sedimentary pyrite formation an update sedimentary pyrite formation during early diagenesis is a major process for controlling the oxygen level of the atmosphere and the sulfate concentration in seawater over geologic time the amount of pyrite that may form in a sediment is limited by the rates of supply of decomposable organic matter dissolved sulfate and reactive detrital iron minerals organic matter appears to be the major control on pyrite formation in normal non euxinic terrigenous marine sediments where dissolved sulfate and iron minerals are abundant by contrast pyrite formation in non marine freshwater sediments is severely limited by low concentrations of sulfate and this characteristic can be used to distinguish ancient organic rich fresh water shales from marine shales under marine euxinic conditions sufficient h2s is produced that the dominant control on pyrite formation is the availability of reactive iron minerals calculations based on a sulfur isotope model indicate that over phanerozoic time the worldwide average organic carbon to pyrite sulfur ratio of sedimentary rocks has varied considerably high cs ratios during permo carboniferous time can be explained by a shift of major organic deposition from the oceans to the land which resulted in the formation of vast coal swamps at that time low cs ratios compared to today during the early paleozoic can be explained in terms of a greater abundance of euxinic basins combined with deposition of a more reactive type of organic matter in the remaining oxygenated portions of the ocean the latter could have been due to lower oceanic oxygen levels and or a lack of transportation of refractory terrestrial organic matter to the marine environment due to the absence of vascular land plants at that time

modelling of the evolution of ground waters in a granite system at low temperature the stripa ground waters sweden abstract from chemical data collected by nordstrom and his colleagues on stripa ground waterswe have tried to model the evolution of the chemical composition of a ground water in a granitic system at low temperature the existence of two end member ground water compositions made it possible first to test the conventional model of a geothermal system according to which an overall equilibrium between the waters and a given mineral assemblage can be defined and then to show that such a model could be extended to low temperatures 10 c conversely if we know the mineral assemblage the equilibration temperature and the charge of the mobile ions in this case cl the composition of the solution is entirely fixed in our model of the stripa ground waters the existence of two end member ground water compositions can be explained by an evolution from a kaolinite albite laumontite equilibrium to a prehnite albite laumontite equilibium the latter requiring less al than the former we have also emphasized the importance of the cl ion concentrions ofof the ground waters because they cab be considered as indicators of the degree of reaction progress between rock and water thus determining the degree of equilibration of the system

electrical resistivity imaging of the architecture of substream sediments 1 the modeling of fluvial systems is constrained by a lack of spatial information about the continuity and structure of streambed sediments there are few methods for noninvasive characterization of streambeds invasive methods using wells and cores fail to provide detailed spatial information on the prevailing architecture and its continuity geophysical techniques play a pivotal role in providing spatial information on subsurface properties and processes across many other environments and we have applied the use of one of those techniques to streambeds we demonstrate through two examples how electrical resistivity imaging can be utilized for characterization of subchannel architecture in the first example electrodes installed in riparian boreholes and on the streambed are used for imaging under the river bed the thickness and continuity of a highly permeable alluvial gravel layer overlying chalk in the second example electrical resistivity images determined from data collected using electrodes installed on the river bed provide a constrained estimate of the sediment volume behind a log jam vital to modeling biogeochemical exchange which had eluded measurement using conventional drilling methods owing to the boulder content of the stream the two examples show that noninvasive electrical resistivity imaging is possible in complex stream environments and provides valuable information about the subsurface architecture beneath the stream channels

zur systematik der kohlenstoff schwefel eisen verhaltnisse in auftriebssedimenten abundances of organic carbon sulfur and reactive iron in sediments of three upwelling environments peru oman and benguela suggest that organic carbon reduced sulfur ratios c s ratios in this category of marine sediments deviate considerably from previously established empirical ratios in normal marine sediments to clarify the discrepancies we investigated those components of the diagenetic system that limit the formation of pyrite sulfate concentrations and reduction rates in pore waters availability of reactive iron and the quantity and quality of organic matter all three limitations are evident in our sample pools the results suggest that c s ratios in recent and fossil marine sediments rich in organic matter may be unsuitable as paleoenvironmental indicators

burial of organic carbon and pyrite sulfur in sediments over phanerozoic time a new theory in present day marine sediments almost all of which are deposited in normal oxygenated seawater rates of burial of organic carbon c and pyrite sulfur s correlate positively and bear a constant ratio to one another c s 3 on a weight basis by contrast calculations based on the isotopic model of garrels and lerman 1981 indicate that at various times during the phanerozoic the worldwide burial ratio must have been considerably different than the present day value this ratio change is caused by the requirement that increases in the worldwide mass of organic carbon must be accompanied by equivalent decreases in the mass of sedimentary pyrite sulfur in order to maintain a roughly constant level of o2 in the atmosphere such apparently contradictory behavior can be explained if the locus of major organic carbon burial has shifted over time from normal marine environments as at present to non marine freshwater or to euxinic environments in the geologic past a shift to predominantly freshwater burial can help explain predicted high c s ratios in permo carboniferous sediments and a shift to euxinic environments can help explain predicted low c s ratios during the early paleozoic it is demonstrated that the three environments today exhibit distinguishably different average c s ratios

combining seismic and electric methods for predicting bedrock depth along a mediterranean soil toposequence abstract bedrock depth provides important information for many environmental and agricultural applications such as shallow groundwater monitoring the determination of soil water availability and the estimation of crop production potential direct estimates of bedrock depth from destructive soil observations are discontinuous and too expensive to be used in large areas geophysical methods are often cited as possible alternatives however their ability to provide reliable estimations of bedrock depth is known to depend greatly on local site characteristics therefore combining geophysical methods based on different physical parameters may help to provide better predictions this study examines the ability of the spectral analysis of surface waves sasw method combined with the classical high resolution electrical resistivity tomography ert method to predict soil depths in a 500 m ranged mediterranean hillslope southern france with increasing soil depths along the slope sasw was performed using the data measured in the field with classical seismic equipment impulse source and geophones distributed along a line in the same place eight transects of ert wenner schlumberger array 1 m electrode spaced were measured under wet and dry conditions to calibrate the geophysical measurements 81 boreholes from two to 5 m deep were interpreted to determine the bedrock depth which was defined as the occurrence in the depth of heterogeneous marine miocene loose sandstone with centimetric laminations ert and sasw were found to have highly variable performances for predicting separately the bedrock depth along the hillslope sasw correctly predicted the bedrock depth in the lower part of the hillslope whereas the data from ert were disrupted by shallow permanent groundwater conversely ert correctly predicted bedrock depth within the upper part of the hillslope whereas a high variability of sasw data near the topsoil caused difficulties for bedrock depth prediction from these results it was possible to define an estimator of bedrock depth according to the presence of shallow groundwater which varies along the slope such that more importance is given to ert estimates in the upper part of the hillslope and more importance is given to sasw in the lower part this study shows the usefulness of such a sensor combination to estimate soil properties when the uncertainties of making predictions vary according to the geophysical methods

sedimentological characteristics heavy metal distribution and magnetic properties in subtidal sediments ria de pontevedra nw spain the rias of nw spain are coastal ecosystems of high biological productivity and great economic importance they are intensively exploited by man for fish and shellfish there are a number of important centres of population and industrial activity along their margins which serve as sources of contamination in this context it is desirable to achieve the best possible understanding of the physico chemical processes that control spatial and temporal variations in the geochemical mineralogical and sedimentological characteristics of near surface sediments in the ria de pontevedra and in particular the distribution and mobility of heavy metal contaminants thus adequate environmental planning can be achieved for this site and understanding gained for comparable contexts core samples were examined from the inner middle and outer parts of the ria grain size distributions reflect the presence of two main populations one dominated by silt and clay derived mainly from terrestrial sources and the other by fine sand to coarse silt which is derived mainly from continental shelf and ria mouth sources mineralogical analysis shows an abundance of terrestrial intensive weathering products near the ria head a dominance of shelf derived sediment towards the mouth and the presence of several diagenetic minerals whose nature varies with location within the ria in the inner ria the near surface sediments are slightly enriched in pb cu and zn from anthropogenic sources these sediments are fine grained and have a high organic content hence they have a higher potential to sorb contaminants than the coarser grained less organic rich sediments of the mid and outer ria the estimated sedimentation rates for the fine grained organic rich sediments from the inner part of the ria are about 1 mm year 1 the dominant authigenic minerals in the inner ria are iron sulphides whereas in the mid and outer ria iron silicates and oxyhydroxides are more important these differences in authigenic iron mineralogy are clearly reflected by the magnetic properties of the sediments

depositional environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china abstract the non marine santanghu basin in northwest china hosts one of the richest and thickest permian lacustrine source rock intervals in the world conventional oil in jurassic sandstone reservoirs and tight oil in the tuffaceous permian tiaohu formation were sourced from mudrocks in the underlying second member of lucaogou formation which also have tight oil potential proved by recent commercial discoveries based on inorganic and organic geochemistry organic petrography and stable isotope geochemistry the depositional environment and the tight oil potential of the second member of permian lucaogou formation were investigated the data imply a gradual evolution of the depositional environment from a stratified saline to a freshwater lake the succession can be subdivided into a lower middle and an upper unit each characterized by decreasing water salinity high bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria water column stratification accelerated the activity of methanothrophs as indicated by low 13c values of hopanes biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of prasinophytae compared to other algae with decreasing salinity enhanced terrigenous organic matter input appeared during periods of high freshwater inflow low total organic carbon toc contents in the lower unit are most likely caused by rapid sedimentation rate high bioproductivity and excellent preservation conditions resulted in high toc contents in the middle unit terrigenous organic matter input increased together with fresh water inflow in the upper unit resulting in high toc values during periods of possibly low sedimentation rates in a deep water column the samples of the second member exhibit a good to very good potential to generate conventional oil high toc and extractable organic matter yields together with the thickness of the fine grained sediments show that the middle and upper units of the second member of lucaogou formation hold significant tight oil potential mineralogical composition of this dolomite rich shale with respect to abundance of brittle minerals including quartz and carbonates and rare clay testifies a good tight oil potential

spatial distribution of sediment storage types and quantification of valley fill deposits in an alpine basin reintal bavarian alps germany spatial patterns of sediment storage types and associated volumes using a novel approach for quantifying valley fill deposits are presented for a small alpine catchment 17 km 2 in the bavarian alps the different sediment storage types were analysed with respect to geomorphic coupling and sediment flux activity the dominant landforms in the valley in terms of surface area were found to be talus slopes sheets and cones followed by rockfall deposits and alluvial fans and plains more than two thirds of the talus slopes are relict landforms completely decoupled from the geomorphic system notable sediment transport is limited to avalanche tracks debris flows and along floodplains sediment volumes were calculated using a combination of polynomial functions of cross sections seismic refraction and gis modelling a total of 66 seismic refraction profiles were carried out throughout the valley for a more precise determination of sediment thicknesses and to check the bedrock data generated from geomorphometric analysis we calculated the overall sediment volume of the valley fill deposits to be 0 07 km 3 this corresponds to a mean sediment thickness of 23 3 m the seismic refraction data showed that large floodplains and sedimentation areas which have been developed through damming effects from large rockfalls are in general characterised by shallow sediment thicknesses 20 m by contrast the thickness of several talus slopes is more than twice as much for some locations e g narrow sections of valley the polynomial generated cross sections resulted in overestimations of up to one order of magnitude whereas in sections with a moderate valley shape the modelled cross sections are in good accordance with the obtained seismic data for the quantification of valley fill deposits a combined application of bedrock data derived from polynomials and geophysical prospecting is highly recommended d 2003 elsevier b v all rights reserved

application of field geophysics in geomorphology advances and limitations exemplified by case studies abstract during the last decade the use of geophysical techniques has become popular in many geomorphological studies however the correct handling of geophysical instruments and the subsequent processing of the data they yield are difficult tasks furthermore the description and interpretation of geomorphological settings to which they apply can significantly influence the data gathering and subsequent modelling procedure e g achieving a maximum depth of 30 m requires a certain profile length and geophone spacing or a particular frequency of antenna for more than three decades geophysical techniques have been successfully applied for example in permafrost studies however in many cases complex or more heterogeneous subsurface structures could not be adequately interpreted due to limited computer facilities and time consuming calculations as a result of recent technical improvements geophysical techniques have been applied to a wider spectrum of geomorphological and geological settings this paper aims to present some examples of geomorphological studies that demonstrate the powerful integration of geophysical techniques and highlight some of the limitations of these techniques a focus has been given to the three most frequently used techniques in geomorphology to date namely ground penetrating radar seismic refraction and dc resistivity promising applications are reported for a broad range of landforms and environments such as talus slopes block fields landslides complex valley fill deposits karst and loess covered landforms a qualitative assessment highlights suitable landforms and environments the techniques can help to answer yet unsolved questions in geomorphological research regarding for example sediment thickness and internal structures however based on case studies it can be shown that the use of a single geophysical technique or a single interpretation tool is not recommended for many geomorphological surface and subsurface conditions as this may lead to significant errors in interpretation because of changing physical properties of the subsurface material e g sediment water content in many cases only a combination of two or sometimes even three geophysical methods gives sufficient insight to avoid serious misinterpretation a good practice guide has been framed that provides recommendations to enable the successful application of three important geophysical methods in geomorphology and to help users avoid making serious mistakes

