strontium isotopes and rare earth elements as tracers of groundwater lake water interactions lake naivasha kenya abstract strontium isotope compositions and rare earth element ree concentrations are presented for groundwater and surface water samples collected from the lake naivasha watershed in the east african rift kenya the chief objective of the study is to test the suitability of rees in conjunction with sr isotopes as tools for investigating groundwater lake water interactions in general the ree concentrations and 87 sr 86 sr ratios support the authors earlier investigations where cl mass balance 18 o d and he isotopes were employed to study groundwater lake water interactions in the naivasha watershed the ree data suggest that a significant amount of the groundwater south of lake naivasha i e 50 85 consists of lake water recharge to the aquifer system specifically mixing calculations conducted using ree data of lake naivasha water and groundwaters indicate that between 70 and 85 of groundwater directly south of the lake is likely lake water these values are somewhat higher than the authors previous estimates determined with conservative stable h isotopes d 50 70 for both cases however the data demonstrate that water originating in lake naivasha contributes significantly to the underlying groundwater flow system hence supporting earlier evidence that the lake s freshness reflects rapid loss of water and dissolved solutes to the local groundwater system overall lake and groundwater sr isotope compositions support seepage of lake water into the underlying aquifer along the lake s south shore the 87 sr 86 sr data also provide additional insight into the geochemical evolution of waters of the lake naivasha watershed indicating that the initial source of sr to these waters is likely chemical weathering reactions involving basaltic rocks within the recharge zones of the watershed along the rift valley flanks furthermore with increasing residence time of groundwaters within the aquifer system and flow down and along the rift valley floor sr isotope compositions of groundwaters become more radiogenic reflecting rock water interactions with chemically differentiated and radiogenic peralkaline rhyolite volcanic rocks the importance of the longer aquifer residence times and radiogenic source rocks is especially apparent for geothermal waters of the olkaria geothermal field that have 87 sr 86 sr ratios i e 0 70747 similar to local comendites

uranium infiltration from a river to shallow groundwater the infiltration of uranium from the polluted river glatt switzerland into a hydraulically connected saturated aquifer was investigated during a period of almost five years the uranium concentrations and the 234u238u activity ratios ars were analysed monthly in the water of the river and of four groundwater sampling wells the speciation of uranium and its relation to other aqueous and solid components were investigated experimentally and in model calculations the uranium concentration and the ars in the river varied seasonally with a maximum and a minimum respectively in summer processes such as photo reductive dissolution of iron oxyhydroxides or the enhanced decomposition of organic matter and calcite in the upstream eutrophic lake greifen may have caused these variations laboratory experiments confirmed a possible release of uranium by photochemical reactions the concentration maximum of uranium was also detected in the shallow groundwater but with a delay of about six months to the maximum in the river under the assumption that the maxima in the river and the groundwater were related an in situ distribution coefficient kd for uranium of 7 ml g 1 can be calculated for this quaternary gravel aquifer uranium was present predominantly as uo2 carbonate complexes whereas the formation of phosphate and organic complexes e g uo2 humates edta nta was negligible particles and colloids played a minor role for the transport of uranium in this aquifer in the course of this study we observed an ongoing general decrease of the uranium concentrations and a disappearance of its summerly maxima in the river glatt we relate this unexpected effect to a better control of the phosphate concentration in surface waters which diminished the growth of aquatic biota this in turn led to changes in the redox conditions of lake and river sediments and herewith to a reduced release of heavy metals including uranium the results of this case study can be applied to estimate the migration behavior of other actinide oxyions e g puo22 npo2 in shallow heterogeneous aquifers which abound in alpine and pre alpine locations

molybdenum and tungsten in volcanic rocks and in surface and 100 c ground waters in iceland abstract the concentrations of mo and w in tholeiite series basaltic to silicic volcanics in iceland increase with the concentrations of incompatible magmatic elements in normal mid ocean ridge basalt morb mo and w levels are as low as 0 03 and 0 01 ppm but in rhyolites they are up to 4 and 1 3 ppm respectively in the slightly evolved tertiary tholeiites of the main study area of skagafjordur northern iceland mo and w concentrations are 1 01 and 0 32 ppm respectively on average surface waters in this area typically contain 10 000 years waters in river and ground waters the average mo w ratio is the same as that of the basalt host rock on the other hand in peat soil waters the average mo w ratio is higher due to adsorption processes involving w in river and ground waters both mo and w display conservative behavior progressive water rock interaction leads to successively lower aquatic b mo and b w ratios however the b mo and b w ratios of the most reacted waters are considerably higher than those of the basalt due to non stoichiometric rock dissolution b is dissolved preferentially to both mo and w because b is largely present in a soluble form but mo and w are concentrated in the fe ti oxides these minerals are stable under both surface and sub surface conditions i e the waters are over saturated with respect to these minerals the main supply of mo and w to surface waters is from dissolution of plagioclase and pyroxene as well as volcanic glass olivine is not an important source due to its scarcity in the basalts in

transgressive dune formation along a cliffed coast at 75 ka in sardinia western mediterranean a record of sea level fall and increased windiness transgressive dunes develop frequently along strandplain coastlines however they may also form along rocky coasts dominated by cliffs and embayments two lithified transgressive dune systems developed along the cliffed alghero coast nw sardinia italy have been investigated one aeolian system forms a cliff front anchored aeolian dune accumulation the other is a valley head anchored sand ramp system optically stimulated luminescence ages indicate that both systems formed around 75 ka this period which corresponds to the beginning of mis 4 was characterized by a relatively low sea level stand 15 m below the present sea level and was preceded by a sea level highstand 1 m asl around 81 ka mis 5a our results show that this rapid sea level fall exposed an enormous amount of marine sand which was transported inland by strong northerly winds and deposited in front of cliffs or in valley heads therefore sediment supply and sea level fall seem to be critical factors controlling dune formation along rocky coasts which generate time transgressive aeolianites terra nova 00 000 000 2010

re assessing the surface cycling of molybdenum and rhenium we re evaluate the cycling of molybdenum mo and rhenium re in the near surface environment world river average mo and re concentrations initially based on a handful of rivers are calculated using 38 rivers representing five continents and 11 of 19 large scale drainage regions our new river concentration estimates are 8 0 nmol kg 1 mo and 16 5 pmol kg 1 re natural anthropogenic the linear relationship of dissolved re and so 2 4 in global rivers r 2 0 76 indicates labile continental re is predominantly hosted within sulfide minerals and reduced sediments it also provides a means of correcting for the anthropogenic contribution of re to world rivers using independent estimates of anthropogenic sulfate approximately 30 of re in global rivers is anthropogenic yielding a pre anthropogenic world river average of 11 2 pmol re kg 1 the potential for anthropogenic contribution is also seen in the non negligible re concentrations in precipitation 0 03 5 9 pmol kg 1 and the nmol kg 1 level re concentrations of mine waters the linear mo so 2 4 relationship r 2 0 69 indicates that the predominant source of mo to rivers is the weathering of pyrite an anthropogenic mo correction was not done as anthropogenically influenced samples do not display the unambiguous metal enrichment observed for re metal concentrations in high temperature hydrothermal fluids from the manus basin indicate that calculated end member fluids i e mg free yield negative mo and re concentrations showing that mo and re can be removed more quickly than mg during recharge high temperature hydrothermal fluids are unimportant sinks relative to their river sources 0 4 mo and 0 1 pre anthropogenic re we calculate new seawater response times of 4 4 10 5 yr smo and 1 3 10 5 yr sre pre

the geochemistry of rhenium and osmium in recent sediments from the black sea abstract the os isotopic composition of recent sediments from the black sea are reported with the concentrations of re os and major and minor elements osmium concentrations range from 0 23 to 0 69 ppb and re concentrations range from 21 to 85 ppb concentrations of both elements are large relative to average crustal material and are positively correlated with organic carbon 187 os 186 os ratios range from 5 7 to 7 1 all of these values are less radiogenic than the estimated 187 os 186 os ratio of seawater and average continental crust material variations in the os isotopic composition of these sediments are attributed to mixing of a hydrogenous component 187 os 186 os ratio between 7 and 9 and a less radiogenic detrital component 187 os 186 os ratio between 1 and 4 a mixing model is used to determine the fraction of os in the sediment associated with each component and the burial fluxes of re and os in the black sea are calculated in addition the data are used to estimate the magnitude of systematic error which such initial os isotopic heterogeneity may introduce into re os age determinations of ancient organic rich sediments

short paper low grade metamorphism of the welsh basin lower palaeozoic succession an example of diastathermal metamorphism the lower palaeozoic succession of the welsh basin has suffered the effects of low grade metamorphism which shows features that do not accord with classical models of regional or burial metamorphism textural evidence demonstrates the development of greenschist facies metamorphism prior to deformation and cleavage development while mineralogical characters indicate a low pressure facies series in order to accommodate these features it is suggested that the area has suffered diastathermal metamorphism in which an enhanced thermal flux develops early in the tectonic cycle in response to an extensional setting temperatures remained relatively high during final closure associated with deformation of the basin sediments and consequent cleavage development such a model adequately resolves previously conflicting interpretations of burial and deformation related metamorphism

