengal basin has led to increased interest in the role that sediment derived organic matter may play in enhancing reductive dissolution and as mobilization higher as concentrations have been observed in groundwater in reduced holocene grey aquifers when compared to oxidized pleistocene orange aquifers in order to evaluate if the differences in the chemical character of dissolved organic matter dom are present in groundwater in the holocene and the pleistocene aquifers that may influence dissolved as concentrations shallow groundwater and surface water samples were collected from four study sites in murshidabad district west bengal india and analyzed for water chemistry parameters and characteristics of dom for wells known to typically contain high as concentrations in holocene sediments in beldanga 10 4622 g l at 35 45 m depth and hariharpara 5 695 g l at 6 37 depth sites as well as wells characterized by low as concentrations pleistocene sediiments in nabagram 0 16 g l at 20 45 m depth and kandi 5 50 g l at 20 55 m depth detailed dom characterization was carried out using fluorescence spectroscopy and parallel factor analysis parafac results from statistical analysis of a variety of optical absorbance and fluorescence dom properties revealed that the dom in groundwater in the holocene aquifer had high humification index hix and low freshness index values whereas groundwater in the pleistocene aquifer comprised more labile and microbial dom sources consistent with the more labile nature of dom in groundwater in the pleistocene aquifer two ratios 1 humic like to protein like components humic protein and 2 terrestrially derived to microbially derived components terr microb obtained from a four component parafac model were 1 9 and 2 9 times greater respectively in groundwater in the holocene aquifer than in that of the pleistocene aquifer which suggests that the absence of humic like dom may be an important limitation to as mobility

phanerozoic atmospheric co2 change evaluating geochemical and paleobiological approaches abstract the theory and use of geochemical modeling of the long term carbon cycle and four paleo pco 2 proxies are reviewed and discussed in order to discern the best applications for each method geochemical models provide pco 2 predictions for the entire phanerozoic but most existing models present 5 10 m y means and so often do not resolve short term excursions error estimates based on sensitivity analyses range from 75 200 ppmv for the tertiary to as much as 3000 ppmv during the early paleozoic the 13 c of pedogenic carbonates provide the best proxy based pco 2 estimates for the pre tertiary with error estimates ranging from 500 1000 ppmv pre devonian estimates should be treated cautiously error estimates for tertiary reconstructions via this proxy are higher than other proxies and models 400 500 ppmv and should not be solely relied upon we also show the importance of measuring the 13 c of coexisting organic matter instead of inferring its value from marine carbonates the 13 c of the organic remains of phytoplankton from sediment cores provide high temporal resolution up to 10 3 10 4 year high precision 25 100 ppmv for the tertiary to 150 200 ppmv for the cretaceous pco 2 estimates that can be near continuous for most of the tertiary its high temporal resolution and availability of continuous sequences is advantageous for studies aiming to discern short term excursions this method however must correct for changes in growth rate and oxygen level at elevated pco 2 750 1250 ppmv this proxy loses its sensitivity and is not useful the stomatal density and stomatal index of land plants also provide high temporal resolution 2 year high precision 10 40 ppmv for the tertiary and possibly cretaceous pco 2 estimates and so also is ideal for discerning short term excursions unfortunately this proxy also loses sensitivity at some level of pco 2 above 350 ppmv which currently is largely undetermined our analysis of the recently developed 11 b technique shows that it currently is not yet well constrained most importantly it requires the assumption that the boron isotopic composition of the ocean remains nearly constant through time in addition it assumes that there are no biological or temperature effects and that diagenetic alteration of the boron isotopic composition does not occur a fifth co 2 proxy based on the redox chemistry of marine cerium has several fundamental flaws and is not discussed in detail here

enhanced cenozoic chemical weathering and the subduction of pelagic carbonate the observed trend of increasing oceanic 87sr 86sr ratios during the late cenozoic led raymo et al 1 to propose that chemical weathering rates increased at this time as a result of enhanced weatherability of silicate rocks they suggested that this was due in turn to continential uplift primarily in the himalayas and the andes because weathering involves the reaction of silicates with atmospheric carbon dioxide considerations of changes in weathering rates must take into account the need to balance the global carbon cycle to maintain this balance on timescales greater than 106yr enhanced weathering requires an increased flux of co2 into the atmosphere2 without such an increased flux weathering rates could not increase and one is then forced to search for other explanations for the observed 87sr 86sr trend such as a changing riverine strontium isotope composition3 6 here i assume that the strontium isotope record does indeed reflect enhanced weathering in the late cenozoic but propose that its cause may have been an increased co2 flux arising from the recycling of pelagic sedimentary carbon at subduction zones since the jurassic sedimentary carbonate accumulation has shifted from primarily cratonic to primarily pelagic environments7 11 because sea floor spreading transports pelagic carbonate to and recycles it through metamorphic environments in subduction zones this shift to pelagic carbonate accumulation would provide the increased co2 flux needed to increase weathering rates12 13

geological controls on groundwater chemistry and arsenic mobilization hydrogeochemical study along an e w transect in the meghna basin bangladesh summary hydrogeochemical investigations along an e w transect in the middle meghna basin show groundwater chemistry and redox condition vary considerably with the change in geology groundwater in the holocene shallow 10 g l and salinity on the other hand groundwater from the pliocene dupi tila sandy aquifer in the eastern part is fresh and low in as hco 3 fe and dissolved organic carbon doc but generally low in so 4 2 and no 3 high hco 3 concentrations 250 716 mg l together with high doc concentrations 1 4 21 7 mg l in these aquifers reflect active sources of degradable natural organic matter that drives the biogeochemical process there is generally de coupling of as from other redox sensitive elements in contrast the pliocene aquifers are low in as hco 3 and doc molar ratio of hco 3 h4sio4 suggests that silicate weathering is dominant in the deeper holocene aquifers and in the pliocene aquifers molar ratios of cl hco 3 and na cl suggest mixing of relict seawater with the fresh water as the origin of groundwater salinity speciation calculations show that saturation indices for siderite and rhodochrosite vary significantly between the holocene and pliocene aquifers stable isotopes 2h and 18o in groundwater indicate rapid infiltration without significant effects of evaporation the isotopic data also indicates groundwater recharge from monsoonal precipitation with some impact of altitude effect at the base of the tripura hills in the east the results of the study clearly indicate geological control i e change in lithofacies on groundwater chemistry and distribution of redox sensitive elements such as as along the transect

light stable isotope systematics of large scale hydrologic regimes in california and nevada surface waters shallow groundwaters and precipitation samples were collected along three traverses which begin at the california coast and are oriented in an east west manner roughly parallel to the atmospheric flow path of meteoric water the hydrogen isotope compositions from short term precipitation records varied as much as 40 at one location and were not representative of the average annual isotopic composition of precipitation the hydrogen isotope ratios of surface waters and shallow groundwaters distinguish segments with isotopic variations that correlate with measured vertical fluxes of meteoric water one coastal segment appears to closely approximate an open system in which precipitation dominates over evapotranspiration most segments are described by rather regular variations in d 3 45 per 100 km which represent different degrees of closure of the hydrologic system caused by variable partitioning of precipitation between runoff and evapotranspiration all partially closed systems imply terrestrial recycling of water a simple model estimates this amount to be about 20 across northern and central california three segments representing the great basin show virtually no geographic variation and appear to represent isotopically closed systems

evolution of carbon cycle over the past 100 million years it is generally accepted that progressive cooling of global climate since the late cretaceous results from decreasing partial pressure of atmospheric co2 pco2 however details on how and why the carbon cycle evolved and how it would affect pco2 have not been fully resolved while the long term decline of pco2 might be caused by the decrease of volcanic degassing through the negative feedback between pco2 and silicate weathering seafloor spreading the major control of co2 degassing seems to have remained relatively constant alternative explanation known as uplift driven climate change hypothesis proposes that tectonic uplift may have enhanced the sink of atmospheric co2 by silicate weathering and thus produced the decline of pco2 however increasing weathering sink of co2 could deplete atmosphere all of its co2 within several million years while holding volcanic outgassing constant in this work major fluxes of long term carbon cycle are calculated based on a reverse model constrained by marine c sr and os isotopic records and the spreading rate of sea floor weathering of island basalt and continental silicate rocks are separated in the new model the results indicate a long term decline of island basalt weathering in consistent with the global cooling trend over the past 100 million years dramatic changes of the co2 fluxes associated continental silicate weathering reverse weathering volcanic degassing and the growth of organic carbon reservoir have been observed disturbance of atmospheric co2 cycle by these fluxes seems to be maintained by the concomitant adjustments of island basalt weathering that were sensitive to the pco2 controlled environment factors such as temperature and runoff the negative feedbacks between pco2 and weathering of island basalt might have played a significant role in stabilizing the long term carbon cycle

hydro acoustic and tsunami waves generated by the 2012 haida gwaii earthquake modeling and in situ measurements detection of low frequency hydro acoustic waves as precursor components of destructive tsunamis can enhance the promptness and the accuracy of tsunami early warning systems tews we reconstruct the hydro acoustic wave field generated by the 2012 haida gwaii tsunamigenic earthquake using a 2 d horizontal numerical model based on the integration over the depth of the compressible fluid wave equation and considering a mild sloped rigid seabed spectral analysis of the wave field obtained at different water depths and distances from the source revealed the frequency range of low frequency elastic oscillations of sea water the resulting 2 d numerical model gave us the opportunity to study the hydro acoustic wave propagation in a large scale domain with available computers and to support the idea of deep sea observatory and data interpretation the model provides satisfactory results compared with in situ measurements in the reproduction of the long gravitational waves differences between numerical results and field data are probably due to the lack of exact knowledge of sea bottom motion and to the rigid seabed approximation indicating the need for further study of poro elastic bottom effects

