origin of maghaemite in chinese loess deposits aeolian or pedogenic maghaemite and magnetite common ferrimagnetic minerals in surficial soils have physical properties which are similar except for the thermal instability of the former utilising this exception a study of thermomagnetic properties has been made to systematically separate these two magnetic components in loess and palaeosol samples from the upper parts of the luochuan section of the central chinese loess plateau this investigation has shown that although maghaemite thermally unstable component occurs in greater amounts in palaeosols ms 0 0187 am2 kg 1 1 1 than in loess units ms 0 0156 am2 kg 1 1 1 in relative terms its contribution to the ferrimagnetic component of magnetisation is higher in the loess units ms 32 2 2 0 than the soils ms 23 5 3 7 such an observation suggests that much of the maghaemite component originates in the aeolian source area with some addition of pedogenic maghaemite occurring in the palaeosols

validity of the environmental chloride method for recharge evaluation of coastal aquifers india the work presented in the paper was carried out with the objective of ascertaining the validity of environmental chloride method for evaluation of groundwater recharge to the coastal aquifers situated in semi arid tropical area under the influence of monsoonic type of hydrologic regime towards this end a comparative study using environmental chloride in conjunction with injected tritium method the more commonly used method was undertaken in the coastal aquifers of pondicherry situated about 160 km south of madras along the coast of bay of bengal five each of environmental chloride repeated twice and injected tritium profiles were studied in the alluvium and cuddalore aquifers of pondicherry recharge from the chloride study was estimated using 1 concentration approach which involves estimating the relative enrichment of soil chloride concentration in relation to the input chloride and 2 flux approach determining the turnover time of soil moisture by estimating the total chloride in the profile and yearly input recharge from the injected tritium profiles was estimated by studying the displacement of soil moisture during the time interval between sampling and injection of the tracer repeated chloride profiles show fairly good reproducibility within 15 30 of recharge rates determined by the two approaches for two different sampling times at the same site also the results compare well among the two approaches used for the chloride method mean recharge rates obtained by the injected tritium method for the cuddalores is about 26 cm yr 1 and by the chloride method about 22 cm yr 1 and for the alluvium the respective rates are 10 and 14 cm yr 1 this shows fairly good agreement between the two methods the study thus demonstrates conformity of recharge rates determined by the environmental chloride method and injected tritium technique and proves the validity of the chloride method for recharge measurements for tropical coastal aquifers situated in semi arid regions

measuring floodplain spatial patterns using continuous surface metrics at multiple scales abstract interactions between fluvial processes and floodplain ecosystems occur upon a floodplain surface that is often physically complex spatial patterns in floodplain topography have only recently been quantified over multiple scales and discrepancies exist in how floodplain surfaces are perceived to be spatially organised we measured spatial patterns in floodplain topography for pool 9 of the upper mississippi river usa using moving window analyses of eight surface metrics applied to a 1 1 m 2 dem over multiple scales the metrics used were range sd skewness kurtosis cv sd curv rugosity and vol area and window sizes ranged from 10 to 1000 m in radius surface metric values were highly variable across the floodplain and revealed a high degree of spatial organisation in floodplain topography moran s i correlograms fit to the landscape of each metric at each window size revealed that patchiness existed at nearly all window sizes but the strength and scale of patchiness changed within window size suggesting that multiple scales of patchiness and patch structure exist in the topography of this floodplain scale thresholds in the spatial patterns were observed particularly between the 50 and 100 m window sizes for all surface metrics and between the 500 and 750 m window sizes for most metrics these threshold scales are 15 20 and 150 of the main channel width 1 2 and 10 15 of the floodplain width respectively these thresholds may be related to structuring processes operating across distinct scale ranges by coupling surface metrics multi scale analyses and correlograms quantifying floodplain topographic complexity is possible in ways that should assist in clarifying how floodplain ecosystems are structured

structural geology of the penobsquis salt structure late bashkirian inversion tectonics in the moncton basin new brunswick eastern canada this study uses new information acquired from field mapping mineral exploration boreholes and seismic reflection profiles to constrain the structural geology deformation mechanisms and timing of the penobsquis salt structure this information is used to place the development of the salt structure into the context of the tectonic evolution of the moncton basin the penobsquis salt structure is an elongate salt wall separated from underlying rocks by a mylonitic detachment horizon it may be divided into two segments a southwestern asymmetric southeast verging structure and a northeastern strongly asymmetric to overturned southeast verging structure associated with the penobsquis fault an initial low amplitude salt anticline formed during deposition of the mabou group serpukhovian time the salt anticline was modified into a high amplitude salt wall after deposition of cumberland group sediments early bashkirian or later the sense of asymmetry of the penobsquis salt structure the presence of thrust faults within the structure the spatial association of the structure with a major reverse fault in the salt cover and the temporal association of salt movement and compressional tectonic events suggest that the salt structure developed in response to tectonic contraction during inversion of the moncton basin

water salinization in arid regions observations from the negev desert israel abstract the processes affecting salinization of precipitation surface water vadose water and groundwater were studied in the negev desert israel observations spanning 18 years included the collection of rainfall at three rain sampling stations flood water at six flood stations vadose water from four coreholes penetrating chalk formations and groundwater from 16 monitoring wells tapping the chalk aquitard dissolved carbonate dust and evaporation of the falling raindrops result in ca hco 3 2 facies and increased ion concentration of the rainwater with respect to inland more humid regions the exposure of flood water to evaporation during flood events is minimal the observed ca hco 3 2 facies and salt enrichment by a factor of three to five in the flood water with respect to precipitation results primarily from interactions of the flood water with the chalk and limestone bedrock including ion exchange on na and k bearing minerals and the dissolution of calcite gypsum and halite the presence of these salts at and near land surface results from the complete evaporation of rainwater in land surface depression storage areas following most rain events except for a small portion moving through the low permeability chalk matrix most of the vadose water moves through preferential pathways and is typically not exposed to evaporation this dual movement of water accounts for the nacl facies of vadose water and the variable rates of isotopic depletion and salt dilution observed in the underlying heterogeneous groundwater in the saturated zone although the variable mixing with low salinity isotopically depleted water percolating from the fractures accounts for the depleted isotopic composition of the groundwater its relatively low solute content cannot modify the groundwater nacl facies consequently only groundwater salinity in the chalk is reduced by the preferentially flowing water but the ca hco 3 2 facies prevailing in the rainwater and flood water disappears and the nacl imprint from the vadose zone prevails

estimation of evaporation from the normally dry lake frome in south australia depth profiles of deuterium composition expressed as delta values have been used to make point estimates of evaporation from the floor of the normally dry lake frome a salt lake in northern south australia values from five sites varying between 90 and 230 mm yr 1 have been used to obtain a relatively crude approximation for mean evaporation rate from the lake of 170 mm yr 1 under the assumption that this represents discharge of water from the regional groundwater system the groundwater inflow into the lake is calculated as 5 108 m3 yr 1 two possible models which describe groundwater inflow into the lake are discussed

the supra ophiolitic sedimentary cover of the asbestos ophiolite quebec canada first geochemical evidence of transition from oceanic to continental sediment flux abstract the 473 5 3 myr asbestos ophiolite complex of the quebec appalachians was formed in a forearc basin and obducted on a margin of laurentia 460 myr ago the complex together with its sedimentary cover is well exposed at burbank hill 130 km sw of quebec city where eight distinct lithologies have been identified 1 pyroxenites and wehrlites with minor dunitic layers 2 fractured gabbros 3 breccia containing gabbro and diabase fragments 4 polygenic conglomerates 5 red mudstone chert sandstone succession 6 tuffs with intercalated grey chert 7 greenish grey mudstones and 8 slates and sandstones of the saint daniel melange the gabbroic and mafic volcanic rocks show the characteristics of arc tholeiites tio2 0 8 0 85 wt and boninites tio2 45 la sm n 1 9 3 3 these rock types also occur as mafic fragments in the polygenic conglomerate the mafic fragments crystals and rocks within the conglomerate and the ophiolitic sandstones also show the same greenschist facies metamorphism as the mafic igneous rocks of the complex the conglomerate was probably formed after the forearc crust was fragmented by pre obduction normal faults these fault scarps would have promoted the erosion of the oceanic crust leading to the accumulation of diverse detritus in grabens the sedimentary lithologies which overlie the conglomerate exhibit a gradual increase in continent derived material la sm n 5 and la yb 20 and a decrease in ophiolitic material moving upward in the stratigraphic sequence the sedimentary rocks at the bottom of the sequence group 3 are mostly composed of ophiolite material with only 20 of crustal material they also have a high content of cr and mgo with values of 350 480 ppm and 5 7 8 respectively the rocks of the uppermost part of the pile group 1 which contain up to 80 crustal material have low abundances of cr and mgo 30 100 ppm and 2 7 4 5 wt continental detritus on the top of the asbestos ophiolite suggests the complex formed near the laurentian continental margin and that the eroded continental material had access to the basin where the ophiolite was formed this is consistent with the obduction of the asbestos and thetford mines ophiolites on the laurentian margin shortly after their formation the proximity of thick laurentian continental crust near the trench could explain why the subduction zone blocked up soon after the ophiolites formation

an isotopic study 2h and 18o of water movements in clayey soils under a semiarid climate we applied the natural variations of stable isotopes in water to the study of infiltration in clayey soils and to the study of groundwater recharge in the small drainage basin of barogo in west africa the comparison between the variations in isotopic contents of soil water and rainwater in 1988 and 1989 led us to characterize two infiltration processes 1 an infiltration through the soil matrix of rainwater that mixed with mobile water which was held in the superficial part of the soil and was enriched in heavy isotopes by evaporation and 2 a fast and deeper infiltration by preferential flow along macropores that bypassed the superficial part of the soil the study of the variations in groundwater isotopic content led us again to separate the recharge process into two components 1 a slow infiltration through the soil matrix and the weathered basement distributed recharge and 2 a fast and direct recharge through conducting fissured zones localized recharge a schematic and local representation of groundwater recharge in the barogo basin allowed us to estimate that direct recharge represented around 70 of the total recharge in 1989

petroleum geology of the puguang sour gas field in the sichuan basin sw china abstract the puguang sour gas field in northeastern sichuan basin is the largest gas discovery in the paleozoic marine strata in china with at least 9 trillion cubic feet tcf of proven gas reserves it is one of the many anticlinal structures formed during the indo sinian orogeny with gas being trapped in a composite structure lithology pool the presence of the upper permian coal measures lower silurian and lower cambrian marine shales provided excellent hydrocarbon source rocks the lower triassic and upper permian oolitic dolomites serve as high quality reservoir rocks with 10 25 porosity and 1 1000 md permeability largely due to diagenetically produced secondary porosity the lower and middle triassic evaporate beds have acted as the direct top seal for the large lower triassic upper permian gas accumulation the thick upper triassic and jurassic mudstone beds regionally cap the underlying marine carbonate strata the deep seated basement faults acted as vertical hydrocarbon migration conduits during faulting and became effective flow barriers when the faulting ceased the deep burial of a paleo oil accumulation in reservoirs rich in sulfate resulted in extensive thermochemical sulfate reduction tsr this together with the new gas injection and structural reconfiguration transformed a paleo oil pool to a large sour gas pool