controls on the geochemistry of rare earth elements along a groundwater flow path in the carrizo sand aquifer texas usa groundwater samples were collected along a groundwater flow path in the carrizo sand aquifer in south texas usa field measurements that included ph specific conductivity temperature dissolved oxygen do oxidation reduction potentials eh in mv alkalinity iron speciation and h2s concentrations were also conducted on site the geochemistry i e concentrations shale normalized patterns and speciation of dissolved rare element elements rees in the carrizo groundwaters are described as a function of distance along a flow path eh and other redox indicators i e do fe speciation h2s u and re indicate that redox conditions change along the flow path in the carrizo sand aquifer within the region of the aquifer proximal to the recharge zone groundwaters exhibit both highly oxidizing and localized mildly reducing conditions however from roughly 10 km to the discharge zone groundwaters are reducing and exhibit a progressive decrease in redox conditions dissolved ree geochemical behavior exhibits regular variations along the groundwater flow path in the carrizo sand aquifer the changes in ree concentrations shale normalized patterns and speciation indicate that rees are not conservative tracers with flow down gradient redox conditions ph and solution composite and adsorption modify groundwater ree concentrations fractionation patterns and speciation

dating the cooloola coastal dunes of south eastern queensland australia abstract the cooloola sand dunes are part of a series of aeolian parabolic dunes that stretch along the east coast of australia they form a chronosequence showing increasing weathering soil formation and water erosion across six geomorphically recognized soil landscapes these landscapes were recognized from air photographs and further refined on the basis of some 150 auger holes across the dunes data about the structure and floristics of the vegetation were collected at the same time there is a significant body of literature about the cooloola dunes but there are two areas that have not been satisfactorily considered first the previous dating which gave inconsistent results has been superseded by single grain osl dates and second cooloola has not been considered in a regional context here we report the results of single grain optically stimulated luminescence osl analyses for 31 samples for 21 sites across the geomorphic landscapes the sites were selected near the apex of each dune as this represents the last depositional date and the least disturbed by sand movement we recognized 10 units across the dunes on the basis of the dates available the dune ages ranged from recent to 725 ka the largest dunes at some 320 m high were dated at around 140 ka and these dunes carry the maximum vegetation biomass of this dunefield beyond this vegetation maximum the dunes had lost their parabolic shape due to prolonged weathering and erosion and the vegetation is greatly reduced in height and biomass the depth to the soil b horizon gradually deepens with age to form giant podzols in the older dunes the depth to the b horizon was remarkably consistent within the geomorphic landscapes across the length and breadth of the dunes these studies place the cooloola dunes in a unique position as the chronosequence is intact the possible processes that lead to the formation of the dunes and the regional implications are discussed secondly it shows the buildup and decline of the dune ecosystems and acts as a model for all ecosystems forest succession models which place less emphasis on soil development miss this important process

holocene coastal dune formation in southern australia a case study abstract the 14 500 km long southern australian coast is exposed to high energy wave and wind regimes which have mobilized shelf derived sediments to produce extensive holocene shoreface deposits the 8000 km of sandy coast are backed by over 2000 km 2 of holocene dunes of varying degrees of stability in places dune deposition above present sea level accompanied the post glacial marine transgression commencing as early as 10 ka b p and has continued episodically to the present day the dunes are widespread in extent but vary in type size and evolution the oldest and often most extensive primary dune fields accompanied the post glacial marine transgression they occurred and in some places continue to form in areas of high wave and wind energy and abundant sand supply many of these systems exhausted their sediment supply by mid holocene and remain as stranded clifftop dunes where sand ramps were eroded or as eroding barriers secondary phases of dune activity occurred on moderate to high energy coasts following an initial period of post stillstand barrier progradation diminished sediment supply resulted in shoreline erosion and secondary dune formation the location size and evolution both of dunes types is largely controlled by the breaker wave regime which in turn influences the rate and volume of sediment supply beach morphodynamics and resulting aerodynamic boundary conditions and foredune erosion a study of dune formation along the 3700 km long south australian coast provides a basis for an overview of dune formation throughout southern australia

some comparative marine chemistries of rhenium gold silver and molybdenum abstract four metals re au ag and mo whose dissolved forms in seawater can potentially be reduced to insoluble states have been measured in a variety of solids depositing under anoxic conditions hydrothermal sulfides coastal sediments and phosphorites for comparative purposes these elements have also been determined in ferromanganese minerals and pelagic sediments which have accumulated under oxidizing conditions rhenium appears to be a unique sentinel for identifying reducing depositional environments where enrichments of greater than three orders of magnitude above crustal concentrations are found molybdenum follows re in these sediments but mo is enriched also in those that accumulate under oxidizing conditions the reported mo crustal concentrations appear low in comparison to our measured sedimentary values gold and ag are concentrated in hydrothermal deposits and sulfides appear to be involved in the precipitation of these elements coastal sediments adjacent to a domestic outfall of los angeles california contain extraordinary high accumulations of anthropogenic au ag and pt the study seeks an understanding of the mobilities and sinks of these metals in the marine environment during the major weathering cycle further anthropogenic contributions to their sedimentary concentrations are identified

the geochemical cycle of rhenium a reconnaissance rhenium re is one of a suite of elements including uranium and molybdenum that display conservative behavior in seawater and are enriched in anoxic sediments the decay of187re to187os provides a geochronometer in ancient sedimentary rocks and gives rise to os isotopic variations in nature in order to better characterize its sources to seawater re was measured in three major rivers amazon orinoco ganges brahmaputra and some of their tributaries re concentrations span four orders of magnitude from 0 02 to 400 pmol kg with the highest concentrations found in rivers draining black shales in the venezuelan andes mainstream re levels in the three rivers are between 1 and 10 pmol kg with a flux weighted average of 2 3 pmol kg the residence time for re in the oceans is estimated to be 750 000 yr with respect to river inputs re profiles from the atlantic and pacific oceans confirm that re behaves conservatively in seawater with no significant uptake onto particles and or recycling within the water column this is also true in the anoxic water column of the black sea re removal into anoxic sediments occurs at or below the sediment water interface as demonstrated in sediment pore waters from chesapeake bay in oxic sediments re is not cycled with manganese oxides and it is not enriched in very slowly accumulating pelagic sediments with a large hydrogenous iron and manganese component or in manganese nodules burial of re in anoxic sediments which accumulate on 0 3 of the ocean floor removes approximately 50 of the riverine re flux to the oceans hence oceanic re concentrations may be very sensitive to changes in the area of anoxic sedimentation

rare earth elements as geochemical tracers of regional groundwater mixing abstract the rare earth elements ree were analyzed in a groundwater system from south central nevada i e ash meadows national wildlife refuge the spring mountains pahranagat national wildlife refuge and the nevada test site in order to investigate their potential use as tracers of regional groundwater flow previous investigations using conservative tracers e g deuterium and uranium isotopes identified recharge in local mountains as the primary source 60 70 of total discharge for the springs in the regional discharge zone i e ash meadows with the remaining contribution being interbasin flow from the northeast initial mixing calculations for these groundwaters using shale normalized ree patterns agreed well with the previous studies however because the rees are not expected to behave conservatively in natural waters the effect of both solution complexation which acts to enhance the stability of the rees in solution as well as surface complexation responsible for the particle reactive behavior of the rees were examined in subsequent mixing calculations in order to assess the roles of solution and surface complexation relative partitioning coefficients were estimated for each ree in each groundwater by evaluating the ratio of the ionic strength corrected co 3 1 ree co 3 2 ree and co 3 2 f to the first hydrolysis binding constants for the rees the relative partitioning coefficients were then used to calculate ree patterns expected to develop and persist in solution as a consequence of solution and surface complexation the calculated ree values closely resembled the actual measured ree concentrations suggesting that the rees are in fact controlled by solution and surface complexation in these groundwaters the calculated ree concentrations were subsequently used to determine mixing ratios the results of which coincided with the initial calculations as well as the previous studies the results of this study suggest that solution complexation of the rees is sufficient to overcome to a certain degree the affinity of the rees to be adsorbed onto surface sites in the aquifers such that distinctive ree signatures develop and persist in solution in groundwaters from different aquifers the ability of solution complexation to overcome surface complexation is likely related to the formation of the negatively charged dicarbonato complex i e ln co 3 2 where ln is any ree which accounts for significant fractions of each ree in these groundwaters

environmental controls morphodynamic processes and ecogeomorphic interactions of barchan to parabolic dune transformations the transformation of barchans into parabolic dunes has been observed in various dune systems around the world precise details of how environmental controls influence the dune transformation and stabilisation mechanism however remain poorly understood a horns anchoring mechanism and a nebkhas initiation mechanism have previously been proposed and selected environmental controls on the transformation have been explored by some modelling efforts but the morphodynamic processes and eco geomorphic interactions involved are unclear and comparison between different dune systems is challenging this study extends a cellular automaton model informed by empirical data from fieldwork and remote sensing to fully explore how vegetation characteristics boundary conditions and wind regime influence the transformation process and the resulting dune morphologies a dynamic growth function is introduced for clump like perennials to differentiate between growing and non growing seasons and to simulate the development of young plants into mature plants over multiple years modelling results show that environmental parameters interact with each other in a complex manner to impact the transformation process the study finds a fundamental power law relation between a non dimensional parameter group so called the dune stabilising index s and the normalised migration distance of the transforming dune which can be used to reconstruct paleo environmental conditions and monitor the impacts of changes in climate or land use on a dune system four basic eco geomorphic interaction zones are identified which bear different functionality in the barchan to parabolic dune transformation the roles of different environmental controls in changing the eco geomorphic interaction zones transforming processes and resulting dune morphologies are also clarified