estimation of evapotranspiration losses in the vadose zone using stable isotopes and chloride mass balance method this study used stable isotope and chloride data of porewater to evaluate water fluxes through the vadose zone and thereby estimate evapotranspiration water losses in parts of the nabogo catchment of the white volta basin in ghana the overall objective was to develop a framework so that the recharge regime can be properly conceptualized for numerical hydrological modeling unsaturated zone material was sampled at regular intervals of 50 cm to a maximum depth of 300 cm in four different locations in the study area rainwater groundwater and surface water were simultaneously sampled and analyzed for their 18o and 2h characteristics porewater extracted from the unsaturated zone material was analyzed for the 18o and 2h and chloride content and profiles were created to gauge the isotopic evolution of precipitation and estimate evaporative losses at each interval of the sampling the chloride mass balance technique was used to estimate the fraction of infiltrating water remaining at each interval of the sampling transpiration losses through the entire profile were then estimated this study finds that the vertical infiltration of water through the vadose zone is dominated by piston flow and a mixture of piston and preferential flows in the shallow subsurface 0 0 3 0 m evaporative losses estimated from stable isotope data fall in the range of 29 3 52 4 322 3 576 4 mm year of the annual precipitation with an average of 40 or 440 mm year estimated vadose zone recharge at the maximum depth of sampling ranges between 11 1 and 185 mm year with an average of 32 9 mm year representing 1 1 18 5 and 3 29 of the annual precipitation respectively estimated transpiration losses within this interval range between 29 1 290 mm year and 69 5 695 mm year with an average of 54 7 547 mm year of the annual precipitation transpiration losses appear to increase down the profile and apparently account for a significant percentage of water losses in the vadose zone a significant proportion of the original precipitation is lost within the upper 300 cm 3 m of the vadose zone the water table fluctuations method was independently used to estimate saturated zone groundwater recharge and indicates that recharge rates range between 64 65 and 151 2 mm year with an average of 102 5 mm year which respectively represent 5 9 13 7 and 9 3 of the average annual precipitation in the area the apparently higher estimates from the water table fluctuations method may arise from uncertainties in the specific yield values used for the vadose zone material

sr isotope evolution of seawater the role of tectonics we use a high resolution seawater sr isotopic evolution curve for the last 100 m y in conjunction with modern riverine sr flux measurements and also geologic tectonic and geochronological data to make the case for a close relationship between seawater sr isotopic composition and the india asia continental collision using a simple seawater sr budget model we begin by showing that the sr flux associated with alteration of seafloor basalts is too small and does not have the right time evolution to account for much of the seawater sr isotopic curve of the last 100 m y the flux of dissolved sr carried by rivers originating in the himalaya tibet region on the other hand is presently a significant fraction of the global sr budget we calculate how this riverine flux would have had to change with time in order to match the observed seawater sr isotopic curve and find that the riverine flux remains relatively constant prior to the collision of india with asia but then increases very significantly after collision we note that the period of most rapid change in seawater sr isotopic ratio from 20 ma to 15 ma is also a period of exceptionally high erosion in parts of the himalayas and the tibetan plateau as further evidence that sr derived from the collision of india with asia plays a major role in the sr isotopic evolution of seawater we show that the total amount erosion of the himalaya tibetan plateau since collision which we calculate separately represents a total amount of sr that is very nearly the same as the cumulative amount required by the sr isotopic change of seawater since collision the relationship between erosion and riverine sr flux allows us to use the sr isotopic evolution of seawater to reconstruct a history of erosion since collision and we find that the erosion rate accelerates with time since collision with the present having the largest rate when we apply the sr budget model to the entire phanerozoic using a new compilation of deformed continental area versus time we find that we can account for the large scale structure of the seawater sr isotopic curve but fail to reproduce several local maxima and minima especially in the period 100 300 ma the present high s7sr s6sr of seawater and similar highs in the devonian and cambrian do correlate with extensive deformation on the continents

stable isotopic and geochemical characteristics of groundwater in kherlen river basin a semi arid region in eastern mongolia summary inorganic solute ion concentrations and stable isotopes of oxygen and hydrogen in groundwater river water and precipitation were investigated to gain insight into the groundwater recharge process in the kherlen river basin a semi arid region in eastern mongolia the solute constituents in the river water main stream were of ca hco3 type spatially invariant and low in concentration groundwater in the upstream region was also characterized by a ca hco3 type though all ion concentrations were higher than in the river water on the other hand the chemical composition of the groundwater in the midstream region southern and eastern was spatially variable and the na mg2 cl and hco 3 concentrations were considerably higher than in the river water and upstream groundwater the stable isotopic compositions showed an evaporation effect on the groundwater and river water as well as an altitude effect in the precipitation and river water preferential recharge by relatively large rainfall events is thought to have caused the depleted isotopic ratio in the groundwater in the dry regions the stable isotope chemical and hydrological data suggest that the main stream water of the kherlen river is recharged by precipitation that falls in a headwater region at an altitude of more than 1650 m and that the interaction between the groundwater and river water is not dominant in the midstream and downstream regions of the river basin

mixed carbonate siliciclastic record on the north african margin malta coupling of weathering processes and mid miocene climate we investigated rock outcrops spanning the middle miocene global climate cooling step on the maltese islands in order to reconstruct continental weathering rates and terrigenous fluxes as well as to explore the coupling between these later regional climate and carbonate accumulations sedimentation at this location was dominated during the oligocene and early miocene by a transitional platform to slope carbonates but progressively switched to a clay rich carbonate slope system in the middle miocene around 13 ma an abrupt change toward clay dominated marls occurred and marl deposition persisted until the tortonian ca 12 ma when a shallow water carbonate ramp was reestablished clay mineralogy and bulk rock oxygen isotope analyses suggest that the deposition of the blue clay formation was mainly caused by global climate change and related change in the rate of continental weathering a significant negative correlation r 2 0 65 exists between the carbonate content and the 1 8 o record this combined with the variation of mass accumulation rate of terrigenous material suggests that shorter term periods of globally cooler climate mi events were associated with higher rates of accumulation in continental derived material since during the miocene malta was attached to the north african margin we propose that the observed trends were due to a regional increase in rainfall during cooler periods which consequently increased continental weathering and runoff we further suggest that this pattern was linked to the perturbation of atmospheric fronts due to an increased thermal gradient during the miocene thus regional increase in rainfall might have been linked to the northward migration of the intertropical convergence zone itcz

the strontium isotopic budget of himalayan rivers in nepal and bangladesh abstract himalayan rivers have very unusual sr characteristics and their budget cannot be achieved by simple mixing between silicate and carbonate even if carbonates are radiogenic we present sr o and c isotopic data from river and rain water bedload and bedrock samples for the western and central nepal himalaya and bangladesh including the monsoon season central himalayan rivers receive sr from several sources carbonate and clastic tethyan sediments high himalayan crystalline hhc gneisses and granitoids with minor marbles carbonates and metasediments of the lesser himalaya lh and miocene recent foreland basin sediment from the siwaliks group and the modern flood plain in the tethyan himalaya rivers have dissolved sr 6 mol l and 87sr 86sr 0 717 with a large contribution from moderately radiogenic carbonate rivers draining hhc gneisses are very dilute with sr 0 2 mol l and 87sr 86sr 0 74 lesser himalayan streams also have low sr 0 4 mol l and are highly radiogenic 87sr 86sr 0 78 highly radiogenic carbonates of the lh do not contribute significantly to the sr budget because they are sparse and have very low sr in large rivers exiting the himalaya sr systematics can be modeled as a mixture between tethyan rivers where slightly radiogenic carbonates mean 87sr 86sr 0 715 are the main source of sr and lesser himalaya waters where extremely radiogenic silicates 0 8 are the main source of sr hhc waters are less important because of their low sr rivers draining the siwaliks foreland basin sediments have sr 4 mol l and 87sr 86sr 0 725 weathering of silicates in the siwaliks and the flood plain results in a probably significant radiogenic 0 72 0 74 input to the ganges and brahmaputra g b but quantification of this flux is limited by uncertainties in the hydrologic budget the g b in bangladesh show strong seasonal variability with low sr and high 87sr 86sr during the monsoon sr in the brahmaputra ranges from 0 9 mol l and 0 722 in march to 0 3 mol l and 0 741 in august we estimate the seasonally weighted flux from the g b to be 6 5 108 mol yr with 87sr 86sr 0 7295

spatial vertical and temporal variation of arsenic in shallow aquifers of the bengal basin controlling geochemical processes a detailed understanding of the geochemical processes that regulate the spatial temporal and vertical variation of dissolved arsenic as in shallow aquifers 50m is a prerequisite for sustainable drinking water management in the bengal basin the present study conducted at chakdaha block of the nadia district west bengal india combined a high resolution hydrogeochemical monitoring study over 20months from two sets of piezometers 2 5 to the sediment geochemistry at areas with high average 146 g l n 5 and relatively low average 53 3 g l n 10 dissolved as concentrations in groundwater the determination of the isotopic composition of 2h and 18o in groundwater of the two sites indicated the recharge of evaporative surface water to the aquifer the concentrations of major aqueous solutes ca2 mg2 na k hco3 and cl and electrical conductivity were considerably higher in wells at the high as site compared to the low as site additionally at the high as site the major ions fe so4 2 electrical conductivity 2h and 18o showed markedly greater enrichment in the shallowest part 24m of the aquifer compared to the deeper part reflecting vertical layering of groundwater composition within the aquifer the oxidation of pyrites has been attributed to the high rate of mineral dissolution resulting in such greater enrichments in this part of the aquifer in addition the anthropogenic input with recharge water possibly increased the concentrations of cl in this part of the aquifer the vertical layering of groundwater was absent in the aquifer at the low as site the absence of such layering and relatively low major ion concentrations and electrical conductivity could be linked to the enhanced aquifer flushing and decreased water sediment interactions influenced by local scale groundwater abstraction the seasonal variations of as concentrations in groundwater were observed only in the shallowest part of the aquifers 30m furthermore the as concentrations in groundwater at the uppermost part of the shallow aquifers 21m increased continuously over the monitoring period at both sites this study supports the view that the reductive dissolution of fe oxyhydroxides coupled with competitive po4 3 sorption reactions in the aquifer sediment enriches as in groundwater of the bengal basin however the additional fe released by the weathering of silicate minerals especially biotite or the precipitation of fe as secondary mineral phases such as siderite vivianite and acid volatile sulfides may result in the decoupling of as and fe enrichment in groundwater the redox zonation within the aquifer possibly regulates the vertical distribution of as in the groundwater

on the resonant behavior of a weakly compressible water layer during tsunamigenic earthquakes tsunamigenic earthquakes trigger pressure waves in the ocean given the weak compressibility of the sea water for particular conditions a resonant behavior of the water layer can occur which influences the energy transfer from the sea bed motion to the ocean in this paper the resonance conditions are explained and analyzed focusing on the hydro acoustic waves in the proximity of the earthquake area a preliminary estimation of the generation parameters sea bed rising time velocity is given by means of parametric numerical simulations for simplified conditions the results confirm the importance of measuring modeling and interpreting such waves for tsunami early detection and warning