effects of drying techniques on grain size analyses of fine grained sediment abstract to assess the effects of drying on subsequent grain size analyses a variety of drying approaches including drying in ambient air oven drying and freeze drying were applied to sediment collected from modern fluvial lacustrine and paludal settings containing a wide range of clay size fraction 16 61 samples were subsequently rehydrated and subjected to grain size analysis in a laser particle size analyzer and histograms compared with those from control samples never subjected to drying results indicate that drying techniques induced no effect on grain size distribution for samples containing 39 clay size material only freeze drying produced reproducible results statistically identical to the control samples

formation and evolution of silurian paleo oil pools in the tarim basin nw china the formation and evolution of silurian sandstone reservoirs which are characterized by the coexistence of reservoir bitumen with different types of commercial oil pools in a very extensive area around the slope and uplift areas of the manjiaer depression in the tarim basin nw china are still in question in this paper we report our investigations on the geological and geochemical characteristics of this reservoir the results show there are four types of oil shows in the reservoir severely biodegraded solid bitumen biodegraded heavy oil normal oils and light oils with slight biodegradation three suites of petroleum inclusions were identified in the reservoir which were formed during the early devonian triassic to cretaceous and late tertiary respectively petroleum in the silurian sandstone reservoirs mainly originated from the mid lower cambrian source rock and mid upper ordovician source rock the thermal maturity evolution of the source rocks in slope areas has shown that there were three main stages of oil generation that controlled the formation of the above three stages of petroleum inclusions this evidence indicates that the silurian reservoir has experienced three petroleum charge events during its geological history the first charge event occurred during the early devonian and it resulted in giant paleopools which gradually evolved into the presently widespread bitumen due to the combination of biodegradation and thermal alteration the second charge covered a long period from triassic to cretaceous and probably was related to both the mid lower cambrian source rock and the mid upper ordovician source rock the petroleum generated during this stage mixed and interacted with the low matured residual bitumen and eventually formed the present soft bitumen and some residual heavy oils in the reservoirs the third charge event mainly associated with the mid upper ordovician source rocks occurred mainly during late tertiary and accounted for most of the present commercial petroleum pools mainly normal and light oils

annual replenishable ground water potential of india an estimate based on injected tritium studies abstract natural recharge is a vital parameter to be known for ground water budgeting management and modelling percolation of a portion of the rainfall through the vadose zone is the principal source of natural recharge to the aquifer systems in india the tritium injection method based on piston flow model is particularly suitable for quantifying the downward flux of moisture in the vadose zone and for measuring natural recharge in indian climatic condition where about 80 of the annual rainfall is received as pulses and occurs during the four monsoon months from june to september natural recharge measurements using the tritium injection method have been carried out in india during the last 25 years in several basins and watersheds located in varying climatic and hydrogeological situations the mean natural recharge values for 35 study areas well distributed over 17 major river basins are presented the recharge rates range from 24 to 198 mm yr 1 or 4 1 to 19 7 of the local average seasonal rainfall the natural recharge data are grouped into four main hydrogeological provinces namely granitic basaltic sedimentary and alluvial and the regression equations between rainfall and natural recharge are derived for each province these equations enable one to determine the approximate value of natural recharge in any watershed basin from the rainfall data for any year the regression equations are used to compute the total annual replenishment of ground water reserves of the country for an average rainfall year the calculated annual input is about 476 10 9 m 3 yr 1 this can be considered as a minimal quantity as it represents the natural recharge due to precipitation alone and does not account for seepage from ponds lakes stream bed canals and return flow from surface water irrigation

a pretreatment method for grain size analysis of red mudstones article i nfo traditional sediment disaggregation methods work well for loose mud sediments but not for tightly cemen ted mudstones by ferric oxide minerals in this paper a new pretreatment method for analyzing the grain size of red mudstones is presented the experimental samples are eocene red mudstones from the dongying de pression bohai bay basin the red mudstones are composed mainly of clay minerals clastic sediments and ferric oxides that make the mudstones red and tightly compacted the procedure of the method is as follows firstly samples of the red mudstones were crushed into fragments with a diameter of 0 6 0 8 mm in size secondly the cbd citrate bicarbonate dithionite treatment was used to remove ferric oxides so that the cementation of intra aggregates and inter aggregates became weakened and then 5 dilute hydrochloric acid was added to further remove the cements thirdly the fragments were further ground with a rubber pes tle lastly an ultrasonicator was used to disaggregate the samples after the treatment the samples could then be used for grain size analysis or for other geological analyses of sedimentary grains compared with other pretreatment methods for size analysis of mudstones this proposed method is more effective and has higher repeatability

contributions of water supply from the weathered bedrock zone to forest soil quality one measure of forest soil quality is the ability of the soil to support tree growth in mediterranean type ecosystems such as most of california s forests there is virtually no rainfall during the summer growing season so trees must rely on water stored within the substrate water is the primary limitation to productivity in these forests many forest soils in california are relatively thin but are underlain by thick zones of weathered bedrock weathered granitic bedrock the most prevalent lithology has available water capacities 0 12 cm water cm rock that approach those of soils 0 2 cm water cm soil and because the weathered rock zone is usually so much thicker several meters than the soil 1 m it almost always constitutes the larger storage reservoir for plant available water the weathered bedrock retains the original rock fabric and is friable and easily excavated but the primary minerals are not thoroughly altered to clay minerals so it is not considered saprolite roots of ponderosa pine pinus ponderosa seedlings penetrate through the soil and encounter weathered bedrock within the first 2 years on many sites thus the influence of the weathered bedrock zone on plant growth begins early root access to the weathered bedrock is restricted to fractures which are often spaced about 50 cm apart water is extracted from the intervening rock matrix through unsaturated flow toward the root mat in the fractures and by mycorrhizal fungal hyphae that penetrate the rock matrix at one site in the sierra nevada 30 year old jeffrey pine p jeffreyi depleted the soil held water by mid june and relied on water stored in the weathered bedrock until the rainy season began in october in this case the weathered bedrock supplied at least 70 of the water used by the trees during the growing season in the same area we found that thin soils are not a detriment to pine productivity when they are underlain by a thick zone of weathered bedrock in mediterranean type ecosystems the weathered bedrock zone is an essential component of the plant water supply system and is thus an important contributor to forest soil quality

a lithofacies study of the peterborough member oxford clay formation jurassic uk an example of sediment bypass in a mudstone succession thirteen samples from the peterborough member oxford clay formation middle jurassic from quest pit stewartby central england were examined in detail using a combination of optical microscopy and backscattered electron imagery the majority of the samples were clay rich mudstones two were silt rich mudstones and one was a muddy sandstone the dominant components of these samples are fine grained clays illite mixed layer illite smectite kaolinite and amorphous organic matter minor components include authigenic pyrite framboidal and euhedral silt sized quartz grains calcareous nannoplankton mainly disarticulated coccolith plates and a variety of early carbonate cements some of the mudstones were found also to contain abundant foraminifera temporal trends between samples in grain size foraminiferal abundance and total organic carbon contents were observed these mudstones were deposited in a shallow epeiric sea where productivity was high and the bottom waters were oxic relative sea level change coupled to a lack of available accommodation space within the basin at low sea level stands is invoked to explain the observed mudstone stacking patterns

recharge in karst and dune elements of a semi arid landscape as indicated by natural isotopes and chloride abstract the rates and mechanisms of local recharge in a semi arid environment have been investigated beneath two major landscape settings in the murray basin in south australia these were calcrete flats with sinkholes and sand dunes in adjacent landscape settings five minor settings were investigated and identified as undisturbed calcrete primary older sinkholes secondary younger sinkholes sand dunes with native vegetation and sand dunes with introduced pasture data from a limited series of boreholes were interpreted to suggest that recharge varied from in excess of 100 mm yr 1 for secondary sinkholes to less than 0 1 mm yr 1 beneath sand dunes with native vegetation the data suggest that recharge under sand dunes has increased by more than two orders of magnitude following clearing of the native vegetation 50 yr ago as 90 of an area of 10 000 km2 has been cleared this clearing has ensured that inflow of saline groundwater to the adjacent river murray will increase and in view of the amount of salt stored in both the unsaturated and saturated zones will continue for a very long time at sites where the inferred recharge is lowest profiles of the chloride concentration of soil water are consistent with the hypothesis that there is in excess of 50 000 yr recharge stored in the thick unsaturated zone some evidence for changes in recharge rate over this time scale is seen

characterising deep vadose zone water movement and solute transport under typical irrigated cropland in the north china plain understanding the dynamics and mechanisms of soil water movement and solute transport is essential for accurately estimating recharge rates and evaluating the impacts of agricultural activities on groundwater resources in a thick vadose zone 0 15 m under irrigated cropland in the piedmont region of the north china plain soil water content matric potential and solute concentrations were measured based on these data the dynamics of soil water and solutes were analysed to investigate the mechanisms of soil water and solute transport the study showed that the 0 15 m vadose zone can be divided into three layers an infiltration and evaporation layer 0 2 m an unsteady infiltration layer 2 6 m and a quasi steady infiltration layer 6 15 m the chloride nitrate and sulphate concentrations all showed greater variations in the upper soil layer 0 1 m compared to values in the deep vadose zone below 2 m the average concentrations of these three anions in the deep vadose zone varied insignificantly with depth and approached values of 125 242 and 116 mg l the accumulated chloride sulphate and nitrate was 2179 113 1760 383 and 4074 421 kg ha respectively the soil water potential and solute concentrations indicated that uniform flow and preferential flow both occurred in the deep vadose zone and uniform flow was the dominant mechanism of soil water movement in this study the piston like flow velocity of solute transport was 1 14 m yr and the average value of calculated leached nitrate nitrogen was 107 kg ha yr below the root zone the results can be used to better understand recharge processes and improve groundwater resources management this article is protected by copyright all rights reserved

assessment and estimation of groundwater recharge for a catchment located in highland tropical climate in central ethiopia using catchment soil water balance swb and chloride mass balance cmb techniques two commonly applied groundwater recharge estimation techniques namely soil water balance swb and the chloride mass balance cmb methods were applied and compared to quantify and analyse groundwater recharge in the akaki catchment located in central ethiopia the semi distributed swb method estimated natural groundwater recharge at 105 mm a 10 of the mean annual areal precipitation maap the chloride mass balance method applied to the same catchment estimated mean annual groundwater recharge at 273 mm a 25 of the maap the swb recharge value is much less than the recharge estimated by cmb method highlighting the importance of preferential flow path recharge mechanism which is not captured by the swb method in situ permeability measurements undertaken as part of this research and an earlier investigation based on environmental isotopes have demonstrated that the catchment gets recharged both from direct and preferential flow recharge mechanisms which explains the discrepancy between recharge estimated through the two methods therefore swb model result which only takes into consideration the piston type flow recharge mechanism should be taken as the minimum possible groundwater recharge for the catchment characterized by fractured aquifers the mean recharge estimate from the two methods represents the maximum possible recharge estimate for the catchment investigated although calibration of the recharge estimates was not possible the swb recharge estimate is found to be highly sensitive to changes in precipitation input the findings of this research underline the fact that multiple recharge estimation methods are important to understand and capture possible recharge mechanisms and to reach to an acceptable recharge estimate