single crystal elasticity of wadsleyites β mg 2 sio 4 containing 0 37 1 66 wt h 2 o doi 10 1016 j epsl 2007 10 045

direct push sensing in wetland geo archaeology high resolution reconstruction of buried canal structures fossa carolina germany abstract geo archaeological trenching techniques in floodplain and wetland environments are challenging due to the impact of groundwater inflow and highly unstable trench edges alternatively classical driving core techniques often correspond with the contraction of organic layers and bias in height accuracies here we present the application of direct push sensing techniques for minimal invasive geo archaeological surveys in zones affected by a high groundwater table especially when high resolution parameterization of buried geo archaeological structures is required two of these direct push applications are electrical conductivity logging and the measurement of colorimetric proxies in unconsolidated sediments the tools provide multi proxy information about layer structure texture and organic parameters the high sensing speed allows recording a large data set with high vertical and lateral resolution in this study we exemplary provide results of a buried canal structure within a valley in sw germany we present a high resolution cross section from a zone of high groundwater table the canal is part of charlemagne s summit canal fossa carolina an early medieval hydro engineering project bridging the central european watershed we compare the direct push sensing data with driving core samples and discuss prediction and generation options of parameter transfer from multiple one dimensional logs to a two dimensional canal cross section of high resolution in this context we use in situ obtained colorimetric data and electrical conductivity as proxies for geo archaeological site characterization we model organic fills of the canal by direct push logs and robust sediment data given the cost and time effectiveness of such tools geo archaeological site information of high depth accuracy was grown rapidly compared to less densely performed drillings that require an additional high effort in laboratory analyses the carolingian excavation depth is 6 m below current surface there is evidence for multiple organic layers in the trench fills which reveal aquatic to semi terrestrial stillwater deposition and therefore evidence of multiple carolingian and post carolingian ponds we have evidence for a conceptual width of the deep buried artificial water course of at least 3 4 m this allows a passage of carolingian cargo scows with a payload of several tons in this central zone of the canal

regional fluid characterisation and modelling of water rock equilibria in the boom clay formation and in the rupelian aquifer at mol belgium abstract interstitial water from the boom clay formation around the hades high activity disposal experimental site an underground research facility belonging to the nuclear research centre sck cen at mol dessel belgium underground research facility at mol belgium and waters sampled at different locations in the rupelian aquifer underlying the clay formation have been studied the boom clay is a tertiary mudrock containing about 55 clay and the rupelian aquifer is located in a silty layer special care was taken to adapt or improve measurement sampling conservation and analysis methods to get a reliable regional and local database for the purpose of testing a general model describing the regulation and acquisition of the composition of these fluids the isotopic and chemical composition of the waters allows them to be assigned to a common origin namely mixing between a marine endmember and the clay interstitial water followed by reequilibration with the host rock through dissolution precipitation reactions involving identified secondary minerals oxidation reduction state and trace element behavior are also discussed and the limits of the model are outlined

geology and geochemistry of the sediment hosted cheshmeh konan redbed type copper deposit nw iran the several hundred m thick miocene upper red formation in northwestern iran hosts stratiform and fault controlled copper mineralization copper enrichment in the percent range occurs in dm thick carbonaceous sandstone and shale units within the clastic redbed sequence and consists of fine grained disseminated copper sulfides chalcopyrite bornite chalcocite and supergene alteration minerals covellite malachite and azurite the copper mineralization formed after calcite cementation of the primary rock permeability copper sulfides occur mainly as replacement of diagenetic pyrite which in turn replaced organic matter electron microprobe analysis on bornite chalcocite and covellite identifies elevated silver contents in these minerals up to 0 12 0 72 and 1 21 wt respectively whereas chalcopyrite and pyrite have only trace amounts of silver 0 26 and 0 06 wt respectively microthermometric data on fluid inclusions in authigenic quartz and calcite indicate that the cu mineralization is related to a diagenetic fluid of moderate to low temperature th 96 160 c but high salinity 25 38 wt cacl2 equiv the range of 34s in pyrite is 41 9 to 16 4 average 31 4 where framboidal pyrite shows the most negative values between 41 9 and 31 8 and fine grained pyrite has relatively heavier 34s values 29 2 to 16 4 consistent with a bacteriogenic derivation of the sulfur the cu sulfides chalcopyrite bornite and chalcocite show slightly heavier values from 14 6 to 9 0 and their sulfur sources may be both the precursor pyrite s and the bacterial reduction of sulfate bearing basinal brines carbonates related to the ore stage show isotopically light values of 13cv pdb from 8 2 to 5 1 and 18ov pdb from 10 3 to 7 2 indicating a mixed source of oxidation of organic carbon ca 20 and hco3 from seawater porewater ca 0 the copper mineralization is mainly controlled by organic matter content and paleopermeability intragranular space to large fracture patterns enhanced by feldspar and calcite dissolution the cheshmeh konan deposit can be classified as a redbed type sediment hosted stratiform copper ssc deposit

tracing bottom water redox conditions during deposition of lower and upper jurassic organic rich sedimentary rocks in the lusitanian basin portugal insights from inorganic geochemistry abstract the lower jurassic agua de madeiros am fm and vale das fontes vf fm formations and the upper jurassic cabacos formation cab fm are considered the most important units with petroleum source rock potential in the lusitanian basin and the likely sources for its widespread hydrocarbon occurrences nonetheless the bottom water redox conditions during their deposition remain debatable to resolve this controversy we investigated whole rock inorganic geochemical data of the most significant organic rich levels of the am vf and cab fms cropping out at basin scale significant variations in toc ts and redox sensitive elements contents and their ratios are evident within and between the organic rich levels of the studied units a positive covariation between primary productivity proxies toc enrichment and paleo redox proxies for the lower jurassic units clearly suggest an interdependence between enhanced primary productivity organic matter accumulation and bottom water redox conditions for the am fm the paleo redox proxies indicate that the black shales deposition took place beneath bottom waters that ranged from suboxic to strongly euxinic conditions with a clear predominance of the latter a toc threshold of 6 7 wt clearly separates samples deposited under suboxic to anoxic conditions from those deposited under true euxinic conditions and is interpreted as the minimum amount of organic matter om accumulation within sediments required to sustain h2s production at rates that outpaced its consumption through precipitation of sulphides and or om sulphurization allowing the diffusion of h2s to the bottom waters for the vale das fontes fm the paleo redox proxies suggest a prevalence of suboxic to anoxic bottom waters despite all black shales displaying toc contents greater than the above threshold the less reducing conditions relative to the am fm euxinic black shales are attributed to i a larger proportion of continental om ii lower reactivity of the om reaching the sediment water interface decreasing oxygen consumption and iii higher availability of reactive iron increasing the buffer effect to h2s produced through om remineralization by sulphate reducing bacteria both units display mo ef vs u ef covariation patterns that deviate from the field of sediments deposited under unrestricted open marine conditions towards higher mo enrichment relative to that of u indicating an accelerated transport of aqueous mo to the sediments consistent with the operation of a metal oxyhydroxide particulate shuttle linked to mn and fe redox cycling within the water column in a weakly restricted basin the mo cot regression line slope indicates a moderate degree of bottom water mass restriction with mo aq concentration of 60 70 of the present day seawater value and bottom water renewal times of 10 20 years akin to the present day cariaco basin the redox conditions of the cab fm organic rich levels are dependent on the location of the depositional environment in the basin with deposition taking place beneath oxygenated bottom waters at cabo mondego and under suboxic conditions at vale de ventos and pedrogao the latter denoting a larger degree of oxygen depletion than the former in this context the overall potential for om preservation should increase from cabo mondego to vale de ventos and pedrogao

floodplain architecture of an actively meandering river the ploucnice river the czech republic as revealed by the distribution of pollution and electrical resistivity tomography abstract the aim of this study was to describe the floodplain architecture of the ploucnice river a naturally meandering river in the czech republic using manual drill coring the element analysis of sediments and electrical resistivity tomography ert the ploucnice river has received diffuse pollution since the early twentieth century mainly pb followed by a prominent temporally well defined pollution pulse from uranium mining in the 1970s and 1980s mainly u and 226ra the pollution created a chemostratigraphic temporal framework for overbank fines we used geographical information systems gis to describe the channel s dynamics and visualise fluvial landforms we sampled and analysed the finest floodplain sediments in the top 1 to 2 m of the floodplain fill silty and sandy deposits and we used ert to visualise bodies of coarser and deeper strata at depths down to 3 m several limits of ert imaging have been found by a comparison of the resistivity domains with lithological descriptions of the cores several decimetre thick strata were not revealed they are below the spatial resolution of that method and humidity affected the results that were obtained in the topmost strata the space for deposition of fluvial sediments in the ploucnice river is being created by 1 natural lateral shifts in the channel up to 0 5 m year 2 meander loop development and cutoffs at the timescale of decades to centuries and spatial scale of up to 1 4 of the floodplain width and 3 more substantial reorganisation of the channel structure by avulsions probably at the timescale of centuries these processes continuously create space for the deposition of overbank fines on the top of former point bars and in swales and abandoned channels as a consequence of the speed of the channel shifts at least 80 of the fine grained top of the floodplain fill overbank fines was reworked over approximately three centuries

applying the squeezing technique to highly consolidated clayrocks for pore water characterisation lessons learned from experiments at the mont terri rock laboratory abstract knowledge of the pore water chemistry in clayrock formations plays an important role in determining radionuclide chemical speciation and migration in the context of nuclear waste disposal among the different in situ and ex situ techniques for pore water sampling in clay sediments and soils the squeezing technique dates back 115 years although different studies have been conducted on the reliability and representativeness of squeezed pore waters most of these involved high porosity high water content and unconsolidated clay sediments very few of them analysed squeezed pore water from low porosity low water content and highly consolidated clayrocks in this paper a specially designed and fabricated one dimensional compression two directional fluid flow cell was used to extract and analyse the pore water composition of opalinus clay core samples from mont terri switzerland with water contents between 6 2 and 7 8 wt a study of the influence of the squeezing pressure on the chemistry of the pore water was performed at pressures of up to 200 mpa to validate and demonstrate the validity of the squeezing technique for obtaining reliable pore water different tests were performed at various pressures and the squeezed waters were compared with those obtained by other methods such as in situ collected borehole waters the reproducibility and quality of the squeezing method was also checked as well as different artifacts which could affect the reliability of the pore water data the results show that the reproducibility of the technique is good and no membrane effect ionic ultrafiltration chemical fractionation anion exclusion was found in opalinus clay at mont terri in the range of pressures analysed 70 200 mpa pore waters extracted in this range of pressures do not decrease in concentration as a function of pressure which indicates that a dilution of water by mixing of the free pore water and the outer layers of diffuse layer water does not occur and a threshold safety squeezing pressure of 175 mpa could be established to avoid membrane effects furthermore a direct comparison against in situ collected borehole waters shows that the pore waters extracted at these pressures are representative of the opalinus clay formation at mont terri extraction artifacts such as temperature effect oxidation and degassing can be avoided or minimised by taking special precautions when preparing and handling the core sample and extracting the pore water finally we show that it is possible to obtain insightful information on anion accessible porosity by combining squeezing data with aqueous leaching data to characterise the pore water composition and solute distribution for different rock porosities

saline groundwaters in the hercynian granites chardon mine france geochemical evidence for the salinity origin abstract in this study the chemical evolution of high cl chardon mine groundwaters is modelled as a mixing between an oxidising recharge and an old marine component on which the water rock interaction is superimposed chemical and isotopic similarities with saline carnmenellis mine groundwaters are emphasised and a general comparison with other brines is discussed the cation content of deep granitic groundwaters is indicative of the water rock interaction in the case of chardon and carnmenellis groundwaters the high na cl ratio can still be related to the contribution of a brine of sedimentary origin to the water salinity the differences in the hydrochemistry related to their geological context only appears at the trace metals level on the contrary brines in plutonic rocks which exhibit a low na cl ratio represent groundwaters having a residence time in the host rock long enough to equilibrate with secondary aluminosilicates in that case the brine origin is difficult to assess if only based on the water cation content