hydrochemical and isotopic investigation of groundwater of al batin alluvial fan aquifer southern iraq major ions and important trace elements in addition to 18o and 2h were analysed for 43 groundwater samples sampled from the al batin alluvial fan aquifer south iraq the most dominant ions with respect to molarity were na cl so4 2 ca2 mg2 no3 hco3 with total dissolved solids tds averaging 7855 mg l high concentrations were found for the trace elements u mo v b sr and cr this study suggests a hydraulic connection exists near the fan apex between the uppermost part of the al batin aquifer and the underlying dammam aquifer by means of the abu jir fault system except for the effects of extensive irrigation fertilizer use and poorly maintained sewers the groundwater chemistry is mainly controlled by geological processes such as dissolution of evaporites and the enrichment of dissolved ions as a result of the high evaporation and low recharge rate furthermore it is shown that the kuwaiti fuel oil burning during gulf war in 1991 contributed to the enrichment of v and mo in the studied aquifer the spatial distribution of most ions appears to generally increase from the south west towards the north east in the direction of groundwater flow the stable isotopes show heavier values in groundwater with a gradually increasing trend in the direction of groundwater flow due to the decreasing depth to groundwater and thus increasing of evaporation from both groundwater or irrigation return water additionally the stable isotope signature suggests that rainfall from sources in the arabian gulf and the arabian sea is the major source of recharge for the al batin aquifer except for two samples of groundwater all samples were not suitable for potable use according to the who standards most of the groundwater is suitable for some agricultural purpose and for livestock water supply apart from the high salinity boron represents the most critical element in the groundwater with respect to agricultural purposes

elevated equilibrium geotherm in stable continental shield evidence from integrated structural hydrological and electromagnetic studies on nonvolcanic hot springs in the eastern ghats belt india

deeper groundwater chemistry and geochemical modeling of the arsenic affected western bengal basin west bengal india abstract a regional scale hydrogeochemical study of a 21 000 km2 area in the western bengal basin shows the presence of hydrochemically distinct water bodies in the main semiconfined aquifer and deeper isolated aquifers spatial trends of solutes and geochemical modeling indicate that carbonate dissolution silicate weathering and cation exchange control the major ion chemistry of groundwater and river water the main aquifer water has also evolved by mixing with seawater from the bay of bengal and connate water the isolated aquifers contain diagenetically altered water of probable marine origin the postoxic main aquifer water exhibits overlapping redox zones metal reducing sulfidic and methanogenic indicative of partial redox equilibrium with the possibility of oxidation in micro scale environments the redox processes are depth dependent and hydrostratigraphically variable elevated dissolved as in the groundwater is possibly related to fe iii reduction but is strongly influenced by coupled fe s c redox cycles arsenic does not show good correlations with most solutes suggesting involvement of multiple processes in as mobilization the main river in the area the bhagirathi hoogly is chemically distinctive from other streams in the vicinity and probably has little or no influence on deep groundwater chemistry arsenic in water of smaller streams jalangi and ichamati is probably introduced by groundwater discharge during the dry season

geochemical and hydrogeological contrasts between shallow and deeper aquifers in two villages of araihazar bangladesh implications for deeper aquifers as drinking water sources sediment and groundwater profiles were compared in two villages of bangladesh to understand the geochemical and hydrogeological factors that regulate dissolved as concentrations in groundwater in both villages fine grained sediment layers separate shallow aquifers 28 m high in as from deeper aquifers 40 90 m containing 10 g l as in one village dari radiocarbon dating indicates deposition of the deeper aquifer sediments 50 ka ago and a residence time of groundwater of thousands of years in the other village bay the sediment is 20 ka old down to 90 m and the deeper aquifer groundwater is younger with a residence time of hundreds of years the shallow aquifers in both villages that are high in as contain bomb 3 h and bomb 14 c indicating recent recharge the major and minor ion compositions of the shallow and deeper aquifers also differ significantly deeper aquifer water is of the na hco3 type with relatively little dissolved nh4 76 192 mol l fe 27 43 mol l and mn 3 2 mol l in contrast shallow aquifer water is of the ca mg hco3 type with elevated concentrations of dissolved nh4 306 355 mol l fe 191 73 mol l and mn 27 43 mol l in both villages the quantity of as extractable from deeper aquifer sands with a 1 mol l phosphate solution 0 2 0 3 mg kg n 12 0 1 0 1 mg kg n 5 is 1 order of magnitude lower than p extractable as from shallow deposits 1 7 1 2 mg kg n 9 1 4 2 0 mg kg n 11 the differences suggest that the concentration of p extractable as in the sediment is a factor controlling the concentration of as in groundwater low p extractable as levels are observed in both deeper aquifers that are low in as even though there is a large difference in the time of deposition of these aquifers in the two villages the geochemical data and hydrographs presented in this study suggest that both holocene and pleistocene deeper aquifers that are low in as should be a viable source of drinking water as long as withdrawals do not exceed recharge rates of 1 cm yr copyright 2005 elsevier ltd

constraining shallow slip and tsunami excitation in megathrust ruptures using seismic and ocean acoustic waves recorded on ocean bottom sensor networks abstract great earthquakes along subduction zone plate boundaries like the 2011 magnitude 9 0 tohoku oki japan event deform the seafloor to generate massive tsunamis tsunami wave heights near shore are greatest when excitation occurs far offshore near the trench where water depths are greatest and fault slip is shallow the tohoku event featuring over 30 m of slip near the trench exemplifies this hazard unfortunately the rupture process that far offshore is poorly constrained with land based geodetic and even most seafloor deformation measurements and seismic inferences of shallow slip are often nonunique here we demonstrate through dynamic rupture simulations of the tohoku event that long period guided waves in the ocean specifically leaking oceanic p wave modes known as pl waves can resolve the shallow rupture process and tsunami excitation near the trench with predicted pressure changes of 0 1 1 mpa along most of the seafloor landward of the trench and periods of several seconds these pl waves should be observable with ocean bottom pressure sensors and or seismometers with cabled sensor networks like those being deployed offshore japan and in other subduction zones these waves could be used to rapidly quantify shallow slip and near trench seafloor uplift and improve local tsunami early warning systems

environmental isotopes investigation on recharge processes and hydrodynamics of the coastal sedimentary aquifers of tiruvadanai tamilnadu state india summary environmental isotopes 2 h 18 o 3 h 13 c 14 c 34 s in conjunction with hydro geological and hydro chemical data were employed to understand the groundwater recharge processes and hydrodynamics of the tiruvadanai aquifers in the tamilnadu state in southern india hydro chemical characterisation of the groundwater indicated that the tertiary aquifers depth 50 200 m un confined semi confined confined contain no dominant ca mg hco 3 cl to brackish na cl type of waters and the deeper 350 500 m cretaceous aquifer confined contains freshwater the concentration of various chemical species along the general groundwater flow direction northwest to east showed a trend with decrease in mg 2 and ca 2 and an increase in na and k in both tertiary and cretaceous aquifers which is also indicated by decreasing saturation index values for dolomite along the flow path this could be attributed to ion exchange processes a higher ph value of cretaceous aquifer samples 7 4 8 6 could also be responsible for the lowering of mg 2 and ca 2 concentrations by facilitating precipitation of carbonates in them on the 2 h 18 o plot the tertiary aquifers samples fall on an evaporation line their 3 h values near the ephemeral rivers range from 2 to 5 tu while those away from the rivers have 14 c dic model ages range from 1 to 13 ka bp the cretaceous aquifer samples measured 3 h values 14 c dic model ages are 20 ka bp indicating palaeo waters based on 14 c model ages the groundwater velocity was estimated tertiary aquifers 10 2 10 3 m d 1 cretaceous aquifer 10 3 m d 1 dissolution of carbonate bearing minerals in the tertiary aquifer and oxidation of organic matter in the cretaceous aquifers seems to be the dominant processes and thus resulting in the corresponding enrichment and depletion in 13 c dic along the flowpaths the values of 34 s aq so 4 2 showed enrichment in the cretaceous aquifer samples compared to that of the tertiary aquifers samples the 34 s aq so 4 2 enrichment could be due to bacterial reduction of sulphate from the investigation three types of recharge processes to the aquifer system are discerned with the overall modern recharge component being low the cretaceous aquifer contains fossil groundwaters and hence the resources may be finite and their exploitation is mining deeper coastal groundwater isotopic evidence of palaeo climatic excursions between arid and humid phases during the holocene and late pleistocene in the southern india has been obtained for the first time

strong influence of water vapor source dynamics on stable isotopes in precipitation observed in southern meghalaya ne india to calibrate 18o time series from speleothems in the eastern indian summer monsoon ism region of india and to understand the moisture regime over the northern bay of bengal bob we analyze the 18o and d of rainwater collected in 2007 and 2008 near cherrapunji india d values range from 18 5 to 144 4 while 18o varies between 0 8 and 18 8 the local meteoric water line lmwl is found to be indistinguishable from the global meteoric water line gmwl late ism september october rainfall exhibits lowest 18o and d values with little relationship to the local precipitation amount there is a trend to lighter isotope values over the course of the ism but it does not correlate with the patterns of temperature and rainfall amount 18o and d time series have to be interpreted with caution in terms of the amount effect in this subtropical region we find that the temporal trend in 18o reflects increasing transport distance during the ism isotopic changes in the northern bob surface waters during late ism and vapor re equilibration with rain droplets using an isotope box model for surface ocean waters we quantify the potential influence of river runoff on the isotopic composition of the seasonal freshwater plume in the northern bob temporal variations in this source can contribute up to 25 of the observed changes in stable isotopes of precipitation in ne india to delineate other moisture sources we use backward trajectory computations and find a strong correlation between source region and isotopic composition palaeoclimatic stable isotope time series from northeast indian speleothems likely reflect changes in moisture source and transport pathway as well as the isotopic composition of the bob surface water all of which in turn reflect ism strength stalagmite records from the region can therefore be interpreted as integrated measures of the ism strength