reply to comment on field study of spatial variability in unsaturated flow beneath and adjacent to playas by bridget r scanlon and richard s goldsmith

local recharge processes in glacial and alluvial deposits of a temperate catchment summary this study demonstrates that the composition and structure of quaternary deposits and topography significantly influence rates of recharge and distribution of diffuse agricultural pollution at the hillslope scale analyses were made of vertical profiles of naturally occurring chloride and nitrate and artificially introduced bromide in unsaturated and saturated sections of borehole cores of glacial till and alluvium under different land uses in the upper eden valley uk estimates of local potential recharge were made based on chloride mass balance and nitrate peak methods persistent chloride bulges below the root zone were observed and are interpreted to result from filtration processes at lithological boundaries changes in the shape of chloride profiles downslope corroborated by nitrate profiles indicate the roles of surface or near surface runoff and runon and the existence of lateral subsurface flows at depth these findings have implications for estimation of recharge rates through unsaturated zones in quaternary deposits and the interpretation of potential hot spots of diffuse agrochemicals particularly nitrates moving through quaternary deposits into groundwater

floodplain river ecosystems lateral connections and the implications of human interference abstract floodplains are ecotones that form a transition between aquatic and terrestrial environments these important ecosystems can be described as dynamic spatial mosaics in which water plays an important role in connecting various patches on the floodplain surface hydrological connections facilitate the exchange of carbon and nutrients between the river channel and the floodplain and therefore influence the productivity of the entire river system this paper examines the influence of hydrological connections on the potential exchange of dissolved organic carbon between a large australian floodplain to a river channel and the effects of land and water developments on these exchanges the paper proposes that an understanding of floodplain ecosystems requires an interdisciplinary approach a recognition of the importance of the three disciplines hydrology geomorphology and ecology large scale water resources and floodplain development has significantly altered the spatial and temporal patterns of hydrological characteristics in the lower balonne floodplain australia the magnitude frequency and duration of flooding events have all been reduced the construction of levees and water storages has also reduced the reactive floodplain surface area the presented data show the impacts of these changes on the potential supply of dissolved organic carbon from the floodplain surface during periods of inundation annual reductions of up to 1293 tonnes of dissolved organic carbon supply were noted and reductions were especially significant for floods with an average recurrence interval of 2 years or less some small flood events no longer facilitate the potential supply of dissolved organic carbon from the floodplain to the river channel because of water resources and floodplain developments

estimation of long term diffuse groundwater discharge in the northern sahara using stable isotope profiles in soil water stable isotope profiles in soil water in the sahara have been interpreted in terms of the hydrologic processes taking place at one site where the water table is at about 10 m depth the isotope data are interpreted using the model of barnes and allison to show that the water loss by evaporation from the water table is about 2mm a 1 at another site nearby there is a net evaporative loss from the water table but the evaporation is interrupted by occasional infiltration events it is suggested that accumulation of chloride in soil water can give information about the onset of aridity in the sahara

isotope amount effects in hydrologic and climate reconstructions of monsoon climates implications of some long term data sets for precipitation abstract many studies of quaternary climate make use of terrestrial stable isotope records which are interpreted based on seasonal patterns of stable isotopes in modern precipitation multi decade records of isotopes in rainfall allow testing of the assumed behavior of isotope signals used for this interpretation on multi year to decadal scales a 32 year record of stable o and h isotopes in precipitation in tucson arizona permits a detailed examination of stable isotope amount effects at time scales ranging from individual events to decades in a location with summer monsoonal and winter frontal rainy seasons amount effects are weak to non existent in tucson at seasonal and longer time scales and are not useful for discriminating either wetter or drier rainy seasons or wetter or drier decades amount effects are also weak to non existent in published data for annual and multi year amount weighted averages for monsoonal precipitation in new delhi and hong kong but an annual amount effect appears to be present on guam u s territory in addition site specific amount effects do not correlate with measures of regional monsoon intensity this data analysis challenges the general validity of paleoclimate reconstructions based on short term sub annual relationships observed in precipitation isotope data when applied to long term records such as speleothem studies

integrated stratigraphy from the vallcebre basin southeastern pyrenees spain new insights on the continental cretaceous tertiary transition in southwest europe abstract an integrated sedimentological magnetostratigraphic and paleontological study of the vallcebre section south eastern pyrenees spain is carried out in order to define and portray the transition from the cretaceous to the tertiary in a continental setting a robust magnetostratigraphy is correlated to the standard polarity scale in light of known biochronological constraints charophyte marine invertebrates eggshells and other dinosaur remains our results show that this section is among the thickest stratigraphic records for the continental maastrichtian in the old world sedimentology indicates a progressive regression from marine through lagoonal to entirely continental environments the section is dominated by mudstones deposited under low energy conditions exceptionally a basin wide regression maximum is recorded some time before the cretaceous tertiary boundary k t this regression maximum is marked by the input of coarse grained alluvial sediments that record a dramatic change in the landscape quiet mud plains changed to sandy floodplains deposited by high energy currents after a period of renewed quiescence following the regression maximum a cenozoic flooding took place such terminal cretaceous sequence of events has been recorded in shorter sections in several other basins from southwestern europe this energetic sediment input suggests that some time before the k t event a sudden paleoenvironmental reorganization took place in the continental basins of south western europe

geochemical estimates of paleorecharge in the pasco basin evaluation of the chloride mass balance technique the pasco basin in southeastern washington state provides a unique hydrogeologic setting for evaluating the chloride mass balance technique for estimating recharge this basin was affected by late pleistocene catastrophic floods when glacial dams in western montana and northern idaho were breached it is estimated that multiple missoula floods occurred between 13 000 and 15 000 years b p and reached a high water elevation of 350 m these floods removed accumulated chloride from the sediment profile effectively resetting the chloride mass balance clock at the beginning of the holocene the rate of chloride accumulation qcl in the sediments was determined by two methods and compared the first method measured qcl by dividing the calculated natural fallout of 36cl by a measured ratio of 36cl cl in the pore water while the second method used the total mass of chloride in the profile divided by the length of time that atmospheric chloride had accumulated since the last flood although the two methods are based on different approaches they showed close agreement in laboratory studies the sediment to water ratio for chloride extraction was sensitive to the grain size of the sediments low extraction ratios in silt loam sediments led to significant underestimation of pore water chloride concentration br cl ratios were useful for distinguishing nonatmospheric e g rock sources of chloride field studies showed little spatial variability in estimated recharge at a given site within the basin but showed significant topographic control on recharge rates in this semiarid environment an extension of the conventional chloride mass balance model was used to evaluate chloride profiles under transient time varying annual precipitation conditions this model was inverted to determine the paleorecharge history for a given soil chloride profile and the parameters of the root extraction model required to estimate paleoprecipitation

effect of citrate bicarbonate dithionite treatment on fine grained magnetite and maghemite mineral magnetic properties of soils and parent materials have been interpreted in terms of paleoclimate and rates of soil formation but it is important to understand which minerals contribute to the mineral magnetic signal citrate bicarbonate dithionite cbd treatment has been used to determine the amounts of fine grained often pedogenic ferrimagnetic minerals relative to coarse grained often inherited magnetic minerals however questions have been raised about the effect of particle size on the efficacy of cbd in dissolving magnetite and maghemite grains in this paper we use magnetic susceptibility and its frequency dependence and the low temperature behavior of a saturation isothermal remanent magnetization to track the dissolution of carefully sized magnetite grains we found that the standard cbd procedure dissolves fine magnetite particles ca 1 etm essentially intact thin oxidized coatings presumably maghemite are also dissolved by the cbd procedure these results support previous interpretations that the cbd procedure can be used to distinguish between pedogenic and lithogenic magnetic grains assuming that most pedogenic magnetic grains are sufficiently small ca 1 im these results also show that the standard procedure is too harsh to differentiate between 1 grm grains of magnetite and maghemite a modified cbd extraction that uses half as much dithionite reduces the magnetic susceptibility of 1 jam magnetite grains by only 10 this method may be useful in distinguishing between magnetite and maghemite grains in this size range

estimation of natural groundwater recharge in the karoo aquifers of south africa abstract a 3 year project to study the natural groundwater recharge of aquifers in the semi arid karoo formations of south africa was undertaken two typical karoo aquifers at dewetsdorp and de aar were selected for study purposes data were collected from both the saturated and unsaturated zone neutron probe measurements showed that there was no increase in the water content beneath a depth of 1m below the surface even with the exceptionally high rainfall in february 1988 neutron measurements indicated that very little soil matrix flow occurred which implied that most of the recharge occurred along preferred pathways a triangular finite element network was used to determine the relative saturated volume fluctuations svf of the aquifers from the observed water level changes over a period of time which allowed determination of the storativity s and the recharge the main advantage of the method lies in determining recharge and storativity which are both unknowns in the water balance equation and which both contribute to the water level response the svf method showed that the recharge in the karoo formations of south africa varies between 2 and 5 of the annual rainfall in areas which are overlain by a thick soil cover the recharge is less than 3 while recharge in hilly areas with a thin soil cover may be of the order of 5

recharge mode and mineralization of groundwater in a semi arid region sidi bouzid plain central tunisia groundwater is the most important source of water supply in sidi bouzid plain located in central tunisia proper understanding of the geochemical evolution of groundwater is important for sustainable development of water resources in this region a hydrogeochemical survey was conducted on the mio plio quaternary aquifer system using stable isotopes radiocarbon tritium and major elements in order to evaluate the groundwater chemistry patterns and the main mineralization processes occurring in this system the chemical data indicate that dissolution of evaporate minerals and evaporation are the main processes controlling groundwater mineralization the isotopic data show that groundwater in the study area is a mixture of recent shallow waters located upstream and along wadi al fakka bed and paleowaters located towards plain limits and discharge areas low 3h and 14c contents are observed in major part of the plain indicating that recharge of the aquifer occurs mainly through direct infiltration at wadi al fakka while there is no evidence of significant recharge in major part of the plain and mountains piedmonts