parabolic dune development modes according to shape at the southern fringes of the hobq desert inner mongolia china since the 1970s parabolic dunes at the southern fringe of the hobq desert inner mongolia china have exhibited many different shapes v shaped u shaped and palmate each with a unique mode of development in the study area parabolic dunes are mainly distributed in regions a b and c with an intermittent river running from the south to the north we used high resolution remote sensing images from 1970 to 2014 and rtk gps measurements to study the development modes of different dune shapes the modes are characterized by the relationship between the intermittent river and dunes formation of the incipient dune patterns the predominant source supply of dunes and the primary formation of different shapes v shaped u shaped and palmate most parabolic dunes in region a are v shaped and closer to the bank of the river the original barchans in this region exhibit disconnected arms behavior with the sand blown out of the riverbed through gullies the nebkhas on the disconnected arms acquire the external sand source through the fertile island effect thereby developing into triangular sand patches and further developing into v shaped parabolic dunes most parabolic dunes in regions b and c are palmate the residual dunes cut by the re channelization of river from transverse dune fields on the west bank are the main sand source of region b the parabolic dunes in region c are the original barchans having then been transformed the stoss slopes of v shaped parabolic dunes along the riverbank are gradual and the dunes are flat in shape the dune crest of v shaped parabolic dune is the deposition area which forms the arc shaped sand ridge their two arms are non parallel the lateral airflow of the arms jointly transport sand to the middle part of dunes resulting in a narrower triangle that gradually becomes v shaped palmate parabolic dunes have a steeper stoss slope and height the dune crest of the palmate parabolic dune is the erosion area which forms a long and narrow trough between nebkhas by the funnelling effect this process forces sand towards lee slopes which transform from concave original barchans into convex ultimately resulting in the formation of palmate parabolic dunes

formation of parabolic dunes from barchan and transverse dunes along israel s mediterranean coast the mediterranean coastal dunes of israel underwent a land use change during the second half of the 20th century due to intense agricultural and pastoral activity the coastal dunes were stripped of natural vegetation until the end of the first half of the 20th century the barchan and transverse dunes were shaped by strong southwesterly winter winds a decrease in human activity during the second half of the 20th century brought about a renewal of natural vegetation on the dune crest the only area with neither erosion nor deposition the establishment of vegetation on the crest changes the dynamics of these barchan and transverse dunes so that not all of the sand eroded from the windward side is carried to the lee slip face some is trapped by plants consequently there is a change in the shape of the windward slope from convex to concave and the dune gradually becomes parabolic in this study we trace the morphodynamics of the dunes by analysing 12 sets of aerial photographs which were taken from 1944 to 1995 the average rate of advance of 15 dunes has decreased from 3 4 m a 1 to 1 9 m a 1 while the vegetation cover has increased from 4 3 to 17 per cent during this period copyright 2002 john wiley sons ltd

origin of rare earth element signatures in groundwaters of circumneutral ph from southern nevada and eastern california usa concentrations of the rare earth elements ree were measured in circumneutral ph groundwaters from southern nevada and death valley ca groundwaters from the regional lower paleozoic carbonate rock aquifer cambrian devonian have flat shale normalized patterns that closely resemble the shale normalized patterns of the aquifer rock samples principally cambrian groundwaters associated with younger carbonate rocks chiefly permian in the study region exhibit heavy ree hree enriched shale normalized ree patterns with substantial negative ce anomalies that also mimic these carbonate rocks in addition groundwaters from the felsic volcanic rock aquifers have the same flat to light ree lree enriched shale normalized patterns with large negative eu anomalies as the felsic volcanic rocks the similar ree patterns of all the groundwaters and associated aquifer rocks studied suggest that the groundwaters inherited ree signatures from the host rocks through which they flow because negative ce anomalies are not an uncommon feature of carbonate rocks of marine origin the negative ce anomalies reported here for these groundwaters may reflect a permian marine ce signature previously we demonstrated that carbonate complexes dominate ree speciation in southern nevada and death valley groundwaters moreover solid liquid partitioning coefficients kd indicate that the affinity of lrees to sorb to aquifer surface sites is substantially greater than for the hrees in the southern nevada carbonate and felsic volcanic rock alluvial aquifers consequently the hrees enrichments reported here for groundwaters associated with younger paleozoic carbonate rocks compared to these source rocks is consistent with ree carbonate complexation and preferential removal of lrees to aquifer surface sites

metal rich fluid inclusions provide new insights into unconformity related u deposits athabasca basin and basement canada the paleoproterozoic athabasca basin canada hosts numerous giant unconformity related uranium deposits the scope of this study is to establish the pressure temperature and composition p t x conditions of the brines that circulated at the base of the athabasca basin and in its crystalline basement before during and after uo2 deposition these brines are commonly sampled as fluid inclusions in quartz and dolomite cementing veins and breccias associated with alteration and u mineralization microthermometry and laser ablation inductively coupled plasma mass spectrometry la icp ms data from five deposits rabbit lake p patch eagle point millennium and shea creek complement previously published data for the mcarthur river deposit in all of the deposits investigated fluid inclusion salinity is between 25 and 40 wt nacl equiv with compositions displaying a continuum between a nacl rich brine end member cl na ca mg k and a cacl2 rich brine end member cl ca mg na k the cacl2 rich brine has the highest salinity and shows evidence for halite saturation at the time of trapping the continuum of compositions between the nacl rich brine and the cacl2 rich brine end members combined with p t reconstructions suggest anisothermal mixing of the two brines nacl rich brine 180 30 c and 800 400 bars cacl2 rich brine 120 30 c and 600 300 bars that occurred under fluctuating pressure conditions hydrostatic to supra hydrostatic however because the two brines were u bearing and therefore oxidized brine mixing was probably not the driving force for uo2 deposition several scenarios are put forward to account for the cl na ca mg k composition of the brines involving combinations of seawater evaporation halite dissolution mixing with a halite dissolution brine mg ca exchange by dolomitization na ca exchange by albitization of plagioclase na k exchange by albitization of k feldspar and mg loss by mg rich alteration finally the metal concentrations in the nacl rich and cacl2 rich brines are among the highest recorded compared to present day sedimentary formation waters and fluid inclusions from basin hosted base metal deposits up to 600 ppm u 3000 ppm mn 4000 ppm zn 6000 ppm cu 8000 ppm pb and 10 000 ppm fe the cacl2 rich brine carries up to one order of magnitude more metal than the nacl rich brine though the exact origin of major cations and metals of the two brines remains uncertain their contrasting compositions indicate that the two brines had distinct flow paths and fluid rock interactions large scale circulation of the brines in the athabasca basin and basement was therefore a key parameter for metal mobility including u and formation of unconformity related u deposits

characterizing earthquake recurrence parameters for offshore faults in the low strain compressional kapiti manawatu fault system new zealand 1 seafloor fault scarps and near surface deformation of late quaternary seismic reflectors occur along the eastern margin of the wanganui basin 200 km behind the active hikurangi subduction front southern north island new zealand the offshore scarps are associated with the low strain compressional kapiti manawatu fault system kmfs which comprises high angle 60 reactivated reverse and normal faults oriented ne sw highly oblique to the coast seafloor scarps range from 10 m high and moderate to long fault seafloor rupture lengths and those in central parts of the fault system are characterized by low scarps 10 000 a suggest that the seismic hazard of the kapiti manawatu region is relatively low incorporation of these new geological data however is likely to increase slightly the expected seismic hazard in southern north island the method of determining the earthquake recurrence parameters of offshore faults has potentially wider applications elsewhere

composition of soils and ground waters at the pampa del tamarugal chile anatomy of a fossil geochemical anomaly derived from a distant porphyry copper deposit the pampa del tamarugal in northern chile is a gravel plain part of the hyperarid atacama desert soil geochemical surveys over the pampa using partial extraction analyses identified a large 100 km2 geochemical anomaly for cu subsequent analyses showed unusually high concentrations of elements that are associated with copper porphyry deposits mo as and se the soils are saline nacl and contain high concentrations of br and i which are abundant in ground waters from northern chile the anomaly lies west of one of the world s most important copper porphyry districts which includes the chuquicamata radomiro tomic and el abra deposits follow up drilling in the center of the anomaly through 300 m of piedmont gravel cover revealed barren andesitic basement rocks the soil anomalies were caused by ground water reaching the surface then evaporating both ground waters and soils share a common element assemblage with higher concentrations of mo as and se than cu the former dissolve as anions in ground water which can travel far from their source whereas dispersion of cu2 is restricted by adsorption the soil anomaly is interpreted to be a fossil anomaly preserved by the hyperarid climate to the south the anomaly is cut by an alluvial fan another nearby fan has been dated at 7 ma to the west the anomaly was eroded in the flood plain of the rio loa prior to the present 50 m deep incision of the rio loa the water table in the area of the anomaly may have been higher than the present depth of 33 to 55 m facilitating capillary rise of water to the surface we suggest that the source for the anomaly was the el abra deposit 75 km east and updrainage from the anomaly