multivariate statistical analysis and environmental isotopes of amman wadi sir b2 a7 groundwater yarmouk river basin jordan multivariate statistical techniques cluster and factor analyses were applied on the amman wadi sir groundwater chemistry yarmouk river basin north jordan the main objective was to investigate the main processes affecting the groundwater chemical quality and its evolution the k means cluster analysis yields three groups with distinct ionic concentrations cluster 1 comprises the vast majority of the sampled wells and the water that belongs to this cluster can be classified as freshwater cluster 2 comprises only 2 of the sampled wells it has the highest ionic concentration the water of this cluster can be classified as brackish water cluster 3 involves 23 of the sampled wells and it has total ionic concentration intermediate to that of clusters 1 and 2 factor analysis yields a three factor model which explains 76 77 of the groundwater quality variation factor 1 salinity factor involves ec na cl so4 2 k and mg 2 and reflects groundwater salinization because of overpumping factor 2 hardness factor includes ca 2 hco3 and the ph value and signifies soil water rock interaction factor 3 nitrate factor involves only no3 and points to groundwater contamination because of human activities mainly untreated wastewater and crops and animal cultivation in the unconfined portion of the aquifer factors 1 and 3 can be described as human induced factors whereas factor 2 can be described as geogenic factor factors scores were mapped to deduce the controlling processes on the groundwater chemistry stable isotope composition of 18o and 2h has revealed that the groundwater is a mixture of two water types the radioactive isotopes tritium and 14 c were used to evaluate present day recharge to the aquifer and to estimate the groundwater age respectively present day recharge to the groundwater is taking place in the unconfined portion of the aquifer as it is indicated by the measurable tritium content and low groundwater age copyright 2012 john wiley sons ltd

lithologic and climatologic controls of river chemistry abstract the chemistries of rivers draining a variety of lithologic and climatic regions have been surveyed for the purpose of quantifying the fluxes of bicarbonate and silica from rivers with respect to bedrock lithology and runoff in all 101 different rivers each draining a primary lithology were examined across the united states puerto rico and iceland to minimize seasonal effects only rivers with at least two years of data were used basaltic catchments were examined in the greatest detail in a survey of hawaiian island watersheds the average river chemistries could be related to the distribution of soil associations within each catchment an analysis of cation activity relationships among rivers draining basaltic catchments shows that the river compositions define slopes which are consistent with an equilibrium ion exchange control on cation ratios among different lithologies unique weathering rate relationships were developed with yields at typical present day runoff rates 1 100 cm y increasing in the order sandstones granites basalts shales and carbonates the bicarbonate and silica fluxes for each of these lithologies have been quantified for use in global studies of chemical denudation our study confirms that the dissolved yield of a given drainage basin is determined by a balance between physical and chemical weathering thus a warm wet climate or the presence of abundant vegetation cannot guarantee high rates of chemical denudation unless accompanied by high rates of physical removal

regional scale stable isotopic signatures of recharge and deep groundwater in the arsenic affected areas of west bengal india summary samples of deep groundwater river water and rainwater were collected for 18o and 2h analyses from an area of 22 000 km2 in the arsenic affected districts of west bengal india in order to examine groundwater recharge a plot of 18o versus 2h of groundwater falls subparallel to the constructed local meteoric water line 2h 7 2 18o 7 7 suggesting a predominance of meteoric recharge with some evaporation the stable isotopic signature of groundwater from the deeper part of the semiconfined main aquifer is similar to that of shallower groundwater which suggests that deeper groundwater has been recharged in the present day climatic regime mostly from monsoonal rainfall groundwater in deeper isolated aquifers falls within the isotopic range observed for the main aquifer a trend of isotopic depletion of groundwater that extends northward and westward from the bay of bengal the monsoonal moisture source area indicates a rain out process following rayleigh type distillation some recharge may have taken place from the rivers ganges and bhagirathi hoogly with minimal inflow from other rivers jalangi and ichamati

the october 28 2012 mw 7 8 haida gwaii underthrusting earthquake and tsunami slip partitioning along the queen charlotte fault transpressional plate boundary the pacific north american plate boundary is undergoing predominantly right lateral strike slip motion along the queen charlotte and fairweather transform faults the queen charlotte fault qcf hosted the largest historical earthquake in canada the 1949 m s 8 1 strike slip earthquake which ruptured from offshore northern haida gwaii several hundred kilometers northwestward on january 5 2013 an m w 7 5 strike slip faulting event occurred near the northern end of the 1949 rupture zone along central and southern haida gwaii the relative plate motion has 20 oblique convergence across the left stepping plate boundary there had been uncertainty in how the compressional component of plate motion is accommodated the october 28 2012 m w 7 8 haida gwaii earthquake involved slightly 20 oblique thrust faulting on a shallow 18 5 northeast dipping fault plane with strike 320 parallel to the qcf consistent with prior inferences of pacific plate underthrusting beneath haida gwaii the rupture extended to shallow depth offshore of moresby island beneath a 25 30 km wide terrace of sediments that has accumulated in a wedge seaward of the qcf the shallow thrusting caused seafloor uplift that generated substantial localized tsunami run up and a modest far field tsunami that spread across the northern pacific prompting a tsunami warning beach closure and coastal evacuation in hawaii although ultimately tide gauges showed less than 0 8 m of water level increase the mainshock rupture appears to have spread with a 2 3 km s rupture velocity over a length of 150 km with slip averaging 3 3 m concentrated beneath the sedimentary wedge the event was followed by a substantial aftershock sequence in which almost all of the larger events involve distributed intraplate normal faulting extending 50 km oceanward from the qcf the highly oblique slip partitioning in southern haida gwaii is distinctive in that the local plate boundary parallel motion on the qcf may be accommodated either by infrequent large strike slip ruptures or by aseismic creep as seems to be the case for deeper oblique relative plate motion beneath haida gwaii while the sedimentary terrace accumulates plate boundary perpendicular compressional strain that releases in almost pure thrust faulting earthquakes seaward of the qcf

isotopic study of water resources in a semi arid region western iraq hydrochemistry and stable isotopic technique were used in studying the water resources interaction in a semi arid area western iraq throughout iraq 28 groundwater samples 7 surface water samples from the study area and 18 rainwater samples were analyzed for 2h and 18o stable isotopes and hydrochemical analysis in this study the temperature altitude and continental effects on the isotopic composition of rain water in iraq were studied the results show that isotopes content in rainwater in the current study increases with increasing temperature and a good correlation exists between increasing latitude with decreasing 18o values rainwater isotopes show evidence of temperature effect and continental effect associated with altitude effect generally due to variation in temperature and altitude throughout iraq the values of isotopic composition of rainwater range from 7 25 to 2 79 and from 45 to 9 7 for 18o and d respectively the similarity of isotopic composition of water of the euphrates river and haditha reservoir with that of groundwater taken from neighbor wells gives indication that intermixing between them is exist while the groundwater of the wells far from the surface water resources is mostly affected by rainwater

understanding groundwater systems and their functioning through the study of stable water isotopes in a hard rock aquifer maheshwaram watershed india summary groundwater degradation through abstraction contamination etc shows a world wide increase and has been of growing concern for the past decades in this light the stable isotopes of the water molecule 18 o and 2 h from a hard rock aquifer in the maheshwaram watershed andhra pradesh india were studied this small watershed 53 km 2 underlain by granite is endorheic and representative of agricultural land use in india with more than 700 bore wells in use in such a watershed the effect of overpumping can be severe and the environmental effects of water abstraction and contamination are of vital importance a detailed and dynamic understanding of groundwater sources and flow paths in this watershed thus is a major issue for both researchers and water managers especially with regards to water quality as well as the delimitation of resources and long term sustainability to this end the input from monsoon precipitation was monitored over two cycles as well as measuring spatial and temporal variations in 18 o and 2 h in the groundwater and in precipitation individual recharge from the two monsoon periods was identified leading to identification of periods during which evaporation affects groundwater quality through a higher concentration of salts and stable isotopes in the return flow such evaporation is further affected by land use rice paddies having the strongest evapotranspiration

quantifying closed basin lake temperature and hydrology by inversion of oxygen isotope and trace element paleoclimate records lake systems are important paleoclimate archives that preserve ecosystem and hydrologic responses to critical periods in earth history such as carbon cycle perturbations and glacial interglacial cycles geochemical measurements of biogenic carbonate for example 18o 13c 87sr 86sr li u sr and mg are indicators of hydrologic variability in lake systems throughout the geologic record in this study we present a new closed basin lake modeling approach hybim the hydrologic balance inverse model that employs a system of total differential equations and uses the measured 18o sr ca and mg ca of biogenic carbonate to determine changes in temperature runoff and lake evaporation using equally spaced time steps these equations are simultaneously solved to constrain the hydrologic parameters of the lake as recorded in biogenic carbonate we use a monte carlo approach to account for uncertainty in the input parameters such as 18o temperature relationships partition coefficient uncertainty and watershed solute chemistry for illustrative purposes we apply the model to two ostracod valve datasets covering different timescales 1 the cretaceous songliao basin northeast china and 2 holocene lake miragoane haiti modern water measurements of water isotopes and cation concentrations from each location are required as model inputs we compare our modeling results with author interpretations and geologic observations the modeling approach presented in this study can be applied to other closed basin lake records can be modified for other calcifying species for example gastropods or mollusks or with calibration to inorganic lacustrine carbonate in addition this approach holds promise for extension with additional proxy measurements that is d u ca or li ca and changing source area on tectonic timescales using proxies that reflect changing source lithology that is sr and pb isotopes future incorporation of age model uncertainty in the monte carlo approach will also provide utility by quantifying temporal uncertainty on the hydrologic response recorded by lake sediments