orbital control on upper triassic playa cycles of the steinmergel keuper norian a new concept for ancient playa cycles abstract the norian steinmergel keuper smk represents a low latitude cyclically bedded playa system of the mid german basin we investigated a drilling site core morsleben and sections from marginal positions dolomite red mudstone beds form rhythmic alternations that were associated with varying monsoon activity hence low k al ratios of dolomite beds suggest increased chemical weathering of the crystalline hinterland and therefore increased monsoonal rainfall high k al ratios in red mudstone beds reflect increased physical weathering of the hinterlands during dryer periods dolomite layers reflect the lake stage maximum monsoon while red mudstones indicate the dry phase minimum monsoon of the playa cycle we distinguished five major types of cyclic facies alternations representing specific facies zones in the playa system we have implemented spectrophotometry as a tool for high resolution cyclostratigraphy the dense sampling increment up to 1 cm allows for the recognition of all orbital frequencies sediment colour profiles reveal striking hierarchical cycles from semi precession sp 99 kyr over precession p 19 8 kyr and obliquity o 36 kyr to eccentricity e1 2 109 kyr e3 413 kyr a significant 2 myr signal is attributed to the longer term eccentricity e4 one monsoonal precession cycle includes two carbonate precipitation events we propose that stratified mudstone and red mudstone are associated with maximum and minimum monsoon during the transition of the solstices in perihelion and aphelion respectively the two carbonate precipitation events were most likely created when equinoxes were in perihelion and aphelion respectively a sedimentary semi precession response cycle is a novel finding for the norian strata the obliquity signal is attributed to incoming atmospheric moisture from the northeast of the smk basin the e4 cycle controls lake level changes over long times apparently e4 is responsible whether or not a threshold value is crossed bundles of 109 kyr and 413 kyr in red mudstones suggest a dry system with reduced monsoonal activity in contrast humid periods reveal thick layers of dolomite beds indicating that during those intervals the monsoonal activity was strong enough to prevent the playa system from drying out completely

a new precipitation weighted method for determining the meteoric water line for hydrological applications demonstrated using australian and global gnip data summary the relationship between 2h and 18o in precipitation at a site known as the local meteoric water line lmwl is normally defined using an ordinary least squares regression olsr which gives equal weighting to all data points regardless of the precipitation amount they represent however smaller precipitation amounts are more likely to have a lower d excess due to re evaporation of raindrops below the cloud base or biases in the sampling method in this paper we present an equation for a precipitation amount weighted least squares regression pwlsr that will correct these biases for use in groundwater and surface hydrology applications new lmwl equations are presented for australian sites in the global network of isotopes in precipitation gnip where the pwlsr consistently produces a lmwl with a larger gradient than the olsr perth and alice springs exhibit the largest change in slope this is consistent with the higher frequency of small monthly precipitation amounts with low d excess values occurring at these sites in summer for perth and throughout the year for alice springs the pwlsr method was also applied to 288 stations in the gnip data base n 36 and the difference between the slopes of the lmwls a slopepwlsr slopeolsr calculated for these stations the mean change in slope a was 0 12 with 56 of sites showing an increase in slope or positive a value and 44 having a decrease in slope or negative a sites with mediterranean climates showed the greatest increase in slope the magnitude of the change in slope followed some general trends showing a positive correlation with average 2h and 18o composition and rainfall variability and negative correlation with period of record n

basin geomorphological controls on the mechanism of recharge and discharge and its effect on salt storage and mobilization comparative study using geophysical surveys abstract downhole electromagnetic em profiles have been used to study the salt distribution in four catchments in the wheatbelt of western australia the good correlation r 2 0 7 0 9 obtained by relating the apparent conductivity profiles measured by the downhole em with salt profiles from soil cores enabled estimation of the salt storage in the uncored wells the salt distribution was compared with ground conductivity surveys using em31 and em34 instruments in three catchments and with an input aerial electromagnetic survey aem in a fourth catchment the study revealed the presence of five types of apparent electrical conductivity profiles eca which are correlated with the basin geomorphological units the conductivity profiles are 1 low eca recharge profile 2 subsurface peak discharge profile 3 two bulge profiles a single bulge accumulation weathering profile and a split aquifer development profile 4 reduced bulge leaching profile 5 high eca irregular palaeochannel profile the salt distribution showed a systematic increase in salinity from the watersheds to the valleys with salinity increasing upstream of geological structures the salt distribution was found to be controlled by the geomorphologic properties of the basins which control the hydrological and hydrogeological processes and by the recharge discharge mechanisms which influence salt mobilization and accumulation

the influence of disaggregation methods on x ray diffraction of clay minerals abstract three a p i day standards macon georgia kaolinite h 4 clay spur wyoming montmorillonite h 26 and fithian illinois illite h 35 were disintegrated mechanically and or chemically in order to determine the most applicable disaggregation technique for argillaceous rocks e g shales bentonites x ray diffraction data and scanning electron microscope observations indicate separation of clay standards in the presence of a na2co3 solution or methanol is less destructive than are dry techniques a probe type ultrasonic device is considered an effective tool for disaggregating all three tested clays three diagrams showing a linear relationship between the relative x ray peak intensity and disaggregation time are presented to allow selection of the most ap licable method for various types of clay constituents

pedostratigraphy of chinese loess deposits and climatic cycles in the last 2 5 myr summary the pedostratigraphy and magnetostratigraphy of several sections in the loess plateau of north central china have been investigated and correlated the most complete and distinct loess paleosol sequence occurs in the baoji section of the southern part of the plateau thirty seven pedostratigraphic units are identifiable in the baoji section and correlated with those in other parts of the plateau the sequence represents thirty seven major cold to warm climatic cycles in the last 2 5 myr at about the time of the matuyama gauss magnetic reversal an abrupt climatic event occurred in north china represented by the shift of the well weathered red clay formation below the m g boundary to the alternating loess and paleosol units above marking the beginning of a new epoch in the course of climatic evolution in addition there are two other major shifts of dominant periods of climatic cycles recorded in the loess paleosol sequences one occurring at about 1 5 myr and another at about 0 8 myr the pedostratigraphy of loess deposits in north central china provides an independent measure of the world wide climatic fluctuations and is now the most complete and reliable record of the major climatic cycles in the last 2 5 myr

diagenesis and evolution of the lower eocene red bed sandstone reservoirs in the dongying depression china abstract the diagenetic evolution of the lower eocene red bed high quality reservoirs in the dongying depression was systematically investigated through an integrated petrographic petrophysical fluid evolution and thermal history analysis the reservoirs experienced several phases of diagenesis including compaction carbonate cementation gypsum and ankerite cementation feldspar and carbonate dissolution quartz overgrowth cementation and clay mineral cementation and transformation an early alkaline diagenetic environment caused significant cementation of calcite and gypsum in the reservoir sandstone units near the sandstone mudstone contacts acidic formation fluids caused widespread dissolution of the feldspar and carbonate cements leading to synchronous occurrences of primary intergranular pores and acidic dissolution pores from the middle parts of the reservoir sandstone units to the sandstone mudstone contacts dissolution wanes gradually with ferro carbonate progressively diminishing migration of exogenetic thermal fluid along faults may have contributed to the gradual decrease in dissolution and the gradual increase in cementation from the lower part to the upper part of fault blocks the alternating alkaline and acidic diagenetic environments and the distribution of diagenetic products caused the development of the high quality red bed reservoirs in the middle part of the thick layered sandstone units in the lower part of fault blocks because of the spatial and temporal relationships between the diagenetic stages and their products lithological traps of a diagenetic origin were developed in the red bed reservoirs

water recharge and solute transport through the vadose zone of fractured chalk under desert conditions this study focuses on water flow and solute migration through unsaturated fractured chalk in an arid area the chalk underlies a major industrial complex in the northern negev desert where groundwater contamination has been observed four dry drilling holes were bored through the vadose zone core and auger samples collected at 30 to 50 cm intervals were used for chemical and isotopic analyses enabling the construction of the following profiles 1 a tritium profile to estimate the rate of water flow through the unsaturated zone 2 oxygen 18 and deuterium profiles to assess the evaporation of water at land surface before percolation and in the upper part of the vadose zone after infiltration and 3 chloride and bromide profiles as tracers for inert solutes and pollutants the tritium and bromide profiles showed the rate of infiltration through the unsaturated matrix to be very slow 1 6 11 cm yr the chemical and isotopic data from the core holes suggested that the pore water changes characteristics with depth close to land surface the pore water is strongly evaporated 18o 5 94 and highly concentrated 29 meq cl 100 g rock but changes gradually with depth to amore dilute concentration 4 meq cl 100 g rock and isotopically depleted composition 18o 4 4 closer to the isotopic composition of precipitation and groundwater nearby monitoring wells have shown anthropogenic contribution of heavy metals organic compounds and tritium nativ and nissim 1992 a conceptual model is proposed in which a small portion of the rainwater percolates downward through the matrix while a larger percentage of the percolating water moves through preferential pathways in fractures the water flowing through the fractures penetrates the matrix across the fracture walls where it increases the tritium concentrations depletes the stable isotopic composition and dilutes the salt concentrations the observed rapid downward migration of tritium and heavy metals through the profuse fractures makes the chalk inefficient as a hydrologic barrier

the occurrence and geochemistry of arsenic in groundwaters of the newark basin of pennsylvania abstract elevated as concentrations in groundwater in the eastern united states have been recognized predominantly in the accretionary geologic terranes of northern new england a retrospective examination of more than 18 000 existing groundwater samples from the pennsylvania department of environmental protection pa dep drinking water and sampling information system database indicates that elevated groundwater as concentrations occur throughout the northern half of the piedmont province of pennsylvania chemical analyses of 53 samples collected in 2005 from drinking water wells in this area all had detectable as and 23 of these samples contained elevated 133 nmol l or 10 g l concentrations of as elevated concentrations of as in the groundwater samples were most common in the mesozoic sedimentary strata composed of sandstone and red mudstone with interbedded gray shale and gray to black siltstone and shale arsenic was typically not elevated in groundwater of diabase intrusions of the newark basin or in crystalline and calcareous aquifers to the north of the newark basin geochemical parameters such as ph and oxidation reduction potential can indicate mobility mechanisms of as in some regions in this area measured groundwater conditions were predominantly oxidizing eh 50 mv and more than 85 of samples contained arsenate as the dominant as species variations in ph were strongly correlated to the as concentration with highest as concentrations observed at ph values greater than 6 4 the original source of as is most likely the black and gray shales that contain some arsenian pyrite with groundwater concentrations likely to be controlled by adsorption desorption reactions with fe oxides in the red mudstone aquifer materials

floodplain river ecosystems fragmentation and water resources development abstract floodplain river ecosystems are natural fragmented systems because of periodic hydrological connections the integrity of these ecosystems is thought to be dependent in part upon exchanges of energy and matter between patches such as the main river channel adjacent floodplain surface and other morphological features during periods of connection flow regulation and its associated infrastructure change the natural character of fragmentation in floodplain river ecosystems and have important consequences for their overall productivity this paper considers the influence of water resources development on the character of fragmentation in a large lowland river in se australia large scale water resources development in the macintyre river australia has significantly altered the spatial and temporal patterns of hydrological connections the construction of weirs and other embankments on the lower macintyre river floodplain prevents water movement through a series of anabranch channels thereby reducing the availability of these floodplain patches by 55 in addition because of flow regulation hydrological connections to these channels occur up to 22 less often data are presented showing the impacts of these changes on the potential supply of dissolved organic carbon from the anabranch channels during periods of inundation over a 98 year period reductions of up to 98 of potential dissolved organic carbon supply from some anabranch channels were noted