geochemical mapping in polluted floodplains using in situ x ray fluorescence analysis geophysical imaging and statistics surprising complexity of floodplain pollution hotspot abstract this study is focused on a pollution hotspot in a floodplain impacted by uranium mining in the second half of the 20th century to image the internal structure of the hotspot we performed surface gamma activity mapping in situ x ray fluorescence spectroscopic analysis xrf using a portable instrument and manually obtained sediment cores and electric resistivity imaging of the shallow subsurface with the help of electric resistivity tomography ert and dipole electromagnetic profiling demp we used two approaches aimed at deciphering the origin of the pollution hotspot i surface pollution mapping and ii identification of the deeper lying lithogenetic units the description of the floodplain subsurface was supported by optically stimulated luminescence osl dating the surface mapping approach was found insufficient to visualise the hotspot and understand its origin we recognised deposition non linear in time or temporally independent of younger overbank fines including mining pollutants over considerably older channel sediments our work documents the value of dense geochemical mapping for documentation of fluvial pollution accessible by portable xrf as well as the need to understand the structure of the floodplain subsurface accessible by electric resistivity imaging and thereby rationalise the hotspot internal structure

comparative compressibility of hydrous wadsleyite and ringwoodite effect of h2o and implications for detecting water in the transition zone review of recent mineral physics literature shows consistent trends for the influence of fe and h2o on the bulk modulus k0 of wadsleyite and ringwoodite the major phases of earth s mantle transition zone 410 660 km however there is little consensus on the first pressure derivative k0 dk dp p 0 which ranges from about 4 to 5 across experimental studies and compositions here we demonstrate the importance of k0 in evaluating the bulk sound velocity of the transition zone in terms of water content and provide new constraints on the effect of h2o on k0 for wadsleyite and ringwoodite by conducting a comparative compressibility study in the experiment multiple crystals of hydrous fo90 wadsleyite containing 2 0 and 0 25 wt h2o were loaded into the same diamond anvil cell along with hydrous ringwoodite containing 1 4 wt h2o by measuring their pressure volume evolution simultaneously up to 32 gpa we constrain the difference in k0 independent of the pressure scale finding that h2o has no effect on k0 whereas the effect of h2o on k0 is significant the fitted k0 values of hydrous wadsleyite 0 25 and 2 0 wt h2o and hydrous ringwoodite 1 4 wt h2o examined in this study were found to be identical within uncertainty with k0 3 7 2 new secondary ion mass spectrometry measurements of the h2o content of these and previously investigated wadsleyite samples shows the bulk modulus of wadsleyite is reduced by 7 0 5 gpa wt h2o independent of fe content for upper mantle compositions because k0 is unaffected by h2o the reduction of bulk sound velocity in very hydrous regions of transition zone is expected to be on the order of 1 6 which is potentially detectible in high resolution regional seismology studies

the use of operationally defined sequential fe extraction methods for mineralogical applications a cautionary tale from mossbauer spectroscopy abstract reactive iron minerals are crucial components of global nutrient cycles directly controlling carbon transport and storage in marine sediments sequential selective extraction is frequently used for quantitatively characterising and chemically isolating individual fe mineral phases reagent specific mineral solubility is fundamental to the success of any sequential extraction but is strongly affected by the varying physical and chemical morphology intrinsic to natural mineral samples natural sediment rock and soil samples often contain a mineral mixture which further modifies solvent efficacy 57fe mossbauer spectroscopy only probes the hyperfine interactions between next nearest neighbouring atomic nuclei in the crystal lattice and is less affected by variation in mineral grain size and crystallinity than conventional x ray based methods in this study we used mossbauer spectroscopy in a novel context to cross calibrate and optimise a popular but frequently misused sequential fe extraction protocol our results showed that incomplete and premature removal of the target fe minerals could occur at nearly every stage of the extraction and in many cases the leachate fe content did not represent the target phase at all crystalline natural siderite and amorphous synthetic goethite were detected in the mossbauer spectrum of the ammonium oxalate extraction for magnetite after which all reactive fe minerals should have been removed consistent with previous studies and unlike many other clay minerals nontronite was extracted as part of the highly reactive fe pool and in fact our data indicate that this mineral was extracted by the initial na acetate extraction that targets carbonate bound fe matrix effects appeared to cause variable yield efficiencies synthetic goethite was successfully removed when present as an individual mineral yet persisted beyond its target extraction when present in an fe mineral mixture although suitable for the quantification of operationally defined fe pools we caution the unverified use of sequential fe extraction protocols for mineral specific applications the application of sequential fe extractions to define the reactive fe pools as a paleoredox proxy of depositional conditions appears relatively robust the premature removal of 2 line ferrihydrite observed in this study due to the use of the more aggressive na acetate extraction for crystalline siderite does not limit the quantitative use of the sequential fe extraction in ancient sediments where such easily reducible oxides are unlikely to persist in contrast attributing the outcomes of operationally defined fe pools to specific fe minerals is precarious and potentially entirely erroneous where fe mineral specificity or separation is required we recommend post extraction validation by another secondary technique mossbauer spectroscopy offers such a method that can independently verify extraction stages and assess mineral specificity

shear wave velocity model of the santiago de chile basin derived from ambient noise measurements a comparison of proxies for seismic site conditions and amplification summary we determined a high resolution 3 d s wave velocity model for a 26 km 12 km area in the northern part of the basin of santiago de chile to reach this goal we used microtremor recordings at 125 sites for deriving the horizontal to vertical h v spectral ratios that we inverted to retrieve local s wave velocity profiles in the inversion procedure we used additional geological and geophysical constraints and values of the thickness of the sedimentary cover already determined by gravimetric measurements which were found to vary substantially over short distances in the investigated area the resulting model was derived by interpolation with a kriging technique between the single s wave velocity profiles and shows locally good agreement with the few existing velocity profile data but allows the entire area as well as deeper parts of the basin to be represented in greater detail the wealth of available data allowed us to check if any correlation between the s wave velocity in the uppermost 30 m v30s and the slope of topography a new technique recently proposed by wald and allen exists on a local scale we observed that while one lithology might provide a greater scatter in the velocity values for the investigated area almost no correlation between topographic gradient and calculated v30s exists whereas a better link is found between v30s and the local geology finally we compared the v30s distribution with the msk intensities for the 1985 valparaiso event pointing out that high intensities are found where the expected v30s values are low and over a thick sedimentary cover although this evidence cannot be generalized for all possible earthquakes it indicates the influence of site effects modifying the ground motion when earthquakes occur well outside of the santiago basin

late glacial and early holocene environmental changes affecting the shallow lake basin of la narce du beage ardeche massif central france abstract the sedimentary sequence of la narce du beage basin is one of the few natural archives covering the last 18 ka cal bp in the french massif central this paper focuses on the palaeoecological reconstruction of environmental and climatic changes affecting this shallow periglacial lake from the late glacial to the early holocene after field surveys and geophysical mapping two cores cores a and d were extracted and dated plant macrofossils pollen non pollen palynomorphs npps and diatom assemblages were compared within the cores to study vegetation temperature ph water level and ice cover changes through time during the oldest dryas 18 14 75 ka cal bp climatic conditions were the coldest with a short ice free season allowing the development of periphytic diatoms only ecologically comparable to arctic ones a cold and dry steppe landscape exposed to severe erosion comprised an herbaceous and shrub flora e g artemisia chenopodiaceae helianthemum ephedra hippophae juniperus animal presence is suggested by coprophilous fungi periphytic diatoms and allochtonous pollen cedrus underline windy conditions and the possible erosion of neo formed soils then during the bolling allerod interstadial 14 75 12 7 ka cal bp the ice free season increased and some trees shrubs salix betula and juniperus established locally within open grasslands during the younger dryas 12 7 11 7 ka cal bp cooler conditions favoured steppe taxa again helianthemum achillea artemisia caryophyllaceae ranunculaceae and erosion increased the ice cover on the lake prevailed even if the conditions were not as cold as during the oldest dryas during the preboreal 11 7 10 ka cal bp isoetes echinospora and i lacustris developed in the eulittoral zone of the lake which was surrounded by a swamp forest with betula nana and b pubescens pinus sylvestris betula pendula corylus avellana and trees from the quercetum mixtum rapidly established in the uplands occurrences of gaeumannomyces and xylomyces fungi both phytopathogens on broadleaved trees and decreasing herb values indirectly hint at a close forest canopy at the beginning of the boreal 10 ka cal bp aquatic and semi aquatic taxa developed on open water due to longer ice free seasons diatoms micro algae alisma plantago aquatica potamogeton typha the final terrestrialization towards a mire occurred as a consequence of the holocene warming and related to water chemistry changes acidification eutrophication

single crystal elasticity of wadsleyites β mg 2 sio 4 containing 0 37 1 66 wt h 2 o the presence of hydrogen can affect elastic properties and seismic velocities of minerals in the earth s upper mantle in this study the secondorder elastic constants of hydrous wadsleyites containing 0 37 0 84 and 1 66 wt h2o were determined by brillouin scattering at ambient conditions measurements were performed on at least three independent crystal planes for each composition the aggregate bulk modulus ks0 and shear modulus g0 were calculated using vrh voigt reuss hill averages the results are ks0 165 4 9 gpa g0 108 6 6 gpa for wadsleyite with 0 37 wt h2o ks0 160 3 7 gpa g0 105 3 6 gpa for 0 84 wt h2o ks0 149 2 6 gpa g0 98 6 4 gpa for 1 66 wt h2o we find that the bulk and shear moduli of hydrous wadsleyites decrease linearly with water content according to the following relations in gpa ks0 170 9 9 13 0 8 ch2o g0 111 7 6 7 8 4 ch2o where ch2o is the h2o weight percentage compared with anhydrous wadsleyite addition of 1 wt h2owillleadtoa7 6 decreaseinthebulkmodulus anda7 0 decreaseintheshearmodulus usingtheseresults weexaminethevelocitycontrast between hydrous olivine and wadsleyite at ambient conditions for an fe free system assuming an h2o partition coefficient between wadsleyite and olivine of 3 the velocity contrast in compressional and shear velocity between wadsleyite and olivine ranges from 12 13 for an h2o free system to7 8 forwadsleyitecontaining1 5wt h2o thus themagnitudeoftheseismicvelocitychangeat410 kmdepthcanbeexpectedtobesensitive

stability of dense hydrous magnesium silicate phases and water storage capacity in the transition zone and lower mantle abstract we evaluated the water storage capacity in the mantle based on the phase relations of silicate systems containing water we conducted high pressure and temperature synthesis experiments on some silicate systems such as the superhydrous phase b phase c and phase g phase d and f compositions in the mgo sio2 h2o system and the cmas pyrolite 2 wt h2o system up to the uppermost part of the lower mantle superhydrous phase b is stable at temperatures below 1200 c at 18 gpa and below 1300 c at 20 gpa the following reaction sequences were observed with increasing temperature from 1200 to 1600 c in the pressure range from 18 to 20 gpa superhydrous phase b phase b liquid wadsleyite periclase liquid anhydrous phase b periclase liquid phase g is stable at temperatures below 1000 c at 18 gpa below 1100 c at 20 22 gpa and below 1200 c at 25 gpa wadsleyite stishovite liquid are stable above 1000 c at 18 gpa ringwoodite or phase e stishovite liquid above 1100 c at 22 gpa ilmenite stishovite liquid above 1100 c at 23 5 gpa and perovskite stishovite liquid above 1200 c at 25 gpa superhydrous phase b is stable at 1200 c at 18 5 and 25 gpa in cmas pyrolite 2 wt h2o composition whereas it decomposes at around 1400 c at 25 gpa in the composition there may be a layered structure in the mantle in its water storage potential solubility of water per unit mass i e the upper and lower mantles have relatively small water storage potentials whereas the transition zone has a larger potential the water content in the transition zone might be large because the primordial water trapped in the lower mantle and the recycled water transported by the slab subduction might have been released upwards and stored in the transition zone during geological time

characterizing large river history with shallow geophysics middle yukon river yukon territory and alaska abstract changes in longitudinal valley fill thickness can provide inferences about fluvial behaviour over millennia increased thickness of channel deposits may reveal climate induced accelerated sediment supply basin subsidence tectonic displacements or rising downstream base level decreases in thickness expressed as terraces may suggest active uplift decreased sediment flux or falling base level within a reach to date methods to characterize valley fills have depended largely on borehole data however recent developments in shallow geophysics make such investigations possible and provide a practical methodology to investigate alluvial rivers we carried out a longitudinal geophysical survey coupled with floodplain chronologies to characterize a 1000 km reach of the middle yukon river between western yukon territory and central alaska ground penetrating radar gpr and electrical resistivity ground imaging ergi profiles along the middle yukon river between central yukon and alaska coupled with channel bottom echo profiles demonstrates that there is little variation in thickness of gravel fill and depth of active scour holes gpr surveys near the white river the largest sediment source in the upper yukon show no significant longitudinal variation in gravel thickness 8 16 m up to near circle alaska 530 km of wandering channels geophysical profiles across the yukon flats sedimentary basin 430 km of braided and wandering channels show an increase in gravel thickness 25 30 m but this is consistent with compaction of underlying lacustrine sediment and maximum depths of contemporary scour holes from the western margin of the yukon flats to the dalton highway bridge 30 km confined valley with no floodplain or braid bars borehole data at the bridge indicates 6 10 m of gravel on bedrock beneath 3 6 m of water floodplain stratigraphy indicates there is little evidence of fluvial aggradation of the middle yukon during the holocene radiocarbon ages from the gravel overbank silt contact near present river level demonstrate a general vertical stability of the river with a period of rapid eolian accumulation during the late pleistocene and early holocene the consistency of gravel fill and scour hole depth and lack of holocene terraces along the 1000 km reach of the yukon indicate that the river has been in a state of mass balance equilibrium of sediment transport input output over the holocene despite massive sediment influxes from the glacial fed white river and crossing major faults variation in valley fill depth is not significant and further the yukon flats reach shows no evidence of bed aggradation during the pleistocene and has probably existed in equilibrium since the late pliocene