molybdenum in the northeast pacific ocean1 the concentration of dissolved molybdenum has been determined in several profiles from the northeast pacific ocean the salinity normalized concentration is essentially constant in all open ocean samples 107 nm 1 2 5 nm the dissolved distribution is not significantly affected by biological cycling

orogenesis vs diagenesis can we use organic rich shales to interpret the tectonic evolution of a depositional basin abstract black shales from the southern appalachian basin and the southwest welsh basin have anomalous u pb and nd model ages suggesting syn and post depositional resetting of the sm nd and u pb isotopic systems this alteration to the primary detrital signature of these two shale sequences is indicative of black shale diagenetic depositional processes that obscure paleo environmental and provenance information recorded prior to and during deposition the trace element and isotopic signatures of these two shale sequences reveal a syn post depositional history that is de coupled from the coeval orogenic history of the region making it difficult to reconstruct the tectonic and oceanographic conditions present at the time of deposition both the ordovivian welsh basin and the devonian appalachian basin sequences host ree and u bearing diagenetic phosphate minerals that play a critical role in the whole rock ree and u budgets in the welsh basin shales early diagenetic apatite and a later monazite phase dominate the ree budget and cause the redistribution of ree early in the basin s history ca 460 ma this redistribution is recorded by the sm nd system 450 90 ma and the nd model ages that are anomalously old by as much as 20 t dm 2 0 ga this early history is complicated by a permo triassic fluid event affecting the whole rock u budget and resetting the u pb isotopic system at 193 45 ma the appalachian basin sequence appears to have a much less complicated history yet still records a significant disturbance in both the sm nd isotopic system 392 76 ma and the pb isotopic system 340 50 ma at about the time of deposition ca 365 ma these two sequences suggest a pattern of diagenetic disturbance common to black shales these processes are unique to black shales and must be considered when interpreting provenance and paleo environmental information from the black shale sequences although these rocks are susceptible to alteration the alteration may provide extensive information on the post depositional history of the basin while still retaining some primary depositional information if black shale processes are considered during the interpretation of isotopic and trace element signatures from organic rich shales it may be possible to recover an extensive basin history

barchan parabolic dune pattern transition from vegetation stability threshold 1 many dune fields exhibit a downwind transition from forward pointing barchan dunes to stabilized backward pointing parabolic dunes accompanied by an increase in vegetation a recent model predicts this pattern transition occurs when dune surface erosion deposition rates decrease below a threshold of half the vegetation growth rate we provide a direct test using a unique data set of repeat topographic surveys across white sands dune field and find strong quantitative support for the model threshold we also show the threshold hypothesis applied to a barchan dune results naturally in its curvature inversion as the point of threshold crossing progresses from the horns to the crest this simple general threshold framework can be an extremely useful tool for predicting the response of dune landscapes to changes in wind speed sediment supply or vegetation growth rate near the threshold a small environmental change could result in a drastic change in dune pattern and activity

source transport and fate of rhenium selenium molybdenum arsenic and copper in groundwater associated with porphyry cu deposits atacama desert chile we collected groundwaters in and around a large 313 mt at 1 08 cu and 0 3 cutoff undisturbed porphyry copper deposit spence in the hyperarid atacama desert of northern chile which is buried beneath 30 180 m of miocene piedmont gravels groundwaters within and down flow of the spence deposit have elevated se up to 800 g l re up to 31 g l mo up to 475 g l and as up to 278 g l concentrations compared to up flow waters interpreted to represent regional groundwater flow in contrast cu is only elevated up to 2036 g l in groundwaters recovered from within the deposit cu concentrations are low down gradient of the deposit the differential behavior of the metals metalloids occurs because the former group dissolves as anions enhancing their mobility whereas the base metals dissolve as cations and are lost from solution most likely through adsorption to clay surface exchange sites and through formation of secondary copper chlorides carbonates and oxides most groundwaters within and down flow of the deposit have eh ph values around the feii feiii phase boundary limiting the impact of fe oxyhydroxides on oxyanions mobility se re mo and as are all mobile with filtered unfiltered samples 1 to the limit of sampling 2 km down gradient from the deposit the increase in ore related metals metalloids and sulfate and decrease in sulfate s isotope ratios from values similar to regional salars 4 to 8 34scdt to lower values closer to hypogene sulfides 1 to 4 34scdt is consistent with active water rock reactions between saline groundwaters and the spence deposit it is likely that hypogene and or supergene sulfides are being oxidized under the present groundwater conditions and mineral saturation calculations suggest that secondary copper minerals antlerite atacamite malachite may also be actively forming suggesting that supergene and exotic copper mineralization is possible even under the present hyperarid climate of the atacama desert

reply to the comment by wu et al 2016 on behavior of re and os during contact between an aqueous solution and oil consequences for the application of the re os geochronometer to petroleum geochim cosmochim acta 158 2015 1 21 abstract we reply here to the questions raised by wu et al concerning the results published by mahdaoui et al 2015 this paper describes experiments in which aqueous solutions containing reo 4 and oscl 6 2 were brought in contact with natural oils at various ranges of concentration time and temperature the main observation is that the transfer of re and os to oils is very efficient under all experimental conditions wu et al argue that thermodynamic equilibrium was not achieved in these experiments as apparent partition coefficients are inconsistent they conclude that the experiments were flawed by possible leaking of reactors and that the conclusions by mahdaoui et al 2015 were not justified in the following reply we explain that mahdaoui et al 2015 never claimed that thermodynamic equilibrium was achieved any calculations or considerations in this context are therefore meaningless we recall the objectives of our publication which were to experimentally test the behavior of reo 4 and oscl 6 two plausible chemical forms of re and os in deep aquifers of petroleum systems in aqueous solution oil systems to our knowledge these are the first experiments of their kind the parameters that could influence the precision and reproducibility of our results were discussed in detail in mahdaoui et al 2015 the essential point is that all 60 of the experiments provide evidence of substantial transfer of re and os from water to oil in contrast to what was mistakenly understood by wu et al the paper does not challenge the use of re os to date geological events affecting petroleum instead by providing a mechanism that might allow os isotopic homogenization on a basin wide scale a critical step missing from most current models it offers a possible explanation of how re os geochronology in oils could potentially work more generally our study suggests that transfer of re and os from waters to oil may be an important phenomenon that should not be overlooked

geochemical and statistical evidence of deep carbonate groundwater within overlying volcanic rock aquifers aquitards of southern nevada usa abstract samples collected from springs and wells in southern nevada were analyzed for major solutes and trace elements as part of a larger study to characterize the geochemical signatures of these groundwaters in this study principal component analysis pca was used to reduce the large data sets including the four major cations ca mg na k and 27 trace elements analyzed in these groundwater samples principal components analysis of the major cation data indicates that groundwaters from cenozoic felsic volcanic rock aquifers aquitards of southern nevada exhibit strong chemical associations to each other but weak relationships to groundwaters from the regional carbonate aquifer which were instead chemically similar to each other however pca of the trace element data demonstrates that some groundwaters from the volcanic aquifers aquitards are chemically similar to those of the underlying regional carbonate aquifer the pca also reveals that these groundwaters from the volcanic aquifers aquitards have significantly different trace element compositions than perched groundwaters contained within similar felsic volcanic rocks moreover rare earth element ree data from groundwaters collected from wells finished in the volcanic aquifers aquitards of southern nevada have similar concentrations and similar shale normalized patterns to the carbonate aquifer groundwaters as well as local carbonate rocks these same southern nevada well waters do not exhibit ree concentrations or shale normalized signatures that resemble the perched volcanic groundwaters or the tuffs of southern nevada the ree data and trace element pca along with previous carbon isotope analyses water temperature data hydraulic head relations and results of a recent pump test of a well near yucca mountain suggest close contact of the regional carbonate groundwaters and groundwaters from the overlying volcanic rocks of southern nevada and possible upwelling of the carbonate groundwaters into the overlying volcanic rock units in the vicinity of yucca mountain

effects of human induced alteration of groundwater flow on concentrations of naturally occurring trace elements at water supply wells the effects of human induced alteration of groundwater flow patterns on concentrations of naturallyoccurring trace elements were examined in five hydrologically distinct aquifer systems in the usa although naturally occurring these trace elements can exceed concentrations that are considered harmful to human health the results show that pumping induced hydraulic gradient changes and artificial connection of aquifers by well screens can mix chemically distinct groundwater chemical reactions between these mixed groundwaters and solid aquifer materials can result in the mobilization of trace elements such as u as and ra with subsequent transport to water supply wells for example in the high plains aquifer near york nebraska mixing of shallow oxygenated lower ph water from an unconfined aquifer with deeper confined anoxic higher ph water is facilitated by wells screened across both aquifers the resulting higher o2 lower ph mixed groundwater facilitated the mobilization of u from solid aquifer materials and dissolved u concentrations were observed to increase significantly in nearby supply wells similar instances of trace element mobilization due to human induced mixing of groundwaters were documented in 1 the floridan aquifer system near tampa florida as and u 2 paleozoic sedimentary aquifers in eastern wisconsin as 3 the basin fill aquifer underlying the california central valley near modesto u and 4 coastal plain aquifers of new jersey ra adverse water quality impacts attributed to human activities are commonly assumed to be related solely to the release of the various anthropogenic contaminants to the environment the results show that human activities including various land uses well drilling and pumping rates and volumes can adversely impact the quality of water in supply wells when associated with naturally occurring trace elements in aquifer materials this occurs by causing subtle but significant changes in geochemistry and associated trace element mobilization as well as enhancing advective transport processes published by elsevier ltd