was the antarctic glaciation delayed by a high degassing rate during the early cenozoic abstract the cenozoic is a period of major climatic changes marked by the formation of the antarctic ice sheet at the eocene oligocene e o boundary the opening of the southern ocean seaways and the decrease in atmospheric co2 are two processes generally evoked to explain this e o cooling the debate is still ongoing but modeling studies tend to demonstrate that the decrease in atmospheric co2 is the main driver of the cooling however uncertainties persist on what drove the decrease in atmospheric co2 during the cenozoic in this study we investigate the impact of continental drift lithology distribution and volcanic degassing rates on the atmospheric carbon dioxide concentration over the cenozoic within a coupled climate carbon model geoclim in the model the continental drift results in driving low atmospheric co2 levels during the eocene and the oligocene the dispersed configuration and the location of a large continental area north africa northern south america within the inter tropical convergence zone itcz promote co2 consumption by weathering forcing co2 to remain low icehouse conditions are also promoted by the drifting of india and the weathering of the deccan basalts in the itcz during the eocene and by the weathering of the ethiopian traps during the oligocene to prevent the building up of the antarctic ice sheet at the eocene the model needs enhanced solid earth degassing flux by 50 so that atmospheric co2 levels stay above the glacial threshold 750 ppm we find that the decrease in atmospheric co2 from the eocene to the oligocene is probably due to a reduction in the source of volcanic co2 rather than an increase in silicate weathering the model results furthermore suggest that during the miocene period the northward drifting of both the african plate and india including the deccan traps might have decreased the continental surface exposed to chemical weathering therefore generating higher co2 values finally the uplift of the tibetan plateau from the miocene to the present day induces in the model an increase in silicate weathering through the intensification of the south eastern asian monsoon causing atmospheric co2 to come back to a pre industrial value

groundwater flow in the ganges delta basu et al 1 1 reported that 2 1011 m3 year of groundwater flows directly into the bay of bengal an outflow equivalent to 19 of the discharge from the ganges brahmaputra river system they showed that this estimate of flow could have important consequences for the interpretation of

modelling the phanerozoic carbon cycle and climate constraints from the 87sr 86sr isotopic ratio of seawater a numerical model describing the coupled evolution of the biogeochemical cycles of carbon sulfur calcium magnesium phosphorus and strontium has been developed to describe the long term changes of atmospheric carbon dioxide and climate during the phanerozoic the emphasis is on the effects of coupling the cycles of carbon and strontium various interpretations of the observed phanerozoic history of the seawater 87sr 86sr ratio are investigated with the model more specifically the abilities of continental weathering volcanism and surface lithology in generating that signal are tested and compared it is suggested that the observed fluctuations are mostly due to a changing weatherability over time it is shown that such a conclusion is very important for the modelling of the carbon cycle indeed it implies that the conventional belief that the evolution of atmospheric carbon dioxide and climate on a long time scale is governed by the balance between the volcanic input of co2 and the rate of silicate weathering is not true rather carbon exchanges between the mantle and the exogenic system are likely to have played a key role too further the increase of the global weathering rates with increasing surface temperature and or atmospheric co2 pressure usually postulated in long term carbon cycle and climate modelling is also inconsistent with the new model other factors appear to have modulated the weatherability of the continents through time such as mountain building and the existence of glaciers and ice sheets based on these observations a history of atmospheric carbon dioxide and climate during phanerozoic time consistent with the strontium isotopic data is reconstructed with the model and is shown to be compatible with paleoclimatic indicators such as the timing of glaciation and the estimates of cretaceous paleotemperatures

chemical denudation and silicate weathering in himalayan glacier basins batura glacier pakistan original article can be found at http www sciencedirect com science journal 00221694 copyright elsevier b v doi 10 1016 s0022 1694 02 00036 7 full text of this article is not available in the uhra

the himalayas organic carbon burial and climate in the miocene cooling ages of rock in the himalayas imply that rapid exhumation between the main central thrust system and the south tibetan detachment system occurred between 21 and 17 ma the generation of relief and enhanced weathering which followed this event may have resulted in a pronounced increase in the delivery of dissolved strontium carbon phosphorus and other chemical weathering products to the ocean richter et al 1992 the increased supply of nutrients stimulated productivity in oceanic upwelling zones and expansion of the oxygen minimum zone leading to enhanced burial and preservation of organic matter in the monterey formation and other deposits from this interval a downdraw of atmospheric co2 associated with enhanced chemical weathering rates and organic matter burial may have led to global cooling and the expansion of the antarctic ice sheet by 15 ma the above scenario differs from the monterey hypothesis of vincent and berger in that co2 downdraw is primarily via silicate weathering rather than organic carbon burial and that organic carbon burial is driven by increased delivery of nutrients to the ocean rather than by stronger upwelling a carbon mass balance calculation which assumes that river fluxes have been increasing over the last 40 ma predicts that absolute organic carbon burial increased over this interval while at the same time the fraction of carbon buried as organic matter versus carbonate decreased this implies that the organic carbon cycle has acted as a net source of co2 to the atmosphere over the late cenozoic

perennial ponds are not an important source of water or dissolved organic matter to groundwaters with high arsenic concentrations in west bengal india excess of 4600 m gk g 1 stable isotope ratios of waters from constructed perennial ponds indicate the ponds are chiefly recharged during the summer monsoon and subsequently undergo extensive evaporation during the dry winter season in contrast groundwaters with high as concentrations plot along the local meteoric water line lmwl near where the annual volume weighted mean precipitation values for d 2 ha ndd 18 o would plot the stable isotope data demonstrate that groundwaters are directly recharged by local precipitation without significant evaporation and thus are not recharged by nor mixed with the pond waters furthermore reactive transport modeling indicates that dissolved organic matter dom derived from pond waters does not fuel microbial respiration and as mobilization at depth in the underlying aquifer because travel times for pond derived dom exceed groundwater ages by thousands of years instead organic matter within the aquifer sediments must drive dissimilatory iron reduction and as release to groundwaters citation datta s a w neal t j mohajerin t ocheltree b e rosenheim c d white and k h johannesson 2011 perennial ponds are not an important source of water or dissolved organic matter to groundwaters with high arsenic concentrations in west bengal india geophys res lett 38 l20404 doi 10 1029 2011gl049301

modeling rock weathering in small watersheds summary many mountainous watersheds are conceived as aquifer media where multiple groundwater flow systems have developed toth 1963 and as bimodal landscapes where differential weathering of bare and soil mantled rock has occurred wahrhaftig 1965 the results of a weathering algorithm pacheco and van der weijden 2012a 2014 which integrates topographic hydrologic rock structure and chemical data to calculate weathering rates at the watershed scale validated the conceptual models in the river sordo basin a small watershed located in the marao cordillera north of portugal the coupling of weathering groundwater flow and landscape evolution analyses as accomplished in this study is innovative and represents a remarkable achievement towards regionalization of rock weathering at the watershed scale the river sordo basin occupies an area of approximately 51 2 km 2 and was shaped on granite and metassediment terrains between the altitudes 185 1300 m the groundwater flow system is composed of recharge areas located at elevations 700 m identified on the basis of 18 o data discharge cells comprehend terminations of local intermediate and regional flow systems identified on the basis of spring density patterns infiltration depth estimates based on 87 sr 86 sr data and spatial distributions of groundwater ph and natural mineralization intermediate and regional flow systems defined where infiltration depths 125 m develop solely along the contact zone between granites and metassediments because fractures in this region are profound and their density is very large weathering is accelerated where rocks are covered by thick soils being five times faster relative to sectors of the basin where rocks are covered by thin soils differential weathering of bare and soil mantled rock is also revealed by the spatial distribution of calculated aquifer hydraulic diffusivities and groundwater travel times

weathering processes in the ganges brahmaputra basin and the riverine alkalinity budget abstract we present river chemistry data for a network of rivers draining the western and central nepal himalaya our sampling locations cover the system from the sources of rivers in tibet to the gangetic plain water samples were collected throughout the year including the monsoon season for rivers in nepal and for the ganges and brahmaputra in bangladesh rivers draining the north himalaya are characterized by low discharge under a cold and arid climate main stream waters have 13 c dic near 0 and high so42 so42 hco3 ratios xso4 with values around 40 eq and high cl ca is the dominant cation ca2 cations 55 to 75 eq after correction of sodium by chloride dissolved sulfate is produced in waters from the tethian sedimentary series whereas chlorine is related to thermal waters dissolved sulfate is primarily derived from sulfide oxidation rather than evaporite dissolution 13 c dic values of up to 3 9 show that metamorphic co2 is an important weathering agent rivers of the north himalayan basins have about 50 of their alkalinity derived from carbonate dissolution 20 from biogenic activity and 30 from metamorphic co2 on the south flank of the himalaya rivers are more depleted in 13 c and have on average lower xso4 most rivers have 13 c dic and xso4 values compatible with a simple mixing between soil co2 and sulfate derived from sulfide oxidation during the monsoon discharge increases by a factor 20 but the total dissolved concentration is only slightly reduced xso4 and 13 c decrease while ca cations increases implying enhanced dissolution of pedogenic calcite as a whole the g b riverine flux of alkalinity derived from silicate weathering is around 2 7 1011 mol year modest at the global scale sulphuric acid controls 20 30 of the weathering reaction in the brahmaputra and 6 to 9 in the ganges na and k balance 60 to 65 of the silicate derived alkalinity flux and the long term co2 consumption by ganges and brahmaputra is near 6 4 1010 mol year the flux of metamorphic co2 converted to alkalinity via weathering reactions is ca 1 1010 mol year

stable isotope evidences on sources and mechanisms of groundwater recharge in hohhot basin china it is extremely important for water resources management to understand the mechanisms of recharge to aquifer monitoring changes in stable isotopes 2h and 18o can be used to learn some information on groundwater recharge processes in this study the stable isotopes from precipitation and groundwater samples were employed to trace the recharge processes in hohhot area inner mongolia the recharge of shallow groundwater is mainly due to precipitation from the eastern mountain area in eastern and southeastern parts and from the northern mountain area in the northern and southwestern parts the recharge mechanisms for shallow groundwater are the infiltration of surface water in the piedmont area and lateral flow recharge the source of deep groundwater in confined aquifer is probably from precipitation in high altitude area or cold weather conditions which perhaps have the same recharge source as shallow groundwater in the northern and southwestern parts compared with the previous data from shao s geotech investig surv 4 41 43 1989 study the variation of groundwater recharge for nearly 30 years in the study area was inferred the recharge zone is the eastern and northern mountain areas the recharge way to shallow groundwater has changed into lateral recharge from surface runoff in the mountain area and from surface runoff and vertical rainfall infiltration in the piedmont area but the recharge mechanism for deep groundwater has a similar origin with the one for northern shallow groundwater namely the lateral recharge