high chloride concentrations in the soil and groundwater under an oak hedge in the west of france an indicator of evapotranspiration and water movement chloride is a major anion in soil water and its concentration rises essentially as a function of evapotranspiration compared to herbaceous vegetation high transpiration rates are measured for isolated trees shelterbelts or hedgerows this article deals with the influence of a tree hedge on the soil and groundwater cl concentrations and the possibility of using cl as an indicator of transpiration and water movements near the tree rows cl concentrations were measured over 1 year at different depths in the unsaturated zone and in the groundwater along a transect intersecting a bottomland oak hedge we observed a strong spatial heterogeneity of cl concentrations with very high values up to 2 g l 1 in the unsaturated zone and 1 2 g l 1 in the upper part of the groundwater this contrasts with the low and homogeneous concentrations 60 70 mg l 1 in the deeper part of the groundwater cl accumulation in the unsaturated zone at the end of the vegetation season allows us to identify the active root zone extension of trees in winter upslope of the tree row downwards leaching partly renews the soil solution in the root zone while the slow water movement under the trees or farther downslope results in cl accumulation and leads to a salinization of the soil and groundwater this salinization is of the same order as experimental conditions produce negative effects on oak seedlings the measurement of cl concentrations in the unsaturated zone under tree rows at the end of the vegetation season would indicate whether certain topographic pedological or climatic conditions are likely to favour a strong salinization of the soil as observed in the present study copyright 2009 john wiley sons ltd

groundwater recharge estimation using chloride stable isotopes and tritium profiles in the sands of northwestern senegal a study of environmental chloride deuterium oxygen 18 and tritium in deep sand profiles 35 m has been carried out in order to estimate their relative value for measuring average groundwater recharge the investigation was located at a 0 1 km2 site in quaternary sands near the northwestern coast of senegal in a zone of rainfed agriculture by using a steady state model for duplicate unsaturated zone chloride profiles the long term average recharge at the site was estimated to be 30 mm yr 1 or around 10 of the average precipitation 290 mm the chloride concentration of adjacent shallow groundwater was relatively uniform and comparable to the unsaturated zone average while the spatial variability in the depth distribution of cl in the unsaturated zone was considerable stable isotope deuterium and oxygen 18 data show that there is some isotopic enrichment due to direct evaporation through the soil surface the degree of heavy isotope enrichment is proportional to the extent of evaporative loss and there is good correspondance with the chloride enrichment nevertheless stable isotopes cannot be used quantitatively to estimate the recharge the excellent preservation of the peak in thermonuclear tritium in precipitation in the unsaturated zone at depths between 12 and 20 m enables an estimated annual recharge of 24 mm yr 1 in this area to be calculated using the piston flow model agreement therefore between cl and3h as tools for recharge measurement is reasonable over the site

groundwater recharge estimation using chloride deuterium and oxygen 18 profiles in the deep coastal sands of western australia the depth distributions of environmental chloride deuterium and oxygen 18 in the deep sands 20 m were monitored with a view to estimate average recharge to groundwater the investigated area is located on the southwestern coast of western australia and supports a perennial native woodland vegetation by using a steady state model based on the conservation of chloride the average areal recharge was estimated to be approximately 15 of the average precipitation 775 mm yr 1 whilst the cl concentration of groundwater was relatively uniform there was a considerable spatial variability in the depth distribution of cl in the unsaturated zone an approximate method of data analysis is developed application of this to cl data shows that possibly some 50 of the total annual recharge occurs via movement of water through preferred pathways thus bypassing the soil matrix stable isotope deuterium and oxygen 18 data show that there has been some isotopic enrichment due to evaporation of the rainfall but the extent of enrichment appears to be too small to estimate recharge rates reliably it is argued that relatively small isotopic enrichment occurs in the system studied since the direct evaporation from soil is a rather small component of the total evapotranspiration the observations on the depth distribution of isotopes qualitatively support the presence of a bimodal system for water movement through the profile as was suggested by the analysis of chloride data

a method for the disaggregation of mudstones we describe a method which effectively and gently disaggregates muds and mudstones by combining a saturation freeze thaw technique with treatment by ultrasonic probe the method works well for samples containing 5 toc and which have been buried to depths less than about 3500 m it does not work for samples strongly cemented with carbonates or silicates scanning electron micrographs of size fractions and the strong mineralogical segregation between size fractions are offered as evidence of complete disaggregation

the eco geomorphological roles of rocky deep crevices for water supply on arid zone mountain slopes case study mehriz yazd iran rocky slope landscapes are widely distributed on arid land mountains where there are many restoration and forestation project sites this study has surveyed the role of deep crevices and stone layers for supplying water to establish trees and shrubs on arid lands rocky slopes the research was concentrated on the layers of limestone granite and andesite in central iran thirty transects each 25 m long were randomly laid out throughout the studied lithologic units correlation of vegetation cover percentage and abundance of trees were studied along with crack dimensions including width depth and length categorized into three classes large medium and low sizes along those transects the amount of ec ph organic materials caso4 caco3 soil texture n p k and soil moisture content in the cracks were also measured the results showed significant differences p 0 05 among crack properties vegetation cover and life forms in the study units also the vegetation cover and life forms have positive significant relationships with increase of crevice width as well as length and depth of each lithologic unit the findings demonstrated that the inherent potential of limestone rocky slopes with deep layers is higher than other rocky units for restoration and afforestation in this arid region

oceanic core complexes and ancient oceanic lithosphere insights from iapetan and tethyan ophiolites canada and albania abstract oceanic ridges are extensional environments characterized by brittle to ductile normal faulting and episodic magma supply studies in modern oceanic settings suggest that the interplay of low angle detachments and high angle normal faults locally lead to the exhumation of lower crust and upper mantle peridotites to the seafloor as oceanic core complexes along the mid atlantic ridge core complexes typically occur in inside corners of intersections between the ridge axis and major transform faults the core complexes were exhumed by movement along long lived detachment faults that extend for 10s of km and that are crosscut by high angle normal faults oriented parallel to the rift axis ridge segments with abundant detachments would be characterized by lithosphere having little or no upper crust similar features in ophiolites may also reflect the dominance of amagmatic extension this contribution presents two examples of fossilized oceanic core complexes preserved in the canadian appalachian and albanian dinaride ophiolite belts in the canadian appalachians the southern quebec ophiolites experienced two paleozoic orogenies after their obduction onto the laurentian margin although locally obscured by tectonic fabrics and structures the original relationships between the ophiolitic mantle the overlying plutonic section and onlapping ordovician siliciclastic rocks are well preserved in the thetford mines ophiolite which also shows similarities with lithological and structural features of the mirdita ophiolite where conformable contacts between the sedimentary cover sequence debris flows and flysch deposits and the mantle and crustal sections are superbly exposed the jurassic mirdita ophiolite in albania underlies ca 4000 km2 and was only slightly affected by the tertiary alpine orogeny of eastern europe well exposed sections of the ophiolite suggest that the oceanic mantle was exhumed prior to obduction and locally records the formation of an oceanic core complex mafic cumulates of the mirdita ophiolite have been totally excised in places and exhumation related shear zones are preserved in the krabbi puka massif the shear zones are manifested both within the mantle and at the contact with overlying basalts the ophiolitic sedimentary sequence was deposited on basalts sheeted dykes or gabbros and typically consists of debris flows intercalated with and overlain by slumped oceanic sedimentary rocks the lithological and structural characteristics of both the thetford mines and the mirdita ophiolites are consistent with extensional tectonism crustal excision and lower crust upper mantle exhumation during formation both ophiolites are believed to have originated during asymmetrical oceanic extension in a suprasubduction zone setting with preservation of the upper plate lower plate segments during obduction

comparison of water table fluctuation and chloride mass balance methods for recharge estimation in a tropical rainforest climate a case study from kelantan river catchment malaysia estimated groundwater recharge for selected locations in northeast peninsular malaysia north kelantan river catchment was determined using the water table fluctuation wtf and chloride mass balance cmb methods the wtf method recharge estimates were compared to the cmb method estimates to see if results are similar and the methods can be applied in a humid tropical region such as malaysia effective specific yields of 0 18 and 0 16 were obtained for sites which are much lower than values in the literature for use with the wtf method the wtf gives mean recharge values of 447 and 319 mm year at pc61 and wakaf bharu wb respectively the difference between sites may be attributed to the difference in lithology whereby less water table fluctuation is observed for finer grained lower permeability soil or sediment and higher water table fluctuation observed for more granular larger grain soil or sediment for the site with lower permeability the time lag between the storm events and water level rise in a well is longer and water does not reach the water table for small storms recharge from chloride profile study was estimated through measurement of enrichment of chloride concentration in soil rain fed groundwater direct recharge ranged from 263 3 to 627 7 mm year in wb and averaged 691 8 mm year for pengkalan chepa recharge estimates from unsaturated zone chloride strongly correlate with soil texture generally and is greater in the coastal area due to a higher percentage of sand content parts of the study area located toward the interior of the peninsula showed lower recharge due to the presence of fine grained sediment comparison of methods from different sites indicates that lithologic setting has a significant role in controlling natural recharge rate the inconsistency observed between recharge value estimated by the wtf and cmb method may in part be due to adsorption desorption process and ion exchange in the unsaturated soil which affects the initial assumption that chloride is a conservative tracer

the effect of weathering on pore geometry and compressive strength of selected rock types from turkey weathering processes cause important changes in rock porosity besides porosity distribution of pore sizes is significant for the identification of changes due to rock weathering and its effects on fabric the formation of secondary porosity in different types of rock taken from different parts of turkey was examined and the results are presented in this paper the aim of this study was to observe changes in porosity due to weathering effective porosity mercury intrusion porosimetry and optical and scanning electron microscopy were used to evaluate the changes in pore geometry of the rocks additionally the dry density water absorption and uniaxial compressive strength of the rocks at different weathering stages were determined analysis of experimental data showed that microstructure of the rocks in relation to weathering is the main feature which controls their physical and mechanical properties the study revealed that fabric characteristics particularly the pore and fracture geometry are very important characteristics for assessment of the behaviour of weathered rock

evaporation and concentration gradients created by episodic river recharge in a semi arid zone aquifer insights from cl δ 18 o δ 2 h and 3 h summary this study has significantly advanced our understanding of the origin of groundwater recharge in a semi arid zone region of the darling river catchment australia the generally accepted hypothesis in arid zone environments in australia that river water forms the primary groundwater recharge source has proven difficult to monitor this is due to the time lags between large floods the remoteness and expense of studying these hydrologically complex systems in detail in addition the highly episodic nature of dryland rivers complicates the interpretation of the groundwater signal a range of hydrochemical tracers chloride oxygen 18 deuterium and tritium measured in rain river water soil water and groundwater were used in this multi year study to trace the pathways of groundwater recharge under wet and dry climatic conditions the evaporation and cl concentrations observed in the unsaturated zone confirmed that small volumetric inputs from periodic rainfall were not the major recharge mechanism sampling which included an overbank flooding event in march 2012 provided firm evidence for groundwater originating from high flow episodic river recharge the use of long term environmental data to understand how economically important water resources respond to climate change with increasing temperatures is considered essential for future sustainability