uranium removal in oceanic sediments and the oceanic u balance pore water uranium data from the nw atlantic ocean cariaco trench black sea and san clemente basin are used to calculate fluxes across the sediment water interface all samples were collected in situ and show depletions in pore water u relative to the overlying water concentration the uptake rate of u derived from pore water gradients reflects the redox environment with lowest fluxes 10 g cm 2 ky in oxic su ic sediments of the nw atlantic dominated by no 3 reduction and higher fluxes 25 70 g cm 2 ky in the anoxic sulfate reducing sediments of the cariaco trench black sea and san clemente basin the anoxic fluxes compare well with previous estimates based on solid phase data calculations indicate that the areally integrated removal of u into su ic hemipelagic sediments is of greater magnitude than that into anoxic sulfate reducing sediments these fluxes are discussed in the context of the oceanic u balance the removal of u in all oceanic sediments is estimated to account for about 65 of the riverine input and this sink plus removal of u in altered oceanic crust balances the most probable value for riverine input

the behavior of u and th series nuclides in groundwater groundwater has long been an active area of research driven by its importance both as a societal resource and as a component in the global hydrological cycle key issues in groundwater research include inferring rates of transport of chemical constituents determining the ages of groundwater and tracing water masses using chemical fingerprints while information on the trace elements pertinent to these topics can be obtained from aquifer tests using experimentally introduced tracers and from laboratory experiments on aquifer materials these studies are necessarily limited in time and space regional studies of aquifers can focus on greater scales and time periods but must contend with greater complexities and variations in this regard the isotopic systematics of the naturally occurring radionuclides in the u and th decay series have been invaluable in investigating aquifer behavior of u th and ra these nuclides are present in all groundwaters and are each represented by several isotopes with very different half lives so that processes occurring over a range of time scales can be studied table 1 within the host aquifer minerals the radionuclides in each decay series are generally expected to be in secular equilibrium and so have equal activities see bourdon et al 2003 in contrast these nuclides exhibit strong relative fractionations within the surrounding groundwaters that reflect contrasting behavior during release into the water and during interaction with the surrounding host aquifer rocks radionuclide data can be used within the framework of models of the processes involved to obtain quantitative assessments of radionuclide release from aquifer rocks and groundwater migration rates the isotopic variations that are generated also have the potential for providing fingerprints for groundwaters from specific aquifer environments and have even been explored as a means for calculating groundwater ages view this table table 1 radionuclides important in groundwater studies the highly fractionated nature of the

what regulates rhenium deposition in euxinic basins abstract rhenium is greatly enriched in black shales and euxinic basin sediments relative to its crustal abundance the enrichment process is generally assumed to involve reduction of reo 4 the principal re species in seawater to an insoluble re iv oxide or sulfide in suboxic and anoxic environments the specific biotic or abiotic mechanism of reduction has so far defeated efforts to discover it here an alternative mechanism of fixing re in sediments is examined experimentally thiolation of reo 4 leading to particle reactive thioperrhenates re vii o n s 4 n or to re vii sulfide precipitates or coprecipitates using optical absorption methodology we obtain the first measurements of equilibrium constants for formation of reo 3 s and res 4 as well as a solubility constant for a colloidal re 2 s 7 polymer from these constants we conclude that most euxinic environments contain insufficient sulfide to stabilize thioperrhenates as major species similarly re 2 s 7 polymers are too soluble to form in near neutral ph waters although they might form in acidic mine waters or during supergene hypogene enrichment processes to explain remarkable similarities between mo and re vertical profiles in the black sea we propose that both elements become thiolated at surfaces of a fe mo s colloidal phase and consequently coprecipitate coprecipitation implies that the triggering mechanism for re removal from euxinic basins is neither reduction nor thiolation of reo 4 but instead saturation of sulfidic waters with the fe mo s phase coprecipitation favors removal of mo more than re from the aqueous phase explaining increasing aqueous phase re mo ratios as these elements are depleted from sulfidic waters the raleigh fractionation law describes the process well similar partition coefficients describe the evolution of re mo ratios quantitatively both in sulfidic black sea waters and in sulfidic hingham bay pore waters

brine rock interaction in the athabasca basement mcarthur river u deposit canada consequences for fluid chemistry and uranium uptake terra nova 22 303 308 2010 abstract the nature of uranium source rocks transport conditions and deposition processes are still highly controversial for world class unconformity related u deposits this article presents the first detailed chemistry of brines associated with the giant mcarthur river u deposit canada la icp ms analysis of individual fluid inclusions suggests mixing between a na ca mg k sr ba brine and a ca mg na k sr ba brine the brines share a common origin evaporated seawater and show evidence for contrasting interaction with basement rocks the na rich brine lost mg and k in alteration haloes around u ores while the ca rich brine results from na ca exchange and sr ba gain u concentrations 0 3 530 g g 1 are anomalously high compared with usual basinal fluids this indicating that u uptake occurred within basement rocks the two brine end members have mixed within the main u deposit area which could be one of the major driving forces for u deposition

development and age structure of holocene coastal sand dunes at horn head near dunfanaghy co donegal ireland two areas of holocene coastal sand dunes on the western side of the horn head peninsula extend from low ground immediately inland of their respective source beaches onto flanking higher ground 100 m od stratigraphic investigations supported by 14c dating of buried organic rich horizons and shells demonstrate several phases of sand accumulation in the pollaguill croaghadara system in contrast to the larger tramore anloge hill system where the available evidence points to relatively recent dune emplacement a broadly synchronous phase of dune development occurred during the thirteenth to fourteenth centuries ad and is viewed as part of a regional northwestern europe dune building episode resulting from climatic deterio ration earlier phases pre 3300 2800 14c years bp of aeolian sand deposition at pollaguill croaghadara have no apparent equivalents at tramore anloge hill and repeated fluvial incision and sand reworking during the last 2000 14c years is also evident at the former site dated organi

rhenium molybdenum and uranium in groundwater from the southern great basin usa evidence for conservative behavior abstract dissolved re mo and u concentrations and the concentrations of the major cations and anions were measured in groundwaters from twenty three springs in the southern great basin usa from june 1992 through march 1994 rhenium concentrations ranged from 5 1 pmol kg to 190 20 pmol kg the highest re values were observed in the saline groundwater of saratoga spring in death valley and cold spring in ash meadows whereas the lowest re concentrations were found in nevares spring in death valley the mean re concentration for all of the spring waters sampled is 44 33 pmol kg the concentrations of re differs dramatically for groundwaters that discharge from the regional paleozoic carbonate aquifer and for local groundwaters from felsic volcanic rocks the mean re concentration for groundwaters issuing from the carbonate aquifer is 37 14 pmol kg which is similar to the average re value reported for seawater i e 39 8 0 2 pmol kg whereas for the spring waters that discharge from the felsic volcanic aquifers the mean re concentration is 18 3 5 pmol kg the overall mean concentrations of u and mo in these groundwaters are 18 12 nmol kg and 120 60 nmol kg respectively differences in the u and mo concentrations for groundwaters from the carbonate aquifer and those from the volcanic aquifer are also observed such that the mean u and mo concentrations in the carbonate groundwaters are 13 5 nmol kg and 106 40 nmol kg respectively and the mean u and mo concentrations in the volcanic spring waters are 31 5 4 nmol kg and 94 12 nmol kg respectively by comparison u and mo concentrations reported for seawater are 13 9 nmol kg and 107 nmol kg respectively in the oxygenated groundwaters of the great basin re mo and u appear to be acting conservatively as in seawater as evidenced by the covariance observed between re mo and u with chloride sodium and sulfate groundwaters discharging from the regional carbonate aquifer in ash meadows typically exhibit a u re ratio of about 300 while groundwaters that discharge in death valley from local felsic volcanic sources have ratios of about 1700 waters in the remainder of the death valley springs are intermediate and may result from the mixing of the carbonate and volcanic derived waters the re mo and u concentrations in addition to the major solute chemistry indicates that dissolution of carbonate rocks is of primary importance in the groundwaters from ash meadows whereas the weathering of felsic volcanic rocks contributes substantially to the chemical signatures of the death valley groundwaters the differences between u re ratios and different aquifer materials suggest that there is a relationship between the dissolved u re ratios and the aquifer materials similar re mo u ratios for the groundwaters from the carbonate aquifer and seawater are strongly suggestive of quantitative uptake of these trace elements from seawater by carbonate mineral precipitation and subsequent quantitative release of these trace elements during dissolution of the carbonate rocks by groundwater the substantially larger salinity normalized re mo and u concentrations in the groundwaters compared to seawater rule out the possibility that these groundwaters represent simple mixing of dilute terrestrial waters and seawaters or reconstitution of evaporite deposits by groundwater dissolution