tetrahedral ferric iron in oxidized hydrous wadsleyite crystals of ferrous and ferric iron bearing hydrous wadsleyite have been synthesized at 1400 c and 12 13 5 gpa in a multi anvil press crystal structure atom positions occupancies and cell parameters have been refined by single crystal x ray diffraction at ambient conditions assuming cation vacancies to be in the m3 site only their concentration has been estimated from the unit cell parameter b a ratio total refined site fe contents are consistent with microprobe chemical analysis there appears to be up to 11 percent iron presumably ferric in the tetrahedral site consistent with reduced silica content fem1 fem2 the presence of ferric iron in the mantle transition zone is expected to partition preferentially into wadsleyite and may expand the stability region of wadsleyite relative to olivine and ringwoodite also the observation of tetrahedral ferric iron in these samples increases the likelihood that there is compositional continuity between wadsleyite and the spinelloid iii phase observed in the mg free system fayalite magnetite

fluvial dynamics of the žitava river sw slovakia during the last 45 ka bp and their influence on early bronze age human occupation as part of a geoarchaeological project exploring the early bronze age settlement of fidvar this geomorphologic study explores the fluvial dynamics of the itava river in southwestern slovakia casting light for the first time on the regional river s holocene and late pleistocene development in order to reconstruct the itava s fluvial evolution floodplain deposits were investigated by electrical resistivity tomography selected percussion drillings and ams radiocarbon dating in combination these methods provided a detailed view into the river s history as a result of the climatic variations engendered by the last glacial cycle the fluvial style repeatedly changed between a braided and anastomosing system however during long time periods of the middle and upper plenivistulian the river retained an anastomosing or even meandering style in contrast to central european rivers therefore in agreement with other investigations our results suggest different climatic conditions in the northern pannonian basin from 40 to 20 ka bp during the early and middle holocene a dense vegetation cover dry mesic oak forests led to stable geomorphological conditions and a meandering channel resulted in lateral erosion of the floodplain fringes accumulation of alluvial loamy sediments did not start until the neolithic and has been related to anthropogenic landscape changes similar to other naturally favoured areas central europe finally two reconstructed river positions indicate a considerable lateral fluvial erosion of the early bronze age settlement at fidvar consequently the original settlement area already thought to be the largest in the region was once significantly larger

correlation of carbon dioxide abundance with temperature in clastic hydrocarbon reservoirs relationship to inorganic chemical equilibrium the mol co2 of gas reservoired in sandstones tends to increase with increasing temperature along both the us gulf coast and the norwegian continental shelf each of these provinces displays identical linear correlations between temperature and the log of the partial pressure of co2 i e pco2 in the reservoir fluid that is the product of the mol co2 the reservoir pressure this correlation is the same both in gulf coast reservoirs younger than 17 ma and in norwegian reservoirs of jurassic to triassic age 144 245 ma indicating that it is not dependent on reaction kinetics norwegian shelf data indicate that the same correlation also applies for gas condensate and oil reservoirs we suggest that the log pco2versus temperature correlation is the result of inorganic chemical equilibria between feldspar clay and carbonate minerals a trend of decreasing ph with increasing temperature is fixed by equilibria between aluminosilicate minerals feldspar kaolinite at lower temperatures followed by various reactions between kaolinite illite chlorite and feldspar as temperatures exceed 110 140 c responding to the ph set by the aluminosilicate system co2 activity in the formation water and thereby co2 partial pressure in any gas phase present is controlled by equilibrium with carbonate minerals this model predicts that co2 released by organic maturation will in general result in precipitation of carbonate minerals below 100 120 c and that there should be widespread carbonate dissolution at higher temperatures

geochemical and petrographic investigation of triassic and late miocene organic rich intervals from onshore cyprus eastern mediterranean abstract in order to improve the understanding of potential petroleum systems in the still underexplored eastern mediterranean sea two field campaigns were performed to investigate potential source rocks onshore cyprus elemental data total organic toc and inorganic carbon tic total sulfur ts fe ni v rock eval pyrolysis biomarker and microscopic analysis organic petrography random vitrinite reflectance vrr palynofacies of the obtained mesozoic to cenozoic samples have proven the existence of organic matter om rich deposits within the following two geological formations 1 the triassic vlambouros formation fm of the mamonia complex comprises frequently occurring few centimeter thin clay layers interbedded between meter thick sandstone units the clay layers of this formation are characterized by toc contents of about 1 wt representing a type iii kerogen showing hydrogen index hi values of 48 mg hc g toc on average vrr values of 0 5 to 0 6 as well as several biomarker ratios indicate low thermal maturity the formation was deposited at the northern margin of gondwana and similar strata may be present in the basement of the levant basin and the eratosthenes seamount there thermal maturity would be higher and such rocks might contribute to thermogenic gas systems 2 in the miocene pakhna fm om bearing intervals are mainly present in the upper part of the formation in outcrops east of the troodos mountain while organic rich intervals are very scarce to absent in the south and southwest of the island the eastern outcrops show abundant fine grained marly mud to wackestones interbedded with coarser grained carbonates the fine grained intervals have toc contents of about 4 wt representing mainly type ii iii kerogen with hi values of 238 mg hc g toc on average the om is immature as indicated by vrr values between 0 3 and 0 5 ts toc 2 8 and several biomarker ratios indicate oxygen depleted even anoxic conditions during deposition a negative correlation between the toc and tic indicates that such conditions were reached during enhanced primary bioproductivity controlled by local and regional clastic derived nutrient input similar conditions may have been present along the southeastern margin of the eratosthenes seamount south of cyprus presence of abundant organic matter and high sedimentation rates during the miocene were favorable for microbial gas generation in the deeper parts of the basins

two dimensional geomorphological characterization of a filled abandoned meander using geophysical methods and soil sampling abstract using geophysical methods for the geomorphological characterization of subsurface features has numerous advantages over traditional exploration methods because of their noninvasive and rapid nature in this study we compared the results of four geophysical methods with each other we also discuss their possibilities and limitations in a geomorphological investigation electrical resistivity tomography ert refraction seismic rs ground penetrating radar gpr and multichannel analysis of surface waves masw methods were applied at an abandoned meander in northern saxony to map a predefined structure by combining these methods we were able to characterize and delineate subsurface features of the abandoned meander including a point bar a channel and a cutbank core samples obtained from sonic drilling were used to validate the findings of both seismic methods however we found that electrical resistivity tomography and ground penetrating radar lacked penetration depth and could only be used to resolve shallower subsurface layers the ert gpr rs and masw can be used to gather images of subsurface structures the masw in particular provides supplementary information about the channel s internal structure with respect to lateral and vertical resolution besides fluvial morphological features we also detected inverse velocity structures within the channel this allowed us to characterize the abandoned meander using information about its layer distribution and material composition however we were only able to characterize and delineate the subsurface features of the abandoned meander by combining all of the aforementioned methods

quaternary sediment architecture in the orkhon valley central mongolia inferred from capacitive coupled resistivity and georadar measurements abstract detailed information on shallow sediment distribution in basins is required to achieve solutions for problems in quaternary geology geomorphology neotectonics geo archaeology and climatology usually detailed information is obtained by studying outcrops and shallow drillings unfortunately such data are often sparsely distributed and thus cannot characterise entire basins in detail therefore they are frequently combined with remote sensing methods to overcome this limitation remote sensing can cover entire basins but provides information of the land surface only geophysical methods can close the gap between detailed sequences of the shallow sediment inventory from drillings at a few spots and continuous surface information from remote sensing however their interpretation in terms of sediment types is often challenging especially if permafrost conditions complicate their interpretation here we present an approach for the joint interpretation of the geophysical methods ground penetrating radar gpr and capacitive coupled resistivity ccr drill core and remote sensing data the methods gpr and ccr were chosen because they allow relatively fast surveying and provide complementary information we apply the approach to the middle orkhon valley in central mongolia where fluvial alluvial and aeolian processes led to complex sediment architecture the gpr and ccr data measured on profiles with a total length of about 60 km indicate the presence of two distinct layers over the complete surveying area i a thawed layer at the surface and ii a frozen layer below in a first interpretation step we establish a geophysical classification by considering the geophysical signatures of both layers we use sedimentological information from core logs to relate the geophysical classes to sediment types this analysis reveals internal structures of orkhon river sediments such as channels and floodplain sediments we also distinguish alluvial fan deposits and aeolian sediments by their distinct geophysical signature with this procedure we map aeolian sediments debris flow sediments floodplains and channel sediments along the measured profiles in the entire basin we show that the joint interpretation of drillings and geophysical profile measurements matches the information from remote sensing data i e the sediment architecture of vast areas can be characterised by combining these techniques the method presented here proves powerful for characterising large areas with minimal effort and can be applied to similar settings

landform characterization using geophysics recent advances applications and emerging tools abstract this paper presents an overview of the strengths and limitations of existing and emerging geophysical tools for landform studies the objectives are to discuss recent technical developments and to provide a review of relevant recent literature with a focus on propagating field methods with terrestrial applications for various methods in this category including ground penetrating radar gpr electrical resistivity er seismics and electromagnetic em induction the technical backgrounds are introduced followed by section on novel developments relevant to landform characterization for several decades gpr has been popular for characterization of the shallow subsurface and in particular sedimentary systems novel developments in gpr include the use of multi offset systems to improve signal to noise ratios and data collection efficiency amongst others and the increased use of 3d data multi electrode er systems have become popular in recent years as they allow for relatively fast and detailed mapping novel developments include time lapse monitoring of dynamic processes as well as the use of capacitively coupled systems for fast non invasive surveys em induction methods are especially popular for fast mapping of spatial variation but can also be used to obtain information on the vertical variation in subsurface electrical conductivity in recent years several examples of the use of plane wave em for characterization of landforms have been published seismic methods for landform characterization include seismic reflection and refraction techniques and the use of surface waves a recent development is the use of passive sensing approaches the use of multiple geophysical methods which can benefit from the sensitivity to different subsurface parameters is becoming more common strategies for coupled and joint inversion of complementary datasets will once more widely available benefit the geophysical study of landforms three cases studies are presented on the use of electrical and gpr methods for characterization of landforms in the range of meters to 100 s of meters in dimension in a study of polygonal patterned ground in the saginaw lowlands michigan usa electrical resistivity tomography was used to characterize differences in subsurface texture and water content associated with polygon swale topography also a sand filled thermokarst feature was identified using electrical resistivity data the second example is on the use of constant spread traversing cst for characterization of large scale glaciotectonic deformation in the ludington ridge michigan multiple cst surveys parallel to an 60 m high cliff where broad 100 m synclines and narrow clay rich anticlines are visible illustrated that at least one of the narrow structures extended inland a third case study discusses internal structures of an eolian dune on a coastal spit in new zealand both 35 and 200 mhz gpr data which clearly identified a paleosol and internal sedimentary structures of the dune were used to improve understanding of the development of the dune which may shed light on paleo wind directions

large scale structure of calamus river deposits nebraska usa revealed using ground penetrating radar the large scale i e bar scale structure of channel deposits of the braided low sinuosity calamus river nebraska is described using ground penetrating radar gpr profiles combined with vibracores basal erosion surfaces are generally overlain by medium scale trough cross stratified sets 3 25 cm thick very coarse to medium sands that are associated with relatively high amplitude discontinuous gpr reflectors overlying deposits are bioturbated small scale cross stratified sets 3 cm thick and vegetation rich fine to very fine sands that are associated with low amplitude discontinuous reflectors near surface peat and turf have no associated gpr reflectors in along stream profiles through braid and point bars most gpr reflectors dip downstream at up to 2 relative to the basal erosion surface but some reflectors in the upstream parts of bars are parallel to the basal erosion surface or dip upstream in cross stream profiles through bars gpr reflectors are either approximately parallel to bar surfaces or have low angle inclinations up to 6 towards cut banks of adjacent curved channels basal erosion surfaces become deeper towards cut banks of curved channels these structures can be explained by lateral and downstream growth of bars combined with vertical accretion convex upwards forms up to 0 5 m high several metres across and tens of metres long represent episodic accretion of unit bars scroll bars and bar heads stratal patterns in channel fills record a complicated history of erosion and deposition during filling including migration of relatively small bars a revised facies model for this type of sandy braided river has been constructed based on this new information on large scale bedding structure