the groundwater recharge regime of some slightly metamorphosed neoproterozoic sedimentary rocks an application of natural environmental tracers isotope data of precipitation and groundwater in parts of the voltaian basin in northern ghana were used to explain the groundwater recharge regime in the area groundwater recharge is an important parameter in the development of a decision support system for the management and efficient utilization of groundwater resources in the area it is therefore important to establish the processes and sources of groundwater recharge 18o and 2h data for local precipitation suggest enrichment relative to the global meteoric water line gmwl and indicate that precipitation takes place at a relative humidity less than 100 the groundwater data plot on an evaporation line with a slope of 5 suggesting a high degree of evaporative enrichment of the precipitation in the process of vertical infiltration and percolation through the unsaturated zone into the saturated zone this finding is consistent with the observation of high evapotranspiration rates in the area and ties in with the fact that significant clay fraction in the unsaturated zone limits vertical percolation and thus exposes the percolating rainwater to the effects of high temperatures and low humidities resulting in high evapotranspiration rates groundwater recharge estimates from the chloride mass balance cmb method suggest recharge in the range of 1 8 32 of the annual average precipitation in the form of rainfall the highest rates are associated with areas where open wells encourage significant amount of groundwater recharge from precipitation in the area in the northern parts of the study area groundwater recharge is lower than 12 the recharge so computed through the application of the cmb methodology takes on a spatial distribution akin to the converse of the spatial pattern of both 18o and 2h in the area as such the locations of the highest recharge are associated with the most depleted values of the two isotopes this observation is consistent with the assertion that low vertical hydraulic conductivities slow down vertical percolation of precipitation down to the groundwater water the percolating precipitation water thus gets enriched in the heavier isotopes through high evapotranspiration rates at the same time the amount of water that finally reaches the water table is considerably reduced copyright 2013 john wiley sons ltd

dissolution behaviour of fine grained magnetite and maghemite in the citrate bicarbonate dithionite extraction method mineral magnetic properties of soils and sediments are increasingly used as proxy parameters for environmental and palaeoclimate analysis to investigate which magnetic minerals contribute to the environmental signal in the samples chemical techniques such as the citrate bicarbonate dithionite cbd extraction method have been introduced in environmental magnetism studies this technique is assumed to distinguish lithogenic magnetite from pedogenic maghemite mineral content in soils and sediments unfortunately interpretation of the cbd extractions is not straightforward because the procedure is sometimes more suitable for distinction between grain size than for distinction between minerals the procedure of the cbd extraction technique was investigated to determine the influence of extraction temperature and iron oxide concentration on the dissolution behaviour of the samples synthetic samples were extracted at three different temperatures 60o 70o and 80oc at similar iron oxide concentration 5 wt and for three different concentrations 0 1 wt 1 wt and 5 wt at the same temperature 60oc our results show that a lower extraction temperature reduces the dissolution rate for all samples while decrease in iron oxide concentration increases the dissolution rate thus the parameters in the cbd procedure have a major influence on the dissolution behaviour of the samples in practice this means that when natural samples of differing iron oxide concentration are extracted with this technique the results of the extractions cannot be compared therefore the outcome of this type of extraction experiment can only be accurately interpreted when the effect of the procedure on the dissolution behaviour is taken into account 1999 elsevier science b v all rights reserved

channel evolution on the dammed elwha river washington usa abstract like many rivers in the western u s the elwha river washington has changed substantially over the past century in response to natural and human forcing the lower river is affected by two upstream dams that are slated for removal as part of a major river restoration effort in preparation for studying the effects of dam removal we present a comprehensive field and aerial photographic analysis of dam influence on an anabranching gravel bed river over the past century with the dams in place loss of the upstream sediment supply has caused spatial variations in the sedimentary and geomorphic character of the lower elwha river channel bed sediment is armored and better sorted than on the naturally evolving bed upstream of the dams on time scales of flood seasons the channel immediately below the lower dam is fairly stable but progresses toward greater mobility downstream such that the lowermost portion of the river responded to a recent 40 year flood with bank erosion and bed elevation changes on a scale approaching that of the natural channel above the dams in general channel mobility in the lowest 4 km of the elwha river has not decreased substantially with time enough fine sediment remains in the floodplain that given sufficient flood forcing the channel position sinuosity and braiding index change substantially the processes by which this river accesses new fine sediment below the dams rapid migration into noncohesive banks and avulsion of new channels allow it to compensate for loss of upstream sediment supply more readily than would a dammed river with cohesive banks or a more limited supply of alluvium the planned dam removal will provide a valuable opportunity to evaluate channel response to the future restoration of natural upstream sediment supply

groundwater chemistry and palaeorecharge in the amadeus basin central australia abstract carbon isotope chemistry indicates episodic palaeorecharge of groundwater in the arid amadeus basin central australia in this hydrogeologically complex region groundwater has been recharged by three important mechanisms direct infiltration of rainwater through sand dune cover or fissures in calcrete through river bed sands following floods and through joints in bedrock outcrops modern and holocene groundwaters 0 5000 years b p are found in the unconfined calcrete and sand dune aquifers which have evolved hydrochemically to cl so4 na waters with ca and mg as a result of evaporative concentration holocene groundwaters 3 10 000 years b p have been dated in river bed recharge situations these groundwaters are mainly of the hco3 cl na type with ca and mg and preserve the hydrochemical signature of the flood recharge waters most groundwater sampled in the folded and jointed rocks of the basin has a low modern 14c content and was recharged in the holocene and late pleistocene 12 32 000 years b p these waters are intermediate in their ionic composition covering a spectrum between the hco3 cl na and cl so4 na types solution is the dominant process int heir hydrochemical evolution stable isotope signatures and derived parameters indicate that the intensity of rainfall is an important factor in the evolution of arid zone groundwaters modern reharged is limited implying that projected large scale groundwater development in this region will use an effectively nonrenewable resource and should be managed accordingly

significance of stemflow in groundwater recharge 1 evaluation of the stemflow contribution to recharge using a mass balance approach stemflow was evaluated in a water balance and its contribution to groundwater recharge determined gross precipitation throughfall and stemflow were measured for one year in a pine forest tsukuba japan to determine each component of the water balance in the forest groundwater recharge rates by stemflow and throughfall were calculated from a mass balance method using chloride in subsurface waters the stemflow in the water balance was relatively small when estimated as a value per canopy projected area of the tree in the forest however the results for the mass balance of chloride in subsurface waters indicated that it was impossible to disregard the stemflow in determining groundwater recharge although the ratio of stemflow to the net precipitation was small in the water balance the effect of stemflow on groundwater recharge was relatively large

deposition and deformation of fluvial lacustrine sediments of the upper triassic lower jurassic whitmore point member moenave formation northern arizona abstract the stratigraphic section of the upper triassic lower jurassic whitmore point member of the moenave formation at potter canyon arizona comprises c 26 m of gray to black shales and red mudstones interbedded with mainly sheet like siltstones and sandstones these strata represent deposition from suspension and sheetflow processes in shallow perennial meromictic to ephemeral lakes and on dry mudflats of the terminal floodout of the northward flowing moenave stream system the lakes were small as indicated by the lack of shoreline features and limited evidence for deltas changes in base level likely forced by climate change drove the variations between mudflat and perennial lacustrine conditions lenticular sandstones that occur across the outcrop face in the same stratigraphic interval in the lower part of the sequence represent the bedload fill of channels incised into a coarsening upward lacustrine sequence following a fall in base level these sandstones are distinctive for the common presence of over steepened bedding dewatering structures and less commonly folding deformation of these sandstones is interpreted as aseismic due to the lack of features typically associated with seismicity such as fault graded bedding diapirs brecciated fabrics and clastic dikes rapid deposition of the sands on a fluid rich substrate produced a reverse density gradient that destabilized and potentially fluidized the underlying finer grained sediments this destabilization allowed synsedimentary subsidence of most of the channel sands accompanied by longitudinal rotation and or ductile deformation of the sand bodies

evolution of chemical and isotopic composition of inorganic carbon in a complex semi arid zone environment consequences for groundwater dating using radiocarbon abstract estimating groundwater age is important for any groundwater resource assessment and radiocarbon 14 c dating of dissolved inorganic carbon dic can provide this information in semi arid zone i e water limited environments there are a multitude of reasons why 14 c dating of groundwater and traditional correction models may not be directly transferable some include 1 the complex hydrological responses of these systems that lead to a mixture of different ages in the aquifer s 2 the varied sources origins and ages of organic matter in the unsaturated zone and 3 high evaporation rates these all influence the evolution of dic and are not easily accounted for in traditional correction models in this study we determined carbon isotope data for dic in water carbonate minerals in the sediments sediment organic matter soil gas co 2 from the unsaturated zone and vegetation samples the samples were collected after an extended drought and again after a flood event to capture the evolution of dic after varying hydrological regimes a graphical method han et al 2012 was applied for interpretation of the carbon geochemical and isotopic data simple forward mass balance modelling was carried out on key geochemical processes involving carbon and agreed well with observed data high values of dic and 13 c dic and low 14 c dic could not be explained by a simple carbonate mineral co 2 gas dissolution process instead it is suggested that during extended drought water sediment interaction leads to ion exchange processes within the top 10 20 m of the aquifer which promotes greater calcite dissolution in saline groundwater this process was found to contribute more than half of the dic which is from a mostly dead carbon source dic is also influenced by carbon exchange between dic in water and carbonate minerals found in the top 2 m of the unsaturated zone this process occurs because of repeated dissolution precipitation of carbonate that is dependent on the water salinity driven by drought and periodic flooding conditions this study shows that although 14 c cannot be directly applied as a dating tool in some circumstances carbon geochemical isotopic data can be useful in hydrological investigations related to identifying groundwater sources mixing relations recharge processes geochemical evolution and interaction with surface water

understanding hydrological processes in a highly stressed granitic aquifer in southern india the results of a study evaluating the recharge discharge conditions of an unconfined stressed granitic aquifer situated in a semi arid region of andhra pradesh southern india are presented over the last three decades excessive withdrawal of groundwater has drastically lowered the water table to the bedrock the watershed studied was divided into four zones based on geomorphology and hydrogeological conditions using environmental chloride data pertaining to groundwater soil depth profiles and some hydrogeologic and hydrochemical observations a recharge model for the watershed was developed the model revealed that the bulk of the vertical recharge in the western elevated land occurs through preferred pathways and that a small fraction occurs through the soil matrix in addition the watershed has a poor hydrogeologic fabric as indicated by the small range of matrix flow recharge 1 to 1 5 of rainfall among the four zones the dominating preferential flow was high 16 of the annual average rainfall in the valley fills but decreased to 5 5 5 in the plains furthermore although the bulk of the recharge occurs vertically considerable lateral movement of groundwater down the slope indicates that sequential hydrochemical changes occur distinct geomorphological features that exist in the watershed support the proposed model situations similar to those described above may exist in numerous watersheds in the granitic hard rock region therefore information obtained from investigations conducted in this watershed can aid in the development of plans enabling the sustainable exploitation of watersheds that have not yet been developed as well as implementation of appropriate rainwater conservation measures in over exploited watersheds copyright 2009 john wiley sons ltd