major phases of coastal erosion ca 6700 6000 and ca 3000 2000 bp between cervantes and dongara western australia abstract relict foredune plains developed along parts of the coast between cervantes and cliff head during holocene time evidence for major episodes of marine erosion was provided by the presence of extensive erosional scarps or discontinuities within or at the inner margin of many of the plains such features often truncate older coastal landforms such as parabolic dunes shells within foreshore deposits immediately seaward of the erosional cuts were dated to obtain an approximate age for the end of erosional episodes at two locations dating suggests that erosion occurred ca 6700 6000 bp dates from four other sites suggest that a major erosional episode occurred between ca 2000 and 3000 bp there was no evidence for the occurrence of major episodes of marine erosion at other times since the attainment of modern holocene sea level the first erosional episode is likely to have been associated with the final stages of the postglacial marine transgression the second which was also associated with the initiation of transgressive dunes was probably caused by an increase in the occurrence and or intensity of either tropical cyclones or winter cyclonic storms however the occurrence at that time of a minor marine transgression cannot be discounted

dune phases as time transgressive phenomena manawatu new zealand abstract new zealand s most extensive holocene dunefield is situated in the manawatu and adjoining regions evidence collected from the area including 25 radiocarbon dates suggests that the dunefield developed in phases with the first probably initiated at the coast earlier than 6000 years ago the first phase may have ceased near the coastline around 4500 years ago but dunes continued to migrate until they reached 16 km inland ca 1600 years ago about 3500 years ago dunes again began migrating inland from the coast with some still active 400 years ago the time transgressive nature of transgressive dune deposits and the possible causes of the dune phases are discussed

rare earth element geochemistry of groundwaters from a thick till and clay rich aquitard sequence saskatchewan canada rare earth elements ree were determined in groundwater samples collected from a thick till and clay rich aquitard sequence located in southern saskatchewan canada the groundwaters are na mg so4 type waters that range from highly concentrated brines e g i up to 2 moles kg near the ground surface to relatively dilute waters i 0 04 moles kg at depth the majority of these groundwaters have ph values between 7 and 8 although the deepest samples are more alkaline 9 ph 9 6 groundwater ree concentrations are relatively constant in the overlying till but increase by up to a factor of 50 in the underlying clay bedrock shallow groundwaters have heavy ree hree enriched shale normalized patterns whereas the ree patterns of the deep groundwaters are relatively flat solution complexation modelling indicates that variations in ree patterns reflect differences in solution complexation across the ree suite in the shallow groundwaters strongly adsorbed positively charged carbonate complexes lnco3 sulfate complexes lnso4 and free metal ion species ln3 dominate the speciation of light rees lree whereas hrees occur chiefly as more stable negatively charged dicarbonato complexes i e ln co3 2 for the deepest groundwaters however all of the rees are predicted to occur in solution as dicarbonato complexes the large hree enrichments of the shallow groundwaters reflect the greater affinity of the positively charged lree solution species to adsorb to clay minerals or coatings on clay minerals in the aquitard sequence compared to the more stable negatively charged hree dicarbonato complexes on the other hand the flat ree patterns of the deep groundwaters reflect the dominance of the negatively charged dicarbonato complex for all rees the solution complexation model along with the strong positive correlation between rees and co32 f 0 79 r 0 95 and to a lesser extent ph 0 57 r 0 72 indicates that carbonate ion concentrations and thus ph exert important controls on aqueous ree concentrations in these groundwaters

rare earth element fractionation and concentration variations along a groundwater flow path within a shallow basin fill aquifer southern nevada usa abstract rare earth element ree concentrations were measured in 5 well water samples and 3 springs located along a groundwater flow path in a shallow tuffaceous alluvial aquifer from southern nevada usa the ree concentrations in these groundwaters decrease in the direction of groundwater flow a previous investigation demonstrated that ree solid liquid phase partitioning coefficients i e kd s for groundwaters from tuffaceous alluvial aquifers in southern nevada are relatively high mean kd 102 6 our groundwater ree data in conjunction with these kd s support strong sorption of aqueous rees to aquifer surface sites as the primary removal mechanism of rees from these groundwaters in addition relatively high aqueous ree concentrations occur at distinct locations along the groundwater flow path the elevated ree concentrations are explained by addition of deeper groundwaters influx of geothermal waters from a hot spring system differences in solution complexation and or mixtures of regional and local recharge sources solution complexation modelling of rees in the groundwaters indicate that carbonate complexes account for more than 99 of each rees in solution moreover groundwater yb nd ratios a measure of ree fractionation are associated with alkalinity hco3 co32 r 0 71 the data and speciation model results indicate that ree fractionation i e the observed heavy ree hree enrichments compared to rock sources is controlled by formation of progressively stronger carbonate complexes in solution with increasing atomic number which inhibits hree sorption compared to light rees lree and a greater affinity for the lrees to sorb to surface sites in the local tuffaceous alluvial aquifers compared to the hrees

multivariate statistical analysis of arsenic and selenium concentrations in groundwaters from south central nevada and death valley california abstract arsenic and selenium concentrations along with the major solutes were measured in ground waters sampled from springs in pahranagat valley and ash meadows nevada death valley california and from wells from the nevada test site and yucca mountain nevada the multivariate statistical technique correspondence analysis was applied to the data to determine relationships between the groundwaters from these areas the aquifer materials and the as and se concentrations and to examine the relationships between as and se and the other chemical parameters included in the statistical analysis the correspondence analysis indicates that a strong relationship exists between chloride and se in the groundwaters and that as is not associated with chloride the strong association between chloride and se suggests that se behaves more conservatively than as in these oxygenated circumneutral ph groundwaters no strong association was observed between the as and or se concentrations of the groundwaters and the aquifer material with which these waters interact i e regional paleozoic carbonate aquifer tertiary tuffaceous volcanic rocks and or basin fill deposits however it is likely that sampling of groundwaters from the various aquifers was insufficient to determine relationships between the aquifer materials and groundwater chemistry associations were observed between the groundwaters of the nevada test site and yucca mountain regions and the groundwaters of the regional carbonate aquifer that discharge at ash meadows and death valley suggesting mixing of these waters ground water from the regional carbonate aquifer in pahranagat valley which is upgradient from the nevada test site yucca mountain ash meadows and death valley exhibited no association with groundwaters from these regions

using multivariate statistical analysis of groundwater major cation and trace element concentrations to evaluate groundwater flow in a regional aquifer groundwater samples were collected from 11 springs in ash meadows national wildlife refuge in southern nevada and seven springs from death valley national park in eastern california concentrations of the major cations ca mg na and k and 45 trace elements were determined in these groundwater samples the resultant data were subjected to evaluation via the multivariate statistical technique principal components analysis pca to investigate the chemical relationships between the ash meadows and death valley spring waters to evaluate whether the results of the pca support those of previous hydrogeological and isotopic studies and to determine if pca can be used to help delineate potential groundwater flow patterns based on the chemical compositions of groundwaters the results of the pca indicated that groundwaters from the regional paleozoic carbonate aquifers all of the ash meadows springs and four springs from the furnace creek region of death valley exhibited strong statistical associations whereas other death valley groundwaters were chemically different the results of the pca support earlier studies where potentiometric head levels 18o and d geological relationships and rare earth element data were used to evaluate groundwater flow which suggest groundwater flows from ash meadows to the furnace creek springs in death valley the pca suggests that furnace creek groundwaters are moderately concentrated ash meadows groundwater reflecting longer aquifer residence times for the furnace creek groundwaters moreover pca indicates that groundwater may flow from springs in the region surrounding scotty s castle in death valley national park to a spring discharging on the valley floor the study indicates that pca may provide rapid and relatively cost effective methods to assess possible groundwater flow regimes in systems that have not been previously investigated copyright 1999 john wiley sons ltd

rhenium in the black sea comparison with molybdenum and uranium rhenium concentrations were measured in the black sea to determine the behavior of this redox sensitive element in an anoxic basin under reducing conditions re is removed from solution leading to its depletion from black sea deep waters compared with uranium water column re and mo profiles show evidence of removal from mid depths suggesting that these elements are scavenged either in the water column or slope sediments to a greater degree than u black sea surface waters are enriched in re reflecting re in rivers draining into the northern black sea that are enhanced up to 80 fold over other large world rivers this enrichment is most likely anthropogenic and may be due to coal burning in the region a simple two box model is used to demonstrate that re concentrations in the black sea are not in steady state with respect to current riverine inputs and authigenic fluxes riverine inputs of u and mo are not as significant perhaps reflecting the fractionation of re from the other elements during a high temperature combustion process re2o7 is volatile above 270 c