late miocene vegetation reconstruction with the caraib model abstract climatic outputs from the atmospheric general circulation model echam4 coupled to a mixed layer ocean model are used as inputs to the caraib global vegetation model to reconstruct the distribution of vegetation and the biosphere carbon stocks over the continents during the late miocene tortonian the results show significant changes in the geographical distribution of vegetation during the late miocene compared to the present with a reduction of desert areas and an expansion of tropical seasonal forests which reached temperate latitudes these changes in vegetation distribution are accompanied by a moderate increase of the total biosphere carbon stock by 159 gt sensitivity tests to atmospheric co 2 have also been performed with the vegetation model only i e while keeping constant all climatic variables to their reference tortonian state these tests point out the potential importance of co 2 fertilization both regarding vegetation distribution and biosphere carbon storage the impact of an atmospheric co 2 decrease from 280 to 200 ppmv or increase from 280 to 560 ppmv on the vegetation distribution appears to be at least as large as that of the climate change between the tortonian and the present while in terms of carbon storage the impact of atmospheric co 2 is far much larger than the climatic one although the actual response of vegetation to co 2 fertilization may be much smaller than its theoretical response in the model these results emphasize the need to consider atmospheric co 2 as an important parameter for palaeovegetation reconstructions

the early paleozoic carbon cycle a review of o c sr and s isotope trends for the entire phanerozoic shows that the present day values of isotope signals are similar to those at the proterozoic termination the sharp rise in 87sr 86sr since 65 ma has been attributed to an uplift and subsequent metamorphism and erosion associated with the himalayas and tibet this orogenic evolution has been postulated to have influenced the global organic and inorganic carbon cycles and climate as well a similar large scale orogeny the pan african event also dominated the neoproterozoic vendian times and the similarity of modern and neoproterozoic isotope values for seawater may therefore have had a comparable tectonic cause in this contribution we present the results of a numerical model of the coupled c alkalinity s sr cycles suggesting that the early paleozoic from early cambrian to late devonian evolution of sr o c and s seawater isotope signals could have been the consequence of progressive oxidation of a large reduced carbon reservoir exhumed during the pan african orogeny the 18o measured in brachiopod shells is used as a forcing of the model postulating that any change in the oxygen isotopic composition of seawater is the result of a disequilibrium in the organic carbon subcycle through the coupling of the oxygen isotopic and carbon cycles the calculated 13c 87sr 86sr and 34s are in good agreement with the data as is the reasonable calculated history for atmospheric pco2 and its relation to global climate

a new model for atmospheric oxygen over phanerozoic time a mathematical model has been constructed that enables calculation of the level of atmospheric o2 over the past 570 my from rates of burial and weathering of organic carbon c and pyrite sulfur s burial rates as a function of time are calculated from an assumed constant worldwide clastic sedimentation rate and the relative abundance and c and s contents of the three rock types marine sandstones and shales coal basin sediments and other non marine clastics red beds arkoses by our model values of o2 versus time using a constant total sedimentation rate agree with those for variable sedimentation derived from present day rock abundances and estimates of erosional losses since deposition this agreement is the result of our reliance on the idea that any increase in total worldwide sediment burial with consequently faster burial of c and s and greater o2 production must be accompanied by a corresponding increase in erosion and increased exposure of c and s on the continents to o2 consumption via weathering it is the redistribution of sediment between the three different rock types and not total sedimentation rate that is important in o2 control to add stability to the system negative feedback against excessive o2 fluctuation was provided in the modeling by the geologically reasonable assignment of higher weathering rates to younger rocks resulting in rapid recycling of c and s we did not use direct o2 negative feedback on either weathering of c and s or burial of c because weathering rates are assumed to be limited by uplift and erosion and the burial rate of c limited by the rate of sediment deposition the latter assumption is the result of modern sediment studies which show that marine organic matter burial occurs mainly in oxygenated shallow water and is limited by the rate of supply of nutrients to the oceans by rivers results of the modeling indicate that atmospheric o2 probably has varied appreciably over phanerozoic time during the late carboniferous and permian periods o2 was higher than previously because of the rise of vascular land plants and the widespread burial of organic matter in vast coal swamps a large decrease in o2 during the late permian was due probably to the drying up of the coal swamps and deposition of a large proportion of total sediment in c and s free continental red beds sensitivity study shows that major parameters affecting results are the mean c concentration in coal basins and the relative sizes of the reservoirs of young rapidly recycled versus old rocks less sensitivity was found for changes over time in total land area undergoing weathering and the use of direct o2 negative feedback on marine carbon burial good agreement for rates of c burial calculated via our model and via independent models which are based on the use of stable carbon isotopes indicates that the dominant factor that has brought about changes in atmospheric o2 level and the isotopic composition of dissolved inorganic carbon in seawater over phanerozoic time is sedimentation and not weathering or higher temperature phenomena such as basalt seawater reaction

neogene growth of the sedimentary organic carbon reservoir we develop a recycling model using 13c 12c mass balance for net growth loss of the sedimentary organic carbon corg reservoir and apply it to the neogene bulk marine carbonate 13c record the model allows for variations in photosynthetic fractionation factors carbon cycling rates and the isotopic composition of riverine carbon inputs to the oceans the sign of the net flux term is controlled by the difference between fractional corg burial and fractional corg weathering independent of any variations in carbon cycling rate these terms are in turn estimated from the carbon isotope mass balance of newly deposited and weathered sediments respectively the magnitude of the net flux is sensitive to the global carbon cycling erosion deposition rate which may be estimated by the use of the records of radiogenic isotopic variations nd sr in paleoseawater a key observation and input to the model is that photosynthetic carbon isotope fractionation by both marine algae and terrestrial plants has decreased during the cenozoic incorporating time dependent carbon isotope fractionation into the model shows that the sedimentary corg reservoir has grown throughout most of the neogene even as marine 13c values fell after 14 ma a similar result is obtained if the variation in the marine 13c record is largely caused by changes in the carbon isotopic composition of river fluxes to the oceans rather than changes in the organic inorganic ratio of output to the burial sink the growth of the sedimentary organic carbon reservoir requires that the neogene sedimentary carbon cycle was a net source of o2 and a net sink of co2 to the atmosphere at least until the plio pleistocene as a consequence neogene co2 consumption by silicate weathering cannot be balanced by oxidation of sedimentary corg placing a significant constraint on global carbon balance models a related prediction of our model is that atmospheric o2 levels rose during the neogene

boron isotope systematics in large rivers implications for the marine boron budget and paleo ph reconstruction over the cenozoic abstract the chemical composition of the oceans and long term climate changes are believed to be linked reconstruction of seawater ph evolution is desirable as ph may be related to atmospheric pco2 and hence to climate evolution boron isotopes in oceanic carbonates have been suggested to be a proxy for oceanic paleo ph reconstruction nevertheless the calculation of paleo ph values over geological periods requires a precise knowledge of the boron isotopic composition of the oceans when calcite precipitated we present the systematics of boron isotopic composition of the world s main rivers we deduce a continental boron flux to the oceans of 38 1010 gb year with a mean isotopic composition of 10 these results lead to a balanced boron budget in the oceans and allow the development of a model for the marine boron secular evolution over the past 100 myr it is shown that the oceanic boron cycle is mainly controlled by the boron continental discharge and the boron uptake from the oceans during low temperature alteration of oceanic crust however the recent important increase of the clastic sediment supply linked to the himalayan erosion impacts the oceanic boron budget by enhancing significantly the boron uptake by adsorption on sediments we predict a boron isotopic composition in the oceans lower during the cenozoic and slightly higher during the cretaceous than today the modelled values for the marine boron isotopes follow the variations of boron isotopes in carbonates over the cenozoic era provided by previous studies suggesting that the variations of the seawater ph may not have been important on this time scale if this is the case it involves that buffering mechanisms occur in the oceans to maintain seawater ph at a roughly constant value against past atmospheric pco2 variations

stable carbon isotopes of amorphous kerogens from phanerozoic sedimentary rocks amorphous kerogens from phanerozoic sedimentary rocks may be divided into two groups on the basis of their 13c values h amorphous kerogens have isotopic values in the range of 24 to 20 per mil and l amorphous kerogens have isotopic values in the range of 35 to 26 per mil the occurrence of amorphous kerogens in the intermediate isotopic range from one rock unit in the data set suggests a weak continuum may exist between these two groups phytoplankton and to a lesser extent zooplankton and bacteria are considered to be the precursors for both kerogen types a plausible explanation for this dichotomy may be found in the source of co2 utilized by phytoplankton which is considered to be controlled by environmental factors h amorphous kerogens are expected to occur in silled basins that are overlain by expansive well circulated deep 500 m water where the prevailing source of carbon in the photic zone is atmospheric derived co2 conversely l amorphous kerogens are expected to occur in restricted basins that are overlain by stratified shallow 200 m water where the prevailing source of carbon in the photic zone may be organic derived co2

fdm simulation of seismic waves ocean acoustic waves and tsunamis based on tsunami coupled equations of motion we have developed a new unified modeling technique for the total simulation of seismic waves ocean acoustic waves and tsunamis resulting from earthquakes based on a finite difference method simulation of the 3d equations of motion using the equilibrium between the pressure gradient and gravity in these equations tsunami propagation is naturally incorporated in the simulation based on the equations of motion the performance of the parallel computation for the newly developed tsunami coupled equations using a domain partitioning procedure shows a high efficiency coefficient with a large number of cpu cores the simulation results show how the near field term associated with seismic waves produced by shallow earthquakes leads to a permanent coseismic deformation of the ground surface which gives rise to the initial tsunami on the sea surface propagation of the tsunami along the sea surface as a gravity wave and ocean acoustic waves in seawater with high frequency multiple p wave reflections between the free surface and sea bottom are also clearly demonstrated by the present simulations we find a good agreement in the tsunami waveform between our results and those obtained by other simulations based on an analytical model and the navier stokes equations demonstrating the effectiveness of the tsunami coupling simulation model based on this simulation we show that the ratio of the amplitude of ocean acoustic waves to the height of the tsunami both of which are produced by the earthquake strongly depends on the rise time of the earthquake rupture this ratio can be used to obtain a more detailed understanding of the source rupture processes of subduction zone earthquakes and for implementing an improved tsunami alert system for slow tsunami earthquakes

balancing the cenozoic carbon and alkalinity cycles constraints from isotopic records a simple model of the carbon alkalinity and strontium cycles is built up and used to interpret the carbon and strontium isotopic evolution of seawater over the cenozoic as recorded in marine limestones the idea that weathering fluxes have increased globally over the cenozoic in response to the himalayan uplift is critically examined it is shown that such an increase of global weathering postulated to explain the sharp increase in the 87sr 86sr ratio is not compatible with the carbon isotopic record if the budgets of carbon alkalinity and strontium are considered simultaneously another scenario of the cenozoic evolution of global weathering consistent with the carbon isotopic record is proposed in which the global weathering flux varies only slightly over the cenozoic with a small increase between 15 ma and the present this second scenario appears more consistent with the reconstructed carbonate sedimentation rate and the evolution of the carbon isotopic fractionation in continental and oceanic environments