pedogenesis and paleoclimate interpretation of the magnetic susceptibility record of chinese loess paleosol sequences in the chinese loess paleosol sequences from luochuan haanxi province china variations in the magnetic susceptibility have been accepted as an excellent proxy for paleoclimate and the standard interpretation is that climatic processes have enhanced the magnetic susceptibility of the paleosols beyond the base line level of the loess by using mineral magnetic properties and a soil chemistry extraction procedure we show that most of the magnetic susceptibility signal in both the paleosols and the loess is due to pedogenesis in effect loess deposition and pedogenesis are competing processes at all times and the presence of a paleosol simply indicates that the latter process was predominant these results imply that any interpretation of the paleoclimate record of loess paleosol sequences must recognize the pedogenic nature of the magnetic susceptibility signal and that the focus of future research must be on the critical role of climate in the development of the paleosols

assessment of β the compression coefficient of mudstones and its relationship with detailed lithology abstract the mechanical compaction of soils and fine grained sediments is commonly described in soil mechanics by a relationship between void ratio and effective stress the relationship is defined by two parameters derived from the slope of the line relating void ratio and log effective stress and e the void ratio at a chosen effective stress e g 100 kpa and e are strongly correlated and are related to the atterburg liquid limit which is itself related in a general way to the grain size and mineralogy of the sediment in general finer grained sediments have higher initial void ratios and compact faster than coarser sediments porosity depth trends for mudstones in sedimentary basins are therefore strongly influenced by lithology steps or changes in the slope of porosity depth trends can be caused by lithological change rather than changes in the pressure regime a method is presented to evaluate for mechanically compacted mudstones using porosities determined from the density log fdc and based on the relationship between effective stress and void ratio developed in soil mechanics the method allows one to obtain rapidly approximate values for materials for which it is essentially impossible to obtain compaction parameters experimentally calculated values for mudstones in wells 8 3 2 and 30 2 1 on the norwegian margin vary between 0 2 and 0 65 the values correlate positively with the clay particle content of the mudstones which we have determined for 50 mudstone samples from the same wells the strong link between mudstone lithology and suggests that a downhole log may be a useful way to visualize downhole variations in mudstone lithology the log also shows how lithology affects the rate of porosity loss with depth or effective stress for example porosity in mudstones within both wells 8 3 2 and 30 2 1 is essentially constant over 700 m sections of normally pressured mudstones the log and grain size data indicate that this reflects changes in the lithological character and of the muds and not as commonly inferred a change in the pressure regime

hydrogeochemical investigation in an arid region of iran tabas central iran groundwater is the most important source of water supply in iran and understanding the geochemical evolution of groundwater is important for sustainable development of the water resources in tabas area a total of 29 samples of groundwater in tabas area have been analyzed for ions and major elements groundwater of the study area is characterized by the dominance of na cl water type groundwater was generally acidic to high alkaline with ph ranging from 5 42 to 10 75 the tds as a function of mineralization characteristics of the groundwater ranged from 479 to 10 957 mg l with a mean value of 2 759 mg l the ca2 mg2 so42 and hco3 were mainly derived from the dissolution of calcite dolomite and gypsum the cu pb and zn ions are not mobile in recent ph eh but these conditions controlled dissolved se v and mo in groundwater the as is released in groundwater as a result of the weathering of sulfide minerals like arsenopyrite

a new chloride leaching approach to the estimation of diffuse recharge following a change in land use abstract a new approach has been developed to estimate the increase in groundwater recharge following land use modification the approach uses the degree of leaching of chloride to quantify soilwater drainage below the root zone which ultimately leads to groundwater recharge it is more general than similar previously reported techniques for analysing transient chloride profiles to infer recharge rates and hence has wider application we have applied the technique to a field situation in southern australia where clearing of native vegetation for agricultural production leads to large increases in groundwater recharge the examples serve to demonstrate the technique and some of the practical difficulties in the application of solutes techniques to recharge estimation

partitioning sources of recharge in environments with groundwater recirculation using carbon 14 and cfc 12 summary groundwater recirculation occurs when groundwater is pumped from an aquifer onto the land surface and a portion of that water subsequently infiltrates back to the aquifer in environments where groundwater is recirculated differentiation between various sources of recharge e g natural rainfall recharge vs recirculated water can be difficult groundwater age indicators in particular transient trace gases are likely to be more sensitive tracers of recharge than stable isotopes or chloride in this setting this is because unlike stable isotopes or chloride they undergo a process of equilibration with the atmosphere and historical atmospheric concentrations are known in this paper groundwater age indicators 14 c and cfc 12 were used as tracers of recharge by surplus mine water that is discharged to streams ternary mixing ratios were calculated based on 14 c and cfc 12 concentrations measured along three transects of piezometers and monitoring wells perpendicular to the creeks and from dewatering wells uncertainty in calculated mixing ratios was estimated using a monte carlo approach ternary mixing ratios in dewatering wells suggest that recharge by mine water accounted for between 10 and 87 of water currently abstracted by dewatering wells the calculated mixing ratios suggest that recharge by mine water extends to a distance of more than 550 m from the creeks these results are supported by seepage flux estimates based on the water and chloride balance along the creeks which suggest that 85 90 of mine water discharged to the creeks recharges the aquifer and recharge by mine water extends between 110 and 730 m from the creeks mixing calculations based on gaseous groundwater age indicators could also be used to partition recharge associated with agricultural irrigation or artificial wetland supplementation

the lithium boron and strontium isotopic systematics of groundwaters from an arid aquifer system implications for recharge and weathering processes abstract saline groundwaters are common to inland australia but their hydrochemical evolution and origin remain largely unknown the saline groundwaters in the alluvial aquifers of the darling river have previously been found to exhibit broad similarity in traditional hydrochemical and isotopic tracers by contrast in this study the trace element isotopes 7li 11b and 87sr 86sr have illuminated more complex hydrogeochemical processes in the same aquifer system this paper reports the first ever set of 7li values in any groundwater system in australia they varied from 5 8 to 16 2 with an average value of 9 7 n 19 in the alluvial aquifers of the darling river catchment the 11b values were all higher than seawater and close to some of the highest 11b values ever reported in the literature for a groundwater system 44 4 to 53 9 average 48 8 n 17 the 87sr 86sr ratios ranged from 0 708 to 0 713 with an average value of 0 709 n 19 the differing signatures in these trace element isotope values highlighted by discovery of the deeper older groundwater system with heavier li isotope values and higher 87sr 86sr is an important finding of this research simple mixing models between river water and saline groundwater cannot explain the observed variation in trace element isotopes hydrochemical evolution was found to be dependent on proximity to the darling river and depth varying degrees of li and b isotopic fractionation during water sediment interaction were interpreted to account for the evolution of the saline groundwaters the measurement of these trace element isotopes has permitted delineation of groundwater end members that would have otherwise not been identified in their absence an inaccurate interpretation of the hydrochemical evolution of these saline groundwaters would have been made this study highlights the importance of a multi tracer approach which includes trace element isotopes in resolving complex geochemical processes in groundwater in semi arid to arid zone environments

an approximation of the sediment budget of the lower mississippi river prior to major human modification a sediment budget is constructed for the lower mississippi river prior to the introduction of most human modifications components of the budget are derived from historical data including mississippi river commission hydrographic survey maps for the period from 1877 to 1924 a quantitative estimate of major sediment sources sinks and storage locations in the lower mississippi valley suggest that the most important sediment source was from bank caving and that at least 50 per cent more sediment was deposited in short term channel storage than in longer term overbank storage the budget indicates that the proportion of sediment transported as bedload was significantly greater than previously estimated the magnitude and variability of these sediment budget components are discussed the results of the study suggest that prior to modifications the river was aggrading over much of its length

mass balance simulation and principal components analysis applied to groundwater resources essaouira basin morocco the water resources of the essaouira coastal basin west of marrakesh are characteristic of a semi arid climate and are severely impacted by the climate in terms of quantity and quality considering the importance of the essaouira aquifer in the groundwater supply of a vast region nearly 1 200 km2 a research study was conducted in order to better understand groundwater evolution in this aquifer system it is a coastal aquifer located on the atlantic coastline southern morocco and salinization problems have been reported covering the palaeozoic bedrock the sedimentary series range from the triassic to the quaternary besides the possibility of seawater intrusion problems the geological structures delineate a syncline bordered by the tidzi diapir of triassic age outcropping to the east and south this is a recharge area for the aquifer whereas the main groundwater flow direction is from se to nw towards the atlantic ocean in spite of the occurrence of calcareous and dolomitic levels all waters in the essaouira basin are of the na cl type based on a range of experimental methodologies combined with pca and geochemical modelling it was possible to identify the mineralization processes occurring in the groundwater system and the importance of the water rock interaction in the water chemistry scenarios were tested using a simple mass balance model through the phreeqc programme the reaction path was assumed to be such that waters observed at shallow depths evolved to more mineralized waters an important contribution of water rock interaction in groundwater mineralization was found corroborating the influence of preferential recharge from the tidzi diapir in the water s signature anthropogenic contamination was also identified and could lead to serious problems with groundwater degradation in the near future in a country with scarce water resources

groundwater flow and radioactivity in namaqualand south africa the namaqualand area is located in the northern cape province of south africa which is characterised by arid climate where groundwater is the only source of water supply for local communities extensive groundwater sampling was carried out in the area and the physico chemical parameters inorganic constituents stable isotopes and trace metals were measured the hydrochemistry of the area indicates dissimilar groundwater composition due to complex geochemical processes where groundwater flow takes place from catchment f30a to the catchment d82b and the chemistry is controlled primarily by redox reaction dissolution and mixing processes the br cl ratio revealed that the salinity in the area is derived from seawater mixing halite dissolution and atmospheric deposition sea aerosol spray under excessive evaporative condition due to climatic aridity groundwater salinity shows increasing trend isotope results show the presence of shallow weathered zone and deep fracture controlled circulating groundwater in the crystalline basement aquifer of the area in comparison to the south african water quality standard the results obtained for gross alpha activity which could be derived from uranium isotopes show that 41 of the reported data in the area fall above the drinking water limit

water movement in desert soil traced by hydrogen and oxygen isotopes chloride and chlorine 36 southern arizona abstract understanding soil water movement is important for water resource management and for analyzing pollutant transport in the vadose zone seasonal variations in shallow soil profiles may have profound effects on deep soil water and solutes we have investigated seasonal soil water movement in the top meter of undisturbed desert soil in the southern arizona using 2 h 18 o cl and bomb 36 c1 six soil profiles were sampled from a young terrace holocene during 1991 to 1992 on a seasonal basis one soil profile was sampled from an older terrace latest pleistocene in october 1992 and one from a yet older fan surface late pleistocene in march 1992 the results indicate that repeated seasonal cyclic movement of soil water in the top 60 80 cm active zone tends to produce a consistent stable isotope composition for the soil water below the active zone in different seasons the deep 18 o on the oldest surface is about 6 heavier than on the younger surfaces probably resulting from greater evaporative loss due to the larger proportion of fines in the older soil this deep isotopic composition is closely related to the composition of the local average annual precipitation an annual average evaporation rate of 35 mm year 1 was estimated using a steady state diffusion model whereas the actual regional evapotranspiration rate is 175 250 mm year 1 this suggests that about 80 of the soil water is lost through transpiration and first stage evaporation before quasi steady state is reached the long term average infiltration rate below the active zone is about 4 mm year 1 for the younger terrace based on both chloride mass balance and bomb 36 cl and 0 02 mm year 1 for the older terrace and the fan surface based on chloride mass balance the correlation between the deep 18 o the reduction of downward flux and the surface age suggests that increasing soil development has resulted in a significant decrease of soil water infiltration and hence an increase in evaporation and surface runoff