geochemical characterization and modelling of the toarcian domerian porewater at the tournemire underground research laboratory abstract for safety evaluation of hazardous waste repositories in clay rocks a thorough assessment of porewater chemistry and water rock interactions is required however this objective is a challenging task due to the low hydraulic conductivity and water content of such rocks which subsequently renders porewater sampling difficult without inducing perturbations for this reason an indirect approach was developed to determine porewater composition of clay rocks by a geochemical model of water rock interaction using some properties of the rock and the solution the goal of this paper is to obtain the porewater composition of the toarcian domerian argillaceous formation at tournemire south of france for which a reliable model is still lacking the following work presents a comprehensive characterization of the geochemical system of the tournemire clay rock including mineralogy petrology mobile anions cation exchange properties accessible porosity and co 2 partial pressure perturbation corrections from fracture water sampling were also computed these water were found in sealed fractures beaucaire et al 2008 and their radiocarbon apparent age is estimated at 20 ka their age together with their equilibrium situation allow considering these fracture waters as representative of the formation porewater the model developed to calculate the tournemire porewater composition is essentially based on cation exchange by a multi site approach but equilibrium with some mineral phases calcite quartz and pyrite is also considered different exchange sites of different affinities towards cations are used which proportions are given by the mineralogy exchange on illite is performed with a three sites model while one site is considered for smectite phases multi site model results are compared with corrected fracture water data and two other models a model only based on mineral equilibrium and a model using cation exchange on one global site the best results were obtained with the models that take into account cation exchange and particularly with the multi site model the interest in considering a model with exchange sites of different affinities is particularly obvious for a satisfactory representation of the k content in solution a dependence of k content to the amount of high affinity sites was observed leading to an improvement of its simulation when uncertainty on mineralogical data is considered once validated the multi site model was applied at different levels of the tournemire argillaceous formation to obtain a profile of the porewater composition

phyllosilicates and zeolite assemblages in the carbonate periplatform of the great bahama bank origin and relation to diagenetic processes odp leg 166 sites 1006 and 1007 abstract the western flank of the great bahama bank drilled during odp leg 166 at seven sites represents a prograding carbonate sequence from late oligocene to holocene eberli et al proc odp init reports 166 1997 the signatures of the detrital input and of diagenetic alteration are evident in clay enriched intervals from the most distal sites 1006 and 1007 in the straits of florida mineralogical and chemical investigations xrd tem sem icp ms run on bulk rocks and on the clay fractions enable the origin and evolution of silicate parageneses to be characterized plio pleistocene silt and clay interbeds contain detrital clay assemblages comprising chlorite illite interstratified illite smectite smectite kaolinite and palygorskite the greater smectite input within late pliocene units than in pleistocene oozes may relate either varying source areas or change in paleoclimatic conditions and weathering intensity the clay intervals from miocene upper oligocene wackestone sections are fairly different with prevalent smectite in the fine fraction whose high crystallinity and mg contents that point towards an authigenic origin the lower miocene section below 1104 mbsf at depths where compaction features are well developed is particularly characterized by abundant authigenic na k clinoptilolite filling foraminifer tests the authigenic smectite and clinoptilolite paragenesis is recorded by the chemical trends both of the sediment and the interstitial fluid this diagenetic evolution implies si and mg rich fluids circulating in deeper and older sequences for lack of any local volcaniclastic input the genesis of zeolite and the terms of water rock interaction are discussed the location of the diagenetic front correlates with that of the seismic sequence boundary p2 dated as 23 2 ma this correspondence may allow the chronostratigraphic significance of some specific seismic reflections to be reassessed

seismic signature of a hydrous mantle transition zone abstract although water has a major influence on tectonic and other geodynamic processes little is known about its quantity and distribution within the deep earth in the last few decades laboratory experiments on nominally anhydrous minerals nams of the transition zone have shown that these minerals can contain significant amounts of water up to 3 3 wt in this study we investigate if it is possible to use seismic observations to distinguish between a hydrous and anhydrous transition zone we perform an extensive literature search of mineral experimental data to generate a compilation of the water storage capacities elastic parameters and phase boundary data for potentially hydrous minerals in the transition zone and use thermodynamic modelling to compute synthetic seismic profiles of density v p and v s at transition zone temperatures and pressures we find that large uncertainties on the mineral phase equilibria ca 2 gpa and elastic properties produce a wide range of seismic profiles in particular there is a lack of data at temperatures corresponding to those along a 1300 c adiabat or hotter which may be expected at transition zone pressures comparing our hydrous transition zone models with equivalent profiles at anhydrous conditions we see that the depths of the 410 and 660 discontinuities cannot at present be used to map the water content of the transition zone due to these uncertainties further while average velocities and densities inside the transition zone clearly decrease with increasing water content there is a near perfect trade off with increases in temperature it is therefore difficult to distinguish thermal from water effects and the conventional view of a slow and thick transition zone for water and slow and thin transition zone for high temperature should be regarded with caution a better diagnostic for water may be given by the average velocity gradients of the transition zone which increase with increasing water content but decrease for increasing temperature however the significance of this effect depends on the degree of water saturation and partitioning between the nams since seismology is better able to constrain the thickness of the transition zone than velocity gradients our study indicates that the most useful input from future mineral physics experiments would be to better constrain the phase relations between hydrous olivine and its high pressure polymorphs especially at high temperatures additionally the uncertainties on the mineral seismic properties could be reduced significantly if the experimentally observable correlations between bulk and shear moduli and their corresponding pressure derivatives would be published

framboidal and idiomorphic pyrite in the upper maastrichtian sedimentary rocks at gabal oweina nile valley egypt formation processes oxidation products and genetic implications to the origin of framboidal pyrite abstract the upper maastrichtian organic rich sediments studied at gabal oweina egypt are moderately enriched in syngenetic and diagenetic pyrite pyrite occurs mostly as layers or bands group of lamina lenses diagenetic intercalated pockets burrow fills and disseminated individual pyrite framboids and crystals within the host sediments the pyritic thin bands and lamina consist mostly of unconsolidated to compact oriented pyrite oriented along the bedding planes in gypsiferous clayey matrix and less common as poorly oriented pyrite crystallites in several cases pyrite crystals of the latter type depict zoning fracturing and micro concretions pyritic burrow fills are composed mainly of pyrite phosphatic ooids microfossils glauconitic grains poorly graphitized carbon and native sulfur pyrite replaces minerals other than gypsum sulfur or carbon it also replaces microfossils thus turning some of the phosphatic ooids and microfossils to pyritized pseudomorphs none of the studied phosphate ooids or framboids contains any mackinawite pyrrhotite or greigite based on the microscopic and sem observations of the micro textures of disseminated pyrite found at gabal oweina section four morphological forms of primary pyrite could be identified 1 grouped multiple framboids 2 individual framboids 3 pyrite idiomorphic crystal overgrowths on framboids and 4 single and aggregates of euhedral pyrite crystals the multiple framboid formation may have emerged from three successive processes nucleation and growth of individual aggregates of the microcrystals to form combined micro framboids the growth of framboids and followed by grouping of the several pyrite framboids direct pyrite nucleation shell formation crystallization and aggregation processes might complete a single framboid the disseminated single and aggregated euhedral pyrite crystals bear evidence indicating that their formation was via nucleation and growth of pyrite crystallites and their aggregation to individual framboids infilling in the interstices by additional pyritic material compaction and homogenization of all these materials furthermore we encounter for the first time in nature idiomorphic pyrite crystals that integrated numerous framboids using them as their nucleation and growth sites without erasing or modifying their pristine morphology elemental sulfur contains minor concentration of sb ni cd and cu strongly suggesting their presence as submicron sulfide crystallite inclusions sem and microprobe investigations revealed that goethite is present as a weathering product in all morphological types of pyrite however only an iron sulfate presumably melanterite was encountered as oxidation product of the multi framboids and the euhedral aggregate crystals the upper maastrichtian sediments not only contain a menagerie of pyrite morphologies but probably a complete record of the formation process and the geochemical conditions of the growth of framboids single pyrite crystals pyrite burrows pyritized mn fe oxide framboids and finally their weathered products the various pyrite forms strongly suggest a multistage process that led to their formation without any evidence for mackinawite pyrrhotite or greigite precursors there is also no evidence in the oweina sediments for post pyrite formation of mackinawite pyrrhotite or greigite the presence of elemental sulfur containing minor concentrations of sb ni cd and cu with pyrite framboids indicates that the pore solutions were geochemically supersaturated in sulfur thus inhibiting the crystallization of any iron sulfide other than pyrite this cast considerable doubt on the assumed mackinawite or greigite precursors as prerequisite for formation of pyrite framboids

early diagenesis of the upper devonian escuminac formation in the gaspe peninsula quebec sedimentological and geochemical evidence abstract clay mineral investigations pyrolysis of organic matter and microscopic observation of palynomorphs are used to interpret the diagenetic conditions of the upper devonian escuminac formation quebec canada pyrolysis of kerogen vitrinite reflectance and the presence of smectite show that the sediments of this formation have been subjected only to a shallow burial diagenesis hence the geochemical signatures are informative on the palaeoenvironment concretions are observed in the escuminac formation sedimentological and geochemical evidence suggest that these concretions were formed during early diagenesis from biodegradation of organic matter the well known fish fauna of the escuminac formation show good preservation due in part to extensive early diagenetic carbonate cementation the occurrence of calcite cements and fibrous calcite is attributed to the early diagenetic transformation of pre existing organic matter

ground penetrating radar images of selected fluvial deposits in the netherlands ground penetrating radar gpr surveys have been carried out in order to characterise reflection patterns and to assess the method s potential for imaging palaeofluvial sediments in the mass rhine former confluence area in the southern netherlands the results show that the deposits of meandering braided and transitional river types produce characteristic radar facies representative examples of each of these river types were selected where the gpr data could be directly correlated with sedimentary information derived from exposures and detailed drilling and geomorphological data could be supplied individual channels may be distinguished by the radar facies of their fills the floodplains of the different river types also show a characteristic radar facies in gpr data from the meander floodplain parallel dipping reflections represent point bar structures while irregular intersecting small channel patterns that alternate with parallel continuous reflections are more typical in the braid plain a transitional river type shows characteristics of both of these types typical examples of gpr sections recorded in each of the different fluvial palaeoenvironments are presented in an interpretative radar facies chart

formation of pyrite in freshwater sediments implications for c s ratios abstract the vertical distribution of pyrite acid volatile sulphide avs carbon and total s st were determined directly in the sediments of three lakes of different trophic status the results showed that freshwater pyrite formation reflects the redox status of the sediment or overlying waters it appears to form chiefly in reducing sediments which are subject to oxidizing influences by either a low turnover of organic carbon or periodic incursions of oxygen although there are high concentrations of avs in the near surface sediments of productive lakes very little is diagenetically converted to pyrite the feasibility of using sulphur ratios to diagnose whether rocks were formed in marine or freshwater environments is assessed new values for fes 2 fes of 0 5 5 show that this ratio does not provide a reliable test values of c sp where sp represents pyrite sulphur lie within the range of 160 700 and are much higher than previously measured ratios of c s t of 1 50 these new determinations show that if pyrite sulphur is unequivocally measured c s ratios may be a more sensitive indicator of salinity than had been previously thought

in situ interaction of cement paste and shotcrete with claystones in a deep disposal context in situ sampling was performed in the andra meuse haute marne france underground research laboratory url allowing the study of two cement based materials claystone interfaces that have undergone 4 to 5 years of interaction the first interface concerned a shotcrete that was sprayed on the wall of an access drift at the laboratory level and the second one a class g cement paste that was injected in a borehole filled from the surface and was intercepted during the excavation of a new gallery in the first case the hydrodynamic conditions were controlled by the ventilation of the drift while in the second the cement paste and claystone materials were considered saturated and far from any mechanical perturbation a multi scale investigation was carried out to identify any evidence of alkaline perturbation in the cement based materials and the claystone chemical mineralogical and textural measurements were thus performed on the different materials in contact at the nanometer to a centimeter scale results showed that all the perturbations resulting from the geochemical contrast between the cement materials and the claystone were limited to a m scale on each side of the interfaces carbonation was observed in the cement materials leading to an opening or a clogging of the porosity according to the hydrodynamic conditions and the formulation of the cement material the distribution of the cation exchange population was also modified in the claystone in contact with the cement paste where a potassium saturation of the exchangeable fraction was identified the originality of the present work is that realistic field controlled samples from the andra url were studied hereby allowing the evaluation of the impact of natural heterogeneities of the in situ experimental conditions that is hydrodynamic conditions engineered damage zone mineralogical variations on the perturbations at the cement paste claystone interfaces an important result is that the clogging of porosity was not homogenous along the interfaces