chemical evolution in the high arsenic groundwater of the huhhot basin inner mongolia pr china and its difference from the western bengal basin india elevated as concentrations in groundwater of the huhhot basin hb inner mongolia china and the western bengal basin wbb india have been known for decades however few studies have been performed to comprehend the processes controlling overall groundwater chemistry in the hb in this study the controls on solute chemistry in the hb have been interpreted and compared with the well studied wbb which has a very different climate physiography lithology and aquifer characteristics than the hb in general there are marked differences in solute chemistry between hb and wbb groundwaters stable isotopic signatures indicate meteoric recharge in the hb in a colder climate distant from the source of moisture in comparison to the warm humid wbb the major ion composition of the moderately reducing hb groundwater is dominated by a mixed ion ca na hco3 cl hydrochemical facies with an evolutionary trend along the regional hydraulic gradient molar ratios and thermodynamic calculations show that hb groundwater has not been affected by cation exchange but is dominated by weathering of feldspars allitization and equilibrium with gibbsite and anorthite mineral weathering and mobilization of as could occur as recharging water flows through fractured argillaceous metamorphic or volcanic rocks in the adjoining mountain front areas and deposits solutes near the center of the basin in contrast wbb groundwater is ca hco3 dominated indicative of calcite weathering with some cation exchange and silicate weathering monosiallitization

an overview of the 28 october 2012 m w 7 7 earthquake in haida gwaii canada a tsunamigenic thrust event along a predominantly strike slip margin the boundary between the pacific and north america plates along canada s west coast is one of the most seismically active regions of canada and is where canada s two largest instrumentally recorded earthquakes have occurred although this is a predominantly strike slip transform fault boundary there is a component of oblique convergence between the pacific and north america plates off haida gwaii the 2012 mw 7 7 haida gwaii earthquake was a thrust event that generated a tsunami with significant run up of over 7 m in several inlets on the west coast of moresby island several over 6 m with a maximum of 13 m damage from this earthquake and tsunami was minor due to the lack of population and vulnerable structures on this coast

exemple d etude geochimique et isotopique de circulations aquiferes en terrain volcanique sous climat semi aride amurga gran canaria iles canaries abstract a hydrochemical and isotopic study of a groundwater flow system in volcanic media has been carried out in the southern part of gran canaria canary islands monthly samples of precipitation were collected over a two year period at stations distributed all over the island sampling of groundwaters took place mainly from drillholes in the amurga phonolitic massif but also from wells and springs discharging from the volcanic and related detrital formations the 2 h vs 18 o relationship of the precipitation is close to the global meteoric water line two distinct altitudinal isotopic gradients are observed on the warm and dry southern slope the combination of a contribution of saharan dusts and seasprays and of partial evaporation explains the high content of dissolved salts cl so 2 4 in precipitation additional processes may be invoked as sources of groundwater mineralization leaching of silicate minerals during infiltration and or from hydrolysis during the long residence time of the waters in the volcanic rocks salt content is increased through a concentration of the percolating solutions by evaporation as shown by their stable isotope contents 18 o 2 h the groundwaters in the phonolitic aquifer are well differentiated from the deeper groundwaters which are recharged at an altitude of about 1000m above sea level or even less if exceptional episodes of rain have a lower heavy isotope content the interpretation of the 13 c contents of soil co 2 sampled throughout the area and of the 13 c and 14 c contents of total dissolved inorganic carbon tdic leads to the concept of an incorporation of pure biogenic carbon under open system conditions in the amurga waters for these groundwaters high estimates of residence time ca 11000 years can be calculated from the low 14 c activities in the neighbouring valleys the input of deep dead volcanic carbon and the occurrence of mixing do not allow an exact quantification of residence time values however they seem to be shorter than those measured for the amurga waters

global change in the late devonian modelling the frasnian famennian short term carbon isotope excursions a model of the global biogeochemical cycles coupled to a energy balance climate model the combine model is used to identify the causes of two large n 13 c value excursions across the frasnian famennian f f boundary we test a scenario that links the sea level rise to stratification of the proto tethys ocean through the formation of warm saline deep waters in extended epicontinental seas even though this scenario can produce dysoxia below 100 m depth it fails to increase the global burial flux of organic carbon and thus seawater n 13 c values since stratification of the ocean leads to decreased productivity in surface waters several scenarios postulating a continental origin of the perturbations in the late devonian biogeochemical cycles are then tested we found that weathering of platform carbonates exposed during the early famennian sea level fall can account for a maximum positive shift in n 13 c value of 0 7x at the end of the sea level fall episode another 1 0x increase in n 13 c might originate from rapid spreading of vascular land plants near the f f boundary postulating that higher plants globally increased the weatherability of continental surface and that colonized continental area increased by 30 across the f f boundary finally the n 13 c excursion observed at the base of upper rhenana zone and the rapid increase of the carbon isotope ratios at the f f boundary require an increase of phosphorus delivery to the ocean by 40 coeval with the sea level rises once the calculated n 13 c values are in agreement with the measured data the combine model calculates a decrease in atmospheric pco2 from pre perturbation 2925 ppmv in the lower rhenana conodont zone to 1560 ppmv in the upper triangularis zone this decrease in pco2 is due to the increase in burial of organic matter during the kellwasser events and increased continental weatherability triggered by the spreading of continental vascular plants these changes occur within 4 million years the corresponding global climatic cooling reaches 4 4 c at the pole and 2 1 c at the equator f 2003 elsevier b v all rights reserved

solute chemistry and arsenic fate in aquifers between the himalayan foothills and indian craton including central gangetic plain influence of geology and geomorphology abstract information on groundwater chemistry in the central ganges basin can provide insights into recharge provenance and fate of solutes in arsenic as affected areas upstream of the more intensively studied bengal basin the geological and geomorphological units of the region are much more discernible than the bengal basin aquifers moreover the region is less affected by groundwater abstraction which complicates interpretation of as distributions in the bengal basin the study area extends from the northern edge of the indian craton outcrops to the foothills of the himalayas geologic units in the area can be broadly classified as pre cenozoic metamorphics and volcanics pc older alluvial deposits of the ganges and its tributaries oa younger or active alluvial deposits of the ganges and its tributaries in the basin ya and sediments of the himalayan foothills piedmont pd stable isotopic analyses indicate groundwater in these units has been recharged by meteoric or surface water that has generally undergone some evaporation the hydrochemical facies is generally a ca hco3 type while most of the solutes in the ya groundwater are derived from carbonate dissolution many of the pd pc and oa groundwater samples are influenced by silicate weathering suggesting that leaching of metamorphics and volcanics acts as a major source of solutes redox conditions are highly spatially variable oxic to methanic dominated by metal reduction with no systematic depth variation within sampled aquifers more than 75 of ya and pd groundwater samples have as 0 01 mg l but as was detected in only one oa sample and no pc samples arsenic is probably mobilized by reductive dissolution of fe mn oxyhydr oxides in the alluvium with possibility of competitive anionic mobilization hence relative to the bengal basin in addition to lower groundwater abstraction influence groundwater chemistry in the study area reflects a greater variety of differences in the geological and geomorphological settings of the aquifers

tsunami generation and associated waves in the water column and seabed due to an asymmetric earthquake motion within an anisotropic substratum in this paper closed form integral expressions are derived to describe how surface gravity waves tsunamis are generated when general asymmetric ground displacement due to earthquake rupturing involving both horizontal and vertical components of motion occurs at arbitrary depth within the interior of an anisotropic sub sea solid beneath the ocean in addition we compute the resultant hydrodynamic pressure within the seawater and the elastic wavefield within the seabed at any position the method of potential functions and an integral transform approach accompanied by a special contour integration scheme are adopted to handle the equations of motion and produce the numerical results the formulation accounts for any number of possible acoustic gravity modes and is valid for both shallow and deep water situations as well as for any focal depth of the earthquake source phase and group velocity dispersion curves are developed for surface gravity tsunami mode acoustic gravity rayleigh and scholte waves several asymptotic cases which arise from the general analysis are discussed and compared to existing solutions the role of effective parameters such as hypocenter location and frequency of excitation are examined and illustrated through several figures which show the propagation pattern in the vertical and horizontal directions attention is directed to the unexpected contribution from the horizontal ground motion the results have important application in several fields such as tsunami hazard prediction marine seismology and offshore and coastal engineering in a companion paper we examine the effect of ocean stratification on the appearance and character of internal and surface gravity waves this article is protected by copyright all rights reserved

geologic geomorphic and hydrologic framework and evolution of the bengal basin india and bangladesh abstract the bengal basin the largest fluvio deltaic sedimentary system on earth is located in bangladesh and three eastern states of india sediment accumulates in the basin from the ganges brahmaputra and meghna gbm river systems and is dispersed into the bay of bengal forming the largest submarine fan in the world the basin is located in the himalayan foreland at the junction of the indian eurasian and burmese plates the basin is bounded by the indian craton on the west and the indo burmese fold belts on the east it can be broadly divided into a stable shelf and a foredeep separated by a deep seismic hinge zone basin sediments overlie gondwanan basement and vary in thickness from a few kilometers on the stable shelf to more than 16 km in the foredeep the basin was initiated at the breakup of gondwanaland in the late mesozoic and evolved through the formation of the proto gbm delta to the present delta starting around 10 5 ma the stratigraphy of the different parts of the basin differs considerably because of contrast in depositional history within the several sub basins that were produced by intra plate tectonic activities associated with ongoing himalayan orogeny the present day geomorphology is dominated by the extensive holocene gbm floodplain and delta the vertical succession of the deltaic plain can be classified into five units on the basis of differences in grain size which reflect differing depositional environments the initiation of the modern gbm delta at the onset of the pleistocene glacial maximum and its evolution to the present configuration are intricately related to holocene fluvio dynamic processes eustatic sea level changes and tectonic movements the sedimentology and mineralogy of the different parts of the basin reflect differences in sediment provenance the mineralogy is dominated by detrital quartz some feldspar and minor amounts of carbonates illite and kaolinite are the main clay minerals the basin has profuse groundwater resources but the architecture of the aquifers is not yet well resolved different classification schemes have been proposed on the basis of lithology regional groundwater flow follows a low hydraulic gradient from north to south but pumping for irrigation during the past several decades appears to have severely distorted regional flow recharge occurs primarily during the monsoon season groundwater chemistry is dominated by anoxic ca hco 3 type water with relatively high concentrations of fe mn and as carbonate dissolution silicate weathering feooh reduction and mixing with saline water are the primary processes controlling hydrochemistry