environmental and injected tracers methodology to estimate direct precipitation recharge to a confined aquifer abstract direct precipitation recharge to a confined aquifer is a vital parameter for groundwater budgeting management and modelling we describe the conjunctive use of environmental isotopes and geochemical tracer technique and injected tracer method to estimate direct precipitation recharge to an important coastal aquifer undergoing large withdrawal stress the methodology evolved delineates the intake area of the confined aquifer based on environmental isotope and geochemical data and then utilises the recharge rates of the intake area only as determined using injected tracer and geochemical data to estimate the amount of recharge by direct precipitation to the confined aquifer

fluoride dynamics in the granitic aquifer of the wailapally watershed nalgonda district india high concentrations of fluoride up to 7 6 mg l are a recognized feature of the wailapally granitic aquifer of nalgonda district andhra pradesh india the basement rocks provide abundant sources of f in the form of amphibole biotite fluorite and apatite the whole rock concentrations of f in the aquifer are in the range 240 990 mg kg calcretes from the shallow weathered horizons also contain comparably high concentrations of f 635 950 mg kg the concentrations of water soluble f in the granitic rocks and the calcretes are usually low 1 of the total or less but broadly correlate with the concentrations observed in groundwaters in the local vicinity the water soluble fraction of fluoride is relatively high in weathered calcretes compared to fresh calcretes groundwater major ion composition shows a well defined trend with flow downgradient in the wailapally aquifer from na ca hco3 dominated waters in the recharge area at the upper part of the catchment through to na mg hco3 and ultimately to na hco3 and na hco3 cl types in the discharge area in the lowest part the evolution occurs over a reach spanning some 17 km groundwater chemistry evolves by silicate weathering reactions although groundwaters rapidly reach equilibrium with carbonate minerals favouring precipitation of calcite and ultimately dolomite in the lower parts of the watershed this precipitation is also aided by evapotranspiration decreasing ca activity downgradient leads to a dominance of fluorite undersaturated conditions and consequently to mobilisation of f despite the clear downgradient evolution of major ion chemistry concentrations of f remain relatively uniform in the fluorite undersaturated groundwaters most being in the range 3 0 7 6 mg l the rather narrow range is attributed to a mechanism of co precipitation with and or adsorption to calcrete in the lower sections of the aquifer the model may find application in other high f groundwaters from granitic aquifers of semi arid regions

paleoclimatic implications of crayfish mediated prismatic structures in paleosols of the paleogene willwood formation bighorn basin wyoming u s a abstract paleosols at polecat bench northern bighorn basin wyoming show prismatic structures not previously described in the paleogene willwood formation prisms are densely spaced 15 50 mm diameter cylinders with vertical to slightly sinuous paths up to 400 mm long subangular to rounded vertical faces and slightly concave to convex tops prism exteriors are coated commonly by 1 mm thick clay films exteriors also commonly show knobby and striated surficial morphologies prismatic structures are nearly exclusive to thin bedded 1 m thick compound paleosols composed of red to red purple sandy mudrock overlying gray to green gray heterolithic units composed chiefly of fine grained sandstone in addition to prismatic structures these paleosols are characterized by large gray mottles slickensides and calcareous rhizocretions which crosscut or more typically follow prism exteriors the architectural and surficial morphology of the soil prisms suggest strongly that these are pedogenically modified freshwater crayfish burrows of the ichnospecies camborygma litonomos at polecat bench an 40 m interval of the willwood formation records a transient episode of global warming known as the paleocene eocene thermal maximum petm the petm interval is characterized by a series of predominantly red cumulative paleosol profiles and increased soil carbonates prismatic soil structures and crayfish burrows are rare or absent in cumulic paleosols typical of the petm whereas they are locally abundant in red compound paleosols outside the petm interval the changes in paleosol morphology and a sharp decrease in crayfish burrows within the petm interval suggest significantly improved soil drainage conditions and lower water tables on the willwood floodplain during the global warming event

climatic and geomorphologic cycles in a semiarid distributive fluvial system upper cretaceous bauru group se brazil abstract studies of distributive fluvial systems and their preserved successions envisage the distribution and orientation of architectural elements to be primarily controlled by channels radiating outward from fan apices in many cases along an elongate basin margin conceptual models for such systems account for the downstream dynamics of the fluvial network but with limited consideration of temporal geomorphic variations resulting vertical organisation of architectural elements or of the interplay of factors controlling system dynamics to understand the external and internal architecture of distributive fluvial systems and the factors that influence their sequential facies organisation a sedimentary succession of the proximal portion of an upper cretaceous semiarid distributive fluvial system located at the north eastern margin of the bauru basin southeast brazil has been analysed in detail three fining and thinning upward fluvial sequences are identified forming an interval separated at the top and the bottom by two palaeosol profiles each sequence is formed of channel and floodplain deposits two types of channel deposits are identified one is composed of stacked sets of small scale dune deposits suggesting perennial and steady fluvial regime associated with more humid climate periods the other is composed of large scale sets indicative of flattened dunes associated with unsteady and fast changing fluvial flow formed in quasi supercritical flow regime conditions associated with drier climate periods the vertical alternation of these two types of channel deposits records the accumulation of a fluvial succession that responded to high frequency climate induced cyclic change in boundary conditions two palaeosol profiles at the top and at the bottom of the succession indicate temporary interruptions and cessation of the fluvial sedimentation likely related to avulsion of the fluvial belt thus the studied succession reveals high frequency climate induced allogenic sedimentary cycles that occur within a long period autogenic geomorphologic induced sedimentary cycle this work suggests that the internal architecture of the channel deposits can be used as a climate proxy and that climate and geomorphology act jointly as notable factors to control the vertical organisation of distributive fluvial systems

a hydrogeological and hydrochemical explanation of the groundwater composition under irrigated land in a mediterranean environment algarve portugal in the campina de faro in the south of portugal agricultural practices have a large impact on groundwater composition these practices involve pumping of water for irrigation from combinations of large diameter shallow wells noras and small diameter deep boreholes furos excess irrigation water returns to the aquifer and mixes with water from the regional groundwater flow system this irrigation return flow is concentrated by strong evapotranspiration and by flushing of fertilisers the concentration increase induces cation exchange whereby ca on the soil exchanger is replaced by na the mixing in the aquifer allows application of a mixing cell model which may then be used to calculate transmissivities from the cl mass balance the calculations are complicated by the time variant behaviour of cl and the method is adjusted to calculate the change of chloride in time results from the calculations appear to be in good agreement with hydrochemical observations

study of evaporation and recharge in desert soil using environmental tracers new mexico usa the purpose of this study is to investigate the rates and mechanisms of recharge and evaporation in soils of a desert environment using two environmental tracers chloride and oxygen 18 the profiles of chloride concentration and oxygen 18 enrichment in soil water together with the depth distribution of water content in soil reveal information about long term recharge and instantaneous evaporation processes without needing to know the physical properties of the soil three holes were hand augured in different desert settings in southeastern new mexico the chloride concentration profiles were used with the chloride mass balance method to estimate long term recharge rates in these three holes as 0 5 0 8 and 2 4 mm yr 1 analysis using a bimodal flow and transport model shows that possibly 85 of the recharge occurs via movement of water through preferred pathways in the root zone preferential flow was evident in all three sampling sites clay layers have a noticeable effect on the development of water content distribution and thus on oxygen 18 enrichment and chloride concentration profiles the spatial variation in clay layering partly explains the variation in recharge rate estimates

isotope study of moisture sources recharge areas and groundwater flow paths within the eastern batinah coastal plain sultanate of oman oxygen and hydrogen isotope analyses of rainfall samples collected on the eastern batinah coastal plain of northern oman between 1995 and 1998 indicate two different principal water vapor sources for precipitation in the area a northern mediterranean source and a southern indian ocean source as a result two new local meteoric water lines were defined for the study area isotopic analyses of groundwater samples from over 200 springs and wells indicate that the main source of water to the batinah coastal alluvial aquifer is high altitude rainfall from the adjacent jabal akhdar mountains originating from a combination of northern and southern moisture sources the groundwater recharged at high altitude forms two plumes of water which is depleted in the heavy isotopes 18o and 2h and stretches from the mountains across the coastal plain to the sea thereby retaining a chemical homogeneity horizontally and vertically down to a depth exceeding 300 m in contrast in areas adjacent to these two plumes the alluvial aquifer is geochemically stratified near the coast saline intrusion results in abrupt changes in chloride concentrations and isotope values

mechanisms of recharge in a fractured porous rock aquifer in a semi arid region abstract eleven porewater profiles in rock core from an upland exposed sandstone vadose zone in southern california with thickness varying between 10 and 62 m were analyzed for chloride cl concentration to examine recharge mechanisms estimate travel times in the vadose zone assess spatial and temporal variability of recharge and determine effects of land use changes on recharge as a function of their location and the local terrain the profiles were classified into four groups reflecting the range of site characteristics century to millennium average recharge varied from 4 to 23 mm y 1 corresponding to 1 moreover the temporal variability of recharge was estimated and along each profile past recharge rates calculated based on the sequence of cl concentrations in the vadose zone recharge rates increased at specific times coincident with historical changes in land use the consistency between the timing of land use modifications and changes in cl concentration and the match between observed and simulated cl concentration values in the vadose zone provide confidence in porewater age estimates travel times recharge estimates and reconstruction of recharge histories this study represents an advancement of the application of the chloride mass balance method to simultaneously determine recharge mechanisms and reconstruct location specific recharge histories in fractured porous rock aquifers the proposed approach can be applied worldwide at sites with similar climatic and geologic characteristics

a stable isotope study of recharge processes in the english chalk the 2h and 18o values of water contained in unsaturated chalk have been measured in drillcore profiles taken over a period of 28 months on arable land in cambridgeshire eastern england the isotopic composition of rainfall and lysimeter drainage on the same site has also been monitored over a period of four years the distribution of isotope values in the upper few metres of soil and unsaturated chalk shows that the mechanism of infiltration is not simple piston like downward displacement since the scale of vertical fluctuations is incompatible with estimated annual infiltration and the apparent rates of movement of matrix water derived from thermonuclear tritium studies lysimeter drainage is not isotopically identical to matrix water at the same depth suggesting that different routes to water table are associated with consistently different isotopic content although there is an apparent difference between matrix water beneath arable and permanent grassland these differences appear to cancel out in the composition of bulk recharge beneath these land types the regional aquifer has a uniform isotopic composition similar in value to weighted average rainfall and lysimeter drainage suggesting that the recharge abstraction system has been in isotopic equilibrium for many years despite changes in pumping rates and land use two other chalk sites in southern england have been investigated in less detail but indicate clear difference in infiltration behaviour from that seen in cambridgeshire this seems to be related to a higher matrix conductivity and annual rainfall amount