bedrock detection beneath river terrace deposits using three dimensional electrical resistivity tomography abstract we describe the use of a fully volumetric geophysical imaging approach three dimensional electrical resistivity 3d ert for bedrock detection below mixed sand and gravel deposits typical of fluvial valley fill terraces we illustrate the method through an analysis of terrace deposits of the great ouse river uk where up to 4 m of sand and gravel have filled the valley bottom during the latest pleistocene we use an edge detector to identify the steepest gradient in first derivative resistivity profiles which yields an estimate of bedrock depth verified by drilling to a precision better than 0 2 m average and 0 4 m standard deviation comparison of a range of drilling techniques at the site has revealed that borehole derived interface depths suffered from levels of uncertainty similar to those associated with the 3d ert indicating that the reliability of bedrock interface depths determined using these two approaches is comparable in this case the 3d ert method provides a high spatial resolution that enabled a previously unknown erosional bedrock structure associated with the change from deeper first terrace to second terrace deposits to be identified in the great ouse valley the method provides a relatively quick method to quantify terrace fill volume over large sites to a greater degree of precision than currently available

groundwater characterisation and modelling of water rock interaction in an argillaceous formation tournemire france abstract chemical na k mg ca cl so 4 hco 3 si al fe mn toc and isotopic 18 o h 2 o 2 h h 2 o 3 h h 2 o 14 c dic 13 c dic 34 s so 4 18 o so 4 data were obtained on groundwater collected from fractures inside the consolidated argillaceous formation of tournemire aveyron and from the aquifers surrounding this formation because of the very low transmissivity of such fractures 10 10 m 2 s 1 specific devices were developed for limiting out gassing and air contamination of groundwater during the sampling two modelling approaches are proposed to account for the chemical evolution of fracture groundwater from na cl hco 3 to na so 4 type the first one is based on mineral equilibria only and the second one also takes into account the ion exchange reactions the two modelling approaches are able to reproduce k concentrations and they led to an almost constant p co 2 10 2 6 atm which only depends on equilibrium with the calcite dolomite kaolinite quartz assemblage the modelling of na ca 2 and hco 3 behaviours is improved by taking the ion exchange reactions into account in some boreholes the time evolution of the chemical composition of fluids was greatly influenced by so 4 reduction combined with oxidation of dissolved organic c the isotopic composition of aqueous so 4 in fracture groundwater confirms that so 4 reduction processes have occurred since the drilling of these boreholes but also previously during the natural evolution of groundwater these redox reactions constitute a source of aqueous inorganic c that has to be considered in the computation of groundwater ages with 14 c for the studied fracture groundwaters the maximum age estimates range from 17 to 29 ka this shows that fractures may induce relatively fast groundwater flow compared to the very long migration times that are calculated by only considering diffusive transport in the rock microporosity

magnetic iron nickel sulphides in the pliocene and pleistocene marine marls from the vrica section calabria italy abstract the rock magnetic properties of the late pliocene and early pleistocene open marine marls from the vrica section in calabria italy point to magnetic sulphide as the main magnetic mineral and remanence carrier the maximum blocking temperatures however are between 340 and 360 c which is too high for stoichiometric monoclinic pyrrhotite magnetic concentrates of the sediment are rich in iron sulphide grains and iron nickel sulphide grains microprobe observations show that most of the grains are of the order of 1 m in size and attached to iron bearing clay flakes microprobe analyses of the sulphides yield a large range of compositions ranging from pyrite through greigite pyrrhotite to sulphur deficient monosulphides and with ni contents varying from zero to a few atom percent in the pyrite grains and from zero to as much as 35 atm in the monosulphides the high ni content of many of the grains is extraordinary and has not been reported before in marine sediments most of the compositions cannot be directly connected with a known mineral phase the marine depositional environment of the marls imposes an authigenic origin for the sulphides and this is supported by several observations the great number of sulphide grains in the magnetic concentrates suggests that at least one of the sulphide compositions must have a ferrimagnetic structure possibly the sulphides with a metal to sulphur ratio close to that of monoclinic pyrrhotite and between 25 and 35 of the fe replaced by ni the ni substitution could possibly be the cause of the high blocking temperatures

a 600 year long stratigraphic record of tsunamis in south central chile the stratigraphy within coastal river valleys in south central chile clarifies and extends the region s history of large earthquakes and accompanying tsunamis our site at quidico 38 1 s 73 3 w

small headwater stream evolution in response to lateglacial and early holocene climatic changes and geomorphological features in the saint gond marshes paris basin france the study focuses on river dynamics and vegetation changes during the last glacial interglacial transition from a headwater stream located in the eastern part of the paris basin we adopt a spatial multiproxy approach combining image analyses geophysical surveys sedimentary and pollen record analyses to document the impact of lateglacial climate changes and geomorphological features on vegetation and fluvial dynamics in the small boitet catchment ca 20 km2 our results show that the sedimentary record is organized into six successive alluvial sequences reflecting changes in discharge and channel morphology in response to short phases of climate oscillations during the lateglacial and early holocene periods the boitet alluvial sequences present some similarities with other nw european rivers that are interpreted as large scale fluvial system evolution to climate changes however some local differences have also been highlighted partly related to the upstream position of the catchment among them two distinctive features of the boitet catchment are 1 the preservation of the oldest dryas deposits which have been rarely described in this area and 2 the recognition of multichannel river dynamics during the oldest dryas and younger dryas we demonstrate that the fluvial evolution is firstly triggered by climate changes and that land surface features may also influence specifically upstream areas revealing contrasting responses of the river system

processes responsible for the development of soft sediment deformation structures ssds in the paleoproterozoic gordon lake formation huronian supergroup canada abstract an exposure of the paleoproterozoic gordon lake formation in the bruce mines area ontario canada contains abundant soft sediment deformation structures ssds including load casts convolute bedding pseudonodules ball and pillow structures flame structures and one dewatering pipe these features are developed in siltstone to fine grained sandstone beds and are between 1 and 120 cm in width and 3 78 cm high the primary trigger mechanism is interpreted to be storm or tsunami activity however seismic shock overloading brought about by density inversions or a combination of these processes may have influenced the formation of ssds to a lesser degree several beds also contain flat to wavy carbonaceous laminae locally with a botryoidal texture and concentrations of heavy minerals which are interpreted as relicts of microbial mats microbial mats may have played a minor role in the formation of ssds but do not appear to have been a prominent driving mechanism soft sediment deformation structures observed in the baie fine flack lake and cobalt plains regions of ontario are smaller and not as abundant as in the study area suggesting that the deposits in the study area were either affected by local events or different magnitudes of sedimentary processes in contrast to the tidal flat paleoenvironment interpreted for the gordon lake formation in the flack lake area the stratigraphically lower beds at the studied outcrop more closely resemble shallow shelf deposits

the river harbour of ostia antica stratigraphy extent and harbour infrastructure from combined geophysical measurements and drillings abstract we performed a combined geophysical and geoarchaeological survey of the harbour of ancient ostia italy to investigate the extent of the former harbour basin the sedimentary infill and possible building remains around the harbour besides geoarchaeological results the paper highlights the advantage of combining vibracore drilling with different geophysical prospection methods which are sensitive to different physical soil parameters geophysical methods applied were electrical resistivity tomography ert ground penetrating radar gpr and seismics with shear and compressional waves the extent and shape of the harbour basin were determined by ert profiling the ert profiles were compiled into a 3d model showing that the early lagoonal harbour basin was at least 100 m 50 m wide its southern border was confirmed by gpr measurements clearly imaging the former land water transition and the onset of ancient onshore building construction at its eastern border a consolidated horizon could be mapped in 2 3 m depth by compressional wave tomography this horizon most likely represents a cemented ramp a small part of which had been excavated in a previous study the sedimentary fill of the former harbour basin was investigated by a combination of vibracoring ert and seismics the ert profiles serve for inter and extrapolating the vibracore stratigraphy from the coring locations over the whole harbour area it turned out that one sedimentary unit which is important for the harbour development could not be resolved by ert but clearly shows up in seismic velocity depth profiles instead it is a thin coarse grained high energy layer in 1 2 m depth which was caused by a tsunami according to a previous study this layer separates two harbour phases an older lagoonal harbour phase underneath and a younger fluvial harbour phase above it the high energy layer represents a thin band of 100 increased shear wave velocity compared to the more fine grained layers in which it is embedded this study is the first to show that tsunami type sedimentary layers may be mapped by shear wave profiling

geochemistry and mineralogy of marine and non marine namurian black shales from the tansley borehole derbyshire the namurian black shales studied have a good palaeontological control pyrite illite and organic matter are higher in the marine shales and siderite and kaolinite are higher in the non marine shales the distribution of the diagenetic iron minerals is attributed to anionic activities controlled by salinity the same control could account for the observed clay mineral distribution by differential flocculation the major element geochemistry closely reflects the above mineral variation mn and zr are higher in the non marine shales due to siderite and zircon respectively co cr rb y and ba are not significantly different and a detrital source mainly clay minerals is suggested in the marine shales the elements pb cu v ni sr and zn are significantly higher using a discriminant function analysis the palaeosalinity groups are separated and the contribution of each element to the separation is calculated the present element locations are thought from correlation analysis to be pyrite and organic matter by analogy with experimental work and modern environments the element enrichment is mainly attributed to reactions involving organic matter and oxyhydroxide material in environments in which salinity and slow rates of sedimentation were important factors the element enrichment cannot be related directly to seawater concentrations unlike some black shales and the accumulation rates for pb and cu are thought to be unusually high

organic geochemistry of an anoxic cycle a case history from the oligocene section hungary total organic carbon extractable organic matter sulfur content kerogen type and saturated hydrocarbons have been determined in 25 core samples from an approximately 100 m thick section of the oligocene tard clay near budapest the tard clay records a five million year long anoxic cycle initiated by isolation of the sea development of a positive water balance and resulting density stratification and terminated by the re opening of access to the sea the lower non and moderately laminated shales record the build up of anoxia they contain 0 5 5 0 of organic carbon and type iii kerogen their saturated hydrocarbon fractions show high abundance of phyllocladanes biomarkers characterising coniferae derived organic matter the overlying moderately and strongly laminated sediments containing 1 5 5 0 organic carbon a predominance of hopanes over the n alkanes and type ii kerogen show the imprint of increased planktonic productivity the nutrients needed for this high productivity were liberated by alteration processes of contemporaneous volcanic glass the upper part of the strongly laminated shales containing a maximum of 2 organic carbon and type iii kerogen deposited after the termination of volcanic ash falls records a drop of planktonic productivity at the top of the tard clay the weak lamination and the low content 1 of organic carbon signifies the end of the bottom water oxygen depletion due to the destruction of density stratification of the water column

in situ infrared spectra of hydroxyl in wadsleyite and ringwoodite at high pressure and high temperature the infrared spectra of hydroxyl in synthetic hydrous wadsleyite mg 2 sio 4 and ringwoodite mg 2 sio 4 were measured at room temperature up to 18 8 gpa for wadsleyite and up to 21 5 gpa for ringwoodite high temperature spectra were measured in an externally heated diamond anvil cell up to 650 c at 14 2 gpa for wadsleyite and up to 900 c at 18 4 gpa for ringwoodite the synthetic samples reproduce nearly all the important oh bands previously observed at ambient conditions only subtle changes were observed in the infrared spectra of both minerals both upon compression at room temperature and upon heating at high pressure for wadsleyite upon compression to 18 8 gpa the frequencies of the bands at 3600 cm 1 remain almost unchanged while the main bands at 3200 3400 cm 1 shift to lower frequencies during heating at 14 2 gpa to 650 c the bands at 3200 3400 cm 1 broaden and shift to slightly lower frequencies for ringwoodite upon compression to 21 5 gpa the main bands at 3115 cm 1 progressively shift to lower frequencies during heating at 18 4 gpa to 900 c no frequency shift was observed for the band at 3700 cm 1 but the band initially at 3115 cm 1 shifts very slightly to higher frequencies which should yield almost the same band positions at 1300 1400 c as those measured at ambient conditions our data suggest that water speciation in hydrous wadsleyite and ringwoodite at ambient conditions may be comparable to that under mantle conditions except perhaps for subtle changes in hydrogen bonding the low oh stretching frequencies in wadsleyite and ringwoodite under transition zone conditions imply a large h d fractionation during degassing of the deep mantle this may explain the apparent disequilibrium between the hydrogen isotopic composition of the upper mantle and the ocean

sound velocities of hydrous ringwoodite to 16 gpa and 673 k article i nfo 0 026 si1 00h0 179o4 with 1 1 wt h2o using brillouin scattering combined with x ray diffraction in an externally heated diamond anvil cell up to 16 gpa and 673 k up to 12 gpa at 300 k the presence of 1 1 wt h2o lowers the elastic moduli of ringwoodite by 5 9 but does not affect the pressure derivatives of the elastic moduli compared to anhydrous ringwoodite the reduction caused by hydration is significantly enhanced when temperatures are elevated at high pressures at 12 gpa increasing temperature by t 100 k leads to a 1 3 2 4 reduction in the elastic moduli c11 c12 and c14 comparing our results with seismic observations we have evaluated the potential h2o content in the lower part of the transition zone our results indicate that the observed seismic velocity anomalies and related depth depression of the 660 km discontinuity could be attributed to thermal variations together with the presence of 0 1 wt h2o 2012 elsevier b v all rights reserved