late quaternary geomorphology of the manawatu coastal plain north island new zealand this review examines the geomorphological evolution of the manawatu coastal plain from the last glacial maximum through the holocene post glacial marine transgression c 7500 cal yr bp until the present providing a context within which to examine the extent to which the holocene evolution of the lower manawatu valley follows tripartite evolutionary models of incised valley infill during the last glaciation the manawatu river incised a broad deep valley while tributaries within the catchment dissected relict marine terraces this occurred concurrently with the formation of a parabolic dune field at koputaroa with sediment sourced from the bars of the manawatu river during the post glacial marine transgression rising sea levels inundated the incised valley at the culmination of the holocene marine transgression the himatangi anticline and poroutawhao high restricted oceanic influences in the proto manawatu estuary which was partially infilled with estuarine sediment estuarine deposition was quickly succeeded by fluvial deposition and floodplain due to high volumes of fluvial sediment introduced by the manawatu river a lack of characteristic bay head delta development may be explained by rapid infill and consequent sediment bypass

dissolved rhenium in the yamuna river system and the ganga in the himalaya role of black shale weathering on the budgets of re os and u in rivers and co 2 in the atmosphere extensive measurements of dissolved re and major ion abundances in the yamuna river system yrs a major tributary of the ganga have been performed along its entire stretch in the himalaya from its source near the yamunotri glacier to its outflow at the foothills of the himalaya at saharanpur in addition re analysis has been made in granites and precambrian carbonates some of the major lithologies of the drainage basin these data coupled with those available for black shales in the lesser himalaya allow an assessment of these lithologies contributions to the re budget of the yrs the re concentrations in the yrs range from 0 5 to 35 7 pm with a mean of 9 4 pm a factor of 4 higher than that reported for its global average concentration in rivers dissolved re and cations na k ca mg are strongly correlated in the yrs indicating that they are released to these waters in roughly the same proportion throughout their course the re cations in most of these rivers are one to two orders of magnitude higher than the re na k mg ca measured in granites of the yamuna basin this leads to the conclusion that on average granites crystallines make only minor contributions to the dissolved re budget of the yrs on a basin wide scale though they may be important for rivers with low dissolved re similarly precambrian carbonates of the lesser himalaya do not seem to be a major contributor to dissolved re in these rivers as their re ca mg is much less than those in the rivers the observation that re concentrations in rivers flowing through black shales and in groundwaters percolating through phosphorite black shale carbonate layers in phosphorite mines are high and that re and so4 are significantly correlated in yrs seems to suggest that the bulk of the dissolved re is derived from black shale carbonaceous sediments material balance considerations based on average re of 30 ng g 1 in black shales from the lesser himalaya require that its abundance in the drainage basin of the yrs needs to be a few percent to yield average re of 9 4 pm furthermore the positive correlation between re and cations would require that these re rich sediments e g black shales and re poor lithologies e g crystallines precambrian carbonates contribute re and cations in roughly the same proportion throughout the drainage basin the available data on the abundance and distribution of black shales in the basin are not adequate to test if these requirements can be met the annual fluxes of dissolved re at the base of the himalaya from the yamuna are 150 mol at batamandi and 100 mol at saharanpur compared to 120 mol from the ganga at rishikesh the total flux from the yamuna and the ganga account for 0 4 of the global riverine re flux much higher than their contribution to global water discharge this is also borne out from the mobilization rate of re 1 to 3 g km 2 y 1 in the ganga and yamuna basins in the himalaya compared to the global average of 0 1 g km 2 y 1 black shale weathering can also significantly influence the budgets of os and u in rivers and co2 in rivers and the atmosphere using dissolved re in rivers as a proxy it is estimated that 6 9 108 kg y 1 of black shales are being weathered in the ganga and yamuna basins in the himalaya weathering of such amounts of black shales can account for the reported concentrations of os and u in these rivers furthermore if the weathering results in the conversion of organic carbon in the black shales to co2 it would release 2 105 mol of co2 km 2 y 1 in the yamuna and ganga basins in the himalaya comparable to the co2 consumption from silicate weathering

numerical simulation of the evolution and propagation of aeolian dune fields toward a desert oasis zone abstract in this study the evolution and propagation of aeolian dune fields toward a desert oasis transitional zone are numerically investigated through considering the spatial variation of wind speed and the influence of vegetation on sand erosion and transportation etc the propagation speed at the edge of desertified land and the influence of a straw checkerboard are quantitatively analyzed results show that evolution time wind speed and sand diameter have obvious impacts on the propagation of desert and desertified land a formula describing the propagation speed of desertified land with respect to wind speed and vegetation coverage is given in addition when considering the effects of straw checkerboards the propagation speed of the downwind desertified land is found to be related to the length of and distance from the checkerboard area

influence of system controls on the late quaternary geomorphic evolution of a rapidly infilled incised valley system the lower manawatu valley north island new zealand abstract the manawatu incised valley estuary was rapidly infilled between 12 000 4700 cal yr bp a combination of empirical measurements of sedimentation rates a reconstruction of relative sea level rsl change and digital elevation models of key surfaces within the holocene sedimentary fill of the valley were integrated to produce a numerical model to investigate the influence of the system controls of sea level change sediment flux and accommodation space on the rapid infilling history of the palaeo estuary the numerical model indicates that sediment flux into the palaeo estuary was greatest during the holocene marine transgression between 12 000 8000 years bp the average rate of sediment deposition in the estuary during this period was 1 0 m m 3 yr 1 this rapid rate of sedimentation was controlled by the rate of accommodation space creation as regulated by the rate of sea level rise and the antecedent configuration of the valley by the time sea levels stabilised c 7500 cal yr bp the palaeo estuary had been substantively infilled limited accommodation space resulted in rapid infilling of the central basin though sediment flux into the estuary between 7100 and 4500 cal yr bp was at a lower rate of 234 000 m 3 yr 1 the limited accommodation space also influenced hydrodynamic conditions in the estuarine central basin driving export of fine grained sediment from the estuary once the accommodation space of the estuarine basin was infilled sediment bypassed the system with a consequent reduction in the sedimentation rate in the valley more accurate partitioning of the sources of sediment driving the infilling is necessary to quantify sediment bypassing post depositional lowering of rsl index points from the valley is driven by neotectonics and sediment compaction

some comparative marine chemistries of platinum and iridium abstract iridium has seawater concentrations about one hundred times less than those of platinum as a consequence of its weaker complexing abilities with halides and of a stronger tendency to hydrolyze iridium like platinum is enriched in some ferromanganese minerals compared to palladium platinum and iridium are probably oxidized during mineral formation from the divalent and trivalent states respectively to the tetravalent ones the pelagic sediment contents of irridium as well as those of platinum are related to the manganese contents for higher platinum contents of the authigenic ferromanganese minerals the pt ir ratios approach the seawater ratio suggesting little dilution by platinum and iridium in detrital minerals the marked enrichments of platinum and iridium in the ferromanganese concretions enhance their value as potential ores for heavy metals

geomorphic response to late holocene climate variation and anthropogenic pressure northeastern prince edward island canada abstract geomorphic response provides an index to climate change and variability differing time scales of both weather climate events and landform response complicate interpretation anthropogenic modification particularly in coastal and aeolian dune environments represents a further geomorphic influence northeastern prince edward island pei canada is a marine dominated environment subjected to rising sea level throughout the late holocene the combination of rising sea levels increased anthropogenic utilization of the coast for residential and tourism purposes and limited offshore winter ice conditions have resulted in accelerated erosion and degradation of the dunes and coastline the aeolian succession indicates that temporal and spatial transitions from isolated shield dunes to parabolic dunes to linked coastal transverse dune complexes are characteristic of the coastal dune fields sand supply is the most significant control on dune morphology development and extent superimposed dome dunes and shield dunes are prevalent in areas of anthropogenic disturbance dune migration along the coastal zone has varied considerably with rates locally in excess of 10 m a over short times winters marked by relatively limited sea ice and scarce snow cover resulting from more temperate winter conditions allow increased erosion by strong storms deflation of dune crests and development of blowouts is notably accentuated along human trails the climate variations recorded in atlantic canada over the past decade fall within the range of those recorded previously within the twentieth century and thus do not indicate conclusive evidence of a pronounced trend of climate change in this region however analysis of northeastern pei demonstrates that dune coastlines can evolve rapidly in response to short term and intermediate term climate variation particularly when coupled with anthropogenic pressure similar geomorphic effects in combination with climate variation and storm activity should be anticipated along other dune coastlines that have been subjected to intense anthropogenic utilization during earlier periods of the quaternary

adsorption of uranium from groundwater by common fracture secondary minerals laboratory studies have been performed on the uptake of uranium by the chief secondary minerals identified on fracture surfaces in groundwater flow systems of the canadian shield the extent of adsorption from prepared solutions onto these materials i e ferric oxyhydroxide uptake chlorite uptake calcite uptake was similar to that previously observed in place on field samples although adsorption on the oxyhydroxide proceeds rapidly to near equilibrium in about 3 weeks slower two stage processes have been postulated for uranium uptake by both chlorite and calcite in some cases the times required to reach equilibrium are greater than 1 year