chemical and isotope composition of the oilfield brines from mishrif formation southern iraq diagenesis and geothermometry abstract this paper focuses on the geochemical composition and isotope geochemistry of brines in the cenomanian turonian carbonate mishrif reservoir of southern iraq main dissolved constituents trace elements 2h and 18o 87sr 86sr mineral saturation indices and thermodynamic calculations were investigated in formation waters from the mishrif formation to obtain a better understanding of brine evolution and diagenetic effects over geological time previous published 11b data were also reinterpreted as a geothermometer tool the results are compared with previous published data for local oilfields and coeval formations in the arabian gulf the mishrif brine has a marine origin and is diagenetically modified to ca excess and na deficit formation waters are quartz supersaturated and are in equilibrium with chalcedony and calcite dolomite in the temperatures range of 50 75 c which is also confirmed by calcite water oxygen isotope fractionation and 11b geothermometer the potential role of clays in conditioning brine chemistry during diagenetic processes was highlighted by activity diagrams in particular their adsorption exchange effect on sodium could explain the lower temperature obtained by the na li geothermometer 42 6 c the 2h and 18o values show that oxygen isotope composition of the brines was isotopically more affected by interaction with limestone during diagenesis than seawater evaporation the main effect is an 18o enrichment on the brine starting from the smow value locally dilution by present day meteoric water was also detected rumaila south which is shifted towards the local meteoric water line the strontium isotope ratios range from 0 707713 to 0 707749 and correspond to a marine strontium of late cenomanian early maastrichtian age except for the majnoon sample which shows a more radiogenic value 0 708043 radiogenic strontium and gypsum and anhydride saturation indices of the majnoon sample could indicate the contribution of calcium and sulphate from the strontium rich sulphate minerals of the cambrian salt domes occurring in the oilfields of southern iraq the higher manganese concentration 4 mg l and the slightly higher temperature inferred by geothermometers up to 74 c in comparison with present day could indicate that the majnoon brine is a hot fluid probably related to a deeper structure such as the zagros foredeep fault

seismic and tsunami wave propagation of the 2011 off the pacific coast of tohoku earthquake as inferred from the tsunami coupled finite difference simulation abstract the 2011 tohoku earthquake m 9 0 caused significant hazards including strong ground motion coseismic ground deformation and tsunamis for a deeper understanding of these phenomena we conducted a large scale parallel computer simulation by means of the finite difference method fdm with newly developed tsunami coupled equations of motion this method is based on the equations of motion for an elastic medium treating seawater as elastic material having zero s wave velocity tsunami waves are included by taking into account gravity and their equilibrium with the pressure gradient an effective method of fdm simulation using the state of the art massively parallelized k computer is also studied with the use of a 3d layered velocity structure that includes topography and bathymetry basement structure moho depth and plate boundaries and use of the appropriate source rupture model based on joint inversion of seismic waves and geodetic observations the simulated seismic waves demonstrate anomalous seismic wave propagation by the thick 3d basin structure inland we also found that the sea column acts as a strong absorber of seismic waves for shallow up dip slip on the ocean side coseismic deformation and tsunamis are dynamically generated in this simulation tsunami attacks on the subsided pacific coast are simulated without any additional assumptions we also modeled the tsunami and seismic records of ocean bottom pressure gauges above the fault because sea bottom tsunami and seismic observation is powerful but very complex recording both seismic and tsunami waves the use of these coupled numerical simulations has great potential for resolving complex source fault rupture processes in a 3d heterogeneous structure online material mpeg movies of fault slip seismic wave propagation seafloor and ground displacement and tsunamic propagation

evidence for glacial control of rapid sea level changes in the early cretaceous lower cretaceous bulk carbonate from deep sea sediments records sudden inputs of strontium resulting from the exposure of continental shelves strontium data from an interval spanning 7 million years in the berriasian valanginian imply that global sea level fluctuated about 50 meters over time scales of 200 000 to 500 000 years which is in agreement with the exxon sea level curve oxygen isotope measurements indicate that the growth of continental ice sheets caused these rapid sea level changes if glaciation caused all the rapid sea level changes in the cretaceous that are indicated by the exxon curve then an antarctic ice sheet may have existed despite overall climatic warmth

modeling of the hydroacoustic signal and tsunami wave generated by seafloor motion including a porous seabed 1 within the framework of a 2 d compressible tsunami generation model with a flat porous seabed acoustic waves are generated and travel outward from the source area the effects of the porous seabed during tsunami generation and propagation processes include wave amplitude attenuation and low pass filtering of both the hydroacoustic signal and tsunami wave the period of the acoustic wave generated by the seafloor motion depends on water depth over the source area and is given by four times the period of time required for sound to travel from the seabed to the surface these waves carry information about seafloor motion the semianalytical solution of the 2 d compressible water layer model overlying a porous seabed is presented and discussed furthermore to include the effects generated by the coupling between compressible porous sedimentary and water layers a simplified two layer model with the sediment modeled as a compressible viscous fluid is presented

the cenozoic evolution of the strontium and carbon cycles relative importance of continental erosion and mantle exchanges the past variations of the seawater 87sr86sr isotopic ratio are related to changes in the relative contribution of the mantle sr input to the ocean and the sr supply from continental weathering recently it has been postulated that the cenozoic increase in the seawater 87sr86sr isotopic ratio was associated with the uplift of the himalayan and andean mountains at that time these orogenies may have changed the sr isotopic ratio of the continental rocks undergoing weathering as a result of extensive metamorphism increased the river flux of sr through enhanced weathering in these regions and possibly caused the global climatic cooling trend of the cenozoic a model of the major geochemical cycles coupled to an energy balance climate model is used to explore the possible causes of the mesozoic cenozoic fluctuations in the seawater 87sr86sr isotopic ratio the contribution of the mantle exchanges at mid ocean ridges of the recycling of seafloor carbonates through plate margin volcanism and of the alteration of seafloor basalts to the fluctuations of the seawater 87sr86sr isotopic ratio are studied finally this model tentatively describes the impact of the himalayan orogeny on the geochemical cycles of sr and c some possible effects of the extensive metamorphism associated with the india asia collision and of the himalayan uplift are modelled the model reproduces the cenozoic increase of the seawater 87sr86sr isotopic ratio however the impact of the himalayan orogeny on the c cycle appears to be limited and insufficient to generate the global climatic cooling of the cenozoic rather in the model the cenozoic cooling is mostly due to the reduction of the co2 emission from mid ocean ridge volcanism and to changes in the chemical weathering rates in the rest of the world excluding the himalayas

monsoonal influence on variation of hydrochemistry and isotopic signatures implications for associated arsenic release in groundwater summary the present study examines the groundwater and surface water geochemistry of two different geomorphic domains within the chakdaha block west bengal in an attempt to decipher potential influences of groundwater abstraction on the hydrochemical evolution of the aquifer the effect of different water inputs monsoon rain irrigation and downward percolation from surface water impoundments to the groundwater system and concomitant as release a low land flood plain and a natural levee have been selected for this purpose although the stable isotopic signatures of oxygen 18o and hydrogen 2h are largely controlled by local precipitation the isotopic composition falls sub parallel to the global meteoric water line gmwl the cl br molar ratio indicates vertical recharge into the wells within the flood plain area especially during the post monsoon season while influences of both evaporation and vertical mixing are visible within the natural levee wells increase in mean doc concentrations from 1 33 to 6 29 mg l from pre to post monsoon season indicates possible inflow of organic carbon to the aquifer during the monsoonal recharge concomitant increase in ast fe ii and hco3 highlights a possible initial episode of reductive dissolution of as rich fe oxyhydroxides the subsequent sharp increase in the mean as iii proportions by 223 particularly in the flood plain samples during the post monsoon season which is accompanied by a slight increase in mean ast 7 may refer to anaerobic microbial degradation of doc coupled with the reduction of as v to as iii without triggering additional as release from the aquifer sediments

14c dating of deep groundwater in the bengal aquifer system bangladesh implications for aquifer anisotropy recharge sources and sustainability summary environmental isotopes and 14 c dating were applied to estimate ages and recharge sources of deep groundwater 150 m bgl in south east bangladesh with one exception deep groundwater is shown to have been recharged more recently than 10 ka range 3 9 ka mean 7 6 ka under climatic conditions indicated by 18 o and 2 h as similar to the present day groundwater age distributions have been used to infer the scale of aquifer hydraulic anisotropy 2d groundwater flow modelling is able to reproduce the observed vertical profiles of groundwater age as determined at two locations when the aquifer is assigned a permeability anisotropy k x k z of at least 10 3 under these conditions deep groundwater originates as recharge in the hill regions at the eastern boundary of the basin recharge rates estimated from the groundwater ages are close to an estimate of the current rate of deep groundwater abstraction cautious development and careful monitoring are therefore necessary as excessive deep groundwater pumping could draw dissolved arsenic from the shallow levels of the bengal aquifer system bas and contaminate the deep groundwater resource

characterization of recharge processes in shallow and deeper aquifers using isotopic signatures and geochemical behavior of groundwater in an arsenic enriched part of the ganga plain abstract arsenic concentrations in groundwater extracted from shallow aquifers in some areas of the ganga plain in the states of bihar and uttar pradesh exceed 50 g l 1 and locally reach levels in the 400 g l 1 range the study covered 535 km2 of active flood plain of the river ganga in bihar where a two tier aquifer system has been delineated in a multi cyclic sequence of quaternary sand clay sandy clay and silty clay all 250 m below ground surface the research used isotopic signatures 18o 2 3h 14c and major chemical constituents hco 3 so 4 2 no 3 cl ca 2 mg 2 na k as total of groundwater to understand the recharge processes and groundwater circulation in the aquifers values of 18o and 2 combined with 3h data indicate that the recharge to the as enriched top 40 m of the deposits is modern