the magnetic structure and palaeomagnetic recording fidelity of sub micron greigite fe3s4 abstract we present the results of a finite element micromagnetic model of 30 nm to 300 nm greigite fe3s4 grains with a variety of equant morphologies this grain size range covers the magnetic single domain sd to pseudo single domain psd transition and possibly also the psd to multi domain md transition the sd psd threshold d 0 is determined to be 50 nm d 0 56 nm depending on grain shape the nudged elastic band method was used to determine the room temperature energy barriers between stable states and thus the blocking volumes it is found that in the absence of interparticle magnetostatic interactions the magnetisation of equant sd greigite is not stable on a geological scale and only psd grains 70 nm can be expected to carry a stable magnetisation over billion year timescales i e all non interacting sd particles are essentially superparamagnetic we further identify a mechanism for the psd to multi domain md transition which is of a continuous nature from psd nucleation up to 300 nm when structures typical of md behaviour like closure domains begin to form

comparing geophysical methods for talus slope investigations in the turtmann valley swiss alps three geophysical methods ground penetrating radar 2d resistivity and seismic refraction were applied to two landform complexes in a high alpine valley in switzerland to investigate their internal structure results of the different methods were analysed separately before conclusions about sediment thickness and geomorphologic implications were drawn the results from the three methods were compared to focus on the quality of the methods and their field utility with respect to portability of equipment required man power and measurement time in this study ground penetrating radar and seismic refraction proved to be the most suitable with respect to the quality and resolution of the subsurface information and the level of field utility sediment thicknesses of 15 m on a rectilinear slope and more than 30 m on a talus cone have been measured a backweathering rate of approximately 700 mm ka 1 was established furthermore the radar delivered detailed internal sediment structure as well as interfaces between talus and rock glacier the combined geophysical investigation produced a detailed image of the subsurface composition of the two landform complexes that enhance the understanding of the paraglacial landform evolution in this hanging valley

effects of hydration on thermal expansion of forsterite wadsleyite and ringwoodite at ambient pressure single crystal x ray diffraction has been used to measure the thermal expansion coefficients of forsterite wadsleyite ringwoodite and their hydrous forms at ambient pressure from temperatures as low as 133 k to as high as 919 k second order polynomial fitting to ln v v0 vs t was applied to derive the expansion coefficients in the form of a1 t a0 the single crystal of anhydrous wadsleyite persisted up to 859 k hydrous forsterite was observed to dehydrate at 919 k whereas hydrous wadsleyite started to dehydrate at 655 k the crystal of ringwoodite with 0 20 wt broke down at 911 k and the two ringwoodite samples with 0 74 and 2 4 wt h2o were observed to break down with an irreversible unit cell expansion at 808 and 606 k respectively from room temperature to high temperatures in this study the mean thermal volume expansion coefficients are 36 4 5 and 38 1 9 10 6 k 1 respectively for anhydrous and hydrous forsterite 28 5 5 and 35 8 8 10 6 k 1

first principles determination of the structure and elasticity of hydrous ringwoodite 1 the mechanism by which hydrogen is incorporated in ringwoodite affects the density composition and elasticity of the mineral with implications on the seismic velocities of earth s transition zone this study uses density functional theory to calculate the structure elasticity and energetics of each of three possible defect mechanisms for the incorporation of hydrogen in ringwoodite relative energetics of the defects predict that the three defects exist in ratios of 64 10 25 for the vmg 2h mgsi 2h and vsi 4h defects respectively results of a least squares fit to existing experimental data on hydrous ringwoodite produce a best fit model including each of the three defects in ratios of 75 11 14 therefore 51 66 of the hydrogen in hydrous ringwoodite is associated with vmg defects 8 10 is associated with mgsi defects and 24 41 is associated with vsi defects one wt h2o decreases seismic wave velocities by an amount equivalent to 200 350 k temperature increase the seismic parameter dlnvs dlnvp owing to hydration is twice that owing to temperature and reduces the impedance contrast at the 520 km boundary allowing for the separation of the effects of water and temperature in the lower transition zone

aquitard characteristics of clay rich till deposits in east anglia eastern england summary an extensive area of quaternary glacial deposits lowestoft till of elsterian anglian age overlies the regionally important cretaceous chalk aquifer in east anglia in eastern england the glacial deposits act as an aquitard potentially affording protection from surface derived mainly agricultural contaminants however there has been little previous research on the physical and chemical characteristics of the glacial tills and contained pore waters in east anglia to demonstrate this benefit hence this study presents the results from the drilling of two boreholes in northern and southern east anglia at morley and cowlinge respectively and the construction of a high pressure squeezing rig to obtain pore water for major and minor ion stable isotope 18 o 2 h and dissolved organic carbon analysis special features of the mechanical squeezing rig included a high diameter to length ratio of the squeezer dual seepage faces and a unique pore water collection system designed to eliminate the risk of alteration of in situ pore water redox characteristics the hydrochemistry of the pore waters is found to be controlled by i incongruent carbonate dissolution given the high proportion of chalk clasts contained in the till ii cation exchange in the unweathered clay rich till and iii pyrite oxidation associated with the mineralogy of both the chalk and clay material content that comprises the till matrix the clay material is sourced from upper jurassic clays oxford and kimmeridge clay formations found to the west of the region these clays are also considered to be the source of organic material contributing relatively high concentrations of dissolved organic carbon above 2 mg l found in till pore waters below the soil zone concentrations of dissolved inorganic constituents increase with depth with a high total dissolved solids tds content in excess of 1500 mg l measured in the unweathered till below a depth of 5 m below ground level with the highest concentrations maximum of 3738 mg l associated with low permeability clay rich till the stable isotope composition of the pore waters with mean values for 18 o and 2 h of 7 01 and 51 7 at cowlinge and 6 44 and 49 9 at morley respectively are similar to local meteoric water and indicate that groundwater recharge of the tills has occurred during the holocene in the last 10 000 years overall the physical and chemical characteristics of the lowestoft till suggest only limited groundwater recharge of the order of 10 mm a or less in interfluve areas where the till deposits are greater than 15 m thick although higher rates are expected where the till becomes more sand rich for example at valley margins and also northwards in east anglia where the lowestoft till is influenced by the component of anglian ice that advanced from the north containing sand material derived from the floor of the north sea basin

olivine hydration in the deep upper mantle effects of temperature and silica activity 1 although water controls the biology and geology of the surface hydrogen is perhaps the most poorly constrained compositional variable in the bulk earth its concentration in the upper mantle appears to be controlled by its solubility as hydroxyl in the nominally anhydrous silicate phases olivine pyroxene garnet wadsleyite and ringwoodite here we describe a series of experiments showing that the solubility of h2o in olivine at 12 gpa increases with temperature to 8900 ppm by weight at 1250 c and decreases at higher temperature with the onset of melting sample characterization by infrared spectroscopy indicates that the primary hydration mechanism is the substitution of 2h for mg2 similar results obtained from samples coexisting with clinohumite low silica and with clinoenstatite high silica indicate that silica activity has minimal effect on hydration under these conditions single crystal x ray diffraction measurements constrain the volume of hydration and indicate significant m site vacancies hydrogen thus appears to become a geochemically compatible element as depths approach 400 km

kerogen origin evolution and structure kerogen commonly defined as the insoluble macromolecular organic matter om dispersed in sedimentary rocks is by far the most abundant form of om on earth this fossil material is of prime importance as the source of oil and natural gas moreover kerogen can provide essential information on major topics such as past environments climates and biota this review reports the main advances in kerogen studies since the comprehensive synthesis edited by durand durand b ed kerogen insoluble organic matter from sedimentary rocks editions technip paris 1980 it is organized into eight sections the first two are concerned with the successive definitions of kerogen and the definition used here the different techniques used for kerogen isolation without loss or degradation and basic kerogen analysis the third and fourth focus on sedimentary om sources and preservation processes in relation to depositional environment including sedimentation conditions favourable for kerogen accumulation and extrapolation to past geological time great strides have been made in the latter topics over the last 25 years owing to a combination of classical studies in organic geochemistry and studies in other domains such as biogeochemistry oceanography hydrology and soil science along with the development of powerful analytical tools the next two sections deal with the different kerogen classifications by type and kerogen evolution and maturation upon burial in sediments structural modelling of coal and kerogen based on physical and or chemical structural analysis is described in the following section although only statistical the models thus derived provide a synthetic view of the main structural resemblances and differences among various samples in relation to source maturity or physicochemical properties finally the last section explores some of the advances in kerogen understanding expected for the near future the review includes a list containing about 500 references

iron species determination to investigate early diagenetic reactivity in marine sediments iron speciation was determined in hemiplegic sediments from a high productivity area to investigate systematically the early diagenetic reactivity of fe a combination of various leaching agents 1 m hci dithionite buffered in citrate acetic acid hf h2so4 acetic cr ii was applied to sediment and extracted more than 80 of total fe subsequent fe species determination defined specific mineral fractions that are available for fe reduction and fractions formed as products of fe diagenesis to determine the fe speciation of sheet silicates we explored an extraction procedure hf h2so4 and verified the procedure by application to standard rocks variations of fe speciation of sheet silicates reflect the possible formation of fe bearing silicates in near surface sediments the same fraction indicates a change in the primary input at greater depth which is supported by other parameters the fe ii fe iii ratio of total sediment determined by extractions was compared with mossbauer spectroscopy at room temperature and showed agreement within 10 m6ssbauer spectroscopy indicates the occurrence of siderite in the presence of free sulfide and pyrite supporting the importance of microenvironments during mineral formation the occurrence of other fe ii bearing minerals such as ankerite ca fe mg carbonate can be presumed but remains speculative

characterization of the reactivity of riverine heterogeneous sediments using a facies based approach the rhine meuse delta the netherlands large groundwater resources are found in densely populated lowland areas which consist often of young unconsolidated and reduced sediments when anthropogenic activities lead to oxygenation of the aquifer breakdown of the main reduced fractions i e sedimentary organic matter som and pyrite could lead to severe groundwater deterioration such as acidification heavy metal mobilization and increased hardness the characterization of the reactive properties of these sediments is important in predicting groundwater deterioration but is often complicated by the high degree of heterogeneity of these sediments in this study the potential reduction capacity prc based on som and pyrite content the potential buffer capacity pbc based on carbonate content potential acidification capacity pac based on the potential acid production by sulfide oxidation and the measured reduction capacity mrc of five facies which are typical of the riverine sediments in the rhine meuse delta the netherlands were determined a universal facies classification model was used to classify the deposits into more homogeneous sub units based on lithologic and geogenic properties with a further sub division into oxic or anoxic redox environment based upon groundwater data and field observations the bulk chemical data show strong variation across facies for the median values of prc 186 9093 mmol o2 kg 1 pbc 17 132 mmol o2 kg 1 and pac 36 1530 mmol h kg 1 the mrc was measured as reactivity to molecular o2 exposure and was 0 5 567 3 mmol o2 kg 1 steady state oxidation rates were in the wide range of 0 001 10 355 mmol o2 kg 1 day 1 but were typically about 3 8 times faster in fine facies than in coarse facies both the prc and mrc depend strongly on grain size but also on the syn post depositional environment and redox conditions the main part of the prc consists of som but pyrite reactivity is higher than som reactivity as shown by the relative depletion of pyrite in oxic subfacies and the preferential oxidation during the oxidation experiments some facies are very prone to acidification because the pac is higher than the pbc but the oxidation experiments also show that acidification could already start before the prc is fully exhausted this study is one of the few that combines bulk chemical data groundwater data and reactivity measurements and shows that a facies based approach is a practical tool in characterizing the reactivity of heterogeneous deposits 2007 elsevier ltd all rights reserved

reducing marine and warm climate conditions during the late cretaceous and their influence on organic matter enrichment in the oil shale deposits of north jordan abstract late cretaceous oil shales located in the yarmouk sub basin north jordan were analysed using techniques of organic and inorganic geochemistry coupled with a microfossil study results of this study were used to reconstruct the paleoenvironmental and paleoclimatic conditions during the late cretaceous and to investigate their influence on organic matter enrichment of the oil shale deposits the analysed oil shales have high toc and s total content values in the ranges of 2 11 12 85 wt and 1 83 8 81 wt respectively the high s total content and its relation with toc values indicate that the sulfur is associated with organic matter and that the oil shales were deposited in a marine environment under reducing conditions this is shown by petrographic observation and supported by biomarker distributions the microscopic investigation indicated that the oil shales contain abundant liptinitic materials i e alginite and amorphous organic matter and planktonic foraminifera the presence of these sapropelic materials and planktonic foraminifera assemblages further suggests a marine origin biomarker distributions are also known to reflect dominantly marine plankton algal and microorganisms source input water column stratification and low oxygen reducing conditions are indicated by narrow pr ph values relatively high v ni elemental ratios and the presence of gammacerane reducing conditions contribute to preservation of organic matter warm water periods during the late cretaceous are also indicated by dominant occurrences of warm water index microfossil taxa the warm climate combined with elevated phosphorus p are the major causes of excessive algae growth and led to enhanced biological productivity within the photic zone of the water column during deposition of the oil shale deposits this increased bio productivity in combination with good preservation of organic matter are the main mechanisms of organic matter enrichment within the late cretaceous oil shales in the north jordan