facies architecture morphostratigraphy and sedimentary evolution of a rapidly infilled holocene incised valley estuary the lower manawatu valley north island new zealand water well logs and vibracores recovered from the lower manawatu valley record the facies architecture morphostratigraphy and sedimentary evolution of this drowned river incised valley estuary over the past c 30 000 years the manawatu incised valley estuary was rapidly infilled during the holocene and as a result preserves a complete record of holocene estuary evolution the base of the holocene fill is marked by fluvial gravels deposited by the manawatu river during the lowstand of the last glacial maximum the gravels are overlain by back stepping transgressive fluvial silts and clays the transgressive fluvial unit is present only in the lower reaches of the valley due to accelerated sea level rise during the latter stages of the marine transgression large volumes of transgressive marine sediment were delivered to the mouth of the valley by rising sea levels during the early holocene forming a large subaqueous tidal delta this delta accreted and subsequently evolved to form a subaerial barrier in the mid holocene as sea levels stabilised during the sea level highstand the central basin of the estuary was rapidly infilled by marine and fluvial sediment and consequently lacks the mud facies characteristic of less rapidly evolved estuaries the transition from the sandy central basin estuarine environment to the overlying floodplain environment was extremely rapid in some locations in the valley the transitional fluvial bay head delta is missing completely while in most locations it is present only as a very thin deposit indicative of this rapid environmental transition infilling of the estuarine central basin was extremely rapid taking only 2000 2700 years the unique features of the manawatu estuary s evolutionary history are interpreted to primarily reflect the rapid infilling of the palaeo estuary driven by the high rates of sediment supplied to the valley from both marine and fluvial sources

precise re os ages of organic rich mudrocks and the os isotope composition of jurassic seawater rhenium and osmium isotope and abundance data have been obtained on precisely located samples from three suites of immature organic rich mudrocks from jurassic coastal outcrops in england the data provide accurate whole rock ages of 207 12 ma 181 13 ma and 155 4 3 ma for suites of hettangian toarcian exaratum subzone and kimmeridgian sensu anglico wheatleyensis subzone samples these new re os ages are indistinguishable within the assigned analytical uncertainties from interpolated depositional ages estimated from published geological timescales and establish the importance of the re os dating technique for chronostratigraphic studies early diagenetic pyrite nodules possess levels of re and os which are 1 2 orders of magnitude lower than in the enclosing organic rich mudrocks indicating that these elements had already been removed from sediment pore waters at the time of nodule formation thus the re os isotope system in these organic rich mudrocks has been closed since or from very soon after the time of sediment deposition because most of the re 98 and os 95 99 8 in the mudrocks is shown to be hydrogenous the 187os 188os i of the samples is interpreted to be that of contemporaneous seawater the data thereby provide the first estimates of the os isotope composition of jurassic seawater during the earliest jurassic hettangian the seawater 187os 188os ratio was extremely unradiogenic 0 15 it had increased to 0 8 at the end of the early jurassic toarcian 20 ma later while in the late jurassic kimmeridgian the seawater 187os 188os ratio was 0 59 the most likely explanation for the unradiogenic os isotope composition of hettangian seawater is that the contribution of unradiogenic os to the oceans from the hydrothermal alteration of oceanic crust greatly exceeded the input of radiogenic os from the continents at that time this interpretation is in line with observations suggesting that global weathering rates were low in the hettangian and that increased hydrothermal and volcanic activity preceded the break up of pangea the re os ratios of hettangian mudrocks and by inference of contemporaneous seawater are similar to those of mudrocks deposited at later times during the jurassic and argues against the unradiogenic os in hettangian seawater being derived from extraterrestrial meteoritic sources

discrimination between different water bodies from a multilayered aquifer kaluvelly watershed india trace element signature in the multilayered aquifer of kaluvelly india comprising various sedimentary layers overlying a charnockitic basement concentrations of trace elements were measured in aquifer formations and in groundwaters to identify geochemical tracers for water bodies the two main sandstones cuddalore and vanur originate from the charnockites and the cuddalore sandstone has experienced lateritization in the studied area two charnockite end members were identified a dioritic and a granitic one mineralogical composition and whole rock ti concentrations confirmed the charnockite which displayed the granitic composition as the parent rock of the two sandstones titanium distribution indicates that the cuddalore sandstone originates from a more intense weathering of the parent material than the vanur sandstone despite extensive differences in trace element contents recorded in aquifer formations only a few trace elements were suitable to distinguish the water bodies among soluble elements li in the vanur aquifer and ba in the charnockite and carbonaceous aquifers can be used as tracers as the input of these elements in solution is mainly regulated by the available stock for a given mineralogical origin there is a direct link between the aquifer formation composition and water signature with the exception of as concentrations of redox sensitive elements were not preserved during pumping because of oxidation preventing their use as tracers low mobility elements such as la ce th zr nb hf or ta were too insoluble to be detected in waters and or to record the aquifer formation signature their input in solution was not regulated by the available stock but by the dissolution rate of rock forming minerals only ti can be used to distinguish between two out of the three aquifers charnockite and vanur the specific behavior of ti recorded in these waters may be linked to rutile inclusions within plagioclases and to the influence of climate on ti solubility

dune phases in the otaki te horo area new zealand a geomorphic history optical dating sedimentological analysis and soil profile development have been used to develop a chronology for and an understanding of the geomorphic evolution of the holocene coastal plain between otaki and te horo north island of new zealand the coastal plain has prograded 0 48 m a 1 since sea levels reached their post glacial maximum 6500 years ago dune development on the plain which is dependent on the supply of sediment suitable for dune building has been episodic three periods of dune activity have been identified the foxton motuiti and waitarere phases the last two of which are believed to have resulted from anthropogenic activities the dunes north of the otaki river and south of mangaone stream are typical of a coastal dune system that extends from patea in the north to paekakariki in the south however this system is disrupted by the otaki river and the gravels it delivers to the coastal zone immediately south of the river mouth the dunes are significantly smaller coarser and contain significantly more magnetic material the character of the landforms is the result of the reworking of the last glacial deposits ongoing coastal progradation variation in the input of sediment suitable for dune formation the change in beach character because of gravel input and the position of the otaki river mouth copyright 2006 john wiley sons ltd

234u 238u 230th 232th systematics in saline groundwaters from central missouri saline groundwaters with 4 7 to 26 total dissolved solids were sampled from springs and artesian wells in mississippian and ordovician carbonates and sandstones in central missouri u th isotopic variations provide a means of evaluating processes of water rock interaction and fluid mixing and estimating the time scales of element transport recently developed mass spectrometric techniques are used to make isotopic measurements on small volume groundwater samples 0 1 4 l with high precision e g 5 for 234 u 238 u activity ratios the groundwaters have a wide range of 238 u concentrations 50 10 12 to 200 10 12 g g 234 u 234 u activity ratios 2 15 16 0 232 th concentrations 0 10 10 12 to 33 10 12 g g and 230 th concentrations 0 91 10 17 to 26 10 17 g g unfiltered and filtered 0 4 m 0 1 m aliquots of a saline sample have the same isotopic composition and concentration of u indicating that 234 u and 238 u occur almost entirely as dissolved species the concentration of 232 th is up to seven times lower in filtered vs unfiltered aliquots indicating that 232 th is predominantly associated with particulates in the groundwaters in contrast most of the 230 th is in solution previous geochemical studies indicate that 1 the saline waters originated as meteoric recharge and evolved through halite dissolution reactions with silicates and saline dilute mixing processes during a long distance flow history and 2 interaction with limestone and dolomite aquifer rocks in central missouri has been limited a consistent relationship between u ca and 234 u 238 u activity ratio is observed in the groundwaters and provides constraints on the u ca ratios and 234 u 238 u activity ratios of end member reservoirs and on the processes of isotopic exchange in this water rock system model calculations that simulate 1 saline dilute groundwater mixing and 2 limited extents of dissolution of carbonate aquifer minerals by the groundwaters can account for the variations in u ca 234 u 238 u and 18 o 16 o in the suite of water samples the model calculations demonstrate that dissolved u isotopic compositions can be a sensitive indicator of water rock interaction which in turn limits the usefulness of 234 u 238 u disequilibria for groundwater age determinations the concentration of dissolved 230 th in the groundwaters is 1 two to three orders of magnitude below 230 th 234 u equilibrium activity levels and 2 significantly in excess of concentrations estimated for the supply of th to solution via desorption and dissolution a model involving the derivation of the excess 230 th from the in situ decay of dissolved 234 u in the groundwaters indicates the operation of an adsorption mechanism on the time scale of 10 10 3 years the results reported here may have broader application to the assessment and management of hazardous chemical species in natural environments

measurements and numerical simulations of the degree of activity and vegetation cover on parabolic dunes in north eastern brazil in this work we present measurements of vegetation cover over parabolic dunes with different degrees of activation along the north eastern brazilian coast we extend the local values of the vegetation cover density to the whole dune by correlating measurements with the relative brightness index c of high resolution quickbird panchromatic satellite images of the dune field we then introduce the vegetation data into a continuous model for vegetated dunes coupling sand erosion and vegetation growth and perform simulations of the evolution of the morphology and vegetation cover of parabolic dunes finally from the comparison of both the measurements and the simulation results we show that the model is able to predict the dune shape and the vegetation distribution of real parabolic dunes as result of the evolution of a blow out