near surface geophysical analysis of the navamuno depression sierra de bejar iberian central system geometry sedimentary infill and genetic implications of tectonic and glacial footprint the geometric and genetic characterization of the navamuno depression peatland system iberian central system is presented here using results from a geophysical survey this depression is a 30 ha pseudo endorheic flat basin over granitic bedrock three geophysical techniques were used to map the subsurface geology and identify and describe the infill sequence shallow seismic refraction sr magnetic resonance sounding mrs and electrical resistivity measurements ves and ert the three main geoelectrical layers g1 g2 g3 identified in previous research have also been identified in the present work using the data obtained in this new research we have been able to analyse these three geological layers in detail and reinterpret them they can be grouped genetically into two sedimentary units an ancient sedimentary body g3 of unknown age and type beneath an upper pleistocene g2 and holocene g1 sedimentary infill the facies distribution and geometry of the upper pleistocene was examined using the sequence stratigraphy method revealing that the navamuno depression was an ice dammed in the last glacial cycle resulting in glaciolacustrine sedimentation a highly permeable sedimentary layer or regolith exists beneath the glaciolacustrine deposits below 40 m depth water content falls dramatically down to a depth of 80 m where unweathered bedrock may be present the information obtained from geophysical geological and geomorphological studies carried out in this research enabled us to consider various hypotheses as to the origin of this depression according to these data the navamuno depression may be explained as the result of a transtensional process from the puerto de navamuno strike slip fault during the reactivation of the iberian central system paleogene lower miocene alpine orogeny and can be correlated with the pull apart type basins described in these areas the neotectonic activity of this fault and the icedammed processes in these areas during the last glacial cycle mis2 were the main causes of recent sedimentary infill in this depression

biogeochemical processes in a clay formation in situ experiment part e equilibrium controls on chemistry of pore water from the opalinus clay mont terri underground research laboratory switzerland the chemistry of pore water particularly ph and ionic strength is an important property of clay rocks being considered as host rocks for long term storage of radioactive waste pore waters in clay rich rocks generally cannot be sampled directly instead their chemistry must be found using laboratory measured properties of core samples and geochemical modelling many such measurements have been made on samples from the opalinus clay from the mont terri underground research laboratory url several boreholes in that url yielded water samples against which pore water models have been calibrated following a first synthesis report published in 2003 this paper presents the evolution of the modelling approaches developed within mont terri url scientific programs through the last decade 1997 2009 models are compared to the composition of waters sampled during dedicated borehole experiments reanalysis of the models parameters and database enabled the principal shortcomings of the previous modelling efforts to be overcome the inability to model the k concentrations correctly with the measured cation exchange properties was found to be due to the use of an inappropriate selectivity coefficient for na k exchange the inability to reproduce the measured carbonate chemistry and ph of the pore waters using mineral water reactions alone was corrected by considering clay mineral equilibria re examination of the measured ca mg activity ratios and consideration of the mineralogical composition of the opalinus clay suggested that ca mg cation exchange rather than dolomite saturation may control the ratio of these ions in solution this re examination also suggests that the ca mg ratio decreases with increasing pore water salinity several possible reasons for this are proposed moreover it is demonstrated that feldspar equilibria must not be included in opalinus clay modelling because feldspars are present only in very small quantities in the formation and because na k ratios measured in pore water samples are inconsistent with feldspar saturation the principal need to improve future modelling is additional or better data on rock properties in particular i a more detailed identification of phases in the opalinus clay that include redox sensitive elements together with evaluation of their thermodynamic properties ii an improved understanding of the distribution of celestite throughout the opalinus clay for sr so4 concentrations control iii improvements in analytic and thermodynamic data for ca mg rock cation exchange and mineral chemical properties and iv the measurement of composition and stability constants of clay minerals actually present in the formation

constraining porewater chemistry in a 250m thick argillaceous rock sequence the geochemistry of an argillaceous rock sequence from a deep borehole in ne switzerland was investigated the focus was to constrain the porewater chemistry in low permeability jurassic rocks comprising the liassic the opalinus clay formation the brown dogger unit and the effingen member malm a multi method approach including mineralogical analysis aqueous and ni ethylenediamine extraction squeezing tests and pco2 measurements as well as geochemical modelling was applied for this purpose a consistent dataset was obtained with regard to the main solutes in the porewaters a fairly constant anionaccessible porosity of 50 of the total porosity was deduced for all analysed samples which displayed variable clay mineral contents sulphate concentrations were shown to be constrained by a sulphate bearing phase presumably by celestite or a sr ba sulphate application of a simple equilibrium model including cation exchange reactions calcite and celestite equilibrium showed good agreement with squeezing data indicating the suitability of the modelling approach to simulate porewater chemistry in the studied argillaceous rocks the modelling highlighted the importance of correct determination of the exchangeable cation population the analysis corroborates that squeezing of the studied rocks is a viable and efficient way to sample porewater

geochemical relationships of late paleozoic carbon rich shales of the midcontinent usa a compendium of results advocating changeable geochemical conditions abstract previous studies have shown that pennsylvanian black shales of the midcontinent us possess a more complex geochemical history than was once thought vine and tourtelot econ geol 65 1970 253 and coveney and glascock appl geochem 4 1989 347 note that the widespread nature of metalliferous pennsylvanian black shales and the diverse geological environments across the midwestern us pose the likelihood that metals contained in the black shales are of complex origins detailed geochemical and statistical representations using characteristics of numerous black shale members have shown that water depth may not have been uniformly deep as previously inferred by numerous workers earlier suggestions that these black shales were associated exclusively with anoxic depositional conditions have been challenged by a more realistic theory of multifaceted fluctuating environmental conditions a wide range of major and trace element concentrations combined with widely varying characteristics and diverse types of organic matter indicate the presence of fluctuating geochemical settings the presumption is that numerous associated chemical reactions occurred syngenetically one geochemical index degree of pyritization dop suggests a dysaerobic to aerobic setting for many of the shales whereas some other geochemical proxies i e v v ni indicate punctuated episodes of bottom water anoxia schieber abstr programs geol soc am 33 6 2001 a102 notes that in some black shales pyrite enrichment due to intermittent organic reworking explains the high dop values once thought to equate with extreme euxinic depositional conditions it seems likely therefore that even during apparent euxinic periods as indicated by bulk geochemistry oxygen deprived events were apparently short lived the seemingly euxinic fingerprint as shown by geochemical characteristics may result through time averaging abstr programs geol soc am 33 6 2001 a102 of intermittent euxinic events providing a misleading indication of dominant euxinic conditions thus detailed microstratigraphic sampling is necessary to delineate short punctuated occurrences of intermittent sub oxic episodes the midcontinent pennsylvanian shales may reflect a complex array of bottom water oxygenation variations and water depth fluctuations in response to climatic and localized events hatch j r and leventhal j s 1992 relationship between inferred redox potential of the depositional environment and geochemistry of the upper pennsylvanian missourian stark shale member of the dennis limestone wabaunsee county kansas usa in meyers p a pratt l m nagy b eds geochemistry of metalliferous black shales chem geol 99 65 82 complicated by post depositional events appl geochem 4 1989 347 this research examines the previous exclusively anoxic origin for midcontinent pennsylvanian black shales from a geochemical perspective and offers an alternative supported by detailed statistical presentations with the hypothesis that events of anoxia were punctuated by short lived dysaerobic or even near oxic events

calcium amphibole exsolution lamellae in chromite from the semail ophiolite evidence for a high pressure origin abstract we report here for the first time aluminous ca amphibole exsolution lamellae in an anhydrous chromite host of podiform chromitite from the nakhl massif of the semail ophiolite transmission electron microscopy observations show that the ca amphibole lamellae have a crystallographic topotaxy and d spacing relationship with the host chromite i e 103 am 11 8 chr 020 am 2 2 0 chr and d060am d220chr that indicate an exsolution origin the presence of ca amphibole exsolution implies the incorporation of si4 and ca2 cations and hydroxyl in the host precursor chromite the reconstructed precursor chromite had sio2 concentrations of 0 33 0 58 wt suggesting upwelling from a minimum pressure of 8 gpa depth of 250 km hydroxyl groups occupy octahedral vacancies which can be introduced in high pressure chromite by substituting 4 cr3 by 3 si4 and a vacancy during upwelling vacancies decrease when si4 cations exsolve stepwise from chromite it leads to a coupled decrease of oh occupied vacancies and exsolution of ca amphibole lamellae at pressures below 3 gpa our results provide new evidence for a deep origin of the chromitite bearing mantle section of the semail ophiolite

joint inversion of h v ratios and dispersion curves from seismic noise estimating the s wave velocity of bedrock 1 a joint inversion of phase velocity and h v ratio curves both obtained from seismic noise recordings permits the retrieval of the shear wave velocity structure of local sedimentary cover our inversion scheme uses a genetic algorithm and considers the influence of higher modes on the data sets encouraged by the results published previously on joint inversion parolai et al 2005 we went one step further we found using a synthetic data set that the impedance contrast at the sediment bedrock interface has a strong influence on the shape of the h v ratio curve which therefore allows the bedrock s wave velocity to be well constrained in the joint inversion procedure our observations were further confirmed using a real data set

application of geomorphic analysis and ground penetrating radar to characterization of paleoseismic sites in dynamic alluvial environments an example from southern california abstract selecting paleoseismic sites in dynamic range front environments can be difficult because they are sites of rapid deposition and poor preservation of coarse grained channelized alluvium the most obvious tectonic landforms tall scarps are often too old to constrain sequences of specific rupture events the faulted deposits that do provide maximum and minimum earthquake ages however are often buried or masked by erosion in active drainage channels subsurface images of stratigraphic and structural relationships at multiple sites are useful prior to excavation ground penetrating radar gpr is an effective tool for locating sites suitable for trenching studies we illustrate the utility of gpr with a case study of a thrust fault in southern california

coupled thermo hydro bio geochemical reactive transport model of cerberus heating and radiation experiment in boom clay abstract final disposal of high level radioactive waste in deep repositories in clay formations is being considered by several countries repository safety assessment requires the use of numerical models of groundwater flow solute transport and chemical processes these models are being developed from data and knowledge gained from in situ experiments such as the cerberus experiment carried out at the hades facility excavated in the boom clay formation at mol belgium this long term experiment is aimed at evaluating the effect of heating and radiation in boom clay the test was performed in a cased well drilled at 223 m depth and lasted from 1989 to 1994 a 60 co source of 400 tbq and two heaters were emplaced inside the well dose rate temperature porewater pressure and ph eh were measured in situ during the experiment and gas and porewater samples were taken for chemical analyses here a coupled thermo hydro geochemical thc model of the cerberus experiment is presented which accounts simultaneously for heating radiation solute diffusion and a suite of geochemical reactions including aqueous complexation acid base redox mineral dissolution precipitation cation exchange and gas dissolution ex solution computed results indicate that heating and radiation causes a slight oxidation a decrease in ph slight changes in porewater chemistry and pyrite dissolution near the well thc model results follow the general evolution of chemical data but cannot fit so 4 data model discrepancies are partly overcome when microbially mediated fe and so 4 reduction are taken into account in a coupled thermo hydro bio geochemical thbc model this thbc model captures the trends of geochemical data improves the fit to dissolved so 4 and predicts pyrite precipitation a process observed near the cerberus well the ability of the thbc numerical model to reproduce the overall trends of geochemical data of the cerberus experiment provides confidence in such a model as a suitable tool for the long term prediction of geochemistry in the near field of a hlw repository in clay however the small number of available chemical data throughout the experiment and the lack of doc and microbial data allow only a partial validation of the thbc model

thermal expansion of wadsleyite ringwoodite hydrous wadsleyite and hydrous ringwoodite abstract the thermal expansions of wadsleyite ringwoodite hydrous wadsleyite and hydrous ringwoodite have been determined by high temperature powder x ray diffraction at ambient pressure wadsleyite and ringwoodite persist up to 700 c and their thermal expansion coefficients are measured as 34 0 5 10 6 and 30 7 6 10 6 k 1 respectively values that are slightly larger than those measured by j phys earth 27 1979 53 j phys earth 28 1980 273 hydrous wadsleyite and hydrous ringwoodite were dehydrated at 450 and 400 c respectively below their dehydration temperatures their thermal expansion coefficients are 30 1 14 10 6 and 27 3 9 10 6 k 1 respectively which are slightly lower than those of their anhydrous forms using the present results combined with the previous thermoelastic data the seismic velocity contrast at the 410 km discontinuity has been calculated for both dry and wet mantle if a pyrolite composition is assumed a hydrous mantle transition zone better explains seismic constraints